Developmental changes in glucose transport of guinea pig erythrocytes.

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Abstract

The developmental changes in the capacity for D-glucose transport of guinea pig erythrocyte membranes were compared to alterations in the electrophoretic pattern of erythrocyte membrane components. Guinea pig erythrocytes lose their D-glucose carrier functions during development. Good correlation was observed between the loss of glucose uptake and apparent decrease of the zone 4.5 of Coomassie Blue-stained membrane proteins on electrophoresis. Reconstitution of membrane preparations in liposomes resulted in a parallel change in the D-glucose uptake and D-glucose penetration of intact erythrocytes. This suggests that the decrease of D-glucose transport capacity during development is caused by the loss of one or more protein components from the erythrocyte membranes.

Authors

T Kondo, E Beutler

Alpha Adrenergic Vasoconstriction and Nitroglycerin Vasodilation of Large Coronary Arteries in the Conscious Dog

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Abstract

The effects of methoxamine and nitroglycerin on measurements of large vessel (left circumflex) coronary dimensions were examined in eight conscious dogs using an ultrasonic dimension gauge, and total coronary resistance was calculated from measurements of arterial pressure and coronary blood flow. Methoxamine (50 μg/kg per min), after transiently increasing left circumflex coronary dimensions, induced sustained reductions in left circumflex diameter (9±2%) and external (18±4%) and internal (27±5%) cross-sectional areas, at a time when mean arterial pressure rose by 65±5%, left ventricular dP/dt had decreased only slightly, and heart rate and mean coronary blood flow remained at control levels. Calculated large vessel and total coronary resistances rose similarly, i.e., by 108±29 and 92±14%, respectively. Methoxamine reduced coronary arterial wall stiffness from control at comparable stress levels, although at any common radius, wall stiffness was augmented substantially. Nitroglycerin (25 μg/kg) induced an initial decrease in coronary dimensions along with the fall in arterial pressure. However, left circumflex coronary dimensions then rose, reaching a maximum 5 min later at a time when left circumflex coronary blood flow was reduced and heart rate and left ventricular dP/dt were at control levels. At this time, significantly different effects were observed on large vessel coronary resistance, which fell by 18±2%, and on total coronary resistance, which rose by 11±4%. Thus, in the conscious dog, large coronary vessels not only react passively to changes in aortic pressure but also undergo substantial active changes. Alpha adrenergic stimulation is sufficiently powerful to reduce cross-sectional area, despite the opposing elevation of distending pressure.

Authors

Stephen F. Vatner, Massimo Pagani, W. Thomas Manders, Ares D. Pasipoularides

Long-term vasectomy: effects on the occurrence and extent of atherosclerosis in rhesus monkeys.

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Abstract

We demonstrated previously that atherosclerosis develops more extensively in vasectomized cynomolgus macaques fed an atherogenic diet and speculated that the immunologic response to sperm antigens may have exacerbated the atherosclerosis. We report here that rhesus monkeys vasectomized for 9-14 yr and fed monkey chow (devoid of cholesterol and low in fat) rather than an atherogenic diet also had more extensive and severe atherosclerosis than did control animals of the same age. The extent of atherosclerosis was considered as the percentage of intimal surface with plaques. No control animals were found to have plaques in the thoracic aorta, but 7 of 10 vasectomized monkeys were affected. The plaques in the vasectomized monkeys occupied about 13% of the intimal surface. In 4 of 7 control monkeys and 7 of 10 vasectomized monkeys there were lesions in the abdominal aortas; the lesions were considerably more extensive and severe in the vasectomized animals. Lesions were also more common in iliac arteries of vasectomized animals, and the extent was increased about threefold. Plaques were seen at the carotid bifurcation in all of the animals of both the control and vasectomized groups. The carotid bifurcation plaques of the vasectomized monkeys were larger than those of the control animals on the right but not on the left side. Histologically, the lesions of vasectomized monkeys did not appear to be qualitatively different from those of control animals, even though they were larger and contained more collagen, lipid, and mucopolysaccharides. Grossly, the distribution of the lesions in the vasectomized animals was different from that in the control animals, and that of lesions induced by atherogenic diets, i.e., the lesions were distributed randomly within the artery rather than around bifurcations. More extensive atherosclerosis was noted among vasectomized animals that were found to lack demonstrable circulating free antisperm antibodies. On the basis of the observations made in this study, we suggest that the antisperm antibodies that form after vasectomy may result in circulating immune complexes that exacerbate atherosclerosis.

Authors

T B Clarkson, N J Alexander

Reduced rate of DNA replication fork movement in megaloblastic anemia.

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Abstract

Chromatography on benzoylated naphthoylated DEAE-cellulose has been used to fractionate fully double-stranded from partially single-stranded DNA molecules. DNA was extracted from phytohemagglutinin-stimulated lymphocytes from patients with megaloblastic anemia resulting from vitamin B12 or folate deficiency after pulse-labeling the cells with [3H]thymidine for 5 min and chasing in unlabeled medium for 24 h. No gross accumulation of partially single-stranded material was observed in the DNA of these cells when compared with DNA from similarly labeled control cells obtained by the addition of 5-formyl tetrahydrofolic acid to the culture medium. When DNA from lymphocytes labeled with a 5-min pulse of [3H]thymidine and sheared to fragments of an average length of 18 micrometer was chromatographed on benzoylated naphthoylated DEAE-cellulose, approximately 80% of the label was recovered in the partially single-stranded fraction. After chasing in unlabeled medium the label was progressively transferred to the double-stranded fraction over a period of 2--3 h. The rate of transfer was slower in megaloblastic lymphocytes than in controls. The difference in rate suggested a slower rate of replication fork movement in megaloblastic lymphocytes and so the density shift technique of Painter and schaeffer (J. Mol. Biol. 45: 467--479, 1969) was used to measure the fork rate directly. [3H]Deoxycytidine was used as the labeled nucleoside to avoid possible complications arising from [3H]thymidine labeling of megaloblastic cells. Investigations on the lymphocytes from four patients showed that the replication fork rate in vitamin-treated control lyphocytes was about 1 micrometer/min. The fork rates in the corresponding untreated cells were invariably lower and rates ranging from 40 to 92% of those of controls were observed. Normal lymphocytes treated with the deoxynucleotide pool-depleting drugs methotrexate or hydroxyurea displayed defects in DNA synthesis similar to those of untreated megaloblastic lymphocytes. We propose that the delayed DNA replication fork movement in cells of patients with megaloblastic anemia results from impaired biosynthesis of DNA precursors.

Authors

R G Wickremasinghe, A V Hoffbrand

Calcium transport in the pars recta and thin descending limb of Henle of the rabbit, perfused in vitro.

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Abstract

Unidirectional calcium flux (JCa) in the superficial pars recta and thin descending limb of Henle (DLH) was examined by the isolated tubule microperfusion technic using 45Ca as the isotopic tracer. In the pars recta sequential measurements of lumen-to-bath flux (JlbCa) and bath-to-lumen flux (JblCa) revealed: JlbCa 22.4 +/- 4.18, JblCa 7.97 +/- 1.95, and calculated net efflux of calcium (JnetCa 13.0 +/- 1.74 peq min-1 mm-u. To measure JnetCa directly, 45Ca of identical specific activity was used to bathe and perfuse the tubule. These studies revealed: JlbCa 14.1 +/- 1.33, JnetCa 11.2 +/- 1.15, and calculated JblCa 2.91 +/- 0.49 peq min-1 mm-1. The addition of ouabain (10 microM) resulted in a rise in potential difference and a fall in water absorption, but not a statistically significant change in JnetCa. Tubules studies at 25 degrees C bath temperature, showed no significant JnetCa, and upon heating the bath to 37 degrees C, showed JnetCa of 3.75--5.00 peg min-1 mm-1. Unidirectional and net efflux studies in six DLH showed no significant transport of calcium. These studies demonstrate substantial active absorption of calcium by the superficial pars recta, which is not inhibitable by ouabain but is inhibited by lowering bath temperature to 25 degrees C. No significant calcium transport was found in the DLH using identical technics.

Authors

D Rouse, R C Ng, W N Suki

Partial purification and characterization of a peptide with growth hormone-releasing activity from extrapituitary tumors in patients with acromegaly.

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Abstract

Growth hormone (GH)-releasing activity has been detected in extracts of carcinoid and pancreatic islet tumors from three patients with GH-secreting pituitary tumors and acromegaly. Bioactivity was demonstrated in 2 N acetic acid extracts of the tumors using dispersed rat adenohypophyseal cells in primary monolayer culture and a rat anterior pituitary perifusion system. The GH-releasing effect was dose responsive and the greatest activity was present in the pancreatic islet tumor. Small amounts of activity were also found in two other tumors (carcinoid and small cell carcinoma of lung) unassociated with GH hypersecretion. Each of the tumors contained somatostatin-like immunoreactivity but the levels did not correlate with the net biologic expression of the tumor. Sephadex G-75 gel filtration indicated the GH-releasing activity to have an apparent molecular size of slightly greater than 6,000 daltons. The GH-releasing activity was adsorbed onto DEAE-cellulose at neutral pH and low ionic strength, from which it could be eluted by increasing ionic strength. The GH-releasing activity was further purified by high pressure liquid chromatography using an acetonitrile gradient on a cyanopropyl column to yield a preparation that was active at 40 ng protein/ml. Partially purified GH-releasing activity, from which most of the bioactive somatostatin had been removed, increased GH release by pituitary monolayer cultures to five times base line. Enzymatic hydrolysis studies revealed that the GH-releasing activity was resistant to carboxypeptidase, leucine-aminopeptidase, and pyroglutamate-amino-peptidase but was destroyed by trypsin and chymotrypsin, indicating that internal lysine and/or arginine and aromatic amino acid residues are required for biologic activity and that the NH2-terminus and CO9H-terminus are either blocked or not essential. The results provide an explanation for the presence of GH-secreting tumors in some patients with the multiple endocrine neoplasia syndrome, type I, and warrant the addition of GH-releasing activity to the growing list of hormones secreted by tumors of amine precursor uptake and decarboxylation cell types.

Authors

L A Frohman, M Szabo, M Berelowitz, M E Stachura

Mechanisms of antibody-dependent cellular cytotoxicity: the use of effector cells from chronic granulomatous disease patients as investigative probes.

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Abstract

The present study characterized the antibody-dependent cellular cytoxicity (ADCC) of leukocyte effector cells (neutrophils, lymphocytes, and monocytes) from normal subjects and from chronic granulomatous disease (CGD) patients. CGD phagocytic cells (neutrophils and monocytes) had depressed ADCC activity against antibody-coated human erythrocyte (HRBC) targets in suspension cultures indicative of abnormal intracellular postphagocytic killing. However, when phagocytosis was prevented by using a monolayer of antibody-coated HRBC targets, CGD monocytes, neutrophils, and lymphocytes exhibited normal ADCC activity. Similarly, antibody-coated HRBC targets in suspension could be lysed normally by CGD effector cells when phagocytosis was inhibited by the addition of in vitro colchicine. Extracellular lysis of autologous antibody-coated lymphoid cell targets in suspension was mediated normally by CGD effector cells. Thus, standard ADCC against HRBC targets in suspension is predominantly indicative of postphagocytic killing and, as such, is dependent upon a normal post-phagocytic respiratory burst of oxidative metabolism which is deficient in CGD neutrophils and monocytes. Extracellular killing of sensitized targets does not appear to be dependent upon the generation of hydrogen peroxide (H2O2) ANd/or superoxide (02-) and is normal in CGD neutrophils and monocytes. Hence, by employing CGD leukocytes as investigative probes in ADCC, fundamental mechanisms of intracellular vs. extracellular expression of cytotoxicity have been delineated.

Authors

P Katz, C B Simone, P A Henkart, A S Fauci

Effect of Heparin and Heparin Fractions on Platelet Aggregation

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Abstract

Porcine intestinal mucosal heparin induced aggregation of platelets in citrated platelet-rich plasma and enhanced platelet aggregation and serotonin secretion induced by other agents. This action of heparin was blocked by substances that elevate platelet cyclic AMP and by EDTA but not by inhibitors of platelet cyclooxygenase. The effect was not inhibited by apyrase or by N-amylthio-5′-AMP and therefore did not require the action of ADP, nor was there activation of platelet phospholipase. Platelet aggregation by heparin required a plasma cofactor different from the cofactor required for ristocetin.

Authors

Edwin W. Salzman, Robert D. Rosenberg, Marianne H. Smith, Jack N. Lindon, Leonard Favreau

Evidence that proteases are involved in superoxide production by human polymorphonuclear leukocytes and monocytes.

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Abstract

The possible participation of proteases in superoxide (O2-) production by human polymorphonuclear leukocytes (PMN) and monocytes was explores using various protease inhibitors and substrates. Protease inhibitors of serine proteases and synthetic inhibitors that modify the active site of serine proteases. Substrates used were synthetic substrates of the chymotrypsin type as well as trypsin type of protease. All these inhibitors and substrates inhibited O2- oroduction by human PMN and monocytes induced by cytochalasin E and concanavalin A, though PMN were more sensitive to these inhibitors and substrates than monocytes. Inhibition appeared rapidly even when the inhibitors were added at the same time as the stimulants, during the "induction time of O2-production" or at the time of maximum O2- production, whereas much greater inhibition was observed when the cells were preincubated with the inhibitors. These observations suggest that enzymatically active serine proteases are essential for these phagocytic cells to initiate and maintain the O2- production in response to the stimuli. The inhibitory effect of the inhibitor and substrate for chymotrypsin type protease was greater than that of those substances for trypsin-type protease. Macromolecular inhibitors also inhibited the O2- production. These findings suggest that the serine proteases involved in the O2- production by human PMN and monocytes are similar to chymotrypsin rather than trypsin, and are possibly located at the cell surface membrane.

Authors

S Kitagawa, F Takaku, S Sakamoto

Influence of the Escherichia coli capsule on complement fixation and on phagocytosis and killing by human phagocytes.

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Abstract

To define mechanisms by which polysaccharide capsules confer enhanced virulence on gram-negative bacteria, we examined the effect of the Escherichia coli capsule on complement fixation to the bacterial surface and on phagocytosis and killing of these bacteria by mouse macrophages and human polymorphonuclear leukocytes (PMN) and monocytes. When E. coli were attached to mouse macrophages with concanavalin A, the macrophages readily phagocytosed unencapsulated but not encapsulated bacteria even in the presence of fresh mouse serum; macrophages did not phagocytose encapsulated E. coli unless antibacterial or anti-Con A antibody was added. Similarly, when these bacteria were attached to human PMN with Con A, PMN ingested unencapsulated but not encapsulated E. coli. PMN phagocytosed and killed encapsulated serum-resistant E. coli only in the presence of both complement and antibacterial antibody; PMN phagocytosed and killed unencapsulated E. coli of the same strain in the presence of complement alone. Fluorescence microscopy showed that antibody had to be present for encapsulated but not unencapsulated E. coli to fix complement to its surface. To examine the role of the complement receptors of human PMN and monocytes in phagocytosis and killing of encapsulated E. coli, we used human and rabbit antibacterial immunoglobulin (Ig)M to fix complement to the bacteria. PMN and monocytes phagocytosed and killed encapsulated E. coli in the presence of both IgM and complement, but not in the presence of either serum opsonin alone. In the presence of antibacterial IgG, PMN and monocytes required complement to effectively phagocytose and kill the E. coli. We conclude that (a) attachment by itself results in ingestion of unencapsulated but not encapsulated E. coli; (b) under physiologic conditions, E. coli are not phagocytosed or killed the absence of antibody, the E. coli capsule blocks complement fixation to the bacterial surface probably by masking surface components, such as lipopolysaccharide, capable of activating the complement pathway; (d) the E. coli capsule imposes a requirement for specific antibacterial antibody for complement fixation; and (e) the complement receptor of human PMN and monocytes mediates phagocytoses of complement-coated encapsulated bacteria and is the primary mediator of phagocytosis and killing of these bacteria.

Authors

M A Horwitz, S C Silverstein

Abnormal Polyamine Metabolism in Hereditary Muscular Dystrophies: EFFECT OF HUMAN GROWTH HORMONE

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Abstract

Previous studies showed hyperre-sponsiveness to human growth hormone (hGH) in men with myotonic or limb girdle dystrophies (MMD or LGD). Because polyamines may mediate some actions of hGH, we have now investigated polyamine metabolism in these and other dystrophies.

Authors

Daniel Rudman, Michael H. Kutner, Rajender K. Chawla, Martin A. Goldsmith

Erythrocyte metabolism in purine nucleoside phosphorylase deficiency after enzyme replacement therapy by infusion of erythrocytes.

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Purine nucleoside phosphorylase deficiency is associated with a severely defective T-cell immunity. A patient with purine nucleoside phosphorylase deficiency was treated with transfusions of irradiated erythrocytes and plasma. This resulted in a remarkable correction of the metabolic disturbances in the patient. The urinary excretion of inosine, deoxyinosine, guanosine, and deoxyguanosine decreased, whereas uric acid excretion as well as serum uric acid concentration increased. It could be shown that the enzyme activity of the circulating erythrocytes correlated inversely with the urinary excretion of nucleosides and directly with the excretion of uric acid. As a consequence of the therapy, several glycolytic intermediates of the erythrocytes were increased, especially 2,3-diphosphoglycerate. The high 2,3-diphosphoglycerate level caused a shift to the right of the oxygen dissociation curve (P50 = 32.9 mm Hg). The immunological status of the patient showed definite improvement after the enzyme replacement therapy.

Authors

G E Staal, J W Stoop, B J Zegers, L H Siegenbeek van Heukelom, M J van der Vlist, S K Wadman, D W Martin

Variant human phosphoribosylpyrophosphate synthetase altered in regulatory and catalytic functions.

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An inherited, structurally abnormal and superactive form of the enzyme 5-phosphoribosyl 1-pyrophosphate (PP-ribose-P) synthetase (EC 2.7.6.1) has been characterized in fibroblasts cultured from a 14-yr-old male (S.M.) with clinical manifestations of uric acid overproduction present since infancy. PP-ribose-P synthetase from the cells of this child showed four- to fivefold greater than normal resistance to purine nucleotide (ADP and GDP) feedback inhibition of enzyme activity and hyperbolic rather than sigmoidal inorganic phosphate (Pi) activation in incompletely dialyzed extracts. Excessive maximal velocity of the enzyme reaction catalyzed by the mutant enzyme was indicated by: enzyme activities twice those of normal at all concentrations of Pi in chromatographed fibroblast extracts; normal affinity constants for substrates and for the activator, Mg2+; and twofold greater than normal activity per immunoreactive enzyme molecule. The mutant enzyme thus possessed deficient regulatory and superactive catalytic properties, two mechanisms previously demonstrated individually to underlie the excessive PPRribose-P and uric acid synthesis of affected members of families with superactive PP-ribose-P synthetases. Increased PP-ribose-P concentration (4-fold) and generation (2.7-fold) and enhanced rates of PP-ribose-P dependent purine synthetic reactions, including purine synthesis de novo, in S.M. fibroblasts confirmed the functional significance of this patient's mutant enzyme. Diminished stability of the variant PP-ribose-P synthetase was manifested in vitro by increased thermal lability and in vivo by deficiency of enzyme activity at Pi concentrations greater than 0.3 mM in hemolysates and by an accelerated, age-related decrement in enzyme activity in lysates of erythrocytes separated by specific density. Despite the diminished amount of PP-ribose-P synthetase in the S.M. erythrocyte population, S.M. erythrocytes had increased PP-ribose-P concentration and increased rates of incorporation of [14C]adenine and hypoxanthine into acid-soluble nucleotides during incubation at 1 mM Pi. These findings provided further confirmation of the extent to which PP-ribose-P synthesis is modulated in the normal cell at physiological Pi concentration by purine nucleotide inhibition of PP-ribose-P synthetase. The activity and kinetic characteristics of PP-ribose-P synthetase from fibroblasts of the mother of patient S.M. indicated that this woman was a heterozygous carrier of the enzyme defect expressed in hemizygous manner by her son.

Authors

M A Becker, K O Raivio, B Bakay, W B Adams, W L Nyhan

Glomerular Endothelial Cells in Uranyl Nitrate-induced Acute Renal Failure in Rats

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Abstract

In uranyl nitrate (UN)-induced acute renal failure (ARF) glomerular ultrafiltration coefficient (Kf) decreases because of unknown reasons. Since transport of water across the glomerular capillary wall occurs predominantly extracellularly through the endothelial fenestrae (EF), a reduction in the diameter and/or the density of EF can reduce the extracellular filtration area and the glomerular Kf. To examine this possibility, ARF was induced in rats by intravenous administration of UN in low (15 mg/kg) and high doses (25 mg/kg). Fenestral density (¯x±SEM) per 5 cm2 from the scanning electron micrographs (×30,000) was 107±10, 103±9, and 101±11 at 2, 7, and 17 h after the intravenous administration of bicarbonate saline to the control rats. In the low-dose UN group the EF density was 91±2, 52±8, and 45±11 at 2, 7, and 17 h after the injection, whereas for the high-dose group at corresponding time intervals the EF density was 95±3, 54±9, and 44±10. Fenestral diameters, in Angstrom units (¯x±SEM), were 751±53, 765±43, and 764±37 at 2, 7, and 17 h after the injection of bicarbonate saline to control rats. At corresponding intervals after the administration of UN, the fenestral diameters were 501±61, 472±28, and 438±98 for the low-dose group and 525±43, 470±39, and 440±56 for the high-dose group. 2, 7, and 17 h after the injection of UN, fenestral area of the low-dose group decreased to 52.1, 30.1, and 24.6% of the controls, whereas in the high-dose group, the fenestral area declined to 54.3, 30.2, and 23.6% of the controls. Administration of UN (15 mg/kg) to sodium-loaded rats did not alter renal function or endothelial cell morphology. It is suggested that in UN-induced ARF the morphological alterations in endothelial cells reduce the Kf of glomerular capillaries by reducing the filtration area.

Authors

P. S. Avasthi, A. P. Evan, D. Hay

Enzymatic Defenses of the Mouse Heart Against Reactive Oxygen Metabolites: ALTERATIONS PRODUCED BY DOXORUBICIN

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The endogenous defenses of the mouse heart against reactive oxygen metabolites were investigated. The activities of three enzymes capable of detoxifying activated oxygen were determined in both the heart and liver; cardiac muscle contains 150 times less catalase and nearly four times less superoxide dismutase than liver. Glutathione peroxidase activities were, however, similar to the two tissues. Assay of glutathione peroxidase in the heart after 6 wk of selenium depletion with both hydrogen peroxide and cumene hydroperoxide as substrates revealed a >80% drop in enzyme activity and gave no indication that murine cardiac tissue contains nonselenium-dependent glutathione peroxidase. The selenium-deficient state, which was characterized by markedly decreased cardiac glutathione peroxidase levels, led to significantly enhanced doxorubicin toxicity at a dose of 15 mg/kg i.p.

Authors

James H. Doroshow, Gershon Y. Locker, C. E. Myers

Detection of immune complexes in acute rheumatic fever and their relationship to HLA-B5.

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Employing five radioimmunoassays for immune complexes, the sera of 45 acute and 27 postacute follow-up sera from patients with acute rheumatic fever were examined. All patients experienced actue polyarthritis. Complexes were detected in 89% of acute-phase sera by one assay, 51% by two, 29% by three, and 7% by four. Immune complex values decreased significantly at followup, although some abnormalities persisted. There was no correlation between extra-articular manifestations and the occurrence of circulating immune complexes. Those positive for HLA-B5 demonstrated a significantly more pronounced immune response as measured by circulating immune complexes. The data indicate that circulating immune complexes occur frequently in adults with acute rheumatic fever. The relative frequency of immune complexes detected by multiple techniques in B5-positive, compared with B5-negative, patients suggests a genetic basis for the development of immune complexes in these patiemts.

Authors

S Yoshinoya, R M Pope

Increased growth hormone response to dopamine infusion in insulin-dependent diabetic subjects: indication of possible blood-brain barrier abnormality.

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To test the hypothesis that cerebral capillaries, which share the embroyologic and morphologic characteristics of retinal capillaries, might have the same abnormal permeability in diabetic patients, we investigated the growth hormone response to a small amount of peripherally administered dopamine (1.5 microgram/kg.min). Consistent with the known exclusion of systemic dopamine from brain parenchyma, no rise was observed in 12 normal subjects. In 10 of 12 juvenile-onset, insulin-dependent diabetic patients, however, a substantial growth hormone rise occurred (peak value, 19.2 +/- 3.0 ng/ml [mean +/- SE]). Comparision of metabolic and cardiovascular responses to the infusion in both groups did not suggest that higher circulating levels of dopamine had been achieved in the diabetics. Other growth hormone stimuli (apomorphine in decreasing amounts, glucagon, and graded physical exercise) failed to indicate that hypothalamic hypersensitivity could account for the consistent rise. We postulate that an abnormal permeability of the blood-brain barrier in the diabetic patients permitted exposure of the hypothalamic structures regulating growth hormone secretion to a greater fraction of the infused dopamine.

Authors

M Lorenzi, J H Karam, M B McIlroy, P H Forsham

Abnormal Adherence of Sickle Erythrocytes to Cultured Vascular Endothelium: POSSIBLE MECHANISM FOR MICROVASCULAR OCCLUSION IN SICKLE CELL DISEASE

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The abnormal shape and poor deformability of the sickled erythrocyte (RBC) have generally been held responsible for the microvascular occlusions of sickle cell disease. However, there is no correlation between the clinical severity of this disease and the presence of sickled RBC. In searching for additional factors that might contribute to the pathophysiology of sickle cell disease, we have investigated the possibility that sickle RBC might be less than normally repulsive of the vascular endothelium. After RBC suspensions are allowed to settle onto plates of cultured human endothelial cells, normal RBC are completely removed by as few as six washes. In contrast, sickle RBC remain adherent despite multiple washes. On subconfluent culture plates, normal RBC are distributed randomly, whereas sickle RBC cluster around endothelial cells. Sickle RBC adherence is not enhanced by deoxygenation but does increase with increasing RBC density. The enzymatic removal of membrane sialic acid greatly diminishes the adherence of sickle RBC to endothelial cells, suggesting that sialic acid participates in this abnormal cell-cell interaction. Although net negative charge appears normal, sickle RBC mainfest an abnormal clumping of negative surface charge as demonstrated by localization of cationized ferritin. These abnormalities are reproduced in normal RBC loaded with nonechinocytogenic amounts of calcium. We conclude that sickle RBC adhere to vascular endothelial cells in vitro, perhaps caused by a calcium-induced aberration of membrane topography. This adherence may be a pathogenetic factor in the microvascular occlusions characteristic of sickle cell disease.

Authors

Robert P. Hebbel, Osamu Yamada, Charles F. Moldow, Harry S. Jacob, James G. White, John W. Eaton

Alpha adrenergic contributions to dysrhythmia during myocardial ischemia and reperfusion in cats.

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Alpha compared to beta adrenergic contributions to dysrhythmias induced by left anterior descending coronary occlusion and by reperfusion were assessed in chloralose-anesthetized cats (n = 96). Alpha receptor blockade with either phentolamine or prazosin significantly reduced the number of premature ventricular complexes during coronary reperfusion (321 +/- 62-14 +/- 10 premature ventricular complexes, P less than 0.001), abolished early ventricular fibrillation (from 25% in controls to 0%), and prevented the increase in idioventricular rate seen with coronary reperfusion. However, beta-receptor blockade was without effect. Ventricular dysrhythmias induced by coronary occlusion alone (without reperfusion) were attenuated markedly by alpha-receptor blockade under conditions in which perfusion (measured with radiolabeled microspheres) within ischemic zones was not affected. Alternative sympatholytic interventions including pretreatment with 6-hydroxydopamine to deplete myocardial norepinephrine from 8.8 +/- 1.4 to 0.83 +/- 0.2 ng/mg protein and render the heart unresponsive to tyramine (120 microgram/kg) attenuated dysrhythmias induced by both coronary occlusion and reperfusion in a fashion identical to that seen with alpha-receptor blockade. Although efferent sympathetic activation induced by left stellate nerve stimulation increased idioventricular rate from 66 +/- 6 to 144+/- 7 beats/min (P less than 0.01) before coronary occlusion, this response was blocked by propranolol but not by phentolamine. In contrast, during reperfusion the increase in idioventricular rate induced by left stellate nerve stimulation (to 203 +/- 14) was not inhibited by propranolol but was abolished by phentolamine (79 +/- 10). Intracoronary methoxamine (0.1 microM) in animals depleted of myocardial catecholamines by 6-hydroxydopamine pretreatment did not affect idioventricular rate before coronary occlusion. However, early after coronary reperfusion, methoxamine increased idioventricular rate from 33 +/- 7 to 123 +/- 21 beats/min (P less than 0.01). Thus, enhanced alpha-adrenergic responsiveness occurs during myocardial ischemia and appears to be primary mediator of the electrophysiological derangements and resulting malignant dysrhythmias induced by catecholamines during myocardial ischemia and reperfusion.

Authors

D J Sheridan, P A Penkoske, B E Sobel, P B Corr

Immune responses in human infections with Brugia malayi: specific cellular unresponsiveness to filarial antigens.

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We evaluated the cellular immune competence of 101 subjects living in an area of South Kalimantan (Borneo) where Malayan filariasis is endemic. All patients with elephantiasis but none with other clinical stages of filariasis reacted with adult worm antigens. The majority of subjects without clinical or parasitological evidence of filariasis and approximately one-half of those with amicrofilaremic filariasis reacted with microfilarial antigens. In contrast, most patients with patent microfilaremia did not respond to microfilarial antigens. The in vitro reactivity of all patient categories to nonparasite antigens was similar to that of the distant control group. These results indicate that patent microfilaremia is associated with a state of specific cellular immune unresponsiveness and are consistent with the current hypothesis that the various clinical manifestations of filariasis result from different types of immune responses to distinct antigens associated with different developmental stages of filarial worms.

Authors

W F Piessens, P B McGreevy, P W Piessens, M McGreevy, I Koiman, J S Saroso, D T Dennis

Effect of magnesium deficiency on renal magnesium and calcium transport in the rat.

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Abstract

Recollection of micropuncture experiments were performed on acutely thyroparathyroidectomized rats rendered magnesium deficient by dietary deprivation. Urinary magnesium excretion fell from a control of 15 to 3% of the filtered load after magnesium restriction. The loop of Henle, presumably the thick ascending limb, was the major modulator for renal magnesium homeostasis. The transport capacity for magnesium, however, was less in deficient rats than control animals. Absolute magnesium reabsorption increased with acute infusions of magnesium chloride but was always less in magnesium-deficient rats than control rats for any given filtered load, which suggests either a defect of a resetting of the reabsorption mechanism. Recollection micropuncture demonstrated that this was a characteristic of the loop of Henle. Proximal magnesium reabsorption remained unchanged at 15% of the filtered load and was unaffected by magnesium deficiency or acute magnesium repletion. Distal tubular magnesium reabsorption was limited during depletion and increased to a similar extent in control and deficient rats with enhanced magnesium delivery. Calcium reabsorption was not altered in magnesium deficiency; however, elevations of extracellular magnesium resulted in a specific inhibition of calcium reabsorption within the loop of Henle. These data suggest that overall control of renal magnesium reabsorption occurs within the loop of Henle and that the proximal tubule reabsorbs a constant fraction of the filtered load despite variations in body magnesium status.

Authors

S L Carney, N L Wong, G A Quamme, J H Dirks

Deformability of oxygenated irreversibly sickled cells.

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The deformability characteristics of isolated subpopulations of irreversibly sickled cells (ISC) have been studied in an ektacytometer. Analysis of laser diffraction patterns of well-oxygenated cells subjected to shear stress in solutions of varying osmolality has demonstrated a profound influence of mean corpuscular hemoglobin concentration and intracellular viscosity on the deformability of ISC. Virtually undeformable at 290 mosM, ISC became almost totally deformable at 130 mosM. In addition, when ISC membranes were loaded with normal hemoglobin at low concentration, they deformed easily in isotonic medium, as did resealed normal cell membranes. The restoration of deformability of ISC upon reduction of their hemoglobin concentration and internal viscosity to normal levels suggests that altered membrane properties are not the primary determinant of decreased deformability in these cells. Rather, cellular dehydration induced by previous sickling would appear to contribute in a major way to their abnormal rheological behavior.

Authors

M R Clark, N Mohandas, S B Shohet

Activation of Rabbit Hageman Factor by Homogenates of Cultured Rabbit Endothelial Cells

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Abstract

Rabbit Hageman factor was proteolytically cleaved and activated by a homogenate prepared from cultured rabbit endothelial cells. Cleavage of radiolabeled Hageman factor was monitored by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. Endothelial cell-mediated cleavage of Hageman factor was demonstrated both in a purified system and in plasma, was time and concentration dependent, and was associated with formation of the characteristic 28,000 Mr form of active Hageman factor. The rate of cleavage of Hageman factor was not affected by Triton X-100 (Rohm and Haas, Co., Philadelphia, Pa.), hexadimethrine bromide (Polybrene, Aldrich Chemical Co., Inc., Milwaukee, Wis.), hirudin, soybean trypsin inhibitor, or antisera to plasminogen or prekallikrein. However, cleavage was enhanced by kaolin, and was inhibited by diisopropyl-fluorophosphate. The enzyme responsible for cleavage of Hageman factor was localized to the 100,000-g-sedimentable, subcellular fraction of the endothelial cell homogenate and was relatively specific, because neither radiolabeled rabbit Factor XI nor rabbit prekallikrein were themselves proteolytically cleaved by the endothelial cell homogenate. However, when these molecules were incubated with the homogenate in the presence of Hageman factor, both Factor XI and prekallikrein were cleaved, demonstrating that Hageman factor had been activated by the endothelial cell homogenate. Furthermore, the kallikrein generated by endothelial cell homogenate-activated Hageman factor was capable of liberating kinin from high molecular weight kininogen as measured by bioassay. Cultured rabbit endothelial cells, therefore, possess the capacity to activate Hageman factor by proteolysis. This may be one mechanism for Hageman factor activation in vivo.

Authors

Roger C. Wiggins, David J. Loskutoff, Charles G. Cochrane, John H. Griffin, Thomas S. Edgington

Adaptations of alpha2- and beta-cells of rat and mouse pancreatic islets to starvation, to refeeding after starvation, and to obesity.

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Abstract

The effects of starvation and refeeding and of obesity on pancreatic alpha2- and beta-cell responses to glucose or tolbutamide were studied with the isolated rat or mouse pancreas perfused with an amino acid mixture in the presence and absence of glucose. It was observed that the physiological adaptation to a regimen of fasting and realimentation and to obesity differed greatly in the two types of endocrine cells. Whereas beta-cells of rats showed a dramatic reduction of glucose- and tolbutamide-stimulated insulin release during starvation that was reversed by refeeding, alpha2-cells preserved their response to stimulators and inhibitors during this experimental manipulation. Amino acid stimulation of glucagon release occurred equally well with the pancreas from fed and starved rats and was suppressed efficiently by glucose and tolbutamide in both nutritional states. Surprisingly, the rate of onset of glucose suppression of alpha2-cells was significantly higher in the fasted than in the fed state. This glucose hypersensitivity was apparent 2 d after after food deprivation and had disappeared again on the 2nd d of refeeding. In the pancreas from animals starved for 3 d, glucose and tolbutamide suppression of alpha2-cells took place in the absence of demonstrable changes of insulin release. In the isolated perfused pancreas taken from the hyperphagic obese hyperglycemic mouse (C57 Black/6J; ob/ob), the observed rate of insulin secretion as a result of a combined stimulus of amino acids and glucose and of glucagon release stimulated by amino acids was about four times higher than achieved by the pancreas of lean controls. However, glucose was unable to suppress the alpha2-cells in the pancreas of obese animals, in spite of the hypersection of the beta-cells, again in contrast to the alpha2-cells of controls that were readily inhibited by glucose. These data imply that the acute suppression of alpha2-cells by glucose is largely independent of a concomitant surge of extracellular insulin levels and that the adaptation of the islet organ to starvation leads to decreased glucose sensitivity of beta-cells, which contrasts with an improved glucose responsiveness of alpha2-cells. However, hyperphagia, which is assumed to be the primary abnormality in the ob/ob mouse, leads to overproduction of insulin and glucagon by the pancreas while greatly reducing the alpha2-cell sensitivity to glucose. An attempt is made to incorporate these data on starvation, refeeding, and obesity, as well as previous results with experimental diabetes, in a comprehensive picture describing a regulative principle underlying the glucose responsivness of alpha2-cells.

Authors

F M Matschinsky, C Rujanavech, A Pagliara, W T Norfleet

Monocytes do not inhibit peripheral blood erythroid burst forming unit colony formation.

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Abstract

To determine a possible role of peripheral blood monocytes in erythroid differentiation, various fractions of peripheral blood mononuclear cells were prepared from normal volunteers. The fractions contained 3-95% monocytes. These freshly prepared monocytes did not inhibit erythroid burst forming unit expression in plasma clot erythroid colony culture. Null cell preparations contaminated by up to 84% monocytes expressed erythroid burst forming unit colony formation when either T lymphocytes or T-cell conditioned medium was added. These results indicate that certain peripheral blood null cells engage the program of erythroid differentiation in the presence of T cells and erythropoietin. Monocytes do not inhibit this engagement.

Authors

J M Lipton, N A Link, J Breard, P L Jackson, B J Clarke, D G Nathan

Magnitude of the fetal hemoglobin response to acute hemolytic anemia in baboons is controlled by genetic factors.

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Abstract

When hemolytic anemia was induced in 26 baboons (Papio cynocephalus), aged 7-22 mo, they increased their production of fetal hemoglobin (HbF). Although the resulting reduction in hematocrits and increases of reticulocyte counts were similar in all stressed animals there was marked variability in the maximal rates of HbF synthesis. The maximal levels of HbF attained appeared to fall into three separate groups: low, intermediate, and high. These differences were not related to sex or several measures of erythrocyte metabolism. Animals exposed to repeated episodes of erythropoietic stress after full hematologic recovery demonstrated some variability in their maximal HbF levels attained from one episode to another, but these variations never extended to adjacent classes. The described biochemical and mating data suggest that the magnitude of the HbF response to hemolytic anemia is controlled by genetic factors.

Authors

J DeSimone, P Heller, J Amsel, M Usman

Elevated Thromboxane Levels in the Rat during Endotoxic Shock: PROTECTIVE EFFECTS OF IMIDAZOLE, 13-AZAPROSTANOIC ACID, OR ESSENTIAL FATTY ACID DEFICIENCY

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Abstract

The potential deleterious role of the proaggregatory vasoconstrictor, thromboxane A2, in endotoxic shock was investigated in rats. Plasma thromboxane A2 was determined by radioimmunoassay of its stable metabolite thromboxane B2. After intravenous administration of Salmonella enteritidis endotoxin (20 mg/kg), plasma thromboxane B2 levels increased from nondetectable levels (<375 pg/ml) in normal control rats to 2,054±524 pg/ml (n = 8), within 30 min to 2,071±429 at 60 min, and decreased to 1,119±319 pg/ml, at 120 min. Plasma levels of prostaglandin E also increased from 146±33 pg/ml in normal controls (n = 5) to 2,161±606 pg/ml 30 min after endotoxin (n = 5).

Authors

J. A. Cook, W. C. Wise, P. V. Halushka