Chronic metal contamination shapes the size structure of Gammarus fossarum populations in French headwater rivers.

Assessing the effects of multigenerational exposure of aquatic animal populations to chemical contamination is essential for ecological risk assessment. However, beyond rare examples reporting the sporadic emergence of a toxicological tolerance within populations that persist in contaminated environments, conclusive results are even more limited from field studies when it comes to the alteration of life-history traits. Here, we investigated whether long-term exposure to cadmium (Cd) influences size-related life-history traits (i.e., size at puberty, median adult size, maximum size) in Gammarus fossarum, a keystone species of European stream ecosystems. We studied 13 field populations of G. fossarum (cryptic lineage B) living in headwater rivers located in natural areas scattered at a large geographical scale and exposed to contrasted bioavailable Cd contamination levels due to different local geochemical backgrounds. We achieved a detailed description of the physical and physicochemical conditions of the river reaches investigated. Land-use parameters, hydrological characteristics (flow, slope, river width, flow structure, mosaic of substrates), and physicochemical conditions (temperature, conductivity, dissolved oxygen) were measured. Metallic bioavailable contamination was assessed using a standardized active biomonitoring procedure (Gammarus caging). Based on the field demographic census of the 13 populations, our results demonstrated that chronic Cd contamination significantly influences life-history in the G. fossarum species, with a significant reduction in all size traits of populations (size at puberty, median adult size, maximum size). In addition, we confirmed Cd-tolerance in contaminated populations during exposure tests in the laboratory. Various hypotheses can be then put forward to explain the modification of size-related life-history traits: a direct toxic effect of Cd, a cost of Cd-tolerance, or an adaptive evolution of life-history exposed to toxic pressure.

Effects of a peroxisome proliferator on beta-oxidation and overall energy balance in obese (fa/fa) rats.

The aim of the study was to examine in the obese Zucker (fa/fa) rats the effect of a peroxisome proliferator nafenopin on liver and brown adipose tissue peroxisomal and mitochondrial beta-oxidation enzyme activities and on the overall energy dissipation. A 17-day nafenopin treatment increased liver wet weight 2.1-fold and liver total acyl-CoA oxidase and mitochondria beta-oxidative activities 32- and 4.6-fold, respectively. It increased the interscapular brown adipose tissue (IBAT) acyl-CoA oxidase activity 2.1-fold but had no effect on the mitochondria beta-oxidative activity. Because nafenopin was found to decrease food intake by 22%, obese nafenopin-treated rats were compared with a group of obese pair-fed rats. Both food restriction and nafenopin treatment decreased body weight gain, but a decrease (14%) in fat content was only observed in nafenopin-treated rats. Food restriction of obese rats decreased the mean metabolic rate by 13%, and nafenopin treatment prevented this decrease. Both food restriction and nafenopin treatment decreased the mean daily respiratory quotient (RQ). However, the RQ of nafenopin-treated rats was steadily lower than that of control, whereas that of food-restricted rats was the same as that of control animals during the feeding period and decreased when food supply was exhausted. The increase in liver and IBAT fatty acid beta-oxidative activities may be the cause of the decreased lipid accretion measured in obese rats.

[Full impressions with silicone elastomers. The wash technic]. / Empreinte globale aux élastomères silicones. La wash-technique.

The wash-technic is one of the most well known and most used impression technic when using elastomeric silicones. It is however one of the most criticized technic. The wash-technic depends on Biomaterials and on operative procedures. After reviewing the two types of elastomeric silicones available and the properties that are required for this technic, the author shows that additive materials are reliable and successful when used for the wash-technic. Nevertheless to eliminate all possible deformations due to internal tensions of the materials, it is very important to follow strict operative procedures (specially for the pre-impression preparation), and to respect the contra-indications of this technic.

Biochemical characterization of brown adipose tissue beta-adrenergic receptor.

The beta-adrenergic receptor of rodent brown fat plays a key role in the control of energy dissipation by this tissue. The aim of the present study was to further characterize the biochemical properties of this receptor. The beta-receptor of rat interscapular brown adipose tissue plasma membranes was found to bind the beta-adrenergic antagonist [125I]cyanopindolol with a high affinity (KD 67 pM). The [125I]cyanopindolol receptor complex could be solubilized by digitonin and the isoelectric point of the solubilized receptor was found to be 5.8. Brown adipose tissue plasma membranes were labeled with the photoaffinity ligand [125I] cyanopindolol diazirine and labeled membrane proteins were separated by sodium dodecylsulfate polyacrylamide gel electrophoresis and analyzed by autoradiography. Autoradiograms revealed a peptide of 62 kDa whose labeling was stereoselectively displaced by alprenolol and isoproterenol. The beta 1-selective antagonist betaxolol was about 100 times more potent in displacing the labeling of this 62 kDa peptide than the beta 2-selective antagonist ICI 118,551. Based upon these data, it appears that the beta-receptor in brown adipose tissue is a beta 1 subtype with molecular weight of 62 kDa.

Mitochondrial and peroxisomal beta-oxidations in pig coronary smooth muscle cells.

1. The total subcellular membranes of pig coronary media were fractionated using a sucrose density gradient. 2. A fraction with high succinate dehydrogenase activity and a mean density of 1.165 was separated from a fraction with high catalase activity and a mean density of 1.145. 3. Acyl CoA beta-oxidation activity measured in the absence of BSA was present in both fractions with 47% of the total activity in the succinate dehydrogenase fraction and 47% in the catalase fraction. 4. In the succinate dehydrogenase fraction bovine serum albumin stimulated the acyl CoA beta-oxidation (maximal stimulation, 3.2 times at a concentration of 15 mg%) while in the catalase fraction it had no effect. 5. It is concluded that, in pig coronary media, the beta-oxidation system has two components, i.e. mitochondrial and peroxisomal beta-oxidation.