Very Low Phytoplankton Diversity in a Tropical Saline-Alkaline Lake, with Co-dominance of Arthrospira fusiformis (Cyanobacteria) and Picocystis salinarum (Chlorophyta).

Lake Dziani Dzaha (Mayotte Island, Indian Ocean) is a tropical thalassohaline lake which geochemical and biological conditions make it a unique aquatic ecosystem considered as a modern analogue of Precambrian environments. In the present study, we focused on the diversity of phytoplanktonic communities, which produce very high and stable biomass (mean2014-2015 = 652 ± 179 µg chlorophyll a L-1). As predicted by classical community ecology paradigms, and as observed in similar environments, a single species is expected to dominate the phytoplanktonic communities. To test this hypothesis, we sampled water column in the deepest part of the lake (18 m) during rainy and dry seasons for two consecutive years. Phytoplanktonic communities were characterized using a combination of metagenomic, microscopy-based and flow cytometry approaches, and we used statistical modeling to identify the environmental factors determining the abundance of dominant organisms. As hypothesized, the overall diversity of the phytoplanktonic communities was very low (15 OTUs), but we observed a co-dominance of two, and not only one, OTUs, viz., Arthrospira fusiformis (Cyanobacteria) and Picocystis salinarum (Chlorophyta). We observed a decrease in the abundance of these co-dominant taxa along the depth profile and identified the adverse environmental factors driving this decline. The functional traits measured on isolated strains of these two taxa (i.e., size, pigment composition, and concentration) are then compared and discussed to explain their capacity to cope with the extreme environmental conditions encountered in the aphotic, anoxic, and sulfidic layers of the water column of Lake Dziani Dzaha.

Phytoplankton distribution and productivity in a highly turbid, tropical coastal system (Bach Dang Estuary, Vietnam).

Phytoplankton diversity, primary and bacterial production, nutrients and metallic contaminants were measured during the wet season (July) and dry season (March) in the Bach Dang Estuary, a sub-estuary of the Red River system, Northern Vietnam. Using canonical correspondence analysis we show that phytoplankton community structure is potentially influenced by both organometallic species (Hg and Sn) and inorganic metal (Hg) concentrations. During March, dissolved methylmercury and inorganic mercury were important factors for determining phytoplankton community composition at most of the stations. In contrast, during July, low salinity phytoplankton community composition was associated with particulate methylmercury concentrations, whereas phytoplankton community composition in the higher salinity stations was more related to dissolved inorganic mercury and dissolved mono and tributyltin concentrations. These results highlight the importance of taking into account factors other than light and nutrients, such as eco-toxic heavy metals, in understanding phytoplankton diversity and activity in estuarine ecosystems.

Survival study of enterotoxigenic Escherichia colistrain in seawater and wastewater microcosms.

In order to survey osmotic and oligotrophic stress consequence on pathogenic enterobacteria discharged in marine areas, we examined enterotoxigenic Escherichia coli (ETEC) and a reference (Ecoli O126:B16) strains during their survival (47 days) in wastewater microcosms, submerged in natural seawater and maintained in laboratory conditions. The results revealed that the survival time for the two strains was prolonged when bacterial cells were previously incubated in wastewater, with less cellular membrane damage. In addition, the wild clinical E. coli strain showed a better survival capacity than the reference E. coli strain one. For both, we noted some modifications in biochemical profiles relatively to the initial state, notably when they were previously incubated in wastewater microcosm.

Survival of Escherichia coli strains in Mediterranean brackish water in the Bizerte lagoon in northern Tunisia.

This study investigated survival and virulence of Escherichia coli strains exposed to natural conditions in brackish water. Two E. coli strains (O126:B16 and O55:B5) were incubated in water microcosms in the Bizerte lagoon in northern Tunisia and exposed for 12 days to natural sunlight in June (231 to 386 W/m2, 26 +/- 1 degrees C, 30 g/L) and in April (227 to 330 W/m2, 17 +/- 1 degrees C, 27 g/L) or maintained in darkness for 21 days (17 +/- 1 degrees C, 27 g/L). The results revealed that sunlight was the most significant inactivating factor (decrease of 3 Ulog within 48 hours for the two strains) compared to salinity and temperature (in darkness). Survival time of the strains was prolonged as they were maintained in darkness. Local strain (E. coli O55:B5) showed better survival capacity (T90 = 52 hours) than E. coli O126:B16 (T90 = 11 h). For both, modifications were noted only for some metabolic activities of carbohydrates hydrolysis. Cytotoxicity of the two strains, tested on Vero cell, was maintained during the period of survival.

[Preliminary study of the environmental effect on Aeromonas hydrophila's survival]. / Etude préliminaire de l'effet des facteurs environnementaux sur la survie d'Aeromonas hydrophila.

A survival of A. hydrophila B3 has been conducted in different conditions (mineral water, seawater exposed or not to the sunlight). Also, unculturable forms have been detected by using epifluorescence microscopy. Thus, different kinds of microcosms were prepared using filtered and autoclaved marine water or mineral water, inoculated by A. hydrophila B3 and maintained or not in room light. Further, we tested the survival of A. hydrophila B3 incubated in seawater and exposed to sunlight. Our results revealed that the culturable count of A. hydrophila B3 incubated in different conditions declined. Nevertheless, no variations were obtained for the total bacterial cells. Morphological, biochemical and antimicrobial modifications were noted.

Water quality and health status of the Senegal River estuary.

The Senegal River estuary was sampled in May 2002 to get the first data on both the trophic and sanitary status of the water of the main river of the northwest African coast. Several physical, chemical and microbiological variables were measured twice along a transect. Inorganic nutrient concentrations were low while phytoplanktonic abundances (0.58-1.8 x 10(5) cells ml(-1)), bacterial abundances (0.27-8.1 x 10(7) cells ml(-1)), activity (22-474 pmol l(-1) h(-1)), were among the highest recorded in such ecosystems. Microbiological variables revealed a eutrophicated status for this estuary. Largest abundances of fecal contamination bacterial indicators were only detected in localized areas (Saint-Louis city and surrounding areas). The apparent good survival of fecal indicator bacteria in the estuarine waters despite a long residence time (4-5 days) has been evaluated by complementary survival experiments. Exposed to a salinity gradient, a local Escherichia coli strain showed a significantly better survival than those of an E. coli reference strain.

Bacterial contamination of Mediterranean coastal seawater as affected by riverine inputs: simulation approach applied to a shellfish breeding area (Thau lagoon, France).

Consequences of short-term changes in thermotolerant coliform loads on their spatio-temporal distribution in a Mediterranean lagoon with large-scale mollusk farming (Thau lagoon, France) were explored using a simulation approach. Simulations were based on bacterial transport and survival coupled models forced by the input of bacterial loads from the two main rivers (Vène and Pallas) that flow into the lagoon. Different flow types (reference, sudden and constant), bringing the same bacterial load, were considered and subsequent spatial and temporal bacterial contamination of lagoon surface water and shellfish was estimated. Simulation results showed that as long as loads were high, hydrodynamical processes governed the distribution of bacterial abundance in receiving areas. As soon as loads decreased or when time supply increased, biological die-off processes became dominant. Bacterial contamination of shellfish induced by the different flow types appeared to depend on the receiving area. In the case of Pallas River area, a sudden input of bacteria led to a high bacterial contamination of shellfish but only during a short period ( approximately 1 day). A constant input of the same amount of bacteria induced a lower but significant contamination during all the simulation period (10 days). On the contrary, bacterial inputs from the Vène River led to shellfish contamination only when bacteria were delivered through a flood event. Exposure time of bacteria to adverse environmental conditions appeared to be the main explanation to the above-mentioned differences. Consequences of our results in terms of environmental management strategy were discussed.

Physiological changes of Salmonella typhimurium cells under osmotic and starvation conditions by image analysis.

The effects of starvation and salinity on the physiology of Salmonella typhimurium were investigated in a microcosm study. The physiological changes were monitored by using fluorochromes dyes such as DAPI (4',6-diamidino-2-phenylindole) for evaluation of the genomic content, CTC (5-cyano-2,3-ditolyl tetrazolium chloride) for respiratory activity and syto 9 and propidium iodide for cytoplasmic membrane damages. The metabolic activity of the cellular population was assessed with the method of Kogure (direct viable count), to enumerate the substrate-responsive cells. These different staining procedures were objectively analysed by an image analysis system. This paper describes the progressive alteration of Salmonella typhimurium physiology under salinity and starvation conditions.

Viability and virulence of experimentally stressed nonculturable Salmonella typhimurium.

Maintenance of pathogenicity of viable but nonculturable Salmonella typhimurium cells experimentally stressed with UV-C and seawater, was investigated relative to the viability level of the cellular population. Pathogenicity, tested in a mouse model, was lost concomitantly with culturability, whereas cell viability remained undamaged, as determined by respiratory activity and cytoplasmic membrane and genomic integrities.

Production and characterization of 22 monoclonal antibodies directed against S 20499, a new potent 5-HT1A chiral agonist: influence of the hapten structure on specificity and stereorecognition.

PURPOSE: An immunoconjugate model was proposed to produce stereoselective monoclonal antibodies (MAbs) for the quantitation of a 5-HT1A agonist, S 20499. MAbs produced were characterized in terms of stereoselectivity and specificity towards the opposite enantiomer and structural analogs. METHODS: The immunogen was formed following the effective addition of a butanoic acid spacer arm between the parent S 20499 structure and bovine serum albumin (BSA). After fusion (modified Köhler and Milstein's procedure), specificity of MAbs was obtained using the Abraham's criteria. Experimental and calculated partition coefficients were determined. RESULTS: Twenty-two hybridoma cell lines were established secreting MAbs (apparent association constants ranging from 1.1 x 10(8) to 2.8 X 10(9) M(-1)). Several MAbs showed cross-reactivity levels of less than 5% with S 20500 (optical antipode), which could allow a stereospecific assay to be set up. Both chroman and azaspiro moieties were part of the epitopic site. Dealkylation and hydroxylation(s) led to various crossreactivity levels. Four antibody families were described in terms of specificity. CONCLUSIONS: This study highlighted the influence of the immunoconjugate construction (coupling site and type of spacer arm) in the immuno-stereospecificity of Abs. The results obtained for two monohydroxylated metabolites suggest that the lipophilicity behavior could be a valuable tool for predicting Ab-crossreactivity.

Production and characterization of polyclonal anti-S 20499 antibodies: influence of the hapten structure on stereospecificity.

Immunoassays were studied as an alternative to HPLC methods for the stereoselective determination of a chiral drug, S 20499, a new anxiolytic compound that is chemically related to buspirone. The production of highly stereospecific polyclonal antibodies was sought following the construction of appropriately optimized hapten-protein conjugates. This process involved the selection of the structure and the length of the spacer arm used to couple S 20499 to the carrier protein as well as deciding on the location of the coupling site with respect to the chiral center. Two haptens were prepared: one a derivative resembling the original structure of S 20499, with the effective addition of a carboxylic acid group, and a second with the effective addition of a butanoic acid moiety that is supposed to favor stereorecognition. Six stereospecific polyclonal antisera were obtained in rabbits with two groups of antibody families defined in terms of specificity. Both approaches gave high levels of stereospecificity (cross-reactivity towards the optical antipode of S 20499 ranged from 4.1% to < 0.1%). Although it did not decrease the mean apparent affinity constant, the longer spacer improved antibody specificity by decreasing cross-reactions towards dealkylated S 20499 derivatives. Hence, the addition of a four carbon atom bridge should be a valuable tool for increasing antibody stereospecificity with no drawbacks in terms of specificity and affinity. It was also shown that long immunization periods appear to have no effect on the stereospecificity of the antibodies obtained.

Acetonitrile as a possible marker of current cigarette smoking.

Volatile nitriles are present in cigarette smoke. We tested the hypothesis that the presence of any of four nitriles in the blood can serve as a marker of recent cigarette smoking. We determined the sensitivity and specificity of these nitriles as indicators of daily cigarette smoking in 24 smokers (Group A) and 18 non-smokers (Group B), as well as the correlation between intensity of daily smoking and the blood concentration of acetonitrile. A new head space GLC assay method was used. Of the four nitriles, only acetonitrile was present in the blood of any study subject. Acetonitrile was moderately sensitive (67%) and entirely specific (100%) for self-reported daily smoking. There was fair correlation between blood acetonitrile concentration and the average daily number of cigarettes smoked (r2 = 0.39; P = 0.001), and the mean blood acetonitrile concentration was significantly higher (P = 0.03) among subjects with higher (> 10 cigarettes per day) current cigarette exposure (148.3 +/- 18.0 micrograms/l) than among smokers with low or minimal (1-10 cigarettes per day) exposure (43.3 +/- 6.0 micrograms/l). Thus, acetonitrile in blood appears to be highly specific and a moderately sensitive marker of cigarette smoking with a dose-effect relationship. As such, acetonitrile shows promise as a marker of current cigarette exposure.

Stereoselectivity of antibodies for the bioanalysis of chiral drugs.

The use of immunoassay techniques represents an alternative approach to the more common chromatographic methods for the determination of the concentrations of chiral drugs. In the development of the former technique, the inherent stereoselectivity of the antibodies used appears to be an important parameter to be studied. The structural features of the drug, including the environment around the asymmetric center, the flexibility of the molecule and the ability of the molecule to undergo racemization, contribute to the molecule's ability to be recognized by stereoselective antibodies. These parameters are intrinsic and can not be influenced by the investigator. On the other hand, other parameters can be modified to favor the raising of highly stereoselective antibodies. These include the synthesis of an appropriate hapten; the selection of an optimal spacer arm between the hapten and the carrier protein used for the immunization procedure; and the choice of appropriate immunization and antibody-screening procedures. The purification of antibodies using affinity chromatography may also facilitate the selection of stereoselective antibodies.

Morphine disposition in opiate-intoxicated patients: relevance of nonspecific opiate immunoassays.

The use of routine nonspecific immunoassays to detect or quantitate opiates in biological fluids raises the question of the relevance of such immunoassays in the investigation of opiate overdose disposition. We investigated the plasma disposition of morphine in 13 patients intoxicated by the intravascular (i.v.) (n = 5) or oral routes (n = 8) using both a highly morphine-specific antibody radioimmunoassay (RIA) and a nonspecific morphine RIA. Both RIAs showed a first-order elimination rate after i.v. intoxication (apparent plasma terminal half-life ranged from 2.9 to 4.7 hours for unchanged morphine and from 3.2 to 4.9 hours for total opiates) and a persistent opiate concentration with rebound after oral ingestion, suggesting a slow release of opiates from the gastrointestinal tract, in dealers and bodypackers. Moreover, i.v. and oral kinetic data were similar for the two RIAs, except for the ratio between total and unchanged morphine concentrations. The nonspecific morphine assay gave a threefold to 16-fold higher concentration than the specific morphine assay but with parallel kinetics for all patients. We conclude that the current, routine nonspecific morphine immunoassays could be a valuable analytical tool for investigating opiate toxicokinetics.

A soluble factor released by CD8+CD57+ lymphocytes from bone marrow transplanted patients inhibits cell-mediated cytolysis.

We report a new inhibitory activity of CD8+CD57+ peripheral blood lymphocytes from allo-bone marrow transplant patients. Positively selected CD8+CD57+ lymphocytes act as potent inhibitors of allospecific cytolytic T lymphocyte and lymphokine activated killer cell cytolytic activities. These suppressor cells are mature T cells expressing the CD2, 5, 7, CD3-TcR alpha beta complex, and lack natural killer cell markers as well as cytolytic function. Their inhibitory activity on both cytolytic processes and T-cell proliferation is mediated by a non-antigen-specific soluble factor released by CD8+CD57+ cells in culture supernatants. Preliminary characterization suggests that the CD8+CD57+ cells' inhibitory activity is mediated by a low molecular weight, glycosylated factor as indicated by its less than 1S coefficient of sedimentation and its binding to concanavalin A lectin.

Morphine pharmacokinetics and pain assessment after intracerebroventricular administration in patients with terminal cancer.

Morphine pharmacokinetics and pain relief were evaluated after intracerebroventricular administration of morphine (0.4 +/- 0.11 mg) in seven patients with cancer suffering from intractable pain. Ventricular cerebrospinal fluid (CSF), lumbar CSF, and plasma morphine concentrations were analyzed by a specific morphine radioimmunoassay. A two-compartment model was sufficient to describe the kinetics of morphine in ventricular CSF. Morphine diffuses to the lumbar level, and the mean maximum concentration was 192 +/- 105 ng/ml at 4.5 +/- 1.3 hours. Ventricular and lumbar CSF morphine kinetics showed a similar decline during the elimination phase, with terminal half-lives of 3.8 +/- 0.6 hours and 4.2 +/- 1.6 hours, respectively. Pain relief was evaluated by a visual analog scale: the test showed a rapid onset of analgesia (less than 10 minutes). Analgesic effectiveness reached a maximum between 6 and 10 hours. The relationship between pharmacologic effect and morphine concentrations in ventricular CSF resulted in an anticlockwise hysteresis curve. The presence of morphine in lumbar CSF suggested an additive spinal action of morphine, which probably plays a role in the duration of analgesia.

[Glycogen synthase activity in parodontal disease (author's transl)]. / Activite glycogene-synthase dans la maladie paradontale.

A biochemical study of an enzyme participating in the synthesis of glycogen is presented, with particular regard to the fluctuations in the amounts of this polysaccharide in human gingival epithelium, during inflammation. The increase in the activity of UDPglucose : glycogen glucosyltransferase can be related to the accumulation of glycogen. Some kinetic parameters of this enzyme are described.