Variation in the number and size of myelinated nerve fibers regenerated after repeated localized freezing of the sciatic nerve of rats]

The number and size of myelinated fibres have been determined in the nerve to medial head of the gastrocnemius muscle of Rats in which the sciatic nerve had been frozen locally 1 to 5 times at monthly intervals. The contralateral nerve was used as a control. When the measurements were made one month after the last freezing, the number of fibres increased progressively until the 3rd freezing, reaching about 220% of the normal value. No higher values were observed after 4 or 5 freezings. The mean diameter of fibres decreased with the number of operations. When the measurements were made 3, 6, 12 or 18 months after the 3rd freezing, the number of fibres decreased by about 30% between the 1st and the 3rd month and then stabilized. The mean diameter of fibres increased progressively. However, at the 18th month, the size of the myelinated fibres had not reached the normal value.     

A histochemical study of denervated marsupial hemidiaphragm

Summary The marsupial (quokka) hemidiaphragm showed postdenervation hypertrophy and subsequent atrophy. The type II muscle fibres hypertrophied up to 20 days postoperation and then regressed. However, the type I fibres hypertrophied throughout the experimental period (100 days) studied. Unlike denervated eutherian hemidiaphragm, fibre-splitting was absent in the denervated marsupial muscle. An enhancement of the ATPase reaction in the denervated type I fibres may be due to dedifferentiation. Presumably innervation exerts a negative control and prevents increase of type I fibre size in the normal hemidiaphragm.I am grateful to Dr O.M. Sola and Professor B.A. Kakulas for their help and encouragement.     

A histochemical study of denervated marsupial hemidiaphragm.

The marsupial (quokka) hemidiaphragm showed postdenervation hypertrophy and subsequent atrophy. The type II muscle fibres hypertrophied up to 20 days postoperation and then regressed. However, the type I fibres hypertrophied throughout the experimental period (100 days) studied. Unlike denervated eutherian hemidiaphragm, fibre-splitting was absent in the denervated marsupial muscle. An enhancement of the ATPase reaction in the denervated type I fibres may be due to dedifferentiation. Presumably innervation exerts a 'negative control' and prevents increase of type I fibre size in the normal hemidiaphragm.     

Histochemical characterization of the red fibres in pigeon pectoralis muscle.

Red fibres of the pigeon pectoralis muscle showed high ATPase reaction at pH 9.4. Veronal-acetate pretreatment completely inhibited the ATPase reaction in these red fibres but not in type I fibres of the gastrocnemius. The former are type II red muscle fibres and hence are unlike type I red, the so-called slow-twitch muscle fibres.     

Histochemical characterization of the red fibres in pigeon pectoralis muscle

Summary Red fibres of the pigeon pectoralis muscle showed high ATPase reaction at pH 9.4. Veronal-acetate pretreatment completely inhibited the ATPase reaction in these red fibres but not in type I fibres of the gastrocnemius. The former are type II red muscle fibres and hence are unlike type I red, the so-called slow-twitch muscle fibres.     

Differentiating abilities of avian somatopleural mesoderm

Summary Quail-to-chick grafting experiments were performed on 2-day embryos in order to test the differentiating abilities of the somatopleure. After orthotopic and heterotopic transplantations of different parts of quail somatopleural mesoderm into chick embryos it is demonstrated that avian somatopleural cells differentiate into skeletal elements, smooth muscles, tendons and connective tissues. However, skeletal muscle fibres do not originate from somatopleural cells.Supported by a grant from the Deutsche Forschungsgemeinschaft (Ch 44/3).     

A comparison between the free grafting of sliced and intact muscles in the rat-1.

Transverse slicing is a new technique whereby a mammalian muscle can be freely grafted with success. This method eliminates contamination of the early graft by surviving muscle fibres and allows one to measure the development of contractile properties on a uniform population of regenerating muscle fibres.?IOAuthor     

A comparison between the free grafting of sliced and intact muscles in the rat

Summary Transverse slicing is a new technique whereby a mammalian muscle can be freely grafted with success. This method eliminates contamination of the early graft by surviving muscle fibres and allows one to measure the development of contractile properties on a uniform population of regenerating muscle fibres.Supported in part by a grant from the Muscular Dystrophy Associations of America, Inc.Part of this research was carried out while on a scientific exchange between the US and Czechoslovak Academies of Sciences.     

Zum Vorkommen von RNS im Nervenfaserbereich

Summary The incorporation of 3H-uridine into the RNA of the perikaryal and fibrous region of the optic tectum of the fish brain was investigated by means of radioautography after incubation times of 11 min to 96 h. There is no transport of RNA from the cell body to the nerve fibres. After RNase-treatment 90% of perikaryal RNA-labelling is washed out, but only a very small amount of the previous very few labelling of the nerve fibres.     

Do peripheral nerves contain a factor inducing acetylcholine sensitivity in skeletal muscle?

A crude extract of the sciatic nerve, eluate of dialyzed nerve extract or 2 folin-positive sephadex fractions induced acetylcholine sensitivity of extrajunctional regions in extensor digitorum longus muscle fibres of the rat, when released from silastic plates implanted for 3--4 days onto the muscle surface.     

Oscillatory after-potentials and triggered-automaticity in mammalian ventricular muscle fibres at high resting potentials.

Oscillatory after-potentials and triggered-automaticity were observed in dog ventricular muscle fibres when the fibres were exposed to K+-free,high-Ca++-solutions after K+-free,Ca++-free perfusion. They appeared at membrane potentials more negative than--60 m V.     

Proteolytic capacity in mouse cardiac muscle following strenuous exercise

Summary Proteolytic capacity in mouse cardiac muscle was analyzed 1, 3, and 6 days after exhaustive intermittent or submaximal prolonged running. No significant changes were recorded in the activities of acid or alkaline proteases, -glucuronidase or trypsin inhibitor. Similarly, no changes were found in the rates of acid or neutral autolysis.Supported by grants (Nos 8840/78/77 and 8208/78/78) from the Ministry of Education and the Academy of Finland.     

Frequencygrams due to the stimulation of dynamic gamma axons exerting type II effects]

Frequencygrams are graphs giving indirect information on the contraction of intrafusal muscle fibres. Frequencygrams of Cat spindle primary endings (flexor hallucis longus, soleus and peroneus brevis muscles) were recorded during repetitive stimulation of dynamic gamma axons exerting type II effects. The features of these frequencygrams (periodic increments whose frequency is equal to that of the stimulation and "driving") show that they can be ascribed to a relatively strong and fast intrafusal contraction. Two interpretations are considered.     

Differentiating abilities of avian somatopleural mesoderm.

Quail-to-chick grafting experiments were performed on 2-day embryos in order to test the differentiating abilities of the somatopleure. After orthotopic and heterotopic transplatations of different parts of quail somatopleural mesoderm into chick embryos it is demonstrated that avian somatopleural cells differentiate into skeletal elements, smooth muscles, tendons and connective tissues. However, skeletal muscle fibres do not originate from somatopleural cells.     

Structural changes of deoxyribonucleoprotein fibres following γ-irradiation under aerobic and hypoxic conditions

Summary The DNP fibres -irradiated under aerobic condition showed a reduction of their diameter, while no remarkable changes were observed in the DNP fibres irradiated under hypoxic condition by scanning electron microscopy.     

Zur zellulären Reaktion des Thymus nach Tumorimplantation

Summary As is shown by electron-microscopic examinations of the thymus, the implantation of ascites-tumour cells usually causes degenerative changes of thymus cells in mice with simultaneous involution of the organ. These changes are already perceptible on the second day. After 7 days most of the lymphocytes give evidence of a so-called segregation of karyoplasm, whereas simultaneously a high dissociation of cells is partially observed. Pyknotic cells could not be observed. Obviously, however, the cellular reaction of the separate thymi is different, which is possibly in relation with tumour growth.     

Studies on muscle fibre splitting in skeletal muscle

Summary Autoradiographic, stereological and histological studies have been carried out to determine the origin of muscle fibre splitting which supposedly occurs during muscle hypertrophy. The results obtained clearly indicate that the supposedly split fibres are a transient response probably derived from satellite cells and are not derived from pre-existing fibres by true splitting. Similarly, increases in muscle fibre size are not achieved by recruitment of satellite structures as indicated by lack of myonuclear recruitment.Acknowledgment. This work was carried out with the aid of a grant from the Medical Research Council of Great Britain. The authors are grateful for the excellent technical assistance of Miss H. Caulton, M.J. Wild and M. Fenner.     

Nerve-growth promoting action of isaxonine in rat.

After sciatic nerve lesion by freezing, the length of the most rapidly regenerating fibres was significantly increased by i.p. injection of isaxonine (N-isopropyl-amino-2-pyrimidine orthophosphate) in the rat. A dose-effect relationship was demonstrated. Both sensory and motor function returned earlier in treated animals.     

Nerve-growth promoting action of isaxonine in rat

Summary After sciatic nerve lesion by freezing, the length of the most rapidly regenerating fibres was significantly increased by i.p. injection of isaxonine (N-isopropyl-amino-2-pyrimidine orthophosphate) in the rat. A dose-effect relationship was demonstrated. Both sensory and motor function returned earlier in treated animals.     

Oscillatory after-potentials and triggered-automaticity in mammalian ventricular muscle fibres at high resting potentials

Summary Oscillatory after-potentials and triggered-automaticity were observed in dog ventricular muscle fibres when the fibres were exposed to K⁺-free, high-Ca⁺⁺-solutions after K⁺-free, Ca⁺⁺-free perfusion. They appeared at membrane potentials more negative than –60 mV.