Stretch Injuries of Skeletal Muscles: Experimental Study in Rats' Soleus Muscle

The study aimed to verify the physiological injury behavior by stretching the soleus muscle of rats, using a noninvasive experimental model. Twenty-four rats were used and divided into three groups of eight animals: control group (A), group that performed tetanus followed by electrical stimulation and a sudden dorsiflexion of the left paw performed by a device equipped with a mechanism of muscle soleus rapid stretching (B); and a group that only received the tetanus (C). Three days later, the animals were killed, and the soleus muscle was resected and divided into three segments. Morphological changes indicative of muscle damage appeared in all three segments of group B. In a lesser degree, similar changes were also detected in muscles subjected to only tetanus. This model was effective; reproducing an injury similar to what occurs in human sports injuries.

Time course of training-induced microcirculatory changes and of vegf expression in skeletal muscles of spontaneously hypertensive female rats

Exercise-induced vessel changes modulate arterial pressure (AP) in male spontaneously hypertensive rats (SHR). Vascular endothelial growth factor (VEGF) is important for angiogenesis of skeletal muscle. The present study evaluated the time course of VEGF and angiogenesis after short- and long-term exercise training of female SHR and Wistar Kyoto (WKY) rats, 8-9 weeks (200-250 g). Rats were allocated to daily training or remained sedentary for 3 days (N = 23) or 13 weeks (N = 23). After training, the carotid artery was catheterized for AP measurements. Locomotor (tibialis anterior and gracilis) and non-locomotor skeletal muscles (temporalis) were harvested and prepared for histologic and protein expression analyses. Training increased treadmill performance by all groups (SHR = 28%, WKY = 64%, 3 days) and (SHR = 141%, WKY = 122%, 13 weeks). SHR had higher values of AP than WKY (174 ± 4 vs 111 ± 2 mmHg) that were not altered by training. Three days of running increased VEGF expression (SHR = 28%, WKY = 36%) simultaneously with an increase in capillary-to-fiber ratio in gracilis muscle (SHR = 19%, WKY = 15%). In contrast, 13 weeks of training increased gracilis capillary-to-fiber ratio (SHR = 18%, WKY = 19%), without simultaneous changes in VEGF expression. Training did not change VEGF expression and capillarity of temporalis muscle. We conclude that training stimulates time- and tissue-dependent VEGF protein expression, independent of pressure levels. VEGF triggers angiogenesis in locomotor skeletal muscle shortly after the exercise starts, but is not involved in the maintenance of capillarity after long-term exercise in female rats.

Myostatin and follistatin expression in skeletal muscles of rats with chronic heart failure

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Skeletal muscles with antagonistic muscular actions: morphological, contractile and metabolic characteristics

The muscles can perform the same function in a specific segment (muscles of fast and slow contraction), and at the same time be antagonistic in relation to muscular action (flexors or extensors). The present research aimed to study the morphology, frequency and metabolism of fiber types and the contractile characteristics of extensor and flexors muscles of rabbit. We studied muscles anterior tibialis (AT), flexor digitorum supeficialis (FDS), extensor digitorum longus (EDL) and posterior tibialis (PT). The muscles were submitted to the techniques HE, NADH-TR and myofibrillar ATPase. In EDL and PT extensor muscles, the frequencies of red (SO + FOG) and white fibers (FG) were 68.77% and 31.23% versus 58.87% and 41.13%, respectively. In the AT and FDS flexor muscles, these frequencies were 75.14% and 24.86% versus 73.89% and 26.11%, respectively. In extensor muscles, the percentage of slow contraction fibers was 8.05% in EDL and 9.74% in PT, and in fast contraction, 91.95% in EDL and 90.26% in PT. In flexors, the slow contraction frequencies were 12.35% in AT and 8.17% in FDS, and in fast contraction, 87.65% and 91.83%, respectively. Skeletal muscles with antagonistic muscular actions (flexors and extensors) the morphological, contractile and metabolic characteristics are identical.

Effects of phonophoresis with Arnica montana onto acute inflammatory process in rat skeletal muscles: An experimental study

This study aimed at verifying the effects of phonophoresis associated with Arnica montana on the acute phase of an inflammatory muscle lesion. Forty Wistar male rats (300 +/- 50 g), of which the Tibialis Anterior muscle was surgically lesioned, were divided into four groups (n = 10 each): control group received no treatment; the ultrasound group (US) was treated in pulsed mode with 1-MHz frequency, 0.5 W/cm(2) intensity (spatial and temporal average - SATA), duty cycle of 1: 2 (2 ms on, 4 ms off, 50%), time of application 3 min per session, one session per day, for 3 days; the phonophoresis or ultrasound plus arnica (US+A) group was treated with arnica with the same US parameters plus arnica gel; and the arnica group (A) was submitted to massage with arnica gel, also for 3 min, once a day, for 3 days. Treatment started 24 h after the surgical lesion. on the 4th day after lesion creation, animals were sacrificed and sections of the lesioned, inflamed muscle were removed for quantitative (mononuclear and polymorphonuclear cell count) and qualitative histological analysis. Collected data from the 4 groups were statistically analyzed and the significance level set at p < 0.05. Results show higher mononuclear cell density in all three treated groups with no significant difference between them, but values were significantly different (p < 0.0001) when compared to control group's. As to polymorphonuclear cell density, significant differences were found between control group (p = 0.0134) and US, US+A and A groups; the arnica group presented lesser density of polymorphonuclear cells when compared (p = 0.0134) to the other groups. No significant difference was found between US and US+A groups. While the massage with arnica gel proved to be an effective anti-inflammatory on acute muscle lesion in topic use, these results point to ineffectiveness of Arnica montana phonophoresis, US having seemingly checked or minimized its anti-inflammatory effect. (C) 2008 Elsevier B. V. All rights reserved.

Morphometry and expression of MyoD and Myogenin in white and red skeletal muscles of juvenile fish Colossoma macropomum (Cuvier 1818)

Colossoma macropomum, also known as tambaqui, is an economically important fish species, and interesting new studies have been published with the aim of improving the growth of this fish. In this work, we describe the morphometric characteristics, as well as the mRNA and protein expression levels of two myogenic regulatory factors (MRFs)-myod/MyoD and myogenin/Myogenin-in the white and red muscle types of tambaqui. A high proportion of white and red muscle fibers with large diameters suggest a hypertrophic growth process in the skeletal muscle during juvenile stages. Comparisons between muscle types showed that, in red muscle, myogenin transcript levels were significantly higher than those of myod. In contrast, MyoD protein levels were significantly higher than those of Myogenin in red muscle. These results suggest that in red and white muscles of juvenile tambaqui, independent post-transcriptional mechanisms for regulating MyoD and Myogenin expression may exist, which could be differentially activated during muscle growth. Furthermore, these data also suggest that specific control mechanisms may regulate distinct muscle phenotypes. © 2013 The Royal Swedish Academy of Sciences.

Differential Expression of Myogenic Regulatory Factor Genes in the Skeletal Muscles of Tambaqui Colossoma macropomum (Cuvier 1818) from Amazonian Black and Clear Water

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

Downhill running excessive training inhibits hypertrophy in mice skeletal muscles with different fiber type composition

The aim of this study was to verify the effects of running overtraining protocols performed in downhill, uphill, and without inclination on the proteins related to hypertrophy signaling pathway in extensor digitorum longus (EDL) and soleus of C57BL/6 mice. We also performed histological and stereological analyses. Rodents were divided into control (CT; sedentary mice), overtrained by downhill running (OTR/down), overtrained by uphill running (OTR/up), and overtrained by running without inclination (OTR). The incremental load, exhaustive, and grip force tests were used as performance evaluation parameters. 36 h after the grip force test, EDL and soleus were removed and immediately used for immunoblotting analysis or stored at -80°C for histological and stereological analyses. For EDL, OTR/down decreased the protein kinase B (Akt) and tuberous sclerosis protein 2 (TSC2) phosphorylation (p), and increased myostatin, receptor-activated Smads (pSMAD2-3), and insulin receptor substrate-1 (pIRS-1; Ser307/636). OTR/down also presented low and high relative proportions of cytoplasm and connective tissue, respectively. OTR/up increased the mammalian target of rapamycin (pmTOR), 70-kDa ribosomal protein S6 kinase 1 (pS6K1) and pSMAD2-3, and decreased pTSC2. OTR decreased pTSC2 and increased pIRS-1 (Ser636). For soleus, OTR/down increased S6 ribosomal protein (pS6RP) and pSMAD2-3, and decreased pIRS-1 (Ser639). OTR/up decreased pS6K1, pS6RP and pIRS-1 (Ser639), and increased pTSC2 (Ser939), and pSMAD2-3. OTR increased pS6RP, 4E-binding protein-1 (p4E-BP1), pTSC2 (Ser939), and pSMAD2-3, and decreased pIRS-1 (Ser639). In summary, OTR/down inhibited the skeletal muscle hypertrophy with concomitant signs of atrophy in EDL. The effects of OTR/up and OTR depended on the analyzed skeletal muscle type. J. Cell. Physiol. 9999: 1-12, 2015. © 2015 Wiley Periodicals, Inc.

Changes of glycogen content in liver, skeletal muscle, and heart from fasted rats

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Effects of nandrolone decanoate and resistance exercise on skeletal muscle in adult male rats

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Heart failure alters MyoD and MRF4 expressions in rat skeletal muscle

Heart failure (HF) is characterized by a skeletal muscle myopathy with increased expression of fast myosin heavy chains (MHCs). The skeletal muscle-specific molecular regulatory mechanisms controlling MHC expression during HF have not been described. Myogenic regulatory factors (MRFs), a family of transcriptional factors that control the expression of several skeletal muscle-specific genes, may be related to these alterations. This investigation was undertaken in order to examine potential relationships between MRF mRNA expression and MHC protein isoforms in Wistar rat skeletal muscle with monocrotaline-induced HF. We studied soleus (Sol) and extensor digitorum longus (EDL) muscles from both HF and control Wistar rats. MyoD, myogenin and MRF4 contents were determined using reverse transcription-polymerase chain reaction while MHC isoforms were separated using polyacrylamide gel electrophoresis. Despite no change in MHC composition of Wistar rat skeletal muscles with HF, the mRNA relative expression of MyoD in Sol and EDL muscles and that of MRF4 in Sol muscle were significantly reduced, whereas myogenin was not changed in both muscles. This down-regulation in the mRNA relative expression of MRF4 in Sol was associated with atrophy in response to HF while these alterations were not present in EDL muscle. Taken together, our results show a potential role for MRFs in skeletal muscle myopathy during HF. © 2006 Blackwell Science Ltd.

Morphology and expression of genes related to skeletal muscle growth in juveniles of pirarucu (Arapaima gigas, Arapaimatidae, Teleostei)

Skeletal muscle growth in the pirarucu (Arapaima gigas) is highly interesting to fish farmers because it provides information about how the mechanism in muscle mass increase, characteristic of the species, is regulated. Pirarucu has specific muscle growth that highlights the species's significance and commercial value. Current research evaluates the morphology and the growth-related gene expression in the red and white skeletal muscles of the pirarucu. Muscle samples were collected from the lateral anterior region and frozen in liquid nitrogen. Histological sections were performed and stained by HE for morphological analysis. Red and white muscle samples were used to determine MyoD, myogenin, and myostatin genes expression by Real-time Polymerase Chain Reaction. Although MyoD and myogenin were not statistically different in the two types of muscles, myostatin was significantly higher in the white rather than in the red muscle. Results show the muscle growth characteristics of the species and may be helpful for improving aquaculture management programs.

Preferential infection sites of Cysticercus bovis in cattle experimentally infected with Taenia saginata eggs

The preferential sites of infection of Cysticercus bovis were evaluated in the skeletal muscle and entrails of 25 cattle that were experimentally infected with Taenia saginata (2 x 10(4) eggs). Two other animals were not inoculated (control). Ninety days after inoculation, all the cattle were euthanized. The carcasses were deboned and dissected into 26 anatomical sections (masseter muscles, brain, tongue, esophagus, heart, diaphragm, lungs, liver, kidneys, spleen, top sirloin butt, bottom sirloin butt, outside round, top (inside) round, transversus abdominus, top sirloin cap, strip loin, full tenderloin, eye of round, knuckle, shoulder clod, foreshank, shank, chuck, back ribs, and tail muscles). The dissected tissues were sliced into 5 mm sections. From the 25 cattle, 9258 C. bovis (cysticerci) were recovered; 75.02% (6946) of these were recovered from skeletal muscles and 24.98% (2312) from the entrails. A high parasitism level was found in the shoulder clod (12.55%), heart (11.02%), liver (9.48%), masseter muscles (8.51%), chuck (8.25%), strip loin and full tenderloin (7.26%), knuckle (6.63%), and back ribs (5.53%), totaling 69.23% (5738) of all of the detected cysticerci. on the other hand, there was a low C. bovis parasitism level in the brain, spleen, tail muscles, kidneys, esophagus, and diaphragm, representing just 3.9% of the total number of cysticerci. Given these results, we conclude that specific skeletal musculature regions, such as the shoulder blade, chuck, strip loin and full tenderloin, knuckle, back ribs and top round, which are not officially examined in many countries, are effective sites to efficiently screen C. bovis infection. To date, these regions have not been considered as preferential sites of C. bovis infection. Based on our work, however, these regions deserve greater attention from health inspectors because they contained a greater number of Cysticercus than the other regions of carcasses that are parasitized by T. saginata larvae. (c) 2010 Elsevier Ltd. All rights reserved.

Mechanisms for consideration for intervention in the development of organophosphorus-induced delayed neuropathy

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

Exercise training prevents hyperinsulinemia, muscular glycogen loss and muscle atrophy induced by dexamethasone treatment

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