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D J Parry

Publications and source records attributed to D J Parry.

53 records · Page 3Linked to original sources
PubMed1978

Histochemical changes in fast and slow muscles of nutritionally dystrophic rabbits.

Rabbits were rendered dystrophic by feeding them a diet deficient in vitamin E and their fast-twitch EDL and slow-twitch SOL muscles were examined histochemically. The soleus muscle of control rabbits consisted largely of type I fibres with occasional areas of scattered type II fibres. In the nutritionally dystrophic rabbits type II fibres were consistently found homogeneously distributed throughout the entire muscle and in increased proportion. A very similar pattern was observed in the solei of rabbits following sciatic nerve section. The normal EDL contained three fibre types (I, IIoxidative and IIglycolytic). Vitamin E deficiency appeared to be associated with a shift towards an increase in the proportion of IIglycolytic fibres at the expense of IIoxidative. In denervation as well as vitamin E deficiency the type I fibres of the EDL appeared to be spared. A small number of the E-deficient rabbits exhibited degenerative changes in their sciatic and sural nerves. When animals were both denervated and E-deprived the resulting muscle changes were very much more severe than in the case of either challenge in isolation. We suggest that although some of the signs of vitamin E deficiency resemble those of a neural defect there is, in addition, a direct myopathic effect.

Adenosine Triphosphatases↗
PubMed1977

The relationship between surface potentials and the number of active motor units.

One of the assumptions inherent in a technique recently devised for enumerating motor units in human muscles is that the surface potentials from active motor units summate in a linear fashion. We present an electrical model of a muscle which predicts that a linear relationship between the number of active units and the electrical response recorded at the surface overlying the muscle would not be expected. The extent of the non-linearity, and hence the error in the calculation of the number of motor units in a given muscle, depends upon the ratio between the mean conductance of the motor units themselves and that of the external conduction pathway through which the electrical signal is fed (Gu/Ge). The extent of non-linearity is assessed experimentally in human hypothenar muscles using a "collision" technique. The average underestimate introduced into the calculation of the number of motor units in this particular case was concluded to be 26%. The value of Gu/Ge derived from these experiments, in 2 subjects, was checked by simulating an intramuscular action potential and determining the attenuation at the surface. The 2 independently obtained values were sufficiently close to suggest that the model may be a valid one. We conclude that caution should be employed in the interpretation of experiments which purport to determine the number of motor units in a muscle by means of surface recordings.

Adult↗
PubMed1968

Lesions associated with gastroduodenal haemorrhage, in relation to aspirin intake.

The incidence of aspirin ingestion during the week preceding overt gastroduodenal bleeding was recorded in 582 patients. A positive aspirin history was found in 80% of patients with acute gastric lesions, in 63% of those in whom no lesion was found, in 52% of those with a chronic duodenal ulcer, and in 49% of patients with a chronic gastric ulcer. In a control series of 542 consecutive patients without overt bleeding admitted to the same wards during part of the time of this investigation the aspirin incidence was 32%.The difference in aspirin habits between these two series confirms that aspirin is a factor in precipitating overt haemorrhage in acute and chronic peptic ulcers, and that it is an important cause of bleeding from the stomach or duodenum, or both, in the absence of a chronic peptic ulcer.

Adult↗
PubMedDate not supplied

Slowing of twitch of dystrophic mouse muscle in partially due to altered activity pattern.

Fast-twitch muscles of the hindlimb of dystrophic (dy2J) mice show a prolongation of both the contraction and relaxation phases of the isometric twitch. Comparable muscles of the forelimb of these mice exhibit relatively little increase in time to peak tension but time to half-relaxation is as severely affected as in the hindlimb. When examined with an immunohistochemical technique to demonstrate the presence of "slow" myosin it was apparent that there were no fibers containing the "slow" isoenzyme in either hindlimb or forelimb muscles of 6-month control mice. In dy2J mice hindlimb muscles contained many fibers with "slow" myosin whereas forelimb muscles did not. It is suggested that the spontaneous twitching activity produced in the hindlimbs, as a result of amyelination of the spinal roots, induces synthesis of "slow" myosin, which in turn leads to prolongation of time to peak twitch tension.

Adenosine Triphosphatases↗