Repro Young

Repro Young

Advances in Ovine and Caprine Reproduction

1.      Ovarian Angiogenesis

            Angiogenesis is a process of vascular growth. The ovarian angiogenesis increases new blood vessels in ovary. They supply nutrients and hormones to the follicles. Thus angiogenesis promotes follicular growth and corpusluteum formation (Tamanini & Ambrogi, 2004). The developing follicles have endothelial cells. They form a network in the theca layer. Growth factors mainly produced by granulose cells as VEGE (Vascular endothelial growth factor) and bFgF (basic fibroblast growth factor) act as stimuli  for promoting follicular growth and antrum formation (Ziecik, 2004; xiao et al, 2001).

            After ovulation, newly formed blood vessels cross basement membrane between theca and granulose cell layers and undergo a rapid growth to form corpus luteum. The luteal vascular growth varies and angiogenesis and angioregression determine corpusluteum growth and regression. Thus in future the improvement in angiogenic development of ovary may help in reproductive performance (Tamanini and Ambrogi, 2004).

            These Hemodynamic changes in ovarian and corpora Luteal walls was studied using colour Doppler ultrasonography. The flow of blood is assessed (Acosta and Miyamoto, 2004). This confirms our earlier studies using Laparoscopy for ovulation (Wani & Sahni, 1988, Wani, 1989 Sharief, 2000).

2. Embryo Block

            Embryo blocks action of antibodies and becomes a homograph and not a heterograph,  Eight cell embryo block was very common block in mammalian embryonic development. Sheep and goat embryos did suffer from this block too. However, in-vitro embryo , an mammalian embryo, makes direct contact with uterine lining only for a short period and thereby thrives on it indirectly through placenta via umbilical cord. It remains protected in an immunologically protected  chamber the amnionic sac. Feotal development and biochemical constituents of foetal fluids and morphological development features observed in our studies  are reported . (Mufti, 1996, Mufti et al, 2000), Wani, 2004 ,  2005. Embryo development can be viewed in web  images ) images  1-2).  Early embryo mesoderm cells called somites differntiatic into myoblasts-resulting into muscle and skeletal tissues. Various MRF(muscle regulatory factors in foetus determine the muscular growth and were professed to  be used in future research. Their exploitation would bring muscular lambs at birth. (Wani 2001). Many advanced aspects of myoblast .Determination flow have been documented. Huskey, 2001. (Robert.J.Huskey, myoblast determination flow interent explorer- Huskey, R.J. 2001. Myoblast Determination flow Microsoft. Internet Explorer.

            Tight junctions prevent ion and water movement between cells and Na/K pumps move into the centre of the blastocyst resulting in to osmotic pressure difflections and formation of blastocoel. Plasmogen and its activator results into enzymatic digestion of zona-pellucida during this process. (www.wisc.Edie/ansici-repro/Lec-18 or search Embryo block sheep Metacrawler- Microsoft Internet explorer Figs 9-16.

3. Genome activation

            Activation of embryo is detected by pronuclear formation, cleavage and blastulation. Addition of vitamins during oocyte maturation helps subsequent blastulation and embryo viability  (Bormann et al, 2003). Pregnancy associated glycoproteins (PAGS) are antigens synthesized in ruminant trophoblast. They enter maternal blood stream and thus signal early pregnancy (Wani, 2005).

            Invitro growth of granulosa cell complexes isolated from cryopreserved ovine ovary has been reported (Newton et al, 1999). These cells have a capacity to produce immunereactive inhibin with FSH, (Compell et all, 1996). The ovine Booroola fecundity gene (Fec B) so widely known has been linked to markers from a region of human chromosome 4q. Thus linking research in ovine or caprine reproduction for improvements or control of reproduction in humans. The VEGF factors (Vascular endothelial growth factors) characterized and expressed in ovine corpus luteum could be of immense “healing touch” value if properly innovated to use in repairs of various body injuries. Ovine FSH has been of value in developing long-term contraceptive vaccine in bonnet (Redmer etal, 1996).

4. Gap-junction network

Mammalian oocytes are surrounded by follicular cells. A communication system exists between these oocytes and follicular cells. This system of communication is called Gap –Junction network. This system provides transfer of nutrients and signals between follicular cells and oocytes. The proteins of connexin family  form these building blocks. Oogenesis, primodial follicle activation and subsequent ovulation is the result of these and some other proteins factors. They are e-kit receptor, transforming growth factor beta (TGF beta) and bone morphogenic proteins. Progressive morphological changes in the oocytes result into structural rearrangements. These generate energy. The increased energy facilitates oocyte development and ultimately determine its capacity and competence to dominate and ovulate (Fair, 2003).

            Pregnancy recognition during day 12-22 in sheep and 15-21 in goats is made on the basis of interferon tau a member of type I interferon. It is the first protein secreted by trophoectoderm of the ruminant conceptus. It blocks the uterine luteolytic mechanism and is responsible for the sustenance of corpus Luteum during early pregnancy days. It acts on the uterine epithelial cells by suppressing their ability for transcription of gene for propogation or activation of oestrogen or oxytocin receptors. It also induces several proteins responsible for embryo implantation.

           

5. Pre- implantation Embryo nutrition:

            The most important nutrients required by the developing mammalian preimplantation embryo are carbohydrates, anino acid which provide energy. It also  prevent cellular stress. Quantification of embryo energy metabolism is thus necessary. An attempt in this direction has been shown in figures. (Jamada, 1998).

            The 8-cell embryo block in development is overcomes by various growth factors incorporated in culture media. The HB-EGF (heparin-binding epidermal growth factor like growth factor) improves the development of 8-cell embryo to the blastocyst stage. This factor is helpful in preimplantation embryo development. (Tamada et al, 1999).

            The method of assessing preimplantation embryo viability by the self-refrencing electophysiological  technique is possible. This is an non-invasive measurement.  The technique measures the gradients of calcium, potassium, oxygen, and hydrogen peroxide (Gardner, 1998).

            Protein, prostaglandins and steroid synthesis in caruncular and intercaruncular endometrium in sheep has been estimated. One day before attachment ie day 15 post coitus few changes exhibited,  however, the dynamics of PgF2 alpha production was effected (Findly et al, 1981)

            Comparing invitro and invivo embryonic development in ruminants is possible by use of immunocytochemistry, confocal laser scanning miscroscopy and fluorescence techniques. By combination of these techniques it has been possible to demonstrate that:

            1.            rRNA gene activation is similar

            2.            Embryonic nuclear development is similar. However, embryo produced through nuclear transfers are associated with increased apoptosis, in the inner cell mass of the blastocysts. Besides embryo produced in-vitro by nuclear transfers or otherwise are associated with mixoploidy. Mixoploidy means embryos with abnormal haploid or polyploidy cells besides normal diploid cells . (Cinobell et al, 2003).

            Use of anthelmintics like  Benacil and tetramisole orally results in toxicity during pregnancy. The embryotoxicity was 100% during 9-18 days post coitus and abnormal lambs delivered by ewes dosed during pregnancy ranged from 34-57% (Grunzhinskas, 1984). Laparoscopy in sheep and goats has been used for ovulation detection, embryo aspiration and diagnosis of pregnancy. (Wani, 1982 Wani and Buchoo, 1990, 1997, 2000) Embryo recovered through laparoscopy in Boer goats have a of 62% and were economically viable. (Besenfelder et al, 1994)

6. Embryo biosafety and disease risk

            Scrapie, an ovine and caprine transmissle spongiform encephalopathy is widely spread among sheep populations in many European Countries. As it is known that susceptibility to scrapie is determined genetically, breeding programmes aiming at providing scrapie- resistant flocks have been established – (sipos et al, 2002).

         The pregnant endometrium secreted a number of neutral –to-acidic proteins which constituted, in part, the histotroph. A vitamin A-transport protein, RBP was identified in cultures, conditioned by the endometrium at days 13-21 of             pregnancy. The endometrium is the only source of retinol for embryonic tissues.             The uterine RBP appears to transport retinol locally toward embryonic tissues. Secretion of RBP by caprine endometrium at days 13, 15 and 21 of pregnancy suggested that retinol played an important role in conceptus development during the periattachment period of early pregnancy –( Lue et al, 2002) (Young et al 2000, 2004).

                  Caprine oviduct epithelial cell (COEC) are commonly used in vitro goat embryo production protocols to stimulate early embryonic development. These feeder cells are usually collected from slaughterhouses from unknown serological status animals. In many regions of the world, issues derived from the resource may be contaminated with CEV and the use of such material in invitro fertilization             systems may contribute to transmission of this pathogen to the cultured embryos and dissemination via embryo transfer (ET). The use in invitro fertilization systems of coculture feeder cells that support efficient replication of CAEV to high titers could represent a serious risk for permanent transmission of virus to the cultured embryos and to the surrogate dam involved –( Lamara et al, 2002).

7. Early pregnancy Factors

Pregnancy – associated glycoproteins (PAGs) are antigens synthesized in the superficial  layers of the ruminant trophoblast. Initially, they were identified either as proteins differed into the maternal bloodstream (where they have applications in pregnancy diagnosis+PAG or as molecules binding to the LH receptor (PAG2). In this study, double radial immunodiffusion was used to test the ability of antisera raised against different PAG molecules (bovine, ovine and caprine) to react with placental extracts from non ruminants (rabbit, cat, mouse, pig and wild pig) and ruminants (cow, ewe and goat) Placental extracts from all nonrumiants tested except rabbit reacted with anti bovine. PAG2 (anti- boPAG2). Extracts of ruminant placentas react with different antisera, confirming the expression of various PAG molecules. According to the time at which the placentas were collected (early or middle pregnancy), the reaction differed as regards the thickness, position and number of precipitation lines, suggesting that PAG expression varies as pregnancy progresses. Bos indicus and Bos Taurus placental extracts exhibited different reactions with anti-boPAG2, a single precipitation line in the former case and two lines in the latter. This suggests differential expression of boPAG2related glycoproteins in these two subspecies – (EL-Amivi, et al, 2003).

About the Author

Proffessor G. M. Wani is Director Extension Education, SKUAST – K, Shalimar Srinagar, J & K, India and Director SAMETI.

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