Chromosome Analysis of Peripheral Leucocytes of the Sheep.

R ECENT development of techniques for in vitro growth of leucocytes and the preparation of chromosome spreads from such cultures have generated renewed interest in the chromosomal complement of animal cells. While such interest has naturally centered on the cells of man, some attention has been given to those of domestic animals. Karyotypes prepared from peripheral leucocyte cultures have been published for the pig (McConnell et al., 1963) and for the horse, donkey, and mule (Trujillo et al., 1962). Successful culture methods for bovine leucocytes have been described by Biggers and McFeely (1963) and by Ulbrich et al. (1963), although these authors did not attempt the tedious job of karyotyping this species. Sasaki and Makino (1962) presented well-assembled models of the chromosomes of cattle and horses taken from cultured somatic cells. Makino (1943) studied histological sections of testes and established that the sheep normally has 54 chromosomes. Borland (1964) has published an idiogram of male sheep chromosomes obtained from bone marrow cells; Melander (1959) presents similar drawings from cultured cells of embryonic origin. The present study was undertaken to determine the requirements for in vitro growth of sheep leucocytes and the chromosomal characteristics of such cells.