In vivo estrogen synthesis by the developing chicken (Gallus gallus) embryo.

The concentrations of unconjugated and conjugated estrogens in the allantoic and amniotic fluids of chicken embryos have been followed during incubation. The estrogens estrone, estradiol-17 beta and estradiol-17 alpha were present as their conjugates in the allantoic fluid of female embryos but not of male embryos. No estrogens were detectable in the amniotic fluid of embryos of either sex. Estradiol-17 beta glucuronide, the most abundant estrogen present in female allantoic fluid, was first detectable (159 pg/ml) at Stage 35 of development increasing in concentration to 4210 pg/ml at Stage 45. The concentration of estrogen in allantoic fluid of the partially decapitated embryos at Day 18 (Stage 41) of incubation was not significantly different from that of the intact Stage 41, approximately Day 15 embryo.

Correlation of chromatin composition with metabolic changes in nuclei of primitive erythroid cells from chicken embryos.

Changes in levels of biosynthesis of DNA, RNA, and histones were compared with relative proportions of each histone class during primitive erythropoiesis in embryonic chicks. We confirmed that erythrocyte-specific histone 5 (H5) was substantial in the earliest accessible, erythroblast-enriched stage and that it doubled in relative amount between polychromatic and orthochromatic stages to about 1 mol per 2 mol of each nucleosomal histone, still considerable less than in adult definitive erythrocytes. No other histones changed during primitive erythropoiesis, but the molar proportion of histone 1 (H1) always exceeded that of H5 in these cells, unlike definitive erythrocytes. The increase in content of H5 was accompanied by continued decline in synthesis of the other histones and DNA. The accumulation of H5 during development appears to occur in steps corresponding to the maturation of the primitive and definitive erythroid cell lines. Lysine-rich histones were more easily extracted from nuclei of the erythrosynthesis in whole cells and in isolated nuclei.

On possible involvement of adrenocorticoids in chicken spleen development.

The possible effects of glucocorticoids on spleen development were assessed by the determination of changes in mean organ weight and histology in chicken (Gallus gallus) embryos at stages 44 and 45 of Hamburger and Hamilton on days 19.5 and 20 of incubation (N = 10--13). After the administration of 1 to 6 mg of metopirone (an 11-beta-hydroxylase inhibitor) the numbers of white-pulp periarterial nests and red-pulp granulocytes decreased. The changes associated with metopirone treatment were less evident after the addition of corticosterone (20 and 200 microgram). After adding corticosterone alone (200 microgram), the white-pulp nests appeared larger than in control. Mean body and spleen weights or spleen-body weight ratios did not change much after treatment. Possibly glucocorticoids normally direct these aspects of spleen histogenesis in chicken embryos.