摘要:

AbstractThe effect of tellurite on ATPase activity of the contractile membrane protein in human erythrocytes was studied. Tellurite, even at a concentration of 0·01 mM, inhibited 25 per cent of the saponin‐stimulated ATPase activity of the contractile membrane protein; the inhibition increased with increasing tellurite concentration, and was reversible. On the other hand, in erythrocytes preincubated with tellurite, the ATPase activity of the membrane contractile protein, non‐stimulated by saponin, increased, and the increase was further enhanced by washing the erythrocytes. The behaviour is analogous to the tellurite effect on erythrocyte morphology: incubation of erythrocytes with tellurite caused morphological changes which were more pronounced after removing the tellurite by washing. The complex effect of tellurite is discu

ISSN:0263-6484    

DOI:10.1002/cbf.290090403

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractWe examined the direct effects of unsaturated fatty acids, oleic (18:1 n‐9), linoleic (18:2 n‐6), eicosapentaenoic (20:5 n‐3) and docosahexaenoic (22:6 n‐3) on tissue factor (TF) activity in the human leukemia monocytic U937 cell line. After exposing cells to fatty acids for 16 h, there were no significant effects on either TF activity or its activation induced by bacterial endotoxin (LPS). When the cells were primed with fatty acids for 24 h, 48 h or 72 h, the TF activity remained essentially unchanged. However, the extent of TF‐activation induced by LPS depended on the length of priming, and the dose and the degree of unsaturation of the fatty acids to which cells were exposed. After a 72‐h priming, 18:1 produced 40–60 per cent elevation in LPS‐challenge. In contrast, approximately 20–50 per cent reduction in LPS‐challenge was achieved by 18:2, 20:5 and 22:6 at high concentrations. The results suggest that chronic exposure of U937 cells to unsaturated fatty acids leads to modulation of the TF‐activati

ISSN:0263-6484    

DOI:10.1002/cbf.290090404

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractCirculating neutrophils, isolated from pigs fed for 8 weeks with a diet supplemented with CLO, had an accentuated n‐3 fatty acid incorporation into the plasma membrane, as evidenced by an approximately four‐fold greater n‐3/n‐6 ratio as compared with the control diet group. Moreover, the neutrophils of the CLO fed pigs produced less superoxide when stimulated with PMA or f‐MLP, as well as showing a more prolonged latency period before O2−‐generation. In the plasma of pigs fed with CLO there were higher levels of thiobarbituric reactive material and lipofuscin, while the content of GSSG was similar in both dietary groups.The results of this study indicate that dietary supplementation with CLO reduces the activation of circulating neutrophils and favours the presence in the plasma of

ISSN:0263-6484    

DOI:10.1002/cbf.290090405

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractUptake of iron by a mammalian epithelial cell line (CNCM I‐221) was shown to be dependent on the nature of the iron complex. Iron uptake was demonstrated by cytochemical staining and determination of redox‐reactive iron in cell lysates. Three classes of ligands were investigated: (i) low molecular weight hydrophilic compounds, represented by ethylenediamine‐tetraacetic acid (EDTA) and other charged ligands such as adenosine phosphates (ATP, ADP, AMP) and diethylenetriaminepentaacetic acid (DTPA), (2) low‐molecular weight lipophilic ligands such as 8‐hydroxyquinoline (8‐HQ) and (3) a high molecular mass ligand, dextran. Iron complexed to 8‐HQ accumulated intracellularly, the uptake rate of iron being 4·16 fmoles cell−1h−1of exposure at 37°C or 3·86 fmoles cell−1h−1at 4°C. Iron‐dextran was endocytosed and retained in phagosomes. The uptake rate of iron following exposure to iron dextrans was found to be 5°6 fmoles cell−1h−1of exposure at 37°C. In contrast to iron/8‐HQ, uptake of iron dextran by cells was inhibited at 4°C. Iron complexed to low molecular weight hydrophilic ligands was not taken up by cells.Cytotoxicity was measured by reduction of plating efficiency or tritiated thymidine incorporation. These tests showed that toxic effects of added iron were demonstrable only in ce

ISSN:0263-6484    

DOI:10.1002/cbf.290090406

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractIn order to evaluate the relationship between glycosaminoglycan (GAG) synthesis and degradation, the effect of NH4Cl, which inhibits lysosomal degradation, on GAG production was analysedin vitroin concanavalin A (Con A) stimulated fibroblasts from 7 and 14‐day‐old chick embryos.35SO4incorporation into total proteoglycan (PG),3H incorporation into individual GAG classes, β‐N‐acetyl‐D‐glucosaminidase and β‐D‐glucuronidase activity were determined. The results indicate a correlation between Con A and NH4Cl effects: NH4Cl induced a reduction principally in the GAG classes most stimulated by Con A. Thus HA and DS are much more stimulated by Con A and inhibited by NH4Cl t

ISSN:0263-6484    

DOI:10.1002/cbf.290090407

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractWe have studied, in streptolysin O‐permeabilized HL‐60 cell membrane preparations, the effects of phorbol 12‐myristate 13‐acetate (PMA) on polyphosphoinositide‐specific phospholipase C (PLC) activity and on terminal differentiation towards macrophagic‐like cells. We showed that terminal differentiation was induced when differentiating concentrations of the drug were present for only 1–2 h in the culture medium. Conditions inducing differentiation also inhibited PLC activity for a long lasting period (at least 5 h). When terminal differentiation affected only part of the cell population, inhibition of phospholipase C activity was found to be less marked and reversible over the period studied. Moreover in experiments done in an HL‐60 clone resistant to PMA, no inhibition of PLC activity was provoked by this tumour promotor.In order to study the involvement of protein kinase C in this process, we measured modifications of PLC activity by PMA in the presence of two different protein kinase C inhibitors, staurosporine and H‐7. They both prevented the inhibition of PLC activity by PMA indicating that this inhibition is likely to be related to the effect of PMA on protein kinase C activity. This was also confirmed by the fact that active protein kinase C, by itself, was able to decrease PLC activity when added to membrane preparations or to streptolysin O‐permeabilized control HL‐60 cells.These results indicate that PMA acts in inhibiting phospholipase C activity through its effect on protein kinase C activation and/or on protein kinase C translocation to the plasma membrane and that terminal differentiation, might be related to changes in both protein kinase

ISSN:0263-6484    

DOI:10.1002/cbf.290090408

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractThe metabolic adjustments which occur in rat liver cells during the first days of cold exposure have been investigated. We have measured both mitochondrial mass and oxidative capacities as well as ATP production after five and 10 days of cold exposure. In addition, we have measured plasma membrane Na+/K+‐ATPase activity. Cold exposure elicited a significant increase in mitochondrial mass as well as in state 3 oxidative rates and ATP production in isolated mitochondria using various substrates. Moreover, our results show that Na+‐pumping activity significantly increased after both five and 10 days of cold exposure.Our results suggest that during the first days of cold exposure liver cells undergo alterations which are useful for survival in the c

ISSN:0263-6484    

DOI:10.1002/cbf.290090409

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractThe possible effect of melatinin, 5‐methoxytryptamine, 5‐methoxytryptophol, 6‐chloromelatonin and 2‐iodomelatonin on testosterone production by Leydig cellsin vitrowas investigated. The ability of individual indoles to inhibit testosterone production was found to depend on the concentration used. The relative inhibitory potency of the compounds tested was: 6‐chloromelationin>2‐iodomelatonin>melatonin>5‐methoxytryptamine>5‐methoxytryptophol. The results revealed that natural indoles which are synthesized in the pineal gland and their halogenized derivatives are capable of influencing directly testosterone production by Leydig cells. Also, these results demonstrated that melatonin exerts its remarkable antigonadotrophic effects, at least in part, through the direct decrease of testosterone production. Moreover, 6‐chloromelationin and 2‐iodomelatonin, which are reported to inhibit melatonin binding to target tissues, possess properties of biological melatonin analogues under the conditions of th

ISSN:0263-6484    

DOI:10.1002/cbf.290090410

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractThe present investigation was undertaken to examine possible noise‐induced alterations in adrenal fasciculata cell (AFC) metabolism, and also to determine if the magnitude of these changes differs in male versus female rats. Wistar rats approximately 3 months old were exposed to intense noise for 60 min (100 dB, re 2 × 10−5N(m2)−1, 350–20 000 Hz); control rats were house under identical conditions, at an ambient noise level of 40–60 dB. Adrenal fasciculata cells (AFC) from each animal were examined for noise‐induced alterations in Feulgen‐DNA reactivity (as an indicator of chromatin template activity) and Coomassie‐total cell protein levels using scanning‐integrating cytophotometry. The results provide evidence that intense noise elicited a marked AFC metabolic enhancement in both male and female rats; the degree of this enhancement was more pronounced in males. This disparity may be due to pre‐existing differences in male versus female AFC enzymatic capability and subsequent responsiveness to nois

ISSN:0263-6484    

DOI:10.1002/cbf.290090411

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

ISSN:0263-6484    

DOI:10.1002/cbf.290090412

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY