Biomedical subjects

R Subramanian

Publications and source records attributed to R Subramanian.

At least 19 recordsLinked to original sources

PubMed2006

Relative element levels in the paired samples of scalp hair and fingernails of patients from New Delhi.

Specific elements are bioconcentrated in human hair and nails, which have unique advantages of application in population monitoring studies thereby, recognized as biological tools for disease diagnosis and prevention. However, investigations are meager for relative element profile in hair and nails of same subjects. In this study, hair and nails were analyzed to find effects of age, sex, smoking habit, diet, urban and rural exposure gradients, occupation, and health on element levels. Scalp hair and fingernails were sampled along with a questionnaire from urban and rural subjects of New Delhi; patients of hypertension, coronary heart disease, and diabetes were identified clinically. Cadmium, chromium, copper, nickel, lead and zinc concentrations were determined by AAS in both the samples; CRM (human hair powder) analysis showed acceptable precision and accuracy in element measurement. In comparison to controls, Cr-H and Zn-H levels were lower respectively in female hypertensive and total hypertensive subjects, whereas, Zn-N and Cu-N were lower respectively in total CHD and diabetic subjects, and hypertensive and CHD urban subjects. Cd concentrations were higher in both the samples of tobacco smoking rural subjects than that of non-smokers. Farmers had lower Pb-H than rural businessmen did. Cr, Cu, Ni, and Zn concentrations were different due to rural and urban gradient but not to the influence of age, sex, and diet. Pb value was alone correlated between the paired samples. Thus, higher Cd levels in the smokers and lower Cr, Cu and Zn levels in the patients were observed.

Adolescent↗

PubMed2006

Membrane technology in degumming, dewaxing, deacidifying, and decolorizing edible oils.

A membrane process offers several advantages over the conventional method of oil refining. Conceptually, membranes could be used in almost all stages of processing. In the present review, various attempts made by the researchers towards degumming, dewaxing, deacidifying, and decolorizing edible oils using membrane technology with and without using solvents have been discussed. Attempts made with UF and nonporous membranes have demonstrated the ability of these membranes to separate phospholipids from undiluted and hexane-diluted oils and a high oil flux was obtained with UF membranes in hexane-diluted oils. MF membranes were very effective for dewaxing undiluted oils while UF membranes were effective in dewaxing hexane-diluted oils without a precooling step. Deacidification was successful only with either addition of an alkali followed by membrane filtration or by following an indirect route of selective solvent extraction of FFA followed by membrane separation. Consistent color reduction in terms of pigments (chlorophyll and xanthophylls) and other instrumental measurements (Lovibond and visible spectra) could be achieved only with nonporous membranes. Interestingly, these membranes did not have selectivity for alpha-and beta-carotenes. UF membranes are best suited for degumming and dewaxing applications, while nonporous membranes appear to be a better choice for achieving simultaneous degumming, dewaxing, and decolorization of oils. Hexane-dilution improved the oil flux of nonporous membranes by one order of magnitude, but further improvement is desirable for industrial adoption.

Food Handling↗

PubMed2005

Smoking reduction does work: resulting alterations in the incidence and histological subtypes of lung cancer in New South Wales in the last 20 years.

BACKGROUND: There is irrefutable evidence of the association between lung cancer and smoking. The effects of public health campaigns to reduce population-smoking rates on the incidence and the histological distribution of lung cancer were examined. METHODS: The data held in the New South Wales Cancer Registry from 1972 to 2001 was accessed. RESULTS: The data revealed a decreasing incidence of lung cancer amongst males and a rate that continued to increase amongst females. Interestingly, there was also an effect on the histological distribution of lung cancers, with falling rates of small cell lung cancer and squamous cell cancer, both of which have a high association with smoking; and an increasing incidence of adenocarcinomas. CONCLUSIONS: These trends reveal patterns seen worldwide. The increasing proportion of adenocarcinomas in particular may be related to the changing composition of cigarettes and filters.

Carcinoma, Small Cell↗

PubMed2004

Isolation and structural characterization of the photolysis products of etoricoxib.

Etoricoxib is a potent and novel selective inhibitor of cyclooxygenase-2 (COX-2) which has been developed for the treatment of osteoarthritis, rheumatoid arthritis and several other inflammatory conditions. To support clinical pharmacokinetics studies, a method for the determination of etoricoxib in human plasma was developed. During the development of the method it was found that highly fluorescent products were formed when etoricoxib was exposed to UV light (254 nm). The formation of highly fluorescent products was the basis for the development of a highly sensitive HPLC/fluorescent assay for the indirect determination of etoricoxib in human plasma; the limit of quantification (LOQ) was 1 ng/mL. To unequivocally determine the chemical structures of the photolysis products of etoricoxib, a series of studies was conducted. When etoricoxib was irradiated online in a photochemical reactor, three products were detected in an HPLC-UV system. These products were characterized by HPLC-UV-fluorescence and HPLC-MS/MS. Possible structures of these products were proposed based on these data. The major photolysis products of etoricoxib were further isolated and their structures were elucidated using NMR and HPLC-NMR. The results of these experiments indicate that etoricoxib undergoes a photocyclization reaction when irradiated with UV light (254 nm), leading to the formation of two major isomeric photocyclization products.

Chromatography, High Pressure Liquid↗

PubMed2003

Cyclic voltammetric and electrochemical impedance studies on the structure, adsorption kinetics, and barrier properties of some organic dithiol self-assembled monolayers on gold.

We have studied the orientation and barrier properties of self-assembled monolayers (SAMs) of two alkanedithiols, hexanedithiol, octanedithiol, and an aromatic dithiol, 1,4-benzene dimethanethiol (BDMT), on gold in acetonitrile. From our studies, we conclude that BDMT molecules can form more organized monolayers on gold than aliphatic dithiol SAMs due to extremely strong lateral van der Waals interaction among the phenyl rings in the former. A study of the adsorption kinetics of octanedithiol in ethanol indicates that the adsorption rate law is concentration dependent just as for alkanethiols. However, the rate of adsorption is considerably faster than for simple alkanethiols.

Journal Article↗

PubMed2001

Protein phosphatase 2A activates the proapoptotic function of BAD in interleukin- 3-dependent lymphoid cells by a mechanism requiring 14-3-3 dissociation.

BAD is a proapoptotic member of the BCL-2 family of proteins, which play a major role in regulating apoptosis in cytokine-dependent hematopoietic cells. The function of BAD is regulated by reversible phosphorylation. Deprivation of survival factors induces BAD dephosphorylation, resulting in apoptosis. Serine-threonine phosphatase activity dephosphorylated BAD in interleukin-3-dependent FL5.12 lymphoid cells. Inhibition of PP2A activity by treatment of cells with PP2A-selective inhibitors, okadaic acid and fostriecin, prevented BAD dephosphorylation in these cells. Conversely, BAD dephosphorylation was not inhibited by the PP1-selective inhibitor tautomycin. In cell-free extracts, BAD phosphatase activity was also inhibited by the PP2A-selective inhibitors okadaic acid and fostriecin, but not by the PP1-specific protein inhibitor I-2. Dissociation of 14-3-3 from BAD was a prerequisite for BAD dephosphorylation in vitro, suggesting a mechanism by which 14-3-3 can regulate the activation of the proapoptotic function of BAD in vivo. Significantly, the inhibition of BAD phosphatase activity rescued cell death induced by survival factor withdrawal in FL5.12 cells expressing wild-type BAD but not phosphorylation-defective mutant BAD. These data indicate that PP2A, or a PP2A-like enzyme, dephosphorylates BAD and, in conjunction with 14-3-3, modulates cytokine-mediated survival.

14-3-3 Proteins↗

PubMed2001

Assessing plasma pharmacokinetics of cholesterol following oral coadministration with a novel vegetable stanol mixture to fasting rats.

The purpose of this project was to assess the plasma pharmacokinetics of [(3)H]cholesterol following coadministration of a novel vegetable stanol mixture composed of sitostanol and campestanol (FCP-3P4) to fasting rats. Following an overnight fast (12-16 h) and 48 h post-surgery, adult male Sprague Dawley rats were divided into six treatment groups and received a single-dose oral gavage at 0700 h of either: [(3)H]cholesterol (25 microCi/mL), FCP-3P4 (5 mg/kg) + [(3)H]cholesterol (25 microCi/mL), FCP-3P4 (12.5 mg/kg) + [(3)H]cholesterol (25 microCi/mL), FCP-3P4 (25 mg/kg) + [(3)H]cholesterol (25 microCi/mL), FCP-3P4 (50 mg/kg) + [(3)H]cholesterol (25 microCi/mL), or FCP-3P4 (100 mg/kg) + [(3)H]cholesterol (25 microCi/mL). Intralipid (10%) was the vehicle used to solubilize and coadminister [(3)H]cholesterol and FCP-3P4. Liquid chromatography-mass spectrometry analysis confirmed minimal cholesterol and vegetable stanol content within 10% Intralipid. Analysis of plasma pharmacokinetics was initiated by sampling 0.5 mL of blood prior to and 0.25, 0.5 1.0, 2.0, 4.0, 6.0, 8.0, 10, 24, 28, 32, and 48 h post-oral gavage. Plasma samples were obtained by centrifugation of the blood samples and analyzed for [(3)H]cholesterol radioactivity. Pharmacokinetics analysis was performed by standard noncompartmental methods using statistical moment theory. Thin-layer chromatography was used to confirm that the majority of radioactivity measured in plasma was cholesterol (in the form of esterified or unesterified cholesterol). Greater than 90% of the radioactivity measured in all plasma samples was cholesterol-associated (in the form of either esterified or unesterified cholesterol). The coadministration of FCP-3P4 significantly decreased the area under the curve of [(3)H]cholesterol concentration versus time from 0 to 48 h (AUC(0-48h)) and maximum concentration (C(max)) in a dose-dependent manner. However, coadministration of FCP-3P4 at 25, 50, and 100 mg/kg resulted in a significant increase in apparent total body clearance (CL/F, where F is the bioavailability constant), apparent volume of distribution (V(d)/F), and oral absorption rate constant (k(a)) of [(3)H]cholesterol compared with controls. These findings suggest that the novel vegetable stanol mixture, FCP-3P4, modifies the plasma pharmacokinetics of [(3)H]cholesterol in fasting rats on oral coadministration.

Administration, Oral↗

PubMed2001

Oral repletion of iron induces free radical mediated alterations in the gastrointestinal tract of rat.

Free radical mediated effects on the gastrointestinal (GI) tract were studied by supplementing 8 mg of iron orally for 15 days to groups of both control (C+) and iron deficient (D+) rats. They were compared with their respective unsupplemented groups C and D. Incorporation of 3H-thymidine into the isolated mucosal cells, as a measure of cell turn over, was lowered significantly in both the D+ and C+ groups compared to their respective controls D and C. It was observed that a single dose of 8 mg of iron given orally to control rats could cause apoptosis of GI tract mucosal cells as shown by the ladder pattern of DNA on electrophoresis. Continuous administration of the same dose of iron for a period of 15 days resulted in necrosis of the GI tract absorptive surface in D+ and C+ rats. In addition to this, a reduction of microvillus height in C+ and complete erosion of the same in D+ were observed by the transmission electron microscopy. EPR spectroscopy identified production of hydroxyl and methoxyl radicals in both the luminal and mucosal contents in the GI tract of rats. These results suggest that when iron is orally administered, free radicals are formed at the site of absorption causing damage to the GI tract mucosa.

Administration, Oral↗

PubMed2001

beta-Oxidation of simvastatin in mouse liver preparations.

All current 3-hydroxy-3-methylglutaryl-CoA reductase inhibitors [simvastatin (SV), lovastatin (LV), atorvastatin, pravastatin, fluvastatin, and cerivastatin] are believed to undergo an atypical beta-oxidation of the dihydroxy heptanoic or heptanoic acid side chain. Metabolites, which are shortened by two- and/or four-carbon units consistent with beta-oxidation products, have been reported exclusively in rodents following LV and SV administration and across species (rodents, dogs, and humans) following the other statins. In this study, in vitro formation of a beta-oxidation product of simvastatin hydroxy acid (SVA) and its intermediates in mouse livers is described. Incubation of SVA with mouse liver preparations fortified with CoASH and ATP led to formation of SV and two major products (P1 and P2). Based on mass spectrometry (MS), tandem mass spectrometry, and/or NMR spectral characteristics, P1 was an alpha,beta-unsaturated metabolite, formed by dehydration of the D,D-dihydroxy heptanoic acid side chain, whereas P2 was probably the L,D-dihydroxy acid isomer of SVA, formed by stereospecific hydration of P1. When NAD(+) was also included in the incubation mixture, there were two additional metabolites with the MS and/or NMR characteristics consistent with a two-carbon shortened product (P3) and its dehydrated derivative (P4). In a complete incubation system with all cofactors (ATP, CoASH, NAD(+), and NADPH) present, there was an additional product with MS spectra and liquid chromatography retention time identical to the beta-oxidized, unsubstituted pentanoic acid metabolite (P5) detected in rats and mice following simvastatin administration. The involvement of CoASH and NAD(+) and the presence of the four metabolic intermediates suggest that SVA (and presumably the other statins) is a substrate for the beta-oxidation enzyme complex in mice. Additionally, the present finding of CoASH-dependent formation of SV substantiates a mechanism proposed previously for the in vivo lactonization of statin hydroxy acids.

Animals↗

PubMed2000

Melanosomal proteins promote melanin polymerization.

In melanocytes, enzymes involved in the generation of melanin monomers are present and active in coated vesicles which are known to be acidic. Melanin polymerization however, occurs only in melanosomes. In vitro, it is not possible to generate melanin at the acidic pH of melanosomes using 3,4-dihydroxyphenylalanine (DOPA) and tyrosinase alone whereas melanin readily forms at higher pH with these reagents. Dimerization and elongation of the melanin polymer is known to require deprotonation. We have hypothesized that the amino acid side chains of melanosomal proteins act as proton acceptors to initiate polymerization and that the protonated basic groups serve to attract the negatively charged oligomers thus aiding polymerization and binding to proteins. We show that basic model proteins and basic premelanosomal proteins promote polymerization at an acidic pH and that positively charged surfaces allow binding of the growing melanin polymer. With progressive polymerization and exhaustion of the proton abstracting ability of melanosomal proteins, melanosomal pH drops further, which, we argue, is an additional controlling step that limits tyrosinase activity and melanin polymerization.

Animals↗

PubMed2000

Severe hypophosphatemia. Pathophysiologic implications, clinical presentations, and treatment.

We conducted this review to heighten the awareness and describe pathologic manifestations of hypophosphatemia. We present 3 cases of varied manifestations of hypophosphatemia where recognition was delayed. In certain settings, severe hypophosphatemia has significant morbidity and potential mortality. Appreciation of the pathophysiologic basis for organ dysfunction in severe hypophosphatemia should result in early recognition and treatment. We reviewed the English-language literature for reported cases and research studies dealing with pathophysiologic mechanisms subserving clinical manifestations. We observed that depletion of adenosine triphosphate (ATP) would explain most of the derangement noted in cellular functions. Phosphate plays a key role in the delivery of oxygen to the tissue. Lack of phosphate, therefore, leads to tissue hypoxia and hence disruption of cellular function. Severe hypophosphatemia becomes clinically significant when there is underlying phosphate depletion. Otherwise, short-term acute hypophosphatemia is not usually associated with any specific disorder. Chronic hypophosphatemia, on the other hand, results in hematologic, neuromuscular, and cardiovascular dysfunction, and unless corrected, the consequences can be grave. Most of the time hypophosphatemia results from renal loss of phosphate, diagnosed by a fractional secretion of phosphate > 5%. It is hard to provide precise estimates of how many patients are seen with hypophosphatemia annually at academic medical centers. This is complicated by use of chemistry panels that do not measure inorganic phosphate unless specifically ordered. This often leads to delay in correct diagnosis, and, therefore, additional delay in providing appropriate management. A high index of suspicion alone avoids the unnecessary withholding of treatment that can be life saving.

Acute Disease↗

PubMed2000

Elements in the hair of workers at a workshop, foundry, and match factory.

The levels of seven elements determined in the hair were compared between male controls and industrial workers from Madras (South India). Particularly, the concentrations of Cd, Cr, Cu, Mn, and Ni in the foundry workers and Cu, Mn, and Ni in the workers of a workshop and match factory were observed to be higher than that of controls working in the office. In addition, the occupation, age, and period of service of workers had an influence, but diet, smoking habits, income of family, and hair color had no influence on the element levels in the hair.

Adolescent↗

PubMed1999

A microcoil NMR probe for coupling microscale HPLC with on-line NMR spectroscopy.

An HPLC NMR system is presented that integrates a commercial microbore HPLC system using a 0.5-mm column with a 500-MHz proton NMR spectrometer using a custom NMR probe with an observe volume of 1.1 microL and a coil fill factor of 68%. Careful attention to capillary connections and NMR flow cell design allows on-line NMR detection with no significant loss in separation efficiency when compared with a UV chromatogram. HPLC NMR is performed on mixtures of amino acids and small peptides with analyte injection amounts as small as 750 ng; the separations are accomplished in less than 10 min and individual NMR spectra are acquired with 12 s time resolution. Stopped-flow NMR is achieved by diversion of the chromatographic flow after observation of the beginning of the analyte band within the NMR flow cell. Isolation of the compound of interest within the NMR detection cell allows multidimensional experiments to be performed. A stopped-flow COSY spectrum of the peptide Phe-Ala is acquired in 3.5 h with an injected amount of 5 micrograms.

Amino Acids↗

PubMed1999

Methylene-only subspectra in (13)C CPMAS using a new double quantum filtering sequence

Methodology for the assignment of (13)C CPMAS spectra is still in its infancy. Previous methods of CPMAS spectral editing have utilized differences in the strength of the (13)C-(1)H dipolar interaction or the rate and spin thermodynamics of crosspolarization from protons to carbon, to differentiate between quaternary, tertiary, and methylene carbons. We introduce a different approach, which is based on the fact that double-quantum coherence develops between the protons of a methylene group considerably faster than between most other proton spin pairs in an organic solid. We generate this coherence, filter it, convert it back to single quantum, and then crosspolarize selectively to carbon, followed by a short period of reversed crosspolarization to null out unwanted coherence generated from longer distance spin pairs. The sequence has been named DQCP. While the signal-to-noise of this method is poorer than ordinary CP, it is comparable to previous methods for generating methylene-only spectra, and the technique is straightforward and easy to implement. Copyright 1999 Academic Press.

Journal Article↗

PubMed1999

Cyclosporine transfer from low- and high-density lipoproteins is partially influenced by lipid transfer protein I triglyceride transfer activity.

PURPOSE: The purpose of this study was to determine if lipid transfer protein (LTP I) facilitated triglyceride (TG) transfer activity regulates the plasma lipoprotein distribution of cyclosporine (CSA). METHODS: To assess the influence of drug concentration and incubation time on the plasma lipoprotein distribution of CSA, 3H-CSA (50 to 1000 ng/ml) was incubated in human plasma for 5 to 120 minutes at 37 degrees C. To determine if LTP I facilitated TG transfer activity regulates the plasma lipoprotein distribution of CSA, 3H-Triolein (TG)- or 3H-CSA-enriched high-density lipoproteins (HDL) or low-density lipoproteins (LDL) were incubated in T150 buffer (50 mM Tris-HCl, 150 mM NaCl, 0.02% Sodium Azide, 0.01% Disodium EDTA), pH 7.4 which contained a 3H-Triolein (TG) or 3H-CSA-free lipoprotein counterpart +/- exogenous LTP I (1.0 microg protein/ml) or in delipidated human plasma which contained 1.0 microg protein/ml of endogenous LTP I for 90 minutes at 37 degrees C. These experiments were repeated in the presence of a monoclonal antibody TPI (15 microg protein/ml) directed against LTP I. RESULTS: No differences in CSA lipoprotein distribution were observed following incubation of the drug at varying concentrations and incubation times in human plasma. The percent transfer of TG from HDL to LDL and LDL to HDL was greater in T150 buffer than in human plasma. However, the percent transfer of CSA from only LDL to HDL was greater in T150 buffer than in human plasma. Furthermore, undetectable 3H-CSA transfer from HDL to LDL in T150 buffer containing purified LTP I was observed. In addition, when the percent transfer of TG and CSA were determined in the presence of TPI, the percent transfer of TG and CSA from only LDL to HDL were significantly decreased in T150 buffer and human plasma compared to controls. CONCLUSIONS: These findings suggest that the transfer of CSA between different lipoprotein particles is only partially influenced by LTP I facilitated TG transfer activity.

Adrenergic Uptake Inhibitors↗

PubMed1998

Design of solenoidal microcoils for high-resolution 13C NMR spectroscopy.

Typical high-resolution natural-abundance 13C NMR experiments require milligrams of material. In this study, solenoidal microcoil direct and inverse detection probes have been designed to explore improvements in the limits of detection (LOD) for 13C NMR at 11.7 T. A direct-detection radio frequency probe with an observe volume (Vobs) of 1 microL has been developed with carbon observe, deuterium lock, and proton decouple channels. The nonspinning line width of a decoupled [3-13C]-L-alanine (99%) peak achieved is 1.3 Hz. The natural-abundance 13C3 sigma LOD for sucrose for a 90-min acquisition time is 18 micrograms (52 nmol). The 3 sigma LOD for [3-13C]-L-alanine (99%) is 375 ng (4.2 nmol) for an acquisition time less than 30 s. The inverse detection probe has proton observe and carbon decouple channels and a Vobs of 550 nL. The 3 sigma LOD for sucrose from a 1 D 13C decoupled HMQC spectrum is 1.6 micrograms (4.5 nmol) for a 14-min acquisition time.

Alanine↗

PubMed1998

Primary structure of ovine fibroblast growth factor-1 deduced by protein and cDNA analysis.

The amino acid sequence of full-length ovine fibroblast growth factor-1 (FGF-1) was determined by a combination of protein and cDNA sequencing. FGF-1 cDNA analysis indicated that ovine kidney cells express mRNAs encoding both full-length FGF-1 and a truncated FGF-1 variant. An overall comparison of the ovine FGF-1 primary sequence to the eight species studied to date revealed a high degree of conservation, with ovine FGF-1 sharing 90 and 95% sequence identity with human FGF-1 and bovine FGF-1, respectively. Additionally, the FGF-1 proteins from the various species have conserved cysteine residues at positions 30 and 97 and contain acetylated amino-terminal alanine residues. Mass spectrometry analysis confirmed that the blocking group of ovine FGF-1 is also consistent with that of an acetyl-moiety. In contrast to the other FGF-1 proteins, the 154 residue primary sequence of ovine FGF-1 contains three unique amino acid differences: Arg9, Arg44, and Ile123. Ovine FGF-1, unlike human FGF-1, is a potent mitogenic factor for NIH 3T3 fibroblasts in the absence of heparin. In the presence of exogenous heparin, the mitogenic activity of ovine FGF-1 is potentiated slightly.

3T3 Cells↗

PubMed1998

Recombinant production and purification of novel antisense antimicrobial peptide in Escherichia coli.

A fusion protein was genetically engineered that contains an antimicrobial peptide, designated P2, at its carboxy terminus and bovine prochymosin at its amino terminus. Bovine prochymosin was chosen as the fusion partner because of its complete insolubility in Escherichia coli, a property utilized to protect the cells from the toxic effects of the antimicrobial peptide. This fusion protein was purified by centrifugation as an insoluble inclusion body. A methionine linker between prochymosin and the P2 peptide enabled P2 to be released by digestion with cyanogen bromide. Cation exchange HPLC followed by reversed-phase HPLC were used to purify the P2 peptide. The recombinant P2 peptide's molecular mass was confirmed by mass spectrometry to within 0.1% of the theoretical value (2480.9 Da), and the antimicrobial activity of the purified recombinant P2 against E. coli D31 was determined to be identical to that of the chemically synthesized peptide (minimal inhibitory concentration of 5 mg/mL). Although the yield of the fusion protein after expression by the cells was high (16% of the total cell protein), the percentage recovery of the P2 peptide in the inclusion bodies was relatively low, which appears to be due to losses in the cyanogen bromide digestion step.

Amino Acid Sequence↗