Sixty-eighth Annual Meeting THE AMERICAN SOCIETY FOR CLINICAL INVESTIGATION

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Authors

Determinants of lung bacterial clearance in normal mice.

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The determinants of the lung clearance of Streptococcus pneumoniae, Klebsiella pneumoniae, Escherichia coli, and Staphylococcus aureus were studied in normal mice after exposure to an aerosol of viable bacteria and 99mTc-labeled dead bacteria. The fraction of bacteria in lungs that remained viable 4 h after exposure were: S. pneumoniae, 7.3%; K. pneumoniae, 121%; E. coli, 88.5%; S. aureus, 27.6%. The rate of physical removal of bacterial particles (Kmc) was determined from the change in lung 99mTc counts with time: Kmc ranged between 7 and 12%/h and and was similar in all species. The rate of mucociliary clearance and of intrapulmonary bacterial killing (Kk + Kmc) was calculated from the change in bacterial counts with time in animals that had received tetracycline to inhibit bacterial multiplication. Kk, the rate of intrapulmonary killing, was obtained by subtraction of Kmc from (Kk + Kmc). The calculated values for Kk were: S. pneumoniae, - 87%/h; K. pneumoniae, - 17%/h; E. coli, - 18%/h; S. aureus, - 22%/h. The rate of intrapulmonary bacterial multiplication (Kg) was estimated from the relationship of bacterial counts in tetracycline and nontetracycline-treated animals, assuming that tetracycline altered only Kg. Kg, expressed as the doubling time, was: S. pneumoniae, 310 min; K. pneumoniae, 217 min; E.coli, 212 min; S. aureus, infinity (no multiplication). The data indicate that the marked differences in the clearance of these species from the normal mouse lung result from the interaction of differing rates of in vivo bacterial multiplication and killing.

Authors

S J Jay, W G Johanson Jr, A K Pierce, J S Reisch

Intrinsic differences in various segments of the proximal convoluted tubule.

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Until recently it has not been possible to compare directly the function of superficial and juxtamedullary nephrons. The present studies, using in vitro microperfusion, were designed to examine whether functional differences exist between proximal convoluted tubule segments of superficial and juxtamedullary nephrons. Electrophysiological studies showed that major differences exist between the relative chloride and sodium permeabilities of these segments. In the 1st mm of the superficial proximal convoluted tubule, the permeability to sodium was greater than that to chloride, whereas in the 2nd mm of the superficial proximal convoluted tubule and all later segments, the permeability to chloride was greater than that to sodium. The juxtamedullary proximal convoluted tubule was found to differ from the superficial proximal convoluted tubule in two respects: first, the relative permeabilities to chloride and sodium did not differ in the various segments of the juxtamedullary proximal convoluted tubule; second, the permeability to sodium was greater than to chloride throughout. When perfused with a solution lacking glucose and amino acids, the superficial and juxtamedullary convolutions exhibited the same transepithelial potential change, a reversible decrease to less than -- 1 mV. It thus appears that in both convolutions there exists electrogenic sodium transport coupled to the transport of these organic solutes. This differs from pars recta of both of these nephrons, which have been shown to exhibit electrogenic sodium transport independent of organic solutes. However, when perfused with a solution lacking glucose and amino acids but also containing high chloride and low bicarbonate concentrations, the superficial convolution developed a significantly more positive potential than the juxtamedullary. This difference reflects greater relative chloride permeability in the superficial proximal convolution. These studies show that intrinsic functional differences exist between proximal convoluted tubules obtained from the superficial and juxtamedullary nephron populations.

Authors

H R Jacobson, J P Kokko

Human bone marrow lymphocytes. Cytotoxic effector cells in the bone marrow of normal individuals.

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This study was undertaken to determine the capability of lymphocytes in the bone marrow of normal individuals to mediate nonspecific killer cell functions in assays of phytohemagglutinin (PHA)-induced cellular cytotoxicity, and antibody-dependent cellular cytotoxicity (ADCC) against 51Cr-labeled chicken erythrocyte target cells. Relatively pure mononuclear cell suspensions were obtained from bone marrow aspirates in 30 normal volunteers by sucrose gradient centrifugations and from the peripheral blood of the same individuals by Hypaque-Ficoll density centrifugations. At an effector: target ratio of 10:1, the PHA-induced cellular cytotoxicity of peripheral blood was 78.8 +/- 1.3%, while that of bone marrow was not significantly less at 66 +/- 9% (P greater than 0.1). At low effector:target ratios, the ADCC of bone marrow was negligible, while at higher effector:target ratios (20:1) bone marrow ADCC was 69 +/- 3.7%, which was comparable to that of peripheral blood. The lymphocytes themselves in the mononuclear cell suspensions of both peripheral blood and bone marrow were capable of cytotoxicity activity since depletion of monocytes from the suspensions by adherence to rayon wool and G-10 Sephadex columns did not remove the cytotoxic activity. Blocking of the Fc receptor on the effector cells by the addition of aggregated gamma globulin to the cultures suppressed the ADCC but not the PHA-induced cellular cytotoxicity of both peripheral blood and bone marrow, indicating that ADCC is dependent on an Fc receptor on the effector cell in both compartments. These studies demonstrate that the bone marrow of normal humans contains populations of lymphoid cells which have highly efficient killer cell capacities. It is uncertain what portion of these cells arise in the bone marrow and what portion enter the bone marrow parenchyma as part of the recirculating lymphocyte pool. These findings have relevance in the clearer understanding of the killer cell potential of grafted human marrow, as well as the bone marrow sequestration of functionally capable lymphocyte subpopulations in disease states and during chemotherapy.

Authors

A S Fauci, J E Balow, K R Pratt

Elaboration of toxic oxygen by-products by neutrophils in a model of immune complex disease.

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Contact between human neutrophils and aggregated immunoglobulin G bound to micropore filters has been studied as a model of the pathogenesis of tissue damage in immune complex disease. Contact with this surface, as well as with plain filters and polystyrene petri dishes, induced neutrophils to elaborate superoxide anion and hydrogen peroxide and to generate chemiluminescence, which has been attributed to singlet oxygen. Pretreatment of the cells with cytochalasin B decreased these activities but increased release of lysosomal beta-glucuronidase, suggesting that degranulation and the burst of oxygen metabolism that characterizes phagocytes are independently regulated functions. Toxic oxygen metabolites released from neutrophils are highly reactive and could mediate tissue injury at sites of inflammation.

Authors

R B Johnston Jr, J E Lehmeyer

The effects of spontaneous obesity on insulin binding, glucose transport, and glucose oxidation of isolated rat adipocytes.

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We have studied insulin, binding, glucose transport, and glucose oxidation, using large adipocytes isolated from older, fatter rats (greater than 12-mo-old, greater than 550 g), and smaller cells obtained from younger, leaner animals (4-5-wk-old, 120-160 g). At media glucose levels less than 5 mM, basal (absence of insulin) rates of glucose oxidation are comparable in both groups of cells. However, in the presence of insulin, the increase in glucose oxidation is much greater in the smaller cells. Maximally effective insulin levels could not overcome the defect in glucose oxidation by larger cells, and thus, even though studies of insulin binding demonstrated a 30-40% decrease in insulin receptors on the larger cells, it is probable that the defect in glucose oxidation is distal to the insulin receptor. Glucose transport was assessed by direct measurement of 2-deoxy glucose uptake. Basal levels of uptake were greater for the larger cells, whereas at maximally effective insulin concentrations, rates of 2-deoxy glucose uptake were the same for both groups of cells. Thus, in the presence of maximally effective levels of insulin, the apparent Km (2.3-2.7 mM) and Vmax values (2.6 and 2.7 nmol/10(5) cells per min) of 2-deoxy glucose uptake were comparable, indicating that the glucose transport system of the larger cells was intact. However, at submaximal levels of insulin, small adipocytes took up more 2-deoxy glucose than larger cells. These findings represent a rightward shift in the insulin dose-response curve in the cells from the older, fatter animals, and this is the predicted functional sequelae of the observed decrease in insulin receptors. Finally, when the amount of insulin bound was plotted as a function of 2-deoxy glucose uptake, no difference was seen between both groups of cells. This indicates that coupling between insulin receptor complexes and the glucose transport system is intact in large adipocytes, and is further evidence that a defect(s) in intracellular glucose metabolism is responsible for the decrease in glucose oxidation of adipocytes from older, fatter rats. In conclusion: (a) insulin-mediated glucose oxidation is markedly decreased in large adipocytes from older, fatter rats, and since this decrease cannot be corrected by maximally effective insulin levels, the defect is probably distal to the insulin receptor; (b) the glucose transport system is basically normal in large adipocytes; (c) insulin binding to receptors is decreased in large cells and the functional sequelae of this decrease in insulin binding i.e., a rightward shift in the insulin dose-response curve for 2-deoxy glucose uptake, was observed, and (d) since the decreased rates of insulin-mediated glucose oxidation can not be attributed to changes in insulin receptors or to changes in glucose transport, an intracellular defect in glucose metabolism is suggested.

Authors

J M Olefsky

The relationship of structure and function in human Hageman factor. The association of enzymatic and binding activities with separate regions of the molecule.

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Three regions of the human Hageman factor molecule termed the c, d, and e regions have been defined. Division of the molecule into these three regions is based on the analysis of fragments obtained by enzymatic cleavage during fluid-phase activation. The three regions have the following properties: (a) the c region has a mol wt of 40,000, has the capacity to bind to negatively charged surfaces, and does not have detectable enzymatic activity; (b) the e region possess a mol wt of 28,000 has enzymatic activity, and does not bind to negatively charged surfaces; (c) the d region has a mol wt of 12,000, is located between the c and e fragments but has not been detected as a freely existing polypeptide, and can bind firmly to negatively charged surfaces. The preparation of antibodies specific for the c and e regions is described as well as their use in defining the electrophoretic characteristics of the cde, cd, de, c, and e polypeptide fragments of Hageman factor. Evidence is given showing that the e region, but not the c or d, is released from a negatively charged surface when bound Hageman factor is exposed to proteolytic enzymes or whole plasma and that when this occurs in the presence of normal plasma, the e fragment becomes bound to C1 esterase inhibitor.

Authors

S D Revak, C G Cochrane

Jejunal and ileal absorption in patients with chronic renal disease. Effect of 1alpha-hydroxycholecalciferol.

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Calcium absorption in 30-cm segments of small intestine was measured by constant perfusion of test solutions containing different concentrations of calcium gluconate. In both the jejunum and ileum, calcium absorption rates increased progressively as luminal calcium concentration was increased stepwise between 1 and 20 mM. Although calcium transport was not saturable within these limits, unidirectional flux ratios of calcium (47Ca) suggest that calcium absorption is active in both the jejunum and ileum. Calcium absorption in patients with chronic renal disease was markedly depressed in both regions of the small intestine. This was due to decreased flux out of the lumen; flux in the reverse direction was normal. Flux ratios in the renal disease patients showed no evidence for active calcium transport. Treatment of these patients for 1 wk within 2 mug/day of 1alpha-hydroxycholecalciferol [1alpha-(OH)-D3] restored net calcium absorption and unidirectional calcium flux out of the lumen to normal values in the jejunum; in the ileum, 1alpha-(OH)-D3 increased calcium absorption 60-83% of normal at the various luminal calcium concentrations. 1alpha(OH)-D3 had no effect on unidirectional calcium flux into the lumen or on xylose and electrolyte absorption in either area of the small intestine.

Authors

P Vergne-Marini, T F Parker, C Y Pak, A R Hull, H F DeLuca, J S Fordtran

Influence of dietary phosphorus on renal phosphate reabsorption in the parathyroidectomized rat.

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Inorganic phosphate (Pi) reabsorption was studied during Pi infusion, after acute or chronic thyroparathyroidectomy (TPTX), in rats stabilized on a high-phosphorus (1% P) or a low-phosphorus (0.02% P) diet. After acute TPTX, there were no consistent differences in Pi reabsorption between the high- and low-phosphorus dietary groups. After chronic TPTX, the rats stabilized on the low-phosphorus diet exhibited nearly complete Pi reabsorption at every plasma Pi level, while the animals receiving the high-phosphorus diet manifested a marked phosphaturic response to Pi infusion. In addition, Pi reabsorption was significantly increased in the chronic TPTX low-phosphorus rats which achieved the highest filtered Pi loads, while their urine remained essentially phosphate-free. Dietary phosphorus-dependent alterations in Pi reabsorption may play a significant role in establishing the rate of Pi excretion per nephron under certain circumstances and should be considered in the interpretation of studies investigating renal Pi handling. The ability of phosphorus-depleted animals to maintain a phosphate-free urine during Pi loading would favor the rapid repletion of body phosphorus stores.

Authors

T H Steele, H F DeLuca

Effects of physiologic levels of glucagon and growth hormone on human carbohydrate and lipid metabolism. Studies involving administration of exogenous hormone during suppression of endogenous hormone secretion with somatostatin.

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To study the individual effects of glucagon and growth hormone on human carbohydrate and lipid metabolism, endogenous secretion of both hormones was simultaneously suppressed with somatostatin and physiologic circulating levels of one or the other hormone were reproduced by exogenous infusion. The interaction of these hormones with insulin was evaluated by performing these studies in juvenile-onset, insulin-deficient diabetic subjects both during infusion of insulin and after its withdrawal. Infusion of glucagon (1 ng/kg-min) during suppression of its endogenous secretion with somatostatin produced circulating hormone levels of approximately 200 pg/ml. When glucagon was infused along with insulin, plasma glucose levels rose from 94 +/- 8 to 126 +/- 12 mg/100 ml over 1 h (P less than 0.01); growth hormone, beta-hydroxy-butyrate, alanine, FFA, and glycerol levels did not change. When insulin was withdrawn, plasma glucose, beta-hydroxybutyrate, FFA, and glycerol all rose to higher levels (P less than 0.01) than those observed under similar conditions when somatostatin alone had been infused to suppress glucagon secretion. Thus, under appropriate conditions, physiologic levels of glucagon can stimulate lipolysis and cause hyperketonemia and hyperglycemia in man; insulin antagonizes the lipolytic and ketogenic effects of glucagon more effectively than the hyperglycemic effect. Infusion of growth hormone (1 mug/kg-h) during suppression of its endogenous secretion with somastostatin produced circulating hormone levels of approximately 6 ng/ml. When growth hormone was administered along with insulin, no effects were observed. After insulin was withdrawn, plasma beta-hydroxybutyrate, glycerol, and FFA all rose to higher levels (P less than 0.01) than those observed during infusion of somatostatin alone when growth hormone secretion was suppressed; no difference in plasma glucose, alanine, and glucagon levels was evident. Thus, under appropriate conditions, physiologic levels of growth hormone can augment lipolysis and ketonemia in man, but these actions are ordinarily not apparent in the presence of physiologic levels of insulin.

Authors

J E Gerich, M Lorenzi, D M Bier, E Tsalikian, V Schneider, J H Karam, P H Forsham

Retention and degradation of 125I-insulin by perfused livers from diabetic rats.

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The retention of degradation of insulin by isolated perfused liver have been examined. Noncyclically perfused livers from streptozotocin-diabetic rats retained 25% and degraded 10% of 125I-insulin administered as a 1-min pulse. On gel filtration (Sephadex G50F), the degradation products released into the vascular effluent eluted in the salt peak. During the 45-min interval after the end of the 125I-insulin infusion, 0.19% of the total dose was excreted in the bile. 60-90% of this material consisted of iodinated, low-molecular-weight degradation products. Inclusion of native insulin with the 125I-insulin in the pulse depressed both the retention and degradation of iodinated material; however, this reflected increased retention and degradation of the total insulin dose (125I-insulin plus native hormone). The log of the total amounts of insulin retained and degraded were linearly related to the log of the total amount of insulin infused at concentrations between 12.7 nM and 2.84 muM. Increasing the amount of native insulin in the infused pulse also depressed the total amount of iodinated material found in the bile and led to the appearance in the bile of intermediate-sized degradation products that did not simultaneously appear in the vascular effluent. Addition of high concentrations of glucagon to the infused 125I-insulin had no effect on the retention or degradation of the labeled hormone, or on the apparent size and amount of iodinated degradation products found in the vascular effluent or in the bile. Preinfusion of concanavalin A inhibited both 125I-insulin retention and degradation. A greater depression by concanavalin A of degradation than binding was also observed with isolated hepatocytes. In contrast to 125I-insulin, the retention and degradation of two iodinated insulin analogues of relative low biological potency, proinsulin and desalanyl-desasparaginyl insulin, were small. The amount of radioactivity appearing in the bile after infusion of these analogues was almost negligible. However, degradation products of these analogues that appeared in the bile and in the vascular effluent was qualitatively similar to those found after the infusion of 125I-insulin. Our findings suggest that the rapid initial uptake of 125I-insulin after its infusion into noncyclically perfused liver, as well as its subsequent degradation, behaves in a qualitatively similar fashion to the binding of 125I-insulin and its degradation by isolated rat hepatocytes. This uptake and the subsequent phase of degradation may be attributable to binding of insulin at specific recognition sites, preliminary to its transfer to a degradative site(s) presumed to be located inside the cell.

Authors

S Terris, D F Steiner

A 25-hydroxylation pathway of cholic acid biosynthesis in man and rat.

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This paper describes a pathway of cholic acid synthesis, in man and in the rat, which involves 25-hydroxylated intermediates and is catalyzed by microsomal and soluble enzymes. The subcellular localization, stereospecificity, and other properties of the enzymes involved were studied with liver fractions of normolipidemic subjects, cerebrotendinous xanthomatosis patients, and rats. 5beta-Cholestane-3alpha,7alpha,12alpha,25-tetrol was converted to 5beta-cholestane-3alpha,7alpha,12alpha,24beta,25-pentol by the microsomal fraction in the presence of NADPH and O2. 5beta-Cholestane-3alpha,7alpha,12alpha,24alpha,25-pentol, 5beta-cholestane-3alpha,7alpha,12alpha,-23xi,25-pentol, and 5beta-cholestane-3alpha,7alpha,12alpha,25,26-pentol were also formed. In the presence of NAD, 5beta-cholestane-3alpha,7alpha,12alpha,24beta,25-pentol, but not the other 5beta-cholestanepentols formed, was converted to cholic acid by soluble enzymes in good yield. These experiments demonstrate the existence of a pathway for side-chain degradation in cholic acid synthesis which does not involve hydroxylation at C-26 or the participation of mitochondria.

Authors

S Shefer, F W Cheng, B Dayal, S Hauser, G S Tint, G Salen, E H Mosbach

Mechanism of production of intestinal secretion by elevated venous pressure.

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A study was carried out to elucidate the physiological mechanisms responsible for the intestinal secretion produced by venous pressure elevation. In dogs, measurements were made of the rate and composition of small intestinal secretion, rate of flow and composition of intestinal lymph, plasma composition, and mucosal water content, all in response to elevations of intestinal venous pressure. Venous pressure elevations above a threshold value of 30-35 cm H2O produce secretion at a rate of approximately proportional to the value of the pressure minus the threshold value. Above the threshold value, there were large increases in the rates of lymph flow and net sustained transcapillary filtration. These rates were also roughly proportional to the incremental venous pressure. It is concluded that intestinal secretion produced by elevated venous pressure is almost surely secretory filtration, a passive process with the driving force for secretion an increase in mucosal tissue fluid pressures to values of only some 4-6 cm H2O. The increased tissue fluid pressure not only provides the driving force but also produces an increase in the hydraulic permeability of the epithelium without which the driving force would be ineffective. The transepithelial channels are large enough to permit insulin to pass freely and even plasma protein to pass in large amounts, and hence are most probably intercellular. Secretory filtration probably represents a general pathophysiological response of transporting epithelia to elevated tissue fluid pressure. It is proposed that the threshold value for secretion and associated changes is explained by dilution of the tissue fluid protein colloid osmotic pressure in a small subepithelial, juxtacapillary compartment.

Authors

M E Yablonski, N Lifson

Effect of aspirin on normal and cholera toxin-stimulated intestinal electrolyte transport.

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The effect of aspirin on normal and cholera toxin-stimulated electrolyte transport has been investigated in vitro, because this drug appears to inhibit cholera toxin-induced intestinal secretion in in vivo animal models. In the Ussing chamber, 10 mM aspirin decreased the control rabbit ileal potential difference and short-circuit current by 50% and increased conductance by 28%. Bidirectional electrolyte flux determinations showed that aspirin significantly increased both Na and Cl absorption and reduced flux (which probably represents HCO3 secretion) to zero. This effect of aspirin appears to be identical to that reported to others with catecholamines as determined with similar techniques. However, alpha-adrenergic blockers did not prevent the electrical effects of aspirin, suggesting that aspirin does not have its effect through release of tissue stores of catecholamines. In the presence of aspirin, cholera toxin increased the potential difference and short-circuit current, and decreased the conductance of rabbit ileum in a fashion qualitatively similar to control tissues. However, aspirin reversed cholera toxin-stimulated Na transport from secretion to absorption, inhibited cholera toxin, induced Cl secretion by 58% and partially, but not significantly, inhibited HCO3 secretion. Thus, the inhibitory effect of aspirin on cholera toxin-induced electrolyte secretion appears to be due to aspirin-stimulated Na and Cl absorption. Although aspirin reduced tissue cyclic AMP concentrations in normal and cholera toxin-stimulated ileum, it also inhibited the electrolyte secretion induced by exogenous cyclic AMP. Thus, if aspirin's stimulatory effect on sodium and anion absorption in normal tissue and its inhibitory effect on cholera toxin-stimulated sodium and anion secretion involves a cyclic AMP-mediated system, the effect must be a step distal to cyclic AMP production or degradation. The exact mechanism of aspirin's effect on normal and cholera toxin-induced electrolyte transport, and its possible usefulness in the treatment of cholera diarrhea, remains to be determined.

Authors

R K Farris, E J Tapper, D W Powell, S M Morris

Studies on human antihemophilic factor. Evidence for a covalently linked subunit structure.

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When purified antihemophilic factor (Factor VIII) was rechromatographed on 4% agarose in 0.15 M NaCl or 1.0 M NaCl, a single protein peak, containing both procoagulant activity and von Willebrand factor activity, as defined by ristocetin-induced platelet aggregation, was eluted in the void volume. Purified Factor VIII immediately lost about 30% of its procoagulant activity when dissolved in 0.25 M CaCl2, and when rechromatographed on 4% agarose in 0.25 M CaCl2, the protein peak and von Willebrand factor activity remained coincident in the void volume; however, most of the remaining procoagulant activity was eluted after the void volume. The elution position of Factor VIII procoagulant activity from 4% agarose in 0.25 M CaCl2, and hence its apparent molecular weight, varied with the protein concentration applied to the column; at low protein concentrations it was eluted close to the inner volume. Yet on Sephadex G-200 in 0.25 M CaCl2, the protein and procoagulant activity were eluted together in the void volume. These observations suggested that the Factor VIII procoagulant activity was not eluting according to size or shape, but was adsorbing to some extent to the agarose. Isolated activity peak material from the 0.25 M CaCl2 columns contained protein and had a typical ultraviolet spectrum. Even at high concentrations, the protein contained no thrombin, Factors IX, X, or Xa activity, or detectable phospholipid. In addition to Factor VIII procoagulant activity, which could be inactivated by a human antibody to Factor VIII, the activity peak protein also contained von Willebrand factor activity. Like native Factor VIII and the void volume protein, the activity peak contained protein that did not enter a sodium dodecyl sulfate 5% polyacrylamide gel in the absence of reducing reagent. After reduction of disulfide bonds, several subunits ranging from 195,000 to 30,000 daltons were observed. These results indicate that the protein in the shifted Factor VIII procoagulant activity peak is large and that its anomalous elution pattern from 4% agarose in 0.25 M CaCl2 results from interaction with the agarose. The Factor VIII-like properties of the activity peak protein and its electrophoretic pattern on sodium dodecyl sulfate gels suggest that it is a species of Factor VIII modified by proteolytic cleavage. These results allow an interpretation that is different from the recently proposed "carrier protein-small active subunit" hypotheses for the structure-function relationships of the Factor VIII molecule.

Authors

M E Switzer, P A McKee

The effect of changes in perfusion pressure on uteroplacental blood flow in the pregnant rabbit.

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The effect of perfusion pressure on uteroplacental blood flow was determined in pregnant rabbits utilizing the radioactive microsphere method. Control mean arterial pressure, 93 mm Hg +/- 2.6 SEM, was raised by carotid ligation to 109 +/- 4.1 mm Hg and then reduced with antihypertensive drugs to 74 +/- 1.3 mm Hg. Over this range of pressure there was no significant change in cardiac output, 605 +/- 36, 523 +/- 37, and 540 +/- 39 ml/min; or uteroplacental blood flow, 30 +/- 3.2, 27 +/- 5.2, and 29 +/- 4.5 ml/min, respectively. When prostaglandin synthesis was inhibited with either indomethacin or meclofenamate (2 mg/kg), uterine vascular resistance was higher but maintenance of uteroplacental flow occurred over a perfusion pressure of 89 +/- 6.7-115 +/- 9.3 mm Hg. With more severe hypotension induced with trimethaphan, control arterial pressure fell from 92 +/- 2.4 to 39 +/- 0.9 mm Hg, cardiac output fell from 514 +/- 17 to 407 +/- 22 ml/min (P less than 0.025) and uteroplacental blood flow fell from 6.1 +/- 0.9 to 2.5 +/- 0.9% of cardiac output (P less than 0.05), which represented an absolute fall from 32.4 +/- 5 to 10.6 +/- 3 ml/min (P less than 0.025). There was no significant change in renal blood flow expressed as percentage of cardiac output, 14.9 +/- 2 and 13 +/- 1.5%, or in absolute flow, 75 +/- 7.7 and 54 +/- 7 ml/min with trimethaphan-induced hypotension. These studies indicate that uteroplacental blood flow is maintained relatively constant over a range of perfusion pressure of 60-140 mm Hg in both normal and prostaglandin-inhibited pregnant rabbits. However, with reduction in pressure to 36-42 mm Hg, uteroplacental blood flow falls, expressed as a percentage of cardiac output and in absolute flow.

Authors

R C Venuto, J W Cox, J H Stein, T F Ferris

Renal handling of Zn-alpha2-glycoprotein as compared with that of albumin and the retinol-binding protein.

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An unusual electrophoretic pattern of the urine from a patient with malignant lymphoma was observed. One of the major proteins, identified Zn-alpha2-glycoprotein (Zn-alpha2), was isolated from the urine and partly characterized. The Stokes radius was found to be 3.24 nm and the molecular weight, determined by sodium dodecyl sulfate polyacrylamide electrophoresis, 42,000. The plasma level in healthy individuals was 39 +/- 7 (SD) mg/liter. In 12 of 25 healthy individuals, Zn-alpha2 was measurable in the urine and was found to be 1.0 +/- 1.1 mg/liter. In 23 patients with chronic glomerulonephritis (CGN), in 9 with proximal tubular dysfunction (PTD), in 23 with various renal diseases (VRD), and in 10 with malignant lymphoma, the plasma level and the urinary excretion were compared with those of albumin (mol wt 67,000) and of the retinol-binding protein (RBP, mol wt 21,000). A close correlation was found between the urine-to-plasma (U/P) ratios of Zn-alpha2 and albumin in the patients with CGN, whereas in the PTD patients the U/P ratios of Zn-alpha2 and RBP were correlated. No significant renal arteriovenous difference in Zn-alpha2 could be demonstrated. The Zn-alpha2 excretion was increased also in two patients with malignant lymphoma and proteinuria of a tubular pattern. The plasma Zn-alpha2 varied inversely with the glomerular filtration rate in the patients with renal disease, but was normal in those with malignant lymphoma. The results are consistent with the assumption of a sieving coefficient of Zn-alpha2, substantially exceeding that of albumin, but notably lower than that of smaller low-molecular-weight proteins. An increased excretion of Zn-alpha2 may be due to increased glomerular permeability as well as to defective proximal tubular reabsorption.

Authors

R Ekman, B G Johansson, U Ravnskov

Leukocyte-platelet interaction. Release of hydrogen peroxide by granulocytes as a modulator of platelet reactions.

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Because of the many potent biological capabilities of the blood granulocytes, and their contact with platelets in various physiologic and pathologic states, a possible interaction between granulocytes and platelets was investigated. Platelets were purified by gel filtration and via a dialysis membrane were separated from suspensions of autologous granulocytes prepared by dextran sedimentation and resuspended in modified Tyrode's buffer. After 20 min at 37 degrees C platelet aggregation was shown to be diminished by such exposure, as compared to the aggregation of platelets incubated with dialysates of buffer only. When granulocytes were stimulated by the addition of 1.1-muM latex spheres as target particles for phagocytes, the dialysate of these cells exhibited greatly enhanced platelet-inhibitory properties. The addition of catalase to the platelets abolished the effect of exposing these cells to the dialysate of resting granulocytes and markedly inhibited the effect of exposing the platelets to the dialysate of phagocytosing granulocytes. Catalase treated with 3-amino-1,2,4-triazole had no platelet-protective capacity. Purified suspensions of lymphocytes released no platelet-inhibitory principle under these experimental conditions. Hydrogen peroxide in the dialysate of granulocytes was measured directly with an assay involving an H2O2-induced decrease in the fluorescence of scopoletin catalyzed by horseradish peroxidase. The dialysate of phagocytosing granulocytes contained 0.86 +/- 0.55 nmol H2O2/2.5 X 10(7) granulocytes when sampled at 20 min. By an alternate measurement technique in which scopoletin and horseradish peroxidase were present in the dialysate from time zero, the mean amount of H2O2 in the dialysate reached 4.0 +/- 1.3 nmol/2.5 x 10(7) granulocytes at 20 min. This discrepancy suggested the consumption of H2O2, possibly mediated by the granulocytes themselves. This possibility was investigated by the addition of exogenous H2O2 to the test system. Both granulocytes and platelets enhanced the disappearance of H2O2 from the dialysate, and the amount consumed was proportional to the amount of H2O2 added to the system. Glucose oxidase at 12 M U/ml plus glucose in excess resulted in the production of H2O2 at a rate and final amount comparable to that produced by phagocytosing granulocytes. This mixture, when substituted for phagocytosing granulocytes in the standard dialysis membrane experiment, induced an inhibition of platelet aggregation similar to that caused by the granulocytes. The observation that the release of H2O2 by the blood granulocyte influences platelet function suggests a potential role for the granulocyte in the regulation of hemostasis or thrombosis.

Authors

P H Levine, R S Weinger, J Simon, K L Scoon, N I Krinsky

Interactions of actin, myosin, and an actin-binding protein of chronic myelogenous leukemia leukocytes.

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Actin, myosin, and a high molecular weight actin-binding protein were purified from chronic myelogenous leukemia (CML) leukocytes. CML leukocyte actin resembled skeletal muscle and other cytoplasmic actins by its subunit molecular weight, by its ability to polymerize in the presence of salts, and to activate the Mg2+-ATPase activity of rabbit skeletal muscle myosin. CML leukocyte myosin was similar to other vertebrate cytoplasmic myosins in having heavy chains and two light subunits. However, its apparent heavy-chain molecular weight and Stokes radius suggested that it was variably degraded during purification. Purified CML leukocyte myosin had average specific EDTA- AND Ca2+-activated ATPase activities of 125 and 151 nmol Pi released/mg protein per min, respectively and low specific Mg2+-ATPase activity. The Mg2+-ATPase activity of CML myosin was increased 200-fold by rabbit skeletal muscle F-actin, but the specific activity relative to that of actin-activated rabbit skeletal muscle myosin was low. CML leukocyte myosin, like other vertebrate cytoplasmic myosins, formed filaments in 0.1 M KCl solutions. Reduced and denatured CML leukocyte-actin-binding protein had a single high molecular weight subunit like a recently described actin-binding protein of rabbit pulmonary macrophages which promotes the polymerization and gelation of actin. Cytoplasmic extracts of CML leukocytes prepared with ice-cold 0.34-M sucrose solutions containing Mg2+-ATP, dithiothreitol, and EDTA at pH 7.0 underwent rapid gelation when warmed to 25 degrees C. Initially, the gel could be liquified by cooling to ice-bath temperature. With time, warmed cytoplasmic extract gels shrunk ("contracted") into aggregates. The following findings indicated that CML leukocyte actin-binding protein promoted the temperature-dependent gelation of actin in the cytoplasmic extracts and that CML leukocyte myosin was involved in the contraction of the actin gels: (a) Cytoplasmic extract gels initially contained actin as their major polypeptide component and consistent of tangled thin filaments; (b) Contracted aggregates of cytoplasmic extract gels contained by large quantities of myosin as well as actin; (c) Purified actin-binding protein underwent a temperature-dependent, reversible aggregation and caused low concentrations of purified muscle or CML leukocyte actins to gel in sucrose solutions; (d) The gels formed from purified actin plus purified actin-binding protein slowly contracted in the presence but not in the absence of purified CML leukocyte myosin; (e) Rabbit antiserum against purified CML leukocyte actin-binding protein but not against purified CML leukocyte myosin inhibited the gelation of warmed CML leukocyte extracts. Antiserum against CML leukocyte myosin had no effect on the gelation of CML leukocyte extracts but partially curtailed the contraction of the CML leukocyte extract gels and of gels formed from purified CML leukocyte actin-binding protein plus rabbit skeletal muscle actin.

Authors

L A Boxer, T P Stossel

Mechanism of the ventilatory response to carbon monoxide.

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Abstract

The effects of carbon monoxide on ventilation were studied in unanesthetized goats. Responses to single breaths of 10-25% CO in O2, which rapidly raised carboxyhemoglobin (COHb) from 5 to 60%, were considered to reflect peripheral chemoreceptor-mediated reflexes whereas responses to continuous inhalation of 1% CO in O2, which slowly raised COHb from 0 to 60%, were considered to reflect both peripheral chemoreceptor and nonperipheral chemoreceptor mechanisms. In each of six goats, single breaths of CO failed to elicit any immediate ventilatory response. However, slow buildup of carboxyhemoglobinemia in the same animals always elicited ventilatory stimulation (from a mean of 7.43 to 16.02 liter/min, P less than 0.001) beginning 5-6 min after onset of 1% CO in O2 inhalation when COHb saturation reached 50-60%. In eight studies of six animals HCO3- concentration fell (from 21.3 to 15.8 meq/liter; P less than 0.001) and lactate concentration rose (from 2.5 to 4.2 meq/liter; P less than 0.05) in the cisternal cerebrospinal fluid during the CO-induced hyperpnea. Additional studies ruled out ventilatory stimulation from left heart failure or enhanced chemo-sensitivity to carbon dioxide. Although the delayed hyperpnea was associated with a hyperdynamic cardiovascular response to CO, blockade of these circulatory effects with propranolol (2 mg/kg) failed to abolish the delayed hyperpnea; however, the propranolol did unmask an element of ventilatory depression which preceded the hyperpnea. Conclusions were: (a) hyperventilation in response to CO inhalation is not mediated by the carotid bodies; (b) the delayed hyperpnea in response to CO inhalation is primarily due to brain-cerebrospinal fluid acidosis; (c) mobilization of body CO2 stores due to the circulatory response to CO may obscure an initial depression of ventilation by CO.

Authors

T V Santiago, N H Edelman

Effect of protein ingestion on splanchnic and leg metabolism in normal man and in patients with diabetes mellitus.

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Abstract

The inter-organ flux of substrates after a protein-rich meal was studied in seven healthy subjects and in eight patients, with diabetes mellitus. Arterial concentrations as well as leg and splanchnic exchange of amino acids, carbohydrate substrates, free fatty acids (FFA), and ketone bodies were examined in the basal state and for 3 h after the ingestion of lean beef (3 g/kg body wt). Insulin was withheld for 24 h before the study in the diabetic patients. In the normal subjects, after protein ingestion, there was a large amino acid release from the splanchnic bed predominantly involving the branched chain amino acids. Valine, isoleucine, and leucine accounted together for more than half of total splanchnic amino acid output. Large increments were seen in the arterial concentrations of the branched chain amino acids (100-200%) and to a smaller extent for other amino acids. Leg exchange of most amino acids reverted from a basal net outut to a net uptake after protein feeding which was most marked for the branched chain amino acids. The latter accounted for more than half of total peripheral amino acid uptake...

Authors

J Wahren, P Felig, L Hagenfeldt

Placenta, transcortin, and localized immune response.

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Abstract

The syncytiotrophoblastic cells of the human placenta contain a cytoplasmic protein recognized by fluorescein-labeled transcortin-specific antibody. Purification of this protein from human placenta, by those methods employed for the purification of human plasma transcortin, yielded a protein that exhibited antigenic and biochemical similarity to plasma transcortin. Placental transcortin differs from plasma transcortin in that it has a smaller sedimentation coefficient (3S vs 3.75S) and binds cortisol less strongly. This purified protein is able to block the phytohemagglutinin response of maternal lymphocytes even more than serum transcortin. It is postulated that the biological role may be that of inhibiting the maternal cell-mediated immune response to the presence of the antigenic conceptus.

Authors

S Werthamer, S Govindaraj, L Amaral

The effect of thyroid hormone on bile salt-independent bile flow and Na+, K+ -ATPase activity in liver plasma membranes enriched in bile canaliculi.

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Abstract

The relationship between bile salt-independent canalicular flow and ATPase activity in liver plasma membranes (LPM) enriched in bile canaliculi, was studied in control, hyperthyroid, and hypothyroid rats. Canalicular bile production was significantly increased in hyperthyroid rats (3.19 +/- 0.23 mul/min per g liver) compared to controls (2.27 +/- 0.24 mul/min per g liver), while it diminished in hypothyroid animals (1.58 +/- 0.17 mul/min per g liver). Although bile salt excretion was also increased in hyperthyroid animals (62.4 +/- 13.3 vs. 41.2 +/- 8.4 nmol/min per g liver), the stimulation in canalicular secretion was primarily related to enhancement of the bile salt-independent fraction of flow (2.47 mul/min per g liver in hyperthyroid rats vs. 1.67 mul/min per g liver in controls). LPM Na+, K+-ATPase activity doubled in hyperthyroid animals (21.5 +/- 5.8 vs. 10.7 +/- 3.1 mumol Pi/mg protein per h) while Mg++-ATPase activity remained unchanged and 5'-nucleotidase activity increased to a small but significant extent. In hypothyroid rats, bile salt excretion remained unchanged from control values so that the reduced secretion was entirely secondary to an inhibition of bile salt-independent secretion (1.19 mul/min per g liver). Na+, K+-ATPase activity in the LPMs from hypothyroid animals decreased by nearly 50% (5.4 +/- 1.6 mumol Pi/mg protein per h), although comparable reductions in the specific activity of Mg++-ATPase and 5'-nucleotidase were also observed. Administration of L-thyroxine to hypothyroid animals restored both bile salt-independent canalicular secretion and membrane enzymes to control values within 2 and 4 days, respectively. Sodium dodecyl sulfate gel electrophoresis demonstrated no significant changes in LPM protein fractions from any of the treatment groups. These studies indicate that thyroid hormone has a parallel effect on bile salt-independent canalicular secretion and LPM Na+, K+-ATPase activity, supporting the hypothesis that Na+ transport and Na+, K+-ATPase may be determinants of bile salt-independent canalicular flow.

Authors

T J Layden, J L Boyer

Reversible changes of the muscle cell in experimental phosphorus deficiency.

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Abstract

Both animal and human studies suggest that either phosphorus depletion or hypophosphatemia might have an adverse effect on muscle function and composition. Recently a possible deleterious effect was noted in patients with chronic alcoholism. In this unexplained disease, a variety of toxic and nutritional disturbances could affect the muscle cell, thus obscuring the precise role of phosphorus. Accordingly, we examined eight conditioned dogs for the possibility that phosphorus deficiency per se might induce an abnormally low resting transmembrane electrical potential difference (Em) and alter the composition of the muscle cell. Eight conditioned dogs were fed a synthetic phosphorus-deficient but otherwise nutritionally adequate diet plus aluminum carbonate gel for a 28-day period followed by the same diet with phosphorus supplementation for an additional 28 days. Sequential measurements of Em and muscle composition were made at 0 and 28 days during depletion and again after phosphorus repletion. Serum inorganic phosphorus concentration (mg/100 ml) fell from 4.2 +/- 0.6 on day 0 t0 1.7 +/- 0.1 on day 28. Total muscle phosphorus content (mmol/100 g fat-free dry wt [FFDW]) fell from 28.5 +/- 1.8 on day 0 to 22.4 +/- 2.1 on day 28. During phosphorus depletion, average Em (-mV) fell from 92.6 +/- 4.2 to 77.9 +/- 4.1 mV (P less than 0.001). Muscle Na+ and Cl- content (meq/100 g FFDW) rose respectively from 11.8 +/- 3.2 to 17.2 +/- 2.8 (P less than 0.01) and from 8.4 +/- 1.4 to 12.7 +/- 2.0 (P less than 0.001). Total muscle water content rose from 331 +/- 12 to 353 +/- 20 g/100 FFDW (P less than 0.05). A slight, but nevertheless, significant drop in muscle potassium content, 43.7 +/- 2.0-39.7 +/- 2.2 meq/100 g FFDW (P less than 0.05) was also noted. After 4 wk of phosphorus repletion, all of these measurements returned toward control values. We conclude that moderate phosphorus depletion can induce reversible changes in skeletal muscle composition and transmembrane potential in the dog, and it apparently occurs independently of profound hypophosphatemia.

Authors

T J Fuller, N W Carter, C Barcenas, J P Knochel

Purine nucleoside metabolism in the erythrocytes of patients with adenosine deaminase deficiency and severe combined immunodeficiency.

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Abstract

Deficiency of erythrocytic and lymphocytic adenosine deaminase (ADA) occurs in some patients with severe combined immunodeficiency disease (SCID). SCID with ADA deficiency is inherited as an autosomal recessive trait. ADA is markedly reduced or undetectable in affected patients (homozygotes), and approximately one-half normal levels are found in individuals heterozygous for ADA deficiency. The metabolism of purine nucleosides was studied in erythrocytes from normal individuals, four ADA-deficiency patients, and two heterozygous individuals. ADA deficiency in intake erythrocytes was confirmed by a very sensitive ammonia-liberation technique. Erythrocytic ADA activity in three heterozygous individuals (0.07,0.08, and 0.14 mumolar units/ml of packed cells) was between that of the four normal controls (0.20-0.37 mumol/ml) and the ADA-deficient patients (no activity). In vitro, adenosine was incorporated principally into IMP in the heterozygous and normal individuals but into the adenosine nucleotides in the ADa-deficient patients. Coformycin (3-beta-D-ribofuranosyl-6,7,8-trihydroimidazo[4,5-4] [1,3] diazepin-8 (R)-ol), a potent inhibitor of ADA, made possible incorporation of adenosine nucleotides in the ADA-deficient patients...

Authors

R P Agarwal, G W Crabtree, R E Parks Jr, J A Nelson, R Keightley, R Parkman, F S Rosen, R C Stern, S H Polmar

N-acetylgalactosamine-6-sulfate sulfatase in man. Absence of the enzyme in Morquio disease.

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Abstract

Human N-acetylgalactosamine-6-sulfate sulfatase (6-sulfatase) activity is measured by using as a substrate a sulfated tetrasaccharide obtained by digesting purified chondroitin-6-sulfate (C-6-S) with testicular hyaluronidase. The amount of inorganic sulfate released is measured turbidimetrically. The enzyme from human kidney has a pH optimum of 4.8; its activity is augmented by low levels of NaCl and inhibited by phosphate and high levels of NaCl. Free glucuronate, acetylgalactosamine, inorganic sulfate, polymeric C-6-S, or tetrasaccharide obtained from chondroitin-4-sulfate do not affect the enzyme activity. The method may be used for the diagnosis of Morquio disease since extracts of Morquio fibroblasts are devoid of 6-sulfatase activity.

Authors

J Singh, N Di Ferrante, P Niebes, D Tavella

IgA and IgG anti-ragweed antibodies in nasal secretions. Quantitative measurements of antibodies and correlation with inhibition of histamine release.

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Abstract

Total secretory IgA and specific anti-antigen E (AgE) antibodies (ab) in the IgA and IgG classes were measured in concentrated nasal washings from ragweed allergic and normal individuals by antigen binding or anti-alpha-radioimmunoassays. Virtually all the allergic patients had significant IgA (45/49) and IgG (46/49) ab to AgE in their nasal washings. By contrast, washings from most normal persons contained no measurable IgA (13/15) ab or IgG (13/15) ab to AgE. The total IgA levels in allergic washings were not significantly different from those in normal washings and they were used to standardize the ab measurements. Parenteral immunotherapy with ragweed extract increased specific nasal IgA ab from 10.6 +/- 2.7 (SEM) to 39.0 +/- 8.7 ng AgE bound/mg IgA and IgG ab from 17.2 +/- 2.6 to 65.1 +/- 7.4 ng AgE bound/mg IgA (P less than 0.001 for both classes). The ratio of IgA:IgG ab was not affected by therapy, and for treated patients, there was no correlation (rs + 0.32, P greater than 0.1) between nasal IgG ab and serum IgG ab. These results suggest that at least part of the nasal IgG ab is produced locally. Blocking activity in the nasal washings was measured by inhibition of histamine release and was found to correlate directly (rs + 0.85, P less than 0.001) with binding activity for AgE. Some washings from normal persons caused slight inhibition of histamine release but others caused enhancement. Nasal washings were fractionated by passage over Sephadex G-200. Inhibition of histamine release by dilutions of the IgA-rich and IgG-rich fractions correlated well with binding activity in these fractions. None of these results support the hypothesis that allergic individuals are deficient in secretory IgA or secretory ab responses. These results, however, are in keeping with the theory that hay fever occurs in a high-responder population which is genetically able to respond to low doses of inhalant antigens.

Authors

T A Platts-Mills, R K von Maur, K Ishizaka, P S Norman, L M Lichtenstein

Modulation of cellular-immune responses in vivo and in vitro by histamine receptor-bearing lymphocytes.

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Abstract

Histamine, one of the mediators involved in the IgE-mediated reaction, was demonstrated to influence in vivo and in vitro components of cellular-immune reactions in orthochlorbenzoyl-bovine gamma globulin-immune guinea pigs. 10(-3) M histamine reduced by half the size of a delayed hypersensitivity skin test at 24 h. Inhibition of skin reactivity by histamine could be partially reversed by H-1 receptor antagonists such as chlorpheniramine and completely prevented by H-2 receptor antagonists such as burimamide. The histamine suppression of cutaneous delayed hypersensitivity could be accounted for in part by its inhibitory effect on certain lymphocyte responses including antigen-induced migration inhibitory factor (MIF) production and proliferation. At concentrations of 10(-3)-10(-5) M histamine reversibly inhibited MIF production and its action could be blocked by H-2 antagonists but not H-1 antagonists. Thus, lymphocytes bearing H-2 receptors modulate MIF production and probably lymphocyte proliferation as well. Histamine did not interfere with the macrophage response to preformed MIF. These studies indicate that immediate hypersensitivity reactions involving histamine release might influence the subsequent expression of cellular-immune reactions.

Authors

R E Rocklin

Manganese-dependent NADPH oxidation by granulocyte particles. The role of superoxide and the nonphysiological nature of the manganese requirement.

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Abstract

Recent work has indicated that superoxide is involved in the manganese-stimulated oxidation of NADPH by crude granule preparations of guinea pig neutrophils. The characteristics of a model manganese-requiring NADPH-oxidizing system that employs a defined O2-generator have now been compared to the original neutrophil-granule system. With respect to pH dependence, cyanide sensitivity, and reduced pyridine nucleotide specificity, the properties of the two systems are very similar. Additional information has been obtained concerning cation specificity and the kinetics of the metal-catalyzed NADPH oxidation. From the similarities between the properties of the model and neutrophil particle systems, we postulate that the manganese-dependent NADPH oxidation observed in the presence of neutrophil granules represents in large part of nonenzymatic free radical chain involving the oxidation of NADPH to NADP, with O2- as both the chain initiator and one of the propagating species. In this reaction, the neutrophil particles serve only as a source of O2-. Further, the same changes in kinetics (decrease in apparent Km for NADPH) observed previously when granules from phagocytizing rather than resting cells were employed could be mimicked by varying the rate of O2-generation by the model system. We conclude from these results that it is unnecessary to invoke a manganese-requiring enzyme as a component of the phagocytically stimulated respiratory system of the neutrophil.

Authors

J T Curnutte, M L Karnovsky, B M Babior

Rosette formation between human lymphocytes and sheep erythrocytes. Inhibition of rosette formation by specific glycopeptides.

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Abstract

Rosette formation with unsensitized sheep erythrocytes is a characteristic of human thymus dependent lymphocytes. Release of glycopeptides from the sheep erythrocyte by trypsin reduces rosette formation. These tryptic glycopeptides inhibit rosette formation by untrypsinized sheep erythrocytes; this suggests that rosetting is mediated by erythrocyte surface glycopeptides. To investigate the molecular nature of this interaction, we examined the abilities of various model compounds to act as haptenic inhibitors of rosette formation. Inhibition is given by glycopeptides bearing oligosaccharide units rich in sialic acid, galactose, N-acetylglucosamine, and mannose linked to asparagine residues through glycosylamine bonds. Among compounds tested, fetuin glycopeptide is most effective, but human transferrin glycopeptide and human erythrocyte glycopeptide I also inhibit rosette formation. Other compounds including human erythrocyte glycopeptide II, human IgG glycopeptide, lacto-N-neotetraose, 3'- and 6'-sialyllactose show no significant inhibition. Neither sialic acid, galactose, manose, nor N-acetyl-glucosamine alone inhibits rosette formation. Stepwise degradation of fetuin glycopeptide established the galactose residues as important determinants of inhibitory activity. Fetuin glycopeptide blocks rosette formation when added to a suspension of human lymphocytes and sheep erythrocytes or when preincubated with human lymphocytes, but not when preincubated with sheep erythrocytes. Studies of the binding of [3H] fetuin glycopeptide to normal lymphocytes demonstrate 7.5 x 10(6) saturable binding sites per cell. No saturable binding of this compound to sheep erythrocyte membranes is observed. Compared to normals, lymphocytes from patients with chronic lymphatic leukemia demonstrate decreased fetuin glycopeptide binding with a mean of 0.9 x 10(6) sites per cell. This decreased binding correlates with the impaired ability of these cells to form rosettes. The data suggest that fetuin glycopeptide inhibits rosette formation by binding to the thymus-dependent cell where competition occurs with sheep erythrocytes for specific lymphocyte surface receptors.

Authors

D H Boldt, J P Armstrong

The pathogenesis of coronary artery disease. A possible role for methionine metabolism.

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Abstract

Homocystinuria, an abnormality of methionine metabolism is associated with severe vascular disease in infancy and childhood. Homocysteine is formed during the metabolism of methionine and accumulations of this and of cysteine-homocysteine mixed disulfide in the plasma indicate a partial block in the methionine degradation pathway. Methionine metabolism was investigated in 25 patients aged under 50 with angiographically proved coronary artery disease and in 22 control patients, of whom 17 had normal coronary arteries at angiography and 5 were healthy volunteers. After an overnight fast, venous blood was drawn before and 4 h after oral L-methionine, 100 mg/kg. Plasma methionine levels at 4 h were not different in the two groups, but there were significant differences in the levels of cysteine-homocysteine mixed disulfide. This was detected in 5 of 22 in the noncoronary group and in higher concentration in 17 of 25 coronary patients (P less than 0-01). Age, weight, height, body-mass index, glucose tolerance, fasting serum urate, and triglycerides were not different, but serum cholesterol was higher in the coronary patients (P lessthan 0.01). These results suggest a reduced ability to metabolise homocysteine in some patients with premature coronary artery disease when this pathway is stressed.

Authors

D E Wilcken, B Wilcken

Insulin release is glucose anomeric specific in the human.

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Abstract

The alpha-glucose anomer produces a greater insulin release than beta-glucose in various animal models. These glucose anomers were dissolved rapidly and administered intravenously to human volunteers at a high dose (0.5 g/kg) over a 3-min period or a low dose (3.5 g) over a 20-s period. Blood samples were obtained at frequent time intervals for measurement of whole blood glucose (ferricyanide), plasma glucose (beta-glucose oxidase) and serum immunoreactive insulin. The high-dose infusion test showed no differences between the anomers of either blood glucose or serum insulin levels. However, at the lower dose, the alpha-glucose anomer stimulated a significantly greater insulin release than did beta-glucose. It is concluded that the alpha-glucose anomer stimulates a greater insulin release than the beta-glucose anomer in human subjects at low but not at high doses intravenously and that this response is not apparently related to approximations of the degree of mutarotation. These results suggest that a steric specific glucose receptor site exists on the beta-cell as a rapid insulin release trigger, although the alpha-anomer does not exclusively produce this stimulation.

Authors

A A Rossini, J S Soeldner

Inhibition of insulin degradation by nonsuppressible insulin-like activity.

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Abstract

Nonsuppressible insulin-like activity, provided by three sources, was evaluated for its effect on the proteolytic degradation of insulin utilizing insulin protease obtained from rat liver homogenate as well as liver cell membranes. All three preparations of nonsuppressible insulin-like activity were found to be competitive inhibitors of insulin degradation. In addition human plasma was fractionated yielding an acetone precipitate which was found to have nonsuppressible insulin-like activity and to be a competitive inhibitor of insulin protease.

Authors

G Burghen, W C Duckworth, A E Kitabchi, S S Solomon, P L Poffenbarger

The induction of prostatic hypertrophy in the dog with androstanediol.

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Abstract

The effects of androstanediol and estradiol on prostatic growth were investigated in castrate dogs. Estrogens along resulted in no significant change in prostatic weight, whereas androstanediol produced growth comparable to that in uncastrated controls. Androstanediol plus estradiol resulted in an even more striking increase in prostate growth. Approximately half the animals receiving androstanediol alone and all of those receiving androstanediol plus estradiol fulfill the weight and histological criteria for prostatic hypertrophy in the dog. Since both these steroid hormones are presumed to be normal secretory products of the testis, it is possible that they are involved in the pathogenesis of prostatic hypertrophy in the dog.

Authors

P C Walsh, J D Wilson

The induction of augmented granulocyte adherence by inflammation. Mediation by a plasma factor.

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Abstract

The adherence of granylocytes to surfaces, measured in vitro in nylon fiber columns, is inhibited by in vivo administration of anti-inflammatory agents. Therefore, the effect of inflammation itself was assessed in blood from patients with acute inflammatory diseases. Mean adherence in these patients was twice normal (56.4 +/- 5.6% vs. 29.4 +/- 5.2%); their plasma contained a factor that augmented adherence of normal cells to 47.5 +/- 5.6% whereas the patient's cells showed a normal level of adherence (34.0 +/- 6.8%) when resuspended in normal plasma. Although exudate fluid from exprimental inflammation also contained the augmenting factor, cells from the exudate maintained their high level of adherence after washing and suspension in normal plasma. The augmenting factor detected in plasma from patients with inflammation was not present in serum and was inactivated by heating plasma to 56 degrees C for 30 min; restoration of augmenting activity was accomplished by addition of 20% guinea pig serum to the heat-treated plasma. Because the guinea pig serum itself did not increase adherence when added to normal plasma, it appears that the augmenting factor is heat-stable, but requires a heat-labile cofactor like complement. Sephadex G-200 fractionation of inflammatory plasma showed adherence-augmenting activity in the majority of fractions, with peak activity in the fractions corresponding to approximate molecular wts of 30,000, 160,000 and 400,000.

Authors

A L Lentnek, A D Schreiber, R R MacGregor

Effect of renal sympathetic nerve stimulation on proximal water and sodium reabsorption.

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Abstract

The renal responses to sympathetic nerve stimulation were studied in saline-expanded rats. The left kidney was partially denervated by crushing the left greater splanchnic nerve. Then the distal portion of the nerve was stimulated with square wave pulses of 0.5 ms duration, voltage twice threshold, and 1 or 2 Hz frequency while monitoring the compound action potential. Fibers with conduction speeds of 13-17 m-s-1 and of 0.7-1 m-s-1 were identified. Only stimulation of the latter appeared to produce changes in renal Na and water excretion. Whole kidney and individual nephron studies were performed alternating control and nerve stimulation periods. Nerve stimulation produced approximately a 25% reduction of the left kidney urine volume and sodium excretion. Glomerular filtration rate and renal plasma flow remained unchanged. Right kidney Na and water excretion, glomerular filtration rate, and renal plasma flow remained constant. In the left kidney, during nerve stimulation, the tubular fluid to plasma inulin concentration ratio increased significantly in the late proximal tubule. We conclude that the antidiuresis and antinatriuresis seen during sympathetic nerve stimulation were caused by increased sodium and water reabsorption in the proximal tubule, probably mediated by the stimulation of slowly conducting unmyelinated fibers. These responses appeared to be unrelated to systemic or intrarenal hemodynamic changes.

Authors

E Bell-Reuss, D L Trevino, C W Gottschalk