A stabilizing action on the nuclear membrane and gel structures, i.e., aster, spindle, and peripheral plasmagel layer of the cytoplasm, can be detected. Prophase and metaphase cells in 80% (v/v) 2H2O remain frozen in the initial state for at least 30 minutes. Furrowing capacity probably is not abolished by 2H2O. The 2H2O-block is released on immersion in 2H2O although cells kept in deuterium-rich media for long periods show multipolar and irregular divisions after removal to 2H2O, and may subsequently cytolyze. The inhibition of mitosis in the fertilized egg is not the only interesting effect of deuterium. The unfertilized egg also responds. It was described by Gross that deuterium parthenogenesis in Arbacia in the following graphic terms: if an unfertilized egg is placed in 2H2O, there appear in the cytoplasm, after half an hour, a number of cytasters. The number then increases with time. If, after an hours immersion in 2H2O, eggs are transferred to normal sea water, a high proportion (80% of the population) raises a fertilization membrane, which gives evidence that activation has occurred.

Deuterium genetics is, for the most part, like genetics itself, conveniently divisible into dipteran mutation studies, the genetics of microorganisms, and miscellaneous studies of which those of Gross and Harding, and Flaumenhaft et al. are examples. The customary procedure in most of the dipteran and bacterial investigations so far reported has been to administer 2H2O to the organism and then to test it for mutation or other chromosomal change. The results obtained by such an investigation have seldom been striking. For example, many researchers found an increase in sex-linked lethals in the sperm of flies that had been exposed to deuterium, either by way of injection into their pupae, or by the inclusion of 2H2O in their food. They introduced 2H2O into Drosophila melanogaster larvae both by feeding and by injection. The males which matured from these larvae were tested for mutation by CIB method. But the test showed no increase in the mutation rate. It was assumed by these scientists that the deuterium which was used in dilute form entered the DNA molecule.

De Giovanni and Zamenhof have carried out the most comprehensive investigations on the genetic effects of deuterium in bacteria. The results are of considerable interest. For example, they found a several mutants of E. coli, including a so called rough mutant 1/D which is more resistant to 2H2O than its parent strain, were isolated from E. coli grown in 2H2O media. The spontaneous frequency of occurerence of this mutant was 10-4, and the mutation rate could be increased 300-fold by ultraviolet irradiation. This mutant was derived only from the strain E. coli 15 thymidine, and no similar mutant was observed in other strains of E. coli or B. subtilis. By application of a fluctuation test, De Giovanni then was able to show convincingly that this mutation to increased deuterium resistance occurred spontaneously and not in response to the mutagenic effect of 2H2O. Back mutations in some instances do seem to occur at higher rates in 2H2O. Reversion from streptomycin dependence to streptomycin sensitivity in E. coli strain Sd/4, or from thymine dependence to thymine independence in strain 1 occurs with higher frequency in 2H2O, but 2H2O does not cause a discernible increase in mutation in the wild type.

De Giovanni further found that deuteriated purines and pryrimidines had no effect upon the growth and back mutation rates of specific base-requiring strains. Thymine containing deuterium in two of the four nonexchangeable positions adequately supplied the requirement for thymine with no concominant genetic changes. It would appear therefore that the preponderance of the evidence from these studies with bacteria is in favor of the view that 2H2O is not a strong mutagenic agent.

It was reported by many researchers a series experiments designed to test the ability of deuterium to produce mutation and nondisjunction. Deuterium like tritium appear to increase nondisjunction, but either agent separately is less effective than the two acting together. Hughes and Hildreth exposed male flies which had been grown on a 20% (v/v) 2H2O diet to an irradiation of 1000 r. of X-rays. It was found that there was not significant difference in the frequency of observed mutations between 2H2O flies and normal flies subjected to the same radiation.

Tumanyan and Shnol also found no mutagenic effect of 2H2O on recessive and dominant lethal marks in D. melanogaster, inbred line Domodedovo 18. Flaumenhaft and Katz grew fully deuteriated E. coli in 99,6% (v/v) 2H2O with fully deuteriated substrates, and found that the mutation rate after ultraviolet irradiation was distinctly lower than that of nondeuteriated organisms. The simultaneous presence of both deuterium and protium in nearly equal proportions in the constituent molecule of an organism could conceivably create difficulties for the organism since the rate pattern would be seriously distorted. They further found that cells grown in 2H2O and then transferred to 2H2O showed an enhanced susceptibility to ultraviolet irradiation. This suggests that organisms containing both hydrogen or deuterium, but it leaves unanswered the question of why serial subculture in H2O-2H2O media is required for adaptation of many organisms.

Many researchers studied the growth of phage T4 in E. coli cells which were cultivated in media containing various concentrations of 2H2O from zero to 95% (v/v). No significant increase in forward mutation in this phage could be observed, but the rate for reverse mutation was increased, and reached a maximum in phage grown in 50% (v/v) 2H2O. Although it was reported that a further increase in H2O concentration up to 90% (v/v) producers little augmentation of the reversion index, the actual data presented by Konrad indicates a decided increase in reverse mutation rate in phage exposed to more than 50% (v/v) 2H2O.

There have been carried out a big deal of cytochemical study of fully deuteriated microorganisms grown autotrophically for very long periods in 2H2O (Flaumenhaft E., Conrad S. M., and Katz J. J., 1960a, 1960b). The main conclusion that could be made from these studies is that the nucleus of deuterated cells was much larger than that of nondeuterated cells, and it contained greater amounts of DNA. Also present were much greater amounts of rather widely scattered cytoplasmic RNA within the cells. It was found also, that deuterated cells stained much more darkly for proteins, indicating higher concentrations of free basic groups. Both fluorescence and electron microscopy indicated that deuteration results in readily observable morphological changes. For example, the chloroplast structure of deuteriated plants organisms was more primitive in appearance, less well-differentiated, and distinctly less well-organized. The very interesting conclusion was made, then a low or/and high temperature grown organisms implied the morphological consequences of extensive isotopic replacement of hydrogen by deuterium so that in some respects resemble with the effects produced by reduction or/and increase in temperature of growth.

But, paradoxically as shown numerious studies on biological adaptation to 2H2O, a many cells of bacterial and algae origin could, nevertheless, well grown on absolute 2H2O and, therefore, to stabilize their biological apparatus and the structure of macromolecules for working in the presence of 2H2O. The mechanism of this stabilization nor at a level of the structure of [U-2H]labeled macromolecules or at a level of their functional properties is not yet complitely understood. We still don't know what possibilities a cell used for adaptation to 2H2O. We can only say, that probably, it a complex phenomenon resulting both from the changes in structural and the physiological level of a macrosystem. That is why there is every prospect that continued investigation of deuterium isotope effects in living organisms will yield results of both scientific and practical importance, for it is precisely. For example, the studies of the structure and the functioning of biolodical important [U -2H]labeled macromolecules obtained via biological adaptaition to high concentrations of 2H2O are most attract an attention of medical scientists as a simple way for creating a fully deuterated forms of DNA and special enzymes could well be working in a certain biotechnological processes required the presence of 2H2O. Secondly, if the structure of fully deuterated proteins may be stabilized in 2H2O in a view of duarability of deuterated bonds, it would be very interesting to study the thermo-stability of [U -2H]labeled proteins for using them directly in processes going at high temperatures.

It would be very perspective if someone could create the thermo-stable proteins simply via deuteration of the macromolecules by growing a cell-producent on 2H2O wit 99% 2H. Third, particular interest have also the studies on the role of primodial deuterium in molecular evolution. The solution of these obscure questions concerning the biological adaptation to 2H2O should cast a new light on molecular evolution in a view of the preferable selection of macromolecules with difined deuterated structures. Thus, the main purpose of the present project is the studies of the structure and the function of fully deuterated macromolecules (particularly DNA and individual proteins and/or enzymes) obtained via biological adaptation to high concentrations of 2H2O.

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