摘要:

AbstractSecondary cultures of human diploid fibroblasts which demonstrated density dependent inhibition of cell growth (DDI) were used to study the possible limitation of growth in cell cultures by diffusion. An oscillating platform system is described which insures constant mixing of the medium during the culturing period. Using this system, it was found that a greater number of cells in density inhibited cultures, grown to confluence for four days after initial seeding, could be stimulated to resume growth by a fresh medium change if the cultures were incubated on the oscillating platform than if the cultures were left undisturbed. This greater stimulation on the platform was probably not due to mechanical alterations on the surface of the cells due to motion of the medium as judged by TCA precipitable material released into the medium from cells prelabeled with glucosamine‐3H. In spite of this greater stimulation after a single treatment with fresh medium, refeeding the cells on the platform every other day over a 12‐day period did not affect the final saturation density achieved in the cultures. The results indicate that diffusion limitation of growth might occur under certain circumstances but that it cannot account entirely for the phenomenon of

ISSN:0021-9541    

DOI:10.1002/jcp.1040860502

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

年代:1975

数据来源: WILEY

摘要:

AbstractWe have studied the kinetics of suppression of tyrosinase activity and tumorigenicity in unsynchronized B16 mouse melanoma cells (clone B559) exposed to 5‐bromodeoxyuridine (BrdU, 3 m̈g/ml) for one or two cell divisions, then cultured in BrdU‐free medium (RM) for five or six days. Bromouracil replaced about 23% of thymine residues after 24 hours (1 cell division) and almost 40% after 48 hours (2 cell divisions) in the presence of BrdU. Upon subsequent growth in RM the extent of replacement declined in a manner consistent with dilution by new DNA synthesis, reaching 5–10% substitution by day 7 of these experiments. Tyrosinase activity was significantly reduced after treatment with BrdU for 24 or 48 hours but continued to decline after the cultures were changed to RM, approaching undetectable levels on day 7. The time course of reduction was similar to that previously determined in cells grown continuously for seven days in the presence of BrdU. Therefore, suppression of tyrosinase activity can result from incorporatpon of BrdU during a single cell cycle, but requires about seven days for full manifestation of the effect. Tumorigenicity decreased to 55% after 24 hours and to 15% after 48 hours with BrdU but rapidly reversed to approach that of untreated melanoma cells when subsequently grown in RM for 5–6 days. The effects of BrdU on total RNA or protein synthesis, or on plating efficiency appeared insufficient to account for the degree of suppression observed. Our results indicate that substitution by bromouracil into either strand of DNA loci controlling tyrosinase activity or tumorigenic potential may be sufficient for suppression. In addition, they demonstrate that such brief treatment with BrdU may be used to probe the regulation of differentiated function and tumorigenicity in these melano

ISSN:0021-9541    

DOI:10.1002/jcp.1040860503

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

年代:1975

数据来源: WILEY

摘要:

AbstractEpidermal Growth Factor (EGF) at concentrations of 10−9to 10−10M initiates cell division in both confluent and low density non‐dividing 3T3 cells. Four days after addition of EGF to confluent or low density non‐dividing 3T3 cells there is a 2‐ and 5‐fold increase, respectively, in

ISSN:0021-9541    

DOI:10.1002/jcp.1040860504

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

年代:1975

数据来源: WILEY

摘要:

AbstractIncubation of Syrian hamster embryo secondary cell cultures in isoleucine or arginine deficient medium inhibited cell multiplication; 4–7% of the cells were synthesizing DNA compared to approximately 40% for cells in complete medium. After the deficient medium was replaced with complete medium, cells resumed multiplication and within 12 hours 65–70% of the cells entered into the S phase. A second peak of labeled cells, approximately 55%, occurred 24 hours after addition of complete medium. Chromosomal damage characteristic for cell lines grown in amino acid deficient medium did not occur with these Syrian hamster cells. Isoleucine or arginine deprivation resulted in chromosome or chromatid aberrations in only 2–5% of the cells, whereas chromosomes of control cells in complete medium occasionally exhibit chromatid gaps (>1% of the c

ISSN:0021-9541    

DOI:10.1002/jcp.1040860505

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

年代:1975

数据来源: WILEY

摘要:

AbstractA chromosomally‐stable mouse‐Chinese hamster hybrid cell line was subjected to five rounds of selection with cytotoxic antisera raised in rabbits against either the parental mouse 3T3 cells or the parental Chinese hamster Wg‐1 cells. Routine karyological analysis of clones isolated at each stage of serum selection revealed that treatment with either serum resulted in a limited loss of chromosomes (compared to the untreated hybrid cell cultured in parallel) and that the pattern of chromosome loss could not be correlated with the particular antiserum used for selection. However, more detailed analysis with the SSC‐formamide C‐banding technique, which identifies chromosomes containing a mouse centromere region, demonstrated that while large‐scale chromosome loss was not achieved as a result of antiserum selection, the limited loss of chromosomes did, in fact, reflect a specific depletion of chromosomes in response to treatment with cytotoxic antiserum. Specific chromosomal elimination was shown to occur as early as the first round of antiserum treatment. Antigenic analysis of the serum‐selected clones revealed a quantitative decrease in the expression of the species‐specific surface antigens selected against, but no qualitative loss of antigens was detected. The results suggest that treatment with cytotoxic antiserum may select for clones that have lost specific chromosomes bearing genes regulating the expression of species‐specific surface antigens, rather than for those demonstrating large‐scale depletion of chromosomes bearing the correspondi

ISSN:0021-9541    

DOI:10.1002/jcp.1040860506

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

年代:1975

数据来源: WILEY

摘要:

AbstractThe incorporation of labelled thymidine (dT) and iododeoxy‐uridine (IdU) into DNA was studied with tissue culture cells and with normal mouse cells in vitro. The rates of incorporation and the ratio dT/IdU incorporation both varied from one type of cell to another and from one suspending medium to another.Despite the known complexity of the regulation of DNA synthesis, the data for incorporation of exogenous dT and IdU could be fitted reasonably well by a model for single‐step enzymic process. Deviations from the theoretical predictions were minimal in the presence of fluorodeoxyurid

ISSN:0021-9541    

DOI:10.1002/jcp.1040860507

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

年代:1975

数据来源: WILEY

摘要:

AbstractThe rates of incorporation of3H‐choline into phospholipid and of3H‐fucose into glycolipid have been measured during the cell cycle of the murine mastocytoma, P815Y, synchronized by either velocity sedimentation or excess thymidine blockade. The rate of3H‐choline incorporation into acid‐insoluble material exhibited two distinct maxima coincident with the early S and G2periods, whereas the rate of incorporation of3H‐fucose into lipid extractable material was maximal during the G2period. Variation in rate of incorporation of3H‐choline could not be accounted for by changes in membrane p

ISSN:0021-9541    

DOI:10.1002/jcp.1040860508

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

年代:1975

数据来源: WILEY

摘要:

AbstractThe biosynthesis and turnover of nicotinamide adenine dinucleotide (NAD) have been examined in mitotic cells of the human culture line, D98/AH2. No significant difference in the incorporation of nicotinic acid or nicotinamide could be detected between mitotic and interphase cells. The distribution of newly‐incorporated nicotinic acid among the various pyridine nucleotides was also identical in mitotic and interphase cells. Whereas previous results have shown that the nucleus is necessary for NAD biosynthesis, the present results show that an intact nucleus is not required.In contrast to the equivalent rates of biosynthesis in mitotic and interphase cells, the pyridine ring of NAD was lost twice as fast from mitotic as from interphase cells. Loss of the pyridine ring to the medium is not necessarily an accurate measure of turnover, and the difference between mitotic and interphase cells may reflect differential reutilization of the pyridine ring within the cell. However, it is clear that NAD turnover is substantial in mitotic cells and possibly greater in mitotic cells than interphase cell

ISSN:0021-9541    

DOI:10.1002/jcp.1040860509

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

年代:1975

数据来源: WILEY

摘要:

AbstractThe electrophysiological properties of guinea pig peritoneal macrophages cultured in vitro were studied using standard intracellular recording techniques. The mean transmembrane potential, input resistance and time constant recorded from these cells were ‐ 13.1 mV, 140 Mohms, and 18 msec respectively. The majority of macrophages exhibited spontaneous hyperpolarizations (HA) of 4–8 seconds in duration and 10–50 mV in amplitude. Mouse peritoneal macrophages and human monocyte‐derived macrophages manifested similar HA. HA could be induced by either mechanical stimulation or application of hyperpolarizing currents of 2–8 namps. HA had a mean reversal potential of ‐ 53 mV. Increasing the extracellular [K+] 10‐fold resulted in a 50 mV shift in reversal potential. Addition of EGTA (1.5 mM) inhibited both spontaneous and evoked macrophage HA in the presence of excess Mg++. The divalent cation ionophore, A23187 induced prolongation of HA at low concentration (0.6 × 10−6M) and resulted in sustained hyperpolarization at higher concentration (2.0 × 10−6M). Addition of EGTA to cells treated with A23187 abolished HA. These data indicate that: (1) cultured macrophages from a variety of species exhibit spontaneous and induced HA, (2) development of HA is related to an increase in membrane permeability to K+, and (3) Ca++may regulate the spontaneous and evoked electrical activity of the macrophage membrane presumably by affec

ISSN:0021-9541    

DOI:10.1002/jcp.1040860510

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

年代:1975

数据来源: WILEY

摘要:

AbstractN6‐O2′‐Dibutyryl adenosine‐3′,5′ monophosphate (DBcAMP) markedly altered the morphology of HeLa cells by increasing average cell size with an increase in total cell protein and RNA. Such effects were not caused by adenosine 3′,5′ monophosphate (cAMP) or related nucleosides and nucleotides. Butyrate, an enzyme catalyzed hydrolysis product of DBcAMP, induced a jagged spindle shape in HeLa cells within 8 hours and then caused them to enlarge and resemble those grown with DBcAMP. These effects were specific for butyrate (C4) and pentanoate (C5) and were not observed with isomers, substituted analogs, or other fatty acid derivatives. These morphological effects were prevented by blocking protein synthesis or by altering the cytoskeleton with Colcemid or

ISSN:0021-9541    

DOI:10.1002/jcp.1040860511

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

年代:1975

数据来源: WILEY