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Biomedical subjects

A J Kumar

Publications and source records attributed to A J Kumar.

At least 19 recordsLinked to original sources
PubMed2006

Vector control in leishmaniasis.

Indoor residual spraying is a simple and cost effective method of controlling endophilic vectors and DDT remains the insecticide of choice for the control of leishmaniasis. However resistance to insecticide is likely to become more widespread in the population especially in those areas in which insecticide has been used for years. In this context use of slow release emulsified suspension (SRES) may be the best substitute. In this review spraying frequencies of DDT and new schedule of spray have been discussed. Role of biological control and environment management in the control of leishmaniasis has been emphasized. Allethrin (coil) 0.1 and 1.6 per cent prallethrin (liquid) have been found to be effective repellents against Phlebotomus argentipes, the vector of Indian kalaazar. Insecticide impregnated bednets is another area which requires further research on priority basis for the control of leishmaniasis. Role of satellite remote sensing for early prediction of disease by identifying the sandflygenic conditions cannot be undermined. In future synthetic pheromons can be exploited in the control of leishmaniasis.

Allethrins↗
PubMed2005

Evaluation of a dot-immunoblot assay for detecting leishmanial antigen in naturally infected Phlebotomus argentipes (Diptera: Psychodidae).

A simple and highly reproducible dot-immunoblot assay was developed to detect leishmanial antigen in Phlebotomus argentipes that were naturally infected with Leishmania donovani. The test was sensitive to as little as 10 ng of antigenic protein (equivalent to the gut content of one laboratory-infected sandfly) and also appeared to be specific, in that it gave a positive result with some P. argentipes (the primary vector of L. donovani in India) and L. donovani but not with P. papatasi or other pathogens. When used to investigate a large number of sandflies collected from two areas of the Indian state of Bihar where visceral leishmaniasis is endemic, the assay appeared sufficiently sensitive and specific to detect the naturally infected insects. The simplicity, reproducibility, high sensitivity and high specificity of the assay should make it useful for field studies, particularly in determining the prevalence of sandfly infection, the local level of transmission, and the impact of vector-control programmes.

Animals↗
PubMed2004

Textiloma (gossypiboma) mimicking recurrent intracranial tumor.

CONTEXT: Resorbable substances used to achieve hemostasis during neurosurgical procedures comprise 3 principal classes based on chemical composition: (1) gelatin sponge, (2) oxidized cellulose, and (3) microfibrillar collagen. Nonresorbable hemostatic aides include various forms of cotton and rayon-based hemostats (cottonoids and kites). Resorbable and nonresorbable hemostatic agents have been reported to cause symptomatic mass lesions, most commonly following intra-abdominal surgery. Histologic examination typically shows a core of degenerating hemostatic agent surrounded by an inflammatory reaction. Each agent exhibits distinctive morphologic features that often permit specific identification. Hemostat-associated mass lesions have been variously referred to as textilomas, gossypibomas, gauzomas, or muslinomas. OBJECTIVES: The aims of this study were to (1) identify cases of histologically proven cases of textiloma in neurosurgical operations, (2) characterize the specific hemostatic agent associated with textiloma formation, and (3) characterize the preoperative magnetic resonance imaging appearance of textiloma. DESIGN: Cases in which a textiloma constituted the sole finding on repeat surgery for recurrent brain tumor, or was a clinically significant component of a radiologically identified mass lesion together with residual tumor, constituted the study set. RESULTS: Five textilomas were identified and evaluated. The primary neoplasm was different in each case and included pituitary adenoma, tanycytic ependymoma, anaplastic astrocytoma, gliosarcoma, and oligodendroglioma. In all cases, preoperative magnetic resonance imaging suggested recurrent tumor. Textilomas included all categories of resorbable hemostatic agent. Other foreign bodies were present in some cases; the origin of these foreign bodies was traced to fibers shed from nonresorbable hemostatic material placed temporarily during surgery and removed before closure (cottonoids and kites). Inflammatory reactions included giant cells, granulomas, and fibroblastic proliferation. Microfibrillar collagen (Avitene) textilomas were associated with a striking eosinophil infiltration that was not seen with any other hemostatic agent. CONCLUSIONS: Hemostatic agents may produce clinically symptomatic, radiologically apparent mass lesions. When considering a mass lesion arising after intracranial surgery, the differential diagnosis should include textiloma along with recurrent tumor and radiation necrosis.

Adolescent↗
PubMed2002

Post-epidural analgesia spinal cord infarction: MRI correlation.

Permanent neurological deficits after epidural analgesia are rare, but have long been believed to be caused by cord ischaemia when no obvious cause is demonstrable. The mechanisms of this injury are uncertain, but a literature review suggests important risk factors. We report a first case of extensive spinal cord infarction confirmed by magnetic resonance imaging (MRI) following post-thoracotomy epidural analgesia and review the literature to explain the mechanism underlying this devastating complication.

Analgesia, Epidural↗
PubMed2001

Testing the validity of a critical sulfur and nitrogen load model in southern Ontario, Canada, using soil chemistry data from MARYP.

The validity of a steady-state mass balance model (Arp et al., 1996; referred to as ARP) was tested using physicochemical soil data from the Monitoring Acid Rain Youth Program (MARYP). Four ARP sites were matched with ten MARYP sites according to proximity, bedrock type and subsoil pH to test the validity of the ARP model for critical load exceedances. Soil solution pH, base concentration and A1 concentration from MARYP sites, which were well matched to ARP sites, validated the modelled critical load exceedances. Higher exceedance areas were associated with more acidic pH and lower base and higher A1 concentrations from matched MARYP sites and vice versa. One ARP site was inappropriately matched with MARYP sites and could not be validated using base and A1 concentrations. This study also confirmed the southern limit of the zero critical load exceedance isopleth from the model. However, variability of the other exceedance isopleths was noted due to the limited number of sites used in the model. The validation of these sites in the ARP model and the zero critical load exceedance isopleth nonetheless allows greater confidence in using this model as a management tool for acidic deposition.

Aluminum↗
PubMed2000

Magnetic resonance imaging of benign spinal lesions simulating metastasis: role of diffusion-weighted imaging.

In an attempt to avoid unnecessary therapy, this article demonstrates benign vertebral body lesions that mimic metastatic disease in cancer patients with back pain. The magnetic resonance imaging features that aid in differential diagnosis are demonstrated. In addition, the value of diffusion-weighted spinal imaging to further aid in distinguishing benign from malignant disease is described.

Diagnosis, Differential↗
PubMed2000

Malignant gliomas: MR imaging spectrum of radiation therapy- and chemotherapy-induced necrosis of the brain after treatment.

PURPOSE: To describe both the common and less frequently encountered magnetic resonance (MR) imaging features of radiation therapy- and chemotherapy-induced brain injury, with particular emphasis on radiation necrosis. MATERIALS AND METHODS: A cohort of 148 adult patients underwent surgical resection of malignant brain (glial) tumors and were subsequently entered into a research protocol that consisted of accelerated radiation therapy with carboplatin followed by chemotherapy with procarbazine, lomustine, and vincristine. Patients typically underwent sequential MR imaging at 6-8-week intervals during the 1st year and at 3-6-month intervals during subsequent years. In all patients, histopathologic confirmation of lesion composition was performed by board-certified neuropathologists. RESULTS: The patients exhibited different types of MR imaging-detected abnormalities of the brain: pure radiation necrosis in 20 patients, a mixture of predominantly radiation necrosis with limited recurrent and/or residual tumor (less than 20% of resected tissue) in 16 patients, radiation necrosis of the cranial nerves and/or their pathways in two patients, radiation-induced enhancement of the white matter in 52 patients, and radiation-induced enhancement of the cortex in nine patients. CONCLUSION: The frequent diagnostic dilemma of recurrent neoplasm versus radiation necrosis is addressed in this study through a description of the varying spatial and temporal patterns of radiation necrosis at MR imaging.

Adolescent↗
PubMed1997

Successful treatment of progressive multifocal leukoencephalopathy with low-dose interleukin-2.

A patient with low-grade lymphoma presented 8 months after autologous marrow transplantation with dizziness, aphasia and hemiparesis. Magnetic resonance imaging (MRI) showed an abnormal T2 signal in the frontoparietal region unilaterally. Biopsy of the area demonstrated progressive multifocal leukoencephalopathy positive for JC virus and p53. Treatment with interleukin-2 at 0.5 MU/m2/day i.v. continuous infusion resulted in near complete resolution of symptoms and MRI abnormalities. The absolute number of CD3+CD4+ and CD3-CD56+ cells in the peripheral blood also increased, and the CD4/CD8 ratio normalized. She remains free of evidence of progressive multifocal leukoencephalopathy 1 year off therapy.

Blood Cell Count↗
PubMed1995

Intracranial metastatic melanoma: correlation between MR imaging characteristics and melanin content.

OBJECTIVE: Preliminary reports based on limited numbers of cases have proposed that specific MR imaging patterns may permit a distinction between melanotic and amelanotic brain metastases in melanoma patients. The purpose of this study was to test this hypothesis by categorizing MR images obtained from a large series of patients and correlating the results with the percentage of melanin-containing cells in surgically resected metastases. SUBJECTS AND METHODS: The MR images of 30 patients with histologically proven intracerebral melanoma were reviewed retrospectively. Precontrast MR images were obtained with T1-weighted spin-echo sequences in axial and sagittal sections and with proton density-weighted and T2-weighted sequences in axial sections. After IV injection of gadopentetate dimeglumine (0.1 mmol/kg of body weight), T1-weighted images were obtained in axial and coronal sections. All patients had undergone gross total resection of the evaluated lesions. MR images of the metastases were reviewed and sorted into four groups on the basis of putative patterns: (1) melanotic pattern--hyperintense in relation to cortex on T1-weighted images, hypointense in relation to cortex on T2-weighted images, and isointense or hyperintense in relation to cortex on proton density-weighted images; (2) amelanotic pattern--hypointense or isointense in relation to cortex on T1-weighted images and hyperintense or isointense in relation to cortex on T2-weighted and proton density-weighted images; (3) indeterminate, or mixed, pattern--MR imaging characteristics that did not conform to those of one of the first two categories; and (4) hematoma pattern--MR imaging features that exhibited only hematoma characteristics. Tissue sections from all evaluated lesions were independently reviewed by a neuropathologist (G.N.F.), and the percentage of melanin-containing tumor cells in each resected metastatic lesion was estimated. The MR imaging data and histologic data were then compared to assess the predictive value of the MR imaging patterns. RESULTS: Forty-two metastatic lesions were identified and categorized by MR imaging pattern as follows: 10 melanotic, 11 indeterminate (mixed), 16 amelanotic, and five hematoma. Correlation with histologic findings revealed that a majority (7/10) of lesions that exhibited a melanotic MR imaging pattern had more than 10% melanin-containing cells, over half (9/16) of lesions that exhibited an amelanotic MR imaging pattern contained histologically identifiable melanin (but always in less than 10% of cells), and lesions that exhibited a mixed MR imaging pattern were either amelanotic or contained less than 10% melanotic cells. Conversely, a majority of lesions containing more than 10% melanotic cells (7/8) demonstrated the typical melanotic MR imaging pattern, lesions with less than 10% melanin-containing cells exhibited a variety of MR imaging patterns, and only about half of patients with amelanotic lesions (6/13) showed the characteristic amelanotic MR imaging pattern. For five lesions, potentially informative imaging data on melanin content was obscured by histologically documented hematoma formation. CONCLUSION: Only a minority of melanoma metastases have the anticipated MR imaging findings of melanotic melanoma, which consist of high signal intensity relative to that of cortex on T1-weighted images and low signal intensity relative to that of cortex on T2-weighted images. Of tumors that do exhibit this melanotic pattern, the majority have more than 10% melanin-containing cells. The putative MR imaging pattern for amelanotic melanoma is nonspecific, as over half of tumors with this pattern contain melanin.

Adult↗
PubMed1994

Basal ganglia volumes and white matter hyperintensities in patients with bipolar disorder.

OBJECTIVE: Accumulating evidence suggests an association between abnormalities of the basal ganglia and affective disorders. The authors hypothesized that patients with bipolar disorder would demonstrate smaller basal ganglia volumes and a greater number of hyperintensities on magnetic resonance imaging than comparison subjects who were matched on age, race, sex, and education. METHOD: Volumes of the caudate, putamen, and globus pallidus were measured in 30 patients with bipolar disorder and 30 matched normal comparison subjects. The presence, number, and location of hyperintensities were also assessed. RESULTS: Male patients with bipolar disorder demonstrated larger caudate volumes than male comparison subjects. Older, but not younger, patients with bipolar disorder demonstrated more hyperintensities than comparison subjects, primarily in frontal lobe white matter. CONCLUSIONS: These results are not consistent with those of previous studies showing reduced basal ganglia volume in subjects with affective disorders, but they are consistent with previous findings of increased white matter hyperintensities, especially in older patients with bipolar disorder. Considered together with results from other studies, the findings suggest that the nature of basal ganglia/subcortical white matter involvement may differ according to the type of depression (unipolar versus bipolar) and the age and sex of the patient.

Adult↗
PubMed1994

Anti-Ro(SS-A) autoantibodies in central nervous system disease associated with Sjögren's syndrome (CNS-SS): clinical, neuroimaging, and angiographic correlates.

OBJECTIVE: To examine in Sjögren's syndrome (SS) the interrelationship between the presence of the anti-Ro(SS-A) antibody response and (1) concomitant presence and type (ie, focal or nonfocal) of CNS disease (CNS-SS), (2) cross-sectional brain MRI or CT, and (3) abnormal cerebral angiography. METHODS: Neurologic, neuroimaging, and angiographic features of CNS-SS patients were correlated with the presence of precipitating anti-Ro(SS-A) autoantibodies detected by gel double-immunodiffusion or quantitative ELISA, which detects antibodies directed against the 60-kd peptide. Statistical analyses were performed using Fisher's exact test (two-tailed) with Haldane's adjustment and odds ratio with Cornfield 95% confidence intervals. RESULTS: Precipitating antibodies against the Ro(SS-A) antigen, determined by gel double-immunodiffusion, were present in an increased frequency in CNS-SS patients with (1) documented clinical CNS disease, (2) focal clinical CNS manifestations and serious complications, (3) large regions of increased signal intensity, consistent with ischemia/infarcts on brain MRI scans or regions of decreased attenuation consistent with infarcts on CT, and (4) abnormal cerebral angiograms consistent with small-vessel angiitis. Finally, the anti-Ro(SS-A) antibody response in CNS was directed against the 60-kd peptide specificity, determined by ELISA. CONCLUSIONS: Clinical, neuroimaging (cerebral CT), and angiographic observation suggest that a subset of anti-Ro(SS-A) antibody-positive, in contrast with -negative, CNS-SS patients have more serious and extensive CNS disease, some with frank cerebral angiopathy. Anti-Ro(SS-A) antibodies are postulated to play a role in mediating or potentiating vascular injury in CNS-SS.

Autoantibodies↗
PubMed1993

Use of the magnetic resonance contrast agent gadodiamide in the central nervous system. Results of a multicenter trial.

To investigate the safety and efficacy of the low-osmolar, nonionic contrast agent, gadodiamide injection (Omniscan, Sanofi Winthrop Pharmaceuticals, New York, NY), for magnetic resonance imaging (MRI) of the head and spine, a multicenter study involving 439 patients was done at 15 centers as part of a Phase II/III clinical trial. Unenhanced MRI scans were obtained after which the patients were injected with 0.1 mmol/kg gadodiamide, and the MRI was repeated. The patients' vital signs were monitored, and laboratory studies were conducted. Neurologic status was examined before and after the study. The images were evaluated for contrast enhancement. No patient had any significant adverse event or serious change in clinical status. Abnormalities were found in 80% (351) of all patients studied, and it was found that, in 75% (266) of these, the postgadodiamide injection images were improved or facilitated visualization of lesions compared with preinjection images. The investigators believe that, based on the results of this study, gadodiamide injection is safe and effective for imaging the head and spine. They suggest that future studies further assess and compare the safety parameters of gadodiamide injection with those of other nonionic and ionic gadolinium ligands.

Central Nervous System Diseases↗
PubMed1992

Proton NMR spectroscopy of Canavan's disease.

Proton Nuclear Magnetic Resonance (NMR) spectroscopy was used to quantitatively determine cerebral N-Acetyl Aspartate (NAA) concentrations in four patients with Canavan's disease and in four age-matched control subjects. Macroscopic NAA concentrations (mumol/gm wet weight) were not found to be significantly different from controls. Reduced levels of choline and creatine were observed in all patients, and increased levels of lactate and inositol in the eldest three patients.

Adolescent↗
PubMed1992

Patterns of cerebral atrophy in HIV-1-infected individuals: results of a quantitative MRI analysis.

Cerebral atrophy is a common radiologic manifestation of HIV dementia. To evaluate the relationship between cognitive impairment and cerebral atrophy, adjusting for age and immune status, we used standardized planimetry to measure the ventricle-brain ratio (VBR) and the bifrontal (BFR) and bicaudate (BCR) ratios, three measures of cerebral atrophy. We analyzed cranial MRIs of 23 HIV-1-seronegative controls (SN) and 116 HIV-1-infected individuals. Of the HIV-1-seropositive individuals, 37 had HIV dementia (DM group), 40 had neurologic or neuropsychological abnormalities insufficient for HIV dementia (NP+ group), and 39 were neurologically normal (NML group). We performed comparisons using analysis of covariance with correction for multiple comparisons. Both the VBR, a general measure of overall cerebral atrophy, and the BCR, a measure of atrophy in the region of the caudate nucleus, are significantly associated with dementia. The association is stronger for BCR enlargement than for VBR enlargement, suggesting that selective caudate region atrophy is associated with HIV dementia. These results indicate that overall cerebral atrophy and prominent caudate region atrophy are important radiographic features of HIV dementia.

AIDS Dementia Complex↗
PubMed1992

The Consortium to Establish a Registry for Alzheimer's Disease (CERAD). Part III. Reliability of a standardized MRI evaluation of Alzheimer's disease.

The Consortium to Establish a Registry for Alzheimer's Disease (CERAD) has developed procedures for standardized imaging and reporting of magnetic resonance (MR) findings in Alzheimer's disease (AD) for use by neuroradiologists in multiple medical centers using a variety of MR equipment and field strengths. After initial pretesting, we revised the protocol, expanded the summary rating scale to seven points, and added more illustrations. Fourteen participating neuroradiologists evaluated 28 MR scans of elderly patients, giving us the basis for judging interrater agreement. We obtained acceptable intraclass correlations (greater than 0.79) for rating the size of the lateral and third ventricles and the temporal horn. Less satisfactory intraclass correlations occurred when rating other areas, including (1) global atrophy of the brain (0.70); (2) dilatation of the sulci of the temporal lobe (0.66); (3) frequency, location, and severity of white matter lesions (0.77); (4) sylvian fissure enlargement (0.70); and (5) cerebral sulcal dilatation (0.64). We also saw considerable variation in the reporting of cortical and lacunar infarcts. Despite careful design of the rating methodology and readings by experienced neuroradiologists, we did not find satisfactory interrater agreement for interpreting MR findings in elderly subjects. These findings may explain the difficulties encountered in applying similar subjective rating techniques that meet with success at one institution to multicenter studies. More objective and reproducible procedures are needed for interpretation of neuroimaging findings of AD in multicenter studies.

Alzheimer Disease↗
PubMed1991

Cisplatin, ara-C and etoposide (PAE) in the treatment of recurrent childhood brain tumors.

Sixteen patients with recurrent childhood brain tumors were treated with intravenous cisplatin, cytosine arabinoside and etoposide (PAE), daily for three days every three to four weeks. Objective responses were observed in 6 of 15 evaluable patients and an additional six patients had stable disease for greater than 6 months. The tumor-specific response rate for astrocytoma/glioma was 3 of 7 and for medulloblastoma was 2 of 4. The mean progression-free interval was 11.0 months and the hazard rate for progression was 0.085 per patient-month of observation. The most common toxicities were neutropenia and thrombocytopenia. Clinically significant ototoxicity was identified in 7 patients. The activity of PAE chemotherapy for recurrent childhood brain tumors warrants further investigation.

Adolescent↗
PubMed1991

Iohexol cervical myelography in adult outpatients.

The incidence of adverse reactions following standard film or screen cervical myelography with iohexol in 32 adult outpatients was reported. Iohexol at a dose of 1,080-3,000 mg of iodine was administered via a lateral C1-C2 approach in 26 patients and via a lumbar route in 6 patients. All 32 patients underwent postmyelographic cervical spine computed tomography and were discharged after the procedure was completed. No adverse reactions occurred in 53.1% of patients. The most common adverse reaction was headache (31.3%); other minor adverse reactions included exacerbation of pre-existing pain (12.5%), neck stiffness (9.4%), and vomiting (6.3%). Good to excellent technical quality was seen on all myelograms and computed tomographic scans. Outpatient cervical myelography with iohexol appears to be a safe and cost-effective alternative to inpatient examination.

Ambulatory Care↗