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Biomedical subjects

A Kumar

Publications and source records attributed to A Kumar.

At least 289 records · Page 16Linked to original sources
PubMed2000

Two cDNAs representing alleles of the nitrate reductase gene of potato (Solanum tuberosum L. cv. Desirée): sequence analysis, genomic organization and expression.

Two, different, full-length cDNAs, StNR2 and StNR3, of 3049 and 3066 nucleotides, respectively, were isolated from a Solanum tuberosum L. cv. Desirée leaf cDNA library by an RT-PCR approach. Conceptual translation of the longest open reading frame of each cDNA showed that they could encode a protein of 911 amino acids in each case with an M(r) of 102.6 and 102.5 kDa, respectively, and with 99.7% identity with each other. The cDNAs have a high degree of sequence similarity with all higher plant nitrate reductases (NRs) and possess structural characteristics expected of NADH-NR proteins, consistent with enzyme activity data. Southern analysis of genomic DNA suggested the presence of a single NR gene in the potato genome whilst studies using the mapping population F1840, and the full-length StNR2 cDNA as hybridization probe, identified a single NR locus within the potato genome that is located on chromosome XI. The two cDNAs identified here are probably derived from two transcribing alleles of this single gene. Distribution of total NR transcript and of NADH-NR activity, in different organs of compost-grown plants, depended on the level of nitrate supplied: at low nitrate level transcript and activity were detected only in leaf and stem tissue whilst at high nitrate level they could also be detected in root and stolon. An RT-PCR approach was used to differentiate between the transcripts derived from the two identified alleles and to show that the pattern of transcription of the two identified alleles of the potato nia gene, in the organs studied, is the same.

Amino Acid Sequence↗
PubMed2000

BK virus infection in AIDS.

The BK virus (BKV) belongs to the family of the polyoma group, which contains three species: JC, which is responsible for progressive multifocal leukoencephalopathy in acquired immunodeficiency syndrome (AIDS); simian virus 40 (SV40), which is a simian virus of little pathologic significance in humans; and BKV, which is usually not pathogenic and is found in the urine of asymptomatic individuals. Recently BKV has been reported to cause symptomatic infection in renal transplant patients. The authors report a rare case of a 14-year-old boy with AIDS who developed a BKV infection of the lung and kidney that progressed to diffuse alveolar damage and death. The infected type II pneumocytes in the lung and the tubular epithelial cells in the kidney showed large, homogenous purple intranuclear inclusions. The absence of necrosis and destruction made it possible to distinguish BKV infection from herpes simplex. The size of the infected cells and the lack of a halo around the nuclear inclusion helped rule out cytomegalovirus as the cause of infection. Electron microscopy detected the presence of 40-nm intranuclear viral particles compatible with BKV, and in situ hybridization established the diagnosis.

AIDS-Related Opportunistic Infections↗
PubMed2000

Value of imaging in disorders of the facial nerve.

Imaging of the facial nerve has proved its usefulness to physicians in the evaluation of pathological conditions of this nerve. Magnetic resonance imaging (MRI) of the facial nerve should always be obtained selectively and should include the parotid gland in case of peripheral facial nerve palsy. Gadolinium-DTPA contrast pulse sequence is the most informative MRI study for evaluation of facial nerve pathology. This article reviews the imaging anatomy of the facial nerve and describes the clinical features and MR characteristics of common disorders of the facial nerve.

Contrast Media↗
PubMed2000

Evaluation of the urological complications of living related renal transplantation at a single center during the last 10 years: impact of the Double-J* stent.

PURPOSE: We evaluated the impact of the routine use of Double-J stents for decreasing urological complications in living related renal transplantation at a single center during the last 10 years. MATERIALS AND METHODS: Our 3-phase longitudinal study included 670 consecutive living related renal transplants from 1989 to 1998. In phase 1 from 1989 to 1993 a stent was introduced as and when required in only 15 of 170 patients. In phase 2 from January 1994 to April 1995 we randomized 57 and 43 cases to stenting and no stenting, respectively. The stent was removed after 4 weeks. In phase 3 from May 1995 to December 1998 all patients received a stent, which was removed 10 to 14 days just before discharge home. We reviewed urological complications at various time frames to determine the impact of routine Double-J stenting on decreasing urological complications. RESULTS: In phase 1 the major ureteral complication rate was 8.8%, which decreased to 3% in phase 2 when half of our cases were stented. In phase 3 there was only 1 ureteral complication (0.04%) in 400 patients, of whom all received a stent. The overall ureteral complication rate in nonstented and stented cases was 8.5% (18 of 213) and 0.22% (1 of 457). There was no difference in urological complications or stent related problems whether the stent was removed at 4 or 2 weeks. However, stent removal at 2 weeks eliminated the possibility of a forgotten stent, avoided repeat hospitalization for stent removal and decreased the cost. Routine stenting was cost-effective and almost eliminated urological complications. CONCLUSIONS: Routine Double-J stenting prevents ureteral complications. Early removal at 2 weeks is advisable. The short duration of stenting is effective and saves the cost of repeat hospitalization at a later date.

Adolescent↗
PubMed2000

Recovery and identification of West Nile virus from a hawk in winter.

West Nile virus was recovered from the brain of a red-tailed hawk that died in Westchester County, N.Y., in February 2000. Multiple foci of glial cells, lymphocytes, and a few pyknotic nuclei were observed in the brain. Three to 4 days after inoculation of Vero cells with brain homogenates, cytopathic changes were detected. The presence of West Nile virus antigen in fixed cells or cell lysates was revealed by fluorescent antibody testing or enzyme-linked immunosorbent assay, respectively. Furthermore, Reverse transcriptase-PCR with primers specific for the NS3 gene of West Nile virus resulted in an amplicon of the expected size (470 bp). Electron microscopy of thin sections of infected Vero cells revealed the presence of viral particles approximately 40 nm in diameter, within cytoplasmic vesicles. The demonstration of infection with the West Nile virus in the dead of the winter, long after mosquitoes ceased to be active, is significant in that it testifies to the survival of the virus in the region beyond mosquito season and suggests another route of transmission: in this case, prey to predator.

Animals↗
PubMed2000

Cell cycle-regulated transcription by the human immunodeficiency virus type 1 Tat transactivator.

Cyclin-dependent kinases are required for the Tat-dependent transition from abortive to productive elongation. Further, the human immunodeficiency virus type 1 (HIV-1) Vpr protein prevents proliferation of infected cells by arresting them in the G(2) phase of the cell cycle. These findings suggest that the life cycle of the virus may be integrally related to the cell cycle. We now demonstrate by in vitro transcription analysis that Tat-dependent transcription takes place in a cell cycle-dependent manner. Remarkably, Tat activates gene expression in two distinct stages of the cell cycle. Tat-dependent long terminal repeat activation is observed in G(1). This activation is TAR dependent and requires a functional Sp1 binding site. A second phase of transactivation by Tat is observed in G(2) and is TAR independent. This later phase of transcription is enhanced by a natural cell cycle blocker of HIV-1, vpr, which arrests infected cells at the G(2)/M boundary. These studies link the HIV-1 Tat protein to cell cycle-specific biological functions.

Cell Cycle↗
PubMed2000

Pathogenic simian/human immunodeficiency virus SHIV(KU) inoculated into immunized macaques caused infection, but virus burdens progressively declined with time.

Using the simian immunodeficiency virus/human immunodeficiency virus (SHIV)-macaque model of AIDS, we had shown in a previous report that a live, nonpathogenic strain of SHIV, further attenuated by deletion of the vpu gene and inoculated orally into adult macaques, had effectively prevented AIDS following vaginal inoculation with pathogenic SHIV(KU). Examination of lymph nodes from the animals at 18 weeks postchallenge had shown that all six animals were persistently infected with challenge virus. We report here on a 2-year follow-up study on the nature of the persistent infections in these animals. DNA of the vaccine virus was present in the lymph nodes at all time points tested, as far as 135 weeks postchallenge. In contrast, the DNA of SHIV(KU) became undetectable in one animal by week 55 and in three others by week 63. These four macaques have remained negative for SHIV(KU) DNA as far as the last time point examined at week 135. Quantification of the total viral DNA concentration in lymph nodes during the observation period showed a steady decline. All animals developed neutralizing antibody and cytotoxic-T-lymphocyte responses to SHIV(KU) that persisted throughout the observation period. Vaccine-like viruses were isolated from two animals, and a SHIV(KU)-like virus was isolated from one of the two macaques that remained positive for SHIV(KU) DNA. There was no evidence of recombination between the vaccine and the challenge viruses. Thus, immunization with the live vaccine not only prevented disease but also contributed to the steady decline in the virus burdens in the animals.

AIDS Vaccines↗
PubMed2000

Comparison of in house polymerase chain reaction with conventional techniques for the detection of Mycobacterium tuberculosis DNA in granulomatous lymphadenopathy.

AIMS: To evaluate the usefulness of the devR based polymerase chain reaction (PCR) in the detection of Mycobacterium tuberculosis in lymph node aspirates and tissues of lymphadenitis and to compare PCR with conventional diagnostic techniques. SUBJECTS AND METHODS: Coded specimens of fine needle aspirates and biopsies from 22 patients with tuberculous lymphadenitis, 14 patients with non-tubercular lymphadenitis, and nine patients with granulomatous lymphadenitis were processed and subjected to analysis by PCR, smear microscopy, M tuberculosis culture, histology, and cytology. RESULTS: Tuberculous lymphadenitis was correctly diagnosed by PCR in 18 patients, by culture in five patients, by histology in 13 patients, and by cytology in seven patients. PCR gave two false positive results in 14 patients with non-tubercular lymphadenitis. The sensitivity of the conventional techniques was significantly higher with biopsies (17 of 22 specimens; 77%) than with fine needle aspirates (nine of 22 specimens; 41%). However, the sensitivity of PCR was not significantly higher with biopsies (68%) in comparison with fine needle aspirates (55%). The sensitivity of either biopsy PCR or fine needle aspirate PCR was not significantly different from that of either histology combined with culture or cytology combined with culture. The overall combined specificity of PCR was 86%. Mycobacterium tuberculosis DNA was detected in six of nine patients with granulomatous lymphadenitis. CONCLUSION: PCR is the most sensitive single technique available to date for the demonstration of M tuberculosis in specimens derived from patients with a clinical suspicion of tuberculous lymphadenitis. The value of PCR lies in its use as an adjunct test in the diagnosis of tuberculous lymphadenitis, particularly in those patients where conventional methods fail. Because fine needle aspiration is not an invasive procedure, it is the procedure of choice, and PCR should be performed initially on these samples. Excisional biopsy histology and PCR should be recommended only for patients in whom fine needle aspirate PCR is negative or when there is discrepancy with the clinical impression.

Biopsy↗
PubMed2000

Recurrent synovial chondromatosis of the index finger--case report and literature review.

We report a case of synovial chondromatosis of the proximal interphalangeal joint of the dominant right index finger with a follow-up of four years. The lesion recurred within a year of complete excision of the fibrous sac containing cartilaginous nodules. Despite early recurrence and extensive calcification around the proximal phalanx, no malignant changes were noted on histological examination. The patient remains asymptomatic for two years after the second operation.

Adult↗
PubMed2000

Infiltrative nonamyloidotic monoclonal immunoglobulin light chain cardiomyopathy: an underappreciated manifestation of plasma cell dyscrasias.

BACKGROUND: Infiltrative cardiomyopathies are characterized by diastolic dysfunction. In monoclonal plasma cell dyscrasias, organ compromise may be produced by tissue deposition of monoclonal immunoglobulins or their constituent peptides independently of the effects of unbridled plasma cell proliferation. The deposits may be fibrillar, as in light chain amyloid (AL) or nonfibrillar, as in light chain deposition disease (LCDD). AL disease of the heart is a restrictive cardiomyopathy. We hypothesized that, despite differences in physical properties, nonamyloidotic light chain deposition in the myocardium could produce similar clinical and physiological abnormalities. METHODS: Cardiac tissue from five patients with LCDD and cardiac dysfunction was examined by immunohistochemical and electron microscopic techniques. Hospital charts, electrocardiograms, echocardiograms and cardiac catheterization results were reviewed. In two cases, the original echocardiograms were reanalyzed. RESULTS: The five patients with nonamyloidotic light chain deposits in the myocardium had either mechanical or electrocardiographic abnormalities. In four with adequate clinical documentation, the diastolic dysfunction and conduction abnormalities were similar or identical to that described in cardiac AL disease. CONCLUSIONS: Although nonamyloidotic immunoglobulin light chain deposits in the myocardium differ in distribution and ultrastructural organization from the fibrillar deposits of AL disease, an analogous pattern of diastolic dysfunction and conduction disturbances results. The diagnosis should be considered in patients with a plasmacytic dyscrasia and restrictive cardiomyopathy in whom Congo red staining of endomyocardial biopsy tissue is negative. The diagnosis can be established by using the appropriate immunohistochemical and ultrastructural tissue examinations.

Adult↗
PubMed2000

Relative sensitivity of undifferentiated and cyclic adenosine 3',5'-monophosphate-induced differentiated neuroblastoma cells to cyclosporin A: potential role of beta-amyloid and ubiquitin in neurotoxicity.

Cyclosporin A is routinely used in transplant therapy following allogeneic or xenogeneic tissue transplantation to prevent rejection. This immunosuppressive drug is also neurotoxic; however, its mechanisms of action for neurotoxicity are poorly understood. Undifferentiated and cyclic adenosine 3',5'-monophosphate (cAMP)-induced differentiated neuroblastoma (NB) cells were used as an experimental model to study the toxicity of cyclosporin A. Results showed that cyclosporin A promoted the outgrowth of neurites and inhibited the growth of undifferentiated NB cells. When cyclosporin A was added simultaneously with RO20-1724, an inhibitor of cyclic nucleotide phosphodiesterase, or with prostaglandin E1, a stimulator of adenylate cyclase, it markedly enhanced the growth inhibitory and differentiation effects of these cAMP-stimulating agents. In addition, cyclosporin A added to cAMP-induced differentiated NB cells caused dose-dependent degeneration of these cells as evidenced by the vacuolization of cytoplasm and the fragmentation of nuclear and cytoplasmic materials; however, neurites remained intact. Cyclosporin A alone did not alter the intensity of cell immunostaining for ubiquitin or beta-amyloid peptide (amino acids 1-14) (Abeta1-14); however, it enhanced the intensity of staining for both ubiquitin and Abeta in cells that were treated with cAMP-stimulating agents. The intensity of staining of amyloid precursor protein (amino acids 44-63) (APP44-66) did not change in any treated group, suggesting that the increase in Abeta staining is due to increased processing of APP to Abeta. We propose that one of the mechanisms of cyclosporin A-induced neurotoxicity involves increased levels of Abeta and ubiquitin.

4-(3-Butoxy-4-methoxybenzyl)-2-imidazolidinone↗