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Biomedical subjects

I R Griffiths

Publications and source records attributed to I R Griffiths.

At least 127 records · Page 7Linked to original sources
PubMed1975

Cholesterol masses in association with spinal cord infarction due to intervertebral disc emboli.

The clinical and autopsy findings are presented from three dogs with spinal cord infarction. At autopsy firm gritty masses and cystic areas were present within the spinal cord. The masses contained numerous cholesterol clefts, collagen and reticulin fibres and were accompanied by a macrophage, giant cell and lymphocytic response. The cholesterol masses were present mainly in white matter. The ventral spinal artery or its branches as well as pial arteries contained fibrillary masses often covered by endothelial cells. The staining characteristics of these emboli suggested that they were fibro-cartilagenous and probably derived from the intervertebral discs. It is assumed that the cholesterol masses were formed from myelin breakdown products within infarcted areas.

Animals↗
PubMed1975

Age changes in the dorsal and ventral lumbar nerve roots of dogs.

Dorsal and ventral nerve roots from clinically normal dogs aged 3 months to 13 years have been examined. The L6, L7 roots were selected and samples removed from the roots within the sub-arachnoid space and within the root sleeves. Routine light microscopy, electron microscopy and single fibre studies have been made. The single teased fibre results have been analysed statistically for the correlation of internodal length and diameter. With increasing age there was marked evidence of demyelination and remyelination. Paranodal and segmental demyelination were present and there were numerous fibres showing a marked variation in internodal length. In younger animals these features were not seen. Wallerian type degeneration was uncommon. In older animals myelin balloons, similar to those described proximal to neuromas, were commonly found. These were present in both dorsal and ventral roots. The ballooning appeared to result from a splitting of the myelin sheath. The intervening space was non-staining but sometimes contained myelin debris. No evidence of neuromas was present in these roots or peripheral nerves. These studies suggest that both the ballooning and demyelination and remyelination are age related.

Age Factors↗
PubMed1975

A myopathy associated with myotonia in the dog.

The pathology of two cases of canine myopathy associated with myotonia are presented. The changes were interpreted as dystrophic. The most obvious features were a rounding on cross section and variation in fibre size with numerous internal nuclei, many of which formed chains. Degeneration and regeneration were seen and there was a slight increase in perimysial and endomysial connective tissue. Only one ringed fibre was seen, but no sarcoplasmic masses. Enzyme histochemistry failed to demonstrate any selective Type I fibre atrophy. The peripheral and central nervous systems were normal in both cases.

Animals↗
PubMed1975

Spinal cord blood flow measured by a hydrogen clearance technique.

Spinal cord blood flow (SCBF) has been measured in segments of the thoracolumbar cord of dogs using the hydrogen clearance technique. Clearances were recorded and flows calculated from electrodes placed in grey and white matter. The position of the recording electrodes was marked by diathermy and confirmed in each experiment. The SCBF in the white matter for 82 clearances was 13.7+/-4.5 ml/100 g/min using pentobarbitone anaesthesia. In the grey matter both monoexponential and biexponential clearances were recorded from electrodes placed in grey matter. There was no difference in flows calculated from the monoexponentail and slow components. SCBF from the slow components or monoexponentials was 12.0+/-4.5 ml/100g/min. The flow from the fast component was 69+/-11 ml/100 g/min. with pentobarbitone anaesthesia and 97.5+/-32.9 ml/100g/min with alpha-chloralopse anaesthesia. The flow calculated from the fast component did not correlate to changes of PaCO2. The slow component of any biexponential clearances was used to calculate flows from electrodes placed in the grey matter. There was no significant difference between flows from the grey matter (calculated from the slow component) and the white matter. Simultaneously recorded cortical and sub-cortical -lows were higher than in spinal grey and white matter. There was considerable variation in flow from animal to animal. The area of spinal grey matter is small and surrounded by white matter and the flow recorded from electrodes placed in grey matter is probably the average SCBF representing a mixture of grey and white flow. This will arise because of the rapid diffusibility of hydrogen gas between the tissues. It is therefore difficult to ascribe the flow from a centrally placed cord electrode to a definite anatomical compartment.

Anesthesia, General↗
PubMed1975

Vasogenic edema following acute and chronic spinal cord compression in the dog.

The T-13 spinal cord segment of dogs was compressed both acutely and chronically by means of a balloon catheter. The vascular permeability to protein was assessed using Evans blue albumin (EBA), and the dorsal column evoked potential recorded to monitor conduction failure. With acute compression sufficient to cause conduction failure there was a marked leakage of EBA from the intermediate gray matter, which spread into the dorsolateral white matter. The degree of edema was similar whether the compression was maintained or released. Chronic compression maintained over 4 to 5 hours did not increase vascular permeability, but following release of compression leakage of EBA occurred in the same cord locations observed with leakage from acute compressions. This increased permeability following release of chronic compression may result from reactive hyperemia. Dorsal column conduction returned after the release of both acute and chronic compression. The extravasated EBA was present both in the extracellular space and within cells. The results and their clinical application are discussed.

Acute Disease↗
PubMed1973

Spinal cord blood flow in dogs. 1. The 'normal' flow.

The spinal cord blood flow has been measured in anaesthetized dogs using an inert radioactive gas ((133)Xenon) clearance technique. The (133)Xe was placed in the cord by direct injection. This study has demonstrated that the flows obtained from the white matter are reproducible and that there is little variation in blood flow in the white matter between different thoracolumbar segments in the same dog. No difference was found in blood flow between dogs anaesthetized with halothane, trichlorethylene, or pentobarbitone.

Animals↗
PubMed1973

Spinal cord blood flow in dogs. 2. The effect of the blood gases.

The effect of CO(2) on the spinal cord blood flow was investigated in nine dogs. The flow was closely correlated with the paCO(2) and at about 85 mmHg was double the normocarbic flow. The effect of pO(2) was studied in a further nine dogs. Hypoxia markedly increased the flow which was maximal at paO(2) 30-40 mmHg. The vasoconstrictor effect of hypocarbia was absent or decreased in hypoxia. The response of the cord vessels to the blood gases was very similar to that of the brain.

Animals↗
PubMed1973

Spinal cord blood flow in dogs: the effect of blood pressure.

A study has been made into the effects of blood pressure on the spinal cord blood flow. Under conditions of normoxia and normocarbia a well-functioning autoregulation was present between 150-60 mmHg. Below 60 mmHg the flow decreased with reductions in pressure. In individual dogs, autoregulation was sometimes present to 40 mmHg. Under conditions of hypoxia or hypercarbia, autoregulation was absent or severely impaired. The results are discussed in relation to the cerebral circulation and to some aspects of experimental cord disease.

Animals↗