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Biomedical subjects

A A Neĭfakh

Publications and source records attributed to A A Neĭfakh.

At least 19 recordsLinked to original sources
PubMed1996

[Properties of inbred Drosophila melanogaster lines obtained from a population selected for an increased rate of embryonic development].

Two heterogeneous Drosophila melanogaster populations were subjected to selection for an increased rate of embryonic development by picking out the first 10% of hatching larvae. After repeating this procedure in 15 generations, "fast" populations were obtained, in which the duration of embryonic development at high temperature (31-32 degrees C) was 30-40 min less than in nonselected control populations. The results of preliminary experiments on substituting the second and third chromosomes in the selected and control populations provide evidence that selected genes responsible for accelerated development are located on the second chromosome. Inbreeding in 12 generations of selected populations was used to obtain about 40 lines homozygous, in particular, at the alcohol dehydrogenase gene. In four lines, the developmental rate was higher than in a homozygous control line, but others did not differ from control or developed more slowly. The duration of embryonic development at 32 degrees C in fast lines was 50-70 min shorter than in control, but this difference was significantly less at lower temperatures (25 and 17 degrees C). Hence, high temperature is primarily a factor in providing conditions for the expression of genes determining the developmental rate, rather than a factor of selection for these genes. It is suggested that selected genes modify developmental rate dependence on temperature.

Animals↗
PubMed1988

[Identification of cells with lowered sensitivity to cytostatic agents by the use of fluorescent dyes].

With a help of stepwise increase of vincristine concentrations in culture medium several lines of mouse myeloma X63 Ag 8.863 cells resistant to low concentrations of vincristine (6-35-fold) were selected. Rhodamine 123 stained resistant cells and wild-type cells with an equal intensity. However, resistant cells differ significantly from the sensitive ones by the rate of rhodamine efflux. The rate of the efflux was in proportion to the degree of resistance. The efflux of the dye could be blocked by the addition to reserpine, the inhibitor of multidrug resistance. Thus, fluorescent dyes can be used for the detection of cells with low levels of multidrug resistance.

Animals↗
PubMed1987

[Focal contacts and the cytoskeleton].

Cultured cells attach to the substratum by means of specialized domains of cell surface, called focal contacts. The inner side of the cell membrane is associated in these structures with cytoskeletal elements, while the outer side is connected with extracellular matrix. The present review describes both light and electron microscopic methods of studying the focal contacts and ultrastructure of adhesion plaque, that is the cytoskeletal domain of focal contact. The proteins of adhesion plaque and focal contact membranes are also characterized. The processes of the formation of focal contacts and their association with the bundles of actin microfilaments in normal cultured fibroblasts are described in detail. Association of focal contacts with other cytoskeletal elements microtubules and intermediate filaments is discussed. The neoplastic transformation induced changes of focal contact system and cytoskeletal structures associated with contact sites are described.

Animals↗
PubMed1985

[Competition of solid and fluid liposomes for binding and metabolism with lipids from the cell surface].

The competitive behavior of solid vs. fluid liposomes in liposome-cell adsorption and cell-to-liposome lipid transfer processes was investigated with L cells and FBT epithelial sheets. Binding and transfer experiments have demonstrated that: solid liposomes adhere to the cell surface as integral vesicles retaining the entrapped substance; fluid liposomes are partly disintegrated at the cell surface with concomitant entry of entrapped substances into the cytoplasm, while their lipids remain on the cell surface; fluid liposomes that escape lysis dissociate from the cell taking away cell lipid molecules. No lipid transfer occurs between the plasma membrane and solid liposomes. Cell-bound solid liposomes interfere with the transfer of cell lipids to fluid liposomes, while these in turn inhibit the binding of solid liposomes to the cell surface.

Animals↗
PubMed1984

[Detection of complexes in the rat liver which contain lactate dehydrogenase, using centrifugation in a medium with a dissolved enzyme].

Liver and muscle extracts were fractionated by ultracentrifugation under conditions providing for the maintenance of the lactate dehydrogenase (LDH) containing complexes in the media with LDH. Under these conditions, part of the LDH activity (20-30%) was detected in the fractions corresponding to the particles with Mr 1 000 000-2 000 000. When LDH was substituted for by albumin, no LDH containing complexes were revealed. After preliminary fractionation of liver extracts into heavy and light components, the LDH containing complexes were found only in the light fraction, which points to their specific binding to the enzyme as well as to the presence of such complexes in the intact cell.

Animals↗
PubMed1983

[Distribution of solid liposomes on the surface of an epithelial cell layer].

A study was made of the adhesion of liposomes, composed of dipalmitoyl- or di-stearoylphosphatidycholine, on the surface of epithelial cells in culture. Sodium fluorescein was entrapped in liposomes for their visualization by fluorescence microscopy. It is found that sonicated unilamellar liposomes adhere predominantly along the sheet margins. Multilamellar liposomes and lipid-coated carmine particles adhere over the whole cellular surface. However, their adhesion along sheet margins was stronger, as evidenced by a brief trypsin treatment. A prolonged trypsin treatment removed all types of liposomes from the cell surface. After the cells were partly detached from each other, small liposomes readily adhered to the newly accessible cell margins. The existence of special lipid membrane-binding proteins on the cell surface is suggested.

Adsorption↗
PubMed1983

[Regulation of the number and function of mitochondria during artificial increase of their mass in fish embryos].

The mechanisms of mitochondrial mass reduction were investigated by microinjection of mitochondria in developing loach embryos. This reduction can be due to the degradation of the injected mitochondria or to the triggering of regulatory mechanisms. In the latter case the decrease of mitochondrial excess should be caused by exogenous and endogenous mitochondria of the embryos. When the protein-labelled mitochondria were injected into unlabelled eggs or the unlabelled mitochondria were injected into the eggs containing labelled mitochondria, the label content in the mitochondrial protein was decreased 2-fold within 12 hours and then remained unchanged at later stages of embryogenesis. After injection of 3H-labelled mitochondria into the 14C-labelled eggs the 3H/14C ratio in the mitochondrial protein during embryogenesis remained unchanged. These data suggest that the restoration of the normal amount of the mitochondrial mass is caused by the triggering of regulatory mechanisms. Oxygen uptake in the embryos with the artificially increased amount of mitochondria is maintained at a control level or even below control, i. e. undergoes regulation. In the homogenates of these embryos the regulatory control is absent and oxygen uptake is proportional to the amount of mitochondria.

Animals↗
PubMed1979

[Injection of mitochondria into oocytes and fertilized eggs].

The suspension of mitochondria isolated from the loach embryos or the frog heart were injected in the oocytes or fertilized eggs of the loach, newt, toad and frog in the amount roughly equivalent to the content of mitochondria in the egg. After the injection the oocytes did not differ during several days from the normal ones and the fertilized eggs of the loach, newt and South Afican clawed toad developed normally. The activity of cytochrome oxidase in the injected oocytes was kept at a somewhat higher level (1.4 to 1.9 vs 1.0 in the control) during several days. In the developing eggs the activity of cytochrome oxidase began to decrease from the blastula stage and attained rapidly the control level. The decrease of the enzyme activity is due to non-specific degradation of excessive mitochondria or to compensatory inactivation of the enzyme ensuring the maintenance of its normal activity during the development.

Animals↗
PubMed1978

[Expression of paternal genes controlling cytochrome oxidase activity in hybrid fish].

The heat resistance of the oxygen consumption by the mitochondria, temperature dependence of the Michaelis' constant (CM) and heat resistance of cytochrome oxidase were studied in the embryos and larvae of fish hybrids (Misgurnus X Brachydanio). The oxygen consumption by the mitochondria from the larvae of Misgurnus ceased (following the 10 min heating) at 50 degrees, from Brachydanio at 54 degrees and from the hybrids at 52 degress suggesting control of the respiratory function. CM of cytochrome oxidase has the same minimum in the larvae of Misgurnus and Brachydanio, therefore this criterion was not used to study the genetic control in their hybrids. The heat resistance of cytochrome oxidase (T50) differed in Misgurnus and Brachydanio and was of intermediate value in their hybrids. At the early stages of hybrid development T50 was of maternal type (Misgurnus) but beginning from the mid-gastrula stage T50 increased and attained the maximum prior to the hatching. Chloramphenicol did not affect the increase of T50 in hybrids, but actinomycin decreased it almost down to the level characteristic of Misgurnus. The data obtained suggest that the genetic control of cytochrome oxidase activity begins earlier than that of other studied enzymes.

Animals↗
PubMed1977

[Expression of genes controlling esterases during the embryonic development of hybrid fish].

The electrophoretic mobility of several enzymes was studied in the embryos and early larvae of the hybrids between the loach (Misgurnus fossilis) and the aquarial cyprinids and cobitids (Acanthophthalmus). The cytosol aspartate aminotransferase is represented by one protein with the same mobility at all developmental stages both in the loach and in the hybrids. Malate dehydrogenase manifests four bands of isozymes which suffer no changes during the development. The electrophoretic profile of lactate dehydrogenase remains constant (10 isozymes) until hatching, but only 5 isozymes are found in the 5 days old larvae. Similar changes occur in the Misgurnus X Acanthophthalmus hybrids. The nonspecific esterases are represented by several proteins with different activities; their number increases after hatching. In the oocytes and adult specimens of Acanthophthalmus a characteristic and very active esterase was found which is absent in the loach. In the Misgurnus X Acanthophthalmus hybrids this esterase appears prior to the hatching and its activity later increases. Thus, the expression of the gene of one esterase begins in the end of embryogenesis.

Animals↗
PubMed1976

[Time of the action of genes controlling the activity of aldolase in embryonal development of groudling].

The time of action of the genes controlling the decrease of aldolase activity (21-23 hrs of development) and its subsequent increase (23-36 hrs) was determined by means of inactivation of the nuclei by actinomycin or heavy doses of irradiation at succesive developmental stages. There exist two distinct periods of gene activity; the former (15-18 hrs) determines the rapid fall of maternal aldolase activity and the latter (21-27 hrs) its subsequent replacement by embryonic aldolase. This result is confirmed by the data concerning the changes in aldolase heat resistance in the hybrids of the loach and tropical cyprinids. The genes controlling the synthesis of the new aldolase and the morphogenesis which takes place at the same developmental stages are functioning at different times, i.e. the biochemical and morphological differentiations may occur relatively independently.

Animals↗
PubMed1976

[Localization of aldolase activity in the embryos of loach].

The activity of aldolase was determined in different parts of the loach (Misgurnus fossilis L.) embryo at the stages from the formation of axial organs till the beginning of embryonic movements (from 19 till 38 hrs of development at 21.5 degrees). In all parts of the embryo, the activity of aldolase at first decreased (21-23 hrs) and then increased. The region of somites is characterized by the highest absolute and specific activity at all developmental stages. The increase in the number of somites is accompanied by the fall and subsequent rise of aldolase activity. In the somites of different degree of differentiation, the enzyme activity changes in a similar way. Hence, there is no correlation between the morphological and biochemical differentiation of somites. Differences in the specific aldolase activity between the anterior and posterior halves of the embryo and the regions of head, somites and tail were found at the stages of 19-23 hrs of development. The maternal aldolase only is present at these stages, as was shown earlier. It means that the early stages of biochemical differentiation may be realized not by means of differential activation of genes controlling the enzyme, but by means of regylation of translation on the templates stored in oogenesis.

Age Factors↗
PubMed1976

[Morphogenetic function of the nuclei in the early development of the common freshwater snail, Limnaea stagnalis].

The early embryos L. stagnalis were placed in the actinomycin solution at the successive developmental stages. The permeability to actinomycin was previously increased by the pricking through egg capsules. The inactivation of nuclei by actinomycin up to the stage of 12 blastomeres resulted in the arrest of development at the 22 cell stage. The inactivation of nuclei at the subsequent development stages resulted in the developmental arrest at later stages. These data suggest that the embryonic development up to the 22 cell stage is provided by the nuclear function during oogenesis. The morphogenetic nuclear function of the embryo begins at the stage of 12 blastomeres and provides the embryonic development beyond the 22 cell stage.

Animals↗