摘要:

AbstractNutrient transport rates and cyclic AMP levels have been implicated in the regulation of cell proliferation. In the present study, however, changes in intracellular cyclic AMP level induced in several lines of cultured cells (normal 3T3 and SV40and polyomavirus‐transformed 3T3 cells; 3T6, C6 glioma, mouse L, and Novikoff rat hepatoma cells) by treatment with papaverine, prostagladine E, or isoproterenol did not correlate with the inhibition of the uridine, hypoxanthine or deoxyglucose transport rates by these chemicals. Transport inhibitions by above chemicals or Persantin or Cytochalasin B occurred in most cell lines in the absence of any measurable change in intracellular cyclic AMP concentration. Furthermore, treatment of several cell lines with 1 mM dibutyryl cyclic AMP had no immediate effect on the transport of uridine, thymidine or deoxyglucose, although the transport capacity of the cells for uridine and thymidine, but not that for deoxyglucose, decreased progressively with time of treatment. We also observed that the uridine transport system of all cell lines derived from 3T3 cells and the hypoxanthine transport system of L cells exhibited high degrees of resistance to inhibition by the various chemicals. On the other hand, deoxyglucose transport was inhibited to about the same extent by these chemicals in all the cell lines investigate

ISSN:0021-9541    

DOI:10.1002/jcp.1040850202

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

年代:1975

数据来源: WILEY

摘要:

AbstractThe concentration of leucine in the growth medium has been found to influence the expression of the temperature sensitive phenotype of a mutant of Chinese hamster ovary cells with an altered leucyl‐tRNA synthetase. Plating efficiency and growth studies showed that increasing the leucine concentration allows cells to survive at normally non‐permissive high temperatures and conversely decreasing the leucine concentration enhances the adverse effects of high temperature. A similar but smaller effect was noted with isoleucine. It is suggested that this observation may form the basis of a rapid test, useful in directing the investigation of the lesion in similar mutants to pathways involving specific amino ac

ISSN:0021-9541    

DOI:10.1002/jcp.1040850203

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

年代:1975

数据来源: WILEY

摘要:

AbstractThe host‐virus interactions of Simian virus 40 (SV40) and polyoma virus (Py) with cell lines established from a teratocarcinoma were studied. The cells utilized in this study were the multipotential stem cell of the teratocarcinoma, embryonal carcinoma, and differentiated cells derived from embryonal carcinoma. Several lines of differentiated cells were established in vitro which included parietal yolk sac, epithelial, and spindle cell types. Embryonal carcinoma cells are not susceptible to infection by either SV40or Py virus. However, differentiated cells are susceptible to infection by these viruses. The differentiated cells are permissive for Py virus replication and nonpermissive for SV40. Several continuously growing cell lines have been established from the SV40infected cultures which express T antigen in 100% of the cells. The results indicate that undifferentiated embryonal carcinoma cells and their differentiated progeny respond quite differently to challenge with these two oncogenic DNA viruse

ISSN:0021-9541    

DOI:10.1002/jcp.1040850204

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

年代:1975

数据来源: WILEY

摘要:

AbstractThe plasma membrane is the postulated site of action of anesthetics on nerve or muscle. The drugs may be useful in the analysis of membrane phenomena in other cells. We show here that cationic anesthetics and tranquilizers inhibit cell adhesion and spreading, metabolically dependent processes that involve membrane motility and changes in cell shape. Adhesion was measured by layering51Cr labeled Sarcoma I (Sa I) cells on glass coverslips for 20 minutes at 34°C, rinsing and estimating the glass‐associated radioactivity. Spreading was evaluated microscopically. Both cell adhesion to untreated glass and the Mn2+dependent adhesion to serum‐coated coverslips were inhibited by the drugs, in the following order of increasing activity: tetracaine, promethazine, cyclomethycaine, chlorpromazine and fluphenazine. Similar ranks of drug activity have been reported for nerve blocking, inhibition of cell fusion and inhibition of induced spreading of macrophages. Microscopic observations showed the drugs also inhibited Mn2+induced spreading of Sa I. Drug treated cells were rounded, refractile, devoid of cell processes or ruffles visible by light microscopy. The effects of the drugs on adhesion and spreading were reversible upon washing of the cells. We postulate that the inhibition of adhesion and spreading are a consequence of the inhibition of cell surface motility by the anesthe

ISSN:0021-9541    

DOI:10.1002/jcp.1040850205

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

年代:1975

数据来源: WILEY

摘要:

AbstractThe erythroblastic leukemia produced in Long‐Evans rats by the administration of 7, 8, 12 trimethylbenz (a) anthracene has been used as a model of the most immature form of the erythrocyte series. In conjunction with studies of the maturation of several other membrane functions, the permeability of this cell to water and to certain definitive non‐electrolytes was measured with osmotic methods. The hydraulic conductivity, Lpwas 6.2 micro (minute)−1, (atm)−1at 25°C, quite high and characteristic of mature erythrocytes, but different from values of 0.65 for immature myeloid cells. The effect of temperature provided an energy of activation of 4.4 kCal/mole, also typical of mature mammalian erythrocytes but again different from 13 to 18 kCal/mole for immature myeloid cells. Urea was compared to thiourea. The permeability coefficient for urea was 76.7 micra (minute)−1± 13.8 (S. E.); the value for thiourea was 1.55 micra (minute)−1± 0.18 (S. E.). Phloretin at 0.25 mM inhibited urea permeability by 90% with 50% inhibition occurring at 0.05 mM. Inhibition was reversible. Permeability to the glycols was also compatible with mature erythrocytes. We infer from these findings that the structure which underlies these basic, passive membrane functions is laid down early and persists after loss of nucleus and subsequ

ISSN:0021-9541    

DOI:10.1002/jcp.1040850206

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

年代:1975

数据来源: WILEY

摘要:

AbstractMurine lymphoblasts grown in suspension culture in the presence of ouabain showed a dose dependent and sequential decrease in86Rb+(K+analogue) influx, cellular potassium content, and growth rate. An increase in eosin staining and a decrease in cell number was observed after two hours in the presence of 1 mM ouabain; 1 μM ouabain was without effect on any of the parameters measured. Ouabain inhibition was rapidly and completely reversible at concentrations that were not cytotoxic

ISSN:0021-9541    

DOI:10.1002/jcp.1040850207

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

年代:1975

数据来源: WILEY

摘要:

AbstractThe effects of ouabain on the growth of murine lymphoblasts in vitro have been studied. Exposure of cells to ouabain (0.1 mM) initially inhibited86Rb+uptake rate, reduced the intracellular potassium concentration, and decreased population growth rates. Continued exposure to the same ouabain concentration resulted in an increase of86Rb+uptake rate, intracellular potassium content and population growth rates to control values (adaptation). When treated cells were resuspended in medium free of ouabain after 12 to 15 hours of ouabain treatment,86Rb+uptake rates and intracellular potassium levels exceeded those of untreated cells. Adaptation was inhibited by cycloheximide (3 μg/ml) and by actinomycin D (0.05 μg/ml). Kinetic analysis of transport suggested that while the total capacity of the Na+, K+transport system increased, the affinity for both the cation (86Rb+) and ouabain decrease

ISSN:0021-9541    

DOI:10.1002/jcp.1040850208

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

年代:1975

数据来源: WILEY

摘要:

AbstractThe inhibition of cell proliferation by ouabain has been analyzed with respect to the cell cycle. Three lines of evidence indicate that growth rate is modified by altering to different degrees the rate of progress through stages of the cell cycle: (1) a three hour lag occurs between the time of ouabain addition and the inhibition of proliferation; (2) ouabain must be present at least two to four hours prior to the mitotic burst of synchronized cells for inhibition of mitosis to occur; (3) parasynchrony is observed when cells are resuspended in ouabain‐free medium after 12 hours of exposure to ouabain.Analysis of the distribution of cells in each of the stages of the cell cycle at various times during ouabain treatment reveals a progressive increase in the fraction of cells in S with a concomitant decrease in the percent of cells in each of the other stages. These results indicate that the prolongation of the cell cycle time in the presence of ouabain is due primarily to an S stage bloc

ISSN:0021-9541    

DOI:10.1002/jcp.1040850209

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

年代:1975

数据来源: WILEY

摘要:

AbstractStudies were carried out on confluent cultures of human fibroblasts to explore the effect of insulin on basal and hormone‐induced elevations of intracellular cyclic AMP content during short‐term incubations in serum‐free medium. Insulin tended to decrease basal levels of cyclic AMP but this was not statistically significant. Similarly, insulin was unable to block the elevations of intracellular cyclic AMP content induced by PGE1, epinephrine and glucagon. Paradoxically, when cells were preincubated with insulin, PGE1‐stimulated cyclic AMP elevation was potentiated, possibly because insulin was conserving factors needed for a maximal PGE1stimulus or retarding the leakage of cAMP itself. The results indicate that insulin has little or no direct effect on cyclic AMP metabolism in cultured human fibroblasts and is consistent with the known insensitivity of these cells to insulin for other par

ISSN:0021-9541    

DOI:10.1002/jcp.1040850210

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

年代:1975

数据来源: WILEY

摘要:

AbstractPhenylglyoxal (PG) is shown to be a cell surface probe specific for arginine moieties in protein: (1) It does not enter the cell as evidenced by lack of PG in the cytoplasm. (2) It does not cause excessive cell leakage as measured by release of51Cr. (3) It reacts with positively‐charged groups in proteins at the cell surface but not with those of phospholipids at the surface; since pronase removes PG from the surface, but phospholipase C does not. (4) Under the conditions used in these experiments, it reacts virtually exclusively with arginine moieties in protein (Freedman et al., '68; Takahashi, '68; Werber and Sokolovsky, '72).Synchronized cells were exposed to radioactive PG to assess quantity of arginine moieties in protein at the surface. There is a sharp decrease in arginine at the cell surface at entry into G1phase from M and a 24‐fold increase upon entry into S phase. There is a slight drop in exposed arginine in late S phase followed by an increase to 26 times the G1level immediately prior to mitosis. Lactoperoxidase‐catalyzed iodination of tyrosine moieties in protein at the surface of synchronized cells shows a very gradual increase in protein as the cells move through the cycle and increase in size. Since the increase in arginine moieties in protein at the surface does hot reflect a similar increase in total protein at the surface, an arginine‐rich protein appears to be exposed at the cell surface during the division‐related phases of the c

ISSN:0021-9541    

DOI:10.1002/jcp.1040850211

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

年代:1975

数据来源: WILEY