Dynamique de la teneur en carbone et en azote des sols dans les systèmes d’exploitation du Ferlo : cas du CRZ de Dahra

Objectif : Cette étude, réalisée au Centre de Recherches Zootechniques (CRZ) de Dahra situé en Région sylvopastorale du Sénégal, a pour objectif d’apprécier l’évolution de la teneur en carbone, en azote et le stock de carbone du sol dans ses différents systèmes d’exploitation.Méthodologie et résultats : En 2011, des échantillons de sols (à 0-20 cm et 20 – 40 cm) ont été prélevés au niveau des mêmes sites que ceux qui ont fait l’objet d’analyse de sols en 1962, afin de déterminer la teneur en carbone et azote du sol. Le nombre d’échantillons est fonction de la superficie des différents types de sols rencontrés. L’utilisation de la cartographie nous a permis de déterminer le nombre d’échantillon prélevé sur chaque système d’exploitation. Au niveau du CRZ de Dahra, l’analyse des paramètres pédologiques (teneur en carbone, en azote et rapport C/N) de l’horizon 0-20 cm, n’a pas révélé de différence significative entre 1962 et 2011. Par contre, dans l’horizon 20-40 cm, seule la teneur en azote présente une hausse significative entre ces deux périodes. S’agissant des systèmes d’exploitation du CRZ de Dahra, l’analyse de la teneur en carbone, en azote et du rapport C/N de l’horizon 0-20 cm, n’a pas révélé de différence significative aussi bien pour l’année 1962 que celle de 2011. Au niveau de l’horizon 20-40 cm, parmi les paramètres étudiés, seul la teneur en carbone de 1962 présentait une différence significative (au seuil de 5%) entre les systèmes de cultures et les pâturages. Le stock de carbone du centre est en moyenne de 0,08±0,03 et 0,06±0,02 t/ha respectivement pour les horizons 0-20 et 20-40 cm. Celui-ci est plus important au niveau des gommiers et plus faibles dans les systèmes de culture et les pâturages.Conclusion et application des résultats : Cette étude a permis de montrer qu’au niveau du CRZ de Dahra à vocation essentiellement pastorale, le carbone et l’azote du sol, présente une certaine stabilité dans les différents systèmes d’exploitation. Toutefois, les gommiers présentent les teneurs en carbone et en azote du sol les plus importantes. Ces résultats peuvent servir de données d’entrée aux modèles de prévision de la séquestration du carbone et de l’azote du sol des écosystèmes sahéliens pastoraux, être valorisés en aménagement pastoral et agro-sylvopastoral en vue d’une meilleure préservation de l’environnement et de la gestion de la fertilité du sol.Mots clés : carbone, l'azote, le contenu, les sol

AfriQA: Cross-lingual Open-Retrieval Question Answering for African Languages

African languages have far less in-language content available digitally, making it challenging for question-answering systems to satisfy the information needs of users. Cross-lingual open-retrieval question answering (XOR QA) systems-those that retrieve answer content from other languages while serving people in their native language-offer a means of filling this gap. To this end, we create AFRIQA, the first cross-lingual QA dataset with a focus on African languages. AFRIQA includes 12,000+ XOR QA examples across 10 African languages. While previous datasets have focused primarily on languages where crosslingual QA augments coverage from the target language, AFRIQA focuses on languages where cross-lingual answer content is the only high-coverage source of answer content. Because of this, we argue that African languages are one of the most important and realistic use cases for XOR QA. Our experiments demonstrate the poor performance of automatic translation and multilingual retrieval methods. Overall, AFRIQA proves challenging for state-of-the-art QA models. We hope that the dataset enables the development of more equitable QA technology

Crystal structure of tarocystatin–papain complex: implications for the inhibition property of group-2 phytocystatins

Tarocystatin (CeCPI) from taro (Colocasia esculenta cv. Kaohsiung no. 1), a group-2 phytocystatin, shares a conserved N-terminal cystatin domain (NtD) with other phytocystatins but contains a C-terminal cystatin-like extension (CtE). The structure of the tarocystatin–papain complex and the domain interaction between NtD and CtE in tarocystatin have not been determined. We resolved the crystal structure of the phytocystatin–papain complex at resolution 2.03 Å. Surprisingly, the structure of the NtD–papain complex in a stoichiometry of 1:1 could be built, with no CtE observed. Only two remnant residues of CtE could be built in the structure of the CtE–papain complex. Therefore, CtE is easily digested by papain. To further characterize the interaction between NtD and CtE, three segments of tarocystatin, including the full-length (FL), NtD and CtE, were used to analyze the domain–domain interaction and the inhibition ability. The results from glutaraldehyde cross-linking and yeast two-hybrid assay indicated the existence of an intrinsic flexibility in the region linking NtD and CtE for most tarocystatin molecules. In the inhibition activity assay, the glutathione-S-transferase (GST)-fused FL showed the highest inhibition ability without residual peptidase activity, and GST-NtD and FL showed almost the same inhibition ability, which was higher than with NtD alone. On the basis of the structures, the linker flexibility and inhibition activity of tarocystatins, we propose that the overhangs from the cystatin domain may enhance the inhibition ability of the cystatin domain against papain

Lymphoid Tissue Damage in HIV-1 Infection Depletes Naïve T Cells and Limits T Cell Reconstitution after Antiretroviral Therapy

Highly active antiretroviral therapy (HAART) can suppress HIV-1 replication and normalize the chronic immune activation associated with infection, but restoration of naïve CD4+ T cell populations is slow and usually incomplete for reasons that have yet to be determined. We tested the hypothesis that damage to the lymphoid tissue (LT) fibroblastic reticular cell (FRC) network contributes to naïve T cell loss in HIV-1 infection by restricting access to critical factors required for T cell survival. We show that collagen deposition and progressive loss of the FRC network in LTs prior to treatment restrict both access to and a major source of the survival factor interleukin-7 (IL-7). As a consequence, apoptosis within naïve T cell populations increases significantly, resulting in progressive depletion of both naïve CD4+ and CD8+ T cell populations. We further show that the extent of loss of the FRC network and collagen deposition predict the extent of restoration of the naïve T cell population after 6 month of HAART, and that restoration of FRC networks correlates with the stage of disease at which the therapy is initiated. Because restoration of the FRC network and reconstitution of naïve T cell populations are only optimal when therapy is initiated in the early/acute stage of infection, our findings strongly suggest that HAART should be initiated as soon as possible. Moreover, our findings also point to the potential use of adjunctive anti-fibrotic therapies to avert or moderate the pathological consequences of LT fibrosis, thereby improving immune reconstitution

Myelin Basic Protein as a Novel Genetic Risk Factor in Rheumatoid Arthritis—A Genome-Wide Study Combined with Immunological Analyses

Rheumatoid arthritis (RA) is a major cause of adult chronic inflammatory arthritis and a typical complex trait. Although several genetic determinants have been identified, they account for only a part of the genetic susceptibility. We conducted a genome-wide association study of RA in Japanese using 225,079 SNPs genotyped in 990 cases and 1,236 controls from two independent collections (658 cases and 934 controls in collection1; 332 cases and 302 controls in collection2), followed by replication studies in two additional collections (874 cases and 855 controls in collection3; 1,264 cases and 948 controls in collection4). SNPs showing p<0.005 in the first two collections and p<10−4 by meta-analysis were further genotyped in the latter two collections. A novel risk variant, rs2000811, in intron2 of the myelin basic protein (MBP) at chromosome 18q23 showed strong association with RA (p = 2.7×10−8, OR 1.23, 95% CI: 1.14–1.32). The transcription of MBP was significantly elevated with the risk allele compared to the alternative allele (p<0.001). We also established by immunohistochemistry that MBP was expressed in the synovial lining layer of RA patients, the main target of inflammation in the disease. Circulating autoantibody against MBP derived from human brain was quantified by ELISA between patients with RA, other connective tissue diseases and healthy controls. As a result, the titer of anti-MBP antibody was markedly higher in plasma of RA patients compared to healthy controls (p<0.001) and patients with other connective tissue disorders (p<0.001). ELISA experiment using citrullinated recombinant MBP revealed that a large fraction of anti-MBP antibody in RA patients recognized citrullinated MBP. This is the first report of a genetic study in RA implicating MBP as a potential autoantigen and its involvement in pathogenesis of the disease

Packages of Care for Epilepsy in Low- and Middle-Income Countries

In the second in a series of six articles on packages of care for mental health disorders in low- and middle-income countries, Caroline Mbuba and Charles Newton discuss treatment for epilepsy

The future of African nowcasting

Nowcasting (weather forecasting predictions from zero to several hours) has enormous value and potential in Africa, where populations and economic activity are highly vulnerable to rapidly changing weather conditions. Timely issuing of warnings, a few hours before an event, can enable the public and decision-makers to take action. Rainfall radar estimates are not widely available in Africa, nor likely to be in the coming years, and numerical weather prediction (NWP) currently has low skill over the African continent. Therefore, for the delivery of nowcasting in Africa, satellite products are the best practical option and needed urgently (Roberts et al., 2021). Fifteen minute (or faster) updates of MSG (Meteosat Second Generation) images and NWC-SAF (Nowcasting Satellite Applications Facility) products are crucial for nowcasting to warn users (e.g. fisherfolk on Lake Victoria, flooding in urban areas, etc.) on pending severe storms. The possibility to have such products every 10 minutes, as well as data from the forthcoming MTG (Meteosat Third Generation) lightning imager, would be highly beneficial to all African countries, saving lives and livelihoods where high population growth and the most extreme impacts of climate change combine

The Genome of Mycobacterium Africanum West African 2 Reveals a Lineage-Specific Locus and Genome Erosion Common to the M. tuberculosis Complex

Mycobacterium africanum, a close relative of M. tuberculosis, is studied for the following reasons: M. africanum is commonly isolated from West African patients with tuberculosis yet has not spread beyond this region, it is more common in HIV infected patients, and it is less likely to lead to tuberculosis after one is exposed to an infectious case. Understanding this organism's unique biology gets a boost from the decoding of its genome, reported in this issue. For example, genome analysis reveals that M. africanum contains a region shared with “ancient” lineages in the M. tuberculosis complex and other mycobacterial species, which was lost independently from both M. tuberculosis and M. bovis. This region encodes a protein involved in transmembrane transport. Furthermore, M. africanum has lost genes, including a known virulence gene and genes for vitamin synthesis, in addition to an intact copy of a gene that may increase its susceptibility to antibiotics that are insufficiently active against M. tuberculosis. Finally, the genome sequence and analysis reported here will aid in the development of new diagnostics and vaccines against tuberculosis, which need to take into account the differences between M. africanum and other species in order to be effective worldwide

Regional research priorities in brain and nervous system disorders

The characteristics of neurological, psychiatric, developmental and substance-use disorders in low-and middle-income countries are unique and the burden that they have will be different from country to country. Many of the differences are explained by the wide variation in population demographics and size, poverty, conflict, culture, land area and quality, and genetics. Neurological, psychiatric, developmental and substance-use disorders that result from, or are worsened by, a lack of adequate nutrition and infectious disease still afflict much of sub-Saharan Africa, although disorders related to increasing longevity, such as stroke, are on the rise. In the Middle East and North Africa, major depressive disorders and post-traumatic stress disorder are a primary concern because of the conflict-ridden environment. Consanguinity is a serious concern that leads to the high prevalence of recessive disorders in the Middle East and North Africa and possibly other regions. The burden of these disorders in Latin American and Asian countries largely surrounds stroke and vascular disease, dementia and lifestyle factors that are influenced by genetics. Although much knowledge has been gained over the past 10 years, the epidemiology of the conditions in low-and middle-income countries still needs more research. Prevention and treatments could be better informed with more longitudinal studies of risk factors. Challenges and opportunities for ameliorating nervous-system disorders can benefit from both local and regional research collaborations. The lack of resources and infrastructure for health-care and related research, both in terms of personnel and equipment, along with the stigma associated with the physical or behavioural manifestations of some disorders have hampered progress in understanding the disease burden and improving brain health. Individual countries, and regions within countries, have specific needs in terms of research priorities.Fil: Ravindranath, Vijayalakshmi. Indian Institute of Science; IndiaFil: Dang, Hoang Minh. Vietnam National University; VietnamFil: Goya, Rodolfo Gustavo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Bioquímicas de La Plata ; ArgentinaFil: Mansour, Hader. University of Pittsburgh; Estados Unidos. Mansoura University; EgiptoFil: Nimgaonkar, Vishwajit L.. University of Pittsburgh; Estados UnidosFil: Russell, Vivienne Ann. University of Cape Town; SudáfricaFil: Xin, Yu. Peking University; Chin