Os organofosforados são um grupo de compostos químicos amplamente utilizados em agropecuária como inseticidas, ocasionando intoxicações acidentais em animais e humanos, e mesmo sendo utilizados em tentativas de suicídio. A toxicidade desses produtos decorre sobretudo de insuficiência cárdio-respiratória por compromentimento do sistema nervoso autônomo. Sabe-se que alguns destes compostos induzem em animais de experimentação e em humanos, uma miopatia caracterizada por degeneração de células musculares, comprometendo sobretudo a musculatura respiratória. Baseado no fato de que este comprometimento contribui para a piora da função respiratória, propõe-se um protocolo de avaliação rotineira de miotoxicidade por compostos organofosforados, através de uma bateria mínima e suficiente de colorações e reações histoquímicas para quantificação 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% das fibras. No grupo tratado com paraoxon mais pralidoxima, a necrose foi mínima, evidenciando o papel mioprotetor deste último antídoto.

Organophosphates comprise a group of chemical compounds extensively used in farming as insecticides, which cause accidental poisoning in animals and men and are also used in suicide attempts. The toxicity of these compounds is due especially to the cardiac and respiratory impairment in consequence of autonomic nervous system disorders. However, it is known that some of these products induce a myopathy in experimental animals and humans. This myopathy is characterized by muscle cell degeneration, involving above all the respiratory muscles. Based on the fact that this involvement certainly enhances the respiratory impairment, this study offers an experimental method for routine evaluation of organophosphate myotoxicity, using a minimal and sufficient battery of stains and histochemical reactions, for muscle necrosis quantification. For this purpose, albino rats (Wistar) treated with the organophosphate paraoxon, were used both with and without antidotes (atropine or pralidoxime). Muscle fiber necrosis in the diaphragm of the rats treated with paraoxon or paraoxon and atropine, that affected about 15% of the fibers in some areas, was detected. In the group treated with paraoxon and pralidoxime, a minimal necrosis was seen, revealing a protective role of this later antidote during the development of myopathy.

Os organofosforados são um grupo de compostos químicos amplamente utilizados em agropecuária como inseticidas, ocasionando intoxicações acidentais em animais e humanos, e mesmo sendo utilizados em tentativas de suicídio. A toxicidade desses produtos decorre sobretudo de insuficiência cárdio-respiratória por compromentimento do sistema nervoso autônomo. Sabe-se que alguns destes compostos induzem em animais de experimentação e em humanos, uma miopatia caracterizada por degeneração de células musculares, comprometendo sobretudo a musculatura respiratória. Baseado no fato de que este comprometimento contribui para a piora da função respiratória, propõe-se um protocolo de avaliação rotineira de miotoxicidade por compostos organofosforados, através de uma bateria mínima e suficiente de colorações e reações histoquímicas para quantificação 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% das fibras. No grupo tratado com paraoxon mais pralidoxima, a necrose foi mínima, evidenciando o papel mioprotetor deste último antídoto.

Organophosphates comprise a group of chemical compounds extensively used in farming as insecticides, which cause accidental poisoning in animals and men and are also used in suicide attempts. The toxicity of these compounds is due especially to the cardiac and respiratory impairment in consequence of autonomic nervous system disorders. However, it is known that some of these products induce a myopathy in experimental animals and humans. This myopathy is characterized by muscle cell degeneration, involving above all the respiratory muscles. Based on the fact that this involvement certainly enhances the respiratory impairment, this study offers an experimental method for routine evaluation of organophosphate myotoxicity, using a minimal and sufficient battery of stains and histochemical reactions, for muscle necrosis quantification. For this purpose, albino rats (Wistar) treated with the organophosphate paraoxon, were used both with and without antidotes (atropine or pralidoxime). Muscle fiber necrosis in the diaphragm of the rats treated with paraoxon or paraoxon and atropine, that affected about 15% of the fibers in some areas, was detected. In the group treated with paraoxon and pralidoxime, a minimal necrosis was seen, revealing a protective role of this later antidote during the development of myopathy.

Estudamos um paciente com quadro clínico rebelde, produzido por intoxicação pelo Parathion. Foi observado um fenômeno miotônico transitório, não descrito na literatura revisada. A constatação de cifras de AchE eritrocitária baixas e de colinesterase plasmática normais, indicou que era portador de déficit congênito de AchE, esclarecendo-se a evolução crônica do seu quadro. O fenômeno miotônico associado ao quadro clínico, eletrofisiológico, histológico e bioquímico fazem deste paciente um modelo clínico, de etiologia conhecida, da discutida síndrome de Isaacs.

A case of 38 year old man who worked with organochlorinated and Parathion during 5 years is reported. His follow-up was up to 2 years. The onset of the disease was characterized by cholinergic signs, headache, loss of weight, trembling, miokimias, fasciculations, ataxia, myotonic phenomena (in hands only) and motor sensitive peripheral polyneuropathy (affecting the lower limbs symmetrically). Low concentrations of blood cholinesterases confirmed the etiology. Myotonic phenomena disappeared spontaneuosly 6 months after the initial observation. One year later, the concentration of erytrocyte acetilcholinesterase was found to be low and plasma cholinesterase was normal, suggesting that the patient was carrier of a congenital deficiency of acetilcholinesterase. in literature relationship between myotonia and intoxication due to organophosphorus was not found. The whole clinical picture, cholinergic symptoms, transitory myotonic phenomena and spontaneous motor activity could be explained by an excess of acetilcholine. Eletromyography (EMG) in the first observation showed neuromuscular transmission blocking characterized by deficiency or absence of voluntary activity, unexcitability of fibular nerves, with fibrilations and positive peaks as described previously with Mipafox (another organophosphorus agent). During 2 years of observation numerous end-plates potentials of muscular fibres persisted in the EMG. A progressive increase in voluntary activity showed by unit motor potential of almost normal amplitude and very increased duration was observed. No potentials of reinnervation were noted. The results of EMG were explained as disturbances of neuromuscular transmission associated with moderate signs of denervation The Eaton-Lambert's test and the stimulation of a single unit motor potential confirmed disorder of neuromuscular synapses. The histochemistry of brachial biceps showed scattered atrophic and angulated type I and II fibres. Teased-fibres preparations showed nerve fibres with B, C, and G alterations as defined by Dyck et al. indicating axonal degeneration. These results were according to velocity of sensitive conduction. The conduction velocity of fibular nerves was strongly delayed during all the evolution indicating serious disorders of motor nerves myelin. We think that intoxication by organophosphorus should not be expressed as an identical alteration of both motor and sensitive nerves. The association of myotonic phenomena with such clinical, electrophysiological and histological picture is characteristic of the Isaac's syndrome model with known etiology.

São apresentados os resultados dos exames clínicos, eletrofisiológicos e do estudo do ponto motor, da imunofluorescência, da histoquímica e da ultrami-croscopia da biópsia muscular de um caso de miopatia miotubular. São discutidos estes resultados em relação aos achados de 56 casos desta moléstia consignados na literatura até 1978, sendo dada enfase à etiopatogenia.

A case of myotubular myopathy in a 10 years old girl is reported. Clinically, palpebral ptosis, ocular movements limitation, facial diplegia, posi-tivity of Gower's test, muscular hypotrophy distal, foot drop and deep absent reflexes were found. These signals were described by most of authors, besides symptoms referred, like partial urinary incontinency and frequent vomits. Reflexes H absents and teary in our patient were observed but were not described in the other cases of the literature. Routine laboratory tests were within normal limits; only aldolase was lightly elevated. In all muscles examinated it was noted a spontaneous electromyographic activity with +- of 2,64 ± 1,33 ms, 36,87 ± 30,87 µV and 88,13 ± 24,82 /s of frequency without characteristics of desenervation potentials of myoneural plates. The voluntary electromyographic activity was of myopathic pattern. A curve I/D made in the motor point of braquial biceps muscle was normal. The biopsy was made in the motor point of this muscle for histochemical, electron, immunofluorescence and vital stain microscopy. The biopsy showed 35% of fibras with central nuclei, predominance and hypotrophy of type I fibres, in some of them there were not myofibrils in the central zone, and poor differentiation between the fibre types in oxidative enzymes reactions. The electron microscopy confirmed the histochemical studies. The direct immunofluorescence was positive in some fibres. The vital stain showed beaded subterminal motor fibres. The clinical, electromyographic and principally histological findings suggest a innervation congenital disorder of muscle fibres.