Object-based characterization of vegetation heterogeneity with sentinel images proves efficient in a highly human-influenced National Park of Côte d'Ivoire.

Forest monitoring requires more automated systems to analyze high ecosystem heterogeneity. The traditional pixel-based detection method has proven to be less and less effective. A novel change detection method is therefore proposed to detect changes in forest cover using satellite images at very high spatial resolution. This is object-oriented classification, which groups pixels into interpreted objects, based on their spectral values, spatial, and textural properties. Using sentinel and Lansat images, we tested for the first time in the West African rainforest zone the effectiveness of this method for better detection, delineation, and analysis of land use and occupation types. The mean shift algorithm was used in both the segmentation and classification processes. Next, we compared the proposed object-oriented method with a pixel-based image classification detection method by implementing both methods under the same conditions. High detection accuracy (> 90%) and an overall Kappa greater than 0.90 were obtained by the object-oriented method, which is about 20% higher than the pixel-based method. The object-based method was free of salt and pepper effects and was less prone to image misregistration in terms of change detection accuracy and mapping results. This study demonstrates that the object-based classifier is a much better approach than the classical pixel-based classifier. In addition, it shows the problems of detecting heterogeneous landscapes and explains the observed confusions between the types of vegetation formations specific to tropical wetlands. The results obtained are encouraging and the contribution of high-resolution images and the object-based method to better discrimination of tropical wetland vegetation is discussed.

Review of national methodologies for rivers' hydromorphological assessment: A comparative approach in France, Romania, and Croatia.

Conducting hydromorphological assessments for evaluating the ecological status of rivers is a key requirement of the Directive 2000/60/EC (Water Framework Directive - WFD) within European Union (EU) Member States. This paper aims at understanding how this requirement was implemented, through an original comparative review of methodologies for rivers' hydromorphological assessment in three EU Member States, which joined the EU at different times, and with many differences in terms of hydrographic features, socio-economic and water management systems: France, Romania, and Croatia. More precisely, the paper aims at identifying and understanding the main principles guiding the hydromorphological assessment methodologies, elements and data used, giving an overview of the results of hydromorphological river status assessment, and concluding on the stage of hydromorphological assessment implementation. France developed numerous methodologies for physical habitat survey since the 1990s and it is currently conducting a rigorous hydromorphological field survey, but it does not yet have any national methodology for rivers' hydromorphological status assessment, nevertheless foreseen for the next cycle of the WFD. Besides, Romania and Croatia have already started the assessment of the hydromorphological status of rivers within the two cycles of the River Basin Management Plans and are making efforts to improve the hydromorphological monitoring activity. The methods generally differ in indicators, data used, and spatial scale of analysis, which makes it difficult to compare the results of the assessments. Despite a common water policy, the methodological dissimilarities seem to be rather usual between EU Member States. Therefore, the standardization of methodologies appears to be necessary, but the current results could be useful for setting priorities for river restoration and for achieving a better status at a national scale.

Impact of hydroxycarbamide and interferon-α on red cell adhesion and membrane protein expression in polycythemia vera.

Polycythemia vera is a chronic myeloproliferative neoplasm characterized by the JAK2V617F mutation, elevated blood cell counts and a high risk of thrombosis. Although the red cell lineage is primarily affected by JAK2V617F, the impact of mutated JAK2 on circulating red blood cells is poorly documented. Recently, we showed that in polycythemia vera, erythrocytes had abnormal expression of several proteins including Lu/BCAM adhesion molecule and proteins from the endoplasmic reticulum, mainly calreticulin and calnexin. Here we investigated the effects of hydroxycarbamide and interferon-α treatments on the expression of erythroid membrane proteins in a cohort of 53 patients. Surprisingly, while both drugs tended to normalize calreticulin expression, proteomics analysis showed that hydroxycarbamide deregulated the expression of 53 proteins in red cell ghosts, with overexpression and downregulation of 37 and 16 proteins, respectively. Within over-expressed proteins, hydroxycarbamide was found to enhance the expression of adhesion molecules such as Lu/BCAM and CD147, while interferon-α did not. In addition, we found that hydroxycarbamide increased Lu/BCAM phosphorylation and exacerbated red cell adhesion to its ligand laminin. Our study reveals unexpected adverse effects of hydroxycarbamide on red cell physiology in polycythemia vera and provides new insights into the effects of this molecule on gene regulation and protein recycling or maturation during erythroid differentiation. Furthermore, our study shows deregulation of Lu/BCAM and CD147 that are two ubiquitously expressed proteins linked to progression of solid tumors, paving the way for future studies to address the role of hydroxycarbamide in tissues other than blood cells in myeloproliferative neoplasms.

Developmental origin and maintenance of distinct testicular macrophage populations.

Testicular macrophages (tMφ) are the principal immune cells of the mammalian testis. Beyond classical immune functions, they have been shown to be important for organogenesis, spermatogenesis, and male hormone production. In the adult testis, two different macrophage populations have been identified based on their distinct tissue localization and morphology, but their developmental origin and mode of homeostatic maintenance are unknown. In this study, we use genetic lineage-tracing models and adoptive transfer protocols to address this question. We show that embryonic progenitors give rise to the interstitial macrophage population, whereas peritubular macrophages are exclusively seeded postnatally in the prepuberty period from bone marrow (BM)-derived progenitors. As the proliferative capacity of interstitial macrophages declines, BM progenitors also contribute to this population. Once established, both the peritubular and interstitial macrophage populations exhibit a long life span and a low turnover in the steady state. Our observations identify distinct developmental pathways for two different tMφ populations that have important implications for the further dissection of their distinct roles in organ homeostasis and testicular function.

AlphaII-spectrin participates in the surface expression of cell adhesion molecule L1 and neurite outgrowth.

AlphaII-spectrin, a basic component of the spectrin-based scaffold which organizes and stabilizes membrane microdomains in most animal cells, has been recently implicated in cell adherence and actin dynamics. Here we investigated the contribution of αΙΙ-spectrin to neuritogenesis, a highly complex cellular process which requires continuous actin cytoskeleton remodeling and cross-talk between extracellular cues and their cell surface receptors, including cell adhesion molecules. Using RNA interference-mediated gene silencing to down-regulate αΙΙ-spectrin expression in human neuroblastoma SH-SY5Y cells, we observed major changes in neurite morphology and cell shape: (1) reduced mean length and a higher number of neurites per cell; occasional long neurites were thinner and displayed abnormal adhesiveness during cell migration resulting in frequent breaks; similar persisting adhesiveness and breaks were also observed in trailing edges of cell bodies; (2) irregular polygonal cell shape in parallel with loss of cortical F-actin from neuronal cell bodies; (3) reduction in protein levels of αΙ- and ßΙ-spectrins, but not ßΙΙ-spectrin (4) decreased global expression of adhesion molecule L1 and spectrin-binding adapter ankyrin-B, which links L1 to the plasma membrane. Remarkably, αΙΙ-spectrin depletion affected L1 - but not NCAM - cell surface expression, and L1 clustering at growth cones. This study demonstrates that αΙΙ-spectrin is implicated in normal morphology and adhesive properties of neuron cell bodies and neurites, and in cell surface expression and organization of adhesion molecule L1.

A prevalent C3 mutation in aHUS patients causes a direct C3 convertase gain of function.

Atypical hemolytic uremic syndrome (aHUS) is a rare renal thrombotic microangiopathy commonly associated with rare genetic variants in complement system genes, unique to each patient/family. Here, we report 14 sporadic aHUS patients carrying the same mutation, R139W, in the complement C3 gene. The clinical presentation was with a rapid progression to end-stage renal disease (6 of 14) and an unusually high frequency of cardiac (8 of 14) and/or neurologic (5 of 14) events. Although resting glomerular endothelial cells (GEnCs) remained unaffected by R139W-C3 sera, the incubation of those sera with GEnC preactivated with pro-inflammatory stimuli led to increased C3 deposition, C5a release, and procoagulant tissue-factor expression. This functional consequence of R139W-C3 resulted from the formation of a hyperactive C3 convertase. Mutant C3 showed an increased affinity for factor B and a reduced binding to membrane cofactor protein (MCP; CD46), but a normal regulation by factor H (FH). In addition, the frequency of at-risk FH and MCP haplotypes was significantly higher in the R139W-aHUS patients, compared with normal donors or to healthy carriers. These genetic background differences could explain the R139W-aHUS incomplete penetrance. These results demonstrate that this C3 mutation, especially when associated with an at-risk FH and/or MCP haplotypes, becomes pathogenic following an inflammatory endothelium-damaging event.

Human RhAG ammonia channel is impaired by the Phe65Ser mutation in overhydrated stomatocytic red cells.

In red cells, Rh-associated glycoprotein (RhAG) acts as an ammonia channel, as demonstrated by stopped-flow analysis of ghost intracellular pH (pH(i)) changes. Recently, overhydrated hereditary stomatocytosis (OHSt), a rare dominantly inherited hemolytic anemia, was found to be associated with a mutation (Phe65Ser or Ile61Arg) in RHAG. Ghosts from the erythrocytes of four of the OHSt patients with a Phe65Ser mutation were resealed with a pH-sensitive probe and submitted to ammonium gradients. Alkalinization rate constants, reflecting NH(3) transport through the channel and NH(3) diffusion unmediated by RhAG, were deduced from time courses of fluorescence changes. After subtraction of the constant value found for Rh(null) lacking RhAG, we observed that alkalinization rate constant values decreased ∼50% in OHSt compared with those of controls. Similar RhAG expression levels were found in control and OHSt. Since half of the expressed RhAG in OHSt most probably corresponds to the mutated form of RhAG, as expected from the OHSt heterozygous status, this dramatic decrease can be therefore related to the loss of function of the Phe65Ser-mutated RhAG monomer.

Complement alternative pathway acts as a positive feedback amplification of neutrophil activation.

Complement alternative pathway plays an important, but not clearly understood, role in neutrophil-mediated diseases. We here show that neutrophils themselves activate complement when stimulated by cytokines or coagulation-derived factors. In whole blood, tumor necrosis factor/formyl-methionyl-leucyl-phenylalanine or phorbol myristate acetate resulted in C3 fragments binding on neutrophils and monocytes, but not on T cells. Neutrophils, stimulated by tumor necrosis factor, triggered the alternative pathway on their surface in normal and C2-depleted, but not in factor B-depleted serum and on incubation with purified C3, factors B and D. This occurred independently of neutrophil proteases, oxidants, or apoptosis. Neutrophil-secreted properdin was detected on the cell surface and could focus "in situ" the alternative pathway activation. Importantly, complement, in turn, led to further activation of neutrophils, with enhanced CD11b expression and oxidative burst. Complement-induced neutrophil activation involved mostly C5a and possibly C5b-9 complexes, detected on tumor necrosis factor- and serum-activated neutrophils. In conclusion, neutrophil stimulation by cytokines results in an unusual activation of autologous complement by healthy cells. This triggers a new amplification loop in physiologic innate immunity: Neutrophils activate the alternative complement pathway and release C5 fragments, which further amplify neutrophil proinflammatory responses. This mechanism, possibly required for effective host defense, may be relevant to complement involvement in neutrophil-mediated diseases.

Human neutrophil integrin alpha9beta1: up-regulation by cell activation and synergy with beta2 integrins during adhesion to endothelium under flow.

Neutrophil beta1 integrin expression and contribution to cell adhesion were revisited in this study. alpha9beta1 and alpha5beta1 appeared here as the main beta1 integrins expressed on the membrane of resting platelet-depleted neutrophils-alpha6beta1 representing <15% and alpha2beta1 undetectable. Neutrophil activation slightly enhanced alpha5 expression, did not change alpha6, but resulted in a two- to threefold increase of alpha9beta1, which then became the major beta1 integrin of the neutrophil membrane. alpha9beta1 was the only beta1 integrin to be up-regulated after transendothelial migration across TNF-alpha-activated HUVECs. As alpha9beta1 binds VCAM-1, we analyzed its participation to neutrophil adhesion to TNF-alpha-activated endothelial cells. Blocking anti-alpha9 mAb had little effect on neutrophil static adhesion, contrasting with the strong inhibition by anti-beta2 mAb. Under flow conditions, the anti-alpha9 mAb had no effect by itself on neutrophil adhesion to activated HUVECs but enhanced the blocking effect of anti-beta2 antibodies significantly and further enhanced the velocity of beta2-blocked rolling neutrophils. In conclusion, we describe here for the first time a nearly exclusive up-regulation of alpha9beta1 expression among all beta1 integrins during neutrophil activation and transendothelial migration and a possibly important synergy between alpha9beta1 and beta2 integrins in stabilizing neutrophil adhesion to endothelium under flow conditions.

AlphaII-spectrin is critical for cell adhesion and cell cycle.

Spectrins are ubiquitous scaffolding components of the membrane skeleton that organize and stabilize microdomains on both the plasma membrane and the intracellular organelles. By way of their numerous interactions with diverse protein families, they are implicated in various cellular functions. Using small interfering RNA strategy in the WM-266 cell line derived from human melanoma, we found that alphaII-spectrin deficiency is associated with a defect in cell proliferation, which is related to a cell cycle arrest at the G1 phase (first gap phase), as evaluated by DNA analysis and Rb phosphorylation. These observations coincided with elevated expression of the cyclin-dependent kinase inhibitor, p21Cip. Concomitantly, spectrin loss impaired cell adhesion and spreading. These cell adhesion defects were associated with modifications of the actin cytoskeleton, such as loss of stress fibers, alterations of focal adhesions, and modified expression of some integrins. Our results provide novel insights into spectrin functions by demonstrating the involvement of alphaII-spectrin in cell cycle regulation and actin organization.

The cleavage of neutrophil leukosialin (CD43) by cathepsin G releases its extracellular domain and triggers its intramembrane proteolysis by presenilin/gamma-secretase.

The highly negatively charged membrane sialoglycoprotein leukosialin, CD43, is shed during neutrophil activation. This is generally thought to enhance cell adhesion. We here describe two novel consequences of this shedding, during neutrophil activation by phorbol esters or by chemoattractants after TNF-alpha priming. CD43 proteolysis was investigated by Western blotting, using a polyclonal antibody to CD43 intracellular domain. Our data emphasize the importance of a juxtamembranous cleavage of about 50% of membrane CD43 molecules by cathepsin G. Indeed, it is inhibited by alpha1-antichymotrypsin and cathepsin G inhibitor I and is reproduced by exogenous purified cathepsin G. The resulting membrane-anchored C-terminal fragment, CD43-CTF, becomes susceptible to presenilin/gamma-secretase, which releases CD43 intracytoplasmic domain: preincubation with three different gamma-secretase inhibitors, before PMN treatment by agonists or by purified cathepsin G, results in the accumulation of CD43-CTF. Because CD43 binds E-selectin, we also investigated the effect of the soluble extracellular domain CD43s, released by cathepsin G juxtamembranous cleavage, on neutrophil adhesion to endothelial cells. A recombinant CD43s-Fc fusion protein inhibited neutrophil E selectindependent adhesion to endothelial cells under flow conditions, while it had no effect on neutrophil static adhesion. We thus propose that, in addition to its potential pro-adhesive role, CD43 proteolysis results in: (i) the release, by cathepsin G, of CD43 extracellular domain, able to inhibit the adhesion of flowing neutrophils on endothelial cells and thus to participate to the natural control of inflammation; (ii) the release and/or the clearance, by presenilin/gamma-secretase, of CD43 intracellular domain, thereby regulating CD43-mediated signaling.