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Biomedical subjects

S Rees

Publications and source records attributed to S Rees.

At least 145 records · Page 8Linked to original sources
PubMed1976

A quantitative electron microscopic study of the ageing human cerebral cortex.

A recent quantitative electron microscopic study of biopsy samples of the cerebral cortex of neurologically normal individuals, aged between 15 and 54 years, has shown that atypical inclusions are present in neuronal and glial processes in small but appreciable numbers (Rees). It would be of interest to know whether these inclusions accumulate with age. This study therefore applied the same quantitative methods used in the previous study, to autopsy samples of frontal and temporal cortex from 3 non-demented ageing human brains (70-76 years). The results showed that in the areas of cortex examined, the number of inclusions in neuronal processes did not increase with age. However, the number of dense deposits in the cell bodies and processes of oligodendrocytes did increase significantly with age. In agreement with previous studies corpora amylacea were found in astrocytic processes. Senile plaques were not observed.

Aged↗
PubMed1976

The watershed: a factor in coronary vein graft occlusion.

In 50 patients with one or more aortocoronary saphenous vein grafts investigated by angiography the patency rate of grafts inserted into arteries with a total proximal occlusion was significantly higher than of those inserted into arteries with a proximal stenosis. The interval between operation and investigation in the two groups was similar. In 10 patients with double grafts, one to an occluded and one to a non-occluded artery, there were 7 with one blocked graft, in each case to the non-occluded artery. In the other 3 both grafts were patent. A watershed was shown at angiography in one patient with a graft inserted into a stenosed artery; the distal run-off appeared good, but reflux of the contrast up the coronary artery into the aorta occurred when injecting into the graft, and vice versa. This watershed may operate to a minor degree in all grafts inserted into non-occluded arteries, and by causing stasis at the anastomosis, could explain the higher incidence of graft occlusion in this group. Ligation of the coronary artery proximal to the anastomosis may therefore be necessary to achieve the highest patency rate.

Adult↗
PubMed1975

A quantitative electron microscopic study of atypical structures in normal human cerebral cortex.

Biopsy samples of the cerebral cortex from four normal human brains were examined in the electron microscope for the presence of abnormalities related to neurones and neuroglia. Atypical forms of axons, axon terminals and dendrites, many of them similar to those described in a variety of pathological and experimental material, were found to occur in small but appreciable numbers. Neuroglia exhibiting atypical inclusions occurred but were much less common. Physiologically altered neuronal perikarya were not encountered apart from one neuronal death. An area of 3.6 x 10(5) mu2 was scanned from each brain and atypical structures were categorised and counted. The possible implications of the presence of these structures in normal brain in discussed and the need for neuropathologists and neuroanatomists to be aware of the existence of atypical forms of neuronal processes in normal human and animal brains is emphasised.

Adolescent↗
PubMed1973

Differential sensitivity of motor and sensory fibres in human ulnar nerve.

The human ulnar nerve has been stimulated with square-wave pulses of various fixed durations. Measurements were made of the growth of hand myograms compared with elbow neurograms and of hand myograms compared with finger neurograms, for fixed durations of pulses and increasing strength. The effect of blocking sensory action potentials with stimuli of various durations has been investigated, as well as the blocking of action potentials in motor nerve fibres by voluntary activity. It is concluded that pulses of long duration (1 msec or more) selectively stimulate sensory fibres at threshold, whereas short duration pulses (less than 200 μsec) selectively stimulate motor fibres.

Action Potentials↗
PubMed1973

Renshaw cell activity in man.

The H-reflex elicited in triceps surae by percutaneous stimulation of the posterior tibial nerve was conditioned by stimuli applied through the same electrode. The differential sensitivity of motor and sensory fibres to duration of the stimulus pulse made it possible to condition the H-reflex with either a motor or a sensory stimulus. With both types of conditioning, the H-reflex was inhibited at conditioning-test intervals of 2-3 msec and was then facilitated, the peak of facilitation occurring at 5-8 msec with motor conditioning and 6-10 msec with sensory conditioning. The phase of facilitation was followed by further inhibition. We have concluded (1) that the effects of motor conditioning on the H-reflex result from the discharge of Renshaw cells activated by the antidromic volley in the motor axons, and (2) that the effects of sensory conditioning (at the times used in these experiments) are largely due to the activation of Renshaw cells secondary to the discharge of alpha motoneurones by the conditioning volley.

Adult↗