Meiotic chromosomes of the spermatocytes ejaculated by bulls

The Sperling and Kaden (1971) approach was used in studies of the bull meiotic chromosomes. The number of meiocytes in the ejaculates of normal bulls ranged from 0.0001 to 0.0114% of the whole set of cellular elements in the ejaculate. Two of the studied bulls had a chromosomal abnormality in somatic cells (60, XX/60, XY mosaic). These bulls displayed no deviation as concerns the quantity of meiocytes in their ejaculates. In two other bulls examined, with cryptorchism and azoospermia, about 0.0017 and 4.75% meiocytes were counted in the ejaculate, respectively. A comparative analysis of ejaculated chromosomes and meiotic chromosomes obtained from the normal testes by biopsy did not reveal any differences in the chromosomal morphology. Various premeiotic and meiotic stages, from spermatogonium A and B to metaphase 1, were identified in the bull ejaculates. This technique may be valuable in cytogenetic diagnosis of meiotic abnormalities in sires.     

Parametric analysis of survival data for doubly irradiated animals

On the basis of their previously reported model of acute radiation sickness development the authors made a parametric analysis of the survival rate of mice after double exposure to ionizing radiation.     

Changes in the activity of enzymes of renin-angiotensin and kinin systems in the rat brain after adrenalectomy and administration of hydrocortisone

It is shown that the activity of enzymes participating in renin-angiotensin and brain kinin systems' metabolism depends on functional state of hypothalamo-pituitary-adrenocortical system. Under experimental hypocorticism the activity of angiotensin-converting enzyme and kininase I in the hypothalamus, hippocamp, corpus striatum and rat pituitary decreases; the renin-like enzyme activity decreases in the corpus striatum but increases in the hypothalamus and hippocamp. After hydrocortisone administration to adrenalectomized rats the angiotensin-converting enzyme activity of the hippocamp and pituitary is shown to be normalized as well as renin-like enzyme and kininase I of the hippocamp and corpus striatum. The activity of the studied enzymes in the hypothalamus decreases in this case.     

Identification of a multihit model for nonhomogeneous cell population]

A generalized multihit-multitarget model for a nonhomogeneous, with respect to radiosensitivity, population of irradiated cells is presented. The least squares and the maximum likelihood estimation of the model parameters is given. The estimates quality is evaluated by the computer-based study. The results obtained show the possibility of the parametric identification of cell radiosensitivity distribution according to the "dose-response" data.