[Topographic and dosimetric considerations in different methods of proton irradiation]. / Topografodozimetricheskie situatsii pri razlichnykh metodakh protonnogo oblucheniia.

Two techniques are employed for proton irradiation: one--to pass a proton beam through a target, the other one--to stop in it. The advantage of the first technique is a very small angular divergence of the beam penetrating tissues or, consequently, a very high lateral edge field gradient. The second technique has two additional advantages: the absence of radiation lesions behind the target and an increase in the stopping power (dose) at the end of the beam range localized in the target. The authors present their considerations concerning the applicability of each technique and certain characteristic problems of the second technique. Dose field deformations as a result of topometric uncertainties are also estimated. A method of dose design aimed at minimizing the above mentioned effect is proposed.

[Cultivation characteristics of Legionella pneumophila in a liquid medium]. / Osobennosti kul'tivirovanii Legionella pneumophila v zhidkoi srede.

The comparative analysis of liquid media for the cultivation of Legionella pneumophila, sterilized by filtration and autoclaving, has shown that, in contrast to media prepared on the basis of yeast extract, the capacity of media based on proteose peptone for supporting the growth of Legionella is not influenced by the method of their sterilization. The possibility of cultivating this organism in liquid media without ferric pyrophosphate has been demonstrated.

[Comparison of endogenous nuclear RNA-polymerase II at different stages of mycoplasmodial growth]. / Sravnenie éndogennoi RNK-polimerazy II v iadrakh Physarum polycephalum na raznykh stadiiakh rosta mikroplazmodiia.

The nuclei of Physarum polycephalum isolated from the 48- and 96-hour-old growing microplasmodium differ 7-8 fold by the rates of [3H]UTP incorporation in vitro accompanied by a slight (approximately 1.6 fold) change in concentration of endogenous RNA-polymerase II. Using mild fragmentation of chromatin nuclei by micrococcal nuclease and DEAE-Sephadex chromatography the bound enzyme was shown to consist of two forms differing in the degree of their binding to the template and in functional significance. Transcription in the Physarum polycephalum nuclei can be regulated by changes in the correlation of these forms.

[Comparative enzymatic study on the structure of chromatin in the nuclei of the growing microplasmodium of Physarum polycephalum]. / Sravnitel'noe fermentativnoe issledovanie struktury khromatina iader rastushchego mikroplasmodiia Physarum polycephalum.

The structure of chromatin in the growing myxomycetes P. polycephalum can be interpreted on the basis of three types of substructure: (i) soluble in a low ionic strength buffer and 2 mM EDTA (I), (ii) soluble in 0.6 M NaCl (II) and (iii) non-soluble and nuclease-insensitive (III). The ratio of these structures in the nuclear pellet obtained after autolysis was found to be 71 : 0, 4 : 12 for the young and 7.7 : 62 : 20.6 for the old cultures, respectively. The ageing of the culture involves transition of substructure I to substructure II. The substructures differ in the nuclease sensitivity. The specific features of enzyme fragmentation of chromatin from P. polycephalum microplasmodium nuclei are discussed.

[UV-light-tested protein--DNA interactions in the nuclei during the cell cycle in Physarum polycephalum]. / Testiruemye uf-svetom belok--DNK-kontakty v iadrakh na raznykh stadiiakh kletochnogo tsikla Physarum polysephalum.

The release of DNAs from nuclear preparations isolated at different steps of the cell cycle of the synchronous culture of Physarum polycephalum and irradiated with UV-light for 5 min (lambda 253.7 A, i = 1.8 . 10(2) j . m-2 . min-1) into 1% Na-DS - 1.5 M NaCl solution was studied. The value obtained correlated well with the degree of binding of interacting proteins with DNA in chromatin and was identical for all the preparations tested with the only exception of the nuclei isolated at the end of the S-phase, when a slight but significant (15 +/- 10%) increase in DNA release was observed. The results obtained are discussed in terms of structural transitions and function of chromatin during the cell cycle of the myxomycete Physarum polycephalum.

[Dependence of RNA synthesis in the cell of Physarum polycephalum on concentration and activity of RNA-polymerase II]. / Sintez RNK v kletochnom tsikle Physarum polycephalum v zavisimosti kontsentratsii i udel'noi aktivnosti RNK-polimerazy II.

The RNA synthesis detected by incorporation of [H3]uridine chase label proceeds in macroplasmodium and in isolated nuclei throughout the cell cycle of a synchronous myxomycetes culture of Physarum polycephalum, producing two well-shaped peaks at the postmitotic and premitotic steps. Such RNA synthesis is due to the activity of alpha-amanitin-sensitive RNA-polymerase II. Concentrations of RNA-polymerase II at various steps of the cell cycle were determined by alpha-amanitin titration; the specific activity of the enzyme was assayed. The increase in the rate of mRNA synthesis was accompanied by a rise in the concentration and specific activity of the enzyme: for the postmitotic peak, for instance, the corresponding values were about 2-2.5 and 2-4 times as high as minimum values revealed during the cycle. The results obtained are discussed in terms of transcription control in eukaryotic systems.