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Biomedical subjects

B Singh

Publications and source records attributed to B Singh.

At least 199 records · Page 11Linked to original sources
PubMed2000

Effect of Kombucha tea on chromate(VI)-induced oxidative stress in albino rats.

The effect of Kombucha tea (KT) on oxidative stress induced changes in rats subjected to chromate treatment are reported. KT feeding alone did not show any significant change in malondialdehyde (MDA) and reduced glutathione (GSH) levels, but did enhance humoral response and delayed type of hypersensitivity (DTH) response appreciably over control animals. Chromate treatment significantly enhanced plasma and tissue MDA levels, decreased DTH response considerably, enhanced glutathione peroxidase and catalase activities; however, no change in GSH, superoxide dismutase and antibody titres was noticed. KT feeding completely reversed the chromate-induced changes. These results show that Kombucha tea has potent anti-oxidant and immunopotentiating activities.

Animals↗
PubMed2000

Arnebins and antimicrobial activities of Arnebia hispidissima DC. cell cultures.

The whole plant of Arnebia hispidissima DC. (Boraginaceae) is used for the treatment of tongue and throat ailments in Indian traditional medicine. The present paper deals with the plants phytochemical constituents, the arnebins, and antimicrobial activities of its root extract. The antimicrobial activities were tested against Gram-positive and Gram-negative bacteria and fungi. The crude hexane extract demonstrated a potent antimicrobial effect against bacteria and a mild effect against fungi. Likewise, the hexane extract of cell cultures of A. hispidissima also showed mild bioefficacy against the select microorganisms.

Anti-Bacterial Agents↗
PubMed2000

B7/CD28 costimulation is essential for the homeostasis of the CD4+CD25+ immunoregulatory T cells that control autoimmune diabetes.

CD28/B7 costimulation has been implicated in the induction and progression of autoimmune diseases. Experimentally induced models of autoimmunity have been shown to be prevented or reduced in intensity in mice rendered deficient for CD28 costimulation. In sharp contrast, spontaneous diabetes is exacerbated in both B7-1/B7-2-deficient and CD28-deficient NOD mice. These mice present a profound decrease of the immunoregulatory CD4+CD25+ T cells, which control diabetes in prediabetic NOD mice. These cells are absent from both CD28KO and B7-1/B7-2KO mice, and the transfer of this regulatory T cell subset from control NOD animals into CD28-deficient animals can delay/prevent diabetes. The results suggest that the CD28/ B7 costimulatory pathway is essential for the development and homeostasis of regulatory T cells that control spontaneous autoimmune diseases.

Abatacept↗
PubMed2000

Epstein-Barr virus in squamous carcinoma of the anterior nasal cavity.

Squamous carcinoma is the most common malignancy of the head and neck, but it rarely occurs in the nasal vestibule. Epstein-Barr virus (EBV) has been detected in and is causally linked to various head and neck tumors, particularly nasopharyngeal carcinoma. The possible role of EBV in squamous carcinoma of the anterior nasal cavity, particularly of the nasal vestibule, has not been previously investigated. Histologic sections from 17 patients with nasal vestibular squamous carcinoma were examined. Material for EBV detection by immunohistochemistry and by in situ hybridization was available in 15 of the 17 cases. The study group consisted of eight men and nine women ranging in age from 40 to 82 years (mean age, 64 years). None of the patients was of Asian descent. The squamous carcinomas were graded as well differentiated (one case), moderately differentiated (11 cases), and poorly differentiated (five cases). Fourteen patients were smokers; the history of smoking ranged from 20 to 60 pack-years. Treatment modalities included surgical resection, radiation, chemotherapy, or a combined approach. The clinical follow-up periods ranged from 7 months to 16 years. Three patients developed metastases, one of whom died of disease after 1 year. Epstein-Barr virus was not detected in any of the 15 of 17 cases tested by either immunohistochemistry or by in situ hybridization. Squamous carcinoma of the nasal vestibule is an uncommon cancer that is not causally related to EBV.

Adult↗
PubMed2000

Immune responses mediating survival of naive BALB/c mice experimentally infected with lethal rodent malaria parasite, Plasmodium yoelii nigeriensis.

The rodent malaria parasite, Plasmodium yoelii nigeriensis is known to cause fatal malaria infections in BALB/c mice. However, we found that nearly 5% of inbred BALB/c mice could overcome primary infections initiated with lethal inoculum of P. y. nigeriensis asexual blood-stages, without any experimental intervention. These 'survivor' mice developed peak parasitemia levels of about 5% and successfully resolved their infections in about two weeks time; infected blood collected during the descending phase of infection in these mice and subinoculated in naive recipients resulted in a normal lethal course of infection. Typically, the parasites in survivor mice looked 'sick' compared to those in the susceptible mice. In experiments to define temporal basis of this protection, we found that purified splenic B cells isolated from such a survivor mouse, plus T cells from an infected or naive mouse, could adoptively transfer this protection to an X-irradiated, naive mouse against a lethal parasite challenge. Purified T cells or B cells alone from the survivor mouse donor provided no protection to the X-irradiated, naive recipient. Passive transfer of sera collected from survivor mice animals a week after recovery from infection was also able to substantially alter the course of preestablished P. y. nigeriensis infection. These findings are discussed in the light of recent reports on the genetic control of blood parasitemia in mouse malaria models. In the generally lethal malaria infections such as those caused by P. y. nigeriensis in mice and by Plasmodium falciparum in naive children, it is not clear what constitutes a protective immune response in cases which survive primary infections without any experimental or therapeutic intervention. An understanding of these mechanisms and their regulation would help design better vaccination strategies.

Animals↗
PubMed2000

Impact of lead exposure on pituitary-thyroid axis in humans.

Thyroid function tests (serum levels of thyroxine-T4, triiodothyronine-T3 and thyroid stimulating hormone-TSH) were performed in fifty-eight men (mean age: 31.7 +/- 10.6 years; mean duration of lead exposure: 156.9 +/- 122.7 months). These subjects were exposed to lead either as petrol pump workers or automobile mechanics. The mean whole blood lead (Pb-B) levels were 2.49 +/- 0.45 micromole/l (51.90 +/- 9.40 microg/dl) in the lead exposed workers and were approximately 5 times higher than in the control (n = 35) subjects. No significant alteration was seen in their mean T3 and T4 levels as compared with the controls. Interestingly, T3 was significantly lower with the longer (210 months) exposure time in comparison with the group having shorter (29 months) exposure duration. The mean TSH levels were significantly (p < 0.01) higher in workers exposed in comparison with the control group. This rise in TSH was independent of exposure time, but it was definitely associated with the Pb-B levels. The increase being more pronounced with mean Pb-B levels of 2.66 +/- 0.2 micromole/l (55.4 +/- 4.25 microg/dl) when compared with the group having mean levels of 1.51 +/- 0.30 micromole/l (31.5 +/- 6.20 microg/dl). The rise is TSH associated with Pb-B levels was only statistical valid, however, the levels fall within the normal laboratory range. We thus conclude that the Pb-B levels of > or = 2.4 micromole/l (50 microg/dl) could enhance the pituitary release of TSH without having any significant alterations in the circulating levels of T3 and T4.

Adult↗
PubMed2000

Research note: HLA degenerate T-cell epitopes from Plasmodium falciparum liver stage-specific antigen 1 (LSA-1) are highly conserved in isolates from geographically distinct areas.

Considerable effort is directed at the development of a malaria vaccine that elicits antigen-specific T-cell responses against pre-erythrocytic antigens of Plasmodium falciparum. Genetic restriction of host T-cell responses and polymorphism of target epitopes on parasite antigens pose obstacles to the development of such a vaccine. Liver stage-specific antigen-1 (LSA-1) is a prime candidate vaccine antigen and five T-cell epitopes that are degenerately restricted by HLA molecules common in most populations have been identified on LSA-1. To define the extent of polymorphism within these T-cell epitopes, the N-terminal non-repetitive region of the LSA-1 gene from Malaysian P. falciparum field isolates was sequenced and compared with data of isolates from Brazil, Kenya and Papua New Guinea. Three of the T-cell epitopes were completely conserved while the remaining two were highly conserved in the isolates examined. Our findings underscore the potential of including these HLA-degenerate T-cell epitopes of LSA-1 in a subunit vaccine.

Amino Acid Sequence↗
PubMed2000

Case report. Subcutaneous phaeohyphomycosis due to Cladosporium cladosporioides.

A case of subcutaneous phaeohyphoymycosis caused by Cladosporium cladosporioides in a 25-year-old male is described. The clinical presentation was an elevated scaly suppurating lesion with sinuses on the right leg. The lesion healed completely with oral fluconazole therapy. The present report constitutes the first record of cutaneous or subcutaneous infection due to Cl. cladosporioides from India.

Adult↗
PubMed2000

Posterior sagittal approach for repair of rectourethral fistula occurring after perineal surgery for imperforated anus at birth.

PURPOSE: Posterior sagittal approach was used for the repair of 11 cases of rectourethral fistula between 1992 and 1998. METHODS: All these patients had rectourethral fistula as a result of perineal procedure performed for imperforate anus at the time of birth. In addition to the fistula repair, an associated anorectal stenosis (3 cases) and urethral stricture 11 case) also were corrected with this approach. All the patients underwent surgery under cover of a protective colostomy. RESULTS: Successful repair was achieved in all patients, and the follow-up period ranged from 10 months to 7 years. As far as bladder and bowel control, urinary control was normal in all 11 patients, whereas bowel control was normal in 10 cases. One patient who had severe scarring of anal sphincters caused by infection in the previous surgery still suffers occasional perianal soiling after 18 months of follow-up. CONCLUSIONS: Posterior sagittal approach not only gives adequate exposure but also suits the basic principles of fistula repair, namely, completely separating the rectum from urethra and leaving normal rectal wall behind the urethral sutures thus eliminating the possibility of recurrence. In addition to fistula repair, one can also correct associated problems like anorectal stenosis or urethral stricture, and a mislocated rectum can be relocated within the sphincter complex.

Adult↗
PubMed2000

Retropharyngeal abscess secondary to penetrating foreign bodies.

A retrospective study was conducted on patients with upper aerodigestive tract foreign bodies requiring operative intervention over a 12-year period to aid in the recognition and management of foreign body associated complications. Oesophagoscopies were performed for the removal of foreign bodies in 37 patients, age one to 82 years with a male to female ratio of 1.2:1. Retropharyngeal abscesses accounted for eight of 11 foreign body-associated complications. Fish bones were the cause in six cases, chicken bone and a pen refill in one case each. An abscess was already present at the time of initial procedure in six cases and developed in two cases after successful removal of the foreign body. A high level of suspicion for a retropharyngeal abscess should be maintained in cases with perforation, and in patients with immunodeficiency.

Adolescent↗
PubMed2000

Screening for genetic aberrations in papillary thyroid cancer by using comparative genomic hybridization.

BACKGROUND: Determination of the genetic composition of papillary thyroid cancers may help explain differences in observed clinical behavior. Comparative genomic hybridization (CGH) is a novel molecular cytogenetic assay that allows simultaneous detection of gains, losses, and amplification of genetic information, making it an ideal screening tool. The aim of this study was to identify genetic aberrations occurring in papillary thyroid cancers by using CGH analysis. METHODS: CGH analysis was performed on 21 individual cases of papillary thyroid cancers. Nonparametric statistical comparisons were performed with the Fisher exact test. RESULTS: Genetic abnormalities were identified by CGH in 10 of 21 cases (48%). A recurrent pattern of aberrations was seen in cases where genetic changes were detected, involving losses at chromosome arms 1p and 9q and chromosomes 17, 19, and 22, and gains at chromosome 4 and chromosome arms 5q, 6q, 9q, and 13q. The loss of chromosome 22 was unique to younger patients (P =.05) and was associated with a higher rate of regional lymphatic metastasis (19% vs 80%, P =.02). CONCLUSIONS: Two genetically unique groups of patients were identified by using CGH analysis. One group had no detectable aberrations; the other had a recurrent pattern of aberrations, localizing to the identical chromosomal loci. This pattern of aberrations suggests that the involved loci may contain genes important in thyroid carcinogenesis. The clinical significance of the presence of copy number changes detected by CGH needs to be determined. In addition, molecular cloning of involved genes in each of the aberrations is warranted.

Adolescent↗
PubMed2000

Acute-phase proteins and hematologic values in ovine lentivirus-infected lambs treated with recombinant ovine IFN-tau.

To evaluate changes in complete blood cell (CBC) counts, haptoglobin and fibrinogen in ovine lentivirus (OvLV)-infected lambs treated with recombinant ovine interferon-tau (rOVIFN-tau), 24 lambs were allocated to one of four groups (n = 6 per group): (1) virus + rOvIFN-tau, VI, (2) virus + placebo, VP, (3) no virus + rOVIFN-tau, NVI, and (4) no virus + placebo, NVP. Three lambs in each group were treated once a day for 12 weeks, and the remaining 3 lambs were treated for 33 weeks. Blood was collected at days 0, 7, and 10 and at weeks 2-10, 12, 32, and 33 to determine CBC counts, as well as haptoglobin and fibrinogen levels. Hematologic values remained within normal limits in all groups. However, hemoglobin (Hb), mean corpuscular volume (MCV), mean corpuscular hemoglobin concentration (MCHC), and packed cell volume (PCV) values decreased (p < 0.05) in the two rOvIFN-tau-treated groups (VI and NVI) compared with the placebo-treated (VP and NVP) groups. Both rOvIFN-upsilon and OvLV had a mild negative effect on neutrophil numbers. Although Hb, MCV, MCHC, PCV, and neutrophil values declined in the rOvIFN-tau-treated lambs compared with the placebo-treated lambs, these values remained within the reference range for sheep. Experimental lambs did not show adverse clinical signs associated with OvLV infection or as a result of rOvIFN-tau treatment. The lack of significant side effects of high-dose rOvIFN-tau in sheep and previous reports of broad-spectrum and cross-species antiviral activity suggest that rOvIFN-tau warrants further investigation as an antiviral therapeutic agent.

Acute-Phase Proteins↗
PubMed2000

The functional role of class II-associated invariant chain peptide (CLIP) in its ability to variably modulate immune responses.

During the process of class II MHC assembly and cell surface expression, the class II-associated invariant chain peptide (CLIP) is removed from the peptide-binding groove of MHC, a task mediated by H-2M. This allows binding and presentation of peptide epitopes. We have previously shown that exogenously added CLIP interferes with this process and down-regulates the cell surface expression of class II molecules. In this study, we explored the effect of exogenously added CLIP on antigen-specific immune responses. In vivo studies with CLIP and various peptide and protein antigens with different affinities for I-A(d) molecules demonstrated that CLIP variably affects the T cell-mediated immune responses. Immunization with CLIP along with the antigen induced a shift from a T(h)1- to T(h)2-like response as determined by the cytokine profile and antibody isotype. These results suggest that the presence of exogenous CLIP can significantly influence the presentation of antigen by class II MHC molecules to CD4 T cells and thereby modulate immune responses. Exogenously added CLIP rapidly localized into the subcellular compartment of antigen-presenting cells where MHC class II molecules are present. We suggest that exogenous CLIP reduces the loading of peptides on the class II molecules, thus down-regulating MHC-peptide complexes on the cell surface. Alternatively, CLIP may bind to cell surface class II molecules and this complex is rapidly internalized resulting in reduced cell surface MHC class II expression. The reduced level of MHC-peptide complexes favors the activation of T(h)2 cells over T(h)1 cells. These results have implications in the regulation of immune responses, particularly the prevention of certain autoimmune diseases where T(h)1-type responses are pathogenic and T(h)2-type responses are protective.

Animals↗
PubMed2000

Time course of nodal enhancement with CT X-ray nanoparticle contrast agents: effect of particle size and chemical structure.

RATIONALE AND OBJECTIVES: Levels of CT enhancement in rabbit lymph nodes were followed with time after subcutaneous injection of four iodinated, insoluble nanoparticle contrast agents to provide experimental support for the hypothesis that clearance of these agents is related to the chemical structure of the agent itself. The impact of particle size was also studied. METHODS: Subcutaneous injections (2 x 0.25 mL) were made in the dorsum of rabbit paws with 15% suspensions of four nanoparticle contrast agents. Images were obtained at 4, 10, 24, 48, and 72 hours and 5, 7, and 14 days after injection. Average attenuation (in Hounsfield units [HU]), node volume, and total iodine uptake were estimated from the CT scans for each lymph node at each time point. RESULTS: All the agents provided adequate enhancement of both the popliteal and axillary lymph nodes of the rabbit (ie, > delta100 HU). Lymph node volume appears to be related to the persistence of enhancement, with long-lived agents demonstrating the greatest increase in size. The rate of clearance from the lymph nodes is related to the structure of the agent. CONCLUSIONS: Clearance of insoluble, iodinated nanoparticle contrast agents from lymph nodes can be modulated by changes in the structure of the agent itself. Using the same agent, smaller particles deliver material to the lymph nodes more quickly and clear more quickly.

Animals↗
PubMed2000

Genome-wide screening for radiation response factors in head and neck cancer.

INTRODUCTION: Radiation therapy is an integral part of the treatment of head and neck cancer. Factors predicting radiation response are ill defined. The aim of this study was to identify genetic aberrations associated with radiation response in cell lines derived from head and neck squamous cell carcinomas (HNSCC) using comparative genomic hybridization (CGH) for genome-wide screening. METHODS: Five cell lines derived from HNSCC were subjected to a single course of radiation (400 cGy) in parallel with a similarly handled, untreated control. Cellular response to radiation was determined on posttreatment days 1, 2, 3, 4, and 5 using a cell viability assay (MTT assay). Radiation response was defined as 35% or greater decrease in cell survival relative to control. Tumor doubling time was determined by cell counts performed at day 0 and 1 for each cell line. All experiments were done in quadruplicate. CGH analysis was performed by differentially labeling DNA from tumor and normal tissue with fluorescent agents. The labeled DNAs were simultaneously hybridized to normal metaphase chromosomes. Image analysis for fluorescence intensity along the entire length of each metaphase chromosome allowed generation of a color ratio, which was used to detect copy number changes. RESULTS: Radioresistance was identified in two of five cell lines. The tumor doubling time was not a predictor of radiation response. CGH identified a complex pattern of aberrations, with gain of 3q common to all cell lines. The number of genetic aberration was higher in radiation-sensitive cell lines than in radiation-resistant ones. No recurrent aberrations were unique to the radiation-resistant cell lines. Recurrent gains at 7p and 17q and losses at 5q, 7q, and 18q were unique to the radiation-sensitive cell lines. CONCLUSIONS: The number of aberrations identified by CGH analysis may be a predictor of radiation response. A large study of primary tumors is warranted to confirm this association and identify specific genetic aberrations associated with radiation response.

Carcinoma, Squamous Cell↗
PubMed2000

Basaloid squamous cell carcinoma of the head and neck.

OBJECTIVE/HYPOTHESIS: Basaloid squamous cell carcinoma (BSCC), an uncommon tumor with predilection for the upper aerodigestive tract, is a distinct variant of squamous carcinoma, because of its unique histological features and ominous clinical behavior. This study reviews the experience in treating BSCC from two institutions. STUDY DESIGN: Retrospective. METHODS: H&E-stained sections from 20 patients with BSCC of the head and neck were reviewed and clinical follow-up was obtained for all patients. RESULTS: The study group consisted of 14 male and 6 female patients. Their ages ranged from 43 to 85 years, with a mean age of 62 years. Sites of origin included the larynx (4), tongue (3), pyriform sinus (3), nose (2), floor of mouth (2), mastoid (1), tonsil (1), epiglottis (1), nasopharynx (1), trachea (1), and palate (1). Pain was the most common presenting symptom (5 cases), followed by hoarseness and bleeding (3 cases each). Tobacco and alcohol abuse was noted in 17 patients. Treatment modalities included surgery with or without chemotherapy or radiotherapy in 13 patients, chemotherapy with irradiation in 2, chemotherapy alone in 2, and radiotherapy alone in 3. Clinical follow-up revealed no evidence of disease in 11 patients. Four were alive with disease at the time of writing and five died of disease. CONCLUSION: BSCC is a highly aggressive malignant tumor that presents in elderly patients who have a history of abuse of tobacco or alcohol, or both. Greater number of patients must be studied and compared with age-matched and stage-matched controls of conventional squamous cell carcinoma to determine whether the poor clinical outcome is related more to high-stage presentation or to the tumor's high-grade malignant cytological features.

Adult↗
PubMed2000

Reversible left ventricular dysfunction.

The extent and degree of myocardial viability are important parameters in the risk stratification of patients with significant left ventricular dysfunction secondary to coronary artery disease. Although several imaging modalities can identify viable myocardium, dobutamine stress echocardiography has gained considerable importance as an accurate, safe, and reliable method. In patients with significant left ventricular dysfunction secondary to coronary artery disease, identification of the presence and extent of contractile reserve and, therefore, viable myocardium during low-dose dobutamine infusion can predict the recovery of left ventricular function after revascularization, survival rate, and future cardiac events.

Contrast Media↗