Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.24.3 (collagenase)
 18,340 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Islets were isolated by mild collagenase digestion and microdissection from rat fetuses 2 days before term and pups 1 or 2 days after birth and their insulin and glucagon secretion studied in vitro. Fetal B cells were stimulated by 16.7 mmol/l glucose, 20 mmol/l leucine or 20 mmol/l arginine. Fetal A cells were not affected by glucose or leucine, but were significantly stimulated by arginine. Somatostatin abolished the effect or arginine on both IRI and IRG output. Neonatal islets proportionally released more insulin and glucagon than their fetal counterparts, but reacted to the tested agents in a similar fashion. During the perinatal period, pancreatic insulin storage increased at a higher rate than that of glucagon. It is concluded that fetal B cells are equipped with sensors to a variety of agents and able to modulate their secretory rate according to the concentration of these agents. A cells are reactive to arginine 2 days before term but do not become glucose reactive until several days after birth.
 ...
PMID:Insulin and glucagon secretion by islets isolated from fetal and neonatal rats. 36 57

Islets of Langerhans were isolated from four human kidney donors, aged 16 to 21 years by the collagenase method described for isolation of rodent islets. So far the human islets have been kept in tissue culture, without attachment, in medium RPMI 1640 supplemented with 10% calf serum for more than 9 months, with preservation of the ability to release insulin in response to glucose stimulation. Replacement of calf serum with serum from normal human subjects did not affect B-cell survival, but resulted in elevated insulin values partly due to lower insulin degrading activity. Thus the described technique presents a valuable tool for studying chronic effects of metabolites and hormones on islet function, as well as for islet storage prior to transplantation into humans.
 ...
PMID:Preservation of beta cell function in adult human pancreatic islets for several months in vitro. 36 59

We tested the effects of vitamin A, a membrane surface-active agent, on glucose (16.7 mM)-induced biphasic insulin release from collagenase-isolated rat islets. Also, efforts were made to correlate the effects of vitamin A with glucose oxidation. Vitamin A (10(-4) M) inhibited first- and second phase insulin release; 10(-5) M vitamin A inhibited second phase release only and to a lesser extent than that observed with 10(-4) M vitamin A; and 10(-6) M vitamin A had no effect. Vitamin A (10(-7) M) stimulated biphasic insulin release. Exposure to high glucose (27.8 mM) overcame the effects of 10(-4) M vitamin A on first phase release, but not on second phase release of insulin. Exposure to 10(-5) M hydrocortisone opposed the effects of 10(-4) M vitamin A on both phases of insulin release. Vitamin A (10(-4) and 10(-5) M) inhibited glucose oxidation by islets, as measured by the production of 14CO2 from [14C]glucose. The effects of vitamin A on insulin release were dissociated in part from those effects on glucose oxidation, in that hydrocortisone opposed the effect of vitamin A on insulin release but not on glucose oxidation. The effects of vitamin A on insulin secretion can best be explained by the interaction of vitamin A at multiple sites affecting the membrane and intracellular glucose oxidation.
 ...
PMID:The effects of vitamin A on insulin release and glucose oxidation in isolated rat islets. 37 52

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.
 ...
PMID:Effect of age on glucose-stimulated insulin release by the beta-cell of the rat. 37 46

(Pro-)Insulin biosynthesis ([3H]leucine incorporation) and insulin secretion were studied in collagenase-isolated rat islets incubated for 3 hours at 1 and 2 mg/ml glucose in the presence of gastric inhibitory polypeptide (GIP). GIP augmented [3H]leucine incorporation and release of insulin at both glucose concentrations. In a second series of experiments it was found that an amino acid mixture was without influence on the insulotrophic action of GIP. Combined stimulation of insulin release by GIP and glucagon did not result in higher insulin output than observed in the presence of each substance alone. Thus GIP, in constrast to many other gastrointestinal peptides, however similar to glucagon, enhances not only release but also biosynthesis of insulin. This insulinotrophic action can be observed already at a glucose concentration of 1 mg/ml. The results underline the outstanding role which GIP appears to play in the regulation of beta-cell function.
 ...
PMID:Stimulation of (Pro-)insulin biosynthesis and release by gastric inhibitory polypeptide in isolated islets of rat pancreas. 38 25

Dispersed cell preparations enriched in beta-cells were obtained by collagenase digestion of fetal bovine pancreas and separation by Ficoll gradient centrifugation. These cells actively incorporated [3H]leucine into proinsulin and insulin. Incubation of these cells in the presence of the arginine analogue, L-canavanine, resulted in the inhibition of conversion of newly formed proinsulin to insulin and the appearance of a radioactive component of molecular weight 11,000-12,000. Incorporation of [35S]methionine into this component was detected in the presence of canavanine, an event not observed in control incubation. Canavanine thus induced the formation of a component possessing molecular weight and compositional properties expected for preproinsulin. Further characterization of cellular products by polyacrylamide slab gel electrophoresis in sodium dodecyl sulfate showed a highly labeled band corresponding to molecular weight 18,000-20,000 which might be involved in insulin biosynthesis.
 ...
PMID:Preparation of beta-cells from fetal bovine pancreas: characterization of insulin biosynthetic activity. 38 31

Alveoli and ducts isolated from virgin rat mammary glands synthesize basement membrane collagen (typeIV) in primary culture. Using purified antibodies to type IV collagen, prominent intracellular and extracellular fluorescence is observed in the epithelium. No fluorescence is observed with antibodies to collagen type I and III. From quantitation of the incorporation of [14c]proline-labeled proteins, 1.5 to 2.5 per cent of the newly synthesized proteins are collagen. Type IV collagen from these cultures was biochemically identified on the basis of (1) the high ratio of labeled 3-hydroxyproline to 4-hydroxyproline (1:10), (2) the gel electrophoretic pattern of the collagenase-sensitive proteins precipitated with 1.7 M NaCl, (3)the failure of the collagen to bind to diethylaminoethyl-cellulose, and(4)the immunologic cross-reactivity with mouse tumor type IV is identical with that of type IV collagen from other sources. When the supportive hormones, insulin, prolactin, hydrocortisone, progesterone, and estradiol are removed from the cultures, there is a 90 per cent reduction in the amount of [3H]proline recovered in collagen synthesis coincides with only a 30 percentdrop in the growht rate and a 20 per cent drop in total protein synthesis of the sells over the 24-hour period without hormones. Pulse-chase experimout hormones. Pulse-chase experiments revealed an enhanced turnover of collagen following hormone withdrawal. This system may be an in vitro model of collagen turnover in mammary gland in involution.
 ...
PMID:Hormonal requirements for basement membrane collagen deposition by cultured rat mammary epithelium. 39 Feb 39

A subpopulation (n = 27) of normoglycaemic Sand rats was characterized as carbohydrate-intolerant by intraperitoneal glucose loading. Five of these animals did not show any rise in peripheral insulin concentrations when injected with glucose. However, when isolated by collagenase digestion their islets still exhibited a significant enhancement of insulin secretion in response to glucose, glyceraldehyde, mannose and theophylline. The in vitro secretory responses were comparable to those of islets from carbohydrate-tolerant Sand rats. The results underline the importance of the natural environment for the B-cell response in vivo.
 ...
PMID:Apparent discrepancy between the insulin secretory responses in vivo and in vitro in carbohydrate-intolerant Sand rats. 39 3

The direct effects of porcine insulin and glucagon on bone collagen and non-collagen protein synthesis have been examined in cultures of calvaria obtained from 21-day fetal rats. Bones were incubated for 24 to 96 h and [3H]proline was added for the last 2 h of culture. Incorporation of the label into collagenase-digestible protein (CDP) and noncollagen protein (NCP) was determined using purified bacterial collagenase. Insulin increased the labeling of CDP by 60 to 115% at concentrations of 10(-9) to 10(-6) M. A smaller stimulatory effect was observed on NCP. The effect on CDP appeared after 12 to 24 h of culture, was maintained for 96 h in the continuous presence of the hormone, but was lost within 3 h of removal of insulin from the culture medium. Insulin appeared to have a direct effect on collagen synthesis and not on collagen breakdown. Insulin did not affect the incorporation of [3H]uridine or [3H]thymidine into the RNA and DNA fractions of bone at 24 h. Insulin opposed the inhibitory effects of parathyroid hormone and dibutyryl cyclic-3',5'-adenosine monophosphate and to a lesser extent, the inhibitory effect of isobutylmethylxanthine on the labeling of CDP. Glucagon did not affect the response to insulin and by itself had small and variable inhibitory effects on proline incorporation.
 ...
PMID:Hormonal control of bone collagen synthesis in vitro. Effects of insulin and glucagon. 40 59

Rats trained to the "8 + 16" controlled feeding cycle where food is only available for the first 8 h of the 12 h dark period exhibit a pronounced diurnal rhythm of hepatic glycogen metabolism. Glycogen is stored within the liver parenchymal cells during the dark period and subsequently mobilized for energy production during the light period. Hepatocytes, isolated by collagenase perfusion, from livers of such animals have differing capacities for glycogen synthesis when incubated with glucose. Cells prepared at the end of the 16 h period without food have very little capacity for synthesis compared with much higher rates obtained in cells obtained during the feeding period. Cells obtained from liver containing a large glycogen concentration produce a net breakdown of glycogen during incubations with glucose, however experiments using radioactively labelled glucose indicate that synthesis does occur in these cells. The changes in the capacity of the cells for glycogen synthesis appear to be due, in part, to changes in the percentage of the cell population involved in synthesis and in the activity of glycogen synthetase a. Attempts of influence the rate of glycogen synthesis at any time of day with insulin or dexamethasone were unsuccessful.
 ...
PMID:The influence of diurnal rhythms of carbohydrate metabolism in adult rat liver on the metabolic characteristics of isolated liver parenchymal cells. 40 61


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>