Modeling the Exchanges of Energy, Water, and Carbon Between Continents and the Atmosphere

Atmospheric general circulation models used for climate simulation and weather forecasting require the fluxes of radiation, heat, water vapor, and momentum across the land-atmosphere interface to be specified. These fluxes are calculated by submodels called land surface parameterizations. Over the last 20 years, these parameterizations have evolved from simple, unrealistic schemes into credible representations of the global soil-vegetation-atmosphere transfer system as advances in plant physiological and hydrological research, advances in satellite data interpretation, and the results of large-scale field experiments have been exploited. Some modern schemes incorporate biogeochemical and ecological knowledge and, when coupled with advanced climate and ocean models, will be capable of modeling the biological and physical responses of the Earth system to global change, for example, increasing atmospheric carbon dioxide.     

Phagocytosis, bactericidal activity, and oxidative metabolism of milk neutrophils from dairy cows fed selenium-supplemented and selenium-deficient diets

Six primiparous Holstein cows were fed a Se-deficient diet, beginning at least 90 days before their first calving, and 6 other primiparous cows were given the same diet plus a supplement of 2 mg of Se/cow/d as sodium selenite. All cows were fed their diets for the duration of the experimental period. One uninfected quarter of each cow was injected with 25 micrograms of Escherichia coli endotoxin at postpartum week 5. Leukocytes were isolated by centrifugation from milk collected at postinjection hour 16. Isolated cells were 92 +/- 3% neutrophils and were incubated with Staphylococcus aureus or E coli in a 1:300 ratio. Phagocytosis and intracellular killing by neutrophils were assessed after 0, 30, 60, and 90 minutes by a fluorochrome assay, using acridine orange. Viability of neutrophils was assessed by use of trypan blue. Superoxide anion production and hydrogen peroxide production by neutrophils also were determined. Cows fed Se-deficient diets had significantly (P less than 0.05) lower blood Se concentration and blood glutathione peroxidase activity than cows fed Se-supplemented diets. Selenium status had no effect on the phagocytic capacity of neutrophils. Neutrophils obtained from cows fed Se-supplemented diets killed a significantly (P less than 0.05) higher percentage of ingested bacteria than did neutrophils from cows fed the Se-deficient diet. Viability was significantly (P less than 0.05) reduced by incubation with S aureus in neutrophils from both groups of cows, with neutrophils from Se-deficient cows having lower viability.(ABSTRACT TRUNCATED AT 250 WORDS)     

Zur Epidemiologie der Tollwut bei Ratten und M?usen

Ohne Zusammenfassung     

Functional convergence in hydraulic architecture and water relations of tropical savanna trees: from leaf to whole plant

Functional convergence in hydraulic architecture and water relations, and potential trade-offs in resource allocation were investigated in six dominant neotropical savanna tree species from central Brazil during the peak of the dry season. Common relationships between wood density and several aspects of plant water relations and hydraulic architecture were observed. All species and individuals shared the same negative exponential relationship between sapwood saturated water content and wood density. Wood density was a good predictor of minimum (midday) leaf water potential and total daily transpiration, both of which decreased linearly with increasing wood density for all individuals and species. With respect to hydraulic architecture, specific and leaf-specific hydraulic conductivity decreased and the leaf:sapwood area ratio increased more than 5-fold as wood density increased from 0.37 to 0.71 g cm(-3) for all individuals and species. Wood density was also a good predictor of the temporal dynamics of water flow in stems, with the time of onset of sap flow in the morning and the maximum sap flow tending to occur progressively earlier in the day as wood density increased. Leaf properties associated with wood density included stomatal conductance, specific leaf area, and osmotic potential at the turgor loss point, which decreased linearly with increasing wood density. Wood density increased linearly with decreasing bulk soil water potential experienced by individual plants during the dry season, suggesting that wood density was greatest in individuals with mostly shallow roots, and therefore limited access to more abundant soil water at greater depths. Despite their taxonomic diversity and large intrapopulation differences in architectural traits, the six co-occurring species and their individuals shared similar functional relationships between all pairs of variables studied. Thus, rather than differing intrinsically in physiological responsiveness, the species and the individuals appeared to have distinct operating ranges along common physiological response curves dictated by plant architectural and structural features. The patterns of water uptake and access to soil water during the dry season appeared to be the main determinant of wood density, which constrained evolutionary options related to plant water economy and hydraulic architecture, leading to functional convergence in the neotropical savanna trees studied.     

Invalidity of three Palaearctic species of Triaenophorus tapeworms (Cestoda: Pseudophyllidea): evidence from morphometric analysis of scolex hooks

A comparative study of the scolex hook morphology of five species of tapeworms of the genus Triaenophorus Rudolphi, 1793 (Cestoda: Pseudophyllidea), parasites of pikes (Esox lucius L. and E. reichertii Dybowski) in the Palaearctic Region, was carried out. Measurements of scolex hooks of 81 plerocercoids and 492 adults from different hosts and regions were compared using basic statistics and forward stepwise linear discriminant analysis. The shape of the scolex and that of tridental hooks were found to be suitable only for differentiation of the taxa with a similar shape of hooks, i.e. Triaenophorus nodulosus (Pallas, 1781) from T. amurensis Kuperman, 1968, and T. crassus Forel, 1868 from T. meridionalis Kuperman, 1968 and T. orientalis Kuperman, 1968, respectively. In contrast, discriminant analysis did not enable reliable separation of specimens of individual taxa of these two morphological groups due to high intraspecific variability and overlaps between species. This was reflected in low classification efficiencies (average 83%) of all species of the T. crassus group, whereas all T. amurensis specimens were misidentified as T. nodulosus. The new data also considerably enlarge (up to twofold) the size range of the species described by Kuperman in 1968, which invalidates suitability of the most important discriminant characteristic, the width of the basal plate, for delimitation of Triaenophorus species. Based on the present data, all Kuperman's taxa are considered to represent only distinct geographical populations of T. nodulosus and T. crassus. As a result, T. anmurensis is synonymized with T. nodulosus, whereas T. orientalis is considered to be a synonym of T. crassus. Previous synonymisation of T. ineridionalis with T. crassus, first proposed by Dubinina (1987), is also accepted.     

Hyperthermia in the rabbit. II. Studies on influencing respiration with exogenic hyperthermia]

Rectal temperature, respiratory rate, arterial and venous pH and arterial and venous pCO2 were recorded at intervals of 15-30 minutes in female broiler rabbits exposed an environmental temperature of 35 degrees C, until they died. Respiratory rate and blood pH rose, and pCO2 fell, until a rectal temperature of 42 degrees C was reached. Upon further increase in rectal temperature the respiratory rate and pH began to fall, while pCO2 began to rise. The rabbits died when rectal temperature reached 43 degrees C. Features of respiratory function peculiar to the rabbit were discussed.     

Effects of supplementation of medium with different antioxidants during in vitro maturation of bovine oocytes on subsequent embryo production

The aim of this study was to assess the effects of different antioxidants on the levels of reactive oxygen species (ROS) and glutathione (GSH) in oocytes during in vitro maturation (IVM), as well as on the production of embryos. Oocyte of slaughterhouse‐derived cattle ovaries were placed in IVM with different antioxidants: quercetin (2 μM), cysteamine (100 μM), carnitine (0.5 mg/ml), vitamin C (50 μg/ml) or resveratrol (2 μM). Oocytes matured without any antioxidant supplementation were used as control. The oocytes were assessed for maturation rates and for ROS and GSH levels by fluorescence staining in 2′,7′‐dichlorodihydrofluorescein diacetate and Cell Tracker Blue, respectively. Embryo production was assessed in terms of cleavage, blastocysts and hatching rates and embryo cell numbers. The results expressed in arbitrary fluorescence units showed ROS reduction (p < .05) in the groups with quercetin (27.5 ± 3.4), vitamin C (27.1 ± 3.0) or resveratrol (28.1 ± 4.7), in comparison with those with cysteamine (34.9 ± 4.5), carnitine (34.6 ± 3.8) or to the control group (36.5 ± 5.2). GSH levels increased (p < .05) in cysteamine (63.5 ± 5.5) or carnitine (60.8 ± 4.4) groups in comparison with quercetin (52.7 ± 5.1), vitamin C (53.0 ± 3.8), resveratrol (53.1 ± 4.4) or to the control (49.6 ± 4.5). Nuclear maturation cleavage and hatched blastocysts rates did not differ (p > .05) between groups. However, blastocyst rates after in vitro fertilization in quercetin (53.5 ± 3.9%), vitamin C (52.1 ± 3.1%) resveratrol (54.2 ± 4.0%), cysteamine (52.4 ± 2.7%) or carnitine (54.2 ± 3.1%) groups were higher (p < .05) than in the control (47.2 ± 2.7%). Total cell numbers in embryos from the vitamin C, resveratrol, cysteamine or carnitine groups were higher than in quercetin and control groups, which were similar to each other. The results suggest that using antioxidants during IVM may reduce oxidative stress either by decreasing ROS levels directly or by increasing GSH levels in oocytes, depending on the type of antioxidant used. Overall, oxidative stress control during IVM with the antioxidants examined here improved blastocyst development with similar efficacy.     

Impact of Salmonella Typhimurium DT104 virulence factors invC and sseD on the onset, clinical course, colonization patterns and immune response of porcine salmonellosis

The present study was conducted to study the impact of the virulence factors invC and sseD of the two type III secretion systems of Salmonella enterica serovar Typhimurium (S. Typhimurium) on the pathogenesis of the porcine S. Typhimurium DT104 infection. For this purpose, two S. Typhimurium mutant strains with a disrupted invC gene of the Salmonella pathogenicity island 1 or with a disrupted sseD gene of the Salmonella pathogenicity island 2 have been studied in experimental infection of pigs. Twenty-two 7-week-old male hybrid pigs were either infected with one of the mutants or the wild-type S. Typhimurium DT104 strain. Each group was examined for clinical signs, Salmonella shedding rate and the specific antibody response. Survival and replication were evaluated by qualitative and quantitative determination of the colonization rate. The humoral and cellular immune responses were examined using isotype-specific ELISA and quantitative real-time PCR of IL-2, IL-4, IL-10, IL-12 and IFN-gamma. The results proved that both mutants had a lower virulence (with marked differences between both mutants) than the wild-type and that both virulence factors have importance in porcine salmonellosis. Only pigs infected with the wild-type S. Typhimurium DT104 exhibited typical clinical symptoms of salmonellosis like anorexia, vomiting, disturbed demeanour, fever and diarrhoea. Deletion of the invC gene resulted in a significantly reduced colonization rate. Interestingly, the mRNA expression of both type-1 and type-2 cytokines were significantly decreased in pigs infected with either the invC-mutant and the sseD-mutant strain.