Charge dependence of Fe(II)-catalyzed DNA cleavage.

The effect of charge of the Fe(II) reagent used to induce DNA strand cleavage reactions in the presence of a source of reducing equivalents is investigated using two oligonucleotide models. The first consists of the two strands dA20 and dT20, and an equimolar complex between them. The second is a short four-arm branched DNA complex composed of four 16-mer strands. In the former case, cleavage of the 1:1 complex by three reagents with different formal charge, Fe(II).EDTA2-, Fe(II).EDDA and Fe2+, is comparable in rate to that of the individual dT20 and the dA20 strands. While the three reagents show similar cleavage rates for the duplex and single stranded molecules, they give distinctive cutting patterns in the DNA tetramer, consistent with the presence of a site of excess negative charge at the branch point. Scission induced by Fe(II).EDTA2- shows lower reactivity at the branch site relative to duplex controls, whereas Fe(II)2+ shows enhanced reactivity. Formally neutral Fe(II).EDDA shows weak loss of cutting reactivity at the branch. The position of attack by Fe(II)2+ in the branched tetramer is shifted with respect to those of Fe(II).EDTA2- or Fe(II).EDDA; a slower migrating species is also detected in the scission of dA20.dT20 duplex by Fe(II) reaction. These results suggest that the Fe(II)2+ reaction proceeds by a different mechanism from the other agents. The difference in cutting profiles induced by the neutral and negatively charged chelated complexes is consistent with a local electrostatic repulsion of a negatively charged source of radicals, not a positively charged one.     

Studies on theStellaria longipes complex (Caryophyllaceae): Isozyme variability and the relationship betweenStellaria longipes andS. longifolia

Genetic variation within and the relationship betweenStellaria longipes Goldie andS. longifolia Muhl. were studied. Ten enzyme systems were assessed in eight natural populations ofS. longipes (25 loci) and three ofS. longifolia (20 loci) using starch and polyacrylamide gel electrophoresis. Patterns of population differentiation corresponded to geographic distance. There was no evidence that polyploidS. longipes had greater electrophoretic variability than diploidS. longipes. The isozyme data confirmed extensive population differentiation in these species and, within that context, a relatively close relationship betweenS. longipes andS. longifolia. It was postulated that diploids of these two species might be the progenitors of tetraploidS. longipes.     

血管平滑肌细胞的钙动力学

血管平滑肌细胞外的Ca~(2+)通过多种通道进入细胞内。Ca~(2+)通道的本质是镶嵌在膜脂质双分子层中的糖蛋白,神经介质和药物可影响Ca~(2+)通道的功能。靠近胞膜的肌质网和胞膜内侧面的高亲和性Ca~(2+)结合位点是血管平滑肌细胞内储存和释放Ca~(2+)的主要部位。胞浆[Ca~(2+)]增高后在钙调蛋白的介导下引起血管收缩。高血压等血管性疾病的发生与其平滑肌细胞的钙动力学异常有关。     

Seasonal and spatial variations in the zooplankton community of an Eastern Antarctic coastal location

Summary The zooplankton community of a shallow coastal area in Eastern Antarctica was found to be one of low species diversity dominated by Copepoda. It was comprised of the more common Antarctic oceanic copepod species, medusae, molluscs, euphausiids, several copepod species associated with the ice-water interface and, in summer, benthic fauna larvae. Most species of copepods displayed a marked seasonality in abundance with peak numbers between March and May. It is proposed that several factors, including phytoplankton seasonality contribute to the zooplankton species composition, zooplankton seasonality, and to the temporal differences in the period of maximum abundance between copepod species. Annual vertical migratory behaviour in conjunction with the circulation of Prydz Bay are important determining factors for those species which can be considered as oceanic; Calanoides acutus, Calanus propinquus, Ctenocalanus citer, Metridia gerlachei, Oithona similis and Oncaea curvata. However, for copepod species which can be classified as inshore residents, such as Stephos longipes, Paralabidocera antarctica and Drepanopus bispinosus, it is their association with the ice water interface that determines their seasonal appearance and abundance. Some differences were established between the zooplankton community of the Vestfold Hills and that of other Antarctic coastal regions. This may be attributed, in part, to the extensive shallow areas of the Vestfold Hills coastal region. Spatial distribution of the zooplankton with depth and between sites was investigated and found to be essentially homogenous. When differences were established, in the majority of cases all species present, all age classes and both sexes contributed to the differences.     

A simple and easy-to-assemble device for polymerase chain reaction

In this paper we describe an efficient polymerase chain reaction device which is easy to assemble and requires minimal investment in dedicated equipment. The polymerase chain reaction device consists of three waterbaths, three dual-head peristaltic pumps, an electronic timer and a fabricated water jacket capable of holding microcentrifuge tubes. This device has been successfully used to amplify human factor X genomic DNA in our laboratory.     

Assignment of 12 loci to rat chromosome 5: evidence that this chromosome is homologous to mouse chromosome 4 and to human chromosomes 9 and 1 (1p arm)

Twelve loci have been assigned to rat chromosome 5: aldolase B (ALDOB), atrial natriuretic factor (ANF = pronatriodilatin, PND), D4RP1, DSI1, galactosyltransferase (GGTB2), glucose transporter (GLUT1), interferon alpha 1 and related interferon alpha (INFA), interferon beta (INFB), lymphocyte-specific protein-tyrosine kinase (LCK), oncogene MOS, alpha 2U-globulin (major urinary protein, MUP), and orosomucoid (ORM, also called alpha 1-acid glycoprotein, AGP). Among these, the interferon alpha and beta genes map in the q22-23 region, which also contains a transformation suppressor gene (SAI1). The other loci reside outside this region. This study also indicated that the rat genome contains 2 LCK genes, unlike the human and murine genomes. These new assignments on rat chromosome 5 demonstrate that this chromosome is highly homologous to mouse chromosome 4 and carries synteny groups conserved on human chromosome 9 (interferon alpha and beta, galactosyltransferase, orosomucoid, and aldolase B genes) and on the short arm of human chromosome 1 (MYCL, glucose transporter, protein kinase LCK, and atrial natriuretic factor genes).     

Primary structure and expression of a sodium channel characteristic of denervated and immature rat skeletal muscle

The alpha subunit of a voltage-sensitive sodium channel characteristic of denervated rat skeletal muscle was cloned and characterized. The cDNA encodes a 2018 amino acid protein (SkM2) that is homologous to other recently cloned sodium channels, including a tetrodotoxin (TTX)-sensitive sodium channel from rat skeletal muscle (SkM1). The SkM2 protein is no more homologous to SkM1 than to the rat brain sodium channels and differs notably from SkM1 in having a longer cytoplasmic loop joining domains 1 and 2. Steady-state mRNA levels for SkM1 and SkM2 are regulated differently during development and following denervation: the SkM2 mRNA level is highest in early development, when TTX-insensitive channels predominate, but declines rapidly with age as SkM1 mRNA increases; SkM2 mRNA is not detectable in normally innervated adult skeletal muscle but increases greater than 100-fold after denervation; rat cardiac muscle has abundant SkM2 mRNA but no detectable SkM1 message. These findings suggest that SkM2 is a TTX-insensitive sodium channel expressed in both skeletal and cardiac muscle.     

Oligo-riboprobes. Tools for in situ hybridisation

In situ hybridisation detection of mRNAs using riboprobes has become a widely used technique. However, the identification of cells producing closely-related yet distinct mRNAs is difficult with the usual size probes. Moreover, it is not always easy to obtain the required cDNA essential for cRNA probe synthesis. To avoid these problems, we have used synthetic oligodeoxynucleotides to generate short, single stranded RNA probes ("oligo-riboprobes"). These probes can be labelled to very high (10(9) cpm/micrograms) specific activity and can be prepared for any published nucleotide sequence. We have used these probes to localise beta (preprotachykinin) PPT mRNA producing neurons in rat hypothalamus and bowel. The results were compared to that obtained with cRNA probes generated from beta preprotachykinin cDNA.