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Biomedical subjects

R Maheshwari

Publications and source records attributed to R Maheshwari.

At least 19 recordsLinked to original sources
PubMed2006

IL-6 protects enterocytes from hypoxia-induced apoptosis by induction of bcl-2 mRNA and reduction of fas mRNA.

Interleukin-6 (IL-6) has been shown to rescue enterocytes from hypoxia-induced apoptosis when given orally following hemorrhagic shock. In vitro models using an intestinal epithelial cell line (IEC-6) cultured with lipopolysaccharide (LPS) under low O2 conditions, to mimic intestinal conditions, show that these cells also undergo apoptosis, which can be reduced by subsequent culture with IL-6. To examine further the mechanisms of rescue, we cultured normal rat intestinal epithelial cells (IEC-6) under both normoxic and hypoxic conditions and analyzed their responses to LPS and IL-6. We showed that IEC-6 expressed IL-6 receptor on its surface. Further, IEC-6 cells could be rescued from hypoxia-induced apoptosis by co-culture with IL-6. RNase protection assay (RPA) examination revealed that under hypoxic conditions, IEC-6 cells that were resistant to apoptosis showed reduced fas expression and increased bcl-2 expression after co-culture with LPS+IL-6.

Animals↗
PubMed2006

Barrage laser photocoagulation for macula-sparing asymptomatic clinical rhegmatogenous retinal detachments.

PURPOSE: To evaluate the efficacy of barrage laser photocoagulation in containing macula-sparing asymptomatic clinical retinal detachments (RD). METHODS: Consecutive patients presenting with asymptomatic clinical RD were prospectively treated with barrage photocoagulation in 2-3 confluent rows, using frequency-doubled Nd:YAG (532 nm) laser on an indirect-ophthalmoscopic delivery system. The patients were reviewed at 0.5, 1.5, 3, and 6 months, and yearly thereafter. Best-corrected visual acuity (BCVA), and stability/progression of rhegmatous retinal detachment beyond the barrage were noted at each visit. RESULTS: Nineteen phakic eyes of 17 patients (nine female patients), aged 12-58 years (average: 26 years), underwent barrage laser treatment. Two women had bilateral RD. Most detachments were caused by atrophic holes, and involved at least a quadrant of retina. Seven (37%) extended superiorly with breaks above the horizontal raphe. Three eyes had partial demarcation lines, and five had posterior vitreous detachment at presentation. The minimum follow-up was 6 months (mean: 21 months; range: 6-108 months). Pretreatment anatomical and functional status was maintained in 18 (95%) eyes till the final visit. One superotemporal RD progressed across the laser barrier into macula 5 months after photocoagulation, and BCVA dropped to 6/18. Scleral buckling was performed successfully, with visual recovery to 6/6. CONCLUSIONS: Barrage photocoagulation may have a place in management of asymptomatic clinical detachments, as an effective and less morbid alternative to scleral buckling.

Adolescent↗
PubMed2006

Structural influence of mono and polyhydric alcohols on the stabilization of collagen.

In the present study, solvents effects on the structure of collagen have been examined by circular dichroism and their interfacial tension at glass/liquid and Teflon/liquid. Changes in the conformations of the protein have been analyzed after equilibration with aqueous solutions of monohydric and polyhydric alcohols like methanol, ethanol, n-propanol, propane-2-diol and glycerol. The results from viscosity and Circular dichroism (CD) spectra suggest a clear distinction in the structural changes for collagen with monohydric alcohols as against polyhydric ones. The surface tension and interfacial tension at glass (high surface energy, HFSE) and Teflon (Low surface energy, LSFE) reflect similar differences between the monohydric and polyhydric alcohols. Studies on the interfacial energy of the adsorbed protein at glass/solution interface compared to that of Teflon/solution interface show that the water structure near glass gets perturbed leading to an increase in the average free energy of the bulk water phase and a reduction in hydrophobic effect near the glass. The results suggest that the different solvents alter the hydrophobic effect on the hydrated protein to different extent and thus influence folding equilibrium of the protein without directly interacting with it. Polyhydric alcohols seem to favor the native collagen structure while monohydric alcohols enhance it.

Acetates↗
PubMed2005

Solid-liquid interfacial energy as a tool to estimate shifts in isoelectric points of adsorbed proteins on solid surfaces.

This work reports the estimation of isoelectric points (pIs) of adsorbed amino acids and proteins on solid surfaces in the pH range between 3.5-11.0 from a measurement of solid/liquid interfacial energy. The values thus obtained are compared with the pIs determined in solution phase by other methods. Both glass and Teflon have been chosen as model solid surfaces. Close agreement between the reference pI values, obtained by the capillary isoelectric focusing and those obtained at solid/liquid interface is observed within an average difference of 0.04-0.08 pH unit when the pIs are above the pI of glass. For systems whose pIs are far away from that of glass (either in the acidic or highly alkaline range), a large shift in the isoelectric point is observed. In case of Teflon the pIs are closer to the reported values than at glass/liquid interface. This could be due to the fact that Teflon being a hydrophobic surface, its surface is dominated by dispersive forces, which may not be seriously affected by pH changes. The shift in the values at solid/liquid interface compared to that in solution have been examined using an 'image charge approach.'

Adsorption↗
PubMed2005

Mucin at solution/air and solid/solution interfaces.

In this paper the surface activity of protein mucin at solution/air interface has been studied. The experiments of the adsorbed protein at solution/air interface have been carried out with a range of protein concentrations at a defined pH. The adsorption of the protein to solid surfaces and the degree of hydrophobicity at solid/solution interface of mucin have been evaluated at different pH and in the presence of Hofmeister electrolyte. The results from these studies have been further substantiated by surface potential measurements of mucin covered surface on stainless steel. Quartz crystal microbalance (QCM) has been used to follow the protein adsorption kinetics from solution to solid surface. The results from these measurements show that the adsorption behavior has a remarkable dependence on the degree of maximum coverage and is almost independent of the ionic strength. Other characteristic features such as maximum adsorption values at the protein isoelectric point (IEP4.7) and low-affinity isotherms that showed surface saturation even under unfavorable electrostatic conditions have been observed. The amount of mucin adsorbed in the presence of electrolytes has been estimated using electron spectroscopy for chemical analysis (ESCA). The study clearly shows that there exists an inverse relationship between the hydrophobicity and surface tension of the protein and also on the hydrated radius of Hofmeister electrolyte used.

Air↗
PubMed2004

Investigation of surface properties of amino acids: polarity scale for amino acids as a means to predict surface exposed residues in films of proteins.

It is of great interest and importance to study how different amino acid residues contribute to and affect the properties of proteins coated as films on solid surface. This work shows that the solid/liquid interfacial energy of surface localized amino acid films and their Gibbs energies of transfer at the air/solution interface have the potential to be used as a rapid and simple method for studying the surface properties of proteins. Based on these results, a new polarity scale for amino acids has been proposed. This scale is compared with existing hydropathy scales in a benchmark test using some proteins with solved 3D structure. The proteins were characterized in terms of surface-exposed residues with a computer program, Graphical Representation and Analysis of Surface Properties (GRASP). It was also shown that each amino acid contribution is relative to the total protein surface and the other residues on the surface.

Amino Acids↗
PubMed2004

Oxidation of benzaldehyde in films by Oxo-Cr(V) salen derivatives at solid/liquid interface.

The oxidation of benzaldehyde as a film on a solid surface by various substituted oxochromium(V) salen in solution has been studied by monitoring the change in contact angle of the oxidant at the film/liquid interface utilizing a Teflon cell of known hydrodynamics and controlled convection/diffusion. The kinetics of the redox reaction in bulk has been monitored by measuring the change in absorbance of the oxidant solution. The interfacial study permits analysis of adsorption of the oxidant followed by the oxidation of the substrate under pseudo-first-order conditions. A comparison of the independent surface-averaged kinetic data with those obtained in the solution phase oxidation reaction is made and a model is presented for the mechanism of the interfacial reaction. The kinetic investigation shows that the rate of oxidation is accelerated in the presence of an electron-withdrawing group and is faster at the solid/liquid interface compared to the bulk. The probable mechanism of the redox reaction is discussed.

Journal Article↗
PubMed2004

Influence of ammonium nitrate in phase transitions of Langmuir and Langmuir-Blodgett films at air/solution and solid/solution interfaces.

The effect of ammonium nitrate on the phase transitions in Langmuir films of amphiphiles-stearic acid, stearyl amine (STAM), stearyl alcohol, dihexadecylphosphate, and the quarternized ammonium salt dioctadecyldimethylammonium bromide have been studied at air/water interface and in local ordering of their Langmuir-Blodgett films (LB films). The study shows that except for the stearyl amine (STAM) all other monolayers exhibit a liquid-expanded to liquid-condensed transition with slight expansion in area in the presence of ammonium nitrate. STAM monolayers show a new phase transition, which possibly arises due to the differently ionized amino groups, and change in solvation sheath due to an ion-dipole type interaction between the amino groups and the ammonium ion in the subphase. Mixed films of the amine with the acid and alcohol did not show such intermediate phases indicating that competing H-bonds between polar groups themselves and dipolar couplings between the polar groups and ammonium nitrate play a major role in the organization of the molecules at the interface. The above effect resulting in a change in the local order is borne out by Brewster angle micrographs (BAM) of the Langmuir films of STAM at air/solution interface. Such behavior is also seen at solid/liquid interfaces where the polar component of surface energy undergoes a drastic change for the amine films transferred onto solid substrates from the air/ammonium nitrate solution interface.

Journal Article↗
PubMed2004

Molecular dipoles at substrate/film interfaces influencing surface energy of Langmuir-Blodgett films.

Langmuir and Langmuir-Blodgett (LB) films of novel rigid Schiff base amphiphiles with different polar groups on aromatic rings have been studied at air/water interfaces and on solid substrates. The local surface potentials for the different substituents on the aromatic groups of the amphiphiles are correlated to the surface energy of LB films on solid substrates. Their contributions are probed on high-surface-energy (hsfe) quartz and hydrophobically modified low-surface-energy (lsfe) quartz. Using theoretical estimates, the long-range effects of the substituents of the polar groups on the alkyl chains have been studied from charge on the carbon and hydrogen atoms of the alkyl tails. The calculations indicate that a substituted carbon atom has a charge that is directly dependent on the nature of the atoms to which it is attached rather than on the charges of any other atoms of the substituents. This work shows that the polar substituents on the head group clearly influence the distal methylene groups of the tail. Thus, any treatment, either theoretical or experimental, of these films in contact with solid substrates should include the local relative permitivities of the polar moieties, which seem to play an important role in determining macroscopic properties such as surface energy.

Journal Article↗
PubMed2004

Spontaneous recurrent haemarthrosis following unicompartmental knee arthroplasty and its successful treatment by coil embolisation.

A case of spontaneous recurrent haemarthrosis of the knee presenting 3 months after the unicondylar knee replacement is described. Femoral arteriography demonstrated hypertrophy of the saphenous branch of descending genicular artery with a prominent vascular blush in the region of posteromedial aspect of the popliteal fossa thought to represent a hypertrophic vascular mass of synovium. Therapeutic embolisation of the saphenous branch of descending genicular artery was performed using three fibred platinum coils with satisfactory clinical results. Since the embolisation, the haemarthrosis has not recurred. To our knowledge, this therapeutic procedure used to treat recurrent haemarthrosis following unicondylar knee arthroplasty has not been previously described in the literature.

Aged↗
PubMed2003

Evaluation of standardized versus individualized total parenteral nutrition regime for neonates less than 33 weeks gestation.

OBJECTIVE: To evaluate the difference in nutrient intakes and biochemical responses in newborn infants <33 weeks gestation who received standardized versus individualized total parenteral nutrition (TPN) regimes. METHOD: Comparison of nutrient intakes and daily biochemical responses in newborn infants <33 weeks gestation who received standardized regime versus those who received individualized TPN regimes from day 2 to day 7 of life. RESULTS: Twenty-seven infants in the standardized TPN group and 31 infants in the individualized TPN group were compared. There were no statistically significant differences (P > 0.05) between the two groups in gestation, birthweight, Clinical Risk Index for Babies scores, daily TPN volume intake and biochemical responses. Infants in the standardized TPN group received less sodium (P < 0.01) and no potassium on day 2 as required, more protein (P < 0.02) every day, and more calcium and phosphate (P < 0.02 from day 4). CONCLUSION: There were no significant clinical and statistical differences in biochemical responses in newborn infants <33 weeks gestation who received standardized versus individualized TPN regimes during the first week of life. The economic cost of TPN provision using standardized TPN formulation was approximately 30% lower.

Cost-Benefit Analysis↗
PubMed2000

Senescent: a new Neurospora crassa nuclear gene mutant derived from nature exhibits mitochondrial abnormalities and a "death" phenotype.

Fungi are capable of potentially unlimited growth. We resolved nuclear types from multinuclear mycelium of a phenotypically normal wild isolate of the fungus Neurospora intermedia by plating its uninucleate microconidia and obtained a strain which, unlike the "parent" strain, exhibited clonal senescence in subcultures. The mutant gene, senescent, was introgressed into N. crassa and mapped four map units to the right of the his-1 locus on linkage group VR. senescent is the first nuclear gene mutant of Neurospora derived from nature that shows the death phenotype. Death of the sen mutant occurred faster at 34 degrees C than at 22 or 26 degrees C. Measurements of oxygen uptake of conidia using respiratory inhibitors and the spectrophotometric analyses of mitochondrial cytochromes showed that in sen cultures grown at 34 degrees C, cytochromes b and aa(3) were present but cytochrome c was absent. By contrast at 26 degrees C, cytochromes b and c were present but cytochrome aa(3) was diminished in the late subcultures. This suggested that the sen mutation does not affect the potential to produce functional cytochromes. The deficiency of the respiratory chain cytochromes may not be the cause of death of the sen mutant because the cytochrome c and aa(3) mutants of N. crassa are capable of sustained growth whereas sen is not. Possible explanations for the observations are discussed.

Cell Nucleus↗
PubMed2000

Juvenile neuronal ceroid lipofuscinosis.

A case of juvenile neuronal ceroid lipofuscinosis (JNCL) diagnosed on the basis of clinical features, electrophysiologic studies and skin electron microscopy is reported. JNCL was suspected on the basis of characteristic symptoms including progressive loss of vision, seizures, mental retardation and motor disabilities. Diagnosis was confirmed by neurophysiological and biopsy studies. The disease is caused by 23 different mutations in a gene recently isolated on chromosome 16 p11.2-12.1. Although universally fatal, characterisation of mutations can help in prenatal diagnosis in future pregnancies.

Adolescent↗
PubMed2000

Thermophilic fungi: their physiology and enzymes.

Thermophilic fungi are a small assemblage in mycota that have a minimum temperature of growth at or above 20 degrees C and a maximum temperature of growth extending up to 60 to 62 degrees C. As the only representatives of eukaryotic organisms that can grow at temperatures above 45 degrees C, the thermophilic fungi are valuable experimental systems for investigations of mechanisms that allow growth at moderately high temperature yet limit their growth beyond 60 to 62 degrees C. Although widespread in terrestrial habitats, they have remained underexplored compared to thermophilic species of eubacteria and archaea. However, thermophilic fungi are potential sources of enzymes with scientific and commercial interests. This review, for the first time, compiles information on the physiology and enzymes of thermophilic fungi. Thermophilic fungi can be grown in minimal media with metabolic rates and growth yields comparable to those of mesophilic fungi. Studies of their growth kinetics, respiration, mixed-substrate utilization, nutrient uptake, and protein breakdown rate have provided some basic information not only on thermophilic fungi but also on filamentous fungi in general. Some species have the ability to grow at ambient temperatures if cultures are initiated with germinated spores or mycelial inoculum or if a nutritionally rich medium is used. Thermophilic fungi have a powerful ability to degrade polysaccharide constituents of biomass. The properties of their enzymes show differences not only among species but also among strains of the same species. Their extracellular enzymes display temperature optima for activity that are close to or above the optimum temperature for the growth of organism and, in general, are more heat stable than those of the mesophilic fungi. Some extracellular enzymes from thermophilic fungi are being produced commercially, and a few others have commercial prospects. Genes of thermophilic fungi encoding lipase, protease, xylanase, and cellulase have been cloned and overexpressed in heterologous fungi, and pure crystalline proteins have been obtained for elucidation of the mechanisms of their intrinsic thermostability and catalysis. By contrast, the thermal stability of the few intracellular enzymes that have been purified is comparable to or, in some cases, lower than that of enzymes from the mesophilic fungi. Although rigorous data are lacking, it appears that eukaryotic thermophily involves several mechanisms of stabilization of enzymes or optimization of their activity, with different mechanisms operating for different enzymes.

Fungi↗
PubMed1999

A comparison of thermal characteristics and kinetic parameters of trehalases from a thermophilic and a mesophilic fungus.

Trehalases from a thermophilic fungus Thermomyces lanuginosus (M(r) 145 kDa) and a mesophilic fungus Neurospora crassa (M(r) 437 kDa) were purified to compare their thermal characteristics and kinetic constants. Both trehalases were maximally active at 50 degrees C, had an acidic pH optimum and were glycoproteins (20% and 43%, w/w, carbohydrate content for T. lanuginosus and N. crassa, respectively). At their temperature optimum, their K(m) was similar (0.57 and 0.52 mM trehalose, for T. lanuginosus and N. crassa, respectively) but the V(max) of N. crassa enzyme was nine times higher than of T. lanuginosus enzyme. The catalytic efficiency, k(cat)/K(m), for N. crassa trehalase was one order of magnitude higher (6.2 x 10(6) M(-1) s(-1)) than of T. lanuginosus trehalase (4 x 10(5) M(-1) s(-1)). At their T(opt) (50 degrees C), trehalase from both sources exhibited similar thermostability (t(1/2)6 h). The energy of activation, E(a), for T. lanuginosus trehalase was 15.12 kcal mol(-1) and for N. crassa trehalase it was 9.62 kcal mol(-1). The activation energy for thermal inactivation for the N. crassa enzyme (92 kcal mol(-1)) was two-fold higher than for the T. lanuginosus enzyme (46 kcal mol(-1)). The present study shows that the trehalase of N. crassa is not only more stable but also a better catalyst than the T. lanuginosus enzyme.

Carbon↗
PubMed1999

An unusual pattern of invertase activity development in the thermophilic fungus Thermomyces lanuginosus.

In the thermophilic fungus Thermomyces lanuginosus, invertase displays an unusual pattern of development: the induced activity begins to diminish even before any substantial quantity of sucrose has been utilized or an appreciable amount of biomass has been produced. Despite this pattern of invertase activity, neither the growth rate nor the final mycelial yield is affected adversely. T. lanuginosus invertase is a thiol protein and the enzyme is active when specific sulfhydryl group(s) is in the reduced state. Measurements of reduced coenzyme and glutathione pools in sucrose-growth mycelia excluded oxidative stress as the primary reason for the observed decline in invertase activity. Rather, this unusual pattern of invertase is considered to be due to its localization in the hyphal tips. At the early stage of growth, the number of hyphal tips per unit mass of mycelium is maximum, whereas at later times their numbers do not increase in proportion to the biomass. As a result invertase activity shows an apparent inverse relationship with biomass. The enzyme activity disappears when the inducing carbon source is consumed and growth is completed.

Animals↗