摘要:

AbstractEvents following F(ab)2anti‐δ immunoglobulin stimulation of monoclonal (leukemic) human B cells prior to Na+‐K+pump activation were investigated in vitro. This pump activation, measured by ouabain‐sensitive86Rb+uptake, appeared susceptible to the phospholipid‐interacting drugs tetracaine and quinacrine, to the antioxydant nordihydroguaiaretic acid (NDGA), and to the calmodulin antagonist trifluoperazine, while much less susceptible to the methylation inhibitor‐3‐deazaadenosine. The Ca++ionophore A 23187 appeared to induce pump activation in a way similar to anti‐δ, as it was susceptible to the same drugs and as anti‐δ had no additional stimulating effect on A 23187‐stimulated cells. However, whereas the anti‐δ‐induced activations appeared independent of the extracellular Ca++activity, [Ca++]e, the activation by A 23187 was potentiated by addition of the CA++chelator ethyleneglycol‐bis (β‐aminoethyl ether) N, N'‐tetracetic acid (EGTA). Estimations by a fluorescent chelator method (quin 2) showed anti‐δ to increase the intracellular Ca++activity, [Ca++]iboth in the absence and presence of EGTA. A 23187 increased [Ca++]istrongly in Ca++medium, but was weaker, more similar to the anti‐δ response, in EGTA medium. It is suggested that Na+‐K+pump activation after anti‐lg stimulation in B cells may follow Ca++mobilization from internal stores. The trifluoperazine susceptibility sugge

ISSN:0021-9541    

DOI:10.1002/jcp.1041170102

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractMany different types of cancer cells have been shown to be methionine‐dependent. These cells, unlike normal cells, grow poorly or not at all when methionine is replaced by its immediate precursor homocysteine in the growth medium (Met−Hcy+medium). We have previously shown that apparently normal total amounts of methionine are synthesized by methionine‐dependent SV40‐transformed human fibroblasts. However, methionine‐dependent cells in Met−Hcy+medium accumulate reduced amounts of S‐adenosylmethionine (AdoMet) and elevated amounts of S‐adenosylhomo‐cysteine (AdoHcy) that together probably limit growth. In this report, we demonstrate that the amount of free methionine is low in methionine‐dependent SV40‐transformed human fibroblasts in Met−Hcy+medium compared to normal human diploid fibroblasts. In contrast, in Met+Hcy−medium, the amount of free methionine is comparable in both cell types. The deficient pool of free methionine in methionine‐dependent cells in Met−Hcy+medium allows only low amounts of AdoMet to be formed. However, large amounts of the biosynthesized methionine are channeled into protein synthesis. Possible mechanisms are discussed to explain this cance

ISSN:0021-9541    

DOI:10.1002/jcp.1041170103

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractRetinyl acetate (RA)‐sensitive variants (RAs‐2 and RAs‐3) of V79 cell line were isolated after mutagenesis with N‐methyl‐N′‐nitro‐N‐nitrosoguanidine. The variants were stable and showed a 3‐ to 4‐fold increase in sensitivity to RA compared to parental V79 cells. The RAs‐2 clone was also sensitive to retinol and retinol palmitate. The RA‐sensitivity behaves as a recessive trait in all hybrids of RAs‐2 and V79. A number of physiological parameters were indistinguishable in V79 and RAs‐2 cells, including the extent of uptake of [3H]retinol, the release of K+from the cells induced by RA, and the levels of retinol and retinoic acid binding proteins. However, one possible correlation with the RA‐sensitive phenotype was observed: Gomori acid‐phosphatase staining of RA‐treated RAs‐2 and V79 cells indicated that lysosomal membrane of RAs‐2 cells was more labi

ISSN:0021-9541    

DOI:10.1002/jcp.1041170104

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractPrevious studies have indicated that intracellular Ca2+is involved in fetal bovine serum (FBS)‐ or growth factor (GF)‐stimulated Na+influx in human foreskin fibroblasts (HSWP). In the present study,45Ca2+efflux from serum‐deprived HSWP cells was measured in response to 10% FBS or GF [lys‐bradykinin, vasopressin, epidermal growth factor, and insulin]. Efflux data were analyzed using a computer program and the best fit indicated the presence of three Ca2+compartments: a compartment (C1) with a very fast turnover rate, one (C2) with a fast turnover rate, and one (C3) with a slow turnover rate. When serum‐deprived cells were treated with 10% FBS, efflux from C2and C3increased significantly (p>0.05). Similar effects on efflux were observed when serum‐deprived cells were treated with individual GFs. Combination of the four GFs produced a higher stimulation than any single factor and a response that was equal to that for FBS. On the other hand, when cells were serum‐treated in the presence of the intracellular Ca2+antagonist, 8‐(N‐N, diethylamino)‐octyl 3,4,5‐trimethoxybenzoate (TMB‐8),45Ca2+efflux from C2was substantially reduced. Finally, when cells were treated with the Na+transport inhibitor amiloride, there was no significant effect on serum‐stimulated Ca2+efflux. These results are consistent with a FBS‐ or GF‐induced mobilization of Ca2+that can be blocked by intracellular Ca2+antagonists, and support the hypothesis that the action of these agents on Na+influx may be via their

ISSN:0021-9541    

DOI:10.1002/jcp.1041170105

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractTumor promoting phorbol esters, such as 12‐0‐tetradecanoyl‐phorbol‐13‐acetate (TPA), stimulate colony formation in vitro by murine granulocyte‐macrophage progenitors (GM‐CFC) without added colony stimulating factors (CSF). To determine whether TPA induces CSF production in vitro, marrow cells were cultured for 1 to 7 days in liquid medium with or without TPA. No CSF was detected in any sample by a double antibody radioimmunoassay (sensitivity = 2 units/0.1 ml), however, colony‐stimulating activity was detected in supernatant fluid from all TPA containing cultures by bioassay. This activity appeared to result from a direct effect of TPA rather than from production of CSF, as equivalent activity was found in TPA‐containing medium incubated in the absence of marrow cells. Rabbit antiserum to purified L‐cell CSF inhibited colony formation stimulated by L‐cell CSF and WEHI‐3 CSF, but had no effect on colony formation induced by TPA. Cells from long‐term marrow cultures responded to TPA with colony formation, despite culture conditions and cell fractionation procedures that reduced the frequency of CSF‐proclucing macrophages to>1.0%. TPA inhibited binding of radioiodinated L‐cell CSF to marrow cells, especially if the cells were first exposeed to TPA. These results do not support induction of CSF production as the major mechanism of phorbol ester stimulation of myelopoiesis. Phorbol esters may directly stimulate GM‐CFC and/or enhance their response to CSF by a mechan

ISSN:0021-9541    

DOI:10.1002/jcp.1041170106

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractUpon binding to receptor‐bearing target cells, viruses cause cell membrane potential changes. Epstein‐Barr Virus causes a biphasic membrane potential change in receptor‐bearing B lymphocytes but not receptor‐negative T lymphocytes, as measured by flow cytometry of cyanine dye uptake. Membrane potential changes upon EBV binding to receptor‐bearing cells resemble electrical responses of other cells following ligand binding to transmembrane

ISSN:0021-9541    

DOI:10.1002/jcp.1041170107

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractKinetic studies were performed on two‐day cultures of rat ovarian granulosa cells to follow the fate of surface‐bound125l‐labeled human chorionic gonadotropin (125l‐hCG). Low pH was used to release hCG from its surface receptor, allowing us to distinguish between surface‐bound and internalized hormone. Because our results indicated that hormone is lost from the cell surface by dissociation as well as internalization, equations were derived to determine independent rate constants for each process. We calculate that if hormone binding were irreversible, the t1/2for internalization would be 8.5 hours. Morphometric studies on the uptake of horseradish peroxidase indicate that the t1/2for internalization of bulk membrane in granulosa cells is 55 to 77 minutes. Thus, the rate of uptake of surface‐bound hCG appears to be seven to nine times slower than the rate of uptake of bulk plasma membrane, which suggests that the LH/hCG receptor may be selectively excluded from the endocytic vesicles of gran

ISSN:0021-9541    

DOI:10.1002/jcp.1041170108

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractInorganic pyrophosphate (PPi) forms an insoluble precipitate with calcium in growth medium when its concentration exceeds about 0.1 mM. This PPiprecipitate can reproduce the effects of 10% calf serum on all cell processes examined in Balb/c 3T3 cells, including hexose uptake and metabolism to lactate,3H‐uridine, and3H‐choline uptake, and the incorporation of3H‐leucine and3H‐thymidine into trichloroacetic acid (TCA)‐insoluble material. Concentrations of PPiinsufficient to form a precipitate are without effect on cell metabolism. The precipitates are most effective when prepared with concentrations of PPijust sufficient to result in precipitate formation and become considerably less effective as the PPiconcentration increases, even though the quantity of precipitate formed continues to increase with PPiconcentration up to 1 mM PPi. Precipitates formed at low PPiconcentrations consist largely of Ca2+(81% of cations). PPi(77% of anions), and Pi(23% of anions). Precipitates formed with higher concentrations of PPicontain proportionately less Ca2+and Piand more monovalent cations and PPi. We have distinguished cell surface‐bound PPifrom intracellular PPiby differential extraction. The quantity of surface‐bound PPiincreases sharply when the PPiconcentration reaches the point of precipitate formation. If the precipitate is prevented from binding to the cell surface by inverting monolayer cultures in precipitate‐containing medium, the cells are not stimulated. These findings suggest that the binding of PPiprecipitate to the cell surface is involved in the stimulation of cell metabolism by PPi. PPiprecipitates do not absorb serum mitogens or inhibitors from the culture medium, nor do they affect the binding of125I‐platelet‐derived growth factor to its specific cell‐surface receptor, suggesting that PPiprecipitates do not act directly through either of these mitogen‐receptor systems. In analogy to cell stimulation by epidermal growth factor and by antigens, we suggest that PPimay be active only in the form of a precipitate because multivalent binding of receptors with formation of clusters is required for stimulation. The inhibitory effects of high concentrations of PPimay be due to interference by free PPiwith formation of a

ISSN:0021-9541    

DOI:10.1002/jcp.1041170109

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractWe have analyzed the regulation of transcription of integrated SV40 DNA and of five cellular genes during the cell cycle of two lines of SV40 transformed mouse 3T3 cells. These cells (ts SV3T3) are temperature sensitive for the expression of the transformed phenotype and at the nonpermissive temperature (39°C) become arrested in G1 at low serum concentrations. SV40 specific RNAs are not detected either in the nuclear or in the cytoplasmic poly(A+)RNA of quiescent cells, suggesting control at the level of transcription. After serum stimulation, however, viral transcription increases and reaches its maximum during S‐phase. The expression of a group of selected housekeeping genes has received parallel analysis to determine whether other cellular genes, beside the integrated SV40, are shut off in G1 arrested cells or are expressed in restricted periods of the cell cycle. We have found that, while the mRNAs for collagen, adenosinphosphoribo‐siltransferase (APRT) and the mouse major histocompatibility complex (H2) are present throughout the cell cycle, the genes coding for the multifunctional protein CAD and dehydrofolate reductase are cell‐cycle reg

ISSN:0021-9541    

DOI:10.1002/jcp.1041170110

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractAddition of theophylline to primary cultures of rat hepatocytes in which tyrosine aminotransferase had been preinduced with dexamethasone caused a further increase in specific activity of the enzyme. This increase was due in part to a reduction in the rate of tyrosine aminotransferase degradation that began about 2 hr after theophylline was added. The level of cGMP also increased with a similar time lag following the addition of theophylline. The concentration of theophylline which produced the above effects (1 mM) did not alter the rate of general protein degradation in hepatocytes. Addition of 8‐bromo‐cGMP (0.5 mM) resulted in an immediate reduction in the rate of tyrosine aminotransferase degradation and in an increase in the activity of the enzyme. Treating hepatocytes with MnCl2(0.9 mM) caused an elevation of cGMP and a concomitant slowing of tyrosine aminotransferase degradation without changing the level of cAMP significantly. These results suggest an inverse relationship between the level of cGMP and the rate of tyrosine aminotransferase degradation in hepatocy

ISSN:0021-9541    

DOI:10.1002/jcp.1041170111

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY