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Biomedical subjects

B Singh

Publications and source records attributed to B Singh.

At least 595 records · Page 33Linked to original sources
PubMed1991

Nucleotide sequences of three different isoforms of beta-tubulin cDNA from Chinese hamster ovary cells.

The complete cDNA sequences of two clones encoding beta-tubulin isotypes and the partial sequence of a third isoform from Chinese hamster ovary cells have been determined. The deduced amino acid sequences of the three isoforms show extensive homology to each other as well as with other alpha and beta-tubulin sequences from various species. These results provide evidence for the expression of three different isoforms of beta-tubulin in Chinese hamster ovary cells.

Amino Acid Sequence↗
PubMed1991

T cells that recognize peptide sequences of self MHC class II molecules exist in syngeneic mice.

T cell reactivity toward self MHC class II molecules has been recognized in syngeneic MLR in a number of studies, where the T cells are believed to recognize the combination of self/nonself peptide and self MHC molecule. We investigated the stimulation of T cell proliferation by synthetic peptides of sequences corresponding to the first polymorphic amino terminal domain of alpha- and beta-chains of self I-A molecules. Both unprimed and primed T cells responded to a number of peptides of alpha 1 and beta 1 domains of self I-Ad molecules. The response was dependent on the presentation of I-Ad peptides by syngeneic APC and was blocked by anti-class II MHC mAb. Upon further investigation it was observed that I-Ad peptides could inhibit the stimulation of Ag-specific MHC class II-restricted T cell hybridoma due to self presentation of peptides rather than to direct binding of free peptides to the TCR, further supporting their affinity/interaction with intact self MHC class II molecules. The peptide I-A beta d 62-78 showed high affinity toward intact self MHC II molecule as determined by the inhibition of Ag-specific T cell stimulation and yet was nonstimulatory for syngeneic T cells, therefore representing an MHC determinant that may have induced self tolerance. Thus we have shown that strong T cell proliferative responses can be generated in normal mice against the peptides derived from self MHC class II molecules and these cells are part of the normal T cell repertoire. Therefore complete tolerance toward potentially powerful immunodominant but cryptic determinants of self Ag may not be necessary to prevent autoimmune diseases.

Amino Acid Sequence↗
PubMed1991

Ventricular arrhythmias in ischemic heart disease.

Ventricular arrhythmias remain the leading cause of death from coronary artery disease. This review summarizes current thinking in several areas relating to the pathophysiology, prognosis, and therapy of ventricular arrhythmias associated with acute and chronic coronary artery disease syndromes. The experimental basis of arrhythmias in the setting of acute myocardial ischemia and chronic myocardial infarction is described, stressing the important pathophysiologic differences between these two conditions. The effects of the autonomic nervous system as a key modulator of ischemic arrhythmogenesis are discussed. Insights, derived from endocardial mapping studies, into the nature of ventricular tachycardia in humans with chronic myocardial infarction are described, including implications for risk stratification and therapy to prevent arrhythmia recurrence. Current therapeutic principles are discussed in the management of ventricular arrhythmias associated with coronary artery disease, including pharmacologic approaches, surgical and catheter ablation, and automatic implantable cardioverting and defibrillating devices.

Acute Disease↗
PubMed1991

A T helper cell hybridoma produces an antigen-specific regulatory activity. Relationship to the T cell receptor by serology and antigenic fine specificity.

We have previously shown that a T cell hybridoma, A1.1, constitutively produces an Ag-specific regulatory factor with specificity for poly-18, a synthetic polypeptide. This cell also responds to poly-18 plus I-Ad by producing lymphokines. The antigenic specificity of the factor and the T cell appeared to be the same. This suggested the possibility that some part of the TCR, responsible for antigenic specificity of the cell, also imparts specificity to the A1.1-derived factor. This was supported by the observation that the factor was bound and eluted from a monospecific anti-TCR antiserum. Further, we demonstrated that antisense oligodeoxynucleotides corresponding to the TCR V alpha of A1.1 (but not TCR V beta) block production of the Ag-specific factor. Herein, we report recent findings that strengthen the proposed relationship between the TCR and the A1.1-derived factor. The factor was bound and eluted from a monoclonal anti-TCR C alpha antibody, but not from anti-TCR beta, anti-V beta 6, nor anti-CD3 epsilon. The anti-TCR C alpha antibody bound a Mr 46-kDa protein from A1.1 supernatants, which is the same apparent size at which activity could be eluted from an SDS-PAGE gel separation of concentrated factor. Antigenic fine-specificity analysis revealed that two amino acids in poly-18 are critical for the recognition of the antigen by the Ag-specific factor. These two amino acids appear to be those recognized by the TCR. The factor that was bound and eluted from the monoclonal anti-TCR C alpha showed this fine-specificity as well. This, combined with our earlier studies, supports the view that the A1.1-derived factor is encoded, at least in part, by TCR-alpha.

Amino Acid Sequence↗
PubMed1991

Rhinosporidium seeberi: light, phase contrast, fluorescent and scanning electron microscopic study.

Phase contrast microscopic study indicated the multilayered structure of the sporangial wall of R. seeberi while the scanning electronmicroscopic study revealed a trilaminated wall compared to a thick double walled light microscopic structure. The scanning electronmicroscopy revealed the spores of varying sizes which were found either discretely or in groups interconnected and seen attached to the inner aspect of the sporangial wall. Autofluorescence of sporangia and spores was observed under microscope. Acridine orange staining revealed the presence of DNA materials in the spore and sporangia.

Acridine Orange↗
PubMed1991

Peanut as a source of protein for human foods.

Peanut has traditionally been used as a source of oil; however, its worldwide annual protein harvest has reached nearly 4.5 million tons. India followed by China and the United States are the major producers of peanut. In recent years, several cereals and legumes-based foods using peanuts as protein supplements have been developed to alleviate protein calories-malnutrition problem. Peanut in the form of flour, protein isolates, and meal in a mixed product have been found to be very desirable from a sensory quality point of view. Peanut protein is deficient with respect to certain essential amino acids, but its true digestibility is comparable with that of animal protein. Even though various processing methods influence the nutritional and sensory quality of peanut fortified human foods available information on these aspects have been reviewed and summarised in this paper in order to optimize the utilization of peanut protein to increase protein value of cereal-based foods in developing countries of the peanut growing regions of the world.

Arachis↗
PubMed1991

Effect of dietary fat on diabetes-induced changes in liver microsomal fatty acid composition and glucose-6-phosphatase activity in rats.

Experimental diabetes may manifest itself in a defect in liver microsomal fatty acid desaturation and increased activity of glucose-6-phosphatase (G-6-Pase). The present study was designed to determine whether these changes could be normalized by a change in the dietary fat consumed. Control and streptozotocin-induced diabetic rats were fed nutritionally adequate diets which varied in fatty acid composition. Fatty acid analysis of liver microsomal phospholipids revealed that non-diabetic control animals fed saturated fat (beef tallow) or a diet high in omega 3 fatty acids (fish oil) exhibited a significantly higher level of 18:2 omega 6 and a lower level of 20:4 omega 6 in the phosphatidylcholine and phosphatidylethanolamine fractions compared with diabetic animals. Control and diabetic animals fed the high linoleic acid diet had similar levels of 18:2 omega 6 in the microsomal phosphatidylcholine and phosphatidylserine fractions. Microsomal G-6-Pase activity was higher in diabetic than in control animals. Activity of G-6-Pase was lower in microsomes of control animals fed the soybean oil or the fish oil diet, but was not significantly reduced in diabetic animals fed high polyunsaturated fats. Blood glucose levels were similar in control groups fed the different diets, but the plasma hemoglobin Alc level was lower in diabetic animals fed the soybean oil diet. Cholesterol and triglyceride levels were lower in diabetic animals fed the fish oil-based diet. The results suggest that dietary fat manipulation has the potential to change at least some of the abnormalities in the microsomal membrane in experimental diabetes.

Animals↗
PubMed1991

Antifertility activity of volatile fraction of neem oil.

NIM-76, the odorous and volatile fraction of neem oil, was investigated for its antifertility activity in vivo in rats, rabbits and rhesus monkeys. The drug is effective when applied before coitus but not so when applied during post-coital stages. It, therefore, appears to act mainly by its spermicidal effect. No alteration in the estradiol (E2) and progesterone (P) values was observed after the application of the drug in monkeys.

Animals↗
PubMed1991

Epitopes of human immunodeficiency virus type 1 (HIV-1) envelope glycoproteins recognized by antibodies in the sera of HIV-1-infected individuals.

Sera from human immunodeficiency virus (HIV)-infected study subjects and controls were analyzed by enzyme-linked immunosorbent assay using 10 synthetic peptides to identify epitopes of HIV envelope glycoproteins (ENVgp) that were recognized by antibodies. Two epitopes of HIV ENVgp, ENVP466 (amino acids 466-481) and ENVP497 (amino acids 497-509), were recognized by antibodies in the sera of most HIV-infected individuals. The frequency of individuals with detectable serum antibodies to these two epitopes was not associated with the stage of HIV disease. Purified antibodies to ENV497 had only very weak neutralizing activity against infectious HIV. These data suggest that a particular dominant type of antibody response to HIV's ENVgp has minimal protective effects. These and other studies to identify and stimulate immune responses to selected epitopes of HIV antigens may be useful in the design of vaccines to prevent or treat HIV infections.

Acquired Immunodeficiency Syndrome↗
PubMed1991

The effects of reprocessing cuprophane and polysulfone dialyzers on beta 2-microglobulin removal from hemodialysis patients.

To further define the relationship between dialyzer reuse and the removal of beta 2-microglobulin (beta 2M) during dialysis, 26 patients who received hemodialysis were studied. Thirteen patients were dialyzed with conventional cuprophane dialyzers, and thirteen patients were dialyzed with high-flux polysulfone dialyzers. Patients in each group were dialyzed with only new dialyzers during the primary-use phase of the study, and reprocessed dialyzers during the reuse phase. Dialyzers were used six times during the reuse phase. Serum beta 2M levels were measured both predialysis and postdialysis, and adjusted for fluid loss. Dialysis with conventional cuprophane new dialyzers during the primary-use phase of the study resulted in a 3.3% increase in serum beta 2M levels, and a 2.4% increase in serum beta 2M levels during the reuse phase. The difference in the change of the concentration of beta 2M between primary-use and reuse phases was not statistically significant. Dialysis with high-flux polysulfone new dialyzers during the primary-use phase was associated with a decrease of 59.5% in the mean postdialysis concentration of serum beta 2M compared with the predialysis level. A corresponding decrease of 62.6% in serum beta 2M levels was observed after dialysis with high-flux polysulfone reprocessed dialyzers during the reuse phase. These data show no evidence of an adverse effect on the clearance of beta 2M during dialysis from the reuse of dialyzers up to six times. The results confirm previous studies that have reported that high-flux dialysis with polysulfone dialyzers removes substantial amounts of beta 2M, and dialysis with conventional cuprophane dialyzers does not.

Adult↗
PubMed1991

Role of surgery in tuberculous mastoiditis.

A study was undertaken in 43 patients to determine the role of surgery in tuberculous mastoiditis. Cortical mastoidectomy was performed on five patients (Group I). Incision and drainage of a post-auricular abscess, removal of sequestrum and meatoplasty in eight (Group II). Thirty patients had no ear surgery (Group III). Of the 17 patients with facial palsy, three were in Group I, two in Group II, 12 in Group III. The patients in all three groups were treated with anti-tuberculous drugs for a period of no less than six months. The average time taken for the otorrhoea to subside and granulation tissue to resolve completely was two months in all three groups. The facial nerve recovery in the non-operated ears (Group III) was 92 per cent and in the operated ears (Group I and II) 80 per cent. The conclusion is that chemotherapy is the management of choice in tuberculous mastoiditis. The only role of surgery is incision and drainage of a post-auricular abscess and removal of sequestrum if present.

Adolescent↗
PubMed1991

A safer transnasal technique for the management of bilateral choanal atresia.

A study was undertaken on a 3.2 kilogram fresh stillborn neonate, to determine ways and means of preventing damage to the skull base. Gruber and Rosen aural specula were inserted separately into the right nostril, to determine the degree of exposure of the choana with each. The position of the surgeon was varied (septoplasty versus tonsillectomy position), to determine on which anatomical site of the choana the surgeon's field of vision was focused. The Gruber aural speculum, gave a completely, uninterrupted view of the choana. In the tonsillectomy position, the entire field of vision was focused on the choana itself, whilst in the septoplasty position, one half was focused on the choana and the other half on the roof. Since the roof is part of the skull base, damage to this area can result in serious intracranial complications, such as CSF leak and meningitis. These complications can be avoided if the surgeon uses the Gruber aural speculum for exposure and operates from a tonsillectomy position.

Cavernous Sinus↗
PubMed1991

Giant cell variant of malignant fibrous histiocytoma of the head and neck.

The giant cell variant of malignant fibrous histiocytoma is a rare entity in head and neck. Only eight well documented cases of this type are reported in the English literature. These tumours affect the superficial and deep structures of the neck most often and are best treated with prompt radical surgery. The prognosis of the giant cell type of malignant fibrous histiocytoma is dependent on the location of the tumour, with superficial tumours having a much better outlook.

Female↗
PubMed1991

Finite-element analysis of oxygen transport in the systemic capillaries.

A mathematical model is formulated for the transport of O2 in the systemic capillaries and surrounding tissue. The model takes into account molecular diffusion, the convective effect of the blood, the nonlinear effects of oxyhaemoglobin, and the consumption of O2 in the metabolic process. A finite-element formulation for solving the equations governing the mass transfer in the capillary is described. A fixed-point iterative technique is used to deal with the nonlinearities in the model. The concentration of O2 is found to decrease from the axis of the capillary to the periphery of the tissue. It is shown that, owing to the nonlinear effects of oxyhaemoglobin, the partial pressure of oxygen (PO2) in the capillary and tissue increases. It is also shown that the tissue PO2 increases as (i) the arterial blood PO2 increases, (ii) the Péclet number increases, and (iii) the diffusive flux of O2 from the capillary decreases.

Capillaries↗
PubMed1991

A mathematical model for the rate of oxygenation of blood in pulmonary capillaries using nth-order one-step kinetics of oxygen uptake by haemoglobin.

A mathematical model is described for the process of gas exchange in pulmonary capillaries by taking into account the transport mechanisms of molecular diffusion, convection, and the facilitated diffusion due to haemoglobin. The nth-order one-step kinetics of oxygen uptake by haemoglobin has been incorporated. The rate k at which blood becomes oxygenated is determined by setting up an appropriate eigenvalue problem. This method eventually leads to a transcendental equation in k. A multiprecision technique due to Verma and Sharan (1980) is employed to obtain a physically acceptable solution. It is shown that, at equilibrium, the saturation of haemoglobin with oxygen computed from the analysis is fairly close to the data of Severinghaus (1966). It was found that 97.15% of the total haemoglobin combined with oxygen. The blood is oxygenated well before it leaves the pulmonary capillary. The dissolved oxygen takes longer to achieve equilibration whereas the carbon dioxide traverses a comparatively smaller distance in the capillary.

Biological Transport↗
PubMed1991

A mycobacterial heat-shock protein-responsive gamma delta T cell clone also responds to the homologous human heat-shock protein: a possible link between infection and autoimmunity.

Prokaryotic and eukaryotic cells respond to a variety of stress conditions by increasing the synthesis of a family of proteins collectively known as heat-shock proteins (HSP). One of these, a 65-kDa HSP that is highly conserved in many bacteria, is a major target of the immune response to mycobacteria. A gamma delta T cell clone from a healthy donor that recognizes not only the 65-kDa mycobacterial HSP but also the recombinant human homologue of this HSP protein was raised. Like alpha beta T cell clones, which recognize mycobacterial HSP, the clone requires antigen-presenting cells for antigen-induced proliferation and can also be directly activated via receptor cross-linking through CD3 or the delta chain of the gamma delta T cell receptor. These data suggest that the induction of a gamma delta T cell response by bacterial antigens could lead to the expansion of cells that respond to autologous proteins and, therefore, may result in the development of autoimmunity.

Antigen-Presenting Cells↗