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Biomedical subjects

A Alavi

Publications and source records attributed to A Alavi.

At least 163 records · Page 9Linked to original sources
PubMed1995

Ab initio calculation of the sound velocity of dense hydrogen: implications for models of Jupiter.

First-principles molecular dynamics simulations were used to calculate the sound velocity of dense hydrogen, and the results were compared with extrapolations of experimental data that currently conflict with either astrophysical models or data obtained from recent global oscillation measurements of Jupiter. Excellent agreement with the extrapolated experimental data was obtained. These results strongly support the notion that the existing models for the jovian interior need to be revised.

Chemical Phenomena↗
PubMed1995

Sex differences in regional cerebral glucose metabolism during a resting state.

Positron emission tomography was used to evaluate the regional distribution of cerebral glucose metabolism in 61 healthy adults at rest. Although the profile of metabolic activity was similar for men and women, some sex differences and hemispheric asymmetries were detectable. Men had relatively higher metabolism than women in temporal-limbic regions and cerebellum and relatively lower metabolism in cingulate regions. In both sexes, metabolism was relatively higher in left association cortices and the cingulate region and in right ventro-temporal limbic regions and their projections. These results are consistent with the hypothesis that differences in cognitive and emotional processing have biological substrates.

Adult↗
PubMed1995

Resting cerebral glucose metabolism in first-episode and previously treated patients with schizophrenia relates to clinical features.

BACKGROUND: Functional neuroimaging can elucidate brain dysfunction in schizophrenia. The frontal, temporolimbic, and diencephalic regions have been implicated. There is a lack of prospective samples of first-episode and previously treated patients followed up longitudinally. METHODS: Patients and controls (42 per group) were studied. Positron emission tomography with flurodeoxyglucose, cross-registered with magnetic resonance imaging, measured metabolism. Scales assessed clinical features, premorbid adjustment, and outcome. RESULTS: There were no differences between groups in whole-brain metabolism or regional ratios or in anterior-posterior gradients, but left midtemporal metabolism was relatively higher in patients. This was pronounced in the negative and Schneiderian and absent in the paranoid subtypes. Higher metabolism and lower relative left hemispheric values were associated with better premorbid adjustment and outcome. A higher subcortical-cortical gradient was noted in first-episode patients. CONCLUSIONS: There are no resting metabolic abnormalities in any brain region, but abnormal gradients are evident. These vary in subtypes, and laterality is associated with functioning. The results support the hypothesis of temporolimbic disturbance in schizophrenia that is all ready present at the onset of illness.

Adult↗
PubMed1995

Beta 1,4-galactosyltransferase variations in rheumatoid arthritis.

Evidence indicating an important link between glycosylation changes and autoimmune rheumatic disease is presented. Attention is especially focused on the interrelationship between reduced galactosylation of the oligosaccharides of IgG, auto-sensitization to which is thought to be of central importance in the pathogenesis of rheumatoid arthritis (RA), and the enzyme beta 1,4-Galactosyltransferase (GTase) that catalyses the addition of galactose to the oligosaccharide chains on this molecule. Data are presented to indicate that GTase undergoes a variety of normal and disease associated changes. These variations are believed to contribute to the pathological processes in rheumatoid disease, and a hypothesis is suggested, whereby disease is associated with the dysregulation of an integrated glycosylation network, comprising IgG galactosylation, lymphocytic GTase and anti-GTase antibodies, that is a component of the normal immune system.

Arthritis, Rheumatoid↗
PubMed1995

Evaluation of beta 1,4-galactosyltransferase in rheumatoid arthritis and its role in the glycosylation network associated with this disease.

Evidence indicating an important link between glycosylation changes and autoimmune rheumatic disease is presented. Attention is especially focused on the interrelationship between reduced galactosylation of the oligosaccharides of IgG, auto-sensitization which is thought to be of central importance in the pathogenesis of rheumatoid arthritis (RA), and the enzyme beta 1,4-galactosyltransferase (GTase) that catalyses the addition of galactose to the oligosaccharide chains on this molecule. Data are presented to indicate that GTase undergoes a variety of normal and disease associated changes. These variations are believed to contribute to the pathological processes in rheumatoid disease, and a hypothesis is suggested, whereby disease is associated with the dysregulation of an integrated glycosylation network, comprising IgG galactosylation, lymphocytic GTase and anti-GTase antibodies, that is a component of the normal immune system.

Arthritis, Rheumatoid↗
PubMed1995

Nuclear imaging of solid hepatic masses.

This review has focused on the unique role of radionuclide scintigraphy in characterization of hepatic mass lesions. Radionuclide scintigraphy, unlike most other imaging modalities, is based on specific physiological and biochemical properties of each pathological entity that affects the liver. Hepatic scintigraphy, with its widespread availability, noninvasive nature, and relatively low cost is a powerful adjunct to other imaging techniques in the investigation of hepatic mass lesions. We have reviewed clinical presentation and characteristic findings of most hepatic lesions and have described reported findings with all available imaging modalities with particular emphasis on hepatic scintigraphy (Table 1) as well as a suggested algorithm for workup of solid hepatic masses (Fig 6). Additionally, the role of newer, more specialized techniques including PET scanning, 123I-labeled VIP, and 111In-labeled DTPA-D-Phe-octreotide scanning are reviewed. Hepatic nuclear scintigraphy continues to play an important role in the management of patients with solid hepatic masses.

Algorithms↗
PubMed1995

Morphine-augmented hepatobiliary scintigraphy: a meta-analysis.

The aim of this study was to compare the sensitivity and specificity of morphine-augmented hepatobiliary scintigraphy (MA-HBS) with that of conventional hepatobiliary scintigraphy (C-HBS) for acute cholecystitis. The results of most MA-HBS studies cannot be compared with C-HBS estimates, since articles describing C-HBS often include non-candidates for MA-HBS. However, using meta-analytic techniques to combine data from eligible studies (4 for C-HBS and 5 for MA-HBS), the specificity of MA-HBS (0.84; 95% CI = 0.75-0.94) was significantly greater (P = 0.008) than that of C-HBS (0.68; 95% CI = 0.61-0.75); there were no differences in sensitivity (MA-HBS; 0.96, 95% CI = 0.92-0.99; C-HBS: 0.97, 95% CI = 0.97-0.99).

Acute Disease↗
PubMed1995

False lateralization of temporal lobe epilepsy with FDG positron emission tomography.

We report 2 patients in whom visual interpretation of interictal positron emission tomography (PET) with [18F]fluorodeoxyglucose (FDG) suggested false lateralization of an epileptic focus. PET scans were interpreted as showing diffuse left temporal lobe hypometabolism in 1 patient and lateral temporal hypometabolism in the other. However, seizures began in the right mesial temporal lobe in both patients, and both responded favorably to right temporal lobectomy. In 1 patient, the intracranial EEG showed continuous asymptomatic subclinical seizure activity emanating from the right amygdala. These limbic discharges probably caused unrecognized right temporal lobe hypermetabolism. In the other case, quantitative analysis of metabolic rates showed conflicting mesial and lateral metabolic indexes. Frequent mesial interictal discharges might have increased lateral temporal metabolism. We conclude that asymptomatic epileptiform activity may alter temporal lobe metabolism and that quantitative PET analysis helps clarify contradictory visual PET interpretations.

Adult↗
PubMed1995

Multi-modal assessment in Alzheimer's disease. ADL in relation to PET, MRI and neuropsychology.

Alzheimer's disease (AD) causes a deterioration in functional status which may best be understood as a multi-dimensional concept. Results of multi-modal functional assessment in two patients with probable AD and comparable Mini-Mental State Examination scores demonstrated the heterogeneity of disease profiles and individual variations in functional status. Measures included direct assessment of ADL performance (SAILS), self and family perception of "current" and "best ever" functioning (NBFADL-60), neuropsychological test battery, magnetic resonance imaging (MRI) and positron emission tomography (FDG-PET). The multi-modal assessment yielded complementary information, and permitted correlation of physiological and behavioral data. Future studies should examine the potential heuristic and clinical utility of this approach.

Activities of Daily Living↗
PubMed1995

Gamma camera scintigraphy for direct visualization of larval migration in Strongyloides stercoralis-infected dogs.

Gamma camera scintigraphy of dogs infected with radiolabeled third-stage larvae of Strongyloides stercoralis was successful for visualizing larval migration in a live host. Ten-day-old pups were infected subcutaneously in a lateral inguinal site with 100,000 75Se-selenomethionine-labeled third-stage S. stercoralis and imaged serially using a clinical gamma camera during the prepatent period. Radioactivity corresponding to the larval inoculum was visualized at the infection site immediately after injection. Radioactivity spread diffusely, corresponding to radial dispersal of larvae from the infection site. The majority of the radioactivity concentrated over or through the abdomen from 48 to 144 hr after infection. Larvae arrived in the small intestine in numbers adequate for visualization beginning at 114 hr after infection. At no time was there concentration of radioactivity associated with the lungs of an infected pup. A control pup injected only with 75Se-selenomethionine showed uniform activity diffusely throughout the entire body at all times. We concluded that the majority of larvae moved to the gut by means other than the pulmonary route.

Abdomen↗
PubMed1995

Single photon emission computed tomography in Alzheimer's disease and related disorders.

Alzheimer's disease and other dementia syndromes can be characterized by single photon emission computed tomography (SPECT). SPECT can be used to measure cerebral blood flow or neurotransmitter activity in these disorders. SPECT can help distinguish various neurologic disorders and also help elucidate their pathophysiologic processes. This article focuses on the use of SPECT in the study of Alzheimer's disease and related neurologic disorders.

Aged↗
PubMed1995

Regional cerebral function determined by FDG-PET in healthy volunteers: normal patterns and changes with age.

UNLABELLED: The main objective of this study was to determine patterns of regional brain metabolic activity utilizing high-resolution PET in normal healthy volunteers and variations in different age groups. METHODS: High-resolution [18F]FDG PET images of the entire brain were obtained in 120 healthy normal volunteers (64 men, 56 women), age range from 19 to 79 yr. Each anatomic region was assessed using a qualitative rating scale with a score ranging from 1 to 6 (1 = definitely normal and 6 = definitely abnormal). Local metabolic activity was also estimated as showing increased (+) or decreased (-) compared to normal (0) states. RESULTS: The most consistent finding in normal aging was decreased cortical metabolism, particularly in the frontal lobes. Temporal, parietal and occipital lobe metabolism varied considerably among subjects within the same age group as well as over decades. Basal ganglia, hippocampal area, thalami, cerebellum, posterior cingulate gyrus and visual cortex remained metabolically unchanged with advancing age. CONCLUSION: These data indicate that qualitative interpretation of FDG-PET images allows accurate assessment of regional metabolic activity of the brain in normal subjects similar to those described with quantitative techniques. Adequate knowledge of normal variations and changes related to normal aging is necessary for optimal assessment of pathologic states.

Adult↗
PubMed1995

PET versus SPECT in distinguishing radiation necrosis from tumor recurrence in the brain.

Two cases of postsurgical brain tumor evaluation in which MRI was inconclusive are discussed. Functional imaging techniques, such as FDG-PET and 201TI SPECT, were used in both cases for distinguishing radiation necrosis from tumor recurrence. These methods proved to be complimentary. For Patient 1, FDG-PET showed more limitations compared to 201TI SPECT. FDG-PET results on the other hand, were consistent with the final diagnosis and the SPECT image was false positive for tumor recurrence in Patient 2.

Adult↗
PubMed1995

Radionuclide studies of the upper gastrointestinal tract in children with feeding disorders.

The case of a female infant with a feeding disorder and with inadequate growth is described. In her workup, there was no evidence of an organic disorder. Barium studies of the upper GI tract showed normal anatomy and function. A radionuclide milk scan was helpful in demonstrating mild reflux and significantly delayed gastric emptying. There was a good response to therapy.

Animals↗
PubMed1995

Comprehensive analysis of the results of the PIOPED Study. Prospective Investigation of Pulmonary Embolism Diagnosis Study.

UNLABELLED: The goals of this review were to summarize the published data from the National Heart, Lung and Blood Institute sponsored Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED) study, present new data from the entire population and provide a comprehensive criteria for ventilation-perfusion (V/Q) lung scan interpretation. METHODS: Data from the PIOPED frequent user tape and journal articles published between 1990 and 1994 and indexed on Medline that presented data from the PIOPED study were reviewed. RESULTS: A normal V/Q lung scan excludes the diagnosis of clinically significant PE. The usefulness of the V/Q lung scan was optimized when interpreted as representing a very low, low or high probability of PE with a concordant clinical likelihood of PE. Patients with a V/Q lung scan interpreted as representing an intermediate probability of PE or patients with discordant clinical likelihood of PE and lung scan interpretation will often require further investigations to diagnose or exclude acute venous thromboembolism. CONCLUSION: The results of the PIOPED study support the use of V/Q lung scanning in the diagnostic evaluation of patients with suspected PE. Amendments to the original PIOPED interpretation criteria should reinforce the role of V/Q lung scanning in patients with suspected PE.

Adult↗