The Synthesis of Glycosaminoglycans by Cultures of Corneal Stromal Cells from Patients with Keratoconus

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Abstract

Keratoconus is a disease that results in thinning and ectasia of the central cornea. Cultures of corneal stromal cells from patients with keratoconus were established and the synthesis of glycosaminoglycans compared with the synthesis of glycosaminoglycans by normal human corneal stromal cells in culture.

Authors

Beatrice Y. J. T. Yue, Jules L. Baum

Erythrocyte membrane proteins in hereditary glucosephosphate isomerase deficiency.

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Abstract

Erythrocytes (approximately equal to 50% reticulocytes) obtained from a splenectomized patient with a thermolabile variant of glucosephosphate isomerase (GPI) deficiency showed a striking degree of crenation and decreased filterability through 3-micrometer Nuclepore filters (Nuclepore Corp., Pleasanton, Calif.). Membranes prepared by hypotonic lysis of such erythrocytes were found to contain a high molecular weight aggregate which was probably disulphide-bonded. The 10% most dense erythrocyte fraction showed an accentuation of aggregate formation while aggregates could not be detected in the 10% least dense erythrocyte fraction. The aggregate consisted mainly of spectrin (band 1) and a protein with the mobility of 4.2. "Extractability" of spectrin from these membranes was also markedly diminished. Incubation of the erythrocytes for 24 h in substrate-free medium caused more pronounced spectrin aggregation than in low or high reticulocyte controls. Incubation of low or high reticulocyte controls for 24 h in medium that contained glucose completely prevented the formation of the high molecular weight aggregate. GPI-deficient erythrocytes incubated with glucose in the medium showed an accentuation of membrane protein aggregate formation; however, this was almost completely reversed by the addition of adenine and inosine to the incubation medium or by the use of fructose, the intermediate just distal to the "block" in glycolysis, as the sole substrate. ATP and reduced glutathione levels in the GPI-deficient erythrocytes incubated with glucose were similar to that found in the low and high reticulocyte controls. Our findings suggest that only a proportion of erythrocytes (the older, more dense population of cells) are susceptible to the formation of disulphide-bonded aggregates, and that this is directly related to an impairment of substrate flow through the glycolytic sequence. The exact mechanism of aggregate formation in these erythrocytes remains to be elucidated.

Authors

T Coetzer, S S Zail

Sympathetic Control of Lower Esophageal Sphincter Function in the Cat: ACTION OF DIRECT CERVICAL AND SPLANCHNIC NERVE STIMULATION

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Abstract

The purpose of this study was to determine the effect of direct stimulation of the sympathetic nerves on the lower esophageal sphincter (LES) in the anesthetized cat. Neither unilateral nor bilateral cervical sympathectomy, or splanchnicectomy significantly modified basal LES pressure in animals with intact vagi, or animals having undergone bilateral cervical vagotomy. Electrical stimulation of the cut, peripheral, cervical sympathetic trunk increased mean arterial blood pressure, but had no effect on LES pressure or LES relaxation as induced by vagal stimulation. Stimulation of the central end of the cervical sympathetic trunk had no effect on LES pressure. Stimulation of the central end of the cut splanchnic nerve produced a decrease in LES pressure with a maximal response of 69.1±16.0% (mean±SEM). This inhibitory response was not modified by either propranolol or bilateral cervical vagotomy. Stimulation of the peripheral end of the cut, greater splanchnic nerve gave an increase in LES pressure with a maximal response of 38.2±7.19 mm Hg. Guanethidine, in the presence or absence of the adrenal glands, significantly augmented this excitatory response. This response was also slightly increased by phentolamine alone at 10 V, 1 Hz, but was not altered by propranolol. The excitatory response was completely antagonized by atropine or by trimethaphan camsylate. Stimulation of the peripheral end of the splanchnic nerve inhibited LES relaxation as induced by vagal stimulation. The results of this study suggest that: (a) the LES in the cat is not affected by either central or peripheral stimulation of the cervical sympathetic trunk; (b) the central portion of the splanchnic nerve carries an afferent inhibitory response to the LES through yet unknown pathways; (c) the peripheral splanchnic nerve carries an atropine-sensitive excitatory response to the LES; and (d) the splanchnic nerves may modulate LES relaxation as induced by vagal stimulation.

Authors

Jacques Fournet, William J. Snape Jr., Sidney Cohen

Effect of Cytochalasin B and D on Groups of Insulin Receptors and on Insulin Action in Rat Adipocytes: POSSIBLE EVIDENCE FOR A STRUCTURAL RELATIONSHIP OF THE INSULIN RECEPTOR TO THE GLUCOSE TRANSPORT SYSTEM

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Abstract

The possible physiological importance of the groups of insulin receptors on rat adipocytes and the relationship of these groups to insulin action were investigated. The effect of cytochalasin B and D on biological actions of insulin was measured and compared with the effect of these agents on the ultrastructural distribution of groups of insulin receptors. Cytochalasin B had no effect on epinephrine-stimulated lipolysis, insulin inhibition of epinephrine-stimulated lipolysis, or insulin stimulation of protein synthesis. Cytochalasin B, over a concentration range of 50 nM to 5 μM, progressively inhibited the basal glucose transport system, as measured by glucose oxidation, 2-deoxyglucose transport, and 3-O-methylglucose transport. Insulin was capable of fully stimulating remaining basal transport at submaximal concentrations of cytochalasin B. Insulin pretreatment of adipocytes partially protected the glucose transport system from inhibition by cytochalasin B. Cytochalasin B markedly altered the distribution pattern of insulin receptors, which caused an increase in the number of single receptor molecules by decreasing the number of larger groups. A significant correlation (r = 0.964; P < 0.001) was found between the percent increase in single receptors and the percent decrease in glucose transport. Ferritin-insulin pretreatment of adipocytes prevented disruption of the groups of insulin receptors by cytochalasin B. Cytochalasin D had no effect on the biological actions of insulin or on the groups of insulin receptors. These data suggest that the ability of insulin to affect adipocyte metabolism is independent of the hormone occupying adjacent, grouped receptor sites. The marked contrast in effects of cytochalasin B and D on groups of insulin receptors and glucose transport suggests that the microfilament system is not involved in insulin action or in holding the groups of insulin receptors together, as both agents are known disrupters of microfilaments and inhibitors of actin gelation. The correlation between the effects of cytochalasin B on insulin receptor distribution and glucose transport leads to the speculation that the glycoprotein molecules containing the insulin receptor are functionally linked with the glucose transport system.

Authors

Leonard Jarett, Robert M. Smith

Production of diglyceride from phosphatidylinositol in activated human platelets.

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Abstract

Human platelets generate diglyceride within 5 s of exposure to thrombin. Production of diglyceride is transient. 15 s after the addition of thrombin, the levels of diglyceride have increased up to 30-fold, but decrease thereafter. Prior incubation of platelets with 2 mM dibutyryl cyclic AMP prevents both the generation of diglyceride and the secretion of serotonin. Acetylsalicylic acid (100 microgram/ml), which completely inhibits prostaglandin endoperoxide synthesis, does not block diglyceride production and serotonin secretion induced by thrombin. Based on studies examining the incorporation of [3H]arachidonic acid into diglyceride of prelabeled platelets exposed to thrombin, it is concluded that neither phosphatidic acid nor triglyceride is the source of the diglyceride. Phosphatidylinositol appears to be the most likely source, both because its loss of radiolabel is sizable and rapid enough to account for the appearance of radiolabel in diglyceride, and because a phosphatidylinositol-specific phosphodiesterase, described in this report, exists in platelets. The phosphatidylinositol-phosphodiesterase, which produces diglyceride and inositol phosphate, requires Ca+2 and shows optimal activity at pH 7. The enzyme does not act upon phosphatidylcholine, phosphatidylethanolamine, or phosphatidylserine.

Authors

S Rittenhouse-Simmons

Thyrotropin-Releasing Hormone is not Required for Thyrotropin Secretion in the Perinatal Rat

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Abstract

To determine the role of thyrotropin-releasing hormone (TRH) in the regulation of thyroid-stimulating hormone (TSH) secretion in the perinatal period, a physiological approach of neutralizing circulating TRH in the fetal and early neonatal rat was employed. TRH-antiserum (TRH-AS) raised in rabbits and administered daily to low iodine-propylthiouracil (LID-PTU)-fed pregnant rats from days 12 to 19 of gestation markedly impaired the rise in serum TSH to LID-PTU when compared with normal rabbit serum-treated controls. In contrast, fetal serum TSH was unaffected by TRH-AS. The binding capacity of TRH-AS in the fetal serum (111 ng/ml) far exceeded circulating TRH in the fetus. Similarly, acute TRH-AS administration to the pregnant rat fed LID-PTU markedly decreased the serum TSH concentration in the mother, but not in the fetus, 60 min after TRH-AS administration. Chronic TRH-AS administration to neonatal rats whose nursing mothers were fed LID-PTU was in-effective in decreasing the elevated serum TSH in the neonate through day 8 of life, whereas a slight but significant decrease in serum TSH was observed on day 10. Chronic daily TRH-AS administration to neonatal rats through day 10 of life had no effect on the later development of the hypothalamic-pituitary-thyroid axis. These findings suggest that TRH does not participate in TSH regulation during the perinatal life in the rat and that thyroid hormones are probably the main regulators of TSH secretion during this period. Placental TRH is not important in regulating TSH secretion in the fetal rat. Furthermore, TRH “deprivation” during neonatal life does not prevent normal later development of the hypothalamic-pituitary-thyroid axis.

Authors

Theodor Theodoropoulos, Lewis E. Braverman, Apostolos G. Vagenakis

Excretion-Reuptake Route of β-Hexosaminidase in Normal and I-Cell Disease Cultured Fibroblasts

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It has been proposed that in cultured fibroblasts the final packaging of enzymes in lysosomes requires excretion followed by pinocytosis by neighboring cells via a carbohydrate-specific receptor mechanism. It has also been proposed that the abnormally high activity of lysosomal enzymes in the medium of cultured fibroblasts from patients with I-cell disease (mucolipidosis II) results from an altered carbohydrate recognition residue on the enzymes which prevents reuptake into the cells. With β-hexosaminidase as a marker, and competitive inhibition of uptake by 2 mM mannose-6-phosphate, we have determined that only 12% of the total (intra- and extracellular) β-hexosaminidase in normal fibroblasts is channeled through the excretion-reuptake route. After 9 d of exposure to mannose-6-phosphate, normal fibroblast cultures accumulated in the medium only a fraction of the enzyme excreted by I-cell disease fibroblasts in the same period. Furthermore, this minimal loss of enzyme to the medium did not result in a decrease of intracellular enzyme activity. Finally, if the defect in I-cell disease were only because of an impairment of a reuptake mechanism that involves only 12% of the total enzyme, then 88% of the newly synthesized enzyme should be retained by I-cell fibroblasts, resulting in intracellular activity three to nine times higher than that which is observed. These data are consistent with our previous proposal that excessive lysosomal enzyme activity in the medium of I-cell disease fibroblasts results from preferential exocytosis.

Authors

Georgirene D. Vladutiu, Mario C. Rattazzi

Pre- and Postoperative Studies of Plasma Calcitonin in Primary Hyperparathyroidism

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Abstract

The importance of calcitonin in the homeostatic response to the chronic hypercalcemia of primary hyperparathyroidism is uncertain. To clarify this issue, we have used a new, sensitive radioimmunoassay for human calcitonin to measure basal plasma calcitonin concentrations in 50 patients with primary hyperparathyroidism (32 female, 18 male). We assayed calcium-stimulated calcitonin concentrations preoperatively in 22 of the patients (16 female, 6 male) and postoperatively in 6. Finally, we assayed pentagastrin-stimulated calcitonin concentrations preoperatively in eight of the patients (three female, five male). Plasma calcitonin values after an overnight fast were indistinguishable from those in normal subjects (mean±SE, males, 48±3 normal and 46±5 pg/ml hyperparathyroid, females, 31±2 normal and 37±3 pg/ml hyperparathyroid.) Among hyperparathyroid patients of both sexes, increases of calcitonin during Ca infusion (15 mg Ca/kg in 4 h) were within normal limits. However, the mean maximal increase of calcitonin was significantly lower in hyperparathyroid than in normal subjects (P < 0.05). In six patients normocalcemic 5-15 mo after parathyroid surgery, fasting plasma calcitonin values were not significantly different, but responses to Ca infusion were greater than preoperatively (Δ calcitonin ±SE: 13±4 preoperatively and 53±35 pg/ml postoperatively). The mean maximal increase of calcitonin after pentagastrin (0.5 μg/kg i.v.) was slightly lower than normal in the patients (mean±SE, males, 45±8 normal and 38±10 pg/ml hyperparathyroid, females, 6±2 normal and 0 pg/ml hyperparathyroid). Thus, primary hyperparathyroidism is accompanied by normal steady-state concentrations of circulating calcitonin, and normal-to-blunted C-cell responses to pentagastrin or induced hypercalcemia, the response to calcium generally increasing after successful parathyroid surgery. These results clearly show that primary hyperparathyroidism is not characterized by hypercalcitoninemia. The seemingly paradoxical absence of elevated steady-state calcitonin concentrations may be accounted for partly by decreased secretory reserve. However, primary hyperparathyroidism may also be accompanied by an increase in the threshold of sensitivity for calcium stimulation of calcitonin secretion.

Authors

Phillip W. Lambert, Hunter Heath III, Glen W. Sizemore

Polymorphonuclear leukocyte and monocyte chemoattractants produced by human fibroblasts.

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The elaboration of leukocyte chemotactic factors by human fibroblasts was studied. 12 lines of normal fibroblasts obtained by skin biopsy and then cultured in vitro produced chemoattractants (assessed by modified Boyden-chamber techniques) for both peripheral blood polymorphonuclear leukocytes and monocytes (obtained by Hypaque-Ficoll and dextran sedimentation). Chemotactic activity was not present performed in fibroblasts, and cycloheximide blocked its elaboration. The chemotactic activity of crude-culture supernate was heat stable (56 degrees C for 30 min), trypsin- and pronase-sensitive, and neuraminidase resistant. Characterization of the chemotactic activity by gel filtration (Sephadex G-75) showed two active fractions, one with mol wt greater than 100,000 and the other less than 10,000. In studies designed to relate these chemotactic factors to collagen, we have confirmed that type I collagen and alpha 1-chain; are chemotactically active for monocytes but not polymorphonuclear leukocytes. However, the chemotactic activity in fibroblast-culture media was media was distinct from collagen in that it attracted neutrophils, it was not precipitated by 25% ammonium sulfate, and it was resistant to collagenase treatment; ascorbic acid, in concentrations known to stimulate fibroblast collagen synthesis, had no effect on the elaboration of the chemotactic factors. Furthermore, amino acid analysis of Sephadex G-75 fractions with chemotactic activity failed to reveal amino acids such as hydroxyproline characteristic of collagen. In addition to the chemotactic factors secreted by fibroblasts, a heat-resistant factor (30 min at 56 degrees C) which generated the chemotactically active fragment of C5 (C5a) from human serum was also secreted. The elaboration of mediators of the inflammatory and immune responses by fibroblasts may initiate and(or) modulate local skin inflammatory reactions and play a protective role in vivo.

Authors

J D Sobel, J I Gallin

Plasma Acetone Metabolism in the Fasting Human

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Abstract

The metabolism of acetone was studied in lean and obese humans during starvation ketosis. Acetone concentrations in plasma, urine, and breath; and rates of endogenous production, elimination in breath and urine, and in vivo metabolism were determined. There was a direct relationship between plasma acetone turnover (20-77 μmol/m2 per min) and concentration (0.19-1.68 mM). Breath and urinary excretion of acetone accounted for a 2-30% of the endogenous production rate, and in vivo metabolism accounted for the remainder. Plasma acetone oxidation accounted for ≅60% of the production rate in 3-d fasted subjects and about 25% of the production rate in 21-d fasted subjects. About 1-2% of the total CO2 production was derived from plasma acetone oxidation and was not related to the plasma concentration or production rate. Radioactivity from [14C]acetone was not detected in plasma free fatty acids, acetoacetate, β-hydroxybutyrate, or other anionic compounds, but was present in plasma glucose, lipids, and proteins. If glucose synthesis from acetone is possible in humans, this process could account for 11% of the glucose production rate and 59% of the acetone production rate in 21-d fasted subjects. During maximum acetonemia, acetone production from acetoacetate could account for 37% of the anticipated acetoacetate production, which implies that a significant fraction of the latter compound does not undergo immediate terminal oxidation.

Authors

G. A. Reichard Jr., A. C. Haff, C. L. Skutches, P. Paul, C. P. Holroyde, O. E. Owen

Binding of immunoglobulin G aggregates and immune complexes in human sera to Staphylococci containing protein A.

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Abstract

Using the Cowan I strain of Staphylococcus aureus, we compared the binding properties of human monomeric immunoglobulin (Ig)G and oligomeric or complexed IgG. Heat-aggregated IgG served as a model for complexed IgG and heat-killed, formalin-fixed S. aureus (StaphA) as a cellular receptor for IgG, in determining the parameters for oligomeric and monomeric binding. Because of its capacity for multipoint attachment, complexed IgG binding was favored over monomeric IgG binding, and this preferential binding was demonstrated kinetically in equivalent forward rates of binding but in a much slower rate of release from StaphA receptors. From binding studies, we determined which conditions maximize complexes IgG binding and minimized monomeric IgG binding and applied them to the development of an assay for aggregated IgG and immune complexes in human sera. The StaphA binding assay that was devised is quantitative, sensitive, and not complement dependent. It is relatively unaffected by factors such as heparin, complement fixation, native antibodies, and immunoglobulin concentrations, but is affected by the presence of rheumatoid factors. It compares favorably with two other complement-dependent assays of immune complexes, the 125I-Clq binding assay and the Raji cell assay, in terms of sensitivity and the size of immune complexes detected. Studies on the potential of the assay for detecting, isolating, and characterizing immune complexes in biological fluids are presented.

Authors

J S McDougal, P B Redecha, R D Inman, C L Christian

Fluoride-mediated activation of the respiratory burst in human neutrophils. A reversible process.

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Fluoride ion (F-) is an effective activator of the respiratory burst in neutrophils, as indicated by its ability to induce O2- production by these cells. Other halide ions did not activate the burst, Cl-, in particular appeared to antagonize the effect of F- on O2- production. F- stimulated O2- production showed a requirement for Ca++, but was independent of other exogenous cations. Neither phagocytosis nor degranulation were necessary for respiratory burst activation by F-. The effect of F- on the respiratory burst was reversible. Washing the cells after treatment with F-, while they were still producing large amounts of O2-, returned them to the resting state. They could then be stimulated again to produce O2- in amounts equivalent to those originally produced. Our experiments indicated that restimulation did not represent the activation of a population of cells that had not been activated during the initial exposure to F-, nor did it represent serial activation of different subpopulation of the O2- forming enzyme molecules present in a given cell. Rather, our data suggest that the entire population of O2- forming enzyme molecules was activated in a reversible fashion by F-.

Authors

J T Curnutte, B M Babior, M L Karnovsky

Generation of chemiluminescence by a particulate fraction isolated from human neutrophils. Analysis of molecular events.

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Abstract

A particulate fraction isolated from human neutrophils by homogenization, then centrifugation at 27,000 g, was demonstrated to generate chemiluminescence. This luminescence required the addition of reduced pyridine nucleotide and was very low in fractions from resting normal cells. Stimulation of neutrophils with opsonized zymosan, phorbol myristate acetate, or ionophore A23187 resulted in marked enhancement of the chemiluminescence measured in subsequently isolated particulate fractions. Stimulation did not boost the luminescence produced by fractions from cells of patients with chronic granulomatous disease. The chemiluminescence of particulate fractions from stimulated neutrophils was linear with increasing protein concentration, had a pH optimum of 7.0, and was higher with NADPH as substrate than with NADH. These results confirm previous studies suggesting that the enzyme system responsible for the respiratory burst in neutrophils is present in this fraction. The particulate fraction was used to examine the nature and origin of neutrophil luminescence by investigating the effect on this phenomenon of certain chemical and enzymatic scavengers of oxygen metabolites. Results suggest that the energy responsible for the luminescence of particulate fractions and, presumably, the intact cell, is derived from more than one oxygen species and that luminescence is a product of the interaction of these species and excitable substrates within the cell.

Authors

L C McPhail, L R DeChatelet, R B Johnston Jr

Demonstration and characterization of specific binding sites for factor VIII/von Willebrand factor on human platelets.

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The presence of specific Factor VIII/von Willebrand factor (FVIII/vWF) binding sites on human platelets has been demonstrated by using 125I-FVIII/vWF and washed human platelets. Binding is ristocetin-dependent and increases in proportion to the concentration of ristocetin from 0.2 to 1 mg/ml. Binding of 125I-FVIII/vWF to platelets can be competitively inhibited by unlabeled human or bovine FVIII/vWF, but not by human thrombin, fibrinogen, alpha 2-macroglobulin, equine collagen, or a lectin of Ricinus communis. Scatchard analysis of binding data indicated that the dissociation constant of FVIII/vWF receptors is 0.45--0.5 nM. There are 31,000 binding sites per platelet at 1 mg/ml of ristocetin concentration. The optimal pH range for binding is from 7.0 to 7.5. At a concentration of 2 mM, EGTA inhibits 86% of the binding; however, 20 mM of Ca++, Mg++, or EDTA have little effect. Binding sites for FVIII/vWF were found only on platelets, and no significant binding was detected with human erythrocytes or polymorphonuclear leukocytes.

Authors

K J Kao, S V Pizzo, P A McKee

Morphologic-physiologic correlates of the severity of fibrosis and degree of cellularity in idiopathic pulmonary fibrosis.

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Abstract

Idiopathic pulmonary fibrosis (IPF) is a progressive disease of lung parenchyma characterized by a chronic inflammatory cellular infiltration and varying degrees of interstitial fibrosis. Current data indicate that the severity of fibrosis and the degree of cellularity determine, in part, the prognosis of IPF and the response to therapy. Whereas lung biopsy gives the best assessement of fibrosis and cellularity, physiologic studies are used to stage and monitor the disease process. To determine which physiologic studies correlate best with severity of fibrosis and degree of cellularity, these parameters were graded in lung biopsies of 23 patients with IPF and compared with a variety of physiologic studies. Although vital capacity, total lung capacity, and diffusing capacity are commonly used as objective monitors of the disease process, none of these parameters correlated with either the severity of fibrosis or the degree of cellularity in biopsy specimens. In contrast, almost all parameters of lung distensibility correlated with the morphologic assessment of degree of fibrosis; compliance had the best correlation. Parameters of distensibility, however, correlated poorly with the degree of cellularity. In comparison, gas exchange during exercise correlated with both morphologic parameters; the exercise-induced changes in arterial oxygen pressure per liter of oxygen consumed had a high correlation with the degree of fibrosis (r = 0.89; P less than 0.001) and correlated to a lesser extent with the degree of cellularity (r = 0.56; P = 0.009). In contrast, neither the resting arterial oxygen tension nor the arterial oxygen tension at maximal exercise correlated with the morphologic assessment of degree of fibrosis or the degree of cellularity. These morphologic-physiologic comparisons suggest that (a) lung volumes and diffusing capacity are poor monitors of both the degree of fibrosis and the degree of cellularity; (b) the fibrotic process contributes, at least in part, to parameters of lung distensibility, and both fibrosis and cellularity contribute to gas exchange alterations during exercise; and (c) parameters of lung distensibility and exercise-induced gas exchange alterations may be useful in staging the severity of disease in IPF.

Authors

J D Fulmer, W C Roberts, E R von Gal, R G Crystal

Thymosin-induced suppression of proliferative response of human lymphocytes to mitogens.

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Abstract

The proliferative response of human peripheral blood lymphocytes to phytohemagglutinin, concanavalin A, and pokeweed mitogen were suppressed by thymosin. Greatest decreases were observed when cells were preincubated with thymosin for 18 h before a 3-d culture with mitogen in the presence of thymosin. However, significant suppression also occurred when lymphocytes were preincubated for 2 h and cultured with thymosin or preincubated for either 2 or 18 h and washed free of thymosin before culture. These effects were related to the concentration of thymosin and time of exposure to thymosin but not merely to a delay in the response to mitogen or to toxicity. The suppression of mitogen-induced proliferation by thymosin appeared to result from effects of thymosin on a suppressor cell because lymphocytes incubated with thymosin did not acquire increased responsiveness to mitogens as did cells incubated for 18 h in its absence and because mixing thymosin-pretreated lymphocytes with cells not preincubated with thymosin resulted in decreased responsiveness to photohemagglutinin.

Authors

R E Wolf

Regulation of hepatic transport of bile salt. Effect of protein synthesis inhibition on excretion of bile salts and their binding to liver surface membrane fractions.

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Abstract

The overall transport of bile salts across the hepatocyte is characterized as a carrier-mediated process whose rate-limiting step is biliary secretion. Specific bile salt binding proteins have been identified in liver surface membrane fractions and were postulated to represent the initial interaction in bile salt translocation across both the sinusoidal and canalicular membranes. To test this hypothesis, cycloheximide was administered to rats to inhibit hepatic protein synthesis. 16 h after cycloheximide administration [14C]leucine incorporation into hepatic protein was inhibited by 93% at 1 h and 47% at 12 h. However, values of liver function tests were not increased, although serum albumin, serum alanine amino-transferase, and alkaline phosphatase were significantly decreased. Light and electron microscopy did not demonstrate necrosis or fat accumulation. The latter demonstrated minimal disorganization of rough endoplasmic reticulum and occasional lamellar whorls. 16 h after cycloheximide administration bile salt independent bile flow, basal bile salt excretion, and basal bile flow were unaltered, but the maximum bile salt transport capacity was reduced to 62% of control and 24 h later to 38%. Decreased bile salt transport was reversible, for it returned to control values after 48 h, when hepatic protein synthesis was also normal. Maximum bromosulfophthalein (BSP) transport, on the other hand, was reduced after 16 h to only 85% of control. Both bile salt and BPS maximum transport capacities decreased with time during inhibition of protein synthesis, apparently following first order kinetics. It was estimated that their half-lives are 20 h for bile salt transport and 55 h for BSP transport. These different turnover rates suggest that cycloheximide does not decrease active transport through generalized hepatic dysfunction or alteration of high energy sources possibly required for transport. The maximum number of [14C]cholic acid binding sites in liver surface membrane fractions was determined by an ultrafiltration assay. They were reduced to 68% of control after 16 h of cycloheximide and to 25% after 24 h. This reduction in the number of binding sites is apparently selective, for the activities of the liver surface membrane enzymes (Na+-K+)ATPase, Mg++-ATPase, and 5'-nucleotidase were not significantly changed. The associated alterations in bile salt transport and the maximum number of binding sites after cycloheximide administration suggests that these receptors may be the bile salt carriers.

Authors

M C Gonzalez, E Sutherland, F R Simon

Role of Tachycardia as an Inotropic Stimulus in Man

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We examined the inotropic effect of tachycardia in nine postsurgical aortocoronary bypass graft patients (with intact cardiac innervation) and nine cardiac allograft recipients (with denervated hearts). The changes in stroke volume (SV) and velocity of circumferential fiber shortening (VCF) which accompany sudden increases and decreases in atrial pacing frequency were determined by computer-aided fluoroscopic analysis of the motion of surgically implanted midwall myocardial markers. Because the first beat after a change in rate retains the frequency characteristics of the preceding rate, we compared the first posttachycardia beat with control beats and late tachycardia beats with the first tachycardia beat; afterload and preload for each pair of beats were similar. For an increase in heart rate of 50 beats/min, SV and VCF rose 79 and 64% from the first tachycardia beat to late tachycardia beats, and SV and VCF rose 8 and 35% from control beats to the first posttachycardia beat in the innervated group. Responses in the denervated group were not significantly different from those in the innervated group. The degree of the inotropic response was positively correlated with the magnitude of the increase in heart rate (r = 0.91). The decay in augmented contractility after decreasing the rate back to control levels fits an exponential relationship with a mean t½ of 1.7 s. Thus, in conscious man, increases in heart rate represent a positive inotropic stimulus, independent of other factors influencing ventricular performance and unaffected by neural innervation, and should be considered when changes in cardiac function are interpreted during serial studies or after drug administration.

Authors

Donald R. Ricci, Arthur E. Orlick, Edwin L. Alderman, Neil B. Ingels Jr., George T. Daughters II, Catherine A. Kusnick, Bruce A. Reitz, Edward B. Stinson

pH and Bicarbonate Effects on Mitochondrial Anion Accumulation: PROPOSED MECHANISM FOR CHANGES IN RENAL METABOLITE LEVELS IN ACUTE ACID-BASE DISTURBANCES

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Abstract

Mitochondria from rabbit and dog renal cortex were incubated with 1 mM 14C-weak acid anions in media containing low (10 mM) or high (40 mM) concentrations of bicarbonate and the steady-state accumulation of labeled anion in the matrix was measured. In the absence of an energy source, no concentration of 14C-anion in the mitochondrial matrix space was present, but the anion concentration was significantly higher at low- than at high-bicarbonate concentration. Addition of an energy source, usually ascorbate plus tetramethyl-p-phenylenediamine, led to increases in matrix space anion levels and to accentuation of the difference in anion uptake between low- and high-bicarbonate media, so that two to four times as much anion was present at low- than at high-bicarbonate concentrations. The anions affected included substrates for which inner membrane carriers are present in mitochondria, such as citrate, α-ketoglutarate, malate, and glutamate, as well as substances which diffuse passively across the inner membrane such as acetate and formate. When a nonbicarbonate medium buffered with Hepes was used, pH change did not alter anion uptake although anion concentrations exceeding those in the medium still developed when an energy source was present. The difference in mitochondrial anion accumulation between low- and high-bicarbonate levels diminished with decreasing temperature or with increasing anion concentration in the medium. Estimation of intramitochondrial pH with [14C]5,5-dimethyl-oxazolidine-2,4-dione showed that the pH gradient across the inner mitochondrial membrane was significantly greater with 10 than with 40 mM bicarbonate in the medium.

Authors

David P. Simpson, Steven R. Hager

Glomerular permeability of macromolecules. Effect of molecular configuration on the fractional clearance of uncharged dextran and neutral horseradish peroxidase in the rat.

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Abstract

Molecular parameters other than size and charge are likely to influence the filtration of macromolecules across the glomerular filter. We have studies, therefore, the glomerular permeability of macromolecules with widely different molecular configuration such as horseradish peroxidase, a plant glycoprotein with an isoelectric point in the physiologic pH range, and dextran, an uncharged sugar polymer of D-glucopyranose. Simultaneous fractional clearances were determined for both test macromolecules in five Wistar-Furth rats. The results indicate that for a molecular radius of 28.45 A, as measured by gel filtration, the sugar polymer has a fractional clearance of 0.483 on the average, exceeding that of the protein tracer, with a value of 0.068, by a factor less than 7. We conclude that other molecular parameters such as shape, flexibility, and deformability play important roles in the transport of macromolecules across the extracellular matrix that constitutes the glomerular filter.

Authors

H G Rennke, M A Venkatachalam

Activity of [des-Aspartyl¹]-Angiotensin II in Primary Aldosteronism

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Abstract

This study describes the effects of [des-Aspartyl1]-angiotensin II ([des-Asp]-AII) on blood pressure and aldosterone production in patients with primary aldosteronism due to aldosterone-producing adrenal adenoma (APA) and idiopathic adrenal hyperplasia (IHA), and in normotensive control subjects. 10 patients with primary aldosteronism, 7 with APA and 3 with IHA, and 6 normotensive control subjects were placed on a constant 150-meq sodium diet for 4 days. [des-Asp]-AII was infused for 30 min at 6, 12, and 18 pmol/kg per min. Three groups of patients were identified on the basis of aldosterone response to [des-Asp]-AII. Group I, composed of normotensive control subjects, showed incremental increases in plasma aldosterone concentration from 6±1 to 14±3 ng/100 ml (P < 0.01) with [des-Asp]-AII infusion. Group II, composed of patients with primary aldosteronism, showed incremental increases in plasma aldosterone concentration from 33±8 to 65±13 ng/100 ml (P < 0.05) with 12 pmol/kg per min of [des-Asp]-AII. Group III, also composed of patients with primary aldosteronism, showed no increase of plasma aldosterone concentration with [des-Asp]-AII. Groups I and II showed similar percentage increases in plasma aldosterone concentration (P = NS). Group III showed significantly lower aldosterone responses than group I (P < 0.01). Group II included all patients with IHA and two patients with APA. Group III included only patients with APA. The blood pressure responses to [des-Asp]-AII of subjects in group I did not differ significantly from those of groups II or III.

Authors

Robert M. Carey, Carlos R. Ayers, E. Darracott Vaughan Jr., Michael J. Peach, Steven M. Herf

Effects of Metoclopramide and Bromocriptine on the Renin-Angiotensin-Aldosterone System in Man: DOPAMINERGIC CONTROL OF ALDOSTERONE

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Abstract

This study was designed to investigate the possible role of dopaminergic mechanisms in the control of the renin-angiotensin-aldosterone system in normal man. Six normal male subjects in metabolic balance at 150 meq sodium, 60 meq potassium constant intake received the specific dopamine antagonist, metoclopramide, 10 mg i.v. or placebo followed by angiotensin II infusion 1 h later on 2 consecutive days. Metoclopramide increased plasma aldosterone concentration from 8.2±2.2 to 21.0±3.3 ng/100 ml (P < 0.005) and plasma prolactin concentration from 18.0±4.0 to 91.7±4.0 ng/ml (P < 0.001) within 15 min of its administration. At 1 h, plasma aldosterone and prolactin concentrations remained elevated at 16.8±2.1 ng/100 ml (P < 0.01) and 86.8±15.9 ng/ml (P < 0.005), respectively. Angiotensin II at 2, 4, and 6 pmol/kg per min further increased plasma aldosterone concentration to 27.2±3.4, 31.9±5.7, and 36.0±6.7 ng/100 ml (P < 0.02), respectively. Placebo did not alter plasma aldosterone or prolactin concentrations, but angiotensin II increased plasma aldosterone concentration to 13.7±2.4, 19.0±1.9, and 23.3±3.2 ng/100 ml (P < 0.005). The increment of plasma aldosterone concentration in response to angiotensin II was similar after metoclopramide or placebo.

Authors

Robert M. Carey, Michael O. Thorner, Elizabeth M. Ortt

Defects in DNA and globin messenger RNA in homozygotes for hemoglobin Lepore.

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Abstract

Globin messenger RNA (mRNA) isolated from three patients homozygous for hemoglobin Lepore is shown to have a marked reduction of the amount of beta-like globin mRNA (Lepore-globin mRNA sequences) compared with alpha-globin mRNA by molecular hybridization. The relative amounts of alpha- and Lepore mRNA are similar to the amounts of alpha- and Lepore globin synthesized in intact cells and by isolated mRNA in a cell-free system. It is also demonstrated that Lepore-globin mRNA can completely hybridize to full-length or nearly full-length beta-globin specific complementary DNA and protect it from nuclease digestion, indicating close homology between the delta-mRNA sequences present in Lepore mRNA and the beta-complementary-DNA probe. We have also quantitated the numbers of beta-like globin gene sequences in genomic Lepore DNA by molecular hybridization and demonstrated a reduction in their number consistent with the Lepore gene being a delta beta-gene fusion product.

Authors

F Ramirez, J G Mears, U Nudel, A Bank, L Luzzatto, G DiPrisco, R D'Avino, G Pepe, L Camardella, R Gambino, R Cimino, N Quattrin

Ricinoleic acid stimulation of active anion secretion in colonic mucosa of the rat.

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Abstract

Perfusion of the colon with ricinoleic acid produces fluid and electrolyte accumulation. The mechanism of these changes in water and electrolyte movement is uknown. These studies were designed to determine whether ricinoleic acid effects active ion transport across isolated rat colonic mucosa. 0.5 mM Na ricinoleate produced significant increases in potential difference (3.8 +/- 0.5 mV) and short-circuit current (Isc) (99.2 +/- 10.1 muA/cm2). The increases in Isc produced by Na ricinoleate were inhibited by both removal of bicarbonate and chloride and by the presence of theophylline. The hydroxy fatty acid also resulted in a significant decrease in net Na absorption from 4.7 +/- 0.8 to 0.1 +/- 0.7 mueq/h cm2 and reversed net Cl transport from absorption (+ 4.5 +/- 0.9) to secretion (-2.2 +/- mueq/h cm2). In parallel studies 0.5 mM Na ricinoleate increased mucosal cyclic AMP content by 58%. The concentrations of Na ricinoleate required to produce detectable and maximal increases in both Isc and cyclic AMP were the same. These results provide evidence in support of the concept that hydroxy fatty acid-induced fluid and electrolyte accumulation is driven by an active ion secretory process.

Authors

L C Racusen, H J Binder

Glucocorticoid Receptors and Actions in Subpopulations of Cultured Rat Bone Cells: MECHANISM OF DEXAMETHASONE POTENTIATION OF PARATHYROID HORMONE-STIMULATED CYCLIC AMP PRODUCTION

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Abstract

We have previously shown that bone cells possess glucocorticoid receptors and that, in addition to being inhibitory to cell growth, glucocorticoid treatment potentiates the ability of parathyroid hormone (PTH) to stimulate cyclic AMP (cAMP) formation. This study extends those observations to specific subpopulations of bone cells and explores the mechanism of the cAMP augmentation. Subpopulations of cultured bone cells derived from 20-d-old fetal rat calvaria were enriched for “osteoblast-like” (OB) and “osteoclast-like” (OC) cells by sequential collagenase digestion. OC cells released during the first 30 min of collagenase digestion were characterized by low alkaline phosphatase activity, a cAMP response to salmon calcitonin (CT), but only a small cAMP response to bovine PTH. In contrast, OB cells released between 30 and 120 min of collagenase digestion, possessed high alkaline phosphatase activity, responded with a large cAMP rise to PTH, but exhibited no response to CT. Glucocorticoid receptors, with similar properties, were demonstrated in both populations (Kd ≅ 5 nM, Nmaximum ≅ 400 fmol/mg cytosol protein). Dexamethasone equivalently inhibited cell growth and alkaline phosphatase activity in both populations. Dexamethasone potentiation of cAMP generation occurred after PTH but not CT stimulation. A greater enhancement of cAMP generation observed in OB cells appears to result from two glucocorticoid actions: (a) stimulation of adenylate cyclase and (b) inhibition of phosphodiesterase. Only the latter mechanism was found in OC cells. Dexamethasone-treated cells showed an increase in both sensitivity and maximal response of cAMP to PTH. The possible relationship of these actions to the mechanism of glucocorticoid-induced osteopenia is discussed.

Authors

Theresa L. Chen, David Feldman

Immunoglobulin G independent activation of the classical complement pathway by monosodium urate crystals.

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Abstract

10 mg of monosodium urate crystals reduced the CH50 of 1 ml of human serum by 57% after 30 min at 37 degrees C. C1, C4, and C3 depletion of 52, 68, and 46% were typical of classical pathway activation. C1 binding and activation occurred when urate crystals were incubated with isolated precursor C1, and required the intact macromolecule, C1qrs. Activation of isolated C1 by urate crystals was not diminished by F(ab')2 anti-Fc under conditions in which C1 activation by aggregated immunoglobulin (G) was blocked by the F(ab')2 antibody.

Authors

P C Giclas, M H Ginsberg, N R Cooper

Hypoxanthine Uptake in Isolated Rat Renal Cortical Tubule Fragments

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Abstract

Isolated renal tubule fragments prepared from adult Sprague-Dawley rats were used to study the cellular uptake of hypoxanthine. This uptake was rapid, reaching a steady state after 30 min of incubation. Analysis of the intracellular pool during the initial uptake and at the steady state revealed a concentration gradient of hypoxanthine consistent with active transport, although only one-third of the transported hypoxanthine remained unmetabolized. The remainder of the transported hypoxanthine was converted to inosine and inosinic acid, but detectable conversion to uric acid was not noted. A kinetic analysis of uptake revealed that two systems for cellular entry of hypoxanthine existed with Km1 = 0.005 and Km2 = 0.80 mM. Hypoxanthine uptake at physiologic concentrations was oxygen, sodium, and temperature dependent, but the addition of metabolic fuels and alteration of the medium pH over the range of from 6.1 to 7.4 had no effect. Adenine, guanine, and inosine inhibited the uptake of hypoxanthine via the low-Km system which mediates the majority of uptake at physiologic levels. Xanthine, uric acid, and probenecid inhibited uptake via the high-Km system, but did not affect uptake via the low-Km system. The data indicate that hypoxanthine at physiologic levels is transported into the renal tubule cell via a system different from that for other oxypurines.

Authors

John W. Foreman, Stanton Segal

Requirement of extracellular complement and immunoglobulin for intracellular killing of micro-organisms by human monocytes.

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Abstract

The role of serum factors in the intracellular killing of bacteria by monocytes was studied on the basis of an assay independent of phagocytosis. After 3 min of phagocytosis of preopsonized bacteria and removal of noningested bacteria, the monocytes containing bacteria are reincubated for various periods and the number of unkilled bacteria is determined by a microbiological method after lysis of the cells. Evidence that this assay measures the killing of ingested bacteria was provided by scanning electron microscopy, lysostaphin treatment, and the effect on the rate of intracellular killing of inactivated serum lacking specific opsonic activity. Intracellular killing of Staphylococcus aureaus, S. epidermidis, and Escherichia coli by human monocytes does not occur or is low in the absence of serum, and maximal killing is only reached when fresh serum is present; intermediate values are obtained in the presence of heat-inactivated serum. These findings indicate that complement stimulates intracellular killing. Isolated heterogeneous immunoglobulin (Ig)G, pFc fragments of heterogeneous IgG, and both IgG1 and IgG3 stimulate intracellular killing of S. aureaus by monocytes to the same degree as heat-inactivated serum. Sphingomyelinase, which decreases the number of Fc receptors, and neuraminidase, which increases these receptors, respectively, decreased and increased the intracellular killing, whereas anti-monocyte serum completely abolished the stimulation of intracellular killing by inactivated serum. These results prove that interaction of the Fc receptor with the Fc part of IgG is required for the intracellular killing. Inhibition of the activation of complement components via the alternative pathway gave a considerable reduction in the intracellular killing of S. aureaus; impairment of the activation via the classical pathway had no effect. The addition of complement components to heat-inactivated serum showed that intracellular killing is maximal only when C3b is generated. Reduction of the number of C3b receptors in the membrane by trypsin or pronase decreased intracellular killing in the presence of fresh serum; anti-monocyte serum completely abolished the stimulation of intracellular killing by fresh serum. These results lead to the conclusion that intracellular killing is also dependent on the interaction between C3b and its receptor in the membrane.

Authors

P C Leijh, M T van den Barselaar, T L van Zwet, M R Daha, R van Furth

Cyclic hematopoiesis. Effects of endotoxin on colony-forming cells and colony-stimulating activity in grey collie dogs.

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Abstract

Cyclic changes in blood neutrophil counts of grey collie dogs with cyclic hematopoiesis can be eliminated by daily endotoxin injections. Studies were performed to determine the mechanism whereby endotoxin alters this disease. Bone marrow granulocyte-macrophage progenitor cells (colony-forming cells [CFUc]) showed cyclic variation in the untreated grey collie, which was eliminated by chronic endotoxin treatment (Salmonella typhosa lipopolysaccharide W, 5 microgram/kg per day). Similar cyclic variation in blood CFUc was eliminated by this treatment. Tritiated thymidine suicide of the marrow colony-forming cells failed to show cyclic changes to explain the marked swing in CFUc numbers in untreated grey collies. The thymidine suicide rates were not significantly changed by chronic endotoxin treatment. Similarly, serum colony-stimulating activity did not show cyclic variation with the cyclic neutrophil counts in untreated grey collies and was not altered by chronic endotoxin treatment. We suggest that endotoxin eliminates neutrophil cycling in cyclic hematopoiesis by a direct effect on the flux of pluripotent stem cells into the committed stem cell compartment and that this occurs independent of changes in serum colony-stimulating activity.

Authors

W P Hammond, E R Engelking, D C Dale

In vitro suppression of serum elastase-inhibitory capacity by reactive oxygen species generated by phagocytosing polymorphonuclear leukocytes.

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Abstract

Human polymorphonuclear leukocytes (PMN) phagocytosing opsonized antigen-antibody complexes, produce dialyzable species of activated oxygen which are capable of partially suppressing the elastase-inhibiting capacity (EIC) of whole human serum or purified human alpha1-proteinase inhibitor. Serum EIC was partially protially protected by superoxide dismutase, catalase, or mannitol, suggesting that hydroxyl radical, formed by interaction of superoxide radical and hydrogen peroxide, might be responsible for this effect. NaN3 also partly protected EIC, implicating myeloperoxidase-mediated reactions as well. An artificial superoxide rradical-generating system, involving xanthine and xanthine-oxidase, could be substituted for phagocytosing PMN with resultant EIC suppression. These results are consistent with previous demonstrations of the release of potent oxidants by stimulated PMN, as well as earlier studies from our laboratory showing sensitivity of alpha1-proteinase inhibitor to inactivation by oxidants. Oxidative inactivation of proteinase inhibitors in the microenvironment of PMN accumulating at sites of inflammation may allow proteases released from these cells to more readily damage adjacent connective tissue structures.

Authors

H Carp, A Janoff

Corticosteroids inhibit complement-induced granulocyte aggregation. A possible mechanism for their efficacy in shock states.

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Abstract

Granulocyte (PMN) aggregation and embolization may underlie complement (C)-mediated organ dysfunction in such syndromes as hemodialysis neutropenia and Purtscher's ischem;c retinopathy. Because of clinical and pathologic parallels, we have further suggested a role for this phenomenon in the genesis of the adult respiratory distress syndrome (ARDS). Because corticosteroids are commonly used in immune diseases, and have particularly been claimed efficacious in shock and ARDS, we tested the capability of methylprednisolone (MP), hydrocortisone (HC), and dexamethasone (DEX) to inhibit PMN aggregation. Aggregation engendered in vitro by zymosan-activated plasma (ZAP) was inhibited by MP and HC at concentrations approximating plasma levels achieved with the large bolus (30 mg/kg i.v) therapy advocated in shock states; DEX was almost without effect. Using intravital fluorescence microscopy, we observed PMN aggregation and embolization in the mesenteric vessels of rats given intra-arterial infusions of ZAP; this was also prevented by pretreatment with 30 mg/kg MP. Steroid inhibition of aggregation seemed not to involve disruption of receptor function, because aggregation induced by alternative agents, n-formyl-Met-Leu-Phe and the ionophore A23187, was also inhibited by MP. Moreover, corticosteroid inhibition of PMN prostaglandin synthesis is also an unlikely explanation for our results, since aspirin and ibuprofen failed to block aggregation and arachidonic acid neither effected aggregation itself nor ameliorated the steroid effect. Our studies provide a plausible rationale for the empiric observation that high-dose corticosteroids may benefit patients with syndromes associated with microvascular leukostasis.

Authors

D E Hammerschmidt, J G White, P R Craddock, H S Jacob

Hemoglobin biosynthesis in individual erythropoietic bursts in culture. Studies of adult peripheral blood.

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Abstract

By using a methylcellulose clonal assay, we cultured peripheral blood erythropoietic precursors from a patient with sickle cell anemia, a patient with sickle cell hemoglobin C disease, and a normal volunteer. We then analyzed the synthetic rates of adult and fetal hemoglobins (Hb) in individual erythropoietic bursts. Bb were labeled with 14C-amino acids in culture, separated by slab gel isoelectric focusing techniques, and quantitated by fluorographic methods. All bursts exhibited both fetal and adult Hb in varying ratios. Frequency distributions of the individual burst differing in percentage of BbF biosynthesis approached normal distributions. Further stimulation of HbF synthesis by higher erythropoietin in culture was associated with increased HbF biosynthesis in individual bursts. Augmentation of human HbF synthesis in culture appears to be controlled by qualitative intracellular changes rather than by changes in cellular population.

Authors

K Kidoguchi, M Ogawa, J D Karam

In vivo inactivation of erythrocyte S-adenosylhomocysteine hydrolase by 2'-deoxyadenosine in adenosine deaminase-deficient patients.

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Abstract

The cytotoxic nucleoside 2'-deoxyadenosine is excreted in excessive amounts by individuals with genetic deficiency of adenosine deaminase, and may be in part responsible for the severe combined immune dysfunction from which they suffer. Earlier studies from this laboratory showed that 2'-deoxyadenosine causes the irreversible inactivation of the enzyme S-adenosylhomocysteine hydrolase by an active site-directed, "suicide-like" process. In this communication we have demonstrated similar inactivation of S-adenosylhomocysteine hydrolase in hemolysate and in intact erythrocytes, as well as a striking deficiency of S-adenosylhomocysteine hydrolase activity in the erythrocytes of three adenosine deaminase-deficient patients. In vivo suicide-like inactivation of S-adenosylhomocysteine hydrolase by 2'-deoxyadenosine may contribute to the cytotoxicity of 2'-deoxyadenosine and to the immune dysfunction in adenosine deaminase deficiency.

Authors

M S Hershfield, N M Kredich, D R Ownby, H Ownby, R Buckley