摘要:

AbstractNovikoff rat hepatoma cells were propagated in suspension cultures containing 0.5 to 10 μC of3H‐methyl‐thymidine,3H‐5‐uridine,3H‐G‐adenosine or3H‐8‐adenine. The presence of the3H‐labeled precursors caused an inhibition of cell replication which was due to a delay or arrest of the cells in G2and M. The degree of inhibition was proportional to the amount of radioactivity incorporated into nucleic acids. Almost immediate and complete inhibition resulted from incubation with 10 μC3H‐thymidine/ml. The presence of 0.5 μC3H‐thymidine/ml caused a significant increase in the relative proportion of cells in G2+ M, even though the population doubling time of the culture

ISSN:0021-9541    

DOI:10.1002/jcp.1040900102

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

年代:1977

数据来源: WILEY

摘要:

AbstractThe way in which the lectins concanavalin A (Con A) andRicinus communisagglutinin (Ricin) alter the K+content of Ehrlich ascites tumor cells was investigated. Unidirectional and net fluxes were determined in unwashed cells during a time course following lectin addition. Total influx, ouabain sensitive influx, Mg++‐ and Na+‐K+‐ATPase activity were all unaffected. Cell ATP content was normal for at least 19 minutes after exposure to Con A. Early after contact with Ricin or Con A efflux was stimulated 2‐3‐fold, resulting in net K+loss, but after 20 minutes efflux had returned to normal. Ricin and Con A acted similarly although Ricin was present at only 1/50 the concentration of Con A. When the findings are evaluated together with previous work it is suggested that a particular membrane glycoprotein may be concerned in the efflux alteration

ISSN:0021-9541    

DOI:10.1002/jcp.1040900103

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

年代:1977

数据来源: WILEY

摘要:

AbstractA quantitative assay for intercellular adhesion, which is a modification of the collecting aggregate assay (Roth et al., 1971) is described. The use of mechanically dissociated single cells labeled with3H‐leucine, and of a gyratory shaker increased considerably the efficiency of cell collection. With chick embryo neural retina, it was shown that isotypic cell adhesion occurs in simple synthetic media and even in sodium chloride solution suggesting that divalent cations do not play a major role in adhesion of these cells. Cell collection in media without serum was not affected by metabolic or protein synthesis inhibitors. However, cell adhesion was temperature‐dependent since no collection occurred at 4°C but was maximal at

ISSN:0021-9541    

DOI:10.1002/jcp.1040900104

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

年代:1977

数据来源: WILEY

摘要:

AbstractThe quantitative assay described in the preceding paper (Pessac et al., 1977) was used to study the effects of serum and various proteins on isotypic adhesion of chick embryo neural retina cells. Fetal bovine, chicken, horse, rabbit and human sera promoted cell adhesion to the same extent. The same sera also enhanced isotypic adhesion of cells from other organs showing that the cell adhesion promoting activity of sera was not organ specific. Neural retina (NR) cell collection in serum supplemented medium was not modified by protein synthesis or metabolic inhibitors and was temperature dependent with a maximum at 38°C. The higher temperature does not seem to be required for repair of the cell surface after dissociation, but for the process of adhesion itself. Various serum fractions and egg albumin showed a cell adhesion promoting activity similar to that of sera

ISSN:0021-9541    

DOI:10.1002/jcp.1040900105

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

年代:1977

数据来源: WILEY

摘要:

AbstractGlycerolated stalks of the sessile peritrich ciliateCarchesium sp.were treated with 10−6g ion/1 Ca2+to disrupt the contractile spasmoneme. The resulting preparation consisted primarily of the fibrillar matrix, a dense extracellular meshwork of microfibrils. Some mechanical properties of this preparation have been investigated. The matrix tensile force‐extension ratio relation for an initial stretch was characteristic of a soft, swollen polymer network, elastic modulus in young stalks 1.7 × 105Nm−2, in mature stalks 4.0 × 105Nm−2. The higher elastic modulus in mature stalks implies an increase in the interchain cross‐link frequency. In young stalks, elastic modulus was found to be independent of the ambient Ca2+concentration in the threshold range for spasmonemal contraction. Stalk relaxation was pronouncedly irreversible, showing stress softening and permanent hysteresis on repeated loading. Hysteresis was time independent and stiffness was not recovered after four hours at zero strain. Hysteresis was enhanced by repeated loading to the same tensile force. Stress‐strain hysteresis at a low extension ratio is characteristic of highly filled polymer networks in which polymer chains are interconnected via rigid filler particles as well as directly

ISSN:0021-9541    

DOI:10.1002/jcp.1040900106

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

年代:1977

数据来源: WILEY

摘要:

AbstractLow passage BHK 21/13 cells contain two cell surface enzymes, a nucleotide pyrophosphatase and a monophosphoester hydrolase, which together hydrolyze exogenous UDP‐galactose to free galactose. During serial passage, BHK cells successively lose both enzymes. Concomitant with the loss of these enzymatic activities, changes in cell morphology, as well as in the serum requirement for the initiation of DNA synthesis, were observed. Clonal sublines of BHK cells were isolated, which differed qualitatively in their ability to hydrolyze UDP‐galactose. Clonal BHK sublines, which exhibited both enzymatic activities on their cell surface, resembled low passage BHK cells in morphology and serum requirement for the initiation of DNA synthesis. Sublines not containing these enzymes resembled BHK cells of high passage cultures. The ability of intact BHK cells to hydrolyze exogenous nucleotide sugars may serve as an indicator for the progression of BHK cells from a normal to a more transformed st

ISSN:0021-9541    

DOI:10.1002/jcp.1040900107

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

年代:1977

数据来源: WILEY

摘要:

AbstractHeparan sulfate from the surface of a variety of mouse cells at different cell densities was examined by ion‐exchange chromatography. The results of this analysis show that:1The heparan sulfate from new isolates of Swiss 3T3 cells transformed SV40 virus (a DNA tumor virus) elutes from DEAE‐cellulose at a lower ionic strength than that from the parent cell type. This finding confirms our earlier observation with an established SV40‐transformed cell line (Underhill and Keller, 1975) and eliminates the possibility that this change is caused by extended passage in culture.2For both parent and transformed 3T3 cells, the heparan sulfates from low and high density cultures were the same as judged by chromatography on DEAE‐cellulose. This result demonstrates that the transformation‐dependent change which we have observed is independent of cell density.3The heparan sulfate from Balb/c 3T3 cells transformed with Kirsten murine sarcoma virus (an RNA tumor virus) elutes from DEAE‐cellulose prior to that from parent Balb/c 3T3 cells. This result extends the transformation dependent change in heparan sulfate to the Balb/c 3T3 cell line and to cells transformed with a

ISSN:0021-9541    

DOI:10.1002/jcp.1040900108

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

年代:1977

数据来源: WILEY

摘要:

AbstractSeveral types of cultured fibroblasts, including chick embryo, human and mouse, were killed by the addition of sodium ascorbate at final concentrations of 0.05–0.25 mM to cultures at the time of inoculation or to attached cells. Ascorbate did not affect the attachment of cells to the substratum. The effect on chick embryo fibroblasts was visible by fours hours and by six hours almost all cells had swelled and were becoming detached. By 24 hours detached cells had either lysed or become crenated in appearance. Other end‐diol reducing agents and also glutathione and cysteine were effective while gulonolactone, a non‐reducing analogue of ascorbate, was ineffective. Preincubation of medium containing ascorbate but no cells, conditions which result in degradation of the vitamin, led to loss of toxicity, indicating that a degradation product was not the lethal agent and that a component of the medium was not converted to a lethal substance. The lethal effect of both ascorbate and glutathione was prevented by the addition of catalase to the medium, suggesting that H2O2formed by intracellular reactions and then excreted into the medium was the cytotoxic agent. This conclusion was supported by the findings that 0.05 mM H2O2added to chick embryo fibroblasts was lethal and that the effect of this compound on cellular morphology was almost identical to that of asco

ISSN:0021-9541    

DOI:10.1002/jcp.1040900109

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

年代:1977

数据来源: WILEY

摘要:

AbstractHybrid clones were obtained between a mouse cell line (3TP) and a temperature‐sensitive Chinese hamster cell line (K12) unable to grow at 40° because of atsdefect apparently located at the G1/S transition. The great majority of hybrid clones grew at 40°, showing thetsdefect to be “recessive.” Chromosome DNA replication was analyzed in some detail in three hybrid clones with balanced complements. Although the S period of these hybrids was longer than that of K12, DNA replication in mouse and hamster chromosomes started and ended synchronously. Upon prolonged culture, mouse chromosomes were lost as they are in hybrids involving a nontsChinese hamster partner, in which case asynchronous chromosome replication appears to be the rule. It seems therefore that asynchronous replication is not the determining factor in chromosome loss from cell

ISSN:0021-9541    

DOI:10.1002/jcp.1040900110

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

年代:1977

数据来源: WILEY

摘要:

AbstractSeven UV‐sensitive clones were isolated from the mouse cell lines, FM3A and L5178Y, using Lederberg style replica plating. The UV‐sensitive clones were found at a frequency of 1 in 886 clones of FM3A and of 6 in 420 clones of L5178Y, after treatment with N‐methyl‐N′‐nitro‐N‐nitrosoguanidine, but no UV‐sensitive clones were obtained in the untreated controls. The Do values of freshly isolated clones were 10 to 21 ergs/mm2(mainly 10 to 13 ergs/ mm2), while the original FM3A and L5178Y lines had Do values of 32 ergs/mm2. The UV‐sensitive clones were found to be rather stable for a period ranging from two to eight months after isolation. However, later some of them tended to lose their UV‐sensitivity, in terms of increase in Do values or n values. More stable UV‐sensitive subclones could be isolated from these populations by cloning using the replica plating method. Caffeine was found to potentiate the lethal action of UV‐irradiation on the UV‐sensitive clones as well as

ISSN:0021-9541    

DOI:10.1002/jcp.1040900111

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

年代:1977

数据来源: WILEY