Protection of sheep by vaccination against experimental challenge with Leptospira borgpetersenii serovar Hardjo and L. interrogans serovar Pomona

AIMS: To evaluate a multivalent leptospiral and clostridial vaccine for prevention of renal colonisation and urinary shedding in sheep, following experimental challenge with New Zealand strains of Leptospira borgpetersenii serovar Hardjo type Hardjobovis and L. interrogans serovar Pomona.

METHODS: Two separate but similarly designed studies were conducted. In both studies, Romney-cross lambs, aged 9–11 weeks, were randomly allocated to a vaccinated group and a control group. Vaccinated lambs each received two 1.5-mL S/C doses of a multivalent leptospiral and clostridial vaccine, 4 weeks apart, and animals in the control groups received the same dose of saline. Groups of 12 vaccinated and 12 control lambs were randomly selected in each study for challenge with serovars Hardjo or Pomona. Challenge was initiated 16 weeks following the second vaccination with three daily doses of live leptospires by intranasal and conjunctival routes. Following challenge, urine samples were collected weekly for 6 weeks, for dark field microscopy and leptospiral culture; 6 weeks after challenge the lambs were slaughtered and kidneys collected for leptospiral culture.

RESULTS: In lambs challenged with serovar Hardjo, 8/12 unvaccinated lambs had ≥1 urine or kidney sample that was positive for leptospires following culture, compared with 0/12 lambs in the vaccinated group (p=0.001). In lambs challenged with serovar Pomona, 9/12 unvaccinated lambs had ≥1 urine or kidney sample that was positive following culture, compared with 0/12 lambs in the vaccinated group (p<0.001). Prevention of renal colonisation and urinary shedding, expressed as the prevented fraction, was 100 (95% CI=61.7–100)% and 100 (95% CI=68.3–100)% against challenge with serovars Hardjo and Pomona, respectively, at 4 months after vaccination.

CONCLUSIONS AND CLINICAL RELEVANCE: Use of a multivalent leptospiral and clostridial vaccine demonstrated protection against challenge from New Zealand strains of serovars of Hardjo and Pomona 4 months after vaccination in lambs first vaccinated at 9–11 weeks of age. Further studies are required to assess the duration of immunity against challenge in sheep.     

Reproductive dominance of pasture trees in a fragmented tropical forest mosaic

Tropical forest fragmentation threatens biodiversity, yet basic information on population responses for major groups such as plants is lacking. Hypervariable genetic markers were used to reconstruct a population-level pedigree in fragmented tropical forest for the tree Symphonia globulifera. Though seedlings occurred only in remnant forest, the pedigree showed that most seedlings had been produced by sequentially fewer adults in pasture, creating a genetic bottleneck. The pedigree also implicated shifts in the foraging of animals that disperse pollen and seed in a secondary constriction of the bottleneck. These results suggest that tropical conservation strategies should anticipate complex, cryptic responses to fragmentation.     

Experimental demonstration of guiding and bending of electromagnetic waves in a photonic crystal

The routing and interconnection of optical signals through narrow channels and around sharp corners are important for large-scale all-optical circuit applications. A recent computational result suggests that photonic crystals may offer a novel way of achieving this goal by providing a mechanism for guiding light that is fundamentally different from traditional index guiding. Waveguiding in a photonic crystal and near 100 percent transmission of electromagnetic waves around sharp 90 degree corners were observed experimentally. Bending radii were made smaller than one wavelength.     

Evidence for extreme climatic warmth from late cretaceous arctic vertebrates

A Late Cretaceous (92 to 86 million years ago) vertebrate assemblage from the high Canadian Arctic (Axel Heiberg Island) implies that polar climates were warm (mean annual temperature exceeding 14 degreesC) rather than near freezing. The assemblage includes large (2.4 meters long) champsosaurs, which are extinct crocodilelike reptiles. Magmatism at six large igneous provinces at this time suggests that volcanic carbon dioxide emissions helped cause the global warmth.     

大豆遗传资源保护的法律法规及其可专利性

大豆起源于中国,中国是世界上大豆遗传资源最为丰富的国家,也曾经是世界上最主要的大豆生产国和出口国。半个多世纪以来,科学技术的进步带动了一些美洲国家大豆产业的迅猛发展,中国的大豆生产量由世界首位降到美国、巴西之后,从大豆出口国变为大豆净进口国,大豆成为中国农产品贸易中最令国际社会关心的贸易作物。随着农业生物技术的快速发展,知识产权保护的法律法规的国际化,尤其是我国加入WTO以后,大豆研究、开发、生产领域遇到了来自比其他作物前所未有的挑战。作为我国最重要的植物蛋白、食用油及动物饲料来源的大豆作物,有效地利用有关的法律法规保护我国大豆种质资源及新品种已经迫在眉睫。本文着重介绍了与大豆遗传资源、新品种保护相关的我国法律法规,进行了大豆保护的可专利性分析,并对大豆研发过程中的知识产权保护问题作了初步探讨,以促进对大豆新品种的申请保护,提高我国应对来自国外竞争的抗衡能力。     

Efficiency of inspection procedures for the detection of tuberculous lesions in cattle

The sensitivity of the abattoir inspection procedure introduced for Australian export beef in 1976 was compared to a detailed necropsy procedure for the detection of tuberculous lesions in cattle. In a sample of cattle that were reactors to the tuberculin test, abattoir inspection failed to detect an estimated 47% of cattle with lesions. The detailed necropsy examination of cattle with lesions of tuberculosis identified 21 sites of infection compared with 13 to 18 in cattle examined by routine meat inspection procedures. Of the lesions detected during detailed necropsy, 15.9% did not involve the thoracic cavity or the medial retropharyngeal lymph nodes. The failure to detect lesions during abattoir inspection has its greatest significance in an animal with a single lesion. If the 245 cattle found with single lesions during detailed necropsy had been examined by abattoir inspection using the 1976 or the 1986 procedures, 0.8 and 8.9%, respectively, of these animals would not have been detected because the diseased tissues would not have been examined. If meat inspection is to provide an effective means of monitoring the level of bovine tuberculosis during the final stages of eradication, a procedure no less sensitive than that introduced in 1976 should be used.