Ultrastructural pathology in skeletal muscle of mice envenomed with Crotalus vegrandis venom.

In this ultrastructural study we examined skeletal muscle fibres from mice intraperitoneally inoculated with a sublethal dose of Crotalus vegrandis (rattlesnake) venom. The group of mice inoculated presented neurological symptoms characterised by respiratory failure and hind limbs paralysis. Skeletal muscle fibres showed different degrees of alterations. Most of them presented the characteristic pattern of necrosis in progress. Atrophied and hypercontracted fibres were frequently seen. Some atrophied and necrotic fibres showed several nucleoli-like bodies in the nucleus. In the atrophic and hypercontracted fibres, sarcoplasmic vacuolation and abnormal mitochondria with stacked cristae were observed. Areas of segmental necrosis were also frequently found. In connection with these altered muscle fibres, capillary abnormalities were detected. This study suggests that in envenomed mice respiratory failure symptoms may be related with muscle damage caused by Crotalus vegrandis venom components.