鸣禽白腰文鸟前脑发声控制核团的性双态性

应用神经示踪、放射免疫测定及组织学方法,对成体鸣禽白腰文鸟前脑发声控制核团的性双态性及血中的睾酮水平进行了研究。结果发现,前脑高级发声中枢、古纹状体粗核和Ｘ区三个发声控制核团均存在明显的性双态性,雄性的上述三个发声控制核团体积分别比雌性大５．３１、４．０１和１．９２倍,在三个选定的平面上,雄性个体的前两个核团神经元数量超过雌性,但神经元分布的密度则小于雌性,差异均显著（Ｐ〈０．０５）。从高级发声中     

A DNA test to sex most birds

Birds are difficult to sex. Nestlings rarely show sex-linked morphology and we estimate that adult females appear identical to males in over 50% of the world's bird species. This problem can hinder both evolutionary studies and human-assisted breeding of birds. DNA-based sex identification provides a solution. We describe a test based on two conserved CHD (chromo-helicase-DNA-binding) genes that are located on the avian sex chromosomes of all birds, with the possible exception of the ratites (ostriches, etc.; Struthioniformes). The CHD-W gene is located on the W chromosome; therefore it is unique to females. The other gene, CHD-Z, is found on the Z chromosome and therefore occurs in both sexes (female, ZW; male, ZZ). The test employs PCR with a single set of primers. It amplifies homologous sections of both genes and incorporates introns whose lengths usually differ. When examined on a gel there is a single CHD-Z band in males but females have a second, distinctive CHD-W band.     

抗单纯疱疹病毒单克隆抗体的研究——Ⅱ.单克隆抗体介导细胞毒效应的研究

建立了单克隆抗体(McAb)介导细胞毒作用(ADCC)~(51)Cr释放试验的测定力法。确定了最适工作条件。ADCC测定结果表明,5株抗HSV McAb介导ADCC的活性不同:McAb 1A12、2A8和1G8无ADCC活性;而1D10和2C5两株McAb作1:10稀释时,~(51)Cr释放率分别为27.09％和25.07％,稀释至1:100或1:1000时仍有ADCC活性。结果提示,不同的McAb抗原决定族诱导产生的抗体,在介导ADCC免疫保护作用上有差异,并为McAh治疗临床单纯疱疹病毒感染的可能性提供了实验资料。     

用投影寻踪回归方法研究红蜡蚧在枸骨球上的空间分布

用投影寻踪回归方法研究红蜡价在枸骨球上的空间分布结果表明,枸骨球上红蜡故的空间分布与枸骨球的方位和层次有关。雌成虫主要聚集在植物的外层和中层,并以球顶部和西面为重,内层和南面轻。用PP回归方法客观地分析和描述了数据的内在结构,为综合治理提供了可靠的依据。     

Point and deletion mutations eliminate one or both methyl group transfers catalysed by the yeast TRM1 encoded tRNA (m22G26)dimethyltransferase.

Guanosine at position 26 in eukaryotic tRNAs is usually modified to N2 , N2 -dimethylguanosine (m22G26). In Saccharomyces cerevisiae , this reaction is catalysed by the TRM1 encoded tRNA (m22G26)dimethyltransferase. As a prerequisite for future studies, the yeast TRM1 gene was expressed in Escherichia coli and the His-tagged Trm1 protein (rTrm1p) was extensively purified. rTrm1p catalysed both the mono- and dimethylation of G26 in vivo in Escherichia coli tRNA and in vitro in yeast trm1 mutant tRNA. The TRM1 gene from two independent wild-type yeast strains differed at 14 base positions causing two amino acid exchanges . Exchange of the original Ser467 for Leu caused a complete loss of enzyme activity in vitro against trm1 yeast tRNA. Comparatively short N- or C-terminal deletions from the 570 amino acid long Trm1 polypeptide decreased or eliminated the enzyme activity, as did some point mutations within these regions. This indicated that the protein is not a two domain peptide with the enzyme activity localised to one of the domains, but rather that both ends of the polypeptide seem to interact to influence the conformation of those parts that make up the RNA-binding site and/or the active site of the enzyme.     

Similarities and differences among 105 members of the Int family of site-specific recombinases.

Alignments of 105 site-specific recombinases belonging to the Int family of proteins identified extended areas of similarity and three types of structural differences. In addition to the previously recognized conservation of the tetrad R-H-R-Y, located in boxes I and II, several newly identified sequence patches include charged amino acids that are highly conserved and a specific pattern of buried residues contributing to the overall protein fold. With some notable exceptions, unconserved regions correspond to loops in the crystal structures of the catalytic domains of lambda Int (Int c170) and HP1 Int (HPC) and of the recombinases XerD and Cre. Two structured regions also harbor some pronounced differences. The first comprises beta-sheets 4 and 5, alpha-helix D and the adjacent loop connecting it to alpha-helix E: two Ints of phages infecting thermophilic bacteria are missing this region altogether; the crystal structures of HPC, XerD and Cre reveal a lack of beta-sheets 4 and 5; Cre displays two additional beta-sheets following alpha-helix D; five recombinases carry large insertions. The second involves the catalytic tyrosine and is seen in a comparison of the four crystal structures. The yeast recombinases can theoretically be fitted to the Int fold, but the overall differences, involving changes in spacing as well as in motif structure, are more substantial than seen in most other proteins. The phenotypes of mutations compiled from several proteins are correlated with the available structural information and structure-function relationships are discussed. In addition, a few prokaryotic and eukaryotic enzymes with partial homology with the Int family of recombinases may be distantly related, either through divergent or convergent evolution. These include a restriction enzyme and a subgroup of eukaryotic RNA helicases (D-E-A-D proteins).     

Lambda integrase cleaves DNA in cis.

In the Int family of site-specific recombinases, DNA cleavage is accomplished by nucleophilic attack on the activated scissile phosphodiester bond by a specific tyrosine residue. It has been proposed that this tyrosine is contributed by a protomer bound to a site other than the one being cleaved ('trans' cleavage). To test this hypothesis, the difference in DNA binding specificity between closely related integrases (Ints) from phages lambda and HK022 was exploited to direct wild type Ints and cleavage- or activation-defective mutants to particular sites on bispecific substrates. Analysis of Int cleavage at individual sites strongly indicates that DNA cleavage is catalyzed by the Int bound to the cleaved site ('cis' cleavage). This conclusion contrasts with those from previous experiments with two members of the Int family, FLP and lambda Int, that supported the hypothesis of trans cleavage. We suggest explanations for this difference and discuss the implications of the surprising finding that Int-family recombinases appear capable of both cis and trans mechanisms of DNA cleavage.     

Evidence of 11 beta-hydroxylase deficiency in a patient with cortical adrenal adenoma

We explored a 61 year old woman with mild hirsutism. An adrenal tumor was found in the left adrenal, which was held responsible for the androgen secretion. The in vitro incubation of the tumor tissue showed an impaired 11 beta-hydroxylation of 11-deoxycortisol. This is a rare and unusual case of adrenal pathology showing that a deficiency in 11 beta-hydroxylase activity does not rule out the presence of an adrenocortical adenoma.     

Suicide recombination substrates yield covalent lambda integrase-DNA complexes and lead to identification of the active site tyrosine

High levels of covalent integrase-DNA complexes accumulate when suicide substrates containing a medial nick within the overlap region are nicked by lambda integrase protein. The tyrosine residue at position 342 is shown to form a covalent bond with DNA at the sites of strand exchange. A mutant integrase in which this tyrosine is changed to phenylalanine is devoid of both topoisomerase and recombinase activity but still binds to both core- and arm-type DNA binding sites with an affinity comparable to wild-type integrase. Tyrosine-342 is located within a 40-amino acid region that is conserved among 15 known recombinases comprising the "integrase family." The present results show that this small region of homology participates in catalysis of strand transfer.