ABSTRACT
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. The rats that were centrifuged inflight (at 1 g) did not display a lower mitotic activity or noticeable destruction of thymocytes. Karyometric measurements demonstrated that the population of thymic lymphocytes was heterogeneous in the nuclear volume: it consisted of three peak classes of nuclear volumes. The variance curves of nuclear volumes of lymphocytes of the medullary matter were drastically shifted toward large numbers. An increase in the nuclei of thymocytes of the cortical matter in the flight rats was stable and persisted till R+25.
Subject(s)
Space Flight , Thymus Gland/cytology , Animals , Cell Count , Gravitation , Karyometry , Male , Mitosis , Rats , Rats, Inbred Strains , Thymus Gland/physiology , Time Factors , USSR , Weightlessness/adverse effectsABSTRACT
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.
Subject(s)
Cell Physiological Phenomena , Environmental Microbiology , Gravitation , Space Flight , Weightlessness , Animals , Bacteria , Chlorella , Culture Techniques , Eukaryota , Humans , Plant Cells , Saccharomyces cerevisiae , VirusesABSTRACT
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. The lack of significant changes in the above mitotic parameters can be attributed either to the absence of a strong stress-reaction of rats postflight or to the discrepancy between the time of animal sacrifice and the time of the maximum post-stressor inhibition of mitotic activity. This study revealed some data suggesting that in weightlessness the rate of cell division remained unaltered. The mean nuclear volumes of corneal epithelial cells changed significantly (P less than 0.01) at late examination stages (days 6 and 29). This may be associated with rearrangements in the regulatory systems of the animal body postflight. It cannot be ruled out that an increased cell activity measured with respect to the nuclear size correlates with the intraocular pressure.
Subject(s)
Cell Nucleus/ultrastructure , Cornea/ultrastructure , Mitosis , Space Flight , Animals , Epithelium/ultrastructure , Karyometry , Male , Rats , Rats, Inbred Strains , USSRABSTRACT
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. Statistical significance of the data thus obtained is not less that of the results provided by the traditional planimetric procedure.
Subject(s)
Karyometry/methods , Cell Line , Cell Nucleus/classification , Cells, CulturedSubject(s)
Cell Physiological Phenomena , Temperature , Amnion/physiology , Animals , Cell Line , Connective Tissue Cells , Cricetinae , Humans , Kidney/physiology , L Cells/physiology , Mice , MitosisABSTRACT
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. Temperature range within which Arreinius' law is valid in different cell strains is not alike. Cultivation of L cells and connective tissue cells from Chinese hamster to 39, 41and 42 degrees demonstrated their upper critical point Tm to be for L cells 39 degrees, for connective tissue cells from the Chinese hamster--41 degrees. Electron microscopic investigations demonstrated that cell cultivation within physiological (mitosis destroying) range of temperatures does not notably effect their ultrastructural organization.
Subject(s)
Cell Line , Mitosis , Animals , Cricetinae , Humans , L Cells , Mammals , Temperature , Time FactorsABSTRACT
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). Density of cell seeding and temperature of their cultivation in the laboratory experiment were calculated in such a way that the whole cycle of the culture development should take place under the conditions of weightlessness: the beginning of lag-phase--before launching and the stationary phase--after landing. The weightlessness was not shown to result in any genetical shifts revealed at chromosomal level. When cultivated after the flight, the cells do not change their mitotic cycle parameters, mitotic course and structural organization. The data obtained in the experiments with AES "Cosmos-368" and "Cosmos-782" (increase of mitotic index, some forms of mitotic pathology during the first terms of cultivation after the flight and enlargement of cellular nuclei) demonstrate the changes in the cell population which have formed under the conditions of weightlessness. Similar changes are observed while the cells propagate in the laboratory conditions. Indirect data on an earlier cell culture aging during the flight do not exclued the possibility that under weightlessness the rate of cell propagation could differ from that under gravitation.
Subject(s)
Cell Cycle , Chromosomes , Weightlessness , Animals , Cell Line , Cell Nucleus/ultrastructure , Chromosome Aberrations , Cricetinae , Karyotyping , L Cells , Microscopy, Electron , Mitosis , Ploidies , Space FlightABSTRACT
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. Some changes that were detected in the cell culture--faster ageing, stable tendency to an increase of the number of cells with enlarged nuclei, an increase of the mitotic index at an early stage of cultivation--need further investigation.
Subject(s)
Cell Nucleus , Mitosis , Space Flight , Cell Line , TemperatureABSTRACT
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. The characteristic curve gradient of T dependence on the temperature showed a sharp change in the direction of greater figures with the temperature reduction from 33 to 30 degrees C. Analysis of the results of other studies on T duration of the human amniotic cells demonstrated that such sharp elevation of the duration of the mitotic cycle occurred with the change from 39 to 40--41 degrees C. The G1 period was the most and G2--THE LEAST Sensitive to changes of the cultivation temperature.
Subject(s)
Cell Line , Mitosis , Animals , Cricetinae , TemperatureABSTRACT
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. Cell division did not end with the temperature fall by over 10 degrees. Various cell strains responded to the temperature decrease in a different way. Most cellular population had three cell types. The majority of the cells were capable of dividing at the threshold temperature; some cells could enter mitosis without completing it and stop at the metaphase. The temperature limits of mitosis were not related to the species and tissue origin of the cells.
Subject(s)
Mitosis , Cell Line , TemperatureABSTRACT
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.
