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Biomedical subjects

A Kumar

Publications and source records attributed to A Kumar.

At least 451 records · Page 25Linked to original sources
PubMed2000

Neuropathogenesis of chimeric simian human immunodeficiency virus infection in rhesus macaques.

Comparative studies were performed to determine the neuropathogenesis of infection in macaques with simian human immunodeficiency virus (SHIV)89.6P and SHIV(KU). Both viruses utilize the CD4 receptor and CXCR4 co-receptor. However, in addition, SHIV89.6P uses the CCR5 co-receptor. Both agents are dual tropic for CD4+ T cells and blood-derived macrophages of rhesus macaques. Following inoculation into macaques, both caused rapid elimination of CD4+ T cells but they varied greatly in mechanisms of neuropathogenesis. Two animals infected with SHIV89.6P developed typical lentiviral encephalitis in which multinucleated giant cell formation, nodular accumulations of microglial cells, activated macrophages and astrocytes, and perivascular accumulations of mononuclear cells were present in the brain. Many of the macrophages in these lesions contained viral RNA. Three macaques infected with SHIV(KU) and killed on days 6, 11 and 18, respectively, developed a slowly progressive infection in the CNS but macrophages were not productively infected and there were no pathological changes in the brain. Two other animals infected with this virus and killed several months later showed minimal infection in the brain even though one of the two developed encephalitis of unknown etiology. The basic difference in the mechanisms of neuropathogenesis by the two viruses may be related to co-receptor usage. SHIV89.6P, in utilizing the CCR5 co-receptor, caused neuropathogenic effects that are similar to other neurovirulent primate lentiviruses.

AIDS Dementia Complex↗
PubMed2000

Evoked potential monitoring in anaesthesia and analgesia.

Electrophysiological monitoring of selected neural pathways of the brain, brainstem, spinal cord and peripheral nervous system has become mandatory in some surgery of the nervous system where preventable neural injury can occur. Evoked potentials are relatively simple methods of testing the integrity of various aspects of the nervous system. This review covers the variety of evoked potentials that can be monitored and outlines the principles of their measurement. Their use in specific situations and how factors such as anaesthesia might affect them is presented.

Analgesics↗
PubMed2000

Generation of mononucleate cells from post-mitotic myotubes proceeds in the absence of cell cycle progression.

The remarkable regenerative ability of adult urodele amphibians depends in part of the plasticity of differentiated cells at the site of injury. Limb regeneration proceeds by formation of a mesenchymal growth zone or blastema under the wound epidermis at the end of the stump. Previous work has shown that when cultured post-mitotic newt myotubes are introduced into the blastema, they re-enter the cell cycle and undergo conversion to mononucleate cells which divide and contribute to the regenerate [11, 13]. In order to investigate the interdependence of these two aspects of plasticity, we have blocked cell cycle progression of the myotubes either by X-irradiation or by transfection of the CDK4/6 inhibitor p16. In each case, the efficacy of the block was evaluated in culture after activation of S phase re-entry by serum stimulation. The experimental myotubes were implanted into limb blastemas along with a differentially labelled control population of myotubes containing an equivalent number of nuclei. X-irradiated myotubes gave rise to mononucleate cells in the limb blastema, and the progeny were blocked in respect of S phase entry. Comparable results were obtained with the p16-expressing myotubes. We conclude that progression through S or M phase is not required for generation of mononucleate cells and suggest that such cells may arise by budding from the muscle syncytium.

Animals↗
PubMed2000

Intravitreal pefloxacin therapy in postoperative endophthalmitis.

PURPOSE: To study the efficacy of intravitreal pefloxacin in the management of suspected bacterial endophthalmitis. METHODS: Twenty eyes with suspected postoperative bacterial endophthalmitis were given an intravitreal injection of pefloxacin (200 microg in 0.1 mL). If required the injection was repeated after 24 h. The main parameters evaluated were visual acuity, response to intravitreal therapy and any complications due to intravitreal pefloxacin. RESULTS: Fourteen eyes (70%) responded to intravitreal pefloxacin therapy alone, while an additional pars plana vitrectomy was required in six eyes (30%). Nineteen eyes retained a visual acuity of 6/60 or better at 3 months after the initiation of therapy. A retinal detachment developed in one of the eyes which received intravitreal therapy. CONCLUSIONS: Intravitreal pefloxacin may be a useful aternative therapy in bacteria endophthalmitis.

Aged↗
PubMed2000

Aluminum increases levels of beta-amyloid and ubiquitin in neuroblastoma but not in glioma cells.

Several epidemiological studies suggest the involvement of aluminum (Al) in the pathogenesis of Alzheimer's disease (AD). There is an increase in the levels of Abeta and ubiquitin in the pathological lesions of AD. Therefore, we have investigated whether aluminum (Al) treatment alters the levels of Abeta and ubiquitin in murine neuroblastoma (NBP2) and rat glioma (C-6) cell cultures. At a low concentration (10 microM), aluminum sulfate stimulated the level of immunoreactive Abeta and ubiquitin in NBP2 cells without changing the levels of the amyloid precursor protein (APP). However, at higher concentrations (100 and 500 microM), aluminum failed to elicit any significant effect on beta-amyloid, whereas ubiquitin levels continued to increase. No changes in the Abeta and ubiquitin content were found in the C-6 glioma cells following treatment with Al at any of the concentrations tested. Exposure of cells to aluminum salts did not alter the rate of proliferation in either of the two cell lines. These data suggest that one of the mechanisms by which Al may play a role in AD is by promoting the formation of Abeta and ubiquitin in neurons.

Alum Compounds↗
PubMed2000

Sestamibi scan-directed unilateral neck exploration for primary hyperparathyroidism due to a solitary adenoma.

AIM: To evaluate the accuracy of Tc-99m sestamibi scintography in pre-operative localization of a single parathyroid adenoma and to determine if neck exploration can be limited to the side of the adenoma. METHODS: Over a period of 4 years, 30 patients with primary hyperparathyroid disease underwent surgical treatment in the form of unilateral neck exploration after localization by Tc-99m sestamibi scintigraphy. The scan findings were interpreted by one radiologist with a special interest in parathyroid imaging and the operative findings were correlated with scan findings. RESULTS: Tc-99 sestamibi scan localized a single parathyroid adenoma in 29 patients. There was doubtful uptake of isotope in one patient. Unilateral cervical exploration confirmed isotope scan findings in 29 patients with a positive scan, and these were subsequently proven by histology. In the patient with doubtful sestamibi scan, bilateral neck exploration was undertaken and three enlarged glands were excised. All the three glands were reported to be abnormal, consistent with either adenomas or hyperplasia. All the patients were normocalcaemic after 6 months follow-up. CONCLUSIONS: Our results demonstrate that Tc-99m sestamibi scintigraphy is highly accurate in pre-operative localization of a single parathyroid adenoma when performed by an experienced radiologist. Unilateral cervical exploration, as directed by a positive Tc-99m sestamibi scintigram, seems to be a logical approach for the patients with primary hyperparathyroid disease due to solitary adenoma.

Adenoma↗
PubMed2000

Increased type-IV collagenase (MMP-2 and MMP-9) activity following preoperative radiotherapy in rectal cancer.

The aim of this study was to investigate the effect of preoperative high-dose radiotherapy (25 Gy in 5 fractions over 5 days) on the type-IV collagenase protein profile, in patients with resectable rectal cancer, by gelatin zymography. Biopsy samples of tumour and distant normal mucosa from 12 patients with resectable rectal cancer were obtained pre- and post-radiotherapy. Expression of type-IV collagenases (both pro- and active forms) was studied using gelatin zymography. Enzyme levels were normalized for total protein content of each sample. Rectal cancer specimens expressed both pro (72 kDa) and active (62 kDa) forms of MMP-2 but only the pro form of MMP-9 (92 kDa). Normal mucosa showed expression of the pro forms of MMP-2 and MMP-9 while no active form of either enzyme was detected in any of the samples. A significant three- to fourfold increase (P < 0.01) of active matrix metalloproteinases (MMP)-2 (62 kDa) was seen in malignant rectal mucosa after radiotherapy. The effect of radiotherapy also led to a twofold increase (P = 0.047) of pro MMP-2 (72 kDa) and a two- to threefold increase (P = 0.03) of the precursor form of MMP-9 (92 kDa). In contrast, in normal mucosa expression of the precursor form of MMP-9 (92 kDa) did not change after radiation, and no significant effect on the levels of pro MMP-2 (72 kDa) was observed. Preoperative high-dose radiotherapy leads to an increase in activity of type-IV collagenases in patients with resectable rectal cancer. Type-IV collagenase inhibition may be a useful therapeutic adjunct to radiotherapy in rectal cancer.

Adenocarcinoma↗
PubMed2000

Newer substituted beta-aminonaphthalenes as potent anti-inflammatory agents.

beta-[2-(3'-Chloro-2'-oxo-4'-substituted aryl-1'-azetidinyl)-thiazol-4- yl]aminonaphthalenes 13-17 and beta-[2-(1',3'-disubstitutedphenyl-formazan-4'-yl)-thiazol-4-yl] aminonaphthalenes 8-12 were synthesized from beta-(2-arylideneamino-thiazol-4-yl)aminonaphthalenes 3-7 by diazotisation and by cycloaddition with monochloroacetyl chloride, respectively, on the azomethine group of the compounds 3-7. The newly synthesized compounds showed potent anti-inflammatory and analgesic activities and were less ulcerogenic than phenylbutazone.

2-Naphthylamine↗
PubMed2000

Dynamic control and conventional strength ratios of the quadriceps and hamstrings in subjects with anterior cruciate ligament deficiency.

The hamstrings:quadriceps muscle strength ratio has been used as an indicator of normal balance between the knee flexors and extensors. A more functional approach to this strength ratio would be to compare opposite muscle actions of antagonistic muscle groups. The dynamic strength control ratio (DSCR) should give a more appropriate measure relating to knee function. There is a lack of normative data relating to DSCR for anterior cruciate ligament (ACL) deficient subjects. Effects of ACL deficiency on isokinetic peak torque for eccentric and concentric muscle actions of the quadriceps and hamstrings, in conjunction with isometric peak torque, were examined in 10 patients awaiting reconstructive surgery (male = 8, female = 2 ; age = 32.8 +/- 8.3 years; height = 1.77 +/- 0.08 m; mass = 72.1 +/- 12.5 kg). These variables were assessed using an isokinetic dynamometer. The results were considered in terms of the conventional ratio and DSCR. Anterior tibial drawer was measured using a knee ligament arthrometer to confirm clinical diagnosis of ACL rupture. The isokinetic peak torque data analysed were for angular velocities of 1.05 rad s(-1) (60 degrees s(-1)). Significant strength deficits were apparent between normal and injured sides for: concentric isokinetic quadriceps action (p < 0.05); isometric quadriceps action at 70 degrees of knee flexion (p < 0.05); isometric quadriceps action at 40 degrees of knee flexion (p<0.01); eccentric isokinetic hamstrings action (p < 0.05). With bilateral comparison, the conventional strength ratios showed no significant difference, as did the DSCR. The bilateral comparison of isometric strength ratios revealed significant losses in quadriceps strength for the injured side (p < 0.05) but no significant losses in hamstring strength (p > 0.05). Thus, differences can be seen in conventional ratios and DSCR for ACL-deficient subjects. This is an area of clinical interest with the increasing frequency of ACL reconstruction using hamstrings tendons.

Adult↗
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↗