Creatine does not promote hypertrophy in skeletal muscle in supplemented compared with nonsupplemented rats subjected to a similar workload

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Mouse extensor digitorum longus and soleus show distinctive ultrastructural changes induced by veratrine

We investigated whether veratrine (5 μl, 10 ng/kg) injected into the mouse extensor digitorum longus (EDL) (fast-twitch) and soleus (SOL) (slow-twitch) muscles provokes distinctive ultrastructural disturbances 15, 30 and 60 min later. The mitochondria in SOL were affected earlier (within 15 min) than in EDL. Swelling of the sarcoplasmic reticulum terminal cisternae was more marked in EDL than in SOL and caused distortion of sarcomeres so that fragmentation of myofilaments was more pronounced in EDL. Hypercontracted sarcomeres were seen mainly in SOL and veratrine caused infoldings of the sarcolemma only in this muscle. In both muscles, the T-tubules remained unaffected and by 60 min after veratrine most of the above alterations had reverted to normal. Pretreatment with tetrodotoxin prevented the alterations induced by veratrine. This suggests that most of the alterations resulted from the enhanced influx of Na+ into muscle fibers. These results emphasize the importance of considering the type of muscle when studying the action of myotoxic agents.

Histoenzymology and morphometry of the masticatory muscles of tufted capuchin monkey (Cebus apella Linnaeus, 1758)

Samples of the anterior and posterior regions of the masseter and temporal muscles and of the anterior belly of the digastric muscle of 4 adult male tufted capuchin monkeys (Cebus apella) were removed and stained with HE and submitted to the m-ATPase reaction (with alkaline and acid preincubation) and to the NADH-TR and SDH reactions. The results of the histoenzymologic reactions were similar, except for acid reversal which did not occur in fibers of the fast glycolytic (FG) type in the mandibular locomotor muscles. FG fibers had a larger area and were more frequent in all regions studied. No significant differences in frequency or area of each fiber type were detected, considering the anterior and posterior regions of the masseter and temporal muscles. The frequency of fibers of the fast oxidative glycolytic (FOG) and slow oxidative (SO) types and of FOG area differed significantly between the anterior belly of the digastric muscle and the mandibular locomotor muscle. The predominance of fast twitch (FG and FOG) fibers and the multipenniform and bipenniform internal architecture of the masseter and temporal muscles, respectively, are characteristics that permit the powerful bite typical of tufted capuchin monkeys.

Morfologia e morfometria dos tipos de fibras do músculo reto abdominal de cadelas (canis familiaris) durante a gestação

The present paper deals with the evaluation of morphological and morphometric alterations of slow-twist (I) and fast-twitch (II) fibers of rectus abdominis muscle of adult female dog during pregestational phase, at 30 and 60 days of pregnancy and at 30 days after the parturition. At the every phases, using the open biopsy technique, muscle samples were collected. The samples were plunged. Histological sections were cut in a microtome. For general morphology, some sections were stained with HE. Subsequent sections were reacted for myofibrillar ATPase (m-ATPase), after alkaline (pH 10.4) and acid (pH 4.4) pre-incubations, in order to identificate type I and II fibers. In the pre-gestational phase, muscle tissue revealed to be composed by fibers with different diameters, presenting polygonal outlines and one or more periphery nuclei. At 30 days of pregnancy, muscle fiber characteristics were similar. At 60 days, in addition to the existence of normal fibers, polymorphic and small diameter fibers were frequent. At 30 days after the parturation, the morphology of muscle fiber were similar to that observed in the pre-gestational phase. In the four phases, type II fiber diameters were lager than type I. The diameters of both fiber types showed a significant reduction in the 30 days phase and a significative increasing at 60 days. The expansion of the abdominal wall during the pregnancy represents a chronic stimulus, induced changes in the morphology and in the fiber type diameters.

Hypertrophied myocardium is more dependent on extracellular calcium than the normal cardiac muscle

Background: The aim of this study was to analyze stable hypertrophied myocardial function and its response to inotropic maneuvers in rats submitted to renovascular hypertension for a 10-week period (RHT group, n=10). Material/Methods: Myocardial performance was studied in isolated left ventricle papillary muscles in isometric contraction under the following conditions: at postrest contraction of 30 seconds (PRC), at extracellular calcium (ECa 2+) chloride concentration of 1.25 and 5.20 mM, and after beta-adrenergic stimulation with 10 -6 M isoproterenol (ISOP). Results: The results were compared with normotensive Wistar controls rats (C group, n=10). In basal condition, resting tension, and contraction time (TPT) were greater, while relaxation time (RT 50) tended to be longer in RHT than C group. PRC and ISOP promoted a similar change in muscle function response intensity (Δ) in both groups. ECa 2+ shift did not change TPT in the C group and decreased TPT in the RHT animals; Δ was different between these groups. RT 50 increased in C and decreased in RHT, both without statistical significance; however, Δ was different. Conclusions: These results suggest that hypertrophied myocardial dysfunction may be attibuted to changes in intracellular calcium cycling. © Med Sci Monit, 2010.

Genome-Wide Analysis Reveals Selection for Important Traits in Domestic Horse Breeds

Intense selective pressures applied over short evolutionary time have resulted in homogeneity within, but substantial variation among, horse breeds. Utilizing this population structure, 744 individuals from 33 breeds, and a 54,000 SNP genotyping array, breed-specific targets of selection were identified using an FST-based statistic calculated in 500-kb windows across the genome. A 5.5-Mb region of ECA18, in which the myostatin (MSTN) gene was centered, contained the highest signature of selection in both the Paint and Quarter Horse. Gene sequencing and histological analysis of gluteal muscle biopsies showed a promoter variant and intronic SNP of MSTN were each significantly associated with higher Type 2B and lower Type 1 muscle fiber proportions in the Quarter Horse, demonstrating a functional consequence of selection at this locus. Signatures of selection on ECA23 in all gaited breeds in the sample led to the identification of a shared, 186-kb haplotype including two doublesex related mab transcription factor genes (DMRT2 and 3). The recent identification of a DMRT3 mutation within this haplotype, which appears necessary for the ability to perform alternative gaits, provides further evidence for selection at this locus. Finally, putative loci for the determination of size were identified in the draft breeds and the Miniature horse on ECA11, as well as when signatures of selection surrounding candidate genes at other loci were examined. This work provides further evidence of the importance of MSTN in racing breeds, provides strong evidence for selection upon gait and size, and illustrates the potential for population-based techniques to find genomic regions driving important phenotypes in the modern horse. © 2013 Petersen et al.

Short periods of fasting followed by refeeding change the expression of muscle growth-related genes in juvenile Nile tilapia (Oreochromis niloticus)

Muscle growth mechanisms are controlled by molecular pathways that can be affected by fasting and refeeding. In this study, we hypothesized that short period of fasting followed by refeeding would change the expression of muscle growth-related genes in juvenile Nile tilapia (Oreochromis niloticus). The aim of this study was to analyze the expression of MyoD, myogenin and myostatin and the muscle growth characteristics in the white muscle of juvenile Nile tilapia during short period of fasting followed by refeeding. Juvenile fish were divided into three groups: (FC) control, feeding continuously for 42. days, (F5) 5. days of fasting and 37. days of refeeding, and (F10) 10. days of fasting and 32. days of refeeding. At days 5 (D5), 10 (D10), 20 (D20) and 42 (D42), fish (n = 14 per group) were anesthetized and euthanized for morphological, morphometric and gene expression analyses. During the refeeding, fasted fish gained weight continuously and, at the end of the experiment (D42), F5 showed total compensatory mass gain. After 5 and 10. days of fasting, a significant increase in the muscle fiber frequency (class 20) occurred in F5 and F10 compared to FC that showed a high muscle fiber frequency in class 40. At D42, the muscle fiber frequency in class 20 was higher in F5. After 5. days of fasting, MyoD and myogenin gene expressions were lower and myostatin expression levels were higher in F5 and F10 compared to FC; at D42, MyoD, myogenin and myostatin gene expression was similar among all groups. In conclusion, this study showed that short periods of fasting promoted muscle fiber atrophy in the juvenile Nile tilapia and the refeeding caused compensatory mass gain and changed the expression of muscle growth-related genes that promote muscle growth. These fasting and refeeding protocols have proven useful for understanding the effects of alternative warm fish feeding strategies on muscle growth-related genes. © 2013.

Qualidade da carne de cordeiros terminados com dietas contendo cana-de-açúcar ou silagem de milho

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Rearing temperature induces changes in muscle growth and gene expression in juvenile pacu (Piaractus mesopotamicus)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Concurrent training effect on muscle fibers in Wistar rats

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Resposta da resistência insulínica de mulheres menopausadas ao protocolo de exercício intervalado em esteira ergométrica

Pós-graduação em Ginecologia, Obstetrícia e Mastologia - FMB

Expression of growth-related factors in skeletal muscle of Pirarucu (Arapaima gigas) during growth

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Exercise training prevents the microvascular rarefaction in hypertension balancing angiogenic and apoptotic factors role of microRNAs-16,-21, and -126

Aerobic exercise training (ET) lowers hypertension and improves patient outcomes in cardiovascular disease. The mechanisms of these effects are largely unknown. We hypothesized that ET modulates microRNAs (miRNAs) involved in vascularization. miRNA-16 regulates the expression of vascular endothelial growth factor and antiapoptotic protein Bcl-2. miRNA-21 targets Bcl-2. miRNA-126 functions by repressing regulators of the vascular endothelial growth factor pathway. We investigated whether miRNA-16, -21 and -126 are modulated in hypertension and by ET. Twelve-week-old male spontaneously hypertensive rats (SHRs; n=14) and Wistar Kyoto (WKY; n=14) rats were assigned to 4 groups: SHRs, trained SHRs (SHR-T), Wistar Kyoto rats, and trained Wistar Kyoto rats. ET consisted of 10 weeks of swimming. ET reduced blood pressure and heart rate in SHR-Ts. ET repaired the slow-to-fast fiber type transition in soleus muscle and the capillary rarefaction in SHR-Ts. Soleus miRNA-16 and -21 levels increased in SHRs paralleled with a decrease of 48% and 25% in vascular endothelial growth factor and Bcl-2 protein levels, respectively. Hypertension increased Bad and decreased Bcl-x and endothelial NO synthase levels and lowered p-Bad(ser112): Bad ratio. ET in SHR-Ts reduced miRNA-16 and -21 levels and elevated vascular endothelial growth factor and Bcl-2 levels. ET restored soleus endothelial NO synthase levels plus proapoptotic and antiapoptotic mediators in SHR-Ts, indicating that the balance between angiogenic and apoptotic factors may prevent microvascular abnormalities in hypertension. miRNA-126 levels were reduced in SHRs with an increase of 51% in phosphoinositol-3 kinase regulatory subunit 2 expression but normalized in SHR-Ts. Our data show that ET promoted peripheral revascularization in hypertension, which could be associated with regulation of select miRNAs, suggesting a mechanism for its potential therapeutic application in vascular diseases. (Hypertension. 2012;59[part 2]:513-520.). Online Data Supplement

Mutation Spectrum in the Large GTPase Dynamin 2, and Genotype-Phenotype Correlation in Autosomal Dominant Centronuclear Myopathy

Centronuclear myopathy (CNM) is a genetically heterogeneous disorder associated with general skeletal muscle weakness, type I fiber predominance and atrophy, and abnormally centralized nuclei. Autosomal dominant CNM is due to mutations in the large GTPase dynamin 2 (DNM2), a mechanochemical enzyme regulating cytoskeleton and membrane trafficking in cells. To date, 40 families with CNM-related DNM2 mutations have been described, and here we report 60 additional families encompassing a broad genotypic and phenotypic spectrum. In total, 18 different mutations are reported in 100 families and our cohort harbors nine known and four new mutations, including the first splice-site mutation. Genotype-phenotype correlation hypotheses are drawn from the published and new data, and allow an efficient screening strategy for molecular diagnosis. In addition to CNM, dissimilar DNM2 mutations are associated with Charcot-Marie-Tooth (CMT) peripheral neuropathy (CMTD1B and CMT2M), suggesting a tissue-specific impact of the mutations. In this study, we discuss the possible clinical overlap of CNM and CMT, and the biological significance of the respective mutations based on the known functions of dynamin 2 and its protein structure. Defects in membrane trafficking due to DNM2 mutations potentially represent a common pathological mechanism in CNM and CMT. Hum Mutat 33: 949-959, 2012. (C) 2012 Wiley Periodicals, Inc.

Characterization of L-type Calcium Channel Binding-Site of a new class of Calcium modulators by a Multidisciplinary approach

Many potential diltiazem related L-VDCC blockers were developed using a multidisciplinary approach. This current study was to investigate and compare diltiazem with to the newly developed compounds by mouse Langendorff-perfused heart, Ca2+-transient and on recombinant L-VDCC. Twenty particular compounds were selected by the ligand-based virtual screening procedure (LBVS). From these compounds, five of them (5b, M2, M7, M8 and P1) showed a potent and selective inotropic activity on guinea-pig left atria driven 1 Hz. Further assays displayed an interesting negative inotropic effect of M2, M8, P1 and M7 on guinea pig isolated left papillary muscle driven at 1 Hz, a relevant vasorelaxant activity of 5b, M2, M7, M8 and P1 on K+-depolarized guinea-pig ileum longitudinal smooth muscle and a significant inhibition of contraction of 5b, M2, M8 and P1 on carbachol stimulated ileum longitudinal smooth muscle. Wild-type human heart and rabbit lung α1 subunits were expressed (combined with the regulatory α2δ and β3 subunits) in Xenopus Leavis oocytes using a two-electrode voltage clamp technique. Diltiazem is a benzothiazepine Ca2+ channel blocker used clinically for its antihypertensive and antiarrhythmic effects. Previous radioligand binding assays revealed a complex interaction with the benzothiazepine binding site for M2, M7 and M8. (Carosati E. et al. J. Med Chem. 2006, 49; 5206). In agreement with this findings, the relative order of increased rates of contraction and relaxation at lower concentrations s(≤10-6M) in unpaced hearts was M7>M2>M8>P1. Similar increases in Ca2+ transient were observed in cardiomyocytes. Diltiazem showed negative inotropic effects whereas 5b had no significant effect. Diltiazem blocks Ca2+current in a use-dependent manner and facilitates the channel by accelerating the inactivation and decelerating the recovery from inactivation. In contrast to diltiazem, the new analogs had no pronounced use-dependence. Application of 100 μM M8, M2 showed ~ 10% tonic block; in addition, M8, M2 and P1 shifted the steady state inactivation in hyperpolarized direction and the current inactivation time was significantly decreased compared with control (219.6 ± 11.5 ms, 226 ± 14.5 vs. 269 ± 12.9 vs. 199.28 ± 8.19 ms). Contrary to diltiazem, the recovery from the block by M8 and M2 was comparable to control. Only P1 showed a significantly decrease of the time for the recovery from inactivation. All of the compounds displayed the same sensitivity on the Ca2+ channel rabbit lung α1 except P1. Taken together, these findings suggest that M8, M2 and P1 might directly decrease the binding affinity or allow rapid dissociation from the benzothiazepine binding site.