Cloning and sequence comparison ofAvaI andBsoBI restriction-modification systems

AvaI andBsoBI restriction endonucleases are isoschizomers which recognize the symmetric sequence 5CYCGRG3 and cleave between the first C and second Y to generate a four-base 5 extension. TheAvaI restriction endonuclease gene (avaIR) and methylase gene (avaIM) were cloned intoEscherichia coli by the methylase selection method. TheBsoBI restriction endonuclease gene (bsoBIR) and part of theBsoBI methylase gene (bsoBIM) were cloned by the endo-blue method (SOS induction assay), and the remainder ofbsoBIM was cloned by inverse PCR. The nucleotide sequences of the two restriction-modification (RM) systems were determined. Comparisons of the predicted amino acid sequences indicated thatAvaI andBsoBI endonucleases share 55% identity, whereas the two methylases share 41% identity. Although the two systems show similarity in protein sequence, their gene organization differs. TheavaIM gene precedesavaIR in theAvaI RM system, while thebsoBIR gene is located upstream ofbsoBIM in theBsoBI RM system. BothAvaI andBsoBI methylases contain motifs conserved among the N⁴ cytosine methylases.     

Mitochondrial DNA variation, population structure, and evolution of mountain sheep in the south-western United States and Mexico

In the south-western United States and Mexico, mountain sheep were found to have low levels of mtDNA sequence divergence among haplotypes and low overall nucleotide diversity. Potential causes for this low diversity are discussed. Significant differences in mtDNA haplotype distributions over short distances and high values of N_ST on a local scale appear to be a result of the tendency of female mountain sheep to disperse less frequently and over shorter distances than males. A lack of concordance between mtDNA haplotype distributions and assumed subspecies boundaries suggest that some taxonomic labels need to be revised.     

Agrobacterium-mediated transformation and regeneration of fertile transgenic plants of chinese cabbage (brassica campestris ssp. pekinensis cv. ‘spring flavor’)

A procedure for the regeneration of fertile transgenic Chinese cabbage (Brassica campestris ssp. pekinensis cv. Spring Flavor) is presented in this report. The protocol is based on infection of cotyledon explants of 5-d-old seedlings with an Agrobacterium tumefaciens strain LBA4404 carrying a disarmed binary vector pTOK/BKS-1. The T-DNA region of this binary vector contains the nopaline synthase/neomycin phosphotransferase II (nptII) chimeric gene for kanamycin resistance and the cauliflower mosaic virus 35S/coat protein gene of tobacco mosaic virus L (TMV-L) chimeric gene. After co-cultivation for 48 h, the cotyledonary petioles were placed on shoot induction media containing 15 mg/L kanamycin sulfate. Shoot induction was continued for 3–4 weeks, then subcultured once and after 2 weeks the shoots were transferred to root induction medium. After 1 week 8 putatively transformed plantlets from 200 cotyledon explants were obtained and transferred to greenhouse. Six of them grew to maturity, produced normal flowers and set seeds. Polymerase chain reaction and Southern blot hybridization analyses confirmed the introduction of the T-DNA into the Chinese cabbage genome. Further, Western blot analysis using polyclonal TMV antiserum showed most of the regenerants (5 out of 6) expressed TMV coat protein gene. Stable inheritance of the inserted clone was investigated in the next generation.     

Evidence against an increase in capillary permeability in subjects exposed to high altitude

Kleger, Gian-Reto, Peter Bärtsch, Peter Vock, BernhardHeilig, L. Jackson Roberts II, and Peter E. Ballmer. Evidence against an increase in capillary permeability in subjects exposed tohigh altitude. J. Appl. Physiol.81(5): 1917-1923, 1996.A potential pathogenetic cofactor for thedevelopment of acute mountain sickness and high-altitude pulmonaryedema is an increase in capillary permeability, which could occur as aresult of an inflammatory reaction and/or free radical-mediatedinjury to the lung. We measured the systemic albumin escape byintravenously injecting 5 µCi of ¹²⁵I-labeled albumin and theplasma concentrations of cytokines, F₂-isoprostanes (products of lipidperoxidation), and acute-phase proteins in 24 subjects exposed to 4,559 m. Ten subjects developed acute mountain sickness, and four subjectsdeveloped high-altitude pulmonary edema. The transcapillary escaperate of albumin was 6.9 ± 2.0%/h (SD) at low (550 m) and 6.3 ± 1.9%/h at high (4,559 m) altitude (P = 0.23; n = 24). The subjects withhigh-altitude pulmonary edema had a modest but insignificant increasein the transcapillary escape rate of albumin (4.6 ± 1.9%/h at lowvs. 5.7 ± 1.9%/h at high altitude;P = 0.42;n = 4). Plasma concentrations offibrinogen, ₁-acidglycoprotein, C-reactive protein, and interleukin-6 were unchanged inthe early phases and significantly increased by the end of theobservation period in the subjects with high-altitude pulmonary edema,whereas tumor necrosis factor- andF₂-isoprostanes did not change atall. This suggests that the inflammatory reaction was rather aconsequence than a causative factor of high-altitude pulmonary edema.In summary, these data argue against a dominant role for increasedsystemic capillary permeability in the development of acute mountainsickness and high-altitude pulmonary edema.

     

Cecal Propionic Acid as a Biological Indicator of the Early Establishment of a Microbial Ecosystem Inhibitory toSalmonellain Chicks

Experiments were conducted to evaluate the effects of different competitive exclusion (CE) cultures on the concentration of cecal propionic acid in 3-day-old broiler chicks, and the correlation between cecal propionic acid concentration and protection againstSalmonellacolonization. CE cultures that significantly (P < 0.05) increased cecal propionic acid in 3-day-old chicks decreased (P < 0.05) cecalSalmonellacolonization in 10-day-old chicks compared with the untreated controls. CE cultures that failed to significantly (P > 0.05) increase cecal propionic acid concentrations in 3-day-old chicks failed to protect (P > 0.05) against cecalSalmonellacolonization in 10-day-old chicks compared with untreated controls. A significant (P < .05) correlation (−.88) was found between cecal propionic acid concentration in 3-day-old chicks and cecalSalmonellacolonization in 10-day-old chicks.     

光系统II核心天线CP43的纯化及性质

菠菜放氧的ＰＳＩ核心复合物经０．８ｍｏｌ／ＬＴｒｉｓ－ＨＣｌ（ｐＨ８．０）洗涤后,用温和的非离子去垢剂ＤＭ和高浓度的ＬｉＣｌＯ４增溶,再经ＤＥＡＥ－Ｔｏｙｏｐｅａｒｌ－６５０Ｓ离子交换柱层析分离,可得到ＰＳＩＩ核心天线４３ｋＤ叶绿素ａ结合蛋白（ＣＰ４３）。ＳＤＳ－ＰＡＧＥ显示一条４３ｋＤ蛋白质带。根据Ａｒｎｏｎ法和Ｍａｒｋｗｅｌ法的结果表明,每个蛋白质分子结合有２０～２１个分子的叶绿素ａ。室温条件下,ＣＰ４３在红光区具有６７１ｎｍ的最大吸收峰和６８３ｎｍ的荧光发射峰,以及Ｗ型的圆二色信号,表明其处于较为天然的状态。文中还制备并鉴定了对ＣＰ４３特异的抗血清。     

The ecology of asociality in Namibian leopards

Data on the ecology of leopards ( Panthera pardus ) from north-eastern Namibia are presented and discussed in terms of the possible costs and benefits of solitary behaviour. In an area of low leopard density, where individuals lived alone, both males and females occupied large home ranges,(♂= 210-1164km², ♀= 183-194km²). Despite resource and reproductive advantages in maintaining exclusive ranges, the degree of range overlap both between and within sexes was substantial. Average overlap between males was 46% and between females 35%. The cost of dispersal appeared high as all three marked sub-adults died, and most recorded mortalities were of sub-adults. Females with dependent young showed a significant increase in per capita food intake compared to single females and males. Higher foraging success by females with cubs was revealed through two energy expenditure parameters (kg/km travelled/day and kg/hunt/day). Differential food intake between females with cubs, single females and males can be explained partly by differences in day ranges, body size and costs of parental care. Females shared 27% of their food with cubs and the costs of sharing food does not appear as high as previously suggested. Inter-specific competition over food and the defence of carcasses is suggested as an important cost to group living. Leopard kills were visited by other large carnivores (12%) but food loss was minimal (2%). Leopards successfully avoided conflict with inter-specific competitors by dragging and hiding kills in thick vegetation. We argue that solitary and secretive behaviour enables leopards to avoid the costs of defending carcasses against larger and gregarious carnivores.