Wellington Ribeiro

Effect of Bothrops leucurus venom in chick biventer cervicis preparations.

Bothrops leucurus is a poorly studied pitviper found in northeastern Brazil. We examined the action of B. leucurus venom (5-100 microg/ml) on contractile responses in chick biventer cervicis preparations. Muscle damage was assessed by quantifying the release of creatine kinase (CK) and by histological analysis. B. leucurus venom dose-dependently inhibited the contractile responses of indirectly stimulated preparations, the maximum inhibition with 100 microg of venom/ml being 74.0+/-6.6% (mean+/-SEM) after 120 min. The venom also reduced contractures to exogenous acetylcholine (55 and 110 microM) and K(+) (13.4mM) (85-100% reduction with 100 microg of venom/ml) and increased the release of CK (348+/-139 U/ml in controls vs 1260+/-263 U/ml with 20 microg of venom/ml after 120 min, p<0.05). The accompanying morphological changes included multivacuolated, swollen, amorphous fibers and agglutinated myofibrils. These results indicate that B. leucurus venom can adversely affect neuromuscular transmission and produce muscle damage in avian preparations.

Neuromuscular action of venom from the South American colubrid snake Philodryas patagoniensis.

Snakes of the opisthoglyphous genus Philodryas are widespread in South America and cause most bites by colubrids in this region. In this study, we examined the neurotoxic and myotoxic effects of venom from Philodryas patagoniensis in biventer cervicis and phrenic nerve-diaphragm preparations and we compared the biochemical activities of venoms from P. patagoniensis and Philodryas olfersii. Philodryas patagoniensis venom (40 microg/mL) had no effect on mouse phrenic nerve-diaphragm preparations but caused time-dependent neuromuscular blockade of chick biventer cervicis preparations. This blockade was not reversed by washing. The highest concentration of venom tested (40 microg/mL) significantly reduced (p<0.05) the contractures to exogenous acetylcholine (55 microM and 110 microM) and K(+) (13.4 mM) after 120 min; lower concentrations of venom had no consistent or significant effect on these responses. Venom caused a concentration- and time-dependent release of creatine kinase (CK) from biventer cervicis preparations. Histological analysis showed contracted muscle fibers at low venom concentrations and myonecrosis at high concentrations. Philodryas venoms had low esterase and phospholipase A(2) but high proteolytic activities compared to the pitviper Bothrops jararaca. SDS-PAGE showed that the Philodryas venoms had similar electrophoretic profiles, with most proteins having a molecular mass of 25-80 kDa. Both of the Philodryas venoms cross-reacted with bothropic antivenom in ELISA, indicating the presence of proteins immunologically related to Bothrops venoms. RP-HPLC of P. patagoniensis venom yielded four major peaks, each of which contained several proteins, as shown by SDS-PAGE. These results indicate that P. patagoniensis venom has neurotoxic and myotoxic components that may contribute to the effects of envenoming by this species.

Efeitos da suplementação oral com creatina sobre o metabolismo e a morfologia hepática em ratos

A creatina e uma amina nitrogenada e tem sido utilizada principalmente por atletas e praticantes de atividade fisica que desejam aumentar a massa muscular e o desempenho fisico. Entretanto seu uso nao esta somente relacionado a pratica esportiva, pois inumeros trabalhos apresentam efeitos beneficos na pratica medica. Alguns estudos demonstraram que a suplementacao oral com creatina resulta em aumento da sua biodisponibilidade plasmatica e tambem de seus estoques em inumeros orgaos. Entretanto, estudos sobre possiveis efeitos toxicos da suplementacao com creatina sao escassos. Portanto, o objetivo deste trabalho foi avaliar os possiveis efeitos toxicos da suplementacao oral com creatina sobre a funcao e morfologia hepaticas em ratos apos 14 dias de suplementacao oral com creatina na dose de 0.5 g/kg/dia. A funcao hepatica foi avaliada atraves de testes bioquimicos e a estrutura hepatica foi avaliada atraves da massa hepatica relativa e da analise histologica. Os resultados demonstraram que 14 dias de suplementacao com creatina nao alteraram a funcao hepatica quando comparado os grupos controle e suplementado: AST (39.5 x 44.4 U/L), ALT (18.6 x 30.8 U/L), ALP (38.5 x 31.4 U/L), GGT (134.8 x 143.8 U/L), proteinas totais (5.1 x 5.5 g/dl), triglicerides (141.0 x 141.0 mg/dl), colesterol total (130.1 x 126.2 mg/dl), colesterol LDL (36.1 x 36.1 mg/dl), colesterol HDL (65.6 x 62.4 mg/dl), colesterol VLDL (25.0 x 28.0 mg/dl), e tambem estrutura hepatica, exceto nos niveis plasmaticos de albumina (3.0 x 3.5 mg/dl - p<0.02). Nossos resultados demonstraram claramente que, ao menos na dose utilizada, a suplementacao oral com creatina nao induziu a nenhum tipo de efeito toxico sobre o figado.

Effect of the rest interval duration between contractions on muscle fatigue

BackgroundWe aimed to investigate the effect of rest interval, between successive contractions, on muscular fatigue.MethodsEighteen subjects performed elbow flexion and extension (30 repetitions) on an isokinetic dynamometer with 80º of range of motion. The flexion velocity was 120º/s, while for elbow extension we used 5 different velocities (30, 75, 120, 240, 360º/s), producing 5 different rest intervals (2.89, 1.28, 0.85, 0.57 and 0.54 s).ResultsWe observed that when the rest interval was 2.89 s there was a reduction in fatigue. On the other hand, when the rest interval was 0.54 s the fatigue was increased.ConclusionsWhen the resting time was lower (0.54 s) the decline of work in the flexor muscle group was higher compared with different rest interval duration.

Influência da suplementação aguda e crônica de creatina sobre marcadores enzimáticos de dano muscular de ratos sedentários e exercitados com natação

O objetivo deste estudo foi investigar os efeitos da suplementacao aguda (5 g.kg-1 durante uma semana) e cronica (1 g.kg-1 durante quatro e oito semanas) de creatina (Cr) sobre as concentracoes plasmaticas de Creatina Quinase (CQ), Lactato Desidrogenase (LDH) e Aspartato Aminotransferase (AST), de ratos sedentarios e exercitados (natacao a 80% da carga maxima tolerada). Setenta e dois ratos Wistar machos (250 ± 10 g) foram utilizados e divididos igualmente em quatro grupos: ratos sedentarios nao suplementados (CON; n = 18); ratos exercitados nao suplementados (NAT; n = 18); ratos sedentarios e suplementados (CRE; n = 18); ratos exercitados e suplementados (CRE + NAT; n = 18). Ao final da primeira, quarta e oitava semanas, seis animais de cada grupo foram sacrificados. Os resultados demonstraram: 1) ao final da primeira semana elevacao plasmatica de CQ, LDH e AST nos grupos NAT-1 e CRE+NAT-1 em relacao aos grupos CON-1 e CRE-1; 2) ao final da quarta semana valores superiores para CQ e LDH somente no grupo NAT-4; e 3) ao final da oitava semana, somente os valores de AST do grupo CRE-8 diferiram dos demais. Estes achados sugerem que a suplementacao de Cr: 1) nao afeta o dano muscular em ratos submetidos a uma semana de treinamento fisico de alta intensidade em meio aquatico; 2) pode ser capaz de reduzir o dano muscular apos quatro semanas de treinamento; e 3) apos oito semanas de suplementacao de Cr, o dano muscular parece ser atenuado pelo proprio exercicio, anulando os efeito da Cr.