摘要:

AbstractFamily trees of rat liver epitheliallike cells (RLECs), which proliferate finitely in primary culture, were obtained by time‐lapse cinemicrography (TLC). In family trees, RLECs were classified into those terminated with division (class D cells), those terminated with incomplete division (class I cells), i.e., division followed by fusion of two daughter cells, and the combined population (class N cells) of those terminated with death and those surviving for 120 hr or more with their termination not detected by TLC. The interphase period, but not the intersibling period, of class D cells became distributed more broadly with time on the family tree. These results for class D cells fit best to a transition probability model with two indeterminate states (Brooks et al., Cell,19:493–504, 1980) when the model is modified in such a way that the transition probability for one of the two indeterminate states decreases with time. During proliferation of RLECs, some of the class D cells reproduce, while others showed transition, in part by way of class I cells, to class N cells. The frequency of transition from class D to class N increased with time in the family tree. Two sibling cells of a parent mitotic cell were simultaneously either class D or class N at a significantly high frequency, suggesting that the transition had been determined in the preceding cells. The present observations confirm previously described observations on human diploid cells, and in addition, reveal some new details of the finitely proliferative nature of somatic diploid ce

ISSN:0021-9541    

DOI:10.1002/jcp.1041190202

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

年代:1984

数据来源: WILEY

摘要:

AbstractQuiescent Swiss mouse 3T3 cells react to a heat treatment at 46°C for 20 min by changing their flat, well‐extended morphology to a round appearance with retracted cytoplasmic processes during the subsequent 2 h at 37°C. The percentage of morphologically changed cells was used to quantify changes in heat sensitivity, or resistance, in response to mitogenic stimulation. Stimulating quiescent cells with serum or with the specific growth factors epidermal growth factor (EGF) and prostaglandin F2α(PGF2α) markedly increased the heat resistance to a 46°C treatment, but only when the heat treatment, but only when the heat treatment was applied within 2–3 h after the addition. When insulin (which is not mitogenic, but synergistic with EGF and PGF2αin these cells) was added alone or in combination with either EGF or PGF2α, it had no effect on the development of heat resistance. Neither did cycloheximide nor tunicamycin inhibit heat resistance induced by EGF, and cycloheximide even enhanced it after 2–4 h. However, adding colcemid before or at the beginning of the heat treatment abolished the increased heat resistance. The results indicate that the resistance to a single heat treatment at 46°C may be related to changes in the metabolic state after mitogenic stimulation, even though these changes need not be reflected in the rate of entry into S phase. Furthermore, the cytoskeletal organization appears to be a crucial component in heat resistance of Sw

ISSN:0021-9541    

DOI:10.1002/jcp.1041190203

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

年代:1984

数据来源: WILEY

摘要:

AbstractThe K+ionophore valinomycin at concentrations of 1 × 10−8M and over, stimulated 2‐deoxy‐D‐glucose (2DG) and 3‐O‐methylglucose (3OMG) uptake in Swiss 3T3 fibroblasts. The rate‐limiting step of 2DG uptake was transport rather than phosphorylation, in the control or valinomycin‐treated cells. Kinetic analysis showed that valinomycin increased the Vmaxfor 2DG uptake without change of the Km. The valinomycin‐stimulated 2DG uptake was insensitive to 10 μg/ml cycloheximide, and extracellular K+concentrations between 0.1 and 50 mM. On the other hand, valinomycin at the concentration of 1 × 10−8M and over, induced a rapid decrease in cellular ATP content, followed by stimulation of 2DG uptake and recovery of the ATP content. A similar relationship between the reduction of cellular ATP content and the subsequent stimulation of 2DG uptake was observed when the cells were treated not only with 2,4‐dinitrophenol and iodoacetic acid, but also with other monovalent cation ionophores or inhibitors of oxidative phosphorylation. These results suggest that valinomycin may posttranslationally stimulate hexose transport by increasing the number of functional carriers of hexose or changing their mobility, and the rapid decrease in cellular ATP pools by valinomycin may be a trigger of the stimulation of the hexose transport

ISSN:0021-9541    

DOI:10.1002/jcp.1041190204

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

年代:1984

数据来源: WILEY

摘要:

AbstractThe biological action of retinoids has been assayed using the differentiated properties of cultured human conjunctival keratinocytes. The effects measured were the suppression of envelope cross‐linking and the promotion of synthesis of a keratin of molecular weight 40,000. Among the retinoids tested, the most powerful was the arotinoid Ro 13–6298, which reduced envelope formation detectably at 10−11M and by 90% at a concentration of 2 × 10−10M. The arotinoid was about 15 times more potent than trans‐retinoic acid. The order of effectiveness of the retinoids in suppressing envelope cross‐linking was the same as the order of effectiveness in promoting the synthesis of the 4

ISSN:0021-9541    

DOI:10.1002/jcp.1041190205

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

年代:1984

数据来源: WILEY

摘要:

AbstractPulmonary artery endothelial cells were isolated from bovine fetal blood vessels and used for biosynthetic studies. At confluence, cultures were incubated in minimal essential medium (MEM) without serum containing [U‐14C]proline. After 24 hours, medium was removed and labeled proteins were precipitated by the addition of ammonium sulfate and fractionated by diethylaminoethyl (DEAE)‐cellulose chromatography. The elution profile showed four major peaks and one minor peak. Fractions within each peak were pooled, subjected to digestion by chymotrypsin and/or collagenase, and analyzed by polyacrylamide gel electrophoresis. Peak I contained a collagen which contained approximately 6% of the 3‐hydroxyproline isomer while total hydroxyproline content was approximately 45%. This material was digested by purified bacterial collagenase and had a mobility slightly slower than that of α1(III) which did not change under conditions that reduce disulfide bonds. Upon digestion with chymotrypsin under conditions where native procollagens are converted to α‐chains, this material was digested. These properties suggest that this material is type VIII or EC (endothelial cell) collagen. Peak 2 contained substantial fibronectin while peak 3 contained primarily type III procollagen. The last major peak contained a mixture of collagenous and noncollagenous material. Upon digestion with chymotrypsin, several peptides were generated which were sensitive to bacterial collagenases. The two major chymotrypsin‐resistant components had mobilities slower than that of α(III) and were not disu

ISSN:0021-9541    

DOI:10.1002/jcp.1041190206

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

年代:1984

数据来源: WILEY

摘要:

AbstractRat serum has been shown to stimulate DNA synthesis in primary cultures of adult rat hepatocytes 2–3 times more potently than serum from several other mammalian sources, including humans. Parallel to its stimulation of thymidine incorporation into DNA, rat serum increased the total DNA content of the hepatocyte cultures over time, and also increased the frequency of nuclear labeling and mitosis. Moreover, normal rat serum, derived from whole blood (NRS), stimulated DNA synthesis in hepatocytes twice as effectively as platelet‐poor rat serum, derived from plasma (ppNRS). Addition of a rat platelet lysate (RPL) to ppNRS restored the activity to equal that of NRS. The avid binding of the active principle to CM Sephadex and its sensitivity to trypsin digestion suggest that it is a cationic polypeptide with an apparent molecular weight of about 65,000, as determined by gel filtration. It was inactivated by reduction of disulfide bonds, or by exposure to pH below 5.5, to NaCl concentration below 0.05 M, to 65°C for 30 min, or to 100°C for 10 min. Although it resembles the human platelet‐derived mitogen platelet‐derived growth factor (PDGF) in several of its properties, it differs in others. Hence the hepatocyte growth factor from rat platelets, which accounts for 50% of the DNA synthesis‐stimulatory activity of rat serum, appears to be a dist

ISSN:0021-9541    

DOI:10.1002/jcp.1041190207

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

年代:1984

数据来源: WILEY

摘要:

AbstractIn an accompanying communication we demonstrated that about half of the potency of rat serum to stimulate DNA synthesis in cultured adult rat hepatocytes resides in a polypetidelike substance from the platelets. A lysate of rat platelets was able to restore the potency of platelet‐poor rat serum, whereas a lysate of human platelets inhibited thymidine incorporation by the hepatocytes. Moreover, addition to these cultures of either highly purified human platelet‐derived growth factor (PDGF) or human platelet factor 4 (PF‐4) failed to influence DNA synthesis either aloneorin the presence of rat or human platelet‐poor serum, which is required for expression of PDGF activity. Unlike the human platelet factors, rat platelet lysate (RPL) was moderately active by itself and was augmented equally well by platelet‐poor serum from either source. At concentrations below 5%, platelet‐poor serum from hypophysectomized rats was as potent as that from normal rats in augmenting RPL activity. This suggests that, unlike PDGF, which is not activated by hypophysectomized rat serum, the hepatotrophic component of RPL does not require the presence of exogenous somatomedins for activity, but interacts instead with other plasma constituents or with somatomedins produced by the hepatocytes in vitro. Rat platelets do, however, appear to contain PDGF or its rat equivalent in addition to the hepatocyte growth factor, since if they are heated to 100°C for 10 min, their ability to stimulate nuclear labeling in confluent BALB/c 3T3 cells is not impaired, while their ability to stimulate DNA synthesis in rat hepatocytes is destroyed. These studies indicate that the hepatocyte growth factor from rat platelets differs from PDGF in its biological as well as physical characteristics, but that rat platelets also contain PDGF or an equivale

ISSN:0021-9541    

DOI:10.1002/jcp.1041190208

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

年代:1984

数据来源: WILEY

摘要:

AbstractChinese hamster ovary (CHO) cell variants resistant to a carboxylic ionophore, monensin, have been isolated. Two monensinresistant variants (MonR–;31 and MonR–32) showed a three‐ to fourfold higher resistance to monensin than did CHO. These MonRclones also showed fourfold higher resistance to another carboxylic ionophore, nigericin, and twofold higher resistance to valinomycin. They were also slightly more resistant to other unrelated drugs such as adriamycin, colchicine, bleomycin, and chloroquine, and in particular, they showed about threefold higher resistance to ricin, a toxin ofRicinus communis.MonRclones were found to retain a normal level of [125l]ricin binding, but internalization of [125l]ricin into the MonRclones was one‐half or less than with CHO. Present data suggest that drug‐resistant clones selected in culture may provide a way to isolate cells with altered response to various bioactive

ISSN:0021-9541    

DOI:10.1002/jcp.1041190209

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

年代:1984

数据来源: WILEY

摘要:

AbstractFrom the Chinese hamster ovary (CHO) cell, genetic variants (MonR–31 and MonR–32) relatively resistant to monensin, an ionophoric antibiotic, have been isolated. Growth of both MonR‐31 and MonR‐32 clones required higher doses of serum than CHO. Addition of insulin to media containing a low dose of serum restored full colony formation, but growth of MonR‐31 or MonR‐32 cells required more insulin than CHO cells. Specific binding of [125l]insulin was observed in these cell lines. The two MonRclones bound about one‐half or less the [125l]insulin bound by CHO cells. Scatchard analysis for [125l]insulin binding at 4°C and 37°C showed altered number of binding sites, but not insulin affinity: The number of binding sites in the MonRcell was about a half or less that of the parental CHO cell. Down‐regulation of insulin receptor was assayed when both CHO and MonRcells were incubated with 1 μg/ml insulin. A 50–60% decrease in levels of insulin surface binding capacities was observed in CHC after exposure to insulin, whereas there was no decrease in MonRcell. The cellular uptake of 2‐[3H]deoxyglucose into CHO cells was significantly enhanced in the presence of insulin, but only slight, if any, increase was

ISSN:0021-9541    

DOI:10.1002/jcp.1041190210

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

年代:1984

数据来源: WILEY

摘要:

AbstractTransformed mouse fibroblasts, such as 3T6, exhibit an increase in plasma membrane permeability to nucleotides and other normally impermeant molecules when incubated with external ATP in an alkaline medium low in divalent cations. Increased nucleotide permeability, induced by external ATP, occurs after a 3‐ to 5‐min lag period. Prior to this event, there is a dramatic Na+influx and K+efflux, a significant reduction in the levels of intracellular ATP and organic phosphates, and a reduction in the plasma membrane potential. Accordingly, we postulate that these cellular responses to external ATP play a role in the efflux of nucleotides.Ouabain, a specific inhibitor of the plasma membrane (Na+, K+)‐ATPase, acts together with low concentrations of external ATP to increase nucleotide permeability in 3T6 cells. This effect occurs at concentrations of ouabain and ATP which alone do not increase nucleotide permeability. In addition, ouabain and low concentrations of ATP alone have little effect on the level of intracellular ATP. This is in contrast to energy inhibitors and uncouplers which appear to enhance nuclectide permeability by lowering the intracellular ATP concentration. Ouabain alone causes a threefold increase in intracellular Na+levels and a similar reduction in intracellular K+levels under our experimental conditions, supporting the idea that ion fluxes are involved in the mechanism of permeabiliz

ISSN:0021-9541    

DOI:10.1002/jcp.1041190211

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

年代:1984

数据来源: WILEY