Studies on the maturation of sex glands in animals with special reference to: colchicine effects and induced polyploidy cells in the testes of mice

The remarkable results of the application of colchicine to plants, first described in 1937, have stimulated many investigations on the induction of polyploidy with this drug. A great number of scientific reports on its action have been published. Altogether more than one hundred genera and two hundred and fifty species of plants have been treated, and a number of polyploid crop plants of economical value has been established during the period 1937 to 1942. Many other chemicals have also been tested, and some have been found to produce similar results, the most effective being acenaphthene and some plant growth substances (auxins) like indolyl -3- acetic acid, indolyl -3- butyric acid, and naphthalene-1-acetic acid. The effects of colchicine treatment on plants comprise chromosome doubling, irregular distribution of chromosomes, and chromosome fragmentation, all of which might be connected with some heritable changes in the plant. In addition to these, tissue hyper-plasia, increase of cell size, and excessive contrastion of chromosomes may also occur. The mechanism of chromosome duplication was attributed to inhibition of the spindle formation and delay in the division of the centromeres. Thus although the chromosomes divided they failed to separate, and remained together until a new nuclear membrane was formed. The process could be repeated a number of times during the course of treatment, provided the chromosomes retained their capacity for division. If part of the treated tissue was not affected, or some of the affected cells returned to the diploid state after the action of colchicine ceased, a rnixoploid tissue resulted. When the polyploid cells divided continuously, a polyploid tissue or plant might be formed. The great disadvantage of this kind of autotetraploid tissue or plant, induced from an ordinary plant, was the sterility of reproductive cells, which limited further investigation and the commercial exploitation of the induced polyploid. On the contrary, the amphidiploid or allotetraploid, induced from the sterile F₁ of either interspecific or intergeneric cross, was fertile. Owing to the inhibition of the spindle formation and the activity of centromeres in the treated cells,. the daughter chromosomes spread in disorderly fashion. and failed to congregate on the enuatorial plate. When the spindle was restored, if some of the chromosomes were still not able to go the poles, or the whole complement of chromosomes was divided into groups by the pressure of the cellular or nuclear division, an irregular distribution of chromosomes to the daughter nuclei or cells occurred. In this case, it was possible to produce chromosome deficiency and chromosome duplication among the cells in subsequent generations, although the cells containing an irregular number of chromosomes possessed very little capacity of division,. When the polyploid cells, either euploid or aneuploid, multiplied themselves along with the normal diploid cells in one plant, a chimerical plant resulted. The breakage or fragmentation of chromosomes induced by colchicine was reported by Eigsti and Krythe. Karpechenko found that some of the chromosomes in the treated materials broke into two parts exactly at the point of attachment of the centromere. This indicated that the effect of the colchicine treatment might have been something more than the alteration of chromosome numbers. In contrast to the ready production of polyploiids in plants, colchicine has not been so effective in animals. Nevertheless, there are numerous indications that the primary action of the substance, that is, the destruction of the spindle, occurs also in animal cells. This does not, however, lead to the formation of polyploid cells as readily in animals as it does in plants, though occasionally polyploids are produced. In the following section, the findings of previous workers who investigated the treatment of animal tissues with colchicine are reviewed, from which it will be seen that the production of polyploid cells in higher animals is not to be regarded as impossible. Experiments with colchicine on the sex cells of mice form the basis of this thesis and conclusions as to the action of colchicine on the mechanics of cell division have been drawn. From the experimental results, it will be seen that the production of functional polyploid spermatogonia and spermatocytes, that is, induction of polyploid sex cells which still have the capacity of multiplication, is possible, and the application of colchicine or other polyploidyinducing substances may be of importance in the animal as well as the botanical field