The importance of gravity vector on adult mammalian organisms: Effects of hypergravity on mouse testis.

In the age of space exploration, the effect of hypergravity on human physiology is a relatively neglected topic. However, astronauts have several experiences of hypergravity during their missions. The main disturbance of altered gravity can be imputed to cell cytoskeleton alteration and physiologic homeostasis of the body. Testis has proved to be a particularly sensible organ, subject to environmental alteration and physiological disturbance. This makes testis an organ eligible for investigating the alteration following exposure to altered gravity. In our study, mice were exposed to hypergravity (3g for 14 days) in the Large Diameter Centrifuge machine (ESA, Netherland). We have observed a morphological alteration of the regular architecture of the seminiferous tubules of testis as well as an altered expression of factors involved in the junctional complexes of Sertoli cells, responsible for ensuring the morpho-functional integrity of the organ. The expression of key receptors in physiological performance, such as Androgen Receptors and Interstitial Cells Stimulating Hormone receptors, was found lower expressed. All these findings indicate the occurrence of altered physiological organ performance such as the reduction of the spermatozoa number and altered endocrine parameters following hypergravity exposure.

Assessing the occurrence of a stress syndrome in mussels (Mytilus edulis) using a combined biomarker/gene expression approach.

A combination of biomarkers and gene expression analyses was used to investigate the occurrence of a stress syndrome in mussels (Mytilus edulis) caged along a copper pollution gradient in the Visnes fjord, Norway. The stress level in mussels, as calculated by a novel algorithm (the "Expert System") from a set of seven biomarkers, was compared with gene expression changes utilising a low-density oligonucleotide microarray, employing 24 different genes involved in both cellular homeostasis and stress-related responses. The biomarker battery included lysosomal membrane stability, lysosomal accumulation of neutral lipids and lipofuscin, lysosomal/cytoplasm volume ratio, Ca(2+)-ATPase and catalase activities, and total metallothionein content. Integration of the biomarkers into the Expert System ranked individuals sampled at site 2 as unstressed, mussels sampled at site 3 as being subject to low stress, and those from site 4, which is adjacent to what used to be a copper mine, as being highly stressed, with respect to specimens sampled from the reference site. Microarray analyses demonstrated that at the two innermost and mostly polluted sites, gene expression patterns where severely altered. In particular, some genes exhibited a linear activation response along the copper gradient, e.g. metallothioneins mt 20 and mt 10, and catalase. In addition, stress responsive kinase (krs), glutathione transferase (gst), major vault protein and histones (h1, h2a and h4) were significantly up-regulated at the innermost site. In conclusion, these results demonstrated that sites could be discriminated using both a physiological and a molecular approach. The development of a stress syndrome along the pollution gradient was evidenced with a novel mussel microarray, both in terms of numbers of regulated genes and level of gene response.

Application of a biomarker battery for the evaluation of the sublethal effects of pollutants in the earthworm Eisenia andrei.

We applied a battery of biomarkers in the earthworm Eisenia andrei to assess the pollutant-induced stress syndrome. Earthworms were exposed to sublethal concentrations of copper (1-10 microM) and benzo[a]pyrene (0.01-10 microM) as models of inorganic and organic pollutants for 1, 3 and 7 days. Four potential biomarkers of stress were measured: lysosomal membrane stability of coelomocytes, lysosomal accumulation of lipofuscin in chloragogenous tissue and of neutral lipids in coelomatic cells, plasma membrane Ca2+-ATPase activity in the intestinal epithelium; metallothionein content was also evaluated as a biomarker of exposure. Significant changes were observed in the parameters measured in earthworms exposed to both contaminants. Certain biomarkers, such as lysosomal membrane stability and Ca2+-ATPase activity, that showed a decreasing trend with increasing pollutant concentration and time of exposure, proved to be particularly suitable to describe the evolution of a stress syndrome from its early phase to the development of pathological conditions. On the other hand, contaminant-induced changes in lysosomal lipofuscin and neutral lipid accumulation showed a bell-shaped trend, indicating that these biomarkers are able to follow the development of pollutant-induced stress syndrome as far as an equilibrium in the cell functions is maintained; therefore, they are particularly useful to describe mild stress conditions.

Colonization pattern of primary tomato roots by Pseudomonas fluorescens A6RI characterized by dilution plating, flow cytometry, fluorescence, confocal and scanning electron microscopy.

Early colonization of primary tomato roots, grown in vitro, by Pseudomonas fluorescens A6RI, introduced by seed bacterization, was monitored for 7 days in three different root zones (zone A, apex+elongation+young hairy zone; zone B, hairy zone; zone C, old hairy zone+collar). Bacterial quantification was assessed by enumeration of (i) colony forming units (cfu) after dilution plating and of (ii) total bacterial cells by flow cytometry. Bacterial distribution and organization in the root zones were analyzed by fluorescence, confocal and scanning electron microscopy. For all sampling dates and zones, the densities of total bacterial cells were significantly higher than those of the cfu. The kinetics of cfu densities varied according to the root zone. Their density decreased with time in zone A, while no variation with time was recorded in zones B and C. Densities of total bacterial cells did not show any significant temporal variation for any of the root zones. Microscopic analyses allowed the characterization of the distribution and organizational patterns of the bacterial cells according to time and space. In 3-day-old plants, bacteria were mostly present as single cells and were evenly distributed in the two root zones analyzed (A and B). In 5- and 7-day-old plants, distribution and organization differed according to the root zone. In zone A, only few single cells were observed, whereas zones B and C were mostly covered by cells localized between epidermal root cells and organized in pairs and strings, respectively.