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Biomedical subjects

B Singh

Publications and source records attributed to B Singh.

At least 703 records · Page 39Linked to original sources
PubMed1987

Protein precipitation assay for quantitation of tannins: determination of protein in tannin-protein complex.

A protein precipitation method for the determination of tannins has been developed. The protein in the tannin-protein complexes was measured using the ninhydrin assay of amino acids released by alkaline hydrolysis of the complex. Standard protein and the complex were hydrolyzed with 13.5 N NaOH at 120 degrees C for 20 min and the amino acids released were measured with ninhydrin. Tannins did not interfere in the determination of protein by ninhydrin assay. The bovine serum albumin (BSA) precipitated (y; mg) increased linearly with increase in tannic acid (x) from 0.2 to 0.9 mg (y = 2.598x - 0.258). The protein precipitation capacities (mg BSA precipitated/g dry wt) measured by the method for young and mature leaves of oaks were Quercus incana (young, 42.21; mature, 79.51), Q. ilex (young, 1.86; mature, 1.86), and Q. semecarpifolia (young, 733.54; mature, 304.32). The method can provide valuable information on the mechanisms of protein-tannin interactions and nutritional and physiological significances of tannins.

Animals↗
PubMed1987

Functionally distinct agretopic and epitopic sites. Analysis of the dominant T cell determinant of moth and pigeon cytochromes c with the use of synthetic peptide antigens.

The dominant T cell determinant on moth and pigeon cytochromes c in B10.A (E beta k:E alpha k) mice is located in the C-terminal portion of the protein, contained within residues 93-103 or 93-104. Thirty-seven antigen analogs, containing single amino acid substitutions at positions 98, 99, 101, 102, 103, and 104, were synthesized. The effects of the substitutions on in vitro antigenicity and in vivo immunogenicity were determined. Functional assays with T cell clones identified residues 99, 101, 102, and 103 as critical, based on their effect on antigenic potency. Peptides containing substitutions at residues 99, 101, and 102 were capable of eliciting unique clones upon immunization of B10.A mice. This was consistent with the identification of these residues as part of the epitope, the site on the antigen that interacts with the T cell receptor. Immunization with peptides substituted at residue 103, however, failed to elicit clones with unique specificity for the immunogen. When these peptides were tested for their ability to stimulate the T cell clones with antigen-presenting cells from B10.A(5R) mice expressing the E beta b:E alpha k Ia molecule, a consistent change in the relative antigenic potency was observed with 50% of the peptides. The effect of the Ia molecule on the antigenic potency ruled out the possibility that residue 103 nonspecifically affected antigen uptake or processing and identified residue 103 as part of the agretope, the site that interacts with the Ia molecule. The locations of the agretope and the epitope on this antigenic determinant appear to be fixed, even in the presence of large numbers of amino acid substitutions. However, some substitutions were found to affect both the agretope and the epitope, placing limits on the functional independence of the two sites. The results are discussed in terms of the trimolecular complex model of T cell activation and the implications of these data for antigen-Ia molecule interactions.

Amino Acid Sequence↗
PubMed1987

Esmolol: a titratable short-acting intravenous beta blocker for acute critical care settings.

Esmolol (Brevibloc) is an intravenous, short-acting, titratable, cardioselective beta blocker with a very rapid onset and offset of action (t1/2 = 9.2 minutes). Esmolol-induced beta blockade can be maintained as long as infusion is continued. It exhibits neither intrinsic sympathomimetic activity nor significant membrane-stabilizing activity. It is rapidly metabolized by an esterase in the erythrocyte cytosol to an inactive acid metabolite. Its hemodynamic and electrophysiologic effects are similar to those of other beta blockers. Unlike the effects of other beta blockers, however, the effects of esmolol dissipate rapidly to baseline within 30 minutes after its discontinuation. Evidence obtained from clinical studies indicates that esmolol is effective and safe in reducing the ventricular rate in patients with supraventricular tachyarrhythmias, and in reducing the heart rate in patients with acute myocardial infarction and/or unstable angina. Esmolol has also been shown to be effective and safe in attenuating the tachycardia and hypertension seen during the intraoperative period. Data from postoperative patients indicate that esmolol is ideal as sole-agent therapy for the treatment of moderate postoperative hypertension associated with a hyperdynamic state. The short duration of action and titratability of esmolol make it an ideal drug for use in patients in whom the clinical need for beta blockade is limited in duration, and it offers additional safety in patients in whom beta blockade is beneficial; however, it might be precluded because of coexisting contraindications. To date, experience with esmolol in over 1200 patients has been gathered, and the adverse effect profile is basically similar to that reported here.

Adrenergic beta-Antagonists↗
PubMed1987

Effect of undernutrition on developing rat cerebellum. Some electrophysiological and neuromorphological correlates.

Electrophysiological studies of Purkinje cells from the developing normal and undernourished rat cerebellar cortex were correlated with the neuromorphological studies. In undernourished animals the firing pattern of Purkinje cells was simpler as compared to complex electrical activity in normal animals. The firing frequency of Purkinje cells remained reduced in all the age-matched undernourished groups. The duration of a spike was also prolonged as compared to their normal age mates. Similarly the mean amplitude was also relatively smaller in the undernourished animals when compared with the normal litter mates. Undernourished animals exhibited typical increased stimulus thresholds, prolonged N-2 peak wave latencies, reduced number of functional components, amplitude and increased duration of mossy fiber response (MFR). The mossy fiber (MF) activity exhibited a sluggish rise in its amplitude, when stimulus intensity was increased in undernourished animals. A phenomenon of fatigue was observed with a significant reduction in the amplitude and frequency of Purkinje cell unit discharge on repeated MF stimulation in the undernourished animals. However, repeated MF stimulation provided a high frequency discharge in the normal as well as undernourished adult rats. Neuromorphological studies at light-microscopic level exhibited delayed cell migration from the external granular layer in the undernourished rats. At electron-microscopic level, intracellular morphology exhibited almost similar ultrastructural details except for a few minor alterations. A free ribosomal pool, immature development of E.R., increased incidence of lysosomes and electron-dense membrane stacks were observed in the Purkinje cells at 30 days in the undernourished animals. The results of the present study indicated that undernutrition affects the maturation of Purkinje cell regional neurocircuitry.

Action Potentials↗
PubMed1987

Amino-sugars inhibit the in vitro cytoadherence of Plasmodium falciparum-infected erythrocytes to melanoma cells.

Twenty-two sugars and related compounds, nine neoglycoproteins, dopamine, four polyamines and oligomers of glucosamine were examined for their effect on the cytoadherence of Plasmodium falciparum-infected erythrocytes to melanoma cells. Inhibition of cytoadherence was high in the presence of the amino-sugars, glucosamine, galactosamine and mannosamine, and dopamine, and significant, although lower, in the presence of the polyamines, spermine, spermidine and putrescine. N-acetylated amino-sugars and the other compounds were not significant inhibitors of cytoadherence.

Amino Sugars↗
PubMed1987

Influence of rostral and caudal brain stem reticular formation on thalamic neurons.

Single neuronal activity was recorded from the diffuse thalamic system. Influence of the rostral desynchronizing and caudal synchronizing structures of the brain stem reticular formation on these neurons was studied. Rostral stimulation produced an increase and caudal stimulation a decrease in the thalamic unit firing. A possible mechanism by which the brain stem reticular structures influence the cortical neurons is proposed on the basis of these findings.

Animals↗
PubMed1987

Anti-inflammatory studies on Polygonum glabrum.

Anti-inflammatory studies were conducted on a hot water decoction and on an ethanol extract of the stems of Polygonum glabrum. Effective anti-inflammatory activity was demonstrated against acute carrageenan-induced paw oedema, exudate and granuloma formation in the granuloma pouch test, acute and delayed reactions in formaldehyde arthritis, and acute primary and delayed secondary reactions in adjuvant-induced polyarthritis in albino rats. The acute toxicity in albino mice and 1-month studies on subacute toxicity in rats suggested a good margin of safety. The extract was more effective parenterally than by oral administration.

Animals↗
PubMed1987

The nonsuppressibility of plasma cortisol persists after pregnancy.

To determine if normal balance is restored to the hypothalamic-pituitary-adrenal axis after pregnancy, we compared the dexamethasone suppressibility of plasma cortisol in women four days after delivery of their infant, with that of nonpregnant women. Plasma concentrations of cortisol before dexamethasone administration were similar in the post-partum women and in women taking oestrogen contraceptives, but both were higher than in normally cycling women. After dexamethasone, plasma cortisol in the post-partum women was significantly higher than in both oestrogen-taking and normally cycling nonpregnant women. The reduced dexamethasone-suppressibility of plasma cortisol, which is characteristic of pregnancy, extends into the post-partum period.

Contraceptives, Oral↗
PubMed1987

Etoposide (VP16) and teniposide (VM26): novel anticancer drugs, strongly mutagenic in mammalian but not prokaryotic test systems.

The mutagenic effect of the antineoplastic drugs VP16 (etoposide; 4'-demethylepipodophyllotoxin-ethylidene-beta-D-glucopyranoside) and VM26 (teniposide; 4'-demethylepipodophyllotoxin-thenylidene-beta-D-glucopyr ano side) in mammalian and prokaryotic test systems have been compared. Both VP16 and VM26 which interact with mammalian DNA topoisomerase II, are strongly mutagenic in Chinese hamster ovary cells as indicated by the induction of mutations at the hypoxanthine-guanine phosphoribosyl transferase and adenosine kinase loci, and production of DNA strand breaks and sister-chromatid exchanges. Mouse L cells treated with these drugs also show a large dose-dependent (0.05-0.2 microgram/ml for VM26 and 0.5-1.5 micrograms/ml for VP16) increase in the frequency of 6-thioguanine-resistant mutants and extensive fragmentation of cellular DNA. In contrast to the results obtained with mammalian cells, VP16, which was extensively investigated, showed no increase in revertant frequencies in the Salmonella typhimurium strains TA98 and TA100 at concentrations up to greater than 500 micrograms/plate, in either the absence or presence of an exogenous rat liver activation system. However, a very weak mutagenic response to VP16 and VM26 (less than 2-fold increase in revertant frequency) at very high drug concentrations was observed in the strain TA102. VP16 also failed to show any mutagenic response (up to greater than 500 micrograms/ml) in an excision repair-proficient Escherichia coli strain 113/143 employing two different forward mutation detection systems [viz. ability to grow in galactose (Gal+) or in presence of 5-methyltryptophan], which are capable of detecting various types of genetic lesions.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

The P55 protein affected by v-mos expression is vimentin.

Rabbit antiserum prepared against a cyclic 19-amino-acid peptide predicted from the sequence of the viral mos gene (v-mos) of Moloney murine sarcoma virus not only recognized v-mos gene products but also specifically detected a 55,000-Mr polypeptide expressed in a variety of cells that grow on solid surfaces. This normal cellular protein, previously shown to be reduced in amount in cells expressing the v-mos gene, was found to be the intermediate filament structural protein, vimentin. This conclusion was reached by comparing relative mobilities in denaturing gels, isoelectric points, immunoreactivities, location in the cell, and peptide maps.

Animals↗
PubMed1987

Central nervous system dysfunction and erythrocyte guanosine triphosphate depletion in purine nucleoside phosphorylase deficiency.

Developmental retardation was a prominent clinical feature in six infants from three kindreds deficient in the enzyme purine nucleoside phosphorylase (PNP) and was present before development of T cell immunodeficiency. Guanosine triphosphate (GTP) depletion was noted in the erythrocytes of all surviving homozygotes and was of equivalent magnitude to that found in the Lesch-Nyhan syndrome (complete hypoxanthine-guanine phosphoribosyltransferase (HGPRT) deficiency). The similarity between the neurological complications in both disorders indicates that the two major clinical consequences of complete PNP deficiency have differing aetiologies: neurological effects resulting from deficiency of the PNP enzyme products, which are the substrates for HGPRT, leading to functional deficiency of this enzyme. immunodeficiency caused by accumulation of the PNP enzyme substrates, one of which, deoxyguanosine, is toxic to T cells. These studies show the need to consider PNP deficiency (suggested by the finding of hypouricaemia) in patients with neurological dysfunction, as well as in T cell immunodeficiency. They suggest an important role for GTP in normal central nervous system function.

Central Nervous System↗
PubMed1987

Minor psychiatric morbidity in a casualty population: identification, attempted intervention and six-month follow-up.

The prevalence of minor psychiatric morbidity (MPM) was investigated in 523 adults presenting to the casualty section of an Australian public hospital. Relationships between subject characteristics and the level of MPM were also examined, together with the acceptability of an offer of short-term intervention and the effectiveness of this intervention in reducing distress. Threshold morbidity on initial presentation to casualty was 41% (using the GHQ-12 with the customary 1/2 cut-off point) and the probable prevalence was estimated to be about 27%. The intervention was initially offered to a random sample of those identified as being 'under stress' (GHQ of three or above), but as there was a 90% rejection rate, it was offered to all symptomatic subjects. Overall, 26% accepted our offer of intervention. Those who accepted intervention and those who rejected it did not differ in their improvement in MPM during the subsequent six months. However, these groups improved slightly more than the group that was eligible for intervention but to whom it was not offered. Forty-seven per cent of subjects who were 'under stress' on initial presentation to casualty fell below the GHQ-12 threshold at the six-month follow-up; this compared with a shift of only 26% in the opposite direction (i.e., non-stressed to stressed). Regression to the mean offered the most parsimonious explanation for these GHQ changes.

Adult↗
PubMed1987

Kinetics of urea hydrolysis and binding of ammonia to wheat straw during ammoniation by urea.

Chaffed wheat straw treated with urea (5% wt/wt) alone or with rumen liquor, a source of urease (EC 3.5.1.5), was stored in polythene bags at 4, 22, and 37 degrees C up to 60 d. Moisture concentration was adjusted to 40%. Urea remaining in the straw and ammonia concentrations in the bags were measured on 2, 4, 8, 12, 16, 25, 40 and 60 d. Urea hydrolysis increased exponentially with time. Hydrolysis of urea was highest at 22 degrees C followed by 37 and 4 degrees C. Addition of rumen liquor substantially increased rate of urea hydrolysis at all temperatures studied, suggesting that treatment time can be reduced by addition of rumen liquor. Rates of ammonia binding at different temperatures were in the order 22 degrees C greater than 37 degrees C greater than 4 degrees C. No hydrolysis of urea was observed up to 7 d of storage at 22 and 37 degrees C when straw was autoclaved and the treatment was carried out under aseptic conditions.

Ammonia↗