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Biomedical subjects

L A Denisova

Publications and source records attributed to L A Denisova.

At least 19 recordsLinked to original sources
PubMed2005

[Application of the method of acoustic microscopy for the study of eye tissues].

The paper describes the results of evaluation of potentialities of the application of scanning acoustic microscopy, which is still relatively new and as yet uncommon method of biological research, for the supravital study of animal eye structure in species with different eyeball size. Using the eyes of a goat, quail embryo (in situ) and frog tadpole (in vivo) as the examples, it was shown that non-destructive nature of the method used allows for the study of peculiarities of major morphologic structures in the state that is close to the natural one. Some acoustic images are presented showing eye structural elements along with the results of quantitative characteristic of the cornea, sclera and iris.

Animals↗
PubMed2004

The use of acoustic microscopy to study the mechanical properties of glass-ionomer cement.

OBJECTIVES: The aim of the study was to investigate the relationship between microstructure, acoustic and mechanical properties of hardened dental cement samples, prepared with different powder/water ratios. METHODS: Glass-ionomer dental cement samples, prepared with a standard amount of cement powder and different amounts of water have been examined after being hardened. Surface microstructure and ultrasound, longitudinal and shear velocities were obtained with a scanning acoustic microscope. Conditional effective elastic modulus and Poisson's ratio have been calculated using longitudinal and shear sound velocity values. Then on the same samples elastic modulus and microhardness have been determined by standard tests. Additional samples have been used to determine compressive strength. RESULTS: Density; conditionally instantaneous elastic modulus; high-elasticity modulus and compression strength of the samples decrease when large amounts of water were used for their preparation. At the same time porosity and microhardness of the cement matrix increase. Acoustic parameters and parameters of elasticity, calculated on the basis of sound velocity, demonstrated changes, similar to those obtained in standard mechanical tests. SIGNIFICANCE: The established relation between microstructure, acoustic and mechanical parameters demonstrated a high capacity of acoustic microscopy application for non-destructive characterization of dental materials. A particular advantage of the acoustic microscopy is the opportunity to evaluate microstructure and mechanical properties on the same sample.

Compressive Strength↗
PubMed2004

[Acoustic histology of dental tissues].

New data on tooth enamel and dentin microstructure, obtained by acoustic microscopy methods, which are based on evaluation of distribution of the local elastic and mechanical properties, are presented. The results demonstrate that the acoustic microscopy methods are more sensitive to changes in mechanical properties of dental tissues in caries in comparison with optic microscopy.

Animals↗
PubMed2004

[Laboratory evaluation of the efficiency of dental root channel filling].

Adhesive strength of gutta-percha stems connection to the root channel walls was evaluated. The pressure on dental root channel walls during tooth filling by the lateral condensation method was evaluated. The study was carried out on an Instron device by the pulling out method. The study showed that for stems Nos. 15-30 the retention strength in the root channel was about 2-fold higher than for stems Nos. 35-45. The results indicate that the value of stem pressure on root channel walls during tooth filling by the lateral condensation method can be considered critical with regard to the strength of the dental root proper.

Adhesiveness↗
PubMed2002

[Acoustic microscopy methods in studies of the filling materials microstructure].

The structure of filling materials (kemfil, polyacrylate cement, and Dentis, material produced by Stomadent Firm in Russia) at the interface with human dentin was studied in teeth subjected to retrograde filling with preliminary appendectomy. A prototype of table wide-field short pulse scanning acoustic microscope (50 mHz) (Acoustic Microscopy Center, Institute of Biochemical Physics of Russian Academy of Sciences) and Elsam acoustic microscope (200 mHz) (Leitz, Germany) were used. The results indicate that analysis of acoustic characteristics, including the data of acoustic microscopy, helps investigate the cement microstructure and evaluate the compactness and elasticity of samples; moreover, structural elements of the material, which are undetectable by other methods, are seen on acoustic images. These data can be used for evaluating the relationship between the microstructure and formation of mechanical properties, and, maybe, the patterns of cement interactions with dental tissues.

Acoustics↗
PubMedDate not supplied

[Water and electrolyte content of the organs and tissues of male rats following a flight on the Kosmos 1667 biosatellite].

After the 7-day space flight onboard the biosatellite Cosmos-1667 the water, Na, K, Ca and Mg content of the liver, kidney, heart, skin and bone of male rats was measured. No significant changes in the weight or water content of the above organs were seen. The exception was a decrease of water contained in the heart and an increase of water contained in the caudal appendage of the epididymis. After flight the mineral composition of the liver was identical to that after control studies. The K content of the heart of the flight rats was lower and that of Na, Ca and Mg was identical to the parameter in the controls. The K content of the skin and bone increased and the Na content of the skin also grew. In the kidney the Ca content did not change whereas the content of K, Na and Mg decreased significantly. In the testis Na decreased and K increased after flight. Thus, changes in fluid-electrolyte homeostasis at the organ and tissue level can develop within 7 days of space flight. They occur not only in the musculoskeletal system but may also evolve in the nonweight-bearing organs.

Adaptation, Physiological↗
PubMedDate not supplied

[The reproductive function of male rats following space flight on the Cosmos-1667 biosatellite].

After the 7-day space flight of Cosmos-1667 the reproductive system of white rats was investigated. No differences between the flight rats and synchronous and vivarium controls were detected with respect to such parameters as the testis and epididymis weight, testicular content of spermatogonia, spermatocytes, spermatids, spermatozoa, Leydig's cells and Sertoli's cells, and the number of normal and atypical spermatozoa in the epididymis. Nuclei of Sertoli's cells were similar in size in the flight and control rats. Electron microscopy of the first order spermatocytes showed no increase in the frequency of chromosome aberrations. Postflight, the flown males were mated with control females; their sex activity and their offspring were normal; the pups did not differ from the norm with respect to the litter size, proportion of males and females in the litter, growth rate in the postnatal period, physical development or function of the nervous system. These observations allow the conclusion that short-term space flight produces no effect on the reproductive system of white rats.

Animals↗
PubMedDate not supplied

[Concentration of water and electrolytes in pregnant rats and their offspring after a flight aboard the biosatellite "Cosmos-1514"].

The female rats were flown on Cosmos-1514 for 5 days during gestation days 13 through 18. The rats showed a significant reduction of the Ca concentration in the liver and kidneys, its smaller decrease in the skin, and no changes in bones. The fetus weight decreased, its water content increased, and the content of Na, K, Ca and Mg remained unchanged. The 15- and 30-day pups of the flown rats did not exhibit any differences in the water and electrolyte content in bones, skin, liver or kidneys as compared to the controls. These data indicate that water and electrolyte homeostasis of growing fetuses was highly stable and the deviations that emerged under the influence of space flight factors on the mother-fetus system rapidly returned to the norm.

Animals↗
PubMedDate not supplied

[Effect of weightlessness on the skeletal development of the rat fetus].

The size of the ossified areas of skeletal bones of fetuses of white rats flown onboard Cosmos-1514 during their pregnancy days 13 to 18 was compared with that of synchronous and vivarium controls. The effect of zero-g on the pregnant animals in the course of an active formation of fetal bones involved a distinct (13-17%) arrest of the development of nearly every area of the fetal skeleton. The signs of the arrest development were more manifest in less mature skeletal structures. Since the Ca2 content was identical in the flight and control rats, it can be concluded that the inhibited ossification of the flight fetuses was produced by the impairment of mechanisms controlling Ca2+ incorporation into the growing skeleton. The ossified areas in the skeleton of the flight newborns were significantly larger than those of the synchronous and vivarium controls. This means that during the readaptation period (pregnancy days 18 to 23) the inhibited ossification of the fetal skeleton was completely compensated and that the flight newborns (i. e. the rats whose prenatal development occurred in part in zero-g) were ahead of the controls with respect to the ossification rate.

Animals↗
PubMedDate not supplied

[Changes in the electrolyte composition of the heart, liver and kidneys of the rat in pre- and postnatal ontogeny].

From the 19th day of embryonic period, within 4 days, i. e. up to the beginning of postnatal life, the weight of the heart in rats increases by 3.3 times, that of the liver--by 2.2 times, and kidneys--by 5.7 times, whereas the content of water (calculated per dry weight of the organs) decreases. Changes in the content of sodium, potassium, calcium and magnesium in these organs are the lowest provided calculations are made per wet weight; during organogenesis, gradual decrease in the content of electrolytes (calculated per dry weight of the tissue) takes place. The value of Na/K ratio decreases during organogenesis. The content of iron and copper in these organs is higher in adult animals, than in younger ones.

Animals↗
PubMedDate not supplied

[General characteristics of an experiment to study the ontogeny of rats on board the Kosmos-1514 biosatellite].

Ten female Wistar rats were exposed to zero-g during 5 days, i. e., from gestation day 13 to day 18. After recovery the flight animals showed a significant delay in weight gain, thymus involution, decreased liver weight, hemoglobin concentration. Nevertheless, their reproductive function did not differ from that of the controls: the rate of preimplantation and total fetal mortality as well as the number of live fetuses were very similar in the experimental and control animals. The flight group showed a slight decline of fetal weight and water content. The size of the litters produced by the flight and control rats was identical but the mortality rate of those former during the first 7 days after birth was significantly higher. This experiment has demonstrated that the mammalian fetus exposed to zero-g during the last term of pregnancy, i. e., at the stage of active organogenesis, can grow and develop in the normal way. A large body of biological material has been obtained for biochemical and histological examinations that will help evaluate the condition of dams, fetuses, and newborns.

Animals↗