[Results of a quantitative cytological analysis of the thymus of rats exposed on biosatellites].

The mitotic activity, destruction and volume of nuclei of thymocytes were investigated on histological preparations of the thymus of rats flown onboard Cosmos-782 and Cosmos-936. The cytological data showed that immediately after touchdown large quantities of thymocytes of the cortical matter perished. The mitotic activity of the remaining undamaged thymocytes declined and returned to normal 9 hours after recovery.

Experimental and theoretical analysis of the influence of gravity at the cellular level: a review.

The present paper is a review of the experimental investigations published in the literature and performed by the authors on space vehicles. The paper also gives an analysis of theoretical concepts concerning gravitational effects on the cell. Taking this into account, the authors put forth a hypothesis that free-living unicellular organisms are indifferent to variations in the magnitude and direction of the gravitational field.

[Mitotic activity and the nuclear volume of the epithelial cells of the rat cornea after a space flight on biosatellites].

On total preparations of the cornea of rats flown on Cosmos-936 and Cosmos-1129 the following parameters of the epithelial mitosis were studied: mitotic index, ratio of mitotic phases, number of abnormalities of cell division, and number of chromosome aberrations in anaphases. These parameters were considered to be indicators of physiological regeneration. The nuclear volume of cells of two inner epithelial layers was measured, using a modified karyometric technique that yielded representative data.

[Method of determining the surface areas of cell nuclei in monolayer tissue cultures].

To measure the surface area of cell nuclei in monolayer tissue cultures, special tables have been development. With respect to the two diameters, the tables allow identification of the logarithmic class to which the nucleus belongs. A specially designed rule with coordinate axes helps to save time involved in karyometry.

[Effect of temperature on the duration of mitosis in mammalian cells cultivated outside the body].

Nine cell strains of different origin were cultivated at 28--36 degrees with the interval of 2 degrees. During the phase of logarithmic culture growth, the duration of mitosis (Tm) was determined by means of colchicine method. A strict temperatural dependence Tm, obeyed to Arrenius' law was revealed.

[Experiments with cultures of mammalian cells aboard the biosatellite "Cosmos-782"].

A considerable contribution to the investigation on biological importance of weightlessness was made by the experiments with animals in the artificial Earth satelites (AES) of "Cosmos" type. Cell cultures can serve as an ideal model to get a direct cell response to the effect of external factors. For the experiment in the AES "Cosmos-782", two thoroughly examined cell strains (L and 237) were chosen, which differed in a number of parameters (for example, duration of their mitotic cycles).

[Results of mammalian cell culture exposure on artificial earth satellites].

The paper presents the results of an exposure of cells of the Syrian hamster strain VNK-21 to space flight effects. In contrast to the cell culture kept in a thermostat at 29 degrees C, the cell culture that was maintained in thermally uncontrolled conditions developed noticeable structural and physiological changes induced by suboptimal temperatures. It was concluded that a 6-day exposure to weightlessness exerted no adverse effect on mammalian cells in vitro and produced no stable structural or physiological changes.

[Duration of the mitotic cycle of Chinese hamster cells cultured at 30--39 degrees].

The duration of the mitotic cycle (T) at temperatures of 30, 33, 36 and 39 degrees C was studied in subline 237 of Chinese hamster cells with the aid of the radioautographic method. T was the least at 39 degrees C and increased with reduction of the cultivation temperature. At the temperature range of 33--39 degrees C prolongation of T and its periods was "proportional" to the temperature under study.

[Temperature limits of mitosis in mammalian cell cultures].

Mammalian cells of different origin (11 strains) were cultivated at the temperature of 25--41 degrees to measure the temperature limits of mitosis. Different strains of the cells reacted to the increase or decrease in the cultivation temperature in a dissimilar way. The difference between the upper temperature limit and the optimum one was not over 5 degrees.

[Method of mathematical description of the dynamics of cell population density].

The paper presents a method of building a mathematical model of the time dynamics of the cell population density and mitotic index which allows the prediction of the population growth as related to the cultivation conditions. The process of mammalian cell division has been shown to delay noticeably with a decrease of the cultivation temperature from 36 to 30 degrees C and an increase of the initial population density. The curve of the population density has a typical sigmoidal pattern.