Muscle Fiber Viability, a Novel Method for the Fast Detection of Ischemic Muscle Injury in Rats

Acute lower extremity ischemia is a limb- and life-threatening clinical problem. Rapid detection of the degree of injury is crucial, however at present there are no exact diagnostic tests available to achieve this purpose. Our goal was to examine a novel technique - which has the potential to accurately assess the degree of ischemic muscle injury within a short period of time - in a clinically relevant rodent model. Male Wistar rats were exposed to 4, 6, 8 and 9 hours of bilateral lower limb ischemia induced by the occlusion of the infrarenal aorta. Additional animals underwent 8 and 9 hours of ischemia followed by 2 hours of reperfusion to examine the effects of revascularization. Muscle samples were collected from the left anterior tibial muscle for viability assessment. The degree of muscle damage (muscle fiber viability) was assessed by morphometric evaluation of NADH-tetrazolium reductase reaction on frozen sections. Right hind limbs were perfusion-fixed with paraformaldehyde and glutaraldehyde for light and electron microscopic examinations. Muscle fiber viability decreased progressively over the time of ischemia, with significant differences found between the consecutive times. High correlation was detected between the length of ischemia and the values of muscle fiber viability. After reperfusion, viability showed significant reduction in the 8-hour-ischemia and 2-hour-reperfusion group compared to the 8-hour-ischemia-only group, and decreased further after 9 hours of ischemia and 2 hours of reperfusion. Light- and electron microscopic findings correlated strongly with the values of muscle fiber viability: lesser viability values represented higher degree of ultrastructural injury while similar viability results corresponded to similar morphological injury. Muscle fiber viability was capable of accurately determining the degree of muscle injury in our rat model. Our method might therefore be useful in clinical settings in the diagnostics of acute ischemic muscle injury

Uso do laser, 670 nm, no quadro álgico de ratos submetidos à modelo experimental de ciatalgia Use of laser, 670 nm, in painful episodes of rats submitted to experimental model of sciatica

A ciatalgia deve-se a compressão do nervo isquiático em algum ponto de seu trajeto, e seu tratamento consiste em solucionar a causa da compressão nervosa, seja por tratamento cirúrgico ou conservador. Alguns recursos fisioterapêuticos atuam basicamente na redução dos sintomas ocasionados por este distúrbio. O objetivo deste estudo foi verificar a eficácia do laser 670 nm, em duas diferentes densidades de energia, na redução do quadro álgico, em ratos submetidos a modelo experimental de ciatalgia. Foram utilizados 18 ratos, divididos em 3 grupos: G1 (n=6) submetidos à ciatalgia e simulado o tratamento (grupo placebo), G2 (n=6) submetido à ciatalgia e tratados com laser 2 J/cm², G3 (n=6) submetidos à ciatalgia e irradiados com laser 4 J/cm². O nervo isquiático do membro posterior direito dos animais foi exposto e compressão com fio catgut em 4 pontos ao redor do nervo foi realizada. No 3° dia pós-operatório, iniciou-se o tratamento com laser na região do procedimento cirúrgico do membro posterior direito durante 10 dias consecutivos. Verificou-se por meio da marcha, o tempo em que o membro permanecia no ar nos períodos: anterior à ciatalgia, pré e pós-tratamento. Os resultados demonstraram que o laser não foi eficaz na redução do quadro álgico, porém com 4 J/cm² houve efeito positivo, sem restabelecimento completo da funcionalidade.<br>Sciatica is caused by the sciatic nerve compression in some point of its course, and its treatment consists of solving the nervous compression cause, either by surgical or conservative treatment. Some physiotherapeutic resources act basically in the reduction of the symptoms caused by this disturbance. The aim of this study was to verify the effectiveness of the laser 670 nm, in two different energy densities, in the pain reduction, in rats submitted to a sciatica experimental model. Eighteen rats, divided in 3 groups were used: G1 (n=6) submitted to sciatica and simulated treatment (placebo group), G2 (n=6) submitted to sciatica and treated with laser 2 J/cm², G3 (n=6) submitted to sciatica and irradiated with laser 4 J/cm². The hamstring nerve of the animals' right hind limb was exposed and compression with catgut thread in 4 points of the nerve was performed. On the 3rd post-operation day, the treatment was begun with laser in the surgical procedure area of the right hind limb for 10 days. The time during which the limb remained on the air was verified through gait in the following periods: previous to the sciatica, before and after treatment. The results have demonstrated that the laser was not effective in the pain reduction; however, with 4 J/cm² there was positive effect, without complete functionality reestablishment