The ontogenesis of melatonin receptors in the anterior pituitary and pars tuberalis of the Golden hamster was studied using [125l]iodomelatonin as a ligand. The affinity of the binding site to the ligand (K<j) was in the range 21 to 54 pM and it did not change significantly during development. The concentration of the [125lliodomelatonin binding sites in the anterior pituitary was highest in one-day-old hamsters (Bmax=14 fmol/mg protein) and thereafter gradually decreased. In adults it reached to about 6 % of the neonatal values. In contrast, the concentration of the binding sites in pars tuberalis did not change significantly during ontogenesis and it was in the range of 3 to 5 fmol/mg protein.
Vitamin E in a dose of 150 mg and 300 mg/kg of body weight, administered i.p., has a protective effect - in the course of the whole ontogenesis - against stagnant hypoxia induced in the laboratory rat by positive radial acceleration + lOxg. The favourable influence of vitamin E is relatively greater In older animals.
We examined 126 wild tortoises to evaluate the shell changes due to sexual dimorphism and ontogenesis by the geometric morphometrics. Adult body shape varies substantially in males and females; adults showed different ontogenetic patterns between sexes: in females the posterior portion of the carapace narrows in the dorsal view, the carapace tends to assume a pyriform shape in the lateral view, and the plastron tends to lengthen of the midline and shows a slight lateral enlargement. Male shape changes towards the posterior portion of the carapace, a bending of the seam between marginal and pleural scutes, allowing the body to assume a hemispherical shape, and ventrally, the plastron narrows strongly, posteriorly. The latter feature was mainly due to the shortening of the anal scutes, probably facilitating copulation by allowing more space to move the long tail. A wider posterior in male angulate tortoises may convey greater stability in male-to-male combat. All the ontogenetic changes suggest a modification of the plastron formula, an important feature for chelonian systematics and taxonomy.