The influence of water depth and flow regime on phytoplankton biomass and community structure in a shallow,lowland river

Hydrobiologia - The taxonomic composition and biomass of phytoplankton in the San Joaquin River, California, were examined in relation to water depth, flow regime, and water chemistry. Without...     

Evolution of the electron Langmuir oscillations in an inhomogeneous magnetized plasma

The conditions under which the energy of the electron Langmuir oscillations can escape from the plasma into vacuum are determined in the simplest model of a plane slab of an inhomogeneous cold magnetized plasma in a uniform magnetic field.     

Effets sur le spermatozoïde humain du Diuron (3-(3,4-dichlorophényl)-1,1-diméthyl-urée) et de l’un de ses produits de transformation, la 3,4-dichloroaniline (3,4-DCA) (Etude préliminaire)

Diuron belongs to the family of halogenophenylureas, one of the main groups of herbicides used for more than 40 years. These herbicides absorb sunlight and can be photochemically transformed in the environment (herbicides are transformed on the soil surface exposed to sunlight) or biotransformed by microorganisms present in soil or in water. The metabolites (chlorohydroxyphenylurea, chlorophenylaniline, respectively) are more toxic than the parent compound, as demonstrated by a bioluminescence inhibition assay performed with a marine bacterium (Vibrio fischeri toxicity test). The lipophilicity of these pesticides makes the cell membrane a target for their action, especially the spermatozoa cell membrane. The aim of this study is to use human spermatozoa to evaluate the effect of this urea pesticide and its biotransformed product on the spermatozoa membrane. We investigated the structural and functional effects of these environmental pollutants on spermatozoa. Three million spermatozoa purified on a 95/47.5% Percoll gradient were suspended in 250 μl of modified Earle’s medium (without phenol red) supplemented with 7.5% of human decomplemented serum. Pesticides (Diuron or 3,4-dichloroaniline (3,4-DCA)) were added at a final concentration of 0.1; 1 and 5 mM. Samples were incubated at room temperature for 24 hours. We show that both Diuron and 3,4-DCA decrease motility and vitality of spermatozoa incubated with the highest concentration of pesticides. Our preliminary results show that the effects are more rapid and more intense with the biotransformed product (3,4-DCA) than with Diuron. Addition of herbicide to human spermatozoa increases membrane fluidity, assessed by measuring the fluorescence polarisation anisotropy with a fluorescent probe: 1,6-diphenyl-1,3,5-hexatriene (DPH). Changes in membrane fluidity may be a primary toxic effect of these herbicides. These results suggest that human spermatozoa may constitute a valuable indicator of the toxic effects of pesticides.     

Detection of albumin mRNAs in rat liver by in situ hybridization: usefulness of paraffin embedding and comparison of various fixation procedures

Our aim was to define optimal conditions for efficient and reproducible albumin mRNA detection in rat liver by in situ hybridization. We used an albumin-specific [3H]-labeled cDNA probe with a specific activity of 6-8.10(6) cpm/microgram DNA. In situ hybridization is as efficient on paraffin sections as on cryostat sections for detecting albumin mRNAs. Perfusion fixation with a 4% paraformaldehyde solution results in homogeneous RNA retention within tissue blocks, in contrast with immersion fixation, which yields heterogeneous RNA preservation. Comparison of immersion fixation with three different fixatives (paraformaldehyde, ethanol-acetic acid, and Bouin's fixative) shows that the highest level of hybridization signal is obtained with paraformaldehyde. Ethanol-acetic acid and Bouin's fixative appear less efficient for albumin mRNA detection. Loss of mRNAs within liver tissue blocks over time is largely although not completely prevented by paraffin embedding.     

A New Species of Acrodipsas Sands (Lepidoptera: Lycaenidae) from Inland New South Wales and Southern Queensland

Acrodipsas mortoni sp.n. from inland New South Wales and southern Queensland is described, figured, contrasted with the related A. arcana (Miller and Edwards) and assigned to the illidgei species-group.