Microsatellite markers for eastern hemlock (Tsuga canadensis)

We describe polymerase chain reaction primer pairs and reaction conditions for amplification of 15 microsatellite loci from eastern hemlock (Tsuga canadensis). The primers were tested on 23 individuals from a natural population in southwestern North Carolina, USA. These primers yielded an average of 5.9 alleles per locus (range of 2-14), an average observed heterozygosity of 0.45 (range 0.14-0.73), and an average polymorphic information content of 0.54 (range 0.28-0.86). In addition, eight of the primer pairs were found to amplify microsatellite loci in one or more additional species of Tsuga.     

The genetic characterization of Pseudomonas syringae pv. tagetis based on the 16S–23S rDNA intergenic spacer regions

Pseudomonas syringae pv. tagetis, a plant pathogen being considered as a biological control agent of Canada thistle (Cirsium arvense), produces tagetitoxin, an inhibitor of RNA polymerase which results in chlorosis of developing shoot tissues. Although the bacterium is known to affect several plant species in the Asteraceae and has been reported in several countries, little is known of its genetic diversity. The genetic relatedness of 24 strains of P. syringae pv. tagetis with respect to each other and to other P. syringae and Pseudomonas savastanoi pathovars was examined using 16S–23S rDNA intergenic spacer (ITS) sequence analysis. The size of the 16S–23S rDNA ITS regions ranged from 508 to 548 bp in length for all 17 P. syringae and P. savastanoi pathovars examined. The size of the 16S–23S rDNA ITS regions for all the P. syringae pv. helianthi and all the P. syringae pv. tagetis strains examined were 526 bp in length. Furthermore, the 16S–23S rDNA ITS regions of both P. syringae pv. tagetis and P. syringae pv. helianthi had DNA signatures at specific nucleotides that distinguished them from the 15 other P. syringae and P. savastanoi pathovars examined. These results provide strong evidence that P. syringae pv. helianthi is a nontoxigenic form of P. syringae pv. tagetis. The results also demonstrated that there is little genetic diversity among the known strains of P. syringae pv. tagetis. The genetic differences that do exist were not correlated with differences in host plant, geographical origin, or the ability to produce toxin.     

机械措施控制加拿大萨斯克彻温草场丛生卷柏生长的经济分析

对加拿大萨斯克彻温省干旱棕色土壤带、湿润棕色土壤带及黑棕色土壤带上的沙土和壤土草场区所应用的挖鱼鳞坑和犁翻两种机械措施控制丛生卷柏侵蚀天然草场的效果进行了经济效益分析。分析结果表明 :当市场折扣率为 8%和 10 %时 ,犁翻处理在任何草场区实施均在 2 0 a内不能收回投入 ,说明该处理在经济上是不可行的 ;而挖鱼鳞坑在黑棕色土壤带实施分别需要10 a和 11a才能收回投入 ,在湿润棕色土壤带分别需 12 a和 14 a,而在干燥棕色土壤带则分别需 15 a和 2 2 a。但在实际中 ,这两种处理是否能发挥 2 0 a以上的经济效益还需进一步研究。草场管理者应根据两种处理控制丛生卷柏效果及饲草产量的增量来确定净现值和内部报酬率 ,估测收回投入的年限 ,最终作出合理的经济决策。当然 ,如果考虑到铲除丛生卷柏所带来的一些生态方面的争议 ,草场管理者应慎重考虑其他一些改良措施 ,如改进放牧管理 ,施化肥及播种目标草种等 ,以达到取得经济效益的目的     

Obesity Research in Canada: Literature Overview of the Last 3 Decades

Objective: To identify research published on obesity in Canada, to explore the range of areas studied, and to identify gaps and areas that merit future research attention. Research Methods and Procedures: Medline and International Pharmaceutical Abstracts databases were searched from 1970 onwards. Original articles were identified and categorized by areas of interest. Results: A total of 1186 relevant articles were identified: 17, 136, 687, and 346 articles during the 1970s, 1980s, 1990s, and 2000 to 2003, respectively. Of the articles, 816 were considered original studies and accepted for this analysis. Twelve research areas were identified: basic science involving animal experiments (29%), human experiments (16%), populations surveys (14%), obesity‐related comorbidities (13%), diagnostic/surgical issues (11%), nonpharmacological approaches (7%), drug‐related issues (4%), anthropometrics (2%), impact of weight loss (2%), cost/healthcare use (1%), attitudes/perceptions (0.9%), and models/procedures (0.5%). Two‐thirds of all research was conducted in Quebec (34%) and Ontario (33%). Discussion: Given the multifactorial nature of obesity, Canadian obesity research covers a broad range of areas with a predominance of basic science but lesser emphasis on community and primary care studies. Furthermore, there was a paucity of research on either clinical management of medical conditions in obese patients or clinical aspects that go beyond weight loss. Thus, although Canada appears well represented in basic research, more attention to exploration of clinical issues and healthcare delivery for obese patients appears warranted.     

加拿大自然保护区规划的启迪

为了更好地国际接轨,搞好自然保护区的管理工作,我们需要学习其他国家的先进经验,本文重点介绍加拿大自然保护区规划方面的典型经验,包括系统规划,综合管理规划,资源管理规划,服务规划,行动规划,以及各种规划之间的关系,并提出了对我们的启迪与可借鉴之处。     

The relationship of 4-aminobutyric acid metabolism to ammoniagenesis in renal cortex

Mitochondrial 4-aminobutyrate aminotransferase in rat kidney can utilize pyruvate as the acceptor for the amino group of 4-aminobutyrate. Renal 4-aminobutyrate aminotransferase activity at saturating equimolar concentration of 4-aminobutyrate and 5 mM pyruvate is 42.8 ± 2.5 μmol/g protein per h (mean ± S.E.M.) or 70% of 4-aminobutyrate aminotransferase activity with equimolar α-ketoglutarate. 4-Aminobutyrate aminotransferase in brain does not transaminate with pyruvate. Since pyruvate is an important mitochondrial metabolite in kidney, net disposal of glutamate via the 4-aminobutyrate pathway is possible. The renal 4-aminobutyrate pathway in the rat has other distinctive features when compared with the pathway in rat brain. Most inhibitors of rat neuronal glutamate decarboxylase were ineffective against the renal form of the enzyme, but 20 mM semicarbazide inhibited the latter form by 80% (P < 0.001) in vitro and reduced renal 4-aminobutyrate content by 75% (P < 0.001) in vivo. In the presence of 20 mM semicarbazide, ammoniagenesis by rat renal cortex slices incubated in 1 mM glutamine was inhibited 26% (P < 0.01). Semicarbazide was proportionately less effective (15% inhibition) when ammoniagenesis was stimulated (+243%) in slices prepared from chronically acidotic animals, and was no deterrant to ammoniagenesis when non-acidotic slices were incubated in supraphysiologic concentrations of 10 mM glutamine. We conclude that whereas integrity of the renal 4-aminobutyrate pathway may contribute to glutamate disposal and thus ammoniagenesis under physiologic conditions, the pathway is a passive participant in the overall process of ammoniagenesis.     

Changes in amino acid transport in the rat pancreas in response to fasting and feeding

Transport of amino acids (in vitro) in the rat pancreas is affected by the nutritional state of the animal. A fast of 24 h (young animals) or 48 h (adult animals) reduces the rate of amino acid uptake in the isolated rat pancreas in vitro. In contrast, refeeding of animals after a fast shows an increase in transport in young as well as adult animals.The effects of refeeding after a fast are mimicked to a significant extent by injection of mixtures of pancreozymin and carbamylcholine. Addition of these agents in vitro has no effect.The incorporation of amino acids into the total proteins of the rat pancreas follows the pattern of amino acid uptake. Even at high external levels of glycine (5 mM), incorporation increases although the glycine level in the cell is in excess of 25 mM. Reduction of glycine uptake by ouabain by 75% results in a substantial (44%) diminution of amino acid incorporation into proteins. The data suggest that inhibition of amino acid incorporation under the various metabolic conditions examined is due largely to a decreased availability of amino acids.     

Epicuticular wax of Cirsium arvense

Epicuticular wax of Cirsium arvense contains hydrocarbons (12%), esters (35%), free acids (3%), free alcohols (10%), triterpene acetates (8%) and 1,3-ditetradecanoyl-2-hexanoylglycerol (8%) as major components. Minor components are triterpene alcohols (3%) and nonacosan-10-ol (2%). The esters contain triterpene alcohol esters (19%) as well as esters of alkanols.