[Blood plasma fibronectin does not influence fibroblast-induced collagen gel contraction].

Human embryo fibroblasts were cultured within three-dimensional collagen gel in the Eagle medium supplemented with 10% calf serum. Addition of fibronectin (Fn) to the nutrient medium neither stimulated nor inhibited gel contraction by fibroblasts. Gel contraction also proceeded in the medium containing ultroser G or Fn exhausted calf serum.

[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.

[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.

[Spread and transfer of plasmid resistance in Escherichia coli].

Drug resistance of 186 E. coli strains isolated in 1977-1978 from patients and carriers, as well as from the environment was studied with respect to 8 widely used antimicrobial drugs, i.e.

[Antibiotic sensitivity and the characteristics of transmissive R plasmids in Shigella belonging to various species].

Sensitivity of 241 Shigella strains isolated from patients at various regions of the USSR in 1975--1978 was tested with respect to 14 antibiotics by the method of serial dilutions. 90.5 per cent of the isolates proved to be resistant to the antibacterial drugs and the greater part of 75.

Effect of a strong magnetostatic field on proliferation of duodenal epithelial cells in mice.

The proliferative activity of duodenal epithelial cells in mice subjected to the effect of a 1000-Oe magnetostatic field (MSF) was studied. It was established that the one-day effect of a strong MSF causes transient disturbance of cell division processes. This is indicated by changes in the mitotic index and content of cells in the duodenal crypt, and also by the increase in the number of pathological forms of mitoses with a predominance of chromosomal damages.

[Formation of recombinants of F' plasmids in recombination-defective E. coli cells and their properties].

As a result of mating of cells carrying plasmid F' lac with cells carrying plasmid F'his merodiploids carrying plasmid complex F'lacF'his were isolated. The plasmid genes of the isolated merodiploids are donated together into the recipient cells and are eliminated jointly from host-cells both spontaneously and by acridine orange. As the formation of the plasmid complex took place in E.

[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.

Mutagenesis in the strains E. coli K-12 with different ability to genetic recombination.

Data on the role of recombination in spontaneous mutagenesis in E. coli K-12 are presented. On the basis of these data it can be presumed that such mutagenesis results from errors in spontaneous recombination.

[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.