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Zen JM, Senthil Kumar A, Chung CR. A glucose biosensor employing a stable artificial peroxidase based on ruthenium purple anchored cinder. Anal Chem 2003; 75:2703-9. [PMID: 12948139 DOI: 10.1021/ac020542u] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Iron-enriched industrial waste cinder (CFe*) has been recycled for efficient and stable anchoring of Ru(CN)6(4-) to the formation of a hybrid ruthenium purple complex. The cinder/ruthenium purple hybrid-modified carbon paste electrode (designated as CPE/CFe*-RP) was worked out for hydrodynamic analysis of H2O2 at a low detecting potential of 0.0 V versus Ag/AgCl in pH 7 ammonium buffer solution. The highly active, selective, and stable electrocatalytic system with a function similar to peroxidase enzyme shows a linear calibration curve up to 0.8 mM H2O2 at a rotation rate of 3600 rpm with slope and detection limit (S/N = 3) of 0.11 microA/microM and 33 nM, respectively. Interference by direct electrochemical oxidation of easily oxidizable substances can be prevented as a result of the low detecting potential of the working system. A glucose biosensor was further constructed by coating with glucose oxidase and Tosflex on the CPE/CFe*-RP (denoted as CPE/CFe*-RP/GOx/Ts). The proposed CPE/CFe*-RP/GOx/Ts with a two-layer configuration, that is, enzyme and protecting layers, exhibits good operational performance in terms of response time, linearity, detection limit, and lifetime.
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Zen J, Liou S, Kumar AS, Hsia M. Angew Chem Int Ed Engl 2003; 115:1366-1366. [DOI: 10.1002/ange.200390313] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Zen JM, Liou SL, Kumar AS, Hsia MS. An Efficient and Selective Photocatalytic System for the Oxidation of Sulfides to Sulfoxides. Angew Chem Int Ed Engl 2003. [DOI: 10.1002/anie.200390341] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Zen JM, Liou SL, Kumar AS, Hsia MS. An efficient and selective photocatalytic system for the oxidation of sulfides to sulfoxides. Angew Chem Int Ed Engl 2003; 42:577-9. [PMID: 12569495 DOI: 10.1002/anie.200390166] [Citation(s) in RCA: 110] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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105
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Rajendran R, Kumari KR, Kumar AS. Liver ultrasound and faecal copper estimation in oral submucous fibrosis. Indian J Dent Res 2003; 14:13-21. [PMID: 12800753] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/03/2023] Open
Abstract
There is no evidence of an increased quantity of ingestion of copper in areca nut chewers by way of habitually swallowing the 'quid juice' allegedly contain 'appreciable quantity' of soluble copper. Our experimental findings are favour of assuming that the amount of copper ingested, if at all, is well within the threshold limit of tolerance and therefore of no clinical significance. In conjunction with our earlier observation this study again proved the absence of visible and clinically/diagnostically detectable fibrosis in visceral organs, that includes liver, in patients suffering from advanced oral submucous fibrosis.
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Zen JM, Song YS, Chung HH, Hsu CT, Kumar AS. Photoelectrochemical oxygen sensor using copper-plated screen-printed carbon electrodes. Anal Chem 2002; 74:6126-30. [PMID: 12498213 DOI: 10.1021/ac020058r] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We report here an efficient photocatalytic amperometric sensor for the determination of dissolved oxygen (DO) in phosphate buffer solution using a disposable copper-plated screen-printed carbon electrode (CuSPE). The photoelectrochemical activity toward DO of the CuSPE was related to the formation of a p-type semiconductor Cu(I)2O. The solution pH and biased potential (E(bias)) were systematically optimized as pH 8 PBS and -0.7 V vs Ag/AgCl, respectively. Under optimized conditions, the calibration plot was linear in the range of 1-8 ppm with sensitivity and regression coefficient of 23.51 (microA cm2)(-1) ppm(-1) and 0.9982, respectively. The reproducibility of the system was good with seven successive measurements of DO yielding a RSD value of 1.87%. Real sample assays for groundwater and tap water were also consistent with those measured by a commercial DO meter. The principle used in DO measurement has an opportunity to extend into various research fields.
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Zen JM, Chung HH, Kumar AS. Selective detection of o-diphenols on copper-plated screen-printed electrodes. Anal Chem 2002; 74:1202-6. [PMID: 11924986 DOI: 10.1021/ac011012l] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Selective detection of o-diphenols (e.g., catechol, dopamine, and pyrogallol) in the presence of simple phenols, m- and p- derivative diphenols, and ascorbic acid has been demonstrated on copper-plated screen-printed electrodes (CuSPEs) in pH 7.4 phosphate buffer solution. The CuSPE showed an unusual catalytic response at -0.05 V versus Ag/AgCl selectively to o-diphenolic compounds. The o-diphenols can thus be determined amperometrically through direct electrochemical oxidation in low potentials (approximately 0 V), where the CuSPE is much less subject to interfering reactions. Such a catalytic phenomenon cannot be observed on conventional Pt and glassy carbon electrodes. The selective mechanism is explained in terms of the formation of cyclic five-member complex intermediate (Cu(II)-o-quinolate). Most important of all, the common drawbacks of electrode fouling through polymerization were completely overcome in this system.
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Zen JM, Yang CC, Senthil Kumar A. Potential scan rate dependence of underpotential and bulk depositions of lead on screen-printed silver electrodes. Electrochim Acta 2001. [DOI: 10.1016/s0013-4686(01)00790-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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109
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Crowder CM, Westover EJ, Kumar AS, Ostlund RE, Covey DF. Enantiospecificity of cholesterol function in vivo. J Biol Chem 2001; 276:44369-72. [PMID: 11598105 DOI: 10.1074/jbc.c100535200] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The importance of the absolute configuration of cholesterol for its function in vivo is unknown. To directly test this question in vivo, we synthesized the enantiomer of cholesterol (ent-cholesterol) and tested its ability to substitute for natural cholesterol (nat-cholesterol) in the growth, viability, and behavior of Caenorhabditis elegans, a cholesterol auxotroph. First-generation animals grown on ent-cholesterol were viable with only mild behavioral defects. However, ent-cholesterol produced 100% lethality/arrest of their second generation progeny. Isotopically labeled ent-cholesterol incorporated into animals, indicating that its lethality was not secondary to cholesterol starvation. When mixed with nat-cholesterol, ent-cholesterol was not inert; rather, it antagonized the activity of nat-cholesterol. These results demonstrate for the first time that the absolute configuration of cholesterol, not just its physical properties, is essential for its functions in vivo.
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Abstract
An artificial enzyme analogue of Nafion/lead-ruthenium oxide pyrochlore (Py) chemically modified electrode (NPyCME) is synthesized by in situ precipitation through blocking of Nafion's hydrophilic zones. The catalytically active Py sites covered with a hydrophobic core of Nafion resemble an enzymatic structure. Moreover, the NPyCME obeys the Michaelis-Menten mechanism for the oxidation of many organic and biological molecules. This Account highlights aspects of the preparation, characterization, and application of the NPyCME.
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Choudhary SK, Talwar S, Juneja R, Kumar AS. Fate of mild aortic valve disease after mitral valve intervention. J Thorac Cardiovasc Surg 2001; 122:583-6. [PMID: 11547313 DOI: 10.1067/mtc.2001.115916] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
OBJECTIVE This study was performed to assess the long-term outcome of untreated mild aortic valve disease present at the time of initial mitral valve intervention. METHODS A total of 284 patients with rheumatic heart disease aged 7 to 62 years (mean, 23.5 +/- 12.2 years) who underwent mitral valve intervention and had mild aortic valve disease initially were followed up for 2 to 18 years (mean, 10.8 +/- 3.7 years). At initial intervention, 232 patients had pure mild aortic regurgitation, and 52 patients had mild aortic stenosis with or without aortic regurgitation. RESULTS Among patients with mild aortic regurgitation initially, 11 (5%) patients progressed to moderate (n = 6) or severe (n = 5) regurgitation over an interval of 9 to 17 years (mean, 12.1 +/- 2.8 years), and 1 patient had moderate aortic stenosis and severe aortic regurgitation after 10 years. Freedom from development of moderate-severe aortic valve disease in patients who initially had mild aortic regurgitation was 100%, 97.0% +/- 1.7%, and 87.4% +/- 4.6% at 5, 10, and 15 years, respectively. Seventeen (35%) patients with initial mild aortic stenosis (with or without regurgitation) had moderate or severe stenosis (with or without moderate-severe regurgitation) after an interval of 4.9 +/- 3.8 years. Freedom from development of moderate-severe aortic valve disease in patients who initially had mild aortic stenosis was 75.6% +/- 6.2%, 61.5% +/- 8.5%, and 46.1% +/- 11.2% at 5, 10, and 15 years, respectively. Ten patients required aortic valve replacement for aortic valve dysfunction. CONCLUSIONS Mild aortic regurgitation present at the time of mitral valve intervention progresses very slowly and less frequently requires reintervention. However, mild aortic stenosis diagnosed initially progresses more often and more rapidly and thus needs closer follow-up.
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Zen JM, Kumar AS, Chen JC, Jayachithra K, Balamurugan K, Chin DH. Electrocatalytic cyclization of dithiothreitol on a chemically modified electrode by analogy with protein action. Analyst 2001; 126:1409-13. [PMID: 11534615 DOI: 10.1039/b102767k] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Electrocatalytic oxidative cyclization of dithiothreitol (DTT(SH)2) to a disulfide product was demonstrated on a Nafion/lead-ruthenium oxide pyrochlore chemically modified electrode (NPyCME). The process at the NPyCME with DTT(SH)2 is similar to the behaviour of protein in a disulfide linkage, which can be demonstrated by product analysis using HPLC coupled with UV spectroscopy. A possible electrocatalytic mechanism for DTT(SH)2 oxidation to dihydroxydithiane [i.e. cyclized DTT(S-S)] on the NPyCME was proposed in terms of Py-Ru(IV)/Py-Ru(VI) redox active sites. This physical aspect was further utilized for high precision analytical assays using flow injection analysis (FIA), with a linearity up to 50 microM and a detection limit (S/N = 3) of 28 nM (8.64 pg) in a 20 microL sample loop. This is the most sensitive method ever reported for DTT(SH)2 detection assays. The interference from dissolved oxygen, disulfide and glucose is almost negligible. The present method offers an easy route for extension to redox-related protein studies.
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Kumar AS, Aggarwal S, Choudhary SK. Mitral valve replacement with the pulmonary autograft: the Ross II procedure. J Thorac Cardiovasc Surg 2001; 122:378-9. [PMID: 11479513 DOI: 10.1067/mtc.2001.114095] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Anjaneyulu A, Reddy VK, Raju PK, Rajagopalaraju A, Kumar AS, Ravichandra R. Acute reversible left ventricular dysfunction following general anesthesia. Indian Heart J 2001; 53:508-10. [PMID: 11759947] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/23/2023] Open
Abstract
Acute reversible left ventricular dysfunction due to myocardial stunning is a known phenomenon during acute myocardial infarction, coronary angiography, coronary angioplasty or after coronary artery bypass surgery. We report a rare case of acute reversible dysfunction of the myocardium as a complication of general anesthesia in a patient with normal coronary arteries. This is a potentially fatal complication unless recognized early and treated aggressively.
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Kumar AS. Chordal replacement or repair. Ann Thorac Surg 2001; 71:2084. [PMID: 11426817 DOI: 10.1016/s0003-4975(00)02462-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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118
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Zen JM, Kumar AS, Chen JC. Mechanistic Studies and Sensitive Determination of Norepinephrine at a Nafion/Lead-Ruthenium Oxide Pyrochlore Chemically Modified Electrode. ELECTROANAL 2001. [DOI: 10.1002/1521-4109(200104)13:6<457::aid-elan457>3.0.co;2-m] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Goel PK, Kumar AS, Kapoor A, Umeshan CV, Gupta DK. Inoue balloon mitral valvotomy in patients with atrial septal aneurysm. Int J Cardiol 2001; 78:127-34. [PMID: 11334656 DOI: 10.1016/s0167-5273(00)00478-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Atrial septal aneurysms (ASA) are not uncommonly detected in patients with rheumatic mitral stenosis and pose problems during transeptal puncture in patients undergoing balloon mitral valvotomy. From a period of August 1995 to May 1998, we performed a total of 680 Inoue Balloon Mitral Valvotomy (IBMV) procedures with ASA noted in 30 patients, 13 of diffuse and 17 localized type. Transesophageal echocardiography (TOE) was used in all patients with suspected aneurysm on transthoracic echo (TTE) for exact three-dimensional delineation of the location and extent of the aneurysm. The localized type of aneurysms were further subcategorized into five types viz. antero-superior and leftwards (6), postero-superior and rightwards (2), antero-inferior and leftwards (2), postero-inferior and rightwards (5), and central (2), depending on their location in the atrial septum. The site for transeptal puncture was decided after this localization and the remainder of the IBMV procedure was as usual. In the set of thirteen patients with diffuse type of atrial septal aneurysms all but one case had a successful transeptal puncture using standard technique except for a somewhat inferior puncture site so as to be perpendicular to the plane of atrial septum and a successful mitral valve dilatation was possible at first attempt. In the set of 17 patients with localized type of aneurysms, all had a successful transeptal puncture except one. In patients with aneurysms localized antero-superiorly and leftwards the septal puncture was done in a slightly inferior location with transeptal needle pointing some what more posterior, i.e. 5 or 6 o'clock position and in patients with aneurysms localized postero-inferiorly the puncture was done more cephalic with needle directed somewhat anterior, i.e. 3-2 o'clock position. In the two patients with Atrial septal aneurysms located postero-superiorly and to the right the puncture was done slightly inferior but with transeptal needle pointing to about 3 or 2 o'clock position and in the single patient with antero-inferior location the puncture was done in slightly higher but with a more posterior directed needle, i.e. 5-6 o'clock position. The two patients with centrally located localized type of aneurysms had successful transeptal puncture with standard needle direction (4 o'clock) but at a slightly inferior location. We conclude that a good localization of atrial septal aneurysms using transesophageal echocardiography and our technique of transeptal puncture leads to a successful outcome in majority of cases undergoing Inoue balloon mitral valvotomy with associated atrial septal aneurysms.
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Zen JM, Wang WM, Kumar AS. Potentiometric Stripping Analysis of Traces of Thallium(III) at a Poly(4-Vinylpyridine)/Mercury Film Electrode. ELECTROANAL 2001. [DOI: 10.1002/1521-4109(200103)13:4<321::aid-elan321>3.0.co;2-u] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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121
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Zen JM, Kumar AS, Chen JC. Electrocatalytic Oxidation and Sensitive Detection of Cysteine on a Lead Ruthenate Pyrochlore Modified Electrode. Anal Chem 2001. [DOI: 10.1021/ac0010781] [Citation(s) in RCA: 103] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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122
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Choudhary SK, Talwar S, Dubey B, Chopra A, Saxena A, Kumar AS. Mitral valve repair in a predominantly rheumatic population. Long-term results. Tex Heart Inst J 2001; 28:8-15. [PMID: 11330754 PMCID: PMC101122] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/19/2023]
Abstract
Valve repair in rheumatic patients poses special problems due to valve deformity and mixed lesions. We present our experience from January 1988 through June 1999, in this retrospective study of 818 patients (377 males). The mean age was 22.8 +/- 11.3 years (range, 2 to 70 years). The cause of mitral regurgitation was rheumatic in 718 (88%) patients, congenital in 51, myxomatous in 34, infective in 7, and ischemic in 8. Most patients (64%) were in New York Heart Association functional class III or IV. Congestive heart failure was present in 116 patients (14%). Reparative procedures included posterior collar annuloplasty (n=710), commissurotomy (n=482), cusp-level chordal shortening (n=237), cusp thinning (n=222), cleft suture (n= 166), and cusp excision/plication (n=42). Operative mortality was 4% (32 patients). Preoperative left ventricular dysfunction, presence of congestive heart failure, and advanced functional class were associated with greater mortality. Follow-up ranged from 1 to 144 months (mean, 44.9 +/- 33.2 months) and was 96% complete. Most survivors (70%) had no or trivial mitral regurgitation. Forty patients required reoperation for valve dysfunction. There were 23 (2.8%) late deaths. Actuarial, reoperation-free, and event-free survival at 11 years were 92.6% +/- 1.0%, 65.0% +/- 10%, and 38% +/- 6.0%, respectively Among the survivors, 85% were in New York Heart Association functional class I. We conclude that mitral valve repair in rheumatic patients, using current techniques, can effectively correct hemodynamic and functional abnormalities with satisfactory results.
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Wasir H, Choudhary SK, Airan B, Srivastava S, Kumar AS. Mitral valve replacement with chordal preservation in a rheumatic population. THE JOURNAL OF HEART VALVE DISEASE 2001; 10:84-9. [PMID: 11206773] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/19/2023]
Abstract
BACKGROUND AND AIM OF THE STUDY Mitral valve replacement (MVR) with preservation of the subvalvular apparatus may maintain postoperative left ventricular (LV) function better than conventional MVR. A prospective study was undertaken to assess the advantages of chordal preservation in rheumatic patients undergoing isolated MVR. METHODS Between January 1996 and January 1999, 240 patients with rheumatic etiology and normal LV ejection fraction (>50%) underwent isolated MVR using a St. Jude Medical prosthesis. Patients were allocated to two groups: in group I (n = 168), both the anterior and posterior chordae were preserved; in group II (n = 72), the entire native mitral valve apparatus was excised. Patients from both groups were evaluated postoperatively (mean 12.5 months) by echocardiography and treadmill testing. RESULTS Demographic and clinical profiles were comparable in both groups. There were three early deaths in group I, and one in group II. There were no late deaths. One patient in group I required reoperation for a stuck mitral prosthesis. LV function (ejection fraction >50%) was better in group I (94%) than in group II (82%) (p <0.05). No patient in either group had LV outflow tract obstruction on echocardiography. Patients in group I showed better exercise performance on treadmill (Bruce protocol): 92% of group I patients versus 88% of group II patients (p >0.05) completed stage I; 16% of group I patients, but no group II patients, were able to complete stage IV (p <0.05). CONCLUSION Mitral valve replacement with preservation of the subvalvular apparatus maintains LV function, and does not cause LV outflow tract obstruction.
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Green PS, Yang SH, Nilsson KR, Kumar AS, Covey DF, Simpkins JW. The nonfeminizing enantiomer of 17beta-estradiol exerts protective effects in neuronal cultures and a rat model of cerebral ischemia. Endocrinology 2001; 142:400-6. [PMID: 11145603 DOI: 10.1210/endo.142.1.7888] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Estrogens are potent neuroprotective compounds in a variety of animal and cell culture models, and data indicate that estrogen receptor (ER)-mediated gene transcription is not required for some of these effects. To further address the requirement for an ER in estrogen enhancement of neuronal survival, we assessed the enantiomer of 17beta-estradiol (ENT-E(2)), which has identical chemical properties but interacts only weakly with known ERs, for neuroprotective efficacy. ENT-E(2) was both as potent and efficacious as 17beta-estradiol in attenuating oxidative stress-induced death in HT-22 cells, a murine hippocampal cell line. Further, ENT-E(2) completely attenuated H(2)O(2) toxicity in human SK-N-SH neuroblastoma cells at a 10 nM concentration. In a rodent model of focal ischemia, 17beta-estradiol (100 microgram/kg) or ENT-E(2) (100 microgram/kg), injected 2 h before middle cerebral artery occlusion, resulted in a 60 and 61% reduction in lesion volume, respectively. ENT-E(2), at the doses effective in this study, did not stimulate uterine growth or vaginal opening in juvenile female rats when administered daily for 3 days. These data indicate that the neuroprotective effects of estrogens, both in vitro and in vivo, can be disassociated from the peripheral estrogenic actions.
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Abstract
Nafion/lead-ruthenate pyrochlore chemically modified electrode (NPyCME) showed a remarkable dual sensing activity toward NO2- oxidation and NO reduction as demonstrated by cyclic voltammetry (CV), ac-impedance spectroscopy and flow injection analysis (FIA). The mechanistic parameters of current function, charge transfer resistance and exchange current for the NPyCME, GCE and Nafion-coated GCE were evaluated and compared. The disproportionation reaction of NIIIO2- into NIVO3- + NIIO in acidic solution was used as a model system for testing the dual sensing ability of the NPyCME. The obtained crossover peak response for NO2- oxidation and NO reduction in pH 1.65 buffer solution gave the direct proof for the applicability of the NPyCME in the dual electrocatalytic action. By flow injection analysis, under optimized conditions, the calibration curve was linear in the range of 100 nM-100 microM and 800 nM-63.3 microM and the detection limit (S/N = 3) was 4.8 nM and 15.6 nM for NO2- and NO, respectively.
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