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Fine structural variations in two different types of muscles of frog (Rana cyanophlictis) subjected to sciatectomy were studied electronmicroscopically. Gastrocnemius muscle showed marked myofibrillar disarray and degeneration due to sciatectomy, while sartorius muscle was relatively less affected. The extent of sciatectomy induced fine structural variation was in proportion to the degree of denervation atrophy (as reflected by loss of wet muscle weight) in these muscles. Differences in the degree of degenerative changes in atrophying muscles may be attributed to variations in fiber type composition and stretch effects imposed during swimming movements.

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Unilateral-sciatectomy for three months in the frog, Rana cyanophlictis resulted in a substantial increase on unit weight basis in the ascorbic acid (ASA) and dehydroascorbic acid (DHA) contents of the sciatectomized gastrocnemius muscle. Diketogulonic acid (DKA) levels did not vary. On whole muscle-weight basis only the ASA level increased. The AChE activity in sciatectomized muscle is significantly lower than that of the control. Partially purified preparation of the AChE from the sciatectomized muscle showed different kinetics compared to that from innervated control. In vitro additions of ASA in physiological concentration to the enzyme assay medium inhibited the AChE activity significantly and the inhibition was an un-competitive type. Reduced activity of the enzyme has been correlated to the increased concentration of ASA in the sciatectomized muscle.

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Total and ionic calcium content, calcium binding capacity of sarcoplasmic proteins and calcium insensitive proteins were examined in atrophying leg muscles of frog after 1-5 months period of denervation. Different muscles showed different levels of atrophy and the total calcium content varied with reference to the type of muscle. Ionic calcium levels doubled in the gastrocnemius muscle after three months denervation. Calcium binding capacity of proteins and calcium insensitive proteins decreased rapidly up to four months after denervation in the gastrocnemius muscle. However no significant changes in the levels of calcium binding capacity and calcium insensitive proteins were found with reference to the type of muscle. Since total calcium content remains constant and wet muscle mass (expressed as atrophy) decreased markedly, an apparent increase in calcium concentration occurs in each muscle on denervation.

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A single sublethal dose of Vacor (1 mg/rat) or Silmurin (50 microgram/rat) brought about dissimilar changes in cardiac physiology of bandicoot rats. Delayed myocardial repolarization and stress on cardiac tissues were noticed. Elevation of S-T segment above the isoelectric axis diagnostic of recent myocardial infarction was observed. Vacor and Silmurin induced differential changes in heartbeat; Vacor poisoning resulted in bradycardia, whereas Silmurin tachycardia. It is inferred that Vacor deaths may be due to bradycardia associated with atrioventricular block and that of Silmurin to delayed myocardial repolarization and tachycardia.

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Single dose (1 mg/rat) administration of VACOR (N-3-pyridyl methyl-N'-nitrophenyl urea) produced significant paralytic symptoms in rats. Such rats which lived for one week were sacrificed and serum AChE was extracted and purified by Sephadex column chromatography. The serum enzyme from the normal rats showed the existence of two isozymes on polyacrylamide gels which could be resolved through column chromatography. Both the isozymes showed non-competitive inhibition with VACOR in vitro; but to a varied degree. The ACh concentration increased by 70-75% in serum and 95-100% in erythrocytes of the poisoned rats. VACOR thus affects ACh hydrolysis thereby causing an accumulation of ACh in the serum of poisoned rats.

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Sciatic denervation for 1 month in the frog Rana hexadactyla resulted in progressive atrophy of the gastrocnemius muscle without any change in the total DNA content of the whole muscle. Histamine content of the muscle decreased; glutamic and acid content increased and histidine level remained unaltered on denervation. Histaminase activity localized in the muscle decreased; glutamic acid content increased and histidine level remained unaltered on denervation. Histaminase activity localized in the muscle mitochondria increased on denervation. The histidine-degrading enzymes, histidine ammonia lyase, urocanate hydratase and imidazol-5yl lactate dehydrogenase, are localized in the sarcoplasm of the muscle and their activities are not altered on denervation. The histidine decarboxylase activity localized in the mitochondria is not altered on denervation. The reduction in the histamine content of the atrophied muscle may be due to increased mitochondrial histaminase activity but not due to increased decarboxylation of histidine. The loss of 'trophic influence' due to denervation may be manifested in the impairment of mitochondrial histaminase activity.

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Denervation of genitofemoralis in the bonnet monkey for 60 days resulted in a significant increase in neutral salt-soluble, alkali-soluble and insoluble collagens as well as glycoproteins. The hydroxyproline content of the salt-soluble and insoluble collagens in the muscle increased on denervation. These changes are discussed to imply the impairment of the action of specific structural genes.

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Abnormalities have been noticed in the phospholipid and cholesterol composition of the atrophied gastrocnemius muscle of frog denervated for 1 month. Cholesterol : phospholipid molar ratios in the muscle increased on denervation. Sphingomyelin and cardiolipin fractions increased in contrast to phosphatidyl choline, phosphatidyl serine and phosphatidyl ethanolamine in the sarcoplasmic reticulum (SR) of denervated muscle. Na-azide sensitive Ca2+ ATPase activity of the mitochondria did not alter whereas that of SR decreased on denervation. Phospholipase C digestion impaired the organelle Ca2+-ATPase activity. The above abnormalities in enzyme activities have been correlated to the changes in the lipid composition of the denervated muscle. On the basis of these changes it is discussed that the primary change in the muscle due to denervation is the change in the permeability of the membrane.

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