Showing papers by "University of Bordeaux published in 1997"

Drug Abuse: Hedonic Homeostatic Dysregulation

Abstract: Understanding the neurobiological mechanisms of addiction requires an integration of basic neuroscience with social psychology, experimental psychology, and psychiatry. Addiction is presented as a cycle of spiralling dysregulation of brain reward systems that progressively increases, resulting in compulsive drug use and a loss of control over drug-taking. Sensitization and counteradaptation are hypothesized to contribute to this hedonic homeostatic dysregulation, and the neurobiological mechanisms involved, such as the mesolimbic dopamine system, opioid peptidergic systems, and brain and hormonal stress systems, are beginning to be characterized. This framework provides a realistic approach to identifying the neurobiological factors that produce vulnerability to addiction and to relapse in individuals with a history of addiction.

Covalent Modification of Carbon Surfaces by Aryl Radicals Generated from the Electrochemical Reduction of Diazonium Salts

Abstract: Electrochemical reduction of a wide variety of aromatic diazonium salts on carbon electrodes (glassy carbon, highly oriented pyrolytic graphite) leads to the covalent attachment of the corresponding aromatic radicals The films thus deposited on glassy carbon surfaces require mechanical abrasion to be removed Cyclic voltammetry, X-ray photoelectron spectroscopy, polarization modulation IR reflection absorption spectroscopy, Auger spectroscopy, and Rutherford backscattering spectroscopy allow the characterization of the overlayer and an estimate of the surface coverage The latter can be controlled through diazonium concentration and electrolysis duration The mechanism of derivatization is discussed on the basis of the kinetic data obtained from cyclic voltammetry and preparative electrolysis This versatile method of surface modification may find applications in the field of carbon−epoxy composites as attested by the successful binding of grafted p-aminophenyl groups with epichlorhydrin

Body mass and encephalization in Pleistocene Homo.

Abstract: Many dramatic changes in morphology within the genus Homo have occurred over the past 2 million years or more, including large increases in absolute brain size and decreases in postcanine dental size and skeletal robusticity. Body mass, as the 'size' variable against which other morphological features are usually judged, has been important for assessing these changes1–5. Yet past body mass estimates for Pleistocene Homo have varied greatly, sometimes by as much as 50% for the same individuals2,3,6–12. Here we show that two independent methods of body-mass estimation yield concordant results when applied to Pleistocene Homo specimens. On the basis of an analysis of 163 individuals, body mass in Pleistocene Homo averaged significantly (about 10%) larger than a representative sample of living humans. Relative to body mass, brain mass in late archaic H. sapiens (Neanderthals) was slightly smaller than in early 'anatomically modern' humans, but the major increase in encephalization within Homo occurred earlier during the Middle Pleistocene (600–150 thousand years before present (kyr BP)), preceded by a long period of stasis extending through the Early Pleistocene (1,800 kyr BP).

Contribution of Southern Ocean surface-water stratification to low atmospheric CO2 concentrations during the last glacial period

Abstract: Contribution of Southern Ocean surface-water stratification to low atmospheric CO 2 concentrations during the last glacial period

Complex polysaccharides as PCR inhibitors in feces: Helicobacter pylori model.

Abstract: A model was developed to study inhibitors present in feces which prevent the use of PCR for the detection of Helicobacter pylori. A DNA fragment amplified with the same primers as H. pylori was used to spike samples before extraction by a modified QIAamp tissue method. Inhibitors, separated on an Ultrogel AcA44 column, were characterized. Inhibitors in feces are complex polysaccharides possibly originating from vegetable material in the diet.

Recurrent Mutations in a Single Exon Encoding the Evolutionarily Conserved Olfactomedin-Homology Domain of TIGR in Familial Open-Angle Glaucoma

Abstract: Primary open-angle glaucoma (POAG) is a highly prevalent cause of irreversible blindness which associates cupping of the optic disc and alteration of the visual field, elevation of intraocular pressure being a major risk factor. Provided diagnosis is made at an early stage, treatments are available to prevent visual impairment. A locus, GLC1A, has been mapped on chromosome 1q23-q25 in several families affected with juvenile-onset POAG (JOAG) and also in some families affected with juvenile and middle-age onset POAG. Recently, three mutations of the TIGR (Trabecular meshwork-Induced Glucocorticoid Response) gene were shown to be responsible for the disease in several American families and in unrelated POAG patients. We now describe five new mutations in eight French families. All mutations known to date appear to concentrate in the evolutionarily conserved C-terminal domain of TIGR which bears homology to frog olfactomedin, an extracellular matrix glycoprotein of the olfactory epithelium, to rat and human neuronal olfactomedin-related proteins and to F11C3.2, a protein from Caenorhabditis elegans . Moreover, this conserved domain of TIGR is encoded by a single exon to which mutation screening could be limited. Surprisingly, the TIGR message, which is abundantly transcribed in the trabecular meshwork and also in the ciliary body and the sclera, is not expressed in the optic nerve whose degeneration is, however, the primary lesion of POAG.

Effects of acute physical exercise on central serotonergic systems

Abstract: This paper reviews data concerning the effects of acute physical exercise (treadmill running) in trained rats. Works from the 1980's have established that acute running increases brain serotonin (5-hydroxytryptamine: 5-HT) synthesis in two ways. Lipolysis-elicited release of free fatty acids in the blood compartment displaces the binding of the essential amino acid tryptophan to albumin, thereby increasing the concentration of the so-called "free tryptophan" portion, and because exercise increases the ratio of circulating free tryptophan to the sum of the concentrations of the amino acids that compete with tryptophan for uptake at the blood-brain barrier level, tryptophan enters markedly in the brain compartment. However, this marked increase in central tryptophan levels increases only to a low extent brain 5-HT synthesis, as assessed by the analysis of 5-hydroxyindoleacetic acid levels, thereby suggesting that exercise promotes feedback regulatory mechanisms. Indirect indices of 5-HT functions open the possibility that acute exercise-induced increases in 5-HT biosynthesis are associated with (or lead to) increases in 5-HT release. Lastly, the hypothesis that training and/or acute exercise triggers changes in 5-HT receptors has been examined in several studies; actually, both positive and negative results have been reached. Taken together, all these data support the need for future studies on the functional effects of exercise on 5-HT, including those related to the hypothesis that the positive mood effects of exercise rely (partly or totally) on central serotonergic systems.

Macrolide resistance in Helicobacter pylori: rapid detection of point mutations and assays of macrolide binding to ribosomes.

Abstract: Resistance of Helicobacter pylori to macrolides is a major cause of failure of eradication therapies. Single base substitutions in the H. pylori 23S rRNA genes have been associated with macrolide resistance in the United States. Our goal was to extend this work to European strains, to determine the consequence of this mutation on erythromycin binding to H. pylori ribosomes, and to find a quick method to detect the mutation. Seven pairs of H. pylori strains were used, the parent strain being naturally susceptible to macrolides and the second strain having acquired an in vivo resistance during a treatment regimen that included clarithromycin. The identity of the strains was confirmed by random amplified polymorphic DNA testing with two different primers, indicating that resistance was the result of the selection of variants of the infecting strain. All resistant strains were found to have point mutations at position 2143 (three cases) or 2144 (four cases) but never on the opposite DNA fragment of domain V of the 23S rRNA gene. The mutation was A-->G in all cases except one (A-->C) at position 2143. Using BsaI and BbsI restriction enzymes on the amplified products, we confirmed the mutations of A-->G at positions 2144 and 2143, respectively. Macrolide binding was tested on purified ribosomes isolated from four pairs of strains with [14C]erythromycin. Erythromycin binding increased in a dose-dependent manner for the susceptible strain but not for the resistant one. In conclusion we suggest that the limited disruption of the peptidyltransferase loop conformation, caused by a point mutation, reduces drug binding and consequently confers resistance to macrolides. Finally, the macrolide resistance could be detected without sequencing by performing restriction fragment length polymorphism with appropriate restriction enzymes.

Light Limitation and Distribution of Chlorophyll Pigments in a Highly Turbid Estuary: the Gironde (SW France)

Abstract: Chlorophyll pigment and suspended particulate matter (SPM) concentrations were measured in two well-differentiated areas in the Gironde Estuary. The maximum turbidity zone (MTZ) was characterized by very high turbidities, low Chl a /SPM ratios and associated low variability of this ratio, and by a highly significant relationship between chlorophyll pigments (chlorophyll a and phaeopigments) and SPM. Seaward of the MTZ, where SPM concentration is lower, the relationship between Chl a and SPM disappeared during phytoplanktonic blooms, the values of Chl a /SPM ratio were higher and there was a high variability of this ratio. Data obtained from stations positioned along the salinity gradient indicate that the spatial distribution of Chl a /SPM ratio in the Gironde is explained by the relation between the mixing depth (Zm) and euphotic depth (Zeu). The estimate of the Zm/Zeu ratio suggests that there is virtually no possibility for phytoplankton primary production in the MTZ but cannot explain the presence of Chl a in very highly turbid areas (>1 g l −1 ). An important percentage of the chlorophyll in the MTZ probably originates from re-suspended microphytobenthos. Photosynthetic activity is reduced as a consequence of light limitation due to high turbidities. This enables the ecosystem to contain a great input of nutrients without eutrophication.

Social relations and depressive symptomatology in a sample of community-dwelling French older adults.

Abstract: This study examined the association between social relations and mental health, specifically the relative contribution of social networks and social support to depressive symptomatology. The culturally unique representative sample consisted of 3,777 noninstitutionalized older persons living in southwestern France. The findings indicated that French older adults generally had more than 8 people in their networks, their networks consisted mostly of family members, and they felt understood by most of their network members. These older adults reported being satisfied with their social relations. Sociodemographic variables contribute (R2 = .143) to depressive symptomatology, as did social network (incremented R2 = .033) and social support (incremented R2 = .09) variables. Sociodemographic, social network, and social support variables together increased the variance explained still further (incremented R2 = .108). Results were consistent with similar analyses in the U.S. and indicated that social support variables account for more variance in depressive symptomatology than social network variables.

200 Year interruption of Holocene sapropel formation in the Adriatic Sea

Abstract: . An interruption of Holocene sapropel S1 is found in cores from various subbasins of the eastern Mediterranean. In core IN68-9 from the Adriatic Sea, sapropel S1 is dated between 8300 and 6340 BP, interrupted between 7100 and 6900 BP (14C years uncorrected for reservoir age). Lithology and variations in the foraminiferal faunas suggest that the interruption is genuine, and not the result of resedimentation. The results indicate that S1 was deposited within a period of enhanced levels of productivity (resulting from increased seasonal contrasts) which started around 9300 BP and ended around 5200 BP. The onset, interruption, and final ending of S1 deposition in the Adriatic Sea, however, appear to have been triggered by changes in ventilation of the basin related to changes in sea surface temperature (SST). Although the rough estimates of SST change are relatively small (