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Biomedical subjects

M J Harrison

Publications and source records attributed to M J Harrison.

At least 127 records · Page 7Linked to original sources
PubMed1995

Toxoplasmosis and primary central nervous system lymphoma in HIV infection: diagnosis with MR spectroscopy.

PURPOSE: To differentiate intracranial lymphoma from Toxoplasma gondii lesions in patients infected with the human immunodeficiency virus, by means of localized spin-echo proton magnetic resonance (MR) spectroscopy. MATERIALS AND METHODS: Twenty-seven lesions were studied (18 T gondii lesions, nine lymphoma lesions) at 1.5 T. Spectra were acquired at an echo time of 135 msec from voxels centered on the lesions. Both visual analysis and spectral fitting were used to obtain metabolite ratios for choline (Cho), creatine (Cr), N-acetyl (NA), lactate, and lipids. RESULTS: Three spectral categories were seen. One had large lipid peaks with suppression of other metabolites. Another had an elevated Cho/Cr ratio with relatively diminished NA. The third had features of the other two. Examples of each spectrum type were acquired from both T gondii and lymphoma lesions. Neither method of analysis allowed differentiation between lesion types. MR spectroscopy showed an overlap of spectra. CONCLUSION: The authors conclude that toxoplasmosis and lymphoma cannot be differentiated with spin-echo proton MR spectroscopy at 135 msec.

AIDS-Related Opportunistic Infections↗
PubMed1995

Symptomatic cavernous malformations affecting the spine and spinal cord.

Ten cases of symptomatic cavernous malformations affecting the spine and spinal cord were retrospectively reviewed. The cases display a spectrum of pathological findings involving the vertebral body, vertebral body with epidural extension, epidural space without bony involvement, intradural extramedullary space, and intramedullary lesions. Lesions at all locations are identical histologically, electron microscopically, and immunohistochemically. This perspective, in which cavernous malformations are envisioned as a single entity arising at numerous locations, runs contrary to the view found in the neurosurgical literature. In most discussions of cavernous malformations, vertebral body lesions are depicted as separate entities from intradural lesions. Cavernous malformations, also called cavernous hemangiomas, are developmental vascular hamartomas that, by definition, do not grow by mitotic activity. Yet, the expansion of these lesions is well documented both in the literature and among our cases. The therapeutic modalities used in our series included observation, embolization, radiation, and surgical resection alone or in combination. All modalities are effective but must be tailored to the specific needs and condition of the patient. The embryology, methods of treatment, and proposed mechanisms of growth, plus similarities and differences between cavernous malformations at each location, are reviewed. Analogies between spinal and intracranial lesions are presented. On the basis of this series and a review of the literature, we conclude that cavernous malformations represent a single entity regardless of location. Segregation based on location, as is prevalent throughout the neurosurgical literature, hinders an overall understanding of these lesions. Cavernous malformations are more appropriately viewed as a single pathological entity arising in a multitude of locations. The difficulties encountered when managing cavernous malformations at various locations are unique to the location and not the lesion.

Adult↗
PubMed1995

Hemangiopericytoma of the sciatic notch presenting as sciatica in a young healthy man: case report.

A case of hemangiopericytoma of the sciatic notch presenting with sciatica in a healthy 33-year-old man is presented. Tumors of the sciatic notch are exceedingly rare, and few data pertaining to the entity are found in the literature. A few series have been published on neurogenic tumors of the sciatic nerve, and one series of hemangiopericytomas mentions a case in which the sciatic nerve in the thigh is involved with tumor. To our knowledge, this is the first case in the literature detailing a hemangiopericytoma spanning the sciatic notch. Hemangiopericytomas are well known to neurosurgeons as durally based lesions and have been categorized as a subtype of meningioma. However, hemangiopericytomas are vascular sarcomas that most commonly occur in the pelvis and thigh. A brief discussion of the symptoms of sciatic notch lesions and hemangiopericytomas is included.

Adult↗
PubMed1995

Ossification of the anterior longitudinal ligament and Forestier's disease: an analysis of seven cases.

A retrospective review was conducted on the records and radiographs of six symptomatic patients and one asymptomatic patient with Forestier's disease. No other series of patients with this disease is found in the neurosurgical literature. Forestier's disease, also known as diffuse idiopathic skeletal hyperostosis (DISH), is an idiopathic rheumatological abnormality in which exuberant ossification occurs along ligaments throughout the body, but most notably the anterior longitudinal ligament of the spine. It affects older men predominantly; all of our patients were men older than 60 years of age. The disease is usually asymptomatic; however, dyspnea, dysphagia, spinal cord compression, and peripheral nerve entrapment have all been documented in association with the disorder. Five of the six symptomatic patients presented with dysphagia due to esophageal compression by calcified anterior longitudinal ligaments, and one patient developed recurrent spinal stenosis when scar tissue from a previous decompressive laminectomy became calcified. All patients responded well to surgery. Two of the four patients who underwent removal of cervical osteophytes required several months following surgery for the dysphagia to resolve. This would support the hypothesis that not all cases of dysphagia in Forestier's disease are due to mechanical compression. Dysphagia may result from inflammatory changes that accompany fibrosis in the wall of the esophagus or from esophageal denervation. Evaluation of dysphagia even in the presence of Forestier's disease must rule out occult malignancy. The authors' experience suggests that dysphagia in the setting of Forestier's disease is an underrecognized entity amenable to surgical intervention.

Aged↗
PubMed1994

Choreoathetosis/ballismus associated with pentamidine-induced hypoglycemia in a patient with the acquired immunodeficiency syndrome.

OBJECTIVE: To describe the association between acute choreoathetosis/ballismus and hypoglycemia related to pentamidine therapy in a patient with the acquired immunodeficiency syndrome. DESIGN: A single case report. MEASURES: Clinical observation, laboratory analysis of blood and cerebrospinal fluid, and magnetic resonance imaging of brain. RESULTS: No association was found apart from hypoglycemia. The abnormal movements and hypoglycemia did not recur following cessation of pentamidine. CONCLUSIONS: Hypoglycemia related to pentamidine therapy can cause neurologic disorders in patients with the acquired immunodeficiency syndrome.

Acquired Immunodeficiency Syndrome↗
PubMed1994

Proton spectroscopy in HIV infection: relaxation times of cerebral metabolites.

In vivo proton spectroscopy has demonstrated abnormalities in the cerebral metabolite ratios from subjects with acquired immunodeficiency syndrome (AIDS). Some of the sequences employed are subject to T1 or T2 weighting, which may affect spectroscopic interpretation. The relaxation times of choline (Cho), creatine (Cr), and N-acetyl (NA) resonances have been estimated at 1.5 T in 21 patients infected with the human immunodeficiency virus (HIV) and 8 controls using gradient localised, spin-echo spectroscopic sequences of varying echo and repetition times. A statistically significant increase in the T2 of NA was found in the HIV seropositive patients who had diffuse abnormalities on MR imaging consistent with HIV encephalopathy (493 +/- 199 ms) when compared to controls (292 +/- 118 ms; p < .05). No other statistically significant differences were found in the relaxation times between patients and control subjects. These results demonstrate that signals from the NA resonance obtained using long echo time sequences in subjects who are HIV seropositive are not solely indicative of metabolite concentration.

Adult↗
PubMed1994

Cerebrospinal fluid-intracranial volume ratio measurements in patients with HIV infection: CLASS image analysis technique.

PURPOSE: To prospectively study the cerebrospinal fluid volume-total intracranial volume ratio (CSF/ICV) in human immunodeficiency virus (HIV)-infected patients at various stages of disease. MATERIALS AND METHODS: A total of 258 volume measurements were obtained with use of a 1.5-T magnetic resonance (MR) imager and the cluster localized automated spherical segmentation technique (which reduces two-dimensional pixel data from dual spin-echo MR images to a one-dimensional histogram) in 69 control subjects and 189 HIV-infected patients. RESULTS: The CSF/ICV was statistically significantly increased in patients with late-stage (Centers for Disease Control and Prevention group IV) acquired immunodeficiency syndrome (AIDS) (0.16 +/- 0.05 [standard deviation]) compared with seronegative control subjects (0.12 +/- 0.03) and patients without symptoms (0.13 +/- 0.03). CONCLUSION: No substantial change in CSF/ICV occurs until development of late-stage AIDS.

Acquired Immunodeficiency Syndrome↗
PubMed1994

Focal ischemia causes an extensive induction of immediate early genes that are sensitive to MK-801.

BACKGROUND AND PURPOSE: There is strong evidence to implicate glutamate in the cerebral damage caused by ischemia. In this study we investigated the role of glutamate receptors in mediating effects of middle cerebral artery occlusion (MCAO) on immediate early gene expression in the rat by quantitation of mRNA levels. METHODS: The effect of MCAO on the induction of immediate early genes was studied in five regions, both ipsilateral and contralateral to the occlusion: the "core" ischemic area of the cortex in the central region of the middle cerebral artery territory, the surrounding area, frontal cortex, occipital cortex, and hippocampus. Levels of c-fos, c-jun, zif-268, and krox-20 mRNA were measured by Northern and slot blot analysis. RESULTS: A large induction of c-fos mRNA was obtained in all four cortical regions ipsilateral to the occlusion, with the greatest effect detected in the core area. Little effect was detected in the ipsilateral hippocampus and in all contralateral regions. Pretreatment with MK-801 (3 mg/kg) largely inhibited the induction of c-fos mRNA, indicating that the induction was mediated through an N-methyl-D-aspartate subtype of glutamate receptor. MCAO also produced a significant induction of c-jun and zif-268 mRNA in ipsilateral cortical regions. CONCLUSIONS: These results indicate that MCAO causes a profound modulation of the expression of multiple genes in an extensive area of cerebral cortex extending beyond the immediate area supplied by the middle cerebral artery. The marked effect of MK-801 indicates the potential importance of glutamate antagonists in restricting the widespread deleterious effects of glutamate.

Animals↗
PubMed1994

Epithelial cystic lesions of the sellar and parasellar region: a continuum of ectodermal derivatives?

Cystic epithelial lesions of the sellar and parasellar region are classified on the basis of histology and location into Rathke's cleft cysts, epithelial cysts, epidermoid cysts, dermoid cysts, and craniopharyngiomas. A retrospective review of the clinical presentation, radiological findings, and histology was performed on 19 such lesions, and a survey of the literature pertinent to the classification, clinical presentation, and embryology of these lesions was conducted. Presentation was nonspecific and not predictive of histology. Imaging studies were generally useful in distinguishing these tumors, with the exception of Rathke's cleft cysts, suprasellar epidermoid cysts, and craniopharyngiomas, which frequently could not be differentiated. On microscopic examination, most lesions fit into distinct categories; however, overlap was common among all and some could not be definitively categorized by histological criteria. Evidence supportive of an ectodermal ancestry for sellar and parasellar epithelial-lined cystic lesions is presented. Based on the current findings and a review of the literature, it is suggested that these lesions represent a continuum of ectodermally derived cystic epithelial lesions.

Adolescent↗
PubMed1994

Localized cerebral proton MR spectroscopy in HIV infection and AIDS.

PURPOSE: To document differences in the cerebral proton MR spectra of patients with early and late stages of human immunodeficiency virus (HIV) infection. METHOD: We studied the relative N-acetyl-aspartate (NAA) levels by localized proton spectroscopy of the parietooccipital region of the brain in 43 HIV-seropositive patients, including 26 with an acquired immunodeficiency syndrome (AIDS)-defining diagnosis, and in eight control subjects. RESULTS: Reduced relative NAA levels were shown in those HIV-1-seropositive patients: 1) with AIDS against HIV-1-seropositive patients without AIDS (P < .04); 2) with HIV-1-associated cognitive/motor complex against neurologically healthy patients (P < .007); 3) with encephalopathic changes on MR against those with normal imaging (P < .001); and 4) on follow-up against their results on initial study (P < .03). CONCLUSIONS: By clinical (Centers for Disease Control classification) and radiologic (MR evidence of white-matter disease) criteria indicating late-stage HIV infection, reduced relative levels of NAA have been demonstrated. Spectroscopic abnormalities can be quantitatively tracked with time. This paper demonstrates the clinical use of detecting NAA as a putative in vivo measure of the neuronal loss that has been demonstrated in postmortem studies of patients with AIDS. This neuronal loss, which is believed to underlie the HIV-1-associated cognitive/motor complex, is thought to be attributable directly or indirectly to the presence of HIV in the brain. Proton spectroscopy may serve as a quantitative noninvasive indicator of this aspect of cerebral involvement in HIV disease.

AIDS Dementia Complex↗
PubMed1993

Carotid endarterectomy improves haemodynamics on the contralateral side: implications for operating contralateral to an occluded carotid artery.

The importance of the patency of the contralateral carotid artery on the haemodynamic effect of a carotid stenosis was investigated. The breath-holding index was used to estimate cerebral perfusion reserve. The percentage rise in middle cerebral blood flow velocity, measured by transcranial Doppler ultrasonography, occurring during breath-holding was divided by the time of breath-holding. In study 1, ten subjects with no carotid stenosis, 13 with unilateral and eight with bilateral stenosis were studied. For unilateral stenosis the breath-holding index was reduced on the stenosed side compared with normal (0.85 versus 1.34 per cent per s, P < 0.05). For bilateral disease, in the presence of severe stenosis on the side contralateral to that being examined, even a moderate stenosis (30-50 per cent) resulted in a much greater reduction in the breath-holding index. In study 2, the breath-holding index was measured before and after carotid endarterectomy in ten patients. The index increased significantly following operation, not only on the operated side (1.31 versus 0.79 per cent per s, P < 0.01), but also on the contralateral side (1.23 versus 0.87 per cent per s, P < 0.05). In three of four patients with contralateral stenosis > 90 per cent or occlusion, operation improved the breath-holding index markedly (> 90 per cent) on the non-operated side above the stenosis or occlusion. These results demonstrate the importance of patency of the contralateral carotid artery in determining the haemodynamic effect of a carotid stenosis. In addition, operating contralateral to an occlusion may improve haemodynamic status above the occlusion. Implications in selecting patients for carotid endarterectomy are discussed.

Aged↗
PubMed1993

Muscle disease, HIV and zidovudine: the spectrum of muscle disease in HIV-infected individuals treated with zidovudine.

Eleven patients with AIDS or AIDS-related complex who developed muscle-related symptoms whilst taking zidovudine were investigated. The clinical details of a further ten patients who did not undergo muscle biopsy are also outlined. The clinical features, quantitative muscle strength testing, electromyographic findings, serial creatine kinase levels, muscle biopsy appearance on light microscopy and the effects of zidovudine withdrawal and rechallenge are described. The spectrum of muscle disease encountered included four cases of frank myopathy diagnosed using clinical, electrophysiological and histological criteria, four patients with mild weakness and myalgia in whom muscle biopsies were normal, three patients with myalgia only and a mild increase in the interstitial cell infiltrate shown by biopsy. The patients presenting with myopathy showed no improvement on withdrawal of zidovudine but responded to immunosuppressive therapy with steroids and, in one case, thalidomide prescribed incidentally. At present, it is not yet possible to clinically define a specific zidovudine-induced myopathy that is distinct from the other effects of HIV infection on muscle structure and function. Our experience suggests that zidovudine may be implicated as a myotoxin in some patients, particularly those with myalgia and mild weakness. In those patients with severe weakness, and with biopsy findings of necrosis and inflammation, the drug effects may be difficult to separate from the primary effects of HIV.

AIDS-Related Complex↗
PubMed1993

The prevalence of paranasal sinus disease in HIV infection and AIDS on cranial MR imaging.

Sinusitis poses a difficult clinical challenge in the management of patients with AIDS because of high rates of relapse and the association with unusual pathogens. To determine the prevalence and severity of sinus disease in this group we prospectively analysed the condition of the paranasal sinuses shown on cranial MR scans of 156 patients referred for the investigation of suspected intracranial pathologies. These included 104 HIV seropositive patients, including 93 with an AIDS-defining diagnosis (CDC IV). Forty-two scans were performed on age-matched controls. The scans were timed to control for seasonal variations in sinus disease and were interpreted by two radiologists who were blinded to the clinical and serological status of the patients. Severe mucosal disease (more than one sinus showing > 75% obliteration) or moderate mucosal disease (only one sinus showing > 75% obliteration) was seen in 15.1% (14/93) patients with AIDS and none of the 42 controls (chi 2 = 6.73, P < 0.01). The mean maximum mucosal thickness in patients with AIDS was significantly greater than the control group (P < 0.001) and also significantly greater than in seropositive patients who had not had an AIDS-defining diagnosis (CDC II/III) (P = 0.006). Paranasal sinus mucosal abnormalities seen on MRI are greater in prevalence and severity in patients with AIDS and about one in seven would be expected to have at least one sinus largely obliterated.

Acquired Immunodeficiency Syndrome↗
PubMed1993

Molecular characterization and expression of alfalfa isoliquiritigenin 2'-O-methyltransferase, an enzyme specifically involved in the biosynthesis of an inducer of Rhizobium meliloti nodulation genes.

A cDNA clone encoding an O-methyltransferase (OMT) from alfalfa has been isolated, which methylates the 2'-hydroxyl of isoliquiritigenin (2',4,4'-trihydroxychalcone) to form 4,4'-dihydroxy-2'-methoxychalcone, the most potent of the nod-gene-inducing flavonoid derivatives released from alfalfa roots. The cDNA clone was identified on the basis of N-terminal sequence identity to purified S-adenosyl-L-methionine:isoliquiritigenin 2'-O-methyltransferase (chalcone OMT) and expression of enzymatically active chalcone OMT protein in Escherichia coli. The deduced amino acid sequence showed significant similarities to other OMTs. Chalcone OMT is encoded by a small gene family in alfalfa and related sequences are present in other legumes. The chalcone OMT gene is expressed primarily in alfalfa roots; transcript levels were highest during the first 2 weeks of development. The OMT transcript was also detected, to a much lesser extent, in root nodules. In contrast, chalcone isomerase (CHI), although expressed at high levels in roots, was found in all plant organs and had a somewhat different developmental expression pattern. Chalcone OMT transcripts were localized primarily to epidermal and cortical cells starting 1.5-2.0 mm behind the root tip, whereas CHI transcripts were present at approximately equal levels in epidermal, cortical and vascular tissues, both at the root tip and throughout the root. Chalcone OMT transcripts were elicitor-inducible in alfalfa cell suspension cultures, although only low levels of methoxychalcone accumulated. The implications of these results for plant-microorganism interactions are discussed.

Amino Acid Sequence↗