Can artificial introductions of diaspore fragments work as a conservation tool for maintaining populations of the rare peatmoss Sphagnum angermanicum?

Species can become regionally rare when limited by the availability of suitable habitats or by limited dispersal ability. We tested if the presence of a rare bryophyte species (Sphagnum angermanicum) was dispersal or habitat limited and at the same time investigated the possibility of establishing new populations of this rare species. Further, we tested how propagule (fragment) size and small scale disturbances affected establishment success. All field experiments were performed by artificially transporting propagules (of various sizes) to new and old sites for the species in Sweden.We show that S. angermanicum is dispersal limited on a regional scale, as no significant differences in establishment success were found between new suitable sites and old occupied sites. The larger the propagule the better was the establishment success; the best establishment success was found when transplanting whole shoots. Disturbances did not increase establishment success, in contrary, when compared to controls success was reduced by the more intensive disturbance treatments. We suggest that disturbance maybe more important for increasing direct dispersal than for making the microhabitat more advantageous for establishment. However, an intermediate disturbance, which slightly reduces the Sphagnum-community length increment, might also be beneficial for the establishment success of S. angermanicum propagules.The reasonably high establishment success of S. angermanicum propagules in new suitable sites suggests that artificial introductions of fragments could be considered as an active management regime for the species if the number of localities continues to decrease.     

Macroinvertebrate Community and Chemistry of the Most Atmospherically Acidified Streams in the Czech Republic

We performed a comparative study of strongly acidified mountain streams covering 10 sites in the Czech Republic in the season 1999/2000. The aim of the study was to determine how acidification influenced macroinvertebrate community structure within a relatively narrow pH range. We focused on strongly acidified, non-humic running waters with low ionic content (pH < 4.6, total organic carbon < 10 mg l^?1, specific conductivity < 100 μS cm^?1) and minimum human influence in the catchment. The actual pH values ranged from 3.98 to 4.65, and concentrations of reactive aluminium ranged from 0.2 to 2.0 mg l^?1. Characteristic macroinvertebrates were the stoneflies Leuctra nigra, Nemurella pictetii, and Protonemura spp.; the chironomids Corynoneura spp.; and the caddisfly Plectrocnemia conspersa – the former two stoneflies formed together 46% of total organisms. The sites were divided into three groups with use of divisive classification. Individual groups reflected similarity in water chemistry, catchment characteristics, and geographical proximity. The largest biotic difference detected by PCA was in the abundance of stoneflies, mainly Diura bicaudata and Leuctra major. The strongest correlation with this gradient was shown by pH (and associated heavy metals), followed by the distance from source. The results show that even in such narrow pH range, the number of taxa is determined by the low pH value and related high concentrations of aluminium and heavy metals.     

Lesions in fetal pigs with transplacentally-induced toxoplasmosis

Two sows (Nos. 1, 2) were each fed 1,000 Toxoplasma gondii oocysts. Sow No. 1 was fed oocysts at 60 day of gestation and was euthanatized 49 days later. Sow No. 2 was fed oocysts at day 45 of gestation and euthanatized 62 days later. Sow No. 1 had eight dead fetuses of which one was mummified and unsuitable for histologic study. Sow No. 2 had 11 fetuses, of which four fetuses were mummified and unsuitable for histologic examination, two fetuses were dead and five were live. Lesions and Toxoplasma parasites were identified in seven fetuses from sow No. 1 and three fetuses from sow No. 2. No lesions were found in four fetuses from sow No. 2. Toxoplasma gondii was present in trophoblasts and produced areas of necrosis of the chorioallantois with focal placental separation. The predominant lesions were necrotizing placentitis, non-suppurative encephalomyelitis, and myocardial degeneration, necrosis and mineralization. Numerous tachyzoites were seen in trophoblast cells lining areolae in placenta.     

The epidemiology and control of swine parasites. Immunity and vaccines

This article discusses the status of two experimental swine helminthic vaccines and how further knowledge of parasite biochemistry and swine immunology and the application of techniques of modern biotechnology may affect their future development.     

Assessment of T lymphocyte responses induced by parasite antigens

Recently developed procedures for the isolation and continuous growth in vitro of T lymphocytes can be used to extend our knowledge of cellular immune responses elicited by parasitic infections. These procedures are adaptable to the study of both the inductive and effector phases of T cell responses. The inductive phase of T cell responses is measured by assessing the level of blastogenesis induced in antigen-primed lymphocyte populations by parasite antigens. The development of limiting dilution analyses and procedures for the repeated in vitro restimulation of such cells have allowed for the quantitation of blastogenic responses, and for the isolation of antigen-reactive T cells. The effector phase of T cell responses is assessed by assays that detect either, cytolytic activity of the antigen-responsive cells, the secretion of lymphokines by the responding cells, or specific or non-specific T cell mediated immunosuppression.     

CpG-oligodeoxynucleotides enhance porcine immunity to Toxoplasma gondii

Protection against a challenge infection with Toxoplasma gondii VEG strain oocysts was examined in pigs after vaccination with T. gondii RH strain tachyzoites with or without a porcine specific synthetic oligodeoxynucleotides (ODN) containing immunostimulatory CpG motifs. Six groups of pigs were immunized with incomplete Freund's adjuvant (IFA) and either vehicle, tachyzoites alone or in combination with three different doses of CpG ODN or with CpG ODN alone. Protection from challenge was significantly (P < 0.05) improved in pigs vaccinated using CpG ODN as an adjuvant with tachyzoites compared to all other groups. The CpG ODN tachyzoite-immunized pigs also had higher serum parasite specific IgG antibody, no clinical signs of disease, and 52% had no demonstrable tissue cysts after the challenge infection. These data indicate that CpG ODN is a potential safe and effective adjuvant for the T. gondii RH strain vaccine in pigs.     

澧阳平原末次冰期-早全新世气候环境演变研究

通过对澧阳平原野外考察、典型剖面YC自然沉积剖面的系统采样、室内地球化学元素Li、Rb、Sr、Ba和Li/Ba、Rb/Sr比值的分析,以及沉积物年代样品的OSL和AMS14C年代测定,探讨了长江中游地区澧阳平原末次冰期-早全新世的气候环境变化过程。结果表明,MIS3阶段晚期(31.80~23.80 ka BP)暖湿期记录明显,对应的沉积物含大量黑色铁锰膜和铁锰结核,地球化学元素Li含量、Rb含量、Rb/Sr比值、Li/Ba比值出现峰值,而Sr含量、Ba含量出现低谷,表明此时期冬季风减弱,夏季风增强,降水量增大,温度上升,风化作用显著增强。澧阳平原YC剖面很好的记录了56.00~6.96 ka BP的气候环境演变过程,大致经历了冷干期(56.00~31.80 ka BP)、相对暖湿期(31.80~23.80 ka BP)、冷湿期(23.80~10.60 ka BP)、暖湿期(10.60~6.96 ka BP)4个气候变化阶段。     

Carcinogenicity of acrylamide: a computational study

This paper reports a series of ab initio, density functional theory (DFT), and semiempirical molecular orbital (MO) calculations concerning the reaction between the ultimate carcinogen of acrylamide and guanine. Acrylamide--a product of the Maillard reaction--is present in a variety of fried and oven-cooked food. After intake, it is epoxidized by cytochrome P450 2E1 to yield the ultimate carcinogen--glycidamide. Effects of solvation were considered using the Langevin dipoles (LD) model of Florian and Warshel and the solvent reaction field (SCRF) model of Tomasi and co-workers. In silico activation free energies are in very good agreement with the experimental value of 22.8 kcal/mol. This agreement presents strong evidence in favor of the validity of the proposed S N2 reaction mechanism and points to the applicability of quantum chemical methods to studies of reactions associated with carcinogenesis. In addition, insignificant stereoselectivity of the studied reaction was predicted. Finally, the competing reaction of glycidamide with adenine was simulated, and the experimentally observed regioselectivity was successfully reproduced.