ISSN:0263-6484    

DOI:10.1002/cbf.290010102

出版商:John Wiley&Sons, Ltd.    

年代:1983

数据来源: WILEY

摘要:

AbstractMicrospectrofluorometry of cell coenzymes (NAD(P)H, flavins) in conjunction with sequential microinjections into the same cell of metabolites and modifiers, reveals aspects of the regulatory mechanisms of transient redox changes of mitochondrial and extramitochondrial nicotinamide adenine dinucleotides. The injection of ADP in the course of an NAD(P)H transient produced by glycolytic (e.g. glucose 6‐phosphate, G6P) or mitochondrial (e.g. malate) substrate leads to sharp reoxidation (state III, Chance and Williams, 1955), followed by a spontaneous state III to IV transition, and an ultimate return to original redox steady state. The response to ADP alone is biphasic, i.e. a small oxidation‐reduction transient followed by a larger reverse transient. Similarities between responses to injected ATP and ADP suggest possible intracellular inter‐conversions. Sequential injections of glycolytic and Krebs cycle substrates into the same cell, produce a two‐step NAD(P) response, possibly revealing the intracellular compartmentation of this coenzyme. A two‐step NAD(P)H response to sequentially injected fructose 1,6‐diphosphate and G6P indicates the dynamic or even structural compartmentation of glycolytic phosphate esters in separate intracellular pools. The intracellular regulation and compartmentation of bioenergetic pathways and cell‐to‐cell metabolic inhomogeneities provide the basis on which the quantitative biochemistry of the intact living cell may be reconciled with these

ISSN:0263-6484    

DOI:10.1002/cbf.290010103

出版商:John Wiley&Sons, Ltd.    

年代:1983

数据来源: WILEY

摘要:

AbstractWhilein vitroincubation of dispersed cell preparations of adrenal cell types has been widely used as an experimental model, few studies have addressed the possibility that the enzymic and mechanical treatments involved may affect tissue functions. Using rat adrenal whole capsule tissue, consisting of glomerulosa cells still attached to the connective tissue capsule together with some fasciculata cells, and dispersed glomerulosa cell preparations formed by a variety of enzymic and incubation treatments, striking differences have been demonstrated between the functions of the various preparations in vitro. Under ACTH stimulation, whole capsules produced (ng per pair ± s.e.) 405 ± 35 ng aldosterone, 650 ± 60 ng 18‐hydroxycorticosterone (18‐OH‐B) and 850 ± 90 ng corticosterone. In cells dispersed by collagenase incubation followed by repeated pipetting and filtration, aldosterone and 18‐OH‐B yields under ACTH stimulation fell to values less than 10% of those produced by whole tissue, whereas corticosterone values were unchanged. Omitting the filtration step gave a less well marked decline in aldosterone and 18‐OH‐B to 50% of intact tissue values. When the tissue was not dispersed after collagenase incubation, aldosterone and 18‐OH‐B outputs were similar in the two preparations. The decline in aldosterone and 18‐OH‐B is not attributable to loss in cell–cell contact alone, since short term culture of collagenase dispersed cells on contracting collagen discs did not restore the capacity to produce these steroids, and a decline in their output also occurred in similar culture of intact capsule tissue. In acute incubations, hyaluronidase had similar effects to collagenase, whereas trypsin, papain and a bacterial protease evoked aldosterone release during the preincubation period, but did not affect subsequent yields of aldosterone and 18‐OH‐B in incubations of dispersed (but not filtered tissue) in the presence of ACTH. Chymo‐trypsin had no effect on preincubation but eliminated subsequent response to ACTH in all incubation conditions. Together with previously published data on the effects of trypsin, the results support the view that in intact rat adrenal glomerulosa tissue, aldosterone and 18‐OH‐B are sequestered into intracellular stores in the form of novel steroid‐protein complexes. These are hydrolysed by trypsin and other preoteases with consequent release of steroid, but are virtually eliminated by conventional methods of cell suspension preparations, using collagenase preincubation with subsequ

ISSN:0263-6484    

DOI:10.1002/cbf.290010104

出版商:John Wiley&Sons, Ltd.    

年代:1983

数据来源: WILEY

摘要:

AbstractThe amount of reducing equivalents from NADPH generated by glucose 6‐phosphate dehydrogenase activity (G6PD) used in mixed function oxidation (pathway I) or in reductive biosynthesis (pathway II) has been determined by cytochemical methods and microdensitometry in cells from the pars recta (PR) and distal convoluted tubule (DCT) of the kidney and from centrilobular (CL) and periportal (PP) hepatocytes from rats fed a normal or a vitamin D‐deficient diet. In the kidney, pathway I activity was similar to that of pathway II in PR, whereas in DCT pathway II was markedly predominant. Feeding a vitamin D‐deficient diet resulted in an increase in the total amount of reducing equivalents in PR and DCT. This increase was due to a rise in pathway I activity in the PR, whereas in the DCT the increase resulted from a stimulation of pathway II activity. Pathway I activity in PR was inversely correlated with plasma calcium, and was significantly decreased when calcium (1 mM) was added in vitro. In the liver the total amount of reducing equivalents generated by G6PD and both hydrogen pathways, was higher in CL than in PP hepatocytes. In CL cells, a vitamin D‐deficient diet induced a significant increase in both NADPH pathways. Furthermore, in these cells pathway I activity was inversely related to plasma calcium and was significantly lowered when 1 mMcalcium was addedin vitro. It is concluded that vitamin D status and calcium influence the production and utilization of cytosolic reducing equivalents both in kidney an

ISSN:0263-6484    

DOI:10.1002/cbf.290010105

出版商:John Wiley&Sons, Ltd.    

年代:1983

数据来源: WILEY

摘要:

AbstractCytophotometric analyses of RNA and acetylcholinesterase responses of caudate and cerebrocortical neurons of soman toxicated rats were conducted to characterize impairments in regulatory aspects of neuronal metabolism occurring in the acute phase of cholinesterase impairment. There was a severe and dose‐dependent suppression (20–60%) in neuronal acetylcholinesterase activity in both a.m. and p.m.‐treated rats; no diurnal differences were apparent in control acetylcholinesterase levels or neuronal acetylcholinesterase responsiveness to soman toxication. RNA levels, however, were markedly higher in p.m. than in a.m. saline‐treated controls. Soman depressed caudate neuron RNA contents in the afternoon, but not in the morning. Cerebrocortical neuron RNA levels were suppressed in both a.m. and p.m.‐toxicated rats, although this RNA depletion was more severe in the afternoon. These results indicate that soman can elicit marked alterations in neuronal transcriptional‐translational capabilities and that there are diurnal variations in cellular metabolic responsiveness to soman toxication. Although functional relationships between soman‐induced cholinesterase inhibition and RNA depletion remain to be elucidated, depressed RNA metabolism appears to be a maladaptive response preventing rapid regeneration of cholinesterase follow

ISSN:0263-6484    

DOI:10.1002/cbf.290010106

出版商:John Wiley&Sons, Ltd.    

年代:1983

数据来源: WILEY

摘要:

AbstractThe subcellular distribution of aldehyde dehydrogenase activity was determined in human liver biopsies by analytical sucrose density‐gradient centrifugation. There was bimodal distribution of activity corresponding to mitochondral and cytosolic localizations. At pH 9.6 cytosolic aldehyde dehydrogenase had a lower apparentK mappfor NAD (0.03 mmol l−1), than the mitochrondrial enzyme (K mappNAD = 1.1 mmol l−1). Also, the pH optimum for cytosolic aldehyde dehydrogenase activity (pH 7.5) was lower than that for the mitochondrial enzyme activity (pH 9.0), and the cytosolic enzyme activity was more sensitive to inhibition by disulfiram in vitro. Disulfiram (40 μmol l−1) caused a 70% reduction in cytosolic aldehyde dehydrogenase activity, but only a 30% reduction in mitochondrial enzyme activity after 10 min incubation. The liver cytosol may therefore be the major site of acetaldehyde oxidationi

ISSN:0263-6484    

DOI:10.1002/cbf.290010107

出版商:John Wiley&Sons, Ltd.    

年代:1983

数据来源: WILEY

摘要:

AbstractBasal lamina (BL) ofTorpedo,DiscopygeandElectrophoruselectric organs was purified in order to establish polypeptide composition and association with acetylcholinesterase (AChE). Results indicate that BL presents a distinct peptide pattern and that the A12form of AChE is directly attached to it. Comparison of the species studied demonstrated similarities both in polypeptide composition and AChE content of the purified BL. Extractions of BL with solutions of high ionic strength, guanidine–HCl and acetic acid indicated the differential solubilization of various domains of BL polypeptide

ISSN:0263-6484    

DOI:10.1002/cbf.290010108

出版商:John Wiley&Sons, Ltd.    

年代:1983

数据来源: WILEY

摘要:

AbstractLipid peroxidation rate in four different hepatomas is quite different and seems to be related to their degree of deviation, low deviation tumours displaying higher peroxidative ability. Moreover, the supernatant of the highly anaplastic Yoshida hepatoma is able to decrease the peroxidation rate in normal liver microsomes. This antioxidant ability is not dependent upon an increased level of glutathione. The concentration of reduced glutathione (GSH) declines strongly during incubation in conditions favouring lipid peroxidation. Unlike normal liver homogenates, this decline of GSH in hepatomas is not due to the transformation of GSH into oxidized glutathione (GSSG) but mostly to the increased activity of the γ‐glutamyl‐transpeptidase pat

ISSN:0263-6484    

DOI:10.1002/cbf.290010109

出版商:John Wiley&Sons, Ltd.    

年代:1983

数据来源: WILEY

摘要:

AbstractThe effects of promethazine (PM) on different aspects of the hepatotoxic action of CCl4in the rat were investigated with the objective of finding rapid and reliable indicators of hepatoprotective effects. The study was based on definitive histological assessment of liver damage caused by CCl4in the presence and absence of PM: PM (78 μmol kg−1, i.p.) protected against CCl4‐induced hepatic necrosis 24 h after a low dose of CCl4(1.3 mmol kg−1) but not against a higher dose (13.0 mmol kg−1). The large increases in plasma activities of GOT, GPT and LDH produced by dosing with CCl4were partially inhibited by the administration of PM. PM and CCl4caused a synergistic and long‐lasting decrease in body temperature (2–3°C for 8–10 h). Modifying the toxicity with PM, together with a low dose of CCl4, helped to minimize secondary effects of CCl4, to clarify the sequence of toxic events, and to assess the sensitivity of some standard tests of hepatotoxicity. Simultaneous measurement of over 20 commonly used biochemical screening tests in individual animals 3 or 6 h after treatment permitted direct correlation of a wide variety of concentrations, activities and effects. For example, liver CHCl3concentrations (as a measure of CCl4metabolism) correlate strongly with increases in diene conjugation of microsomal lipids (as a measure of CCl4‐induced lipid peroxidation); malonaldehyde production appears to be less sensitive as a measure of lipid peroxidation in vivo than diene conjugation. The changes induced in each parameter and the correlations between them are discussed with reference to the overall nature of the hepatotoxic reaction and its m

ISSN:0263-6484    

DOI:10.1002/cbf.290010110

出版商:John Wiley&Sons, Ltd.    

年代:1983

数据来源: WILEY

ISSN:0263-6484    

DOI:10.1002/cbf.290010111

出版商:John Wiley&Sons, Ltd.    

年代:1983

数据来源: WILEY