Biomedical subjects
L K Lozina-Lozinsky
Publications and source records attributed to L K Lozina-Lozinsky.
Antigen rearrangements in Colpoda maupasi cells after freezing at -196 degrees C, and after shortwave ultraviolet irradiation.
Explore the source record for details and available documents.
Some potentialities of living organisms under simulated Martian conditions.
Temperature, humidity, pressure, composition of the atmosphere and radiation are the main factors conditioning life on the surface of Mars. When studying the Martian ecology, one must know the total effect of these factors. One may expect that, as a result of adaptation to low temperatures, there is a corresponding shift in the temperature optimum of enzymatic activity. Dryness is the main obstacle to active life. We suggest the presence of some soil moisture and water vapour. Moreover, there can be areas of permafrost. This minimum supply of water and periodic fluctuations of humidity may create conditions for the existence of drought-resistant organisms. Decreased atmospheric pressure alone does not affect micro-organisms, plants, protozoa and even insects. Ciliates reproduce in a flowing atmosphere of pure nitrogen containing 0.0002-0.0005% oxygen as an impurity. Protozoa may also develop in an atmosphere of 98-99% carbon dioxide mixed with 1% O2. Therefore, even traces of oxygen in the Martian atmosphere would be sufficient for aerobic unicellular organisms. Cells and organisms on earth have acquired various ways of protection from uv light, and therefore may increase their resistance further by adaptation or selection. The resistance of some organisms to ionizing radiation is high enough to enable them to endure hard ionizing radiation of the sun. Experiments with unicellular [correction of unicellar] organisms show that the effect of short wave uv radiation depends on the intensity of visible light, long-wave solar uv radiation, temperatures, cell repair processes, and the state of cell components, i.e. whether the cell was frozen, dried or hydrated.
The apparatus "Photostat-I" for simulating Martian environmental conditions.
One of the main tasks of exobiology is to determine conditions required for life on different planets of our solar system. At present, experimental ecological methods permitting the study of responses of living systems to extreme influences and, in particular, to simulated environmental Martian conditions, are widely used. To study the reaction of Earth organisms, special chambers and mechanisms are used which allow the modelling of conditions different from ours, mainly Martian. Existing devices capable of simulating the Martian environment. Our apparatus "Photostat-I" permits the simulation of pressure and visible light illumination (up to 60,000 lux), the irradiation of biological objectives in UV light (220-400 nm) and the production of a daily temperature cycle typical of Mars with a high degree of accuracy.
Resistance of the protozoan Colpoda maupasi to Martian conditions of atmospheric pressure and low partial pressure of oxygen.
Among the most important factors limiting the active life of animal organisms in Martian conditions are low atmospheric pressure and insignificant amounts of oxygen in the atmosphere (no more than 0.15% of the Earth's atmosphere). The experiments with aerobic protozoon C. maupasi have shown that in conditions of hermetically sealed chambers, for instance in 2.5 liter anaerostats, the protozoon can survive for a long time and reproduce in an atmosphere of air or nitrogen containing 1 or 0.0005% oxygen at a pressure from 15 mm Hg and higher. At the atmospheric pressure 10 mm Hg we observed a considerable decrease in the survival percentage and no reproduction. The exposure to 5 mm Hg resulted in a 100 per cent mortality of the protozoon. In a specially-constructed chamber "Photostat", in which current atmosphere pressure were automatically maintained during an experiment of many days, the reaction of the infusoria was somewhat different: they reproduced and existed not only at the pressure of 10-15 mm Hg, but also at 5 mm Hg, in an atmosphere of both air and nitrogen containing from 1 to 0.0005% O2. This indicates not only low-oxygen consumption of unicellular animals but also the capability of cells to extract some traces of this gas from the atmosphere. Low pressure and some traces of oxygen in the Martian atmosphere are not an impediment for the existence of some of the Earth's animals, such as the protozoon C. maupasi for example.
Resistance of organisms to extreme influences in relation to some exobiological problems.
The conditions to which organisms have not been able to adapt in the process of evolution are called extreme influences or extreme conditions. The experiments show that organisms and cells have a potential for resistance; among animals, there are forms that are able to stand extremely low temperatures (from -80 to -269 degrees) when the water content of their tissues is large enough. Some species of protozoa can tolerate ionizing radiation in doses (500-1800 kr) of many orders exceeding those existing on the Earth and out in space. There are different ways of obtaining "protection" against ultraviolet (UV) shortwave sun radiation detained by the ozone layers of the Earth's atmosphere (photoreactivation, biological screens non-permeable for UV light, etc.). Many insects, especially alpine species, do not require as much oxygen as is contained in lower layers of the Earth's atmosphere. Hence, earth organisms possess some "margins of safety", enabling us to suggest the existence of similar biological systems in conditions different from the Earth's. The resistance to the action of extreme factors is probably connected with the resistance of biopolymers, protein complexes of cells and also with the capability of the organism to recover from damage.