Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P01275 (glucagon)
 26,492 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The specificity of thermomycolase toward glucagon and the oxidized A and B chains of insulin was investigated. Extensive digestion of glucagon occurred when conducted at pH 7.0 and 45 degrees C for 40 min, whereas hydrolysis of only three peptide bonds occurred at pH 7.0 and 28 degrees C for 5 min. A similar situation was observed for the oxidized B chain of insulin, which exhibited only a single major cleavage after 5 min at 25 degrees C. No well-defined specificity for particular amino acid residues was evident, but ready hydrolysis of peptide bonds occurred within sequences containing non-polar residues. This endoproteinase must therefore possess an extended hydrophobic binding site for polypeptides. Thermomycolase hydrolysed acetylalanylalanylalanine methyl ester and elastin-Congo Red at 22 and 8.5 times the rate of porcine elastase respectively. A limited degradation of native collagen and significant hydrolysis of benzyloxycarbonyl-Gly-Pro-Leu-Gly-Pro were suggestive of some collagenase-like activity. No keratinase activity was apparent.
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PMID:The substrate specificity of thermomycolase, an extracellular serine proteinase from the thermophilic fungus Malbranchea pulchella var. sulfurea. 0 73

Adult rat parenchymal hepatocytes can be maintained in primary culture on floating collagen membranes of prolonged periods of time. In this system the enzyme tyrosine aminotransferase is induced by glucagon, (10(-6) to 10(-8) M) hydrocortisone (10(-5) to 10(-8) M), and cyclic adenosine 3':5'-monophosphate (cAMP) (10(-4) to 10(-5) M). Epinephrine (10(-4) M) induces the enzyme only in the presence of hydrocortisone. Addition of actinomycin D inhibited the induction of tyrosine aminotransferase by hydrocortisone and cAMP. Maintenance of the cultured hepatocytes in the presence of glucose (3g/liter) results in partial suppression of the inducing effects of glucagon and cAMP. Cyclic quanosine 3':5'-monophosphate does not mimic the effects of glucose. These results demonstrate that the phenomenon of glucose repression of enzyme induction, demonstrated in vivo in mammalian liver, is independent of changes in levels of serum hormones, which occur in vivo as a result of glucose administration. This study also demonstrates that glucose repression is not mediated by changes in intracellular levels of cAMP and cyclic quanosine 3':5'-monophosphate.
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PMID:Hormonal regulation and the effects of glucose on tyrosine aminotransferase activity in adult rat hepatocytes cultured on floating collagen membranes. 2 9

Liver parenchymal cells were isolated from adult rats and cultured in collagen-coated plastic petri dishes in serum-free medium. Glucagon induced 4- to 5-fold increases in alpha-aminoisobutyric acid (AIB) transport within 6 hr. Dexaemthasone had no direct effect on AIB transport but greatly potentiated the induction by glucagon ("permissive effect"). Levels of 3':5'-cyclic AMP increased 30- to 100-fold within 30 min after glucagon addition to cultures that had been treated with dexamethasone, and dibutyryl cyclic AMP mimicked the glucagon induction of AIB transport. Additionally, dexamethasone exerted a "permissive" effect on induction of AIB transport by dibutyryl cyclic AMP, whereas the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine induced AIB transport only in cultures that had been treated with dexamethasone. Induction of AIB transport was not dependent upon the continued presence of glucagon, but induced AIB transport activity decayed to uninduced levels within 3-4 hr after glucagon removal. The protein syntesis inhibitors puromycin and cycloheximide inhibited both induction and decay of glucagon induced AIB transport, but had a stabilizing effect if added once induction or decay had commenced. Unlike cycloheximide, the inhibitory effect of puromycin on the glucagon induction of AIB transport was reversible.
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PMID:Induction and decay of glucagon-induced amino acid transport in primary cultures of adult rat liver cells: paradoxical effects of cycloheximide and puromycin. 18 42

Rat hepatocytes have been studied in suspension culture for 10-h periods. Levels of extractable lactate dehydrogenase (LDH) have been measured in these hepatocytes at hourly intervals in order to note the balance between biosynthesis and degradation of this enzyme. Newly synthesized LDH has been measured by following the rate of incorporation of [3H]leucine into radiochemically pure LDH of high specific catalytic activity as isolated by a rapid affinity chromatographic procedure. The effects of the addition of physiological concentrations of the following hormones at the beginning of 10-h culture periods immediately following preparation of the hepatocytes by the collagen perfusion procedure have been recorded. The hormones triiodothyronine (T3), insulin, glucagon, and dexamethasone have been added singly or in combination. The culture medium has supplied variable amounts of these hormones in the 10% of fetal calf (or other) serum added, and the hepatocytes themselves have provided intracellular amounts of hormones. In addition to the added hormones, N6,O2'-dibutyryl cyclic AMP (Bt2cAMP) has also been studied. Control suspensions of hepatocytes show reproducible initial levels of extractable LDH which are maintained or slightly increased during 10 h. Such control systems also incorporate [3H]leucine into total protein and into highly purified LDH at reproducible rates during 10 h of incubation. The effects of added hormones on LDH lavels are as follows: (a) T3 causes about a 2-fold increase in LDH at 7 to 8 h in hepatocytes from young adult animals, an effect which is lowered in either younger or older animals or in thyroidectomized animals. (b) Insulin leads to a similar increase in LDH at 5 to 6 h and a falling off at 8 to 10 h. (c) Glucagon also causes an approximate doubling of the amount of extractable LDH during a 10-doubling of the amount of extractable LDH during a 10-h period. (d) Dexamethasone does not produce an increase. (e) Bt2-cAMP produces an effect indistinguishable from that of glucagon. Paired combinations of these hormones fail to produce an additive response in any case. The combinations of T3 plus dexamethaseon and insulin plus dexamethasone lead to significant reductions in levels of extractable LDH when compared to the single hormone effects cited above. With respect to rates of synthesis of total protein as measured by [3H]leucine incorporation, only glucagon, glucagon plus Bt2-cAMP, glucagon plus insulin, T3 plus Bt2cAMP, and T3 plus insulin produce significant increases during a 10-h period. However, when [3H]leucine incorporation into highly purified LDH is measured as an index of LDH biosynthesis, T3, insulin, and glucagon consistently increase the biosynthetic rates during a 10-h period. Bt2cAMP produces a smaller increase. Dexamethasone fails to produce any significant change when compared to controls. Paired combinations of hormones again do not produce any additive effect on LDH biosynthesis when the hormone producing the higher level is taken as the reference...
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PMID:Hormonal effects on the biosynthesis of lactate dehydrogenase in rat hepatocytes. 22 47

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.
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PMID:Hormonal control of bone collagen synthesis in vitro. Effects of insulin and glucagon. 40 59

Twenty previously pancreatectomized dogs were heterotopically transplanted with duct-ligated allografts. Sixteen of the grafts were preserved for 24 hours, nine with continuous hypothermic albumin perfusion, seven with hypothermic storage. Five dogs died from early postoperative bleedings. Fifteen surviving dogs had a satisfying endocrine function assessed by blood glucose and serum insulin during fasting and after glucose load. In six dogs the glucagon release from the graft was investigated and significant release was evident in all dogs. A high release was found after L-arginine stimulation. The endocrine function was satisfying after 24 hour preservation both with hypothermic storage and continuous hypothermic albumin perfusion. During such perfusion the pancreas became very oedematous. This did not influence on the outcome of the transplantation. The grafts were enlarged four to eight days after transplantation. Oedema, fibrotic changes and collagen depositions in the interstitial tissue were observed in light microscopy. These changes seemed to come earlier in glands preserved for 24 hours. Islet cells were identified in all functioning grafts and seemed histopathologically and ultrastructurally unchanged. A duct-ligated pancreatic segment was allografted to one diabetic patient in a pilot experiment. There was a satisfying endocrine function for 40 days. After that the graft became necrotic due to thrombus formation.
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PMID:Studies on the duct-ligated pancreas as allograft for islet cell function. 110 97

Isolation and culture techniques for hepatocytes from whole livers of the cynomolgus monkey, Macaca fascicularis, are described. Hepatocytes were isolated by two-step perfusion of livers, using collagenase with hyaluronidase; fructose and trypsin inhibitor were included to reduce cell loss. Yields from a single liver average 4 X 10(9) cells with viabilities of 90.8 +/- 5.7%. Cells, plated on collagen substrates, were assessed for changes in morphology and various marker enzyme activities over a period of 7 d in culture. Cells exhibited a morphology similar to that observed for this species in vivo; little change in attached and spread cells was observed over the length of time monitored. Enzyme activities for catalase, succinate dehydrogenase, and tyrosine aminotransferase were observed to decrease significantly (though considerable activity remained), whereas acid phosphatase and 5'-nucleotide phosphodiesterase remained unchanged. Activity of cytochrome P-450 reductase was observed to increase slightly for the first 2 d, then decrease to about 60% of initial levels. Activity of alpha-mannosidase was stable for 4 d but was observed to be increased at Day 7. Cells were observed to retain metabolic responsiveness, demonstrated by glucose production by both gluconeogenesis and glycogenolysis in response to glucagon stimulation. The monkey hepatocytes obtained by methods described here thus retain hepatocellular morphology and activity through at least 1 wk in culture without medium or culture modification.
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PMID:Isolation and culture of hepatocytes from the cynomolgus monkey (Macaca fascicularis). 197 77

Liver cells of new-born rats, which were found to be able to form spheroidal aggregates when cultured on a nonadherent plastic substratum, were studied under various conditions of culture, mainly by adding different nutrients and growth factors to the culture medium. Analysis of hepatocyte-specific functions was carried out by immunoprecipitation to detect specific proteins newly secreted by liver cell spheroids on different days of culture. When no supplement was added to culture medium, the secretion of albumin and transferrin by liver cell spheroids was no longer detectable after 2 weeks of culture. When dexamethasone, glucagon, insulin, and EGF were added to culture medium, the secretion of albumin and transferrin remained detectable at least until 60 days of culture. This was even more striking when trace elements were added in addition to the three hormones and EGF. The effects of addition of these various factors to culture medium were also detectable with respect to alpha-FP secretion. Even after 54 days of culture in total supplemented medium, these liver cell spheroids could be transferred on a collagen-coated plastic substratum to form a monolayer of uniform liver parenchyma-like cells. The presence of extracellular matrix-like material was observed on the surface of cell spheroids. This could be responsible for attachment and fusion between cell spheroids. Thus, liver cell spheroids cultured in total supplemented medium ensured cell attachment to a biological matrix and cell-cell contact, which is thought to help maintain cell differentiation. Liver cell spheroids offer the possibility of toxicological and pharmacological studies as well as cultures in biomatrix and coculture systems. In addition these liver cells can be used for experiments in liver cell transplantation.
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PMID:Long-term culture of rat liver cell spheroids in hormonally defined media. 218 40

Alcoholic hepatitis is a necrotizing, often inflammatory, process that is an important precursor to the development of cirrhosis. Acetaldehyde, which is derived from alcohol by the action of alcohol dehydrogenase, is apparently the most important factor leading to alcohol-induced liver injury. Other factors of importance in determining the appearance and rate of progression of liver diseases in patients who are chronic alcoholics include sex, nutritional status, and various immunologic reactions. In addition, there is an incompletely understood genetic predisposition to the development of alcoholic hepatitis. Several histologic features found in patients with alcoholic hepatitis have been evaluated in efforts to determine which are of prognostic value. The predominance of the alcohol-induced injury in zone III of the hepatic lobule; deposition of collagen, IgA, and fibronectin in the space of Disse; defenestration of endothelial cells; and transformation of lipocytes and myofibroblasts to fibroblasts have been investigated. Prolongation of the prothrombin time and marked elevation of serum bilirubin levels are indicators of a subgroup of patients with alcoholic hepatitis who have a poor prognosis, especially if there is also evidence of hepatic encephalopathy. Supportive care and abstinence from alcohol are the foundations of therapy. Corticosteroid therapy appears to decrease the number of early deaths in patients with severe alcoholic hepatitis. Other experimental approaches to therapy include the use of propylthiouracil, anabolic-androgenic steroids, and insulin and glucagon.
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PMID:Alcoholic hepatitis: pathogenesis and approaches to treatment. 223 74

Liver cells isolated from newborn rats and seeded on a non-adherent plastic substratum were found to spontaneously re-aggregate and to form, within a few days, spheroidal aggregates that eventually reached a plateaued diameter of 150-175 micron. Analyses on frozen sections from these spheroids by immunofluorescence microscopy using antibodies to various cytoskeletal elements and extracellular matrix components revealed a sorting out and a histotypic reorganization of three major cell types. A first type consisted of cells that segregated out on the aggregate surface forming a monolayer cell lining; a second type was identified as hepatocytes that regrouped in small islands often defining a central lumen; and a third group of cells reorganized into bile duct-like structures. This intercellular organization in the aggregates was paralleled by the accumulation of extracellular matrix components (laminin, fibronectin, and collagen) and their deposition following a specific pattern around each cell population structure. Determinations of albumin secretion and tyrosine aminotransferase induction by dexamethasone and glucagon at various times after the initiation of the cultures revealed a maintenance of the hepatocyte-differentiated functions for at least up to 2 mo at the levels measured at 3-5 d. It is concluded that cells dispersed as single cells from newborn rat liver conserve in part the necessary information to reconstruct a proper three-dimensional cyto-architecture and that the microenvironment so generated most likely represents a basic requirement for the optimal functioning of these differentiated cells.
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PMID:Spheroidal aggregate culture of rat liver cells: histotypic reorganization, biomatrix deposition, and maintenance of functional activities. 241 40


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