摘要:

AbstractThe scrapie prion protein, PrPSc, is formed from its isoform, the cellular PrPc. There is evidence available indicating that PrPScis necessary component of the infectious prion particle to cause a series of transmissible spongiform encephalopathies. We have used immunocytochemistry and RNA blotting techniques to investigate if infection with prions results in an increased PrP gene expression. For the experiments we used N2a cells which had been infected with prions (ScN2a cells). We demonstrated by confocal laser scanning microscopy that PrP‐protein was present in the nucleus (predominantly in the nucleoli) of ScN2a cells. Analysis of the PrP‐mRNA levels both in N2a‐ and in ScN2a cells using cDNA encoding PrPcrevealed no marked alteration of the mRNA steady state level between the two cell strains. Likewise, in run‐off experiments no changes in either PrP‐specific transcription or in general transcriptional activity were found. The half‐life of PrP‐mRNA was found to be identical in both cell strains (7 h). Taken together, these results show that PrPScand /or PrPcis present in the nucleus (nucleoli) of ScN2a cells but does not display and effect on the expression of

ISSN:0263-6484    

DOI:10.1002/cbf.290110102

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractOsteoblast‐like cells possess Na‐dependent transporters which accumulate orthophosphate (Pi) from the extracellular medium. This may be important in bone formation. Here we describe parallel measurements of Pi uptake and cellular [Pi] in such cells from the rat (UMR 106–01 and UMR 106–06) and human (OB), and in non‐osteoblastic human fibroblasts (Detroit 532 (DET)). In UMR 106–01, cellular [Pi]was weakly dependent on extracellular [Pi] and higher than expected from passive transport alone. [32Pi]‐uptake was inhibited by Na deprivation, but paradoxically increased on K deprivation. With Na, 87 per cent of cellular32P was found in organic phosphorus pools after only 5 min. Na deprivation also decreased cellular [Pi], in both UMR 106–01 and DET, but the decrease was smaller than that in [32Pi]‐uptake. Ouabain decreased [32Pi]‐uptake and cellular [Pi]in DET, but not in UMR 106–01. Regulation of cellular [Pi] is therefore at least partly dependent on Na/Pi co‐transport, but this does not seem to be an exclusive

ISSN:0263-6484    

DOI:10.1002/cbf.290110103

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractUptake of orthophosphate (Pi) by osteoblast‐like cells is known to be stimulated by parathyroid hormone (PTH), but effects on intracellular [Pi] have not been investigated. Here we show in rat osteoblast‐like cells (UMR 106‐06) that PTH (10−11to 10−7M) increases both32Pi uptake and cellular [Pi] by up to 50 per cent. 1,25 Dihydroxyvitamin D3(1,25D) (10−12to 10−6M) and salmon calcitonin (CT) (10−12to 10−6g ml−1) also increased cellular [Pi] (by up to 60 per cent), but the percentage increases in total cellular32Pi uptake were smaller. The effects of 1,25D were transient (observable at 80 min and 6 h but not 24 h), and were also observed with 24,25 dihydroxy‐ and 25 hydroxyvitamin D3. Transient degradation of organic phosphorus pools to Pi might contribute to this increased [Pi]. These pools remain to be identified but were not shown to be phospholipids. Foetal bovine serum also affected cellular [Pi]. Care is therefore needed in distinguishing direct hormonal effects on cellular [Pi] from indirect effects arising from changes in th

ISSN:0263-6484    

DOI:10.1002/cbf.290110104

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe effect of tunicamycin (TM) on the metabolism of acetylated low‐density lipoprotein (AcLDL) was examined to determine whetherN‐linked glycosylation is required for the proper function of the AcLDL pathway. Proteolytic degradation of [125I]‐AcLDL was increased twofold in the presence of TM. This did not occur via an increase in total lysosomal enzyme activity or extracellular proteolysis; rather, the rate of uptake of [125I]‐AcLDL was increased. The enhanced degradation of AcLDL did not lead to a commensurate increase in the rate of synthesis of cholesteryl oleate. Conversely, the rate of cholesterol esterification was reduced in the presence of TM. The uptake of [125I]‐AcLDL was more sensitive to inhibition by chloroquine in TM‐treated cells. However, the presence of TM did not affect the ability of chloroquine to inhibit constitutive recycling of AcLDL binding sites. These results suggest thatN‐linked glycosylation may be involved in the regulation of AcLDL metabolism

ISSN:0263-6484    

DOI:10.1002/cbf.290110105

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractWe have determined the extent to which acute ethanol administration perturbs the synthesis of ventricular contractile and non‐contractile proteinsin vivo. Male Wistar rats were treated with a standard dose of ethanol (75 mmol kg−1body weight; i.p.). Controls were treated with isovolumetric amounts of saline (0·15 mol 1−1NaCl). Two metabolic inhibitors of ethanol metabolism were also used namely 4‐methylpyrazole (alcohol dehydrogenase inhibitor) and cyanamide (acetaldehyde dehydrogenase inhibitor) which in ethanol‐dosed rats have been shown to either decrease or increase acetaldehyde formation, respectively. After 2·5 h, fractional rates of protein synthesis (i.e. the percentage of tissue protein renewed each day) were measured with a large (i.e. ‘flooding’) dose ofL‐[4‐3H]phenylalanine (150 μmol (100 g)−1body weight into a lateral vein). This dose of phenylalanine effectively floods all endogenous free amino acid pools so that the specific radioactivity of the free amino acid at the site of protein synthesis (i.e. the amino acyl tRNA) is reflected by the specific radioactivity of the free amino acid in acid‐soluble portions of cardiac homogenates. The results showed that ethanol alone and ethanol plus 4‐methylpyrazole decreased the fractional rates of mixed, myofibrillar (contractile) and sarcoplasmic (non‐contractile) protein synthesis to the same extent (by approx. 25 per cent). Profound inhibition (i.e. 80 per cent) in the fractional rates of mixed, myofibrillar and sarcoplasmic protein synthesis occurred when cyanamide was used to increase acetaldehyde formation. There was also a significant decrease in cardiac DNA content. The results suggest that acute ethanol‐induced cardiac injury in the rat may be mediated by

ISSN:0263-6484    

DOI:10.1002/cbf.290110106

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractInjection ofD‐myo‐inositol‐1,4,5‐trisphosphate (IP3) was found to induce a transient increase of intracellular Ca2+concentration in cancerous mammary cells (MMT060562) and in normal mammary cells treated with epidermal growth factor. Responses to injection of eitherD‐myo‐inositol‐1,4‐bisphosphate (IP2) orD‐myo‐inositol‐1,3,4,5‐tetrakisphosphate (IP4) were small or absent. Furthermore, normal mammary cells cultivated with low‐protein serum replacement alone or in the presence of differentiation‐inducing hormones (insulin + cortisol + prolactin) were less sensitive to IP3.Thapsigargin induced a transient increase of Ca2+due to the release of Ca2+from an intracellular pool. There was no difference in the peak heights of the thapsigargin‐induced Ca2+increase when mammary cells were cultivated in the presence or absence of epidermal growth factor or insulin + cortisol + prolactin. These findings suggest that the releasable intracellular Ca2+pool remained unchanged whereas sensitivity to IP3 increases during the proliferation stage.Mechanical stimulus of a mammary cell induces an increase of intracellular Ca2+in the stimulated cell. A certain stimulating factor is released from the mechanically stimulated cell into the extracellular space, and it induces an increase of Ca2+in surrounding cells.18In contrast, the IP3‐induced Ca2+increase in both cancerous and epidermal growth factor‐treated normal mammary cells did not spread to adjacent cells. Therefore, increase of Ca2+is not sufficient to account for the release of stimulating substances from mammary cells in the mechan

ISSN:0263-6484    

DOI:10.1002/cbf.290110107

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe normal amount of DNA in human diploid nuclei was determined by the use of the Feulgen reaction measured by microdensitometry. The DNA‐content of nuclei in normal human articular cartilage was determined in nuclei of zones 3 and 4 of cartilage of the femoral head removed from osteoporotic fractured necks of femur. Analysis of the results indicated that a degree of synthesis of DNA occurred even in these zones of very elderly persons. Results on these zones in the articular cartilage of osteoarthritic joints indicated that different populations occurred. In some there was DNA‐synthesis related to tetraploidy; in others, the DNA was very stable to acid hydrolysis with no sign of biosynthetic activity; in the last group, which contained erosions of the superficial zones, the DNA was unstable to hydroly

ISSN:0263-6484    

DOI:10.1002/cbf.290110108

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe combination of carbon tetrachloride (CCl4) and 1,2‐dibromoethane (DBE) in isolated rat hepatocytes led to a significant potentiation of both lipid peroxidation and of plasma membrane damage observed after a single treatment with CCl4. Such a synergistic effect appeared to be related to the CCl4‐induced shift of DBE metabolism from the cytosolic conjugation with glutathione towards the microsomal transformation into toxic intermediates. In fact, CCl4significantly inactivated hepatocyte total GSH‐transferase, i.e. the DBE detoxification pathway. Furthermore, while the microsomal metabolism of CCl4was not affected by the simultaneous presence of DBE, the amount of DBE reactive metabolities covalently bound to hepatocyte protein was significantly enhanced in the presence of

ISSN:0263-6484    

DOI:10.1002/cbf.290110109

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

ISSN:0263-6484    

DOI:10.1002/cbf.290110111

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

ISSN:0263-6484    

DOI:10.1002/cbf.290110101

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY