Experimental Studies of Abnormal Nuclear and Cell Divisions

V. Observation by fixation method of the effects of various chemicals

抄録

In the present investigation, the effects of KClO₃, KCN, chloralhydrate, caffeine, colchicine, acenaphthene, sodium cacodylate, auramin, tannin and ethyl urethan were examined with fixation method for the purpose of comparing the results with those obtained with living material.
1) Under the influence of KClO₃, dehydration figures are observed in higher concentrations chiefly as a result of osmotic effect and in lower concentrations as some injurious effect of the salt, accompanied in the latter case with the vacuolization in the cytoplasm. Di-diploid nuclei and bi-nucleate cells are observed in the material fixed after transferring the root in water. These results are in accord with those obtained with living material under the influence of neutral salts.
2) In root-tips of Vicia Faba, KCN causes dehydration of chromosomes and the spindle and an accompanying phenomenon, the enlargement of the vacuoles in the cytoplasm, just in the same manner as in the case of living material, and di-diploid nuclei and bi-nucleate cells are found in the root-tips transferred in saw-dust. After a long interval of time in saw-dust these abnormal nuclei enter a further mitosis, and those cells with two prophasic nuclei, with two metaphase figures, with a metaphase figure of tetraploid chromosome complements, etc. are produced. In root-tips of Allium Cepa, on the other hand, bi-nucleate cells and di-diploid nuclei are obtained, though in a low frequency, without transferring the roots in saw-dust. In a long treatment, those cells with several chromatic masses or scattered chromosomes and those which appear quite homogeneous are observed. The abnormalities may be regarded as swelling phenomena of the chromosomes, spindle and nucleus
3) Under the influence of chloralhydrate in higher concentrations, chromosomes and the nucleus become a pycnotic homogeneous mass owing to a dehydration taking place in connection with the strong enlargement of vacuoles in the cytoplasm. In a dilute solution, di-diploid nuclei and bi-nucleate cells are formed without transferring the root-tips in sawdust, though in a low frequency. The present investigation with fixation method indicates that in the case of chloralhydrate it is necessary to obtain these abnormal cells and nuclei in a high frequency that the immersion medium is of a high concentration, and that this medium is replaced with water or the roots are transferred in saw-dust.
4) Under the influence of auramin and tannin dehydration phenomena take place in association with the vacuolization in the cytoplasm, but the formation of di-diploid nuclei and bi-nucleate cells is not observed. In coincidence with the results of experiment with living material it is difficult to obtain by these agents the di-diploid nuclei and bi-nucleate cells.
5) The effects of urethan was examined in the present investigation only with 1% and 2% solutions, and it was observed that bi-nucleate cells were formed only in a low frequency in those cells with strongly vacuolized cytoplasm, without transferring the roots in saw-dust or water.
6) In caffeine solutions of high concentrations, the dehydration occurring in association with the enlargement of vacuoles in the cytoplasm causes the chromosomes and nucleus to become a homogeneous pycnotic mass, and the spindle to decrease in volume. In a dilute solution, the vacuoles in the cytoplasm is not so strongly enlarged, but the spindle be-comes dehydrated as the only dehydrated element, and the septum membrane fails to be formed. Daughter chromosomes can migrate to poles, and undergo the process of nuclear reconstruction. Thus bi-nucleate cells are easily formed without transferring the root in saw-dust. In the root-tips fixed after a long treatment, abnormal cells such as those with a tetraploid metaphase figure, those with a tetraploid anaphase figure, those with two figures of diploid metaphase, those with four free nuclei, etc.