Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.4.24.3 (collagenase)
18,340 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The present study confirms and extends previous observations that whole pancreatic islets form a monolayer culture in vitro. Our technique, using a medium containing 3-isobutyl-1-methylxanthine (IBMX), clearly demonstrated enzymatic disruption of the islets and cellular organization of isolated pancreatic islets. Insulin or glucagon secretion of monolayer culture was measured during incubation in a medium containing 5.5 mM D-glucose, then in 16.7 mM D-glucose, and finally in a combination of 16.7 mM D-glucose and IBMX, or of low glucose and 20 mM L-arginine. Clearly, such a technique might permit the recovery of collagenase-isolated pancreatic islets during the culture period and also an increase in glucose-induced insulin secretion and arginine stimulated glucagon secretion.
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PMID:A study of insulin and glucagon secretion from adult rat pancreatic monolayer islets. 241 96

Studies on hormone action in isolated islets have generally been carried out using concentrations far above physiologic levels. This study investigates whether glucagon at concentrations close to the physiologic level is insulinotropic in isolated islets and how this relates to islet cyclic AMP levels. Collagenase isolated rat islets were tested directly after isolation or after a 24-hour tissue culture. Insulin release and islet cyclic AMP content were determined during a 30-minute incubation by radioimmunoassay. After maintenance in tissue culture glucose-induced (16.7 mmol/L) insulin release was clearly enhanced by glucagon concentrations between 2 and 1,000 ng/mL in a dose-related manner. Islet cyclic AMP was increased only by glucagon 1 mumol/L (3.8 micrograms/mL). When phosphodiesterases were inhibited (0.1 mmol/L 3-isobutyl-1-methylxanthine) insulin release was stimulated by 1 ng/mL and cyclic AMP by 100 ng/mL. By contrast, in freshly isolated islets, glucagon concentrations in the range of 1 to 100 micrograms/mL were needed to augment glucose-induced insulin release. These findings demonstrate that the hormone sensitivity of collagenase isolated islets is markedly improved by short-term maintenance in tissue culture. The threshold level for a detectable effect on islet cyclic AMP is considerably higher than for glucose-induced insulin release. Since in hepatocytes two signal transduction systems for glucagon have recently been demonstrated, the results could mean that at low concentrations glucagon effects may not be mediated via cyclic AMP.
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PMID:Effect of low concentrations of glucagon on insulin release and cyclic AMP content in isolated rat islets. 244 91

Fragmented islets, obtained by mild overdigestion of the adult rat pancreas with collagenase, readily formed monolayer cultures on dishes coated with extracellular matrix derived from bovine corneal endothelial cells. Contaminating fibroblasts were removed by treatment with sodium ethylmercurithiosalicylate. The cultured islets remained functional for over 6 weeks in primary culture and up to 9 weeks in secondary culture, as indicated by their substantial insulin response to an acute glucose stimulus. Insulin secretion from islet monolayers showed biphasic kinetics. The functional competence of the monolayers was further evaluated by studying glucose-stimulated insulin release in the presence of various modulators of B-cell function. The response to physiological agents such as somatostatin, epinephrine, glucagon, and arginine was retained for at least 4 weeks in culture. The sensitivity to inhibition by somatostatin and epinephrine (ID50 = 10 ng/ml) and that to stimulation by glucagon (ED50 = 3 ng/ml) were similar to or better than those for freshly isolated islets. We have thus obtained a fibroblast-free monolayer culture of pancreatic islets from adult rats containing B-cells that retain normal function for long periods. This experimental system appears ideally suited for studying chronic modulations of islet cell function under controlled in vitro conditions, which can allow the stimulation of normal and diabetic environments.
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PMID:Monolayer culture of adult rat pancreatic islets on extracellular matrix: long term maintenance of differentiated B-cell function. 245 5

Isolation of islets of Langerhans from the pancreas by action of collagenase, a major breakthrough for physiological studies in vitro, has long appeared empirical, and the results were sometimes unpredictable. Isolation yields (number of islets obtained per pancreas) and their reproducibility, purification from exocrine remnants and vitality of the islets obtained, can improve owing to precise techniques, adapted to the architecture of collagen in the pancreas. We have tested four isolation-purification techniques in the rat pancreas. The best results were obtained by combining intra-ductal collagenase injection, with complete but moderate distension of the gland, avoiding leakage, multistep digestion (in situ and then in vitro), followed by purification on a discontinuous bovine serum albumin (BSA) gradient. Average yields were 670 +/- 40 islets per pancreas (range 570-800), versus 170 +/- 9 (range 40-350) with the technique used initially. The use of BSA discontinuous gradient improved the purification yield: 90-96% of islets obtained were concentrated in the 26/29% BSA interface. Furthermore, this technique shortened the duration of purification step: 1 hr (centrifugation gradient) vs 3 hrs (handpicked). It was verified that islets were morphologically free of exocrine tissue. Islet structure was well preserved either in conventional histology or insulin and glucagon immunoperoxidase staining. Islet vitality, as assessed by trypan blue exclusion test, was 100% of freshly isolated islets, and 89% after 24 hrs culture. Insulin secretory responses to a given stimulus were stronger than in the case of islets isolated by former techniques: 10-12 times the basal release (vs 5 times) with clear dose-response proportionality.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Reproducible high yields of rat islets of Langerhans. 254 70

A large-scale isolation of islets is required for islet transplantation. We improved our conventional method, and could obtain about three times more islets than by the conventional methods. Pancreata of adult Wistar rats were inflated by injection of buffer with (A) or without 1.3 mg/ml collagenase (B). The rats were bled from the inferior vena cava and the aorta in (A) simultaneously with the inflation. They were further digested with collagenase and filtered through two different meshes (pore size: 1190 and 590 microns) (A1) or three different meshes (pore size: 1190, 590 120 microns) (A2) in order. Insulin released from islets isolated in this manner was determined by 1-h incubation with 3.3 and 16.7 mM glucose. Besides, 600 islets each were transplanted into the liver of streptozotocin-induced diabetic Wistar rats and their fasting plasma glucose was measured at weekly intervals. (1) With these methods more numerous islets were harvested by A1 (mean: 554) and A2 (mean: 746) than B (mean: 224). (2) Insulin released at both glucose concentrations was similar among islets obtained by A1, A2 and B. (3) The plasma glucose-lowering effect was similar among the islets obtained by these methods. (4) A more selected range of islet sizes was obtained by A2 than A1. These observations indicate that the present techniques (A1 and A2) are less time-consuming and simpler for a large-scale isolation of islets.
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PMID:Sophisticated mesh filtration technique of a large-scale isolation of islets and their function. 264 40

Skeletal abnormalities commonly reported in both human and experimental diabetes include impaired linear growth and osteopenia. In the present study we examined the effect of diabetes and insulin therapy on collagen, the major protein constituent of extracellular matrix. Insulin-deficient diabetes was induced in growing rats by injection of 90 mg/kg of streptozotocin. Articular cartilage and long bone (femur) were removed, and tissues incubated with [3H]-proline in vitro for 2 hours at 37 degrees C. Uptake of [3H]-proline into both collagen and noncollagen proteins was determined using purified bacterial collagenase. In cartilage, collagen production decreased to 46% of buffer-injected control animals within one week of induction of diabetes (p less than 0.01), and remained at this level for three weeks. A similar degree of suppression was found in long bone from untreated animals, in which collagen production decreased to 58% of control (p less than 0.01). Insulin administration at the onset of diabetes prevented the expected decrease in collagen production such that after one week of therapy, collagen production in bone and cartilage was 98% and 93% of control (p +/- 0.01 vs. untreated), respectively. When insulin therapy was delayed for one week after the induction of diabetes, collagen production in articular cartilage increased from 46% to 92% and 97% of control at the end of one and two weeks of therapy (p less than 0.01 vs. untreated), respectively. Noncollagen protein production in untreated rats decreased to 49% of control in long bone and to 72% of control in articular cartilage after one week (p less than 0.01), with correction to control levels in both tissues within one week of insulin therapy.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Correction of altered collagen metabolism in diabetic animals with insulin therapy. 267 27

In order to obtain an appropriate tissue model to study human diabetes we isolated islet cells from pancreata obtained from brain-dead, heart-beating kidney donor subjects by collagenase dispersion and tissue culture. The presence of viable islet cells was confirmed by both immunofluorescence staining and hormone release experiments. Insulin and somatostatin release were determined on culture day 3 or 4 when amylase measurements indicated an absence of functional exocrine cells. Glucose, alpha-ketoisocaproic acid, theophylline, glucagon, and tolbutamide each stimulated insulin release 2- to 3-fold and somatostatin release 1.5- to 2-fold. Epinephrine and somatostatin both inhibited glucose-stimulated insulin release. Successful subculture of islet cells was achieved after dispersion of primary cultures with dispase. Subcultured islet cells released insulin into the medium during a subsequent 8-day period and when challenged with glucose responded with a 1.6-fold increase in insulin output. Cells cultured on glass coverslips were used to detect, by indirect immunofluorescence, islet cell surface antibodies (ICSA) in the sera of patients with insulin-dependent diabetes mellitus. Of 15 sera from patients with newly diagnosed insulin-dependent diabetes mellitus 9 were ICSA positive, whereas all of 10 control sera were negative; in contrast, using rat insulinoma cells only 4 diabetic sera were positive, as well as 2 control sera. These findings demonstrate the functional viability of adult human islet cells in primary and secondary culture. Cultured human islet cells are a novel, sensitive, and specific system for detecting ICSA and for studying autoimmune effects, and provide a potential source of islet cells for transplantation.
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PMID:Adult human pancreatic islet cells in tissue culture: function and immunoreactivity. 286 82

Adipocytes were isolated from mesenteric adipose tissue of rainbow trout (Salmo gairdnerii) by incubation of tissue slices at 20 degrees C in a buffer containing 3 mg collagenase per ml. These cells were compared to adipocytes from the cat and the rat, isolated by conventional technique (1 mg collagenase per ml buffer, incubation temperature 37 degrees C). Uptake studies of some metabolites were performed with fish, rat and in some cases cat adipocytes. At a glucose concentration of 0.33 mM, the glucose uptake into rat cells was more than twice as fast as in cells from the cat, and more than five times as fast as in trout cells. 2-Amino butyrate resembled glucose in relative uptake rates between species. Metabolite uptake into rat cells was specific, with different uptake rates for different metabolites. The uptake into trout adipocytes proceeded at similar rates for all metabolites tested, provided the concentrations were the same. The uptake rate of glucose into rat cells was stimulated by insulin. Insulin had no effect on glucose uptake into adipocytes from trout.
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PMID:Uptake studies in adipocytes isolated from rainbow trout (Salmo gairdnerii). A comparison with adipocytes from rat and cat. 286 1

This investigation was initiated to characterize the stimulation of insulin secretion by phenazine methosulfate (PMS). Islets of Langerhans, isolated by the collagenase method from normal rats and rats pre-injected with either streptozotocin or 6-aminonicotinamide, were exposed to PMS under various experimental conditions and insulin secretion in response to PMS, glucose and pyridine nucleotides was determined. Insulin releasing action of PMS was dose-, time- and temperature-related, occurred in the absence of glucose, and was inhibited by epinephrine, but not by mannoheptulose. In the perifusion system, the pattern of response induced by PMS was spike-like release reaching a maximum in 5 min and declining rapidly to half-maximal value in 10 min. After exposure of islets to beta-cytotoxin either in vivo or in vitro, complete reversal of the cytotoxic effect was obtained with PMS which induced release of insulin in both normal and beta-cytotoxin islets pre-treated. It is concluded that islets depleted of coenzymes could still secrete insulin in response to a reactive proton donor, which might act by substituting for coenzymes and that the immediate action of beta-cytotoxins does not completely arrest the secretory mechanisms in islets of Langerhans.
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PMID:The characterization of phenazine methosulfate stimulated insulin secretion. 295 17

Insulin has been reported to degrade inside the islets and islet lysosomal proteases have been thought to take part. As chloroquine is regarded as a potent lysosomotropic agent, an attempt has been made to see whether chloroquine has an influence on intrainsular degradation of insulin. After preculture of collagenase-isolated rat islets at 11 mM glucose together with [3H]leucine for 3 days for labelling newly synthesized insulin, islets were cultured for 1 day at 2.2 or 22 mM glucose with or without 0.02 mM chloroquine. Afterwards, radioactivity was measured in the proinsulin/insulin fraction. For control, the influence of chloroquine during 3-h incubation of both freshly isolated and precultured islets was also studied. During the 1-day culture at 2.2 mM glucose, prelabelled insulin was degraded significantly and addition of chloroquine did not alter the amount of insulin degraded. At 22 mM glucose, no significant amount of insulin had been degraded. During the 3-h incubation of freshly isolated as well as precultured islets, chloroquine was found to inhibit significantly glucose-induced biosynthesis of insulin. Glucose-induced release of insulin, however, was not influenced by chloroquine. It is concluded that chloroquine does not influence glucose-induced release or intra-insular degradation of insulin, but it interferes with the biosynthesis of insulin.
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PMID:Effect of chloroquine on biosynthesis, release and degradation of insulin in isolated islets of rat pancreas. 304 45


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