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)

Experiments were performed to determine the effects of agents that modify Kupffer cells on the mannose-N-acetylglucosamine-glycoprotein receptor on hepatic sinusoidal cells. Cells were prepared by collagenase liver perfusion, centrifugation on Percoll gradients, and centrifugal elutriation. The uptake of 125I-labeled agalacto-orosomucoid (125I-AGOR), an N-acetylglucosamine-terminated glycoprotein, was greatest (53% of total uptake) by elutriator fractions containing equal proportions of endothelial and Kupffer cells ("mixed cell" fraction). Uptake was specific and time and concentration dependent. The apparent Km (0.4 mumol/L) and the patterns of inhibition by monosaccharides were similar in all the elutriator fractions, suggesting that only one class of receptor was present. The highest apparent maximal velocity (18 pmol/hr/5 X 10(6) cells) was found in the mixed cell fraction, indicating this fraction contained the highest proportion of receptor-bearing cells. Latex (0.8 micron) and bacillus Calmette-Guerin pretreatments did not influence the hepatic uptake of the glycoprotein in vivo. Iron sorbitol significantly reduced hepatic glycoprotein uptake and caused a twofold increase in the proportion of the ligand remaining in the circulation. Uptake of 125I-agalacto-orosomucoid by cells from latex-treated rats was similar to controls, but uptake by bacillus Calmette-Guerin-treated rat cells was only 25% of control uptake. This was related to a marked increase in sinusoidal cell number caused by bacillus Calmette-Guerin. In contrast, iron sorbitol caused a selective suppression of 125I-agalacto-orosomucoid uptake (10% of control uptake) by cells in the mixed cell fraction. This study showed that maximal uptake of 125I-agalacto-orosomucoid was by elutriator fractions containing equal proportions of endothelial and Kupffer cells and that iron sorbitol suppressed ligand uptake by these cells, possibly by influencing the mannose-N-acetylglucosamine receptor on Kupffer cells.
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PMID:Effects of iron loading and bacillus Calmette-Guerin on a glycoprotein recognition system on rat hepatic sinusoidal cells. 650 2

Rabbit aortic intima-media fragments were incubated with [14C]mannose and [3H]fucose for 6 h to detect glycoproteins synthesized in situ. The radioactively labelled and the non-labelled samples were extracted with 0.2 mM-CaCl2/0.5 mM-dithiothreitol/0.5 mM-ATP and chloroform/methanol/water (4:4:1, by vol.). The delipidated residue was extracted with 5 M-guanidinium chloride/0.05 M-dithiothreitol/0.1 M-Tris/0.4% Na2EDTA, pH 7.5, before (extract 1) and after hydrolysis with collagenase (extract 2). The proteins in extracts 1 and 2 were S-carboxamidomethylated and separated by molecular-sieve chromatography, polyacrylamide-gel electrophoresis and isoelectric focusing in sucrose gradients in urea. The apparent molecular weights of glycoproteins were 36 000 (glycoprotein I) from extract 1, 50 000 (glycoprotein II) and 130 000 (glycoprotein III) from extract 2. The molecular weights of the non-labelled and radioactively labelled glycoproteins were identical. Glycoproteins I, II and III contain large amounts of polar amino acids and methionine. They contain neither hydroxyproline nor 3-methylhistidine. A hydroxyproline-containing component of 160 000-apparent-mol.wt. relatively rich in polar amino acids and labelled with incorporated sugars was isolated from extract 1. The incorporation in vitro of radioactive sugars into glycoproteins I, II, III and collagenous glycoproteins indicates that they are synthesized in the surviving aorta by the smooth-muscle cells.
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PMID:Structural glycoproteins from rabbit aortic media. 687 Aug 24

Fibroblasts from normal human subjects and from a patient who had osteogenesis imperfecta were incubated with [3H]mannose, and types I and III procollagens were isolated from the culture medium. The type I procollagen from the patient's fibroblasts contained 2-3 time more [3H]mannose than the type I procollagen from the normal fibroblasts. In contrast, there was no difference in the [3H]mannose content of the type III procollagen simultaneously synthesized and secreted by the same cells. Isolation of a collagenase-resistant peptide fragment from the type I procollagen showed that the excess mannose was located in the COOH-terminal propeptide of the protein. Radioimmunoassays of the medium and the cell layer showed that the type I procollagen synthesized by the patient's fibroblasts was secreted into the medium more slowly than the type I procollagen synthesized by normal fibroblasts. These results appear to provide evidence for an alteration in the structure of procollagen in osteogenesis imperfecta.
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PMID:A defect in the structure of type I procollagen in a patient who had osteogenesis imperfecta: excess mannose in the COOH-terminal propeptide. 693 45

The JB6 mouse epidermal cell line has been developed to study promotion of neoplastic transformation in vitro. Treatment of JB6 cells with 12-O-tetradecanoylphorbol 13-acetate (TPA) or other tumor promoters resulted in the irreversible acquisition by JB6 cells of tumorigenicity in nude mice and anchorage-independent growth in soft agar. As previously reported, one of the biochemical responses that occurs during TPA treatment is a greater than 75% reduction in a mannose-labeled glycoprotein with an apparent molecular weight of 180,000. This TPA-sensitive glycoprotein has now been identified on the basis of collagenase and pepsin sensitivity as procollagen pro-alpha 1(I) chain. [3H]proline labeling also demonstrated a parallel decrease in the 150,000 procollagen pro-alpha 2(I) component. Two nonphorbol promoters, mezerein and epidermal growth factor, were also active in decreasing procollagen synthesis. Promotion-sensitive and promotion-resistant clonal derivatives of JB6 showed similar basal levels of collagen synthesis as well as similar degrees of TPA-dependent procollagen loss indicating that the collagen decrease may be necessary but is not sufficient to produce the promotion response. Comparison of chemically transformed mouse epidermal cell lines with paried nontransformants suggests the reduced procollagen synthesis is a stably acquired phenotypic change and may therefore be involved in maintenance of the transformed phenotype as well as in its induction.
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PMID:Inhibition by tumor-promoting phorbol esters of procollagen synthesis in promotable JB6 mouse epidermal cells. 695 59

Efflux of 36Cl- from prelabeled, collagenase-isolated islets of noninbred ob/ob mice, inbred diabetic [C57BL/KsJ(db/db)] mice, and nondiabetic [C57BL/KsJ(+/+)] mice was studied by nonrecirculating perifusion. Islets of both ob/ob mice and nondiabetic KsJ mice showed similar rates of basal 36Cl- efflux, D-glucose stimulation of the 36Cl- efflux, and net uptake of 36Cl- at apparent isotope equilibrium. The 36Cl- efflux in islets from both young and old KsJ-db/db mice was almost insensitive to the D-glucose concentration. The basal rate of 36Cl- efflux in islets from young and old db/db mice was increased, indicating an abnormally high Cl- permeability. It is suggested that the defective regulation of the membrane potential in B-cells from [C57BL/KsJ(db/db)] mice may at least partly be caused by a db-mediated defect in the regulation of Cl- permeability.
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PMID:Defective regulation of Cl- permeability in islets of diabetic mice [C57BL/KsJ(db/db)]. 698 1

A detailed dose-response study relating mannose and glucose oxidation with the induction of 45Ca uptake and insulin release was performed using in vitro incubation of collagenase digested rat islets of Langerhans. The threshold value for 14C-U-D-glucose oxidation, glucose-stimulation of 45Ca uptake, and insulin release was about 5.5 mM. The half maximal response for these 3 parameters occurred at 13.4 mM, 11.6 mM, and 12.2 mM, respectively. Their maximal responses were obtained at approximately 20 mM. The threshold level for mannose oxidation, induction of 45Ca uptake and insulin release was about 11.0 mM, with half maximal responses obtained at 24.6 mM, 20.5 mM, and 22.2 mM, respectively. The maximum response of the 3 parameters to mannose was obtained at 38.8 mM and appeared to reach the same level obtained for glucose. These results suggest that hexose degradation has a significant role in controlling Ca uptake and subsequent insulin release. A lower rate of mannose oxidation appeared to account for its weaker stimulating efficacy for Ca uptake and insulin release.
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PMID:Metabolism, 45Ca uptake and insulin releasing capacities of glucose and mannose. 699 61

Islets of Langerhans were isolated by collagenase digestion from the pancreas of a 39 year-old female renal transplant donor. The islets were subjected to three consecutive periods of tissue culture, after each of which they were incubated in vitro with various agents whose effects on insulin release from islets of laboratory animals have previously been established. After the first culture period, the basal insulin secretion rate of 5.2 microunits/islet/h seen with 2 mmol/l glucose was increased approx. 5-fold on raising the glucose concentration to 20 mmol/l. The islets retained the insulin-secretory response to 20 mmol/l glucose throughout the period of study. Insulin secretion was also stimulated by mannose, leucine, alpha-ketoisocaproate, dihydroxyacetone and 3-hydroxybutyrate, but not by fructose or N-acetyl-glucosamine. Fructose however increased insulin release in the presence of 4 mmol/l glucose. Caffeine elicited insulin release in the absence of glucose and enhanced insulin release in response to 10 mmol/l glucose. Glucose-stimulated insulin release was inhibited by trifluoperazine (25 mumol/l).
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PMID:Insulin release from human pancreatic islets in vitro. 699 14

The cellular location and carbohydrate specificities of a glycoprotein recognition system on rat hepatic sinusoidal cells have been determined. Purified preparations of endothelial, Kupffer, and parenchymal cells were prepared by collagenase liver perfusion, centrifugation on Percoll gradients, and centrifugal elutriation. (125)I-labeled agalactoorosomucoid, an N-acetylglucosamine-terminated glycoprotein, was selectively taken up in vitro by endothelial cells. Uptake was shown to be protein dependent, calcium ion dependent, and saturable, and could be described by Michaelis-Menten kinetics (apparent K(m) 0.29 muM; apparent maximum velocity 4.8 pmol/h per 5 x 10(6) cells). Uptake was inhibited not only by N-acetylglucosamine, mannose, and mannan but also by glucose, fructose, and a glucose-albumin conjugate. Inhibition by glucose was competitive over a wide range of concentrations and was almost 100% at a glucose concentration of 56 mM. Fasting and the induction of diabetes mellitus prior to isolation of cells was associated with 60% reductions in the recovery of endothelial cells. Uptake by cells isolated from fasted rats was enhanced (apparent maximum velocity 14.3 pmol/h per 5 x 10(6) cells without change in the apparent K(m)). These observations suggest that fasting is associated with a marked increase in the mean number of glycoprotein receptors per endothelial cell isolated from normal rats. This effect of fasting could be due to upregulation of glycoprotein receptors on endothelial cells or to the selective isolation of a subpopulation of endothelial cells from fasted animals that bears more glycoprotein receptors per cell than does another subpopulation of these cells. In addition, in vivo studies of the fate of intravenously administered (125)I-agalactoorosomucoid indicated that its rate of disappearance from plasma, hepatic accumulation, and catabolism were slower in diabetic than in normal rats. The results suggest that modulation of a carbohydrate-mediated glycoprotein recognition system located on hepatic endothelial cells can be induced by glucose and glucose-conjugated proteins and by fasting and diabetes mellitus. The findings in this study suggest a mechanism for abnormal glycoprotein metabolism in diabetes mellitus.
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PMID:Modulation of a glycoprotein recognition system on rat hepatic endothelial cells by glucose and diabetes mellitus. 708 77

1. Glycoproteins of hamster, rat and baboon lung parenchyma were investigated by using [14C]glucosamine incorporation in vitro followed by sequential extraction of the macromolecular components and characterization of the glycoproteins in the extracts. 2. Slices of lung parenchyma maintained in vitro incorporated [U-14C]glucosamine linearly with time into non-diffusible macromolecules for up to 5h. All the macromolecule-associated 14C label was present as [14C]glucosamine. 3. These 14C-labelled macromolecules were extracted from previously delipidated and salt-extracted lung by 5M-guanidinium chloride in the presence of dithiothreitol and proteinase inhibitors before (extract A1) and after (extract A2) hydrolysis of the collagen by collagenase. The [14C]glucosamine-labelled glycoproteins in extracts A1 and A2 contained 55 and 5% respectively of the total [14C]glucosamine incorporated in the lung of all three species studied. 4. The [14C]glucosamine-labelled glycoproteins were analysed by gel-filtration chromatography, sodium dodecyl sulphate/polyacrylamide-gel electrophoresis and isoelectric focusing. The major [14C]glucosamine-labelled glycoproteins of baboon lung parenchyma had apparent mol.wts. of about 400 000, 140 000 and 65 000 with isoelectric points respectively of 4.8, 5.4 and 5.4. The hamster lung glycoproteins with isoelectric points of 4.1 and 5.8 were devoid of hydroxyproline and contained galactose, mannose and N-acetylglucosamine. These experiments indicate that several distinct glycoproteins are synthesized in situ by the cells of pulmonary parenchyma and may well play a role in its structure and function.
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PMID:Isolation and characterization of lung connective-tissue glycoproteins. 711 3

Secretion of thyroglobulin was studied by incubating pig thyroid follicles, isolated by collagenase digestion and opened up by trypsinization. When followed over periods of 4 h, the secretion of [14C]leucine-labeled thyroglobulin into the medium was reduced by 60-95% in the presence of 1 microgram/ml and 5 micrograms/ml of tunicamycin. These concentrations of the antibiotic reduced incorporation of [3H]mannose into the follicle proteins by 70-80% but did not significantly influence the incorporation of [14C]leucine. Rat thyroid lobes were labeled with [3H]leucine for 20 min and chase-incubated for 0-4 h. In electron microscopic autoradiographs obtained immediately after labeling, the label was restricted to the follicle cells and concentrated over the endoplasmic reticulum both in controls and in specimens exposed to tunicamycin (5 micrograms/ml). After 4 h chase most radioactivity was located in the follicle lumen in controls whereas in tunicamycin-exposed lobes almost all labeled material was retained in the follicle cells. It is concluded that tunicamycin suppresses thyroglobulin secretion and that this is not due to inhibited protein synthesis.
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PMID:Effect of tunicamycin on thyroglobulin secretion. 711 56


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