XX/XY mosaicism in lymphocyte cultures from a pig with freemartin characteristics

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Abstract
Extract The freemartin condition as a cause of intersexuality in the adult pig has been suggested but never demonstrated. Hughes ( 1929 Hughes, W. 1929. The freemartin condition in swine. Anat. Rec., 41: 213–245. [Google Scholar] ) and Benoit ( 1964 Benoit, R. 1964. Quelques considerations sur l'hermaphroditism. Schweizer Arch Tierheilk., 106: 63–73. [Google Scholar] ), both described cases of placental anastomosis between opposite sexed piglets with the formation of a freemartin-like condition in one of the foetuses. It is surprising, however, from the numerous studies over an anatomically wide range of adult pig intersexes, that none of these has shown characteristics consistent with freemartinism as described in other species. Bovine and ovine freemartins show varying degrees of intersexuality from near male in some cases to near female in others (Lillie, 1917 Lillie, F. R. 1917. The freemartin; a study of action of the sex hormones in the foetal life of cattle. J. exp. Zool., 23: 371–452. [Google Scholar] ; Bruere and McNab, 1967 Bruere, A. N. and McNab, Joan . 1967. A cytogenetical studyof six intersex sheep shown to be freemartins. Res. vet. Sci., in press [Google Scholar] ). In both the bovine and ovine freemartin cases cited, certain anatomical and histological features are apparently constant. These include a blind urogenital sinus, absence of a formed scrotum even in the presence of descended gonads, and characteristic sex cord formation without spermatogenic elements (Lillie, 1917 Lillie, F. R. 1917. The freemartin; a study of action of the sex hormones in the foetal life of cattle. J. exp. Zool., 23: 371–452. [Google Scholar] ). The certain diagnosis of freemartinism depends in addition, however, on the demonstration of foetal placental anastomosis having taken place between opposite sexes (Lillie, 1917 Lillie, F. R. 1917. The freemartin; a study of action of the sex hormones in the foetal life of cattle. J. exp. Zool., 23: 371–452. [Google Scholar] ). That anastomosis between placentae of opposite sexes has occurred can now be demonstrated consistently by mixed blood cell chimaerism in freemartin animals (Herschler et al., 1966 Herschler, M. S. , Fechheimer, N. S. and Gilmore, L. O. 1966. Identification of freemartins by chromosomal analysis. J. Dairy Sci., 49: 113–114. [Google Scholar] ; Bruere and McNab. 1967 Bruere, A. N. and McNab, Joan . 1967. A cytogenetical studyof six intersex sheep shown to be freemartins. Res. vet. Sci., in press [Google Scholar] ). Other non-haemopoetic tissues of the same animals have been found by the majority of investigators to be genetically female (Goodfellow et al, 1965 Goodfellow, S. A. , Strong, S. J. and Stewart, J. S. S. 1965. Bovine freemartins and true hermaphroditism. Lancet, i: 1040–1041. [Google Scholar] ; Gerneke 1965 Gerneke, W. H. 1965. Chromosomal evidence of the freemartin condition in sheep (Ovis aries). J. S. Afr. vet. med. Ass., 36: 99–104. [Google Scholar] , 1967 Gerneke, W. H. 1967. Cytogenic investigations on normal and malformed animals with special reference to intersexes. Onderstepoort J. vet. Res., 54: 219–300. [Google Scholar] ; Bruere, 1966 Bruere, A. N. 1966. “A study in cytogenetics in the sheep”. In Ph.D. Thesis, Glasgow, Scotland: Glasgow Univ. Library. [Google Scholar] ; Ilbery and Williams, 1967 Ilbery, P. L. T. and Williams, D. 1967. Evidence of the freemartin condition in the goat. Cytogenetics, 6: 276–285. [Google Scholar] ). The occasional demonstration of chimaerism in other tissues of the freemartin (Kanagawa et al., 1965 Kanagawa, H. , Muramoto, J. , Kawata, D. and Ishikawa, T. 1965. Chromosome studies on heterosexual twins in cattle: I. Sex-chromosome chimerism (XX/XY). II. Significance of sex chromosome chimerism (XX/XY) in early diagnosis of freemartins. Jap. J. vet. Res., 13(2): 33–50. [Google Scholar] ) is at present questionable. In all cases cited, the number of male (XY) cells was very low and could be explained by culture contamination with XY lymphocytes (Bruere, 1966 Bruere, A. N. 1966. “A study in cytogenetics in the sheep”. In Ph.D. Thesis, Glasgow, Scotland: Glasgow Univ. Library. [Google Scholar] ; Gerneke, 1967 Gerneke, W. H. 1967. Cytogenic investigations on normal and malformed animals with special reference to intersexes. Onderstepoort J. vet. Res., 54: 219–300. [Google Scholar] ).