• Korean Journal of Veterinary Research
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• v.30 no.4
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• pp.355-360
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• 1990

Single nuclei from two-, four- and eight-cell mouse embryos were transplanted into enucleated two-cell embryos by micromanipulation and Sendai virus mediated fusion. The developmental potential of these reconstituted embryos in vitro and in vivo was examined. It was found that the single nuclei which were transplanted to enucleated two-cell embryos were not only able to develop to the blastocyst stage in vitro(two-cell nuclei, 76.5%; four-cell nuclei, 68.4%; eight-cell nuclei, 48.3%), but also able to develop to full term in vivo after transfer to recipient mice(two-cell nuclei, 37.1%; four-cell nuclei, 29.6%; eight-cell nuclei, 16.3%). Although the proportion of live young produced after transfer of nucler of nuclear transplant embryos which received eight-cell nuclei was significantly (p<0.05) reduced, it would be suggested that the overall efficiency in producing identical offspring is greater when eight-cell embryos were selected for nuclear donor than two- or four-cell embryos were selected.

• Development and Reproduction
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• v.13 no.4
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• pp.207-215
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• 2009

Numerous factors can affect the activities of hypothalamus-pituitary-gonad (HPG) hormonal axis, resulting in alteration of reproductive capacity or status such as onset of puberty and menopause. Soon after the finding of leptin, a multifunctional hormone secreted from adipocytes, a close relationship between reproduction and body energy balance have been manifested. Ghrelin, another multifunctional hormone from gastrointestinal tract, is an endogenous ligand of growth hormone secretagogue receptor (GHSR), and is thought to be a counterpart of leptin in the regulation of energy homeostasis. As expected, ghrelin can also modulate the reproductive capacity through the modulation of activities of HPG axis. This paper summarizes the current knowledge on the discovery, gene structures, tissue distribution and roles of ghrelin and GHSRs in mammalian reproduction in particular modulation of reproductive hormone secretion in HPG axis. Like POMC gene expression in pituitary gland, preproghrelin gene can generate a complex repertoire of transcripts which further undergo alternative splicing and posttranslational modifications. Concerning the roles of preproghrelin gene products in the control of body physiology except energy homeostasis, limited knowledge is available so far. Several lines of evidence, however, show the interplay of ghrelin between metabolism and reproduction. In rat and human, the distribution of ghrelin receptor GHSRs (GHSR1a and GHSR1b) has been confirmed not only in the hypothalamus and pituitary which were originally postulated as target of ghrelin but also in the testis and ovary. Expression of the preproghrelin gene in the brain and gonads was also verified, suggesting the local role (s) of ghrelin in HPG axis. Ghrelin might play a negative modulator in the secretions of hypothalamic GnRH, pituitary gonadotropins and gonadal steroids though the action on pituitary is still questionable. Recent studies suggest the involvement of ghrelin in regulation of puberty onset and possibly of menopause entry. It is now evident that ghrelin is a crucial hormomal component in 'brain-gut' axis, and is a strong candidate links between metabolism and reproduction. Opposite to that for leptin, ghrelin signaling is likely representing the 'hunger' state of body energy balance and is necessary to avoid the energy investment into reproduction which has not a top priority in maintaining homeostasis. Further researches are needed to gain a deep insight into the more precise action mechanism and role of ghrelin in reproduction, and to guarantee the successful biomedical applications.