Measles virus-substance preceptor interactions. Possible novel mechanism of viral fusion

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Pulmonary surfactant and its apoproteins.

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S Hawgood, J A Clements

The role of fibronectin binding in the rat model of experimental endocarditis caused by Streptococcus sanguis.

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Inactivation of fibronectin (Fn) binding by insertional mutagenesis of Streptococcus sanguis with Tn916 reduces virulence of this bacterium in the rat model of infective endocarditis (IE). Transconjugants were screened for Fn adherence using an ELISA adherence test. One transconjugant had a decreased adherence to immobilized Fn. Southern hybridization demonstrated that the insertion occurred only once in this mutant. The parent strain and mutant strain JL113 were used as challenge strains in a rat endocarditis model. These experiments demonstrated that the mutant had a reduced ability (P less than 0.05) to produce IE. Spontaneous excision of Tn916 from JL113 produced strains identical to both the parental and mutant phenotypes. One strain (JLR-19) that retained the mutant phenotype and one (JLR-15) that regained the parental phenotype for Fn binding were tested for their ability to produce IE. These strains demonstrated that the ability to bind Fn and to produce IE were correlated after Tn916 excision. The reduced virulence of the mutant suggested that adherence of S. sanguis to immobilized Fn plays an important role in the production of IE.

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J H Lowrance, L M Baddour, W A Simpson

Arginine vasopressin gene regulation in the homozygous Brattleboro rat.

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The Brattleboro rat, which has an autosomally recessive form of diabetes insipidus, has been reported to have a marked defect in the regulation of arginine vasopressin (AVP) gene expression. However, it is not known whether this is a primary genetic defect or occurs secondary to the urinary water losses which occur in the absence of circulating AVP in the Brattleboro rat. This present study was therefore undertaken to study AVP gene regulation in the Brattleboro rat after chronic AVP treatment by osmotic minipump for 2 wk. In Brattleboro rats without AVP treatment, neither urinary osmolality (Uosm) nor hypothalamic AVP mRNA was significantly changed after 24 h of fluid deprivation (Uosm, 413 +/- 33 to 588 +/- 44, NS; AVP mRNA, 39.33 +/- 2.95 to 46.39 +/- 2.71 pg/micrograms total RNA, NS). In contrast, when Brattleboro rats were treated with AVP for 2 wk, the regulation of AVP gene occurred in response to 24 h of fluid deprivation. In these studies, hypothalamic AVP mRNA was significantly increased compared with the Brattleboro rats still receiving AVP with free access of water (28.9 +/- 3.5 vs. 65.0 +/- 3.3 pg/micrograms total RNA, P less than 0.001). Further studies in Long-Evans rats demonstrate a similar response to a comparable degree of fluid deprivation as Uosm and AVP mRNA were significantly increased after 72 h of fluid deprivation (Uosm, 1,505 +/- 186 to 5,460 +/- 560 mosmol/kg, P less than 0.001; AVP mRNA, 31.7 +/- 3.9 to 77.5 +/- 4.6 pg/micrograms total RNA, P less than 0.001). These results indicate that AVP-replaced homozygous Brattleboro rats can regulate AVP gene expression normally in response to fluid deprivation. This finding indicates that the defect in AVP gene regulation in the Brattleboro rat not receiving AVP replacement is a secondary phenomenon rather than a primary genetic defect.

Authors

J K Kim, F Soubrier, J B Michel, L Bankir, P Corvol, R W Schrier

Measurement of growth hormone-releasing hormone and somatostatin in hypothalamic-portal plasma of unanesthetized sheep. Spontaneous secretion and response to insulin-induced hypoglycemia.

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To elucidate the role of growth hormone (GH)-releasing hormone (GRH) and somatostatin (SRIH) in the regulation of the growth hormone (GH) secretory pattern, we collected portal blood from five unanesthetized ovariectomized ewes for repeated measurements of GRH and SRIH simultaneous with those of peripheral GH. Hormones were measured at 10-min intervals for 5.5 h and their interrelationships analyzed. Mean portal GRH was 20.4 +/- 6.7 (SD) pg/ml and the estimated overall secretion rate was 13 pg/min. GRH secretion was pulsatile with peaks of 25-40 pg/ml and a mean pulse interval of 71 min. Mean portal SRIH was 72 +/- 33 pg/ml and the estimated overall secretion rate was 32 pg/min. SRIH secretion was also pulsatile with peaks of 65-160 pg/ml and a mean pulse interval of 54 min. The GH pulse interval was 62 min. A significant association was present between GRH and GH secretory peaks though not between GRH and SRIH or SRIH and GH. Insulin hypoglycemia resulted in a rapid and brief stimulation of SRIH secretion followed by a decline in GH levels. No effect was observed on GRH secretion until 90 min, when a slight increase occurred. The results suggest (a) the presence of an independent neural rhythmicity of GRH and SRIH secretion with a primary role of GRH in determining pulsatile GRH secretion, and (b) that the inhibitory effects of insulin hypoglycemia on GH in this species are attributable to a combination of enhanced SRIH secretion and possibly other factors, though without significant inhibition of GRH.

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L A Frohman, T R Downs, I J Clarke, G B Thomas

Variant Bernard-Soulier syndrome type bolzano. A congenital bleeding disorder due to a structural and functional abnormality of the platelet glycoprotein Ib-IX complex.

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We have studied a patient with a congenital bleeding disorder and phenotypic manifestations typical of Bernard-Soulier syndrome, including giant platelets with absent ristocetin-induced von Willebrand factor binding. Two monoclonal antibodies reacting with distinct epitopes in the amino-terminal domain of the alpha-chain of glycoprotein (GP) Ib were used to estimate the number of GP Ib molecules on the platelet membrane. In the patient, binding of one antibody (LJ-Ib10) was approximately 50% of normal, while binding of the other (LJ-Ib1) was absent. Binding of both antibodies was reduced to approximately 50% of normal in the mother and one sister of the propositus, and their platelets exhibited approximately 70% of normal von Willebrand factor binding. Immunoblotting studies confirmed the presence of GP Ib alpha, as well as GP IX, in patient platelets. Antibody LJ-Ib10, but not LJ-Ib1, could immunoprecipitate the patient's GP Ib alpha from surface-labeled proteins. Thus, platelets from the propositus contained a structurally and functionally altered GP Ib-IX complex lacking a specific antibody epitope and the ability to bind von Willebrand factor. In contrast, the binding of human alpha-thrombin to the patient's platelets was normal, and three classes of binding sites with high, intermediate, and low affinity could be detected. These studies define a distinct variant form of Bernard-Soulier syndrome and provide evidence, based on a naturally occurring mutant molecule, that the amino-terminal region of GP Ib alpha contains a von Willebrand factor-binding domain distinct from the high affinity thrombin-binding site. Use of different monoclonal antibodies with distinct epitope specificities appears to be essential for a correct identification of variant Bernard-Soulier syndrome.

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L De Marco, M Mazzucato, F Fabris, D De Roia, P Coser, A Girolami, V Vicente, Z M Ruggeri

Effect of bath and luminal potassium concentration on ammonia production and secretion by mouse proximal tubules perfused in vitro.

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To determine the effects of acute changes in K+ concentration in vitro on ammonia production and secretion by the proximal tubule, we studied mouse S2 segments perfused with and bathed in Krebs-Ringer bicarbonate buffers containing various K+ concentrations. All bath solutions contained L-glutamine as the ammoniagenic substrate. High bath and luminal K+ concentrations (8 mM), but not high luminal K+ concentration alone, inhibited total ammonia production rates by 26%, while low bath and luminal K+ concentrations (2 mM), but not low luminal K+ concentration alone, stimulated total ammonia production rates by 33%. The stimulation of ammonia production by low bath K+ concentration was not observed when L-glutamine was added to the luminal perfusion solution. On the other hand, high luminal K+ concentration stimulated, while low luminal K+ concentration inhibited, net luminal secretion of total ammonia in a way that was: (a) independent of total ammonia production rates, (b) independent of Na(+)-H+ exchange activity, and (c) not due to changes in transepithelial fluxes of total ammonia. These results suggest that luminal potassium concentration has a direct effect on cell-to-lumen transport of ammonia.

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G T Nagami

Mapping the gene causing X-linked recessive idiopathic hypoparathyroidism to Xq26-Xq27 by linkage studies.

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Idiopathic hypoparathyroidism has been reported to occur as an X-linked recessive disorder in two multigeneration kindreds. Affected individuals, who are males, suffer from infantile onset of epilepsy and hypocalcemia, which appears to be due to an isolated congenital defect of parathyroid gland development; females are not affected and are normocalcemic. We have performed linkage studies in these two kindreds (5 affected males, 11 obligate carrier females, and 44 unaffected members) and have used cloned human X chromosome sequences identifying restriction fragment length polymorphisms to localize the mutant gene causing this disorder. Our studies established linkage between the X-linked recessive idiopathic hypoparathyroid gene (HPT) and the DXS98 (4D.8) locus, peak LOD score = 3.82 (theta = 0.05), thereby mapping HPT to the distal long arm of the X chromosome (Xq26-Xq27). Multilocus analysis indicated that HPT is proximal to the DXS98 (4D.8) locus but distal to the F9 (Factor IX) locus, thereby revealing bridging markers for the disease. The results of this study will improve genetic counseling of affected families, and further characterization of this gene locus will open the way for elucidating the factors controlling the development and activity of the parathyroid glands.

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R V Thakker, K E Davies, M P Whyte, C Wooding, J L O'Riordan

Cyclic adenosine monophosphate and diacylglycerol. Mutually inhibitory second messengers in cultured rat inner medullary collecting duct cells.

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Studies were performed to examine interactions between the adenylyl cyclase (AC) and phospholipase C (PLC) signaling systems in cultured rat inner medullary collecting duct cells. Stimulation of AC by either arginine vasopressin (AVP) or forskolin or addition of exogenous cAMP inhibits epidermal growth factor (EGF)-stimulated PLC. This inhibition is mediated by activation of cAMP-dependent kinase as it is prevented by pretreatment with the A-kinase inhibitor, N-[2-(methylamino)ethyl]-5-isoquinoline-sulfonamide (H8) but not by the C-kinase inhibitor, 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine (H7). Exposure to EGF eliminates AVP-stimulated cAMP generation. This is not mediated by a cyclooxygenase product as inhibition by EGF is observed even in the presence of the cyclooxygenase inhibitor, flurbiprofen. Inhibition by EGF is not due to an increase in inositol trisphosphate (IP3) as exposure of saponin-permeabilized cells to exogenous IP3 is without effect. Inhibition by EGF is prevented by pretreatment with the C-kinase inhibitor, H7, but not by the A-kinase inhibitor, H8. Exposure to the synthetic diacylglycerol (DAG), dioctanoylglycerol, also inhibits AVP-stimulated AC activity; therefore, inhibition by EGF is due to activation of protein kinase C. Thus, in cultured rat inner medullary collecting duct cells, cAMP and DAG function as mutually inhibitory second messengers with each impairing formation of the other.

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I Teitelbaum

Prostaglandins regulate the synthesis and secretion of the atrial natriuretic peptide.

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We have examined the effects of several PGs on the synthesis and release of the atrial natriuretic peptide (ANP) in vivo and in vitro. PGF2 alpha infusion in anesthetized rats resulted in a significant increase in plasma immunoreactive (ir) ANP levels in vivo despite effecting only modest changes in hemodynamics. The PGs were also effective at promoting irANP secretion in primary cultures of neonatal rat atrial and ventricular cardiocytes. PGF2 alpha increased irANP release with half-maximal induction seen at approximately 10(-8) M; PGE2 was somewhat less effective and prostacyclin (PGI2) was without effect. The PGs also increased ANP mRNA levels in these cells, suggesting that these agents exert a major effect on the synthesis as well as the secretion of the prohormone. Transient expression analysis of atrial cells transfected with 2,500 bp of human (h) ANP 5' flanking sequence linked to a chloramphenicol acetyltransferase (CAT) reporter demonstrated that PGF2 alpha (10(-5) M) increased hANP promoter activity approximately twofold relative to the control. PGF2 alpha had no effect on the promoterless control (pSV0-lamin CAT). Treatment of cultured atriocytes with high concentrations of a cyclooxygenase inhibitor resulted in a significant suppression of ANP secretion in vitro and a truncation of the plasma ANP response to volume infusion in vivo. Taken together these studies support a role for PGs as regulators of cardiac ANP synthesis and secretion, and suggest an additional mechanism whereby eicosanoids may act to control cardiovascular and renal homeostasis.

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D G Gardner, H D Schultz

Hydrogen peroxide stimulates rat colonic prostaglandin production and alters electrolyte transport.

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The changes in short circuit current (electrogenic Cl- secretion) of rat colon brought about by xanthine/xanthine oxidase in the Ussing chamber were inhibited by catalase and diethyldithiocarbamate, but not by superoxide dismutase. These results, the reproduction of the response with glucose/glucose oxidase and with exogenous H2O2, and the lack of effect of preincubation with deferoxamine or thiourea implicate H2O2, and not O2- or OH., as the important reactive oxygen metabolite altering intestinal electrolyte transport. 1 mM H2O2 stimulated colonic PGE2 and PGI2 production 8- and 15-fold, respectively, inhibited neutral NaCl absorption, and stimulated biphasic electrogenic Cl secretion with little effect on enterocyte lactic dehydrogenase release, epithelial conductance, or histology. Cl- secretion was reduced by cyclooxygenase inhibition. Also, the Cl- secretion, but not the increase in prostaglandin production, was reduced by enteric nervous system blockade with tetrodotoxin, hexamethonium, or atropine. Thus, H2O2 appears to alter electrolyte transport by releasing prostaglandins that activate the enteric nervous system. The change in short circuit current in response to Iloprost, but not PGE2, was blocked by tetrodotoxin. Therefore, PGI2 may be the mediator of the H2O2 response. H2O2 produced in nontoxic concentrations in the inflamed gut could have significant physiologic effects on intestinal water and electrolyte transport.

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S S Karayalcin, C W Sturbaum, J T Wachsman, J H Cha, D W Powell

Endogenous circulating DNA in systemic lupus erythematosus. Occurrence as multimeric complexes bound to histone.

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Little is known about endogenous systemic lupus erythematosus (SLE) plasma DNA even though it is the presumed precursor of DNA-containing immune complexes, thought to play a central role in lupus glomerulonephritis. DNA purified from SLE plasma formed discrete bands, corresponding to sizes of about 150-200, 400, 600, and 800 bp, closely resembling the characteristic 200 bp "ladder" found with oligonucleosomal (ON) DNA. By radiolabeling DNA while in whole plasma, the very small amounts present could be further characterized. All of 24 such specimens formed two or more discrete bands on 6% PAGE. Detergent treatment of plasma resulted in a DNA migration pattern similar to that of purified DNA, suggesting disruption of DNA-protein complexes. DNA purified from authentic ON and detergent-treated ON behaved similarly. A significant portion of DNA, labeled in SLE plasma could be specifically immunoprecipitated with monoclonal antihistone antibody as was the case with ON. These immunoprecipitates, when redissolved, exhibited the expected size distribution upon PAGE. It is concluded that DNA in SLE plasma occurs as a series of multimeric complexes, at least a portion of which is noncovalently bound to histone. These results are consistent with an ON-like structure for SLE plasma DNA as had been suggested by theoretical considerations and may have important implications for its immunologic behavior in SLE and perhaps other disorders.

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P M Rumore, C R Steinman

Oxidized low density lipoproteins cause contraction and inhibit endothelium-dependent relaxation in the pig coronary artery.

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The direct vasoactive effects of native and oxidatively modified low density lipoproteins as well as their effects on endothelium-dependent relaxations to 5-hydroxytryptamine were studied in isolated rings of pig right coronary artery. Slowly developing contractions were caused by native low density lipoproteins (100 micrograms protein/ml). The contractions were more pronounced in the absence than in the presence of the trace metal chelator, EDTA, and coincided with the formation of lipid peroxides during the response. The lipophilic antioxidant, butylated hydroxytoluene, prevented the oxidation of, and contraction to, native low density lipoproteins. Low density lipoproteins oxidized by exposure to copper contracted coronary arteries more rapidly with a threshold of only 1 micrograms protein/ml, but with a similar maximal contraction at 100 micrograms protein/ml. Superoxide dismutase inhibited the contraction to native low density lipoproteins, but not to oxidized low density lipoproteins. Catalase blocked contractions to both native and oxidized low density lipoproteins. Contractions to oxidized low density lipoproteins were unaffected by indomethacin, but were abolished by removal of the endothelium or by inhibitors of endothelium-derived relaxing factor. Oxidized low density lipoproteins but not native low density lipoproteins inhibited endothelium-dependent relaxations to 5-hydroxytryptamine. Thus, oxidized low density lipoproteins caused endothelium-dependent coronary artery contractions which are mediated by a hydroperoxide. Contractions to native low density lipoproteins are due to their oxidation in the organ chamber by the superoxide anion radical. Oxidized, but not native, low density lipoproteins impair normal endothelial cell vasodilator function in vitro. Oxidized low density lipoproteins, important in the pathogenesis of atherosclerosis, may directly contribute to the increased risk of vasospasm seen in hypercholesterolemia and atherosclerosis.

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B C Simon, L D Cunningham, R A Cohen

Inability of mitogen-activated lymphocytes obtained from patients with malignant primary intracranial tumors to express high affinity interleukin 2 receptors.

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Patients with primary malignant brain tumors manifest a variety of abnormalities in cell-mediated and humoral immunity. Diminished T cell reactivity has been shown in these patients to be linked to deficiencies in interleukin 2 (IL-2) production that cannot be overcome by exogenous IL-2. In this study, specific binding of radiolabeled IL-2 to PHA-stimulated lymphocytes from brain tumor patients demonstrates that the number of high affinity interleukin 2 receptors (IL-2R) is greatly reduced. FACS analysis indicates that the relative density of the p55 protein (Tac protein) is lower on the mitogen-activated lymphocytes obtained from patients than on comparably treated lymphocytes from normal individuals. These data indicate that mitogen-stimulated lymphocytes obtained from patients have fewer functional high affinity IL-2R principally because of the failure to express sufficient levels of the p55 protein for association with the p75 protein. Northern analysis of total RNA isolated from mitogen-stimulated T cells from patients demonstrates normal levels of steady state mRNA, which codes for the p55 protein. Moreover, there is no defect in the postranslational processing of the primary translation product of this mRNA suggesting that normal levels of the p55 protein are produced in activated T cells from patients.

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L H Elliott, W H Brooks, T L Roszman

Epithelial basement membrane of mouse jejunum. Evidence for laminin turnover along the entire crypt-villus axis.

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Little is known regarding turnover of the epithelial basement membrane in adult small intestine. Are components degraded and inserted along the length of the crypt-villus axis or selectively in the crypt region with subsequent migration of basement membrane from crypt to villus tip in concert with epithelium? We injected affinity-purified sheep anti-laminin IgG or sheep anti-laminin IgG complexed to horseradish peroxidase (HRP) into mice to label basement membrane laminin in vivo. Fluorescence microscopy revealed linear fluorescence along the length of the jejunal epithelial basement membrane 1 d after anti-laminin IgG injection. By 1 wk, small nonfluorescent domains were interposed between larger fluorescent domains. Over the next 5 wk the lengths of nonfluorescent domains increased progressively whereas those of fluorescent domains decreased. Additionally, electron microscopy revealed HRP reaction product along the length of the epithelial basement membrane after 1 d whereas unlabeled or lightly labeled domains that increased in length with time were observed interposed between heavily labeled domains by 2 and 4 wk along the entire crypt-villus axis. We conclude that laminin turnover occurs focally in the epithelial basement membrane of mouse jejunum along the crypt-villus axis over a period of weeks and that this basement membrane does not comigrate in concert with its overlying epithelium.

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J S Trier, C H Allan, D R Abrahamson, S J Hagen

Molecular basis of complement C3 deficiency in guinea pigs.

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In experiments to ascertain the biochemical basis of a genetically determined deficiency of the third component of complement (C3) in guinea pigs, we found that C3-deficient liver and peritoneal macrophages contain C3 messenger RNA of normal size (approximately 5 kb) and amounts, that this mRNA programs synthesis of pro-C3 in oocytes primed with liver RNA and in primary macrophage cultures. In each instance, heterodimeric native C3 protein was secreted with normal kinetics but the C3 protein product of the deficient cells failed to undergo autolytic cleavage and was unusually susceptible to proteolysis. These data and a selective failure of C3 in plasma of deficient animals to incorporate [14C]methylamine suggested either a mutation in primary structure of the C3 protein or a selective defect in co- or postsynthetic processing affecting the thiolester bridge, a structure important for C3 function. A mutation in the primary structure of C3 was ruled out by comparison of direct sequence analysis of C3 cDNA generated from two C3 deficient and two C3 sufficient guinea pig liver libraries. Three base pair differences, none resulting in derived amino acid sequence differences were identified. Finally, restriction fragment length polymorphisms were identified in the C3 gene that are independent of the deficiency phenotype. This marker of the C3 gene permits testing of these hypotheses using molecular biological and classical genetic methods.

Authors

H S Auerbach, R Burger, A Dodds, H R Colten

Neonatal plasminogen displays altered cell surface binding and activation kinetics. Correlation with increased glycosylation of the protein.

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Plasminogen isolated from 60 full-term newborns differs from adult plasminogen in carbohydrate composition, kinetic activation constants, and cell binding. Amino acid composition and amino-terminal sequence analysis data indicate that the plasminogens of neonates and adults have the same amino acid sequence. Like the adult, the neonate has two glycoforms, but both have significantly more mannose and sialic acid than the adult forms. The difference in the neonatal glycosylation is probably responsible for the altered migration observed by isoelectric focusing. Moreover, the difference in carbohydrate composition appears to be the basis of the decreased functional activity of the neonatal plasminogen. The kcat/Km ratios indicate that the overall activation rates of the two neonatal plasminogen glycoforms are lower compared with the adult glycoforms. In addition, neonatal plasminogen does not bind as well to cellular receptors compared with adult plasminogen. These studies suggest a basis for the decreased fibrinolytic activity observed in neonates.

Authors

J M Edelberg, J J Enghild, S V Pizzo, M Gonzalez-Gronow

Productive infection of isolated human alveolar macrophages by respiratory syncytial virus.

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Respiratory syncytial virus (RSV) is a significant cause of lower respiratory tract disease in children and individuals with cell-mediated immunodeficiencies. Airway epithelial cells may be infected with RSV, but it is unknown whether other cells within the lung permit viral replication. We studied whether human alveolar macrophages supported RSV replication in vitro. Alveolar macrophages exposed to RSV demonstrated expression of RSV fusion gene, which increased in a time-dependent manner and correlated with RSV protein expression. RSV-exposed alveolar macrophages produced and released infectious virus into supernatants for at least 25 d after infection. Viral production per alveolar macrophage declined from 0.053 plaque-forming units (pfu)/cell at 24 h after infection to 0.003 pfu/cell by 10 d after infection and then gradually increased. The capability of alveolar macrophages to support prolonged RSV replication may have a role in the pulmonary response to RSV infection.

Authors

J R Panuska, N M Cirino, F Midulla, J E Despot, E R McFadden Jr, Y T Huang

Clonal composition of benign and malignant human thyroid tumors.

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We determined clonality of thyroid tumors from female patients who had restriction fragment length polymorphisms (RFLP) in the X chromosome genes hypoxanthine phosphoribosyltransferase (HPRT) or phosphoglycerate kinase (PGK). We screened normal thyroid tissue from 59 female patients; of the informative cases 14 were heterozygous for a Bgl I site on PGK and 4 were heterozygous for a Bam HI site on HPRT. In monoclonal tumors, one of the polymorphic alleles was selectively digested after additional digestion with Hpa II, a methylation sensitive enzyme, whereas in polyclonal tissue both were decreased to a similar extent. Normal thyroid tissue from all patients showed a polyclonal pattern. Of the 18 tumors studied, 12 were solitary thyroid nodules, and 6 were obtained from multinodular goiters (MNG). The following were monoclonal: 6/6 follicular adenomas, 2/2 follicular carcinomas, and 1/1 anaplastic carcinoma. Two of the three papillary carcinomas showed intermediate patterns, possibly due to contaminating effects of stromal tissue present in most of these neoplasms. Of the six nodules from MNG, four were polyclonal. The two largest gave a distinct monoclonal pattern. Most solitary thyroid tumors are monoclonal, supporting a somatic cell mutation model of thyroid neoplasm formation. Nodules from MNG are largely hyperplastic, although monoclonal neoplasms do occasionally arise within these glands. The specific somatic mutations leading to clonal expansion and determination of tumor phenotype are presently unknown.

Authors

H Namba, K Matsuo, J A Fagin

Rhizomelic chondrodysplasia punctata. Deficiency of 3-oxoacyl-coenzyme A thiolase in peroxisomes and impaired processing of the enzyme.

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The rhizomelic form of chondrodysplasia punctata (RCDP) is a peroxisomal disorder characterized biochemically by an impairment of plasmalogen biosynthesis and phytanate catabolism. We have now found that the maturation of peroxisomal 3-oxoacyl-CoA thiolase is impaired in fibroblasts from RCDP patients. To establish the subcellular localization of the 3-oxoacyl-CoA thiolase precursor protein, cultured skin fibroblasts were fractionated on a continuous Nycodenz gradient. Only a small amount of 3-oxoacyl-CoA thiolase activity was present in the catalase-containing (peroxisomal) fractions of RCDP fibroblasts in comparison with control fibroblasts. Moreover, the amount of thiolase protein in immunoblots of the catalase-containing fractions was below the limit of detection. Finally, the beta-oxidation of [14C]palmitoyl-CoA was found to be reduced in these fractions. We conclude that the mutation in RCDP leads to a partial deficiency of 3-oxoacyl-CoA thiolase activity in the peroxisomes and, concomitantly, an impairment in the ability to convert the precursor of this protein to the mature form. The reduction of 3-oxoacyl-CoA thiolase activity results in a decrease in the rate of peroxisomal beta-oxidation of palmitoyl-CoA. However, the capacity of the peroxisomes to oxidize very-long-chain fatty acids must be sufficient to prevent excessive accumulation of these compounds in vivo.

Authors

J C Heikoop, C W van Roermund, W W Just, R Ofman, R B Schutgens, H S Heymans, R J Wanders, J M Tager

Coexpression of platelet-derived growth factor (PDGF) and PDGF-receptor genes by primary human astrocytomas may contribute to their development and maintenance.

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The present studies investigated the expression of the two PDGF genes (c-sis/PDGF-2 and PDGF-1) and the PDGF-receptor b gene (PDGF-R) in 34 primary human astrocytomas. Northern blot analysis demonstrated the coexpression of the c-sis/PDGF-2 protooncogene and the PDGF-R gene in all astrocytomas examined. The majority of the tumors also expressed the PDGF-1 gene. There was no correlation between the expression of the two PDGF genes. Nonmalignant human brain tissue expressed the PDGF-R and PDGF-1 genes but not the c-sis/PDGF-2 protooncogene. In situ hybridization of astrocytoma tissue localized the expression of the c-sis and PDGF-R mRNA's in tumor cells. Capillary endothelial cells also expressed c-sis mRNA. In contrast, nonmalignant human brain tissue expressed only PDGF-R mRNA but not c-sis/PDGF-2 mRNA. The coexpression of a potent mitogenic growth factor protooncogene (c-sis) and its receptor gene in astrocytoma tumor cells suggests the presence of an autocrine mechanism that may contribute to the development and maintenance of astrocytomas. The expression of c-sis mRNA in tumor cells but not in nonmalignant brain cells may serve as an additional diagnostic criterion for the detection of astrocytomas in small tissue specimen using in situ hybridization for the detection of c-sis mRNA and/or immunostaining for the recognition of its protein product.

Authors

M Maxwell, S P Naber, H J Wolfe, T Galanopoulos, E T Hedley-Whyte, P M Black, H N Antoniades

Expression of the potent vasoconstrictor endothelin in the human central nervous system.

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Endothelin is a potent vasoconstrictive peptide initially characterized as a product of endothelial cells. To examine the potential role of endothelin as a neuropeptide, we studied its distribution in the human central nervous system. RNA blot hybridization provided evidence of endothelin gene transcription in a variety of functional regions of the brain. In situ hybridization confirmed the widespread pattern of endothelin transcription and indicated that the highest density of cells containing endothelin mRNA is in the hypothalamus. This technique localized endothelin transcription to cells of the nervous system as well as the vascular endothelium. Immunocytochemical studies detected endothelin immunoreactivity in neurons, providing evidence of the synthesis of the peptide in this cell type and confirming that endothelin is a neuropeptide. Although the prominent expression of endothelin in the hypothalamus may indicate a central vasoregulatory role for the peptide, the widespread distribution of endothelin in neurons in other areas of the brain implies a more fundamental role in the regulation of nervous system function.

Authors

M E Lee, S M de la Monte, S C Ng, K D Bloch, T Quertermous

Production of interleukins in human immunodeficiency virus-1-replicating lymph nodes.

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To document the in vivo interactions occurring between the immune system and HIV replicating cells, we analyzed using in situ hybridization the production of IL-1 beta, IL-6, IL-2, and INF-gamma in eight hyperplastic lymph nodes from HIV-1 infected patients. Numerous IL-1 beta- and IL-6-producing cells associated in clusters were detected in sinuses. Few individual IL-1 beta- and IL-6-producing cells were present in interfollicular and follicular areas. IL-2- and INF-gamma-producing cells were observed in all lymph node compartments, with a selective enrichment in germinal centers. The amount and distribution of IL-1 beta, IL-6-, and IL-2-producing cells in HIV lymph nodes were not different from those found in six HIV unrelated hyperplastic lymph nodes. In contrast, a higher level of INF-gamma production was observed in HIV-1 lymph nodes. The CD8+ cells that accumulate in germinal centers of HIV lymph nodes (and not in non-HIV germinal centers) were actively involved in this INF-gamma production. INF-gamma synthesizing cells were in direct contact with cells containing HIV core antigens and HIV RNA. Thus a high INF-gamma production may characterize anti-HIV T cell immune response, potentially contributing to control of viral spreading as well as to the development of follicle lysis.

Authors

D Emilie, M Peuchmaur, M C Maillot, M C Crevon, N Brousse, J F Delfraissy, J Dormont, P Galanaud

Prolonged exposure of rat aorta to low levels of endotoxin in vitro results in impaired contractility. Association with vascular cytokine release.

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Treatment of volunteers or animals with endotoxin in vivo results in reduced vascular reactivity to catecholamines. Endotoxin also causes liberation of the vasoactive cytokines interleukin-1 (IL-1) and tumor necrosis factor (TNF) from vascular smooth muscle and endothelial cells in culture. This study tested whether defects in contractility could be induced in isolated vascular tissue by prolonged exposure to endotoxin (1-100 ng/ml) in vitro, and whether IL-1 and TNF release by blood vessels is altered during the establishment of endotoxin induced contractile dysfunction. A concentration of endotoxin as low as 1 ng/ml suppressed contractions to norepinephrine (NE) and KCl; aortic sensitivity to NE also decreased. The presence of serum constituents or an intact endothelium were not necessary for endotoxin-induced vascular suppression. Aortas incubated with endotoxin liberated IL-1 and TNF in a dose-dependent fashion. The addition of dexamethasone or indomethacin during the incubations generally suppressed release of the cytokines and improved tissue reactivity to NE. The endotoxin-induced diminished vascular contraction and augmented IL-1 and TNF liberation required de novo protein synthesis; tissue incubated with endotoxin plus actinomycin D was completely shielded from the influence of endotoxin on vascular reactivity to NE. The association between endotoxin-induced vascular cytokine release and diminished contraction suggests a possible role for cytokines derived from the vasculature in the regulation of contractile function.

Authors

T M McKenna

Renin release and gene expression in intact rat kidney microvessels and single cells.

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Abstract

To investigate whether newborn kidney microvessels and isolated single microvascular cells have the capacity to release renin and/or alter the expression of the renin gene in response to adenylate cyclase stimulation, newborn kidney microvessels were isolated and purified (95%) using an iron perfusion/enzymatic digestion technique. Incubation of microvessels with either vehicle (control; C) or 10(-5) M forskolin (F) in media resulted in an increase in microvessel cAMP (0.67 +/- 0.13 vs. 22 +/- 4.6 pmol/min per mg protein) (P less than 0.005) and renin released into the culture media (1,026 +/- 98 vs. 1,552 +/- 159 pg angiotensin I/h per mg protein) (P = 0.008) (C vs. F). Renin mRNA levels in the newborn kidney microvessels increased 1.6-fold with forskolin treatment. Renin release by isolated, single microvascular cells (with or without forskolin) was assessed using the reverse hemolytic plaque assay. Forskolin administration resulted in an increase in the number of renin-secreting cells without changes in the amount of renin secreted by individual cells. In conclusion, newborn kidney microvessels and isolated renin-releasing microvascular cells possess a functionally active adenylate cyclase whose short-term stimulation results in accumulation of cAMP, a significant increase in renin release, and an enhancement of renin gene expression. The increase in renin release is due to recruitment of microvascular cells secreting renin. Recruitment of hormone-secreting cells in response to stimuli may prove to be a mechanism of general biological importance shared by many endocrine cell types.

Authors

A D Everett, R M Carey, R L Chevalier, M J Peach, R A Gomez

Uptake of extracellular enzyme by a novel pathway is a major determinant of cathepsin L levels in human macrophages.

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Abstract

The phorbol myristate acetate (PMA)-differentiated myelomonocytic cell line, THP-1, and human alveolar macrophages contain the cysteine proteinase cathepsin L. This enzyme is synthesized as a 43-kD proenzyme and processed to the active 25-kD form. Differentiation of THP-1 cells in the presence of human serum resulted in an increase in the size of the vacuolar compartment and the accumulation of more 25-kD cathepsin L antigen, as compared with THP-1 cells differentiated in the presence of fetal calf serum. Cells cultured in both types of sera have equivalent levels of cathepsin L mRNA. Metabolic labeling experiments demonstrated equivalent rates of synthesis, processing to the active form, and persistence in both culture conditions. An extracellular source of enzyme was documented by immunoblotting human serum which demonstrated 25-kD cathepsin L antigen; furthermore, we demonstrated that both THP-1 cells, differentiated in human serum, and human alveolar macrophages take up the 43-kD proenzyme and process it to the 25-kD form. Thus, human serum contains a factor(s) that induces both a marked increase in the size of the vacuolar compartment in differentiated THP-1 cells and a novel pathway that is responsible for the uptake and processing of extracellular cathepsin L. The activity of this inducible pathway is a major determinant of levels of intracellular cathepsin L. Cathepsin L is a potent elastase and the regulation of its uptake and processing may play a role in the pathogenesis of disease processes characterized by the destruction of elastin, such as pulmonary emphysema.

Authors

J J Reilly Jr, P Chen, L Z Sailor, R W Mason, H A Chapman Jr

The tumor necrosis factor receptor and human neutrophil function. Deactivation and cross-deactivation of tumor necrosis factor-induced neutrophil responses by receptor down-regulation.

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Abstract

Despite numerous reports, the role of tumor necrosis factor (TNF) in polymorphonuclear leukocyte (PMN) function remains controversial. We found TNF to be a potent, pertussis toxin-independent stimulator of PMN adhesion (ED50 2.6 pM). TNF-stimulated PMN under adherent conditions released up to 65% of their transcobalamine content (ED50 3.9 pM) and increased their burst activity 10-fold (ED50 3.2 pM) as measured by the hexose monophosphate shunt, whereas PMN held in suspension hardly degranulated at all and only little burst activity was demonstrable. However, preincubation of PMN with TNF in suspension led to a decrease in cellular adhesiveness, degranulation, and burst activity in response to a secondary stimulus of TNF under adherent conditions, although cells remained fully responsive toward phorbol myristate acetate. A concomitant dose-dependent decline of TNF receptor numbers that correlated well with the inhibition of PMN function (r = 0.91) suggests receptor down-regulation as the mechanism of functional PMN deactivation. Remarkably, preincubation with other PMN stimuli such as N-formyl-methionyl-leucyl-phenylalanine, platelet-activating factor, leukotriene B4, complement component fragment 5a (C5a)/C5a (desarginated), and endotoxin also led to a reduction of TNF-specific PMN responses (cross-deactivation) from 35% (LTB4) to 90% (endotoxin), corresponding with the down-regulation of TNF receptors. Deactivation and receptor down-regulation are independent of pertussis toxin-sensitive G proteins and protein kinase C but seemed to depend on changes in calcium metabolism. Granulocyte hyporesponsiveness towards TNF in sepsis (with elevated blood levels of endotoxin and TNF) might be a mechanism of self-protection or, to the contrary, might impair a possibly central mode of host defense.

Authors

B Schleiffenbaum, J Fehr

Impaired metabolic function and signaling defects in phagocytic cells in glycogen storage disease type 1b.

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Abstract

Patients with glycogen storage disease (GSD) type 1b (1b), in contrast to patients with GSD type 1a (1a), are susceptible to recurrent bacterial infections suggesting an impairment in their immune system. In this study, phagocytic cell (neutrophil and monocyte) respiratory burst activity, as measured by superoxide anion generation, oxygen consumption, and hexose monophosphate shunt activity, was markedly reduced in both neutrophils and monocytes from GSD 1b patients as compared with either GSD 1a patients or healthy adult control cells. Degranulation, unlike respiratory burst activity, was not significantly different in neutrophils from GSD 1b patients as compared with controls. Both neutrophils and monocytes from GSD 1b patients showed decreased ability to elevate cytosolic calcium in response to the chemotactic peptide f-Met-Leu-Phe. In addition, calcium mobilization in response to ionomycin was also attenuated suggesting decreased calcium stores. Thus, reduced phagocytic cell function in GSD 1b is associated with diminished calcium mobilization and defective calcium stores. Defective calcium signaling is associated with a selective defect in respiratory burst activity but not degranulation.

Authors

L Kilpatrick, B Z Garty, K F Lundquist, K Hunter, C A Stanley, L Baker, S D Douglas, H M Korchak

Urokinase has direct catalytic activity against fibrinogen and renders it less clottable by thrombin.

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Abstract

Recently, we demonstrated that tissue plasminogen activator directly releases fibrinopeptides A and B (FPA and FPB) from fibrinogen. The purpose of this study was to determine whether urokinase has similar activity. Incubation of urokinase with fibrinogen or heparinized plasma results in concentration-dependent FPB release unaccompanied by FPA cleavage. For equivalent amidolytic activity, high molecular weight urokinase releases twofold more FPB than the low molecular weight species. In contrast, prourokinase does not release FPB until activated to urokinase. Contaminating thrombin or plasma is not responsible for urokinase-mediated FPB release because this activity is unaccompanied by FPA or B beta 1-42 cleavage, and is unaffected by heparin, hirudin, a monospecific antibody against thrombin, aprotinin, or alpha 2-antiplasmin. FPB release reflects a direct action of urokinase on fibrinogen because release is completely inhibited by a monospecific antibody against the enzyme. Further, urokinase releases FPB from the FPB-containing substrate B beta 1-42, thus confirming its specificity for the B beta 14 (Arg)-B beta 15 (Gly) bond. In addition to FPB release, SDS-PAGE analysis of the time course of urokinase-mediated fibrinogenolysis indicates progressive proteolysis of both the A alpha- and B beta-chains of fibrinogen that occurs after FPB release is completed. As a consequence of urokinase-mediated fibrinogenolysis, there is progressive prolongation of the thrombin clotting time. These studies indicate that urokinase has direct catalytic activity against fibrinogen. By releasing FPB, a potent chemoattractant, and by rendering fibrinogen less clottable by thrombin, urokinase may participate in processes extending beyond fibrinolysis.

Authors

J I Weitz, B Leslie

Effect of heme arginate administration on blood pressure in spontaneously hypertensive rats.

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Abstract

Cytochrome P450 content and activities are increased in the kidneys of spontaneously hypertensive rats (SHR) as compared with those of normotensive, Wistar-Kyoto (WKY), control rats during the period of rapid elevation of blood pressure. We studied the effect of heme arginate, a potent inducer of heme oxygenase (EC 1.14.99.3), on microsomal cytochrome P450 levels and activities and blood pressure in SHR at 7 wk of age. Administration of heme arginate (15 mg/kg body weight for 4 d) resulted in a marked decrease in blood pressure from 156.3 +/- 4.7 to 129.8 +/- 4.5 mm Hg (P less than 0.001), whereas blood pressure in SHR receiving the vehicle control was not affected. The blood pressure of age-matched WKY was not affected by heme arginate. Heme oxygenase activity increased in both hepatic and renal microsomes of SHR and WKY by two- to four-fold after treatment with heme arginate. Maximal increase of heme oxygenase mRNA occurred 5-7 h after the last injection of heme arginate and returned to control levels after 24 h. The increase in heme oxygenase activity was associated with a parallel decrease in cytochrome P450 content and in the activity of cytochrome P450 omega/omega-1 arachidonate hydroxylases in kidneys of SHR. It is postulated that heme arginate treatment resulted in induction of heme oxygenase which consequently led to a diminution of cytochrome P450, especially the arachidonate omega/omega-1 hydroxylases leading to a marked decrease in 19-hydroxyeicosatetraenoic acid (HETE) and 20-HETE. The effect of heme arginate on blood pressure may be mediated via these biochemical events inasmuch as both 19-HETE and 20-HETE produced by the kidney may promote hypertension by causing vasoconstriction and sodium retention.

Authors

R D Levere, P Martasek, B Escalante, M L Schwartzman, N G Abraham

The rat hepatocyte plasma membrane organic anion binding protein is immunologically related to the mitochondrial F1 adenosine triphosphatase beta-subunit.

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Abstract

A 55-kD organic anion binding protein (OABP) was identified previously in liver cell plasma membrane sinusoidal subfractions. Although this protein was localized to the surface of hepatocytes by immunofluorescence, immunoblot analysis revealed reactivity toward both plasma membrane and mitochondrial fractions. To clarify these findings, an immunoreactive clone from a rat liver cDNA expression library was isolated, the 1,500-base pair cDNA insert was sequenced, and the corresponding beta-galactosidase fusion protein was expressed and purified. The resulting sequence corresponded to that of the rat mitochondrial F1-adenosine triphosphatase (F1-ATPase) beta-subunit. This protein and OABP are of similar size and are mutually immunologically cross-reactive. That the antigen was present on the cell surface as well as in mitochondria was suggested from studies of immunoprecipitation after cell-surface iodination, and light- and electron-microscopic immunocytochemistry. Photoaffinity labeling of bovine F1-ATPase with high-specific-activity [35S]sulfobromophthalein revealed binding only to the beta-subunit. Hepatocyte uptake of bilirubin and sulfobromophthalein requires cellular ATP and mitochondria also transport these organic anions, which at high doses inhibit respiration. The presence of an organic anion binding site on the F1-ATPase beta-subunit suggests that it may play a role in these processes.

Authors

T Goeser, R Nakata, L F Braly, A Sosiak, C G Campbell, R Dermietzel, P M Novikoff, R J Stockert, R D Burk, A W Wolkoff

Impaired vasodilation of forearm resistance vessels in hypercholesterolemic humans.

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Abstract

The effect of hypercholesterolemia on vascular function was studied in humans. To eliminate the potential confounding effects of atherosclerosis, vascular reactivity was measured in the forearm resistance vessels of 11 normal subjects (serum LDL cholesterol = 111 +/- 7 mg/dl) and 13 patients with hypercholesterolemia (serum LDL cholesterol = 211 +/- 19 mg/dl, P less than 0.05). Each subject received intrabrachial artery infusions of methacholine, which releases endothelium-derived relaxant factor, and nitroprusside which directly stimulates guanylate cyclase in vascular smooth muscle. Maximal vasodilatory potential was determined during reactive hyperemia. Vasoconstrictive responsiveness was examined during intra-arterial phenylephrine infusion. Forearm blood flow was determined by venous occlusion plethysmography. Basal forearm blood flow in normal and hypercholesterolemic subjects was comparable. Similarly, reactive hyperemic blood flow did not differ between the two groups. In contrast, the maximal forearm blood flow response to methacholine in hypercholesterolemic subjects was less than that observed in normal subjects. In addition, the forearm blood flow response to nitroprusside was less in hypercholesterolemic subjects. There was no difference in the forearm vasoconstrictive response to phenylephrine in the two groups. Thus, the vasodilator responses to methacholine and nitroprusside were blunted in patients with hypercholesterolemia. We conclude that in humans with hypercholesterolemia, there is a decreased effect of nitrovasodilators, including endothelium-derived relaxing factor, on the vascular smooth muscle of resistance vessels.

Authors

M A Creager, J P Cooke, M E Mendelsohn, S J Gallagher, S M Coleman, J Loscalzo, V J Dzau

Structural and kinetic analyses of herpes simplex virus type 1 latency-associated transcripts in human trigeminal ganglia and in cell culture.

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Abstract

Only one herpes simplex virus type 1 (HSV-1) gene is expressed in sensory neurons of latently infected animals and humans, yielding two RNAs, called latency-associated transcripts (LATs). The LATs appear to modulate virus reactivation. In mice and rabbits the 5' origins, kinetics of synthesis, and splicing pattern of the LATs are well established. Because these details of LAT structure and expression have not been defined in humans, we sought to do so. Using primer extension and Northern hybridization analyses, we demonstrate that in human trigeminal ganglia, the smaller (1.35 kb) HSV-1 transcript differs from the larger (1.85 kb) LAT by excision of an intron near its 5' end; they are otherwise colinear, and 5' coterminal. In infected cells only the 1.85 kb LAT is detected. Its expression is inhibited by cycloheximide or acyclovir, indicating this LAT is synthesized late in the viral replicative cycle. All of these features of the LATs in humans are consistent with those reported in rabbits and mice and further validate the animal models of human HSV-1 infection.

Authors

P R Krause, K D Croen, J M Ostrove, S E Straus

Maple syrup urine disease. Complete primary structure of the E1 beta subunit of human branched chain alpha-ketoacid dehydrogenase complex deduced from the nucleotide sequence and a gene analysis of patients with this disease.

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Abstract

A defect in the E1 beta subunit of the branched chain alpha-ketoacid dehydrogenase (BCKDH) complex is one cause of maple syrup urine disease (MSUD). In an attempt to elucidate the molecular basis of MSUD, we isolated and characterized a 1.35 kbp cDNA clone encoding the entire precursor of the E1 beta subunit of BCKDH complex from a human placental cDNA library. Nucleotide sequence analysis revealed that the isolated cDNA clone (lambda hBE1 beta-1) contained a 5'-untranslated sequence of four nucleotides, the translated sequence of 1,176 nucleotides and the 3'-untranslated sequence of 169 nucleotides. Comparison of the amino acid sequence predicted from the nucleotide sequence of the cDNA insert of the clone with the NH2-terminal amino acid sequence of the purified mature bovine BCKDH-E1 beta subunit showed that the cDNA insert encodes for a 342-amino acid subunit with a Mr = 37,585. The subunit is synthesized as the precursor with a leader sequence of 50 amino acids and is processed at the NH2 terminus. A search for protein homology revealed that the primary structure of human BCKDH-E1 beta was similar to the bovine BCKDH-E1 beta and to the E1 beta subunit of human pyruvate dehydrogenase complex, in all regions. The structures and functions of mammalian alpha-ketoacid dehydrogenase complexes are apparently highly conserved. Genomic DNA from lymphoblastoid cell lines derived from normal and five MSUD patients, in whom E1 beta was not detected by immunoblot analysis, gave the same restriction maps on Southern blot analysis. The gene has at least 80 kbp.

Authors

Y Nobukuni, H Mitsubuchi, F Endo, I Akaboshi, J Asaka, I Matsuda

A neuropathic deficit, decreased sweating, is prevented and ameliorated by euglycemia in streptozocin diabetes in rats.

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Decreased sweating, especially of feet and legs, occurs in human diabetic neuropathy. It might be studied in experimental diabetes to characterize it, elucidate its mechanisms, and determine whether it can be prevented or treated. The pilocarpine-induced sweat responses (SR) in the hind foot pads of groups of control and streptozocin diabetic rats, in good (GC) and in poor (PC) glycemic control and with a crossover design after 20 wk of diabetes, were evaluated with the silicone mold sweat test to determine the number of sweat droplets per group of foot pads. The SR was dose dependent and reproducible. The SR disappeared with denervation and reappeared with reinnervation; denervation hypersensitivity did not develop. In the GC group, euglycemia was achieved by regulating the caloric intake and using multiple daily injections of Ultralente insulin. The SR was not different from that of the control group for up to 136 d. In the PC group, the SR became abnormal (P less than 0.005) at 16 d and progressively worsened: 40% of baseline values at 14 wk (P less than 0.001). After restoring euglycemia in the PC group, a normal SR occurred at 12 d. These results show that one human neuropathic deficit, failure of sweating, can be prevented or ameliorated by good glycemic control.

Authors

C Cardone, P J Dyck

Five mutant alleles of the insulin receptor gene in patients with genetic forms of insulin resistance.

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Abstract

The nucleotide sequence was determined for all 22 exons of the insulin receptor gene from three patients with genetic syndromes associated with extreme insulin resistance. In all three patients, insulin resistance was caused by decreased insulin binding to the cell surface. The patient with leprechaunism (leprechaun/Winnipeg) came from a consanguineous pedigree and was homozygous for a missense mutation substituting arginine for His209 in the alpha-subunit of the insulin receptor. The other two patients were both compound heterozygotes with a nonsense mutation in one allele of the insulin receptor gene, and a missense mutation in the other allele. In the patient with the Rabson-Mendenhall syndrome (patient RM-1), the missense mutation substituted lysine for Asn15 in the alpha-subunit. In the patient with type A extreme insulin resistance (patient A-1), the missense mutation substituted serine for Asn462 in the alpha-subunit. Both nonsense mutations markedly reduced the levels of insulin receptor mRNA transcribed from the alleles with the nonsense mutation as compared to the transcripts from the other allele. The reduction in the level of mRNA would be predicted to greatly reduce the rate at which the truncated receptors would be synthesized. Furthermore, the truncated receptors would be severely impaired in their ability to mediate insulin action.

Authors

T Kadowaki, H Kadowaki, M M Rechler, M Serrano-Rios, J Roth, P Gorden, S I Taylor

Human growth hormone prevents the protein catabolic side effects of prednisone in humans.

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Abstract

Prednisone treatment causes protein wasting and adds additional risks to a patient, whereas human growth hormone (hGH) treatment causes positive nitrogen balance. To determine whether concomitant administration of hGH prevents the protein catabolic effects of prednisone, four groups of eight healthy volunteers each were studied using isotope dilution and nitrogen balance techniques after 7 d of placebo, hGH alone (0.1 mg.kg-1.d-1), prednisone alone (0.8 mg.kg-1.d-1), or prednisone plus hGH (n = 8 in each group). Whether protein balance was calculated from the leucine kinetic data or nitrogen balance values, prednisone alone induced protein wasting (P less than 0.001), whereas hGH alone resulted in positive (P less than 0.001) protein balance, when compared to the placebo-treated subjects. When hGH was added to prednisone therapy, the glucocorticoid-induced protein catabolism was prevented. Using leucine kinetic data, negative protein balance during prednisone was due to increased (P less than 0.05) proteolysis, whereas hGH had no effect on proteolysis and increased (P less than 0.01) whole body protein synthesis. During combined treatment, estimates of proteolysis and protein synthesis were similar to those observed in the placebo treated control group. In conclusion, human growth hormone may have a distinct role in preventing the protein losses associated with the administration of pharmacologic doses of glucocorticosteroids in humans.

Authors

F F Horber, M W Haymond

Analysis of the role of antibody-dependent cellular cytotoxic antibody activity in murine neonatal herpes simplex virus infection with antibodies to synthetic peptides of glycoprotein D and monoclonal antibodies to glycoprotein B.

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Abstract

The role of antibody in neonatal herpes simplex virus (HSV) infection remains controversial. A battery of well-characterized monoclonal antibodies to HSV glycoprotein B (gB), and polyclonal antibodies against synthetic peptides of predicted epitopes of HSV glycoprotein D (gD) were used to determine in vitro functional activity and association with protection against lethal infection in a murine model of neonatal HSV disease. Antiviral neutralization activity of HSV was not associated with antibody-dependent cellular cytotoxicity (ADCC) activity to HSV-infected cells in vitro. In a model of high dose challenge (10(4) PFU), protection was not afforded by any antibody alone, but was by antibody plus human mononuclear cells, and highly associated with ADCC functional activity (P less than 0.001). In a low dose challenge model, neutralizing activity of antibody alone was associated with protection in vivo (P less than 0.001). Of the nine neutralizing epitopes of gD in vitro, eight were predicted surface regions. Four of the five epitopic sites of gD (2-21, 267-276, 288-297, and 303-312) that were determined to be important targets of ADCC and in vivo protection were also predicted to be surface regions. The only exception was the antiserum to region 52-61 which was predicted to be buried and also showed these activities. ADCC as well as neutralizing antibody activity are important in protection against neonatal HSV infection.

Authors

S Kohl, N C Strynadka, R S Hodges, L Pereira

The 210-kD nuclear envelope polypeptide recognized by human autoantibodies in primary biliary cirrhosis is the major glycoprotein of the nuclear pore.

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Abstract

We have recently reported a new family of nuclear autoantibodies in a subset of patients with primary biliary cirrhosis. These antibodies bind to a nuclear envelope polypeptide(s) of approximately 200 kD, the exact identity of which was not established. In this study, we show that all of these autoantibodies are directed against a 210-kD integral membrane glycoprotein of the nuclear pore.

Authors

J C Courvalin, K Lassoued, E Bartnik, G Blobel, R W Wozniak

Troponin-tropomyosin abnormalities in hamster cardiomyopathy.

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Abstract

Cardiac myofibrils from cardiomyopathic hamsters exhibit elevated Mg2+ ATPase activity and a parallel upward shift of the calcium ATPase dose response curve. To explore the mechanism, myofibrils from control and cardiomyopathic hamster hearts were incubated with isolated troponin-tropomyosin complex (Tn.Tm) from cardiomyopathic and control hamster or from dog hearts. Tn.Tm from control hamster or dog hearts restored normal Mg2+ ATPase activities to myofibrils from myopathic hearts. However, the maximum ATPase response to calcium stimulation was less in cardiomyopathic myofibrils compared to controls, even when control Tn.Tm was included. Electrophoretic patterns of Tn.Tm from myopathic and control hearts were similar. Electrophoresis of the hamster myofibrils mixed with dog cardiac Tn.Tm and then washed demonstrated binding of this complex to myopathic myofibrils. To further confirm that the incubation experiments resulted in binding, 125I troponin-tropomyosin was cross-hybridized with myofibrils, extensively washed, and then analyzed enzymatically and autoradiographically. Autoradiograms demonstrated similar percent binding of 125I Tn.Tm to all myofibrillar preparations and enzymatic effects like those found using cold Tn.Tm. These studies suggest that Tn.Tm from cardiomyopathic hearts inhibits Mg2+ myofibrillar ATPase activity to a lesser degree than Tn.Tm from control hearts. Decreased stimulation by calcium in myopathic preparations may be due to abnormalities in troponin-tropomyosin and/or to the decreased myosin ATPase activity observed previously.

Authors

A Malhotra, J Scheuer

Functional and phenotypic evidence for a selective loss of memory T cells in asymptomatic human immunodeficiency virus-infected men.

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Abstract

In addition to a well-documented depletion of CD4+ T helper cells in later stages of human immunodeficiency virus (HIV) infection, evidence has been provided for a specific unresponsiveness to triggering either by specific antigen in the context of autologous major histocompatibility molecules (self + X) or anti-CD3 monoclonal antibodies (MAb) in both CD4 and CD8 cells from asymptomatic HIV-infected individuals. In the present study we analyzed this unresponsiveness using mitogenic antibodies to distinct T cell membrane receptors. T cells from HIV-infected men who had normal numbers of CD4+ T cells responded poorly to activation signals via the CD3 membrane antigen in both accessory cell-dependent as well as accessory cell-independent culture systems. A similar low response was observed in an anti-CD2-driven system. In contrast, proliferation induced by anti-CD3, anti-CD2, or the phorbol ester Phorbol myristate acetate could be normally enhanced by anti-CD28 MAb. We demonstrated that this unresponsiveness is not due to a failure to induce early events required for activation, such as increased intracellular concentration of free calcium and activation of protein kinase C, but is caused by an imbalance between naive and memory T cells. In HIV-infected asymptomatic men, CD29+ memory T cells are selectively depleted which results in a poor responsiveness to self + X. These findings provide new insights that may have implications for our understanding of the immunopathogenesis of AIDS.

Authors

C J van Noesel, R A Gruters, F G Terpstra, P T Schellekens, R A van Lier, F Miedema

Neutrophil elastase cleaves C3bi on opsonized pseudomonas as well as CR1 on neutrophils to create a functionally important opsonin receptor mismatch.

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Abstract

Neutrophil elastase has been implicated as a factor that impairs local host defenses in chronic Pseudomonas aeruginosa (Pa) lung infection in cystic fibrosis (CF). We recently showed that this enzyme cleaves the C3b receptor, CR1, from neutrophils (PMN) in the lungs of infected CF patients. The C3bi receptor on these cells, CR3, is resistant to elastase. We now show that purified neutrophil elastase markedly impairs complement-mediated PMN-Pa interactions including phagocytosis of opsonized Pa, stimulation by opsonized Pa of PMN superoxide production, and killing of opsonized Pa by PMN. When PMN and opsonized Pa were treated separately with elastase, additive levels of inhibition were observed in each of the above assays. The effects on the bacteria were due to cleavage of the bound C3bi from the surface of opsonized Pa by neutrophil elastase. C3bi was also cleaved by pseudomonas elastase, or bronchoalveolar lavage fluid from CF patients with chronic Pa lung infection. Inhibitors of neutrophil elastase eliminated C3bi cleavage by BAL fluid, while inhibitors of pseudomonas elastase had no effect. Blocking CR1 and CR3 on PMN with specific monoclonal antibodies reduced phagocytosis of opsonized Pa to an extent similar to that caused by elastase cleavage of CR1 on PMN and C3bi on Pa. We conclude that neutrophil elastase in the lungs of chronically infected CF patients cleaves C3bi from opsonized Pa as well as CR1 from PMN, creating an "opsonin-receptor mismatch" that severely impairs complement-mediated phagocytic host defenses against these bacteria.

Authors

M F Tosi, H Zakem, M Berger

Progressive increases in luminal glucose stimulate proximal sodium absorption in normal and diabetic rats.

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Abstract

The effect of progressive increases in intraluminal glucose concentration on proximal tubule sodium absorption was studied in normal and streptozotocin diabetic rats by microperfusion. Each tubule was perfused twice, with and without glucose added to the perfusion fluid. Net sodium and water absorption were markedly enhanced by 300-500 mg% intraluminal glucose in both normal and diabetic rats. Substituting the transported but nonmetabolized glucose analogue, alpha-methyl D-glucoside for glucose also resulted in marked stimulation of sodium absorption, whereas substituting bicarbonate and acetate for chloride in the perfusion solution inhibited the effect of glucose. These observations suggest that the stimulation of sodium absorption by glucose was mediated by the brush border Na/glucose cotransporter. Sodium concentration and osmolality were found to fall markedly to hypotonic levels when high glucose concentrations were in the perfusion fluid. This luminal hypotonicity may be an important driving force for proximal fluid absorption. In poorly controlled diabetes, high filtered glucose concentrations may lead to enhanced proximal sodium and water absorption, which could in turn contribute to volume expansion, hypertension, and renal hypertrophy.

Authors

N Bank, H S Aynedjian

Significant phenylalanine hydroxylation in vivo in patients with classical phenylketonuria.

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Indirect measurements have previously suggested that patients with classical phenylketonuria (PKU) do not convert significant amounts of phenylalanine to tyrosine. Low-dose continuous infusion techniques employing [2H5]phenylalanine and [2H2]tyrosine were used to quantitate in vivo phenylalanine hydroxylation in 10 subjects with classical phenylketonuria, 2 with hyperphenylalaninemia (HPA), and 7 controls. Plasma phenylalanine concentration ranged from 523 to 1,540 mumols/liter in PKU, 402 to 533 in HPA, and 49 to 54 in controls. Subjects with classical PKU hydroxylated mean +/- SD 4.8 +/- 2.2 mumols/kg per h (range 0.9-8.4) of phenylalanine to tyrosine and those with HPA 4.4 and 5.3, respectively. These rates were substantial in comparison with those in controls (6.3 +/- 1.6, 3.2-8.2). The significant hydroxylation in PKU and HPA subjects is likely to result from induction of activity of tyrosine hydroxylase towards phenylalanine by the greatly elevated phenylalanine concentration. The presence of such activity in PKU suggests that therapy aimed at promotion of this usually latent hydroxylating capacity may be a future alternative to dietary treatment of PKU.

Authors

G N Thompson, D Halliday

Protective action of luminal bile salts in necrotizing acute pancreatitis in mice.

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Abstract

Bile salts in the intestinal lumen act to inhibit the release of cholecystokinin (CCK). Recent studies have shown that CCK may play a permissive role in the development of acute pancreatitis. In this study, the amount of luminal bile salts in female Swiss Webster mice was either decreased by feeding 4% (wt/wt) cholestyramine or increased by feeding 0.5% sodium taurocholate for 1 wk. Plasma levels of CCK were stimulated by cholestyramine and inhibited by taurocholate. Then, acute pancreatitis was induced either by caerulein injections, or by feeding a choline-deficient, ethionine-supplemented (CDE) diet. Feeding of cholestyramine significantly decreased survival from 25% to 0% in the CDE pancreatitis, and increased the magnitude of elevation of serum amylase levels and the extent of pancreatic necrosis in both models of pancreatitis; CCK-receptor blockade with CR-1409 completely abolished the adverse effects of cholestyramine. In contrast, feeding of taurocholate significantly increased survival to 100% and decreased the elevation of serum amylase and pancreatic necrosis; CCK-8 antagonized these actions of taurocholate. Luminal bile salts appear to provide a physiologic protection against necrotizing pancreatitis, at least in part, both by inhibiting the release of CCK and by promoting resistance of the pancreas to CCK excessive stimulation in vivo.

Authors

G Gomez, C M Townsend Jr, D W Green, S Rajaraman, T Uchida, G H Greeley Jr, R D Soloway, J C Thompson

A human Ro/SS-A autoantigen is the homologue of calreticulin and is highly homologous with onchocercal RAL-1 antigen and an aplysia "memory molecule".

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Abstract

The Ro/SS-A (Ro) autoantigens consist of at least four immunologically distinct proteins which are recognized by autoantibodies typically found in sera from patients with primary Sjogren's syndrome and in subsets of patients with lupus erythematosus. We recently isolated a 1.9-kb human cDNA clone which encodes one of these Ro autoantigens. Synthetic oligonucleotides corresponding to the human Ro sequence were used to amplify the homologous gene from a murine B cell cDNA library using the polymerase chain reaction. The mouse cDNA-encoded amino acid sequence was found to be 94% homologous to the human Ro sequence and is 100% homologous to murine calreticulin, a high affinity calcium-binding protein which resides in the endoplasmic and sarcoplasmic reticulum. The amino acid sequence of rabbit calreticulin is 92% homologous to both murine calreticulin and human Ro. Onchocerca volvulus and Drosophila melanogaster also have molecules that are highly homologous to human Ro. In addition, human Ro has a molecular mass, isoelectric point, and significant amino acid sequence similar to the Aplysia californica snail neuronal protein 407. These homologies suggest that this Ro protein has a very basic cellular function(s) which may in part involve calcium binding.

Authors

D P McCauliffe, E Zappi, T S Lieu, M Michalak, R D Sontheimer, J D Capra

Clinically nonfunctioning pituitary tumors are monoclonal in origin.

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Abstract

Clinically nonfunctioning pituitary adenomas are benign neoplasms comprising approximately 25-30% of pituitary tumors. Little is known about the pathogenesis of pituitary neoplasia. Clonal analysis allows one to make the important distinction between a polyclonal proliferation in response to a stimulatory factor versus a monoclonal expansion of a genetically aberrant cell. We investigated the clonal origin of pituitary tumors using X-linked restriction fragment length polymorphisms at the phosphoglycerate kinase and hypoxanthine phosphoribosyl-transferase genes. Restriction enzymes were used to distinguish maternal and paternal X-chromosomes, and combined with a methylation-sensitive restriction enzyme to analyze allelic X-inactivation patterns in six pituitary adenomas. All six tumors showed a monoclonal pattern of X-inactivation. These data indicate that nonfunctioning pituitary adenomas are unicellular in origin, a result consistent with the hypothesis that this tumor type is due to somatic mutation.

Authors

J M Alexander, B M Biller, H Bikkal, N T Zervas, A Arnold, A Klibanski

An abnormality of the gene that encodes neutrophil Fc receptor III in a patient with systemic lupus erythematosus.

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Abstract

In the course of examining the structure and function of Fc receptors on peripheral blood cells of patients with systemic lupus erythematosus, we identified a patient whose neutrophils did not react with either monoclonal or polyclonal antibodies to Fc receptor III. However, neutrophils from the patient were comparable to neutrophils from healthy controls with respect to their expression of Fc receptor II, complement receptor 1, complement receptor 3, and the phosphatidylinositol-linked, complement regulatory protein, decay-accelerating factor. The abnormality of expression of Fc receptor III was limited to the patient's neutrophils (her natural killer cells reacted normally with anti-Fc receptor III antibodies), and was associated with abnormal recognition and binding of IgG-coated erythrocytes. Analysis of genomic DNA revealed evidence that failure of the patient's neutrophils to express Fc receptor III was most likely due to an abnormality of the gene that encodes this receptor.

Authors

M R Clark, L Liu, S B Clarkson, P A Ory, I M Goldstein

Molecular basis of argininemia. Identification of two discrete frame-shift deletions in the liver-type arginase gene.

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Abstract

Argininemia results from a deficiency of arginase (EC 3.5.3.1), the last enzyme of the urea cycle in the liver. We examined the molecular basis for argininemia by constructing a genomic library followed by cloning and DNA sequencing. Discrete mutations were found on two alleles from the patient, a product of a nonconsanguineous marriage. There was a four-base deletion at protein-coding region 262-265 or 263-266 in exon 3 that would lead to a reading-frame shift after amino acid residue 87 and make a new stop codon at residue 132. The other was a one-base deletion at 77 or 78 in exon 2 that would lead to a reading-frame shift after residue 26 and make a stop codon at residue 31. For confirmation, genomic DNAs from the patient and from her parents were amplified by the polymerase chain reaction method. The patient was shown to be a compound heterozygote, inheriting an allele with the four-base deletion from the father and the other allele with the one-base deletion from the mother. These data seem to be the first evidence of a case of argininemia caused by two different deletion mutations.

Authors

Y Haraguchi, J M Aparicio, M Takiguchi, I Akaboshi, M Yoshino, M Mori, I Matsuda

A single nucleotide change in the prolidase gene in fibroblasts from two patients with polypeptide positive prolidase deficiency. Expression of the mutant enzyme in NIH 3T3 cells.

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Abstract

Prolidase deficiency is an autosomal recessive disorder characterized by mental retardation and various skin lesions. Cultured skin fibroblasts were obtained from two independent patients with abnormal prolidase. Using the polymerase chain reaction, we amplified the entire coding region of human prolidase mRNA derived from patients' fibroblasts. Nucleotide sequence analysis of amplified cDNA products revealed a G to A substitution at position 826 in exon 12, where aspartic acid was replaced by asparagine at the amino acid residue 276, in cells from both patients. An analysis of the DNA showed that the substitution was homozygous. An expression plasmid clone containing a normal human prolidase cDNA (pEPD-W) or mutant prolidase cDNA (pEPD-M) was prepared, transfected, and tested for expression in NIH 3T3 cells. Incorporation of pEPD-W and pEPD-M resulted in the synthesis of an immunological polypeptide that corresponded to human prolidase. Active human enzyme was detected in cells transfected with pEPD-W, but not in those transfected with pEPD-M. These results were compatible with our observation of fibroblasts and confirmed that the substitution was responsible for the enzyme deficiency. As active prolidase was recovered in prolidase-deficient fibroblasts transfected with pEPD-W, this restoration of prolidase activity after transfection means that gene replacement therapy for individuals with this human disorder can be given due consideration.

Authors

A Tanoue, F Endo, A Kitano, I Matsuda

Growth stimulation by coexpression of transforming growth factor-alpha and epidermal growth factor-receptor in normal and adenomatous human colon epithelium.

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Abstract

Autocrine stimulation of the epidermal growth factor receptor (EGF-R), by coexpression of transforming growth factor-alpha (TGF-alpha), causes malignant transformation of some fibroblast cell lines. TGF-alpha and EGF-R are both known to be expressed in colon carcinoma tissue and have been shown coexpressed in colon carcinoma cell lines. TGF-alpha autocrine activation of EGF-R has been suggested as a potential mechanism contributing to abnormal growth control in colon cancer. We now report coexpression of TGF-alpha and EGF-R transcripts in morphologically normal colonic epithelium from five individuals, in colonic adenomas from three individuals, and in a nontumorigenic colon adenoma cell line, VACO-330. Functional studies demonstrate VACO-330 growth is stimulated by exogenous TGF-alpha and is completely abolished by a blocking anti-EGF-R antibody. Autocrine stimulation of EGF-R by TGF-alpha is therefore required for growth of the adenoma cell line. Autocrine stimulation of EGF-R by TGF-alpha does not cause malignant transformation of the colonic epithelial cell. In normal and adenomatous human colon TGF-alpha, via either an autocrine or paracrine mechanism, is likely an important physiologic stimulant of epithelial proliferation.

Authors

S D Markowitz, K Molkentin, C Gerbic, J Jackson, T Stellato, J K Willson

Identification of intronic point mutations as an alternative mechanism for p53 inactivation in lung cancer.

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Abstract

The p53 gene initially was thought to be an oncogene, but recent evidence suggests that wild-type p53 can function as a tumor suppressor gene in lung, colon, and breast cancer as well as less common malignancies. This study reports the first identification of intronic point mutations as a mechanism for inactivation of the p53 tumor suppressor gene. Abnormally sized p53 mRNAs found in a small cell and a non-small cell lung cancer cell line were characterized by sequence analysis of cDNA/PCR products, the RNase protection assay and immunoprecipitation. These mRNAs were found to represent aberrant splicing leading to the production of abnormal or no p53 protein. Sequence analysis of genomic DNA revealed that a point mutation at the splice acceptor site in the third intron or the splice donor site in the seventh intron accounts for the abnormal mRNA splicing. In one patient the same intronic point mutation was found in the tumor cell line derived from a bone marrow metastasis and in multiple liver metastases but not in normal DNA, indicating that it occurred as a somatic event before the development of these metastases. These findings further support the role of inactivation of the p53 gene in the pathogenesis of lung cancer and indicate the role of intronic point mutation in this process.

Authors

T Takahashi, D D'Amico, I Chiba, D L Buchhagen, J D Minna

Lysis of myotubes by alloreactive cytotoxic T cells and natural killer cells. Relevance to myoblast transplantation.

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Abstract

The aim of this study was to investigate the susceptibility of human myotubes to lysis by the two major types of cytotoxic effector cells, CD3+CD8+ cytotoxic T cells (CTL) and CD16+CD56+ natural killer (NK) cells. The myoblasts preparations used as target cells were greater than 90% pure as assessed by immunostaining with the Leu19 monoclonal antibody (MAb) that cross-reacts with the neural cell adhesion molecule N-CAM. Allospecific CTL lines were generated from mixed lymphocyte cultures, and freshly isolated allogeneic and autologous peripheral blood cells were used as a source of NK cells. The cytotoxicity was observed under phase optics and by immunoelectron microscopy, and was quantitated with a chromium release assay. Myotubes were efficiently killed by allospecific CTL and by autologous and allogeneic NK cells. The killing by CTL was inhibited with an anti-class I HLA MAb, and the killing by NK cells was inhibited by depleting peripheral blood cells of CD16+ cells with anti-CD16 MAb and complement. The results have important implications for myoblast transplantation, an experimental therapy of muscular dystrophy.

Authors

R Hohlfeld, A G Engel