Universality of rain event size distributions

We compare rain event size distributions derived from measurements in climatically different regions, which we find to be well approximated by power laws of similar exponents over broad ranges. Differences can be seen in the large-scale cutoffs of the distributions. Event duration distributions suggest that the scale-free aspects are related to the absence of characteristic scales in the meteorological mesoscale.

The nuclear matrix: a critical appraisal.

It is becoming increasingly clear that the cell nucleus is a highly structurized organelle. Because of its tight compartmentalization, it is generally believed that a framework must exist, responsible for maintaining such a spatial organization. Over the last twenty years many investigations have been devoted to identifying the nuclear framework. Structures isolated by different techniques have been obtained in vitro and are variously referred to as nuclear matrix, nucleoskeleton or nuclear scaffold. Many different functions, such as DNA replication and repair, mRNA transcription, processing and transport have been described to occur in close association with these structures. However, there is still much debate as to whether or not any of these preparations corresponds to a nuclear framework that exists in vivo. In this article we summarize the most commonly-used methods for obtaining preparations of nuclear frameworks and we also stress the possible artifacts that can be created in vitro during the isolation procedures. Emphasis is placed also on the protein composition of the frameworks as well as on some possible signalling functions that have been recently described to occur in tight association with the nuclear matrix.

Pathology of the spleen in hepatosplenic schistosomiasis. Morphometric evaluation and extracellular matrix changes

Histological, ultrastructural, morphometric and immunohistochemical data obtained from the study of spleens removed by splenectomy from 34 patients with advanced hepatosplenic schistosomiasis revealed that the main alterations were congestive dilatation of the venous sinuses and diffuse thickening of the splenic cords. Splenic cord thickening was due to an increase of its matrix components, especially type IV collagen and laminin, with the conspicuous absence of interstitial collagens, either of type I or type III. Deposition of interstitial collagens (types I and III) occurred in scattered, small focal areas of the red pulp, but in the outside of the walls of the venous sinuses, in lymph follicles, marginal zone, in the vicinity of fibrous trabeculae and in sidero-sclerotic nodules. However, fibrosis was not a prominent change in schistosomal splenomegaly and thus the designation "fibro-congestive splenomegaly" seems inadequate. Lymph follicles exhibited variable degrees of atrophy, hyperplasia and fibrous replacement, sometimes all of them seen in different follicles of the same spleen and even in the same examined section. Changes in white pulp did not seem to greatly contribute to increasing spleen size and weight, when compared to the much more significant red pulp enlargement.

Break zones in the distributions of alleles and species in alpine plants

Aim  We test for the congruence between allele-based range boundaries (break zones) in silicicolous alpine plants and species-based break zones in the silicicolous flora of the European Alps. We also ask whether such break zones coincide with areas of large elevational variation.Location  The European Alps.Methods  On a regular grid laid across the entire Alps, we determined areas of allele- and species-based break zones using respective clustering algorithms, identifying discontinuities in cluster distributions (breaks), and quantifying integrated break densities (break zones). Discontinuities were identified based on the intra-specific genetic variation of 12 species and on the floristic distribution data from 239 species, respectively. Coincidence between the two types of break zones was tested using Spearman's correlation. Break zone densities were also regressed on topographical complexity to test for the effect of elevational variation.Results  We found that two main break zones in the distribution of alleles and species were significantly correlated. Furthermore, we show that these break zones are in topographically complex regions, characterized by massive elevational ranges owing to high mountains and deep glacial valleys. We detected a third break zone in the distribution of species in the eastern Alps, which is not correlated with topographic complexity, and which is also not evident from allelic distribution patterns. Species with the potential for long-distance dispersal tended to show larger distribution ranges than short-distance dispersers.Main conclusions  We suggest that the history of Pleistocene glaciations is the main driver of the congruence between allele-based and species-based distribution patterns, because occurrences of both species and alleles were subject to the same processes (such as extinction, migration and drift) that shaped the distributions of species and genetic lineages. Large elevational ranges have had a profound effect as a dispersal barrier for alleles during post-glacial immigration. Because plant species, unlike alleles, cannot spread via pollen but only via seed, and thus disperse less effectively, we conclude that species break zones are maintained over longer time spans and reflect more ancient patterns than allele break zones.Conny Thiel-Egenter and Nadir Alvarez contributed equally to this paper and are considered joint first authors.

Extracellular matrix and platelet function in patients with musculocontractural Ehlers-Danlos syndrome caused by mutations in the CHST14 gene.

We report on a consanguineous, Afghani family with two sisters affected with characteristic facial features, multiple contractures, progressive joint and skin laxity, hemorrhagic diathesis following minor trauma and multisystem fragility-related manifestations suggestive of a diagnosis of musculocontractural Ehlers-Danlos syndrome (EDS). This novel form of connective tissue disorder was recently reported in patients of Japanese, Turkish, and Indian descent who were formerly classified as having EDS type VIB and has now been recognized to be a part of spectrum including patients previously classified as having adducted thumb-clubfoot syndrome. We identified a previously unreported mutation in the CHST14 gene, which codes for the enzyme dermatan 4-O-sulfotransferase. We discuss the prenatal presentation, detailed clinical manifestations, and neurological findings in two sisters with this newly described musculocontractural EDS-CHST14 type. We demonstrate that fibroblasts from one of our patients produce more chondroitin sulfate than normal and show lower than normal deposition of collagens I and II and fibrillin 1-containing microfibrills. These findings suggest that the imbalance in the glycosaminoglycan content in developing tissues might interfere with normal deposition of other extracellular matrix components and ultimately contribute to the development of the phenotype observed in these patients. Furthermore, we ruled out the contribution of intrinsic platelet factors to the bleeding diathesis observed in some affected individuals. © 2012 Wiley Periodicals, Inc.

Predicting reptile distributions at the mesoscale: relation to climate and topography

Aim To explore the respective power of climate and topography to predict the distribution of reptiles in Switzerland, hence at a mesoscale level. A more detailed knowledge of these relationships, in combination with maps of the potential distribution derived from the models, is a valuable contribution to the design of conservation strategies. Location All of Switzerland. Methods Generalized linear models are used to derive predictive habitat distribution models from eco-geographical predictors in a geographical information system, using species data from a field survey conducted between 1980 and 1999. Results The maximum amount of deviance explained by climatic models is 65%, and 50% by topographical models. Low values were obtained with both sets of predictors for three species that are widely distributed in all parts of the country (Anguis fragilis , Coronella austriaca , and Natrix natrix), a result that suggests that including other important predictors, such as resources, should improve the models in further studies. With respect to topographical predictors, low values were also obtained for two species where we anticipated a strong response to aspect and slope, Podarcis muralis and Vipera aspis . Main conclusions Overall, both models and maps derived from climatic predictors more closely match the actual reptile distributions than those based on topography. These results suggest that the distributional limits of reptile species with a restricted range in Switzerland are largely set by climatic, predominantly temperature-related, factors.

Quantitave and qualitative interferences of pentoxifillyne on hepatic Schistosoma mansoni granulomas: effects on extracellular matrix and eosinophil population

Mast cells and eosinophils actively participate in tissue repair and are prominent components of Schistosoma mansoni granulomas. Since pentoxifillyne (PTX) is an immunomodulatory and antifibrotic substance, we aimed to characterize, by morphological techniques, the effect of this drug on fibrosis developed inside murine hepatic schistosomal granulomatous reaction, beyond the quantification of eosinophil and mast cell populations. The drug (1 mg/100 g animal weight) was administrated from 35 to 90 days post-infection, when the animals were killed. The intragranulomatous interstitial collagen network was analyzed by confocal laser scanning microscopy, the number of eosinophils and mast cells was quantified and the results were validated by t-student test. Treatment did not interfere on the granuloma evolution but caused a significant decrease in the total and involutive number of hepatic granulomas (p = 0.01 and 0.001, respectivelly), and in the intragranulomatous accumulation of eosinophils (p = 0.0001). Otherwise, the number of mast cells was not significantly altered (p = 0.9); however, it was positively correlated with the number of granulomatous structures (r = 0.955). In conclusion, PTX does not affect development and collagen deposition in S. mansoni murine granuloma, but decreases the intragranulomatous eosinophil accumulation possibly due to its immunomodulatory capability, interfering in cellular recruitment and/or differentiation.

Derris (Lonchocarpus) urucu (Leguminosae) Extract Modifies the Peritrophic Matrix Structure of Aedes aegypti (Diptera:Culicidae)

Aqueous suspension of ethanol extracts of Derris (Lonchocarpus) urucu (Leguminosae), collected in the state of Amazonas, Brazil, were tested for larvicidal activity against the mosquito Aedes aegypti (Diptera:Culicidae). The aim of this study was to observe the alterations of peritrophic matrix in Ae. aegypti larvae treated with an aqueous suspension of D. urucu extract. Different concentrations of D. urucu root extract were tested against fourth instar larvae. One hundred percent mortality was observed at 150 µg/ml (LC50 17.6 µg/ml) 24 h following treatment. In response to D. urucu feeding, larvae excreted a large amount of amorphous feces, while control larvae did not produce feces during the assay period. Ultrastructural studies showed that larvae fed with 150 µg/ml of D. urucu extract for 4 h have an imperfect peritrophic matrix and extensive damage of the midgut epithelium. Data indicate a protective role for the peritrophic matrix. The structural modification of the peritrophic matrix is intrinsically associated with larval mortality.

Early functional differentiation in the chick embryonic disc: interaction between mechanical activity and extracellular matrix

The mechanical behaviour of ectodermal cells in the area opaca and the supracellular organization of fibronectin in the adjacent extracellular matrix were studied in whole chick blastoderms developing in vitro. The pattern of spontaneous mechanical activity and its modification by immunoglobulins against fibronectin were determined using a real-time image-analysis system. The pattern of fibronectin was studied using immunocytochemical techniques. It was found that the ectodermal cells in the area opaca actively develop a radially oriented contraction, which leads to a distension of the area pellucida from which the embryo develops. Abnormally increased tension resulted in perturbations of gastrulation and neurulation. An optimized mechanical equilibrium within the blastoderm seems to be necessary for normal development. Anti-fibronectin antibodies applied to the basal side of the blastoderm led rapidly and reversibly to an increase of tension in the contracted cells. This observation indicates that modifications of the extracellular matrix can be transmitted to cytoskeletal elements within adjacent cells. The extracellular matrix of the area opaca contains fibronectin arranged in radially oriented fibrils. This orientation corresponds to the direction of migration of the mesodermal cells. Interestingly, the radial pattern of fibronectin is found in the regions where the ectodermal cells are contracted and develop radially oriented forces. This observation suggests that the supracellular assembly of the extracellular materials could be influenced by the mechanical activity of adjacent cells. Possible modulations of the supracellular organization of extracellular matrix by other factors, e.g. diffusible metabolites, is also discussed. The presence of characteristically organized extracellular matrix components, of spatially differentiated cell activities and of reciprocal interactions between them makes the young chick blastoderm an excellent system for physiological studies of the coordinated cellular activities that lead to changes in form, complexity and function.

Fibrogenesis and collagen resorption in the heart and skeletal muscle of Calomys callosus experimentally infected with Trypanosoma cruzi: immunohistochemical identification of extracellular matrix components

Intense inflammatory lesions and early development of interstitial fibrosis of the myocardium and skeletal muscle with spontaneous regression, have been described in Calomys callosus infected with Trypanosoma cruzi. The genetic types of collagen present in this model were investigated through immunohistochemistry using specific antibodies, combined with histopathology and Picro-Sirius staining of collagen. Thirty-five calomys were infected with the Colombian strain of T. cruzi and sacrificed at 24, 30, 40, 60 and 90 days post-infection. Inflammatory lesions and fibrogenesis were prominent at the early phase of infection and significantly decreased during late infection. Immunoisotyping of the matrix components was performed by indirect immunofluorescence on 5 µm thick cryostat sections using specific antibodies against laminin, fibronectin and isotypes I, III and IV of collagen. In the early phase, positive deposits of all the matrix components were present, with predominance of fibronectin, laminin and collagens types I and III in the myocardium and of types III and IV in the skeletal muscles. From the 40th day, type IV collagen predominates in the heart. At the late phase of infection (60th to 90th day), a clear fragmentation and decrease of all the matrix components were detected. Findings of the present study indicate that a modulation of the inflammatory process occurs in the model of C. callosus, leading to spontaneous regression of fibrosis independent of the genetic types of collagen involved in this process.

Morphometric discrimination of females of five species of Anopheles of the subgenus Nyssorhynchus from Southern and Northwest Colombia

The most important vectors of human Plasmodium in the neotropics belong to the subgenus Nyssorhynchus. These species are generally sympatric in terms of their geographical distributions. Some are difficult to identify based solely on examination of adult females using the available morphological keys, in these cases examination of immature stages and male genitalia is required to make correct determinations. However, in epidemiological studies it is necessary to identify the species of adult females which are found near humans, i.e. in studies of malaria transmission or evaluation of control measures. The purpose of the present study was to evaluate the discrimination of adult females of different species of Nyssorhynchus isolated mainly from Southern Colombia (department of Putumayo), using morphometric analysis. Adult females were obtained after rearing larvae collected in natural breeding places and from the progeny of females collected on humans. The morphological characteristics of the immature stages allowed the identification of four species of the subgroup Oswaldoi from Southern Colombia: Anopheles rangeli Gabaldon, Cova Garcia & Lopez, An. oswaldoi (Peryassu), An. benarrochi Gabaldon, Cova Garcia & Lopez and An. triannulatus (Neiva & Pinto). The species An. nuneztovari (Gabaldon) from the Northwest of Colombia was included for comparison. Morphometric analysis allowed differentiation of the females of all species to a confidence level approaching 90% using principal components analysis of 10 wing and leg variables, followed by canonical variate analysis of the first four principal components. We conclude that morphometrics may represent a useful taxonomic tool for this group and that its use should be further studied.

Extra-cellular matrix changes in Schistosoma mansoni-infected Biomphalaria glabrata

Reactivity of snails against parasites exhibits a primitive focal reaction, with encapsulation, phagocytosis and destruction of parasite larvae by macrophage-like cells - the hemocytes. This reaction mimics granulomatous inflammation seen in higher animals. However, different from the latter, little is known about the participation of extra-cellular matrix in such snail defense reactions. Normal and Schistosoma mansoni-infected Biomphalaria glabrata of different strains were submitted to cytological, histological, ultrastructural and biochemical methods in order to investigate the behavior of extra-cellular tissues at the site of anti-parasite reactions. In spite of the presence of two cell-types in peripheral hemolymph, only one cell-type was present at the sites of tissue reactions. Although pre-existent collagen and elastic fibers and microfibrils sometimes appeared slightly compressed around focal reactions, no evidences of duplication, synthesis or deposition of connective-tissue extra-cellular components were observed within or around the zones of reactive cell accumulations. Thus, tissue reactions against S. mansoni in the snail B. glabrata appeared exclusively dependent on one specific population of hemocytes.

Tissue-specific and SRSF1-dependent splicing of fibronectin, a matrix protein that controls host cell invasion.

Cell invasion targets specific tissues in physiological placental implantation and pathological metastasis, which raises questions about how this process is controlled. We compare dermis and endometrium capacities to support trophoblast invasion, using matching sets of human primary fibroblasts in a coculture assay with human placental explants. Substituting endometrium, the natural trophoblast target, with dermis dramatically reduces trophoblast interstitial invasion. Our data reveal that endometrium expresses a higher rate of the fibronectin (FN) extra type III domain A+ (EDA+) splicing isoform, which displays stronger matrix incorporation capacity. We demonstrate that the high FN content of the endometrium matrix, and not specifically the EDA domain, supports trophoblast invasion by showing that forced incorporation of plasma FN (EDA-) promotes efficient trophoblast invasion. We further show that the serine/arginine-rich protein serine/arginine-rich splicing factor 1 (SRSF1) is more highly expressed in endometrium and, using RNA interference, that it is involved in the higher EDA exon inclusion rate in endometrium. Our data therefore show a mechanism by which tissues can be distinguished, for their capacity to support invasion, by their different rates of EDA inclusion, linked to their SRSF1 protein levels. In the broader context of cancer pathology, the results suggest that SRSF1 might play a central role not only in the tumor cells, but also in the surrounding stroma.