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Biomedical subjects

M J Harrison

Publications and source records attributed to M J Harrison.

At least 19 recordsLinked to original sources
PubMed1992

The pathology of the posterior root ganglia in AIDS and its relationship to the pallor of the gracile tract.

The spinal cord and the thoracic and lumbar posterior root ganglia (PRGs) of 14 HIV-positive men and 7 age- and sex-matched controls were studied by routine histology, morphometric analysis of the number of nodules of Nageotte (nN) and the diameters of sensory ganglion cells, immunohistochemistry and in situ hybridization. In 7 patients (2 of whom had evidence of cytomegalovirus ganglionitis) there were increased numbers of nN and diffuse, mild infiltration with CD45R+ T lymphocytes; no B lymphocytes were observed. Macrophages were increased in number in all cases. Whenever more than one ganglion was examined from the same patient, the appearances were similar in all. There was no alteration in the distribution of ganglion cell diameters. Changes in the spinal cord included vacuolar myelopathy (5 cases), HIV myelitis (1 case), microglial nodules (3 cases) and pallor of the gracile tracts (GTP) in 7 cases, in 6 of whom it co-existed with increased numbers of nN. Seven cases had no abnormalities, except the increase in number of macrophages in PRGs. In spite of a correlation between sensory nerve cell loss and GTP our findings suggest that other mechanisms, such as 'dying back' may contribute to the pathogenesis of GTP. Moreover, sensory disturbances were found most commonly in association with nerve cell loss; however, loss of sensory ganglion cells was not necessarily associated with evidence of sensory impairment.

Acquired Immunodeficiency Syndrome↗
PubMed1992

rCBF abnormalities detected, and sequentially followed, by SPECT in neuro-Behçet's syndrome with normal CT and MRI imaging.

Conventional imaging with computed tomography (CT) and magnetic resonance imaging (MRI) may show abnormalities in central nervous system Behcet's syndrome but is normal in some cases. Recently in two cases positron emission tomography has shown abnormalities in blood flow and glucose metabolism far more extensive than the abnormalities seen on CT and MRI scans in the same patients. We report a patient with neuro-Behcet's syndrome presenting with headache and personality change in whom CT and MRI brain imaging was normal, but regional cerebral blood flow imaging using single photon emission tomography with the tracer HMPAO showed extensive perfusion deficits which partially reversed after 3 months of prednisolone therapy. This technique may aid the diagnosis of cerebral involvement in Behcet's syndrome, although the cause and incidence of the perfusion deficits need further evaluation.

Behcet Syndrome↗
PubMed1992

Neurological and neuropsychological performance in HIV seropositive men without symptoms.

Ninety five HIV seropositive and 32 seronegative homosexual men were recruited to a prospective study of the early features and natural history of the neurological manifestations of HIV infection. There was no evidence from the initial neurological examination, a neuropsychological test battery, nerve conduction studies, somatosensory evoked potentials from the legs, P300 event related auditory evoked potentials, magnetic stimulation of the motor cortex, or MRI scans that HIV infected men without symptoms in CDC groups II/III differed significantly from a well matched seronegative comparison group. Only the subgroup in CDC IV showed evidence of impairment, and this was restricted to their performance on some of the cognitive tests. The results imply that, despite early invasion of the CNS by HIV, major disturbances of function manifest themselves only when the patient becomes immunosuppressed. The importance of an appropriate comparison group and awareness of the potentially confounding influences such as age, education, exposure to alcohol and drugs, and mood and anxiety in such studies is stressed. The essentially negative findings are important in the understanding of the pathogenesis of neurological effect in HIV infection and in the design and interpretation of therapeutic trials.

AIDS Dementia Complex↗
PubMed1992

Influence of fatty acid content of lysophosphatidyl choline on its myelinotoxic properties.

The efficacy of lysophosphatidyl choline (LPC) type I and type IV in producing demyelination was assessed in rat tibial and sural nerve. By light and electron microscopy, a greater myelinolytic activity was demonstrated with type I, and concomitantly electrophysiology showed a more severe conduction block. In teased nerve preparations and 1-microns thin sections, demyelinated fibres were more frequent with LPC type I. At 1 h after injection, electron microscopy showed much more extensive myelin lysis in the form of fine vesicular debris. By 6 days, completely demyelinated fibres were much more common and associated Schwann cells contained either small quantities or no myelin debris. With type IV LPC, cytopathological changes were more extensive at 1 h. A minority of Schwann cells showed swollen hydropic cytoplasm and degradation of organelles. Axonal retraction from the myelin sheath occurred in occasional fibres, and in a few unmyelinated fibres axoplasm showed organelle depletion and increased granularity. By 6 days, Schwann cells still contained large quantities of gross myelin debris and had often retracted to expose extensive areas of axolemma. The findings suggest that the two types of LPC have different myelinolytic actions, which may be related to their different fatty acid content. A possible role for the two types of LPC in 'bystander demyelination' is considered.

Animals↗
PubMed1992

Estimation of cerebrovascular reactivity using transcranial Doppler, including the use of breath-holding as the vasodilatory stimulus.

BACKGROUND AND PURPOSE: A proportion of individuals with carotid artery stenosis show a reduced cerebrovascular reserve as measured by a reduced cerebral arterial vasodilatory response to carbon dioxide. Two methods of quantifying this vasodilatory response, using transcranial Doppler ultrasonography, have been in general use: the total range of vasodilation between hypocapnia, induced by hyperventilation, and hypercapnia induced by breathing carbon dioxide, and the response to breathing a fixed concentration of 5% carbon dioxide. We studied whether it is possible to use the rise in carbon dioxide occurring during breath-holding as the vasodilatory stimulus. METHODS: Using transcranial Doppler, cerebral reactivity to carbon dioxide was measured in 23 subjects undergoing intravenous digital subtraction angiography of their carotid arteries for symptoms of cerebrovascular disease. A breath-holding method was compared with the two previous methods, which required administration of carbon dioxide. RESULTS: All three methods gave results that correlated highly significantly with the degree of carotid stenosis, although the correlation was highest when the full vasodilatory range was measured. This method was adopted as the gold standard, and the other methods were compared with it. The breath-holding method correlated at least as well (rho = 0.67) as the 5% CO2 method (rho = 0.64). It identified a similar group of low reactors to our gold standard method, whereas the 5% CO2 method gave some discrepant results. CONCLUSIONS: The breath-holding method offers potential as a convenient, well-tolerated screening method of assessing carbon dioxide reactivity not requiring the administration of carbon dioxide, although further validation against more established methods of measuring cerebrovascular reserve is first required.

Aged↗
PubMed1992

Creutzfeldt-Jakob disease in recipients of human growth hormone in the United Kingdom: a clinical and radiographic study.

In the past 3 years there have been five further cases, in addition to one case reported in 1985, of Creutzfeldt-Jakob disease in recipients of human growth hormone in the United Kingdom. The clinical findings of two of these cases are described, demonstrating a typical presentation with a predominantly cerebellar syndrome at onset which is not commonly a presenting feature of sporadic Creutzfeldt-Jakob disease. In one case a 99mTc hexamethylpropylenamine single photon emission tomographic scan showed marked impairment of tracer uptake in the basal ganglia and cerebral cortex at a time when the clinical picture was predominantly cerebellar. This technique may be useful in early diagnosis. In the other case post mortem examination of the brain showed prominent amyloid deposition in the cerebellum, which has not been described previously in pituitary-hormone related Creutzfeldt-Jakob disease. The previously published cases of growth hormone-related Creutzfeldt-Jakob disease are reviewed and reasons for the particular clinical pattern seen are discussed.

Adult↗
PubMed1992

Protection against ischaemia: the basis of acute stroke therapy.

The search for effective therapy of acute stroke, centres on the two strategies of restoring blood flow before ischaemia causes irreversible infarction, and moderation of the biochemical changes in ischaemic tissue that cause neuronal death. This review concentrates on the role of lactacidosis, calcium ions, free radicals, and excitatory neurotransmitters in the pathogenesis of neuronal death, and on the therapeutic possibilities in acute stroke emerging from studies in animal models.

Acidosis, Lactic↗
PubMed1979

Multi-infarct dementia.

Fifty-two patients presenting with dementia were divided into a group in whom clinical features suggested an ischaemic basis (multi-infarct dementia) and a group in whom a primary degenerative process seemed more likely. Focal EEG changes and angiographic evidence of ischeamic areas and atheromatous disease of intracranial vessels were more common in the "ischaemic" than in the primary degenerative group. CBF was significantly reduced in the former but the regional pattern was equally distorted in the two groups. These findings strengthen the belief that the ischaemic score can identify those patients whose dementia is associated with vascular disease.

Adult↗
PubMed1979

The normal fundus.

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Fundus Oculi↗
PubMed1979

Optic atrophy.

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Humans↗
PubMed1979

Chronic subdural haematoma.

A retrospective case note survey of chronic subdural haematomata was carried out in an attempt to throw some light on the difficulties encountered in clinical diagnosis. The combination of raised intracranial pressure headache, fluctuating drowsiness and mild hemiparesis, although highly suggestive of subdural haematoma, is not always encountered, and epilepsy, aphasia, hemianopia and dense hemiplegia can all occur contrary to 'text book' descriptions. Head injury or other aetiological factors are commonly absent. The presentation may mimic tumour, dementia, cerebrovascular accident or subarachnoid haemorrhage. Non-invasive investigations may yield false negative results, although in the case of radionucleide scanning and computerized axial tomography the reliability is approaching 90 per cent. The diagnosis will, however, remain an unexpected finding at angiography in a percentage of cases.

Adolescent↗
PubMed1979

Papilloedema.

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Diagnosis, Differential↗