摘要:

AbstractInsulin action is thought to be mediated by an inositol‐, glucosamine‐ and galactose‐containing oligosaccharide liberated by phosphodiesterase hydrolysis of a glycosyl‐phosphatidylinositol. This oligosaccharide inhibits insulin biosynthesis and secretion in pancreatic islets. In the present study, two main glycolipids (peak I and II) were resolved by sequential TLC of lipids extracted from islet cells labelled with tritiated glucosamine, galactose or myristate. The two glycolipids displayed comparable sensitivity to β‐galactosidase but differed from one another by their sensitivity to phosphatidylinositol‐specific phospholipase C. Moreover, structural heterogeneity within each peak was suggested by their partial resistance to nitrous acid deamination. These findings support the presence in islet cells of glycolipids similar to those currently considered as a possible postreceptor target for insulin in othe

ISSN:0263-6484    

DOI:10.1002/cbf.290090202

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractThein vitroeffect of 2‐(diethylamino)‐7‐ethoxychromone (RC39XVIII) on human platelet aggregation induced by several agonists and on thromoboxane B2formation, granule release and intracellular cAMP elevation has been studied. The chromone‐derivative exerts a dose‐dependent inhibitory effect on aggregation producted by U46619, arachidonic acid, thrombin, collagen and ADP. RC39XVIII inhibits aggregation, TxB2formation and granule release in parallel. Moreover the drug potentiates cAMP accumulation induced by iloprost and forskolin. The drug also inhibits soluble cAMP phosphodiesterase in dose‐dependent manner. No effect on adenylate cyclase activity measured in platelet membranes

ISSN:0263-6484    

DOI:10.1002/cbf.290090203

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractA cell line derived from human embryonic epithelium (EUE cells) shows an enhanced expression of a 33 kDa protein when adapted to grow in a hypertonic medium containing 0·246MNaCl (1·8 × the isotonic concentration). The maximum amount of this protein, followed by SDS‐PAGE electrophoresis, was found after 4 days of adaptation; thereafter, the protein band remained fairly constant up to 30 days. When the cells were transferred back to a medium containing 0·137MNaCl (isotonic medium), the protein pattern reverted to that of control cells. This protein is mainly localized in the cytosol, although a small part is associated with the 150 000gpellet and needs detergents to be extracted. The molecular weight and the cellular location suggest a possible analogy with the so‐called amphitropic proteins, that are known to interact with both the epidermal growth factor receptor and hydrophobic structures, such as the membrane phospholipids and the cytoskeletal com

ISSN:0263-6484    

DOI:10.1002/cbf.290090204

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractThis study focused on the potent cytotoxic effect that mitoxantrone produces on Ehrlich ascites tumour cells. Host mice treated with mitoxantrone showed a life span three times higher than control non‐treated host mice. Mitoxantrone also showed a potent cytotoxic effect on Ehrlich cells incubatedin vitrofor only a few hours. Studies on the effect of mitoxantrone on a plasma membrane redox system showed that mitoxantrone inhibits this activity, which is apparently related to cell proliferatio

ISSN:0263-6484    

DOI:10.1002/cbf.290090205

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractThe damage to articular cartilage, characteristic of arthritic disease, is usually ascribed to increased degradative activity by enzymes or free radicals from locally activated cells.1–3We propose that inhibition of matrix synthesis, and consequential impairment of the natural repair process, may be at least as important in chronic joint diseas

ISSN:0263-6484    

DOI:10.1002/cbf.290090206

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractThe biochemical and quantitative cytochemical assays of the activity of uridine diphosphoglucose dehydrogenase (UDPG‐D) have produced perplexing results. It is now shown that the perplexity may be due to the possibility that the coenzyme (NAD) required for UDPG‐D activity, may be acting as a substrate for a second dehydrogenase, namely xanthine dehydrogenase, which may utilize NAD as its substrate. The activity of UDPG‐D can be distinguished selectively by the pH of its optimal activity and by decreasing the concentration of the coenzyme used in the

ISSN:0263-6484    

DOI:10.1002/cbf.290090207

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractIsolated rat hepatocytes exposed to CCl4showed a stimulated formation of malonaldehyde after only 30–60 min incubation. Conversely, the onset of hepatocyte death was a relatively late event, being significant only after 2–3 h of treatment. A cause–effect relationship between the two phenomena has been demonstrated by using hepatocytes isolated from rats pretreated with alpha‐tocopherol. Comparable results were obtainedin vivowhere supplementation with alpha‐tocopherol 15 h before CCl4dosing induced a partial or complete protection against the drug's necrogenic effect, depending on the concentration of the haloalkane used. Moreover, the vitamin supplementation prevented the CCl4‐induced increase of liver total calcium content, probably by blocking alterations in the liver cell plasma membranes due to lipid p

ISSN:0263-6484    

DOI:10.1002/cbf.290090208

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractThe chromatin extracted from rat hepatocytes of different ages has been shown to contain a phospholipid fraction representing 0·47–0·59 per cent of total chromatin in newborn animals and 0·22 per cent in 45‐day‐old animals. No such age‐related differences are observed in the nuclei.The phospholipid composition of the nuclei at different ages shows a higher level of sphingomyelin and a lower level of phosphatidylserine in newborn than in adult animals. Chromatin phospholipids have a completely different composition from that of nuclei with respect to age, particularly in newborn rats, where there is a decrease in phosphatidylcholine and an increase in phosphat

ISSN:0263-6484    

DOI:10.1002/cbf.290090209

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractThiol levels were measured in three cell lines derived from rat hepatocytes with different growth rates and degrees of tumorigenicity: IAR20 having normal epithelial morphology and no tumour forming ability: IAR6.1 being a chemically‐transformed malignant cell line; and IAR6.1RT7 derived from an epithelial tumour obtained after injection of IAR6.1 cells into a syngeneic animal. The mean levels of GSH, GSSG, low molecular weight thiols (LMWT), macromolecular thiols (MT) and total reactive protein sulphur (TRPS), expressed as nmoles‐SH mg−1protein, were found to be 25·5, 7·5, 50·1, 114·5 and 143·6 respectively for IAR20; 37·6, 3·9, 65·4, 126·8 and 148·4 for IAR6.1; 17·2, 4·4, 52·3, 141·0 and 168·2 for IAR6.1RT7.Cultures were treated with D, L‐buthionine‐S, R‐sulphoximine (BSO) to cause greater than 70 per cent depletion of GSH and the measurements of cellular thiols repeated. Although treatment with BSO caused a substantive decrease in the LMWT fraction, there were no major changes in macromolecular thiols or in total reactive protein sulphur. The respective mean values for LMWT, MT and TRPS (expressed as nmoles‐SH mg−1protein) were 19·4, 109·8, 136·3 for IAR20; 17·2, 119·3, 143·6 for IAR6.1; 21·6, 150·7 and 163·5 for IAR6.1RT7.It is concluded that significant differences in thiol levels exist between the three rat liver cell lines studied. However, severe acute depletion of GSH is not reflected by changes in the levels of macromolecular thiols which suggests that there is only a slow equilibr

ISSN:0263-6484    

DOI:10.1002/cbf.290090210

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractThe incorporation of32Pi into phospholipids was studied in Friend erythroleukemia cells either induced or not to erythroid differentiation with 4 mM hexamethylenebisacetamide (HMBA). The effect of the differentiating agent on the recovery of radiolabelled phospholipids was compared in whole cells, isolated nuclei and nuclear matrix afterin vivolabelling for 1 hr. The procedure employed for the isolation of nuclei was demonstrated to allow only negligible lipid redistribution caused by cell manipulations. Among the lipids extractable from nuclei, acidic phospholipids, and particularly polyphosphoinositides, were more represented than in whole cells, while small differences were found in the other phospholipid classes examined. The comparison between the uninduced and induced condition showed that the relative amounts of nuclear inositol lipids were modified by HMBA treatment of the cells, with a decreased recovery of phosphatidylinositol 4,5 bisphosphate.These results indicate that phosphatidylinositol and its phosphorylation products synthesizedin vivoshow a different metabolism in nuclei and whole cells. They appear to be tightly bound nuclear components, also present in membrane‐deprived nuclei and nuclear matrix, and are probably related to the nuclear events involved in erythroid differentiatio

ISSN:0263-6484    

DOI:10.1002/cbf.290090211

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY