Action of vanillin (Vanilla planifolia) on the morphology of tibialis anterior and soleus muscles after nerve injury / Ação da vanilina (Vanilla planifolia) sobre a morfologia dos músculos tibial anterior e sóleo após lesão nervosa

ABSTRACT Objective To evaluate the action of vanillin (Vanilla planifolia) on the morphology of tibialis anterior and soleus muscles after peripheral nerve injury. Methods Wistar rats were divided into four groups, with seven animals each: Control Group, Vanillin Group, Injury Group, and Injury + Vanillin Group. The Injury Group and the Injury + Vanillin Group animals were submitted to nerve injury by compression of the sciatic nerve; the Vanillin Group and Injury + Vanillin Group, were treated daily with oral doses of vanillin (150mg/kg) from the 3rd to the 21st day after induction of nerve injury. At the end of the experiment, the tibialis anterior and soleus muscles were dissected and processed for light microscopy and submitted to morphological analysis. Results The nerve compression promoted morphological changes, typical of denervation, and the treatment with vanillin was responsible for different responses in the studied muscles. For the tibialis anterior, there was an increase in the number of satellite cells, central nuclei and fiber atrophy, as well as fascicular disorganization. In the soleus, only increased vascularization was observed, with no exacerbation of the morphological alterations in the fibers. Conclusion The treatment with vanillin promoted increase in intramuscular vascularization for the muscles studied, with pro-inflammatory potential for tibialis anterior, but not for soleus muscle.

RESUMO Objetivo Avaliar a ação da vanilina (Vanilla planifolia) sobre a morfologia dos músculos tibial anterior e sóleo após lesão nervosa periférica. Métodos Ratos Wistar foram divididos em quatro grupos, com sete animais cada, sendo Grupo Controle, Grupo Vanilina, Grupo Lesão e Grupo Lesão + Vanilina. Os animais dos Grupos Lesão e Grupo Lesão + Vanilina foram submetidos à lesão nervosa por meio da compressão do nervo isquiático, e os Grupos Vanilina e Grupo Lesão + Vanilina foram tratados diariamente com doses orais de vanilina (150mg/kg) do 3o ao 21o dia após a indução da lesão nervosa. Ao término do experimento, os músculos tibial anterior e sóleo foram dissecados e seguiram o processamento de rotina em microscopia de luz, para posterior análise morfológica. Resultados A compressão nervosa promoveu alterações morfológicas características de denervação, sendo que o tratamento com vanilina foi responsável por respostas distintas nos músculos estudados. Para o tibial anterior, houve aumento do número de células satélites, núcleos centrais e atrofia das fibras, bem como desorganização fascicular. Já no sóleo, houve apenas aumento da vascularização, sem exacerbação das alterações morfológicas nas fibras. Conclusão O tratamento com vanilina promoveu o aumento da vascularização intramuscular para os músculos estudados, com potencial pró-inflamatório para o tibial anterior, o que não ocorreu no músculo sóleo.

Myostatin promotes distinct responses on protein metabolism of skeletal and cardiac muscle fibers of rodents

Myostatin is a novel negative regulator of skeletal muscle mass. Myostatin expression is also found in heart in a much less extent, but it can be upregulated in pathological conditions, such as heart failure. Myostatin may be involved in inhibiting protein synthesis and/or increasing protein degradation in skeletal and cardiac muscles. Herein, we used cell cultures and isolated muscles from rats to determine protein degradation and synthesis. Muscles incubated with myostatin exhibited an increase in proteolysis with an increase of Atrogin-1, MuRF1 and LC3 genes. Extensor digitorum longus muscles and C2C12 myotubes exhibited a reduction in protein turnover. Cardiomyocytes showed an increase in proteolysis by activating autophagy and the ubiquitin proteasome system, and a decrease in protein synthesis by decreasing P70S6K. The effect of myostatin on protein metabolism is related to fiber type composition, which may be associated to the extent of atrophy mediated effect of myostatin on muscle.

Epidemiology of coronary artery bypass grafting at the Hospital Beneficência Portuguesa, São Paulo / Epidemiologia da cirurgia de revascularização miocárdica do Hospital Beneficência Portuguesa de São Paulo

Introduction: The knowledge of the prevalence of risk factors and comorbidities, as well as the evolution and complications in patients undergoing coronary artery bypass graft allows comparison between institutions and evidence of changes in the profile of patients and postoperative evolution over time. Objective: To profile (risk factors and comorbidities) and clinical outcome (complications) in patients undergoing coronary artery bypass graft in a national institution of great surgical volume. Methods: A retrospective cohort study of patients undergoing coronary artery bypass graft in the hospital Beneficência Portuguesa de São Paulo, from July 2009 to July 2010. Results: We included 3,010 patients, mean age of 62.2 years and 69.9% male. 83.8% of patients were hypertensive, 36.6% diabetic, 44.5% had dyslipidemia, 15.3% were smokers, 65.7% were overweight/obese, 29.3% had a family history of coronary heart disease. The expected mortality calculated by logistic EuroSCORE was 2.7%. The isolated CABG occurred in 89.3% and 11.9% surgery was performed without cardiopulmonary bypass. The most common complication was cardiac arrhythmia (18.7%), especially acute atrial fibrillation (14.3%). Pneumonia occurred in 6.2% of patients, acute renal failure in 4.4%, mediastinites in 2.1%, stroke in 1.8% and AMI in 1.2%. The in-hospital mortality was 5.4% and in isolated coronary artery bypass graft was 3.5%. The average hospital stay was 11 days with a median of eight days (3-244 days). Conclusion: The profile of patients undergoing coronary artery bypass graft surgery in this study is similar to other published studies. .

Introdução: O conhecimento da prevalência dos fatores de risco e comorbidades, bem como a evolução com complicações nos pacientes submetidos à cirurgia de revascularização miocárdica, permite a comparação entre instituições e a comprovação de modificações no perfil de pacientes e na evolução pós-operatória ao longo do tempo. Objetivo: Conhecer o perfil (fatores de risco e comorbidades) e a evolução clínica (complicações) nos pacientes submetidos à cirurgia de revascularização miocárdica em uma instituição nacional de grande volume cirúrgico. Métodos: Estudo de coorte retrospectivo de pacientes submetidos ao procedimento de cirurgia de revascularização miocárdica no Hospital Beneficência Portuguesa de São Paulo, no período de julho de 2009 a julho de 2010. Resultados: Foram incluídos 3010 pacientes, com idade média de 62,2 anos e 69,9% do sexo masculino. 82,8% dos pacientes eram hipertensos, 36,6% diabéticos, 44,5% dislipidêmicos, 15,3% tabagistas, 65,7% com sobrepeso/obesidade e 29,3% tinham antecedentes familiares de doença coronária. A mortalidade média esperada calculada pelo EuroSCORE logístico foi de 2,7%. A cirurgia de revascularização miocárdica isolada ocorreu em 89,3% e em 11,9% foi realizada cirurgia sem circulação extracorpórea. A complicação mais comum foi arritmia cardíaca (18,7%), especialmente a fibrilação atrial aguda (14,3%). Pneumonia ocorreu em 6,2% dos pacientes, lesão renal aguda em 4,4%, mediastinite em 2,1%, acidente vascular encefálico em 1,8% e infarto agudo do miocárdio em 1,2%. A mortalidade intra-hospitalar foi de 5,4% e na cirurgia de revascularização miocárdica isolada foi de 3,5%. O tempo de permanência hospitalar médio foi de 11 dias, com mediana de oito dias (3 - 244 dias). Conclusão: O perfil dos pacientes submetidos à cirurgia de revascularização miocárdica neste estudo assemelha-se ao de outros estudos publicados. .

Histomorphometric evaluation of soleus and lateral gastrocnemius muscles of animals submitted to pharmacological manipulation with fluoxetine / Evaluación histomorfométrica de los músculos sóleo y gastrocnemio lateral de animales sometidos a manipulación farmacológica con fluoxetina

The pharmacological manipulation with selective inhibitor of serotonin reuptake (SSRIs) can modify the operation of the serotonergic system and may facilitate or inhibit the action of this system, inducing changes in the morphology of the skeletal muscle of rats. The objective of this study was to evaluate the action of the treatment with fluoxetine during the critical period of the animal´s life on development of the soleus and lateral gastrocnemius muscles, under the aspects of weight, the number of nuclei of myocyte cells and cross-sectional area of muscle fibers. Twenty four (30 and 90-day-old) male Wistar rats were used. They were treated with saline solution (NaCl 0.9%; 1 ml/100 g of body weight) or fluoxetine (10 mg; 1 ml/100g of body weight). The animals were divided in Saline Group (GS-30 and GS-90) and Fluoxetine Group (GF-30 and GF-90). The fluoxetine group showed a reduction on weight (g) of soleus (p=0.046) and lateral gastrocnemius (p=0.02) muscles in rats with 90 days. A lesser number of myonuclei was observed in fluoxetine group than saline group of 30 days (soleus, p<0.001; lateral gastrocnemius, p0.007) and 90 days (soleus, p=0.002; lateral gastrocnemius, p0.038). The cross section area of fluoxetine groups is also smaller than the saline groups with 30 days (soleus, p=0.03; lateral gastrocnemius, p=0.041) and 90 days (soleus, p=0.042; lateral gastrocnemius, p=0.012). The treatment of fluoxetine during the critical period of development of the nervous system of rats, causes early changes in the structure of muscle fibers that seem to be related to reducing the weight of the soleus and gastrocnemius muscles only in late stage of the animal's life. Thus, the dosage used ISRS, suggests an inhibitory effect of 5-HT in relation to variables on the development of the skeletal muscle tissue of rats.

La manipulación farmacológica con inhibidores selectivos de la recaptación de la serotonina (ISRS) pueden cambiar el funcionamento del sistema serotoninérgico y facilitar o inhibir la acción de este sistema, induciendo cambios en la morfología del músculo esquelético de ratones. El objetivo fue analizar los efectos de la manipulación farmacológica neonatal con fluoxetina en el desarrollo de la masa muscular, número de núcleos y área de la sección transversa de las fibras de los músculos sóleo y gastrocnemio lateral. Se utilizaron 24 ratones Wistar machos, de 30 y 90 días de edad, tratados con solución salina (NaCl 0,9%, 1m/100 g de peso corporal) y fluoxetina (1 mg; 1 ml/100 g de peso corporal). Los animales fueron divididos en grupos con solución salina (GS-30 y GS-90) y fluoxetina (GF-30 y GF-90). El grupo tratado con fluoxetina mostró una reducción de peso (g) de los músculos sóleo (p=0,0046) y gastrocnemio lateral (p=0,02) en 90 días. Además, se observó en este mismo grupo una reducción de núcleos en 30 días (M. sóleo, p<0,001; M. gastrocnemio lateral, p0,007) así como en el período de 90 días (M. sóleo, p=0,002; M. gastrocnemio lateral, p0,038). También se observó reducción del área de la sección transversal en los animales tratados con fluoxetina durante el período de 30 días (M. sóleo, p=0,03; M. gastrocnemio lateral, p= 0,041;) y 90 días (M. sóleo, p=0,042; M. gastrocnemio lateral, p=0,012). El tratamiento con fluoxetina durante el período crítico del desarrollo del sistema nervioso de ratones, induce cambios prematuros en la estructura de la fibra muscular, los que parecen estar relacionados con la reducción de peso de los músculos sóleo y gastrocnemio en una fase tardía de vida del animal. En consecuencia, la dosis utilizada de ISRS, sugiere un efecto inhibidor de la 5-HT, en relación a las variables estudiadas sobre el desarrollo del tejido muscular esquelético de ratones.

Effects of ischemic preconditioning and cilostazol on muscle ischemia-reperfusion injury in rats

PURPOSE: To evaluate effects of ischemic preconditioning and Cilostazol on muscle ischemia-reperfusion injury. METHODS: Male Wistar rats were submitted to muscle ischemic and reperfusion injury (4h of the left common iliac artery occlusion followed by 1h of reperfusion). Five experimental groups were constituted: Control group (n=4); Ischemia-Reperfusion (IR, n=5); Ischemic preconditioning group (IP, n=6); Ischemia-Reperfusion group treated with cilostazol (IRCi, n=6) and Ischemic preconditioning group treated with cilostazol (IPCi, n=6). At the end, left gracile muscle was removed and embedded in paraffin. Histopathology, neutrophil infiltration, myocyte necrosis and edema were analyzed. RESULTS: When compared with the control group, IR group showed increased neutrophil infiltration, severe necrosis and edema. There was significant difference between myocytes necrosis of IR group and IP group. There was no difference between the histopathological changes between IP, IRCi and IPCi groups. CONCLUSIONS: The model of IR caused severe muscle injury in the rat hind limb and ischemic preconditioning has a protective effect, reducing myocyte necrosis, however, treatment with cilostazol and also the association between cilostazol and preconditioning has no protective effect on the skeletal muscle subjected to ischemia and reperfusion injury. .

Effects of Nitric Oxide Synthase Inhibitor on Hindlimb Muscles in Rats with Neuropathic Pain Induced by Unilateral Peripheral Nerve Injury

PURPOSE: The purpose of this study was to examine effects of nitric oxide synthase (NOS) inhibitor on muscle weight and myofibrillar protein content of affected and unaffected hindlimb muscles in rats with neuropathic pain induced by unilateral peripheral nerve injury. METHODS: Neuropathic pain was induced by ligation and cutting of the left L5 spinal nerve. Adult male Sprague-Dawley rats were randomly assigned to one of two groups: The NOSI group (n=19) had NOS inhibitor (L-NAME) injections daily for 14 days, and the Vehicle group (n=20) had vehicle injections daily for 14 days. Withdrawal threshold, body weight, food intake and activity were measured every day. At 15 days all rats were anesthetized and soleus, plantaris and gastrocnemius muscles were dissected from hindlimbs. Muscle weight and myofibrillar protein content of the dissected muscles were determined. RESULTS: The NOSI group showed significant increases as compared to the Vehicle group for body weight at 15 days, muscle weight and myofibrillar protein content of the unaffected soleus and gastrocnemius. The NOSI group demonstrated a higher pain threshold than the vehicle group. CONCLUSION: NOSI for 14 days attenuates unaffected soleus and gastrocnemius muscle atrophy in neuropathic pain model.

Changes produced by "nandrolone" in the general structure and ultrastructure of skeletal muscle fibers

Anabolic androgenic steroids [AAS] are compounds formed from testosterone or one of its derivatives, which are largely used by amateur and professional athletes to improve the athletic performance. Nandrolone is an anabolic steroid widely used in some sports in which muscle mass and strength are important factors. The aim of this work was to evaluate the effects of nandrolone on skeletal muscle general structure and ultrastucture. Male albino rats were used in this study. They were divided into two groups, control and treated groups. The treated group received i.m. injections of Deca-Durabolin for 10 weeks. At the end of the experiment, the animals were anaesthetized, and blood samples were obtained for determination of both lactate dehydrogenase [LD] and creatine kinase [CK] activity then soleus muscles were removed for light and electron microscopic studies. Nandrolone treatment caused variation in size and shape of muscle fibers. Small atrophic angular fibers next to hypertrophic ones were seen. Muscle fibers were separated with increased connective tissue. Cross sectional area [CSA] of muscle fibers were slightly increased. The mean LD activity was increased and the mean CK activity was markedly increased. In conclusion nandrolone produced hypertrophy of the skeletal muscles

Effect of Dehydroepiandrosterone on Affected and Unaffected Hindlimb Muscles in Rats with Neuropathic Pain Induced by Unilateral Peripheral Nerve Injury

PURPOSE: The purpose of this study was to examine the effect of DHEA (Dehydroepiandrosterone) on muscle weight and Type I and II fiber cross-sectional area of affected and unaffected hindlimb muscles in rats with neuropathic pain induced by unilateral peripheral nerve injury. METHODS: Neuropathic pain was induced by ligation and cutting of the left L5 spinal nerve. Adult male Sprague-Dawley rats were randomly assigned to one of two groups: The DHEA group (n=10) had DHEA injections daily for 14 days, and the Vehicle group (n=10) had vehicle injections daily for 14 days. Withdrawal threshold, body weight, food intake and activity were measured every day. At 15 days all rats were anesthetized and soleus, plantaris and gastrocnemius muscles were dissected from the both hindlimbs. Body weight, food intake, activity, muscle weight and Type I, II fiber cross-sectional area of the dissected muscles were measured. RESULTS: The DHEA group showed significant increases (p<.05), as compared to the vehicle group for muscle weight of the unaffected plantaris, and in Type II fiber cross-sectional area of the gastrocnemius muscle. The DHEA group demonstrated a higher pain threshold than the vehicle group whereas total diet intake and activity score were not significantly different between the two groups. CONCLUSION: DHEA administration for 14 days attenuates unaffected plantaris and gastrocnemius muscle atrophy.

The effect of a low dose of clenbuterol on rat soleus muscle submitted to joint immobilization

The aim of the present study was to evaluate the effect of joint immobilization on morphometric parameters and glycogen content of soleus muscle treated with clenbuterol. Male Wistar (3-4 months old) rats were divided into 4 groups (N = 6 for each group): control, clenbuterol, immobilized, and immobilized treated with clenbuterol. Immobilization was performed with acrylic resin orthoses and 10 µg/kg body weight clenbuterol was administered subcutaneously for 7 days. The following parameters were measured the next day on soleus muscle: weight, glycogen content, cross-sectional area, and connective tissue content. The clenbuterol group showed an increase in glycogen (81.6 percent, 0.38 ± 0.09 vs 0.69 ± 0.06 mg/100 g; P < 0.05) without alteration in weight, cross-sectional area or connective tissue compared with the control group. The immobilized group showed a reduction in muscle weight (34.2 percent, 123.5 ± 5.3 vs 81.3 ± 4.6 mg; P < 0.05), glycogen content (31.6 percent, 0.38 ± 0.09 vs 0.26 ± 0.05 mg/100 mg; P < 0.05) and cross-sectional area (44.1 percent, 2574.9 ± 560.2 vs 1438.1 ± 352.2 µm²; P < 0.05) and an increase in connective tissue (216.5 percent, 8.82 ± 3.55 vs 27.92 ± 5.36 percent; P < 0.05). However, the immobilized + clenbuterol group showed an increase in weight (15.9 percent; 81.3 ± 4.6 vs 94.2 ± 4.3 mg; P < 0.05), glycogen content (92.3 percent, 0.26 ± 0.05 vs 0.50 ± 0.17 mg/100 mg; P < 0.05), and cross-sectional area (19.9 percent, 1438.1 ± 352.2 vs 1724.8 ± 365.5 µm²; P < 0.05) and a reduction in connective tissue (52.2 percent, 27.92 ± 5.36 vs 13.34 ± 6.86 percent; P < 0.05). Statistical analysis was performed using Kolmogorov-Smirnov and homoscedasticity tests. For the muscle weight and muscle glycogen content, two-way ANOVA and the Tukey test were used. For the cross-sectional area and connective tissue content, Kruskal-Wallis and Tukey tests were used. This study emphasizes the importance of anabolic pharmacological...

Resveratrol stimulates glucose transport in C2C12 myotubes by activating AMP-activated protein kinase

trans-Resveratrol (t-RVT), a naturally occurring polyphenol found in Polygonum cuspidatum, grape, and red wine, has been reported to have anti- inflammatory, cardioprotective, and cancer chemopreventive properties. However antidiabetic effect of t-RVT has not yet been reported. In this study, we show that t-RVT increases glucose uptake in C2C12 myotubes by activating AMP-activated protein kinase (AMPK), uncovering an antidiabetic potential of t-RVT for the first time. AMPK plays a central role in the regulation of glucose and lipid metabolism, and hence it is considered a novel therapeutic target for metabolic syndrome such as type 2 diabetes. t-RVT significantly induced glucose uptake in C2C12 cells, via AMPK activation, but not a phosphatidylinositol-3 kinase (PI-3 kinase) signal pathway. The induced glucose uptake was attenuated by pretreatment with a pharmacological inhibitor for AMPK, indicating that the effect of t-RVT primarily depends on AMPK activation. However, in the presence of insulin, t-RVT also potentiated the effect of insulin on glucose uptake via AMPK activation, which led to further activation of PI-3 kinase/Akt signal pathway.

Effects of Exercise before Steroid Treatment on Type I and Type II Hindlimb Muscles in a Rat Model / 간호학회지

PURPOSE: The purpose of this study was to examine the effects of daily exercise before steroid treatment on mass, the type I and II fiber cross-sectional area, and myofibrillar protein content of hindlimb muscles in a rat model. METHOD: Adult male Sprague-Dawley rats were randomly assigned to one of three groups: a control group(n=10) that had a normal saline injection for 7days, a steroid group(n=10) that had a steroid injection for 7days, and an exercise-steroid group(n=10) that ran on the treadmill for 7days before a steroid treatment. Body weight and food intake were measured every day. At 15 days all rats were anesthetized and the soleus, plantaris and gastrocnemius muscles were dissected. RESULT: The exercise-steroid group showed significant increases as compared with the steroid group in body weight, muscle weight of the soleus and gastrocnemius, type II muscle fiber cross-sectional area of plantaris, and myofibrillar protein content of the soleus, plantaris, and gastrocnemius. As compared with the control group, the steroid group showed significant decreases in body weight and diet intake, muscle weight, the type II fiber cross-sectional area and myofibrillar protein content of the soleus, plantaris, and gastrocnemius muscles. CONCLUSION: Daily exercise before steroid treatment attenuates hindlimb muscle atrophy, with type II muscle changes more apparent than type I muscle changes.

Mechanisms of the UTP-induced tension in mammalian skeletal muscles

The mechanisms of UTP-induced tension in human and rat skinned fibers were investigated using isometric tension recordings, electrophysiological techniques and biochemical methods. In fast-type fibers from rat extensor digitorum longus (EDL) the UTP-induced tension: a) required previous loading of CA2+ into the sarcoplasmic reticulum (SR); b) was inhibited by previous exposure to caffeine; c) was abolished by functional disruption of the SR; d) was not affected by blockade of the SR Ca2+-release channels by ruthenium red or heparin; e) was prevented by spermidine. These data point to the SR as the target of UTP action and suggest a pathway of UTP-induced Ca2+-release independent of the ryanodine- or the IP3-sensitive Ca2+-release channels. Accordingly, UTP failed to stimulate the electrophysiological activity of ryanodine-sensitive channels, incorporated into lipid bilayers. We suggest that UTP-induced Ca2+-release might occur via the channel form of the SR Ca2+-ATPase. The UTP-induced tension in human slow-type fibers was not affected by the SR Ca2+ content or by disruption of the SR, but was accompanied by changes in the tension-pCa relationship, namely increase in maximum Ca2+-activated tension, and in apparent Ca2+-affinity of troponin. The UTP-induced tension in slow-type fibers from rat soleus was partially inhibited by Ca2+-depletion from, or by disruption of the SR, and was accompanied by changes in tension/pCa relationship, similar to those observed in human fibers. Both in skinned fibers and in isolated SR vesicles, UTP was less effective than ATP as a substrate for the SR Ca2+-ATPase. This effect might contribute to UTP-induced tension.

Avaliaçäo da concentraçäo das fibras do tecido conjuntivo quando da associaçäo de poligractina 910 e silicone: estudo experimental em ratos / Association of poliglactin 910 and silicon: concentration evaluation of conjuntive tissues fibers: experimental study in rats

Neste estudo observamos a reaçäo tecidual após implantaçäo de próteses de silicone associadas à poliglactina 910. Telas de borracha de silicone com 1,5 x 1,5 cm de diâmetro e 0,7mm de espessura polifenestradas, foram implantadas no subcutâneo do dorso de ratos. Dois grupos foram observados, no primeiro apenas telas fenestradas eram implantadas, no segundo as fenestraçöes das telas eram preenchidas com fios de poliglactina 910. Os animais foram observados por 30, 60 e 90 dias quando eram sacrificados e as telas mais o tecido adjacente ressecados. Näo se observou diferenças na quantidade de fibras colágenas entre os subgrupos de um mesmo grupo e ou quando comparados com os subgrupos do grupo em estudo. No grupo controle, onde se usou apenas as telas fenestradas de silicone houve uma diferença significante entre as fibras reticulares, em maior número nos grupos de 30 e 60 dias de observaçäo, quando comparadas ao grupo de 90 dias. A poliglactina 910 associada ao silicone näo alterou o número de fibras do tecido conjuntivo, contadas nas fenestraçöes das telas

Bovine serum albumin potentiates caffeine - or ATP - induced tension in human skinned skeletal muscle fibers

Human skinned muscle fibers were used to investigate the effects of bovine serum albumin (BSA) on the tension/pCa relationship and on the functional properties of the Ca2+- release channel of the sarcoplasmic reticulum (SR). In both fast-and slow-type fibers, identified by their tension response to pSr 5.0, BSA (0.7-15 muM) had no effect on the Ca2+ affinity of the contractile proteins and elicited no tension per se in Ca2+-loaded fibers. In contrast, BSA (>1.0 muM) potentiated the caffeine induced tension in Ca2+-loaded fibers, this effect being more intense in slow-type fibers. Thus, BSA reduced the threshold caffeine concentration required for eliciting detectable tension, and increased the amplitude, the rate of rise and the area under the curve of caffeine-induced tension BSA also potentiated the tension elicited in Ca2+-loaded fibers by low-Mg2+ solutions containing 1.0 mM free ATP. These results suggest that BSA modulates the response of the human skeletal muscle SR Ca2+-release channel to activators such as caffeine and ATP.

Miotoxicidade por organofosforados / Organophosphate myotoxicity

Os organosfosforados säo um grupo de compostos químicos amplamente utilizados em agropecuária como inseticidas, ocasionando intoxicaçöes acidentais em animais e humanos, e mesmo sendo utilizados em tentativas de suicídio. A toxidade desses produtos decorre sobretudo de insuficiência cárdio-respiratória por comprometimento do sistema nervoso autônomo. Sabe-se que alguns destes compostos induzem em animais de experimentaçäo e em humanos, uma miopatia caracterizada por degeneraçäo de células musculares, comprometendo sobretudo a musculatura respiratória. Baseado no fato de que este comprometimento contribui para a piora da funçäo respiratória, propöe-se um protocolo de avaliaçäo rotineira de miotoxicidade por compostos organofosforados, através de uma bateria mínima e suficiente de colaboraçöes e reaçöes histoquímicas para quantificaçäo da necrose muscular. Utilizaram-se como modelo experimental, grupos de ratos albinos (Wistar) intoxicados com o organofosforado paraoxon, com e sem antídotos (atropina ou pralidoxima). Verificou-se nos grupos tratados com paraoxon e paraoxon mais atropina, necrose de fibras musculares no diafragma, que atingia em determinadas áreas até 15 por cento das fibras. No grupo tratado com paraoxon mais pralidoxima, a necrose foi mínima, evidenciando o papel mioprotetor deste último antídoto

Effect of vasoactive drugs on muscle fibre types and capillares

The effect of nitroglycerin, nifedipine, diltiazem or propranolol on fibre types and capillaries was studied in extensor digitorum longus (EDL) and soleus (S) muscles of the rat. In EDL muscle nifedipine increased the proportion of type I fibres (7.9 percent +/- 1.7 vs. 4.7 percent +/- 2.7). Nitroglycerin and dialtiazem decreased IIB fibres (40.7 percent +/- 10.6 and 37.3 percent +/- 14.6 respectively vs. 52.3 percent +/- 9.4). Propranolol increased IIB fibres to 66.3 percent +/- 8.1, while reducing IIA fibres (25.3 percent +/- 6.6 vs. 42.2 percent +/- 6.9). No changes in fibre type proportion were found in S muscle. Capillary density was increased in EDL by nitroglycerin (965 +/- 171 vs. 818 +/- 98 cap/mm2). Propranolol had a dual effect on this parameter, decreasing it in EDL to 570 +/- 85 and augmenting it in S (754 +/- 117 vs. 601 +/- 121). No change was found in capillary to fibre ratio with any of the drugs either in EDL or S muscles. In EDL all the drugs except propranolol, which had the opposite effect, decreased the area of IIA fibre per capillary around 20 percent this effect can be interpreted as a reduction of diffusion distance from blood to fibre

Estudo das junçöes mioneurais de cobaia através das técnicas de esterase inespecífica e azul de metileno / Study of myoneural junctions of guinea-pig through non-specific esterase and methylene blue techniques

As junçoes mioneurais e o calibre das fibras musculares de músculos da parede abdominal de cobaia foram medidas após serem corados com esterase inespecífica e Azul de Metileno. Demonstrou-se que existe correlaçao direta entre diâmetro da fibra muscular e dimensao da sua junçao mioneural. Nao existe, entretanto, correspondência precisa entre os valores obtidos nos dois métodos utilizados. Este último aspecto deixa claro que, embora importante para o estudo da morfologia das junçoes mioneurais, o método para demonstraçao da esterase inespecífica nao se presta para estudos morfométricos ou onde se objetiva estudar os axonios pré-terminais, já que ele provoca acentuada retraçao do tecido e nao marca os axonios.