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

---

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

The mechanism of albumin biosynthesis was studied in Morris hepatoma 5123tc in vivo and in hepatoma cell suspensions obtained by solubilizing the intercellular matrix with collagenase and hyaluronidase. In the in vivo experiments, L-[-14C]leucine was injected i.v. into rats bearing hepatomas in the muscles of both hind legs. After 14 min, tumors were removed and homogenized. A protein fraction quantitatively precipitable with antialbumin was isolated from the homogenate by acetone fractionation and precipitation with antiserum against serum albumin. This protein fraction was not homogeneous. With the use of 3 consecutive chromatographies on diethylaminoethyl cellulose, a very highly radioactive albumin-like protein could be separated from a large amount of only slightly radioactive albumin. In hepatoma cell suspensions incubated with L-[1-14C]leucine followed by a chase with excess nonradioactive L-leucine, radioactivity was incorporated first into the albumin-like protein and transferred thereafter into albumin, suggesting that albumin was synthesized via the albuminlike protein as precursor. In vivo, 1.8% of newly synthesized hepatoma protein was albumin or its precursor, compared with 1.2% in cell suspensions.
...
PMID:Biosynthesis of albumin via a precursor protein in Morris hepatoma 5123tc. 18 40

The uptake of 45Ca2+ by a lanthanum-non-displaceable pool in pancreatic islets was studied; Raising the extracellular D-glucose concentration from 3 to 20 mM stimulated the 45Ca2+ uptake in hand-dissected islets of ob/bo-mice as well as in collagenase-isolated islets of ob/ob or normal mice. The effect was dose-dependent in the range of 0-20 mM D-glucose and was seen throughout a wide range of extracellular calcium concentrations (16 mumol-2.56 mmol of Ca2+ added per litre of medium). The 45Ca2+ uptake was also enhanced by other known insulin secretagogues (D-mannose, L-leucine, tolbutamide) and was uninfluenced by compounds lacking insulin-releasing capacity (3-O-methyl-D-glucose, L-glucose, D-galactose, D-leucine). The stimulatory effect of D-glucose was blocked by inhibitors of glucose-induced insulin release (D-mannoheptulose, diazoxide, L-adrenaline). The results support the view that the lanthanum-nondisplaceable calcium pool is related to the insulin-releasing mechanism, although the exact nature of this relationship is still unclear.
...
PMID:Effects of various modifiers of insulin release on the lanthanum-nondisplaceable 45Ca2+ uptake by isolated pancreatic islets. 19 76

Attempts to design an agent which would release cytotoxic nitrogen mustards within collagenase-producing tumors led to the synthesis of Cbz-L-Pro-L-Leu-Gly-L-Pro-Gly-NHC6H4N(CH2CH2Cl)2 (10). 10 was cleaved in vitro by bacterial and tumor-associated collagenase as expected at the peptide bond joining L-leucine and glycine to give Gly-L-Pro-Gly-NHC6H4N(CH2CH2Cl)2 which was over six times more toxic, on a molar basis, than 10. In vivo tests of 10 against well-advanced Sarcoma-180 gave disappointing results. The lack of specific antitumor activity may be accounted for by the presence of competing cleavage reactions by collagenases in certain normal tissues.
...
PMID:Collagenase-sensitive peptidyl-nitrogen mustards as potential antitumor agents. 21 58

Conditions to obtain high yields of intact acini from lactating bovine mammary glands and certain structural and functional characteristics of isolated acini were investigated. A two-factor experiment with three collagenase concentrations (100, 150, and 200 mg/100 ml) and incubation periods (40, 60, and 90 min) demonstrated that increases in both factors significantly increased net acini yield. Largest amounts of acini obtained, based on content of deoxyribonucleic acid, were 10.3% of the original tissue. Morphologically, fractions consisted primarily of acini or large cell clumps, and nearly all cells excluded trypan blue. Acini cultured in complete nutrient medium incorporated radioactive leucine into proteins. When acini were incubated in medium without supplemental amino acids, specific activity of synthesized proteins was correlated negatively with incubation time. During pulse labeling with radioactive L-leucine over 16 min, true labeling of acinar proteins occurred after 4 min. Sequential kinetics of pulse-chase labeling demonstrated a response pattern unique to the in vitro acinar system. Acinar protein synthesis was inhibited by cycloheximide and strongly stimulated by by 3',5'-cyclic adenosine monophosphate.
...
PMID:Isolation of functionally active acini from bovine mammary gland. 22 19

An enzymatic procedure for the isolation of metabolically active tumour cells from human renal cell carcinoma is described. The cells were suspended by a multistep incubation procedure of the tissue in the presence of collagenase (10 mg enzyme/g tumour wet weight) dissolved in a calcium-free buffer solution. About 90% of the isolated tumour cells were viable, as judged by routine trypan blue staining. Electron microscopic examination revealed tumour cells in various stages of dedifferentiation. The cells had retained their capability of protein synthesis. In short term experiments the effects of 17 beta-oestradiol and progesterone on the incorporation of [U - C] L-leucine into cellular proteins was studied; Progesterone was found to exhibit a slight tumour antianabolic or catabolic action. A 17 beta-oestradiol-dependent modulation of the rates of protein synthesis was not observed.
...
PMID:[Viable cells from human renal cell carcinoma: isolation procedure and analysis of hormone sensitivity (author's transl)]. 22 52

The mechanism of the biosynthesis of albumin was studied in cell suspensions from rat liver. The cells were prepared by continuous perfusion of the liver in situ with 0.05% collagenase and 0.10% hyaluronidase and incubated under conditions optimized for the incorporation of amino acids into protein. Seven minutes after starting the incubation L-[1-14C]leucine was added, followed after 25 min by a 15 or 30-min chase with an 830-fold excess of non-radioactive L-leucine. Total protein, an albumin-like protein, and albumin were isolated from samples withdrawn immediately of total protein was found to remain constant after addition of the non-radioactive L-leucine, whereas that of the albumin-like protein decreased and that of albumin increased with incubation time. The increase in albumin radioactivity accounted for the decrease in radioactivity of the albumin-like protein, suggesting that the latter is a precursor of albumin. The precursor protein differed from albumin by an oligopeptide extension at the N-terminal end.
...
PMID:Synthesis of albumin via a precursor protein in cell suspensions from rat liver. 126 47

Human fetal pancreatic islets were isolated from 16- to 20-week-old fetuses by a collagenase technique and cultured 48 hr in RPMI 1640 containing 10% human adult serum and unlabeled 0 to 5 micrograms cyclosporine A (CsA)/ml. Insulin secretory capacity of human fetal islets was expressed as a fractional stimulatory ratio FSR = F2/F1 of the fractional secretion rates during two successive 1 hr static incubations first with 2 mM glucose (F1) to stabilize secretion followed by maximal stimulus, i.e., 25 mM glucose plus 10 mM L-leucine and 10 mM L-arginine (F2). Unlabeled CsA at the above concentrations had no significant effects on the insulin secretory capacity expressed by FSR-values. Studies of net uptake of 3H-CsA by islets cultured for varying periods up to 40 hr and expressed as picomole 3H-CsA per picomole islet insulin content demonstrated that uptake rate was slow and did not reach isotopic equilibrium over the 40 hr of culture. When isolated fetal islets were cultured for 48 hr in the presence of 3H-CsA and varying concentrations of unlabeled CsA it was found during two successive 1 hr static incubations that fetal islets secrete insulin concomitantly with 3H-CsA following maximal stimulus for secretion. An optimal secretory molar ratio of 3H-CsA to insulin of 4.0 +/- 1.3 (n = 7) was found after islets were cultured 48 hr in the presence of a saturating 2.128 micrograms 3H-CsA per milliliter culture medium. In three successive 30-min static incubations of 3H-CsA loaded islets, first with low glucose, followed by high glucose plus L-arginine and L-leucine, and finally with high glucose plus L-arginine and L-leucine and 10 mM theophylline, the proportional fractional secretion rates of insulin and 3H-CsA were of the same magnitude. It is concluded that human fetal pancreatic islets during 48 hr of culture in the presence of pharmacologically relevant concentrations of CsA can internalize the drug, which is compartmentalized and concomitantly secreted with insulin following maximal stimuli. Transplanted human fetal islets utilized as delivering units for CsA could be beneficial for the induction of immunotolerance to allografted fetal islets.
...
PMID:3H-cyclosporine internalization and secretion by human fetal pancreatic islets. 305 4

Anionic fluxes during the membrane realignments of stimulated insulin release have not been characterized previously although cations have been implicated in stimulus-secretion coupling. We have shown that a limited packet pulse of phosphate release ("phosphate flush") begins at the same time that the first phase of insulin secretion may occur. To demonstrate this phenomenon, we have prelabeled islets, obtained from rat pancreas by collagenase digestions, by incubation with [(32)P]orthophosphate. When such prelabeled islets are perifused with Krebs-Ringer bicarbonate containing 0.5 mg/ml D-glucose, a basal rate of efflux of radioactivity is established; transfer to perifusates containing 3.0 mg/ml D-glucose elicits an increased (32)P efflux within 1-2 min to peak values which are 7- to 21-fold greater than basal. The total duration of this "phosphate flush" approximates 10 min and exceeds the duration of the first phase of stimulated insulin secretion. With lesser concentrations of glucose, the flush exhibits dose-response relationships, and with 3 mg/ml glucose, a second flush can be elicited by restoring basal conditions and stimulating anew with 3 mg/ml glucose. The phenomenon is highly specific and can be reduplicated by other secretagogues (L-leucine) or sugars (D-mannose) which are also known to elicit insulin release but not by sugars which fail to affect insulin secretion (D-galactose, D-fructose, i-inositol, L-glucose). The efflux of radioactivity consists entirely of [(32)P]orthophosphate. Phosphate flush persists in phosphate-free media, Ca(++)-free media, and when insulin release is obtunded by adding Ni(++) (2 mM) to the perifusates. Thus, efflux of [(32)P]orthophosphate can be dissociated from insulin extrusion, and from net influx of ionic phosphate or calcium. Membrane stabilization with D(2)O or 1.0 mM tetracaine reversibly inhibits phosphate flush. Although the mechanism by which this effect occurs has not yet been established, the phosphate flush appears to constitute one of the earliest and hitherto unknown indices of the excitatory state in pancreatic islets.
...
PMID:Rapid transient efflux of phosphate ions from pancreatic islets as an early action of insulin secretagogues. 460 16

Column perifusion of collagenase-isolated mouse pancreatic islets was used to study the dynamics of insulin release in experiments lasting for several hours. The methyl esters of L-leucine and L-arginine were synthesized. Whereas L-arginine methyl ester (L-arginine OMe) had no effect, L-leucine OMe stimulated the release of insulin. The effect of L-leucine OMe was maximal at 5 mmol/liter. Whereas the Km for glucose-stimulated insulin release was unaffected by 1 mmol/liter L-leucine OMe, the maximal release of D-glucose was increased by the amino acid derivative that appeared more effective than L-leucine. L-Leucine OMe was also a potent stimulus of insulin release from the perfused mouse pancreas. In the presence of 10 mmol/liter L-glutamine, 1 mmol/liter L-leucine OMe induced a 50- to 75-fold increase in insulin release. A similar stimulatory effect was also observed in column-perifused RIN 5F cells, a cloned rat islet tumor cell line. A twofold increase in islet glutamate dehydrogenase activity was induced by 5 mmol/liter L-leucine OMe, a larger effect than that of L-leucine (P less than 0.02), whereas L-arginine OMe had a small inhibitory effect. We conclude that L-leucine OMe is a potent stimulus of insulin secretion and that its effect on the beta-cells may be exerted by activating islet glutamate dehydrogenase.
...
PMID:L-leucine methyl ester stimulates insulin secretion and islet glutamate dehydrogenase. 619 91

Glucose induced insulin release, from collagenase isolated islets of Langerhans obtained from non diabetic male New Zealand White rabbits, was inhibited in vitro by E. coli L-asparatinase. This inhibition was time and dose dependent with maximal inhibition being attained after 1 1/2 hr incubation using a dose of 1000 I.U. L-asparaginase/ml. Tolbutamide potentiated glucose-induced insulin release in the presence of inhibitory doses of the L-asparaginase. This potentiation was decreased at higher dose levels of L-asparaginase. L-leucine, L-arginine and theophylline also potentiated glucose-induced insulin release in the presence of L-asparaginase. This potentiation was intact in the presence of all doses of L-asparaginase tested. Glucose induced insulin release, from collagense isolated islets obtained from male New Zealand White rabbits rendered hypoinsulinemic and diabetic by daily intravenous injections of L-asparaginase in vivo, was similar to that of islets of non diabetic control rabbits when the islets were incubated in vitro in te absence of L-asparaginase. These data suggest that the hypoinsulinemic diabetic syndrome produced by the anti-tumor enzyme, L-asparaginase, is produced at least in part by the suppression of insulin release and that this suppression requires the enzyme to be present.
...
PMID:E. coli L-asparaginase and insulin release in vitro. 675 34


1 2 Next >>

---