ISSN:0021-9541    

DOI:10.1002/jcp.1040850302

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

年代:1975

数据来源: WILEY

摘要:

AbstractThe rate of cell division ofTetrahymenagrowing in an observational high pressure vessel was measured at selected pressures of helium, hydrogen and at high hydrostatic pressure. Pressures greater than 100 atm reduced the rate of division, but the gases inhibited division to a lesser degree than pure hydrostatic pressure. Hydrogen's effect was distinguishable from that of hydrostatic pressure at 130 atm or more, while helium's effect appeared at 175 atm. These inert gases probably counteract the action of pressure by stabilising apolar pressure‐labile target

ISSN:0021-9541    

DOI:10.1002/jcp.1040850303

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

年代:1975

数据来源: WILEY

摘要:

AbstractThe densities of cationized ferritin (CF) particles binding to the surfaces of cultured Ehrlich ascites tumor cells were determined at pH 7.4, where the ferritin stain was applied either prior to or following glutaraldehyde fixation. The densities were also determined with CF adjusted to pH 1.9 and applied after fixation. For all fixed samples there was a higher density of particles bound to microvilli than to the spaces between them. Treatment with neuraminidase removed more particles from microvilli than from the intermicrovillus spaces, but did not reduce the levels of binding to the same value.When cationized ferritin is applied prior to fixation, an aggregation of the CF particles at the cell surface was observed, with the internalization of some clusters. This effect was independent of neuraminidase treatment.

ISSN:0021-9541    

DOI:10.1002/jcp.1040850304

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

年代:1975

数据来源: WILEY

摘要:

AbstractThe inclusion of DMSO in the media of suspension cultures of Friend erythroleukemia cells results in the erythroid differentiation of these cells. The studies reported here were directed towards answering two questions: (1) How long an exposure to DMSO is necessary to induce the differentiation of these cells; and (2) What is the fate of the differentiating cells when DMSO is removed from the medium. Exposure to DMSO for less than 24 hours failed to produce any detectable evidence of erythroid differentiation. On the other hand, culture in the presence of DMSO for 24 hours followed by culture in DMSO‐free medium for four additional days produced a small but detectable increment in the proportion of benzidine positive cells in the culture. Once the differentiation of an individual cell was initiated, the process continued after removal of DMSO from the medium. The cell became progressively more differentiated as evidenced by increases in the intensity of benzidine staining as well as in the rate of heme synthesis and heme content. However, when cells which had been induced to differentiate by DMSO were cultured in DMSO‐free medium for more than 3–4 days, they became vacuolated and apparently died. This latter phenomenon, as well as the more rapid proliferation of the undifferentiated cells in the culture, accounts for the observation that when new cultures are established from cultures which have been grown in the presence of DMSO for several days, the culture which results ultimately contains only differentiated

ISSN:0021-9541    

DOI:10.1002/jcp.1040850305

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

年代:1975

数据来源: WILEY

摘要:

AbstractAggregation of chick embryonic liver and kidney cells was completely abolished by a treatment with carboxypyridine disulfide which binds –SH groups. The effect could be reversed by a subsequent treatment with some thiols. Inhibition of RNA synthesis or respiratory metabolism did not prevent cell aggregation. Cell adhesion is discussed in the light of these observation

ISSN:0021-9541    

DOI:10.1002/jcp.1040850306

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

年代:1975

数据来源: WILEY

摘要:

Abstract(1) Determinations were carried out on the incorporation of fucose‐6‐[3H] and glucosamine‐6‐ [3H] into trichloracetic acid insoluble macromolecules which remained bound to the cells or were released into the medium of chick embryo muscle cell cultures. The radioactivity determined in the medium was corrected for unspecific binding of label to components of the medium. (2) During an incorporation period of six hours the incorporation per microgram DNA with fucose as label into cell bound macromolecules is about twice as high as the incorporation into macromolecules released into medium. With glucosamine about twice as much is incorporated into medium released than into the cell bound macromolecules. (3) The incorporation per microgram DNA increases during a culture period of three days but the increase ceases at different times during this culture period when determined with fucose or glucosamine or for cell bound and medium released material. (4) An increase in cell density increases the incorporation per DNA of fucose and to a much slighter extent that of glucosamine. Reduction of cell density by addition of cytosine arabinoside to the medium does not decrease the incorporation per microgram DNA. (5) The effect of changes of fibroblast/myoblast ratios on the incorporation of fucose and glucosamine were examined. No significant effect was observed for a ratio of 10–30% fibroblasts when control cultures or cultures after cell sedimentation were maintained in complete medium. Marked changes were observed after culture in medium without protein components. Under these conditions an increase in the fibroblast/myoblast ratios were observed as well as an increase in the incorporation of label into medium released and a decrease into cell bound macro

ISSN:0021-9541    

DOI:10.1002/jcp.1040850307

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

年代:1975

数据来源: WILEY

摘要:

AbstractDespite the genetic interruption of the Leloir pathway both galactosemic patients and galactosemic fibroblasts can convert galactose to CO2and TCA precipitable products, although at less than the normal rate. These observations stimulated investigations into the identity of the alternative metabolic routes which allow for galactose metabolism in the absence of in vitro galactose‐1‐P‐uridyl transferase. Four lines of galactosemic cells, each without detectable gal‐transferase, produced14CO2from [1‐14C]‐galactose (0.094 μmoles in 20 cc of medium) at approximately 39% ± 16% the rate of transferase positive cells over a 48‐hour period. However, galactokinase deficient fibroblasts produced14CO2and TCA precipitable products from [1‐14C] ‐galactose or [U‐14C] ‐galactose at only 3% to 9% the rate of normal fibroblasts. Therefore it seems likely that galtransferase deficient fibroblasts must first synthesize galactose‐1‐P for furt

ISSN:0021-9541    

DOI:10.1002/jcp.1040850308

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

年代:1975

数据来源: WILEY

摘要:

AbstractCytochalasin B was used as a tool to study the inter‐relationships between cell movement, the reinitiated DNA synthesis and the enhanced transport of specific small molecules stimulated by serum in quiescent 3T3 cells. Cytochalasin at concentrations of less than 1 μg/ml inhibits serum‐stimulated movement within the monolayer and migration into a wound. Even at ten times this concentration there is little effect on the increase in DNA in the culture, indicating that movement away from neighboring cells is not required for the initiation of DNA synthesis.While DNA synthesis is not inhibited by concentrations of cytochalasin up to 10 μg/ml, the increased thymidine transport which is associated with the onset of the S phase of the cell cycle is inhibited and DNA synthesis cannot be measured by the labelling of nuclei with radioactive thymidine.Cytochalasin has a differential effect on the early transport changes produced by serum addition. Glucose transport is inhibited by low concentrations of the drug (<1 μg/ml) while the enhanced uptake of phosphate and uridine is unaffected by a 10‐fold increase in concentration. Although the doses of cytochalasin required for 50% inhibition of hexose uptake and of cell movement are the same, no causal relationship between sugar transport and locomotion can be demonstrated.Cytochalasin affects membrane functions in at least two different ways. The drug inhibits the uptake of glucose directly but affects only the S‐phase associated increase in thymidine

ISSN:0021-9541    

DOI:10.1002/jcp.1040850309

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

年代:1975

数据来源: WILEY

摘要:

AbstractD+but not D−myeloid leukemic cells can be induced by the appropriate conditioned medium or by serum from endotoxin treated mice, to undergo cell migration in agar, cell attachment to the surface of a Petri dish and differentiation to mature macrophages and granulocytes. Inhibition of cell multiplication by cytosine arabinoside, hydroxyurea, mitomycin C, thymidine, 5‐bromodeoxyuridine, 5‐iododeoxyuridine, 5‐fluorodeoxyuridine or actinomycin D, but not by vinblastine or cycloheximide, induced cell migration, cell attachment to the Petri dish and the formation of macrophages in D+cells. There was no induction of cell migration or formation of macrophages and a much lower induction of cell attachment in D−cells. The induction of these changes in D+cells required protein synthesis and the inhibitors showed the same toxicity for D+and D−cells. The results indicate, that the inhibitors induced specific surface membrane changes in D+but not

ISSN:0021-9541    

DOI:10.1002/jcp.1040850310

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

年代:1975

数据来源: WILEY

摘要:

AbstractIn several respects, notably the high velocity of shortening, Ca2+dependence, and ATP independence, contraction ofSpirostomumresembles the spasmonemal mechanism of the peritrich ciliates. In this report further mechanical properties of the contractile apparatus are described that extend this comparison. The velocity‐load characteristic is more appropriate to an elastomer than to a muscle where contraction force is load‐dependent. Active tension is found to relate linearly to cell length for extensions up to and beyond resting length (lr), an elastic limit is reached around 1.5 lr. At resting length this tension, measured by the deformation of a glass microbalance, is similar to that predicted from consideration of the hydrodynamic forces normally resisting shortening. The tension‐length relation for the unstimulated (passive) cell is also linear between lrand the elastic limit, but is displaced from the active tension‐length curve and is of reduced stiffness. Kinetic studies suggest that maximum tension and maximum velocity coincide. Calculations are presented that support a model of contraction inSpirostomumin which the myonemes behave as a mechanochemical engine powered directly by the chemical potential

ISSN:0021-9541    

DOI:10.1002/jcp.1040850311

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

年代:1975

数据来源: WILEY