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Biomedical subjects

R N Singh

Publications and source records attributed to R N Singh.

At least 37 records · Page 2Linked to original sources
PubMed1996

Human growth hormone deletion mutant (hGH44-191) binds with high affinity to lactogenic receptors but not to somatogenic receptors.

The carboxyl-terminal hGH fragment, hGH44-191, displays diabetogenic activity. To understand whether this biological activity is mediated through somatogenic or lactogenic receptors, we investigated the ability of hGH44-191 to bind both receptor classes. We found that hGH44-191 could not compete with [125I]hGH or [125I]bGH for bovine liver somatogenic binding sites. Additionally, hGH44-191 could not displace [125I]hGH from the somatogenic receptor sites when human liver microsomes were used as the receptor source. In contrast, hGH44-191 effectively competed with [125I]hGH for lactogenic receptor sites of lactating mammary gland microsomes and of bovine liver microsomes. In summary, hGH44-191 does not bind to somatogenic receptors but does not bind to lactogenic receptors. These data suggest that the biological actions of hGH44-191 could be mediated through lactogenic receptors.

Animals↗
PubMed1995

Fine structure and primary sensory projections of sensilla located in the sacculus of the antenna of Drosophila melanogaster.

Sensilla lining the inner walls of the sacculus on the third antennal segment of Drosophila melanogaster were studied by light and transmission electron microscopy. The sacculus consists of three chambers: I, II and III. Inside each chamber morphologically distinct groups of sensilla having inflexible sockets were observed. Chamber I contains no-pore sensilla basiconica (np-SB). The lumen of all np-SB are innervated by two neurons, both resembling hygroreceptors. However, a few np-SB contain one additional neuron, presumed to be thermoreceptive. Chamber II houses no-pore sensilla coeloconica (np-SC). All np-SC are innervated by three neurons. The outer dendritic segments of two of these neurons fit tightly to the wall of the lumen and resemble hygroreceptor neurons. A third, more electron-dense sensory neuron, terminates at the base of the sensillum and resembles a thermoreceptor cell. Chamber III of the sacculus is divided into ventral and dorsal compartments, each housing morphologically distinct grooved sensilla (GS). The ventral compartment contains thick GS1, and the dorsal compartment has slender sensilla GS2. Ultrastructurally, both GS1 and GS2 are double-walled sensilla with a longitudinal slit-channel system and are innervated by two neurons. The dendritic outer segment of one of the two neurons innervates the lumen of the GS and branches. On morphological criteria, we infer this neuron to be olfactory. The other sensory neuron is probably thermoreceptive. Thus, the sacculus in Drosophila has sensilla that are predominantly involved in hygroreception, thermoreception, and olfaction. We have traced the sensory projections of the neurons innervating the sacculus sensilla of chamber III using cobaltous lysine or ethanolic cobalt (II) chloride. The fibres project to the antennal lobes, and at least four glomeruli (VM3, DA3 and DL2-3) are projection areas of sensory neurons from these sensilla. Glomerulus DL2 is a common target for the afferent fibres of the surface sensilla coeloconica and GS, whereas the VM3, DA3 and DL3 glomeruli receive sensory fibres only from the GS.

Animals↗
PubMed1995

Transglutaminase-catalyzed reaction is important for molting of Onchocerca volvulus third-stage larvae.

Highly insoluble proteins, which are probably cross-linked, are common in the cuticle and epicuticle of filarial parasites and other nematode species. We have investigated the possible involvement of transglutaminase (TGase)-catalyzed reactions in the development of Onchocerca volvulus fourth-stage larvae (L4) by testing the effects of TGase inhibitors on the survival of third-stage larvae (L3) and the molting of L3 to L4 in vitro. The larvae were cultured in the presence of three specific TGase inhibitors: monodansylcadaverine, cystamine, and N-benzyloxycarbonyl-D,L-beta-(3-bromo-4,5-dihydroisoxazol-5-yl)-al anine benzylamide. None of the inhibitors reduced the viability of either L3 or L4. However, the inhibitors reduced, in a time- and dose-dependent manner, the number of L3 that molted to L4 in vitro. Molting was completely inhibited in the presence of 100 to 200 microM inhibitors. Ultrastructural examination of L3 that did not molt in the presence of monodansylcadaverine or cystamine indicated that the new L4 cuticle was synthesized, but there was an incomplete separation between the L3 cuticle and the L4 epicuticle. The product of the TGase-catalyzed reaction was localized in molting L3 to cuticle regions where the separation between the old and new cuticles occurs and in the amphids of L3 by a monoclonal antibody that reacts specifically with the isopeptide epsilon-(gamma-glutamyl)lysine. These studies suggest that molting and successful development of L4 also depends on TGase-catalyzed reactions.

Animals↗
PubMed1995

Normal parameters of ventricular system in healthy infants.

Six hundred healthy inborn newborns and infants upto the age of 18 months were studied. Cranial sonography was performed by real time 2D scanner with 5 MHz transducer and images were obtained through anterior fontanelle and temporo-squamal suture. Various parameters related to ventricular system were measured for different ages till the fontanelle remained open. These values will prove useful for diagnosing hydrocephalus at an early stage of the disease and also to find out the blocks at various levels in ventricular system.

Age Factors↗
PubMed1994

Neuroarchitecture of the tritocerebrum of Drosophila melanogaster.

The organisation of the tritocerebrum of Drosophila melanogaster was studied by Bodian-Protargol reduced silver staining, Golgi-silver impregnation, horseradish peroxidase (HRP), and cobalt-chloride labelling of neurones and transmission electron microscopy. Nerve fibres of six categories were found to project to the tritocerebrum. (1 and 2) The sensory fibres from the internal mouthpart sensilla known to course along pharyngeal and accessory pharyngeal nerves were found to project in mainly two tiers, in the tritocerebrum. (3) Stomodaeal nerve fibres also project along the pharyngeal nerve, to the tritocerebrum. (4) Cells of the pars intercerebralis (PI) project along the median bundle and arborise in the tritocerebrum. HRP labelling and subsequent examination by transmission electron microscopy indicated their neurosecretory nature. (5 and 6) Two tracts of ascending fibres, designated as dorsal and ventral ascending tracts, were found to project to the tritocerebrum. Some of the sensory fibres from the labial nerve extend close to the sensory projections of the tritocerebrum, suggesting a possible convergence of the two sensory inputs. In the tritocerebrum, the sensory input, the stomodaeal input, the neurosecretory fibres of PI, and the ascending fibres were found to have overlapping fields, suggesting mutual interaction. The medial subesophageal ganglion and the tritocerebrum may interact through the ventral ascending tract.

Afferent Pathways↗
PubMed1994

Purification and characterization of a novel transglutaminase from filarial nematode Brugia malayi.

A transglutaminase (pTGase) was purified from filarial nematode, Brugia malayi. The steps used for purification were thermoprecipitation, ammonium sulfate precipitation, gel filtration on Superose 12 HR 10/30, ion-exchange chromatography on a Mono-Q column and further gel filtration on Superose 12 HR 10/30. The last step yielded an electrophoretically homogenous enzyme protein with 2200-fold purification and a reproducible yield of approximately 20%. The purified enzyme had a molecular mass of 56 kDa, specific activity of 2.25 U/mg protein and an isoelectric point of 7.2. The enzyme was active in the basic pH range with an optimum activity at pH 8.5. The pTGase activity was Ca(2+)-dependent and was inhibited by ammonia, primary amines, EDTA, and -SH group blocking reagents. The enzyme activity was also inhibited by high salt (NaCl and KCl) concentrations, detergents, metal ions, and organic solvents. Ampholine (pH 6-8) at 1% (by vol.) caused about 20% inhibition of pTGase activity but at 3% (by vol.) the inhibition increased up to 80%. Similarly, the micromolar concentrations of GTP inhibited the enzyme activity only moderately but at millimolar concentration a significant inhibition was observed. The stability of the pTGase was not affected by 0.1% SDS or other physical parameters such as freezing and thawing. Further, the pTGase was found to be highly thermostable (stable at 60 degrees C for several hours) with optimum activity observed at 55 degrees C. The distinct substrate specificity, unique N-terminal sequence along with the other physico-chemical properties studied, suggested that pTGase is a novel member of transglutaminase family.

Animals↗
PubMed1994

Lower anion gap increases sensitivity in predicting elevated lactate.

OBJECTIVE: The normal reference range for the anion gap (AG) has recently been questioned by several authors. Lowering the upper limit of normal of the AG has been found to be more sensitive in predicting elevated lactate in critically ill adults. The objectives of this study are i) to define a new upper limit of normal of the AG in a study population of healthy adult volunteers, ii) to determine the sensitivity, specificity, the positive predictive value and the negative predictive value of the new upper limit for AG in detecting elevated lactate in critically ill children and to compare these results to the old upper limit of normal of AG (16 mmol/l), iii) to construct a receiver-operating-characteristic (ROC) curve for anion gap as a predictor of elevated lactate, iv) to determine the relationship between anion gap and serum lactate levels in critically ill patients. DESIGN: A prospective, cohort study. SETTING: Paediatric Intensive Care Unit of a University Hospital. SUBJECTS: Part I: Convenience sample of healthy adult volunteers to provide a reference range for anion gap calculation. Part II: Consecutive children admitted to the Paediatric Intensive Care Unit who had lactate levels measured for clinical reasons. MEASUREMENTS: Part I: Electrolytes and blood gases were measured from blood samples drawn from 25 adult volunteers. The reference range for AG was calculated using the equation, AG = Na - (Cl + HCO3). The upper limit of normal was calculated as mean + 2 SD. Part II: Eligible ICU patients were included in this study if they had lactate, electrolytes and blood gases obtained simultaneously. The AG was calculated as above. The new upper limit of normal AG was compared to an AG of 16 for diagnosing an elevated plasma lactate. RESULTS: The mean anion gap in the normal population was 9.4 +/- 1 mmol/l with 11 mmol/l being used as the new upper limit of normal. Thirty-six ICU patients had 189 arterial blood samples from which lactate, electrolytes and blood gas were measured simultaneously. The sensitivity, specificity, positive predictive value and negative predictive value of using an AG of 11 mmol/l as the upper limit of normal were 86%, 40%, 65% and 69% respectively, compared to 49%, 84%, 80% and 55% respectively using the upper limit of normal of AG of 16 mmol/l. The ROC curve supported lowering the upper limit of normal for the anion gap to predict an elevated lactate. There was a linear relationship between anion gap and serum lactate levels. CONCLUSIONS: An AG of 11 mmol/l as the upper limit of normal has a higher sensitivity and higher negative predictive value but lower specificity and lower positive predictive value for detecting elevated lactate in critically ill children.

Acid-Base Equilibrium↗
PubMed1994

Isolation and characterization of a complex forming hydrophilic endoglucanase of Clostridium thermocellum.

An endoglucanase (EG5) of Clostridium thermocellum was purified to the homogeneity from the recombinant strains of Escherichia coli. The elution pattern of EG5 on gel filtration column showed the Mr of 100 kDa. However, the SDS-PAGE of the same protein showed the Mr of 35 kDa. This indicates the formation of a soluble trimeric complex by EG5 in non-denaturing conditions. The complex was found to be stable in 100 mM Na-taurocholate or 0.1% (w/v) Nonidet P-40. The hydrophilic nature of EG5 was confirmed by its unretarded elution at high salt concentrations from gel filtration columns. pI of EG5 was determined as 4.75. The EG5 was shown to possess high thermostability (stable at 65 degrees C for several days) and a broad pH range of activity from 5.5 to 7.5. The EG5 was capable of degrading a variety of soluble cellulosic substrates, and was able to enhance the rate and extent of soluble and natural crystalline cellulose hydrolysis by a cellobiohydrolase (CBH3) of C. thermocellum. The combination of properties, like intramolecular complex formation, high thermostability and positive synergistic effect offered by a cellulolytic component of C. thermocellum is being reported for the first time.

Cellulase↗
PubMed1993

Isolation of a cellobiohydrolase of Clostridium thermocellum capable of degrading natural crystalline substrates.

A cellobiohydrolase (CBH3) of Clostridium thermocellum was isolated from the recombinant strains of Escherichia coli. The enzyme was shown to have a Mr of 78 kDa and isoelectric point of 4.75. The hydrophilic nature of the enzyme was confirmed by its unretarded elution on gel filtration column. The enzyme had a binding affinity for the microcrystalline substrate (Avicel). The pH and temperature optimum were determined as 6.5 and 60 degrees C. The enzyme was found to be active on p-nitrophenyl cellobioside, carboxymethyl cellulose, Avicel, amorphous cellulose, lichenan and xylan. The most distinguishing feature of CBH3 was the degradation of a variety of natural crystalline substrates, with maximum activity on filter paper. The enzyme was tolerant to high levels of cellobiose, susceptible to heavy metals and was protected by DTT and calcium at higher temperatures. This is the first report of a highly active cellobiohydrolase produced in C. thermocellum.

Cations, Divalent↗
PubMed1992

A bacteriological study of the environment of pediatric ward and neonatal nursery.

The hospital environment is full of pathogens which may cause nosocomial infections. A bacteriological survey of hospital air, floor, water, milk and fomites was done. The air survey showed large number of bacteria carrying particles in air. A direct relation between floor area per person and bacterial contamination of air was established. The floor survey showed that there is abundance of bacteria on the hospital floors, much more than the accepted fair standards of house keeping. The hospital water had a high coliform and total bacterial count and stored tank water was more dirty. Neonatal nursery milk also had high total bacterial and coliform counts. Regular surveillance of hospital environment may help to reduce the incidence of cross infection.

Cross Infection↗
PubMed1991

Isolation and biochemical properties of four forms of glycosylated porcine prolactin.

Four isoforms of glycosylated prolactin (G-pPRL) were isolated from porcine pituitary glands by affinity chromatography and concanavalin A-Sepharose, based upon differences in their affinity for the lectin. Structural analysis indicated differences in the carbohydrate units of the four G-pPRLs. N-glycanase treatment cleaved the oligosaccharide from the G-pPRLs, establishing N-linked glycosylation. The binding of G-pPRLs to receptors from lactating rabbit mammary glands was only 3-8% that of nonglycosylated pPRL (NG-pPRL). The immunological crossreactivity of the G-pPRLs varied from 36 to 65% that of NG-pPRL. When tested in the pigeon crop sac bioassay, G-pPRLs were only 11-40% as active as NG-pPRL. The metabolic clearance rate of one of the G-pPRLs was slower and another faster than that of NG-pPRL. We conclude that there are several forms of G-PRL of variable immuno- and bio-potencies in the porcine pituitary, and that the current radioimmunoassay for the hormone does not measure the actual bioactivity.

Animals↗