Biomedical subjects
Publications and source records attributed to J Shah.
We present a 65 year old, relatively asymptomatic man, who was found to have an intrasacral meningocele with tethered cord syndrome on Magnetic Resonance Imaging (MRI). Incidental detection of this entity at such an old age is very unusual.
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Scrotal haematoma is an unusual complication following percutaneous transluminal angioplasty. It carries significant morbidity and causes extreme discomfort to the patient. We describe the case of a 75-year-old diabetic man who developed this complication. Recommendations are made for investigation and management of this problem, which is so infrequently encountered in clinical practice.
Symmetrical mediatinal lipomatosis is a rare benign condition characterized by deposition of a large amount of mature adipose tissue within the mediastinum. Usually secondary to exogenous obesity, administration of steroids and Cushing's disease, it is more common in middle-aged males and is associated with alcohol abuse. Various other associations have been reported. CT and MRI can decisively diagnose this benign condition, which also helps in deciding treatment options. We present a case of a young female with a bizarre appearance on chest radiographs. Isolated, bilaterally symmetrical mediastinal lipomatosis was diagnosed on CT and MRI. The patient was thin and did not consume alcohol or steroids. Cushing's disease and other known associations were excluded.
Resonance Rayleigh scattering by periodic semiconductor multiple quantum-well structures is studied experimentally and theoretically. Polaritonic effects are found to dominate disorder in the secondary emission dynamics. The coexistence of several radiant polaritonic modes with different radiative decay times leads to polarization beating between modes, strongly influences the rise times, and determines the fast decay times of the resonance Rayleigh scattered signals.
OBJECTIVE: To analyze the clinical utility of [11C]flumazenil (FMZ) PET to detect perilesional and remote cortical areas of abnormal benzodiazepine receptor binding in relation to MRI, 2-deoxy-2-[18F]fluoro-d-glucose (FDG) PET, and electrocorticographic (ECoG) findings as well as clinical characteristics of the epilepsy in epileptic patients with brain lesion. BACKGROUND: The success of resective surgery in patients with medically intractable epilepsy and brain lesion depends not only on removal of the lesion itself but also on the reliable presurgical delineation of the epileptic cortex that commonly extends beyond it. PET could provide a noninvasive identification of such epileptogenic areas. METHODS: Seventeen patients underwent high resolution MRI, FDG and FMZ PET, and presurgical EEG evaluation, including chronic intracranial ECoG monitoring or intraoperative ECoG. Regional cortical FDG/FMZ PET abnormalities were defined on partial volume-corrected PET images using an objective method based on a semiautomated definition of areas with abnormal asymmetry. Structural lesions were defined on coregistered MRI. The marked PET abnormalities visualized on three-dimensional cortical surface were compared with each other, to the extent of MRI-defined lesion, as well as to ECoG findings. RESULTS: The mean surface extent of FMZ PET abnormalities was significantly larger than the corresponding structural lesions, but it was significantly smaller than areas of glucose hypometabolism. The size of perilesional FDG PET abnormalities showed a correlation with the lifetime number of seizures (r = 0.93, p = 0.001). The extent of perilesional FMZ PET abnormalities was independent of the seizure number and showed an excellent correspondence with spiking cortex, the resection of which resulted in seizure-free outcome in all but one operated patient. Remote FMZ PET abnormalities (n = 6) were associated with early age at seizure onset (p = 0.048) and appeared in ipsilateral synaptically connected regions from the lesion area. CONCLUSIONS: Three-dimensional surface-rendered FMZ PET is able to delineate perilesional epileptic cortex, and it may be especially useful to localize such areas in patients with extensive perilesional glucose hypometabolism associated with a large number of seizures. Remote FMZ PET abnormalities in patients with early onset and long duration of epilepsy might represent secondary epileptogenesis, but this requires further study.
Among 1,211 patients hospitalized with documented CAD at either a university hospital or a large suburban community hospital, 36% failed to receive appropriate evaluation and treatment for dyslipidemia. Younger patients, those admitted to a university hospital, and those undergoing percutaneous coronary intervention were substantially more likely to receive appropriate lipid management than other subgroups.
Salicylic acid (SA) plays a critical signaling role in the activation of plant defense responses after pathogen attack. We have identified several potential components of the SA signaling pathway, including (i) the H(2)O(2)-scavenging enzymes catalase and ascorbate peroxidase, (ii) a high affinity SA-binding protein (SABP2), (iii) a SA-inducible protein kinase (SIPK), (iv) NPR1, an ankyrin repeat-containing protein that exhibits limited homology to IkappaBalpha and is required for SA signaling, and (v) members of the TGA/OBF family of bZIP transcription factors. These bZIP factors physically interact with NPR1 and bind the SA-responsive element in promoters of several defense genes, such as the pathogenesis-related 1 gene (PR-1). Recent studies have demonstrated that nitric oxide (NO) is another signal that activates defense responses after pathogen attack. NO has been shown to play a critical role in the activation of innate immune and inflammatory responses in animals. Increases in NO synthase (NOS)-like activity occurred in resistant but not susceptible tobacco after infection with tobacco mosaic virus. Here we demonstrate that this increase in activity participates in PR-1 gene induction. Two signaling molecules, cGMP and cyclic ADP ribose (cADPR), which function downstream of NO in animals, also appear to mediate plant defense gene activation (e.g., PR-1). Additionally, NO may activate PR-1 expression via an NO-dependent, cADPR-independent pathway. Several targets of NO in animals, including guanylate cyclase, aconitase, and mitogen-activated protein kinases (e.g., SIPK), are also modulated by NO in plants. Thus, at least portions of NO signaling pathways appear to be shared between plants and animals.
We develop a self-consistent, microscopic theory of coherent resonant secondary emission from semiconductor microcavities in the normal-mode-coupling regime. Our theory provides a quantitative description of the spectral, temporal, and angular properties of the disorder-induced emission component-resonant Rayleigh scattering-and offers an intuitive physical explanation of emission properties.
The large dielectric constant and small effective mass in a semiconductor allows a description of its electronic states in terms of envelope wavefunctions whose energy, time, and length scales are mesoscopic, i.e., halfway between those of atomic and those of condensed matter systems. This property makes it possible to demonstrate and investigate many quantum mechanical, many-body, and quantum kinetic phenomena with tabletop experiments that would be nearly impossible in other systems. This, along with the ability to custom-design semiconductor nanostructures, makes semiconductors an ideal laboratory for experimental investigations. We present an overview of some of the most exciting results obtained in semiconductors in recent years using the technique of ultrafast nonlinear optical spectrocopy. These results show that Coulomb correlation plays a major role in semiconductors and makes them behave more like a strongly interacting system than like an atomic system. The results provide insights into the physics of strongly interacting systems that are relevant to other condensed matter systems, but not easily accessible in other materials.
OBJECTIVE: To compare abnormalities determined in 2-deoxy-2-[18F]fluoro-D-glucose (FDG) and [11C]flumazenil (FMZ) PET images with intracranial EEG data in patients with extratemporal lobe epilepsy. BACKGROUND: Although PET studies with FDG and FMZ are being used clinically to localize epileptogenic regions in patients with refractory epilepsy, the electrophysiologic significance of the identified PET abnormalities remains poorly understood. METHODS: We studied 10 patients, mostly children (4 boys, 6 girls, aged 2 to 19 years; mean age, 11 years), who underwent FDG and FMZ PET scans, intracranial EEG monitoring, and cortical resection for intractable epilepsy. EEG electrode positions relative to the brain surface were determined from MRI image volumes. Cortical areas of abnormal glucose metabolism or FMZ binding were determined objectively based on asymmetry measures derived from homotopic cortical areas at three asymmetry thresholds. PET data were then coregistered with the MRI and overlaid on the MRI surface. A receiver operating characteristics (ROC) analysis was performed to determine the specificity and sensitivity of PET-defined abnormalities against the gold standard of intracranial EEG data. RESULTS: FMZ PET detected at least part of the seizure onset zone in all subjects, whereas FDG PET failed to detect the seizure onset region in two of 10 patients. The area under the ROC curves was higher for FMZ than FDG PET for both seizure onset (p = 0.01) and frequent interictal spiking (p = 0.04). Both FMZ and FDG PET showed poor performance for detection of rapid seizure spread (area under the ROC curve not significantly different from 0.5). CONCLUSIONS: [11C]flumazenil (FMZ) PET is significantly more sensitive than 2-deoxy-2-[18F]fluoro-D-glucose (FDG) PET for the detection of cortical regions of seizure onset and frequent spiking in patients with extratemporal lobe epilepsy, whereas both FDG and FMZ PET show low sensitivity in the detection of cortical areas of rapid seizure spread. The application of PET, in particular FMZ PET, in guiding subdural electrode placement in refractory extratemporal lobe epilepsy will enhance coverage of the epileptogenic zone.
We describe the MRI findings in two patients with giant hypothalamic hamartomas with cystic areas. Cystic change within hypothalamic hamartomas is rarely reported in the literature.
OBJECTIVE: To describe the imaging findings in sterno-clavicular tubercular involvement. DESIGN AND PATIENTS: Fifteen patients with pathologically proven tuberculosis of the sternum and clavicle were retrospectively evaluated. Routine radiography, computed tomography (CT) and magnetic resonance imaging (MRI) were used in some or all of the patients. Clinical information and imaging features were evaluated in each case. RESULTS: Eight patients had sternoclavicular joint (SCJ) involvement, five had isolated sternal involvement and two had isolated clavicular involvement. Seven patients were evaluated with only CT, six with only MRI and two with both. There were eight male and seven female patients, varying in age between 16 and 78 years. Fever, swelling and pain were common presenting symptoms. Two patients were HIV positive. Radiographs were positive in only eight patients. Destruction and signal intensity (SI) changes of the sternum and clavicle, destruction of the cartilage, soft tissue changes representing granulation tissue/abscess, displacement of the adjacent structures (vessels, trachea, etc.) and inflammatory changes in the adjacent structures in the form of cellulitis and myositis were common imaging features. CONCLUSIONS: All imaging methods can provide complementary information regarding sterno-clavicular tubercular involvement that is helpful for determination of the therapy. MRI is useful in determining the extent of the lesion, particularly marrow involvement and soft tissue extent.
OBJECTIVE: To review imaging studies of isolated involvement of the sacrum due to tuberculosis and determine the role of imaging in the diagnosis and management of these patients. DESIGN AND PATIENTS: A retrospective analysis of 15 cases of isolated sacral tuberculosis imaged with MR imaging was performed. The CT images were also reviewed where available, and the various lesion characteristics were identified. We also reviewed the medical records in an attempt to determine the impact of the imaging studies on the management of these patients. RESULTS: Fifteen patients (5 male, 10 female) presented with symptoms of 3-15 months' duration. Chronic localized backache with muscle spasm was the commonest presenting symptom; discharging sinuses with abscess formation was found in six patients, five of whom were children. MR imaging of the sacrum revealed a hypointense marrow signal on T1-weighted images and hyperintense signal on T2-weighted images in 14 of 15 patients, the S2 vertebra being always involved. CT revealed osteolytic changes in the sacrum in all the five patients in whom CT was performed. All patients showed marked clinical improvement within 1 year of anti-tuberculous chemotherapy. CONCLUSION: Isolated tuberculosis of the sacrum is uncommon but should be suspected in patients presenting with chronic low backache or children with discharging sinuses/abscesses and showing sacral destruction on CT or MR imaging. MR imaging can identify cases and enables early institution of antituberculous chemotherapy.
Eleven right-handed subjects performed uni- and bimanual tapping tasks. Hemodynamic responses as measured with functional magnetic resonance imaging (fMRI) in the primary somato-motor cortex (SMC) showed that during bimanual activity the SMC contralateral to the hand taking the faster rate was more strongly activated than the SMC contralateral to hand taking the slower rate. There were no asymmetries, left SMC activation during the right fast/left slow tapping condition was comparable to the right SMC activation during the left fast/right slow condition. A given SMC showed similar activation levels for bimanual and unimanual activity (i.e. left SMC activation for right fast/left slow was similar to left SMC activation for the right fast unimanual condition). In contrast, a given supplementary motor area (SMA) showed significantly more activation for the bimanual than for the unimanual activity. In addition, an asymmetry was observed during bimanual activities: during the right fast/left slow activity, the left SMA showed more activation than the right SMA, but during the left fast/right slow activity, the right SMA was not significantly more activated than the left SMA. For unimanual activities, a clear rate effect (greater activation for faster rate) was seen in the SMC but not in the SMA.
OBJECTIVE: To determine whether diagnostic amniocentesis should be part of evaluations of women under consideration for rescue cerclage. METHODS: We reviewed the obstetric records of 25 candidates for rescue cerclage seen between June 30, 1995, and July 1, 1997. Rescue cerclage was defined as a procedure on a cervix with an internal os dilated at least 2 cm and 50% effaced, with membranes visible at the external os. Transabdominal amniocentesis was offered as part of the preoperative evaluation, and amniotic fluid (AF) was sent for glucose and lactate dehydrogenase level determinations, Gram staining, and culture for aerobic and anaerobic bacteria. Placentas were examined for histopathologic evidence of inflammation. The women were divided into three groups. Eleven women had rescue cerclage after amniocentesis, seven had rescue cerclage after declining amniocentesis, and seven had amniocentesis but were treated conservatively because of AF markers of infection. Analysis of variance and chi(2) statistics were used. RESULTS: The group that had rescue cerclage after amniocentesis had a significantly longer mean admission-to-delivery interval, higher mean gestational age at delivery, higher mean birth weight, and higher neonatal survival rate than did the group that had rescue cerclage without amniocentesis and the group that had no cerclage after amniocentesis (P <.001). CONCLUSION: Amniocentesis before rescue cerclage placement identified women with subclinical chorioamnionitis who would not benefit from cerclage.
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Pigmented villonodular synovitis (PVNS) is usually a mono-articular disorder. Bilateral symmetrical affection of this disease process is exceptional. A case is reported of a patient with PVNS with bilateral, symmetrical hip joint involvement.