A limnological reconnaissance of Lake Tebenquiche,Salar de Atacama,Chile

A number of expeditions to the area of Salar de Atacama, Chile, 68° 15'W, 20° 30'S, have involved studies of the biological and chemical features of Lake Tebenquiche, situated in the interior of the salar. Chemically, Tebenquiche is hypersaline, with practically anoxic waters dominated by sodium and chloride ions but with high concentrations of sulphate also. The lake is surrounded and invaded by macrophytes, dominated by Scirpus olmeyi and Juncus, which provide organic material for the formation of bacterial mats. The fauna of limnetic crustaceans is almost exclusively of Artemia salina. The most important genera of bacteria are: Marinomonas, Halobacterium, Acinetobacter and the sulphur reductors Vibrio and Bacillus. The Cyanobacteria are represented exclusively by Oscillatoria.     

Trypanosoma cruzi: defined medium for continuous cultivation of virulent parasites.

A liquid medium was developed for the continuous cultivation of Trypanosoma cruzi. Among the several highly purified macromolecules tested only bovine liver catalase, horseradish peroxidase, lactoperoxidase, and bovine hemoglobin supported the continuous growth, at high yield, of mice-virulent Trypanosoma cruzi; other hemoproteins were inactive. Bovine liver catalase showed optimal Trypanosoma cruzi growth-promoting activity, parasites reaching 20 × 10⁶ parasites/ml (95% epimastigotes) at about 10 days in most of the 45 subpassages to date. Furthermore, this protein in the incubation medium provided all the amino acid requirements of actively growing parasites, thus eliminating the need for exogeneous free amino acids. Additional experiments revealed that the hemoprotein's growth-promoting activity was independent of any enzymatic activity and that reconstituting the exact protein composition by means of exogeneous amino acids did not support parasite multiplication, suggesting the importance of the primary structure of the active proteins for growth-promoting activity. These active macromolecules supported the multiplication of five different strains of Trypanosoma cruzi, but did not support Leishmania brasiliensis or Leishmania mexicana proliferation, suggesting species specificity.     

Dual interference of hygromycin B with ribosomal translocation and with aminoacyl-tRNA recognition.

RNA-dependent DNA polymerases from Rous-associated virus-O and avian myeloblastosis virus were partially purified by affinity chromatography and compared to each other. The enzymes are indistinguishable in the immunoglobulin inhibition test and by several enzymological criteria, such as optimum curves for the concentrations of Mg2+, K+, H+; monophasic Lineweaver-Burk plot for dTTP and biphasic Lineweaver-Burk plot for dGTP. In thermal inactivation studies a small difference can be observed, suggesting a minor difference in the physical structures of the enzymes. Our findings are consistent with the idea that the RNA-dpendent DNA polymerases of endogenous and exogenous avian leukosis viruses are very closely related to each other and therefore may be regarded as one group of polymerases.     

Micrococcus lysodeikticus membrane ATPase. effect of trypsin on stimulation of a purified form of the enzyme and identification of its natural inhibitor

A soluble purified form of Micrococcus lysodeikticus ATPase (form B_AT, from strain B, active, trypsin-stimulated) was stimulated 100% by trypsin and this stimulation was inhibited by preincubation of the protease with phenyl methyl sulphonylfluoride. This form of the enzyme was also stimulated 125–150% by filtration on Sephadex G-200. Analysis by sodium dodecyl sulphate-gel electrophoresis showed that stimulation of this form of M. lysodeikticus ATPase was always accompanied by the disappearance of a subunit of mol. wt. 25 000 (ε subunit). It suggests that this subunit is the natural inhibitor of M. lysodeikticus ATPase. In the case of ATPase stimulation by trypsin, a partial and limited degradation of the α subunit was also observed. The interaction between the ε subunit and the rest of the ATPase complex was reversibly affected by pH, suggesting its non-covalent nature.     

Immunoelectrotransfer blot assay in acute and chronic human trichinellosis

An immunoelectrotransfer blot assay (IETB) using excretory secretory products of muscle larvae of Trichinella spiralis (ML-ESP) and the avidin biotin system was developed in order to characterize reactivity against ML-ESP in sera from patients with acute and chronic trichinellosis. A complete pattern of up to 13 bands was developed by sera from individuals with trichinellosis where doublets, triplets, or single bands were shown to have molecular weights of roughly 66, 55, 45, 36, 29, 24, and 14 kDa. The bands at approximately 55, 36, 29, and 14 kDa proved specific for T. spiralis. The band at approximately 55 kDa was present in all trichinellosis sera, whereas the approximately 14-kDa band was present in only a small percentage of sera. The development of approximately 36- and 29-kDa bands suggests a modulation of the reactivity against ML-ESP over time. IETB proved more sensitive for the population of chronic trichinellosis under study than a conventional diagnostic enzyme-linked immunosorbent assay, allowing negative or borderline serum samples to be determined. Thus, this technique, when applied for human trichinellosis surveillance, should provide a useful tool in endemic areas.     

Long-Term Biomonitoring of Soil Contamination Using Poplar Trees: Accumulation of Trace Elements in Leaves and Fruits

Phytostabilization aims to immobilize soil contaminants using higher plants. The accumulation of trace elements in Populus alba leaves was monitored for 12 years after a mine spill. Concentrations of As and Pb significantly decreased, while concentrations of Cd and Zn did not significantly over time. Soil concentrations extracted by CaCl₂ were measured by ICP-OES and results of As and Pb were below the detection limit. Long-term biomonitoring of soil contamination using poplar leaves was proven to be better suited for the study of trace elements. Plants suitable for phytostabilization must also be able to survive and reproduce in contaminated soils. Concentrations of trace elements were also measured in P. alba fruiting catkins to determine the effect on its reproduction potential. Cadmium and Zn were found to accumulate in fruiting catkins, with the transfer coefficient for Cd significantly greater than Zn. It is possible for trace elements to translocate to seed, which presents a concern for seed germination, establishment and colonization. We conclude that white poplar is a suitable tree for long-term monitoring of soil contaminated with Cd and Zn, and for phytostabilization in riparian habitats, although some caution should be taken with the possible effects on the food web.

Supplemental materials are available for this article. Go to the publisher's online edition of International Journal of Phytoremediation to view the supplemental file.     

半干旱区沙质退化草地造林对土壤质量的影响

采用野外调查与室内培养相结合的方法,研究了我国北方半干旱区科尔沁沙地退化草地营造樟子松人工林32年后0～10 cm表层土壤理化性状、土壤碳氮矿化量、土壤微生物量以及土壤酶活性等的变化. 结果表明32年生樟子松人工林土壤有机碳、全氮和全磷等养分含量分别下降了21%、42%和45%;5月和11月樟子松人工林土壤NH4 -N显著高于草地(P=0.001;P=0.019),而5、8和11月草地土壤NO3--N含量显著高于樟子松人工林(P＜0.001;P=0.048;P=0.031);5、8和11月樟子松人工林土壤有机碳日矿化释放的CO2-C量均大于草地,而二者土壤氮矿化率差异不显著(P＞0.05);5和8月樟子松人工林土壤微生物量碳含量与草地相比差异不显著,11月则显著高于草地;土壤养分和水分含量是影响土壤微生物量碳含量的重要因素;与草地相比,樟子松人工林土壤脲酶和蔗糖酶活性降低,而土壤过氧化氢酶活性升高. 上述结果说明半干旱区沙质退化草地营造樟子松人工林32年后土壤质量出现一定程度的下降;由于植被的改变,樟子松人工林土壤理化性状和生物学性状等表现出与草地不同的季节动态特征.造林作为我国北方半干旱区沙地退化生态系统的一种恢复手段具有一定的局限性.     

Lipid content and apoptosis of in vitro-produced bovine embryos as determinants of susceptibility to vitrification

The objective was to evaluate supplementation of fetal calf serum (FCS) and phenazine ethosulfate (PES), a metabolic regulator that inhibits fatty acid synthesis, in culture media during in vitro production (IVP) of bovine embryos. Taking oocyte fertilization (n = 4,320) as Day 0, four concentrations of FCS (0, 2.5, 5, and 10%) and three periods of exposure to PES (without addition—Control; after 60 h—PES Day 2.5 of embryo culture; and after 96 h—PES Day 4) were evaluated. Increasing FCS concentration in the culture media enhanced lipid accumulation (P < 0.05), increased apoptosis in fresh (2.5%: 19.1 ± 1.8 vs 10%: 28.4 ± 2.3, P < 0.05; mean ± SEM) and vitrified (2.5%: 42.8 ± 2.7 vs 10%: 69.2 ± 3.4, P < 0.05) blastocysts, and reduced blastocoele re-expansion after vitrification (2.5%: 81.6 ± 2.5 vs 10%: 67.3 ± 3.5, P < 0.05). The addition of PES in culture media, either from Days 2.5 or 4, reduced lipid accumulation (P < 0.05) and increased blastocoele re-expansion after vitrification (Control: 72.0 ± 3.0 vs PES Day 2.5: 79.9 ± 2.8 or PES Day 4: 86.2 ± 2.4, P < 0.05). However, just the use of PES from D4 reduced apoptosis in vitrified blastocysts (Control: 52.0 ± 3.0 vs PES Day 4: 39.2 ± 2.4, P < 0.05). Independent of FCS withdrawal or PES addition to culture media, the in vivo control group had lesser lipid accumulation, a lower apoptosis rate, and greater cryotolerance (P < 0.05). The increased lipid content was moderately correlated with apoptosis in vitrified blastocysts (r = 0.64, P = 0.01). In contrast, the increased apoptosis in fresh blastocysts was strongly correlated with apoptosis in vitrified blastocysts (r = 0.94, P < 0.0001). Therefore, using only 2.5% FCS and the addition of PES from Day 4, increased the survival of IVP embryos after vitrification. Moreover, embryo quality, represented by the fresh apoptosis rate, was better than lipid content for predicting embryo survival after vitrification.