Attenuation of soman-induced lesions of skeletal muscle by acetylcholinesterase reactivating and non-reactivating antidotes.

It has been reported recently that some oximes reactivating acetylcholinesterase (AChE) exhibit concomitant ganglion-blocking effects which presumably could contribute independently to their powerful antidotal action in organophosphate inhibitor (OPI) poisoning, thus mimicking some unrelated substances which are effective antidotes without reactivating AChE. This raises the question whether OPI-induced muscle lesions, like some other symptoms could also be attenuated by oximes and other antidotes in the absence of AChE reactivation. To test this possibility, the oxime HI-6 was applied at increasing time intervals after the injection of soman until and beyond the point when soman-AChE complex becomes completely "aged" and not capable of reactivation. As the examples of OPI antidotes which do not reactivate AChE, the muscarinic antagonist atropine and the ganglion-blocking agent hexamethonium were also tested on possible attenuation of muscle lesions. The proportions of fibers with lesions, AChE inhibition and muscle fasciculations in experimental groups relative to the controls treated with soman only were evaluated. The results show that HI-6 can attenuate lesions only if AChE is partially reactivated and muscle fasciculations are permanently eliminated. However, atropine does not affect either AChE inhibition or muscle fasciculations and is also ineffective in counteracting the lesions in spite of its potency as an effective general antidote. Hexamethonium also does not affect AChE inhibition, but abolishes fasciculations and effectively attenuates muscle lesions. The latter findings reveal the existence of lesion-protecting mechanisms unrelated to AChE reactivation, which if further elucidated might become potentially relevant for additional treatment in OPI poisoning.

Histochemical type I fibres in the soleus of the rat.

Based on oxidative enzyme activity levels, fibres exhibiting moderate and high levels may be identified in the soleus of the rat. Fibres showing moderate activity are classified as Type I fibres, while those showing high activity may belong to Type I or Type II. According to the level of ATPase activity in fixed sections, we can distinguish three types of fibres in the soleus of the rat (IA, IB and II) and, by application of acid pre-incubation, also sub-classes of Type II (IIA and IIC). Type IB fibres possess high oxidative and glycolytic enzyme activities, moderate ATPase activity after fixation, and behave in the same way as Type I fibres after alkaline and acid pre-incubation. For the histochemical classificationof fibre types, we should consider not only reactions to ATPase, and after acid pre-incubation, but also reactions to the enzymes of oxidative and glycolytic metabolism.

Vascularization of the ureter after experimental ureterolysis in rabbits.

The left ureter was isolated and its nutritive arteries interrupted in 43 rabbits. The blood flow in the isolated and in the control ureters was estimated intravitally by measuring the temperature in the wall of the ureters, and postmortally by counting the capillaries injected with India ink. The vascularization of the isolated ureter was lowered at 3 days after surgery and returned to normal values at 14 days.