Semen from 15 healthy volunteers was assessed for basic semen measures every 2 weeks over a 6-month period to determine the relative stability of these factors. The parameters were: sperm count, semen volume, sperm motility, and normal morphology, along with the type of abnormal morphologic forms. Basic semen measures were generally more stable than the morphologic forms. Using three samples, seven semen factors (sperm count, normal morphology, semen volume, sperm motility, microcephaly, tapering and round tail) were found to be stable and contributed to the identification of the fifteen individuals with a classification accuracy of 75.0%. While individuals do have characteristic patterns of spermatogenesis, the biologic basis for these findings is as yet undetermined.

Adult↗

PubMedDate not supplied

Catabolic capacity of the muscles of shorebird chicks: maturation of function in relation to body size.

Newly hatched precocial chicks of arctic shorebirds are able to walk and regulate their body temperatures to a limited extent. Yet, they must also grow rapidly to achieve independence before the end of the short arctic growing season. A rapid growth rate may conflict with development of mature function, and because of the allometric scaling of thermal relationships, this trade-off might be resolved differently in large and small species. We assessed growth (mass) and functional maturity (catabolic enzyme activity) in leg and pectoral muscles of chicks aged 1-16 d and adults of two scolopacid shorebirds, the smaller dunlin (Calidris alpina: neonate mass 8 g, adult mass 50 g) and larger whimbrel (Numenius phaeopus; neonate mass 34 g, adult mass 380 g). Enzyme activity indicates maximum catabolic capacity, which is one aspect of the development of functional maturity of muscle. The growth rate-maturity hypothesis predicts that the development of catabolic capacity should be delayed in faster-growing muscle masses. Leg muscles of both species were a larger proportion of adult size at hatching and grew faster than pectoral muscles. Pectoral muscles grew more rapidly in the dunlin than in the whimbrel, whereas leg muscles grew more rapidly in the whimbrel. In both species and in both leg and pectoral muscles, enzyme activities generally increased with age, suggesting increasing functional maturity. Levels of citrate synthase activity were similar to those reported for other species, but l-3-hydroxyacyl-CoA-dehydrogenase and pyruvate kinase (PK) activities were comparatively high. Catabolic capacities of leg muscles were initially high compared to those of pectoral muscles, but with the exception of glycolytic (PK) capacities, these subsequently increased only modestly or even decreased as chicks grew. The earlier functional maturity of the more rapidly growing leg muscles, as well as the generally higher functional maturity in muscles of the more rapidly growing dunlin chicks, contradicts the growth rate-maturity function trade-off and suggests that birds have considerable latitude to modify this relationship. Whimbrel chicks, apparently, can rely on allometric scaling of power requirements for locomotion and the thermal inertia of their larger mass to reduce demands on their muscles, whereas dunlin chicks require muscles with higher metabolic capacity from an earlier age. Thus, larger and smaller species may adopt different strategies of growth and tissue maturation.

Animals↗

PubMedDate not supplied

Likelihood-based models for genetic linkage analysis using affected sib pairs.

Risch [Am J Hum Genet 1990; 46:229-253] recently developed a likelihood method for testing genetic linkage using affected sib pairs. This paper proposes a reparameterization of the Risch likelihood in terms of genetic variance components divided by the affected-sib-pair ascertainment probability. The new parameters allow for ease of interpretation, particularly for multilocus models. A single-degree-of-freedom test of the total disease genetic effect at a marker locus can be constructed that has power comparable to the likelihood ratio 'triangle' test. Extension of the models to other types of relative pairs is also discussed. The models may be used in genome scanning and in studying single or multilocus models of inheritance.

Genetic Linkage↗