Possible role of anti-idiotypic antibodies in the induction of tumor immunity.

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Authors

R C Kennedy, E M Zhou, R E Lanford, T C Chanh, C A Bona

Monoclonal antibodies to human erythrocyte membrane Ca++-Mg++ adenosine triphosphatase pump recognize an epitope in the basolateral membrane of human kidney distal tubule cells.

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Human calcium transporting tissues were examined to determine whether they contained a protein similar to the Ca++-Mg++ adenosine triphosphatase (Ca++-Mg++ATPase) pump of the human erythrocyte membrane. Tissues were processed for immunoperoxidase staining using monoclonal antibodies against purified Ca++-Mg++ATPase. In human kidneys, specific staining was found only along the basolateral membrane of the distal convoluted tubules. Glomeruli and other segments of the nephron did not stain. Staining of erythrocytes in human spleen was readily observed. Human small intestine, human parathyroid, and human liver showed no antigens that crossreacted with the antibodies to Ca++-Mg++ATPase. Specific staining of distal tubule basolateral membranes from the kidney of a chimpanzee was also noted. Our experiments show, for the first time, that basolateral membranes of the human distal convoluted tubule contain a protein that is immunologically similar to the human erythrocyte Ca++-Mg++ATPase. These observations suggest that the cells of the distal convoluted tubules of human kidney may have a calcium pump similar to that of human erythrocyte membranes.

Authors

J L Borke, J Minami, A Verma, J T Penniston, R Kumar

Atrial natriuretic peptide protects against acute ischemic renal failure in the rat.

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Because of its ability to increase glomerular filtration, antagonize the actions of vasoconstrictors, and produce vasodilation, alpha human atrial natriuretic peptide (alpha-hANP) was evaluated for its potentially beneficial effects in experimental ischemic renal failure induced by 45-60 min of renal artery occlusion in bilaterally or unilaterally renally intact Sprague-Dawley rats. After ischemia, a 4-h intrarenal infusion of alpha-hANP restored 14C-inulin clearances in bilaterally and unilaterally intact animals from 0.05 +/- 0.006 and 0.05 +/- 0.01 ml/min per 100 g to 0.314 +/- 0.04 and 0.25 +/- 0.01 ml/min per 100 g, respectively (P less than 0.001, n = 8), compared with normal values of 0.49 +/- 0.023 ml/min per 100 g. Histologically, there was a progressive decrease in medullary hyperemia and prevention of intratubular cell shedding and granulocyte margination as a result of the 4-h alpha-hANP infusion such that after 24 and 48 h the histological appearance of the tissue was essentially normal. The results show that a 4-h intrarenal infusion of alpha-hANP after renal ischemia can preserve glomerular filtration rate and reduce renal tissue damage.

Authors

S G Shaw, P Weidmann, J Hodler, A Zimmermann, A Paternostro

Isolation of the galactose-binding lectin that mediates the in vitro adherence of Entamoeba histolytica.

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Entamoeba histolytica adheres to human colonic mucus, colonic epithelial cells, and other target cells via a galactose (Gal) or N-acetyl-D-galactosamine (GalNAc) inhibitable surface lectin. Blockade of this adherence lectin with Gal or GalNAc in vitro prevents amebic killing of target cells. We have identified and purified the adherence lectin by two methods: affinity columns derivatized with galactose monomers or galactose terminal glycoproteins, and affinity columns and immunoblots prepared with monoclonal antibodies that inhibit amebic adherence. By both methods the adherence lectin was identified as a 170-kD secreted and membrane-bound amebic protein. The surface location of the lectin was confirmed by indirect immunofluorescence. Purified lectin competitively inhibited amebic adherence to target cells by binding to receptors on the target Chinese hamster ovary cells in a Gal-inhibitable manner.

Authors

W A Petri Jr, R D Smith, P H Schlesinger, C F Murphy, J I Ravdin

Rat and human colonic mucins bind to and inhibit adherence lectin of Entamoeba histolytica.

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Establishment of adherence by Entamoeba histolytica is mediated by a 170-kD Gal/GalNAc inhibitable lectin and is required for cytolysis and phagocytosis of mammalian target cells. We studied the biochemical mechanisms of the in vitro interaction between rat and human colonic mucins and axenic E. histolytica trophozoites. Crude mucus prevented amebic adherence to Chinese hamster ovary (CHO) cells by up to 70%. Purification of the colonic mucins by Sepharose 4B chromatography, nuclease digestion, and cesium chloride gradient centrifugation resulted in a 1,000-fold enrichment of the inhibitory mucins. Purified rat mucin inhibited amebic adherence to and cytolysis of homologous rat colonic epithelial cells. Oxidation and enzymatic cleavage of rat mucin Gal and GalNAc residues completely abrogated mucin inhibition of amebic adherence. The binding of rat 125I-mucin to amebae was galactose specific, saturable, reversible, and pH dependent. A monoclonal antibody specific for the 170-kD amebic Gal/GalNAc lectin completely inhibited the binding of rat 125I-mucin. Rat mucin bound to Affigel affinity purified the amebic lectin from conditioned medium. Colonic mucin glycoproteins act as an important host defense by binding to the parasite's adherence lectin, thus preventing amebic attachment to and cytolysis of host epithelial cells.

Authors

K Chadee, W A Petri Jr, D J Innes, J I Ravdin

Osmoprotective activity for Escherichia coli in mammalian renal inner medulla and urine. Correlation of glycine and proline betaines and sorbitol with response to osmotic loads.

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Escherichia coli are protected against hypertonic NaCl by human urine. We have shown that this is due in part to the presence of glycine betaine and proline betaine. Several investigators have proposed that betaines and sorbitol are concentrated in the cells of the renal inner medulla where they exert a protective role against urea and extracellular osmotic forces. E. coli was used in the present studies as an "osmosensor" to detect osmoprotective activity in mammalian tissues. The greatest activity was found in extracts of renal inner medulla and to a lesser extent in the renal outer medulla and cortex of several mammalian species. Liver extracts were more active than other nonrenal tissues. Bacterial osmoprotective activity and concentration of glycine betaine in the renal inner medulla of rabbits were found to correlate closely with urinary osmolarity. Concentrations of sorbitol were found to be also increased in the renal inner medulla during osmotic stress, but this compound is not osmoprotective for E. coli. Glycine and proline betaine were recovered in urine of rabbits and were increased in those given high osmotic loads. Only small amounts of proline betaine were recovered in the renal inner medulla. The source from which proline betaine is derived is unknown.

Authors

S T Chambers, C M Kunin

Sex steroids and bone mass. A study of changes about the time of menopause.

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To examine the relationships between bone loss and sex steroids, 84 peri- and postmenopausal women were studied at 4-mo intervals for 3 yr. At each visit, measurements were made of bone mass at the midshaft and distal radius, of steroids, of gonadotropins, and of bone gla protein (BGP). Bone loss was approximately 1% per yr among late perimenopausal and postmenopausal groups, whereas the early perimenopausal group lost no bone. Mean serum estrogen and BGP concentrations predicted rates of bone loss. BGP was negatively correlated with the rate of bone loss (r = -0.45) and with mean estrogen concentrations (r = -0.40). Multivariate regressions showed estrogen concentrations to be strong independent predictors of the slope of bone mass over time. When BGP concentrations were added to the models, the significance of estrogen was reduced, suggesting that a portion of the estrogen effect was mediated through effects on rates of bone remodelling.

Authors

C Slemenda, S L Hui, C Longcope, C C Johnston

Role of fibronectin on the clearance and tissue uptake of antigen and immune complexes in rats.

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In the present study, we have evaluated how plasma fibronectin (FN) and tissue FN can affect the clearance from the circulation and organ uptake of antigen or immune complexes (IC) that have the capacity to bind to FN. Phenylated gelatin (DNP-GL) (a FN binding antigen) and IC composed of DNP-GL and monoclonal IgGl anti-dinitrophenol (DNP) antibodies were tested. These probes were compared with DNP-bovine serum albumin (BSA) (a non-FN-binding antigen) and DNP-BSA IC formed with the same anti-DNP antibody used for the preparation of DNP-GL IC. We found evidence that DNP-GL, but not DNP-BSA, formed complexes with soluble FN in vitro and the data strongly suggest that DNP-GL-FN complexes form in vivo. The formation of complexes with plasma FN aided in the clearance of DNP-GL from the circulation, as shown by the facts that DNP-GL was removed from the circulation much faster than DNP-BSA and that complexes of DNP-GL with plasma FN were removed from the circulation faster than uncomplexed DNP-GL. The sites of deposition of DNP-GL were also different from those of DNP-BSA. Thus, DNP-GL demonstrated higher hepatic, splenic, and renal uptake than did DNP-BSA. Renal uptake of DNP-GL was quite high despite the fact that DNP-GL is anionic. Indeed, expressed per gram of tissue, liver and kidney deposition of DNP-GL was not significantly different. By immunofluorescence microscopy, DNP-GL could be demonstrated in hepatic sinusoids and glomerular mesangium. In vitro, DNP-GL bound to FN in the mesangium of frozen sections of kidney tissue. IC formed with DNP-GL or DNP-BSA demonstrated virtually the same size, yet the fate of DNP-GL IC was strikingly different from that of DNP-BSA IC. The removal of DNP-GL IC from the circulation was mediated by the antigen and not by Fc receptors since gelatin (an inhibitor of DNP-GL clearance) but not aggregated IgG (an inhibitor of Fc receptors) inhibited the removal of DNP-GL IC from the circulation. In summary, these studies suggest that the ability of an antigen or IC to bind to FN markedly influences the fate of that antigen or IC. Specifically, binding to FN accelerates clearance from the circulation and favors hepatic and renal (primarily mesangial) uptake of the FN binding antigen of IC.

Authors

F G Cosio, A P Bakaletz

Regulation of the expression of tissue inhibitor of metalloproteinases and collagenase by retinoids and glucocorticoids in human fibroblasts.

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The regulation of the expression of interstitial collagenase and tissue inhibitor of metalloproteinases (TIMP) was examined in response to both retinoid compounds and glucocorticoids. Effective retinoids induced a dose-dependent, specific increase in the production of TIMP of approximately two- to threefold by monolayer cultures of human fibroblasts derived from various tissues, while simultaneously causing a decrease in collagenase secretion of similar magnitude. These effects were apparent by 8-12 h in culture and disappeared within 24 h after the withdrawal of retinoid compounds. The retinoid effect on TIMP production was mediated via an increased biosynthesis of new inhibitor protein. Similarly, increased steady state levels of TIMP messenger RNA (mRNA) accompanied by decreased quantities of collagenase mRNA were demonstrated, suggesting transcriptional control of the retinoid action. The data suggest that retinoids co-regulate the expression of collagenase and TIMP, and do so in an inverse manner. Dexamethasone caused a dose-dependent, specific decrease in collagenase production without altering the biosynthesis of TIMP. These findings were paralleled by a marked reduction in collagenase mRNA, without any accompanying change in TIMP mRNA. Therefore, TIMP and collagenase expression appear to be independently modulated by glucocorticoids.

Authors

S D Clark, D K Kobayashi, H G Welgus

Oxidants spontaneously released by alveolar macrophages of cigarette smokers can inactivate the active site of alpha 1-antitrypsin, rendering it ineffective as an inhibitor of neutrophil elastase.

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Current concepts relating to the pathogenesis of emphysema associated with cigarette smoking is that an imbalance exists within the lower respiratory tract between neutrophil elastase and the local anti-neutrophil elastase screen, enabling uninhibited neutrophil elastase to destroy the alveolar structures over time. The possible role of alveolar macrophages in contributing to this imbalance was investigated by evaluating the ability of cigarette smokers' alveolar macrophages to inactivate alpha 1-antitrypsin (alpha 1AT), the major anti-neutrophil elastase of the human lower respiratory tract. In vitro, alveolar macrophages of smokers spontaneously released 2.5-fold more superoxide anion and eightfold more H2O2 than macrophages of nonsmokers (P less than 0.01, both comparisons). Using a model system that reproduced the relative amounts of alveolar macrophages and alpha 1AT found in the epithelial lining fluid of the lower respiratory tract, we observed that smokers' macrophages caused a 60 +/- 5% reduction in the ability of alpha 1AT to inhibit neutrophil elastase. In marked contrast, under the same conditions, nonsmokers' macrophages had no effect upon the anti-neutrophil elastase function of alpha 1AT. Addition of superoxide dismutase, catalase, mannitol, and methionine prevented inactivation of alpha 1AT by smokers' macrophages, implying that the release of oxidants mediated the inactivation of alpha 1AT. In addition, by utilizing a recombinant DNA produced modified form of alpha 1AT containing an active site substitution (met358----val), the inactivation of alpha 1AT by smokers' alveolar macrophages was prevented, suggesting that the smokers' macrophages inactivate alpha 1AT by oxidizing the active site of the alpha 1AT molecule. These results suggest that in cigarette smokers, the alveolar macrophage can modulate the activity of alpha 1AT as an inhibitor of neutrophil elastase and thus play a role in the pathogenesis of emphysema associated with cigarette smoking.

Authors

R C Hubbard, F Ogushi, G A Fells, A M Cantin, S Jallat, M Courtney, R G Crystal

Concentration of NADH-cytochrome b5 reductase in erythrocytes of normal and methemoglobinemic individuals measured with a quantitative radioimmunoblotting assay.

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The activity of NADH-cytochrome b5 reductase (NADH-methemoglobin reductase) is generally reduced in red cells of patients with recessive hereditary methemoglobinemia. To determine whether this lower activity is due to reduced concentration of an enzyme with normal catalytic properties or to reduced activity of an enzyme present at normal concentration, we measured erythrocyte reductase concentrations with a quantitative radioimmunoblotting method, using affinity-purified polyclonal antibodies against rat liver microsomal reductase as probe. In five patients with the "mild" form of recessive hereditary methemoglobinemia, in which the activity of erythrocyte reductase was 4-13% of controls, concentrations of the enzyme, measured as antigen, were also reduced to 7-20% of the control values. The concentration of membrane-bound reductase antigen, measured in the ghost fraction, was similarly reduced. Thus, in these patients, the reductase deficit is caused mainly by a reduction in NADH-cytochrome b5 reductase concentration, although altered catalytic properties of the enzyme may also contribute to the reduced enzyme activity.

Authors

N Borgese, G Pietrini, S Gaetani

Determination of Krebs cycle metabolic carbon exchange in vivo and its use to estimate the individual contributions of gluconeogenesis and glycogenolysis to overall glucose output in man.

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Current isotopic approaches underestimate gluconeogenesis in vivo because of Krebs cycle carbon exchange and the inability to measure intramitochondrial precursor specific activity. We therefore applied a new isotopic approach that theoretically overcomes these limitations and permits quantification of Krebs cycle carbon exchange and the individual contributions of gluconeogenesis and glycogenolysis to overall glucose output. [6-3H]Glucose was infused to measure overall glucose output; [2-14C]acetate was infused to trace phosphoenolpyruvate gluconeogenesis and to calculate Krebs cycle carbon exchange as proposed by Katz. Plasma [14C]3-OH-butyrate specific activity was used to estimate intramitochondrial acetyl coenzyme A (CoA) specific activity, and finally the ratio between plasma glucose 14C-specific activity and the calculated intracellular phosphoenolpyruvate 14C-specific activity was used to determine the relative contributions of gluconeogenesis and glycogenolysis to overall glucose output. Using this approach, acetyl CoA was found to enter the Krebs cycle at twice (postabsorptive subjects) and three times (2 1/2-d fasted subjects) the rate of pyruvate, respectively. Gluconeogenesis in postabsorptive subjects (3.36 +/- 0.20 mumol/kg per min) accounted for 28 +/- 2% of overall glucose output and increased twofold in subjects fasted for 2 1/2-d (P less than 0.01), accounting for greater than 97% of overall glucose output. Glycogenolysis in postabsorptive subjects averaged 8.96 +/- 0.40 mumol/kg per min and decreased to 0.34 +/- 0.08 mumol/kg per min (P less than 0.01) after a 2 1/2-d fast. Since these results agree well with previously reported values for gluconeogenesis and glycogenolysis based on determinations of splanchnic substrate balance and glycogen content of serial liver biopsies, we conclude that the isotopic approach applied herein provides an accurate, noninvasive measurement of gluconeogenesis and glycogenolysis in vivo.

Authors

A Consoli, F Kennedy, J Miles, J Gerich

Contribution of lymphatic absorption to loss of ultrafiltration and solute clearances in continuous ambulatory peritoneal dialysis.

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The contribution of peritoneal cavity lymphatic absorption to ultrafiltration kinetics and solute clearances in continuous ambulatory peritoneal dialysis was evaluated in patients with normal (group 1) and high (group 2) peritoneal permeability X area during 4-h exchanges using 2 liters 2.5% dextrose dialysis solution with 30 g added albumin. Cumulative lymphatic drainage in all continuous ambulatory peritoneal dialysis (CAPD) patients averaged 358 +/- 47 ml per 4-h exchange and reduced cumulative net transcapillary ultrafiltration at the end of the exchange by 58 +/- 7.2%. The peak ultrafiltration volume was observed before osmotic equilibrium between serum and dialysate was reached and occurred when the net transcapillary ultrafiltration rate had decreased to equal the lymphatic absorption rate. Thereafter the lymphatic absorption rate exceeded the net transcapillary ultrafiltration rate, and intraperitoneal volume decreased. Extrapolated to 4 X 2 liters, 2.5% dextrose, 6-h exchanges per d, lymphatic drainage reduced potential daily net ultrafiltration by 83.2 +/- 10.2%, daily urea clearance by 16.9 +/- 1.9%, and daily creatinine clearance by 16.5 +/- 1.9%. Although lymphatic absorption did not differ between the two groups, lymphatic drainage caused a proportionately greater reduction in net ultrafiltration in group 2 (P less than 0.025), because these patients had more rapid dialysate glucose absorption (P less than 0.05) and less cumulative transcapillary ultrafiltration (P less than 0.01). These findings indicate that cumulative lymphatic drainage significantly reduces net ultrafiltration and solute clearances in CAPD and that ultrafiltration failure in CAPD occurs when daily lymphatic absorption equals or exceeds daily transcapillary ultrafiltration. Reduction of lymphatic absorption may provide a means for future improvement in the efficiency of CAPD.

Authors

R A Mactier, R Khanna, Z Twardowski, H Moore, K D Nolph

Herpes simplex virus infection in human arterial cells. Implications in arteriosclerosis.

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Herpesviruses have been implicated as etiologic factors in the pathogenesis of human arteriosclerosis. We have examined the pathobiological effects of human herpes simplex virus (HSV-1) infection in influencing lipid accumulation and metabolism in human and bovine arterial smooth muscle cells (SMC). Significantly greater amounts of saturated cholesteryl esters (CE) and triacylglycerols (TG) accumulate in HSV-1-infected human and bovine arterial SMC than uninfected cells. This CE accumulation results, in part, from decreased CE hydrolysis. Furthermore, arachidonate-stimulated, HSV-1-infected arterial SMC have a reduced capacity to produce prostacyclin (an agonist of intracellular CE hydrolytic activity) than uninfected, stimulated SMC. It appears that HSV-1 may induce lipid accumulation in arterial SMC similar, in part, to the lipid accumulation observed in vivo during human atherogenesis. Thus, herpesviruses may contribute to lipid accumulation, which is a characteristic feature of atherosclerosis.

Authors

D P Hajjar, K B Pomerantz, D J Falcone, B B Weksler, A J Grant

Polyamines mediate uncontrolled calcium entry and cell damage in rat heart in the calcium paradox.

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Brief perfusion of heart with calcium-free medium renders myocardial cells calcium-sensitive so that readmission of calcium results in uncontrolled Ca2+ entry and acute massive cell injury (calcium paradox). We investigated the hypothesis that polyamines may be involved in the mediation of abnormal Ca2+ influx and cell damage in the calcium paradox. The isolated perfused rat heart was used for these studies. Calcium-free perfusion promptly (less than 5 min) decreased the levels of polyamines and the activity of their rate-regulating synthetic enzyme, ornithine decarboxylase (ODC), and calcium reperfusion abruptly (less than 15-180 s) increased these components. alpha-Difluoromethylornithine (DFMO), a specific suicide inhibitor of ODC, suppressed the calcium reperfusion-induced increase in polyamines and the concomitant increase in myocardial cellular 45Ca influx, loss of contractility, release of cytosolic enzymes, myoglobin, and protein, and structural lesions. Putrescine, the product of ODC activity, nullified DFMO inhibition and restored the calcium reperfusion-induced increment in polyamines and the full expression of the calcium paradox. Putrescine itself enhanced the reperfusion-evoked release of myoglobin and protein in the absence of DFMO. Hypothermia blocked the changes in heart ODC and polyamines induced by calcium-free perfusion and calcium reperfusion and prevented the calcium paradox. These results indicate that rapid Ca2+-directed changes in ODC activity and polyamine levels are essential for triggering excessive transsarcolemmal transport of Ca2+ and explosive myocardial cell injury in the calcium paradox.

Authors

H Koenig, A D Goldstone, J J Trout, C Y Lu

Norepinephrine metabolism in humans. Kinetic analysis and model.

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The present study was undertaken to quantify more precisely and to begin to address the problem of heterogeneity of the kinetics of distribution and metabolism of norepinephrine (NE) in humans, by using compartmental analysis. Steady-state NE specific activity in arterialized plasma during [3H]NE infusion and postinfusion plasma disappearance of [3H]NE were measured in eight healthy subjects in the supine and upright positions. Two exponentials were clearly identified in the plasma [3H]NE disappearance curves of each subject studied in the supine (r = 0.94-1.00, all P less than 0.01) and upright (r = 0.90-0.98, all P less than 0.01) positions. A two-compartment model was the minimal model necessary to simultaneously describe the kinetics of NE in the supine and upright positions. The NE input rate into the extravascular compartment 2, estimated with the minimal model, increased with upright posture (1.87 +/- 0.08 vs. 3.25 +/- 0.2 micrograms/min per m2, P less than 0.001). Upright posture was associated with a fall in the volume of distribution of NE in compartment 1 (7.5 +/- 0.6 vs. 4.7 +/- 0.3 liters, P less than 0.001), and as a result of that, there was a fall in the metabolic clearance rate of NE from compartment 1 (1.80 +/- 0.11 vs. 1.21 +/- 0.08 liters/min per m2, P less than 0.001). We conclude that a two-compartment model is the minimal model that can accurately describe the kinetics of distribution and metabolism of NE in humans.

Authors

O A Linares, J A Jacquez, L A Zech, M J Smith, J A Sanfield, L A Morrow, S G Rosen, J B Halter

Carbohydrate heterogeneity of fibronectins. Synovial fluid fibronectin resembles the form secreted by cultured synoviocytes but differs from the plasma form.

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Large quantities of fibronectin (Fn) are present in inflammatory synovial fluid. Inflammatory synovial fluid Fn, while indistinguishable from plasma Fn on the basis of reactivity to polyclonal antibodies, displays alterations in molecular size and charge. Since biochemical differences between plasma and synovial fluid fibronectins might be in part due to differences in glycosylation we have compared the carbohydrate composition of plasma Fn, synovial fluid Fn, and Fn from synoviocyte conditioned medium by biochemical assay, glycopeptide analysis, and binding to a series of lectins. Synovial fluid Fn has a greater carbohydrate content but contains less sialic acid when compared with plasma Fn. Glycopeptides formed from synovial fluid Fn are smaller than plasma Fn glycopeptides. These data suggest the presence of an additional N-linked oligosaccharide chain on synovial fluid Fn. In addition, synovial fluid Fn contains N-acetyl galactosamine indicating the presence of O-linked oligosaccharides. Synovial fluid Fn and Fn isolated from rheumatoid synoviocyte-conditioned medium display strong reactivity with the lectins wheat germ agglutinin (WGA) and peanut agglutinin (PNA), whereas normal and rheumatoid plasma Fn react weakly. The PNA reactivity of synovial fluid Fn is mediated by terminal beta-galactose residues on the gelatin-binding domain, whereas the enhanced WGA reactivity of synovial Fn is mediated by a sialic acid containing oligosaccharide located on a 27-kD C-terminal fragment. These data demonstrate domain-specific biochemical differences between plasma and synovial fluid fibronectins. These differences suggest a local origin for synovial fluid Fn and may contribute to functional differences between these forms of the protein.

Authors

S Carsons, B B Lavietes, A Slomiany, H S Diamond, E Berkowitz

Endothelium-dependent responses in autogenous femoral veins grafted into the arterial circulation of the dog.

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Endothelium-dependent responses differ in arteries and veins of the dog. Experiments were performed to determine whether chronic grafting of veins into the arterial circulation would alter the endothelium-dependent responses of the veins. Segments of femoral veins were grafted to the femoral artery of the dog. 6 wk after surgery the venous grafts were removed from the dog, cut into rings, and suspended in organ chambers for isometric tension recording. In some rings the endothelial cells were removed. Acetylcholine and alpha 2-adrenergic agonists did not cause endothelium-dependent relaxations in venous grafts. The calcium ionophore (A23187) initiated such relaxations which were not mediated by prostanoids. Endothelium-dependent relaxations were also observed in venous grafts to ADP, thrombin, and arachidonic acid. In segments of graft where myo-intimal hyperplasia was prominent, relaxations to ADP, thrombin, and A23187 were blunted and in some segments contractions were observed. These results demonstrate the ability of the endothelium of venous grafts to initiate changes in tone of the smooth muscle.

Authors

V M Miller, M M Reigel, L H Hollier, P M Vanhoutte

Effects of potassium on ammonia transport by medullary thick ascending limb of the rat.

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Renal ammonium excretion is increased by potassium depletion and reduced by potassium loading. To determine whether changes in potassium concentration would alter ammonia transport in the medullary thick ascending limb (MAL), tubules from rats were perfused in vitro and effects of changes in K concentration within the physiological range (4-24 mM) were evaluated. Increasing K concentration from 4 to 24 mM in perfusate and bath inhibited total ammonia absorption by 50% and reduced the steady-state transepithelial NH+4 concentration gradient. The inhibition of total ammonia absorption was reversible and occurred when K replaced either Na or N-methyl-D-glucamine. Increasing K concentration in the luminal perfusate alone gave similar inhibition of total ammonia absorption. At 1-2 nl/min per mm perfusion rate, increasing K concentration in perfusion and bathing solutions had no significant effect on transepithelial voltage. With either 4 or 24 mM K in perfusate and bath, an increase in luminal perfusion rate markedly increased total ammonia absorption. Thus, both potassium concentration and luminal flow rate are important factors capable of regulating total ammonia transport by the MAL. Changes in systemic potassium balance may influence renal ammonium excretion by affecting NH+4 absorption in the MAL and altering the transfer of ammonia from loops of Henle to medullary collecting ducts.

Authors

D W Good

Z-type alpha 1-antitrypsin is less competent than M1-type alpha 1-antitrypsin as an inhibitor of neutrophil elastase.

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Alpha 1-antitrypsin (alpha 1AT) deficiency resulting from homozygous inheritance of the Z-type alpha 1AT gene is associated with serum alpha 1AT levels of less than 50 mg/dl and the development of emphysema in the third to fourth decades. Despite the overwhelming evidence that the emphysema of PiZZ individuals develops because of a "deficiency" of alpha 1AT and hence an insufficient antineutrophil elastase defense of the lung, epidemiologic evidence has shown that levels of alpha 1AT of only 80 mg/dl protect the lung from an increased risk of emphysema. With this background, we hypothesized that homozygous inheritance of the Z-type may confer an added risk beyond a simple deficiency of alpha 1AT by virtue of an inability of the Z-type alpha 1AT molecule to inhibit neutrophil elastase as effectively as the common M1-type molecule. To evaluate this hypothesis, the functional status of alpha 1AT from PiZZ individuals (n = 10) was compared with that of alpha 1AT from PiM1M1 individuals (n = 7) for its ability to inhibit neutrophil elastase (percent inhibition) as well as its association rate constant for neutrophil elastase (K association). Plasma alpha 1AT concentration, measured by radial immunodiffusion, was 34 +/- 1 mg/dl in PiZZ patients vs. 237 +/- 14 mg/dl for PiM1M1 plasma, a sevenfold difference. When titrated against neutrophil elastase, the present inhibition of PiZZ plasma was significantly less than Pi M1M1 plasma (ZZ 78 +/- 1% vs. M1M1 95 +/- 1%, P less than 0.001) as was purified Z type alpha 1AT (ZZ, 63 +/- 2% vs. M1M1 86 +/- 2%, P less than 0.001). Sodium dodecyl sulfate (SDS) gel comparisons of the complexes formed with M1-type alpha 1AT and Z-type alpha 1AT with elastase demonstrated the Z alpha 1AT-elastase complexes were less stable than the M1 alpha 1AT-elastase complexes, thus releasing some of the enzyme to continue to function as a protease. Consistent with these observations, the K association of purified Z-type alpha 1AT for neutrophil elastase was lower than that of M1-type alpha 1AT (ZZ 4.5 +/- 0.3 X 10(6) M-1s-1 vs. M1M1 9.7 +/- 0.4 X 10(6) M-1s-1, P less than 0.001), suggesting that for the population of alpha 1AT molecules, the active Z-type molecules take more than twice as long as the active M1-type alpha 1AT to inhibit neutrophil elastase. Consequently, not only is there less alpha1AT in PiZZ individuals, but the population of Z-type alpha1AT molecules is less competent as an inhibitor of neutrophil elastase than M1-type alpha1AT molecules. This combination of defects suggests that PiZZ individuals have far less functional antielastase protection than suggested by the reduced concentrations of alpha1AT alone, further explaining their profound risk for development of emphysema.

Authors

F Ogushi, G A Fells, R C Hubbard, S D Straus, R G Crystal

Involvement of fertilization antigen (FA-1) in involuntary immunoinfertility in humans.

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Abstract

Sera from immunoinfertile patients (n = 32) and fertile controls (n = 20) were analyzed for cross-reaction with a purified and characterized sperm-specific glycoprotein, the fertilization antigen (FA-1), employing an enzyme-linked immunosorbent assay. The immunoinfertile sera demonstrated a strong reaction with FA-1 when compared with fertile control sera. There was no correlation between the reaction of sera with FA-1 and the titers obtained through the sperm agglutination technique and the sperm immobilization technique. Immunoinfertile sera showed binding with the protein bands in the regions corresponding to FA-1 on Western blots involving sodium deoxycholate-solubilized human sperm. Antigens isolated with immunoaffinity chromatography involving immunoinfertile sera also demonstrated antigen bands corresponding to FA-1 in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Of the seven immunoinfertile couples, three that had antibodies to FA-1 in the male as well as female partners demonstrated a block of fertilization (IVF) due to antibodies bound on the sperm surface. The anti-FA-1 antibody activity was detected in serum as well as in follicular fluid and seminal plasma. Immunoinfertile sera that showed an inhibition of human sperm penetration of zona-free hamster ova showed a significant (P less than 0.001) increase in penetration rates after absorption with FA-1. These results indicate that sera from immunoinfertile patients had antibodies reacting with FA-1, and these antibodies are involved in the fertilization process.

Authors

R K Naz

Protein synthesis in hepatocytes isolated from patients with gastrointestinal malignancy.

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To investigate the effect of remote and proximate cancer on hepatic protein metabolism, we determined rates of total protein synthesis by hepatocytes (HPS) isolated from 31 patients undergoing liver wedge biopsy: 7 patients with benign disease, 14 with gastric cancer, and 10 with colorectal cancer (5 of whom had liver metastases). Patients with malignant disease without weight loss had a threefold higher rate of total HPS (4,980 +/- 814 pmol/h per 10(5) viable cells) than patients with benign disease without weight loss (1,278 +/- 318 pmol/h per 10(5) viable cells, P less than 0.001). Among the patients with gastric cancer, eight with preoperative weight loss had lower rates of HPS (380 +/- 90 pmol/h per 10(5) viable cells) than those without weight loss (4,061 +/- 401 pmol/h per 10(5) viable cells, P less than 0.002). The highest rates of HPS were seen in patients with colorectal cancer with liver metastases (8,005 +/- 1,975 pmol/h per 10(5) viable cells) vs. colorectal cancer patients without liver metastases (3,060 +/- 575 pmol/h per 10(5) viable cells, P less than 0.03). These data indicate that modulation of hepatic protein synthesis occurs in malignancy in man. However, the stimulatory influence of the tumor-bearing state may be overridden by the inhibitory effects of cachexia.

Authors

H F Starnes Jr, R S Warren, M F Brennan

alpha 2-Antiplasmin Enschede: dysfunctional alpha 2-antiplasmin molecule associated with an autosomal recessive hemorrhagic disorder.

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Abstract

alpha 2-Antiplasmin (alpha 2-AP) is a major fibrinolysis inhibitor, whose complete, congenital absence has been found to be associated with a distinct hemorrhagic diathesis. We studied a 15-yr-old male with a hemorrhagic diathesis after trauma from early childhood on. This bleeding tendency was associated with a minimal alpha 2-AP level recorded functionally in the immediate plasmin inhibition test: less than or equal to 4% of normal. However, a normal plasma concentration of alpha 2-AP antigen (83%) was found. His sister (5 yr old) showed similar results (2 and 92%). In their family, eight heterozygotes could be identified by half-normal activity results and normal antigen concentrations. The inheritance pattern is autosomal recessive. On analysis, the alpha 2-AP of the propositus was homogeneous in all respects tested, suggesting a homozygous defect. We designated the abnormal alpha 2-AP as alpha 2-AP Enschede. alpha 2-AP Enschede showed the following characteristics: (a) complete immunological identity with normal alpha 2-AP; (b) normal molecular weight (sodium dodecyl sulfate-polyacrylamide gel electrophoresis); (c) normal alpha-electrophoretic mobility; (d) presence in plasma of both molecular forms excluding an excessive conversion to the less reactive non-plasminogen-binding form; (e) quantitatively normal binding to lys-plasminogen and to immobilized plasminogen kringle 1-3; and (f) normal Factor XIII-mediated binding to fibrin. Functional abnormalities were found in: (i) no inhibition of amidolytic activities of plasmin and trypsin, even on prolonged incubation; (ii) no formation of plasmin-antiplasmin complexes in plasma with plasmin added in excess; and (iii) no inhibition of fibrinolysis by fibrin-bound alpha 2-AP. In the heterozygotes, the presence of abnormal alpha 2-AP did not interfere with several functions of the residual normal alpha 2-AP. One-dimensional peptide mapping showed an abnormal pattern of papain digestion. We conclude that in this family, abnormal antiplasmin molecules, defective in plasmin inhibition but with normal plasminogen-binding properties, have been inherited. The residual plasminogen-binding properties do not protect against a hemorrhagic diathesis.

Authors

C Kluft, H K Nieuwenhuis, D C Rijken, E Groeneveld, G Wijngaards, W van Berkel, G Dooijewaard, J J Sixma

In vivo regulation of human mononuclear leukocyte 3-hydroxy-3-methylglutaryl coenzyme A reductase. Decreased enzyme catalytic efficiency in familial hypercholesterolemia.

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Abstract

3-Hydroxy-3-methylglutaryl coenzyme A reductase (HMG CoA reductase) controls the rate of cholesterol biosynthesis and is itself modulated through feedback suppression by internalized low density lipoprotein (LDL) cholesterol. We measured HMG CoA reductase protein concentration and microsomal enzyme activity in freshly isolated mononuclear leukocytes from normal individuals and patients with heterozygous or homozygous familial hypercholesterolemia (FH). Reductase protein concentration was similar in normal and heterozygous subjects, but was over twofold elevated in patients with homozygous FH. Reductase protein concentration was inversely related to LDL receptor status. Total activity and catalytic efficiency of reductase, however, were decreased in heterozygous and homozygous FH patients. The decrease in catalytic efficiency was not due to enzyme phosphorylation or thiol-disulfide formation. Reduction of plasma cholesterol concentration over 2 h by plasmapheresis increased reductase activity, the degree of which was directly proportional to the LDL-receptor status of the subjects. Decreased HMG CoA reductase activity and catalytic efficiency in mononuclear leukocytes and perhaps other cells in FH may represent a fundamental abnormality in the regulation of this enzyme independent of that induced by the LDL-receptor defect and may provide new insight into the control of cholesterol metabolism in FH.

Authors

P W Stacpoole, D M Bridge, I M Alvarez, R B Goldberg, H J Harwood Jr

Human adenine phosphoribosyltransferase. Identification of allelic mutations at the nucleotide level as a cause of complete deficiency of the enzyme.

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Abstract

This study reports the first demonstration of specific mutations leading to human adenine phosphoribosyltransferase (APRT) deficiency. The molecular basis of the deficiency was investigated by determining the sequence of both alleles of a patient with a complete deficiency in APRT activity. A trinucleotide deletion, corresponding to phenylalanine on the deduced amino acid sequence, was confirmed on one allele. A single nucleotide insertion, immediately adjacent to the splice site at the 5' end of the fourth intervening sequence, was confirmed on the other allele. This insertion lead to aberrant splicing, as was demonstrated by the absence of exon 4 in the complementary DNA sequence and by altered RNase mapping analysis of the abnormal messenger RNA.

Authors

Y Hidaka, T D Palella, T E O'Toole, S A Tarlé, W N Kelley

An initiation codon mutation (AUG----GUG) of the human alpha 1-globin gene. Structural characterization and evidence for a mild thalassemic phenotype.

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Abstract

alpha-globin is encoded by two adjacent genes, alpha 1 and alpha 2. Recent evidence suggests that these genes are not equally expressed and that the alpha 2-globin gene encodes the majority of alpha-globin. This finding would predict that a thalassemic mutation of the alpha 2-globin gene would result in a more severe loss of alpha-chain synthesis than a similar mutation in the alpha 1-globin gene. In a previous study we described a nondeletion alpha-thalassemia defect in the alpha 2-globin gene resulting from an AUG----ACG initiation codon mutation. In the present study we describe a different initiation codon mutation, AUG----GUG, present in the alpha 1-globin gene. The alpha 1- and alpha 2-globin gene initiation codon mutations result in similarly lowered levels of encoded mRNA. Despite the similarity of these two mutations, the alpha 2 mutant results in a more severe loss of alpha-globin synthesis and a more severe clinical alpha-thalassemia phenotype than the corresponding alpha 1-globin gene mutation. This difference reflects the dominant role of alpha 2-globin gene in overall alpha-globin synthesis.

Authors

P Moi, F E Cash, S A Liebhaber, A Cao, M Pirastu

P-31 nuclear magnetic resonance spectroscopic study of obstructive uropathy in the rat.

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Abstract

P-31 nuclear magnetic resonance (NMR) spectroscopy of the rat kidney with ureteral ligation resulted in a rapid and major increase in a peak resonating at 7096.63 +/- 0.65 Hz from the reference frequency of phosphorus (32.60 MHz). This corresponded to an increase in the concentration of the substance responsible for peak X from 0.34 +/- 0.04 mumol/g wet weight in normal kidneys to 1.45 +/- 0.27 mumol/g wet weight in unilaterally obstructed kidneys and 2.00 +/- 0.34 mumol/g wet weight in bilaterally obstructed kidneys at 3 h (P less than 0.01). Further NMR studies performed with in vivo kidneys and tissue extracts revealed that inorganic phosphate in the urine, resonating at a lower frequency due to the acid pH environment, was responsible for the increase in this peak. These findings may prove to be of fundamental interest as well as potential clinical significance.

Authors

J I Shapiro, L Chan

Human placental transport of cimetidine.

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Abstract

This study addresses the mechanism of transport of the H2-receptor antagonist, cimetidine, by the human placenta. A 4-h recycling perfusion of a single placental cotyledon of normal, term, human placenta was used. At a maternal concentration of 1 microgram/ml, cimetidine clearance from the maternal circulation was 0.58 +/- 0.16 ml/min per g placenta, a rate about one third that of antipyrine. There was no evidence of cimetidine metabolism by the placenta. Transfer of cimetidine from maternal to fetal compartments showed no saturation kinetics and was not inhibited by putative carrier competitors. Cimetidine did not accumulate against a drug concentration gradient. Fetal clearance of cimetidine was similar to maternal clearance. Studies with placental apical vesicles confirmed lack of saturability of cimetidine transport and of its concentration within vesicles. Thus, (a) cimetidine is transported across the human placenta bidirectionally at a rate about one third that of antipyrine, (b) the drug is not metabolized by the placenta, and (c) the transport is a passive one.

Authors

S Schenker, J Dicke, R F Johnson, L L Mor, G I Henderson

Role of proaggregatory and antiaggregatory prostaglandins in hemostasis. Studies with combined thromboxane synthase inhibition and thromboxane receptor antagonism.

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Abstract

Thromboxane synthase inhibition can lead to two opposing effects: accumulation of proaggregatory cyclic endoperoxides and increased formation of antiaggregatory PGI2 and PGD2. The elimination of the effects of the cyclic endoperoxides by an endoperoxide-thromboxane A2 receptor antagonist should enhance the inhibition of hemostasis by thromboxane synthase blockers. We have carried out a series of double-blind, placebo-controlled, crossover studies in healthy volunteers to check if this hypothesis may be operative in vivo in man. In a first study, in 10 healthy male volunteers, the combined administration of the thromboxane receptor antagonist BM 13.177 and the thromboxane synthase inhibitor dazoxiben gave stronger inhibition of platelet aggregation and prolonged the bleeding time more than either drug alone. In a second study, in 10 different healthy male volunteers, complete inhibition of cyclooxygenase with indomethacin reduced the prolongation of the bleeding time by the combination BM 13.177 plus dazoxiben. In a third study, in five volunteers, selective cumulative inhibition of platelet TXA2 synthesis by low-dose aspirin inhibited platelet aggregation and prolonged the bleeding time less than the combination BM 13.177 plus dazoxiben. In vitro, in human platelet-rich plasma stimulated with arachidonic acid, the combination of BM 13.177 and dazoxiben increased intraplatelet cAMP while the single drugs did not affect it. Our results indicate that prostaglandin endoperoxides can partly substitute for the activity of TXA2 in vivo in man and that an increased formation of endogenous antiaggregatory and vasodilatory prostaglandins, as obtained with selective thromboxane synthase inhibitors, may contribute to the impairment of hemostasis.

Authors

P Gresele, J Arnout, H Deckmyn, E Huybrechts, G Pieters, J Vermylen

Cytoprotective effects of glycine and glutathione against hypoxic injury to renal tubules.

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Abstract

Roles for both the tripeptide, GSH, and individual amino acids in modifying the cellular response to oxygen deprivation-induced injury have been suggested by prior work in kidney and other tissues, but the precise interrelationships have not been clearly defined. We have studied the effects of GSH, its component amino acids, and related compounds on the behavior of isolated renal proximal tubules in a well characterized model of hypoxic injury in vitro. GSH, the combination of cysteine, glutamate, and glycine and glycine alone, when present in the medium during 30 min hypoxia, a duration sufficient to produce extensive irreversible injury in untreated tubules, were protective. Significant effects were detected at 0.25 mM concentrations of the reagents, and protection was nearly complete at concentrations of 1 mM and above. Glutamate and cysteine alone were not protective. The exogenous GSH added to the tubule suspensions was rapidly degraded to its component amino acids. Treatment of tubules with GSH or cysteine, but not glycine, increased intracellular GSH levels. Oxidized GSH was protective. Serine, N-(2-mercaptopropionyl)-glycine, and a panel of agents known to modify injury produced by reactive oxygen metabolites were without benefit. These observations identify a novel and potent action of glycine to modify the course of hypoxic renal tubular cell injury. This effect is independent of changes in cellular GSH metabolism and appears to be unrelated to alterations of cell thiols or reactive oxygen metabolites. Further elucidation of its mechanism may provide insight into both the basic pathophysiology of oxygen deprivation-induced cell injury and a practical way to ameliorate it.

Authors

J M Weinberg, J A Davis, M Abarzua, T Rajan

Selective binding of somatostatin-14 and somatostatin-28 to islet cells revealed by quantitative electron microscopic autoradiography.

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Abstract

Quantitative electron microscopic autoradiography was used for comparing the binding of labeled somatostatin-14 (S-14) and somatostatin-28 (S-28 section) to islet cells. Monolayer cultures of rat islet cells were incubated with [125I-Tyr11]S-14 (S-14 section) or [125I-Leu8, D-Trp22, Tyr25]S-28 (S-28 section) in the presence or absence of excess unlabeled peptides. Autoradiographic grains (ARG) associated with individual islet cells were identified and expressed as the mean number per B, A, and D cells. Specific ARG associated with S-14 were found over B and A cells. S-28 section-related specific ARG were concentrated over B, A, as well as D cells. The highest density of S-14 section labeling occurred over A cells, which under conditions of maximum labeling (37 degrees C for 60 min) contained five times as many ARG as did B cells. By contrast, under the same incubation conditions, the labeling density with S-28 section was maximal over B cells, which contained four and five times as many grains as A and D cells, respectively. These observations show preferential association of S-14 section with the A cell and S-28 section with the B cel provide strong evidence for the existence of separate binding sites for S-14 section and S-28 section on A and B cells, respectively, which presumably mediate the previously reported glucagon selective inhibitory effect of S-14 and the insulin-selective action of S-28.

Authors

M Amherdt, Y C Patel, L Orci

Rapid formation of large molecular weight alpha-polymers in cross-linked fibrin induced by high factor XIII concentrations. Role of platelet factor XIII.

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Abstract

After fibrin polymerization, activated Factor XIII catalyzes the formation of intermolecular cross-links between gamma-chain pairs and also among two or more alpha-chains to form polymers. In this report we characterize the size and heterogeneity of alpha-chain polymers, establish the role of high concentrations of Factor XIII in determining the extent and rate of alpha-polymer formation, and also provide evidence that the Factor XIII required can be provided by platelets. Fibrin prepared from purified fibrinogen or platelet-deficient plasma contained a series of cross-linked alpha-chain polymers with Mr from 140,000 to 770,000 with a mean Mr difference of 32,000 consistent with a staggered, overlapping addition of monomers to the growing alpha-polymer chain. In plasma containing no platelets, alpha-polymer formation was incomplete with residual alpha-monomer remaining, but higher platelet counts facilitated more rapid cross-linking into larger polymers. Purified Factor XIII was equally effective as platelets in facilitating cross-linking. We conclude that cross-linked alpha-polymer chains are heterogeneous in size reaching a molecular weight of several million and that high concentrations of Factor XIII as provided by platelets are required for maximum cross-linking.

Authors

C W Francis, V J Marder

Apparent tolerance to the acute effect of nicotine results in part from distribution kinetics.

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Abstract

Persons exposed to nicotine develop tolerance to many of its effects. When heart rate and forearm venous blood concentration are plotted against time after intravenous administration of nicotine, a greater increase in heart rate is seen for a given nicotine concentration during the rising phase of nicotine concentrations than during the decreasing phase. This could be due to acute tolerance or to more rapid distribution of drug to effect site (brain) than to venous blood. To distinguish between these possibilities, six rabbits were given nicotine intravenously. Blood samples were taken from the internal jugular vein (reflecting brain concentration), and the femoral vein and artery. Brain concentrations peaked before femoral venous concentrations. Seven men received intravenous infusions of nicotine. Peripheral venous blood concentrations and cardiovascular responses were measured. Heart rate peaked before venous concentrations. A physiological kinetic model, fit to the rabbit data, was scaled to humans and used to predict "brain" concentrations in them. Heart rate and predicted brain concentrations peaked simultaneously. We conclude that the rapid development of tolerance to the cardioaccelerating effect of nicotine can be attributed, at least in part, to its distribution kinetics.

Authors

H C Porchet, N L Benowitz, L B Sheiner, J R Copeland

Glycoprotein hormone genes are expressed in clinically nonfunctioning pituitary adenomas.

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Abstract

Approximately 25% of patients with pituitary adenomas have no clinical or biochemical evidence for excess hormone secretion and are classified as having null cell or nonfunctioning adenomas. To characterize the cell type of these tumors, we analyzed pituitary hormone gene expression in clinically nonfunctioning pituitary adenomas using specific oligonucleotide probes for the messenger (m)RNAs encoding growth hormone, prolactin, ACTH, and the glycoprotein hormone subunits, alpha, luteinizing hormone (LH)beta, follicle-stimulating hormone (FSH)beta, and thyroid-stimulating hormone (TSH)beta. Expression of one or more of the anterior pituitary hormone genes was found in 12/14 (86%) of the patients with clinically classified nonfunctioning adenomas. Expression of one or more of the glycoprotein hormone genes (alpha, LH beta, FSH beta, TSH beta) was identified most commonly (79%) with expression of multiple beta-subunit genes in many cases. Expression of alpha-subunit mRNA was found in each of the adenomas from patients expressing one of the beta-subunit mRNAs and in three patients with no detectable beta-subunit mRNA. Although FSH beta and LH beta mRNAs were found with similar frequencies in nonfunctioning adenomas, expression of FSH beta mRNA was generally much more abundant. TSH beta mRNA was detected in only one adenoma. The levels of glycoprotein hormone subunit mRNAs were variable in different adenomas, but the lengths of the mRNAs and transcriptional start sites for the alpha- and beta-subunit genes were the same in the pituitary adenomas and in normal pituitary. Growth hormone and prolactin gene expression were not observed in the nonfunctioning adenomas, but ACTH mRNA was found in a single case. Immunohistochemistry of the adenomas confirmed production of one or more pituitary hormones in 13/14 (93%) nonfunctioning tumors, with a distribution of hormone production similar to that of the hormone mRNAs. These data indicate that pituitary adenomas originating from cells producing glycoprotein hormones are common, but are difficult to recognize clinically because of the absence of characteristic endocrine syndromes and defective hormone biosynthesis and secretion.

Authors

J L Jameson, A Klibanski, P M Black, N T Zervas, C M Lindell, D W Hsu, E C Ridgway, J F Habener

Characterization of the enzymatic defect in late-onset muscle phosphofructokinase deficiency. New subtype of glycogen storage disease type VII.

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Abstract

Human phosphofructokinase (PFK) exists in tetrameric isozymic forms, at least in vitro. Muscle and liver contain homotetramers M4 and L4, respectively, whereas red cells contain five isozymes composed of M (muscle) and L (liver) type subunits, i.e., M4, M3L, M2L2, and ML3, and L4. Homozygous deficiency of muscle PFK results in the classic glycogen storage disease type VII characterized by exertional myopathy and hemolytic syndrome beginning in early childhood. The genetic lesion results in a total and partial loss of muscle and red cell PFK, respectively. Characteristically, the residual red cell PFK from the patients consists of isolated L4 isozyme; the M-containing hybrid isozymes are completely absent. In this study, we investigated an 80-yr-old man who presented with a 10-yr history of progressive weakness of the lower limbs as the only symptom. The residual red cell PFK showed the presence of a few M-containing isozymes in addition to the predominant L4 species, indicating that the genetic lesion is a "leaky" mutation of the gene coding for the M subunit. The presence of a small amount of enzyme activity in the muscle may account for the atypical myopathy in this patient.

Authors

S Vora, S DiMauro, D Spear, D Harker, M J Danon

Human red cells scavenge extracellular hydrogen peroxide and inhibit formation of hypochlorous acid and hydroxyl radical.

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Abstract

The ability of intact human red cells to scavenge extracellularly generated H2O2 and O2-, and to prevent formation of hydroxyl radicals and hypochlorous acid has been examined. Red cells inhibited oxidation of ferrocytochrome c by H2O2. Cells treated with aminotriazole no longer inhibited, indicating that protection was almost entirely due to intracellular catalase. Contribution by the GSH system was slight, and apparent only with low H2O2 concentrations when catalase was inhibited by aminotriazole. The cells were about a quarter as efficient at inhibiting cytochrome c oxidation as an equivalent concentration of purified catalase. No inhibition of O2(-)-dependent reduction of ferricytochrome c or nitroblue tetrazolium was observed, although extracted red cell superoxide dismutase inhibited nitroblue tetrazolium reduction at one fortieth the concentration of that in the cells. Red cells efficiently inhibited deoxyribose oxidation by hydroxyl radicals generated from H2O2, O2- and Fe(EDTA), and myeloperoxidase-dependent oxidation of methionine to methionine sulfoxide by stimulated neutrophils. Most of the red cell inhibition of hydroxyl radical production, and all the inhibition of methionine oxidation, was prevented by blocking intracellular catalase with aminotriazole. Thus red cells are able to efficiently scavenge H2O2, but not O2-, produced in their environment, and to inhibit formation of hydroxyl radicals and hypochlorous acid. They may therefore have an important role in extracellular antioxidant defense.

Authors

C C Winterbourn, A Stern

Activation of terminal components of complement in patients with Guillain-Barré syndrome and other demyelinating neuropathies.

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Abstract

In the present study, the role of antiperipheral nerve myelin antibody (anti-PNM Ab) in demyelination by generating the terminal attack complex (C5b-9) of complement was explored in patients with Guillain-Barré syndrome (GBS) and other demyelinating neuropathies. The presence in serum of SC5b-9, an inactive C5b-9 containing S protein, was assessed quantitatively by enzyme-linked immunosorbent assay using an antibody (Ab) to neoantigens expressed on C9 when complexed with C5b-8 or after tubular polymerization. SC5b-9 was detected in all 19 GBS, four patients with paraprotein-associated neuropathy and five of six patients with chronic recurrent polyneuritis. No SC5b-9 was detected in 10 normal controls. Kinetic studies from six GBS patients showed the highest values of SC5b-9 on the 3rd to 5th d of admission; in contrast, the anti-PNM Ab were highest on the day of admission. Anti-PNM Ab fell rapidly to very low levels by the 15th to 20th d. SC5b-9 declined with similar kinetics to undetectable levels by the 30th d. Levels of Ab and SC5b-9 did not quantitatively correlate with soluble immune complexes in these patients' serum. Membrane-bound C5b-9 was also detected by immunohistochemistry in the peripheral nerves from a GBS patient. These results, which show a relationship between levels of complement-fixing anti-PNM Ab and the tissue-damaging C5b-9 complex, suggest that peripheral nerve myelin may serve as the target for Ab-mediated complement attack.

Authors

C L Koski, M E Sanders, P T Swoveland, T J Lawley, M L Shin, M M Frank, K A Joiner

Soybean protein diet increases low density lipoprotein receptor activity in mononuclear cells from hypercholesterolemic patients.

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Abstract

The effect of two diets containing different protein sources (animal vs. soybean) on the low density lipoprotein (LDL) receptor activity was tested in freshly isolated mononuclear cells from 12 individuals with severe type II hyperlipoproteinemia. The two diets, both taken for 4 wk in a crossover design were of otherwise identical composition. During the soybean protein diet period, total cholesterol was reduced by 15.9% and LDL-cholesterol by 16.4%. The diet containing animal proteins exerted no significant change in plasma lipid levels vs. the baseline findings. The soybean diet regimen dramatically affected the degradation of LDL by mononuclear cells. Degradation was increased 16-fold vs. the basal activity and 8-fold compared with the standard low lipid diet with animal proteins. There was, however, no clear relationship between the reduction of total and LDL-cholesterolemia and the increased LDL degradation. These findings confirm similar data previously obtained in cholesterol-fed rats and suggest that some factor/s, most likely of a protein nature, may regulate the expression of lipoprotein receptors in peripheral cells, particularly when receptor activity is suppressed by experimental diets and/or spontaneous hypercholesterolemia.

Authors

M R Lovati, C Manzoni, A Canavesi, M Sirtori, V Vaccarino, M Marchi, G Gaddi, C R Sirtori

Potentiated adherence of sickle erythrocytes to endothelium infected by virus.

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Abstract

Systemic viral infection is a known precipitant of vasocclusive crisis in sickle patients, but the mechanism underlying this clinical observation is unknown. In the present studies, human umbilical vein endothelial cells were infected with Herpes simplex virus type 1 (HSV) to model systemic viral disease. The already abnormal adherence of sickle erythrocytes to control endothelium is enhanced 1.8 +/- 0.4-fold to HSV-infected endothelium (P less than 0.001). This component of potentiated adherence is eliminated by maneuvers that block Fc receptors, it is prevented by tunicamycin, and it is not seen using a mutant HSV that is unable to express the Fc receptor glycoprotein. Thus, the incremental adherence seen here occurs due to expression of Fc receptor activity on HSV-infected endothelium and the consequent recognition of abnormal amounts of IgG on sickle erythrocytes. We conclude that systemic viral infection potentially can induce a novel mechanism for enhancement of erythrocyte adherence to endothelium and that this may increase the likelihood of vasocclusion during viral infection.

Authors

R P Hebbel, M R Visser, J L Goodman, H S Jacob, G M Vercellotti

Direct evidence of a role for mast cells in the pathogenesis of antigen-induced bronchoconstriction.

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Abstract

We measured bronchoalveolar lavage (BAL) fluid histamine levels in allergic asthmatics and nonallergic normal subjects after local airway antigen and cold 22 degrees C normal saline challenges. Immediately after instillation of antigen through a bronchoscope wedged into a subsegmental airway, all 17 allergic asthmatics but none of the nine normal subjects had visible airway constriction. The asthmatics had a concomitant mean increase in BAL histamine of 23% (P = 0.005), whereas the normals had no change in BAL histamine. Among the allergic asthmatics, the change in BAL histamine content in response to antigen directly correlated with the control (baseline) BAL histamine content (r = 0.66, P = 0.003). Moreover, asthmatics with large antigen-induced changes in BAL histamine had greater airway methacholine sensitivity than did asthmatics without measurable increases in BAL histamine (8 +/- 2 vs. 41 +/- 31 breath units). Neither asthmatics nor normal subjects had airway constriction or changes in BAL histamine levels in response to nonspecific challenge with cold saline. Our data suggest that when allergic asthmatics are exposed to relevant antigens they have in vivo lung mast cell degranulation which results in airway constriction and contributes to nonspecific airway hyperresponsiveness.

Authors

T B Casale, D Wood, H B Richerson, B Zehr, D Zavala, G W Hunninghake

Expression of Bcl-2 and Bcl-2-Ig fusion transcripts in normal and neoplastic cells.

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Abstract

We examined the expression of the Bcl-2 gene at chromosome segment 18q21, that is translocated into the Ig heavy chain gene locus in t(14;18) bearing lymphomas. Bcl-2, while B cell associated, is expressed in a variety of hematopoietic lineages including T cells. Bcl-2 mRNA levels are high during pre-B cell development, the time at which the t(14;18) translocation occurs, but are down regulated with maturation. Like certain other oncogenes, Bcl-2 is quiescent in resting B cells but up-regulated with B cell activation. Mature B cell lymphomas with a t(14;18) have log-folds more mRNA than matched counterparts without the translocation. A sensitive S1 protection assay revealed that all transcripts in t(14;18) B cells were Bcl-2-Ig fusion mRNAs and originated from the translocated allele. Thus, there is a marked deregulation of Bcl-2 when it is introduced into the Ig locus in t(14;18) lymphomas.

Authors

W B Graninger, M Seto, B Boutain, P Goldman, S J Korsmeyer

Basic fibroblast growth factor as a growth inhibitor for cultured human tumor cells.

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Abstract

Basic fibroblast growth factor (bFGF) stimulates the proliferation of many cells and it is found in a wide variety of normal or transformed tissues. As demonstrated here, bFGF is also present in cultured human Ewing's sarcoma cells. Unexpectedly, however, bFGF isolated from these cells inhibits their own proliferation, indicating that bFGF can act as an endogenous (autocrine) growth inhibitor for cultured Ewing's sarcoma cells. Since bFGF also inhibits the proliferation of some further tumor cells, but stimulates that of others, it can be considered a bifunctional regulator of tumor cell proliferation. The autocrine growth-inhibitory effect of bFGF in Ewing's sarcoma cells may explain the low mitotic activity of Ewing's sarcomas.

Authors

L Schweigerer, G Neufeld, D Gospodarowicz