[Heterogeneous packing of the Escherichia coli chromosome and its decompaction in in vitro experiments]. / Geterogennaia upakovka khromosomy Escherichia coli i ee dekompaktizat siia v opytakh in vitro.

The chromatin organization of E. coli cells, taken on various growth stages of the culture (active, stationary, grown with heightened density), displays different characters when examined by the Miller method. In the active phase of growth, the cell chromatin is released as threads and loops of DNA, threads of nucleosome-like particles and granules 25-38 nm in size. The chromatin from cells in the stationary phase of growth, grown in heightened density conditions, contains not only granules of average size 30 and 100 nm, but also larger conglomerates consisting of several 100 nm particles. The chromatin decompaction of cells grown under heightened density, in conditions of weak alkali medium and low salt buffer, was in general of two types: creation of diffusion cloud with no clear-cut outlines, and spherical structure of 1.5-2 microns in diameter with electron dense centre. In one chromosome both the types of chromatin decompaction can be found at the same time with regions of compact chromatin, which undoubtedly shows different functional activity of some regions of the chromosome.

[Characteristics of the ultrastructural organization of the nuclei of somatic cell hybrids]. / Osobennosti ul'trastrukturnoi organizatsii iader gibridov somaticheskikh kletok.

A study was made of the ultrastructure of cell nuclei of two types of hybrid clones obtained from the fusion of Chinese hamster with human skin fibroblasts, and from that of mouse hepatoma cells with mink fibroblasts. In cell nuclei of the eight hybrid clones deep invaginations of the inner membrane, not characteristic of the parent cells, were revealed. Analysis of serial sections, and application of electron microscopic radioautography and histochemistry have suggested that these structures are associated with the nuclear envelope which is necessary for regulating the superfluous chromosome localization in the hybrid nucleus.

[Electron microscopic research on the extrachromosomal genetic elements of Escherichia coli]. / Elektronno-mikroskopicheskoe issledovanie vnekhromosomnykh geneticheskikh élementov Escherichia coli.

The structural organization of extrachromosomal genetic elements were studied in a subfraction obtained after centrifugation of the lysate of E. coli spheroplasts. With this method of isolation, the tertiary structure of the extrachromosomal genetic elements was preserved. The majority of DNA macromolecules were released in the form of single and connected rosettes. Typical rosettes composed of radial loops of DNA clustered around the central dense core (the diameter is about 60 nm). The mean length of the rosette loops was 1.06 +/- 0.4 micron. Both relaxed folded and supercoiled folded forms of DNA were observed on the preparation. Sometimes the rosettes were connected with large aggregates of DNA (possibly the material of bacterial chromosomes) and had the appearance of thick fibers with numerous lateral loops. Linear, cyclic and various replicative forms of DNA have also been observed. It is assumed that rosettes of the extrachromosomal elements of E. coli reflect one of the levels of organization of prokaryotic genetic material.

[New method of encapsulating isolated nuclei into a lipid membrane]. / Novyi metod zakliucheniia izolirovannykh iader v lipidnuiu obolochku.

A new method of the coating of isolated cell nuclei with additional phosphatidylcholine membranes is described. The additional membrane was visualized under the electron microscope using ferritin as a label. The coating diminished leakage of the content of the nuclei and restricted permeability of the nuclei for exterior macromolecules.

[Use of cell enucleation in studying the stability of cytoplasmic organelles and cytoplasm organization]. / Primenenie énukleatsii kletok dlia izucheniia stabil'nosti tsitoplazmaticheskikh organell i organizatsii tsitoplazmy.

A study was made of the viability and ultrastructure of cytoplasts produced by enucleation of cytochalasin-induced A9 cells in suspension. These cytoplasts are in general as viable as cells enucleated in the monolayer. The organization of the cytoplasm, i.e. a specific distribution of cytoplasmic organelles, is conserved for at least 24 hours in the absence of the nucleus. This fact may reflect a high degree of autonomy of the cytoskeleton.

[Quantitative analysis of the ultrastructure of gastric mucocytes in the rat after prostaglandin treatment]. / Kolichestvennyi analiz ul'trastruktury mukotsitov zheludka krys posle deistviia prostaglandina.

Effect of prostaglandin E2 (PGE2) on mucus secretion by mucocytes of the fundal part of the rat stomach has been studied electron microscopically, morphometrically and biochemically. PGE2 is found to stimulate synthesis of glycoproteins and their secretion by the mucocytes that results in increasing the relative volume of Golgi complex and in decreasing that of secretory granules. Actinomycin does not affect and cycloheximide blocks the stimulating activity of prostaglandin. This demonstrates that prostaglandin produces its action at the posttranscriptional (translational) level controlling mucus secretion of mucocytes. Owing to the results of the investigation and of those previously obtained on incorporation of 3H-pentagastrin and 3H-histamine into the cells of the mucous tunic, at least two mechanisms are supposed to control the gastric mucus secretion.

[Changes in the RNA-dependent DNA-polymerase activity of retrovirus-like particles in the rat liver during postnatal ontogeny]. / Izmenenie RNK-zavisimoi DNK-polimeraznoi aktivnosti retrovirusopodobnykh chastits pecheni krys v protsesse postnatal'nogo ontogeneza.

The RNA-dependent DNA-polymerase activity was studied in the postmicrosomal fraction and in the microsomal sediment of the liver of the newborn and adult Wistar rats. In the microsomal sediment of 4-6 day old rats the RNA-dependent DNA-polymerase activity was approximately by one order of magnitude higher than in that of 2 week old and adult rats. In the postmicrosomal fraction of 3 day old rats the RNA-dependent DNA-polymerase activity was also higher, but only by 30-35%, than in that of animals of the other age groups. Particles with density of 1.17 g/ml were found in the microsomal sediment of all studied animals. The characteristic morphology, sensitivity of the particle RNA-dependent DNA-polymerase activity to RNAse and the presence of reverse transcriptase allow for these particles to be referred to as retroviruses. A suggestion is put forward that the high intensity of reverse transcription during the early postnatal period can be due to still continuing processes of cell differentiation and enzymatic imprinting.

[Relation of RNA-dependent DNA-polymerase from the rat liver with virus-like particles]. / Sviaz' RNK-zavisimoi DNK-polimerazy iz pecheni krys s virusopodobnymi chastitsami.

RNA-dependent DNA-polymerase activity was found in the 165 000 g supernatant and pellet of the postmitochondrial rat liver fraction. Further fractionation of the 165 000 g pellet in the linear sucrose gradient (20-50%) showed that RNA-dependent DNA-polymerase activity was distributed between fractions with densities 1.18-1.19 g/ml and 1.09-1.1 g/ml. In the fractions with 1.18-1.19 g/ml density the enzymic activity could be detected only after Triton X-100 treatment and disappeared after the incubation with pancreatic ribonuclease A. Triton X-100 treatment of the 165 000 g supernatant and the fractions with density 1.09-1.1 g/ml did not increase further the enzymic activity. Electron microscopy revealed in the 1.18 g/ml fraction virus-like particles resembling retroviruses of A and C type. In the light peak "non-mature" virus-like particles were found. The 165 000 g supernatant devoid of virus-like particles contained free RNA-dependent DNA-polymerase activity. The virus-like particles of both types seem to be endogenous rat retroviruses serving as a source of the particular and free reverse transcriptase in the rat liver.

[Electron microscopy study of deoxyribonuclease penetration into chick embryo fibroblasts and the effect of the enzyme on the cells]. / Elektronno-mikroskopicheskoe issledovanie proniknoveniia dezoksiribonukleazy v fibroblasti kurinykh émbrionov i vliianie fermenta na kletki.

Peroxidase labeled DNase (0.25 g/ml) penetrated into the chick fibroblast culture cells by means of pinocytosis to be localized in pinocytotic vacuoles. Within a 24 hour-incubation of the cell culture with DNase a relative volume of vacuoles in cells increased from 4.6 to 19.5 per cent, the majority of pinocytic vacuoles being filled with labeled DNase. The incubation of cells with non-labeled DNase (24 hours) did not damage DNA-containing cell structures. The data obtained permit to explain the selective effect of the enzyme on the viral DNA and the inhibition of reproduction of DNA-containing viruses by the interaction of the viral DNA and DNase inside pinocytic vacuoles which protect the cells from the enzyme damaging effect.

[Comparative study of the ultrastructure of cells of the zona fasciculata of the adrenal cortex of rats of different lines]. / Sravnitel'noe izuchenie ul'trastruktury kletok puchkovoi zony kory nadpochechnikov krys raznykh linii.

By means of morphometric analysis, some tissue and cellular parameters of the zona fasciculata of the adrenal cortex of three rat inbred strains (Wistar, Sprague-Dawley, August) and of the wild grey rats were calculated. Significant genotypic differences were found in the absolute volume in the number of cells per mm3 of tissue, and in relative volumes of basis cellular compartments (smooth endoplasmic reticulum, liposomes) which take part in corticosteroid biosynthesis. A hypothesis is put forward that these differences determine different potential possibilities of rat adrenals, which are realized when their functional activity is enhanced under extreme conditions.

[An electron microscopic and morphometric study of the gastric parietal cells of rats following administration of gastrin, histamine and cyclic 3',5'-adenosine monophosphate]. / Elektronnomikroskopicheskoe i morfometricheskoe izuchenie obkladochnykh kletok zheludka krys pri vvedenii gastrina, gistamina i tsiklicheskogo 3',5'-adenozinmonofosfata

The ultrastructure of the gastric parietal cells was studied in rats affected by a genetic inductor of the hydrochloric acid secretion and its mediators in this process - histamine and cyclic 3', 5'-adenozinemonophosphate playing the role of the enzyme activators. All these stimulators caused similar changes in the cell structure. The square surface of the intracellular secretory tubules was shown to become 2,5 times larger, and that of the canaliculi - vesiculoid elements which seemed to be the cell membrane depot became 2,5 times less. It may be supposed that the gastric mucosa parietal cells are not the target-cells for pentagastrine (gastrine).