Regulation of Opioid Receptors by Their Endogenous Opioid Peptides

Cellular and Molecular Neurobiology - Activation of μ, δ, and κ opioid receptors by endogenous opioid peptides leads to the regulation of many emotional and physiological responses....     

Distinctive Effects of Cytochalasin B in Chick Primary Myoblasts and Fibroblasts

Actin-based structures play fundamental roles in cellular functions. However it remains controversial how cells cope with the absence of F-actin structures. This report focuses on short- and long-term effects of cytochalasin B (CB) on actin-complexes in fibroblasts and myoblasts. Thirty min of CB treatment dispersed subplasma actin cortices, lamellipodia, ruffled membranes, stress fibers and adhesion plaques into actin patches in fibroblasts and muscle cells. In contrast, 72 hrs CB treatment showed distinct morphological effects. Fibroblasts became giant multinucleated-finger shaped with 5 to 10 protrusions, 3–8 μm in width, and >200 μm in length. They lacked cortical actin, stress fibers, adhesion plaques and ruffled membranes but contained immense lamelliopodia with abnormal adhesion plaque protein complexes. Muscle cells transformed into multinucleated globular-shaped but contained normal I-Z-I and A-bands, indicating that CB did not interfere with the assembly of myofibrils. Within 30 min after CB removal, finger-shaped fibroblasts returned to their original shape and actin-containing structures rapidly reappeared, whereas muscle cells respond slowly to form elongated myotubes following CB washout. The capacity to grow, complete several nuclear cycles, assemble intermediate filaments and microtubules without a morphologically recognizable actin cytoskeleton raises interesting issues related to the role of the actin compartments in eukaryotic cells.     

Isoproterenol induces an increase in muscle fiber size by the proliferation of Pax7‐positive cells and in a mTOR‐independent mechanism

β‐Adrenergic signaling regulates many physiological processes in skeletal muscles. A wealth of evidence has shown that β‐agonists can increase skeletal muscle mass in vertebrates. Nevertheless, to date, the specific role of β‐adrenergic receptors in different cell phenotypes (myoblasts, fibroblasts, and myotubes) and during the different steps of embryonic skeletal muscle differentiation has not been studied. Therefore, here we address this question through the analysis of embryonic chick primary cultures of skeletal muscle cells during the formation of multinucleated myotubes. We used isoproterenol (ISO), a β‐adrenergic receptor agonist, to activate the β‐adrenergic signaling and quantified several aspects of muscle differentiation. ISO induced an increase in myoblast proliferation, in the percentage of Pax7‐positive myoblasts and in the size of skeletal muscle fibers, suggesting that ISO activates a hyperplasic and hypertrophic muscle response. Interestingly, treatment with ISO did not alter the number of fibroblast cells, suggesting that ISO effects are specific to muscle cells in the case of chick myogenic cell culture. We also show that rapamycin, an inhibitor of the mammalian target of rapamycin signaling pathway, did not prevent the effects of ISO on chick muscle fiber size. The collection of these results provides new insights into the role of β‐adrenergic signaling during skeletal muscle proliferation and differentiation and specifically in the regulation of skeletal muscle hyperplasia and hypertrophy.     

Leaf functional traits and monodominance in Southern Amazonia tropical forests

Tropical monodominant forests are rare communities with low tree species diversity. Species monodominance is not the product of a single mechanism, but the result of a set of not yet fully understood integrated ecological factors acting together. We compared populations of Brosimum rubescens in monodominant and mixed forests in Southern Amazonia to test whether leaf functional traits are ecological factors related to monodominance. Individuals of B. rubescens in the mixed forest invest in conservative strategies, while those in the monodominant forest invest in acquisitive strategies. Leaf functional traits, such as petiole length and adaxial cuticle thickness, could be associated with the monodominance of B. rubescens. Our study highlights for the first time the power of integrating leaf functional traits as a component of the set of ecological conditions to explain species monodominance. B. rubescens showed different functional strategies to establish and maintain its population in different forests, which makes it a strong competitor for resources, such as water and light, through variation in its leaf functional traits. We also suggest that such high plasticity can be an important condition for the persistence of the species over time.

     

Isolation and identification of mycobacteria from livestock specimens and milk obtained in Brazil

The prevalence of Mycobacterium bovis and other mycobacterial species in livestock specimens and milk was evaluated. An emphasis was placed upon the distribution of these organisms in milk that is readily available to the public that was either untreated, pasteurized, or treated using ultra high temperature. Twenty-two pathologic specimens from livestock (bovine, swine and bubaline) in five Brazilian states and 128 bovine milk samples from retail markets in the State of S o Paulo were examined for mycobacteria. Identification was made by classical biochemical tests, thin layer chromatography of mycolic acids and polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis. Mycobacteria were isolated from 15 (68.2%) caseous lesions and from 23 (18%) milk samples. Eleven isolates were identified as M. bovis, and the remaining 27 nontuberculous mycobacterial isolates were represented by five species and six unidentified rapidly growing mycobacterial strains. The data demonstrate that animal products in Brazil are frequent reservoirs of mycobacteria and may pose a risk to the public.     

A new classification of resin-based aesthetic adhesive materials

The purpose of this article is to illustrate a new classification of resin based aesthetic materials laying on the characterization of their matrix and their filler morphology. Four samples per material have been prepared for SEM evaluation. Each sample has been treated with chloroform to dissolve its matrix in order to evidence the filler morphology. A general schema of four different matrix systems which characterize the material's level of hydrophobicity can be put in evidence. The subsequent filler analysis individuates a more complex schema based on filler size and construction. A new classification based on matrix nature and filler morphology has been proposed. Based on this concept mechanical and aesthetic characteristics of the materials can be presumed.     

Digestive tract ontogeny of Dicentrarchus labrax: implication in osmoregulation

The ontogeny of the digestive tract (DT) and of Na(+)/K(+)-ATPase localization was investigated during the early postembryonic development (from yolk sac larva to juvenile) of the euryhaline teleost Dicentrarchus labrax reared at two salinities: seawater and diluted seawater. Histology, electron microscopy and immunocytochemistry were used to determine the presence and differentiation of ion transporting cells. At hatching, the DT is an undifferentiated straight tube over the yolk sac. At the mouth opening (day 5), it comprises six segments: buccopharynx, esophagus, stomach, anterior intestine, posterior intestine and rectum, well differentiated at the juvenile stage (day 72). The enterocytes displayed ultrastructural features similar to those of mitochondria-rich cells known to be involved in active ion transport. At hatching, ion transporting cells lining the intestine and the rectum exhibited a Na(+)/K(+)-ATPase activity which increased mainly after the larva/juvenile (20 mm) metamorphic transition. The immunofluorescence intensity was dependent upon the stage of development of the gut as well as on the histological configuration of the analyzed segment. The appearance and distribution of enteric ionocytes and the implication of the DT in osmoregulation are discussed.     

Alterations in the masseter muscle and plasma IL-6 level following experimentally induced occlusal interference and chronic stress--a study in rats

This study was undertaken to examine the alteration of masseter and plasma interleukin-6 after inducing occlusal interference and chronic stress. Male Wistar rats were submitted to chronic stress procedure, exposed to occlusal interference, or exposed to both mentioned procedures. Whole blood and masseter tissue were collected to determine interleukin-6 level, measured by means of ELISA. Masseter pain was evaluated using the orofacial formalin test. Masseter interleukin-6 level was significantly higher in animals submitted to combination of occlusal interference and chronic stress than in the control group (p<0.05). There was positive and significant correlation between pain response and masseter interleukin-6 level (r=0.5741; p<0.0003). No significant differences in plasma interleukin-6 level were found between groups (p>0.05), as well as no correlation with pain (p>0.05). Combination of occlusal interference and chronic stress leads to strong local reaction characterized by high levels of masseter interleukine-6. High concentrations of muscle interleukin-6 and its correlation with pain point to inflammatory background of masticatory muscle pain.