Search

Your search keyword '"Kulkarni, Sameer"' showing total 393 results
Start Over Author "Kulkarni, Sameer"
393 results on '"Kulkarni, Sameer"'

114. NASA Environmentally Responsible Aviation High Overall Pressure Ratio Compressor Research Pre-Test CFD

Author

Celestina, Mark L, Fabian, John C, and Kulkarni, Sameer

Subjects
Fluid Mechanics And Thermodynamics
Abstract

This paper describes a collaborative and cost-shared approach to reducing fuel burn under the NASA Environmentally Responsible Aviation project. NASA and General Electric (GE) Aviation are working together aa an integrated team to obtain compressor aerodynamic data that is mutually beneficial to both NASA and GE Aviation. The objective of the High OPR Compressor Task is to test a single stage then two stages of an advanced GE core compressor using state-of-the-art research instrumentation to investigate the loss mechanisms and interaction effects of embedded transonic highly-loaded compressor stages. This paper presents preliminary results from NASA's in-house multistage computational code, APNASA, in preparation for this advanced transonic compressor rig test.

Published
2012

115. Development and Applications of a Stage Stacking Procedure

Author

Kulkarni, Sameer, Celestina, Mark L, and Adamczyk, John J

Subjects
Aerodynamics
Abstract

The preliminary design of multistage axial compressors in gas turbine engines is typically accomplished with mean-line methods. These methods, which rely on empirical correlations, estimate compressor performance well near the design point, but may become less reliable off-design. For land-based applications of gas turbine engines, off-design performance estimates are becoming increasingly important, as turbine plant operators desire peaking or load-following capabilities and hot-day operability. The current work develops a one-dimensional stage stacking procedure, including a newly defined blockage term, which is used to estimate the off-design performance and operability range of a 13-stage axial compressor used in a power generating gas turbine engine. The new blockage term is defined to give mathematical closure on static pressure, and values of blockage are shown to collapse to curves as a function of stage inlet flow coefficient and corrected shaft speed. In addition to these blockage curves, the stage stacking procedure utilizes stage characteristics of ideal work coefficient and adiabatic efficiency. These curves are constructed using flow information extracted from computational fluid dynamics (CFD) simulations of groups of stages within the compressor. Performance estimates resulting from the stage stacking procedure are shown to match the results of CFD simulations of the entire compressor to within 1.6% in overall total pressure ratio and within 0.3 points in overall adiabatic efficiency. Utility of the stage stacking procedure is demonstrated by estimation of the minimum corrected speed which allows stable operation of the compressor. Further utility of the stage stacking procedure is demonstrated with a bleed sensitivity study, which estimates a bleed schedule to expand the compressors operating range.

Published
2012

118. Results of an Advanced Fan Stage Operating Over a Wide Range of Speed and Bypass Ratio

Author

Celestina, Mark L, Suder, Kenneth L, and Kulkarni, Sameer

Subjects
Fluid Mechanics And Thermodynamics
Abstract

NASA and GE teamed to design and build a 57 percent engine scaled fan stage for a Mach 4 variable cycle turbofan/ramjet engine for access to space with multipoint operations. This fan stage was tested in NASA's transonic compressor facility. The objectives of this test were to assess the aerodynamic and aero mechanic performance and operability characteristics of the fan stage over the entire range of engine operation including: 1) sea level static take-off; 2) transition over large swings in fan bypass ratio; 3) transition from turbofan to ramjet; and 4) fan wind-milling operation at high Mach flight conditions. This paper will focus on an assessment of APNASA, a multistage turbomachinery analysis code developed by NASA, to predict the fan stage performance and operability over a wide range of speeds (37 to 100 percent) and bypass ratios.

Published
2010

123. The plant product quinic acid activates Ca 2+ ‐dependent mitochondrial function and promotes insulin secretion from pancreatic beta cells

Author

Heikkilä, Eija, primary, Hermant, Aurelie, additional, Thevenet, Jonathan, additional, Bermont, Flavien, additional, Kulkarni, Sameer S., additional, Ratajczak, Joanna, additional, Santo‐Domingo, Jaime, additional, Dioum, El Hadji, additional, Canto, Carles, additional, Barron, Denis, additional, Wiederkehr, Andreas, additional, and De Marchi, Umberto, additional

Published
2019
Full Text
View/download PDF

126. Understanding determinants of carbohydrate metabolism and their contribution to metabolic health; the impact of AMY1 CNV (P21-015-19)

Author

O'Callaghan, Nathan, Valsesia, Armand, Kulkarni, Sameer, Marquis, Julien, Leone, Patricia, Mironova, Polina, Walter, Ondine, Saris, Wim, Descombes, Patrick, Hager, Jorg, Astrup, Arne, Darimont, Chrsitian, O'Callaghan, Nathan, Valsesia, Armand, Kulkarni, Sameer, Marquis, Julien, Leone, Patricia, Mironova, Polina, Walter, Ondine, Saris, Wim, Descombes, Patrick, Hager, Jorg, Astrup, Arne, and Darimont, Chrsitian

Abstract

Objectives: Salivary α- amylase (AMY1) is responsible for the breakdown of starch into oligosaccharides, tri and di-saccharides giving a start to the starch digestion in the oral cavity on food consumption. Several studies recently reported contradicting results regarding the link between AMY1 copy numbers (CNs) and obesity and type 2 diabetes. Objective: We investigated whether CN in the AMY1 gene was associated with differential anthropometrics and glycaemic outcomes in obese individuals who underwent a dietary plan varying in macronutrient intake, as a part of weight loss and weight maintenance program. We also investigated whether there existed an interaction between nutrient intakes and AMY1 CNs and if AMY1 CNs have influence on body weight, body composition and glycemic trajectories during dietary interventions.Methods: Using the Paralogue Ratio Test, we accurately measured the AMY1 CNs in 761 obese individuals from the Diogenes study. Subjects underwent first an 8-week low-caloric diet (LCD, at 800 kcal/d) and those achieving >8% weight loss were then randomized to a 6-month weight maintenance dietary (WMD) intervention. The association between AMY1 CNs and weight- and glycemic- parameters was tested at baseline and following each intervention phase (LCD, WMD) with the use of linear mixed effect models adjusting for gender, age, center and total energy intake.Results: At baseline, a modest association between AMY1 CN and BMI (P = 0.04) was observed. AMY1 CN was not associated with baseline glycemic variables. Additionally, AMY1 CN was not associated with anthropometric or glycemic-outcomes following either LCD or WMD. Interaction analyses between AMY1 CN and nutrient intake did not reveal significant association with any clinical parameters (at baseline and following LCD or WMD) or when testi

Published
2019

129. REINFORCE

Author

Kulkarni, Sameer G, primary, Liu, Guyue, additional, Ramakrishnan, K. K., additional, Arumaithurai, Mayutan, additional, Wood, Timothy, additional, and Fu, Xiaoming, additional

Published
2018
Full Text
View/download PDF

130. Distinct patterns of skeletal muscle mitochondria fusion, fission and mitophagy upon duration of exercise training

Author

Arribat, Yoan, primary, Broskey, Nicholas T., additional, Greggio, Chiara, additional, Boutant, Marie, additional, Conde Alonso, Sonia, additional, Kulkarni, Sameer S., additional, Lagarrigue, Sylviane, additional, Carnero, Elvis A., additional, Besson, Cyril, additional, Cantó, Carles, additional, and Amati, Francesca, additional

Published
2018
Full Text
View/download PDF

135. MiCOMP

Author

Ashouri, Amir H., primary, Bignoli, Andrea, additional, Palermo, Gianluca, additional, Silvano, Cristina, additional, Kulkarni, Sameer, additional, and Cavazos, John, additional

Published
2017
Full Text
View/download PDF

136. NFVnice

Author

Kulkarni, Sameer G., primary, Zhang, Wei, additional, Hwang, Jinho, additional, Rajagopalan, Shriram, additional, Ramakrishnan, K. K., additional, Wood, Timothy, additional, Arumaithurai, Mayutan, additional, and Fu, Xiaoming, additional

Published
2017
Full Text
View/download PDF

141. The plant product quinic acid activates Ca2+ -dependent mitochondrial function and promotes insulin secretion from pancreatic beta cells.

Author

Heikkilä, Eija, Hermant, Aurelie, Thevenet, Jonathan, Bermont, Flavien, Kulkarni, Sameer S., Ratajczak, Joanna, Santo‐Domingo, Jaime, Dioum, El Hadji, Canto, Carles, Barron, Denis, Wiederkehr, Andreas, De Marchi, Umberto, and Santo-Domingo, Jaime

Subjects
PANCREATIC beta cells, QUINIC acid, RESPIRATION, PLANT products, PANCREATIC secretions, INSULIN, BLOOD sugar, CALCIUM metabolism, BIOCHEMISTRY, BIOLOGICAL products, COFFEE, CELL culture, CRANBERRIES, QUINIDINE gluconate, PHENOMENOLOGICAL biology, KIWIFRUIT, MITOCHONDRIA, PLANTS, RATS, BILBERRY, DOSE-effect relationship in pharmacology, MICE, ANIMALS, PHARMACODYNAMICS
Abstract

Background and Purpose: Quinic acid (QA) is an abundant natural compound from plant sources which may improve metabolic health. However, little attention has been paid to its effects on pancreatic beta-cell functions, which contribute to the control of metabolic health by lowering blood glucose. Strategies targeting beta-cell signal transduction are a new approach for diabetes treatment. This study investigated the efficacy of QA to stimulate beta-cell function by targeting the basic molecular machinery of metabolism-secretion coupling.Experimental Approach: We measured bioenergetic parameters and insulin exocytosis in a model of insulin-secreting beta-cells (INS-1E), together with Ca2+ homeostasis, using genetically encoded sensors, targeted to different subcellular compartments. Islets from mice chronically infused with QA were also assessed.Key Results: QA triggered transient cytosolic Ca2+ increases in insulin-secreting cells by mobilizing Ca2+ from intracellular stores, such as endoplasmic reticulum. Following glucose stimulation, QA increased glucose-induced mitochondrial Ca2+ transients. We also observed a QA-induced rise of the NAD(P)H/NAD(P)+ ratio, augmented ATP synthase-dependent respiration, and enhanced glucose-stimulated insulin secretion. QA promoted beta-cell function in vivo as islets from mice infused with QA displayed improved glucose-induced insulin secretion. A diet containing QA improved glucose tolerance in mice.Conclusions and Implications: QA modulated intracellular Ca2+ homeostasis, enhancing glucose-stimulated insulin secretion in both INS-1E cells and mouse islets. By increasing mitochondrial Ca2+ , QA activated the coordinated stimulation of oxidative metabolism, mitochondrial ATP synthase-dependent respiration, and therefore insulin secretion. Bioactive agents raising mitochondrial Ca2+ in pancreatic beta-cells could be used to treat diabetes. [ABSTRACT FROM AUTHOR]

Published
2019
Full Text
View/download PDF

142. Mitochondrial Post-translational Modifications and Metabolic Control: Sirtuins and Beyond

Author

Kulkarni, Sameer S., Canto, Carles, Kulkarni, Sameer S., and Canto, Carles

Abstract

Introduction: In order to maintain metabolic homeostasis, organisms adjust the capacity and efficiency of ATP generation to changes in energetic demand and supply. While the transcriptional control of mitochondrial biogenesis allows to adapt mitochondrial respiratory capacity with long-term requirements for differential energy demand (e.g.: exercise training), bioenergetic adaptation also needs to take place within shorter time frames in order to properly fine-tune nutrient availability, energy production and demand, either in a circadian fashion or after a meal. These quick metabolic responses can be achieved through exquisite modulation of diverse post-translational modifications, which influence a variety of mitochondrial processes, including mitochondrial dynamics, fatty acid oxidation, lipogenesis and bioenergetic efficiency. Conclusion: In this review, we will specially focus on the role of mitochondrial sirtuin enzymes as modulators of mitochondrial ac(et) ylation and the possible interactions with other posttranslational modification events.

Published
2017
Full Text
View/download PDF

145. NRK1 controls nicotinamide mononucleotide and nicotinamide riboside metabolism in mammalian cells

Author

Ratajczak, Joanna, Joffraud, Magali, Trammell, Samuel A.J., Ras, Rosa, Canela, Nuria, Boutant, Marie, Kulkarni, Sameer S., Rodrigues, Marcelo, Redpath, Philip, Migaud, Marie E., Auwerx, Johan, Yanes, Oscar, Brenner, Charles, Cantó, Carles, Ratajczak, Joanna, Joffraud, Magali, Trammell, Samuel A.J., Ras, Rosa, Canela, Nuria, Boutant, Marie, Kulkarni, Sameer S., Rodrigues, Marcelo, Redpath, Philip, Migaud, Marie E., Auwerx, Johan, Yanes, Oscar, Brenner, Charles, and Cantó, Carles

Abstract

NAD + is a vital redox cofactor and a substrate required for activity of various enzyme families, including sirtuins and poly(ADP-ribose) polymerases. Supplementation with NAD + precursors, such as nicotinamide mononucleotide (NMN) or nicotinamide riboside (NR), protects against metabolic disease, neurodegenerative disorders and age-related physiological decline in mammals. Here we show that nicotinamide riboside kinase 1 (NRK1) is necessary and rate-limiting for the use of exogenous NR and NMN for NAD + synthesis. Using genetic gain- and loss-of-function models, we further demonstrate that the role of NRK1 in driving NAD + synthesis from other NAD + precursors, such as nicotinamide or nicotinic acid, is dispensable. Using stable isotope-labelled compounds, we confirm NMN is metabolized extracellularly to NR that is then taken up by the cell and converted into NAD + . Our results indicate that mammalian cells require conversion of extracellular NMN to NR for cellular uptake and NAD + synthesis, explaining the overlapping metabolic effects observed with the two compounds.

Published
2016

147. NRK1 controls nicotinamide mononucleotide and nicotinamide riboside metabolism in mammalian cells

Author

Ratajczak, Joanna, primary, Joffraud, Magali, additional, Trammell, Samuel A. J., additional, Ras, Rosa, additional, Canela, Núria, additional, Boutant, Marie, additional, Kulkarni, Sameer S., additional, Rodrigues, Marcelo, additional, Redpath, Philip, additional, Migaud, Marie E., additional, Auwerx, Johan, additional, Yanes, Oscar, additional, Brenner, Charles, additional, and Cantó, Carles, additional

Published
2016
Full Text
View/download PDF

148. Mfn1 Deficiency in the Liver Protects Against Diet-Induced Insulin Resistance and Enhances the Hypoglycemic Effect of Metformin

Author

Kulkarni, Sameer S., primary, Joffraud, Magali, additional, Boutant, Marie, additional, Ratajczak, Joanna, additional, Gao, Arwen W., additional, Maclachlan, Catherine, additional, Hernandez-Alvarez, Maria Isabel, additional, Raymond, Frédéric, additional, Metairon, Sylviane, additional, Descombes, Patrick, additional, Houtkooper, Riekelt H., additional, Zorzano, Antonio, additional, and Cantó, Carles, additional

Published
2016
Full Text
View/download PDF

149. Peptide Ligation at High Dilution via Reductive Diselenide-Selenoester Ligation

Author

Chisholm, Timothy S., Kulkarni, Sameer S., Hossain, Khondker R., Cornelius, Flemming, Clarke, Ronald J., and Payne, Richard J.

Abstract

Peptide ligation chemistry has revolutionized protein science by providing access to homogeneously modified peptides and proteins. However, lipidated polypeptides and integral membrane proteins—an important class of biomolecules—remain enormously challenging to access synthetically owing to poor aqueous solubility of one or more of the fragments under typical ligation conditions. Herein we describe the advent of a reductive diselenide-selenoester ligation (rDSL) method that enables efficient ligation of peptide fragments down to low nanomolar concentrations, without resorting to solubility tags or hybridizing templates. The power of rDSL is highlighted in the efficient synthesis of the FDA-approved therapeutic lipopeptide tesamorelin and palmitylated variants of the transmembrane lipoprotein phospholemman (FXYD1). Lipidation of FXYD1 was shown to critically modulate inhibitory activity against the Na+/K+pump.

Published
2020
Full Text
View/download PDF

150. Diselenide–selenoester ligation for chemical protein synthesis

Author

Kulkarni, Sameer, Watson, Emma, Premdjee, Bhavesh, Conde-Frieboes, Kilian, and Payne, Richard

Abstract

Chemoselective peptide ligation methods have provided synthetic access to numerous proteins, including those bearing native post-translational modifications and unnatural labels. This protocol outlines the chemical synthesis of proteins using a recently discovered reaction (diselenide–selenoester ligation (DSL)) in a rapid, additive-free manner. After ligation, the products can be chemoselectively deselenized to produce native peptide and protein products. We describe methods for the synthesis of suitably functionalized peptide diselenide and peptide selenoester fragments via Fmoc-solid-phase peptide synthesis (SPPS) protocols, fusion of these fragments by DSL, and the chemoselective deselenization of the ligation products to generate native synthetic proteins. We demonstrate the method’s utility through the total chemical synthesis of the post-translationally modified collagenous domain of the hormone adiponectin via DSL–deselenization at selenocystine (the oxidized form of selenocysteine) and the rapid preparation of two tick-derived thrombin-inhibiting proteins by DSL–deselenization at β-selenoaspartate and γ-selenoglutamate. This method should find widespread use for the rapid synthesis of proteins, including cases in which other peptide ligation methods cannot be used (or cannot be used efficiently), e.g., at sterically hindered or deactivated acyl donors. The method’s speed and efficiency may render it useful in the generation of synthetic protein libraries. Each protein discussed can be synthesized within 15 working days from resin loading and can be readily produced by practitioners with master’s-level experience in organic chemistry. Each synthesis using these protocols was performed independently by two labs (one academic and one industrial), which attained comparable yields of the protein products. This protocol outlines the chemical synthesis of proteins via a recently discovered reaction called diselenide–selenoester ligation (DSL) in a rapid, additive-free manner. After ligation, products can be chemoselectively deselenized to produce native peptide and protein products.

Published
2019
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results