Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.3.9 (glucose-6-phosphatase)
 3,081 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The significance of glucose-6-phosphatase (G6P) expression by bile duct-like cells proliferating during hepatocarcinogenesis in the histogenesis of hepatocellular carcinoma is not clear. To this end, we measured the histochemical and biochemical activity of G6P in normal rat liver, and in rat livers in which bile duct-like proliferation was induced by either hyperplastic (bile duct ligation for 14 days or feeding alpha-naphthylisothiocyanate for 28 days) or neoplastic (feeding a choline-devoid diet containing 0.1% ethionine for 60 days) regimens. In normal, hyperplastic, and preneoplastic livers, G6P histochemical activity was confined to the hepatocytes; proliferated bile duct-like cells, like normal bile ducts, did not display visible G6P staining. When the enzyme activity was determined biochemically, however, hydrolysis of glucose-6-phosphate was observed in both parenchymal and nonparenchymal liver cells isolated from all experimental animals. In elutriated nonparenchymal fractions, G6P activity was directly proportional to the number of cells positive for gamma-glutamyl transpeptidase and cytokeratin no. 19 (markers of bile duct cells) and inversely proportional to the number of cells positive for vimentin (marker of mesenchymal cells). These results indicate that, while by light microscopy hepatic G6P histochemical activity is detectable only in the hepatocytes, the biochemical activity is also expressed in proliferating bile duct-like cells. However, the nonparenchymal activity is observed during both neoplastic and hyperplastic liver growth, thus indicating that the presence of this enzyme in bile duct-like cells proliferating during hepatocarcinogenesis should not necessarily be construed as supporting their stem cell nature nor their neoplastic commitment.
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PMID:Distribution of glucose-6-phosphatase activity in normal, hyperplastic, and preneoplastic rat liver. 168 20

The cellular origin of estrogen-induced kidney tumors in male Syrian hamsters has been repeatedly the subject of controversy. Several authors have proposed that the tumors arise from proximal tubules, from a combination of tubular and interstitial stromal cells, or solely from interstitial cells. Because of the model character of this tumor for hormone-associated cancer, it was further investigated in this study with respect to morphology, enzyme and intermediate filament pattern, the expression of alpha-smooth muscle actin and the extracellular matrix proteins fibronectin and tenascin. These analyses were carried out with early and late tumors as well as metastases to determine possible changes in expression of biochemical parameters during the development and progression of this neoplasm. The enzyme histochemical and intermediate filament patterns were usually the same as those described previously for proliferative foci and early tumors, i.e. highly elevated activities of glucose-6-phosphate dehydrogenase, adenylate cyclase and alkaline phosphatase, a lack of glucose-6-phosphatase and gamma-glutamyltransferase and coexpression of vimentin and desmin, alpha-smooth muscle actin could not be detected in early lesions. In five of 24 advanced tumors inclusions of kidney tubules were found which showed various degrees of alteration in their morphology and enzyme histochemical pattern, but were often directly connected with tubular segments of normal appearance outside the tumor. Like the normal tubules, the enclosed tubular segments were strongly positive for cytokeratin but never expressed vimentin or desmin. Among the 24 tumors studied, two contained cysts which expressed cytokeratin and sometimes also vimentin but not desmin. The enzyme histochemistry of the cells lining the cysts was similar to that of the surrounding tumor mass, except adenylate cyclase was lacking and alkaline phosphatase was not uniformly distributed. In tumors containing cytokeratin-positive cysts, there often were cytokeratin-positive, vimentin-negative and desmin-negative tumor formations in close contact to these cysts. With the exception of cyst formation, the pattern of metastases were identical to that of the primary tumors. All large tumors and the main component of the metastases expressed vimentin, desmin and fibronectin. Mesothelia surrounding metastatic tumor complexes were positive for vimentin, desmin, alpha-smooth muscle actin, fibronectin, cytokeratin and tenascin. It was concluded from these and previous observations on early stages of tumor development that the estrogen-induced hamster kidney tumor originates from mesenchymal interstitial cells (probably pericytes) which may rarely acquire an epithelial phenotype by metaplastic transformation during tumor progression.
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PMID:Changes in the cellular phenotype and extracellular matrix during progression of estrogen-induced mesenchymal kidney tumors in Syrian hamsters. 171 81

Histamine release from mast cells is intimately related with degranulation. When basic histamine releasers such as compound 48/80 were applied extracellularly to isolated rat mast cells by means of microelectrophoresis, localized degranulation was evoked near the tip of micropipet in a few seconds. In response to the second electrophoretic application at the opposite side of the membrane of the same mast cells, similar local degranulation was induced. This fact clearly indicates that local degranulation does not damage mast cells to the extent of blocking following degranulation. As intracellular electrophoretic application of compound 48/80 caused a swelling of mast cell, although no degranulation was elicited. When antigen-antibody reaction was induced in a single rat mesentery mast cell by means of microelectrophoresis, the application of antigen was made extracellularly or intracellularly. At the site of extracellular application, localized degranulation and histamine release were evoked. Histamine release was evidenced by the disappearance of histamine fluorescence in the degranulated area. Neither degranulation nor histamine release was induced by intracellular application of antigen. In freeze-fracture electronmicroscopy of the resting rat mast cells, intra-membrane particles (IMPs) were randomly distributed on the plasma membrane. When sensitized cells were exposed to antigen, IMPs were markedly dispersed so as to surround bulging regions of the membrane elicited by swollen granules. As the particles gathered at the periphery of the bulges, actually no particle was seen on the protuberant region. When rat mast cells loaded with quin 2 were exposed compound 48/80 in a Ca-free medium, a marked increase of quin 2 fluorescence was noticed, indicating that Ca2+ was released from intracellular Ca store. The binding of 45Ca was at its peak in the fractions where the highest activity of glucose-6-phosphatase, a marker enzyme for the endoplasmic reticulum, when organelles of mast cells were fractionated. This may indicate that intracellular Ca store is endoplasmic reticulum. It has been shown that microfilaments, and microtubules play some important roles in histamine release from rat mast cells. When permeabilized mast cells were stimulated with Ca2+, a translocation of protein kinase C from cytosol to membrane fraction was observed. This leads to phosphorylation of vimentin, one of intermediate filaments. In membrane skeletons of rat mast cells, alpha- and beta-fodrin, ankyrin and actin were found by means of western blotting analysis. It was supposed that membrane skeleton may be useful as a barrier between the plasma membrane and the granule membrane.
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PMID:[Development of the research in the field of histamine release]. 751 63