Amadou Diouf

Relationship between physicochemical characterization and toxicity of fine particulate matter (PM2.5) collected in Dakar city (Senegal).

The massive increase in emissions of air pollutants due to economic and industrial growth in developing countries has made air quality a crucial health problem in this continent. Hence, it is somewhat critical to have a better knowledge on the air pollution in Sub-Saharan Africa countries. Three air pollution PM2.5 samples were also collected in two urban sites (i.e., Fann and Faidherbe) in Dakar (Senegal) and in a rural site near Dakar (i.e., Ngaparu). The two urban sites mainly differ in the type of used vehicles: in Fann, most of the traffic is made of buses, which are absent, in Faidherbe. The physicochemical characteristics of the three PM2.5 samples revealed their high heterogeneities and complexities, related to the multiple natural and anthropogenic emission sources. Results from 5-bromodeoxyuridine incorporation into DNA, mitochondrial dehydrogenase activity, and extracellular lactate dehydrogenase activity in PM2.5-exposed BEAS-2B cells suggested the exposure conditions (i.e., 3 and 12 μg PM/cm² during 24, 48, and 72 h) to further consider. The organic fractions (i.e., mainly PAHs) of the PM(2.5) samples were able to induce a time and/or concentration-dependent gene expression of CYP1A1 and CYP1B1, and, to a lesser extent, NQO1. There was a time and/or dose-dependent increase of both the gene expression and/or protein secretion of inflammatory mediators (i.e., TNF-α, IL-1β, IL-6, and/or IL-8) in PM(2.5)-exposed BEAS-2B cells. In agreement with the physicochemical characterization, urban PM(2.5) samples caused greater biological responses in BEAS-2B cells than the rural one. Variable concentrations of transition metals (i.e., Fe, Al, Pb, Mn, Zn) and organic compounds (i.e., PAHs) founded in the three PM2.5 samples might be firmly involved in a time- and/or dose-dependent toxicity, relying on inflammatory processes.

Randomized, comparative study of the efficacy and safety of artesunate plus amodiaquine, administered as a single daily intake versus two daily intakes in the treatment of uncomplicated falciparum malaria

BackgroundArtesunate plus amodiaquine is a coblistered ACT, given as a single daily intake. It has been suggested that, in view of the number of tablets to be taken (particularly in adults), it may be possible to improve compliance by allowing patients to divide the daily dose. The objectives of this randomized, comparative, open-label, multicentre study, conducted in Senegal and in Cameroon in 2005, was to demonstrate the non-inferiority and to compare the safety of artesunate plus amodiaquine, as a single daily intake versus two daily intakes.MethodsA three-day treatment period and 14-day follow-up period was performed in any subject weighting more than 10 kg, presenting with a malaria paroxysm confirmed by parasitaemia ≥ 1,000/μl, after informed consent. Patients were randomly allocated into one of the two regimens, with dosage according to bodyweight range. All products were administered by an authorized person, blinded to both the investigating physician and the biologist. The primary endpoint was an adequate response to treatment on D14 (WHO definition). The two-sided 90% confidence interval of the difference was calculated on intent to treat (ITT) population; the acceptance limit for non-inferiority was 3%. The safety was evaluated by incidence of adverse events.ResultsThree-hundred and sixteen patients were included in the study. The two patient groups were strictly comparable on D0. The adequate responses to treatment were similar for the two treatment regimens on D14, PCR-corrected (99,4% in the one-daily intake group versus 99,3% in the comparative group). The statistical analyses demonstrated the non-inferiority of administering artesunate/amodiaquine as two intakes. The drug was well tolerated. The main adverse events were gastrointestinal disorders (2.5%) and pruritus (2.5%); safety profiles were similar in the two groups.ConclusionThis pilot study confirms the efficacy and good tolerability of artesunate plus amodiaquine, administrated either in one or in two daily intakes.

Effects of environmental cadmium and lead exposure on adults neighboring a discharge: Evidences of adverse health effects

The purpose of the study was to determine Pb and Cd concentrations in humans and to assess the effect of co-exposure to these metals on biomarkers of oxidative stress and nephrotoxicity. Blood and urine levels of Pb and Cd, oxidative stress and urinary renal biomarkers were measured in 77 subjects neighboring a discharge and 52 in the control site. Exposed subjects showed significantly higher levels of lead and cadmium in blood and urine than the controls. Excessive production of reactive oxygen species induced by these metals in exposed subjects conducted to a decrease in antioxidant defense system (GPx, Selenium, GSH) and an increase in lipid peroxidation (MDA). Moreover, changes in markers of nephrotoxicity (high urinary concentrations of total protein, RBP and CC16, as well as GSTα and LDH increased activities) suggested the occurrence of discrete and early signs of impaired renal function for the discharge neighboring population.

Assessment of contamination, distribution and chemical speciation of trace metals in water column in the Dakar coast and the Saint Louis estuary from Senegal, West Africa

The water column from Dakar coast and Saint Louis estuary in Senegal, West Africa, was sampled in order to measure the contamination level by trace metals. The speciation of metals in water allowed performing a distribution between dissolved and particulate trace metals. For the dissolved metals, the metallic concentration and repartition between the organic fraction and the inorganic fraction were performed. The results show that the pollution of the estuary was more serious than in Dakar coast for Co, Cr, Ni, Pb and Zn; while, Cd and Cu were higher in Dakar coast. A strong affinity between metals and suspended particles has been revealed. Dissolved metals that have a tendency to form organic metal complexes are in decreasing order: Cd, Zn, Pb, Co=Cr=Mn, Cu and Ni. The results showed that the mobility of trace metals in estuary is controlled by dissolved organic carbon, while in coast it depends on chlorides.

Assessment of trace element contamination and bioaccumulation in algae (Ulva lactuca), mussels (Perna perna), shrimp (Penaeus kerathurus), and fish (Mugil cephalus, Saratherondon melanotheron) along the Senegalese coast.

Concentrations of 11 elements were quantified in five marine species from different trophic levels of a food web (algae, mussel, shrimp and fish), representative for shallow Senegalese coastal waters, and including species of commercial importance. Significant differences in element concentrations and bioaccumulation were demonstrated, revealing the utility of employing a suite of organisms as bioindicators to monitor metal contamination in coastal areas. There was no clear seasonal pattern in concentration of elements, however inter-site differences were observed. Calculations of transfer factors for all the studied elements showed that transfer factors from water were greater than those from sediments. For shrimp and mussel, the concentrations of Pb and Cd were below the EUs maximum level for human consumption, however high concentrations of arsenic in shrimp were recorded at all sites.

Low-level environmental exposure to lead and renal adverse effects: a cross-sectional study in the population of children bordering the Mbeubeuss landfill near Dakar, Senegal.

This study deals with the health effects within a child population, neighbouring a landfill. After detecting metals in soil and air samples collected in the surroundings of the landfill and in a control site, we have studied: (i) levels of lead (Pb) and exposure biomarkers in blood and urine, (ii) oxidative stress biomarkers and (iii) renal injury by applying a set of early effect biomarkers. Levels of Pb were higher in the exposed site (i.e. 1129 mg/kg and 640 ng/m3 in soil and air samples, respectively) versus those in the control site (i.e. 14.3 mg/kg and 9.3 ng/m3 in soil and air samples, respectively). Pb impregnation and levels of delta-aminolevulinic acid in urine were influenced by the living site that shows the prevailingly alarming situation in the Mbeubeuss landfill. Malondialdehyde changes indicated Pb-induced excessive production of reactive oxygen species. Lactate dehydrogenase activities and proteinuria were found to be higher in the children living in the exposed site. These evidences may reveal the usefulness of these two effect biomarkers to monitor the kidney injury entailed by relatively low-environmental exposure to Pb. Overall, these results show that the Mbeubeuss landfill constitutes a real source of environmental and health risk, be it living or working on site, of the surrounding population, predominantly for children.

Spatial and seasonal variations of trace elements concentrations in liver and muscle of round Sardinelle (Sardinella aurita) and Senegalese sole (Solea senegalensis) along the Senegalese coast.

Concentrations of 11 elements (As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Se,V and Zn) were quantified in liver and muscle from two commercially important fish species from the Senegalese coast. The fish, a small pelagic species (the round sardinella) and a benthic species (the Senegalese sole) were collected from five sites during the dry and wet seasons in 2013. For both species, elements were more concentrated in liver than in muscle. There was no clear seasonal pattern in concentration of elements, however inter-site differences were observed. We found significant differences in element concentrations between the two studied species, likely associated with their behavior, feeding and habitat use. The concentrations of Cd, Fe, and Pb were significantly higher in sardinella whereas concentration of As, Cu, Cr, Mn and Se were highest in sole. The concentration of cadmium was particularly high in the liver of sardinella (from 0.9 to 56 mg kg(-1), with a mean ± sd of 17.2 ± 11.5 mg kg(-1)) and may be related to anthropogenic pressure such as the phosphate industry but also to the upwelling current which brings dissolved elements to the surface that are taken up by plankton. The results showed that concentrations of Cd and Pb were below the limit values established by the European Community and pose no threat to public health.

Mutagenicity of diesel engine exhaust in the Ames / Salmonella assay using a direct exposure method

The aim of this study was to investigate the potential mutagenic activity of diesel engine exhaust in the Ames/Salmonella assay using a direct aerosol exposure system. So, TA 98 and TA 100 strains, with or without added S9 mix, were exposed to diesel emissions after varying degrees of filtration. Variants of these two strains, deficient in nitroreductase (TA 98NR and TA 100NR) or over-expressing O-Acetyl Transferase (YG 1024 and YG 1029), were also exposed to total (unfiltered) diesel exhaust to highlight the putative mutagenicity of any nitro-PAHs present in these emissions. Mutagenic activity of the diesel exhaust was demonstrated on Salmonella typhimurium, strains TA 100 and variants TA 100 NR and YG1029. The use of a particle filter did not modify the genotoxicity of the diesel emissions, indicating a major contribution of the gas phase to the mutagenicity of these diesel emissions. The prominent role of the particulate-associated nitro-polycyclic aromatic hydrocarbons (nitro-PAHs) claimed by some authors working on diesel exhaust organic extracts was not confirmed by our results with native diesel exhaust exposure. Our results show that the gas phase is potentially more mutagenic than the particles alone.

Report of the 4th International Conference on Envenomations by Snakebites and Scorpion Stings in Africa, Dakar, April 25-29, 2011.

The authors present a summary of the proceedings and the recommendations of the the 4th International Conference on Envenomations by Snakebites and Scorpion Stings in Africa, held from April 25th to 29th in Dakar. After a two day training workshop for Senegalese health personnel on the most relevant aspects of the management of envenomations, about 270 participants met to share their experiences in the field. Nearly a hundred oral and poster contributions concerning the epidemiology of snakebites and scorpion stings in Africa, the composition and action of venoms, as well as the manufacture and use of antivenoms, were presented and discussed. The last day was devoted to an institutional debate joining experts, representatives of national health authorities and concerned professionals (physicians, pharmacists, nurses and traditional healers) as well as members of the pharmaceutical industry, to discuss and elaborate a set of recommendations. It was agreed that it is necessary to improve knowledge of the epidemiological situation by case reporting. Quality control of anivenoms and procedures for their registration at the level of national health authorities should aim at improving the distribution of safe and effective antivenoms in peripheral health centers, which bear the heaviest burden of cases. It was also recommended that adequate training of health personnel in all aspects of medical management of envenomations should constitute a priority. Finally, financing mechanisms to ensure an equitable distribution of resources must be sought, as well as the constitution of a network of African experts were discussed at length.

Assessment of freshness and freeze-thawing of sea bream fillets (Sparus aurata) by a cytosolic enzyme: Lactate dehydrogenase.

The evaluation of freshness and freeze-thawing of fish fillets was carried out by assessment of autolysis of cells using a cytosolic enzyme lactate dehydrogenase. Autolysis plays an important role in spoilage of fish and postmortem changes in fish tissue are due to the breakdown of the cellular structures and release of cytoplasmic contents. The outflow of a cytosolic enzyme, lactate dehydrogenase, was studied in sea bream fillets and the Sparus aurata fibroblasts (SAF-1) cell-line during an 8day storage period at +4°C. A significant increase of lactate dehydrogenase release was observed, especially after 5days of storage. The ratio between the free and the total lactate dehydrogenase activity is a promising predictive marker to measure the quality of fresh fish fillets. The effect of freeze-thawing on cytosolic lactate dehydrogenase and lysosomal α-d-glucosidase activities was also tested. Despite the protecting effect of the tissue compared to the cell-line, a loss of lactate dehydrogenase activity, but not of α-d-glucosidase, was observed. In conclusion, lactate dehydrogenase may be used as a marker to both assess freshness of fish and distinguish between fresh and frozen-thawed fish fillets.