ISSN:0021-9541    

DOI:10.1002/jcp.1040690102

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

年代:1967

数据来源: WILEY

摘要:

AbstractThe role of ionic interactions in the adenosinetriphosphate (ATP) dependent Na binding by rat liver microsomes was investigated. In the concentration range of 0 to 20 mM, Mg and Ca are demonstrated to compete strongly against Na for microsome binding sites. In the presence of Ca, the nonbiological complexing agent ethylenediaminetetraacetate (EDTA) produced a marked increase in Na binding accompanied by a concomitant decrease in Ca binding. Under similar conditions ATP, which is a weaker complexing agent than EDTA, produced quantitatively smaller but qualitatively similar changes in binding. The data show that the effect of ATP on Na binding is not dependent upon the formation of a hypothetical Na binding intermediate in the hydrolysis of ATP as other investigators have postulated. Rather, the effect of ATP is demonstrated to depend upon the presence of unhydrolyzed ATP and its ability to complex divalent cations, and thereby to reduce divalent cation competition against monovalent cations for membrane binding sites.

ISSN:0021-9541    

DOI:10.1002/jcp.1040690103

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

年代:1967

数据来源: WILEY

摘要:

AbstractIn the presence of Na, K, Mg and Ca at physiological pH, complexing agents can affect cation binding by rat liver microsomes in a manner not always readily predictable simply from a knowledge of individual formation constants. Increasing concentrations (0 to 20 mM) of the strong nonbiological complexing agent, ethylenediaminetetraacetate (EDTA), produced a sharp decrease almost to zero in bound Ca, an increase to a high plateau in bound Na and K and an initial increase followed by a sharp decrease in bound Mg. Increasing concentrations of the Ca‐preferring analogue of EDTA, ethylene bisglycol (β‐aminoethylether) tetraacetate (EGTA), produced similar changes except that bound Mg increased and remained elevated, indicating that this agent complexes Mg very weakly at physiological pH. The biological complexing agent, adenosine triphosphate (ATP), caused a gradual rectilinear and parallel decrease in bound Mg and Ca and a concomitant and parellel increase in bound Na and K at about 4°C and pH 6.4. Results with EDTA and EGTA suggest, however, that under different conditions, enhancement by ATP of divalent cation binding may be possible. Reactions of this nature may be of significance in ATP stimulated divalent cation uptake by subcellular part

ISSN:0021-9541    

DOI:10.1002/jcp.1040690104

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

年代:1967

数据来源: WILEY

摘要:

AbstractThe electrical potential difference (PD) across the membrane of the Ehrlich mouse ascites tumor cell has been measured with intracellular microelectrodes. The mean for 111 cells in control Ringer solution was − 11.2 mV ± 0.29 (SE), interior negative. When sulfate replaced chloride in the external medium the PD fell to − 2.8 mV if measured as soon as possible after mixing the cells with a sulfate medium, but when nitrate replaced chloride the PD fell only to − 8.5 mV. Cellsequilibratedin nitrate had the same PD as those in control Ringer. These results indicate that the PD is sensitive to changes in the external chloride concentration and that nitrate can substitute for chloride electrically. However, since the PD for chloride, based on the Nernst equation and calculated on the basis of 70% exchangeability of cell chloride, is three times greater than the measured PD, it is hypothesized that sodium contributes significantly to the membrane potential in addition to chloride. On the other hand, potassium does not influence the PD to any great

ISSN:0021-9541    

DOI:10.1002/jcp.1040690105

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

年代:1967

数据来源: WILEY

摘要:

AbstractIn vitrohybridization of seven pairs of genetically different murine cell has been demonstrated by the use of karyological markers, and pure cultures of these hybrids have been isolated. All somatic hybrids showed a progressive loss of chromosomes during this proliferationin vitro.

ISSN:0021-9541    

DOI:10.1002/jcp.1040690106

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

年代:1967

数据来源: WILEY

摘要:

AbstractRNA synthesis was studied by autoradiographic analysis using tritiated uridine incorporation in the Chinese hamster cell line Dede after a one‐minute pulse labeling period. RNA synthesis continues during all stages of interphase and mitosis except during metaphase and anaphase. Cytoplasmic RNA was apparently synthesized in the nucleus, since no grains were observed above the background level in the sample immediately following the labeling. Nucleoli synthesize their own RNA and are not reservoirs for RNA synthesized elsewhere. Both actinomycin D and nogalamycin inhibited the RNA synthetic activity of chromatin and nucleoli. However, the nucleolar synthetic activity was more susceptible to these agents than that of chromatin. Furthermore, actinomycin D was a stronger inhibitor than nogalamyci

ISSN:0021-9541    

DOI:10.1002/jcp.1040690107

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

年代:1967

数据来源: WILEY

摘要:

AbstractPartially synchronized secondary cultures of chicken embryo fibroblasts were exposed to Rous sarcoma virus (RSV) at various times in the cell cycle. The initiation of normal virus production could be inhibited by treatment with excess thymidine or with cytosine arabinoside without any effect on mitosis. This result is consistent with the hypothesis that the provirus of RSV is DNA, although the virion of RSV contains only RNA. It was, also, found that treatment which prevented or interferred with the first mitosis after exposure to virus prevented the initiation of normal virus production. Later mitoses did not appear to be necessary. A corollary of this finding is that virus production is synchronized by mitosis and that the length of the latent period depends upon when in the cell cycle a cell is exposed to virus.

ISSN:0021-9541    

DOI:10.1002/jcp.1040690108

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

年代:1967

数据来源: WILEY

摘要:

AbstractThe cellular composition of individual hemopoietic spleen colonies has been studied using techniques which tested primarily for cell function rather than cell morphology. Erythroblastic cells were recognized by their capacity to incorporate radioiron, granulocytic cells by their content of peroxidase‐positive material, and hemopoietic stem cells by their ability to form spleen colonies in irradiated hosts. It was found that, 14 days after the initiation of spleen colonies, the distribution of these cell types among individual colonies was very heterogeneous, but that most colonies contained detectable numbers of erythroblasts, granulocytes and colony‐forming cells. An appreciable proportion of the cells in the colonies could not be identified as any of these three cell types. No strong correlations between numbers of erythroblasts, granulocytes and colony‐forming cells in individual colonies were observed, though there was a tendency for colonies containing a high proportion of erythroblasts to contain a low proportion of granulocytes, and for colonies containing a high proportion of granulocytes to contain a higher proportion of colony‐forming cells. An analysis of colonies which contained cells bearing radiation‐induced chromosomal markers indicated that 83–98% of the dividing cells within 14‐day spleen colonies were derived from sing

ISSN:0021-9541    

DOI:10.1002/jcp.1040690109

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

年代:1967

数据来源: WILEY

摘要:

AbstractBuoyant density distributions of hemopoietic colony‐forming units (CFU) from normal mouse marrow were determined by equilibrium density gradient centrifugation in bovine serum albumin (BSA) gradients. The distributions were compared with those obtained for the total population of nucleated cells from normal mouse marrow. The buoyant density distribution for CFU was found to differ from the density distribution for the total nucleated cell population, and the portion of the total cell population with densities much less than the mean value was found to contain up to a 30‐fold greater proportion of CFU than an uncentrifuged control. These results provide a preliminary approach to the purification and characterization of normal hemopoietic colony‐forming stem

ISSN:0021-9541    

DOI:10.1002/jcp.1040690110

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

年代:1967

数据来源: WILEY

摘要:

AbstractUsing a modification of the agar gel method for bone marrow culture, serum from various strains of mice has been tested for colony stimulating activity. Ninety percent of sera from AKR mice with spontaneous or transplanted lymphoid leukemia and 40–50% of sera from normal or preleukemic AKR mice stimulated colony formation by C57B1 bone marrow cells. Sera from 6% of C3H and 30% of C57B1 mice stimulated similar colony formation. The incidence of sera with colony stimulating activity rose with increasing age. All colonies were initially mainly granulocytic in nature but later became pure populations of mononuclear cells.Bone marrow cells exhibited considerable variation in their responsiveness to stimulation by mouse serum. Increasing the serum dose increased the number and size of bone marrow cell colonies and with optimal serum doses, 1 in 1000 bone marrow cells formed a cell colony. Preincubation of cells with active serum did not stimulate colony formation by washed bone marrow cells.The active factor in serum was filterable, non‐dialysable and heat and ether lab

ISSN:0021-9541    

DOI:10.1002/jcp.1040690111

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

年代:1967

数据来源: WILEY