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Biomedical subjects

A I Nikitin

Publications and source records attributed to A I Nikitin.

At least 19 recordsLinked to original sources
PubMed2003

[The vanishing gender?].

The literature data indicating a significant impairment of the basic parameters of male reproductive function in the last decades are analyzed and summarized. This impairment is expressed in the reduction of spermatogenic activity, increased incidence of genital malformations and testicular tumors. The listed changes are reviewed in comparative aspect and include examples of some species of wild animals. The data on the factors responsible for occurrence of pathological changes in male reproductive system are analyzed.

Animals↗
PubMed1998

[Environmental factors and human reproductive system].

Problems concerning regularities and mechanisms of the environmental factor influence on human reproductive system are discussed. It is indicated that the response of reproductive system to external challenges is based on the evolutionary formed links between the structures responsible for reproductive organ function (epiphysis, hypothalamus, pituitary), the nature of environmental factors and the regularities of their changes depending on the season and geographical location. Damaging external challenges caused by biosphere pollution by waste products of human economic activity and extreme ecological conditions are realized both by direct influence on target tissues (ionizing radiation) and indirectly through neuroendocrine mechanisms regulating reproductive organs function. Factors and regularities of the development of diseases and pathological conditions of human reproductive system, caused by external challenge including the injurious industrial factor influence were analyzed.

Animals↗
PubMed1997

Radioactive contamination from dumped nuclear waste in the Kara Sea--results from the joint Russian-Norwegian expeditions in 1992-1994.

Russian-Norwegian expeditions to the Kara Sea and to dumping sites in the fjords of Novaya Zemlya have taken place annually since 1992. In the fjords, dumped objects were localised with sonar and ROV equipped with underwater camera. Enhanced levels of 137Cs, 60Co, 90Sr and 239,240Pu in sediments close to dumped containers in the Abrosimov and Stepovogo fjords demonstrated that leaching from dumped material has taken place. The contamination was inhomogeneously distributed and radioactive particles were identified in the upper 10 cm of the sediments. 137Cs was strongly associated with sediments, while 90Sr was more mobile. The contamination was less pronounced in the areas where objects presumed to be reactor compartments were located. The enhanced level of radionuclides observed in sediments close to the submarine in Stepovogo fjord in 1993 could, however, not be confirmed in 1994. Otherwise, traces of 60Co in sediments were observed in the close vicinity of all localised objects. Thus, the general level of radionuclides in waters, sediments and biota in the fjords is, somewhat higher or similar to that of the open Kara Sea, i.e. significantly lower than in other adjacent marine systems (e.g. Irish Sea, Baltic Sea, North Sea). The main sources contributing to radioactive contamination were global fallout from atmospheric nuclear weapon tests, river transport from Ob and Yenisey, marine transport of discharges from Sellafield, UK and fallout from Chernobyl. Thus, the radiological impact to man and the arctic environment of the observed leakages from dumped radioactive waste today, is considered to be low. Assuming all radionuclides are released from the waste, preliminary assessments indicate a collective dose to the world population of less than 50 man Sv.

Aluminum Silicates↗
PubMed1996

[The achievements of medical embryology and the successes in treating infertility].

In connection with the decade of the first test-tube children appearance in Russia a contribution of medical embryology to the working out of auxiliary reproduction method is discussed. The significance of close interaction and mutual understanding between embryologists and representatives of other professions (gynaecologists, endocrinologists and geneticists) in successful solving of the problem is emphasized Main stages of the modern reproductive technology forming were followed up so as the role of medical embryology in sterility treatment. Certain ethic and lawful problems concerning reproduction including the limits of research on human embryos were discussed.

Embryology↗
PubMed1991

[The effect of hormones and growth factor on the course of meiosis in murine oocytes in culture].

The role of some intraovarian regulators of the final stages of gametogenesis is analysed. It is shown that the epidermal growth factor (EGF) in concentration of 1 and 10 ng/ml is able to induce reinitiation of meiosis from dictyotene stage during cultivation of the ovarian follicles of prepuberal mice in the serum-free medium after gonadotrophic stimulation. The pattern of maturation was analogous to that of maturation after HCG (LH) administration. Also, the EGF is able to stimulate meiosis reinitiation in the culture of cumulus-free oocytes blocked with cAMP at the stage of dictyotene. At the same time fibroblast growth factors and insulin do not demonstrate such an activity. Taking into consideration a high sensibility of oocytes to the EGF action, and also the fact that the character of changes of steroid hormones secreted by the ovary in culture under the action of EGF is the same as that under the influence of LH it is suggested that, the EGF and EGF-like proteins secreted by somatic follicle cells are the paracrinic regulators of the mammalian oocyte maturation which modulate neuroendocrine factors of the oogenesis control.

Animals↗
PubMed1991

[Ovarian steroid synthesis in tissue culture after administration of hormones and epidermal growth factor].

The features of steroidogenesis of immature mouse ovaries in culture under the influence of follicle-stimulating hormones (FSH), human chorionic gonadotropin (hCG), epidermal growth factor (EGF) and insulin have been investigated during the period of reinitiation of meiosis in the oocytes. Secretion of progesterone is stimulated after addition of FSH, hCG and of insulin and EGF combination to the medium. EGF increases FSH-stimulated progesterone secretion and inhibits estradiol secretion. The ratios progesterone/estradiol and testosterone/estradiol increase, when EGF is added to the culture medium. It is analogous to the action of hCG. It is suggested that EGF may be an intrafollicular EGF regulator of luteinizing hormone action on the sex and somatic cells of the mammalian ovaries.

Animals↗
PubMed1990

[Variants of chromosome compactization and the estimation of the capacity of mammalian oocytes for further development].

The morphology of chromatin in spontaneously ovulated rat's oocytes was investigated. The degree of chromatin condensation was shown to vary widely: along with the typical cytological picture of metaphase II, both highly condensed (clamped) and decondensed ("not typical") forms of chromosomes were observed. A direct relation was discovered between the prevalence of the not typical morphological forms of oocyte chromosomes and the level of embryonal death. The shape of clamped and decondensed forms increased in the oocytes from old rats and in post-ovulatory aged oocytes.

Aging↗
PubMed1990

[Nature of the estrous cycle, incidence of anovulation, chromosome gametopathies and fetal death in female rats with 2,4-dichlorophenoxyacetic acid (2,4-D) before pregnancy].

The effect of herbicide--2,4-D, injected before pregnancy begins, on the main parameters of the reproductive function of the female rats has demonstrated that chronic administration in doses 1 mg/kg and 12 mg/kg per day for 2 months results in certain disturbances in the estrus cycle, manifesting as prolongation of the diestrus phase and in changes of estrus and meta-estrus++ duration, as well as in an essential increase in rates of anovulatory cycles. Single administration of the preparation during the preovulatory period (50 mg/kg) produces certain disturbances in the chromosomal complex, manifesting as appearance of numerical chromosomal aberrations. When the administration is acute (10 mg/kg and 50 mg/kg) an essential increase of the embryonal death takes place, in the first case--at the expense of ++pre-implantational, and in the second--both at the expense of pre- and ++post-implantational death. At chronic administration increasing rate of the intrauterine death takes place mainly at the expense of ++post-implantational death of embryos.

2,4-Dichlorophenoxyacetic Acid↗
PubMed1990

[Chromosome aberrations and dominant lethals in rat oocytes during acute and chronic alcoholic intoxication].

The influence of a single dose and of long-term alcohol administration on cytogenetic processes in the oocytes of Wistar white rats was studied. It is shown that a single dose of alcohol in preovulatory period when the oocytes are in the stage of diakinesismeiosis metaphase I significantly increases the rate of aneuploid gametes and dominant lethality. Analogous effect follows after long-term alcohol administration. Similarity of cytogenetic effects of acute and chronic alcohol intoxication suggests that both types of influence trigger common mechanism which results in chromosome abnormalities and, consequently, in embryonic death, i.e. dominant lethality. Taking into account that alcohol-like colchicine disturbs normal functioning of the spindle filaments, the appearance of pathology under alcohol intoxication may well be induced by disorders occurring in the stage of cell formation.

Alcoholic Intoxication↗
PubMed1988

[Factors regulating the differentiation of somatic cells of mammalian ovarian follicles].

Experimental data on regulation of the cytodifferentiation of theca and the granulosa cells in mammalian ovaries are reviewed, in addition to mechanisms of cooperative interactions of these cell types in steroidogenesis. Evidence is provided on the gonadotropin induced differentiation in the cultured ovarian somatic cells, and on a modifying effect exerted on this process by some central (prolactin, LH-RH, etc.) or local factors (steroids, growth factors, low-molecular fraction of follicular fluid, etc.). A possible physiological importance of endocrine and also of auto- and paracrine regulators of differentiation in growth processes and selection of the dominant follicle in the mammalian ovaries is discussed.

Animals↗
PubMed1987

[Human extracorporeal fertilization with subsequent successful embryo implantation and the birth of a child].

With the aim to use a previously elaborated method of extracorporeal fertilization of human ova for treating sterility, resulted from obstruction or absence of the uterine tubes, ova were obtained at laparoscopy after a previous hormonal stimulation of women. From 119 women 159 ova were obtained. Fertilization of the ova was performed in the medium Ham F-10 previously capacitated with the husband's spermatozoa. Fertilization rate was 66%. Embryos at the stage of 2-8 blastomeres were implanted transcervically into the uterine cavity with a special catheter. The embryo transfer was performed in 37 women with tubular infecundity. Menoschesis up to 3 weeks was noted in 5 women. In one woman on the 35th day after implantation, by means of hormonal-biological reaction and ultrasound investigation, pregnancy was diagnosed, it terminated in timely birth of a boy with body mass 3,500 gr. A conclusion was made that the main cause of failures at the embryo transfer was an inadequate preparation of the uterine mucosa (resulted from the main disease) to accept the fertilized ovum.

Adult↗
PubMed1987

[Changes in the cytologic and electrophysiologic parameters of rat oocytes in response to prostaglandins F2 alpha and E2].

Influence of prostaglandins F-2 alpha and E-2 on ovulation character and on the state of the ovulated gametes has been studied in rats at the preovulatory period (the preparations have been injected for 3 days, beginning from the 1st day of early proestrus). Under the effect of prostaglandins the amount of postovulated ova decreases, especially in the animals given prostaglandin E-2. Inhibition of ovulation in these animals is accompanied with an increased part of hyperpolarized ova, appearance of some signs of degeneration in the group of depolarized oocytes and absence of oocytes with polarized membrane at the metaphase I stage. These facts can be interpreted as desynchronization of maturation processes and ova ovulation. Mechanisms of the changes revealed in the ovulatory process and the state of gametes under the prostaglandins effect are discussed.

Animals↗
PubMed1987

[Non-Hodgkin's lymphomas located in the abdomen in children].

Long-term results of treatment of 126 cases of abdominal non-Hodgkin's lymphomas under 14 years are discussed. Survival doubled (from 24 to 49%) on application of modern methods of complex treatment. Such factors as stage, general symptoms, biologic activity and localization within the abdominal cavity at presentation were found to be of the highest prognostic value.

Abdominal Neoplasms↗