周口店地区仓鼠材料的重新观察

经重新鉴定,周口店地区第四纪期间共有4属7种仓鼠,包括大型种类Allocricetus ehiki、A. teilhardi sp. nov. 及Cricetinus varians和小型种类Cricetulus longicaudatus, C. barabensis griseus, C. b. obscurus, C. cf. migratorius, Phodopus sp.其中A. ehiki-A. teilhardi sp. nov.,C. varians-现生种“C.”triton及小型仓鼠可能分别和中国新第三纪晚期的Sinocricetus, Kowalskia等有较密切的亲缘关系。     

Mitotic arrest and enhanced nuclear protein phosphorylation in human leukemia K562 cells by okadaic acid, a potent protein phosphatase inhibitor and tumor promoter.

We investigated the effects of the non-phorbol tumor promoter okadaic acid on human leukemia K562 cells. It was found that okadaic acid potently and reversibly inhibited cell growth, with a nearly complete inhibition of thymidine uptake seen at about 10 nM. The cytotoxicity of okadaic acid was characterized by a marked mitotic arrest of the cells exhibiting scattered chromosomes and abnormal anaphase-like structures, a phenomenon distinct from the typical metaphase arrest caused by colchicine. Okadaic acid (10-1,000 nM) greatly stimulated phosphorylation of a number of nuclear proteins in K562 cells. Phosphorylation of many of the same proteins was also stimulated by 12-O-tetradecanoylphorbol-13-O-acetate, a protein kinase C activator. The present findings, consistent with recent reports that okadaic acid is a potent inhibitor of protein phosphatases 1 and 2A (PP1 and PP2A) shown to be essential for normal mitosis, provided evidence for the first time that okadaic acid inhibition of PP1/PP2A resulted in enhanced nuclear protein phosphorylation and subsequent mitotic arrest.     

甲肝病毒在人血白细胞中体外连续传代和在分类白细胞中增殖的研究

1985年我们采用间接免疫荧光法(IF法)检测出甲肝患者外周血白细胞中有甲肝抗原(HAAg)存在,继而又将HAAg阳性白细胞直接种入PLC/PRF/5细胞,分离到两株甲肝病毒(HAV)NJ—3株和H—1株。为了弄清白细胞所携带的病毒究竟仅为吸附吞饮,抑或能在其中复制增殖,我们将分离到的HAV用正常人血白细胞进行体外增殖试验,现将结果报告如下。     

Aberrant splicing caused by the insertion of the B2 sequence into an intron of the complement C4 gene is the basis for low C4 production in H-2k mice.

The serum level of the fourth component of complement (C4) in mice bearing the H-2k haplotype is only 1/10 to 1/20 of that of non-H-2k mice. We have analyzed C4 cDNA clones from B10.BR(H-2k) mouse liver and found aberrant C4 cDNA which contained a 200-base pair (bp) insertion between the exon 13 and exon 14 encoded sequences in addition to the normal C4 cDNA. The 5' 148 bp and the 3' 52 bp of this insert were derived from the B2 sequence, the short interspersed repeats of mouse genome, and the central part of intron 13, respectively. Sequence analysis of intron 13 of the C4k gene showed the presence of a complete copy of a B2 consensus sequence. The structure of aberrant C4 mRNA indicated that the possible 3' splice site in the B2 sequence and the cryptic 5' splice site in intron 13 were used. Both the insertion of the B2 sequence into intron 13 and the presence of aberrant mRNA in the liver were specific to H-2k-bearing mice, suggesting that the aberrant splicing due to the B2 insertion is the basis for low C4 expression in H-2k mice.     

Strong electrostatic loop-helix interactions in bundle motif protein structures.

Based on CHARMM potential (Brooks et al., 1983) an energetic analysis has been carried out for four typical 4-alpha-helix bundle proteins, i.e., methemerythrin, cytochrome b-562, cytochrome c', and bovine somatotropin. The bovine somatotropin possesses long loops, but all the other three proteins have short loops. It was found that in all these four 4-alpha-helix bundle motif structures the interaction between loops and helices was much stronger than the interaction among the four helices themselves. Particularly for the electrostatic interaction energy, the loop-helix interaction is overwhelmingly stronger than the interhelix interaction although the latter involves the favorable helix dipole interaction due to the antiparallel arrangement of neighboring alpha-helices. The present study indicates that such a conclusion holds true regardless of what loops, long or short, are in the 4-alpha-helix bundle protein, and also regardless of which empirical potential, ECEPP or CHARMM, is used for calculations although in CHARMM the electrostatic energy is much more heavily emphasized than in ECEPP. Therefore, no appropriate conclusion can be drawn in arguing whether the dipole interaction among the four alpha-helices play a stabilizing role or destabilizing role for a 4-alpha-helix bundle protein without taking into consideration the effect of interaction between helices and loops. The calculated results reported here provide, from a different point of view, insights that might be useful for revealing the essence of the driving forces during the folding of proteins.     

The use of ejaculated boar semen after freezing in 2 or 6% glucerol for in vitro fertilization of porcine oocytes matured in vitro

Two concentrations of glycerol in a freezing diluent were tested with respect to the in vitro fertilizing capacity of frozen-thawed boar spermatozoa which, before exposure to oocytes, were subjected to 3 methods of fractionation. These were 1) the upper fraction, 2) the swim-up and 3) percoll gradinet-centrifugation. The highest proportions of motile spermatozoa were obtained by the swim-up procedure, while acrosomal integrity was best preserved by the upper fraction procedure. Raising the glycerol concentration from 2 to 6% (v/v) during freezing decreased the proportion of spermatozoa with a normal apical ridge. Spermatozoa separated by the upper fraction method showed the greatest penetration of oocytes and produced the highest indidence of polyspermy. The glycerol level affected penetration and polyspermy only with spermatozoa separated in a percoll gradient, where the higher level of glycerol increased oocytes penetration and polyspermy. Pronuclei formation was influenced by the separation procedure and by the glycerol concentration in the freezing diluent. The results indicate that frozen boar semen can be used for in vitro fertilization more successfully than fresh semen since penetration by frozen upper fraction spermatozoa was similar to, the degree of polyspermy was lower, and the formation of two pronuclei was greater (P<0.01) than in oocytes exposed to fresh semen.     

Functional analysis of Arg-308 mutants of Flp recombinase. Possible role of Arg-308 in coupling substrate binding to catalysis

The arginine residue at position 308 in the Flp recombinase corresponds to the only invariant arginine within the Int family of recombinases. Alterations of this residue result in Flp variants that retain substrate recognition, but form weaker protein-DNA complexes than wild type Flp. Furthermore, their DNA cleavage activity is significantly diminished. A conservative change of R308K results in a functional Flp variant; however, this protein has a lowered temperature optimum for recombination. The Arg-308 mutants can be stabilized on the DNA substrate through cooperativity with a partner Flp mutant that is tight binding. Thus, interactions between Flp monomers must be a relevant feature of the normal recombination reaction.     

南美蟛蜞菊内参基因Actin的克隆及其分析

看家基因Actin常被用作定量、半定量PCR试验的内参基因.为研究其他基因在南美蟛蜞菊响应环境变化的表达调控机制,根据GenBank上已登录的肌动蛋白基因(Actin)的同源核苷酸保守序列,设计特异性引物,利用RT-PCR的方法克隆获得了南美蟛蜞菊Actin基因的全长序列,并将该序列命名为WtAct.序列分析结果表明W...