Myeloperoxidase-Mediated Iodination by Granulocytes INTRACELLULAR SITE OF OPERATION AND SOME REGULATING FACTORS

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Abstract

The intracellular site of operation of the myeloperoxidase-H2O2-halide antibacterial system of granulocytes has been determined by utilizing measurements of the fixation of iodide to trichloracetic acid (TCA) precipitates of subcellular fractions, including intact phagocytic vesicles. Na125I was added to suspensions of guinea pig granulocytes in Krebs-Ringer phosphate buffer, and they were then permitted to phagocytize different particles. Phagocytic vesicles were formed by allowing cells to ingest a paraffin oil emulsion (POE) and collected by flotation on sucrose after homogenization. Measurement of 125I bound to TCA precipitates of the different fractions and the homogenates disclosed that the lysosome-rich fraction obtained by centrifugation from control (nonphagocytizing) cells accounted for a mean 93.1% of the total cellular activity. With phagocytosis of POE, TCA-precipitable iodination increased two- to sevenfold, and the lysosomal contribution fell to a mean 36.9% of the total. The appearance of activity within phagocytic vesicles accounted for almost the entire increase seen with phagocytosis (a mean 75.7%), and iodide was bound within these structures with high specific activity. More iodide was taken up by cells than fixed, regardless of iodide concentration, and was distributed widely throughout the cell rather than selectively trapped within the vesicles.

Authors

Richard K. Root, Thomas P. Stossel

Measurement of Diaphragmatic Blood Flow and Oxygen Consumption in the Dog by the Kety-Schmidt Technique

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To assess energy expenditure of the diaphragm directly, a method was devised for percutaneous catheterization of the left inferior phrenic vein in dogs. Necropsy studies, including retrograde injection of india ink and measurement of radioactivity in diaphragmatic muscle strips, suggested that the territory drained by the inferior phrenic vein was uniformly perfused, and that there were no major anastomoses between this bed and adjacent ones.

Authors

Dudley F. Rochester

Interaction of Baroreceptor and Chemoreceptor Reflexes MODULATION OF THE CHEMORECEPTOR REFLEX BY CHANGES IN BARORECEPTOR ACTIVITY

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The purpose of this study was to determine whether the level of arterial pressure and degree of baroreceptor activation affect responses to stimulation of chemoreceptors. Chemoreceptors were stimulated by injecting nicotine into the common carotid artery of anesthetized and paralyzed dogs. Responses were observed in the innervated gracilis muscle, perfused at constant flow while perfusion pressure was measured. Arterial pressure was lowered by bleeding the animals and raised by transient occlusion of the descending aorta. Vasoconstrictor responses to stimulation of chemoreceptors were enhanced by hypotension and inhibited by elevation of arterial pressure. Potentiation of the chemoreceptor reflex by hemorrhagic hypotension was not the result of altered vascular resistance in the gracilis muscle, sensitization of chemoreceptors by catecholamines or acidosis, or changes in cerebral perfusion pressure.

Authors

Donald D. Heistad, Francois M. Abboud, Allyn L. Mark, Phillip G. Schmid

Familial Hypercholesterolemia (One Form of Familial Type II Hyperlipoproteinemia) A STUDY OF ITS BIOCHEMICAL, GENETIC, AND CLINICAL PRESENTATION IN CHILDHOOD

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Abstract

Primary hyperbetalipoproteinemia (type II hyperlipoproteinemia) is a common disorder associated with premature vascular disease. It is frequently due to genetic abnormalities, some of which are expressed in childhood. We have examined the manner in which that form of hyperbetalipoproteinemia known as familial hypercholesterolemia may be expressed in 236 children aged 1-19 born of 90 matings in which one parent had hyperbetalipoproteinemia of this variety and one parent did not.

Authors

Peter O. Kwiterovich Jr., Donald S. Fredrickson, Robert I. Levy

The Effect of Cyclic AMP and Dibutyryl Cyclic AMP on the Permeability Characteristics of the Renal Tubule

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The effect of adenosine-3′,5′-cyclic monophosphate (cyclic AMP) and N6,O2-dibutyryl adenosine-3′,5′-cyclic monophosphate (dibutyryl cyclic AMP) on renal tubular permeability was studied by microinjection techniques in anesthetized diuretic rats. Radioactive inulin and mannitol were microinjected simultaneously into superficial proximal and distal convolutions and recovery of the isotopes was measured in the urine.

Authors

William B. Lorentz Jr.

The Reduction of Glyceraldehyde by Human Erythrocytes L-HEXONATE DEHYDROGENASE ACTIVITY

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Abstract

Incubation of red cell suspensions with D-glyceraldehyde resulted in disappearance of glyceraldehyde and appearance of glycerol. Concomitantly, there was an increase of CO2 formation from glucose. This indicated that the reduction of glyceraldehyde to glycerol occurred through a NADPH-linked system. Studies in hemolysates revealed the presence of an enzyme with the capacity to catalyze the reduction of glyceraldehyde to glycerol by NADPH. This enzyme was partially purified by DEAE chromatography. The elution pattern of the enzyme and its kinetic characteristics indicated that the enzyme was L-hexonate dehydrogenase (L-gulonate: NADP oxidoreductase, EC 1.1.1.19), not aldose reductase (Alditol: NADP oxidoreductase, EC 1.1.1.21), which had previously been thought present in erythrocytes. The reduction of glyceraldehyde to glycerol is one of a number of pathways for the metabolism of glyceraldehyde that have been found in red cells and/or other mammalian tissues.

Authors

E. Beutler, E. Guinto

Effects of Dobutamine on Left Ventricular Performance, Coronary Dynamics, and Distribution of Cardiac Output in Conscious Dogs

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Abstract

The effects of dobutamine ([±]-4-[2-[[3-(p-hydroxyphenyl)-1-methyl propyl] amino] ethyl] pyrocatechol hydrochloride), a new synthetic cardioactive sympathomimetic amine, were examined on direct and continuous measurements of left ventricular (LV) diameter (D), pressures (P), velocity of shortening (V), dP/dt, dP/dt/P, arterial pressure, cardiac output, and regional blood flows in the left circumflex coronary, mesenteric, renal, and iliac beds in healthy, conscious dogs. At the highest dose of dobutamine examined, 40 μg/kg/min, the drug increased dP/dt/P from 65±3 to 128±4 s-1 and isolength velocity from 72±4 to 120±7 mm/s without affecting LV end diastolic D significantly. Mean arterial P rose from 92±2 to 104±3 mm Hg and heart rate from 78±3 to 111±7 beats/min, while LV end systolic D fell from 24.1±1.4 to 19.9±1.8 mm, reflecting a rise in stroke volume from 30±4 to 42±3 ml. Cardiac output rose from 2.41±0.23 to 4.35±0.28 liter/min, while calculated total peripheral resistance declined from 0.042±0.005 to 0.028±0.003 mm Hg/ml/min. The greatest increases in flow and decreases in calculated resistance occurred in the iliac and coronary beds, and the least occurred in the renal bed. Propranolol blocked the inotropic and beta2 dilator responses while vasoconstricting effects mediated by alpha adrenergic stimulation remained in each of the beds studied. When dobutamine was infused after a combination of practolol and phentolamine, dilatation occurred in each of the beds studied. These observations indicate that dobutamine is a potent positive inotropic agent with relatively slight effects on preload, afterload, or heart rate, and thus may be a potentially useful clinical agent. The one property of this drug which is not ideal is its tendency to cause a redistribution of cardiac output favoring the muscular beds at the expense of the kidney and visceral beds.

Authors

Stephen F. Vatner, Robert J. McRitchie, Eugene Braunwald

Isolation and Characterization of an Abnormal Human Intrinsic Factor

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A patient has been described previously who presented at age 13 with vitamin B12 (B12) deficiency secondary to a functionally abnormal intrinsic factor (IF). IF has now been isolated from the gastric juice of the patient, his sister, and both parents, who are first cousins, by using affinity chromatography on B12-Sepharose. Patient IF appeared normal in terms of (a) B12 binding, (b) mol wt, (c) total amino acid and carbohydrate composition, and (d) immunodiffusion with rabbit anti-patient and anti-normal IF sera. After adsorption with normal IF, however, anti-patient IF serum precipitated the various IFs as follows: patient IF (> 95%); mother, father, and sister IF (50%); and normal IF (< 10%). Additional adsorption with mother, father, or sister IF completely inhibited the precipitation of patient IF. The association constant determined for patient IF-B12 and human ileal mucosal homogenates (0.1 × 109 M-1) was 60-fold lower than that determined with normal IF-B12 (6.0 × 109 M-1). Intermediate amounts of ileal IF-B12 binding were observed with mother, father, and sister IF-B12. These in vitro studies were supported by multiple Schilling tests, performed with a totally gastrectomized volunteer, that gave the following mean urinary excretions of [57Co]B12: free B12 (0.5%); + patient gastric juice (2.6%); + mother or father gastric juice (17%); and + normal gastric juice (26%). These studies demonstrate that the patient is homozygous and that the mother, father, and sister are heterozygous for a structurally abnormal IF that has a markedly decreased, but not absent, affinity for ileal IF-B12 receptors. These studies also indicate that the B12 and ileal binding sites are located on different portions of the IF molecule.

Authors

Max Katz, Carol S. Mehlman, Robert H. Allen

Effects of Alterations of Plasma Free Fatty Acid Levels on Pancreatic Glucagon Secretion in Man

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The present investigation was undertaken to ascertain whether alterations in plasma free fatty acids (FFA) affect pancreatic glucagon secretion in man since FFA have been reported to influence pancreatic alpha cell function in other species. Elevation of plasma FFA from a mean (±SE) basal level of 0.478±0.036 mM to 0.712±0.055 mM after heparin administration caused plasma glucagon levels to fall approximately 50%, from a basal value of 122±15 pg/ml to 59±14 pg/ml (P < 0.001). Lowering of plasma FFA from a basal level of 0.520±0.046 mM to 0.252±0.041 mM after nicotinic acid administration raised plasma glucagon from a basal level of 113±18 pg/ml to 168±12 pg/ml (P < 0.005). Infusion of glucose elevated plasma glucose levels to the same degree that heparin raised plasma FFA levels. This resulted in suppression of plasma glucagon despite the fact that plasma FFA levels also were suppressed. Glucagon responses to arginine were diminished after elevation of plasma FFA (P < 0.01) and during infusion of glucose (P < 0.01). Diminution of plasma FFA by nicotinic acid did not augment glucagon responses to arginine.

Authors

John E. Gerich, Maurice Langlois, Victor Schneider, John H. Karam, Claudio Noacco

Importance of Free Fatty Acids as a Determinant of Myocardial Oxygen Consumption and Myocardial Ischemic Injury during Norepinephrine Infusion in Dogs

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Increased delivery of free fatty acids raises myocardial oxygen consumption (ṀVO2) without influencing mechanical performance. The effects of norepinephrine on ṀVO2 and on the size of ischemic injury after acute coronary occlusion were therefore studied before and during inhibition of lipolysis with β-pyridylcarbinol. In spite of similar mechanical responses to norepinephrine, ṀVO2 increased by 57±11% before and significantly less, 31±6%, (P < 0.01) during inhibition of lipolysis. After coronary occlusion the ischemic injury associated with norepinephrine infusion, as evidenced by epicardial mapping of S-T segment elevation, was larger before (7.9±1.1 mV) than during inhibited lipolysis (2.8±0.4 mV; P < 0.005). Average S-T segment elevation associated with norepinephrine infusion during inhibited lipolysis (2.8±0.4 mV) was even lower (P < 0.05) than during control occlusion alone, before drug administration (4.4±0.7 mV). In conjunction with an antilipolytic agent, norepinephrine was shown to reduce the extent and magnitude of the myocardial ischemic injury produced by acute coronary occlusion; this could be due to an improved balance between myocardial oxygen supply and requirement.

Authors

Ole D. Mjøs, John K. Kjekshus, Jon Lekven

A Study of Intercellular Spaces in the Rabbit Jejunum during Acute Volume Expansion and after Treatment with Cholera Toxin

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Abstract

The effects of acute volume expansion and of intraluminal administration of cholera toxin have been examined in rabbit jejunum.

Authors

Donald R. DiBona, Lincoln C. Chen, Geoffrey W. G. Sharp

Fibrinogen Cleveland II AN ABNORMAL FIBRINOGEN WITH DEFECTIVE RELEASE OF FIBRINOPEPTIDE A

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An abnormal fibrinogen (fibrinogen Cleveland II) was detected in the plasma of a 23-yr-old white man with a mild bleeding diathesis. The one-stage prothrombin time, thrombin time, and Reptilase time were all prolonged. 16 of 24 tested relatives had the defect, which appeared to be transmitted as an autosomal dominant characteristic. The thrombin time of normal plasma was slightly inhibited by the proband's plasma. The abnormally long thrombin time of fibrinogen Cleveland II was partially corrected by addition of calcium ions. Fibrinogen Cleveland II was indistinguishable from normal fibrinogen by immunoelectrophoresis, DEAE-cellulose column chromatography, or polyacrylamide gel electrophoresis of reduced fibrinogen in sodium dodecyl sulfate. The major defect detected appeared to be impaired release of fibrinopeptide A when fibrinogen Cleveland II was incubated with thrombin. This defect was localized to the NH2-terminal disulfide knot portion of the molecule. An abnormality of polymerization of fibrin monomers was also present, but the abnormal fibrin demonstrated relatively normal crosslinking. Despite these defects, fibrinogen Cleveland II achieved a degree of coagulability similar to normal fibrinogen and appeared to incorporate some molecules of fibrin with intact fibrinopeptide A into the clot. The fibrin clot that was formed appeared to be abnormal by electron microscopy. These functional defects and other descriptive characteristics appear to distinguish fibrinogen Cleveland II from other inherited abnormal fibrinogens.

Authors

Edward D. Crum, John R. Shainoff, Richard C. Graham, Oscar D. Ratnoff

Bacterial Growth In Vivo AN IMPORTANT DETERMINANT OF THE PULMONARY CLEARANCE OF DIPLOCOCCUS PNEUMONIAE IN RATS

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Lung clearance of Diplococcus pneumoniae was markedly reduced in rats with acute hemorrhagic pulmonary edema produced by instillation of hydrochloric acid. Bacterial clearance was enhanced in both control and acid-instilled animals by pretreatment with a bacteriostatic antibiotic, tetracycline, 30 mg/kg. From these data the contributions of bacterial multiplication and bacterial elimination to net lung bacterial clearance were estimated. In control animals the constant for exponential bacterial elimination was -1.4283 (fractional clearance = 76% per h), and the doubling time for the pneumococcus was 170 min. In acid-instilled rats the elimination constant was -0.5336 (fractional clearance = 41% per h), and the doubling time of the pneumococcus was 47 min, approximating the doubling time of 42 min observed with pneumococci grown in broth.

Authors

Waldemar G. Johanson Jr., Stephen J. Jay, Alan K. Pierce

Measurement of δ-Aminolevulinic Acid Synthetase Activity in Human Erythroblasts

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A new, specific, and simple method for the determination of δ-aminolevulinic acid (ALA) synthetase activity in human bone marrow cells has been developed. ALA synthetase of erythroblasts was partially purified so as to permit the use of [14C]succinyl-CoA as a substrate for this enzyme. In this enzyme preparation there were negligible activities of succinyl-CoA hydrolase, α-ketoglutarate dehydrogenase, and succinyl-CoA synthetase and there was no activity of ALA dehydrase.

Authors

Yosuke Aoki, Gumpei Urata, Osamu Wada, Fumimaro Takaku

Transmissible Gastroenteritis MECHANISMS RESPONSIBLE FOR DIARRHEA IN AN ACUTE VIRAL ENTERITIS IN PIGLETS

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We studied 3-wk-old piglets 40 h after experimental infection with transmissible gastroenteritis (TGE) virus to identify the mechanisms of diarrhea in this disease and to better understand infectious diarrhea in humans. Using continuous segmental marker perfusion in four regions along the gut, we found significant increases in net intraluminal accumulation of water and electrolytes only in the proximal jejunum, the region infected by the virus. In this jejunal segment studied in vivo, unidirectional sodium flux, extracellular fluid (ECF) to lumen, significantly increased, lumen to ECF significantly decreased, compared with matchfed littermates. The standard perfusate rendered hypertonic by adding mannitol (450 mosmol/kg), in the same segment of normal pigs, caused only an increase in ECF to lumen flux of sodium. TGE did not alter gross villous structure or intraluminal bacteria, bile salts, lactate, pH, or osmolality. Epithelial cell migration was accelerated in the jejunum of infected pigs. Isolated in suspension, these cells from TGE pigs exhibited increased active and passive sodium efflux, cells from mannitol-perfused pigs exhibited only increased active sodium efflux. In this viral enteritis, altered sodium transport occurring in the jejunum, the region of the intestine infected appears to be associated with defective epithelial cell function. The precise nature of the abnormalities in sodium transport, their relationship to disturbances of transport of other solutes, and to virus epithelial cell interaction remain to be defined.

Authors

D. G. Butler, D. G. Gali, M. H. Kelly, J. R. Hamilton

An Inhibitor of Histamine Release from Human Leukocytes

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Abstract

Lysates of human leukocytes, prepared by ultrasonic disruption, contained heat-labile histamine-releasing factors. An inhibitor of histamine release was generated from such lysates during thermal inactivation of the histamine-releasing activity. Lysates inactivated at 38°C for 60 min produced up to 90% inhibition of histamine release from human leukocytes. Heated lysates produced significant inhibition (P < 0.001) of leukocyte histamine release induced by goat antihuman IgE (51±3% inhibition), compound 48/80 (69±7% inhibition), and fresh leukocyte lysate (63±6% inhibition).

Authors

Michael T. Kelly, Arthur White

Development of Cellular and Humoral Immunity in the Respiratory Tract of Rabbits to Pseudomonas Lipopolysaccharide

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Abstract

Immunization with Pseudomonas lipopolysaccharide induced both cellular and humoral immunity in rabbits, particularly in the respiratory tract after intranasal immunization. Either parenteral (i.m.) or intranasal immunization elicited an IgG antibody response in respiratory secretions, but only intranasal immunization produced secretory IgA antibody. Immunization by both routes stimulated serum IgM and IgG agglutinative antibodies. Because both methods of immunization produced skin test reactivity which had components of both Arthus and tuberculin-like reactions, cellular immunity was more readily assessed by the measurement of migration inhibitory factor (MIF) released from immune lymphocytes in respiratory and spleen cell suspensions after challenge with the lipopolysaccharide antigen. After intranasal vaccination, MIF activity was detected in the respiratory tract by direct assay; in contrast, i.m. immunized rabbits did not produce respiratory MIF. Both modes of immunization resulted in splenic MIF activity. However, lymphocytes were only capable of producing MIF for short periods after primary immunization had ended, apparently losing this function in about 2-3 wk. Therefore, it was concluded that cellular immunity by in vitro assay was transient after primary immunization with this Pseudomonas antigen in contrast to the more persistent humoral immunity. The biological significance of immune lymphocytes as part of the coordinated host defense of the lung needs further evaluation.

Authors

Herbert Y. Reynolds, Russell E. Thompson, Henry B. Devlin

Thrombocytopenia in Experimental Trypanosomiasis

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The effect of experimental trypanosomiasis on coagulation was studied because a patient in this hospital with Rhodesian trypanosomiasis developed thrombocytopenia with disseminated intravascular coagulation. Rats injected intraperitoneally with this strain of Trypanosoma rhodesiense consistently developed trypanosomiasis and severe thrombocytopenia without changes in hematocrit or concentration of fibrinogen or fibrin split products. At the time of 50% mortality (4-5 days) mean platelet counts per cubic millimeter of infected rats were 18,000±9,000 (±2 SEM) compared to 1,091,000±128,000 in uninfected controls.

Authors

Charles E. Davis, Robert S. Robbins, Richard D. Weller, Abraham I. Braude

Functional Characterization of Dipeptide Transport System in Human Jejunum

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The present studies were performed to determine whether dipeptide absorption in human jejunum exhibits the characteristics of carrier-mediated transport. 15-cm jejunal segments from human volunteers were perfused with test solutions containing varying amounts of either glycylglycine, glycylleucine, glycine, leucine, glycylglycine with leucine or glycine, glycylglycine with glycylleucine, or glycylleucine with an equimolar mixture of free glycine and leucine. Jejunal absorption rates of both glycylglycine and glycylleucine followed the kinetics of a saturable process. The Km value in millimoles/liter of glycylglycine was significantly greater than the Km value of glycylleucine (43.3±2.6 vs. 26.8±5.9, P < 0.05); and the Km value of glycine was also significantly greater than the Km value of leucine (42.7±7.5 vs. 20.4±5.4, P < 0.05). While overlapping occurred among the Km values of free amino acids and dipeptides, the transport kinetics of dipeptides were characterized by higher Vmax values (in micromoles per minute per 15 centimeters) than those of free amino acids. For example, the Vmax values for glycylglycine and glycine were 837±62 and 590±56, respectively (P < 0.02). While jejunal absorption rates of glycylglycine were not significantly affected by free leucine or free glycine, they were competitively inhibited by glycylleucine. The jejunal absorption rate of glycylleucine was not significantly altered by an equimolar mixture of free glycine and leucine. The selective absorption of dipeptides was investigated by infusing three equimolar mixtures, each containing two different dipeptides. Among the three dipeptides examined, glycylglycine was the least absorbed. There was no significant difference between the absorption of glycylleucine and leucylglycine.

Authors

Siamak A. Adibi, Mohammad R. Soleimanpour

Immunofluorescent Localization of Antihemophilic Factor Antigen and Fibrinogen in Human Renal Diseases

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Tissue localization of antihemophilic factor (AHF, factor VIII) antigen and fibrinogen by immunofluorescent microscopy was determined in 146 specimens of normal and diseased kidneys. AHF antigen was present in the endothelial cells of glomeruli, peritubular capillaries, arteries, and veins of normal kidneys; a distribution similar to that in other tissues. In scleroderma and malignant hypertension, deposition of AHF antigen and fibrinogen was limited to the markedly thickened endothelial layers of arteries. More extensive intense deposition of both AHF antigen and fibrinogen in glomeruli and in arterial walls were present in hyperacute renal homograft rejection, hemolyticuremic syndrome, postpartum renal failure, and in some cases of acute homograft rejection. In contrast, deposition of fibrinogen was observed in glomerular epithelial cresents in severe proliferative glomerulonephritis, but AHF deposition was not present in these lesions. Glomerular deposition of fibrinogen without increased AHF standing was also detected in renal tissue from patients with anaphylactoid purpura nephritis and in recurrent macroscopic hematuria with focal glomerulonephritis. Increased staining of peritubular capillaries with anti-AHF was seen in diseased kidneys irrespective of etiology. Immunofluorescent localization of AHF, a participant in the intrinsic coagulation pathway, offers a new way by which to analyze the mechanisms responsible for fibrinogen deposition in disease.

Authors

John R. Hoyer, Alfred F. Michael, Leon W. Hoyer

Urea Metabolism in Chronic Renal Failure

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Abstract

Urea degradation was measured during 16 experiments in 13 chronic uremic patients being treated with essential amino acids or their analogues. [14C]Urea was injected i.v. and the clearance of labeled urea from its volume of distribution was compared with the simultaneous renal clearance of ordinary urea, which averaged 2.0 liters/day. The difference, extrarenal clearance of urea, averaged 3.1 liters/day as compared with a previously reported mean of 18 liters/day in normal subjects. Thus urea-splitting activity in the gut of uremic subjects expressed in these terms is far less than in normal individuals. Nevertheless, the amount of ammonia N formed from urea in these patients, 3.5 g/day, is not significantly different from normal, owing to their elevated plasma urea. In the same subjects, urea appearance rate was measured as the sum of urea excretion and the daily change in the urea pool. No negative correlation was noted between urea appearance and urea degradation, as might be expected if portal ammonia were being utilized for protein synthesis. However, urea production was positively correlated (r = 0.76) with urea degradation, suggesting that most of the resulting portal ammonia is converted back to urea. The results fail to support the view that degradation of urea in the gut promotes N conservation in uremic subjects maintained on low protein diets.

Authors

Mackenzie Walser

A Biochemical Abnormality in Cerebrotendinous Xanthomatosis IMPAIRMENT OF BILE ACID BIOSYNTHESIS ASSOCIATED WITH INCOMPLETE DEGRADATION OF THE CHOLESTEROL SIDE CHAIN

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Bile acid production in cerebrotendinous xanthomatosis (CTX) is subnormal, yet the activity of cholesterol 7α-hydroxylase, the rate-determining enzyme of bile acid synthesis, is elevated. To explain this discrepancy, bile acid precursors were sought in bile and feces of three CTX subjects. Over 10% of the total sterols excreted in bile and feces consisted of compounds more polar than cholesterol. Chromatographic analysis of the polar fractions in conjunction with gasliquid chromatography (GLC)-mass spectrometry indicated two major constituents, 5β-cholestane-3α,7α,12α,25-tetrol and 5β-cholestane-3α,7α,12α,24ξ,25-pentol. After i.v. injection of [4-14C]cholesterol both bile alcohols were radioactive proving that they were derived from cholesterol. The accumulation of alcohols hydroxylated at C-25 and C-24,25 suggests that decreased bile acid synthesis in CTX results from impaired oxidation of the cholesterol side chain. This finding and the virtual absence of intermediates hydroxylated at C-26 indicate that current views of the major pathway of bile acid synthesis may require revision.

Authors

T. Setoguchi, Gerald Salen, G. S. Tint, E. H. Mosbach

Pathophysiology of Experimental Glomerulonephritis in Rats

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Micropuncture, clearance, immunofluorescence and light microscopy techniques were used to study kidney structure and single nephron function in rats with autologous immune complex nephritis (AICN), a membranous glomerulonephritis developing over 5 to 20 mo, in the more acute and proliferative glomerular basement membrane (GBM) nephritis and in controls. Both models are known to have clinical counterparts in human disease. Kidney functional abnormalities correlated with the degree of architectural derangement. In both AICN and anti-GBM nephritis filtration fraction fell in direct proportion to the fall in glomerular filtration rate (GFR), renal plasma flow being unchanged. Fractional electrolyte excretion increased as the GFR fell. Despite marked heterogeneity of single nephron filtration rate (SNGFR) (AICN, 5-93 nl/min; anti-GBM, 0-50 nl/min) and of proximal tubular hydrostatic pressure (4-48 mm Hg), each nephron showed almost complete glomerulotubular balance, absolute reabsorption to the late proximal convolution varying directly with filtration rate. In addition SNGFR could be related both to proximal intratubular hydrostatic pressure and to calculated glomerular capillary pressure (Pg), being lowest in those nephrons with the highest intratubular pressure. Nephrons with very high filtration rates did not apparently reach filtration equilibrium. Mean SNGFR was significantly lower in the anti-GBM group, while calculated Pg was the same in both. This probably reflects the acute and diffuse involvement of the anti-GBM lesion with different filtration characteristics from the more chronic AICN disease. Tubular damage was more marked in AICN, and extraction of p-aminohippurate was reduced in this group.

Authors

Marjorie E. M. Allison, Curtis B. Wilson, Carl W. Gottschalk

The Effect of Glucose on Urinary Cation Excretion during Chronic Extracellular Volume Expansion in Normal Man

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Both glucose administration and extracellular volume expansion augment urinary calcium and magnesium excretion. While volume expansion also augments sodium excretion, glucose induces an antinatriuresis. To examine the interrelationships of volume expansion and of glucose administration on sodium, calcium, and magnesium excretion, the effects of glucose were evaluated during clearance studies in the same subjects before and after chronic extracellular volume expansion produced by desoxycorticosterone acetate (DOCA) and a normal dietary sodium intake. The augmentation of UCaV and UMgV by glucose was simply additive to the increments in divalent cation excretion caused by “escape” from the sodium-retaining effects of DOCA. Glucose administration reduced UNaV, an effect exaggerated after DOCA escape and associated with reductions in volume/glomerular filtration rate (V/GFR) and CNa + CH2O/GFR, suggesting augmented proximal tubular reabsorption. Before glucose, UNa was inversely correlated with UG, and after glucose administration CNa/GFR was inversely correlated with TG/GFR. We propose that the availability of glucose in the proximal tubule stimulates Na reabsorption while delaying development of a chloride diffusion potential, thereby inhibiting tubular reabsorption of Ca and Mg.

Authors

Edward J. Lennon, J. Lemann Jr., W. F. Piering, L. S. Larson

Immunoglobulin in Clinically Uninvolved Skin in Systemic Lupus Erythematosus ASSOCIATION WITH RENAL DISEASE

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23 of 42, or 55%, of patients with systemic lupus erythematous had immunoglobulin deposits along the epidermal basement membrane of uninvolved skin (positive lupus band test [LBT]). In patients with low serum complement levels, 91% had a positive LBT), as compared with 15% in those with normal complement levels. The LBT was positive in 70% of patients with clinical and laboratory evidence of renal disease, but in only 31% of patients without renal disease. 81% of patients with the more severe histologic forms of lupus nephritis, i.e., proliferative glomerulonephritis and membranous glomerulonephritis, and positive tests, whereas only 23% with mesangial glomerulitis or normal histologic findings were positive. Immunoglobulins of the same class found in the skin were detected in the glomeruli of patients examined by renal biopsy. These results suggest that there is a relationship between the occurrence of immunoglobulin in the epidermal basement membrane and the presence of the more severe forms of lupus nephritis.

Authors

James N. Gilliam, Don E. Cheatum, Eric R. Hurd, Peter Stastny, Morris Ziff

Adrenergic Modulation of Pancreatic Glucagon Secretion in Man

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In order to characterize the influence of the adrenergic system on pancreatic glucagon secretion in man, changes in basal glucagon secretion during infusions of pure alpha and beta adrenergic agonists and their specific antagonists were studied. During infusion of isoproterenol (3 μg/min), a beta adrenergic agonist, plasma glucagon rose from a mean (±SE) basal level of 104±10 to 171±15 pg/ml, P < 0.0002. Concomitant infusion of propranolol (80 μg/min), a beta adrenergic antagonist, prevented the effects of isoproterenol, although propranolol itself had no effect on basal glucagon secretion. During infusion of methoxamine (0.5 mg/min), an alpha adrenergic agonist, plasma glucagon declined from a mean basal level of 122±15 to 75±17 pg/ml, P < 0.001. Infusion of phentolamine (0.5 mg/min), an alpha adrenergic antagonist, caused a rise in plasma glucagon from a mean basal level of 118±16 to 175±21 pg/ml, P < 0.0001. Concomitant infusion of methoxamine with phentolamine caused a reversal of the effects of phentolamine.

Authors

John E. Gerich, Maurice Langlois, Claudio Noacco, Victor Schneider, Peter H. Forsham

Release of Adenosine from Human Hearts during Angina Induced by Rapid Atrial Pacing

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This study was designed to determine whether human hearts release adenosine, a possible regulator of coronary flow, during temporary myocardial ischemia and, if so, to examine the mechanisms involved. Release of adenosine from canine hearts had been reported during reactive hyperemia following brief coronary occlusion, and we initially confirmed this observation in six dogs hearts. Angina was then produced in 15 patients with anginal syndrome and severe coronary atherosclerosis by rapid atrial pacing during diagnostic studies. In 13 of these patients, adenosine appeared in coronary sinus blood, at a mean level of 40 nmol/100 ml blood (SE = ±9). In 11 of these 13, adenosine was not detectable in control or recovery samples; when measured, there was concomitant production of lactate and minimal leakage of K+, but no significant release of creatine phosphokinase, lactic acid dehydrogenase, creatine, or Na+.

Authors

Arthur C. Fox, George E. Reed, Ephraim Glassman, Alfred J. Kaltman, Barbara B. Silk

Assay of Total Plasma Apolipoprotein B Concentration in Human Subjects

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Abstract

We have developed a double antibody radioimmunoassay (RIA) for human apolipoprotein B (ApoB). The assay measures not only the ApoB content of β-lipoproteins (low density lipoproteins [LDL]) but also that contained in the other lipoproteins in plasma.

Authors

Gustav Schonfeld, Robert S. Lees, P. K. George, Barbara Pfleger

Formation of an Intermediate in Prostaglandin Biosynthesis and Its Association with the Platelet Release Reaction

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Abstract

A compound that could be converted to prostaglandin F2α by mild chemical reduction was formed by human platelets in response to arachidonic acid, collagen, or L-epinephrine. It was present in maximal amounts at about 1 min after addition of arachidonic acid or collagen to platelet-rich plasma. Its initial formation appeared to precede platelet aggregation by these agents and was closely correlated with the release of adenine nucleotides and radioactive 5-hydroxytryptamine from platelets. Moreover, the compound was itself found outside the platelets. This compound is probably an endoperoxide intermediate in prostaglandin biosynthesis and may be a trigger for the platelet release reaction.

Authors

J. B. Smith, Carol Ingerman, J. J. Kocsis, M. J. Silver

Partial Purification of Osteoclast-Activating Factor from Phytohemagglutinin-Stimulated Human Leukocytes

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Abstract

Osteoclast-activating factor (OAF) is a soluble mediator found in supernates of human peripheral leukocytes which have been cultured with antigens or phytomitogens. OAF is a potent stimulator of osteoclastic resorption of fetal bone in organ culture. The present studies were designed to characterize OAF chemically. Bone resorbing activity from supernates of leukocytes cultured without added plasma was not lost on dialysis using a membrane with a molecular weight cutoff of 3,500, but was lost when heated to 60°C for 30 min. The activity was lost after treatment with trypsin or pronase but not after treatment with ribonuclease or neuraminidase. Papain, which inactivated parathyroid hormone at a concentration of 25 μg/ml, did not inactivate OAF at 250 μg/ml. OAF did not react with an antibody to bovine parathyroid hormone which cross-reacts with human parathyroid hormone. OAF was also distinguished from active metabolites of vitamin D and from prostaglandin by extraction procedures and immunoassay for prostaglandin E2.

Authors

Richard A. Luben, Gregory R. Mundy, Clarence L. Trummel, Lawrence G. Raisz

A Model of the Kinetics of Insulin in Man

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Abstract

The design of the present study of the kinetics of insulin in man combines experimental features which obviate two of the major problems in previous insulin studies. (a) The use of radioiodinated insulin as a tracer has been shown to be inappropriate since its metabolism differs markedly from that of the native hormone. Therefore porcine insulin was administered by procedures which raised insulin levels in arterial plasma into the upper physiologic range. Hypoglycemia was prevented by adjusting the rate of an intravenous infusion of glucose in order to control the blood glucose concentration (the glucose-clamp technique). (b) Estimation of a single biological half-time of insulin after pulse injection of the hormone has been shown to be inappropriate since plasma insulin disappearance curves are multiexponential. Therefore the SAAM 25 computer program was used in order to define the parameters of a three compartment insulin model.

Authors

Robert S. Sherwin, Karl J. Kramer, Jordan D. Tobin, Paul A. Insel, John E. Liljenquist, Mones Berman, Reubin Andres

Proteolysis of Myosin during Platelet Storage

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Abstract

Physical properties of actomyosin from either fresh or stored platelets have been compared. Actomyosin obtained from platelets after 3 days of storage contained myosin that was 60-80% degraded to myosin rod. No myosin rod was detected in fresh platelets. The platelet myosin rod is similar to the rod produced by limited proteolysis of skeletal muscle myosin.

Authors

Joel Abramowitz, Alfred Stracher, Thomas C. Detwiler

Nephron Stop-Flow Pressure Response to Obstruction for 24 Hours in the Rat Kidney

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Abstract

Complete ureteral ligation of 24-h duration significantly reduced stop-flow and estimated glomerular capillary pressures in nephrons accessible to micropuncture in obstructed kidneys. In kidneys without ureteral obstruction, a similar response occurred in single tubules blocked for 24 h without affecting nearby unblocked tubules. Thus, the response to tubular obstruction occurs on an individual nephron basis and results from constriction of individual afferent arterioles. The mechanism leading to the response is unknown, but a feedback mechanism operating through the juxtaglomerular apparatus of individual nephrons is an attractive possibility.

Authors

William J. Arendshorst, William F. Finn, Carl W. Gottschalk

Micropuncture studies of phosphate transport in the proximal tubule of the dog. The relationship to sodium reabsorption

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Abstract

Authors