• 한국수정란이식학회지
• /
• 제18권1호
• /
• pp.61-68
• /
• 2003

본 실험은 개의 인공수정에 사용할 신선정액, 그리고 동결정액을 이용한 자연교미와 발정유도된 실험견에 인공수정시 임신율과 산자수를 검증하여 그 효율성을 조사하였다. 1. 개의 인공수정시에 자연발정, clomifene, bromocriptine 단독 투여 그리고 GnRH + bromocriptine/GnRH 혼합 투여에 따른 발정유도방법은 임신율과 산자수에 영향을 미치지 않는 것으로 나타났으며, 신선정액을 이용한 인공 수정방법은 자연교미방법과 유사한 임신율과 산자수를 보였으나, 동결정액을 이용한 인공수정 시에는 비교적 낮게 나타났다. 2. 자연발정 유도군 또는 clomifen, bromocriptine 단독 투여군, GnRH + bromocriptine/GnRH 병용 투여로 발정이 유도된 암캐를 자연교배시 생산된 총 산자수는 54두, 신선정액을 이용한 인공수정에서는 50두로 유의적(P<0.05)인 차이가 없었고, 동결정액을 이용한 인공수정에서는 35두를 분만하여 자연교배에 비해 유의적(P<0.05)으로 총 산자수가 적었다. 본 실험의 결과에서 무발정견에 호르몬을 투여하여 발정을 유도시켜 수정을 해도 수태율과 산자수는 영향을 미치지 않으며, 신선정액에 의한 인공수정과 자연교배 시의 수태율과 산자수에는 차이가 없으나, 동결정액에 의한 인공수정 시에는 수태율과 산자수가 낮아짐을 알 수 있었다.

• Toxicological Research
• /
• 제8권2호
• /
• pp.343-357
• /
• 1992

Tumor necrosis factor-${\alpha}$(TNF), a polypeptide hormone secreted primarily by activated macrophages, was originally identified on the basis of its ability to cause hemorrhagic necrosis and tumor regression in vivo. Subsequently, TNF has been shown to be an important component of the host responses to infection and cancer and may mediate the wasting syndrome known as cachexia. These systemic actions of TNF are reflected in its diverse effects on target cells in vitro. TNF initiates its diverse cellular actions by binding to specific cell surface receptors. Although TNF receptors have been identified on most of animal cells, regulation of these receptors and the mechanisms which transduce TNF receptor binding into cellular responses are not well understood. Therefore, in the present study, the mechanisms how TNF receptors are being regulated and how TNF receptor binding is being transduced into cellular responses were investigated in rat liver plasma membranes (PM) and ME-180 human cervical carcinoma cell lines. $^{125}I$-TNF bound to high ($K_d=1.51{\pm}0.35nM$)affinity receptors in rat liver PM. Solubilization of PM with 1% Triton X-100 increased both high affinity (from $0.33{\pm}0.04\;to\;1.67{\pm}0.05$ pmoles/mg protein) and low affinity (from $1.92{\pm}0.16\;to\;7.57{\pm}0.50$ pmoles/mg protein) TNF binding without affecting the affinities for TNF, suggesting the presence of a large latent pool of TNF receptors. Affinity labeling of receptors whether from PM or solubilized PM resulted in cross-linking of $^{125}I$-TNF into $M_r$ 130 kDa, 90 kDa and 66kDa complexes. Thus, the properties of the latent TNF receptors were similar to those initially accessible to TNF. To determine if exposure of latent receptors is regulated by TNF, $^{125}I$-TNF binding to control and TNF-pretreated membranes were assayed. Specific binding was increased by pretreatment with TNF (P<0.05), demonstrating that hepatic PM contains latent TNF receptors whose exposure is promoted by TNF. Homologous up-regulation of TNF receptors may, in part, be responsible for sustained hepatic responsiveness during chronic exposure to TNF. As a next step, the post-receptor events induced by TNF were examined. Although the signal transduction pathways for TNF have not been delineated clearly, the actions of many other hormones are mediated by the reversible phosphorylation of specific enzymes or target proteins. The present study demonstrated that TNF induces phosphorylation of 28 kDa protein (p28). Two dimensional soidum dodecyl sulfate-polyacrylamide gel electrophoresis(SDS-PAGE) resolved the 28kDa phosphoprotein into two isoforms having pIs of 6.2 and 6.1. The pIs and relative molecular weight of p28 were consistent with those of a previously characterized mRNA cap binding protein. mRNA cap binding proteins are a class of translation initiation factors that recognize the 7-methylguanosine cap structure found on the 5' end of eukaryotic mRNAs. In vitro, these proteins are defined by their specific elution from affinity columns composed of 7-methylguanosine 5'-triphosphate($m^7$GTP)-Sepharose. Affinity purification of mRNA cap binding proteins from control and TNF treated ME-180 cells proved that TNF rapidly stimulates phosphorylation of an mRNA cap binding protein. Phosphorylation occurred in several cell types that are important in vitro models of TNF action. The mRNA cap binding protein phosphorylated in response to TNF treatment was purifice, sequenced, and identified as the proto-oncogene product eukaryotic initiation factor-4E(eIF-4E). These data show that phosphorylation of a key component of the cellular translational machinery is a common early event in the diverse cellular actions of TNF.