21 research outputs found
Epidemiological role of humans, dogs and cats in the transmission of Trypanosoma cruzi in a central area of Argentina
Do monospecific stands of three Fucus species (Phaeophyta) comply with the ‘self-thinning rule’?
Development of biomass and density in experimental monospecific stands of Fucus serratus, F. vesiculosus and F. spiralis was followed on Helgoland (southern North Sea) in plots with three different initial germling densities. As biomass increased over time, considerable mortality occurred. Mortality was significantly higher in stands with higher initial densities, leading to similar final densities. The self-thinning law, which describes boundary conditions for combinations of biomass and density of plants, was refuted in two ways for all three Fucus species: (i) several data points on a bi-logarithmic plane lay considerably above self-thinning lines with conventional parameters from terrestrial plant ecology; however, ‘overall boundaries’ (i.e. a self-thinning line that constrains all lines found) from terrestrial plant ecology were not significantly transgressed, (ii) lines fitted with principal components analysis (PCA) revealed a positive correlation between stand biomass and density. Reasons are proposed why seaweeds generally seem to show higher maximum biomass for a given density than terrestrial plants. Size distributions at the end of the experiment were positively skewed with high Gini coefficients that lay in the range found in other seaweed studies. Inequality decreased with individual mass and increased with density. Gini coefficients were highly correlated with other measurements of inequality (coefficient of variation, skewness)
Simulated acid rain and the reproduction of mountain birch [Betula pubescens ssp. tortuosa (Ledeb.) Nyman]: a cautionary tale
Species diversity based on vertical structure as indicators of artificial restoration for coniferous forests in Southwest China
Edge Structure Determines the Magnitude of Changes in Microclimate and Vegetation Structure in Tropical Forest Fragments1
La enfermedad del adyuvante en ratas infectadas experimentalmente con Trypanosoma cruzi
Se estudió la evolución de la artritis por adyuvante en ratas que habÃan sido infectadas previamente con Trypanosoma cruzi, con el objeto de evaluar su competencia inmunológica a través de la respuesta artrÃtica. La artritis por adyuvante se indujo en ratas adultas, endocriadas de ambos sexos, con 0.1 mi de adyuvante completo de Freund en la almohadilla plantar, en 2 lotes: a) inyectadas 90 dÃas antes con 1 x 10(6) T. cruzi y b) testigos normales simultáneos. Se midieron, la lesión artrÃtica macroscópicamente con una escala semicuantitativa, y con microscopÃa óptica la histopatologÃa de la lesión local y la del corazón, a los 180 dÃas post-infecoión. La magnitud de las lesiones artrÃticas en las ratas con T. cruzi fue significativamente menor (p < 0.001) que la de los testigos, en todo el perÃodo. El infiltrado inflamatorio local, formado por linfocitos, plasmocitos y macrófagos fue significativamente menor (p < 0.001) en las ratas chagásicas, con respecto al de los testigos. Se postula que en las ratas que recibieron T. cruzi la respuesta artrÃtica menor podrÃa deberse a una competición antigénica con los determinantes del parásito o a mecanismos inmunosupresores que interfieren en la producción de la entidad experimental