Leptin and insulin induce mutual resistance for nitric oxide synthase III activation in adipocytes

Obesity‐induced hyperleptinemia is frequently associated with insulin resistance suggesting a crosstalk between leptin and insulin signaling pathways. Our aim was to determine whether insulin and leptin together interfere on NOS activation in adipocytes. We examined insulin and leptin‐induced nitric oxide synthase (NOS) activity, protein amount and NOS III phosphorylation at Ser¹¹⁷⁹ in isolated epididymal adipocytes from rat, in the presence or not of inhibitors of kinases implicated in insulin or leptin signaling pathways. Insulin or leptin induced NOS III phosphorylation at Ser¹¹⁷⁹ leading to increased NO production in rat adipocytes, in agreement with our previous observations. When insulin and leptin at a concentration found in obese rats (10 ng/ml) were combined, NOS activity was not increased, suggesting a negative crosstalk between insulin and leptin signaling mechanisms. Chemical inhibitors of kinases implicated in signaling pathways of insulin, such as PI‐3 kinase, or of leptin, such as JAK‐2, did not prevent this negative interaction. When leptin signaling was blocked by PKA inhibitors, insulin‐induced NOS activity and NOS III phosphorylation at Ser¹¹⁷⁹ was observed. In the presence of leptin and insulin, (i) IRS‐1 was phosphorylated on Ser³⁰⁷ and this effect was prevented by PKA inhibitors, (ii) JAK‐2 was dephosphorylated, an effect prevented by SHP‐1 inhibitor. A mutual resistance occurs with leptin and insulin. Leptin phosphorylates IRS‐1 to induce insulin resistance while insulin dephosphorylates JAK‐2 to favor leptin resistance. This interference between insulin and leptin signaling could play a crucial role in insulin‐ and leptin‐resistance correlated with obesity. J. Cell. Biochem. 108: 982–988, 2009. © 2009 Wiley‐Liss, Inc.     

Geographic Structuring of the Plasmodium falciparum Sarco(endo)plasmic Reticulum Ca2+ ATPase (PfSERCA) Gene Diversity

Artemisinin, a thapsigargin-like sesquiterpene has been shown to inhibit the Plasmodium falciparum sarco/endoplasmic reticulum calcium-ATPase PfSERCA. To collect baseline pfserca sequence information before field deployment of Artemisinin-based Combination therapies that may select mutant parasites, we conducted a sequence analysis of 100 isolates from multiple sites in Africa, Asia and South America. Coding sequence diversity was large, with 29 mutated codons, including 32 SNPs (average of one SNP/115 bp), of which 19 were novel mutations. Most SNP detected in this study were clustered within a region in the cytosolic head of the protein. The PfSERCA functional domains were very well conserved, with non synonymous mutations located outside the functional domains, except for the S769N mutation associated in French Guiana with elevated IC₅₀ for artemether. The S769N mutation is located close to the hinge of the headpiece, which in other species modulates calcium affinity and in consequence efficacy of inhibitors, possibly linking calcium homeostasis to drug resistance. Genetic diversity was highest in Senegal, Brazil and French Guiana, and few mutations were identified in Asia. Population genetic analysis was conducted for a partial fragment of the gene encompassing nucleotide coordinates 87-2862 (unambiguous sequence available for 96 isolates). This supported a geographic clustering, with a separation between Old and New World samples and one dominant ancestral haplotype. Genetic drift alone cannot explain the observed polymorphism, suggesting that other evolutionary mechanisms are operating. One possible contributor could be the frequency of haemoglobinopathies that are associated with calcium dysregulation in the erythrocyte.     

A dual role for TGF-beta1 in the control and persistence of fungal pneumonia

TGF-beta1 (TGF) has been implicated in the pathogenesis of several chronic infections and is thought to promote microbial persistence by interfering with macrophage function. In rats with experimental pulmonary cryptococcosis, increased lung levels of TGF were present at 12 mo of infection. Within the lung, expression of TGF localized to epithelioid cells and foamy macrophages in areas of inflammation. Increased TGF expression was also observed in the lungs of experimentally infected mice and a patient with pulmonary cryptococcosis. TGF reduced Ab and serum-mediated phagocytosis of Cryptococcus neoformans by rat alveolar macrophages (AM) and peripheral blood monocytes, and this was associated with decreased chemokine production and oxidative burst. Interestingly, TGF-treated rat AM limited both intracellular and extracellular growth of C. neoformans. Control of C. neoformans growth by TGF-treated rat AM was due to increased secretion of lysozyme, a protein with potent antifungal activity. The effects of TGF on the course of infection were dependent on the timing of TGF administration relative to the time of infection. TGF treatment of chronically infected rats resulted in reduced lung fungal burden, while treatment early in the course of infection resulted in increased fungal burden. In summary, our studies suggest a dual role for TGF in persistent fungal pneumonia whereby it contributes to the local control of infection by enhancing macrophage antifungal efficacy through increased lysozyme secretion, while limiting inflammation by inhibiting macrophage/monocyte phagocytosis and reducing associated chemokine production and oxidative burst.     

Le score de risque dystocique (SRD) : un outil d’aide à la décision médicale pour combattre la mortalité maternelle

As a way to prevent maternal mortality and stillbirth, the dystocia risk score includes three components: a left column provides a list of eight characteristics to check for in the woman; an upper horizontal section provides a checklist of possible outcomes of the pregnancy itself: and a rectangular grid indicates the prognosis in three zones: a large red (dangerous), a medium-sized grey (doubtful) and a small blue (hopeful). The DRS is positive if there is at least one cross in the dangerous zone and/or two crosses in the doubtful zone (it indicates that the woman should be referred to a center specialized in obstetric emergency care); elsewhere, the DRS is negative. The validation test gives good results (sensitivity = 83.61%, specificity = 90.05%, positive predictive value = 72.34%, and negative predictive value = 94.04%). Its large-scale use would accelerate the identification of pregnant women with a high risk of dystocia. Their timely referral to specialized emergency obstetrics centers would increase the efficacy of care and reduce the levels of maternal mortality and stillbirth.     

人HCN4通道的滞后现象:影响窦房结起搏的潜在决定因素(英文)

超极化活化环核苷酸门控(hyperpolarization-activated cyclic-nucleotide-gated,HCN)通道参与调制心脏跳动的节律和速率。与HCN1和HCN2有所不同,慢通道HCN4可能不存在电压依赖的滞后现象。本研究采用单细胞膜片钳方法,在稳定转染hHCN4的HEK293细胞上进行电生理记录,观察hHCN4通道是否存在滞后现象,以及cAMP对其的调制作用;同时采用实时定量RT-PCR方法检测窦房结和心房组织中HCNs的表达。电压钳实验结果显示hHCN4电流(Ih)激活随着保持电位超极化的变化而向去极化方向移动。三角电位变化钳(triangular ramp)和动作电位钳的结果也显示了hHCN4的滞后现象。cAMP增加Ih电流幅度,且使电流激活向去极化方向移动,从而改变内源性hHCN4滞后行为。RT-PCR结果显示,人窦房结组织主要表达HCN4,占75%,HCN1占21%,HCN2占3%,HCN3占0.7%。以上结果提示,人窦房结组织主要表达HCN4亚型,hHCN4的Ih存在电压依赖性的滞后现象,且受cAMP调制。由此推断,hHCN4通道的滞后现象可能在窦房结起搏活动中起到了关键作用。     

Nucleotide sequence of the first cosmid from the Mycobacterium leprae genome project: structure and function of the Rif-Str regions

The nucleotide sequence of cosmid B1790, carrying the Rif-Str regions of the Mycobacterium leprae chromosome, has been determined. Twelve open reading frames were identified in the 36716bp sequence, representing 40% of the coding capacity. Five ribosomal proteins, two elongation factors and the β and β'subunits of RNA polymerase have been characterized and two novel genes were found. One of these encodes a member of the so-called ABC family of ATP-binding proteins while the other appears to encode an enzyme involved in repairing genomic lesions caused by free radicals. This finding may well be significant as M. leprae, an intracellular pathogen, lives within macrophages.     

Characterization of M. tuberculosis strains from west African patients by spoligotyping

Analysis of Mycobacterium tuberculosis strains was carried out using isolates collected from 69 Senegalese and 20 Ivory Coast tuberculosis patients. These 89 isolates were typed by means of the spoligotyping technique, showing clusterized populations of bacterial strains. In the Senegalese patients, 35 genetic profiles were observed with 10 clusters of spoligotypes from 44 isolates. Among Ivory Coast patients, 11 spoligotypes were found for 20 isolates. A particular cluster of isolates was evident both in Senegalese (10) and Ivory Coast (11) patients. These results show the existence of polymorphism of the direct repeat region for African M. tuberculosis strains. However they suggest that additionnal markers are needed for accurate epidemiological studies in areas that are highly endemic for tuberculosis.     

Efficacy of artesunate-amodiaquine for the treatment of acute uncomplicated falciparum malaria in southern Mauritania

Mathematical analyses and modelling have an important role informing malaria eradication strategies. Simple mathematical approaches can answer many questions, but it is important to investigate their assumptions and to test whether simple assumptions affect the results. In this note, four examples demonstrate both the effects of model structures and assumptions and also the benefits of using a diversity of model approaches. These examples include the time to eradication, the impact of vaccine efficacy and coverage, drug programs and the effects of duration of infections and delays to treatment, and the influence of seasonality and migration coupling on disease fadeout. An excessively simple structure can miss key results, but simple mathematical approaches can still achieve key results for eradication strategy and define areas for investigation by more complex models.     

Phlebotomine sand flies from Ouagadougou, Burkina Faso: first record of Phlebotomus (Larroussius) longicuspis south of the Sahara

During a brief entomological survey carried out in Ouagadougou, Burkina Faso, in March 2002, 178 phlebotomine sand flies (Diptera, Psychodidae) were caught using CDC miniature light traps. They were identified as Phlebotomus duboscqi Neveu-Lemaire, P. longicuspis Nitzulescu, Sergentomyia adleri (Theodor), S. affinis vorax (Parrot), S. antennata (Newstead), S. bedfordi (Newstead), S. christophersi (Sinton), S. fallax (Parrot), S. magna (Sinton) and S. schwetzi (Adler, Theodor & Parrot). This is the first record south of the Sahara of P. longicuspis sensu lato. This proven vector of Leishmania infantum Nicolle is a species closely related to P. perniciosus. It was identified by morphology and by the sequencing of a fragment of mitochondrial cytochrome b. There was 100% sequence homology with typical Tunisian specimens, and all characters identified the specimen as P. longicuspis sensu stricto. Epidemiological and biogeographical consequences are discussed.