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Biomedical subjects

Rajeev Gupta

Publications and source records attributed to Rajeev Gupta.

At least 37 records · Page 2Linked to original sources
PubMed2004

Utilization of hydrogen bonds to stabilize M-O(H) units: synthesis and properties of monomeric iron and manganese complexes with terminal oxo and hydroxo ligands.

Non-heme iron and manganese species with terminal oxo ligands are proposed to be key intermediates in a variety of biological and synthetic systems; however, the stabilization of these types of complexes has proven difficult because of the tendency to form oxo-bridged complexes. Described herein are the design, isolation, and properties for a series of mononuclear Fe(III) and Mn(III) complexes with terminal oxo or hydroxo ligands. Isolation of the complexes was facilitated by the tripodal ligand tris[(N'-tert-butylureaylato)-N-ethyl]aminato ([H(3)1](3-)), which creates a protective hydrogen bond cavity around the M(III)-O(H) units (M(III) = Fe and Mn). The M(III)-O(H) complexes are prepared by the activation of dioxygen and deprotonation of water. In addition, the M(III)-O(H) complexes can be synthesized using oxygen atom transfer reagents such as N-oxides and hydroxylamines. The [Fe(III)H(3)1(O)](2-) complex also can be made using sulfoxides. These findings support the proposal of a high valent M(IV)-oxo species as an intermediate during dioxygen cleavage. Isotopic labeling studies show that oxo ligands in the [M(III)H(3)1(O)](2-) complexes come directly from the cleavage of dioxygen: for [Fe(III)H(3)1(O)](2-) the nu(Fe-(16)O) = 671 cm(-1), which shifts 26 cm(-1) in [Fe(III)H(3)1((18)O)](2-) (nu(Fe-(18)O) = 645 cm(-1)); a nu(Mn-(16)O) = 700 cm(-1) was observed for [Mn(III)H(3)1((16)O)](2-), which shifts to 672 cm(-1) in the Mn-(18)O isotopomer. X-ray diffraction studies show that the Fe-O distance is 1.813(3) A in [Fe(III)H(3)1(O)](2-), while a longer bond is found in [Fe(III)H(3)1(OH)](-) (Fe-O at 1.926(2) A); a similar trend was found for the Mn(III)-O(H) complexes, where a Mn-O distance of 1.771(5) A is observed for [Mn(III)H(3)1(O)](2-) and 1.873(2) A for [Mn(III)H(3)1(OH)](-). Strong intramolecular hydrogen bonds between the urea NH groups of [H(3)1](3-) and the oxo and oxygen of the hydroxo ligand are observed in all the complexes. These findings, along with density functional theory calculations, indicate that a single sigma-bond exists between the M(III) centers and the oxo ligands, and additional interactions to the oxo ligands arise from intramolecular H-bonds, which illustrates that noncovalent interactions may replace pi-bonds in stabilizing oxometal complexes.

Ethylamines↗
PubMed2004

Prevalence of metabolic syndrome in an Indian urban population.

OBJECTIVES: To determine prevalence of the metabolic syndrome using United States Adult Treatment Panel-3 (ATP-3) guidelines in an urban Indian population. METHODS: Randomly selected adults >20 years were studied using stratified sampling. Target study sample was 1800 with population proportionate distribution (men 960, women 840). Evaluation of anthropometric variables, blood pressure, fasting blood glucose and lipids was performed. Subjects (1123; response 62.4%) were examined, fasting blood samples were available in 1091 (532 men, 559 women) and analysed for prevalence of metabolic syndrome. Atherosclerosis risk factors were determined using the current guidelines. Metabolic syndrome was diagnosed when any three of the following were present: central obesity, raised triglycerides >/=150 mg/dl (>/=1.7 mmol/l), low high-density lipoprotein (HDL) cholesterol, blood pressure >/=130/>/=85 mm Hg, and diabetes or fasting glucose >110 mg/dl (>6.1 mmol/l). Intergroup comparisons were performed using t-test or chi-square test. RESULTS: Metabolic syndrome was present in 345 (31.6%) subjects; prevalence was 122 (22.9%) in men and 223 (39.9%) in women (p<0.001); the age-adjusted prevalence was 24.9%, 18.4% in men and 30.9% in women. There was a significant age-related increase in its prevalence (Mantel-Haenzel chi(2) for trend p<0.05). Prevalence of components of metabolic syndrome in men and women was: central obesity (waist, men >102 cm, women >88 cm) in 116 (25.6%) and 246 (44.0%); low HDL cholesterol (men<40 mg/dl, <1.0 mmol/l), women<50 mg/dl, <1.3 mmol/l) in 292 (54.9%) and 504 (90.2%); high triglycerides >/=150 mg/dl (>/=1.7 mmol/l) in 172 (32.3%) and 160 (28.6%); and impaired fasting glucose or diabetes in 90 (16.9%) and 90 (16.1%). The prevalence of physical inactivity, hypertension, hypercholesterolemia (>/=200 mg/dl, >/=5.2 mmol/l) and high LDL cholesterol (>/=130 mg/dl, >/=3.4 mmol/l) was greater in the metabolic syndrome group in both men and women (p<0.05). CONCLUSIONS: There is a high prevalence of metabolic syndrome in an urban Indian population. Focus of cardiovascular prevention should be at this high-risk group.

Adult↗
PubMed2004

Molecular signatures of self-renewal, differentiation, and lineage choice in multipotential hemopoietic progenitor cells in vitro.

The molecular mechanisms governing self-renewal, differentiation, and lineage specification remain unknown. Transcriptional profiling is likely to provide insight into these processes but, as yet, has been confined to "static" molecular profiles of stem and progenitors cells. We now provide a comprehensive, statistically robust, and "dynamic" analysis of multipotent hemopoietic progenitor cells undergoing self-renewal in response to interleukin-3 (IL-3) and multilineage differentiation in response to lineage-affiliated cytokines. Cells undergoing IL-3-dependent proliferative self-renewal displayed striking complexity, including expression of genes associated with different lineage programs, suggesting a highly responsive compartment poised to rapidly execute intrinsically or extrinsically initiated cell fate decisions. A remarkable general feature of early differentiation was a resolution of complexity through the downregulation of gene expression. Although effector genes characteristic of mature cells were upregulated late, coincident with morphological changes, lineage-specific changes in gene expression were observed prior to this, identifying genes which may provide early harbingers of unilineage commitment. Of particular interest were genes that displayed differential behavior irrespective of the lineage elaborated, many of which were rapidly downregulated within 4 to 8 h after exposure to a differentiation cue. These are likely to include genes important in self-renewal, the maintenance of multipotentiality, or the negative regulation of differentiation per se.

Animals↗
PubMed2004

Choroidal melanoma with macular hole.

A rare case of choroidal melanoma with exudative retinal detachment and a full-thickness macular hole is reported in an Indian patient.

Choroid Neoplasms↗
PubMed2003

Monomeric MnIII/II and FeIII/II complexes with terminal hydroxo and oxo ligands: probing reactivity via O-H bond dissociation energies.

Non-heme manganese and iron complexes with terminal hydroxo or oxo ligands are proposed to mediate the transfer of hydrogen atoms in metalloproteins. To investigate this process in synthetic systems, the monomeric complexes [M(III/II)H(3)1(OH)](-/2-) and [M(III)H(3)1(O)](2-) have been prepared, where M(III/II) = Mn and Fe and [H(3)1](3-) is the tripodal ligand, tris[(N'-tert-butylureaylato)-N-ethyl)]aminato. These complexes have similar primary and secondary coordination spheres, which are enforced by [H(3)1](3-). The homolytic bond dissociation energies (BDEs(O-H)) for the M(III/II)-OH complexes were determined, using experimentally obtained values for the pK(a)(M-OH) and E(1/2) measured in DMSO. This thermodynamic analysis gave BDEs(O-H) of 77(4) kcal/mol for [Mn(II)H(3)1(O-H)](2-) and 66(4) kcal/mol for [Fe(II)H(3)1(O-H)](2-). For the M(III)-OH complexes, [Mn(III)H(3)1(OH)]- and [Fe(III)H(3)1(OH)]-, BDEs(O-H) of 110(4) and 115(4) kcal/mol were obtained. These BDEs(O-H) were verified with reactivity studies with substrates having known X-H bond energies (X = C, N, O). For instance, [Fe(II)H(3)1(OH)](2-) reacts with a TEMPO radical to afford [Fe(III)H(3)1(O)](2-) and TEMPO-H in isolated yields of 60 and 75%, respectively. Consistent with the BDE(O-H) values for [Mn(II)H(3)1(OH)](2-), TEMPO does not react with this complex, yet TEMPO-H (BDE(O-H) = 70 kcal/mol) reacts with [Mn(III)H(3)1(O)](2-), forming TEMPO and [Mn(II)H(3)1(OH)](2-). [Mn(III)H(3)1(O)](2-) and [Fe(III)H(3)1(O)](2-) react with other organic substrates containing C-H bonds less than 80 kcal/mol, including 9,10-dihydroanthracene and 1,4-cyclohexadiene to produce [M(II)H(3)1(OH)](2-) and the appropriate dehydrogenated product in yields of greater than 80%. Treating [Mn(III)H(3)1(O)](2-) and [Fe(III)H(3)1(O)](2-) with phenolic compounds does not yield the product expected from hydrogen atom transfer but rather the protonated complexes, [Mn(III)H(3)1(OH)]- and [Fe(III)H(3)1(OH)]-, which is ascribed to the highly basic nature of the terminal oxo group.

Electrochemistry↗
PubMed2003

Prevalence of diabetes, impaired fasting glucose and insulin resistance syndrome in an urban Indian population.

OBJECTIVE: Epidemiological study among urban subjects in western India to determine prevalence of diabetes, insulin resistance syndrome (IRS) and their risk factors. METHODS: Randomly selected adults > or =20 years were studied using stratified sampling. Target sample was 1,800 (men 960, women 840). 1123 subjects (response 62.4%) were evaluated and blood samples were available in 532 men and 559 women (n=1091, 60.6%). Measurement of anthropometric variables, blood pressure, fasting blood glucose and lipids was performed. Atherosclerosis risk factors were determined using current guidelines. Diabetes was diagnosed when the subject was a known diabetic or fasting blood glucose was > or =126 mg/dl, impaired fasting glucose (IFG) diagnosed when fasting glucose was 110-125 mg/dl. IRS was diagnosed when any three of-IFG, high triglycerides >150 mg/dl, low HDL cholesterol (men<40 mg/dl, women<50 mg/dl), central obesity (men>102 cm, women>88 cm), or high normal blood pressure (>130/>85 mmHg) or hypertension-were present. RESULTS: Diabetes was present in 70 men (13.2%) and 64 women (11.5%). Age-adjusted prevalence of diabetes was 9.3% in men (95% confidence intervals (CI) 6.7-11.8), 8.1% in women (CI 5.8-10.4) and 8.6% overall (CI 6.9-10.3). IFG was in 28 men (5.3%) and 29 women (5.2%). IRS was present in 52 men (9.8%) and 114 women (20.4%) with age-adjusted prevalence of 7.9% in men (CI 6.7-9.1) and 17.5% in women (CI 14.4-20.6) with an overall prevalence of 12.8% (CI 10.8-14.8). Other metabolic abnormalities of IRS in men and women were high triglycerides in 32.1 and 28.6%, low HDL cholesterol in 54.9 and 90.2%; central obesity in 21.8 and 44.0%, and high normal blood pressure or hypertension in 35.5 and 32.4%. IFG subjects had similar atherosclerosis risk factor profile as normal subjects while those with IRS and diabetes had significantly greater prevalence of obesity, central obesity, hypertension, high triglycerides and low HDL (P<0.01). CONCLUSIONS: There is s significant prevalence of diabetes and IRS in this urban Indian population. Subjects with diabetes as well as IRS have greater prevalence of obesity, central obesity, hypertension, hypertriglyceridemia and low HDL as compared with normal subjects.

Adult↗
PubMed2003

CBL1, a calcium sensor that differentially regulates salt, drought, and cold responses in Arabidopsis.

Although calcium is a critical component in the signal transduction pathways that lead to stress gene expression in higher plants, little is known about the molecular mechanism underlying calcium function. It is believed that cellular calcium changes are perceived by sensor molecules, including calcium binding proteins. The calcineurin B-like (CBL) protein family represents a unique group of calcium sensors in plants. A member of the family, CBL1, is highly inducible by multiple stress signals, implicating CBL1 in stress response pathways. When the CBL1 protein level was increased in transgenic Arabidopsis plants, it altered the stress response pathways in these plants. Although drought-induced gene expression was enhanced, gene induction by cold was inhibited. In addition, CBL1-overexpressing plants showed enhanced tolerance to salt and drought but reduced tolerance to freezing. By contrast, cbl1 null mutant plants showed enhanced cold induction and reduced drought induction of stress genes. The mutant plants displayed less tolerance to salt and drought but enhanced tolerance to freezing. These studies suggest that CBL1 functions as a positive regulator of salt and drought responses and a negative regulator of cold response in plants.

Arabidopsis↗
PubMed2003

Modified circuit for retrograde cerebral perfusion.

A modified circuit for delivery of retrograde cerebral perfusion during ascending aortic or aortic arch surgery is described. The technique was applied in 15 patients who showed good postoperative recovery.

Aortic Dissection↗
PubMed2003

Predictors of screening for breast and colorectal cancer among middle-aged women.

BACKGROUND AND OBJECTIVES: Rates of breast and colorectal cancer screenings among women in the United States fall below current guidelines set forth by the American Cancer Society and Healthy People 2010. This study examined predictors of breast and colorectal cancer screening behaviors among women patients (ages 50-75) at a university-based family practice clinic. METHODS: A random sample of 600 women patients were sent a comprehensive written questionnaire assessing demographic characteristics and breast and colorectal cancer screening behaviors and beliefs via the US Postal Service. RESULTS: Rates of clinical breast examinations, mammography, fecal occult blood testing, and sigmoidoscopy/colonoscopy exceeded national and state trends. A greater proportion of women reported receiving breast cancer information as compared to colorectal cancer information. Receiving information from one's physician was significantly related to having had a clinical breast examination, a fecal occult blood test, and sigmoidoscopy/colonoscopy. Significant predictors of fecal occult blood testing included lower perceived barriers, married, receiving information from physician, and greater perceived benefits. Significant predictors of sigmoidoscopy/colonoscopy included receiving information from physician, lower perceived barriers, and advanced age. CONCLUSIONS: The family physician can play an instrumental role in encouraging patients to adhere to current breast and colorectal cancer screening guidelines.

Aged↗
PubMed2003

Insulin levels in low birth weight neonates.

BACKGROUND & OBJECTIVES: Foetal undernutrition may have important role in adult insulin resistance and diabetes but insulin kinetics in very early life has not been well studied. The present study was undertaken to determine insulin levels in low birth weight neonates and compare with the levels in normal weight and high birth weight neonates. METHODS: Ten 7 day old children each of low birth weight (< 2500 g, Group 1), normal birth weight (2500-3500 g, Group 2) and high birth weight (> 3500 g, Group 3) selected successively over a period of one month were studied. All children were normally delivered at full term and were not suffering from any major illness. Detailed anthropometry was performed, a 6 h fasting blood sample was obtained for blood glucose, lipids, insulin and C-peptide estimation; 60 min after an intravenous glucose load a second sample was obtained for glucose and insulin. Insulin resistance was calculated using the homeostasis model assessment (HOMA). RESULTS: Levels of total cholesterol, triglycerides, low density and high density lipoprotein cholesterol and glucose were not significantly different in the three groups. Mean fasting and post-glucose load insulin levels (microU/ml) were 2.78 +/- 2.23 and 3.28 +/- 2.04 in Group 1, 1.67 +/- 1.20 and 2.60 +/- 2.32 in Group 2 and 3.37 +/- 2.08 and 4.40 +/- 3.05 in Group 3 and fasting C-peptide levels (microg/ml) were 0.296 +/- 0.22, 0.208 +/- 0.09 and 0.327 +/- 0.23 respectively. There was no inter-group difference in insulin-glucose ratio, insulin levels adjusted for ponderal index and HOMA indices. A significant inverse quadratic correlation (U-shaped curve) of body weight with insulin (fasting and post-glucose) and C-peptide levels was observed (P < 0.05). INTERPRETATION & CONCLUSION: Both low and high birth weight term neonates have high fasting and post-glucose insulin levels. This U-shaped trend suggests influence of foetal undernutrition (environmental) as well as genetic factors in these children.

Blood Glucose↗
PubMed2002

Characterization of an ultraviolet and a vacuum-ultraviolet irradiance meter with synchrotron radiation.

We have constructed and characterized a simple probe that is suitable for accurate measurements of irradiance in the UV to the vacuum UV spectral range. The irradiance meter consists of a PtSi detector located behind a 5-mm-diameter aperture. The probe was characterized at various wavelengths ranging from 130 to 320 mm by use of continuously tunable synchrotron radiation from the Synchrotron Ultra-violet Radiation Facility III. We determined the irradiance responsivity by scanning a small monochromatic beam over the active area of the irradiance meter and measuring its response on a grid with regular spacing. The angular response was also determined and shown to be suitable for applications such as photolithography. In addition, we studied the radiation damage using a 157-nm excimer laser and found that the irradiance meter can endure more than 100 J/cm2 of 157-nm radiation before a noticeable change occurs in its responsivity. Many industrial applications such as UV curing, photolithography, or semiconductor chip fabrication that require accurate measurement of the irradiance would benefit from having such a stable, accurate LTV irradiance meter.

Journal Article↗
PubMed2002

A chloroplast FKBP interacts with and affects the accumulation of Rieske subunit of cytochrome bf complex.

Immunophilins are intracellular receptors of the immunosuppressants cyclosporin A, FK506, and rapamycin. Although all immunophilins possess peptidyl-prolyl isomerase activity and are identified from a wide range of organisms, little is known about their cellular functions. We report the characterization and functional analysis of an FK506 and rapamycin-binding protein (AtFKBP13) from Arabidopsis. The AtFKBP13 protein is synthesized as a precursor that is imported into chloroplasts and processed to the mature form located in the thylakoid lumen, as shown by chloroplast import assays and Western blot analysis. Experiments show that AtFKBP13 is translocated across the thylakoid membrane by the DeltapH-dependent pathway. Yeast two-hybrid screening identified Rieske FeS protein, a subunit of the cytochrome bf complex in the photosynthetic electron transport chain, as an interacting partner for AtFKBP13. Both yeast two-hybrid and in vitro protein-protein interaction assays showed that the precursor, but not the mature form, of AtFKBP13 interacted with Rieske protein, suggesting that interaction between the two proteins occurs along the import pathway. When AtFKBP13 expression was suppressed by RNA interference method, the level of Rieske protein was significantly increased in the transgenic plants.

Amino Acid Sequence↗
PubMed2002

Synthesis and characterization of completely delocalized mixed-valent dicopper complexes.

The multidentate ligands tris[(N'-tert-butylureayl)-N-ethyl)]amine (H(6)1) and 1-(tert-butylaminocarbonyl)-2,2-dimethylaminoethane (H(2)2) have been used to investigate the assembly and properties of complexes with Cu(1.5)Cu(1.5) units. The complexes [Cu(H(5)1)](2)(+) and [Cu(H2)](2)(+) have been isolated and structurally characterized by X-ray diffraction methods. [Cu(H(5)1)](2)(+) has a Cu(1.5)Cu(1.5) core, with each copper ion having square planar coordination geometry. The copper ions are linked through two mono-deprotonated urea ligands, which coordinate as mu-1,3-(kappaN:kappaO) ureate bridges to produce a Cu-Cu distance of 2.39 A. The remaining two urea arms of [H(5)1](-) form intramolecular hydrogen bonds, the result of which is to confine the Cu(1.5)Cu(1.5) unit within a pseudomacrocycle. The structure of [Cu(H2)](2)(+) lacks intramolecular hydrogen bonds and thus does not have a pseudomacrocyclic structure. However, the structural properties of the Cu(1.5)Cu(1.5) core in [Cu(H2)](2)(+) are nearly identical to those of [Cu(H(5)1)](2)(+). Both complexes exhibit rhombic EPR spectra at 77 K, which do not change upon cooling to 4 K. The optical spectra of [Cu(H(5)1)](2)(+) and [Cu(H2)](2)(+) are dominated by an intense band at approximately 700 nm. These spectral characteristics are consistent with [Cu(H(5)1)](2)(+) and [Cu(H2)](2)(+) being classified as fully delocalized (type III) mixed-valent species.

Amines↗
PubMed2002

Functional relationship of cytochrome c(6) and plastocyanin in Arabidopsis.

Photosynthetic electron carriers are important in converting light energy into chemical energy in green plants. Although protein components in the electron transport chain are largely conserved among plants, algae and prokaryotes, there is thought to be a major difference concerning a soluble protein in the thylakoid lumen. In cyanobacteria and eukaryotic algae, both plastocyanin and cytochrome c(6) mediate electron transfer from cytochrome b(6)f complex to photosystem I. In contrast, only plastocyanin has been found to play the same role in higher plants. It is widely accepted that cytochrome c(6) has been evolutionarily eliminated from higher-plant chloroplasts. Here we report characterization of a cytochrome c(6)-like protein from Arabidopsis (referred to as Atc6). Atc6 is a functional cytochrome c localized in the thylakoid lumen. Electron transport reconstruction assay showed that Atc6 replaced plastocyanin in the photosynthetic electron transport process. Genetic analysis demonstrated that neither plastocyanin nor Atc6 was absolutely essential for Arabidopsis growth and development. However, plants lacking both plastocyanin and Atc6 did not survive.

Amino Acid Sequence↗
PubMed2002

Absolute refractive indices and thermal coefficients of CaF2, SrF2, BaF2, and LiF near 157 nm.

We present high-accuracy measurements for wavelengths near 157 nm of the absolute index of refraction, the index dispersion, and the temperature dependence of the index for the ultraviolet optical materials with cubic symmetry: CaF2, SrF2, BaF2, and LiF. Accurate values of these quantities for these materials are needed for designs of the lens systems for F2 excimer-laser-based exposure tools for 157-nm photolithography. These tools are expected to use CaF2 as the primary optical material and possibly one of the others to correct for chromatic aberrations. These optical properties were measured by the minimum deviation method. Absolute refractive indices were obtained with an absolute accuracy of 5 x 10(-6) to 6 x 10(-6).

Journal Article↗