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Biomedical subjects

J M Stevens

Publications and source records attributed to J M Stevens.

At least 163 records · Page 9Linked to original sources
PubMed1985

Post-traumatic cystic and non-cystic myelopathy.

Sixty-four patients with suspected cystic myelopathy following spinal cord trauma were examined radiologically. In twenty-seven of these, spinal cord cysts were confirmed at surgery; in five, cysts were excluded by surgery and/or autopsy; the rest were unconfirmed. In water soluble myelography the most frequent sign in those with confirmed cysts was distention of the involved segments of the spinal cord. A less frequent but reliable sign was variation in cord size with position in a paradoxical fashion to the well established changes which occur with air myelography. Focal concentrations of contrast medium were visible within cord substance at CT in two of the patients in whom no cyst was found at surgery or autopsy. Some correlations between clinical features, including rate of progression and results of surgery, and radiological findings are unexpected on the basis of existing theories on pathogenesis.

Cysts↗
PubMed1985

Surgical treatment of cervical cord compression in rheumatoid arthritis.

Cervical myelopathy is a rare but potentially dangerous complication of rheumatoid arthritis and presents considerable therapeutic problems. A conservative approach carries high mortality and surgical intervention is not without serious risks. Reduction of subluxation and posterior fusion is widely practised but may require prolonged bed rest and continuous skull traction, sometimes for many weeks. When anterior decompression has been attempted prolonged immobilisation and external fixation have created problems. In this series 23 rheumatoid patients with cervical myelopathy were investigated over a four-year period. Seventeen underwent anterior decompression of the cervical cord, of whom 14 had a transoral removal of the odontoid peg and pannus and posterior occipitocervical fusion during the same anaesthetic without mortality or serious postoperative complications; all but one have improved. The authors believe that early mobilisation after a combined cord decompression and internal fixation has reduced the mortality and morbidity. Management of cervical myelopathy in rheumatoid arthritis and indications for operation are discussed.

Adult↗
PubMed1984

Radiological features of subependymoma with emphasis on computed tomography.

The features of 17 symptomatic subependymomas on X-ray computed tomography are described. Thirteen were reviewed from isolated case reports and 4 were original material. Over half were entirely intraventricular, 6 extended into brain substance and 2 into subarachnoidal cisterns. Twelve were isodense, 15 showed diffuse but irregular enhancement, and 5 contained nodular calcification. Large low density cysts, intratumoural haemorrhage and brain oedema were found almost exclusively in lesions extending into brain substance. It is concluded that subependymomas resemble ependymomas too closely on CT to be distinguished radiographically from them as a separate group. However subependymomas contain calcification slightly less frequently, and usually appear as mainly intraventricular lesions even when they occur above the tentorium.

Adolescent↗
PubMed1983

Observation on peritumoural oedema in meningioma. Part I: Distribution, spread and resolution of vasogenic oedema seen on computed tomography.

The distribution of oedema detected by computed tomography in 46% of 160 patients with cerebral meningiomas was studied. Oedema occurred most frequently in the centrum semiovale and deep white matter around the ventricular trigones and frontal horns, the distribution reflecting mainly the size of the interstitial spaces adjacent to the tumour. Other theoretically relevant factors such as hydrocephalus and cerebral atrophy did not influence oedema distribution. Cyst like spaces of various types were observed in 20% and their aetiology is discussed. Oedema usually resolved after surgery, but in at least 13% it persisted after 3 months. Atrophy related to tumour size and not to presence or extent of oedema. Increased oedema after surgery was never of vasogenic type and could nearly always be ascribed to a definable complication.

Brain Diseases↗
PubMed1983

Observations on peritumoral oedema in meningioma. Part II: Mechanisms of oedema production.

Meningiomas occurring in 160 patients were studied in relation to oedema production using computerised tomography. Statistically significant positive correlations with oedema production were found with tumours of large surface area, anterior parasagittal position, prominent vascularity, involving dural sinuses, and with short clinical history. Significant negative correlations were found with small tumour size and the presence of calcification. It is considered that hydromechanical factors predominate in oedema production with meningioma.

Blood-Brain Barrier↗
PubMed1983

Defective neutrophil chemotaxis resulting from thermal injury: restoration of directed migration by increasing Boyden chamber filter pore size.

Decreased chemotaxis of burn patient neutrophils has been observed in many studies. This study attempts to analyze the basis of this defect by determining the effect of filter pore size on chemotaxis, utilizing the Boyden chamber technique. Directed migration of burn patient neutrophils, as compared to normal controls, was greatly decreased when 3.0-micron filters were used. When 8.0-micron filters were used, however, the directed migration of burn patient neutrophils was identical to that of the normal controls. These findings indicate that the failure of burn patient neutrophils to undergo directed migration using Boyden chambers is not due to an inability to migrate toward a chemoattractant. Our data suggests that when utilizing the Boyden chamber technique to measure chemotaxis, the failure to give a normal response should not necessarily be interpreted as a chemotactic defect. In fact, mechanical impediments may play a major role in the decreased migration.

Adolescent↗
PubMed1983

Neutrophil migratory activity in severe hemorrhagic shock.

Sepsis continues to be a major cause of patient death following hemorrhagic shock. To explain this increased susceptibility to infection on a cellular level, neutrophil function was studied in nine adult baboons subjected to severe hemorrhage. Neutrophil migratory activity was found to be significantly decreased immediately after hemorrhage (P less than 0.05 vs control) and continued to decline throughout the experiment. After an initial small decline, neutrophil adherence increased to significant levels after 4 h of hypotension (P less than 0.05 vs control). The present data support the hypothesis that increased susceptibility to infection after sustained hemorrhage is a result of impaired neutrophil function.

Animals↗
PubMed1982

Cavernous sinus thrombosis.

Four patients with clinical and investigative features suggestive of cavernous sinus thrombosis are reported. Radiological investigations included computed tomography of head and orbits. The problem of clinical and radiological distinction from orbital infection is discussed. Serious intracranial complications developed in two patients and the value of computed tomography in detecting these is stressed.

Adult↗
PubMed1981

Vascular anatomy in the suboccipital region and lateral cervical puncture.

The theoretical risk of injuring the vertebral artery or anomalous vessels at lateral cervical puncture is assessed. In just less than 30% of vertebral arteries the vessel overlies the lateral aspect of the spinal canal between the first and second cervical vertebrae, usually the antero-inferior quadrant. Directing the spinal needle to the posterior third of the canal virtually eliminates the possibility of injuring this and most anomalous arteries traversing the region. The likelihood of inducing subarachnoid haemorrhage by injuring these vessels would appear to be considerably less in lateral cervical than in cisternal puncture.

Adolescent↗
PubMed1979

Structure--activity relationships of n-substituted dopamine and 2-amino-6,7-dihydroxy-1,2,3,4-tetrahydronaphthalene analogues: behavioral effects in lesioned and reserpinized mice.

N,N-Disubstituted dopamine and 2-amino-6,7-dihydroxy-1,2,3,4-tetrahydronaphthalene (6,7-ADTN) analogues were synthesized and tested intraperitoneally in mice for dopamine agonism. Compounds inducing asymmetric postures in unilaterally caudectomized mice were further tested in mice treated with reserpine and alpha-methyl-p-tyrosine methyl ester. ED50 values determined for reversal of reserpine-induced catalepsy were used to rank drug potency and correlated with molecular structure. N-n-Propyl N-substituted compounds were more effective than other N,N-dialkyl homologues. Of these, analogues with one alkyl group larger than propyl became inactive or their dopaminomimetic effect was reduced when the propyl was replaced with a larger group. N-Monosubstituted analogues were inactive as dopamine agonists. N-n-P-r-N-n-Bu-6,7-ADTN was six times more potent than N-n-propyl-N-n-pentyl- and N-n-propyl-N-phenethyldopamine but ten times less potent than apomorphine. The availability of an array of structurally related dopamine analogues with dopaminomimetic properties may make it possible to test the hypothesis that there are more than one type of dopamine receptor and that stereotypy and locomotor activity may have different central nervous system loci. Moreover, they may be of potential use in the treatment of parkinsonism and other extrapyramidal disorders.

Animals↗
PubMed1978

Assessing personal, role, and organizational predictors of managerial commitment.

Using a role and exchange theory framework, this study examines the commitment to their organization and to the federal service of 634 managers in 71 federal government organizations. Results indicate that certain role factors such as tenure and work overload and personal factors such as attitude toward change and job involvement are strong influences on commitment. Implications of the findings and the need for further theoretical and methodological refinements are discussed.

Administrative Personnel↗