Analysis of dendrometric characteristics of Acacia senegal (L.) Willd. (Fabaceae) in the semi-arid Sahelian area: A case study of silvopastoral zone in Senegal

The study gives an analysis of the dendrometric parameters of a middle Sahelian species (Acacia senegal) in semi-arid environment to get better knowledge of its behavior. The research lays the principle that the species behaves differently according to the ecogeographical stations. So, its characteristics change from one environment to another. That is why it is important to do a specific study for every big zone. The study was done in Silvopastoral zone, more particularly in the area where A. senegal is popular in the country. The study aims to deepen the knowledge of A. senegal dendrometric parameters. The following parameters were measured: diameter of the base, breastheight diameter (1.3 m), breast- height circumference, total height of the tree, length of the trunk and width of the houppier. The sample consists of a population of 76 feet locust trees in Senegal. The study confirmed the hypothesis that the characters of the species vary according to the zone where it is found.Keys words: Acacia senegal, dendrometry, Sahel, Senegal

Production de litière de la mangrove du Parc National du Delta du Saloum (Sénégal)

Le delta du Saloum est un estuaire poissonneux du Sénégal. Les palétuviers y jouent le rôle de nurserie et de frayère à cause essentiellement de leur production de litière qui est la base de la chaîne alimentaire dans l’écosystème mangrove. Afin de monter l’importance de la litière qui tombe dans le milieu, des trappes ont été installées dans deux sites pour le captage du matériel végétal qui chute. Les productions moyennes les plus élevées sont de l’ordre de 4,6 g/m²/J pour les feuilles et de 4,09 g/m²/J pour les fleurs chez R. racemosa/harisonnii. Elles sont d’environ 4,07 g/m²/J pour les feuilles et de 0,194 pour les fleurs chez R. mangle. Ces statistiques montrent que dans l’année, les quantités de feuilles qui chutent des palétuviers varient dans le même ordre de grandeur chez le genre Rhizophora. Par contre, les corrélations notées, entre la production de litière florale et la composition floristique des peuplements, montrent que R. mangle perd moins de fleurs par avortement que R. racemosa/harisonnii. Cette dernière contribuerait donc plus à l’enrichissement du milieu que les autres palétuviers.Most clés : palétuviers, production, litière, Rhizophora, feuilles, fleur

Quantification de la biomasse aérienne des palétuviers du genre Rhizophora au Delta du Saloum (Sénégal)

L’étude de la biomasse aérienne des palétuviers a fait l’objet d’un  inventaire dans quatre unités d’échantillonnage. Quinze parcelles  permanentes ont aussi permis d’étudier les effets de certains facteurs dumilieu sur la biomasse. Dans les strates de hauteur moyenne, la biomasse sèche des racines aériennes la plus élevée est de 67 tonnes à l’hectare chez R. mangle. Dans les strates hautes, celle la plus élevée est de 83,3tonnes à l’hectare. Ces deux grandes quantités de biomasse racinaire supportent aussi les biomasses sèches de tiges et autres parties les plus élevées dans la zone. En termes de comparaison, le pic de la biomasse sèche des tiges et autres parties est observé chez R. mangle. Quant à la biomasse racinaire sèche, le pic est noté chez R. racemosa/harisonnii. Dans les strates de hauteur moyenne, la biomasse sèche des tiges et autres parties est en général plus élevée que celle des racines. Dans les strates hautes, ces rapports de biomasse sont inversés. L’analyse de corrélation entre la biomasse racinaire et les facteurs étudiés montre que l’augmentation de celleci est plus liée à la hauteur de submersion qu’au type de sol. Cette augmentation serait le résultat d’une adaptation morphologique des palétuviers aux vasières meubles et à leur  submersion.Mots clés : Biomasse sèche, strates, milieu, racinaire, tiges, autres parties

Studies of the Woody Vegetation of the Welor Forest Reserve (Senegal) for Sustainable Use

The Welor area has been classified as a forest reserve since 1935 while waiting for the outcome of studies for its appropriate exploitation based on its biological potential. Due to lack of information on this potential, the plant resources of this forest reserve have been used improperly and excessively. The present study aims at gathering, with an appropriate approach and efficient tools, information necessary for designing a management plan to ensure a sustainable use of the woody resources of Welor Forest Reserve. The results obtained have provided information on the present condition of the woody flora and the vegetation, the potential and the dynamics of the most exploited woody species, and the root causes of the present state of the vegetation of the Welor Forest Reserve. Forty-six woody species, which belong to 39 genera and 25 families, were identified in this Forest Reserve. The most numerous families were Combretaceae, Capparidaceae, Mimosaceae and Caesalpiniaceae. The shrubs represented about 95% of the woody individuals. The average density of the woody individuals was 75–181 individuals per hectare. Acacia seyal and Balanites aegyptiaca were the dominant woody species with the best population structure. None of the woody species exploited for timber reveals a good structure and a good regeneration. Considering the socio-economic context of the area, it appears that the Welor Forest Reserve could be used as a source for firewood.West African Journal of Applied Ecology Vol. 13 2008: pp. 67-7

Élaboration de modèles allométriques d’Acacia Sénéga

La présente étude s’est appesantie sur l’élaboration de modèles allométriques d’une espèce soudanosahélienne (Acacia Sénégal ) dans le but d’asseoir une base de calcul des stocks de carbone. La recherche s’est effectuée en zone sylvopastorale, au nord du Sénégal. Au préalable, l’étude a tenté d’approfondir les connaissances sur la dendrométrie de Acacia Sénégal. Sur le terrain, les paramètres suivants ont été mesurés et fait l’objet d’analyses et interprétations : diamètre à la base, hauteur totale de l’arbre, longueur du tronc, diamètre à hauteur de poitrine, circonférence à hauteur de poitrine et largeur du houppier. La pesée des échantillons de chaque partie (tronc, branche, rameau) de l’échantillon d’arbres composés de 38 pieds d’Acacia Sénégal et leur séchage à l’étuve ont permis de connaître la biomasse sèche de chaque sujet. Ensuite, des modèles allométriques spécifiques (entre la biomasse sèche et les paramètres dendrométriques) ont été générés et les coefficients de corrélation déterminés. Les différentes analyses ont permis d’affirmer que le diamètre à hauteur de poitrine (DHP) est la variable qui offre la meilleure corrélation avec la biomasse aérienne. Parmi les modèles, et par ordre décroissant, nous avons obtenu la relation polynomiale, logarithmique et de puissance. Les modèles retenus ont comme entrée le DBH. De ce fait, le modèle polynomiale (y = 0,032DBH3 - 1,016DBH2 + 10,87DBH + 7,429) présente la meilleure corrélation (R² = 0,963), suivi du modèle logarithmique (y = 13,61ln(DBH) + 17,89) avec une corrélation R² = 0,933 et du modèle de puissance (y = 22,23DBH0,357) pour une corrélation R² = 0,909. L’étude a confirmé l’hypothèse selon laquelle, au sein d’une même espèce, l’élaboration de modèle spécifique reflète plus la réalité et permet de faire une quantification des stocks de carbone plus proche de la réalité que le modèle générique.Mots-clés : modèle allométrique, grande muraille verte, Acacia Sénégal, séquestration de carbone

An auto-luminescent fluorescent BCG whole blood assay to enable evaluation of paediatric mycobacterial responses using minimal blood volumes

Introduction: Understanding protective human immunity against mycobacteria is critical to developing and evaluating new vaccines against tuberculosis. Children are the most susceptible population to infection, disease, and death from tuberculosis, but also have the strongest evidence of BCG-inducible protection. Limited amounts of blood can be obtained for research purposes in paediatrics and therefore there is a need for high-yield, low-volume, human immunology assays. Methods: We transformed BCG Danish with plasmids encoding luciferase full operon derived from Photorhabdus luminescens together with Green Fluorescent Protein and antibiotic selection markers. We characterised the luminescent and fluorescent properties of this recombinant BCG strain (BCG-GFP-LuxFO) using a luminometer and flow cytometry and developed a paediatric whole blood in vitro infection model. Results: Luminescence of BCG-GFP-LuxFO correlated with optical density (Spearman Rank Correlation coefficient r = 0.985, p < 0.0001) and colony forming units (CFUs) in liquid culture medium (r = 0.971, p < 0.0001). Fluorescence of BCG-GFP-LuxFO in paediatric whole blood was confirmed by flow cytometry in granulocytes and monocytes 1 h following infection. Luminescence of BCG-GFP-LuxFO in whole blood corresponded with CFUs (r = 0.7123, p < 0.0001). Conclusion: The BCG-GFP-LuxFO assay requires 225 μL whole blood per sample, from which serial luminescence measurements can be obtained, together with biochemical analysis of supernatants and cellular assay applications using its fluorescent properties. This offers the opportunity to study human-mycobacterial interactions using multiple experimental modalities with only minimal blood volumes. It is therefore a valuable method for investigating paediatric immunity to tuberculosis

Protection against mycobacterial infection: A case-control study of mycobacterial immune responses in pairs of Gambian children with discordant infection status despite matched TB exposure

Background Children are particularly susceptible to tuberculosis. However, most children exposed to Mycobacterium tuberculosis are able to control the pathogen without evidence of infection. Correlates of human protective immunity against tuberculosis infection are lacking, and their identification would aid vaccine design. Methods We recruited pairs of asymptomatic children with discordant tuberculin skin test status but the same sleeping proximity to the same adult with sputum smear-positive tuberculosis in a matched case-control study in The Gambia. Participants were classified as either Highly TB-Exposed Uninfected or Highly TB-Exposed Infected children. Serial luminescence measurements using an in vitro functional auto-luminescent Bacillus Calmette–Guérin (BCG) whole blood assay quantified the dynamics of host control of mycobacterial growth. Assay supernatants were analysed with a multiplex cytokine assay to measure associated inflammatory responses. Findings 29 pairs of matched Highly TB-Exposed Uninfected and Highly TB-Exposed Infected children aged 5 to 15 years old were enroled. Samples from Highly TB-Exposed Uninfected children had higher levels of mycobacterial luminescence at 96 hours than Highly TB-Exposed Infected children. Highly TB-Exposed Uninfected children also produced less BCG-specific interferon-γ than Highly TB-Exposed Infected children at 24 hours and at 96 hours. Interpretation Highly TB-Exposed Uninfected children showed less control of mycobacterial growth compared to Highly TB-Exposed Infected children in a functional assay, whilst cytokine responses mirrored infection status. Funding Clinical Research Training Fellowship funded under UK Medical Research Council/Department for International Development Concordat agreement and part of EDCTP2 programme supported by European Union (MR/K023446/1). Also MRC Program Grants (MR/K007602/1, MR/K011944/1, MC_UP_A900/1122)

Monitoring anti-tuberculosis treatment response using analysis of whole blood Mycobacterium tuberculosis specific T cell activation and functional markers

Background: Blood-based biomarkers have been proposed as an alternative to current sputum-based treatment monitoring methods in active tuberculosis (ATB). The aim of this study was to validate previously described phenotypic, activation, and cytokine markers of treatment response in a West African cohort. Methods: Whole blood immune responses to Mycobacterium tuberculosis ESAT-6/CFP-10 (EC) and purified protein derivative (PPD) were measured in twenty adults at baseline and after 2 months of standard TB treatment. Patients were classified as fast or slow responders based on a negative or positive sputum culture result at 2 months, respectively. Cellular expression of activation markers (CD38, HLA-DR), memory markers (CD27), and functional intracellular cytokine and proliferation (IFN-γ, Ki-67, TNF-α) markers were measured using multi-color flow cytometry. Results: There was a significant increase in the proportion of CD4+CD27+ cells expressing CD38 and HLA-DR following EC stimulation at 2 months compared to baseline (p = 0.0328 and p = 0.0400, respectively). Following PPD stimulation, slow treatment responders had a significantly higher proportion of CD8+CD27–IFN-γ+ (p = 0.0105) and CD4+CD27+HLA-DR+CD38+ (p = 0.0077) T cells than fast responders at baseline. Receiver operating curve analysis of these subsets resulted in 80% sensitivity and 70 and 100% specificity, respectively (AUC of 0.82, p = 0.0156 and 0.84, p = 0.0102). Conclusion: Our pilot data show reductions in expression of T cell activation markers were seen with treatment, but this was not associated with fast or slow sputum conversion at 2 months. However, baseline proportions of activated T cell subsets are potentially predictive of the subsequent speed of response to treatment