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11.
12.
S. C. Ng A. H. Sathananthan P. C. Wong S. S. Ratnam J. Ho H. Mok M. N. Lee 《Molecular reproduction and development》1988,19(3):253-263
Previous studies by a French group (Fertil Steril 44:645–651, 1985) have shown that two-to eight-cell human embryos can survive slow freeze-thawing with propanediol in a biological freezer. These embryos were assessed for morphological appearance by phase-contrast microscopy. We assessed the structure of 25 frozen-thawed one- to 12-cell embryos, obtained from our in vitro fertilization (IVF) and GIFT programmes, by phase-contrast and electron microscopy, using the same method of cryopreservation. One-fourth of the embryos examined had all cells intact, and more than one-half the embryos had over 50% of their cells well preserved. Some of these embryos had unequal blastomeres and cytoplasmic fragments. Ultrastructural assessment revealed good preservation of fine structure in the intact blastomeres of all embryos and maintenance of cell-to-cell contacts. Most cytoplasmic organelles, cell membranes, and nuclei were well preserved compared to nonfrozen controls. The cells that were cryoinjured showed varying degrees of disorganization of the cell membrane, cytosol, and cellular membranes, including swelling and disruption of the nuclear envelope. Disruption of the zona was somewhat rare. Small cytoplasmic fragments were less prone to cryoinjury than blastomeres. The use of propanediol for embryo cryopreservation seems to be feasible; frozen embryos with more than 50% cells intact have produced 10 pregnancies after embryo transfer (Fertil Steril 46:268–272, 1986). Replacement of 17 frozen embryos in seven patients has resulted in a twin pregnancy in Singapore. However, the effects of freezing on the mitotic spindles of embryonic cells need to be investigated further. 相似文献
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14.
Transglutaminase (R-glutaminyl-peptide:amine alpha-glutamyl-yltransferase [EC 2.3.2.13]) has been purified to apparent homogeneity from extracts of rabbit liver. The enzyme is a single polypeptide chain of approximately 80 000 molecular weight containing one catalytic site per molecule. That the isolated enzyme is the rabbit counterpart of the well-characterized guinea pig liver transglutaminase is evidenced by the similarities in their amino acid compositions and in their enzymic activities toward several substrates, together with the fact that the isolated rabbit enzyme is immunologically distinct from both rabbit plasma and rabbit platelet blood coagulation factor XIII. A striking difference between the catalytic activities of the rabbit and guinea pig enzymes is the low activity of rabbit transglutaminase for hydroxylamine incorporation into benzyloxycarbonyl-L-glutaminylglycine, a reaction for which the guinea pig enzyme shows a high reactivity. This finding reveals the cause of error in an earlier report (Tyler, H.M., and Laki, K. (1967) Biochemistry 6, 3259) that rabbit liver contains little, if any, of the enzyme. Preparation of, and analytical data on, several glutamine-containing peptide derivatives used in this study are reported here. 相似文献
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The amounts of cAMP and cGMP in the rat pinealocyte are regulated by norepinephrine acting through synergistic dual receptor mechanisms involving alpha 1- and beta-adrenoceptors (Vanecek, J., Sugden, D., Weller, J.L., and Klein, D.C. (1985) Endocrinology 116, 2167-2173; Sugden, L., Sugden, D., and Klein, D.C. (1986) J. Biol. Chem. 261, 11608-11612). Based on the available evidence, it appears that Ca2+-phospholipid-dependent protein kinase is involved in the alpha 1-adrenergic potentiation of beta-adrenergic stimulation of cAMP, but not in the stimulation of cGMP (Sugden, D., Vanecek, J., Klein, D.C., Thomas, T.P., and Anderson, W.B. (1985) Nature 314, 359-361). In the present study the role of protein kinase C in the adrenergic stimulation of cGMP was reinvestigated, with the purpose of determining whether protein kinase C activators would potentiate the effects of beta-adrenergic agonists on cGMP if cells were also treated with agents known to elevate intracellular free Ca2+. The protein kinase C activator 4 beta-phorbol 12-myristate 13-acetate (PMA) markedly elevated the cGMP content of beta-adrenergically stimulated pinealocytes which had also been treated with 1 microM A23187, 15 mM K+, or 1 microM ouabain. The effects of A23187 were blocked by EGTA and those of K+ were blocked by nifedipine, establishing the involvement of Ca2+. The stimulatory effects of PMA on cGMP accumulation were mimicked by other protein kinase C activators. PMA also stimulated cGMP accumulation in cells treated with cholera toxin (1 microgram/ml) and A23187 (1 microM), but not in cells treated only with cholera toxin. These results suggest that protein kinase C, which is activated in the pinealocyte by the alpha-adrenergic agonist phenylephrine, is probably involved in the adrenergic regulation of cGMP accumulation at a step distal to receptor activation. 相似文献
17.
88 rice and 75 soybean samples were collected from 8 provinces of Korea from March through September in 1988. The Fusarium mycotoxins, zearalenone was analyzed by direct competitive enzyme linked immunosorbent assay. 10.2% of rice and 9.3 % of soybean samples contained detectable zearalenone. The average levels of zearalenone of rice and soybean samples were 11.78μg/kg and 7.70μ/kg, respectively. 相似文献
18.
Sung Ho Son Sung Mee Choi Kum Boo Choi Yun Hee Lee Dea Sook Lee Myung Suk Choi Young Goo Park 《Biotechnology and Bioprocess Engineering》1999,4(2):112-118
Calli were induced from 300,000 embryos isolated from immature to mature stage of seeds collected on late September from 14
elite trees. When the embryos were cultured onto plastic Petri-dish containing 20 mL of modified B5 basal medium supplemented
with 3% (w/v) sucrose, 500 mg/L casein hydrolysate, 250 mg/L myo-inositol, 0.5% (w/v) polyvinyl polypyrrolidon (PVPP), 2×MS
vitamins, 0.5 mg/L gibberellic acid, and 10 mg/L 2,4-D after 2 weeks of culture, yellowish-white calli were immediately formed
on the surfaces of embryos, and subcultured for 4 weeks in same culture medium. Because most of calli maintained for more
than 3 months were revealed differences in their colors, surface texture, and growth rate, visual selection was made for first
round screening. When the size of visually selected calli larger than 19 mm in their diameter were inoculated, persistent
proliferation was observed. Among the plating methods tested for the selection of rapid growing cell lines at single cell
and/or small cell aggregate level, 2-layer spread plating revealed as the best for single cell cloning. To enhance cell growth
and maintain high rate of viability for long-term culture of yew cells in bioreactor, final cell volume less than 50% in SCV
seemed to be the best. Time course study revealed that 30% of inoculum density was suitable for fed batch culture. Among the
tested conditional media, the rate of 1∶2 (old medium: fresh medium) was recorded at the best for cell growth. 相似文献
19.
Y S Ho P J Sheffield J Masuyama H Arai J Li J Aoki K Inoue U Derewenda Z S Derewenda 《Protein engineering》1999,12(8):693-700
Platelet-activating factor acetylhydrolases (PAF-AHs) are unique PLA2s which hydrolyze the sn-2 ester linkage in PAF-like phospholipids with a marked preference for very short acyl chains, typically acetyl. The recent solution of the crystal structure of the alpha(1) catalytic subunit of isoform Ib of bovine brain intracellular PAF-AH at 1.7 A resolution paved the way for a detailed examination of the molecular basis of substrate specificity in this enzyme. The crystal structure suggests that the side chains of Thr103, Leu48 and Leu194 are involved in substrate recognition. Three single site mutants (L48A, T103S and L194A) were overexpressed and their structures were solved to 2.3 A resolution or better by X-ray diffraction methods. Enzyme kinetics showed that, compared with wild-type protein, all three mutants have higher relative activity against phospholipids with sn-2 acyl chains longer than an acetyl. However, for each of the mutants we observed an unexpected and substantial reduction in the V(max) of the reaction. These results are consistent with the model in which residues Leu48, Thr103 and Leu194 indeed contribute to substrate specificity and in addition suggest that the integrity of the specificity pocket is critical for the expression of full catalytic function, thus conferring very high substrate selectivity on the enzyme. 相似文献
20.
Jean L. Santos Paulo R. Yamasaki Chung Man Chin Célio H. Takashi Fernando R. Pavan Clarice Q.F. Leite 《Bioorganic & medicinal chemistry》2009,17(11):3795-3799
New phthalimide derivatives were easily prepared through condensation of phthalic anhydride and selected amines with variable yields (70–90%). All compounds (3a–l) were evaluated against Mycobacterium tuberculosis H37Rv using Alamar Blue susceptibility. The compounds 3c, 3i, and 3l have the minimum inhibitory concentrations (MICs) of 3.9, 7.8, and 5.0 μg/mL, respectively, and could be considered new lead compounds in the treatment of tuberculosis and multi-drug resistant tuberculosis. 相似文献