1. The cytogenetical studies were carried out on F1's (Triticum Timopheevi× Secale cereale) obtained by embryo-culture technique and open F2 progenies derived from them. 2. In somatic cells of F1's, 21 chromosomes were ascertained, and their modal chromosome configuration at MI of PMCs was in 1II+19II. 3. From two F1's, 26 mature open F2 plants were obtained, the 2n chromosome numbers of which varied from 23 to 30 successively, except one plant having 2n=41. No amphidiploid was to be found among them. 4. From the results of cytogenetical and morphological studies, it was concluded that all of the open F2 plants, except one having 2n=41, were natural back-crossed plants with the rye pollen, normal, accessory chromosomic or translocated with x-ray grown adjacent to F1's the preceding year. Only one plant having 2n=41 was also proved to be a natural back-crossed plant with the common wheat pollen.
The Yoshida ascites sarcoma is one of the well-kown and long-lasting transplantable tumors of the rat and has furnished a favorite material for experimental studies in the field of cancer research since its establishment in 1943 by T. Yoshida. Recently, it has been reported that this tumor shows a derivation into serveral sublines which differ in the chromosome pattern with a change in the tumor type. Makino and Sasaki (1958) have established the occurrence of four chromosomal sublines, referred to as A, B, C and D, that were derived from the Yoshida stock tumor. It may not be uncalled for to make a comparative survey of the transplantability of these four sublines in order to provide a back-ground for various fields of cancer research. Four sublines of the Yoshida sarcoma have been maintained in Makino's laboratory during over 100 serial transfer-generations using rats of the following seven strains, Wistar (W/Ma), Wistar (wp), Wistar Pacific, Wistar King-A, Gifu, Tokyo and Castle's Black×Wistar King-A. The data presented in this paper were based on the above transplantation records. In addition, the following four strains of rats, Long-Evans, Buffalo, Fischer and Albany, were used for the examination of the susceptibility of the Yoshida sublines, but not for the serial transfer of the tumors. The transplantation rate and survival days of tumor-rats were observed in four sublines of the Yoshida sarcoma with various strains of rats. The results are presented in Table 1. For the rats of the following eight strains, Wistar (W/Ma), Wistar (wp), Wistar Pacific, Wistar King-A, Gifu, Tokyo, Castle's Black×Wistar King-A and Long-Evans, the four tumor sublines under study gave a similar transplantability showing 70 to 100 per cent lethal takes. For the rats of Buffalo, Fischer and Albany strains, however, the transplantability of the four sublines was different in more or less degree. Noteworthy is the fact that subline C was wholly nonsusceptible to rats of Fischer strain, while subline D showed a high transplantability at 80 per cent to rats of the same strain. A similar situation seems to occur in rats of Baffalo strain: the transplantability in them was 33 per cent for subline C and 75 per cent for subline D. It is interesting to note that subline D was derived from subline C through the inoculation of their tumor cells subjected to freezing (cf. Makino & Sasaki 1958, Sasaki 1958). In rats of Wistar (W/Ma), Gifu, and Tokyo strains, the four sublines showed a considerably high transplantability giving 90 to 100 per cent lethal takes; especially in the W/Ma strain over 97 per cent of animals died of the tumor. It is rather interesting to know that the transplantation rate and survival days of tumor-rats somewhat differ by the strain of rats used for translpantation. For instance, the transplantability of the Yoshida sarcoma in Wistar rats, which contain several substrains, differs according to the rats of different substrains. Such differences may be caused on the one hand by the difference of the tumor line or subline, and on the other hand by the difference of the strain of rats employed. A similar situation seems to exist in the life span of tumor-bearing animals: the life span differs either by the rat strains or by the tumor sublines (table 1 and 2).
The present paper is to report the results of some microscopical observations on naturally and artificially induced ovulation in mature and immature rats, with special reference to the number, stage and some other morphological features of ovulated ova. Based on the data obtained from the observations of the whole 288 adult females under study, the duration of each stage of the oestrus was estimated in average as follows: 56.5 hours for the dioestrus stage, 13.5 hours for the preoestrus stage, 25.3 hours for the oestrus stage, and 13.3 hours for the metooestrus stage. It is then evident that the whole duration necessary for an oestrus cycle is 108.7 hours (approximately 4.5 days) on an average (cf. Table 1). The ovulation seems to be taken place during the period from 12 to 20 hours in the oestrus stage. The number of eggs discharged at natural ovulation shows a variation from 8 to 10 in the majority of cases, being 8.8 on an average (cf. Table 2). These eggs are 75 to 81 micra in diameter, and possess the second polar spindle at metaphase. Through the injection of the gonadotropic hormone “Hypohorin” (Teikoku Hormone MFG. Co.), ovulation was artificially induced in mature females, though it was necessary to determine the effective time of hormone application in the oestrus cycle. In an extreme case, a mature rat discharged 40 eggs, 31 from the left ovary and 9 from the right ovary, following the application of 30 rabbit units Hypohorin which was used during the period from the dioestrus stage to the preoestrus stage. A rat which recieved injection at the same dosage in the period from the preoestrus stage to the oestrus stage discharged 37 eggs (26 left: 11 right), while the other laid 19 eggs (9 left: 10 right) by hormone application during the period from the dioestrus stage to the preoestrus stage. The data together with those from some other rats are given in Table 3. In every case, the ova discharged by hormone injection show cytologically normal maturation: they carry the second maturation spindle which has persisted in the metaphase stage, and have a diameter ranging from 75 to 81 micra. The artificial ovulation was successfully induced in immature rats 15 to 20 hours after the injection of Hypohorin at a dose of 2-10 rabbit units. The data are shown in Table 4. The eggs discharged by this treatment are nearly normal both in size and in some other morphological aspects, as compared with those from adult rats. The evidence presented indicates that the ova which were discharged by gonadotropic hormone are essentially similar, not only in nature but also in morphology, to those obtained in natural ovulation.
In present study the chromosomes of tumor cells were investigated in human tumors, with particular reference to the number and morphology of chromosomes. The type of tumors under study are shown in Table 1. The results of the chromosome investigation have revealed that every of these five tumors is characterized by near-diploid tumor cells. The following four tumors, Nos. 26, 32, 40 and 46, are provided with stem-cells having the chromosome number mode at 46 or 48. The uterine carcinoma (No. 30) here studied contains at least two distinct stemlines, consisting of a cell-line of near-diploid chromosomes (48 in number) and that of hyperdiploid chromosomes (55 in number). The chromosome constitutions of the tumor stem-cells of five tumors here considered show a general likeness to the normal somatic complex, so far as they were compared with the human complex reported by Tjio and Levan (1956).
The present paper deals with the chromosomes of a human gastric carcinoma in the ascites form, with special regard to the analysis of the number and morphology of chromosomes. It was found that there are present in this tumor at least three populations of tumor cells which are characterized by the chromosome numbers of 42, 45 and 82-84, by particular chromosome patterns and by high frequencies of occurrence. It is highly probable that these tumor cells form at least three stem-cell lineages, the members of which serves as the primary progenitors in the growth of this tumor. Based on the observations of 201 reliable metaphase plates, it became evident that the stemline ideograms were represented by 17M+21S+4T for the 42-cell, 21M+18S+6T for the 45-cell, and 34M+40 (or 42) S+8T for the 82-(or 84-) cell. Evidence was obtained that the frequency of these different cell-lines varied in three samplings made at different intervals. In the first sample the 45-cell line appeared at the highest frequency, while in the second and third samples the 42-cell line showed a remarkable increase in frequency with a decrease of the 45-cell line (Table 1). Probably such a variation as above may be regarded as a result of adaptation of stem-cells to certain physiological changes of the host. The analysis of the chromosomes has revealed that the chromosome complex of the tumor cells having 82-84 chromosomes is a duplication of that of the cells having 42 chromosomes. This sufficiently suggests that the hypotetraploid complex showing 82-84 chromosomes is induced by endoreduplication of the hypodiploid complex showing 42 chromosomes.
By backcrossing to the clonal stocks of perennial F1's between common wheat (including an amphidiploid, timopheevi-squarrosa) and Agropyron glaucum with wheat pollens, 11 mature BF1 plants were obtained. Among female stocks used, there were some clones derived from F1's which failed to multiply their chromosomes in spite of their being treated with colchicine in the first year. As a result of such careless selection of material, 7 out of 11 BF1 plants showed the abnormalities of either 2n chromosome numbers or meiotic chromosome behaviours. Namely, some possessed more than 63 somatic chromosomes, surpassing theoretical 2n numbers to be expected in BF1's and others showed the formation of aneuploid cells (chromosome mosaics), syncytes, telocentrics or a much quantity of multivalent chromosomes. Normal plants assumed to be derived from normal F1's were only four, one of which, the plant No. 4, showed simple associations having its modal configuration in 25II+11I (30%). Meiotic chromosome behaviour and fertility were in good agreement. Normal four plants showed relatively high fertility in pollens and seeds. The chromosome numbers of 4 BF1 plants obtained from F1 (Martin×A. glaucum)×Fultz No. 1 in 1958 were 48, 51, 58 and 59 respectively. No plant was to be found among them having more than 63 chromosomes, although every one of them showed a lot of multivalents. Culms of BF1's were tall, ears approaching vulgare-type but long and lax. The tillering-ability was so great that young tillers sprouted constantly throughout the summer like a perennial, but withered up and died after overwinter. An individual of plant No. 11, which possessed telocentric chromosomes, was dwarf, had a few tillers, and ended its life before winter. They all were highly resistant to the most virulent race group 21B of leaf-rust, Puccinia triticina Eriks.