Nematode parasites show a characteristic aggregated distribution among hosts. This observation has important implications for pathogenesis, immunology, and control of these infections, but the relative roles of environment and genetics in determining these patterns have remained uncertain. This paper presents the results of the first genome scan for susceptibility to infection with roundworm (Ascaris lumbricoides). Data on 375 genetic markers were generated for each of 444 members of a genetically isolated Nepalese population, the Jirels. Ascaris worm burden as assessed by egg counts was measured in these same individuals by using the Kato Katz thick smear method. The extensive genealogical data available for the population allowed assignment of all 444 individuals to a single pedigree that contained 6,209 pairs of relatives that were informative for genetic analysis. A variance components linkage analysis resulted in the unequivocal localization of two genes (one on chromosome 1 and another on chromosome 13) with clear, significant effects on susceptibility to Ascaris infection. This is the first evidence that individual quantitative trait loci influence variation in Ascaris burden in humans.

Because of their unique function, germ cells require unique gene products. Thus, although the glycolytic enzyme phosphoglycerate kinase (PGK) is required in all metabolically active cell types, there are two functional PGK genes in the mammalian genome, one, PGK-1, that is X-linked and ubiquitously expressed in all somatic tissues, and a second, PGK-2, that is autosomal and expressed only in spermatogenic cells. Expression of the PGK-2 gene may function solely to compensate for repressed expression of the PGK-1 gene due to X-chromosome inactivation in spermatocytes. Alternative y, the PGK-2 gene could encode an isozyme with unique characteristics that are beneficial to spermatozoa. We have isolated a cDNA of the human PGK-2 gene and used this as probe to demonstrate that transcription of this gene in spermatocytes and spermatids coincides with a period of repressed transcription of the X-linked PGK-1 gene during spermatogenesis in the human testis. We have also analyzed the amino acid sequence and protein characteristics of the PGK-2 isozyme deduced from this cDNA and compared them with that of the human PGK-1 isozyme to show that known structural and functional motifs are conserved in both proteins. Finally, we have examined the distribution of the PGK-1 and PGK-2 isozymes during spermatogenesis in the mouse to show that while the PGK-2 protein does not appear to possess any unique intracellular localization signal, it is more stable in vivo than the PGK-1 protein.

Family data for 14 biochemical genetic markers fo squirrel monkeys (genus Saimiri) were derived from 73 pedigreed progeny and both parents of each, as well as from 16 additional progeny and one parent of each. The data for each marker and the phenotypic patterns were consistent with autosomal codominant inheritance. It was concluded from the genetic marker data that the pedigree records of seven progeny were incorrect. Retrospective investigations of colony records followed by typing of animals that might possibly have been a parent enabled five of the pedigree records to be corrected. Although five of the pedigree errors were cases of mistaken paternity, the other two apparently were the consequence of infant swapping between dams shortly after birth. Because squirrel monkeys exhibit a high degree of allomaternal behavior, infant swapping between dams may occur more frequently than in many other nonhuman primate species.

In order to develop standard conditions for rearing the gray short-tailed opossum, Monodelphis domestica, as a potentially useful experimental laboratory animal, the effects of four different diets on growth and reproduction were assessed. One diet was a meat-based diet prepared in the laboratory. The other three diets were commercially produced fox foods designated Reproduction diet, Lactation diet, and Growing and Furring diet. All pairs of M. domestica fed the Reproduction diet produced at least one litter, but only two-thirds or fewer of the pairs fed any of the other three diets reproduced. There were no significant differences in the number of young born per litter or the number of young weaned per litter among the diets. Weight at weaning was significantly lower for individuals on the meat-based diet compared to those on the fox food diets. Young on the meat-based diet suffered 50% mortality within 6 weeks after weaning, whereas none of the animals fed the fox food diets died within the same 6-week period. Age-weight data were described using the Bertalanffy growth function. In terms of growth and overall reproductive performance, the fox food diets were clearly superior to the meat-based diet, and the Reproduction diet was judged to be the best of the fox food diets tested. Growth curves, from birth to 550 days of age, of individuals fed the Reproduction diet were developed and can be used as standards for the species under laboratory conditions. The maximal weights attained by animals fed the fox food diets were similar to the weights of the wild-caught founders of the laboratory population, indicating that the fox food diets provide adequate nutrition for normal growth. An additional observation was that females housed singly past the normal age of sexual maturity attained significantly lower adult weights than did females that were paired with males at 6 months of age.