Improved diagnosis of Duchenne/Becker muscular dystrophy.

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Abstract

Authors

A H Beggs, L M Kunkel

Normal immunoglobulin G (IgG) for therapeutic use (intravenous Ig) contain antiidiotypic specificities against an immunodominant, disease-associated, cross-reactive idiotype of human anti-thyroglobulin autoantibodies.

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Pooled normal polyspecific IgG for therapeutic use (IVIg) contain anti-idiotypes against idiotypic determinants expressed by autoantibodies from patients with a variety of autoimmune diseases. In the present study, antiidiotypes in IVIg are shown to recognize a cross-reactive idiotype on human anti-thyroglobulin (TG) autoantibodies, that was defined by heterologous antiidiotypic antibodies, termed anti-T44 antibodies. The T44 idiotype is located outside the antibody-combining site of anti-TG autoantibodies. F(ab')2 fragments from anti-T44 antibodies inhibited the binding of IVIg to affinity-purified F(ab')2 anti-TG autoantibodies. Anti-T44 antibodies bound to F(ab')2 fragments of patients' antibodies, which were retained on an affinity column of Sepharose-bound F(ab')2 fragments from IVIg, but not to F(ab')2 fragments from the effluent of the column. The T44 idiotype was expressed on antibodies that bound to IVIg from eight of nine patients with autoimmune thyroiditis, but not on IVIg-binding Igs from healthy individuals. A small amount of the T44 idiotype was also expressed on the fraction of IVIg that bound to itself upon affinity chromatography. The T44 idiotype was cross-reactive between antibodies from patients with autoimmune thyroiditis. Thus, IVIg contain antiidiotypic antibodies directed against an immunodominant disease-associated cross-reactive alpha-idiotype of human anti-TG autoantibodies. These results support the concept that IVIg may be beneficial in selected autoimmune diseases by modulating the function of the idiotypic network.

Authors

G Dietrich, M D Kazatchkine

Potent mitogenic effects of parathyroid hormone (PTH) on embryonic chick and rabbit chondrocytes. Differential effects of age on growth, proteoglycan, and cyclic AMP responses of chondrocytes to PTH.

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The effect of PTH on chondrocyte proliferation as a function of cartilage age was examined. PTH[1-34] induced a 12- to 15-fold increase in the efficiency of colony formation in soft agar by chondrocytes from embryonic 13- to 19-d-old chickens and fetal 25-d-old rabbits with a 10-fold increase in their DNA content. It also caused a 2.5-fold increase in [3H]thymidine incorporation into DNA in fetal 25-d-old rabbit chondrocytes. No mitogenic responses to PTH were observed, however, in postnatal 7- to 21-d-old chick chondrocytes or postnatal 21-d-old rabbit chondrocytes. This age dependency was observed only with PTH: fibroblast growth factor, epidermal growth factor, and insulin stimulated chondrocyte proliferation irrespective of cartilage age. The absence of a mitogenic effect in postnatal chondrocytes was not due to a decrease in number or a reduction in affinity of receptors for PTH. PTH also increased [35S]sulfate incorporation into proteoglycans and the cyclic AMP level in fetal and postnatal chondrocytes, but at 100-fold higher concentrations (10(-8)-10(-7) M) than those (10(-10)-10(-9) M) required for the stimulation of cell division. These results suggest that PTH is a potent mitogen for embryonic chondrocytes, and that its mitogenic effect disappears selectively after birth.

Authors

T Koike, M Iwamoto, A Shimazu, K Nakashima, F Suzuki, Y Kato

Oxygen-derived free radicals stimulate osteoclastic bone resorption in rodent bone in vitro and in vivo.

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The mechanisms by which bone resorbing osteoclasts form and are activated by hormones are poorly understood. We show here that the generation of oxygen-derived free radicals in cultured bone is associated with the formation of new osteoclasts and enhanced bone resorption, identical to the effects seen when bones are treated with hormones such as parathyroid hormone (PTH) and interleukin 1 (IL-1). When free oxygen radicals were generated adjacent to bone surfaces in vivo, osteoclasts were also formed. PTH and IL-1-stimulated bone resorption was inhibited by both natural and recombinant superoxide dismutase, an enzyme that depletes tissues of superoxide anions. We used the marker nitroblue tetrazolium (NBT) to identify the cells that were responsible for free radical production in resorbing bones. NBT staining was detected only in osteoclasts in cultures of resorbing bones. NBT staining in osteoclasts was decreased in bones coincubated with calcitonin, an inhibitor of bone resorption. We also found that isolated avian osteoclasts stained positively for NBT. NBT staining in isolated osteoclasts was increased when the cells were incubated with bone particles, to which they attach. We confirmed the formation of superoxide anion in isolated avian osteoclasts using ferricytochrome c reduction as a method of detection. The reduction of ferricytochrome c in isolated osteoclasts was inhibited by superoxide dismutase. Our results suggest that oxygen-derived free radicals, and particularly the superoxide anion, are intermediaries in the formation and activation of osteoclasts.

Authors

I R Garrett, B F Boyce, R O Oreffo, L Bonewald, J Poser, G R Mundy

Effects of a cholecystokinin receptor antagonist on intestinal phase of pancreatic and biliary responses in man.

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Abstract

The present study was designed (a) to characterize the activity of loxiglumide as a peripheral cholecystokinin (CCK) antagonist in healthy human subjects, and (b) to determine whether CCK is a physiologic regulator of the intestinal phase of meal-stimulated exocrine pancreatic and biliary secretions in man. Intravenous loxiglumide (22 mumol/kg per h) was highly potent in antagonizing CCK8-induced pancreatic enzyme and bile acid secretion as well as pancreatic polypeptide release. The potency and selectivity of loxiglumide as an antagonist of CCK provides the tool for evaluating the role of CCK as a physiological mediator of meal-induced pancreatic and biliary responses in humans. Infusion of a liquid test meal into the duodenum evoked an immediate response of pancreatic enzyme and bilirubin outputs, respectively. Intravenous loxiglumide significantly inhibited the meal-induced pancreatic amylase output by 63% (P less than 0.05), lipase output by 43% (P less than 0.05), and bilirubin output by 59% (P less than 0.05). These data suggest that CCK is a physiological mediator of the intestinal phase of meal-stimulated pancreatic and biliary responses.

Authors

P Hildebrand, C Beglinger, K Gyr, J B Jansen, L C Rovati, M Zuercher, C B Lamers, I Setnikar, G A Stalder

Defective venous beta-adrenergic response in borderline hypertensive subjects is corrected by a low sodium diet.

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Hypertensive patients have reduced lymphocyte beta-adrenergic responsiveness which is corrected by a low sodium (Na) diet. To determine if this represents a more generalized abnormality in beta adrenoceptor response, we studied beta adrenergic-mediated vasodilation in hand veins of borderline hypertensive subjects and controls. Subjects received a 5-d diet containing high Na/low potassium (K), high Na/high K, or low Na/high K. Venous distension, as evaluated by a linear variable differential transformer, was measured in relation to infusion of phenylephrine followed by isoproterenol and nitroglycerin. On both the high Na/high K and high Na/low K diets, hypertensive subjects had significantly decreased isoproterenol-mediated vasodilation (47% decrease, P less than 0.01 and 36% decrease, P less than 0.01, respectively). On the low Na/high K diet, isoproterenol-mediated vasodilation in hypertensive subjects increased 41% (P less than 0.01) to a level not different from controls. Nitroglycerin-mediated vasodilation was not different in normotensive and hypertensive subjects, nor was it altered with Na intake. Phenylephrine-mediated vasoconstriction did not differ between normotensive and hypertensive groups. Venous beta-adrenergic response correlated with lymphocyte beta adrenoceptor density in normotensive (r = 0.53, P less than 0.005) but not hypertensive subjects. This study demonstrates that beta-adrenergic responsiveness is selectively reduced in peripheral veins of borderline hypertensive subjects, and this is corrected by a low Na diet. In view of our previous findings of reduced lymphocyte beta-adrenergic responsiveness in borderline hypertension, these studies suggest a generalized defect of beta adrenoceptor responsiveness in human hypertension. Further, dietary Na may play an important role in regulating this abnormality.

Authors

R D Feldman

Endothelin receptor is coupled to phospholipase C via a pertussis toxin-insensitive guanine nucleotide-binding regulatory protein in vascular smooth muscle cells.

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Abstract

The mechanisms of endothelin-1 (ET) actions were investigated in cultured rat aortic vascular smooth muscle A-10 cells. The A-10 cells have a single class of high affinity binding sites for ET with an apparent Mr of 65,000-75,000 on SDS-PAGE. Stimulation of cells with ET induces mobilization of Ca2+ from both intra- and extracellular pools to produce a biphasic increase in cytoplasmic free Ca2+ concentration. ET increases cellular levels of inositol trisphosphate and 1,2-diacylglycerol, indicating activation of phospholipase C by ET. ET stimulates production of inositol phosphates in membranes prepared from A-10 cells in the presence of guanosine 5'-O-(thiotriphosphate) (GTP gamma S), but not in its absence. Further, specific binding of 125I-labeled ET to A-10 cell membranes is shown to be inhibited by GTP gamma S in a dose-dependent manner. Treatment of A-10 cells with pertussis toxin induces ADP-ribosylation of a 41,000-D membrane protein but fails to block the ET-induced increases in inositol phosphate production and Ca2+ mobilization. These results indicate that the receptor for ET is coupled to phospholipase C via a guanine nucleotide-binding regulatory protein which is distinct from the pertussis toxin substrate in A-10 cells.

Authors

Y Takuwa, Y Kasuya, N Takuwa, M Kudo, M Yanagisawa, K Goto, T Masaki, K Yamashita

Role of thyroid hormones in apolipoprotein A-I gene expression in rat liver.

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Abstract

To study the regulation of hepatic apo A-I gene expression, we measured synthesis and abundance of cellular apo A-I mRNA and its nuclear precursors in livers of hypothyroid and hyperthyroid rats. In hypothyroid animals, both synthesis and abundance of apo A-I mRNA was reduced to half of control values. After injection of a receptor-saturating dose of triiodothyronine into euthyroid rats, apo A-I gene transcription increased at 20 min, reached a maximum of 179% of control (P less than 0.01) at 3.5 h, and remained elevated for up to 48 h. The abundance of nuclear and total cellular apo A-I mRNA increased at 1 and 2 h, respectively, and exceeded the levels expected from enhanced transcription more than two fold at 24 h after hormone injection. Upon chronic administration of thyroid hormones, levels of nuclear and cytoplasmic apo A-I mRNA remained elevated but transcription of the apo A-I gene fell to 42% of control (P less than 0.01). Thus, thyroid hormones rapidly stimulate apo A-I gene transcription. Posttranscriptional events leading to increased stability of nuclear apo A-I RNA precursors become the principal mechanism for enhanced gene expression in chronic hyperthyroidism and may cause feedback inhibition of apo A-I gene transcription. Our results furthermore imply that the majority of hepatic nuclear apo A-I RNA precursors are degraded in euthyroid animals.

Authors

W Strobl, N L Gorder, Y C Lin-Lee, A M Gotto Jr, W Patsch

Accumulation of hyaluronan (hyaluronic acid) in myocardial interstitial tissue parallels development of transplantation edema in heart allografts in rats.

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By using biotin-labeled proteoglycan core protein, hyaluronan (hyaluronic acid; HA) was visualized in rat heart grafts at different times (2, 4, and 6 d) after transplantation. In normal, nontransplanted hearts HA was present in the adventitia of arteries and veins and in the myocardial interstitial tissue. An increased accumulation of HA was evident in the edematous interstitial tissue, infiltrated with lymphocytes, on day 4 after allogeneic transplantation, and was even more pronounced by day 6. No apparent increase in HA was seen in syngeneic grafts. Biochemical assay of HA in heart tissue demonstrated that the myocardial content of HA had increased 60% by day 2 after transplantation in allogeneic as well as syngeneic grafts, indicating that surgical trauma may induce some HA accumulation in heart grafts. The extractable amount of HA declined during the following days in the syngeneic grafts, but increased progressively during the development of rejection in the allogeneic grafts, and increased on average three times by day 6. The relative water content also increased progressively during rejection of allogeneic grafts and correlated with the HA accumulation. The interstitial accumulation of HA, a glycosaminoglycan with unique water-binding qualities, is presumably implicated in the development of interstitial edema during rejection of heart grafts.

Authors

R Hällgren, B Gerdin, A Tengblad, G Tufveson

Transfection of cells from patients with leukocyte adhesion deficiency with an integrin beta subunit (CD18) restores lymphocyte function-associated antigen-1 expression and function.

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Abstract

Leukocyte adhesion deficiency (LAD) is an inherited immunodeficiency disease that is characterized by the deficient expression of the leukocyte adhesion glycoproteins lymphocyte function-associated antigen-1 (LFA-1), Mac-1, and p150,95. This loss of expression is attributed to heterogeneous defects in the common beta subunit shared by these glycoproteins. Here we demonstrate that expression of the LFA-1 alpha beta heterodimer in EBV-transformed B lymphoblastoid cells from LAD patients can be recovered after transfection with the beta subunit cDNA contained in an EBV-based vector. Four patients with differing severities of LAD comprising three distinct classes of mutations were studied. Flow cytometry analysis of stably transfected patient cells revealed near normal levels of expression of both the alpha and beta chains of LFA-1, and immunoprecipitation studies confirmed that fully processed alpha and beta chains were being expressed at the cell surface. In addition, Northern analysis of mRNA expression also demonstrated that the transfected LAD patient cells were expressing high quantities of exogenous beta subunit mRNA. Functional studies such as homotypic adhesion and adhesion to a purified counterreceptor for LFA-1, intracellular adhesion molecule-1, demonstrated that LFA-1 function had been restored in the stably transfected LAD patient cell lines. These studies unequivocally show that the defect in cells from patients with LAD is in the leukocyte integrin beta subunit.

Authors

M L Hibbs, A J Wardlaw, S A Stacker, D C Anderson, A Lee, T M Roberts, T A Springer

Neutrophil elastase and cathepsin G stimulate secretion from cultured bovine airway gland serous cells.

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Abstract

To investigate the hypothesis that neutrophil proteases stimulate airway gland secretion, we studied the effect of human cathepsin G and elastase on secretion of 35S-labeled macromolecules from cultured bovine airway gland serous cells. Both proteases stimulated secretion in a concentration-dependent fashion with a threshold of greater than or equal to 10(-10) M. Elastase was more potent than cathepsin G, causing a maximal secretory response of 1,810 +/- 60% over baseline at 10(-8) M. The maximal response to cathepsin G (1,810 +/- 70% over baseline at 10(-7) M) was similar to the maximal response to elastase. These responses were greater than 10-fold larger than the response to other agonists such as histamine. Protease-induced secretion was noncytotoxic and required catalytically active enzymes. The predominant sulfated macromolecule released by proteases was chondroitin sulfate proteoglycan. Immunocytochemical staining demonstrated chondroitin sulfate in cytoplasmic granules and decreased granular staining after stimulation of cells with elastase. The neutrophil proteases also degraded the proteoglycan released from serous cells. Cathepsin G and elastase in supernatant obtained by degranulation of human peripheral neutrophils also caused a secretory response. Thus, neutrophil proteases stimulate airway gland serous cell secretion of chondroitin sulfate proteoglycan and degrade the secreted product. These findings suggest a potential role for neutrophil proteases in the pathogenesis of increased and abnormal submucosal gland secretions in diseases associated with inflammation and neutrophil infiltration of the airways.

Authors

C P Sommerhoff, J A Nadel, C B Basbaum, G H Caughey

In vitro responses to Leishmania antigens by lymphocytes from patients with leishmaniasis or Chagas' disease.

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Abstract

T cell responses are correlated with recovery from and resistance to leishmaniasis. Antigens of Leishmania chagasi were evaluated by determining their ability to elicit in vitro proliferation and cytokine production in peripheral blood lymphocytes and in T cell lines and clones from patients with histories of leishmaniasis or Chagas' disease. Antigens tested were selected by their reactivity with patient antibodies. Several of the antigens induced proliferative responses in peripheral blood lymphocytes from patients recovered from visceral or cutaneous leishmaniasis or with chronic Chagas' disease. Two purified glycoproteins, 30 and 42 kD, were consistently among the most effective in eliciting high proliferative responses and IL-2 production. Lymphocytes from a recovered visceral leishmaniasis patient were used to produce T cell lines against either the 30- or 42-kD antigen. Each of the lines responded to both of these antigens as well as to crude leishmania lysate. CD4+ T cell clones specific for either or both of these antigens were also isolated from a visceral leishmaniasis patient. In contrast, rabbit antisera produced against these two antigens were not crossreactive. Both antigens were effective in inducing the production of IFN-gamma from T cell lines from both leishmaniasis and Chagas' disease patients. These studies demonstrate the potential for defining parasite antigens with broad immunostimulatory capabilities.

Authors

S G Reed, E M Carvalho, C H Sherbert, D P Sampaio, D M Russo, O Bacelar, D L Pihl, J M Scott, A Barral, K H Grabstein

Experimental non-O group 1 Vibrio cholerae gastroenteritis in humans.

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In this study, 27 volunteers received one of three non-O group 1 Vibrio cholerae strains in doses as high as 10(9) CFU. Only one strain (strain C) caused diarrhea: this strain was able to colonize the gastrointestinal tract, and produced a heat-stable enterotoxin (NAG-ST). Diarrhea was not seen with a strain (strain A) that colonized the intestine but did not produce NAG-ST, nor with a strain (strain B) that produced NAG-ST but did not colonize. Persons receiving strain C had diarrhea and abdominal cramps. Diarrheal stool volumes ranged from 154 to 5,397 ml; stool samples from the patient having 5,397 ml of diarrhea were tested and found to contain NAG-ST. The median incubation period for illness was 10 h. There was a suggestion that occurrence of diarrhea was dependent on inoculum size. Immune responses to homologous outer membrane proteins, lipopolysaccharide, and whole-cell lysates were demonstrable with all three strains. Our data demonstrate that V. cholerae of O groups other than 1 are able to cause severe diarrheal disease. However, not all strains are pathogenic for humans: virulence of strain C may be dependent on its ability both to colonize the intestine and to produce a toxin such as NAG-ST.

Authors

J G Morris Jr, T Takeda, B D Tall, G A Losonsky, S K Bhattacharya, B D Forrest, B A Kay, M Nishibuchi

Relationship between myocardial metabolites and contractile abnormalities during graded regional ischemia. Phosphorus-31 nuclear magnetic resonance studies of porcine myocardium in vivo.

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Abstract

The mechanisms responsible for changes in myocardial contractility during regional ischemia are unknown. Since changes in high-energy phosphates during ischemia are sensitive to reductions in myocardial blood flow, it was hypothesized that myocardial function under steady-state conditions of graded regional ischemia is closely related to changes in myocardial high-energy phosphates. Therefore, phosphorus-31 nuclear magnetic resonance spectroscopy was employed in an in vivo porcine model of graded coronary stenosis. Simultaneous measurements of regional subendocardial blood flow, high-energy phosphates, pH, and myocardial segment shortening were made during various degrees of regional ischemia in which subendocardial blood flow was reduced by 16-94%. During mild reductions in myocardial blood flow (subendocardial blood flow = 83% of nonischemic myocardium), only the ratio of phosphocreatine to inorganic phosphate (PCr/Pi), Pi, and [H+] were significantly changed from control. PCr, ATP, and PCr/ATP were not significantly reduced from control with mild reductions in blood flow. Changes in myocardial segment shortening were most closely associated with changes in PCr/Pi (r = 0.94). Pi and [H+] were negatively correlated with segment shortening (r = -0.64 and -0.58, respectively) and increased over twofold when blood flow was reduced by 62%. Thus, these data demonstrate that PCr/Pi is sensitive to reductions in myocardial blood flow and closely correlates with changes in myocardial function. These data are also consistent with a role for Pi or H+ as inhibitors of myocardial contractility during ischemia.

Authors

S Schaefer, G G Schwartz, J R Gober, A K Wong, S A Camacho, B Massie, M W Weiner

Two cytosolic components of the human neutrophil respiratory burst oxidase translocate to the plasma membrane during cell activation.

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The superoxide-forming respiratory burst oxidase of human neutrophils is composed of membrane-associated catalytic components and cytosolic constituents required for oxidase activation. This study concerns the hypothesis that cytosolic oxidase components translocate to a membrane fraction when neutrophils are stimulated and the oxidase is activated. A polyclonal antiserum that recognizes two discrete cytosolic oxidase components of 47 and 67 kD was used to probe transfer blots of electrophoresed membrane and cytosol fractions of resting and stimulated neutrophils. In contrast to their strictly cytosolic localization in unstimulated cells, both proteins were detected in membrane fractions of neutrophils activated by phorbol esters and other stimuli. This translocation event was a function of stimulus concentration as well as time and temperature of exposure to the stimulus. It was inhibited by concentrations of N-ethylmaleimide that blocked superoxide formation but was unaffected by 2-deoxyglucose. There was a correlation between translocation of the cytosolic proteins and activation of the oxidase as determined by superoxide formation. Quantitative analyses suggested that approximately 10% of total cellular p47 and p67 became membrane-associated during phorbol ester activation of the oxidase. Analysis of Percoll density gradient fractions indicated that the target membrane for translocation of both proteins was the plasma membrane rather than membranes of either specific or azurophilic granules. In the cell-free oxidase system arachidonate-dependent but membrane-independent precipitation of the cytosolic oxidase proteins was demonstrated. The data show that activation of the respiratory burst oxidase in stimulated human neutrophils is closely associated with translocation of the 47- and 67-kD cytosolic oxidase components to the plasma membrane. We suggest that this translocation event is important in oxidase activation.

Authors

R A Clark, B D Volpp, K G Leidal, W M Nauseef

Impaired response of fibroblasts from patients with hyperapobetalipoproteinemia to acylation-stimulating protein.

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Acylation-stimulating protein (ASP) is a small, basic, human plasma protein that markedly stimulates triglyceride synthesis in human adipocytes and cultured human skin fibroblasts. The present studies examine the response to ASP of cultured skin fibroblasts from normal subjects patients with hyperapobetalipoproteinemia, patients with familial hypercholesterolemia, and patients with hypertriglyceridemia without hyperapobetalipoproteinemia. Triglyceride synthesis induced by ASP did not differ significantly among the normals, the patients with familial hypercholesterolemia, and the patients with hypertriglyceridemia with normal low density lipoprotein (LDL) apolipoprotein B levels; however, on average, it was markedly reduced in the patients with hyperapobetalipoproteinemia. In all groups studied, evidence of specific saturable binding of radioiodinated ASP was present. Binding, however, was significantly reduced in the groups with hyperapobetalipoproteinemia whereas the other three groups were indistinguishable. By contrast, LDL-specific binding was reduced only in the patients with familial hypercholesterolemia. There was a significant direct relation between the degree of ASP binding and the triglyceride synthesis inducible by ASP. In addition, with the exception of the patients with familial hypercholesterolemia, there was an inverse relation between both ASP-specific binding and ASP-induced triglyceride synthesis in fibroblasts to LDL levels in plasma whereas no relation was evident to plasma high density lipoprotein and very low density lipoprotein.

Authors

K M Cianflone, M H Maslowska, A D Sniderman

Proliferating or interleukin 1-activated human vascular smooth muscle cells secrete copious interleukin 6.

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The cells that make up blood vessel walls appear to participate actively in local immune and inflammatory responses, as well as in certain vascular diseases. We tested here whether smooth muscle cells (SMC) can produce the important inflammatory mediator IL6. Unstimulated SMC in vitro elaborated 5 X 10(3) pg recIL6/24h (i.e., biological activity equivalent to 5 X 10(3) pg recombinant IL6 (recIL6), as determined in B9-assay with a recIL6 standard). Several pathophysiologically relevant factors augmented IL6 release from SMC including 10 micrograms LPS/ml (10(4) pg recIL6), 10 ng tumor necrosis factor/ml (4 X 10(4) pg recIL6), and most notably 10 ng IL1/ml (greater than or equal to 3.2 X 10(5) pg recIL6). Production of IL6 activity corresponded to IL6 mRNA accumulation and de novo synthesis. SMC released newly synthesized IL6 rapidly, as little metabolically labeled material remained cell-associated. In supernatants of IL1-stimulated SMC, IL6 accounted for as much as 4% of the secreted proteins. In normal vessels SMC seldom divide, but SMC proliferation can occur in hypertension or during atherogenesis. We therefore tested the relationship between IL6 production and SMC proliferation in response to platelet-derived growth factor (PDGF) in vitro. Quiescent SMC released scant IL6 activity, whereas PDGF (1-100 ng/ml) produced concentration-dependent and coordinate enhancement of SMC proliferation and IL6 release (linear regression of growth vs. IL6 release yielded r greater than 0.9). IL6 itself neither stimulated nor inhibited SMC growth or IL6 production. Intact medial strips studied in short-term organoid culture produced large quantities of IL6, similar to the results obtained with cultured SMC. These findings illustrate a new function of vascular SMC by which these cells might participate in local immunoregulation and in the pathogenesis of various important vascular diseases as well as in inflammatory responses generally.

Authors

H Loppnow, P Libby

Dependence on O2- generation by xanthine oxidase of pathogenesis of influenza virus infection in mice.

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Abstract

We evaluated various biochemical parameters in influenza virus-infected mice and focused on adenosine catabolism in the supernatant of bronchoalveolar lavage fluid (s-BALF), lung tissue, and serum (plasma). The activities of adenosine deaminase (ADA) and xanthine oxidase (XO), which generates O2-, were elevated in the s-BALF, lung tissue homogenate, and serum (plasma). The elevations were most remarkable in s-BALF and in lung tissue: We found a 170-fold increase in ADA activity and a 400-fold increase in XO activity as measured per volume of alveolar lavage fluid. The ratio of activity of XO to activity of xanthine dehydrogenase in s-BALF increased from 0.15 +/- 0.05 (control; no infection) to 1.06 +/- 0.13 on day 6 after viral infection. Increased levels of various adenosine catabolites (i.e., inosine, hypoxanthine, xanthine, and uric acid) in serum and s-BALF were confirmed. We also identified O2- generation from XO in s-BALF obtained on days 6 and 8 after infection, and the generation of O2- was enhanced remarkably in the presence of adenosine. Lastly, treatment with allopurinol (an inhibitor of XO) and with chemically modified superoxide dismutase (a scavenger of O2-) improved the survival rate of influenza virus-infected mice. These results indicate that generation of oxygen-free radicals by XO, coupled with catabolic supply of hypoxanthine from adenosine catabolism, is a pathogenic principle in influenza virus infection in mice and that a therapeutic approach by elimination of oxygen radicals thus seems possible.

Authors

T Akaike, M Ando, T Oda, T Doi, S Ijiri, S Araki, H Maeda

Amplification of T cell blastogenic responses in healthy individuals and patients with acquired immunodeficiency syndrome.

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Abstract

Human immunodeficiency virus (HIV) infection is associated with a profound impairment of T cell function. Hence, enhancement of T cell reactivity to viral and bacterial antigens is important in the treatment of patients with AIDS. To develop tools for amplifying T cell reactivity, we have immunized mice with human helper T cell clones and selected monoclonal antibodies (MAbs) that enhance in vitro blastogenic responses. MAb NDA5, which recognizes the leukocyte common antigen CD45, amplifies human T cell responses to mitogens and soluble antigens including HIV-1 glycoprotein (gp)-120 and peptides derived from the HIV-1 gp-120 sequence. In the presence of MAb NDA5, peripheral blood mononuclear cells (PBMC) from healthy, HIV-1-seronegative individual displayed augmented blastogenic responses to HIV-1 gp-120 and to HIV-1 gp-120 synthetic peptides. In vitro memory responses to various vaccines and to alloantigens were also enhanced in cultures with MAb. Similarly, the response of PBMC from AIDS patients to pokeweed mitogen, HIV-1 gp-120, and tetanus toxoid was enhanced with MAb NDA5. The finding that the in vitro immune response of patients with AIDS can be amplified with MAb NDA5, suggests that the in vivo immune response of immunodeficient individuals can also be enhanced.

Authors

P E Harris, K Strba-Cechova, P Rubinstein, D Mann, D W King, N Suciu-Foca

Calcium oscillations index the extent of calcium loading and predict functional recovery during reperfusion in rat myocardium.

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Abstract

Delayed recovery of contractile function after myocardial ischemia may be due to prolonged recovery of high-energy phosphates, persistent acidosis, increased inorganic phosphate, and/or calcium loading. To examine these potential mechanisms, metabolic parameters measured by 31P nuclear magnetic resonance spectroscopy, and spontaneous diastolic myofilament motion caused by sarcoplasmic reticulum-myofilament calcium cycling indexed by the scattered light intensity fluctuations (SLIF) it produces in laser beam reflected from the heart, were studied in isolated atrioventricularly blocked rat hearts (n = 10) after 65 min of ischemia at 30 degrees C. All metabolic parameters recovered to their full extent 5 min after reperfusion. Developed pressure evidenced a small recovery but then fell abruptly. This was accompanied by an increase in end diastolic pressure to 37 +/- 5 mm Hg and a fourfold increase in SLIF, to 252 +/- 58% of baseline. In another series of hearts initial reperfusion with calcium of 0.08 mM prevented the SLIF rise and resulted in improved developed pressure (74 +/- 3% vs. 39 +/- 13% of control), and lower cell calcium (5.9 +/- 3 vs. 10.3 +/- 1.4 mumol/g dry wt). Thus, during reperfusion, delayed contractile recovery is not associated with delayed recovery of pH, inorganic phosphate, or high-energy phosphates and can be attributed, in part, to an adverse effect of calcium loading which can be indexed by increased SLIF occurring at that time.

Authors

R G Weiss, G Gerstenblith, E G Lakatta

Expression of two "immediate early" genes, Egr-1 and c-fos, in response to renal ischemia and during compensatory renal hypertrophy in mice.

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Abstract

To identify specific genetic regulatory mechanisms associated with renal ischemia, we measured the accumulation of Egr-1 and c-fos mRNAs in the mouse kidney after occlusion of the renal artery and reperfusion. At 1 h after right nephrectomy and arterial occlusion of the contralateral kidney for 10 or 30 min, Egr-1 mRNA levels were three to five times greater in these kidneys as compared with those in control animals that had sustained unilateral nephrectomy alone and were much greater than levels in the normal organ. Whether ischemia was imposed for 10 or for 30 min, renal Egr-1 mRNA contents were equivalent and remained elevated after 24 h of reperfusion subsequent to 30 min of ischemia. Although c-fos mRNA also accumulated in response to ischemia and reperfusion, the pattern differed from that of Egr-1 in that c-fos mRNA content varied with the duration of ischemia and was undetectable 24 h after injury. Contralateral nephrectomy was not necessary to see the marked accumulation of Egr-1 and c-fos mRNAs with unilateral ischemia. Reflow was necessary, however, since only minimal sequence accumulation occurred by the end of the ischemic period. After left uninephrectomy alone, Egr-1 mRNA levels in the remaining kidney were maximal 30 min after surgery, but were not detectable thereafter; c-fos mRNA levels did not change after unilateral nephrectomy. Differential expression of early growth-related genes implicated in transcriptional activation may influence tissue recovery after renal ischemia.

Authors

A J Ouellette, R A Malt, V P Sukhatme, J V Bonventre

Lipoxin formation during human neutrophil-platelet interactions. Evidence for the transformation of leukotriene A4 by platelet 12-lipoxygenase in vitro.

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Abstract

Human neutrophils from peripheral blood may physically interact with platelets in several settings including hemostasis, inflammation, and a variety of vascular disorders. A role for lipoxygenase (LO)-derived products has been implicated in each of these events; therefore, we investigated the formation of lipoxins during coincubation of human neutrophils and platelets. Simultaneous addition of FMLP and thrombin to coincubations of these cells led to formation of both lipoxin A4 and lipoxin B4, which were monitored by reversed-phase high pressure liquid chromatography. Neither stimulus nor cell type alone induced the formation of these products. When leukotriene A4 (LTA4), a candidate for the transmitting signal, was added to platelets, lipoxins were formed. In cell-free 100,000 g supernatants of platelet lysates, which displayed 12-LO activity, LTA4 was also transformed to lipoxins. Platelet formation of lipoxins was inhibited by the LO inhibitor esculetin and partially sensitive to chelation of Ca2+, while neither acetylsalicylic acid nor indomethacin significantly inhibited their generation. In contrast, neutrophils did not transform LTA4 to lipoxins. Cell-free 100,000 g supernatants of neutrophil lysates converted LTA4 to LTB4. These results indicate that neutrophil-platelet interactions can lead to the formation of lipoxins from endogenous sources and provide a role for platelet 12-LO in the formation of lipoxins from LTA4.

Authors

C N Serhan, K A Sheppard

Dihydropyridine receptor gene expression is regulated by inhibitors of myogenesis and is relatively insensitive to denervation.

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Abstract

To evaluate developmental and physiological signals that may influence expression of the dihydropyridine-sensitive "slow" Ca2+ channel, we analyzed dihydropyridine receptor (DHPR) mRNA abundance in mouse skeletal muscle. Using synthetic oligonucleotide probes corresponding to the rabbit skeletal muscle DHPR, a 6.5 kb DHPR transcript was identified in postnatal skeletal muscle and differentiated C2 or BC3H1 myocytes, but not cardiac muscle or brain. DHPR gene expression was reversibly suppressed by 0.4 nM transforming growth factor beta-1 or by transfection with a mutant c-H-ras allele, nominal inhibitors of myogenesis that block the appearance of slow channels and DHPR. In contrast, both BC3H1 and C2 myocytes containing the activated ras vector expressed the gene encoding the nicotinic acetylcholine receptor delta subunit, demonstrating that not all muscle-specific genes are extinguished by ras. Denervation stimulated DHPR gene expression less than 0.6-fold, despite 8-fold upregulation of delta-subunit mRNA and reciprocal effects on the skeletal and cardiac alpha-actin genes. Thus, DHPR gene induction is prevented by inhibitors of other muscle-specific genes, whereas, at most, relatively small changes in DHPR mRNA abundance occur during adaptation to denervation.

Authors

H T Shih, M S Wathen, H B Marshall, J M Caffrey, M D Schneider

Endothelin-1 stimulates contraction of rat glomerular mesangial cells and potentiates beta-adrenergic-mediated cyclic adenosine monophosphate accumulation.

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Abstract

The newly isolated peptide, endothelin-1 (ET-1), is a potent pressor agent that reduces GFR and the glomerular ultrafiltration coefficient. Recent evidence demonstrates that ET-1 mobilizes intracellular Ca2+ [( Ca2+]i) in glomerular mesangial cells by activating the phosphoinositide cascade. The present experiments were designed to examine whether ET-1 stimulates mesangial cell contraction and regulates the synthesis of PGE2 and cAMP, which dampen vasoconstrictor-induced mesangial contraction. ET-1 (greater than or equal to 1 nM) reduced the cross-sectional area of rat mesangial cells cultured on three-dimensional gels of collagen type I. ET-1 also caused complex rearrangements of F-actin microfilaments consistent with a motile response. Contraction in response to ET-1 occurred only at concentrations that activate phospholipase C, and contraction was unaffected by blockade of dihydropyridine-sensitive Ca2+ channels. Elevation of [Ca2+]i with ionomycin, to equivalent concentrations of [Ca2+]i achieved with ET-1, also reduced mesangial cell cross-sectional area. ET-1 (0.1 microM) also evoked [3H]arachidonate release and a fivefold increase in PGE2 synthesis as well as increased synthesis of PGF2 alpha and small changes of TXB2. ET-1 caused a minor increase in intracellular cAMP accumulation only in the presence of 3-isobutyl-1-methylxanthine. ET-1 also amplified cAMP production in response to isoproterenol. TPA and ionomycin, alone and in combination, failed to mimic the potentiating effect of ET-1; however, indomethacin blocked ET-1-induced potentiation of isoproterenol-stimulated cAMP, which was restored by addition of exogenous 10 nM PGE2. Thus the present data demonstrate that ET-1 stimulates mesangial cell contraction via pharmacomechanical coupling and activates phospholipase A2 to produce PGE2, PGF2 alpha, and TXB2. ET-1 also amplified beta adrenergic-stimulated cAMP accumulation by a PGE2-dependent mechanism.

Authors

M S Simonson, M J Dunn

Heterogeneity in hormone responses and patterns of collagen synthesis in cloned dermal fibroblasts.

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Abstract

Fibroblasts cultured from normal human dermis are heterogeneous with respect to growth kinetics, synthetic function, and morphologic features. There are many examples of clonal heterogeneity in apparently homogeneous connective tissue cell populations, and it has been suggested that selection of cell populations with particular phenotypic features is the basis for the development of pathologic connective tissue changes in inflammatory disorders. In these studies we report characterization of the pattern of matrix biosynthesis and responses to hormones in cells cloned from normal human dermis. The results indicate that cloned dermal fibroblasts are heterogeneous with respect to synthesis of collagens as well as their responses to prostaglandin E2 and parathyroid hormone. Selective expansion of clonal populations with unique patterns of matrix synthesis and cell surface receptors could provide the basis for abnormal connective tissue remodeling in certain pathologic states.

Authors

S R Goldring, M L Stephenson, E Downie, S M Krane, J H Korn

Measurement of very low density and low density lipoprotein apolipoprotein (Apo) B-100 and high density lipoprotein Apo A-I production in human subjects using deuterated leucine. Effect of fasting and feeding.

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Abstract

Six normolipidemic male subjects, after an 8-h overnight fast, were given a bolus injection and then a 15-h constant intravenous infusion of [D3]L-leucine. Subjects were studied in the fasted state and on a second occasion in the fed state (small, physiological meals were given every hour for 15 h). Apolipoproteins were isolated by preparative gradient gel electrophoresis from plasma lipoproteins separated by sequential ultracentrifugation. Incorporation of [D3]L-leucine into apolipoproteins was monitored by negative ionization, gas chromatography-mass spectrometry. Production rates were determined by multiplying plasma apolipoprotein pool sizes by fractional production rates (calculated as the rate of isotopic enrichment [IE] of each protein as a fraction of IE achieved by VLDL (d less than 1.006 g/ml) apo B-100 at plateau. VLDL apo B-100 production was greater, and LDL (1.019 less than d less than 1.063 g/ml) apo B-100 production was less in the fed compared with the fasted state (9.9 +/- 1.7 vs. 6.4 +/- 1.7 mg/kg per d, P less than 0.01, and 8.9 +/- 1.2 vs. 13.1 +/- 1.2 mg/kg per d, P less than 0.05, respectively). No mean change was observed in high density lipoprotein apo A-I production. We conclude that: (a) this stable isotope, endogenous-labeling technique, for the first time allows for the in vivo measurement of apolipoprotein production in the fasted and fed state; and (b) since LDL apo B-100 production was greater than VLDL apo B-100 production in the fasted state, this study provides in vivo evidence that LDL apo B-100 can be produced independently of VLDL apo B-100 in normolipidemic subjects.

Authors

J S Cohn, D A Wagner, S D Cohn, J S Millar, E J Schaefer

Identification of the cutaneous basement membrane zone antigen and isolation of antibody in linear immunoglobulin A bullous dermatosis.

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Abstract

Linear IgA bullous dermatosis (LABD) is a rare blistering skin disease characterized by basement membrane zone deposition of IgA. This study identifies a tissue antigen detected by patient serum and then isolates the autoantibody using epidermis and protein bands blotted on nitrocellulose as immunoabsorbents. Sera from 10 patients (9 with cutaneous disease and 1 with cicatrizing conjunctivitis) were evaluated. Indirect immunofluorescence revealed an IgA anti-basement membrane antibody in 6 of 10 sera with monkey esophagus substrate and 9 of 10 sera with human epidermal substrate. Immunoblotting was performed on epidermal and dermal extracts prepared from skin separated at the basement membrane zone with either sodium chloride or EDTA. Saline-separated skin expressed a 97-kD band in dermal extract alone that was recognized by 4 of 10 sera. EDTA-separated skin expressed the 97-kD band in both epidermal (4 of 10 sera) and dermal (6 of 10 sera) extract. Immunoabsorption of positive sera with epidermis purified an IgA antibody that reacted uniquely with the 97-kD band. In addition, IgA antibody bound to nitrocellulose was eluted from the 97-kD band and found to uniquely bind basement membrane zone. It is likely that the 97-kD protein identified by these techniques is responsible for basement membrane binding of IgA in LABD.

Authors

J J Zone, T B Taylor, D P Kadunce, L J Meyer

Ultrastructural localization of cytochrome b in the membranes of resting and phagocytosing human granulocytes.

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Abstract

Affinity-purified rabbit anti-neutrophil cytochrome b light or heavy chain antibodies were used to immunocytochemically and biochemically localize cytochrome b in neutrophils and eosinophils. The antibodies were monospecific, recognizing polypeptides of 91 and 22 kD, respectively, on Western blots of whole neutrophil extracts. The antibodies were used in Western blot analysis of subcellular fractions of purified neutrophils to confirm that the distribution of cytochrome b spectral absorbance matched that of the two subunits. Thin sections of cryofixed, molecular distillation-dried granulocytes were labeled with the anti-cytochrome b antibodies, followed by incubation with biotin-conjugated secondary antibody, and final labeling with streptavidin-conjugated colloidal gold. Electron microscopy revealed that the cytochrome b light and heavy chains were localized primarily (80%) to 0.1-0.2-micron round or elliptical granule-like structures in neutrophils and 0.4-0.5-micron granules in eosinophils. Approximately 20% of the cytochrome b was localized to the surface, confirming the subcellular fractionation studies. Double staining experiments on the neutrophils, using polyclonal rabbit anti-lactoferrin antibody, indicated that the cytochrome-bearing structures also contained lactoferrin and thus were specific granules. When the analysis was performed on neutrophils that had phagocytosed Staphylococcus aureus, cytochrome b was found in the phagosomal membrane adjoining the bacterial cell wall.

Authors

A J Jesaitis, E S Buescher, D Harrison, M T Quinn, C A Parkos, S Livesey, J Linner

Suppression of ventricular arrhythmias in man by d-propranolol independent of beta-adrenergic receptor blockade.

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Abstract

To investigate the mechanisms of ventricular arrhythmia suppression by propranolol, we determined the antiarrhythmic efficacy of d-propranolol in 10 patients with frequent ventricular ectopic depolarizations (VEDs) and nonsustained ventricular tachycardia. After an initial placebo phase, 40 mg d-propranolol was administered orally every 6 h with dosage increased every 2 d until arrhythmia suppression (greater than or equal to 80% VED reduction), intolerable side effects, or a maximal dosage (1,280 mg/d) was reached. Response was verified by documenting return of arrhythmia during a final placebo phase. Arrhythmia suppression occurred in six patients while two more had partial responses. Effective dosages were 320-1,280 mg/d (mean 920 +/- 360, SD) of d-propranolol with corresponding plasma concentrations of 60-2,280 ng/ml (mean 858 +/- 681). For the entire group, the QTc interval shortened by 4 +/- 4% (P = 0.03). Arrhythmia suppression was accompanied by a reduction in peak heart rate during exercise of 0-29%. To determine whether arrhythmia suppression could be attributed to beta-blockade, racemic propranolol was then administered in dosages producing the same or greater depression of exercise heart rate. In 3/8 patients, arrhythmias were not suppressed by racemic propranolol indicating that d-propranolol was effective via a non-beta-mediated action. By contrast, in 5/8 patients racemic propranolol also suppressed VEDs. We conclude that propranolol suppresses ventricular arrhythmias by both beta- and non-beta-adrenergic receptor-mediated effects.

Authors

K T Murray, C Reilly, R P Koshakji, D M Roden, M D Lineberry, A J Wood, L A Siddoway, J T Barbey, R L Woosley

Phosphorus-31 nuclear magnetic resonance analysis of transient changes of canine myocardial metabolism in vivo.

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Abstract

The time course of the relative myocardial phosphocreatine and adenosine triphosphate contents (PCr/ATP) during step changes in heart rate in vivo was studied in 14 dogs using 31P nuclear magnetic resonance (NMR) to determine if transient changes in the high energy phosphates occur with changes in cardiac work. Coronary sinus blood flow (CF), oxygen consumption (MVO2), and NMR data were simultaneously measured during brief (approximately 3 min), paced increases in heart rate in these open chest animals. 31P spectra were collected with a time resolution of 15-16 s (PCr signal to noise 22-41:1). Paced tachycardia associated with increased CF and MVO2 had no significant transient or sustained effect on PCr/ATP. Higher heart rates, associated with decreased CF and blood pressure, caused rapid decreases of PCr/ATP that were reversible upon return to control rates. These data indicate that there are no transient changes in 31P metabolites (on a 15-16-s time base) during step changes in cardiac work associated with increased CF. This lack of change demonstrates that ATP hydrolysis and production are closely matched and that the feedback mechanism linking these processes occurs rapidly with no detectable transient change in the phosphate metabolites. In contrast, when the CF response to tachycardia is insufficient PCr is quickly depleted. This latter result suggests that the PCr/ATP ratio may be a sensitive, rapidly responding indicator of coronary supply/demand mismatching in vivo.

Authors

F W Heineman, R S Balaban

Separation of sublethal and lethal effects of the bactericidal/permeability increasing protein on Escherichia coli.

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Abstract

Binding of the bactericidal/permeability increasing protein (BPI) of granulocytes to Escherichia coli promptly produces several discrete outer envelope alterations and growth arrest without major impairment of bacterial structure or biosynthetic capabilities, raising the question whether these early effects of BPI are sufficient to cause bacterial death. In this study, the bactericidal action of BPI was examined more closely. We have found that bovine or human serum albumin blocks bacterial killing without preventing BPI binding or an increase in outer membrane permeability. Moreover, addition of serum albumin after BPI results in growth resumption without displacement of bound BPI and without (early) repair of the envelope alterations. These effects are opposite to those produced by Mg2+ (80 mM), which displaces greater than 85% of bound BPI and rapidly initiates outer envelope repair without restoration of bacterial growth. The extent of rescue by serum albumin depends on the time and pH of preincubation of BPI with E. coli: e.g., for E. coli J5 treated with human BPI, t1/2 = 79 min at pH 7.4 and 10 min at pH 6.0. The serum albumin effects on BPI action are the same in wild-type E. coli and in a mutant strain lacking an activatable phospholipase, indicating that serum albumin does not act by sequestering membrane-damaging products of bacterial phospholipid hydrolysis. The progression from reversible to irreversible growth arrest, revealed by the subsequent addition of serum albumin at different times, is paralleled by a decrease in amino acid uptake and an increase in the permeability of the cytoplasmic membrane to o-nitrophenyl-beta-D-galactoside. These findings demonstrate at least two stages in the action of BPI: (a) an early, reversible, sublethal stage in which BPI has effects on the outer envelope and causes growth arrest, and (b) time- and pH-dependent progression to a lethal stage, apparently involving cytoplasmic membrane damage, possibly caused by penetration of a small subpopulation of BPI.

Authors

B A Mannion, J Weiss, P Elsbach

Plasma native and peptidase-derivable Met-enkephalin responses to restraint stress in rats. Adaptation to repeated restraint.

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Abstract

Met-enkephalin and related proenkephalin A-derived peptides circulate in plasma at picomolar concentration as free, native pentapeptide and at nanomolar concentration in cryptic forms. We have optimized conditions for measurement of immunoreactive Met-enkephalin in plasma and for generation by trypsin and carboxypeptidase B of much greater amounts of total peptidase-derivable Met-enkephalin in plasma of rats, dogs, and humans. Free Met-enkephalin (11 pM) is constituted by native pentapeptide and its sulfoxide. Characterization of plasma total Met-enkephalin derived by peptidic hydrolysis revealed a small amount (38 pM) of Met-enkephalin associated with peptides of molecular mass less than 30,000 D, and probably derived from proenkephalin A, but much larger amounts of Met-enkephalin associated with albumin (1.2 nM) and with a globulin-sized protein (2.8 nM). Thus, plasma protein precursors for peptidase-derivable Met-enkephalin differ structurally and chemically from proenkephalin A. Met-enkephalin generated from plasma by peptidic hydrolysis showed naloxone-reversible bioactivity comparable to synthetic Met-enkephalin. Prolonged exposure of adult, male rats to restraint stress produced biphasic plasma responses, with peaks occurring at 30 s and 30 min in both free native and total peptidase-derivable Met-enkephalin. Repeated daily exposure to this 30-min stress resulted in adaptive loss of responses of both forms to acute restraint. Initial plasma responses of Met-enkephalin paralleled those of epinephrine and norepinephrine, but subsequently showed divergence of response. In conclusion, Met-enkephalin circulates in several forms, some of which may be derived from proteins other than proenkephalin A, and plasma levels of both free native, and peptidase-derivable Met-enkephalin are modulated physiologically.

Authors

K Pierzchala, G R Van Loon

Regulation of 3-hydroxy-3-methylglutaryl-coenzyme A reductase activity in murine epidermis. Modulation of enzyme content and activation state by barrier requirements.

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Abstract

Epidermal cholesterol biosynthesis is regulated by barrier function. We quantitated the amount and activation state (phosphorylation-dephosphorylation) of the rate-limiting enzyme, 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase, in epidermis before and after barrier disruption. In murine epidermis we found high enzyme activity (1.75 +/- 0.02 nmol/min per mg protein). After acute barrier disruption, enzyme activity began to increase after 1.5 h, reaching a maximum increase by 2.5 h, and returned to normal by 15 h. Chronic barrier disruption increased total enzyme activity by 83%. In normal epidermis, measurement of HMG CoA reductase activity in microsomes isolated in NaF- vs. NaCl-containing buffers demonstrated that 46 +/- 2% of the enzyme was in the active form. After acute or chronic barrier disruption, a marked increase in the percentage of HMG CoA reductase in the active form was observed. Acute disruption increased enzyme activation state as early as 15 min, reaching a maximum after 2.5 h, with an increase still present at 15 h, indicating that changes in activation state had a close temporal relationship with barrier function. Increases in total HMG CoA reductase activity occurred only after profound barrier disruption, whereas changes in activation state occur with lesser degrees of barrier disruption. Artificial correction of barrier function prevented the increase in total HMG CoA reductase activity, and partially prevented the increase in enzyme activation. These results show that barrier requirements regulate epidermal cholesterol synthesis by modulating both the HMG CoA reductase amount and activation state.

Authors

E Proksch, P M Elias, K R Feingold

Postprandial plasma retinyl ester response is greater in older subjects compared with younger subjects. Evidence for delayed plasma clearance of intestinal lipoproteins.

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Abstract

Postprandial vitamin A and intestinal lipoprotein metabolism was studied in 86 healthy men and women, aged 19-76 yr. Three independent experiments were carried out. In the first experiment, a supplement dose of vitamin A (3,000 retinol equivalents [RE]) was given without a meal to 59 subjects, aged 22-76 yr. In the second experiment, 20 RE/kg body wt was given with a fat-rich meal (1 g fat/kg body wt) to seven younger subjects (aged less than 50 yr) and seven older subjects (aged greater than or equal to 50 yr). In both experiments, postprandial plasma retinyl ester response increased significantly with advancing age (P less than 0.05). In the third experiment, retinyl ester-rich plasma was infused intravenously into nine young adult subjects (aged 18-30 yr) and nine elderly subjects (aged greater than or equal to 60 yr), and the rate of retinyl ester disappearance from plasma during the subsequent 3 h was determined. Mean (+/- SE) plasma retinyl ester residence time was 31 +/- 4 min in the young adult subjects vs. 57 +/- 8 min in the elderly subjects (P less than 0.05). These data are consistent with the concept that increased postprandial plasma retinyl ester concentrations in older subjects are due to delayed plasma clearance of retinyl esters in triglyceride-rich lipoproteins of intestinal origin.

Authors

S D Krasinski, J S Cohn, E J Schaefer, R M Russell

Adrenergic regulation of lipolysis in situ at rest and during exercise.

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Abstract

The adrenergic regulation of lipolysis was investigated in situ at rest and during standardized bicycle exercise in nonobese healthy subjects, using microdialysis of the extracellular space in subcutaneous adipose tissue. The glycerol concentration was about two times greater in adipose tissue than in venous blood. At rest, the glycerol concentration in adipose tissue was rapidly increased by 100% (P less than 0.01) after the addition of phentolamine to the ingoing perfusate, whereas addition of propranolol did not alter the adipose tissue glycerol level. Glycerol in adipose tissue and plasma increased during exercise and decreased in the postexercise period. Propranolol in the perfusate almost completely inhibited the increase in the tissue dialysate glycerol during the exercise-postexercise period. Phentolamine, however, was completely ineffective in this respect. During exercise, the lipolytic activity was significantly more marked in abdominal than in gluteal adipose tissue; this was much more apparent in women than in men. Thus, in vivo lipolysis in subcutaneous adipose tissue is regulated by different adrenergic mechanisms at rest and during exercise. Alpha-adrenergic inhibitory effects modulate lipolysis at rest, whereas beta-adrenergic stimulatory effects modulate lipolysis during exercise. In addition, regional differences in lipolysis are present in vivo during exercise, which seem governed by factors relating to sex.

Authors

P Arner, E Kriegholm, P Engfeldt, J Bolinder

In vitro autoantibody production by normal adult and cord blood B cells.

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Abstract

To investigate the repertoire of autoantibodies in humans, anti-DNA and rheumatoid factor (RF) production in vitro was assessed in cultures of adult peripheral blood B cells and neonatal umbilical venous blood B cells. B cells were stimulated under various culture conditions, using an immobilized monoclonal anti-CD3 antibody and adult T cells or Staphylococcus aureus (SA) in the presence or absence of adult T cells or factors derived from mitogen-stimulated adult T cells as polyclonal B cell activators. Total IgM, as well as IgM anti-DNA and RF, were assessed by ELISA. Total IgM production was induced from adult and neonatal B cells with SA plus T cell factors, as well as anti-CD3-stimulated T cells. RF was induced from adult and cord blood B cells by either mode of stimulation, whereas significant anti-DNA production was observed only when B cells were stimulated with anti-CD3-activated T cells. These results confirm the presence of B cell precursors for autoantibodies in the preimmune as well as normal adult repertoire, and indicate that the production of anti-DNA and RF appears to be regulated independently.

Authors

D S Pisetsky, D F Jelinek, L M McAnally, C F Reich, P E Lipsky

Azurocidin and a homologous serine protease from neutrophils. Differential antimicrobial and proteolytic properties.

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Abstract

Two 29-kD polypeptides, azurocidin and p29b, were purified to homogeneity from human neutrophils by acid extraction of azurophil granule membrane-associated material followed by gel filtration and reverse-phase chromatography. Azurocidin and p29b share NH2-terminal sequence homology with each other as well as with elastase, cathepsin G, and other serine proteases. p29b bound [3H]diisopropyl fluorophosphate and hydrolyzed elastin, casein, and hemoglobin. A peptide substrate for p29b could not be identified. Azurocidin neither bound [3H]diisopropyl fluorophosphate nor hydrolyzed any of the proteins, peptides, or esters tested. In microbicidal assays, purified azurocidin was comparable to p29b in activity against Escherichia coli, Streptococcus faecalis, and Candida albicans. The antimicrobial activity of azurocidin was enhanced under mildly acidic conditions, but was inhibited in a dose-dependent manner by NaCl, CaCl2, or serum. Immunoblot analysis with monospecific antibodies localized greater than 90% of the azurocidin and greater than 75% of the p29b to azurophil granule-rich fractions of PMN lysates. Immunoelectron microscopy confirmed the localization of azurocidin to the azurophil granules. Azurocidin associated with the azurophil granule membrane, but did not appear to be an integral membrane protein. Thus, azurocidin and p29b are members of a family of serine protease homologs stored in azurophil granules and may play a role in inflammatory and antimicrobial processes involving PMN.

Authors

D Campanelli, P A Detmers, C F Nathan, J E Gabay

Differential effects of the various isoforms of platelet-derived growth factor on chemotaxis of fibroblasts, monocytes, and granulocytes.

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Abstract

The chemotactic activities of three different isoforms of platelet-derived growth factor (PDGF) on fibroblasts, monocytes, and granulocytes of human origin were investigated. PDGF-AB and PDGF-BB induced strong, dose-dependent responses in both fibroblasts and monocytes, whereas PDGF-AA did not stimulate chemotaxis of these cell types. Instead, PDGF-AA inhibited the chemotactic activity of PDGF-AB and PDGF-BB on fibroblasts and monocytes. However, PDGF-AA was not able to block monocyte chemotaxis induced by FMLP. In contrast, in granulocytes, dose-dependent chemotactic responses were obtained with all three isoforms of PDGF. All isoforms gave maximal responses at concentrations between 5 and 20 ng/ml. At higher concentrations the migration was reduced. Reduction and alkylation of the PDGF molecule, which leads to loss of the mitogenic activity, also caused a loss of the chemotactic activities for all three cell types. The data suggest that the various isoforms of PDGF stimulate and inhibit chemotaxis in an isoform- and cell type-specific manner.

Authors

A Siegbahn, A Hammacher, B Westermark, C H Heldin

L-histidine augments the response to 1-deamino-8-D-arginine vasopressin in Brattleboro homozygous (di/di) rats.

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Abstract

Studies in vitro have shown that L-histidine increases the hydroosmotic response to vasopressin. We examined whether this phenomenon occurs also in vivo. Homozygous Brattleboro rats (di/di) were fed a regular diet (0.5% histidine) or a diet enriched with histidine and received 1 ng of 1-deamino-8-D-arginine vasopressin (dDAVP) daily. Addition of histidine (1% by weight) increased post-dDAVP urine osmolality to a level higher than that of control (502 +/- 62 vs. 316 +/- 36 mosmol/kg, P less than 0.05). Similar results were seen with 3.0% and 5.5% dietary histidine. There were significant increases in free-water reabsorption and in the ratio of free-water reabsorption to osmolar clearance, but no difference in osmolal clearance. No significant effect was found with supplemental histidine of 0.5% or less. The cause for these findings appears not to be the metabolism of histidine, since the nonmetabolizable D-histidine had a significant, albeit smaller, effect, and the isonitrogenous addition of albumin, alanine, arginine, or glutamine was ineffective. In part, histidine may operate by increasing cAMP since the renal cAMP content in response to vasopressin is increased in histidine-fed rats (13.1 +/- 0.9 vs. 9.8 +/- 0.8 nmol/g dry weight, P less than 0.01). The role of prostaglandins appears less clear. Histidine greatly decreased urinary PGE2 during baseline (1.5 +/- 0.3 vs. 7.0 +/- 2.3 micrograms/mg creatinine, P less than 0.001), but it profoundly augmented urinary prostaglandin excretion after dDAVP stimulation (40.0 +/- 4.2 vs. 7.0 +/- 2.0 micrograms/mg creatinine, P less than 0.001).

Authors

G Charnogursky, A M Moses, R Coulson, M Bernstein, C P Carvounis

Elevated glucose promotes generation of endothelium-derived vasoconstrictor prostanoids in rabbit aorta.

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Abstract

The effects of glucose on endothelium-dependent responses and vasoactive prostanoid production were determined by incubating isolated rabbit aortae in control (5.5 or 11 mM) or elevated (44 mM) glucose for 6 h to mimic euglycemic and hyperglycemic conditions. Rings of aortae incubated in elevated glucose, contracted submaximally by phenylephrine, showed significantly decreased endothelium-dependent relaxations induced by acetylcholine compared with the aortae incubated in control glucose. Treatment with indomethacin, a cyclooxygenase inhibitor, or SQ29548, a prostaglandin H2/thromboxane A2 receptor antagonist, restored acetylcholine relaxations of rings in elevated glucose to normal, while these agents had no effect on the relaxation of rings incubated in control glucose. Aortae incubated with mannose (44 mM) as a hyperosmotic control relaxed to acetylcholine normally. The relaxations in response to A23187 and sodium nitroprusside were not different between rings exposed to control and elevated glucose. Radioimmunoassay measurements showed a significant increase in acetylcholine-stimulated release of thromboxane A2 and prostaglandin F2 alpha in aortae with, but not without endothelium incubated with elevated, but not with control glucose. Thus a possible mechanism for endothelium dysfunction in diabetes mellitus is the hyperglycemia-induced increased generation of endothelium-derived vasoconstrictor prostanoids.

Authors

B Tesfamariam, M L Brown, D Deykin, R A Cohen

Familial hypobetalipoproteinemia caused by a mutation in the apolipoprotein B gene that results in a truncated species of apolipoprotein B (B-31). A unique mutation that helps to define the portion of the apolipoprotein B molecule required for the formation of buoyant, triglyceride-rich lipoproteins.

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Abstract

Apolipoprotein B-100 has a crucial structural role in the formation of VLDL and LDL. Familial hypobetalipoproteinemia, a syndrome in which the concentration of LDL cholesterol in plasma is abnormally low, can be caused by mutations in the apo B gene that prevent the translation of a full-length apo B-100 molecule. Prior studies have revealed that truncated species of apo B [e.g., apo B-37 (1728 amino acids), apo B-46 (2057 amino acids)] can occasionally be identified in the plasma of subjects with familial hypobetalipoproteinemia; in each of these cases, the truncated apo B species has been a prominent protein component of VLDL. In this report, we describe a kindred with hypobetalipoproteinemia in which the plasma of four affected heterozygotes contained a unique truncated apo B species, apo B-31. Apolipoprotein B-31 is caused by the deletion of a single nucleotide in the apo B gene, and it is predicted to contain 1425 amino acids. Apolipoprotein B-31 is the shortest of the mutant apo B species to be identified in the plasma of a subject with hypobetalipoproteinemia. In contrast to longer truncated apo B species, apo B-31 was undetectable in the VLDL and the LDL; however, it was present in the HDL fraction and the lipoprotein-deficient fraction of plasma. The density distribution of apo B-31 in the plasma suggests the possibility that the amino-terminal 1425 amino acids of apo B-100 are sufficient to permit the formation and secretion of small, dense lipoproteins but are inadequate to support the formation of the more lipid-rich VLDL and LDL particles.

Authors

S G Young, S T Hubl, R S Smith, S M Snyder, J F Terdiman

Counterregulatory effects of interferon-gamma and endotoxin on expression of the human C4 genes.

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Abstract

Susceptibility to autoimmune disease is associated with null alleles at one of the two genetic loci encoding complement protein C4. These two genetic loci, C4A and C4B, are highly homologous in primary structure but encode proteins with different functional activities. Expression of C4A and C4B genes is regulated by IFN-gamma in human hepatoma cells and in murine fibroblasts transformed with the respective genes. In these cell lines, IFN-gamma has a significantly greater and longer-lasting effect on expression of C4A than that of C4B. In this study we examined synthesis and regulation of C4A and C4B in peripheral blood monocytes from normal, C4A-null, and C4B-null individuals. Synthesis of C4 in human peripheral blood monocytes decreases during time in culture. IFN-gamma mediates a concentration- and time-dependent increase in steady-state levels of C4 mRNA and a corresponding increase in synthesis of C4 in normal human monocytes. LPS decreases monocyte C4 expression and completely abrogates the effect of IFN-gamma on the expression of this gene. In contrast, LPS and IFN-gamma have a synergistic effect in upregulating expression of another class III MHC gene product, complement protein factor B. The effect of LPS on constitutive and IFN-gamma-regulated C4 synthesis is probably not mediated via release of endogenous monokines IL-1 beta, TNF-alpha, or IL-6. Synthesis of C4, and regulation of its synthesis by IFN-gamma and LPS, are similar in normal, C4A-, and C4B-null individuals. These results demonstrate the synthesis of C4 at extrahepatic sites and tissue-specific regulation of C4 gene expression.

Authors

J Kulics, H R Colten, D H Perlmutter

Complex regulation of calcium current in cardiac cells. Dependence on a pertussis toxin-sensitive substrate, adenosine triphosphate, and an alpha 1-adrenoceptor.

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Abstract

We investigated regulation of the cardiac L-type calcium channel by intracellular ATP and by alpha 1-adrenergic agonism using single adult guinea pig ventricular cells and the whole-cell patch clamp method. Inclusion of 5 mM ATP in the patch clamp pipette prevented calcium current rundown but did not increase the maximal magnitude of the slow inward calcium current (ICa). During beta 1-adrenergic blockade with 10 microM (-)-propranolol, cells preincubated with 1 microgram/ml pertussis toxin for 2-5 h exhibited a rapid twofold increase in ICa after rupture of the membrane patch when 5 mM ATP was present in the patch clamp pipette. In the absence of ATP, the increase in ICa did not occur. In pertussis toxin-treated cells, 100 microM (-)-phenylephrine inhibited the augmentation of ICa. This inhibitory effect was blocked by 100 nM terazosin, a selective alpha 1-antagonist. The inhibitory effect of alpha 1-adrenergic agonism was not mediated by cAMP-dependent phosphodiesterase since incubation with 100 microM (-)-phenylephrine did not augment the activity of this enzyme. We conclude that regulation of the L-type calcium channel in cardiac cells is complex, and is dependent on a pertussis toxin-sensitive substrate, ATP, and an alpha 1-adrenergic receptor. The marked increase in ICa after pertussis toxin treatment in the presence of ATP indicates significant inhibition of ICa by a pertussis toxin substrate, presumably the guanine nucleotide inhibitory protein (Gi) in the basal state. The inhibitory action of (-)-phenylephrine in pertussis toxin-treated cells is consistent with modulation of ICa by an alpha 1-adrenergic receptor not coupled to Gi.

Authors

E C Keung, J S Karliner

Granulocyte-macrophage colony-stimulating factor promotes differentiation and survival of human peripheral blood dendritic cells in vitro.

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Abstract

Interest in human dendritic cells (DC) has been heightened recently by the discovery that this cell type is a primary target of the human immunodeficiency virus, the causative agent of AIDS. DC are bone marrow-derived cells with an extraordinarily potent ability to promote the immunological activity of T lymphocytes. Unfortunately, since DC constitute less than 0.5% of peripheral blood mononuclear cells and die within a few days of their isolation, they are not readily accessible to study. We report here that granulocyte-macrophage colony-stimulating factor (GM-CSF), a cytokine with well-recognized effects on granulocyte and macrophage maturation, profoundly affects the morphology and viability of DC isolated from peripheral blood. GM-CSF not only promotes DC survival but also induces DC differentiation to mobile, reversibly adherent cells with long-branched projections. DC cultured in GM-CSF survive for up to 6 wk and retain their ability to stimulate the proliferation of T cells in allogeneic and autologous mixed leukocyte reactions.

Authors

S Markowicz, E G Engleman

Glucose transporter levels in spontaneously obese (db/db) insulin-resistant mice.

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Abstract

In the present study we examined mRNA and protein levels for the muscle/adipose tissue glucose transporter (GLUT-4) in various tissues of spontaneously obese mice (C57BL/KsJ, db/db) and their lean littermates (db/+). Obese (db/db) mice were studied at 5 wk of age, when they were rapidly gaining weight and were severely insulin resistant, evidenced by hyperglycemia (plasma glucose 683 +/- 60 vs. 169 +/- 4 mg/dl in db/+, P less than 0.05) and hyperinsulinemia (plasma insulin 14.9 +/- 0.53 vs. 1.52 +/- 0.08 ng/ml in db/+, P less than 0.05). The GLUT-4 mRNA was reduced in quadriceps muscle (67.5 +/- 8.5%, P = 0.02), but unaltered in adipose tissue (120 +/- 19%, NS), heart (95.7 +/- 6.1%, NS), or diaphragm (75.2 +/- 12.1%, NS) in obese (db/db) mice relative to levels in lean littermates. The GLUT-4 protein, measured by quantitative immunoblot analysis using two different GLUT-4 specific antibodies, was not different in five insulin-sensitive tissues including diaphragm, heart, red and white quadriceps muscle, and adipose tissue of obese (db/db) mice compared with tissue levels in lean littermates; these findings were consistent when measured relative to tissue DNA levels as an index of cell number. These data suggest that the marked defect in glucose utilization previously described in skeletal muscle of these young obese mice is not due to a decrease in the level of the major muscle glucose transporter. An alternate step in insulin-dependent activation of the glucose transport process is probably involved.

Authors

L Koranyi, D James, M Mueckler, M A Permutt

Acetylation pharmacogenetics. The slow acetylator phenotype is caused by decreased or absent arylamine N-acetyltransferase in human liver.

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Abstract

The biochemical basis underlying the genetic polymorphism of drug N-acetylation was investigated using a combination of in vivo and in vitro assays for arylamine N-acetyltransferase (NAT) activity and content in human liver. The acetylator phenotype of 26 surgical patients was determined using caffeine as an innocuous probe drug by measurement of the 5-acetyl-amino-6-formylamino-3-methyluracil to 1-methylxanthine molar ratio in urine. Liver wedge biopsies from these patients and livers from 24 organ donors were then used for measurement of N-acetyltransferase activity with the substrate sulfamethazine and for quantitation of immunoreactive N-acetyl-transferase protein. In vivo (caffeine metabolites in urine) and in vitro (sulfamethazine acetylation) measures of N-acetyl-transferase activity correlated very highly (r = 0.98). Moreover, in all subjects tested, slow acetylation both in vivo and in vitro was associated with a decrease in the quantity of immunodetectable N-acetyltransferase protein in liver cytosol relative to that seen in cytosols from rapid acetylator livers. Two kinetically distinct enzyme activities, designated NAT-1 and NAT-2, were partially purified from low- and high-activity livers and their relationship to acetylator status was determined. Low acetylation capacity was related to decreases in the liver content of both of these immunologically related proteins. The results demonstrate that genetically defective arylamine N-acetylation is due to a parallel decrease in the quantity of two structurally and functionally similar acetylating enzymes.

Authors

D M Grant, K Mörike, M Eichelbaum, U A Meyer

Amylin secretion from the rat pancreas and its selective loss after streptozotocin treatment.

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Abstract

Amylin, a peptide copackaged with insulin in beta-cell granules, was measured in the effluent of the perfused rat pancreases by means of a newly developed specific radioimmunoassay. Its secretion parallels that of insulin in response to 20 mM glucose, 10 mM arginine, or the combination thereof. The relative molar amount of secreted amylin was estimated to be 25-37% that of insulin. Treatment with a borderline diabetogenic dose of streptozotocin reduced amylin response without significantly changing the insulin response. A severely diabetogenic dose of streptozotocin totally abolished amylin release and markedly reduced insulin release. The selective impairment of amylin secretion in streptozotocin-treated rats could represent an early manifestation of beta-cell depletion or injury.

Authors

A Ogawa, V Harris, S K McCorkle, R H Unger, K L Luskey

Point mutations impairing cell surface expression of the common beta subunit (CD18) in a patient with leukocyte adhesion molecule (Leu-CAM) deficiency.

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Abstract

The leukocyte adhesion molecules CD11a/CD18, CD11b/CD18, and CD11c/CD18 (Leu-CAM) are members of the integrin receptor family and mediate crucial adhesion-dependent functions in leukocytes. The molecular basis for their deficient cell surface expression was sought in a patient suffering from severe and recurrent bacterial infections. Previous studies revealed that impaired cell surface expression of Leu-CAM is secondary to heterogeneous structural defects in the common beta subunit (CD18). Cloning and sequencing of complementary DNA encoding for CD18 in this patient revealed two mutant alleles, each representing a point mutation in the coding region of CD18 and resulting in an amino acid substitution. Each mutant allele results in impaired CD18 expression on the cell surface membrane of transfected COS M6 cells. One substitution involves an arginine residue (Arg593----cysteine) that is conserved in the highly homologous fourth cysteine-rich repeats of other mammalian integrin subfamilies. The other substitution involves a lysine residue (Lys196----threonine) located within another highly conserved region in integrins. These data identify crucial residues and regions necessary for normal cell surface expression of CD18 and possibly other integrin beta subunits and define a molecular basis for impaired cell surface expression of CD18 in this patient.

Authors

M A Arnaout, N Dana, S K Gupta, D G Tenen, D M Fathallah