Chromosome analysis was carried out on 28 heterosexual cattle twins consisting of 14 freemartins, 9 males co-twined with a freemartin and 5 females without freemartinism, as well as 15 control animals consisting of 3 homosexual male twins, 4 single born males and 8 single born females. Culture of leukocytes from blood, colchicine treatment of bone marrow cells and tissue cultures of gonads, kidneys, lungs, etc. were used. For preparing chromosome preparations, the air-drying method was also employed.
The results are summarized as follows :
1) The diploid number of chromosomes in controls was 60. All of the 29 pairs of autosomes were acrocentric, while X and Y sex-chromosomes were submetacentric. X and Y sex-chromosomes were easily distinguished from autosomes by the size, shape and position of the centromere.
2) In all cases of freemartins and their male co-twins, sex-chromosome chimerism (XX/XY) was detected in cultured leukocytes and bone marrow cells. Whereas, in all cases of heterosexual twin females without freemartinism and of control animals, no sex-chromosome chimerism was observed. The incidental rate of chimerism in cultured tissues from some organs was low and the degree was inferior. But, chimerism occurred in gonads of freemartins, while did not in those of their co-twins. The statistical analyses of the incidental rate of chimerism between freemartins and their co-twins and also between leukocytes and bone marrow cells showed no significant differences (P<0.05).
3) It is hopeful to use chromosome analysis with leukocyte culture as an accurate early diagnostic method for freemartins.
4) It seems reasonable to think that males co-twined with a freemartin should be cytologically distinguished from single born males, because the former was of sex-chromosome chimerism.
5) Basic mechanisms of the bovine freemartinism were discussed in viewpoint of the chromosomal cytology.

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The chromosome constitution of a set of bovine heterosexual triplets consisting of two freemartins and one male was studied by means of blood culture, colchicine treatment of bone marrow cells and tissue cultures from several organs. As controls, four multiparous cows, including one female from another heterosexual triplets origin and a set of homosexual triple females, were also studied chromosomally using the blood culture technique. The sexual organs of the freemartins were examined macroscopically and histologically.
The results are summarized as follows:
1) Cultured leucocytes and bone marrow cells in both freemartins and the co-tripled male manifested 2 A-XX/2 A-XY chimerism. The chimera ratios were parallel with each other among these three individuals. Tissue cultures from thyroid, kidney, lung, gonads and seminal vesicule-like structures of these animals failed to show chimerism. No chimerism was observed, on the other hand, in cultured leucocytes from the control animals. Thus, freemartins involved in heterosexual triplets can also be diagnosed chromosomally as well as in the case of twins.
2) Two freemartins submitted to this study considerably differed in the morphological characteristics of the sexual organs, despite having similar characters in sex-chromosome chimerism.

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[in Japanese]

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[in Japanese]

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