硒蛋白

硒(Se)已被确认为是一种生物微量元素,它能共价结合到生物大分子、尤其是蛋白质中。硒蛋白是某些细菌、鸟类、哺乳动物(可能也包含植物)的酶系统的基本成份。一、细菌硒蛋白最早被鉴定的细菌硒蛋白是依赖硒的甲酸脱氢酶,该酶催化无氧条件下HCOOH?H_2+CO_2。Pinsent(954)指出,E·Coli甲酸脱氢酶的表达需要硒。Lester和Demoss(1971)则     

Proteolytic processing of Blattella germanica vitellin during early embryo development

In the eggs of the cockroach Blattella germanica, vitellin (Vt) utilization is initiated 4 days postovulation by the proteolytic processing of its three subunits. These reactions yield a specific set of peptides that are consumed by the developing embryo. A yolk proteinase activity, believed central to this processing event, has been investigated. First expressed at day 3 postovulation, just prior to Vt's processing, its specific activity with synthetic substrates increased four-fold to 18-fold through day 6. In addition, a mixing experiment showed that these proteinases(s) can also process Vt's large subunits in vitro. A relationship between Vt processing and proteinase specific activity was also noted with two B. germanica translocation heterozygotes, which displayed differences in the extent of Vt processing. One group of eggs (group A) failed to process any Vt subunit. A second group (B) processed the M_r 102,000 subunit but not the M_r 95,000. A third group (C) processed their Vt normally. Proteinase specific activities in the yolk of translocant's eggs at day 6 mirrored the extent of processing, being highest in group C eggs and effectively absent from the yolk of group A eggs. Eggs defective in Vt processing also contained arrested embryos. It is concluded that the yolk proteinase activity described here participates in Vt processing at day 4 postovulation. Microscopic examination of yolk obtained from eggs of wild type females showed that, as processing began in vivo (day 4), the yolk granules also underwent an abrupt decrease in size from diameters of 15–30 μm to 3–10 μm. Yolk granules of those translocant's eggs that were defective in Vt processing did not undergo this size decrease, suggesting that granule reorganization and Vt proteolysis may be linked functionally.     

Enantioselective hydrolysis of oxazepam 3-acetate by esterases in human and rat liver microsomes and rat brain S9 fraction

Rates of hydrolysis of racemic and enantiomeric oxazepam 3-acetates (OXA) by esterases in human and rat liver microsomes and rat brain S9 fraction were compared. When rac-OXA was the substrate, esterases in human and rat liver microsomes were highly enantioselective toward (R)-OXA. In contrast, esterases in rat brain S9 fraction were highly enantioselective toward (S)-OXA. Hydrolysis rates of rac-OXA were highly dependent on the amount of esterases used. At 0.05 mg protein equivalent of esterases and 150 nmol of rac-OXA per ml of incubation mixture, the (R)-OXA was hydrolyzed 3.6-fold and 18.5-fold faster than (S)-OXA by rat and human liver microsomes, respectively. The specific activities (nmol of OXA hydrolyzed/mg microsomal protein/min) of liver microsomes in the hydrolysis of enantiomerically pure (R)-OXA were approximately 120 (rat) and 1,980 (human), and in the hydrolysis of enantiomerically pure (S)-OXA were 4 (rat) and 7 (human), respectively. In the incubation of rac-OXA with rat brain S9 fraction, (S)-OXA was hydrolyzed approximately 6-fold faster than (R)-OXA. Results also indicated an enantiomeric interaction in the hydrolysis of rac-OXA by esterases in rat and human liver microsomes; the presence of (R)-OXA stimulated the hydrolysis of (S)-OXA, whereas the presence of (S)-OXA inhibited the hydrolysis of (R)-OXA. In rat brain S9 fraction, the presence of (R)-OXA inhibited the hydrolysis of (S)-OXA, whereas the presence of (S)-OXA appeared to have stimulated the hydrolysis of (R)-OXA.     

Callus culture ofPterocladia capillacea (Rhodophyta) and analysis of cell wall polysaccharides

Calluses induced fromPterocladia capillacea have been kept in culture for more than three years. They exhibit a fast growth rate, owing to the release of single cells, which in turn develop into new callus. The effect of various media and culture conditions upon growth was investigated. In order to confirm the identity of the callus cells, a 0,45 mg incoculum was grown that yielded 15 g dried callus within six weeks. Polysaccharides from this material (5.5 g) were analysed by¹³C NMR spectroscopy. This produced a spectrum typical of agar and very similar to the one obtained for agar extracted fromP. capillacea plants. However, the callus agar displayed no gel-forming properties, even after alkali modification.author for correspondence     

Basal prostaglandin synthesis by the isolated perfused rat kidney

In order to assess the main characteristics of the prostaglandin (PG) biosynthesis by the isolated perfused rat kidney, the urinary and venous outputs of PGE2, PGF2alpha, 6-keto-PGF1alpha and of thromboxane (Tx)B2 were followed during 120 min after an equilibration period of 30 min. Single pass kidneys were perfused with a Krebs-Henseleit solution added with Polygeline at a constant flow rate providing a perfusion pressure about 90 mm Hg. From the beginning of the study, major differences could be observed in the renal biosynthetic rate of the 4 PG studied which were mainly excreted into the venous effluent. During the perfusion, urinary and venous outputs of PGE2, PGF2alpha and of TxB2 remained stable whereas those of 6-keto-PGF1alpha sharply increased and were found inversely related to the glomerular filtration rate (r = -0.95; p n 0.001). Finally, the urinary and venous outputs of each of the four PGs studied were found positively related. It is concluded that the isolated perfused rat kidney is a valuable preparation for studying the biosynthesis of PGs and that, at least in thi model, the urinary excretion of PGs is a good index of their renal synthesis.     

Production of somatic and germline chimeras in the chicken by transfer of early blastodermal cells

Cells were isolated from stage X embryos of a line of Barred Plymouth Rock chickens (that have black pigment in their feathers due to the recessive allele at the I locus) and injected into the subgerminal cavity of embryos from an inbred line of Dwarf White Leghorns (that have white feathers due to the dominant allele at the I locus). Of 53 Dwarf White Leghorn embryos that were injected with Barred Plymouth Rock blastodermal cells, 6 (11.3%) were phenotypically chimeric with respect to feather colour and one (a male) survived to hatching. The distribution of black feathers in the recipients was variable and not limited to a particular region although, in all but one case, the donor cell lineage was evident in the head. The male somatic chimera was mated to several Barred Plymouth Rock hens to determine the extent to which donor cells had been incorporated into his testes. Of 719 chicks hatched from these matings, 2 were phenotypically Barred Plymouth Rocks demonstrating that cells capable of incorporation into the germline had been transferred. Fingerprints of the blood and sperm DNA from the germline chimera indicated that both of these tissues were different from those of the inbred line of Dwarf White Leghorns. Bands that were present in fingerprints of blood DNA from the chimera and not present in those of the Dwarf White Leghorns were observed in those of the Barred Plymouth Rocks.(ABSTRACT TRUNCATED AT 250 WORDS)     

喜马拉雅土拨鼠非冬眠期乳酸脱氢酶同工酶基因表达特征

用聚丙烯酰胺凝胶电泳和紫外光谱法分析非冬眠期喜马拉雅土拨鼠4种组织的乳酸脱氢酶(LDH)同工酶的酶谱及其活力,该鼠骨骼肌酶带的多态分布,可能是潜在的调节基因调控所致。另外,本文还对构象异构体产生的亚带进行了研讨。     

甘蓝型油菜芥酸和二十碳烯酸含量的基因效应

以甘蓝型油菜的4种纯合芥酸基因型之间所有可能的6个杂交组合的P_1、P_2、F_1、P_2、B_1和B_2世代为材料,用生统遗传学方法研究了芥酸和二十碳烯酸的基因作用形式及效应。发现无论亲本是单基因差异还是二基因差异,F_1和F_2代的芥酸含量都接近中亲值,F_1略大于中亲值和F_(20)世代均值分析表明,芥酸含量的遗传符合加性显性模型,加性效应占绝对优势,显性效应不显著。用数量遗传学方法估计的芥酸基因数与已知的结果相近。     

Effects of itraconazole on the sporocysts wall of the entomopathogenic fungi Ascosphaera apis as revealed by the scanning electron microscope

The young sporocysts had a wrinkled sporocyst wall, numerous papillae on the wall surface and the wall was granular and porous. In the itraconazole-treated culture, the walls of the young sporocysts were also wrinkled, but the characteristic papillae were replaced by larger lumps which were densely packed and coated the entire surface of the sporocyst wall. The mature sporocysts walls were smooth and possessed numerous papillae. In the itraconazole-treated culture, the walls of mature sporocysts walls were also smooth but possessed densely packed larger lumps instead of papillae. At higher magnification, each of the lumps were found to consist of numerous globules. No pores were observed as they were in the normal sporocyst wall.