Issue published August 1, 1979
Volume 64, Issue 2, Pages 351-693
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42 total articles
Selective Depression of the Xenogeneic Cell-Mediated Lympholysis in Systemic Lupus Erythematosus
The immunological responsiveness of a panel of 17 patients with systemic lupus erythematosus (SLE) was studied in an in vitro model of xenogeneic sensitization against mouse lymphoid cells. Generation of cytotoxic thymus-derived (T) cells evaluated by a chromium release assay against labeled target cells was found to be drastically impaired in these lupus patients. Such depression was independent of drug therapy at the time of the study, clinical status, and other immunological parameters such as antibodies against native DNA, complement levels, cryoglobulinemia, circulating immune complexes, or T- and bone marrow-derived (B)-cell numbers. In contrast to the cytotoxic response, the proliferative responses to phytohemagglutinin, to allogeneic lymphocytes, and to xenogeneic lymphocytes were not significantly different from those of normal individuals. The latter response was shown to be H-2 restricted with the primed lymphocyte test. These results suggest the presence of a selective defect in the generation or in the expression of killer cells rather than a deficiency in antigen recognition by T cells. The role of serum factor(s) was examined by educating the lymphocytes of normal subjects in the presence of serum from SLE patients. Such manipulation affected both the generation of killer cells and the proliferative response. Finally our observations indicate that depression of cell-mediated immunity in SLE patients may be associated with several mechanisms including a cellular one, specifically affecting the generation of killer T cells, and a humoral one possibly as a result of antilymphocytic antibodies and(or) immune complexes.
Chick embryo pancreatic transplants reverse experimental diabetes of rats.
The effectiveness of xenogeneic embryonic tissue in the treatment of experimental diabetes has been investigated in rats. The splenic lobes (80) of 15- to 18-d-old chick embryos, composed almost exclusively of endocrine tissue, were implanted directly into the hepatic parenchyma of the rat recipient. The biochemical and metabolic changes in the recipients suggest that embryonic transplants of 15-d-old chick pancreases were able to significantly improve, for a prolonged period of time (18 mo), the diabetic state of nonimmunosuppressed rats. None of the recipients of 18-d-old embryos splenic lobes exhibited a long-term improvement of the diabetic state after transplantation. The complete destruction of the pancreatic B cells of the recipients was assessed by: (a) immunocytochemical investigations of the recipient's pancreas, (b) measurement of insulin in the liver and pancreas of the recipients and (c) in situ vascular perfusion of their pancreas submitted to high glucose challenge. The results suggest that pancreatic tissue of the 15-d-old embryos is immunologically immature lacking one or several lymphocyte subsets implicated in the afferent lood of "non-self" recognition.
Cholinergic Stimulation of Norepinephrine Release in Man: EVIDENCE OF A SYMPATHETIC POSTGANGLIONIC AXONAL LESION IN DIABETIC ADRENERGIC NEUROPATHY
Amplification of endogenous cholinergic activity—produced by the intravenous injection of edrophonium, an acetylcholinesterase inhibitor which does not enter the central nervous system, into normal subjects—resulted in significant and briefly sustained increments in the plasma concentrations of norepinephrine (153±15−234±29 pg/ml, P < 0.01) and epinephrine (16±3−34±5 pg/ml, P < 0.01) measured with a single-isotope derivative method. These increments were not attributable to reflex responses to hemodynamic changes and similar increments in plasma norepinephrine occurred in adrenalectomized (epinephrine deficient) patients. Thus, cholinergic activation results in direct stimulation of sympathetic postganglionic neurons, with augmented norepinephrine release, and of the adrenal medullae, with augmented epinephrine release, in man. Four diabetic patients with hypoadrenergic postural hypotension exhibited blunted sympathetic postganglionic neural responses, and normal adrenomedullary responses, to cholinergic stimulation (and to standing) indicative of the presence of a sympathetic postganglionic axonal lesion in diabetic adrenergic neuropathy. Nondiabetic patients with hypoadrenergic postural hypotension due to documented or probable central nervous system lesions exhibited normal responses to cholinergic stimulation produced in this fashion demonstrating the presence of intact sympathetic postganglionic neurons and adrenal medullae in these patients and providing further support for the conceptual soundness of this approach to the study of human adrenergic physiology and pathophysiology.
Gangliosides sensitize unresponsive fibroblasts to Escherichia coli heat-labile enterotoxin.
Chemically transformed mouse fibroblasts did not raise their cyclic AMP level in response to Escherichia coli heat-labile enterotoxin. These fibroblasts did, however, incorporate exogenous mono-, di-, and trisialogangliosides. After the uptake of monosialoganglioside galactosyl-N-acetylgalactosaminyl-[N-acetylneuraminyl]-galactosylglucosylceramide (GM1), the cells responded to E. coli heat-labile enterotoxin. The di- and trisialogangliosides were considerably less effective. GM1, the putative cholera toxin (choleragen) receptor, has been implicated previously as the receptor for E. coli heat-labile enterotoxin based on the ability of the free ganglioside to inhibit the effects of toxin. This investigation establishes that the ganglioside, when incorporated into fibroblasts, serves a functional role in mediating the responsiveness to the toxin.
Hyper Immunoglobulin M Immunodeficiency (Dysgammaglobulinemia): PRESENCE OF IMMUNOGLOBULIN M-SECRETING PLASMACYTOID CELLS IN PERIPHERAL BLOOD AND FAILURE OF IMMUNOGLOBULIN M-IMMUNOGLOBULIN G SWITCH IN B-CELL DIFFERENTIATION
Raif S. Geha, Newton Hyslop, Samih Alami, Fuad Farah, Eveline E. Schneeberger, Fred S. RosenAbstract | Full text | PDF (Page 385)
The peripheral blood lymphocytes of nine patients with hyper immunoglobulin (Ig)M immunodeficiency were studied in an attempt to define the cellular basis of this disorder. B cells were normal in number but qualitatively abnormal in all patients. Approximately one-half of the B cell consisted of small lymphocytes (7-9 μm in diameter) bearing surface IgM and IgD, as well as C3 receptors. These cells were driven to secrete IgM but not IgG after in vitro stimulation by pokeweed mitogen. In the blood there were also large lymphocytes (10-14 μm in diameter) that possessed surface as well as intracytoplasmic IgM but lacked C3 receptors. These cells spontaneously secreted large amounts of IgM in vitro and on electron microscopy were found to be rich in rough endoplasmic reticulum. Such a subpopulation of lymphoid cells was not detected in normal peripheral blood and was unique for all patients with hyper IgM immunodeficiency studied.
Subset derivation of T-cell acute lymphoblastic leukemia in man.
Normal human peripheral blood T cells can be characterized as belonging to either the TH+2 or TH-2 T-cell subset. Approximately 20% of T cells are TH+2, whereas 80% are TH-2 utilizing specific heteroantisera. To determine shether human T-cell acute lymphoblastic leukemia (T-ALL) cells belong to one or another T-cell subset, cell surface phenotyping was performed on tumor populations from 25 patients with T-ALL. Tmuor cells from these 25 individuals were either TH+1 or TH-2, but not both. 5 of 25 patients had TH+2 T-ALL cells. These TH+2 tumor populations were found exclusively in children and often without an accompanying thymic mass. TH-2 T-ALL, in contrast, occurred in both children and adults and was almost always associated with thymic enlargement. Although children with TH+2 T-ALL had as high or higher peripheral blast counts on presentation than their TH-2 T-ALL counterparts, overall survival was greater for the TH+2 group (greater than 36 mo) than the TH-2 group (less than 12 mo). These studies demonstrate that T-cell leukemias in man arise from distinct T-cell subsets and that cell surface characterization of T-cell malignancies may provide useful clinical data related to prognosis.
Endocrine Consequences of Continuous Antiestrogen Therapy with Tamoxifen in Premenopausal Women
Barry M. Sherman, Frederick K. Chapler, Kent Crickard, Dorothy WycoffAbstract | Full text | PDF (Page 398)
Daily administration of estrogen antagonists to premenopausal women has been incorporated into the adjuvant treatment of breast cancer. We have studied the changes in reproductive hormones, pituitary responses to hypothalamic-releasing hormones, and endometrial histology during treatment with the antiestrogen tamoxifen in five healthy, premenopausal women. These studies were carried out during one menstrual cycle before and during two cycles of antiestrogen treatment. All subjects continued to have regular menses with biphasic basal body temperature records. During treatment, estradiol (E2) levels were increased but followed the usual pattern reflecting follicular maturation and corpus luteum formation. The mean E2 concentration at the midcycle peak and during the luteal phase was twice that observed during the non-treatment cycle. By contrast, the concentrations and secretory patterns of luteinizing hormone and follicle-stimulating hormone were not greatly changed, and the gonadotropin responses to gonadotropin-releasing hormone were not suppressed.
Paradoxical Effects of Clofibrate on Liver and Muscle Metabolism in Rats: INDUCTION OF MYOTONIA AND ALTERATION OF FATTY ACID AND GLUCOSE OXIDATION
Chronic clofibrate intake, on occasion, results in a muscular syndrome in man. We have investigated the effects of chronic clofibrate administration in rats on the electrical activity of a skeletal muscle (gastrocnemius), its composition, and its oxidation of palmitate and glucose. These effects have been compared with those in the liver. Clofibrate administration altered electromyographic pattern of gastrocnemius muscle (characteristic of myotonia), decreased its protein content, and impaired its oxidation of palmitate and glucose. These effects were quite different in the liver, because clofibrate intake increased the liver protein content and oxidation of palmitate without affecting the oxidation of glucose by this tissue. Whereas chronic clofibrate administration markedly increased the concentration of carnitine as well as the activity of mitochondrial carnitine palmitoyl-transferase in the liver, it decreased the activity of this enzyme in the gastrocnemius muscle without a significant effect on carnitine concentration in this tissue. Greater in vivo fatty acid oxidation by clofibratefed than by control rats was evidenced (a) by greater rate of production of 14CO2 in the expired air after injection of a tracer dose of [14C]palmitate and (b) by greater plasma and tissue concentrations of ketone bodies. We conclude that (a) paradoxical effects of clofibrate on fatty acid oxidation by the liver and skeletal muscle are related to changes in the activity of carnitine acyltransferase, (b) an increase in hepatic fatty acid oxidation may contribute to hypolipidemic effect of clofibrate, and (c) impairment of fatty acid and glucose oxidation by the muscle may be a factor in the development of muscular syndrome in patients receiving clofibrate treatment.
Tyramine kinetics and metabolism in cirrhosis.
B A Faraj, J T Fulenwider, E B Rypins, B Nordlinger, G L Ivey, R D Jansen, F M Ali, V M Camp, M Kutner, F Schmidt, D RudmanAbstract | Full text | PDF (Page 413)
Hypertyraminemia is common in hepatic cirrhosis and correlates in severity with encephalopathy. The mechanism of cirrhotic hypertyraminemia has not been established. The alternative possibilities are increased production from tyrosine and impaired degradation by monoamine oxidase. This investigation determined the pharmacokinetics of tyramine after an intravenous bolus injections of [3H]-tyramine (180--200 muCi 12 Ci/mmol sp act) in 13 cirrhotics and 9 controls. In normals, [3H]tyramine levels initially declined rapidly (alpha-phase) followed by a slower decline (beta-phase) with an average t 1/2 of 20.8 min. Average normal metabolic clearance rate and production rate were 13.2 liters/min and 15.4 microgram/min, respectively. In cirrhotic patients, the plasma disappearance curve for [3H]tyramine was qualitatively similar to that of the control subjects with no apparent different in beta-t 1/2 (17.2 min). The hypertyraminemia of cirrhosis resulted primarily from overproduction of tyramine, as the production rate (32.0 microgram/min) in these patients was significantly greater (P less than 0.05) than in controls, whereas the metabolic clearance rate remained normal (average 12.2 liters/min). A difference in ratio of tyramine metabolic products was noted as well. Cirrhotics had a high ratio of plasma 4-hydroxyphenylethanol:4-hydroxyphenylacetic acid (60:40 vs. 30:70) as compared with normals. Although the tyramine clearance rates are similar in normals and cirrhotics, different mechanisms may be responsible for catabolism.
Effects of exerimental right ventricular hypertrophy on myocardial blood flow in conscious dogs.
The effects of right ventricular hypertrophy on the overall and regional distribution of myocardial blood flow in the absence of an elevated coronary arterial driving pressure were evaluated in 18 concscious dogs subjected to a chronic pressure overload of the right ventricle induced by pulmonary artery constriction. The sustained pressure overload for duration of 4--6 wk or 4--5 mo resulted in significant increases in right ventricular mass (45 and 110%, respectively) and right ventricular fiber diameter (22 and 60%, respectively). Moreover, the presence of moderate and severe hypertrophy was associated with marked increases in transmural blood flow per gram to the right ventricle proportional to the observed increases in mass, i.e., of 36 and 109%, respectively, from a normal value of 0.67 +/- 0.04 ml/min per g, whereas left ventricular blood flow remained unaltered from a normal value of 1.00 +/- 0.06 ml/min per g. Despite the large increase in blood flow per gram to moderately and severely hypertrophied right ventricle, no significant changes in the ratio of capillary:muscle fiber number were observe. These data suggest that the development of right ventricular hypertroph is characterized by a sustained compensatory response of the coronary circulation to the augmented work load and mass, and that is not associated with a proliferative response of the vasculature supplying the enlarged ventricle.
Complement Lysis of Human Erythrocytes: DIFFERING SUSCEPTIBILITY OF TWO TYPES OF PAROXYSMAL NOCTURNAL HEMOGLOBINURIA CELLS TO C5b-9
Charles H. Packman, Stephen I. Rosenfeld, David E. Jenkins Jr., Patricia A. Thiem, John P. LeddyAbstract | Full text | PDF (Page 428)
Although enhanced sensitivity of erythrocytes to complement-mediated lysis is a hallmark of paroxysmal nocturnal hemoglobinuria (PNH), subpopulations of erythrocytes in such patients vary significantly in this respect. One PNH erythrocyte subpopulation (termed type III) comprises exquisitely sensitive cells, whereas type II PNH erythrocytes are intermediate in complement sensitivity between PNH type III and normal human erythrocytes. Differences in the action of the terminal complement components that would account for the differing lytic behavior of types II and III PNH erythrocytes have been proposed but not directly demonstrated.
Sensitivity of lymphocytes to prostaglandin E2 increases in subjects over age 70.
We examined the sensitivity of lymphocytes from different age groups to inhibition by prostaglandin E2. Phytohemagglutinin-stimulated cultures of peripheral blood mononuclear cells from 12 healthy subjects over the age of 70 were much more sensitive to inhibition by exogenously added prostaglandin E2 than were cells from 17 young controls (ID50 congruent to 10 nM for the subjects over 70 vs. greater than 3 micronM for the young controls). The more senstivie lymphocytes from a subject over 70 were to prostaglandin E2, the lower was his or her response to phytohemagglutinin (r = 0.75, P less than 0.01). The mean responses to phytohemagglutinin of the peripheral blood mononuclear cells from the subjects over 70 were significantly depressed compared to the young controls. Addition of indomethacin, a prostaglandin synthetase inhibitor, to the cultures resulted in an increase in [3H]thymidine incorporation of 140 +/- 16% in the cells of the subjects over 70 vs. a 36 +/- 3% increase in the young controls (mean +/- SEM, P less than 0.001). The mean phytohemagglutinin response of the subjects over 70 was 40% of the control response without indomethacin. With addition of indomethacin the response of subjects over 70 rose to 72% of control. Thus, increased sinsitivity to prostaglandin E2 appears to be responsible in part for the depressed mitogen response of peripheral blood mononuclear cells from healthy subjects over 70.
Effects of Carnitine in Ischemic and Fatty Acid Supplemented Swine Hearts
Free fatty acids (FFA) in excess FFA: albumin molar ratios have been determined to additionally compromise mechanical performance in ischemic hearts. Carnitine, an intracellular carrier of FFA and an agent which is lost to the heart during ischemia, has been postulated to in part restore function with its replacement. To test whether its benefits are also operative in a setting of excess FFA, these studies were performed. In the main protocol, four groups of perfused swine hearts (n = 45) were compared during 50 min of control flow (179.7 ml/min) and 40 min of global ischemia (106.1 ml/min). Initial base-line serum FFA:albumin molar ratios and carnitine levels in all groups were 1.3:1 and 8.5 nmol/ml, respectively. In two of these groups FFA:albumin ratios were increased to 5.9:1 with constant infusions of Intralipid. In two alternate groups (one with and one without extra FFA supplements) dl-carnitine was supplied, sufficient to increase serum levels nearly 200-fold. Ischemia per se in 14 hearts significantly decreased several parameters of global and regional mechanical function including left ventricular (LV) and mean aortic pressures, LV isovolumetric pressure development (max dp/dt), LV epicardial motion, and LV work, together with concomitant decreases in myocardial oxygen consumption. Elevated FFA in 12 hearts rendered similarly ischemic further decreased mechanical function (LV pressure: −20.8%, P < 0.05; mean aortic pressure −26.9%, P < 0.05; LV max dp/dt: −39%, P < 0.05; regional LV shortening: −51.1%, P < 0.05; and LV work: −50.3%, P < 0.05) as compared with nonsupplemented hearts. dl-Carnitine treatments in nine hearts, not supplemented with extra FFA were without apparent effect in improving overall hemodynamic performance. However, dl-carnitine in 10 high FFA-ischemic hearts effected several improvements as compared with the untreated group: LV pressure was increased 25.6%, P < 0.025; mean aortic pressure: +43.5%, P < 0.05; LV max dp/dt: +41.5%, P < 0.05; regional LV shortening: +241.3%, P < 0.001; and LV work: +76.2%, P < 0.05 at comparable levels of myocardial oxygen consumption. In a separate protocol, the effects of stereospecificity were also studied by comparing l- with dl-carnitine in globally perfused, palmitate-supplemented hearts (five hearts in each treatment group). At similar conditions of flow and serum FFA, changes in mechanical function were comparable, except for a tendency to perform greater LV work at reduced flows in the l-carnitine-treated hearts. Thus, it was demonstrated that carnitine in ischemic hearts is capable of preserving mechanical function under conditions of excess FFA, presumably by modifying the toxic effects of FFA intermediates. The major therapeutic actions appeared to derive from the l-isomer of carnitine.
Role of Renal Prostaglandins in Sympathetically Mediated Renin Release in the Rat
Renal prostaglandins (PG) appear to mediate renin release due to stimulation of the intrarenal baroreceptor, but not that due to activation of the macula densa. However, as the role of PG in sympathetically mediated renin release remains unclear, a possible interrelationship between these factors was examined in conscious rats. Hydralazine increased the serum renin levels from 3.1±0.8 to 16.7±3.0 ng/ml per h at a dose of 1 mg/kg. Indomethacin (5 mg/kg) suppressed urinary PGE2 and PGF2α excretion by 89 and 74%, respectively, arachidonate hypotension by 82%, and inhibited the elevated renin levels from hydralazine by 100% without altering the hypotensive effect of the drug. Another PG synthetase inhibitor, meclofenamate, was also effective in attenuating hydralazine-induced renin release, urinary PGE2 and PGF2α excretion, and arachidonate hypotension. Isoproterenol, a nonselective beta-adrenergic agonist, increased heart rate, lowered blood pressure, and also stimulated the release of renin when administered intraperitoneally. However, intrarenal infusion of the drug only resulted in increased renin release. Indomethacin inhibited isoproterenol-induced renin release by 66 and 67%, respectively, without altering the hemodynamic effects associated with the intraperitoneal administration of the drug. The selective beta1 agonist, H133/22, increased the release of renin and heart rate in a dose-related manner without altering blood pressure. H133/22-induced renin release was inhibited by 80% by indomethacin pretreatment. Finally, intrarenal infusions of dibutyryl cyclic AMP (3 mg/kg per min) increased the serum activity from 4.1±0.2 to 20.4±3.9 ng/ml per h without altering mean arterial pressure. Indomethacin inhibited this renin response to dibutyryl cyclic AMP by 96%. Thus, renal PG appear to be important mediators of sympathetically stimulated renin release acting as a site distal to the beta-adrenergic receptor.
Anaphylactic release of a basophil kallikrein-like activity. I. Purification and characterization.
These studies describe the IgE-mediated relase of a basophil kallikrein-like enzyme that is an arginine esterase and is inhibited by plasma, diisopropylphosphofluoridate, and Trasylol. The substrate specificity for the synthetic amino acid ester substrates p-toluenesulfonyl-L-arginien methyl ester, benzoyl-arginine methyl ester, and acetyl-tyrosine methyl ester is similar for the basophil enzyme and plasma kallikrein. The interaction of arginine esterase-active fractions from ion-exchange (DEAE-Sephacel) and gel filtration (Sepharose 6B) chromatography, with human plasma kininogen, generates immunoreactive kinin. The basophil arginine esterase and kinin-generating activities co-chromatograph on Sepharose 6B and the quantity of kinin generated is, in general, proportional to the arginine esterase activity of the column fractions, suggesting that these two activities are subserved by the same protease. The ability of this protease to generate kinin equally well from heat- and acid-treated plasma, as from fresh human plasma, suggests that this protease has kallikrein-like activity. These data suggest that kallikrein-like activity can be generated from human basophils as a direct result of a primary IgE-mediated immune reaction, thus providing a potential link between reactions of immediate hypersensitivity and the plasma and(or) tissue kinin-generating systems.
Anaphylactic relase of a basophil kallikrein-like activity. II. A mediator of immediate hypersensitivity reactions.
This report describes the immune release of a new mediator from human peripheral leukocytes, a basophil kallikrein-like activity (BK-A). The release process is initiated by the interaction of antigen on anti-IgE with cell-bound IgE, and appears to be similar in mechanism to the relase of histamine and other mediators of the immediate hypersensitivity reaction. The dose-response relationships and kinetics of histamine and BK-A release from antigen-challenged peripheral leukocytes are similar. The relase of the BK-A is calcium and temperature dependent, requires metabolic energy, and is controlled by hormone-receptor interactions that influence the cellular level of cyclic AMP, as has been described for other mediators of immediate hypersensitivity reactions. The data indicate that the interaction of BK-A with human plasma kininogen, generates immunoreactive kinin. We conclude that the antigen-IgE interation leads to the release from human basophils of a new mediator, a basophil kallikrein-like activity which may well be a link between reactions of immediate hypersenstivitity and the plasma and/or tissue kinin-generating systems.
Micropuncture determination of pH, PCO2, and total CO2 concentration in accessible structures of the rat renal cortex.
Previous studies evaluating the mechanism of renal HCO-3 reabsorption have assumed equilibrium between systemic arterial blood and tubular fluid PCO2. We have recently reported that the PCO2 in proximal and distal tubular fluid as well as the stellate vessel significantly exceeded arterial PCO2 by 25.9 +/- 0.92 mm Hg. The purpose of this study was to determine directly, for the first time, pH, PCO1, and total CO2 concentration in the accessible structures of the rat renal cortex with both microelectrodes and microcalorimetry. In addition, the concentrations of chloride and total CO2 were compared in the stellate vessel. The data demonstrate that: (a) values for total [CO2] in both the proximal tubule and stellate vessel calculated from in situ determination of pH and PCO2 closely agree with the measured values for total [CO2]: (b) values for chloride concentration in the stellate vessel are significantly less than the corresponding values in systemic plasma (delta[Cl-] = 5.6 meq/liter); and (c) the rise in [HCO-3] from systemic to stellate vessel plasma closely approximates the observed reciprocal fall in [Cl-] in this structure.
Reconstitution of spectrin-deficient, spherocytic mouse erythrocyte membranes.
To study directly the role of spectrin in erythrocyte membrane function, we have designed a reconstituted membrane system using erythrocyte membranes from spectrin-deficient mice and purified spectrin from normal mice. The normal spectrin is inserted into the spectrin-deficient spherocytes by exchange hemolysis. Thereafter, raising the ionic strength and temperature reseals the cells and, with time, facilitates binding of the spectrin to the spectrin-deficient membranes. The binding is apparently specific as shown by its dependence upon the concentration of undenatured spectrin and the concentration of salt used, as well as by the immunofluorescent appearance of the reconstituted cells after treatment with specific antispectrin antibody. In terms of in vitro cellular behavior, the reconstituted preparations show marked changes in comparison to the untreated spherocytes. In particular, membrane stability, as measured by the reduction of myelin figure formation and lipid loss, is considerably enhanced. In addition, membrane fusion, which occurs readily with the untreated spherocytes, is virtually eliminated. Finally, the osmotic behavior of the native spherocytes is appreciably altered, such that the early phase of osmotically induced swelling, as measured in a high-speed stop-flow apparatus, is delayed and modified. Taken together, these findings indicate specific roles for spectrin in the stabilization of the erythrocyte membrane, in the limitation of membrane fusion, and in the modulation of the membrane's response to osmotic stress.
Effect of prostaglandin E2 on chloride transport across the rabbit thick ascending limb of Henle. Selective inhibitions of the medullary portion.
Prostaglandins are present in large quantities in the kidney and have been shown to directly affect transepithelial transport. The present studies were designed to examine whether prostaglandin E2 could affect chloride transport across the thick ascending limb of Henle. Isolated segments of the cortical and medullary thick ascending limb of Henle were perfused in vitro and the transepithelial voltage and net chloride flux were measured. Exposure of the medullary thick ascending limb to 2 microM prostaglandin E2 resulted in a fall in net chloride transport of 40--50% with a concomitant fall in voltage. In contrast, net chloride transport in the cortical thick ascending limb was not affected by prostaglandin E2. Under similar conditions, the medullary thick ascending limb possessed twice the capacity to transport chloride than did the cortical thick ascending limb. The results suggest that endogenous renal prostaglandins may play a modulating role in the addition of salt to the renal medullary interstitium and may, under some circumstances, by chloruretic.
Glomerular Hemodynamics in Rats with Chronic Sodium Depletion: EFFECT OF SARALASIN
In chronic sodium depletion the glomerular filtration rate may be reduced, and alterations in proximal tubular function may contribute to the maintenance of antinatriuresis. Measurements were made by micropuncture technique in superficial nephrons of the Munich-Wistar rat of (a) the determinants of glomerular filtration rate, (b) peritubular capillary hydrostatic and oncotic pressure, and (c) proximal tubular fractional and absolute reabsorption in both a control group (group 1, n = 12) and a group of chronically sodium-depleted rats (group 2, n = 12). Single nephron filtration rate (sngfr) was 37.2±1.2 in group 1 and 31.6±1.0 nl/min/g kidney wt (P < 0.05) in group 2. Of the factors potentially responsible for the observed reduction in sngfr, there was no change in systemic oncotic pressure or the transglomerular hydrostatic pressure gradient. Sngfr was lower in group 2 because of both a reduced single nephron plasma flow (rpf) (128±6 vs. 112±5 nl/min per g kidney wt, P < 0.05) and additionally to a decrease in the glomerular permeability coefficient, LpA, from a minimum value of 0.105±0.012 in group 1 to 0.054±0.01 nl/s per g kidney wt per mm Hg (P < 0.01) after chronic sodium depletion. There was no difference in fractional proximal tubular reabsorption between group 1 and group 2. Absolute proximal reabsorption (APR) was reduced from 20.8±1.3 in group 1 to 16.3±0.9 nl/min per g kidney wt in group 2.
Effects of Reduced Renal Mass and Dietary Protein Intake on Amino Acid Release and Glucose Uptake by Rat Muscle In Vitro
Herschel R. Harter, Irene E. Karl, Saulo Klahr, David M. Kipnis, Elise Tegtmeyer, Dale F. Osborne, Thomas HowardAbstract | Full text | PDF (Page 513)
Epitrochlearis muscles obtained from normal male Holtzman rats used as controls (C) and rats with reduced renal mass (Nx) fed isocaloric diets of varying protein content were incubated in Krebs-Ringer buffer containing 5 mM glucose for 1 or 3 h with or without insulin.
Metabolic Studies in Familial Hypercholesterolemia: EVIDENCE FOR A GENE-DOSAGE EFFECT IN VIVO
To investigate the gene-dosage effect in familial hypercholesterolemia (FH), metabolic studies were conducted in a group of well-characterized patients with either heterozygous (n = 7) or homozygous (n = 7) FH and the results were compared to those obtained in normal subjects (n = 6). The turnover of 125I-labeled low-density lipoprotein (LDL) was measured in all of the normals, all but one of the FH heterozygotes, and in all of the homozygotes. Chemical cholesterol balance was performed simultaneously with the 125I-LDL turnover in all seven of the homozygotes.
Catecholamine regulation of human erythrocyte membrane protein kinase.
The effect of catecholamines on membrane-associated protein kinase in the mature human erythrocyte was investigated. Protein kinase activity was assayed after isolation of membranes from intact erythrocytes incubated with and without catecholamines. Activation of the enzyme is expressed as the ratio of the extent of phosphorylation of exogenous protein substrate in the absence to that in the presence of 2.5 microM cyclic AMP (cAMP). The potent beta-adrenergic agonist, (-)isoproterenol (2 microM), (-)epinephrine (10 microM) and (-)norepinephrine (10 microM) stimulated the cAMP-dependent protein kinase in membranes, 38 +/- 7%, 31 +/- 6%, and 30 +/- 6%, respectively. Maximal stimulation of membrane protein kinase by 10 microM (-)epinephrine was obtained approximately equal to 30 min after initiation of the incubation of erythrocytes with the hormone. The concentrations of (-)catecholamines that gave half-maximal stimulation of the membrane protein kinase were 0.17 microM for isoproterenol, 0.35 microM for epinephrine, and 0.63 microM for norepinephrine. The membrane protein kinase response to beta-adrenergic agonists was found to be stereospecific. The stimulation of membrane protein kinase by 10 microM (-)epinephrine was inhibited by the beta-adrenergic antagonist, (-)propranolol with EC50 = 0.60 microM, and the inhibition of agonist stimulation of the cAMP-dependent protein kinase by propranolol was stereospecific. These studies suggest that a functional beta-adrenergic receptor exists in the mature human erythrocyte.
A critical assessment of the mechanism by which hyperoxia attenuates exercise-induced asthma.
Recent data demonstrate that the magnitude of the heat loss that occurs from the respiratory tract during exercise correlates with the degree of post-exertional obstruction that develops in asthmatics. Respiratory heat loss relates directly to the minute ventilation and heat capacity of the inspired gas and inversely to its water content and temperature. Because it has been shown that inhaling 100% oxygen during exercise blunts the obstructive response, we wondered if this effect could be accounted for by differing values of heat exchange with air and oxygen breathing. To examine this question, we studied 10 asthmatics by measuring multiple aspects of pulmonary mechanics before and after four bouts of exhausting leg work during which the subjects inhaled either air or oxygen conditioned to provide widely differing thermal burdens on their airways. Under all inspired gas conditions, oxygen breathing produced significantly less obstruction than air. Minute ventilation was also significantly less with oxygen as was the total heat lost. As the latter fell, so did the magnitude of the postexercise obstruction. When the differences in ventilation and respiratory heat loss between air and oxygen were eliminated by eucapnic hyperventilation, the differences in the obstructive responses also disappeared. Thus, the effects of hyperoxia on exercise-induced asthma can be accounteed for solely by alterations in heat exchange.
Effect of Volume Expansion on Hemodynamics of the Hypoperfused Rat Kidney
Paul A. Johnston, David B. Bernard, John F. Donohoe, Nancy S. Perrin, Norman G. LevinskyAbstract | Full text | PDF (Page 550)
The hemodynamics of the rat kidney were studied during reduction of renal arterial pressure to 35-40 mm Hg (H), and after volume expansion at that pressure with 0.9% NaCl (IS), 1.7% NaCl (HS), 5% mannitol in 0.9% NaCl (MS), 5% mannitol in water (MW), or 50 mM mannitol + 125 mM NaCl. During H, left renal blood flow (RBF) was 0.8±0.1 ml/min. Expansion with IS did not alter RBF, but expansion with HS, MS, MW, and 50 + 125 mM NaCl elevated RBF to 200-250% of hypoperfusion values. Glomerular capillary pressure rose significantly from 15.7±0.7 mm Hg during H to 22.3±1.1, 24.4±0.7, and 26.6±0.7 mm Hg following expansion with HS, MS, or MW, respectively. Efferent arteriolar pressure also rose significantly to 6.9±0.5, 9.7±0.8, and 9.5±0.9 mm Hg, respectively. Preglomerular resistance fell to 18-24% of H values, and postglomerular resistance fell to 58-74% of H values after expansion with HS, MS, or MW. Glomerular filtration (GFR) could not be detected during H or after IS expansion. HS and mannitol-containing solutions restored GFR to 0.10±0.02-0.15±0.02 ml/min, and single nephron glomerular filtration to 6-12 nl/min. Papaverine, acetylcholine, and kinins had no effect on RBF or GFR at a perfusion pressure of 35-40 mm Hg. We conclude that mannitol and HS have the capacity to augment RBF during hypoperfusion by reducing arteriolar resistance. The mechanism of the rise in RBF is uncertain; it may be due to changes in effective osmolality of the extracellular fluid or to a direct action of mannitol on vascular smooth muscle. Other potent vasodilators were ineffective during hypoperfusion. Restoration of GFR occurs as a result of the combined effects of augmented RBF and elevated net filtration pressure.
Experimental Arterial Thromboembolism in Baboons: MECHANISM, QUANTITATION, AND PHARMACOLOGIC PREVENTION
A quantitative primate model of arterial thromboembolism has been characterized with respect to mechanism and usefulness in evaluating modifying variables. The model involved the kinetic measurements of 51Cr-platelets and 125I-fibrinogen consumption by femoral arteriovenous cannulae in chaired baboons.
Effects of Anion-Transport Inhibitors on NaCl Reabsorption in the Rat Superficial Proximal Convoluted Tubule
The effects of anion-transport inhibitors on volume reabsorption, and total CO2 concentrations were examined by in vivo microperfusion of superficial proximal convoluted tubules of rats. The luminal perfusion solution was a high-chloride, low-bicarbonate solution like that in the in vivo late proximal tubule. The anion-transport inhibitors were only added to the luminal perfusion solutions.
Neutropenia, Inflammation, and the Kinetics of Transfused Neutrophils in Rabbits
A rabbit model was used to study the effects of neutropenia and inflammation on the intravascular distribution, survival, and tissue accumulation of transfused neutrophils. Donor blood labeled with [3H]thymidine was infused into normal or neutropenic (vinblastine treated) animals. Inflammation was created by subcutaneous implantation of polyvinyl sponges, some with added endotoxin. Initial circulating neutrophil pool recovery, survival, and inflammatory site accumulation of labeled neutrophils were measured.
Characterization of the Platelet Prostaglandin D2 Receptor: LOSS OF PROSTAGLANDIN D2 RECEPTORS IN PLATELETS OF PATIENTS WITH MYELOPROLIFERATIVE DISORDERS
Prostaglandin (PG) D2 is synthesized in platelets at concentrations which could inhibit aggregation via activation of adenylate cyclase. To more directly define platelet-PG interactions, a binding assay has been developed for platelet PG receptors with [3H]PGD2 as ligand. [3H]PGD2 binding to intact platelets was saturable and rapid with the ligand bound by 3 min at 20°C. PG competed with the [3H]PGD2 binding site with a potency series: PGD2 (IC50 = 0.08 μM) ≫ PGI2 (IC50 = 2 μM) > PGE1 (IC50 = 6 μM) > PGF2α (IC50 = 8 μM). Scatchard analysis of binding data from six normal subjects showed a single class of binding sites with a dissociation constant (Kd) of 53 nM and 210 binding sites per platelet. This PGD2 receptor assay was then used to study platelets from five patients with myeloproliferative disorders (polycythemia vera, essential thrombocythemia, and chronic myelogenous leukemia), as over 90% of these patients have platelets resistant to the effects of PGD2 on aggregation and adenylate cyclase activity (1978. Blood.52: 618-626.). In the presence of 50 nM [3H]PGD2, the patients' platelets bound 7.1±2.9 fmol ligand/108 platelets compared with 15.1±1 fmol/108 platelets in normals, a decrease of 53% (P < 0.01). Scatchard analysis showed that the Kd of [3H]PGD2 binding (33 nM) was comparable to normal platelets, which indicates that the decreased PGD2 binding in these platelets represented fewer receptors rather than altered affinity of the ligand for the binding site. The 53% decrease in [3H]PGD2 binding correlated with a 48% decrease in PGD2-activated platelet adenylate cyclase. The characterization of the platelet PGD2 binding site provides further direct evidence that there are at least two PG receptors on platelets, one for PGE1 and PGI2, and a separate receptor for PGD2. Direct binding analysis will be a useful tool for studying the role of PG in regulating platelet function, as demonstrated by the selective loss of PGD2 binding sites in patients with myeloproliferative disorders.
Effect of age on glucose-stimulated insulin release by the beta-cell of the rat.
To assess the effect of age on beta-cell insulin release, collagenase-isolated islets of Langerhans were obtained from rats aged 2--18 mo and incubated with increasing concentrations of glucose. Similar islets were analyzed for insulin content or subjected to morphometric measurements to identify both the number of beta-cells and the volume of beta-granules per islet. In parallel studies, the islet content of intact pancreata was also determined. The results showed that beta-cell number increased from 2,300 t0 5,000 cells as rats aged from 2 to 18 mo and islet insulin content doubled. However, glucose-stimulated insulin release decreased progressively with age, and this was especially striking when considered in terms of the increase in number of beta-cells/islet; e.g., mean (+/- SEM) insulin secretion (nanounits per minute per beta-cell) of islets incubated with 450 mg/dl of glucose was 1.3 (+/- 0.02), 1.0 (+/- 0.1), 0.4 (+/- 0.05), and 0.3 (+/- 0.01), respectively for 2-, 6-, 12-, and 18-mo-old rats. Thus, insulin secretion per beta-cell was decreased, despite increased stores of insulin per cell. These findings demonstrate that the aging process leads to a profound defect in glucose-stimulated insulin release from the beta-cell. Whether this is a global secretory defect, or solely a failure of the beta-cell to respond to glucose, remains to be defined.
Changes in Sedimentation of Surfactant in Ventilated Excised Rat Lungs: PHYSICAL ALTERATIONS IN SURFACTANT ASSOCIATED WITH THE DEVELOPMENT AND REVERSAL OF ATELECTASIS
Lyn Aung Thet, Linda Clerch, Gloria D. Massaro, Donald MassaroAbstract | Full text | PDF (Page 600)
We ventilated excised rat lungs at a constant tidal volume (CTV); they developed areas of atelectasis which could be reversed by a large inflation (CTV + I) or prevented by the addition of positive end-expiratory pressure to the CTV. To explore the possibility that these modes of ventilation led to changes in surfactant, we lavaged the lungs and centrifuged the returns at 500 g; we measured the amount of disaturated phosphatidylcholine (DSPC) in the resultant pellet and supernatant fluid as a marker for surfactant. We found 16.9±1.5 (mean±SE), 38.0±2.4, 18.3±1.6, and 21.7±2.3% of the total lavage DSPC, in the pellet from freshly excised, CTV, CTV + I, and positive end-expiratory pressure to the CTV lungs, respectively. The total amount of lavage DSPC was the same in all groups.
Biphasic effects of prostaglandin E2 on the human fat cell adenylate cyclase.
Adenylate cyclase of human fat cell ghosts shows a biphasic response towards prostaglandin E2 with inhibition occurring at nanomolar concentrations of the hormone and stimulation at concentrations beyond 10(-6) mol/liter. The expression of the inhibitory effect is critically dependent on GTP. Under the conditions employed (1 mmol/liter ATP, 5 mmol/liter Mg2+, 30 degrees C) the inhibitory component of prostaglandin E2 became apparent at GTP concentrations exceeding 10(-6) mol/liter. The prostaglandin E2-induced inhibition displayed characteristic features of prostaglandin action in intact fat cells with respect to the effective concentrations and degree of inhibition. It is concluded that prostaglandin E2 is capable of inducing antagonistic effects upon lipolysis via interaction with the membrane-bound adenylate cyclase.
Conditioning Effects of Chronic Infusions of Dobutamine: COMPARISON WITH EXERCISE TRAINING
Chang-Seng Liang, Ronald R. Tuttle, William B. Hood Jr., Haralambos GavrasAbstract | Full text | PDF (Page 613)
We studied the conditioning effects of chronic infusion of dobutamine and exercise training in three groups of chronically instrumented dogs. One group was infused with normal saline, a second group was infused with dobutamine (40 μg/kg per min), and the third group was exercised on a treadmill at 4 mph, up a 10° incline. Each group was either infused or exercised for 2 h a day, 5 d a week for 5 consecutive wk. Resting heart rate and arterial blood lactate concentration, measured at weekly intervals, decreased progressively in the dobutamine and exercise groups, but not in the group that received normal saline infusion. Cardiovascular responses to submaximal treadmill exercise were not changed by 5 wk of normal saline infusion. However, the increases in heart rate, cardiac output, mean aortic blood pressure, arterial blood lactate, plasma renin activity, and norepinephrine concentration during exercise were significantly smaller after 5 wk of conditioning with either dobutamine or exercise training. After conditioning, the increases in arteriovenous oxygen difference during exercise were larger in the latter two groups, but the increases in total body oxygen consumption did not differ before and after conditioning.
Reflex Cardiovascular Depression during Unilateral Lung Hyperinflation in the Dog
Sharon S. Cassidy, William L. Eschenbacher, Robert L. Johnson Jr.Abstract | Full text | PDF (Page 620)
We have examined whether lung hyperinflation in the anesthetized dog reflexly depresses cardiac output, stroke volume, heart rate, and blood pressure and whether these changes persist for more than a minute. To eliminate any mechanical restriction to venous return and pulmonary blood flow during lung hyperinflation, a model was developed in which all pulmonary artery blood flow and all ventilation were directed to the right lung in dogs with widely open chest and the left lung was hyperinflated before and after left cervical vagotomy. Heart rate, stroke volume, and blood pressure decreased by 24, 20, and 27%, respectively, within 15 s of left lung inflation to 30 cm H2O. Heart rate increased to preinflation levels by 1 min, but stroke volume and blood pressure remained depressed during lung hyperinflation for at least 15 min. Upon deflation, stroke volume and blood pressure returned to control levels within 1 min. Division of the left vagosympathetic trunk at the neck interrupted all autonomic afferent and efferent nerves of the left lung, but left intact the right vagal sympathetic and parasympathetic afferent and efferent nerves of the heart. After left cervical vagotomy the transient fall in heart rate, stroke volume, and blood pressure during left lung hyperinflation was greatly reduced or eliminated. These results suggest that unilateral lung hyperinflation reflexly depresses heart rate and blood pressure, which are partially compensated with time, and reflexly depresses stroke volume, which persists uncompensated until the lung is deflated. These findings may explain the depressed cardiovascular function observed during regional lung overdistention especially when it occurs during positive pressure ventilation.
An acid transporting enzyme in human gastric mucosa.
Isolation of a microsomal fraction from human gastric mucosa followed by density gradient centrifugation yielded a vesicular membrane preparation free of mitochondrial markers, containing a K+-activated, ouabain-insensitive ATPase with an activity of 20.7 mumol P1 released/mg protein per h. Sodium dodecyl sulfate gel electrophoresis showed that the human gastric membrane vesicles contained a major polypeptide of 110,000 daltons, which accounted for approximately or equal to 30% of the total protein stained and was phosphorylated by [gamma-32P]ATP and dephosphorylated in the presence of K+. Electron microscopy revealed the presence of vesicles with an average size of 0.13 micrometer in diameter. Addition of 0.65 microM ATP to this vesicular preparation resulted in the uptake of 17 nmol H+/mg protein which was dependent on the presence of K+. The gradient was dissipated by a combination of valinomycin and protonophore after consumption of the ATP. Incubation of fixed human fundic sections or human gastric biopsy with monospecific hog gastric membrane antibody followed by fluorescein-conjugated goat anti-rabbit gamma-globulin, showed fluorescent staining in the middle portion of the gastric glands. These data indicate that human stomach contains a H+ transport ATPase with characteristics similar to those established for lower species.
Concentrations of Insulin and of Insulin Receptors in the Brain are Independent of Peripheral Insulin Levels: STUDIES OF OBESE AND STREPTOZOTOCIN-TREATED RODENTS
In view of the potent influences of the central nervous system on glucose metabolism and on its hormonal regulators, and our recent finding of insulin and insulin receptors throughout the central nervous systsem, we have examined extreme conditions of hyperinsulinemia (obese mice) and hypoinsulinemia (streptozotocin-treated rats) with respect to changes in brain insulin and receptor content. Sprague-Dawley rats given streptozotocin (100 mg/kg body wt) developed severe diabetes and by 48 h showed no change in brain insulin. Rats given 65 mg/kg streptozotocin also had severe diabetes, but survived longer. Both at 7 d and at 30 d after streptozotocin treatment there was no significant change in brain insulin or in brain content of insulin receptors, despite the fact that peripheral hepatic receptors were elevated and pancreatic insulin was markedly depleted.
Aortic Input Impedance during Nitroprusside Infusion: A RECONSIDERATION OF AFTERLOAD REDUCTION AND BENEFICIAL ACTION
Carl J. Pepine, W. W. Nichols, R. C. Curry Jr., C. Richard ContiAbstract | Full text | PDF (Page 643)
Beneficial effects of nitroprusside infusion in heart failure are purportedly a result of decreased afterload through “impedance” reduction. To study the effect of nitroprusside on vascular factors that determine the total load opposing left ventricular ejection, the total aortic input impedance spectrum was examined in 12 patients with heart failure (cardiac index <2.0 liters/min per m2 and left ventricular end diastolic pressure >20 mm Hg). This input impedance spectrum expresses both mean flow (resistance) and pulsatile flow (compliance and wave reflections) components of vascular load. Aortic root blood flow velocity and pressure were recorded continuously with a catheter-tip electromagnetic velocity probe in addition to left ventricular pressure. Small doses of nitroprusside (9-19 μg/min) altered the total aortic input impedance spectrum as significant (P < 0.05) reductions in both mean and pulsatile components were observed within 60-90 s. With these acute changes in vascular load, left ventricular end diastolic pressure declined (44%) and stroke volume increased (20%, both P < 0.05). Larger nitroprusside doses (20-38 μg/min) caused additional alteration in the aortic input impedance spectrum with further reduction in left ventricular end diastolic pressure and increase in stroke volume but no additional changes in the impedance spectrum or stroke volume occurred with 39-77 μg/min. Improved ventricular function persisted when aortic pressure was restored to control values with simultaneous phenylephrine infusion in three patients. These data indicate that nitroprusside acutely alters both the mean and pulsatile components of vascular load to effect improvement in ventricular function in patients with heart failure. The evidence presented suggests that it may be possible to reduce vascular load and improve ventricular function independent of aortic pressure reduction.
Altered mineral metabolism in glucocorticoid-induced osteopenia. Effect of 25-hydroxyvitamin D administration.
Parameters of mineral and bone metabolism were studied in 17 patients treated chronically with supraphysiologic doses of glucocorticoids. When compared to 15 matched normal subjects, the patient group exhibited similar serum 25-hydroxyvitamin D (25-OHD) levels, decreased intestinal 47Ca absorption, increased serum immunoreactive parathyroid hormone, and decreased forearm bone mass. Iliac crest bone biopsies revealed a decreased bone formation rate and increased osteoclast number. Treatment with 25-OHD (mean dose 4.03 micrograms/d) and calcium (500 mg/d) in nine patients produced a 46% increase in 47Ca absorption (P less than 0.001) and a 54% decrease in serum immunoreactive parathyroid hormone (P less than 0.001) by 3 mo. In addition, by 12 mo the treatment group exhibited (a) a 13.2 +/- 5.1% increase in metaphyseal (P less than 0.001) and a 2.1 +/- 0.4% increase in diaphyseal (P less than 0.05) forearm bone mass, and (b) significant decreases in cortical and endosteal osteoclast number. Biochemical and bone mass changes persisted through 18 mo. No significant changes in any parameter occurred in eight control patients administered calcium 100 mg/d. It is concluded that treatment with 25-OHD and calcium can significantly improve parameters of mineral and bone metabolism in patients with glucocorticoid-induced osteopenia.
Role of Cytochrome P-450 in Alveolar Hypoxic Pulmonary Vasoconstriction in Dogs
Alveolar hypoxia induces pulmonary vasoconstriction by an unknown mechanism. Cytochrome P-450 (C-P450) is found in the lung and may modify pulmonary vascular tone via its sensitivity to changes in oxygen tension or by affecting metabolism of a chemical mediator. Metyrapone and carbon monoxide are both inhibitors of C-P450. We tested alveolar hypoxic pulmonary vasoconstriction (AHPV) in 20 dogs before, during, and after separate administration of each inhibitor. Anesthetized dogs were ventilated through a double lumen endotracheal tube allowing ventilation of one lung with N2 or CO as a hypoxic challenge and ventilation of the other lung with O2 to maintain adequate systemic oxygenation. Distribution of lung perfusion was determined with intravenous 133Xenon and external chest detectors. Before infusion of metyrapone, mean perfusion to the test lung decreased 30% with alveolar hypoxic challenge, but decreased only 10% during metyrapone infusion and returned to a base-line mean decrease of 31% after completion of metyrapone infusion. Prostaglandin F2 α and angiotensin II infusions produced equivalent increases in pulmonary vascular resistance before and during metyrapone infusion. Before CO, mean test lung perfusion decreased 31% with alveolar hypoxia but was reduced only 10% from control when unilateral end-tidal CO% was >75%. Washout of alveolar CO with unilateral N2 ventilation restored AHPV, with perfusion decreasing 29% from control. Thus, both metyrapone and carbon monoxide can reversibly inhibit AHPV. C-P450 may, therefore, be involved in the transduction process of the vasoconstrictor response to alveolar hypoxia.
Secretion of Cholesterol-Rich Lipoproteins by Perfused Livers of Hypercholesterolemic Rats
Simon-Pierre Noel, Laurence Wong, Peter J. Dolphin, Ladislav Dory, David RubinsteinAbstract | Full text | PDF (Page 674)
Rats maintained on a high-fat diet supplemented with propylthiouracil develop a hypercholesterolemia, an increased serum level of apolipoprotein (apo) E, abnormal very low density lipoproteins (VLDL) and low density lipoproteins (LDL), and a fatty liver which contains cholesterol ester as its major lipid. The fatty liver secretes apoE into a recirculating perfusate at a significantly higher rate and produces cholesterol ester-rich, apoC-deficient VLDL with slower electrophoretic mobility than the triacylglycerol-rich VLDL produced by perfused normal livers. LDL, secreted in significant quantities by the perfused fatty liver, but not by the normal liver, is also cholesterol rich and contains apoE as well as apoB. The incorporation of [3H]leucine into apoVLDL and apoLDL secreted by the livers of the hypercholesterolemic animals and the apoVLDL secreted by the normal liver corresponds to the pattern visualized when the apoproteins are separated by polyacrylamide gel electrophoresis. Similar patterns are noted when non-recirculating perfusates are studied. These results indicate that the cholesterol ester-rich, apoC-deficient VLDL and the apoE-containing LDL found in the serum of hypercholesterolemic rats are not solely catabolic remnants of VLDL and chylomicrons but are secreted by the liver. Separation of the perfusate lipoproteins by agarose gel filtration revealed that most of the apoE secreted by the livers of hypercholesterolemic rats is found in the VLDL and LDL, whereas apoE secreted by the normal livers is distributed equally between VLDL, high density lipoproteins, and a low molecular weight fraction which corresponds to the virtually delipidated apoprotein. Thus the distribution of apoE among the lipoprotein fractions may be related to the total amount of cholesterol being transported in the circulation.
Osmotic blood-brain barrier disruption. Computerized tomographic monitoring of chemotherapeutic agent delivery.
E A Neuwelt, K R Maravilla, E P Frenkel, S I Rapaport, S A Hill, P A BarnettAbstract | Full text | PDF (Page 684)
The present study describes a canine model of transient reversible blood-brain barrier disruption with hyperosmolar mannitol infusion into the internal carotid artery. Studies in this model show that osmotic blood-brain barrier disruption before intracarotid infusion of methotrexate results in markedly elevated (therapeutic) levels of drug in the ipsilateral cerebral hemisphere. Levels in the cerebrospinal fluid correlate poorly and inconsistently with brain levels. Computerized tomograms in this canine model provide a noninvasive monitor of the degree, time-course, and localization of osmotic blood-brain barrier disruption.
Serotonin and the control of ventilation in awake rats.
In awake, unrestrained, intact rats, reserpine, para-chlorophenylalanine, 6-fluorotryptophan, and para-chloroamphetamine depleted whole brain serotonin and produced a substantial and sustained hyperventilation as evidenced by a 5--9 torr drop in PaCO2. Administration of 5-hydroxytryptophan to rats treated with para-chlorophenylalanine partially alleviated the hyperventilation. No change in ventilation was observed after alpha-methyltyrosine. 5,7-Dihydroxytryptamine produced contradictory results. On the basis of these pharmacological studies, we propose that some serotonin-mediated nerve transmissions might function under physiological conditions to inhibit the central nervous system output which controls normal breathing.