Structure d'âge et croissance de Clarias anguillaris (Pisces, Clariidae) dans le Delta Central du Niger au Mali (Afrique de l’Ouest)

L’étude de l’âge et de la croissance de C. anguillaris dans le Delta Central du Niger a porté sur 390 individus, de taille comprise entre 144 et 670 mm et échantillonnés sur un cycle annuel. L'âge individuel des poissons a été déterminé par squelettochronologie au moyen des coupes transversales de rayons épineux pectoraux dont l'épaisseur était de 100 μm. La validité des lectures d'âge a été appréciée par le calcul des indices de cohérence inter-lecteurs. L’évolution mensuelle de la marge relative du diamètre (dr) de la coupe du rayon épineux a été utilisée pour déterminer la périodicité de formation des marques de croissance et le cycle saisonnier de croissance. Ce dernier se caractérise par l'absence d'une période tranchée d'arrêt de croissance même si une reprise précoce, dès l'étiage, liée à une amélioration des conditions physico-chimiques et alimentaires, est observée. La longévité au sein de la population est de 4 ans bien qu’une forte proportion soit pêchée avant 2 ans d’âge. Le modèle théorique de croissance révèle, outre la grande taille que pourraient atteindre certains individus, une très importante croissance linéaire la première année avec 244.81±12.15 mm, ce qui augure de très bonnes performances aquacoles.Mots clés: Clarias anguillaris, squelettochronologie, marques de croissance, longévité, Delta Central du Niger, Mal

Modelling the regulation of telomere length: the effects of telomerase and G-quadruplex stabilising drugs

Telomeres are guanine-rich sequences at the end of chromosomes which shorten during each replication event and trigger cell cycle arrest and/or controlled death (apoptosis) when reaching a threshold length. The enzyme telomerase replenishes the ends of telomeres and thus prolongs the life span of cells, but also causes cellular immortalisation in human cancer. G-quadruplex (G4) stabilising drugs are a potential anticancer treatment which work by changing the molecular structure of telomeres to inhibit the activity of telomerase. We investigate the dynamics of telomere length in different conformational states, namely t-loops, G-quadruplex structures and those being elongated by telomerase. By formulating deterministic differential equation models we study the effects of various levels of both telomerase and concentrations of a G4-stabilising drug on the distribution of telomere lengths, and analyse how these effects evolve over large numbers of cell generations. As well as calculating numerical solutions, we use quasicontinuum methods to approximate the behaviour of the system over time, and predict the shape of the telomere length distribution. We find those telomerase and G4-concentrations where telomere length maintenance is successfully regulated. Excessively high levels of telomerase lead to continuous telomere lengthening, whereas large concentrations of the drug lead to progressive telomere erosion. Furthermore, our models predict a positively skewed distribution of telomere lengths, that is, telomeres accumulate over lengths shorter than the mean telomere length at equilibrium. Our model results for telomere length distributions of telomerase-positive cells in drug-free assays are in good agreement with the limited amount of experimental data available

Blastic plasmacytoid dendritic cell leukemia in a black Malian

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare, clinically aggressive hematologic malignancy, that most commonly manifests as cutaneous lesions. A 19-year-old Malian female was admitted to the Unit of Medicine of Hopital du Mali with anemia, fever, weakness, and weight loss. On physical examination she was wasted, pale, febrile (37.4°C), and had inguinal and axillary lymphadenopathies. The complete blood count found pancytopenia with Hemoglobin level of 4.8 g/dL, Leucocytes count of 1900/μL (neutrophil: 300/μL), and platelets count of 56 000/μL. The ultrasonographic examination found hepatomegaly and splenomegaly. The bone marrow biopsy and flow cytometer analysis were in keeping with a diagnosis of BPDCN. The patient, unfortunately, was lost four months later after her hospital admission due to late diagnosis by septicemia. The early diagnosis and availability of specific drugs for acute leukemia could improve the clinical outcome of patients with BPDCN in Mali.Keywords: Acute Leukemia, black african, dendritic cell, Mal

Viable route towards large-area 2D MoS₂ using magnetron sputtering

Abstract Structural, interfacial, optical, and transport properties of large-area MoS₂ ultra-thin films on BN-buffered silicon substrates fabricated using magnetron sputtering are investigated. A relatively simple growth strategy is demonstrated here that simultaneously promotes superior interfacial and bulk MoS₂ properties. Few layers of MoS₂ are established using x-ray reflectivity, diffraction, ellipsometry, and Raman spectroscopy measurements. Layer-specific modeling of optical constants show very good agreement with first-principles calculations. Conductivity measurements reveal that few-layer MoS₂ films are more conducting than many-layer films. Photo-conductivity measurements reveal that the sputter deposited MoS₂ films compare favorably with other large-area methods. Our work illustrates that sputtering is a viable route for large-area device applications using transition metal dichalcogenides