Biology bulletin of the Academy of Sciences of the USSR最新文献

A model of the phenomenon of selectivity of antineoplastic phase-specific preparations in leukemia, based on the assumption that any proliferating cells are equally sensitive to the action of such preparations, is suggested. Therefore, selectivity, the concept and fundamental significance of which were formulated and substantiated by the authors earlier, can be expressed in terms of the proliferative pathways of the normal and leukemic populations, the ratio between which thus plays the deciding role in the selection of the optimum system of therapy. The concept of maximum selectivity, which is a convenient numerical characteristic of a preparation, was introduced. A comparative quantitative analysis was made of a number of antineoplastic preparations (vinblastine, vincristine, amethopterin, arabinosylcytosine, azaserine); it showed that the conclusions of the model do not contradict the experimental data.

A highly active preparation of diacetyl(acetoin) reductase was isolated from cell-free extracts of the yeast Saccharomyces vini. Since the activity ratio of 2,3-butanediol dehydrogenase and diacetyl(acetoin) reductase was practically unchanged in the process of 65-fold purification, it can be assumed that the yeast cells contain one enzyme, which catalyzes both the reversible oxidation of 2,3-butanediol to acetoin by NAD and the practically irreversible reduction of diacetyl to acetoin by NAD-H2. Some properties of this enzyme were studied.

The fine structure of a fragmenting and sporulating mycelium of cultures of actinomycetes possessing biochemical properties characteristic of the genus Nocardia--a cell wall of type IV and lipid LCN a--was studied. It was found that fragmenting hyphae are similar in structure to the vegetative hyphae of known actinomycetes. Sporulation takes place through the simultaneous division of a sporulating hypha by numerous septa. Spores differ from vegetative cells in the presence of a thickened electron-dense cell wall, dense internal contents, and the presence of vacuoles.

The ability of Mycobacterium globiforme 193 cells immobilized in polyacrylamide gel (Paag) to transform soluble and microcrystalline hydrocortisone was investigated under conditions to periodic aeration. It was found that the specific 3-oxosteroid-delta'-dehydrogenase activity of immobilized cells hardly differs from that of free cells and averages 0.06 mumole/mg cells . min; the quantitative and qualitative composition of the transformation products formed by free and immobilized cells was identical. The linear relation between the accumulation of the reaction product, prednisolone, and the transformation time, the absence of an activating effect of SAA [surface-active agents] on the 3-oxosteroid-delta'-dehydrogenase activity, the correlation between enzymatic activity and viability, and the absence of an increase in activity during repeated transformations indicate that the cytoplasmic membrane of Myc. globiforme is not a significant diffusion barrier for the reaction substrate and product. Maintenance of immobilized cells in a viable state is a necessary condition of the retention of enzymatic activity by these cells. "Activation" of immobilized cells is achieved by incubating the granules in nutrient medium. The cause of the "activation," in our opinion, is the appearance of a new surface and, probably, internal cell population.

The short day in the thawing of hardened winter wheat, yarovized to a different degree, increased its frost resistance in comparison with uninterrupted illumination. Interruption of darkness of the short-day cycle by red light reduced frost resistance, far-red light had the opposite effect, but to a different degree, on the length of yarovization. Maximal resistance developed toward the end of the yarovization period. There were observed changes connected with the stabilization of the photoacceptor of the phytochrome system in the process of yarovization. The phytochrome complex participated in regulation of the movement and utilization of metabolites. There was revealed the variety specificity of winter wheat in relation to the investigated characters.

The optimal conditions for the manifestation of the lipase activity of an enzyme preparation from the culture liquid of the fungus Geotrichum asteroides were determined. It was found that the rate of hydrolysis depends on the substrate concentration, the enzyme concentration, and the reaction time. The lipase from G. asteroids is rather stable--it loses practically no activity in a year at 4 degrees C. The temperature optimum of the enzyme preparation is 37 degrees. The lipase from G. asteroides is most active at pH 8.0; it retains its activity when kept for 3 h in a reaction medium with a pH from 3 to 10.

The following separation of the main growth forms of Pteridophyta is proposed: thin-rhizomatous, creeping-rosetted, ascending-rosetted, vertical-rosetted, and arborescent. Each of these can be divided into life forms according to a series of morphological and other characters. The most primitive growth form of Pteridophyta is acknowledged as the thin-rhizomatous. In the course of evolution toward polymerization and integration of fronds, the group of arborescent Pteridophyta were transformed into shoot plants, initially of the Cycas type. Water ferns (Salviniaceae) and seed ferns (Pteridospermae) are known as the arbitrary type of Lycopsida which did not reach the state of shot structure of the body. In this respect, Equisetales occupy an intermediate position. It may be assumed that in the evolution of plants, the change in their life forms was of paramount significance.

A mathematical description of the inflow of dibunol from the site of administration and its distribution by organs and tissues in experimental animals and man are examined. Parameters quantitatively characterizing the behavior of the preparation in the organism were obtained. The mechanism of the accumulation of dibunol in the tissues and its subsequent transfer to the blood are described within the framework of the proposed model. The model of the pharmakinetics of dibunol makes possible a calculation of the concentration of the preparation in the tissues depending on the method of administration and special features of the medicinal form. In clinical practice when administered per os microcapsules, which provided maximum absorbability, proved to be the best medicinal form. Satisfactory agreement of the concentrations of the preparation actually observed in a human tumor with those calculated theoretically on the basis of the proposed model was observed.

Phycobilisomes (PBS) were isolated from Aphanizomenon flos-aquae and Anabaena variabilis. The absorption spectra and second derivative of the absorption spectra of isolated PBS indicate the presence of phycoerythrocyanin, and allophycocyanin. The fluorescence spectra of PBS were measured at room temperature and -196 degrees C. Undamaged PBS have the principal fluorescence maximum in the region of 660 nm at room temperature and in the region of 685-690 nm at -196 degrees. When the PBS were heated from ) to 60 degrees the fluorescence at 685-690 nm disappeared and it increased in the region of 650-660 nm. This is apparently due to disruption of the structure of PBS, which results in a disturbance in the migration of energy along the chain phycoerythrocyanin leads to phycocyanin leads to allophycocyanin.