ISSN:0021-9541    

DOI:10.1002/jcp.1040700302

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

年代:1967

数据来源: WILEY

摘要:

AbstractIn two heteroploid cell lines synchronized with thymidine double block, activity of alkaline phosphatase decreased during the 12 hour period preceding mitotic peak. A return to high values was observed during the next 12 hours of synchronous cycle. Prednisolone (11β, 17α, 21‐trihydroxy‐1,4‐pregnadiene‐3,20‐dione), when added to such cell cultures increased alkaline phosphatase activity in one of the cell lines (Henle embryonic intestine) but had the opposite effect on another line (HeLa‐S3) in which the enzyme activity was decreased. Neither effect could be demonstrated if the hormone was added at the end of S phase or if cells were arrested in metaphase by vinbla

ISSN:0021-9541    

DOI:10.1002/jcp.1040700303

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

年代:1967

数据来源: WILEY

摘要:

AbstractThe permeability of the membranes of several strains of Ehrlich mouse ascites tumor cells to a series of homologous glycols was analyzed with equations from irreversible thermodynamics. Experimental data were fitted to the appropriate equations of Kedem and Katchalsky by means of an analog computer and values for σ, Lp, and ωRT were calculated. These parameters would become part of a functional profile of the membrane of the tumor cell. The glycols cross the membrane with energies of activation ranging from 16 kcal/mole for ethylene glycol to 20 kcal/mole for triethylene glycol. Entropies of activation ranged from 17 to 27 entropy units. This analysis provided several additional dividends. It is one of the few examples with a mammalian cell where the kinetics of non‐electrolyte transport have been described completely by the equations of irreversible thermodynamics. It has provided the means to distinguish how much of the transport occurred through porous paths in the membrane and how much involved solution within the matrix of the membrane. Finally, several tumor cell populations have been distinguished through these functional properties of their membra

ISSN:0021-9541    

DOI:10.1002/jcp.1040700304

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

年代:1967

数据来源: WILEY

摘要:

AbstractIn concentrations having no effect on the evoked alpha‐A fiber spike, adenosine triphosphate (ATP), adenosine monophosphate (AMP) and several other nucleotides produced antagonism of spontaneous impulses in isolated desheathed frog nerve soaked in Ca free solution. ATP was only slightly more potent than AMP, indicating that high‐energy phosphate bonds and Ca complexing are not important for stabilizing action. Furthermore, sub‐effective concentrations of Ca potentiated the stabilizing action of ATP to a minimal degree and that of AMP not at all, suggesting a direct action of the nucleotide per se rather than a Ca‐nucleotide complex. Ca45washout experiments showed that the nucleotides did not depress efflux of Ca from nerve axons but, in fact, caused release of Ca. It was proposed that nucleotide stabilization is associated with replacement of nucleotide lost from the excitable membrane into the Ca free

ISSN:0021-9541    

DOI:10.1002/jcp.1040700305

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

年代:1967

数据来源: WILEY

摘要:

AbstractThe kinetics of RNA synthesis have been studied under various growth conditions using synchronizedTetrahymena pyriformisGL. The curves obtained are approximately linear in growth‐supporting media but vary under other circumstances. The presence of amino acids in the medium stimulates RNA synthesis inTetrahymenaas it does in bacteria. Since these induced variations do not influence the essential features of the pre‐cytokinetic period it is inferred that fluctuations in the rate of RNA synthesis described by others are probably not essential features of temperature‐induced synchrony. In addition, the translational stability of division‐related templates at synchronizing temperatures has been investigated. The synthesis of proteins necessary for cytokinesis is shown to be greatly reduced under conditions simulating a heat‐shock. Inhibitor studies using cycloheximide indicate that protein synthesis is required longer into the cytokinetic phase than had previously been thought. Collectively the data are all compatible with the hypothesis that synthesis of division‐related proteins is drastically reduced in heat‐shockedTetrahymenaand that the basis for this reduction is hydrolysis of template RNA without concurren

ISSN:0021-9541    

DOI:10.1002/jcp.1040700306

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

年代:1967

数据来源: WILEY

摘要:

AbstractSingle cell suspensions were prepared from the choroids of adult rabbit eyes using Pronase digestion, gentle pipetting and centrifugation. When diluted and inoculated into medium F12 supplemented with 5% fetal bovine serum and 10% rabbit serum, the choroid cell suspensions yielded large, healthy colonies with an average plating efficiency of about 45%. The growth in culture of a large portion of the cells from a normal non‐embryonic tissue opens new possibilities for the study of cellular differentiationin vitr

ISSN:0021-9541    

DOI:10.1002/jcp.1040700307

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

年代:1967

数据来源: WILEY

摘要:

AbstractTo evaluate the possible role of mycoplasma contamination of tissue cultures in virus induced chromosome breakage, human leukocyte cultures were inoculated with three mycoplasma strains;M. salivarium, M. hominis type 2andM. fermentans. All three strains caused mitotic inhibition when an inoculum of approximately 106CFU was used, the effect ofM. fermentansbeing less severe than the one produced by the two other strains. Using a lower inoculum of 103CFU an increase of chromosome breakage could be produced withM. salivariumwhen the leukocytes were cultivated for five days. No chromosome changes were seen withM. hominis type 2andM. fermentans.The mitotic inhibition and chromosome breaks induced byM. salivariumwere discovered to be related to an arginine deficiency of the culture medium produced by the mycoplasma. This conclusion is dervied from the fact that arginine addition was able to inhibit the mitotic inhibition and the increase of chromosome breakage, and secondly, that similar changes could be produced in leukocytes grown in argining deficient medidum without mycoplasma.The growth ofM. salivariumwas inhibited in leukocyte cultures treated with kanamycin, but the mycoplasma induced mitotic inhibition was still present, indicating that replication of mycoplasma organisms was not required for the production of arginine deficiency.

ISSN:0021-9541    

DOI:10.1002/jcp.1040700308

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

年代:1967

数据来源: WILEY

摘要:

AbstractUsing the harvesting method of synchronizing L cells, the relationship of RNA synthesis of DNA replication was studied by the use of selective inhibitors of RNA synthesis such as actinomycin D and chromomycin succinate. The synthesis of the early replicating DNA fraction is a process sensitive to the inhibition of RNA synthesis during the G1 period.The synthesis of early replicating DNA was inhibited by chromomycin succinate without affecting the initation of DNA synthesis. However, actinomycin D inhibited the synthesis of early replicating DNA and prevented the initiation of DNA synthesis in 50% of the synchronized cells. However, it was found that the continued synthesis of RNA during the S period is not essential for the synthesis of late replicating DNA.In addition to this specific response of DNA synthesis to the inhibitors of RNA synthesis, another function of early and late replicating DNA was determined relative to the cell viability. Cells synthesizing early replicating DNA were killed more efficiently by chromomycin than at other stages of the cell cycle. This indicates that the early replicating DNA unit plays a more important role in cell reproduction than the late replicating DNA unit.

ISSN:0021-9541    

DOI:10.1002/jcp.1040700309

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

年代:1967

数据来源: WILEY

摘要:

AbstractChick embryo cells transformed by Rous sarcoma virus (RSV) were able to grow in suspension, either as colonies when trapped in nutrient agar, or in spinner cultures using liquid medium. Two strains of RSV, RSV (RAV‐1) and Schmidt‐Ruppin RSV, were able to increase the ability of chick embryo cells to grow in suspension but Rous‐associated virus (RAV‐1) and polyoma virus were not. Cells growing in suspension supported high levels of RSV production and a simple method for propagating large amounts of virus is suggested. Suspended noninfected cells, which do not grow extensively, lose their ability to be infected by RSV, suggesting that cellular divisions must be in progress for successful infection

ISSN:0021-9541    

DOI:10.1002/jcp.1040700310

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

年代:1967

数据来源: WILEY

ISSN:0021-9541    

DOI:10.1002/jcp.1040700301

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

年代:1967

数据来源: WILEY