摘要:

AbstractEffects of hyperthermia on the intracellular calcium concentration (Cai) of an established mouse breast cancer cell line, MMT060562, were studied using fura‐2 fluorescence microscopy and the whole‐cell clamp technique. A sudden change of temperature from 37 to 45°C induced a transient increase in the fluorescence ratio permeability of the cell membrane and inward current. Deletion of extracellular calcium abolished the fluorescence ratio response to the rise in temperture. Caiof some cells increased after hyperthermia treatment at 44–48°C for 20 min, but the average increase of Caiwas negligible. After hyperthermia treatment, spontaneous oscillation of Cai, chemical responses to ATP and bradykinin and the mechanically‐induced spreading reponse diminished. However, the mechanically induced increase of Caiwithin the stimulated cell remained even after hyperthermia treatment. Suppression of the ATP‐induced Cairesponse recovered to about half the original level within 12 h. Blockage of protein synthesis with cycloheximide (100 μM) had no effect on the recovery. TheD‐myo‐inositol 1,4,5‐triphosphate (IP3)‐dependent increase of Cairemained intact even after hyperthermia treatment. It is concluded that hyperthermia treatment increases both the permeability of the cell membrane and Cai, but decreases the sensitivity of cells to ATP and bradykinin, presumably due to modification of the signal tr

ISSN:0263-6484    

DOI:10.1002/cbf.290100403

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

摘要:

AbstractBrain Na+K+ATPase activity has been found to decrease in experimental trypanosomiasis in rats infected withTrypanosoma congolense. Some physical features that affect membrane fluidity were also observed to be altered. The levels of cholesterol in the brain and free fatty acids in the serum were found to increase in the infected animals. These findings might be relevant to the development of brain lesions.

ISSN:0263-6484    

DOI:10.1002/cbf.290100404

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

摘要:

AbstractThe membrane ATPase (EC 3.6.1.3) ofBacillus cereuswas solubilized by a ‘shock‐wash’ process and purified. The non‐specific phosphatase contaminant was separated by glycerol density gradient centrifugation. The optimum temperature was 39·5°C and the pH optimum at 7·5. On SDS‐polyacrylamide gel electrophoresis two classes of subunits were observed in equal proportions with molecular weights of 70 K and 83 K. The effect of various compounds on the enzymatic activity was studied. The enzyme was insensitive to NaN3, oligomycin and to divalent cations, but was inhibited by citrate

ISSN:0263-6484    

DOI:10.1002/cbf.290100405

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

摘要:

AbstractIsolation of thymocytes from rat thymus resulted in the disappearance of the high activity of ornithine decarboxylase (ODC) that characterizes the thymus of young rats, together with the appearance of an antizyme‐like ODC inhibiting activity, which showed a chromatographic profile that resembled that of dexamethasone‐treated rat thymus. Omission of serum or addition of dexamethasone or spermidine did not affect appreciably the extent of the antizyme‐like activity. On the other hand, a variety of hormonal effectors, i.e. insulin, glucagon, adrenalin and T3, as well as the phorbol ester, PMA or the mitogen, concanavalin A (Con A) induced ODC activity in cultured thymocytes together with the disappearance of the antizyme‐like activity. A paradoxical, transient induction of ODC was caused by the transcriptional inhibitor, actinomycin D. Complexed ODC was detected in rat thymus, but not in thymocytes, either quiescent or stimulated by mitogens. These results indicate that thymic lymphocytes can express either ODC activity or its inhibitor depending on the hormonal and proliferative status of th

ISSN:0263-6484    

DOI:10.1002/cbf.290100406

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

摘要:

AbstractRecent studies have shown that the gene encoding for the slow skeletal troponin isoform T (TNNT1) is located on the proximal long arm of human chromosome 19 in the myotonic dystrophy (DM) region. In order to test TNNT1 as a candidate gene for DM, we have isolated TNNT1 cDNA from skeletal muscle from two healthy individuals and from two patients with DM. Sequencing of the TNNT1 cDNA from the DM and normal muscle revealed two sequence variants but no transcriptionally significant mutations. This work rules out a defect in the coding segment of TNNT1 as a cause of DM and provides a polymerase chain reaction protocol for studying troponin T gene expression.

ISSN:0263-6484    

DOI:10.1002/cbf.290100407

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

摘要:

AbstractThe effect of variation in the intracellular and extracellular phosphate concentration on the Pi efflux across the basolateral membrane of pre‐loaded enterocytes has been examined. Efflux rate constants for Pi fell from 0·89 h−1to 0·68 h−1as the extracellular Pi concentration was increased from 0·5 mMto 5 mM. As the intracellular Pi concentration was raised from 0·5 to 3 mMthe rate constant dropped from 0·95 h−1to 0·77 h−1. The findings are indicative of the presence of Pi‐specific transporter at the basolateral membrane. The efflux rate constant of Pi at pH 7·1 was higher than that at pH 7·4 suggesting that the Pi flux across the basolateral membrane of enterocytes follows a similar pattern towards pH changes as do fluxes across the br

ISSN:0263-6484    

DOI:10.1002/cbf.290100408

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

摘要:

AbstractThe effect of chemically‐induced diabetes on the handling of phosphate (Pi) by rat jejunal enterocytes has been investigated in the presence of a Na‐ or a choline‐gradient. Pi uptake was significantly increased in both gradients. The Pi efflux rate constants for enterocytes from diabetic rats were similar to those of control rats. The effect of diabetes on both the protein and alkaline phosphatase isoenzymes of the rat small intestinal brush‐border membranes was examined using SDS‐PAGE. The patterns given by membranes from rats 14 days after the induction of diabetes were no different from those of

ISSN:0263-6484    

DOI:10.1002/cbf.290100409

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

摘要:

AbstractPrimary exposure ofTetrahymenacells to insulin gave rise to hormonal (insulin) imprinting in the offspring generations, as judged from the increase in binding upon reexposure to insulin. Vanadate mimicked the action of insulin, inasmuch as it also induced imprinting for insulin, whereas the other tyrosine kinase activator tested, namely H2O2, had no such effect. However, combined treatment with vanadate + H2O2+ insulin induced a more pronounced imprinting for insulin than either insulin or vanadate on their own. The tyrosine kinase inhibitor genistein, a plant flavonoid, did not change the value for insulin binding significantly relative to the control immediately after exposure, but increased it slightly in the offspring generations after 24 h at high dilution. Upon combination with insulin, 10−4M genistein inhibited imprinting by insulin. These experimental observations suggest that there may be a key role for tyrosine kinase activity in the mechanism (development) of imprintin

ISSN:0263-6484    

DOI:10.1002/cbf.290100410

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

摘要:

AbstractBiochemical analysis of the male germ cell‐associated kinase (mak) gene, which was isolated recently by using weak cross‐hybridization with the v‐rostyrosine kinase gene, revealed that the gene was highly expressed in mammalian testicular germ cells, but not in ovarian cells. In order to identify the cells which express themakgene in more detail, we localizedmakmRNA in frozen sections of mouse testis by non‐radioactivein situhybridization. In this study, we utilized thymine–thymine (T‐T) dimerizedmakcDNA as a haptenic, non‐radioactive probe, and the signal was detected enzyme‐immunohistochemically by using an anti‐T‐T antibody. As a result,makmRNA was localized intensely in late pachytene (stage X) and diplotene (stage XI) spermatocytes, and faintly in dividing spermatocytes (stage XII) and early round spermatids (stage I–II), suggesting that the gene may play an important role in the phase around meiotic cell division, but not througho

ISSN:0263-6484    

DOI:10.1002/cbf.290100411

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

摘要:

AbstractIn the present study, using immunofluorescence microscopy, we have demonstrated that normal and Ha‐ras‐1 transformed Buffalo rat liver (BRL) cells which were exposed to cytoskeletal protein inhibitors, showed a differential resistance of their microfilament and microtubule networks. One hour exposure of normal BRL cells to 10−5M cytochalasin B provoked a clear and already total breakdown of actin filaments. However, at this concentration of cytochalasin B, the microfilaments of transformed BRLHO6T1–1cells were not seriously affected; a higher cytochalasin B concentration (≥ 2 × 10−5M) was required to induce a significant breakdown of microfilaments in these transformed cells. The two cell lines also demonstrated differential microtubule stability when they were treated with either colchicine or triethyllead. Three hours exposure to 10−6M of either antimicrotubule agents was sufficient to disrupt the microtubules of normal BRL cell, without affecting their counterparts in the transformed BRLHO6T1–1cells. A 10‐fold higher drug concentration (10−5M) was required to induce microtubular breakdown in the transformed BRL cells. The differential stability of microfilaments and microtubules in normal and transformed BRL cells that was observed could not be attributed to a differential internalization of the agents, as shown by experiments on the uptake of [3H]‐cytochalasin B and triethyllead. In addition, the transformed BRLHO6T1–1cells did not express altered actin and tubulin isoforms, as demonstrated by isoelectric focusing followed by immunoblotting analysis. We conclude that the transformation of BRL cells with the Ha‐ras‐1 oncogene results in a greater stability of microfilaments and microtubules, leading to a structurally firmer cell shape. Transformed BRLHO6T1–1cells offer an interesting model for the study of the molecular and cellular mechanisms by which oncogenic transformation

ISSN:0263-6484    

DOI:10.1002/cbf.290100412

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY