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Volume 43 (1968)
- Issue 6 Pages 399-
- Issue 5 Pages 329-
- Issue 4 Pages 243-
- Issue 3 Pages 167-
- Issue 2 Pages 89-
- Issue 1 Pages 1-
Volume 43, Issue 5
Displaying 1-8 of 8 articles from this issue
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RALPH E. CLELAND1968 Volume 43 Issue 5 Pages 329-334
Published: 1968
Released on J-STAGE: May 21, 2007
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FUMIE INABA, YUMIKO SOTOKAWA1968 Volume 43 Issue 5 Pages 335-348
Published: 1968
Released on J-STAGE: May 21, 2007
JOURNAL FREE ACCESSThe nuclear changes during binary fission in a heterotrichous ciliate, Blepharisma wardsi were studied by electron microscopy.
The macronucleus in the interphase is in the form of 4-6 nodes. At the beginning of binary fission, the macronuclear nodes aggregate and coalesce into a mass (stage 1), then the macronucleus elongates (stage 2) and finally becomes nodulatod (stage 3). The chromatin bodies in the macronucleus gradually uncoil into their component fine fibrils at the end of stage 1, and the macronucleus becomes entirely filled with these fine fibrils in stage 2, then the fine fibrils gradually recoil to form chromatin bodies in stage 3. Nucleoli decrease both in size and in number in stage 2 and increase again in size and number during stage 3. The spherical bodies containing protein, on the other hand, have maximum size and electron-density in stage 2. The macronuclear envelope persists throughout the division cycle. The extra-nuclear microtubules seem to arise from the nuclear pores. These microtubules become most prominent in stage 2, and probably participate in the elongation of the macronucleus.
Micronuclear division is initiated in stage 1, proceeds rapidly and ends in stage 2 of macronuclear division.View full abstractDownload PDF (5975K) -
MASAKATSU HORIKAWA1968 Volume 43 Issue 5 Pages 349-364
Published: 1968
Released on J-STAGE: May 21, 2007
JOURNAL FREE ACCESSA cell line resistant to γ-irradiation was isolated from the original mouse strain L cells after seven successive irradiations with total dose of 14, 000R and was designated Lγ7. The various biochemical and genetical properties of these resistant cells were investigated.
The Lγ7 cells manifested a resistance to radiation, although the degree of resistance was not so high. The mean generation time of the original L cells was 27 hours during the logarithmic phase of growth, whereas that of the Lγ7 cells was 84 to 90 hours. Their cell morphology also differed from that of the original L cells; the Lγ7 cells were spherical, whereas the original L cells were fibrous.
The lower metabolic activity of oxidative phosphorylation in the Lγ7 cells seems to have a relation to their reduced multiplication rate and radioresistance. Furthermore, the content of SH groups per cell in both protein and non-protein SH reactions were significantly greater in the radioresistant Lγ7 cells than in the original L cells. The high content of SH groups in the radioresistant cells also may have some relation to their radioresistance.
The original L cells had a mode of chromosome number at 63. The Lγ7 cells had a mode of 44 chromosomes. Thus there was a shift in chromosome number. This decrease in chromosome number in the latter cells was gradually derived by seven repeated γ-irradiations of 2, 000R each. Similar phenomenon was observed in the changes in number of chromosomes in irradiated Ehrlich ascites tumor cells. The original Ehrlich ascites tumor cells had a mode around 58 chromosomes, whereas EX4 cells, isolated after four successive irradiation with total dose of 8, 000R of X-rays, had a mode of 51 chromosomes.
In the present investigation it was indicated that a correlation may exist between chromosome number and radioresistance in mammalian cells. In addition, the gradual shift in the chromosome number of the radioresistant cells (Lγ7 cells and EX4 cells) from the original L cells and Ehrlich ascites tumor cells seems to suggest that radioresistant cells may be derived from the pre-existing resistant cells in the original unirradiated population.View full abstractDownload PDF (2062K) -
II. DIFFERENCES IN THE RESISTIBILITY AT DIFFERERENT DEVELOPMENTAL STAGESYASUHIRO MIYOSHI, KENJI NAKAMURA1968 Volume 43 Issue 5 Pages 365-376
Published: 1968
Released on J-STAGE: May 21, 2007
JOURNAL FREE ACCESS(1) On the resistibility of D. melanogaster to sodium chloride, the present authors examined the resistibility to NaCl of high concentrations in the medium at the different developmental stages in both the resistant and the susceptible strains.
(2) Eggs of both the resistant and the susceptible strains are quite insensitive to NaCl in the medium unless they are dechorionated. However, when they are subjected to the NaCl medium after being dechorionated, the mortality of embryos is markedly high. The strain differences in the resistibility are more clearly demonstrated as the concentration of NaCl increases. By examining the morphology of the unhatched embryos, it becomes evident that the critical period of the susceptible embryos lies prior to the preblastokinetic stage.
(3) Larvae of D. melanogaster are more sensitive to high concentration of NaCl at the 1st instar larval stage than at succeeding stages. The strain differences in the resistibility are most clearly demonstrated at the 1st instar larval stage but do not correspond to the strain differences in the viability under the normal conditions.
(4) The viability of the 2nd instar larvae is less affected by the NaCl medium than that of the 1st instar larvae.
(5) In the 3rd instar larval stage, even NaCl susceptible strains are hardly affected by high concentrations of NaCl.
(6) Time required for completing the 1st and the 2nd instar larval stages is considerably prolonged in the NaCl medium. At the 3rd instar stage, the development of survivors is more or less delayed.
(7) Flies are not fatally affected by the NaCl medium at the pupal stage, but the time for completion of the pupal stage is markedly prolonged. The strain differences in the prolongation of the development also seem to correspond to those in the susceptibility to NaCl at the larval stage.View full abstractDownload PDF (1172K) -
YASUSHI TAKENOUCHI1968 Volume 43 Issue 5 Pages 377-382
Published: 1968
Released on J-STAGE: May 21, 2007
JOURNAL FREE ACCESSThe chromosomes of a Japanese weevil species, Scepticus insularis Roelofs, collected from 10 localities, were investigated in germ cells. The species has a diploid bisexual race as well as diploid, triploid, and pentaploid parthenogenetic races. The bisexual and pentaploid races are apparently sexually isolated from each other.View full abstractDownload PDF (556K) -
TATSURO IKEUCHI, SEIICHIRO FUJIMOTO1968 Volume 43 Issue 5 Pages 383-387
Published: 1968
Released on J-STAGE: May 21, 2007
JOURNAL FREE ACCESSA clinically and mentally normal woman and her aborted specimen had the 17th chromosome pair showing a heterozygous condition. A familial survey related to the woman revealed that her mother of normal phenotype was also a carrier of the same aberrant chromosome. A possible origin of the abnormal chromosome and its some genetical significance were discussed.View full abstractDownload PDF (1209K) -
N.M. NAYAR, H.S. CHAUHAN1968 Volume 43 Issue 5 Pages 389-392
Published: 1968
Released on J-STAGE: May 21, 2007
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MUNEO IIZUKA, TAKESHI HASHIZUME1968 Volume 43 Issue 5 Pages 393-394
Published: 1968
Released on J-STAGE: May 21, 2007
JOURNAL FREE ACCESSDownload PDF (322K)
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