Issue published August 1, 1979

T he 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.

T he 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.

A mplification 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.

C hemically 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.

T he 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.T cells from all patients were normal in number and in function both in vivo and in vitro and were able to generate adequate T-cell help to support IgG synthesis by normal B cells. No evidence was obtained for T cells capable of suppressing normal IgG synthesis in any of the patients after coculture with normal peripheral blood lymphocytes. The defect in hyper IgM immunodeficiency is intrinsic to B cells, which fail to switch from IgM to IgG synthesis.

N ormal 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.

D aily 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.Endometrial biopsies obtained during the follicular phase of control and tamoxifen treatment cycles showed no differences whereas biopsies obtained during the luteal phase of tamoxifen cycles uniformly showed a lack of changes attributed to progesterone action with no progression of histologic changes beyond those expected on day 7-8 of the luteal phase.These observations are consistent with maturation of multiple ovarian follicles, a surprising finding considering the normal gonadotropin concentrations. The retarded development of the endometrium in the presence of supranormal serum E₂ and progesterone concentrations is a morphologic demonstration of the antiprogestational effect of antiestrogens. The lack of gonadotropin suppression in the presence of hyperestrogenemia suggests a major antiestrogen action on the hypothalmus and pituitary gland.

C hronic 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.

H ypertyraminemia 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.

T he 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.

A lthough 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.The present studies, making use of carefully selected cases with pure populations of type II or type III erythrocytes, confirm a prior observation that antibody-coated PNH erythrocytes of both types II and III display comparably supranormal C3 binding in whole human serum. However, when lysis was induced by the isolated C5b-9 membrane attack mechanism, bypassing the requirement for C3 binding, only type III PNH cells exhibited greater than normal lysis. This finding suggests that type III PNH erythrocytes have an additional membrane abnormality not present in type II cells. Thus, the differing lytic behavior of these two cell types in whole serum may reflect the additive effects on type III cells of both exaggerated C3 binding and enhanced sensitivity to C5b-9, whereas the more moderate lysis of type II PNH cells may be determined mainly or entirely by the earlier-acting mechanism producing augmented C3 binding.The failure of guinea pig C8 and C9, as opposed to human C8 and C9, to reveal the true lytic sensitivity of PNH-III E in our earlier study is illustrated, and its implications briefly discussed.

W e 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.

F ree 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.

R enal 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 PGF_2α 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 PGF_2α 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.

T hese 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.

T his 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.

P revious 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.

T o 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.

P rostaglandins 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.

I n 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, L_pA, 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.The role of angiotensin II (AII) in maintaining glomerular and proximal tubular adaptations to chronic sodium depletion was assessed in subsets of groups 1 and 2 by the infusion of the AII antagonist Saralasin at a rate of 1 μg/kg per min. In group 1 rats, Saralasin had no effect on sngfr, rpf, or L_pA, because animals remained at filtration pressure equilibrium. In group 2 rats, AII blockade was associated with an increase in sngfr from 31.6±1.0 to 37.1±1.7 nl/min per g kidney wt (P < 0.01). Rpf increased during Saralasin infusion solely as a result of a decrease in afferent arteriolar resistance from 21.7±2.3 to 15.2±2.3 10⁹ dyn-s-cm⁻⁵ (P < 0.01). Saralasin infusion did not affect the reduced L_pA in group 2, as L_pA remained 0.056±0.02 nl/s per g kidney wt per mm Hg and rats remained disequilibrated. In spite of the increase in sngfr in group 2, AII antagonism further decreased APR to 13.1±1.5 (P < 0.01). Distal delivery therefore, increased from a control value of 15.3±1.3 to 24.3±1.5 nl/min per g kidney wt (P < 0.01).In conclusion, both a decrease in L_pA and a reduction in rpf were major factors mediating the decrease in glomerular filtration rate observed in chronic sodium depletion. Saralasin infusion revealed a significant effect of AII on rpf and afferent arteriolar resistance in chronic sodium depletion, but no effect of AII on either efferent arteriolar resistance or the decrease in L_pA could be demonstrated. Saralasin had no effect in rats that were not chronically sodium depleted. In group 2 rats AII antagonism reduced APR even though sngfr increased, suggesting an influence of AII on proximal reabsorption. The marked changes observed during Saralasin infusion in the chronically sodium-depleted rat reveal important modifying effects of endogenously generated AII on both the glomerulus and proximal tubule.

E pitrochlearis 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.Alanine (ALA) release rates from muscles of Nx rats were increased 40% above C values after 1 h of incubation regardless of protein intake. Addition of insulin decreased the ALA release from muscles of Nx rats to C values in animals fed 10 and 20% casein and chow but did not in rats fed 40% casein. After 3 h of incubation, all ALA release rates decreased by ≅40%. The ALA release from muscles of Nx rats fed 10% casein was comparable to C values and decreased further with the addition of insulin. On the other hand, ALA release from muscles of Nx rats fed 20 and 40% casein as well as chow remained significantly elevated above C values, but responded to the addition of insulin with a reduction in release rates to C values, except from the muscles of Nx animals fed 40% casein.Tyrosine (TYR) and phenylalanine (PHE) release rates also were increased in muscles from Nx rats compared with C after 1 h of incubation. Release rates were highest in the Nx group fed 10% casein and decreased with increasing protein intake. Addition of insulin decreased the release rates of Nx rats to C values in each group. After 3 h of incubation, release rates of TYR and PHE in muscles from Nx rats remained significantly above C values for all groups, but responded to the addition of insulin with a decrease to C values. Glutamine and glutamate release were not significantly affected by reduction in renal mass.Base-line glucose uptake by all groups of muscles from Nx rats was significantly greater than corresponding C values, but maximal insulin-stimulated glucose uptake was comparable in all groups. Tissue pool sizes for glycogen, ATP, phosphocreatine, ALA, glutamate, and glutamine were unaffected by reduction in renal mass.The results indicate that Nx is associated with accelerated ALA, TYR, and PHE release from muscle. ALA release rose with increasing protein intake and decreased to values observed from C muscles after addition of insulin except in Nx animals fed 40% casein. TYR and PHE release decreased with increasing protein intake and also decreased to C values with the addition of insulin. The data also suggest that ALA release is not dependent upon glucose uptake in muscles from either C or Nx rats.

T o 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.With regard to ¹²⁵I-LDL turnover, FH homozygotes, who possess two doses of the mutant FH gene, exhibited a threefold increase in the rate of apoLDL synthesis while the fractional catabolic rate (FCR) for the apoprotein was only about one-third of normal. Heterozygotes, who have only one dose of the mutant FH gene, exhibited intermediate values for both parameters; that is, the FCR was two-thirds of normal and the apoLDL synthetic rate was 1.7-fold greater than normal.The data indicate that the single gene defect in FH produces two distinct abnormalities of LDL metabolism: (a) an increase in the synthetic rate for apoLDL and (b) a decrease in the efficiency of apoLDL catabolism. Both defects are more severe in FH homozygotes than in heterozygotes.The FCR for apoLDL in the homozygotes appeared to be fixed at ≅ 17%/d whereas the plasma LDL level varied about twofold. These findings suggest that the twofold variation in plasma LDL levels observed in these seven patients is caused by variation in the plasma apoLDL synthetic rates. Consistent with this conclusion was the finding that the correlation between the plasma LDL level and the apoLDL synthetic rates in the seven FH homozygotes was 0.943.The rate of total body cholesterol synthesis determined by chemical cholesterol balance did not appear to clearly differ between normals and patients with either one or two mutant FH genes. Two of the youngest FH homozygotes exhibited cholesterol overproduction but the other five did not. No consistent abnormality of bile acid metabolism was observed in these patients. Because the daily plasma flux of cholesterol on LDL is about threefold greater than the amount of cholesterol produced per day, a significant amount of the cholesterol liberated from LDL degradation must be reused.

T he 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.

R ecent 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.

T he 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.

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.Cannula platelet consumption correlated directly with exposed cannular area for irradiated Silastic and polyurethane (correlation coefficients of 0.940 and 0.901, respectively; P < 0.001) and remained steady state for months. Nonirradiated Silastic was only minimally reactive with platelets. Despite increased rates of platelet consumption circulating fibrinogen was not measurably destroyed by any of the cannulae tested. Cannula platelet consumption was independent of cannula flow rate, platelet count, heparin anti-coagulation, and ancrod defibrinogenation.¹¹¹In-platelet imaging of irradiated Silastic cannulae demonstrated luminal accumulation and subsequent embolization of irregular platelet masses. When irradiated Silastic cannulae were inserted as extension segments in the renal arteries of four animals the glomerular vessels became progressively occluded with nonfibrin-containing platelet thromboemboli. Nonirradiated Silastic cannulae in control arteries produced no significant vascular occlusion. Because the survival of platelets from animals with consumptive cannulae was not shortened in normal recipient animals we concluded that platelets were either irreversibly removed through thromboembolic consumption or unaffected in their viability.Oral administration of dipyridamole and sulfinpyrazone decreased cannula platelet consumption in a dose-dependent manner with complete interruption at 20 and 250 μmol/kg body wt per d (in three divided doses), respectively, whereas oral acetylsalicylic acid (10-330 μmol/kg per d) had no measurable effect on cannula platelet consumption.We conclude that this primate model simulates arterial thrombotic processes in man and that this model is suitable for the in vivo evaluation of biomaterials and of drugs that modify platelet behavior.

T he 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.In tubules perfused with the control high-chloride solution, the rate of volume reabsorption (J_v) was 2.3±0.2 nl/mm·min (n = 18), and the collected total CO₂ concentration was 4.0±0.3 mM. Furosemide (3 mM) caused a marked reduction in volume reabsorption to 0.8±0.3 nl/mm·min (n = 20) and only a slight increase in the total CO₂ concentration of collected samples of perfusate (7.8±0.5 mM). 0.8 mM acetazolamide caused a more pronounced rise in the collected total CO₂ concentrations to 10.7±0.5 mM but only a slight fall in J_v to 1.7±0.3 nl/mm·min (n = 19). Hence, we inferred that inhibition of carbonic anhydrase only partially accounted for the inhibition of J_v by furosemide. 4-acetamido-4′-iso-thiocyanato-stilbene-2,2′-disulphonic acid (0.1 mM), a well-characterized inhibitor of erythrocyte anion exchange mechanisms, also reduced J_v to 1.6±0.3 nl/mm·min (n = 15) without changing the total CO₂ concentrations of the collected perfusates (3.6±0.4 mM). The effect of 4-acetamido-4′-iso-thiocyanato-stilbene-2,2′-disulphonic acid on volume reabsorption could not be explained by carbonic anhydrase inhibition because there was no increase in the total CO₂ concentration of the collected fluids. Furosemide did not significantly inhibit the rate of tracer glucose efflux out of the tubules, which suggests that the effect of furosemide on volume reabsorption was not a result of some nonspecific depression of active sodium transport. These results are discussed with respect to the possible effects of anion-transport inhibitors on the paracellular shunt pathway, active sodium reabsorption, and neutral sodium chloride transport.

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.Neutropenia was associated with a relative increase in the marginal pool size, manifested by a diminished initial circulating pool (CNP) recovery of transfused cells. The CNP recovery was directly proportional to recipient neutrophil count. Neutropenia had no effect on the intravascular survival of transfused cells and was accompanied by only a modest decrease in the inflammatory site recovery of the transfused neutrophils (10.4±5.4 vs. 14.4±4.0% in normals).Inflammation in the form of subcutaneous polyvinyl sponges was accompanied by an increase in margination with initial CNP recoveries of 24.3±4.7 and 27.6±8.8% at zero and 4 h after implantation respectively (normal, 38.2±9.9%). Transit through the CNP was hastened by inflammation with a t_½ of 2.02±0.72 h (normal, 3.2±1.0 h).Addition of endotoxin to the sponges further perturbed cell kinetics. CNP recoveries were considerably lower and half-lifes were initially shorter and subsequently uninterpretable in studies done after endotoxin sponge insertion. Inflammatory site accumulation was markedly diminished to 7.4±1.9% of injected neutrophil label in the endotoxin sponge animals, suggesting that many of the transfused cells were functionally unavailable rather than marginated. These studies demonstrate that neutropenia and inflammation with or without endotoxin markedly alter the kinetics of transfused neutrophils and that CNP recovery of transfused cells is not necessarily predictive of their inflammatory site accumulation.

P rostaglandin (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) > PGF_2α (IC₅₀ = 8 μM). Scatchard analysis of binding data from six normal subjects showed a single class of binding sites with a dissociation constant (K_d) 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 K_d 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.

T o 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.

W e 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.The ultrastructure of acellular material pelleted by sequential centrifugation of lavage returns at 500, 1,000, and 60,000 g was examined. We found mostly tubular myelin in the 500-g and 1,000-g pellets, but no tubular myelin in the 60,000-g pellet.Air inflation pressure-volume measurements from the degassed state revealed that the opening pressure and recoil pressures up to 75% of total lung capacity were significantly higher in the CTV than in the CTV + I lungs. There were no differences between these groups in air deflation or in saline inflation and deflation pressure-volume measurements. Our findings suggest that CTV leads to increases in the tubular myelin form of surfactant and that this leads to increased surface tension in alveoli which results in alveolar collapse.

A denylate 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.

W e 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.To assess ventricular function, we intravenously infused methoxamine both before and after conditioning. The slope of the line that related systolic aortic blood pressure and mean left atrial pressure increased in the animals conditioned with either dobutamine or exercise, indicating enhanced myocardial contractility. Left ventricular blood flow was lower in these two groups of animals than it was in the normal saline group. Left ventricular weight did not differ among the three groups.Our results show that chronic infusion of dobutamine produced cardiovascular and metabolic conditioning effects like those produced by exercise training, and further suggest that sympathetic stimulation during exercise plays a role in physical conditioning.

W e 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.

I solation 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.

I n 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.The obese mice were studied at 8-10 wk when peripheral plasma insulin concentrations were 50-fold elevated and receptors on peripheral target cells were reduced to ≅40-50% of normal; brain insulin concentrations and receptor content were indistinguishable from those of thin littermates. Thus, brain insulin, which is typically 10 times higher than plasma insulin concentrations, and brain receptor content, which is equivalent to receptor content on peripheral tissues, appears to be regulated entirely independently of hormone and receptor in the periphery. These findings are consistent with the hypothesis that insulin in the central nervous system is synthesized by the neural elements, and plays a role in the central nervous system which is unrelated to peripheral glucose metabolism.

B eneficial 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.

P arameters 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.

A lveolar 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.

R ats 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.

T he 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.

I n 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.