Three experiments were conducted utilizing broiler-type breeder hens which were 36, 52, or 64 weeks of age. Eggs were collected at 2-hr intervals from 0800 to 1600 or 1800 hr and specific gravity determined the following morning. Eggs were held 1 week at 11 C, separated into groups according to specific gravity, and set. They were candled prior to transfer, and all eggs appearing infertile were broken to determine true fertility and/or age that embryonic death occurred. In the third experiment, egg weights were recorded prior to specific gravity determination, setting, and transfer to establish weight loss during holding time and incubation.Results demonstrated that eggs with the lowest specific gravities had the greatest weight losses, highest early embryonic mortalities, and lowest hatchabilities. In eggs with specific gravities higher than 1.080, there appeared to be little relationship between specific gravity and hatchability.It was concluded that shell quality may be a significant factor in declining hatchability as the hen ages.

Position 57 in the a3 chain of HLA class II molecules maintains an Asp/non-Asp dimorphism that has been conserved through evolution and is implicated in susceptibility to some autoimmune diseases. The latter effect may be due to the influence of this residue on the ability of class II alleles to bind specific pathogenic peptides. We utilized highly homologous pairs ofboth DR and DQ alleles that varied at residue 57 to investigate the impact of this dimorphism on binding of model peptides. Using a direct binding assay of biotinylated peptides on whole cells expressing the desired alleles, we report several peptides that bind differentially to the allele pairs depending on the presence or absence of Asp at position 57. Peptides with negatively charged residues at anchor position 9 bind well to alleles not containing Asp at position 57 in the f3 chain but cannot bind well to homologous Asp-positive alleles. By changing the peptides at the single residue predicted to interact with this position 57, we demonstrate a drastically altered or reversed pattern of binding.Ala analog peptides confirm these interactions and identify a limited set of interaction sites between the bound peptides and the class II molecules. Clarification of the impact of specific class II polymorphisms on generating unique allele-specific peptide binding "repertoires" will aid in our understanding of the development of specific immune responses and HLAassociated diseases.

The absence of HLA class II

Eggs from Single Comb White Leghorn chickens were divided into two approximately equal groups with the range of specific gravities being present in each group. One group was incubated in a darkened Humidaire Hatchett while the other was incubated in an identical machine equipped with two 20 Watt fluorescent tubes which produced 8.3 X 10(3) ergs/cm.2-sec. at the surface of the eggs. The recommended temperature and humidity settings were used in both machines. After 7 days of incubation embryos from the lighted incubator were significantly (P less than .01) larger than those incubated in the dark. There were significantly more live embryos from low and high specific gravity eggs in the light than in the dark. There was no difference in embryonic mortality between groups for the eggs with intermediate specific gravities. Embryos from White Leghorn eggs incubated in the presence of light were significantly (P less than .01) larger on each day of incubation from day 2 through hatch. Eggs incubated in the lighted incubator hatched at 18 and 19 days and produced larger chicks than those hatched at 20 and 21 days in the dark.

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