Renal Net Glucose Release In Vivo and Its Contribution to Blood Glucose in Rats

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Abstract

This study describes the contribution of de novo glucose synthesis by the kidney to blood glucose homeostasis in rats. The net glucose release by the kidney in vivo was measured by an isotope-dilution method, which calculated the extent of dilution of injected [14C]glucose by glucose newly synthesized in the kidney. The extent of dilution was determined from the difference between the decrease of the actual blood glucose concentration and that of the radioactivity of [14C]glucose, after injecting [14C]glucose into functionally hepatectomized rats.

Authors

Kaichi Kida, Shinjiro Nakajo, Fumitada Kamiya, Yoshiko Toyama, Takashi Nishio, Hachiro Nakagawa

Characterization of proinsulin-insulin intermediates in human plasma.

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Abstract

This work addressed the problem of heterogeneity of immunoreactive insulin (IRI) in human plasma. Subjects with normal glucose tolerance were given 75g of an oral glucose solution, followed in 30 min by an intravenous infusion of 30g of arginine over 30 min. At the end of the infusion blood was withdrawn for analysis. IRI was extracted from plasma of individual subject by immunosorbent columns and was fractionated by gel filtration, disc gel electrophoresis and isoelectric focusing. Human IRI components were identified by molecular size, immunoreactivity with a human proinsulin antibody, sensitivity to trypsin, and by comparison of electrophoretic mobility and isoelectric point with porcine pancreatic products, after suitable correction for electric charge and molecular weight differences. The pattern of IRI heterogeneity was the same among six healthy subjects. Heterogeneity of proinsulin-size IRI in circulation was more marked than that of insulin-size material. Proinsulin and desdipeptide proinsulin were present in approximately equal amounts accompanied by minor amounts of split proinsulin and monodesamido-desdipeptide proinsulin. Insulin-size IRI contained over 80% insulin. Minor amounts of monodesamidoinsulin and diarginylinsulin were observed in some cases. The types of IRI components observed in plasma are evidence in support of a physiologic role of trypsin-and carboxypeptidase B-like enzymes in the conversion of proinsulin to insulin. Moreover, this study provides a base line for investigation of abnormalities in proinsulin-to-insulin conversion that may be associated with certain pathologic states.

Authors

C de Haën, S A Little, J M May, R H Williams

Role of Plasma Vasopressin in Impaired Water Excretion of Glucocorticoid Deficiency

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Abstract

In the present study, the effect of selective glucocorticoid deficiency on renal water excretion was investigated in conscious, trained, adrenalectomized dogs. The animals were studied before and after a water load while on replacement therapy of desoxycorticosterone acetate, 5 mg/day, and dexamethasone, 0.8 mg/day (group I), and while off dexamethasone for 5-9 days (group II). Before the water load the weight, inulin space, cardiac output, blood pressure, glomerular filtration rate, renal blood flow, plasma osmolality, and plasma antidiuretic hormone measured by radioimmunoassay were similar in both groups I and II. However, after a 40 ml/kg water load a marked impairment in renal water excretion in the glucocorticoid deficient dogs became apparent. Maximal free water clearance was −0.046±0.16 vs. 6.51±0.72 ml/min (P < 0.001) and minimal urinary osmolality was 425±56 vs. 82±3.5 mosmol/kg H2O (P < 0.001) in group II as compared to group I. Plasma antidiuretic hormone was maximally suppressed during the water load in group I to 0.34±0.08 pg/ml but remained elevated at 9.18±1.79 pg/ml (P < 0.005) in group II. This nonsuppressibility of plasma antidiuretic hormone during water loading in group II was associated with a significant tachycardia of 145±6 vs. 87±6 beats/min (P < 0.001) in group I and a significantly lower stroke volume of 27±0 vs. 59±0.5 ml/beat (P < 0.001). In conclusion, our results implicate a persistent secretion of antidiuretic hormone as an important factor in the impaired water excretion of glucocorticoid deficiency. A deleterious effect of glucocorticoid deficiency on cardiac function was observed and this hemodynamic alteration could be involved in initiating a nonosmolar, baroreceptor-mediated release of vasopressin.

Authors

John Boykin, Antoine Detorrenté, Abby Erickson, Gary Robertson, Robert W. Schrier

Cold-insoluble globulin (fibronectin) in connective tissues of adult human lung and in trophoblast basement membrane.

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Abstract

Cold-insoluble globulin (CIG), which is immunochemically indistinguishable from the fibroblast surface protein known as large external transformation-sensitive glycoprotein and fibronectin, was detected immunologically in connective tissue fractions from adult human lung. The fractions tested were (a) intact parenchyma, (b) acidic structural glycoproteins (ASG) extracted from lung parenchyma with 0.3 M acetic acid, and (c) isolated alveolar basement membrane (ABM). For comparison with ABM, preparations of human glomerular basement membrane and human trophoblast basement membrane (TBM) were tested. CIG was not detected in glomerular basement membrane but was present in large amounts in TBM. The CIG antigen could be solubilized from the parenchyma and from ABM by collagenase digestion which indicates that CIG occurs in lung connective tissue in association with collagen. Fibrinogen antigenic determinants were present in the ASG fraction, but the question of whether CIG and fibrin(ogen) are associated in lung connective tissue requires further study. When CIG was quantified by electroimmunoassay, intact lung parenchyma contained approximately equal to 0.4% CIG, ASG contained 3-4.5% CIG, ABM contained 0.1-0.9% CIG and TBM contained 1.5%-7.2% Cg. the evidence suggests that CIG is a chemical constituent of lung connective tissue matrix where it may influence the function of alveoli.

Authors

B A Bray

Prostaglandin Suppression of Mitogen-Stimulated Lymphocytes In Vitro: CHANGES WITH MITOGEN DOSE AND PREINCUBATION

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Abstract

In this study we further characterize the properties of the prostaglandin-producing suppressor cell. Overnight preincubation of peripheral blood mononuclear cells results in an increased response of the cells to phytohemagglutinin or Concanavalin A compared to the response of fresh cells. This increase in mitogen response with preincubation was similar in magnitude to the increase in mitogen response of fresh cells after the addition of indomethacin. The two manipulations were not additive; that is, after preincubation, indomethacin caused much less enhancement of mitogen stimulation of peripheral blood mononuclear cells (100 ± 12% increase before preincubation vs. 12 ± 6% after preincubation; mean±SEM, P < 0.001). Preincubated cells also lose sensitivity to inhibition by exogenous prostaglandin E2. It requires the addition of 100- to > 1,000-fold more exogenous PGE2 to produce comparable inhibition of phytohemagglutinin-stimulated preincubated cells than is required for inhibition of phytohemagglutinin-stimulated fresh cells.

Authors

James S. Goodwin, Ronald P. Messner, Glenn T. Peake

Role of Large Arteries in Regulation of Cerebral Blood Flow in Dogs

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Abstract

Previous studies have demonstrated a significant pressure gradient from carotid artery to pial or middle cerebral arteries. This pressure gradient suggests that large cerebral arteries contribute to cerebral resistance. We have tested the hypothesis that large cerebral arteries contribute to regulation of cerebral blood flow during changes in blood gases and arterial pressure. Microspheres were used to measure brain blood flow in anesthetized dogs. Resistance of large cerebral arteries was estimated by determining the pressure gradient between common carotid and wedged vertebral artery catheters. Systemic hypercapnia and hypoxia dilated large cerebral arteries, and hypocapnia constricted large cerebral arteries. Resistance of large arteries was 0.6±0.1 (mean ± SE) mm Hg per ml/min per 100 g during normocapnia. During hypercapnia and hypoxia, large artery resistance decreased significantly to 0.2 ± 0.03 and 0.3 ± 0.05, respectively. During hypocapnia large artery resistance increased significantly to 1.0 ± 0.1. In other experiments, we found that large cerebral arteries participate in auto-regulatory responses to hemorrhagic hypotension. When arterial pressure was reduced from 110 to 58 mm Hg, autoregulation maintained cerebral blood flow constant, and resistance of large cerebral arteries decreased significantly from 1.0 ± 0.2 to 0.6 ± 0.1 mm Hg per ml/min per 100 g. In absolute terms, we calculated that 20-45% of the change in total cerebral resistance during these interventions was accounted for by changes in large artery resistance. These studies indicate that large cerebral arteries, as well as arterioles, participate actively in regulation of cerebral blood flow during changes in arterial blood gases and during autoregulatory responses to hemorrhagic hypotension.

Authors

Donald D. Heistad, Melvin L. Marcus, Francois M. Abboud

Mechanism of Effect of Hypoxia on Renal Water Excretion

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Abstract

The effect of lowering the pressure of oxygen from 80 to 34 mm Hg was examined in anesthetized dogs that were undergoing a water diuresis. This degree of hypoxia was associated with an antidiuresis as urine osmolality (Uosm) increased from 107 to 316 mosmol/kg H2O (P < 0.001) and plasma arginine vasopressin increased from 0.06 to 7.5 μU/ml, (P < 0.05). However, hypoxia was not associated with significant changes in cardiac output (CO, from 4.2 to 4.7 liters/ min), mean arterial pressure (MAP, from 143 to 149 mm Hg), glomerular filtration rate (GFR, from 46 to 42 ml/min), solute excretion rate (SV, from 302 to 297 mosmol/min), or filtration fraction (from 0.26 to 0.27, NS). Hypoxia was associated with an increase in renal vascular resistance (from 0.49 to 0.58 mm Hg/ml per min, P < 0.01). The magnitude of hypoxia-induced antidiuresis was the same in innervated kidneys and denervated kidneys. To further examine the role of vasopressin in this antidiuresis, hypoxia was induced in hypophysectomized animals. The effect of hypoxia on CO, MAP, GFR, SV, and renal blood flow in hypophysectomized animals was the same as in intact animals. In contrast to intact animals, however, hypoxia did not induce a significant antidiuresis in hypophysectomized animals (Uosm from 72 to 82 mosmol/kg H2O). To delineate the afferent pathway for hypoxia-stimulated vasopressin release, hypoxia was induced in dogs with either chemo- or baroreceptor denervation. The effect of hypoxia on CO, MAP, GFR, SV, and renal blood flow in the denervated animals was the same as in nondenervated animals. Hypoxia resulted in an antidiuresis in chemoreceptor (Uosm from 113 to 357 mosmol/kg H2O, P < 0.001) but not in baroreceptor (Uosm from 116 to 138 mosmol/kg H2O, NS) denervated animals. To determine if hypoxia alters renal response to vasopressin, exogenous vasopressin was administered to normoxic and hypoxic groups of dogs. The antidiuretic effect of vasopressin was no different in these two groups. These results demonstrate that hypoxia induces an antidiuresis which is independent of alterations in CO, MAP, SV, filtration fraction, renal nerves, or renal response to vasopressin and occurs through baroreceptor-mediated vasopressin release. The nature of the baroreceptor stimulation remains to be elucidated.

Authors

Robert J. Anderson, Richard G. Pluss, Arnold S. Berns, James T. Jackson, Patricia E. Arnold, Robert W. Schrier, Keith M. McDonald

Pemphigus antibody interaction with human epidermal cells in culture.

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Abstract

The mechanism of pemphigus acantholysis has been studied with an in vitro system. Freshly prepared human skin epidermal cells were incubated in F-10 medium which contained the immunoglobulin G fraction from either pemphigus serum or normal human serum. During 18-h incubation periods, the pemphigus antibody became bound to the surface of the epidermal cells, caused the destruction of 75% of the viable cells as compared to only 14% in the normal immunoglobulin G controls (trypan blue exclusion), prevented the accumulation of newly synthesized proteins by nearly 60% as determined by radioactive tracer studies, and caused a dramatic shift in distribution of the newly synthesized proteins from an insoluble cell-associated fraction to an extracellular soluble fraction. These effects on the accumulation and partitioning of newly synthesized proteins were antibody concentration-dependent. Kinetic studies showed that at a fixed pemphigus antibody concentration the inhibition of protein accumulation preceded solubilization by about 1 h, at which time rapid solubilization of up to 70% of the insoluble cellular material occurred. Several lines of evidence suggested that this phenomenon was caused by enzymatic activity. Epidermal extracts solubilized a prepared substrate of radioactivity labeled insoluble epidermal cell material. This activity was heat labile and pH dependent, with pH optima ranging from 4.5 to 6.5. Enzymes with pH optima between 6 and 6.5 were recovered in the culture medium after a 2-day incubation of pure, intact epidermis with the pemphigus antibody. We proposed the following hypothesis to account for pemphigus acantholysis. The pemphigus antibody reacts with the epidermal cell surface and produces such a severe disturbance that the integrity of the cell surface is lost. As a result of these primary perturbations, the cell is killed and during the process, responds by release or activiation of soluble hydrolytic enzymes. This autolytic process results in the characteristic acantholysis of pemphigus.

Authors

J R Schiltz, B Michel, R Papay

Suppressor-Cell Dysfunction in Systemic Lupus Erythematosus: CELLS INVOLVED AND IN VITRO CORRECTION

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Abstract

To characterize the cell(s) responsible for the suppressor-cell dysfunction in active systemic lupus erythematosus (SLE), we fractionated blood mononuclear cells into thymus-derived (T), bone marrow-derived (B), and monocyte-depleted populations. Various cell populations from active SLE, inactive SLE, or normals, were activated with Concanavalin A, washed, and then co-cultured with active SLE cells. Soluble immune response suppressor (SIRS) from culture supernates of the activated cells was also used for the possible correction of the suppressor-cell dysfunction. Suppression was tested by enumerating DNA-binding cells by radioautography and by quantitating anti-DNA antibody in culture supernates by radioimmunoassay; and immunoglobulin was tested in cells and supernates by the immunofluorescence and the immunofluor techniques, respectively. Except for the numbers of DNA-binding cells, which were not suppressed, all the other three parameters in co-cultures with cells from active SLE patients were suppressed by Concanavalin A-activated cells (P < 0.001), or by SIRS (P < 0.05) from normals or inactive SLE patients. Concanavalin A-activated autologous or allogeneic active SLE cells and nonactivated cells from active or inactive SLE failed to suppress the various B-cell functions. Nonactivated normal cells suppressed levels of anti-DNA and immunoglobulin in supernates (P < 0.05).

Authors

Akira Sagawa, Nabih I. Abdou

Influence of methylprednisolone of the sequential redistribution of cathepsin D and other lysosomal enzymes during myocardial ischemia in rabbits.

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Abstract

Occlusion of the circumflex coronary artery induced a profound redistribution in ischemic rabbit myocardium of several lysosomal acid hydrolases, including cathepsin D, B-acetylglycosaminidase, and acid phosphatase. 30-45 min after ligation non-sedimentable cathepsin D activity rose from 36% of the total activity to 42-48%, and in immunohistochemical preparations cathepsin D appeared to have diffused from lysosomes into the cytosol of injured cells. A pharmacologic dose of methylprednisolone (50mg/kg) significantly delayed the subcellular redistribution of cathepsin D and the other hydrolases in ischemic heart. Thus, in treated hearts the nonsedimentable activity of cathepsin D rose to only 38% after 30 min of ischemia and 42% after 45 min (P is less than 0.05 compared to untreated ischemia at each time). Similarly, unlike untreated hearts, noevidence of enzyme diffusion from lysosomes could be demonstrated immunohistochemically in corticosteroid-treated ischemic hearts for over 45 min. After 1-2 h of ischemia, however, steroid-protected myocytes deteriorated and the biochemical activity and anatomical distribution of cathepsin D were indistinguishable from untreated ischemic hearts. This study demonstrates that corticosteroid pretreatment does not prevent alterations in cardiac lysosomes during severe ischemia indefinitely, but does delay their development significantly.

Authors

R S Decher, A R Poole, J T Dingle, K Wildenthal

Adherence of Glucan-Positive and Glucan-Negative Streptococcal Strains to Normal and Damaged Heart Valves

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Abstract

The adherence of 18 strains of streptococci to sections of normal canine and human aortic, mitral, and tricuspid valves and to canine interatrial septum was compared in an in vitro system. Quantitative measurements of adherence ratios were performed by two independent methods. Adherence ratios for Streptococcus mutans, S. sanguis, S. bovis, and Group D streptococci were higher (0.0058-0.0101) than for the other streptococcal strains studied (0.0025-0.0041). With the exception of Group D streptococci, adherence ratios for each bacterial strain were similar with the aortic, mitral, and tricuspid valve sections. Adherence ratios with normal human and canine valve leaflets were similar, but adherence ratios with interatrial septum were lower than with normal valve sections.

Authors

Carlos H. Ramirez-Ronda

Chronic Myelocytic Leukemia: ORIGIN OF SOME LYMPHOCYTES FROM LEUKEMIC STEM CELLS

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Abstract

In three patients with chronic myelocytic leukemia who were heterozygous at the X-linked glucose-6-phospháte dehydrogenase locus, lymphocytes were studied to determine if they had the same stem cell origin as the leukemic myeloid cells. Normal tissues such as skin had both B and A glucose-6-phosphate dehydrogenase isoenzymes, but the leukemic myelogenous cells displayed only one isoenzyme type, consistent with their clonal origin. A population of cells with undoubted thymus-derived (T)-lymphocyte characteristics had both isoenzymes. Presumably, then, these T cells did not arise from the leukemic stem cell, either because they antedated the development of leukemia in that stem cell or, more likely, because they arose from progenitors not involved by the disease. In contrast, another population of lymphocytes showed only one isoenzyme type, suggesting that it arose from the chronic myelocytic leukemia stem cell. However, although this population contained many cells with the characteristics of bone marrow-derived (B) lymphocytes, it is not certain that the single enzyme produced by the cells over all can be attributed to B lymphocytes rather than to contaminating non-B-lymphoid cells.

Authors

Philip J. Fialkow

Patients with Congenital Factor V Deficiency have Decreased Factor X_a Binding Sites on their Platelets

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Abstract

Human platelets have binding sites for plasma coagulation Factor Xa that are available only after the platelet release reaction. Platelets from 15 normal donors bound 216±52 (SD) molecules of Factor Xa per platelet. The association of Factor Xa with its platelet surface receptor results in a 300,000-fold increase in the catalytic activity of Factor Xa in forming thrombin from prothrombin. The turnover number for platelet-bound Factor Xa was 1,850±460 mol thrombin/ml per min per mol Factor Xa in experiments with platelets from 15 normal donors. Platelets from five patients with varying degrees of Factor V deficiency were investigated to determine whether or not coagulation Factor V participates in either aspect of the Factor Xa-platelet interaction. The binding of Factor Xa to platelets and the accompanying increase in rate of thrombin formation were either reduced in parallel or absent in each case with values ranging from 0 to 45% of control values. The apparent affinity of Factor Xa from Factor V-deficient patients was normal when platelet binding was detected. The supernate from thrombin-treated control platelets, which contains Factor V activity, corrected the Factor Xa binding deficiency of the platelets from three patients tested. Immunoreactive Factor V determined with an homologous antibody corresponded to the functional Factor V activity of platelets from one patient with Factor V deficiency, suggesting that the patient's platelets have a decreased amount of normal Factor V.

Authors

Joseph P. Miletich, David W. Majerus, Philip W. Majerus

Immunoglobulin Secreting Cells in Normal Human Bronchial Lavage Fluids

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Abstract

Immunoglobulin secreting cells were quantitated in the bronchial lavage fluids of 12 normal volunteers and compared with immunoglobulin secreting cells in peripheral blood, by a reverse hemolytic plaque assay. The mean number of cells secreting immunoglobulin (Ig)G in bronchial lavage fluids was 489 per million lymphocytes vs. a mean of 175 IgG secreting cells per million lymphocytes in peripheral blood (P < 0.02). The mean number of IgA secreting cells in bronchial lavage fluids was 633 per million lymphocytes as compared to 100 per million lymphocytes in peripheral blood (P < 0.005). Thus, compared to peripheral blood, cells from the lavage fluids were relatively enriched for both IgG and IgA secreting cells. However, IgA secreting cells were the major class of immunoglobulin secreting cells in bronchial lavage fluids, whereas IgG secreting cells predominated in peripheral blood. The prominence of IgA secreting cells in bronchial lavage fluids was further demonstrated by a mean ratio of IgA/IgG secreting cells in bronchial lavage fluids of 1.26 compared to a ratio in peripheral blood of 0.57 (P < 0.02). Cells secreting IgM were identified in only four of seven bronchial lavage fluid samples studied but in all peripheral blood samples. IgE secreting cells were not present in normal peripheral blood but could be demonstrated in 5 of 11 lavage fluid specimens. Thus, cells actively secreting immunoglobulins can be identified in the lower bronchial-alveolar tree of normal human subjects. Cells secreting IgG, IgA, or IgM may function in local lung defenses against infection; cells secreting IgE may contribute to hypersensitivity reactions in the lung.

Authors

E. Clinton Lawrence, R. Michael Blaese, R. Russell Martin, Paul M. Stevens

Interaction of collagen with the lipids of tendon xanthomata.

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Abstract

To determine the physical state of lipids in tendon xanthomata, six specimens surgically removed from three patients with familial hypercholesterolemia were studied by microscopy, calorimetry, and x-ray diffraction. The major constituents of the xanthomata were lipid (33% of dry weight) and collagen (24% of dry weight). The principal lipids were cholesterol ester and cholesterol. Light microscopy and thin-section electron microscopy showed occasional clusters of foam cells separated by masses of extracellular collagen. Polarized light microscopy of fresh, minced tissue showed rare droplets of free cholesterol ester. When heated, the tissue shrank abruptly at approximately equal to 70 degrees C and, consequently, a large amount of cholesterol ester was released. Scanning calorimetry of fresh pieces of xanthoma showed a single, broad, reversible liquid crystalline transition of cholesterol ester with peak temperature from 32 to 38 degrees C. The enthalpy (0971 +/- 0.07 cal/g) was reduced compared with the isolated cholesterol ester from each xanthoma (1.1+/-0.01 cal/g). There was a large irreversible collagen denaturation endotherm (peak temperature = 67 degrees C; enthalpy 9.9 cal/g collagen) that corresponded to the tissue shrinkage noted by microscopy. After the collagen denaturation, the sample displayed double-peaked reversible liquid crystalline transitions of cholesterol ester, of enthalpy 1.18 +/- 0.1 cal/g, that were identical to transitions of isolated cholesterol ester. Fibers dissected fron xanthomata were examined by X-ray diffraction at temperatures below and above the cholesterol ester transition. At 20 degrees C there was a weakly oriented equatorial reflection of Bragg spacing 36A, which corresponded to the smectic phase of cholesterol ester, and a series of oriented collagen reflections. At 42 degrees C the cholesterol ester reflection disappeared. Stretched fibers examined at 10 degrees C showed good orientation of collagen and cholesterol ester reflections, and in addition, meridional spacings which indicated oriented crystallization of cholesterol ester. These studies suggest that a major component of tendon xanthomata is extracellular cholesterol ester which displays altered melting and molecular orientation as a result of an interaction with collagen. At xanthoma temperatures, the cholesterol ester is in a smectic liquid crystalline state, probably layered between collagen fibrils, with the long axis of the cholesterolester molecules perpendicular to the axis of the collagen fiber. Such collagen-cholesterol ester interactions may favor the extracellular deposition of cholesterol ester derived either from intracellular sources or directly from plasma lipoproteins.

Authors

A R Tall, D M Small, R S Lees

Effect of Aspirin on Thrombin-Induced Adherence of Platelets to Cultured Cells from the Blood Vessel Wall

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Abstract

An in vitro method was used to detect adherence of 51Cr-labeled platelets to monolayers of cultured human endothelial, fibroblast, and smooth muscle cells. Washed platelets did not adhere to untreated or aspirin-treated endothelial monolayers in the absence of thrombin. In contrast, thrombin-induced platelet aggregates adhered to all of the monolayers but adherence to endothelium was significantly less than to the other cells. Additional evidence for adherence of platelets to the endothelium was provided by scanning and transmission electron microscopy. Thrombin-induced platelet adherence to endothelium was inhibited by hirudin. Platelet adherence induced by thrombin was enhanced significantly by treatment of the endothelial monolayer with 1—2 mM aspirin. This increase in adherence was seen even when aspirin-treated platelets were used; adherence values approached those seen with fibroblasts and smooth muscle cells. An aspirin concentration of 0.1 mM was sufficient to block thrombin-induced malonaldehyde production in platelets but it did not interfere with the inhibitory effect of the endothelium against platelet adherence. The effect of aspirin on the endothelium was temporary and inhibitory activity of the endothelium was restored 1 h after aspirin had been removed from the incubation system. The ability of thrombin to cause adherence of platelets to undamaged endothelium, and the potential for aspirin to enhance this adherence have implications for mechanisms which operate in platelet interaction with the blood vessel wall.

Authors

Robert L. Czervionke, John C. Hoak, Glenna L. Fry

Decreased insulin sensitivity of forearm muscle in myotonic dystrophy.

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Abstract

Previous studies of patients with myotonic dystrophy have demonstrated hyperinsulinism after glucose loading. This hyperinsulinism has been attributed by some investigators to tissue insulin resistance. We have directly studied insulin sensitivity of forearm muscle in patients having such hyperinsulinism. The effect of an intrabrachial arterial insulin infusion (100 mu U/kg per min) on glucose uptake was determined in six cases of myotonic dystrophy, six normal subjects, and in seven disease control subjects with myotonia or wasting from other disorders. There was no significant difference in insulin tolerance comparing myotonic dystrophy patients to the normal and disease control groups. Glucose tolerance and basal insulin levels were normal in the myotonic dystrophy patients, but hyperinsulinism occurred after glucose ingestion. After 25 min of intra-arterial insulin, the mean peak muscle glucose uptake in myotonic dystrophy was 2.54 +/- 0.54 mu mol/min per 100 ml forearm compared to 5.24 +/- 0.86 mu mol/min per 100 ml for disease controls (P is less than 0.05). Myotonic dystrophy patients showed a peak glucose uptake increment of only 2.6 +/- 0.2-fold over basal contrasted with the disease control value of 6.5 +/- 1.0-fold (P is less than 0.02) and the normal control value of 8.8 +/- 1.1-fold (P is less than 0.01). Thus, there was an absolute as well as a relative decrease in muscle insulin sensitivity in myotonic dystrophy patients compared to both control groups. The peak increments in arterio-superficial venous glucose concentration differences after insulin infusion were not significantly different comparing myotonic dystrophy and control groups. These data suggest that in myotonic dystrophy, there is insulin insensitivity of skeletal muscle.

Authors

R T Moxley III, R C Griggs, D Goldblatt, V VanGelder, B E Herr, R Thiel

The stimulus-secretion coupling of glucose-induced insulin release. Metabolic and functional effects of NH4+ in rat islets.

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Abstract

NH4+ caused a dose-related, rapid, and reversible inhibition of glucose-stimulated insulin release by isolated rat islets. It also inhibited glyceraldehyde-, Ba2+-, and sulfonylurea-stimulated insulun secretion. NH4+ failed to affect glucose utilization and oxidation, glucose-stimulated proinsulin biosynthesis, the concentration of ATP, AD, and AMP, and the intracellular pH. NH4+ also failed to affect the ability of theophylline and cytochalasin B to augment glucose-induced insulin release. However, in the presence and absence of glucose, accumulation of NH4+ in islet cells was associated with a fall in the concentration of NADH and HADPH and a concomitant alteration of 86Rb+ and 45Ca2+ (or 133Ba2+) handling. These findings suggest that reduced pyridine nucleotides, generated by the metabolism of endogenous of exogenous nutrients, may modulate ionophoretic processes in the islet cells and by doing so, affect the net uptake of Ca2+ and subsequent release of insulin.

Authors

A Sener, J C Hutton, S Kawazu, A C Boschero, G Somers, G Devis, A Herchuelz, W J Malaisse

Failure to detect an effect of prolactin on pulmonary surfactant and adrenal steroids in fetal sheep and rabbits.

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Abstract

Recent reports have indicated an association between low cord prolactin (PRL) and the occurrence of respiratory distress syndrome in premature infants, and it is reported that PRL administration increases the lecithin content of fetal rabbit lung. We administered 1 mg ovine PRL to 32 rabbit fetuses on day 24 of gestation and evaluated lung phospholipid synthesis and content on day 26. Compared with diluent-injected littermates, PRL had no effect on the rate of choline incorporation into lecithin, tissue content of phospholipid and disaturated lecithin, or plasma corticoids. However, both choline incorporation and corticoids were increased in all animals undergoing surgery compared with unoperated controls. We also infused PRL (1 mg/day, i.v.) into three fetal sheep continuously over five periods of 5-8 days. Although supraphysiologic concentrations of PRL were achieved in plasma and amniotic fluid, there was no effect of this treatment on the flux of tracheal fluid surfactant or on plasma concentrations of corticoids of dehydroepiandrosterone sulfate. Thus, in this study, we failed to detect either a stimulation of the surfactant system or an adreno-corticotropic effect by PRL as previously postulated. This suggests that the relationship between PRL and respiratory distress sundrome is an indirect association.

Authors

P L Ballard, P D Gluckman, A Brehier, J A Kitterman, S L Kaplan, A M Rudolph, M M Grumbach

Overproduction of adenine deoxynucleosides and deoxynucletides in adenosine deaminase deficiency with severe combined immunodeficiency disease.

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Abstract

The deoxynucleotide, dATP, is elevated 50- to 1,000-fold above normal in erythrocytes, lymphocytes, and bone marrow from a child with adenosine deaminase deficiency and severe combined immunodeficiency disease. The child, when 17 mo of age, was also excreting approximately 30 mg of deoxyadenosine per day in urine (normal is less than 0.1 mg/day). Urinary excretion of uric acid was decreased. Elevated dATP levels in lymphocytes and bone marrow, and increased urinary excretion of deoxyadenosine, persisted despite hypertransfusion of the child with irradiated erythrocytes from a donor with normal adenosine deaminase. Overproduction of deoxynucleotides by increased salvage of adenosine appears to be the primary metabolic abnormality in patients with adenosine de aminase deficiency.

Authors

J Donofrio, M S Coleman, J J Hutton, A Daoud, B Lampkin, J Dyminski

Inhibition of erythrocyte sickling in vitro by pyridoxal.

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Abstract

To test the antisickling activity of pyridoxal, we compared the oxygen affinity and the percent sickling at low PO2 of untreated erythrocytes with values for cells from the same blood sample incubated with pyridoxal, glyceraldehyde, or pyridoxine. Pyridoxal increased oxygen affinity much more than glyceraldehyde. 20 mM pyridoxal and glyceraldehyde had equivalent antisickling activity. At PO2 levels above 20 mm Hg, both agents reduced sickling to less than 2%. In samples examined by electron microscopy, pyridoxal reduced the percent sickled cells and the percent cells that contain hemoglobin S fibers by the same amount (from 74 to 3%). Pyridoxine had no effect on oxygen affinity or sockling. Pyridoxal reacts with intracellular hemoglobin to increase oxygen affinity, which inhibits hemoglobin S polymerization and sickling.

Authors

J A Kark, M P Kale, P G Tarassoff, M Woods, L S Lessin

Thrombogenic Effect of High-Dose Aspirin in Rabbits: RELATIONSHIP TO INHIBITION OF VESSEL WALL SYNTHESIS OF PROSTAGLANDIN I₂-LIKE ACTIVITY

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Abstract

Aspirin is a promising antithrombogenic agent. It inhibits the generation of thromboxane A2 by acetylating platelet cyclo-oxygenase. Aspirin also inhibits vessel wall production of PGI2 which is an inhibitor of platelet aggregation, and therefore is potentially thrombotic. To investigate these two opposing effects we studied the effects of aspirin upon fibrin accretion onto experimentally induced venous thrombi in rabbits and on the PGI2-like activity of vessel wall using the thrombin-induced [14C]serotonin release assay. A 200-mg/kg dose of aspirin significantly augmented thrombus size when compared to (a) sodium salicylate administered in equal doses, (b) aspirin in a 10-mg/kg dose or (c) controls (P < 0.001). A 200-mg/kg dose of aspirin totally inhibited vessel wall PGI2-like activity whereas aspirin in a 10-mg/kg dose produced less inhibition, and 200 mg/kg sodium salicylate had no effect. Local instillation of tranylcypromine, an inhibitor of PGI2 formation, also significantly augmented thrombus size compared to saline-treated controls and totally inhibited the production of PGI2-like activity. The thrombogenic effect of high dose aspirin was lost if an interval of 2.5 h or longer elapsed between vessel damage and drug administration, indicating that in contrast to the platelet, the effect of aspirin on vessel wall prostaglandin synthesis is relatively short-lived. It is concluded that aspirin, in doses higher than those used clinically, can augment experimental thrombosis, presumably by inhibiting the synthesis of vessel wall PGI2.

Authors

J. G. Kelton, J. Hirsh, C. J. Carter, M. R. Buchanan