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Biomedical subjects

A Singh

Publications and source records attributed to A Singh.

At least 109 records · Page 6Linked to original sources
PubMed2001

Aspergillus nidulans alpha-1,3 glucanase (mutanase), mutA, is expressed during sexual development and mobilizes mutan.

We established a subtractive cDNA library of Aspergillus nidulans to identify differentially expressed genes during sexual development. One of the clones displayed homology to fungal alpha-1,3 glucanases (mutanase). Since alpha-1,3 glucan is considered the main reserve material accumulated during vegetative growth as a cell wall component and consumed during sexual development, we analyzed this gene in detail. The gene, mutA, is disrupted by three introns and encodes a putative protein of 48 kDa molecular mass with a signal peptide for secretion at the N terminus. The deduced protein displays amino acids 24-42% identical to mutanases of other fungi. A proposed mutan binding domain characterized in, e.g., Penicillium is not present in A. nidulans. Mutanase transcript and GFP reporter analysis in A. nidulans revealed specific induction of the gene during sexual development in Hülle cells. To study the role of mutA during sexual differentiation, we constructed a mutA deletion strain. Although degradation of mutan was affected in this strain, it was still able to form cleistothecia at a number similar to that of wildtype. These results suggest that additional carbon sources are available during sexual development.

Amino Acid Sequence↗
PubMed2001

The wings of Bombyx mori develop from larval discs exhibiting an early differentiated state: a preliminary report.

Lepidopteran insects present a complex organization of appendages which develop by various mechanisms. In the mulberry silkworm, Bombyx mori a pair of meso- and meta-thoracic discs located on either side in the larvae gives rise to the corresponding fore- and hind-wings of the adult. These discs do not experience massive cell rearrangements during metamorphosis and display the adult wing vein pattern. We have analysed wing development in B. mori by two approaches, viz., expression of patterning genes in larval wing discs, and regulatory capacities of larval discs following explantation or perturbation. Expression of Nubbin is seen all over the presumptive wing blade domains unlike in Drosophila, where it is confined to the hinge and the wing pouch. Excision of meso- and meta-thoracic discs during the larval stages resulted in emergence of adult moths lacking the corresponding wings without any loss of thoracic tissues suggesting independent origin of wing and thoracic primordia. The expression of wingless and distal-less along the dorsal/ventral margin in wing discs correlated well with their expression profile in adult Drosophila wings. Partially excised wing discs did not show in situ regeneration or duplication suggesting their early differentiation. The presence of adult wing vein patterns discernible in larval wing discs and the patterns of marker gene expression as well as the inability of these discs to regulate growth suggested that wing differentiation is achieved early in B. mori. The timings of morphogenetic events are different and the wing discs behave like presumptive wing buds opening out as wing blades in B. mori unlike evagination of only the pouch region as wing blades seen in Drosophila.

Animals↗
PubMed2001

Evaluation of the genetic variability of 13 microsatellite markers in native Indian pigs.

We analysed polymorphism of 13 microsatellites in two Indian domesticated pig types (North Indian and Northeast Indian). Heterozygosity, polymorphism information content, and probability of identity of two random individuals were calculated for all microsatellites in both types. The number of alleles observed at a locus varied between five and 12. The evaluated microsatellites exhibited a very high heterozygosity and polymorphism information content. The probability of identity of two random individuals from different populations taking into account all the 13 microsatellites was as low as 3.51 x 10(-19). On the basis of these results, we propose that these microsatellite markers may be used with reliability for studying the genetic diversity and for identification of individuals in Indian pig types.

Alleles↗
PubMed2001

Acute pulmonary edema as a complication of anti-snake venom therapy.

Polyvalent Anti-snake Venom (ASV) is a life-saving antivenin for severe envenomation due to snake bite in India. ASV infusion is occasionally associated with severe allergic reactions, i.e. anaphylaxis and death. We report a rare instance of non-cardiogenic pulmonary edema due to ASV infusion in an eleven years old boy.

Anaphylaxis↗
PubMed2001

Highly stable vesicles composed of a new chain-terminus acetylenic photopolymeric phospholipid.

Stability, ease of production, and storage convenience were addressed for polymerized vesicles composed of 1,2-bis(trideca-12-ynoyl)-sn-glycero-3-phosphocholine. The following vesicle properties were investigated before and after polymerization: size, shape, lamellarity, dispersity, degree of polymerization, membrane fluidity, and structural stability. A fairly monodisperse, unilamellar sub-micron vesicle suspension undergoes nearly complete polymerization of the chain-terminus acetylenic to polyacetylenic conversion as monitored by Fourier transform infrared spectroscopy. (1)H nuclear magnetic resonance spectroscopy and thin layer chromatography provide additional evidence for extensive lipid polymerization. Using differential scanning calorimetry, a gel/liquid transition was not observed for either polymerized or non-polymerized vesicles within the temperature range of 5-65 degrees C. These polymerized vesicles remained structurally stable and suspended for months at room temperature. However, vesicle size did decrease with increasing degree of polymerization. Polymerized vesicles remained spherical but decreased in size by 15% when subjected to 52 wt.% aqueous ethanol and did not change significantly in size and dispersity after a freeze-dry/resuspend cycle.

Alkynes↗
PubMed2001

Development and validation of a stability indicating HPLC assay method for cyclosporine in cyclosporine oral solution USP.

The suitability of the United States Pharmacopeia (USP) assay method for analysing stressed samples of cyclosporine oral solution USP was evaluated for stability samples by analyzing cyclosporine oral solution after acid, alkali, hydrogen peroxide, heat and light treatment. Some of the degradants generated during stress testing, as well as dihydrocyclosporine A, which is a known degradant of cyclosporine A, were not adequately resolved from the cyclosporine peak and mobile phase adjustments did not improve the resolution. In addition, isocyclosporine A, another known degradant of cyclosporine, could not be quantitated as it was eluting too early with the system peaks. Therefore, a binary gradient, reverse phase, stability indicating, HPLC method for the assay of cyclosporine in cyclosporine oral solution USP has been developed and validated. Analysis of degraded samples showed that the cyclosporine A eluted as a spectrally pure peak resolved from its degradation products.

Administration, Oral↗
PubMed2001

The ICH guidance in practice: stress degradation studies on ornidazole and development of a validated stability-indicating assay.

The present study describes degradation of ornidazole under different ICH prescribed stress conditions (hydrolysis, oxidation and photolysis), and establishment of a stability-indicating reversed-phase HPLC assay. Degradation was found to occur in alkaline medium, under high acidic conditions, under oxidative stress, and also in the presence of light in acid conditions. Previously the drug is only known to decompose under alkaline conditions. Separation of drug and the degradation products under various conditions was successfully achieved on a C-18 column utilising water-acetonitrile in the ratio of 86:14. The detection wavelength was 310 nm. The method was validated with respect to linearity, precision, accuracy, selectivity, specificity and ruggedness. The response was linear in the drug concentration range of 5-500 microg ml(-1). The mean values (+/-RSD) of slope, intercept and correlation coefficient were 45251 (+/-1.59), 104418 (+/-2.49) and 0.9996 (+/-0.03), respectively. The RSD values for intra- and inter-day precision studies were <1 and <2.6%, respectively. The recovery of the drug ranged between 100-103% from a mixture of degradation products. The method was specific to drug and also selective to degradation products.

Chromatography, High Pressure Liquid↗
PubMed2001

Biotransformations using plant cells, organ cultures and enzyme systems: current trends and future prospects.

Plants are valuable sources of a variety of chemicals including drugs, flavours, pigments and agrochemicals. Some of the biochemical reactions occurring in plant cells are complex and cannot be achieved by synthetic routes. In vitro plant cell and organ cultures and plant enzymes act as suitable biocatalysts to perform these complex reactions. A wide variety of chemical compounds including aromatics, steroids, alkaloids, coumarins and terpenoids can undergo biotransformations using plant cells, organ cultures and enzymes. The biocatalyst-mediated reactions are regiospecific and stereospecific. Reaction types include oxidations, reductions, hydroxylations, methylations, acetylations, isomerizations, glycosylations and esterfications. Genetic manipulation approaches to biotransformation offer great potential to express heterologous genes and to clone and overexpress genes for key enzymes. Biotransformation efficiencies can further be improved using molecular techniques involving site-directed mutagenesis and gene manipulation for substrate specificity.

Journal Article↗
PubMed2001

Peptide inhibition of cytokine-stimulated aromatase activity in breast tissue fibroblasts.

The cytokine interleukin-6 (IL-6) and its soluble receptor (IL-6sR) can act synergistically to stimulate aromatase activity in cultured stromal fibroblasts derived from breast tissues. In this study, a 16 amino acid peptide, AROHIB, has been used in an attempt to block the ability of IL-6 plus IL-6sR to stimulate aromatase activity in stromal fibroblasts. Pre-incubation of cells with AROHIB for a 3-h period before the addition of IL-6 and IL-6sR resulted in a marked (67%) reduction in the ability of these factors to stimulate aromatase activity. AROHIB was found to be rapidly degraded when exposed to MCF-7 breast cancer cells or fibroblasts. Analysis by FAB-MS was used to identify the site of peptide cleavage. Subsequently, a series of 10 amino acid peptides, DP1-DP4, were designed, synthesised and tested for their ability to resist proteolytic degradation and to inhibit IL-6 plus IL-6sR-stimulated aromatase activity. Peptide DP2, a modified version of the active fragment of AROHIB, had N-acetyl and C-amino terminal protection and an internal D-amino acid (instead of L form) at the site of proteolytic cleavage. Using cells cultured in the presence of 2% stripped foetal calf serum, peptide DP2 resulted in a 74% reduction in cytokine-stimulated aromatase activity. Under serum-free conditions, peptides DP1-DP3 showed modest inhibitory properties. Results from this study suggest that it may be possible to develop small peptides to inhibit cytokine-stimulated aromatase activity in a tissue-specific manner.

Amino Acid Sequence↗
PubMed2001

The effects of olanzapine on neurocognitive functioning in medication-refractory schizophrenia.

Neurocognitive deficits are an enduring characteristic of schizophrenia, and remain prominent in patients whose positive symptoms have decreased after treatment with typical neuroleptics. Recent research has reported that olanzapine improves cognitive functioning in relapsing schizophrenia followed in an outpatient setting. Whether olanzapine will have an effect on improving cognitive function in chronic schizophrenics who have been hospitalized for long periods of time, and have shown a poor response to other conventional and atypical neuroleptics, has not been established. This study investigated cognitive function in chronic medication refractory schizophrenics who were treated with olanzapine or haloperidol in a double-blind study for 8 wk, and followed in an open olanzapine study for several additional months. Patients were evaluated with psychopathology rating scales and a battery of neuropsychological tests at baseline, end of double-blind and end of open-label phases of the study. At the end of the double-blind phase there were no significant differences between olanzapine and haloperidol, except for a trend for improvement on the Wisconsin Card Sort Test on olanzapine, which was significant at traditional but not corrected significance levels. After an additional 3 months of treatment with olanzapine doses of 20-40 mg/d, our statistical analysis showed significant improvement on overall neuropsychological test performance and specific cognitive tasks assessing verbal memory. However, these open-label results are difficult to interpret definitively because of the lack of a comparison drug group and the olanzapine dose escalation over time. Neurocognitive changes were not correlated with changes in psychopathology as assessed by PANSS or SANS scores.

Antipsychotic Agents↗
PubMed2001

Studies on some blood parameters of crossbred calves with experimental Theileria annulata infections.

Subcutaneous inoculation of 1 ml of ground Theileria annulata tick tissue stabilate (0.75 tick equivalent) into crossbred calves (n = 6, average age 53 days) resulted in the development of acute theileriosis. The percentage parasitaemia was 71.7% +/- 3.3% on day 20 after inoculation. Macroschizonts were observed in lymphocytes and monocytes. Phagocytosed schizonts were observed in neutrophils, along with cytoplasmic vacuolation in monocytes and neutrophils. There was progressive decrease (p < 0.05) in the haemoglobin and packed cell volume, along with a marked reticulocytosis. Serum analysis revealed a decrease (p <0.05) in the concentrations of calcium, cholesterol and triglycerides, while there was an increase (p < 0.05) in the concentrations of blood urea nitrogen as compared to day 0 values. The total serum proteins, albumin and serum immunoglobulin concentrations and the albumin-to-immunoglobulin ratio showed marked decreases (p<0.05). Coagulopathies included thrombocytopenia and an increased prothrombin time, along with a non-significant increase in the bleeding time and activated partial thromboplastin time during the terminal stages of the disease. There was an increase in the osmotic fragility of erythrocytes during the disease. Morphological alterations in the erythrocytes were observed with the developing parasitaemia.

Animals↗
PubMed2001

Factors limiting the rate of living-related kidney donation to children in an inner city setting.

A recent review of our center experience revealed that only 38% of our pediatric renal transplants come from living-related donors (LRD), which is 11% lower than the national average. The present study was designed to identify factors that limit the availability of LRD in our population pool. Retrospective chart reviews and subsequent telephone interviews were conducted with parents of all children who received renal replacement therapy (RRT) at our institution from 1990 to 1999. The availability of parents and their willingness to donate a kidney were noted. Self-reported willingness was defined as the verbal expression of a desire to donate. Firm willingness was defined as the completion of the steps necessary for donation, unless excluded by the medical team. Factors that may impact the ability to donate, such as donor age, ethnicity, religion, educational attainment, employment, and presence of other siblings younger than 18 yr of age, were evaluated. Statistical analyses were performed using the Student's t-test and chi-square analysis. Significant results were entered into a single-step multiple regression analysis. Sixty children were identified with RRT, of whom 60% were Blacks, 30% Hispanics, 7% Caucasians, and 3% Asian. Fifty-five mothers were available for interview. Forty-four mothers reported a desire to donate, nine were unwilling to donate, and two were undecided. However, only 35 attended for screening. Only 30 fathers were available and, of these, 27 reported willingness to donate, yet only 20 attended for screening. Seventy-four per cent (26 out of 35) of mothers screened and 55% (11 out of 20) of fathers screened were medically unsuitable for kidney donation. Nineteen potential donors had hypertension, diabetes and/or obesity, seven had renal disease, four had anemia, two had hepatitis C, and five had other conditions. Expressed unwillingness to donate was associated with a greater number of children (3.1 compared to 1.5 children in addition to the child with end-stage renal disease [ESRD]) (odds ratio 2.91, p < 0.05) and employment (26.3% vs. 4.0%, p < 0.05) (odds ratio 31.2, p = 0.05). Comparing mothers who were firmly willing to donate with mothers who did not complete screening and evaluation, unwilling mothers had, likewise, a greater number of children (2.9 vs. 1.2 in addition to the child with ESRD) (odds ratio 3.23, p < 0.01) and a greater number of years of education (12.4 vs. 10.4) (odds ratio 2.14, p < 0.05). Hence, the availability of living kidney donors for our inner city children is severely limited by a high rate of single parenthood and a high rate of comorbid conditions in the parental donor pool. Furthermore, there is a diminished capacity of the available parent, particularly the mother, to donate as she tends to have numerous other dependents.

Black or African American↗
PubMed2001

Membranous lupus nephritis in a renal allograft: response to mycophenolate mofetil therapy.

Membranous lupus nephritis in a renal allograft is considered rare. A 43-year-old man with quiescent systemic lupus erythematosus (SLE) received a HLA identical transplant from his sister and 4 years later developed persistent nephrotic range proteinuria and morphological features most compatible with membranous lupus nephritis on biopsy. Angiotensin-converting enzyme (ACE) inhibitors and angiotensin II receptor antagonists, although successful in reducing proteinuria, were associated on three occasions with acute allograft dysfunction. Sustained reduction of proteinuria and stable graft function were achieved using mycophenolate mofetil (MMF). MMF is emerging as a new therapy for primary renal disease in SLE. This is the first report of successful treatment of membranous lupus nephritis in an allograft using MMF. We review all cases of transplant-associated membranous lupus nephritis in the English literature.

Adult↗
PubMed2001

Microbial treatment of a styrene-contaminated air stream in a biofilter with high elimination capacities.

A styrene-utilizing mixed microbial culture was isolated and utilized in a biofilter for the biological treatment of a contaminated air stream. Biofilter media consisted of composted wood bark and yard waste. The biofilters were acclimated at 120 s residence time and further evaluated at 60 and 30 s gas residence times. The biofilters received organic loading rates of up to 350 g/m(3) h. The styrene volumetric removal rate was a function of the organic loading rate and increased with increasing loading rates. Average volumetric removal rates of 69-118 g/m(3) h observed in our studies were higher than reported values for styrene biofilters. Average styrene removal efficiencies ranged from 65% to 75% (maximum 100%). Axial analysis of styrene concentration along the column indicated that the bulk of the styrene removal occurred in the first section of the biofilter. Analyses of the media indicated that the moisture content of the first section (50-55% w/w) was significantly lower than in the second and third sections (65-70% w/w). The pressure drops across the biofilter were low due to the high concentration of large media particles. The total pressure drops were 1-3, 4-6, and 10-16 mm for the 120-, 60-, and 30-s residence time periods, respectively.

Air↗
PubMed2001

Enzyme treatment to reduce solids and improve settling of sewage sludge.

The effect of microbial enzymes in reducing the disposable solid content of sludge was investigated. A mixture of industrial cellulase, protease, and lipase, in equal proportion by weight, reduced total suspended solids (TSS) by 30-50% and improved settling of solids. An increase in solid reduction was observed with increasing enzyme concentration. The effect of combinations of enzyme treatments indicated that two-enzyme combinations of protease and cellulase produced better solid reduction than individual enzymes and that lipase further augmented this effect. Among the individual enzymes, protease produced a more settleable sludge as compared to cellulase and lipase. Adjustment of the pH of the enzymatically treated sludge to the acidic range (pH 2-4) further improved solid reduction, and adjustment to the alkaline range (pH 10-12) improved settleability.

Biodegradation, Environmental↗