Myostatin is a key mediator between energy metabolism and endurance capacity of skeletal muscle

Myostatin (Mstn) participates in the regulation of skeletal muscle size and has emerged as a regulator of muscle metabolism. Here, we hypothesized that lack of myostatin profoundly depresses oxidative phosphorylation-dependent muscle function. Toward this end, we explored Mstn/ mice as a model for the constitutive absence of myostatin and AAV-mediated overexpression of myostatin propeptide as a model of myostatin blockade in adult wild-type mice. We show that muscles from Mstn/ mice, although larger and stronger, fatigue extremely rapidly. Myostatin deficiency shifts muscle from aerobic toward anaerobic energy metabolism, as evidenced by decreased mitochondrial respiration, reduced expression of PPAR transcriptional regulators, increased enolase activity, and exercise-induced lactic acidosis. As a consequence, constitutively reduced myostatin signaling diminishes exercise capacity, while the hypermuscular state of Mstn/ mice increases oxygen consumption and the energy cost of running. We wondered whether these results are the mere consequence of the congenital fiber-type switch toward a glycolytic phenotype of constitutive Mstn/ mice. Hence, we overexpressed myostatin propeptide in adult mice, which did not affect fiber-type distribution, while nonetheless causing increased muscle fatigability, diminished exercise capacity, and decreased Pparb/d and Pgc1a expression. In conclusion, our results suggest that myostatin endows skeletal muscle with high oxidative capacity and low fatigability, thus regulating the delicate balance between muscle mass, muscle force, energy metabolism, and endurance capacity.

Dystrophin-related protein, utrophin, in normal and dystrophic human fetal skeletal muscle.

Dystrophin is the product of the Duchenne muscular dystrophy (DMD) gene. Dystrophin-related protein (utrophin), an autosomal homologue of dystrophin, was studied in skeletal muscle from normal fetuses aged 9-26 weeks and one stillbirth of 41 weeks' gestation, and compared with low- and high-risk DMD fetuses aged 9-20 weeks. Utrophin was present at the sarcolemma from before 9 weeks' gestation, although there was variability in intensity both within and between myotubes. Sarcolemmal immunolabelling became more uniform, and levels of utrophin increased to a maximum at approximately 17-18 weeks. Levels then declined, until by 26 weeks sarcolemmal labelling was negligible and levels were similar to adult control muscle. By 41 weeks there was virtually no sarcolemmal labelling, although immunolabelling of capillaries was bright. Similar results were obtained with normal and DMD fetal muscle. Utrophin is therefore expressed in the presence and absence of dystrophin and down-regulated before birth in normal fetal muscle fibres. Samples were not available to determine whether or when, utrophin levels decline in DMD fetal muscle. On Western blots, utrophin was shown to have a smaller relative molecular mass than adult dystrophin, but similar to the fetal isoform. Blood vessels were brightly immunolabelled at all ages, although utrophin immunolabelling of peripheral nerves increased with gestational age.

Characterisation of dystrophin during development of human skeletal muscle.

Dystrophin, the 427 x 10(3) Mr product of the Duchenne muscular dystrophy (DMD) gene, was studied in human foetal skeletal muscle from 9 to 26 weeks of gestation. Dystrophin could be detected from at least 9 weeks of gestation at the sarcolemmal membrane of most myotubes, though there was differential staining with antibodies raised to various regions of the protein. Dystrophin immunostaining increased and became more uniform with age and by 26 weeks of gestation there was intense sarcolemmal staining of all myotubes. On a Western blot, a doublet of smaller relative molecular mass than that seen in adult tissue was detected in all foetuses studied. There was a gradual increase in abundance of the upper band from 9 to 26 weeks, and the lower band, although present in low amounts in young foetuses, increased significantly between 20 and 26 weeks of gestation. These data indicate that there are several specific isoforms of dystrophin present in developing skeletal muscle, though the role of these is unknown.

Childhood trauma: methods for the identification of physeal fractures in non-adult skeletal remains

Objectives Today, fractures at the growth plate (or physis) are common injuries in children, but provide challenges of identification in skeletonized remains. Clinical studies provide detailed information on the mechanisms, locations, age of occurrence, and complications associated with physeal fractures, enabling the development of new criteria for identifying this injury in non-adults. To test these criteria, skeletal remains from five rural and urban medieval cemeteries were examined. Methods The sample consisted of 961 skeletons (0-17 years) with open epiphyses. Macroscopic observation looked for any irregularities of the metaphysis or epiphysis which was consistent with the clinical appearance of physeal fractures or resulting complications. Radiographic examination was applied to identify fracture lines or early growth arrest. Results This study revealed 12 cases of physeal trauma (1.2%). Physeal fractures occurred predominantly at the distal end (75%), and while they were identified in all age categories, they were most frequent in those aged 12-17 years (0.2% TPR). The humerus was the most commonly affected location (3/12 or 25%). Conclusions This study highlights the potential for recognizing physeal fractures in children of all ages, enhancing our understanding of non-adult trauma, and enabling us to assign a more precise age of the injury to build up a picture of their activities in the past.

Bone Formation Following Implantation of Titanium Sponge Rods into Humeral Osteotomies in Dogs: A Histological and Histometrical Study

Background: Titanium (Ti) is widely proven to enhance bone contact and growth on its surface. It is expected that bone defects could benefit from Ti to promote healing and to increase strength of the implanted area. Purpose: The present study aimed at comparing the potential of porous Ti sponge rods with synthetic hydroxyapatite (HA) for the healing of bone defects in a canine model. Material and Methods: Six mongrel dogs were submitted to three trephined osteotomies of 6.0 x 4.0 mm in one humerus and after 2 months another three osteotomies were performed in the contralateral humerus. A total of 36 defects were randomly filled either with Ti foam, particulate HA, or coagulum (control). The six animals were killed 4 months after the first surgery for histological and histometrical analysis. Results: The Ti-foam surface was frequently found in intimate contact with new bone especially at the defect walls. Control sites showed higher amounts of newly formed bone at 2 months - Ti (p = 0.000) and HA (p = 0.009) - and 4 months when compared with Ti (p = 0.001). Differently from HA, the Ti foam was densely distributed across the defect area which rendered less space for bone growth in the latter`s sites. The use of Ti foams or HA resulted in similar amounts of bone formation in both time intervals. Nevertheless, the presence of a Ti-foam rod preserved defect`s marginal bone height as compared with control groups. Also, the Ti-foam group showed a more mature bone pattern at 4 months than HA sites. Conclusion: The Ti foam exhibited good biocompatibility, and its application resulted in improved maintenance of bone height compared with control sites. The Ti foam in a rod design exhibited bone ingrowth properties suitable for further exploration in other experimental situations.

Effect of arginine on the development of the pectoralis muscle and the diameter and the protein:deoxyribonucleic acid rate of its skeletal myofibers in broilers

This work aimed at evaluating the effects of the supplementation of starter diet with Arg on breast muscle development in broilers and the activation of satellite cells and the aggregation of myofibrillar protein. Male Cobb chicks (n = 990) were randomly assigned to 1 of 5 treatments in a complete random design. Measurements of 33 chicks per treatment were made in 6 repetitions. The treatments consisted of a basal diet with 1.390% digestible Arg (without supplementation) and 4 dietary levels of Arg (1.490, 1.590, 1.690, and 1.790%) with Arg:Lys ratios of 1.103, 1.183, 1.262, 1.341, and 1.421, respectively. Arginine supplementation was used only in the starter phase (1 to 21 d). Dietary supplementation with Arg had a positive effect (P < 0.05) on breast and breast fillet weight on d 7 and 21 and on myofiber diameter on d 14 and 21. However, no effect was observed (P > 0.05) on the protein: DNA ratio, which demonstrates that Arg does not interfere with the mitotic activity of the satellite cells. Independently from mechanism, Arg affected muscle growth in the starter phase positively. Dietary supplementation with Arg in the starter phase had no effect (P > 0.05) on the carcass yield of broilers on d 42. Diet supplementation with Arg at levels above the ones recommended for the starter phase may be necessary for improved muscle development in broilers.

Comparative leaf anatomy and morphology of some neotropical Rutaceae: Pilocarpus Vahl and related genera

Previous anatomical studies have been restricted to the foliar aspects of Pilocarpus. However, no anatomical studies analyzing the foliar aspects of Pilocarpus in relation to related genera have been carried out. Therefore, the aim of this study was to identify characters for future taxonomic and phylogenetic studies in Rutaceae, particularly in Pilocarpus, and to discuss the characteristics associated with the simple or compound leaf condition for the group. The petiole and the leaf blade of 14 neotropical Rutaceae species were analyzed, and the following characteristics were observed in all leaves studied: stomata on both surfaces; secretory cavities, including mesophyll type; camptodromous-brochidodromous venation pattern; and free vascular cylinder in the basal region of the petiole. Additional promising characters were identified for future taxonomic and phylogenetic studies in the Rutaceae family, especially for the Pilocarpus genera.

Placement of Kuhlmanniodendron Fiaschi & Groppo in Lindackerieae (Achariaceae, Malpighiales) confirmed by analyses of rbcL sequences, with notes on pollen morphology and wood anatomy

The phylogenetic placement of Kuhlmanniodendron Fiaschi & Groppo (Achariaceae) within Malpighiales was investigated with rbcL sequence data. This genus was recently created to accommodate Carpotroche apterocarpa Kuhlm., a poorly known species from the rainforests of Espirito Santo, Brazil. One rbcL sequence was obtained from Kuhlmanniodendron and analyzed with 73 additional sequences from Malpighiales, and 8 from two closer orders, Oxalidales and Celastrales, all of which were available at Genbank. Phylogenetic analyses were carried out with maximum parsimony and Bayesian inference; bootstrap analyses were used in maximum parsimony to evaluate branch support. The results confirmed the placement of Kuhlmanniodendron together with Camptostylus, Lindackeria, Xylotheca, and Caloncoba in a strongly supported clade (posterior probability = 0.99) that corresponds with the tribe Lindackerieae of Achariaceae (Malpighiales). Kuhlmanniodendron also does not appear to be closely related to Oncoba (Salicaceae), an African genus with similar floral and fruit morphology that has been traditionally placed among cyanogenic Flacourtiaceae (now Achariaceae). A picrosodic paper test was performed in herbarium dry leaves, and the presence of cyanogenic glycosides, a class of compounds usually found in Achariaceae, was detected. Pollen morphology and wood anatomy of Kuhlmanniodendron were also investigated, but both pollen (3-colporate and microreticulate) and wood, with solitary to multiple vessels, scalariform perforation plates and other features, do not seem to be useful to distinguish this genus from other members of the Achariaceae and are rather common among the eudicotyledons as a whole. However, perforated ray cells with scalariform plates, an uncommon wood character, present in Kuhlmanniodendron are similar to those found in Kiggelaria africana (Pangieae, Achariaceae), but the occurrence of such cells is not mapped among the angiosperms, and it is not clear how homoplastic this character could be.

Morphology and anatomy of inflorescence and inflorescence axis in Paepalanthus sect. Diphyomene Ruhland (Eriocaulaceae, Poales) and its taxonomic implications

Paepalanthus sect. Diphyomene has inflorescences arranged in umbels. The underlying bauplan seems however to be more complex and composed of several distinct subunits. Despite appearing superficially very similar, the morphology and anatomy of the inflorescences can supply useful information for the understanding of the phylogeny and taxonomy of the group. Inflorescences of Paepalanthus erectifolius, Paepalanthus flaccidus, Paepalanthus giganteus, and Paepalanthus polycladus were analyzed in regard to branching pattern and anatomy. In P. erectifolius, P. giganteus and P. polycladus the structure is a tribotryum, with terminal dibotryum, and with pherophylls bearing lateral dibotrya. In P. flaccidus, the inflorescence is a pleiobotryum, with terminal subunit, and without pherophylls. Secondary inflorescences may occur in all species without regular pattern. Especially when grown in sites without a pronounced seasonality, the distinction between enrichment zone (part of the same inflorescence) and new inflorescences may be obscured. The main anatomical features supplying diagnostic and phylogenetic information are as follows: (a) in the elongated axis, the thickness of the epidermal cell walls and the cortex size; (b) in the bracts, the quantity of parenchyma cells (c) in the scapes, the shape and the presence of a pith tissue. Therefore, P. sect. Diphyomene can be divided in two groups; group A is represented by P. erectifolius, P. giganteus and P. polycladus, and group B is represented by P. flaccidus. The differentiation is based in both, inflorescence structure and anatomy. Group A presents a life cycle and anatomical features similar to species of Actinocephalus. Molecular trees also point that these two groups are closely related. However, inflorescence morphology and blooming sequence are different. Species of group B present an inflorescence structure and anatomical features shared with many genera and species in Eriocaulaceae. The available molecular and morphology based phylogenies still do not allow a precise allocation of the group in the bulk of basal species of Paepalanthus collocated in P. sect. Variabiles. The characters described and used here supply however important information towards this goal. (C) 2009 Elsevier GmbH. All rights reserved.

Stem anatomy of Rhipsalis (Cactaceae) and its relevance for taxonomy

Several species of the genus Rhipsalis (Cactaceae) are extremely important as ornamentals and are endangered in their natural habitat. However, only a few studies have addressed its taxonomy, morphology (including anatomy), phylogeny and evolutionary history. Consequently, the limited knowledge of the genus coupled with the problematic delimitation of species had led to problems in the identification of taxa. In the current work six species of Rhipsalis, R. cereoides, R. elliptica, R. grandiflora, R. paradoxa, R. pentaptera and R. teres were studied to evaluate the relevance of anatomical characters for the taxonomy of the genus. An anatomical characterization of the primary structure of the stem of Rhipsalis is provided highlighting the differences between species. Features of the stem epidermis are found to discriminate best between species and therefore provide clear and useful characters for the separation of species.

WNT5A Mutations in Patients With Autosomal Dominant Robinow Syndrome

Robinow syndrome is a skeletal dysplasia with both autosomal dominant and autosomal recessive inheritance patterns. It is characterized by short stature, limb shortening, genital hypoplasia, and craniofacial abnormalities. The etiology of dominant Robinow syndrome is unknown; however, the phenotypically more severe autosomal recessive form of Robinow syndrome has been associated with mutations in the orphan tyrosine kinase receptor, ROR2, which has recently been identified as a putative WNT5A receptor. Here, we show that two different missense mutations in WNT5A, which result in amino acid substitutions of highly conserved cysteines, are associated with autosomal dominant Robinow syndrome. One mutation has been found in all living affected members of the original family described by Meinhard Robinow and another in a second unrelated patient. These missense mutations result in decreased WNT5A activity in functional assays of zebrafish and Xenopus development. This work suggests that a WNT5A/ROR2 signal transduction pathway is important in human craniofacial and skeletal development and that proper formation and growth of these structures is sensitive to variations in WNT5A function. Developmental Dynamics 239:327-337, 2010. (C) 2009 Wiley-Liss, Inc.

Potential Role of Growth Hormone in Impairment of Insulin Signaling in Skeletal Muscle, Adipose Tissue, and Liver of Rats Chronically Treated with Arginine

We have shown that rats chronically treated with Arginine (Arg), although normoglycemic, exhibit hyperinsulinemia and decreased blood glucose disappearance rate after an insulin challenge. Attempting to investigate the processes underlying these alterations, male Wistar rats were treated with Arg (35 mg/d), in drinking water, for 4 wk. Rats were then acutely stimulated with insulin, and the soleus and extensorum digitalis longus muscles, white adipose tissue (WAT), and liver were excised for total and/or phosphorylated insulin receptor (IR), IR substrate 1/2, Akt, Janus kinase 2, signal transducer and activator of transcription (STAT) 1/3/5, and p85 alpha/55 alpha determination. Muscles and WAT were also used for plasma membrane (PM) and microsome evaluation of glucose transporter (GLUT) 4 content. Pituitary GH mRNA, GH, and liver IGF-I mRNA expression were estimated. It was shown that Arg treatment: 1) did not affect phosphotyrosine-IR, whereas it decreased phosphotyrosine-IR substrate 1/2 and phosphoserine-Akt content in all tissues studied, indicating that insulin signaling is impaired at post-receptor level; 2) decreased PM GLUT4 content in both muscles and WAT; 3) increased the pituitary GH mRNA, GH, and liver IGF-I mRNA expression, the levels of phosphotyrosine-STAT5 in both muscles, phosphotyrosine-Janus kinase 2 in extensorum digitalis longus, phosphotyrosine-STAT3 in liver, and WAT as well as total p85 alpha in soleus, indicating that GH signaling is enhanced in these tissues; and 4) increased p55 alpha total content in muscles, WAT, and liver. The present findings provide the molecular mechanisms by which insulin resistance and, by extension, reduced GLUT4 content in PM of muscles and WAT take place after chronic administration of Arg, and further suggest a putative role for GH in its genesis, considering its diabetogenic effect. (Endocrinology 150: 2080-2086, 2009)

Sympathetic hyperactivity differentially affects skeletal muscle mass in developing heart failure: role of exercise training

Bacurau AV, Jardim MA, Ferreira JC, Bechara LR, Bueno CR Jr, Alba-Loureiro TC, Negrao CE, Casarini DE, Curi R, Ramires PR, Moriscot AS, Brum PC. Sympathetic hyperactivity differentially affects skeletal muscle mass in developing heart failure: role of exercise training. J Appl Physiol 106: 1631-1640, 2009. First published January 29, 2009; doi:10.1152/japplphysiol.91067.2008.-Sympathetic hyperactivity (SH) is a hallmark of heart failure (HF), and several lines of evidence suggest that SH contributes to HF-induced skeletal myopathy. However, little is known about the influence of SH on skeletal muscle morphology and metabolism in a setting of developing HF, taking into consideration muscles with different fiber compositions. The contribution of SH on exercise tolerance and skeletal muscle morphology and biochemistry was investigated in 3- and 7-mo-old mice lacking both alpha(2A)- and alpha(2C)-adrenergic receptor subtypes (alpha(2A)/alpha(2C)ARKO mice) that present SH with evidence of HF by 7 mo. To verify whether exercise training (ET) would prevent skeletal muscle myopathy in advanced-stage HF, alpha(2A)/alpha(2C)ARKO mice were exercised from 5 to 7 mo of age. At 3 mo, alpha(2A)/alpha(2C)ARKO mice showed no signs of HF and preserved exercise tolerance and muscular norepinephrine with no changes in soleus morphology. In contrast, plantaris muscle of alpha(2A)/alpha(2C)ARKO mice displayed hypertrophy and fiber type shift (IIA -> IIX) paralleled by capillary rarefaction, increased hexokinase activity, and oxidative stress. At 7 mo, alpha(2A)/alpha(2C)ARKO mice displayed exercise intolerance and increased muscular norepinephrine, muscular atrophy, capillary rarefaction, and increased oxidative stress. ET reestablished alpha(2A)/alpha(2C)ARKO mouse exercise tolerance to 7-mo-old wild-type levels and prevented muscular atrophy and capillary rarefaction associated with reduced oxidative stress. Collectively, these data provide direct evidence that SH is a major factor contributing to skeletal muscle morphological changes in a setting of developing HF. ET prevented skeletal muscle myopathy in alpha(2A)/alpha(2C)ARKO mice, which highlights its importance as a therapeutic tool for HF.