摘要:

AbstractThe onset of the lipoprotein secretory block provoked by CCl4in the whole animal was monitored after purification of liver Golgi membranes. Both lipid transit through the apparatus the apparatus and hexosylation of the lipoprotein are markedly inhibited 5–15 min after poisoning. Pre‐treating the animal with alpha‐tocopherol, shown to prevent lipid peroxidation without modifying the covalent binding due to CCl4metabolites, affords little protection against lipid accumulation in the Golgi, but total preservation of galactosyl transferase activity. While haloalkylation therefore appears to be the major mechanism of damage in the early phases of CCl4‐induced derangement of lipid secretion, lipid peroxidation is probably more involved later, this is indicated by the marked, though never complete, protection against fatty liver afforded at 24 h after CCl4poisoning by supplementation of the membrane with alpha‐t

ISSN:0263-6484    

DOI:10.1002/cbf.290080102

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

摘要:

AbstractWe have studied the effects of several different macronutrients on the kinetic behaviour of rat renal glucose 6‐phosphate dehydrogenase (G6PDH) and 6‐phosphogluconate dehydrogenase (6PGDH). Rats were meal‐fed with high‐carbohydrate/low‐protein, high‐protein/low‐carbohydrate and high‐fat diets. High‐protein increased renal G6PDH and 6PDGH activities by 66 per cent and 70 per cent respectively, without significantly changing theKmvalues of either and each Hexose monophosphate dehydrogenase activity increased steadily, reaching a significant difference on day 4. A rise in carbohydrate or fat in the diets, produced no significant change in either the activity or the kinetic parameters,VmaxandKmof the two dehydrogenases. In addition, the administration of a high‐protein diet for 8 days significantly increased both the pentose phosphate pathway flux (92·6 per cent) and the kidney weight (35 per cent), whereas no significant changes in these parameters were found when the animals were treated with the other diets. Our results suggest that an increase in the levels of dietary protein induces a rise in the intracellular levels of these enzymes. The possible role of this metabolic pathway in the kidneys under these nutritional conditio

ISSN:0263-6484    

DOI:10.1002/cbf.290080103

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

摘要:

AbstractPapillary necrosis was observed in the kidneys of rats, 72 h after receiving a single injection of bromoethylamine (BEA). This effect was associated with renal glutathione (GSH) depletion 1 h after the administration of BEA. Stimulation of renal GSH synthesis by pretreatment of the animals either with glutamine + glucine + cystine orN‐acetyl‐L‐cysteine was attempted. Low doses of these precursors administered previously to BEA, respectively, decreased or abolished the GSH depletion. Nevertheless, both pretreatments failed to modify the magnitude of renal papillary necrosis. High doses of these precursors did not modify the BEA‐induced GSH depletion, but they significantly increased GSH levels 24 h after BEA administration. At this time, although a smaller intensity of renal papillary necrosis was observed with the amino acid mixture pretreatment,N‐acetyl‐L‐cysteine pretreated rats showed no papillary necrosis. It is suggested that the observed protective effects against BEA‐induced renal papillary injury may be ascribed in some measure, to a mechanism ind

ISSN:0263-6484    

DOI:10.1002/cbf.290080104

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

摘要:

AbstractThe anti‐diuretic hormone, arginine vasopressin (AVP) stimulates the activity of Na+K+ATPase in the rat renal medullary thick ascending limb of Henle's loop (mTAL). Atrial natriuretic factor (ANF) has been suggested to exert a tubular effect on the mammalian nephron, perhaps in part, by interacting with other hormones. In the present study, we investigated the effect of rat ANF with and without AVP upon mTAL Na+K+ATPase activity using cytochemical methods. ANF alone failed to inhibit or stimulate Na+K+ATPase activity in mTAL at any of the concentrations tested (10 nmol–0·1 pmol l−1). Unlike the rat hypothalamic digitalis‐like factor, ANF (10 nmol–10 fmol l−1) did not inhibit Na+K+ATPase activity after stimulation with AVP (l fmol l−1) for either 4 or 10 min. The results suggest that ANF does not exert an effect on mTAL, either alone or in conjun

ISSN:0263-6484    

DOI:10.1002/cbf.290080105

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

摘要:

AbstractPidepletion of proximal tubule cells isolated from mouse kidney results in a decrease in the cell content of fructose‐2,6‐bisphosphate and an increase in the rate of gluconeogenesis from pyruvate, malate and succinate. Gluconeogenesis from glycerol is unaffected by Pidepletion. Introduction of fructose‐2,6‐bisphosphate into the cytosol of ATP‐permeabilized cells is accompanied by a fall in gluconeogenesis.The presence of external Ca2+stimulates gluconeogenesis. When cytosolic Ca2+is raised to 1·8 μM by permeabilization, the resealed cells still require 2·5 mM Ca2+in the bathing medium in order to perform gluconeogenesis at the maximum rate. Cells permeabilized in the presence of cAMP show a decreased rate of glucose production. Phorbol ester stimulates gluconeogenesis provided that the phorbol treatment is performed in the absence of Ca2+ions.It is suggested that Pidepletion may stimulate pyruvate carboxylase activity and facilitate the entry of certain gluconeogenic substrates into mitochondria. It is also proposed that important aspects of the control of renal gluconeogenesis by parathyroid hormone are mediated by prot

ISSN:0263-6484    

DOI:10.1002/cbf.290080106

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

摘要:

AbstractFructose‐1, 6‐diphosphate (FDP) decreases the effect of ethanol on Ca++entry and inhibits the ethanol‐stimulated phosphate efflux in rat heart slices. FDP also inhibits the ethanol‐stimulated [36Cl−]‐uptake by rat brain microvesicles and affects the isolated GABA‐receptor in a way opposite to that of ethanol. Thein vivoeffects of FDP include a dose‐dependent decrease in ethanol‐induced gastric ulcers and a decrease in the serum transaminase levels raised by chronic ethanol administration. Other central actions of ethanol such as diuresis, narcosis, dependence and withdrawal symptoms are also co

ISSN:0263-6484    

DOI:10.1002/cbf.290080107

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

摘要:

AbstractTetrahymena pyriformisGL cells pretreated (imprinted) and not pretreated with insulin showed dissimilar quantitative relations of FITC‐insulin binding. Displacement of FITC‐insulin by unlabelled insulin was considerably less in the control than in the imprinted series. The curve for saturation of the binding sites with FITC‐insulin resembled a true saturation curve. The imprinted cells bound considerably more hormone in a shorter time than the control cells at identical levels of exposure. The dissociation of bound hormone from the imprinted cells increased over the control at 23°C, and to a still greater degree at 4°C. The effect of the pH of the medium on the dissociation of bound FITC‐insulin also differed between the imprinted and not imprinted cells. Thus the proposed cytofluorimetric assay of binding kinetics demonstrated the actual conditions of receptor activity, and indicated that the induced insulin binding sites ofTetrahymenabehaved similarly to ‘classical

ISSN:0263-6484    

DOI:10.1002/cbf.290080108

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

摘要:

AbstractWhen polymorphonuclear leukocytes (neutrophils) and soluble or particulate matter interact, the cells produce superoxide anions (O2−) and hydrogen peroxide (H2O2). The chemotactic peptide formylmethionyl‐leucylphenylalanine (FMLP) induced a very weak response in normal neutrophils. The cellular response was changed, however, as a result ofin vitroaging of the cells, i.e. the magnitude of the response was increased following storage of the cells at 22°C for up to 120 min, in the absence of any stimulus, and before the addition of the peptide. When phorbol myristate acetate was used as a stimulus, there was a pronounced production of O2−and H2O2, but no change in magnitude as a result ofin vitroaging. When neutrophil cytoplasts (granule‐free vesicles of cytoplasm enclosed by plasmalemma) were exposed to the peptide FMLP of PMA, the vesicles produced both O2−and H2O2. There was, however, no increase in oxidative metabolite production in cytoplasts as a result ofin vitroaging when either FMLP or PMA was used as a stimulus. The results thus indidate that mere incubation at room temperature primed the cells to increase their production of oxidative metabolites as a result of spontaneous exposure of hidden receptors. The fact that no such effects were observed with cytoplasts indicates that spontaneous receptor recruitment is a granule‐depen

ISSN:0263-6484    

DOI:10.1002/cbf.290080109

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

摘要:

AbstractNeonatal smooth muscle cells were seeded in standard plastic Falcon flasks, on top of another 2‐month‐old culture of the same cell population or on top of an acellular matrix prepared by removal of these cells. The effect of both complete and acellular layers on the production of elastin, collagen and total extracellular matrix (EM) proteins as well as on cell division was measured. Compared with the standard population grown on plastic, the complete cell layer almost completely prevented the newly seeded cells from dividing. The acellular matrix did not affect cell doubling but caused a distinct decrease in the production of EM compone

ISSN:0263-6484    

DOI:10.1002/cbf.290080110

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

摘要:

AbstractSkin fibroblasts from chick embryos of 7 and 14 days incubation have been tested for their ability to bind, internalize and degrade [3H]‐hyaluronan. Seven‐day fibroblasts internalize and degrade a greater amount of labelled hyaluronan than 14‐day cells. The implications of these findings in the regulation by the fibroblasts of extracellular matrix composition in glycosaminoglycans are disc

ISSN:0263-6484    

DOI:10.1002/cbf.290080111

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY