Biomedical subjects
E I Zaar
Publications and source records attributed to E I Zaar.
[Mars as a habitat for life].
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.
[Lev Konstantinovich Lozina-Lozinskiĭ (on his 70th birthday)].
Explore the source record for details and available documents.
[Effect of circadian temperature change on the multiplication of Paramecium caudatum].
Explore the source record for details and available documents.
On the interrelations between ultraviolet and visible light during their simultaneous action on the cell.
Beyond the Earth's atmosphere, ultraviolet (UV) light that is a component of the Sun's spectrum appears as one of the limiting factors to life in space and on the planets which have no ozone layer in their atmosphere. At early stages in the evolution of life, the Earth's atmosphere contained neither free oxygen nor the layers serving as a screen for short-wave UV light. Under such conditions, the UV radiation lasted for 8-10 hours a day. Similar radiation conditions may be found on Mars. Still, we do not know to what extent the photo-reactivating region of sun radiation (3000-5490 angstroms) can protect cells from the action of short UV light. Therefore, it will be of interest to study a prolonged action of UV radiation on living systems (protozoa, bacteria, fungi, animal and plant cells) in the presence of visible rays capable of reactivating UV damage. We subjected infusoria (Paramecium caudatum) to prolonged action of UV light (2537 angstroms). The cells were irradiated daily for 8-16 hours with doses of 1.5-40 and 120 mkvt. A sharp reduction in the rate of division and the lethality to the infusoria were observed from the second to the fifth day of experimentation. In the light variant, UV radiation was performed simultaneously with the application of visible light (2800-15000 lux). In such conditions, the cells kept their normal rate of division for 12 days. In the next 30 days without irradiation, no deviation from the normal rate was noted. The experimental results permit the conclusion that under certain conditions of interaction between visible and UV light, UV does not produce a deleterious effect on cell division.
[The reaction of Paramecium caudatum to the lasting influence of low single and fractional doses of ultraviolet rays].
Explore the source record for details and available documents.