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Biomedical subjects

T Tsvetkov

Publications and source records attributed to T Tsvetkov.

At least 19 recordsLinked to original sources
PubMed1991

Some seasonal changes in the thecal gland in the ovaries of hibernators (Citellus citellus L.).

The ovaries of 36 ground squirrels were studied in March, April, July, and December. Morphological and functional seasonal characteristics of theca interna were studied by histological methods, electron microscopy, and quantitative methods for determinating the volume density and histoenzyme activity of NADH2-tetrazolium reductase, glucose-6-phosphate dehydrogenase, and delta 5-3 beta-hydroxysteroid dehydrogenase. Maximal activity of theca interna as a steroid-producing structure was observed during spring awakening. A significant increase in the histoenzyme activity of delta 5-3 beta-hydroxysteroid dehydrogenase in December, versus two other enzymes studied, indicated steroid synthesis in theca terna.

3-Hydroxysteroid Dehydrogenases↗
PubMed1990

[The HLA system in normal and pathological pregnancies].

The authors investigated 205 women, 50 of whom were nonpregnant, 32 with normally progressing pregnancy, 30 parturients, 30 with abortions, 30 with prolonged pregnancy and 35 with pre-eclampsia. There were no statistically significant changes between the percentage of cases with positive lymphocytotoxic test, presence of leucoagglutinins and thrombocytic antibodies among the single groups. There were HLA-antibodies, which were not titrated due to the low titre in 4 of the women with pre-eclampsia.

Adolescent↗
PubMed1989

Cytology of oocytes in ground squirrels (Citellus citellus L.).

Oocytes of primordial, primary, growing, and Graaf follicles of the ovaries of 96 ground squirrels (Citellus citellus L.) were studied during the four seasons of the year. Multilamellar bodies in the oocytes were observed by electron microscopy. The bodies underwent changes during the follicle growth. The vesicles included in the multilamellar bodies were filled with an amorphous substance, while in Graaf follicles trapezoidal, rhomboidal, and hexagonal inclusions were found. The primordial follicle of the oocyte had no Balbiani body. In the hibernating ground squirrel the functions of the Balbiani body were probably performed by the multilamellar bodies, which were considered to be analogous to the Balbiani body.

Animals↗
PubMed1989

The ovarium of the hibernator (Citellus citellus L.) after spring arousal.

The ovaries of 20 ground squirrels (Citellus citellus L.) were studied after spring arousal, while the animals were in the stage of estrus. The membrana granulosa of the preovulatory folic was luteinized. Epithelial cords were observed in the ovarial stroma. Cells in different stages of differentiation were found in the cords. For the first time nucleoli-like bodies in the nucleus and in the interstitial cells of the ovary of the ground squirrels. Probably, these nucleoli-like bodies played a definite role in the process of membrane formation during the cell differentiation. The NADH2 reductase and 3 beta-hydroxy-delta 5-steroid dehydrogenase activity confirmed that the process of differentiation of the interstitial cells was still in an initial stage. The findings were compared with the changes that took place during the puberty period.

Animals↗
PubMed1989

Seasonal changes of the ovarian atretic follicles of the ground squirrel (Citellus citellus L.).

The ovaries of 84 ground squirrels (C. Citellus L.) were studied during the four seasons of the year. The ovarian atretic follicles were examined by histological methods and by electron microscopy. The histoenzyme activities of NAD.H2-tetrazolium reductase, glucose-6-phosphate dehydrogenase, and 3 beta-hydroxy-delta 5-steroid dehydrogenase were photometrically demonstrated. The steroid-producing atretic follicles were mainly described as they reached their highest enzyme activity during the lactation period in April. The atresia of the primordial and primary follicles was manifested by disappearance of the oocyte and preservation of the granulose cells surrounded by basal lamina. Atresia of follicles with two oocytes was a typical process for the ground squirrel. Later on the oocytes and the granulose cells around it disappeared. The remaining part of the follicle continued its development and reached maturity. Atresia was observed mainly in March, April, and May.

Animals↗
PubMed1989

Studies on the estrus cycle of the ground squirrel (Citellus citellus L.) at experimentally induced hibernation.

Eighty-five ground squirrels (C. citellus L.) were examined immediately after arousal (March-June). It was established that the animals were in estrus at the end of March; in April they were pregnant; in May they were in lactation; and in June they were already at rest, a postlactation period. Fifteen ground squirrels were treated with Hibernal and then placed in a chamber for 30 days at external temperature, 8-12 degrees C. In this case the estrus cycle of hypothermic ground squirrels was not changed. A retarded involution of corpus luteum persisted for a month and cystic follicles appeared in the ovary.

Animals↗
PubMed1988

Dependence of trehalose protective action on the initial phase state of dipalmitoylphosphatidylcholine bilayers.

Dipalmitoylphosphatidylcholine (DPPC) bilayers hydrated in the presence of trehalose were equilibrated at various temperatures (4, 20, and 60 degrees C) corresponding to the crystalline Lc, gel L beta', and liquid-crystalline L alpha phases, respectively, and then desiccated at these temperatures or freeze-dried at -80 degrees C to ca. DPPC dihydrate. The thermotropic behavior of the resulting DPPC/trehalose mixtures was investigated by differential scanning calorimetry and found to be dependent not only on the trehalose concentration but also on the phase state of the hydrated bilayers prior to their drying. Trehalose was most effective when the desiccation was carried out from the L alpha phase at 60 degrees C. In this case, one trehalose molecule per two DPPC molecules was sufficient to depress the melting temperature from values typical of DPPC dihydrate to 45 degrees C. Trehalose's influence decreased when dried from the L beta' phase and was significantly less pronounced when dried from the Lc phase. These data show that trehalose's protective influence depends on the initial phase state of the lipid bilayer and reaches its maximum in the liquid-crystalline state. The possible role of this effect in anhydrobiosis is pointed out.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1988

Histoenzymatic activity of the delta 5-3 beta-hydroxysteroid dehydrogenase of ovary in hibernators (Citellus citellus L).

The ovaries of 24 ground squirrels (Citellus citellus L) were studied in spring (March, April), summer (July), and winter (December). The animals hibernated in a chamber at a temperature of 6-8 degrees C. The activities of the interstitial gland, theca interna, atretic follicles with theca interna and yellow bodies were measured densitometrically and studied by a specially modified histoenzymatic technique. Measurements showed that the endocrine structures were most active in March and least active in July. The atretic follicles had the highest enzymatic activity in April. The quantitative histoenzymatic approach presents an objective base for morphofunctional studies of organs and tissues at different body temperature levels in hibernators.

3-Hydroxysteroid Dehydrogenases↗
PubMed1987

Activity of ATP synthetase complex after low temperature treatment or freeze-drying of mitochondria isolated from skeletal muscles.

The influence of freezing, thawing, or freeze-drying on ATP synthetase complex of isolated skeletal muscle mitochondria was studied. Cooling to -60 or to -196 degrees C and rapid thawing did not change activity significantly. Slow warming stimulated the release of latent ATP-ase activity and decreased ATP synthesis. These changes were more pronounced after freeze-drying.

ATP Synthetase Complexes↗
PubMed1986

A quantitative evaluation of the extent of inner mitochondrial membrane destruction after freezing-thawing based on functional studies.

An assay based on comparative investigation of ATPase and ATP synthetase changes in the activity in rat liver mitochondria after low temperature and uncoupler 2,4-dinitrophenol treatment is considered. By varying the activity of the respiratory chain, three extents of membrane cryoinjury could be distinguished by monitoring the changes in ATPase activity under different types of cryoinfluence. The first extent corresponds to a minimum membrane destruction, where the action of the respiratory chain compensates the changes in proton permeability and the cryotreatment does not change the ATPase activity. The second extent corresponds to changes in ion permeability which is partially compensated by the respiratory chain action. The third extent corresponds to a maximum membrane destruction and, therefore, maximum increase in permeability which is related to the irreversible stimulation of the ATPase activity and complete inhibition of the phosphorylation. In this study the extent of cryoinjury in mitochondrial preparations frozen and thawed at different rates was evaluated using this method.

2,4-Dinitrophenol↗
PubMed1986

Isolation and cryopreservation of human peripheral blood monocytes.

A modification of the Freundlich and Avdalovic method (J. Immunol. Methods 62, 31 (1983] is reported. Buffy coats, separated and pooled together, are used for isolation of monocytes (70% yield, 100% purity). Cell density of working suspension is increased up to 0.65 X 10(9) cells/75 cm2 surface by multiplication of the active fibronectin sites. For the purpose, cryoprecipitate is used instead of plasma for coating the glass-gelatin surface. Monocytes, isolated by that procedure, could be successfully cryopreserved with dimethyl sulfoxide cryoprotective solution.

Blood Preservation↗
PubMed1985

Aggregate formation in cryopreserved leukocyte suspensions.

During cryopreservation of leukocytes, a great part of the granulocytes is injured. The latter is responsible for aggregate formation in the suspension and a loss in the number of preserved cells. The formation of aggregates in the suspension is potentiated in the presence of serum in the cryoprotective medium. On the other hand, the presence of sugar (sucrose, lactose, dextrose) in the washing solution diminishes the aggregate formation, the latter effect being directly proportional to the final concentration of the sugar in the suspension. The aggregates contain mainly cells and very rarely amorphous or fibrous zones. They appear only in the presence of serum. Their formation is not connected with presence of traces of fibrinogen in the serum.

Blood Preservation↗
PubMed1985

Functional changes in mitochondrial properties as a result of their membrane cryodestruction. I. Influence of freezing and thawing on succinate-ferricyanide reductase of intact liver mitochondria.

The interaction of the succinate dehydrogenase complex of rat liver mitochondria with an artificial electron acceptor (K3Fe(CN)6), impermeable to the mitochondrial membrane as an index of a cryoinjury is investigated. It is shown that the freeze-thawing stimulates succinate-ferricyanide reductase (SFCR) activity of intact mitochondria. The increase of the freezing and thawing rates leads to a decrease in the released SFCR activity. The released SFCR activity after low-temperature treatment is a consequence of a nonspecific change in membrane ferricyanide permeability. The released SFCR activity decreases as the freezing and thawing rates increase.

Animals↗
PubMed1985

Functional changes in mitochondrial properties as a result of their membrane cryodestruction. II. Influence of freezing and thawing on ATP complex activity of intact liver mitochondria.

The influence of the freeze-thawing rates on ATP synthetase (ATPase) complex of intact liver mitochondria was investigated. It was shown that the increase in latent ATPase activity and decrease in ATP synthetase activity resulted from an influence on the inner mitochondrial membrane. An increase in freeze-thawing rates led to the preservation of ATP synthetase activity and ATP hydrolysis reduction. Kinetic parameter changes of the ATP synthetase reaction resulted from an insignificant nonspecific increase in the inner mitochondrial membrane permeability and changes in its electrochemical potential level.

ATP Synthetase Complexes↗
PubMed1985

Preservation of integrity of the inner mitochondrial membrane after freeze-thawing and freeze-drying.

The results of this paper illustrate that trehalose partially preserves inner mitochondrial membrane integrity after freeze-thawing and freeze-drying with subsequent rehydration in water. The 2,4-dinitrophenol stimulation of ATPase activity was used as a criterion for membrane integrity. The results show that ATPase activity of lyophilized-rehydrated mitochondria was stimulated up to two to three times.

Animals↗
PubMed1984

A method for preparation of dry thrombin for topical application.

Thrombin for topical hemostasis can be prepared from bovine or human blood plasma. The prothrombin is isolated by means of adsorption on DEAE-Sephadex A-50 and consecutively activated by CaCl2 and thromboplastin. Thrombin is precipitated and purified by acetone. The specific activity of the thrombin preparation is 122 + 23 IU/mg protein while the yield is 36,360 +/- 6623 IU/liter plasma.

Administration, Topical↗
PubMed1984

Antibodies and thermolabile opsonins in the phagocytosis of human red and white blood cells pretreated with formaldehyde.

Erythrophagocytosis is conditioned by serum immunoglobulins. The extent of phagocytosis depends on the haematocrit of the red cell suspension pretreated with formaldehyde. The higher the haematocrit value, the lower will be the extent of phagocytosis. Phagocytosis of white blood cells pretreated with formaldehyde by granulocytes and monocytes is conditioned mainly by a thermolabile fraction of the serum, probably the complement.

Blood Physiological Phenomena↗