Cathepsin B localizes to plasma membrane caveolae of differentiating myoblasts and is secreted in an active form at physiological pH

Our in vitro studies support a functional link between the induction of cathepsin B gene expression and the catabolic restructuring associated with myotube formation during myogenesis in vivo. We have tested two predictions that are basic to this hypothesis: (1) that active cathepsin B is localized to plasma membrane caveolae of fusing myoblasts; and (2) that active cathepsin B is secreted from fusing myoblasts at physiological pH. During differentiation, L6 rat myoblasts demonstrated a fusion-related increase in activity associated with the 25/26-kDa, fully processed, active form of cathepsin B. Immunocytochemical studies demonstrated a redistribution of lysosomal cathepsin B protein toward the membrane of fusing myoblasts, and a colocalization of cathepsin B with caveolin-3, the muscle-specific structural protein of membrane caveolae. Sucrose density fractionation and Western blot analysis demonstrated that an active form of cathepsin B localizes to caveolar fractions along with caveolin-3, annexin-VII, beta-dystroglycan and dystrophin. Finally, 'real-time' activity assays and Western blot analysis demonstrated that active cathepsin B is secreted from fusing myoblasts at physiological pH. Collectively, these studies support an association of active cathepsin B with plasma membrane caveolae and the secretion of active cathepsin B from differentiating myoblasts during myoblast fusion.     

Oxygen-bound Hell's gate globin I by classical versus LB nanotemplate method

X‐ray atomic structure of recombinant Hell's gate globin I (HGbI) from Methylacidophilum infernorum was calculated from the X‐ray diffraction data of two different types of crystals: obtained by classical hanging drop and by LB nanotemplate method under the same crystallization conditions. After the accurate comparison of crystallographic parameters and electron density maps of two structures they appears to be quite similar, while the quality of the crystals grown by LB nanotemplate method was higher then of those grown by classical method. Indeed, the resolution of the LB crystal structure was 1.65 Å, while classical crystals showed only 3.2 Å resolution. Moreover, the reproducibility of this result in the case of LB crystals was much better—nine crystals from 10 gave the same structural results, while only two of 10 classical crystals were appropriate for the X‐ray structure resolution. J. Cell. Biochem. 113: 2543–2548, 2012. © 2012 Wiley Periodicals, Inc.     

Research on arbuscular mycorrhizae in Mexico: an historical synthesis and future prospects

This review analyzes the historical development and advances of the research on arbuscular mycorrhizal fungi (AMF) in Mexico, as well as the prospects for future research. AMF-research has been focused on studying both diversity and functionality in several ecosystems of Mexico, but mainly in the tropical dry and rainy ecosystems, and the agricultural systems. In Mexico, 95 species of AMF have been recorded, representing 41% of the known species worldwide. The functional effects of AMF colonization have been examined in approximately 10% of the known host plants, but greenhouse studies continue to dominate over those conducted under field conditions. Even though research to date has been at the organismic level, further effort is needed due to the high plant diversity in Mexico. Studies on AMF biomass under field conditions and more taxonomic determination are required based on morphological features, biochemical determinations (fatty acids) and molecular tools. In addition, ecophysiological and ecological in situ studies would help in understanding the relationships among AMF, soil fauna, nutrients, and host plants. The contribution of AMF to ecosystemic processes is a priority line of research that requires an integrated approach (inter- and multidisciplinary) in order to define the role of AM symbioses for biogeochemical models. The creation of a Mexican mycorrhizal research network has and will help to identify the main challenges. Generating similar research protocols, and sharing databases and experience will assist mycorrhizologists working under the diverse financial and ecological contexts that is to be found in Mexico and Latin America.     

Neurovascular Unit: a Focus on Pericytes

The blood–brain barrier (BBB) is a highly specialized system that controls the exchanges between the blood and the central nervous system (CNS). This barrier shields the CNS from toxic substances in the blood and provides nutrients to CNS, thus playing an essential role in the maintenance of homeostasis. The anatomical basis of the BBB is formed by the endothelial cells of brain microvasculature, with elaborated tight and adherens junctions, which together with pericytes, the basement membrane, and astrocytes, as well as neurons, microglia and oligodendrocytes form the neurovascular unit. The interaction between all these components guarantees a proper environment for neural function and a restricted permeability and transport. Pericytes were initially reported by Rouget in 1873 and since then they have been recognized as an important component of the BBB, despite the difficulty of their identification. Diverse functions have been assigned to pericytes, including a role in BBB properties, hemostasis, and angiogenesis, as well as a contractile, immune, and phagocytic function. These cells are also seen like multipotent cells and so with a great potential for therapy. Here, we review the neurovascular unit composition and the interplay between the diverse components, addressing pericytes with a particular detail.     

Shifting of immune responsiveness to house dust mite by influenza A infection: genomic insights

Respiratory viral infections have been associated with an increased incidence of allergic asthma. However, the mechanisms by which respiratory infections facilitate allergic airway disease are incompletely understood. We previously showed that exposure to a low dose of house dust mite (HDM) resulted in enhanced HDM-mediated allergic airway inflammation, and, importantly, marked airway hyperreactivity only when allergen exposure occurred during an acute influenza A infection. In this study, we evaluated the impact of concurrent influenza infection and allergen exposure at the genomic level, using whole-genome microarray. Our data showed that, in contrast to exposure to a low dose of HDM, influenza A infection led to a dramatic increase in gene expression, particularly of TLRs, C-type lectin receptors, several complement components, as well as FcεR1. Additionally, we observed increased expression of a number of genes encoding chemokines and cytokines associated with the recruitment of proinflammatory cells. Moreover, HDM exposure in the context of an influenza A infection resulted in the induction of unique genes, including calgranulin A (S100a8), an endogenous damage-associated molecular pattern and TLR4 agonist. In addition, we observed significantly increased expression of serum amyloid A (Saa3) and serine protease inhibitor 3n (Serpina3n). This study showed that influenza infection markedly increased the expression of multiple gene classes capable of sensing allergens and amplifying the ensuing immune-inflammatory response. We propose that influenza A infection primes the lung environment in such a way as to lower the threshold of allergen responsiveness, thus facilitating the emergence of a clinically significant allergic phenotype.     

Using the Hard, Randy, and Rittler Test to Evaluate Color Vision in Capuchins (Cebus libidinosus)

The identification of color vision types in primates is fundamental to understanding the evolution and biological function of color perception. The Hard, Randy, and Rittler (HRR) pseudoisochromatic test categorizes human color vision types successfully. Here we provide an experimental setup to employ HRR in a nonhuman primate, the capuchin (Cebus libidinosus), a platyrrhine with polymorphic color vision. The HRR test consists of plates with a matrix composed of gray circles that vary in size and brightness. Differently colored circles form a geometric shape (X, O, or Δ) that is discriminated visually from the gray background pattern. The ability to identify these shapes determines the type of dyschromatopsy (deficiency in color vision). We tested six capuchins in their own cages under natural sunlight. The subjects chose between two HRR plates in each trial: one with the gray pattern only and the other with a colored shape, presented on the left or right side at random. We presented the test 40 times and calculated the 95?% confidence limits for chance performance based on the binomial test. We also genotyped all subjects for exons 3 and 5 of the X-linked opsin genes. The HRR test diagnosed two subjects as protan dichromats (missing or defective L-cone), three as deutan dichromats (missing or defective M-cone), and one female as trichromat. Genetic analysis supported the behavioral data for all subjects. These findings show that the HRR test can be applied to diagnose color vision in nonhuman primates.     

Application of the Apn2/MAT locus to improve the systematics of the Colletotrichum gloeosporioides complex: an example from coffee (Coffea spp.) hosts

To improve phylogenetic resolution of the Colletotrichum gloeosporioides species complex we developed and tested the performance of a new set of primers for the Apn2/MAT locus with a case study of 22 isolates. These were isolated mainly from coffee plants and represent six divergent and well characterized species within the C. gloeosporioides complex. Following previous studies on this locus, we have generated sequence data from an expanded region (> 4600 bp), revealing increased phylogenetic informativeness when compared to other commonly used markers such as ITS, β-tub2 and GS. Within the Apn2/MAT locus the ApMAT marker alone was almost as informative in terms of phylogenetic resolution as a seven-gene concatenated dataset. Our results further revealed that gene-tree discordance may come to be a common issue in resolving evolutionary relationships in the C. gloeosporioides complex, highlighting the importance of multilocus approaches. The use of state-of-the-art data analysis techniques and a highly informative dataset as employed here may abate this issue and hopefully assist in disentangling the C. gloeosporioides complex.