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Query: UMLS:C0432222 (SEM)
 47,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Regional differences in cell size in the hearts of rats with and without cardiac hypertrophy were studied using isolated muscle cells. Isolated cardiac myocytes were prepared from left ventricular free wall inner and outer halves and the right ventricle of six male 12-week-old spontaneously hypertensive (SHR), Wistar-Kyoto (WKY) and Fischer-344 rats. In SHR, blood pressure was increased to 188 +/- 4 (SEM) mm Hg versus 143 +/- 2 and 133 +/- 10 for WKY and Fischer rats, respectively (p less than 0.001). Total heart weight was increased to 1103 +/- 29 mg in SHR compared to 824 +/- 21 in WKY and 951 +/- 23 in Fischer rats (p less than 0.001. Isolated cardiac myocytes were prepared by perfusion of isolated hearts with Ca++ free Hanks' solution containing EGTA followed by collagenase-containing media. Mean length, width and volume of 150 cells stained with hematoxylin and eosin from each site were measured with a sonic digitizer. Two nuclei were present in 85 to 87% of isolated cells from all strains and regions. There was no difference among strains in right ventricular cell length, width, or volume, nor between left ventricular inner and outer halves within each strain. Left ventricular cells were larger than right ventricular cells (p less than 0.05) in all strains. Left ventricular cells of SHR were larger than left ventricular cells of WKY of Fischer rats in proportion to the increase in total heart weight, indicating that cardiac enlargement in SHR is due to increased cell size rather than increased cell number.
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PMID:Regional myocyte size in normotensive and spontaneously hypertensive rats. 16 52

In order to study the oeffect of somatostatin on the endocrine pancreas directly, islets isolated from rat pancreas by collagenase were incubated for 2 hrs 1) at 50 and 200 mg/100 ml glucose in the absence and presence of somatostatin (1, 10 and 100 mg/ml) and2) at 200 mg/100 ml glucose together with glucagon (5 mug/ml), with or without somatostatin (100 ng/ml). Immunologically measurable insulin was determined in the incubation media at 0, 1 and 2 hrs. Insulin release was not statistically affected by any concentration stomatostatin. On the other hand, somatostatin exerted a significant inhibitory action on glucagon-potentiated insulin secretion (mean +/- SEM, mu1/2 hrs/10 islets: glucose and glucagon: 1253 +/- 92; glucose, glucagon and somatostatin: 786 +/- 76). The insulin output in th epresence of glucose, glucagon and somatostatin was also significantly smaller than in thepresence of glucose alone (1104 +/- 126) or of glucose and somatostatin (1061 +/- 122). The failure of somatostatin to affect glucose-stimulated release of insulin from isolated islets contrasts its inhibitory action on insulin secretion as observed in the isolated perfused pancreas and in vivo. This discrepancy might be ascribed to the isolation procedure using collagenase. However, somatostatin inhibited glucagon-potentiated insulin secretion in isolated islets which resulted in even lower insulin levels than obtained in the parallel experiments without glucagon. It is concluded that the hormone of the alpha cells, or the cyclic AMP system, might play a part in the machanism of somatostatin-induced inhibition of insulin release from the beta-cell.
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PMID:Somatostatin-induced inhibition of insulin secretion from isolated islets of rat pancreas in presence of glucagon. 16 38

Rat cardiac muscle was dissociated into single cells by a coronary perfusion technique with collagenase and hyaluronidase in a Ca-free medium. Retention of the cylindrical shape of isolated muscle cells could be achieved by regulation of [Ca2+]0 and temperature. Cells kept at 4 degrees C, and 0-01 mM CaCl2 remained cylindrical for more than a week and contracted spontaneously upon warming at 37 degrees C. At [Ca2+]0 between 0-1-2 mM and 37 degrees C, cells underwent contracture and rounded up. Scanning (SEM) and transmission electron microscopy were used to analyze the structure of cylindrical and rounded muscle cells. The extracellular aspect of the sarcolemma at lateral cell surfaces and intercalated disc regions were clearly revealed for SEM analysis. Both the distribution and number of T-tubule openings on the surfaces can be estimated and a three-dimensional description of the intercalated disc obtained. This study reveals that isolated adult heart cells are extremely sensitive to [Ca2+]0, but with careful control of this cation, this preparation should be helpful in the analysis of both sarcolemmal structure and the pathological changes which accompany myocardial injury.
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PMID:Studies of isolated adult rat heart cells: the surface morphology and the influence of extracellular calcium ion concentration on cellular viability. 20 Oct 46

22 human pancreases were removed soon after circulatory arrest from donors aged 15--63 years. Part of the pancreas was used for isolation of islets by the collagenase technique. The mean yield +/- SEM, expressed as the number of islets isolated from 4 g pancreas was 79 +/- 15. The yield varied considerably even when the pancreas was removed immediately after circulatory arrest and the histology was normal, and there was no correlation with the age of the donors. The islet content of insulin (ng/microgram dry islet) was 8.5 +/- 1.2 (mean +/- SEM). Isolated islets were loaded with 45Ca in the presence of 20 mM glucose and placed in a perfusion apparatus for further studies of the 45Ca washout. The decrease of washout of radioactivity in Ca2+-deficient medium offers support for the existence of a Ca2+-Ca2+ exchange process. When added in a concentration of 20 mM, glucose tended to stimulate 45Ca efflux in perfusion medium of ordinary ionic composition but inhibited this process when the medium was deficient in Ca2+. Exposure to the calcium ionophore X-537A resulted in immediate stimulation of of 45Ca efflux from human islets as previously observed for islets from rats and mice. This suggests that Ca2+ has a direct regulatory role for insulin release also in humans.
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PMID:Collagenase isolation and 45Ca efflux studies of human islets of Langerhans. 21 85

To assess the effect of age on beta-cell insulin release, collagenase-isolated islets of Langerhans were obtained from rats aged 2--18 mo and incubated with increasing concentrations of glucose. Similar islets were analyzed for insulin content or subjected to morphometric measurements to identify both the number of beta-cells and the volume of beta-granules per islet. In parallel studies, the islet content of intact pancreata was also determined. The results showed that beta-cell number increased from 2,300 t0 5,000 cells as rats aged from 2 to 18 mo and islet insulin content doubled. However, glucose-stimulated insulin release decreased progressively with age, and this was especially striking when considered in terms of the increase in number of beta-cells/islet; e.g., mean (+/- SEM) insulin secretion (nanounits per minute per beta-cell) of islets incubated with 450 mg/dl of glucose was 1.3 (+/- 0.02), 1.0 (+/- 0.1), 0.4 (+/- 0.05), and 0.3 (+/- 0.01), respectively for 2-, 6-, 12-, and 18-mo-old rats. Thus, insulin secretion per beta-cell was decreased, despite increased stores of insulin per cell. These findings demonstrate that the aging process leads to a profound defect in glucose-stimulated insulin release from the beta-cell. Whether this is a global secretory defect, or solely a failure of the beta-cell to respond to glucose, remains to be defined.
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PMID:Effect of age on glucose-stimulated insulin release by the beta-cell of the rat. 37 46

This work was undertaken to study the effect of prednisolone on glucagon release in mouse pancreatic islets isolated by the collagenase technique. Pretreatment of the donors with prednisolone (0.2--0.3 mg daily) induced an increase in glucagon release both in the absence (1005+/-75, SEM, vs. 796+/-46 pg/10 islets/60 min, p=0.019) and in the presence of 7.5 mM arginine (1500+/-119 vs. 1236+/-61 pg/10 islets/60 min, p=0.05). The glucagon content of the islets was not modified by the treatment (28.6+/-1.1 vs. 28.0+/-1.1 ng/50 islets). The addition of prednisolone (5 - 10(-5) M) into the medium, failed to affect significantly glucagon secretion. In agreement with previous human studies, our data indicate that chronic glucocorticoid administration augments the secretory activity of the A-cell. This does not seem to be a result of increased glucagon synthesis nor a direct effect of glucocorticoids on the glucagon-releasing mechanism. Rather, environmental changes induced by these hormones could be responsible for A-cell hyperfunction.
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PMID:Enhanced glucagon secretion by pancreatic islets from prednisolone-treated mice. 78 66

Using an in vitro rabbit pancreas system, we studied the effect of monoamine oxidase (MAO) inhibitors on flucose-stimulated insulin secretion. We evaluated the effect of both brief (15 min) and prolonged (60 min) exposure of pancreas segments to non-hydrazine (harmine, alpha-methyltryptamine, tranylcypromine and pargyline) and hydrazine (phenelzine, nialamide, iproniazid) type MAO inhibitors. All of the hydrazine type MAO inhibitors potentiated glucose-stimulated insulin secretion. Of the non-hydrazine inhibitors, only harmine and alpha-methyltryptamine potentiated glucose-stimulated insulin secretion. Hydrazine, although not itself an MAO inhibitor, also potentiated insulin secretion. Sixty minutes of exposure to tranylcypromine or alpha-methyltryptamine caused a decrease in insulin secretion. These MAO inhibitors are primary amines and primary amines can inhibit insulin secretion. The dopamine (DA) or serotonin (5-HT) content of the B-cells was increased by incubating rabbit pancreas with L-3, 4-dihydroxyphenylalanine (L-Dopa) or 5-hydroxytryptophan (5-HTP) for forty-five minutes prior to stimulation with glucose. Non-hydrazine MAO inhibitors increased dopamine inhibition of insulin secretion and either did not alter, or decreased serotonin inhibition of insulin secretion. Rabbit pancreatic islets were isolated using the collagenase digestion technique. The MAO activity of islet homogenates was determined using 5-HT and DA as substrates. Rabbit islet MAO has only one-tenth the specific activity against 5-HT (35 +/- 8.7 mumumoles/mg/min, M +/- SEM) that it has against DA (357 +/- 62.3 mumumoles/mg/min). This suggests that one reason that MAT inhibitors do not increase serotonin inhibition of insulin secretion is because MAO is not the major pathway for 5-HT inactivation in rabbit pancreatic islets. These studies suggest that MAO inhibitors alter insulin secretion, by both decreasing B-cell monoamine degradation and by mechanisms that do not involve MAO inhibition.
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PMID:Monoamine oxidase inhibitors: nature of their interaction with rabbit pancreatic islets to alter insluin secretion. 110 23

Determination of the long-term function of islet transplantation in relation to the implantation site and the numbers of islets is of scientific interest and, with human islet transplant trials in progress, is a pressing clinical question. In this study, highly purified canine islets were isolated by collagenase digestion and Ficoll purification, and autotransplanted into either the spleen (in 10 dogs) or the liver (in 12 dogs). Dogs transplanted with islets into the spleen or liver received 264,300 +/- 20,300 (mean +/- SEM) and 158,600 +/- 15,000 islet equivalents (150-microns-sized islets) respectively. Graft survival at 1 yr was 86% in intrasplenic islet autografts (ISTx) and 50% in intraportal islet autografts (IPTx). Intravenous glucose tolerance tests and mixed meal-oral glucose tests were performed 1-12 mo from islet transplantation. Compared to controls, ISTx and IPTx dogs showed a similar decrease of glucose tolerance after both intravenous glucose tolerance tests and mixed meal-oral glucose tests. On intravenous glucose tolerance tests, plasma insulin levels were lower in ISTx than in IPTx dogs and controls. On mixed meal-oral glucose tests, insulin values were higher in IPTx dogs than in controls. There was a positive correlation (r = .56, p < 0.05) between the number of transplanted islet equivalents and the K values. These results demonstrate that, in dogs with islet transplant: 1) long-term islet survival can be achieved in the spleen better than in the liver; 2) islet survival is related to the mass of transplanted islets in the spleen, but not in the liver, where other factors probably affect islet survival; 3) the ability of metabolizing glucose is reduced after both intrasplenic and intraportal islet autografts; 4) both reduced insulin secretion (predominant in ISTx dogs on intravenous glucose tolerance testing) and insulin resistance (predominant in IPTx dogs on mixed meal-oral glucose tests) are the probable causes of the decreased glucose tolerance.
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PMID:The effect of transplantation site and islet mass on long-term survival and metabolic and hormonal function of canine purified islet autografts. 134 96

Gastrin-releasing polypeptide (GRP) has been implicated in the development of the human fetal lung. To determine whether GRP has a wider role in fetal development, its actions on DNA synthesis and cell replication by isolated epiphyseal growth plate chondrocytes obtained from ovine fetuses between 35 days gestation and near term (145 days) were examined. Chondrocytes were isolated using collagenase from the proximal tibia and cultured in monolayer. Synthesis of DNA was assessed from the incorporation of [3H]thymidine into previously growth-restricted cells after incubation in medium supplemented with GRP1-27 (40-1280 nM). Increase in cell number was assessed after incubation with test medium for 1 week. GRP caused a dose-dependent increase in both cell number and DNA synthetic rate compared to control incubations. Cell number was increased by 50% in the presence of a maximally effective 160 nM GRP and DNA synthesis by up to 800% utilizing chondrocytes obtained from animals of 75-80 days gestation. The mean (+/- SEM) half-maximal concentration of GRP for the stimulation of DNA synthesis was 97 +/- 12 nM (5 separate fetuses). Concentrations of GRP in excess of 160 nM caused a sharp reduction in both cell replication and DNA synthesis. To determine where within the cell cycle GRP exerted its mitogenic action, synchronized chondrocytes were transiently exposed to fetal bovine serum and cultured with GRP for increasing periods of time before pulse labeling with [3H]thymidine during S phase. GRP was as effective in stimulating DNA synthesis when present for the initial 4 h of G1 as when present for the entire G1 period. Since isolated fetal growth plate chondrocytes release insulin-like growth factor II (IGF II) and basic fibroblast growth factor (basic FGF) the possible mediation of GRP action by the release of these peptides or synergistic interactions were examined. Specific antibodies shown to negate the mitogenic actions of exogenous IGFs or basic FGF on chondrocytes did not alter GRP-stimulated DNA synthesis. The release of radioimmunoassayable IGF II by chondrocytes was not altered in the presence of GRP. Coincubation of GRP with submaximal concentrations of IGF I or basic FGF showed additive effects on DNA synthesis. When the actions of galanin were examined it was found to inhibit basal DNA synthesis by chondrocytes at a concentration of 167 nM. However, 66 nM or greater galanin was able to render 160 nM GRP inactive as a mitogen. These results suggest that GRP may potentially influence skeletal development in the ovine fetus and may interact with locally released peptide growth factors or other neuropeptides.
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PMID:Mitogenic action of gastrin-releasing polypeptide on isolated epiphyseal growth plate chondrocytes from the ovine fetus. 157 94

To determine whether specific hormonal responses were involved in the production of cryoprotectant (glucose) by liver of the freeze tolerant wood frog, Rana sylvatica, metabolically active hepatocytes were isolated in reasonable yields (mean 20.1 +/- 1.30% SEM, n = 29) by in situ liver perfusion with collagenase. Freshly isolated cells from autumn-collected frogs contained large amounts of glycogen (650 mumol glucosyl units/g packed cells) and produced glucose from this endogenous reserve at a rate of 10 mumol g-1 hr-1 at 0 degrees. Glucose output from cells was highly responsive to the addition of hormones; rates of glucose release increased 2.1-, 1.7-, and 1.7-fold with the addition of 10(-7) M bovine glucagon, 10(-7) M epinephrine, and 5 x 10(-6) M dibutyryl-cyclic AMP, respectively. Norepinephrine, 5-hydroxytryptamine, and bovine insulin were without effect at 0.1 microM/l. Hormone stimulation of glucose release was correlated with an increase in both the total activity and the percentage a of glycogen phosphorylase in hepatocytes. However, none of the hormones tested affected the kinetic properties of hepatocyte pyruvate kinase, suggesting the absence of covalent modification control of the enzyme. The data indicate that the freezing-stimulated production of large quantities of glucose as a cryoprotectant by R. sylvatica liver does not involve qualitative differences in the hormonal control of liver glycogenolysis, compared with other lower vertebrates. However, quantitative differences were seen, such as the much greater phosphorylase activity, 4.38 +/- 0.33 mumol min-1 g-1 packed cells, in freshly isolated R. sylvatica hepatocytes compared with 0.36 +/- 0.06 mumol min-1 g-1 in Rana pipiens hepatocytes.
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PMID:Hormonal effects on glycogen metabolism in isolated hepatocytes of a freeze-tolerant frog. 162 97


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