Characterization of binding of human fibrinogen to the surface of germ-tubes and mycelium of candida albicans

The binding of human fibrinogen to germ-tubes and mycelium of Candida albicans, forms usually found in infected tissues, was studied in vitro by an immunofluorescence assay. Binding was quantified by using 125I-labelled fibrinogen. The degree of binding differed according to the morphological form of the fungus. Binding relative to that of the yeast form was greater for mycelium (12-fold) than for germ-tube (7.7-fold). Pretreatment of yeasts with fragments D and E (terminal degradation products of fibrinogen) before fibrinogen binding showed that fragment D possessed a higher affinity for C. albicans than fragment E. Binding of fibrinogen was diminished when C. albicans was pretreated with 2-mercaptoethanol alone or in combination with pronase, or pretreated with alpha-mannosidase or trypsin. Binding was not decreased by pretreatment with pronase alone or chitinase. Inhibition experiments using C. albicans dialysed culture filtrate, C. albicans mannan, chitin, sugars or amino sugars were done by preabsorbing the fibrinogen with each of the above mentioned compounds. C. albicans dialysed culture filtrate inhibited the binding more strongly than C. albicans mannan. However, fibrinogen binding to C. albicans was not significantly reduced by mannose, several other sugars or chitin. These studies demonstrate the existence of a fibrinogen-binding factor (FBF) strongly associated with the surface of germ-tube and filamentous forms of C. albicans, and indicate a possible role for FBF in the pathogenicity of C. albicans.     

Opinion Formation Models on a Gradient

Statistical physicists have become interested in models of collective social behavior such as opinion formation, where individuals change their inherently preferred opinion if their friends disagree. Real preferences often depend on regional cultural differences, which we model here as a spatial gradient g in the initial opinion. The gradient does not only add reality to the model. It can also reveal that opinion clusters in two dimensions are typically in the standard (i.e., independent) percolation universality class, thus settling a recent controversy about a non-consensus model. However, using analytical and numerical tools, we also present a model where the width of the transition between opinions scales , not as in independent percolation, and the cluster size distribution is consistent with first-order percolation.     

Picturing beach erosion and deposition trends using PSInSAR: an example from the non-barred southern west coast of India

Coastal dynamics can rapidly alter beach morphology. In some places, such as the non-barred southern west coast of India, studying changes to beach morphology is a relatively arduous task. Persistent Scatterer Interferometric Synthetic Aperture Radar (PSInSAR), a remote sensing technique that utilizes stacks of radar images for accurate long-term monitoring of ground features, allows for detailed observations of coastal morphodynamics. Twenty-two single look complex (SLC) synthetic aperture radar (SAR) Sentinel-1A images, acquired from 4 March 2016 to 3 June 2017, are used to monitor geomorphological processes such as coastal erosion and deposition. Ground deformation measurements from PSInSAR processing shows the coast stretching?~?70 km between Thaickal and Munambam is highly dynamic, characterized by phases of erosion and deposition. The highest negative displacement of ? 24.9 mm at Thaickal versus the?+?7.6 mm at Chellanam in the north show the co-existing milieus of erosion and deposition. PSInSAR results concur with corresponding Google Earth images. In addition, beach sediment texture and scanning electron microscope grain micro-texture in the beach segment further corroborate temporal phases of erosion and deposition. Two locations are identified as typical erosional sites, while one location typified deposition. Erosion and deposition or rebuilding of beaches, usually correspond respectively with the onset and offset of SW monsoon wave climate in the Arabian Sea. When zones of deposition are mainly located in the proximity of river and/or lake inlets, stretches characterized by erosion are distal to inlets. Linear regression analyses of displacement–time series plots were used to identify general erosion or depositional regimes along beach segments. Results from this study illustrate how PSInSAR is a capable and reliable processing tool for monitoring temporal phases of coastal morpho-dynamics.

     

The K-Segments of the Wheat Dehydrin DHN-5 are Essential for the Protection of Lactate Dehydrogenase and β-Glucosidase Activities In Vitro

The wheat dehydrin DHN-5 has been previously shown to exhibit heat protecting effect on enzymatic activities. In order to understand the molecular mechanism by which DHN-5 exerts its protective function, we performed an approach to dissect the functional domains of DHN-5 responsible for this feature. In two distinct enzymatic assays, we found that the truncated forms of DHN-5 containing only one K- or two K-segments are able to protect albeit to less extent than the wild type protein, lactate dehydrogenase and β-glucosidase against damage induced by various stresses in vitro. However, the YS- and Φ-segments alone have no protective effects on these enzymes. Therefore, our study provides the evidence that the protective function of DHN-5 seems to be directly linked to its K-segments which through their amphipatic α-helical structure, may act to prevent protein aggregation.     

Differentiation of Fanconi anemia and aplastic anemia using mitomycin C test in Tunisia

Fanconi anemia (FA) is a recessive chromosomal instability syndrome that is clinically characterized by multiple symptoms. Chromosome breakage hypersensitivity to alkylating agents is the gold standard test for FA diagnosis. In this study, we provide a detailed laboratory protocol for accurate assessment of FA diagnosis based on mitomycin C (MMC) test. Induced chromosomal breakage study was successful in 171 out of 205 aplastic anemia (AA) patients. According to the sensitivity of MMC at 50 ng/ml, 38 patients (22.22%) were diagnosed as affected and 132 patients (77.17%) as unaffected. Somatic mosaicism was suspected in an 11-year-old patient with a FA phenotype. Twenty-six siblings of FA patients were also evaluated and five of them (19.23%) were diagnosed as FA. From this study, a standard protocol for diagnosis of FA was developed. It is routinely used as a diagnostic test of FA in Tunisia.     

Fanconi anemia: contribution of molecular analyses to the identification of bone marrow graft donors and the study of chimerism in grafted patients

We report on the effectiveness of molecular studies regarding Fanconi anemia (FA) for a better selection of bone marrow graft donors and for post-transplant follow up. Ten unrelated FA patients and their families were analyzed by microsatellite markers. In 9 cases, the cytogenetic investigation of potential human leukocyte antigen (HLA)-identical related donors was normal, and the molecular analyses confirmed that they were also either normal or heterozygous carriers. For 1 patient, cytogenetic analysis of an HLA-identical sibling donor yielded ambiguous results with a relatively high number of chromosomal breakages using cross-linking agents. However, genotyping of this potential donor demonstrated his heterozygous state. Nine patients have received allogeneic bone marrow transplantation from HLA-matched related donors. Microsatellite analysis showed complete chimerism (CC) in all cases. The median follow up was 54 months (range 8-144 months). One patient out of 9 with CC rejected her graft without prior detection of a transitional mixed chimerism. Among these patients, 1 died 25 months after the transplantation of a chronic graft-versus-host-disease (GVHD). We conclude that, when the cytogenetic studies are not conclusive, molecular analyses are crucial to distinguish heterozygous carriers from asymptomatic FA Tunisian patients. Molecular analyses also allowed the evaluation of hematopoietic chimerism after allogeneic bone marrow transplantation and might be of value to identify patients with a high risk for graft rejection.     

Sequence Polymorphism of Cytochrome b Gene in Theileria annulata Tunisian Isolates and Its Association with Buparvaquone Treatment Failure

Background

Buparvaquone (BW 720C) is the major hydroxynaphtoquinone active against tropical theileriosis (Theileria annulata infection). Previous studies showed that buparvaquone, similarly to others hydroxynaphtoquinone, probably acts by binding to cytochrome b (cyt b) inhibiting the electron transport chain in the parasite. Several observations suggested that T. annulata is becoming resistant to buparvaquone in many endemic regions (Tunisia, Turkey and Iran), which may hinder the development of bovine livestock in these areas.

Methodology/Principal Findings

In the present study we sought to determine whether point mutations in T. annulata cytochrome b gene could be associated to buparvaquone resistance. A total of 28 clones were studied in this work, 19 of which were obtained from 3 resistant isolates (ST2/12, ST2/13 and ST2/19) collected at different time after treatment, from a field treatment failure and nine clones isolated from 4 sensitive stocks of T. annulata (Beja, Battan, Jed4 and Sousse). The cytochrome b gene was amplified and sequenced. We identified five point mutations at the protein sequences (114, 129, 253, 262 and 347) specific for the clones isolated from resistant stocks. Two of them affecting 68% (13/19) of resistant clones, are present in the drug-binding site Q₀₂ region at the position 253 in three resistant clones and at the position 262 in 11 out of 19 resistant clones. These two mutations substitute a neutral and hydrophobic amino acids by polar and hydrophilic ones which could interfere with the drug binding capabilities. When we compared our sequences to the Iranian ones, the phylogenetic tree analyses show the presence of a geographical sub-structuring in the population of T. annulata.

Conclusions/Significance

Taken together, our results suggest that the cytochrome b gene may be used as a tool to discriminate between different T. annulata genotypes and also as a genetic marker to characterize resistant isolates of T. annulata.     

TMKP1 is a novel wheat stress responsive MAP kinase phosphatase localized in the nucleus

The regulation of plant signalling responses by Mitogen-Activated Protein Kinases (MAPKs)-mediated protein phosphorylation is well recognized. MAP kinase phosphatases (MKPs) are negative regulators of MAPKs in eukaryotes. We report here the identification and the characterization of TMKP1, the first wheat MKP (Triticum turgidum L. subsp. Durum). Expression profile analyses performed in two durum wheat cultivars showing a marked difference in salt and drought stress tolerance, revealed a differential regulation of TMKP1. Under salt and osmotic stress, TMKP1 is induced in the sensitive wheat variety and repressed in the tolerant one. A recombinant TMKP1 was shown to be an active phosphatase and capable to interact specifically with two wheat MAPKs (TMPK3 and TMPK6). In BY2 tobacco cells transiently expressing GFP::TMKP1, the fusion protein was localized into the nucleus. Interestingly, the deletion of the N-terminal non catalytic domain results in a strong accumulation of the truncated fusion protein in the cytoplasm. In addition, when expressed in BY2 cells, TMPK3 and TMPK6 fused to red fluorescent protein (RFP) were shown to be present predominantly in the nucleus. Surprisingly, when co-expressed with the N-terminal truncated TMKP1 fusion protein; both kinases are excluded from the nuclear compartment and accumulate in the cytoplasm. This strongly suggests that TMKP1 interacts in vivo with TMPK3 and TMPK6 and controls their subcellular localization. Taken together, our results show that the newly isolated wheat MKP might play an active role in modulating the plant cell responses to salt and osmotic stress responses.