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Biomedical subjects

R Singh

Publications and source records attributed to R Singh.

At least 559 records · Page 31Linked to original sources
PubMed1989

Properties of Pyrophosphate:Fructose-6-Phosphate Phosphotransferase from Endosperm of Developing Wheat (Triticum aestivum L.) Grains.

Pyrophosphate:fructose-6-phosphate phosphotransferase (PFP, EC 2.7.1.90) from endosperm of developing wheat (Triticum aestivum L.) grains was purified to apparent homogeneity with about 52% recovery using ammonium sulfate fractionation, ion exchange chromatography on DEAE-cellulose and gel filtration through Sepharose-CL-6B. The purified enzyme, having a molecular weight of about 170,000, was a dimer with subunit molecular weights of 90,000 and 80,000, respectively. The enzyme exhibited maximum activity at pH 7.5 and was highly specific for pyrophosphate (PPi). None of the nucleoside mono-, di- or triphosphate could replace PPi as a source of energy and inorganic phosphate (Pi). Similarly, the enzyme was highly specific for fructose-6-phosphate. It had a requirement for Mg(2+) and exhibited hyperbolic kinetics with all substrates including Mg(2+). K(m) values as determined by Lineweaver-Burk plots were 322, 31, 139, and 129 micromolar, respectively, for fructose-6-phosphate, PPi, fructose-1,6-bisphosphate and Pi. Kinetic constants were determined in the presence of fructose-2,6-bisphosphate, which stimulated activity about 20-fold and increased the affinity of the enzyme for its substrates. Initial velocity studies indicated kinetic mechanism to be sequential. At saturating concentrations of fructose-2,6-bisphosphate (1 micromolar), Pi strongly inhibited PFP; the inhibition being mixed with respect to both fructose-6-phosphate and PPi, with K(i) values of 0.78 and 1.2 millimolar, respectively. The inhibition pattern further confirmed the mechanism to be sequential with random binding of the substrates. Probable role of PFP in endosperm of developing wheat grains (sink tissues) is discussed.

Journal Article↗
PubMed1989

Orcein-alcian blue staining: a new technique for demonstrating acid mucins in gastrointestinal epithelium.

Orcein-alcian blue staining, a new method for the simultaneous demonstration of sulphated and sialomucins in gastrointestinal epithelium was compared with the standard high iron diamine-alcian blue technique. Sections were oxidised with potassium permanganate and decolourised in oxalic acid. They were stained with orcein for four hours, differentiated for a few seconds in acid alcohol, and then counterstained with alcian blue for half to one minute. There was a good correlation of results between the two methods. Orcein-alcian blue is a safer, cheaper, and quicker method than high iron diamine-alcian blue which can be safely introduced into routine laboratories for the study of acid mucins in the gastrointestinal diseases.

Adenocarcinoma↗
PubMed1989

Cardiopulmonary fitness in a sample of Malaysian population.

Lung capacity and maximum oxygen uptake (VO2max) were measured directly in 167 healthy males, from all the main races in Malaysia. Their ages ranged from 13 to 59 years. They were divided into five age groups (A to E), ranging from the second to the sixth decade. Lung capacities were determined using a dry spirometer and VO2max was taken as the maximum rate of oxygen consumption during exhaustive exercise on a cycle ergometer. Mean forced vital capacity (FVC) was 3.3 +/- 0.5 l and it correlated negatively with age. Mean VO2max was 3.2 +/- 0.2 l.min-1 (56.8 +/- 3.5 ml.kg-1.min-1) in Group A (13-19 years) compared to 1.7 +/- 0.2 l.min-1 (28.9 +/- 2.9 ml.kg-1.min-1) in Group E (50-59 years). Regression analysis revealed an age-related decline in VO2max of 0.77 ml.kg-1.min-1.year-1. Multiple regression of the data gave the following equations for the prediction of an individual's VO2max: VO2max (l.min-1) = 1.99 + 0.035 (weight)-0.04 (age), VO2max (ml.kg-1.min-1) = 67.7-0.77 (age), where age is in years, weight in kg. In terms of VO2max as an index of cardiopulmonary performance. Malaysians have a relatively lower capacity when related to the Swedish norms or even to those of some Chilean workers. Malaysians were, however, within the average norms of the American Heart Association's recommendations. Age-related decline in VO2max was also somewhat higher in the Malaysians.

Adolescent↗
PubMed1989

Possible muscarinic supersensitivity in Alzheimer's disease.

In contrast to the well established presynaptic cholinergic deficits which are associated with Alzheimer's Disease (AD), the functional status of the remaining muscarinic receptors has not received adequate attention. This paper examined the possibility that the presynaptic cholinergic deficits in AD may be accompanied by muscarinic supersensitivity. While the majority of QNB binding studies have failed to find an upregulation of muscarinic receptors in AD patients, most of those studies did not differentiate between presynaptic and postsynaptic receptors. In addition, receptor density and functional response are not necessarily correlated. To determine whether AD is accompanied by alterations in the functional status of central muscarinic receptors, we studied the biological responses to a muscarinic agonist in AD patients and controls. In this pilot study, AD patients demonstrated an increased arecoline-induced HVA response in the CSF. This finding is consistent with the hypothesis that AD is accompanied by muscarinic supersensitivity.

Alzheimer Disease↗
PubMed1988

A case of carnitine palmitoyltransferase II deficiency in human skeletal muscle.

A 20-year-old man was shown to have a deficiency of carnitine palmitoyltransferase (CPT) II in skeletal muscle. The evidence was: (i) there was no significant oxidation of [9,10-3H]-palmitate or of [1-14C]palmitate in mitochondrial fractions from fresh skeletal muscle from the patient; (ii) all the CPT activity in a homogenate of fresh muscle from the patient was overt (CPT I) with no increase in activity after the inner membrane was disrupted; (iii) all the CPT activity in the patient's muscle was inhibited by malonyl-CoA; and (iv) an immunoreactive peptide of 67 kDa corresponding to CPT II, present in mitochondria from controls, was absent in those from the patient.

Acyltransferases↗
PubMed1988

Fetal antigen retained by mature neurons and ependyma studied with a monoclonal antibody (6B9).

A mouse monoclonal antibody (MAb 6B9, isotype IgM) was raised against autopsy tissue samples from the central nervous system (CNS) of multiple sclerosis (MS) patients. By immunofluorescence microscopy, MAb 6B9 intensely stains most or all cells in fetal rats. However, MAb 6B9 differentially stains various cell types in adult rats. Neurons, ependymal cells, and adrenal chromaffin cells are stained intensely, whereas astrocytes and oligodendrocytes are not stained. The 6B9-reactive antigen (6B9 antigen) is sensitive to periodic acid, but insensitive to treatment with protease, RNase, or hyaluronidase. Results from immunofluorescence microscopy on semithin sections and cultured neuroblastoma cells indicate that 6B9 antigen is intracellular. This is supported by immunoelectron microscopy, where labeling for 6B9 antigen appears in the cytoplasm distinct from any identifiable organelle. Further studies on 6B9 antigen should reveal its chemical nature as well as the significance of developmental changes in its distribution.

Animals↗
PubMed1988

Characterization of seed storage proteins of urdbean (Vigna mungo).

Dehulled and defatted flour of urdbean (Vigna mungo), Var T-9, contained 25% protein with maximum contribution by globulins (63%). Albumins and glutelins contributed 12% and 21% respectively, whereas prolamins were present only in traces (1%). Globulins were further fractionated into legumin and vicilin type proteins which were present in the ratio of 4:1. All the protein fractions were heterogenous in nature as revealed by high performance liquid chromatography. SDS-polyacrylamide gel electrophoresis revealed the total protein sample to contain 21 different components with molecular weights ranging from 8.92 to 117.49 kd. Albumins, globulins, prolamins and glutelins resolved into 4, 8, 6 and 13 different sized components of molecular weights ranging from 10.23 to 25.53, 10.84 to 112.72, 10.33 to 51.52 and 8.91 to 112.72 kd, respectively. Amino acid analysis of all fractions revealed that glutamic acid was present in maximum concentration followed by aspartic acid and lysine. Just like other pulse proteins, the urdbean proteins were also deficient in sulphur containing amino acids.

Albumins↗
PubMed1988

Nuclear acceptor sites for steroid hormone receptors: comparisons of steroids and antisteroids.

The respective chromatin binding sites (acceptor sites) for both the avian oviduct progesterone receptor (PR) and the rabbit uterine estrogen receptor (ER) reported by two separate laboratories are compared. Support for a saturable, high affinity binding to the chromatin acceptor sites by both receptors is described. Nonradiolabelled PR or ER compete with their homologous radiolabelled receptors for binding. However, there is no competition between the heterologous ER and PR for the nuclear binding sites. In both receptor systems, evidence for a receptor dependent, receptor specific binding, which mimics the binding measured in vivo, is reported. With both the PR and ER, evidence for extensive masking in chromatin of many of the acceptor sites is described. The PR and ER acceptor sites appear to be composed of specific acceptor proteins bound to DNA. The dissociation of these proteins from DNA causes a loss of specific binding. Reannealing of these same chromatin protein fractions, but not other protein fractions, back to the DNA reinstates the specific PR binding. Antibodies against the PR acceptors proteins are described. These antibodies block PR but not ER binding to the chromatin acceptor sites, supporting the steroid receptor specific acceptor sites. In the rabbit uterine system, the ER acceptor proteins dissociate from chromatin in three distinct fractions according to their affinity for the DNA. Each of these fractions contains acceptor activity in that each can be reannealed to the DNA to reconstitute specific ER binding sites, i.e. those which are saturable, high affinity, and receptor dependent. Interestingly, the antiestrogen receptor complexes do not bind to one fraction of acceptor proteins which does bind the native estrogen receptor complex. This ER acceptor protein fraction contains two regions of acceptor activity in the molecular mass range of 50,000 and 12,000 daltons. The latter species is in the size range of the PR acceptor proteins. This difference in binding to chromatin acceptor sites by the estrogen receptor, complexed with an estrogen or antiestrogen, may explain the differential regulation of gene expression and the differential biological response to antiestrogens compared to the native estrogens.

Animals↗
PubMed1988

Malignant myoepithelial carcinoma (myoepithelioma) arising in a pleomorphic adenoma of the parotid gland. An immunohistochemical study and review of the literature.

A 66-year-old woman presented with a giant tumor of the parotid gland, which under a light microscope had a sarcomatous appearance with spindle-shaped myoepithelial cells (malignant myoepithelioma). Histochemical examination showed longitudinal fibrils in the cytoplasm of the myoepithelial cells. Immunohistochemical studies showed positive staining for S-100 protein, vimentin, and actin in the myoepithelial cells. Cytokeratin was seen in the ductular epithelial cells and in the periductular myoepithelial cells, but it was absent from malignant myoepithelial cells. Ultrastructurally, these cells contained several longitudinally oriented slender structures resembling myofilaments without dense bodies. A review of the literature confirms the rarity of malignant myoepithelial carcinoma (myoepithelioma) arising in the parotid gland, and we therefore add another case.

Adenoma, Pleomorphic↗
PubMed1988

Age-related change in the multiple unit activity of the rat brain parietal cortex and the effect of centrophenoxine.

In this study, spontaneous multiple unit activity (MUA, action potentials derived simultaneously from a number of neurons in a given brain region) was recorded through electrodes chronically implanted in the parietal cerebral cortex of the rats of 1, 3, 6, 9, 12, and 26 months of age (cross-sectional study). Electrophysiological recordings were obtained from unrestrained conscious rats using standard techniques. The results indicated that multiple unit activity was decreased with aging (senescence). Maximum firing rate (MUA counts) was found at the age of 3 months. At 6 months of age, the MUA was decreased by about 30%, while during 6 to 12 months of age the activity seemed to remain unchanged. At 26 months of age the firing rate was, however, further decreased (about 40%). Centrophenoxine administration led to an increase in MUA in the rats of 12 and 26 months of age. The results, thus, further showed that centrophenoxine, a nootropic drug known for its antiaging effects in experimental animals as well as in humans, also manifested beneficial effects electrophysiologically. The data presented in this work are new and significant, since although age effects on gross electrophysiological signals (EEG, evoked potentials, etc.) are known, the aging changes in cellular level electrophysiological signals (action potentials) have not been generally studied particularly in conscious animals.

Aging↗
PubMed1988

Complications of a pressure sore of the chest wall: case report.

A female tetraplegic patient developed a pressure sore of the chest wall leading to an empyema of the lung and respiratory failure. The pressure sore resulted from the commonly practised habit of grasping the upright of the wheel chair with the upper arm in order to gain stability.

Adult↗
PubMed1988

Partial Purification and Characterization of NADP-Isocitrate Dehydrogenase from Immature Pod Walls of Chickpea (Cicer arietinum L.).

NADP(+)-isocitrate dehydrogenase (threo-DS-isocitrate: NADP(+) oxidoreductase [decarboxylating]; EC 1.1.1.42) (IDH) from pod walls of chickpea (Cicer arietinum L.) was purified 192-fold using ammonium sulfate fractionation, ion exchange chromatography on DEAE-Sephadex A-50, and gel filtration through Sephadex G-200. The purified enzyme, having a molecular weight of about 126,000, exhibited a broad pH optima from 8.0 to 8.6. It was quite stable at 4 degrees C and had an absolute requirement for a divalent cation, either Mg(2+) or Mn(2+), for its activity. Typical hyperbolic kinetics was obtained with increasing concentrations of NADP(+), dl-isocitrate, Mn(2+), and Mg(2+). Their K(m) values were 15, 110, 15, and 192 micromolar, respectively. The enzyme activity was inhibited by sulfhydryl reagents. Various amino acids, amides, organic acids, nucleotides, each at a concentration of 5 millimolar, had no effect on the activity of the enzyme. The activity was not influenced by adenylate energy charge but decreased linearly with increasing ratio of NADPH to NADP(+). Initial velocity studies indicated kinetic mechanism to be sequential. NADPH inhibited the forward reaction competitively with respect to NADP(+) at fixed saturating concentration of isocitrate, whereas 2-oxoglutarate inhibited the enzyme noncompetitively at saturating concentrations of both NADP(+) and isocitrate, indicating the reaction mechanism to be random sequential. Results suggest that the activity of NADP(+)-IDH in situ is likely to be controlled by intracellular NADPH to NADP(+) ratio as well as by the concentration of various substrates and products.

Journal Article↗