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Volume 7 (1982)
- Issue 4 Pages 295-
- Issue 3 Pages 193-
- Issue 2 Pages 91-
- Issue 1 Pages 1-
Volume 7, Issue 4
Displaying 1-6 of 6 articles from this issue
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Toshio Kuroki, Teruomi Ito, Jiro Hosomi, Kimie Munakata, Tsutomu Uchid ...1982 Volume 7 Issue 4 Pages 295-305
Published: 1982
Released on J-STAGE: April 18, 2008
JOURNAL FREE ACCESSThe function of cyclic AMP in the growth of epidermal and dermal cells was investigated. Cholera toxin was used to increase the amount of intracellular cyclic AMP. This toxin had a stimulatory effect on human epidermal cells only when growth was limited; i.e., when a small number of cells was plated for colony formation, when cells from frozen stock were cultured, and when cells were in the initial phase of primary culture. Cholera toxin, however, had no significant effect on the growth rate during exponential growth or on the saturation density during the stationary phase.
The stimulatory effect of the toxin was specific to epidermal keratinocytes. In other types of cells, the effect varied : with human dermal fibroblasts there was no ffeect, or some inhibition.
A membrane receptor for cholera toxin, GM 1 ganglioside, was isolated from human epidermal cells. Cyclic AMP was induced markedly by cholera toxin in human epidermal keratinocytes, which suggests that an increase in the amount of cyclic AMP may act as a mitotic signal in these cells. Cholera toxin also induced cyclic AMP in human dermal fibroblasts irrespective of the growth response, an indication that in dermal fibroblasts the content of cyclic AMP is not necessarily related to the proliferation of the cells.View full abstractDownload PDF (3323K) -
Ryoko Kuriyama1982 Volume 7 Issue 4 Pages 307-315
Published: 1982
Released on J-STAGE: April 18, 2008
JOURNAL FREE ACCESSMitotic spindles were isolated from Chinese hamster ovary cells with an isolation medium that contained 5% glycerol, 1% dimethyl sulfoxide, 5% polyethylene glycol, 5 mM piperazine-N, N'-bis(2-ethanesulfonic acid), 1 mM ethylene glycol bis(β-aminoethylether)tetraacetic acid, 0.5 mM MgSO4, 0.5% Triton X-100, 0.5 mM GTP and 0.5 mM dithiothreitol at pH 6.8. The chromosomes generally were lost from the preparation; thus, electron microscopy of whole-mount preparations showed isolated spindles with a microtubule array in the spindle that attached to the centrosomes at each pole.
An increase in the concentration of MgSO4 to 5 mM stabilized the chromosomal structure, and mitotic spindles with chromosomes attached in almost the same configuration as in vivo could be isolated.
A general discussion of the procedures for isolating mitotic spindles from tissue cultured cells is included.View full abstractDownload PDF (10433K) -
Hiroyoshi Hoshi, Mikio Kan, Isao Yamane1982 Volume 7 Issue 4 Pages 317-325
Published: 1982
Released on J-STAGE: April 18, 2008
JOURNAL FREE ACCESSCell cycle-dependent growth regulation by hydrocortisone (HC) and specific glucocorticoid binding were studied in human embryonic lung fibroblasts (HEL) in a serum-free, defined medium. Confluent and quiescent HEL cells could stimulate DNA synthesis when polypeptide growth factors (EGF, insulin, and transferrin) were present.
HC promoted DNA synthesis only in the presence of EGF. When cells were exposed to HC after being refed growth factor-containing, serum-free medium (RITC 80-7), the rate of entry of cells into DNA synthesis was increased and, thus, the cell number.
The cell cycle period was not altered by an addition of HC. HC-induced 3H-thymidine incorporation was found in the prereplicative phase of the cell cycle in kinetic pulse experiments. 3H-dexamethasone binding activity persisted throughout the cell cycle, high activity being noted during the middle G1 phase and at the Gl/S boundary. Our results show a close relation between the presence of specific glucocorticoid binding and hormonal responsiveness in a defined medium.View full abstractDownload PDF (887K) -
Jiro Aoshima, Takao Nishimura, Tatsuichi Iwamura1982 Volume 7 Issue 4 Pages 327-340
Published: 1982
Released on J-STAGE: April 18, 2008
JOURNAL FREE ACCESSDNA polymerase activity (DPA) was investigated in a syn-chronous culture of the unicellular green alga, Chlorella ellipsoidea (Tamiya's strain). During the algal cell cycle, which was observed in the synchronous growth, nuclear DNA (nDNA) is synthesized near the end of the light phase, whereas the major chloroplast DNA (chDNAM) is synthesized in the middle preceeding the synthesis of nDNA (1). The DPA on a per cell basis correlated well with the synthetic patterns of the cellular DNAs, except during the early stages. The two marked rises in total cellular DPA, thus corresponded directly to the syntheses of the two DNA species.
Fractionation of DNA-depleted enzyme preparations by DEAE-cellulose column chromatography showed two kinds of DNA polymerases. One was eluted at 0.13 M-KC1 (Pol I) and the other at 0.15 M-KC1 (Pol II). Pol II activity (DPA-II) reached its maximum during chDNA synthesis, whereas Pol I activity (DPA-I) reached its maximum at the end of nDNA synthesis period. We concluded that Pol II synthesizes or replicates chDNA in vivo and Pol I, nDNA; hence, we have designated them "chloroplastic" and "nuclear" DNA polymerases.
We also examined the inhibitory effects of chloramphenicol (CP) and cyclo-heximide (CH) on the development of the two DPAs during the cell cycle. DPA-II was inhibited principally by CP, and DPA-I by CH. Moreover, CH somewhat inhibited DPA-II development during the early phase, and CP greatly inhibited DPA-I development after chDNA synthesis.
Thus, Chlorella cells contain at least two kinds of DNA polymerases, chloro-plastic and nuclear. The former probably is synthesized on chloroplastic ribosomes and the latter on cytoplasmic ribosomes.View full abstractDownload PDF (1404K) -
David J. Patterson, Klaus Hausmann1982 Volume 7 Issue 4 Pages 341-348
Published: 1982
Released on J-STAGE: April 18, 2008
JOURNAL FREE ACCESSThe distribution and appearance of morulate bodies in the heliozoon Actinophrys sol is described using electron-microscopy. The morulate bodies occur around the sites typically occupied by microtubular axonemes in well-fixed cells. The incidence of morulate bodies increases when fixation pro-cedures which preserve axonemes poorly are adopted; and they are absent when microtubules are stabilized with Taxol. If axonemes are removed by pretreatment of the cell with cold and colchicine, the incidence of morulate bodies is greatly reduced.
It is concluded that morulate bodies are associated with disassembly of axonemes and may be derived from the axonemes.View full abstractDownload PDF (1202K) -
T. Choku Takahashi, H. Sato1982 Volume 7 Issue 4 Pages 349-357
Published: 1982
Released on J-STAGE: April 18, 2008
JOURNAL FREE ACCESSD2O increases the volume of the mitotic spindle and its bire-fringence. This effect is completely reversible and repeatable within an optimum range of temperature and D2O concentration. We made a thermodynamic analysis of the D2O effect on the first mitotic spindle in dividing sea urchin eggs at metaphase because of the possibility of a dynamic equilibrium existing between cytoplasmic tubulin molecules and the oriented microtubules in the spindle.
D2O has been thought to promote hydrophobic interactions between tubulin molecules. Thermodynamic factors such as changes in enthalpy or in entropy should, therefore, be increased by an application of D2O. No significant changes in the thermodynamic factors, however, were found in our experiments. Our data indicate that D20 increases the available pool of polymerizable tubulin molecules in the cell. This is evidence that a pool of unpolymerizable tubulin molecules is present in the dividing eukaryotic cell.View full abstractDownload PDF (893K)
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