Utilization of ascorbic acid during post-embryonic development of chick skeletal muscle

Summary Ascorbic acid is utilized during the post-embryonic differentiation of skeletal muscle fibres in chick. While the fibres lose their heterogeneity with regard to ascorbic acid, they continue to exhibit differences in their metabolic rates in terms of the succinate dehydrogenase activity throughout life.The investigations were carried out at the Department of Zoology, Panjab University, Chandigarh. We thank ProfessorG. P. Sharma, Head of the Department, for providing the necessary loboratory facilities.     

Immunocytologic differentiation of hypophyseal innervation in carp using anti met-enkephalin and anti-alpha-endorphin serums]

The immunocytological reactions with anti-met-enkephalin and anti-alpha-endorphin reveal two types of fibres in the intermediate lobe of the Carp. Their pathways through the adenohypophysis and the localization of their terminals are different. The anti-met-enkephalin positive fibres terminate mainly in a zone close to the proximal pars distalis; however some fibres terminate deeper in the intermediate lobe. The anti-alpha-endorphin positive fibres penetrate mainly in the central and ventral part where thye are more numerous than the former. It seems that the anti-met-enkephalin positive fibres belong to the gomori positive preoptico-hypophyseal tract, whereas the anti-alpha-endorphin positive fibres are gomori negative.     

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

The DNP fibres gamma-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.     

Das Spitzenwachstum der Fasern beiLinum perenne L

Summary In shoots ofLinum perenne apical growth was observed at both ends of the fibres. Their rounded tips, rich in protoplasm, protude into the middle lamellae of adjacent fibres or parenchyma cells. In addition to their apical growth, the fibre walls undergo symplastic growth with the walls of neighbouring cells. The formation of the pointed ends of fully developed fibres is described.     

Immunocytology of alpha-endorphin positive hypothalamic fibers of Carassius auratus L. and Cyprinus carpio L.]

An immunocytological study of the basal hypothalamus of Carassius auratus and Cyprinus carpio with an alpha-endorphin antiserum shows the different nerve processes belonging probably to the immunoreactive cells of the lateral part of the N.L.T. According to their pathways, two main fibre tracts have been distinguished: many fluorescent fibres converge towards the pituitary gland into which they enter, other fibres run caudally through the tuber towards the nucleus tuberis inferior (Baumgarten and Braak) where they could not be followed further.     

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.     

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.     

Sekretomotorische Fasern und Endigungen in der Adenohypophyse

Summary We demonstrated, in the pituitary of the animals examined, fibres which emerge from the Tr. hypothalamo-hypophyseal system and enter partly into the Pars intermedia and partlyvia the Pars tubularis into the Pars distalis and take their course directly towards the glandular cells. In the Pars distalis the nerve fibres end around the glandular cells in a special pericellular net.     

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.     

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.     

Non-uniformity of regional vasomotor activity indicating the existence of 2 different systems in the sympathetic cardiovascular outflow

Summary In rabbits, 2 populations of sympathetic postganlionic fibres innervating the skin, heart, muscle and kidney could be classified by their different spike heights and their different susceptibility to noradrenaline and angiotensin amide. The ability of the 2 populations to respond to physiological stimuli in a highly differentiated manner leads to the assumption that 2 different systems in the cardiovascular sympathetic outflow exist.     

A simple silver nitrate impregnation of nerve fibres with preservation of acetylcholinesterase activity at the motor end-plate

Summary A rapid silver nitrate impregnation of nerve fibres has been devised to maintain a histochemically detectable acetylcholinesterase activity at the motor end-plates.We thank Mrs Paulette Cloup and Mr D. Levieux for their valuable technical assistance.     

Blocking by picrotoxin of nigra-evoked inhibition of neurons of ventromedial nucleus of the thalamus

Summary The transmitter substance released by nigro-thalamic fibres is proposed to be -aminobutyric acid, since picrotoxin blocked nigra-evoked monosynaptic inhibition of thalamic neurons.Supported by grants Nos 212009 and 311410 from Ministry of Education of Japan.The authors wish to thank Dr Marjorie Anderson, University of Washington, Seattle, for improving the English.     

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.     

Coordinated activation of muscle fibres by different conduction velocities in branches of a crustacean motor axon

Summary Higher conduction velocities in branches of the fast excitor axon to distal muscle fibres ensure that these fibres are activated almost simultaneously with proximal fibres in the claw closer muscle of lobsters, producing a contraction of maximal force.Supported by Muscular Dystrophy Association and National Research Council of Canada.Supported by National Institute of Health and Muscular Dystrophy Association of America.     

The process of survival of denervated and freely autotransplantated skeletal muscle.

The study shows that two distinct processes occur in free autografts of denervated intact muscle during the early critical phase of the transplantation: survival of transplanted fibres at the periphery of the graft, and regeneration of new muscle fibres following breakdown of the originally transplanted fibres in the central areas.     

The modulus of elasticity of lobster aorta microfibrils

The presence of elastic fibres in the extracellular matrix (ECM) provides physiologically important elastic properties for many tissues. Until recently, microfibrils, one component of the ECM, were thought primarily to serve as a scaffolding on which elastin is deposited during development to form elaunin fibres [1]. The most prominent protein that forms mammalian microfibrils is fibrillin. It is known that mutations in the fibrillin gene cause a heterogenous connective tissue disease called marfan syndrome [2], so information on mechanical properties of microfibrils or their role in tissue function would be useful. Microfibrils are also found in the ECM of some invertebrate tissues, and there is growing evidence that the protein forming the structure is homologous to mammalian fibrillin [3, 4]. It has been shown that the microfibril-based arterial wall of the lobster has viscoelastic properties [5], and we have now utilized this primitive artery to measure the modulus of elasticity of microfibrils. It is similar to that of the rubber-like protein elastin.     

Responses of skeletal muscle fibres to lanthanide ions. Dependence of the twitch response on ionic radii.

A study of the effects of the lanthanide series of ions on toad skeletal muscle fibres reveals that they a) inhibit the twitch response, b) exhibit a marked dependence on ionic radius, and c) apparently exert their effects on the sarcolemma.     

Degeneration of unmyelinated axons in the dental root canal induced by 6-OH-dopamine

Summary The pulpal nerve fibres of feline incisors were examined ultrastructurally after i.v. administration of 6-OH-dopamine. The presence of degenerating unmyelinated fibres at this site provides conclusive morphological evidence that sympathetic fibres enter the dental pulp.     

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.