The authors, together with other co-workers, have already estimated the average effective population size of the Kiso horses in a period from 1955 to 1961 as about 90 per year from the number of male parents and the variability in progeny number of male parents. In the present work the average effective size of this horse population was estimated from the random fluctuation of the frequencies of genes controlling polymorphism for coat-colors and red blood cell antigens by using a method developed by one of the authors (Nozawa 1963). The value obtained, 88.51 (57.78-152.59) per year, was considered to agree with the estimate from the breeding record.
Damaging effects of an antibiotic, Chromomycin A3 (Toyomycin, TAKEDA) were cytologically examined on tumor cells of the MTK-sarcoma III (an ascites sarcoma of white rats), HeLa cells and human embryonic cells. Chromomycin A3 exerted severe damaging effects on tumor cells in vivo and invitro as well as on embryonic cells in vitro: the pycnotic disintegration of resting nuclei and the depression of DNA substances were remarkable under treatment. Remarkable prolongation of life span was observed by single application of this agent at dose level of 20μg/100g, and in some cases by repeated injections at daily dose of 10μg/100g body weight.
1. It was found from a cytological observation that the giant cells formed in a completely sterile rice plant induced by X-rays are syncytes and not coenocytes. 2. There was not observed any morphological difference that distingushed the syncyte-forming and normal plants. 3. Twenty-four chromosomes were counted in the somatic cells of the sterile plant. 4. The cell fusion to form syncytes was found to have started already at the early stage of meiosis. 5. Number of nuclei per PMC varied from 0 to 21. 6. Chromosome configulations per nucleus varied from 8II+8I to 69II+3I. 7. The muximum chromosome number counted was about 220. 8. No data on the genetic behavior of syncyte formation were obtained because of the complete sterility of this plant. 9. There was a great variation in the size of pollen grains.
An eye color mutant of Drosophila melanogaster, ry, contains no uric acid at any developmental stage, but accumulates a large amount of hypoxanthine compared with the amount of xanthine at pupal and imaginal stages. An enzyme concerned with uric acid production in D. melanogaster of the wild type is a xanthine dehydrogenase, which has both the activities of xanthine oxidation and DPNH oxidation. The xanthine dehydrogenase from ry mutant, however, does not have xanthine oxidative activity, but retains the activity of DPNH oxidation. The enzymatic activity of DPNH oxidation in ry is at the same level as in the wild strain. The xanthine oxidative activity in the enzyme from heterozygous strain, ry/+, is one-half of the activity in the wild strain, but the DPNH oxidative activity is at the same level as in a wild strain. These results suggest that xanthine dehydrogenase produced in the ry mutant is an enzyme molecule lacking the active site of xanthine oxidation. The activity of guanase, which catalyzes the conversion of guanine to xanthine, is observed in pupal and imaginal stages of both wild and ry strains. From these results, it is shown that xanthine, which is a precursor of uric acid, is derived not only from hypoxanthine with dehydrogenase but also from guanine with guanase.
Ten eye-color mutants (ge and its allele ge2, ocra and its allele ocrac, w57, do, car, cm, rb and bu) of the housefly, Musca domestica L., were studied for tryptophan metabolism. 1) A great amount of accumulation of tryptophan was observed in pupae of the ge mutant, while neither kynurenine nor 3 OH-kynurenine were detected. No xanthommatin exists in eyes of adults of this mutant. Therefore, ge is a mutant blocked at the first step of tryptophan metabolism. It was proved that ge and ge2 have no activity of tryptophan pyrrolase in cell-free extracts. 2) In pupae of ocra and ocrac mutants, an excessive amount of kynurenine was accumulated, but 3 OH-kynurenine was undetectable. Thus, these are mutants whose activities of kynurenine hydroxylase are genetically blocked. Xanthommatin was undetected in eyes of adults of ocra. In ocrac, however, it was proved that a little amount of the pigment was accumulated (8 to 10% of the wild type). The ocrac may be a leaky mutant of kynurenine hydroxylase. 3) In do (dark-orange), tryptophan accumulated in 5 times the amount of that in the wild-type pupae, while accumulations of kynurenine and 3 OH-kynurenine were normally observed. Enzymatic activity of over-all conversion from tryptophan to kynurenine in the cell-free extract of this mutant was half of the wild-type. 4) It is likely that ge and ocra mutants of the housefly are homologous to the v and cn mutants of D. melanogaster, respectively. 5) Separation of tryptophan pyrrolase from kynurenine formamidase was obtained by gradient elution chromatography on a DEAF-column.
RNA synthesis during mitosis was studied by autoradiographic techniques in the root meristematic cells of Luzula purpurea (n=3). Comparisons of the synthetic activity of the interphase with those of other mitotic phases were made using whole nuclear grain counts. Incorporation of uridine-H3 in chromosomes decreased during early-prophase and completely stopped at mid-prophase. Incorporation of uridine-H3 in nucleoli was retained until late-prophase, just before nucleolar disintegration. No incorporation of uridine-H3 was observed in meta-anaphase chromosomes. Incorporation of uridine-H3 into the daughter chromosomal groups began at early-telophase and continued until late-telophase. Pre-nucleolar material appeared on the surface of each chromosome as early as in late-anaphase before RNA synthesis resumed in daughter nuclei. Nucleolus developed in parallel with an increase of the incorporation of uridine-H3 in chromosomes and nucleolus itself.
Frog eggs γ-irradiated before insemination developed normally during the early stages, and then most of them became abnormal embryos. From the remainings a few metamorphosed haploid frogs and a few non-viable haploid tadpoles were obtained. The transfers in which the cytoplasm had been irradiated and the nucleus was introduced from a normal blastula cell were very low in developmental capacity, as compared with the control transfers whose cytoplasm and nucleus had not been irradiated. However, two metamorphosed frogs and a tadpole were obtained from among rN transfers. All the transfers in which the cytoplasm was normal and the nucleus was introduced from an irradiated blastula cell did not develop beyond the heart-beat stage, as irradiated blastulae did not.
In spite of recent rapid advances in tissue culture techniques for mammalian animals, there has been relatively little attention devoted to in vitro cultivation of tissues from lower vertebrates. The present paper deals with the cultivation of tissues from cold-blooded animals in comparison with several culture methods employed by various investigators. Both anuran and urodelan cells generally grow to primary culture by a routine method using mammalian media, but any specific technique for amphibian material is highly desirable to obtain adequate proliferation of cells. A method used to get a sufficient number of cells in vitro from certain organ systems of frog and newt has been described. Kidney tissue of frog and pulmonary epithelium from newt have been used as suitable material for the cultivation. These tissues were incubated constantly at 26°C for 7 to 10 days in Rose's chambers with the special amphibian medium. The tissues showed a remarkably large outgrowth of cells, particularly available for cytological studies. The cells were able to alive for more than a month in vitro without any medium change. The in vitro cell from amphibians has not been successfully subcultured for more than a few generations, and therefore, it is needed to make much more improvement, especially for the establishment of a cell strain, in order to obtain suitable material for investigations in various fields with large-sized cells of amphibians.
This paper deals with some cytological effects of Endoxan (ASTA), a new alkylating antitumor agent, on HeLa cells in vitro, with special reference to general morphology, stainability, chromosomes, as well as to growth rate of cells after treatment. For general morphological observations, HeLa cells were cultured in 17×17×38mm culture flasks in which a 12×32mm coverslip was inserted previously. For chromosome study, cells were cultured in TD-15 flasks. They were divided into two groups: one group received Endoxan-treatment just after setting up the cultures (early stage of cell growth), while the other received the same treatment at 48 to 72 hours after cultivation (the most marked proliferating stage of cell growth). Endoxan was dissolved with culture medium at concentrations of 10, 100, 500, 1000 and 2000μg/ml. Observations were carried out by using the air-drying technique for chromosome study, and also May-Grünwald and Giemsa stainig method for studying general morphology of cells. Remarkable growth-inhibiting effects were observed when the cells were exposed to Endoxan just after cultivation, but no such effects were detected in the cells being exposed to the drug at 48 to 72 hours after setting up the cultures. Neither the morphological alterations nor the chromosomal changes were produced by this agent in every case here examined. The possible significance of this finding was discussed.