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Biomedical subjects

B A Mehta

Publications and source records attributed to B A Mehta.

At least 19 recordsLinked to original sources
PubMed2000

The persistent stapedial artery.

The persistent stapedial artery is a rare congenital vascular anomaly that may present as a pulsatile middle ear mass or that may appear as an incidental finding. Five cases of persistent stapedial artery are presented. The CT findings include the absence of the ipsilateral foramen spinosum and a soft-tissue prominence in the region of the tympanic segment of the facial nerve. Three cases were associated with an aberrant internal carotid artery. Imaging identification of this variant may obviate unnecessary surgery and may help in planning surgical or endovascular interventions.

Adolescent↗
PubMed1998

Spontaneous intracranial hypotension: report of four cases and review of the literature.

Spontaneous intracranial hypotension is an unusual syndrome of postural headache and low cerebrospinal fluid pressure without an established cause. We present four cases, analyze those previously reported in the literature, examine the MRI, CT, angiographic and cisternographic finding and discuss the clinical picture, proposed pathophysiologic mechanisms and potential treatment.

Adult↗
PubMed1998

Imaging of spinal intradural arachnoid cysts: MRI, myelography and CT.

Imaging studies in eight patients with surgically-confirmed spinal arachnoid cysts were analyzed retrospectively. All patients had preoperative MRI of the spine and seven preoperative myelography with postmyelographic CT. In all cases the correct diagnosis could be made preoperatively on the basis solely of MRI. The diagnosis could also be established from myelography and postmyelographic CT in six of the seven cases. In one case myelography and CT simply demonstrated an intradural extramedullary mass.

Adult↗
PubMed1998

Embolization of intracranial aneurysms with Guglielmi detachable coils augmented by microballoons.

We describe two cases in which balloons were used to aid in the occlusion of intracranial aneurysms with Guglielmi detachable coils. In both patients, initial attempts to place coils within the aneurysmal sac failed, as the loops of the coil repeatedly protruded through a wide aneurysmal neck into the parent vessel. Temporary balloons placed across the neck of these small, wide-necked aneurysms, the bridging balloon technique, effectively narrowed the necks, providing support for the formation of a proper coil basket, which was not possible without the balloon. Follow-up studies at 1 year showed good results in both patients.

Adult↗
PubMed1997

Simultaneous detection of DNA synthesis and cytokine production in staphylococcal enterotoxin B activated CD4+ T lymphocytes by flow cytometry.

Assessment of T cell activation has traditionally been performed by measuring proliferation as a function of 3[H]-thymidine incorporation, or secretion of cytokines from activated peripheral blood mononuclear cells (PBMC) in culture. An alternative method for detection of proliferation at the single cell level utilizes incorporation of bromodeoxyuridine (BrdU), an analog of thymidine, into cellular DNA. After appropriate fixation and permeabilization of the cells, a monoclonal antibody (mAb) against BrdU conjugated with a fluorescent dye is employed to measure by flow cytometry the incorporated BrdU. Here, we report a flow cytometric procedure which can be used for the simultaneous detection of BrdU incorporation, activation markers such as CD69 and CD25, and intracellular cytokines in T cell subsets from activated PBMC. Our observations are consistent with the proposal that cytokine synthesis and cell proliferation occur sequentially in CD4+ T cells stimulated with the superantigen staphylococcal enterotoxin B (SEB). The majority of cells expressing the cytokines IFN-gamma and IL-2 at 48 h appear to have undergone DNA synthesis, however all proliferating cells do not express IFN-gamma or IL-2. The methods presented in this report offer a unique approach for studying simultaneous expression of key cellular activation events in phenotypically resolved lymphocyte populations.

Antigens, CD↗
PubMed1996

Sensitivity of multidrug-resistant tumor cell lines to immunologic effector cells.

The ability of malignant cells to survive exposure to cytotoxic agents is a major obstacle to cure in patients with cancer. Multidrug resistance and the expression of P-glycoprotein are emerging as a cause of chemotherapy failure. Immunologic effector cells such as lymphokine-activated killer (LAK) cells or cytokine-induced killer (CIK) cells are capable of killing a broad range of tumor cell lines or freshly isolated tumor cells. As demonstrated here, LAK, and CIK cells possess a high level of cytotoxic activity against tumor cell lines both resistant and sensitive to chemotherapeutic agents such as doxorubicin or vinblastine. CIK cells possessed a higher level of cytotoxic activity than LAK cells as determined by 51Cr release and a tumor colony assay. Monoclonal antibodies against P-glycoprotein did not block the lysis of tumor cells resistant to chemotherapy by CIK cells. In contrast, antibodies to LFA-1 and ICAM-1 blocked CIK cell-mediated tumor cell lysis. These data demonstrate that immunological approaches to cancer therapy may be useful in overcoming disease caused by drug resistance.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1995

Two pathways of exocytosis of cytoplasmic granule contents and target cell killing by cytokine-induced CD3+ CD56+ killer cells.

Cytokine-induced killer (CIK) cells are non-major histocompatibility complex-restricted cytotoxic cells generated by incubation of peripheral blood lymphocytes with anti-CD3 monoclonal antibody (MoAb), interleukin-2 (IL-2), IL-1, and interferon-gamma. Cells with the greatest effector function in CIK cultures coexpress CD3 and CD56 surface molecules. CIK cell cytotoxicity can be blocked by MoAbs directed against the cell surface protein leukocyte function associated antigen-1 but not by anti-CD3 MoAbs. CIK cells undergo release of cytoplasmic cytotoxic granule contents to the extracellular space upon stimulation with anti-CD3 MoAbs or susceptible target cells. Maximal granule release was observed from the CD3+ CD56+ subset of effector cells. The cytoplasmic granule contents are lytic to target cells. Treatment of the effector cells with a cell-permeable analog of cyclic adenosine monophosphate (cAMP) inhibited anti-CD3 MoAb and target cell-induced degranulation and cytotoxicity of CIK cells. The immunosuppressive drugs cyclosporin (CsA) and FK506 inhibited anti-CD3-mediated degranulation, but did not affect cytotoxicity of CIK cells against tumor target cells. In addition, degranulation induced by target cells was unaffected by CsA and FK506. Our results indicate that two mechanisms of cytoplasmic granule release are operative in the CD3+ CD56+ killer cells; however, cytotoxicity proceeds through a cAMP-sensitive, CsA- and FK506-insensitive pathway triggered by yet-to-be-identified target cell surface molecules.

Biomarkers↗
PubMed1995

Efficacy of gadolinium administration in magnetic resonance imaging screening of patients with complex partial seizures and results of a normal neurologic examination.

RATIONALE AND OBJECTIVES: Magnetic resonance imaging has become a standard screening tool in the evaluation of patients with complex partial seizures. This study prospectively addresses the efficacy, if any, of routinely adding gadolinium-enhanced images to routine T2-weighted images in patients with a normal neurologic examination. METHODS: One hundred consecutive patients with electroencephalogram and clinical evidence of complex partial seizures and no other neurologic abnormalities were examined prospectively with axial and coronal T2-weighted spin-echo images, followed by axial and coronal gadolinium-enhanced T1-weighted scans. RESULTS: The scans in 73 patients were interpreted as normal, 14 had nonspecific white matter lesions, 5 had asymmetry of the temporal horns, and 2 had asymmetric signal intensity in the temporal lobes, and the scans in 6 showed abnormal gadolinium enhancement. Of the lesions in the six patients whose scans showed abnormal enhancement, four were seen well on the T2-weighted images. Of the remaining two, one was a small cerebellar venous angioma, and the other, a probable tiny convexity meningioma. One temporal lobe glioma seen on the T2 scans did not enhance with gadolinium. CONCLUSIONS: Routine administration of gadolinium does not appear to be of benefit in imaging patients with complex partial seizures who are otherwise neurologically normal.

Adult↗
PubMed1994

The role of N-linked carbohydrate residues in lymphokine-activated killer cell-mediated cytolysis.

We evaluated LAK cell cytotoxicity toward a sensitive B cell lymphoma and several resistant EBV-transformed cell lines in order to explore the mechanism by which some cells are preferentially recognized as targets. Cytolysis of the sensitive cells was inhibited by monoclonal antibodies against the surface proteins LFA-1 and ICAM-1; however, surface expression of ICAM-1 was similar on the resistant and sensitive cell lines. Prevention of post-translational addition of N-linked oligosaccharides by treatment of the resistant cells with tunicamycin resulted in a dramatic enhancement in LAK cell cytotoxicity which was partially inhibited by antibodies against LFA-1 and ICAM-1. Treatment of the resistant cells with the endoglycosidase N-glycanase also increased LAK cell sensitivity. Tunicamycin treatment caused a decrease in the molecular weight of ICAM-1 from approximately 95,000 to 50,000 Da. Conjugate formation between the LAK cells and the sensitive and resistant target cells was similar before and after deglycosylation. We conclude that carbohydrate modification of ICAM-1 or an alternative glycoprotein confers resistance to LAK cell cytotoxicity in some cell lines.

Antibodies, Monoclonal↗
PubMed1994

Dural arteriovenous malformation of the skull base with intraosseous vascular nidus. Report of two cases.

Intracranial arteriovenous malformations (AVM's) have been classified as pure pial, pure dural, and mixed pial and dural. Dural AVM's are relatively uncommon, with 377 cases documented up to 1990. These lesions were believed to be situated within the walls of the sinuses, but during the last decade researchers discovered a small subgroup of dural AVM's in extrasinusal locations such as the skull base and tentorium. Two of the 17 patients who were studied between 1976 and 1993 had dural AVM's that were entirely intraosseous except for their venous drainage, which was via the dural venous sinuses. Although such intraosseous dural AVM's have not been previously described, the authors elected to group these malformations with dural AVM's because their venous drainage was intracranial and angiograms revealed identical features.

Cerebral Angiography↗
PubMed1993

Phenotypic characterization and identification of effector cells involved in tumor cell recognition of cytokine-induced killer cells.

Cytokine-induced killer (CIK) cells are highly efficient cytotoxic effector cells capable of lysing tumor cell targets. Cultures of human CIK cells have been shown to have enhanced cytotoxicity and to proliferate more rapidly than lymphokine activated killer (LAK) cells by both in vitro and in vivo studies. In this report, we have further characterized the phenotype of CIK cells and explored the molecular structures involved in CIK-mediated cell lysis of tumor target cells. The dominant cell phenotype in CIK cell cultures expresses the alpha, beta T cell receptor (TCR-alpha/beta). In addition, CD56 is expressed on the main effector cell on a per-cell basis. Interestingly, the total number of CD56+ cells increases more than 1000-fold during the generation of CIK cells, mainly due to expansion of CD56+ cells coexpressing CD3. The higher lytic activity of CIK cells as compared to LAK cells is mainly due to the higher proliferation of CD3+CD56+ cells and to the cytotoxic activity of TCR-alpha/beta+ cells in CIK cell cultures. CIK-mediated cellular lysis is non-major histocompatibility antigen (MHC) restricted. The cytotoxic effect of CIK cells against tumor targets is blocked by antibodies directed against lymphocyte function-associated antigen (LFA-1) and its counter receptor, intercellular adhesion molecule-1 (ICAM-1).

Animals↗
PubMed1989

In vitro modulation of natural killer cell activity in non-Hodgkin's lymphoma patients after therapy.

The depressed natural killer (NK) activity, anti-body-dependent cellular cytotoxicity (ADCC) and NK cytotoxic factor cytotoxicity in untreated non-Hodgkin's lymphoma patients were found to be elevated after chemotherapy. In vitro treatment of the effector NK cells with interferon alpha could augment the NK activity in normal subjects and treated patients to a comparable degree. Chemotherapy mainly affected the post-binding events in the NK cytotoxic process by causing an increase in the active killing potential of the NK cells. This study provides a better understanding of changes in the NK cytotoxic mechanism in non-Hodgkin's lymphoma patients and the role of interferon in this process.

Adjuvants, Immunologic↗
PubMed1989

Natural killer activity and NK cytotoxic factors in peripheral blood and lymph node cells from non-Hodgkin's lymphoma patients.

Natural killer (NK) activity and natural killer cytotoxic factors (NKCF) were found to be depressed in large granular lymphocytes (LGL) from the peripheral blood and lymph node lymphocytes (LNL) from untreated non-Hodgkin's lymphoma (NHL) patients. The LGL number was also reduced in NHL patients as compared to the normal subjects. The depression in all the activities mentioned above showed a correlation with the clinical status of the patients. Exogenous interferon-alpha (IFN-alpha) treatment of the effector cells could augment the NK activity to a comparable extent in normal as well as patient's LNL. The results indicate that the production of interferon may be affected in cases of NHL and therefore it would be worthwhile to test the tolerance and efficacy of IFN-alpha in these patients.

Adult↗
PubMed1988

Epidural lipomatosis.

The authors report six new cases of epidural lipomatosis--a rarely described entity characterized by increased extradural fat within the spinal canal causing compression of the spinal cord and neurologic deficits. Five of the six patients had a history of chronic steroid use. Myelography of the thoracic spine, followed by computed tomography (CT), was performed in five patients, and magnetic resonance (MR) imaging was done in three. Myelographic findings were abnormal in three patients and normal in two, compared with those of postmyelography CT, which revealed increased accumulation of extradural fat in all five patients. In the three patients in whom it was performed, MR imaging also showed the increased spinal canal fat. Four patients underwent surgery, which revealed an increased amount of histologically normal, unencapsulated fat in all cases. The diagnosis of epidural lipomatosis should be based on a combination of clinical, imaging, surgical, and histologic findings. If the clinical suspicion is high, even if results of myelography are normal, further evaluation with post-myelography CT or MR imaging should be considered.

Adult↗
PubMed1986

Ultrasonic features of two cases of spinal cord hemangioblastoma.

Two patients with proven intramedullary spinal cord hemangioblastomas were examined with intraoperative ultrasound. The ultrasonic features of a hyperechoic intramedullary mass accompanied by nearby cysts and, in one case, by a syrinx correspond with well-known pathological and computed tomographic descriptions of these tumors. Ultrasonic guidance enabled the surgeon to identify the exact location of the tumors and to proceed with the surgery, limiting the dissection to the area detected. The ultrasound also revealed cysts associated with the tumors, thus providing valuable information to guide the progress of surgery.

Adolescent↗