• Institute of Biology and Immunology of Reproduction
      "Acad. Kiril Bratanov"

      • Scientific achievements

        Most significant scientific achievements during last 10 years

        • Successful inter-breed transfer of embryos of endangered aborigine Bulgarian animal breeds has been carried out. In aid of preserving the national genefund, an experimental cryobank of cryopreserved embryos of aborigine national breeds of sheep, goats and cattle has been established.
        • By observing the toxic dynamic and biochemistry of several xenobiotics (nitrates, phosphoorganic substances and synthetic pyrethroids) and their influence on the glutathione-dependent defense system operating in reproductive organs, it’s been found that the system is linked to detoxification of the endogenous and exogenous xenobiotics and has great importance in processes of xenobiotics’ biotransformation and cell protection against their toxic effects
        • Studies aimed at clarification of the toxic biology of reproductive processes revealed decreased activity of the enzymes from the glutathione family (GST, TSH, NP-SH, GSH) in the uterus and ovaries of experimental animals. Reduced activity of the enzymes may result in corresponding attenuation of defense cellular functions against xenobiotics influence.
        • Laboratory model of lung neoplastic disease in sheep has been introduced (lung adenomathosis) which has been proved as a zoonosis. The model has found application by sheep immune prophilaxis and by examinations of other similar viral infections in ruminants and adenocarcinoma in men, which is manifested in association with certain professional occupation in unfavourable milieu.
        • Methodology has been introduced for the establishment of safety control and prevention of risks for inoculation with viral pathogens from germinal plasma (oocytes, spermatozoa, embryos) by manipulations during the conduction of reproductive biotechnologies. Application of embryotransplantation has been adopted as a strategy for the achievement of healthy generation from ill donors of valuable breeds.
        • Influence of ultra-low temperatures on the ultra-structural organization of intracellular Ca++ in ram spermatozoa has been examined. Differences in the quality, amount and distribution of the deposits have been found in association with the functional and metabolic status of spermatozoa. The intracellular cytosol Ca++ concentration remains lower in comparison with the extracellular space, which results in disturbances of its regulation and the sensitivity to cold shock.
        • It has been found that activities of the enzymes LDH, NADH-diaphorase, alkaline and acidic phasphatases in spermatozoa of the muscus duck have been in correlation with the quality parameters of motility and concentration of spermatozoa. It has been demonstrated that sperm with high activity of LDH and NADH- diaphorase posseses higher fertilization capacity.
        • By employment of biochemical and microscopic techniques it has been shown that the cryopreservation of cattle sperm in the presence of the cryoprotectant GX results in: significant number of spermatozoa with injured acrosomal membrane; enhancement of the activity of alkaline phosphatase, acidic phosphatase and LDH; reduction of the activity of NADH-diaphorase and glucose-6-phosphate-dehydrogenase. Based on the obtained results prognostic evaluation of the fertilization capacity of cryopreserved cattle sperm by the use of the solvent GX has been made.
        • Comparative morphological and functional characterization of buffalo spermatozoa has been carried out in association with age, season and period of storage and cryopreservation. By employment of electron microscopy it has been found that the sperm solvents Triladil, Tris-Fructose, and Begly can cause reduction to a different degree of the activity of NADH-dehydrogenase, cytochrome reductase, cytochrome oxidase and LDH in spermatozoa, which is linked to a loss of membrane integrity and to a differentially manifested morphological injury.
        • The effect of Н2О2 in different concentrations on the vitality of spermatozoa in bulls, rams and boars has been examined. It has been found that cytochemically and electrophoretically determined activity of NADH, NADPH-diaphorase and LDH, has been influenced to different level in the particular species and depends on the concentration of the agent.
        • Line of research has been devoted to clarify the effects of hormonal and non-hormonal preparations (contraceptives) on the reproductive status and oogenesis of laboratory and farm animals.
        • Echography examinations of the reproductive apparatus in sheep and bulls during different seasons have been performed. Follicular waves have been observed, which are manifested during the oestrous season. Results may have relevance for the conduction of appropriate schedules of treatment for superovulation and synchronization
        • During morphological investigations of the ovarian dynamic and the folliculogenesis in bulls and sheep differences have been found, which have relevance to the embryotransplantation in these species.
        • The ultra-structure of male germinal cells of the water buffalo breed “Bulgarian Mura” and of the oocytes and embryos obtained after hormonal treatment for superovulation have been examined by means of scanning and transmission microscopy. Number of morphological characteristic features has been observed in the breed, as well as differences in the quality and quantity of germinal cells and embryos, obtained for embryotransfer.
        • Line of research has been devoted to examine the influence of hormonal treatment for the induction of superovulation on the properties of oocytes and embryos from sheep, goats and buffaloes. Based on the obtained results schedules of treatment have been made for the purposes of the embryotransplantation.
        • Team consisting of Bulgarian and Egyptian scientists (Principal Investigator on Bulgarian part Dr. D. Kacheva) has conducted successful embryotransfer and in 2005 and 2006 the first buffalo-calfs were born in Egypt. The results have been promising and give reason to continue the collaboration on buffalo embryotransfer and to expand studies on the technology in other species like sheep and goats. Under way are collaborated experiments for the induction of twin pregnancies in buffaloes aimed at enhancement of their reproductive capacity.
        • Schedules of hormonal synchronization of the oestrous cycle of the Greek milk-sheep breed Chios have been introduced and after cross-breeding with Bulgarian milk-sheep breeds the development in F1 has been examined. The follicular dynamic in the animals was studied by ultra-sonography and based on the findings the most appropriate time for insemination was chosen. Early diagnostic of pregnancy was introduced by means of echographic examinations of the inseminated animals. These studies have importance for the elaboration of approaches for maximum use of the natural reproductive capacity of the particular breeds.
        • It has been found that application of ethylene glycol as a cryoprotectant for the preservation of pre-implantation goat embryos ensures their successful long-term preservation without obvious aberrations in the morphology and vitality, which has been confirmed by the outcome of pregnancies after performed embryotransfer.
        • In progress are experiments to carry out embryotransfer of freshly obtained sheep and goats during the anoestrous cycle by the employment of laparoscopic and echographic methods.
        • Studies aimed at search of possibilities to achieve ecologically healthy animal production have revealed that the preparation Tribestan can exert positive effect on the sperm production of rams during the oestrous season. In New Zeeland rabbits the addition of optimum doses of Tribestan to the dietary regime has improved the ovarian dynamic of the animals.
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