The Experts below are selected from a list of 2025 Experts worldwide ranked by ideXlab platform

Clayton J. Radke - One of the best experts on this subject based on the ideXlab platform.

  • In Vivo Corneal Oxygen Uptake During Soft-Contact-Lens Wear
    2020
    Co-Authors: Sho C. Takatori, Percy Lazon De La Jara, Klaus Ehrmann, Clayton J. Radke, Brien Holden
    Abstract:

    PURPOSE. We develop a new method to compute in situ corneal oxygen uptake during softcontact-lens (SCL) wear using a micro-polarographic Clark Electrode. METHODS. After steady SCL wear and subsequent removal, a membrane-covered polarographic microElectrode is immediately placed onto the cornea. The resulting polarographic signal is related to the steady-state corneal oxygen uptake rate during soft-contact-lens wear. We devise a new analysis to quantify oxygen uptake into the cornea during lens wear. The proposed procedure is applied to new polarographic data for 10 human subjects with 12 different commercial lenses during open eye. We compare our results with recent theory. RESULTS. Average corneal oxygen uptake rates at open eye during SCL wear for 10 subjects wearing 12 different commercial lenses vary from 2 to 10 lL(STP)/cm 2 /h. High oxygen permeability lenses have uptake rates of~10 lL(STP)/cm 2 /h, in close agreement with our previously obtained no-lens human uptake rates of 9 to 13 lL(STP)/cm 2 /h at open eye. 40 Application of the classical data-interpretation procedure to our experimental data gives corneal-uptake results that are approximately three to five times smaller than those obtained with our new interpretation scheme. CONCLUSIONS. We provide a simple and reliable tool to quantify corneal-oxygen-uptake rates during in vivo soft-contact-lens wear. Comparison of our newly measured in vivo oxygen uptakes to model prediction for SCLs of varying oxygen transmissibility is in good agreement with available theory. Keywords: corneal-oxygen uptake, soft contact lens, polarographic oxygen sensor, long-time analysis, corneal oxygenation T he human cornea is nourished and supplied anteriorly with oxygen by the environment. Contact lenses with low oxygen where D L k L is the lens oxygen permeability and L L is the lens thickness) impede environmental oxygen supply 1-3 and may cause corneal edema, acidosis, and various adverse events associated with oxygen deficiency. 7-27 Most efforts focus on mathematical modeling, 1-3,7,24,28-32 but-with some exceptions 1-3 -do not incorporate the metabolic processes of the human cornea. Consequently, in vivo experimental methods to ascertain the corneal oxygen uptake have received attention, 33-36 most notably the polarographic oxygen sensor (POS) of Fatt et al. 40 The POS technique employs a Clark oxygen microelectrod

  • in vivo corneal oxygen uptake during soft contact lens wear
    Investigative Ophthalmology & Visual Science, 2013
    Co-Authors: Sho C Takatori, Percy Lazon De La Jara, Brien A. Holden, Klaus Ehrmann, Clayton J. Radke
    Abstract:

    Purpose We develop a new method to compute in situ corneal oxygen uptake during soft-contact-lens (SCL) wear using a micro-polarographic Clark Electrode. Methods After steady SCL wear and subsequent removal, a membrane-covered polarographic microElectrode is immediately placed onto the cornea. The resulting polarographic signal is related to the steady-state corneal oxygen uptake rate during soft-contact-lens wear. We devise a new analysis to quantify oxygen uptake into the cornea during lens wear. The proposed procedure is applied to new polarographic data for 10 human subjects with 12 different commercial lenses during open eye. We compare our results with recent theory. Results Average corneal oxygen uptake rates at open eye during SCL wear for 10 subjects wearing 12 different commercial lenses vary from 2 to 10 μL(STP)/cm(2)/h. High oxygen permeability lenses have uptake rates of -10 μL(STP)/cm(2)/h, in close agreement with our previously obtained no-lens human uptake rates of 9 to 13 μL(STP)/cm(2)/h at open eye.(40) Application of the classical data-interpretation procedure to our experimental data gives corneal-uptake results that are approximately three to five times smaller than those obtained with our new interpretation scheme. Conclusions We provide a simple and reliable tool to quantify corneal-oxygen-uptake rates during in vivo soft-contact-lens wear. Comparison of our newly measured in vivo oxygen uptakes to model prediction for SCLs of varying oxygen transmissibility is in good agreement with available theory.

  • In vivo oxygen uptake into the human cornea.
    Investigative ophthalmology & visual science, 2012
    Co-Authors: Sho C. Takatori, Percy Lazon De La Jara, Brien A. Holden, Klaus Ehrmann, Clayton J. Radke
    Abstract:

    PURPOSE. We provide a new procedure to quantify in situ corneal oxygen uptake using the micropolarographic Clark Electrode. METHODS. Traditionally, upon placing a membrane-covered Clark microElectrode onto a human cornea, the resulting polarographic signal is interpreted as the oxygen partial pressure at the anterior corneal surface. However, the Clark Electrode operates at a limiting current. Hence, oxygen flux is directly detected rather than partial pressure. We corrected this misunderstanding and devised a new analysis to quantify oxygen uptake into the cornea. The proposed analysis is applied to new polarographic data for 10 human subjects during open-eye oxygen uptake. RESULTS. Average open-eye corneal oxygen uptake over 10 subjects is approximately 11 lL/(cm 2 h), approximately five times larger than the average reported by researchers who invoke the original mathematical analysis. Application of the classical interpretation scheme to our experimental data also garners uptake values that are approximately a factor of three to five times smaller than those obtained with our new procedure. CONCLUSIONS. The classical procedure originally developed by Fatt and colleagues misinterprets the behavior of the Clark microElectrode. We corrected the analysis of the in situ polarographic technique to provide a simple yet rigorous procedure for analyzing both previous data in the literature and those newly obtained. Our proposed interpretation scheme thus provides a reliable tool for in vivo assessment of corneal oxygen uptake. (Invest Ophthalmol Vis Sci. 2012;53:6331‐ 6337) DOI:10.1167/iovs.12-10059

Hani N Sabbah - One of the best experts on this subject based on the ideXlab platform.

  • cyclosporine a attenuates mitochondrial permeability transition and improves mitochondrial respiratory function in cardiomyocytes isolated from dogs with heart failure
    Journal of Molecular and Cellular Cardiology, 2007
    Co-Authors: Victor G Sharov, Anastassia Todor, Sanjaya Khanal, Makoto Imai, Hani N Sabbah
    Abstract:

    Abstract We used isolated cardiomyocytes to investigate a possible role of mitochondrial permeability transition pore in mitochondrial abnormalities associated with heart failure. Cardiomyocytes were isolated from LV myocardium of normal control dogs and dogs with heart failure produced by intracoronary microembolizations. Mitochondrial permeability transition was measured in isolated cardiomyocytes with intact sarcolemma with and without 0.2 μM cyclosporin A using calcein AM and the fluorometer. State-3 mitochondrial respiration was also measured with the Clark Electrode. Mitochondrial membrane potential was measured with JC-1 probe using the fluorometer. Propidium iodide was used to ensure sarcolemma integrity. 200 min after loading with calcein AM, mitochondria of failing cardiomyocytes showed only 50% of maximal level of calcein fluorescence while it remained unchanged in normal cells. The mitochondrial membrane potential in failing cardiomyocytes was significantly decreased by 38% compared to normal cardiomyocytes. Cyclosporine A significantly slowed the exit of calcein from mitochondria of failing cardiomyocytes and increased mitochondrial membrane potential by 29%. State-3 respiration was not affected with cyclosporine A in normal cardiomyocytes while it was significantly increased in failing cardiomyocytes by 20%. Exit of calcein (m.w. 1.0 kDa) from mitochondria of viable failing cardiomyocytes with intact sarcolemma suggests an existence of a reversible transitory permeability transition opening in high conductance mode. Attenuation of calcein exit, Δ Ψ m and improvement of state-3 respiration achieved with CsA (0.2 μM) show that permeability transition opening could be a cause of mitochondrial dysfunction described in the failing heart.

  • abnormal mitochondrial respiration in skeletal muscle in patients with peripheral arterial disease
    Journal of Vascular Surgery, 2003
    Co-Authors: Iraklis I Pipinos, Victor G Sharov, Alexander D Shepard, Petros V Anagnostopoulos, Asterios N Katsamouris, Anastasia Todor, Konstantinos Filis, Hani N Sabbah
    Abstract:

    Abstract Objective Discrete morphologic, enzymatic and functional changes in skeletal muscle mitochondria have been demonstrated in patients with peripheral arterial disease (PAD). We examined mitochondrial respiration in the gastrocnemius muscle of nine patients (10 legs) with advanced PAD and in nine control patients (nine legs) without evidence of PAD. Methods Mitochondrial respiratory rates were determined with a Clark Electrode in an oxygraph cell containing saponin-skinned muscle bundles. Muscle samples were obtained from the anteromedial aspect of the gastrocnemius muscle, at a level 10 cm distal to the tibial tuberosity. Mitochondria respiratory rate, calculated as nanoatoms of oxygen consumed per minute per milligram of noncollagen protein, were measured at baseline (V 0 ), after addition of substrates (malate and glutamate; (V SUB ), after addition of adenosine diphosphate (ADP) (V ADP ), and finally, after adenine nucleotide translocase inhibition with atractyloside (V AT ). The acceptor control ratio, a sensitive indicator of overall mitochondrial function, was calculated as the ratio of the respiratory rate after the addition of ADP to the respiratory rate after adenine nucleotide translocase inhibition with atractyloside (V ADP / V AT ). Results Respiratory rate in muscle mitochondria from patients with PAD were not significantly different from control values at baseline (0.31 ± 0.06 vs 0.55 ± 0.12; P = .09), but V sub was significantly lower in patients with PAD compared with control subjects (0.43 ± 0.07 vs 0.89 ± 0.20; P ADP (0.69 ± 0.13 vs 1.24 ± 0.20; P P = .08). Compared with control values, mitochondria from patients with PAD had a significantly lower acceptor control ratio (1.41 ± 0.10 vs 2.90 ± 0.20; P Conclusion Mitochondrial respiratory activity is abnormal in lower extremity skeletal muscle in patients with PAD. When considered in concert with the ultrastructural and enzymatic abnormalities previously documented in mitochondria of chronically ischemic muscle, these data support the concept of defective mitochondrial function as a pathophysiologic component of PAD.

  • abnormal mitochondrial respiration in skeletal muscle in patients with peripheral arterial disease
    Annual Meeting of the Association for Academic Surgery, 2003
    Co-Authors: Iraklis I Pipinos, Victor G Sharov, Alexander D Shepard, Petros V Anagnostopoulos, Asterios N Katsamouris, Anastasia Todor, Konstantinos Filis, Hani N Sabbah
    Abstract:

    Objective: Discrete morphologic, enzymatic and functional changes in skeletal muscle mitochondria have been demonstrated in patients with peripheral arterial disease (PAD). We examined mitochondrial respiration in the gastrocnemius muscle of nine patients (10 legs) with advanced PAD and in nine control patients (nine legs) without evidence of PAD. Methods: Mitochondrial respiratory rates were determined with a Clark Electrode in an oxygraph cell containing saponin-skinned muscle bundles. Muscle samples were obtained from the anteromedial aspect of the gastrocnemius muscle, at a level 10 cm distal to the tibial tuberosity. Mitochondria respiratory rate, calculated as nanoatoms of oxygen consumed per minute per milligram of noncollagen protein, were measured at baseline (V 0 ), after addition of substrates (malate and glutamate; (V SUB ), after addition of adenosine diphosphate (ADP) (V ADP ), and finally, after adenine nucleotide translocase inhibition with atractyloside (V AT ). The acceptor control ratio, a sensitive indicator of overall mitochondrial function, was calculated as the ratio of the respiratory rate after the addition of ADP to the respiratory rate after adenine nucleotide translocase inhibition with atractyloside (V ADP /V AT ). Results: Respiratory rate in muscle mitochondria from patients with PAD were not significantly different from control values at baseline (0.31 ± 0.06 vs 0.55 ± 0.12; P = .09), but V sub was significantly lower in patients with PAD compared with control subjects (0.43 ± 0.07 vs 0.89 ± 0.20; P <.05), as was V ADP (0.69 ± 0.13 vs 1.24 ± 0.20; P <.05). Respiratory rates after atractyloside inhibition in patients with PAD were no different from those in control patients (0.47 ± 0.07 vs 0.45 ± P=.08). Compared with control values, mitochondria from patients with PAD had a significantly lower acceptor control ratio (1.41 ± 0.10 vs 2.90 ± 0.20; P <.001). Conclusion:Mitochondrial respiratory activity is abnormal in lower extremity skeletal muscle in patients with PAD. When considered in concert with the ultrastructural and enzymatic abnormalities previously documented in mitochondria of chronically ischemic muscle, these data support the concept of defective mitochondrial function as a pathophysiologic component of PAD.

  • abnormal mitochondrial respiration in failed human myocardium
    Journal of Molecular and Cellular Cardiology, 2000
    Co-Authors: Victor G Sharov, Anastassia Todor, Norman H Silverman, Sidney Goldstein, Hani N Sabbah
    Abstract:

    Chronic heart failure (HF) is associated with morphologic abnormalities of cardiac mitochondria including hyperplasia, reduced organelle size and compromised structural integrity. In this study, we examined whether functional abnormalities of mitochondrial respiration are also present in myocardium of patients with advanced HF. Mitochondrial respiration was examined using a Clark Electrode in an oxygraph cell containing saponin-skinned muscle bundles obtained from myocardium of failed explanted human hearts due to ischemic (ICM, n=9) or idiopathic dilated (IDC, n=9) cardiomyopathy. Myocardial specimens from five normal donor hearts served as controls (CON). Basal respiratory rate, respiratory rate after addition of the substrates glutamate and malate (V(SUB)), state 3 respiration (after addition of ADP, V(ADP)) and respiration after the addition of atractyloside (V(AT)) were measured in scar-free muscle bundles obtained from the subendocardial (ENDO) and subepicardial (EPI) thirds of the left ventricular (LV) free wall, interventricular septum and right ventricular (RV) free wall. There were no differences in basal and substrate-supported respiration between CON and HF regardless of etiology. V(ADP)was significantly depressed both in ICM and IDC compared to CON in all the regions studied. The respiratory control ratio, V(ADP)/V(AT), was also significantly decreased in HF compared to CON. In both ICM and IDC, V(ADP)was significantly lower in ENDO compared to EPI. The results indicate that mitochondrial respiration is abnormal in the failing human heart. The findings support the concept of low myocardial energy production in HF via oxidative phosphorylation, an abnormality with a potentially impact on global cardiac performance.

  • 965 49 abnormal mitochondrial respiration in myocardium of dogs with chronic heart failure
    Journal of the American College of Cardiology, 1995
    Co-Authors: Victor G Sharov, Norman H Silverman, Hani N Sabbah, Jane M Cook, Ramesh C Gupta, Michael Lesch, Sidney Goldstein
    Abstract:

    We previously showed that abnormalities of mitochondria (M IT) exist in the failing heart and include hyperplasia, reduced organelle size and structural injury. In the present study, we examined MIT respiration in LV tissue obtained from 11 normal (NL) dogs and 8 dogs with heart failure (HF) produced by intracoronary microembolizations (LV ejection fraction 23 ± 3%). Tissue specimen (30 mg) were obtained from the subendocardial (ENDO) and subepicardial (EPI) halves of the LV wall. Basal (V o ) and state 3 (maximal) respiration (V ADP , after addition of 1 mM ADP) were measured with an oxygraph and Clark Electrode using saponin skinned fiber bundles (0.2–0.3 mm). Respiratory rate was calculated in ngatoms of oxygen/min/mg of noncollagen protein. The respiration control ratio (RCR) was calculated as V ADP /V o . V o V ADP V ADP /V o ENDO EPI ENDO EPI ENDO EPI NL 9 ± 2 7 ± 1 46 ± 6 47 ± 1 6 ± 1 7 ± 1 HF 6 ± 1 6 ± 1 20 ± 5 22 ± 5 4 ± 1 4 ± 1 P-value l0.07 l0.5 l0.001 l0.005 l0.04 l0.004 MIT state 3 respiration is significantly reduced in myocardium of dogs with chronic HF. The observed reduction in the RCR confirms the presence of injury to inner MIT membrane. The abnormalities in MIT oxygen utilization support the concept of low energy production in the failing heart.

Percy Lazon De La Jara - One of the best experts on this subject based on the ideXlab platform.

  • In Vivo Corneal Oxygen Uptake During Soft-Contact-Lens Wear
    2020
    Co-Authors: Sho C. Takatori, Percy Lazon De La Jara, Klaus Ehrmann, Clayton J. Radke, Brien Holden
    Abstract:

    PURPOSE. We develop a new method to compute in situ corneal oxygen uptake during softcontact-lens (SCL) wear using a micro-polarographic Clark Electrode. METHODS. After steady SCL wear and subsequent removal, a membrane-covered polarographic microElectrode is immediately placed onto the cornea. The resulting polarographic signal is related to the steady-state corneal oxygen uptake rate during soft-contact-lens wear. We devise a new analysis to quantify oxygen uptake into the cornea during lens wear. The proposed procedure is applied to new polarographic data for 10 human subjects with 12 different commercial lenses during open eye. We compare our results with recent theory. RESULTS. Average corneal oxygen uptake rates at open eye during SCL wear for 10 subjects wearing 12 different commercial lenses vary from 2 to 10 lL(STP)/cm 2 /h. High oxygen permeability lenses have uptake rates of~10 lL(STP)/cm 2 /h, in close agreement with our previously obtained no-lens human uptake rates of 9 to 13 lL(STP)/cm 2 /h at open eye. 40 Application of the classical data-interpretation procedure to our experimental data gives corneal-uptake results that are approximately three to five times smaller than those obtained with our new interpretation scheme. CONCLUSIONS. We provide a simple and reliable tool to quantify corneal-oxygen-uptake rates during in vivo soft-contact-lens wear. Comparison of our newly measured in vivo oxygen uptakes to model prediction for SCLs of varying oxygen transmissibility is in good agreement with available theory. Keywords: corneal-oxygen uptake, soft contact lens, polarographic oxygen sensor, long-time analysis, corneal oxygenation T he human cornea is nourished and supplied anteriorly with oxygen by the environment. Contact lenses with low oxygen where D L k L is the lens oxygen permeability and L L is the lens thickness) impede environmental oxygen supply 1-3 and may cause corneal edema, acidosis, and various adverse events associated with oxygen deficiency. 7-27 Most efforts focus on mathematical modeling, 1-3,7,24,28-32 but-with some exceptions 1-3 -do not incorporate the metabolic processes of the human cornea. Consequently, in vivo experimental methods to ascertain the corneal oxygen uptake have received attention, 33-36 most notably the polarographic oxygen sensor (POS) of Fatt et al. 40 The POS technique employs a Clark oxygen microelectrod

  • in vivo corneal oxygen uptake during soft contact lens wear
    Investigative Ophthalmology & Visual Science, 2013
    Co-Authors: Sho C Takatori, Percy Lazon De La Jara, Brien A. Holden, Klaus Ehrmann, Clayton J. Radke
    Abstract:

    Purpose We develop a new method to compute in situ corneal oxygen uptake during soft-contact-lens (SCL) wear using a micro-polarographic Clark Electrode. Methods After steady SCL wear and subsequent removal, a membrane-covered polarographic microElectrode is immediately placed onto the cornea. The resulting polarographic signal is related to the steady-state corneal oxygen uptake rate during soft-contact-lens wear. We devise a new analysis to quantify oxygen uptake into the cornea during lens wear. The proposed procedure is applied to new polarographic data for 10 human subjects with 12 different commercial lenses during open eye. We compare our results with recent theory. Results Average corneal oxygen uptake rates at open eye during SCL wear for 10 subjects wearing 12 different commercial lenses vary from 2 to 10 μL(STP)/cm(2)/h. High oxygen permeability lenses have uptake rates of -10 μL(STP)/cm(2)/h, in close agreement with our previously obtained no-lens human uptake rates of 9 to 13 μL(STP)/cm(2)/h at open eye.(40) Application of the classical data-interpretation procedure to our experimental data gives corneal-uptake results that are approximately three to five times smaller than those obtained with our new interpretation scheme. Conclusions We provide a simple and reliable tool to quantify corneal-oxygen-uptake rates during in vivo soft-contact-lens wear. Comparison of our newly measured in vivo oxygen uptakes to model prediction for SCLs of varying oxygen transmissibility is in good agreement with available theory.

  • In vivo oxygen uptake into the human cornea.
    Investigative ophthalmology & visual science, 2012
    Co-Authors: Sho C. Takatori, Percy Lazon De La Jara, Brien A. Holden, Klaus Ehrmann, Clayton J. Radke
    Abstract:

    PURPOSE. We provide a new procedure to quantify in situ corneal oxygen uptake using the micropolarographic Clark Electrode. METHODS. Traditionally, upon placing a membrane-covered Clark microElectrode onto a human cornea, the resulting polarographic signal is interpreted as the oxygen partial pressure at the anterior corneal surface. However, the Clark Electrode operates at a limiting current. Hence, oxygen flux is directly detected rather than partial pressure. We corrected this misunderstanding and devised a new analysis to quantify oxygen uptake into the cornea. The proposed analysis is applied to new polarographic data for 10 human subjects during open-eye oxygen uptake. RESULTS. Average open-eye corneal oxygen uptake over 10 subjects is approximately 11 lL/(cm 2 h), approximately five times larger than the average reported by researchers who invoke the original mathematical analysis. Application of the classical interpretation scheme to our experimental data also garners uptake values that are approximately a factor of three to five times smaller than those obtained with our new procedure. CONCLUSIONS. The classical procedure originally developed by Fatt and colleagues misinterprets the behavior of the Clark microElectrode. We corrected the analysis of the in situ polarographic technique to provide a simple yet rigorous procedure for analyzing both previous data in the literature and those newly obtained. Our proposed interpretation scheme thus provides a reliable tool for in vivo assessment of corneal oxygen uptake. (Invest Ophthalmol Vis Sci. 2012;53:6331‐ 6337) DOI:10.1167/iovs.12-10059

Victor G Sharov - One of the best experts on this subject based on the ideXlab platform.

  • cyclosporine a attenuates mitochondrial permeability transition and improves mitochondrial respiratory function in cardiomyocytes isolated from dogs with heart failure
    Journal of Molecular and Cellular Cardiology, 2007
    Co-Authors: Victor G Sharov, Anastassia Todor, Sanjaya Khanal, Makoto Imai, Hani N Sabbah
    Abstract:

    Abstract We used isolated cardiomyocytes to investigate a possible role of mitochondrial permeability transition pore in mitochondrial abnormalities associated with heart failure. Cardiomyocytes were isolated from LV myocardium of normal control dogs and dogs with heart failure produced by intracoronary microembolizations. Mitochondrial permeability transition was measured in isolated cardiomyocytes with intact sarcolemma with and without 0.2 μM cyclosporin A using calcein AM and the fluorometer. State-3 mitochondrial respiration was also measured with the Clark Electrode. Mitochondrial membrane potential was measured with JC-1 probe using the fluorometer. Propidium iodide was used to ensure sarcolemma integrity. 200 min after loading with calcein AM, mitochondria of failing cardiomyocytes showed only 50% of maximal level of calcein fluorescence while it remained unchanged in normal cells. The mitochondrial membrane potential in failing cardiomyocytes was significantly decreased by 38% compared to normal cardiomyocytes. Cyclosporine A significantly slowed the exit of calcein from mitochondria of failing cardiomyocytes and increased mitochondrial membrane potential by 29%. State-3 respiration was not affected with cyclosporine A in normal cardiomyocytes while it was significantly increased in failing cardiomyocytes by 20%. Exit of calcein (m.w. 1.0 kDa) from mitochondria of viable failing cardiomyocytes with intact sarcolemma suggests an existence of a reversible transitory permeability transition opening in high conductance mode. Attenuation of calcein exit, Δ Ψ m and improvement of state-3 respiration achieved with CsA (0.2 μM) show that permeability transition opening could be a cause of mitochondrial dysfunction described in the failing heart.

  • abnormal mitochondrial respiration in skeletal muscle in patients with peripheral arterial disease
    Journal of Vascular Surgery, 2003
    Co-Authors: Iraklis I Pipinos, Victor G Sharov, Alexander D Shepard, Petros V Anagnostopoulos, Asterios N Katsamouris, Anastasia Todor, Konstantinos Filis, Hani N Sabbah
    Abstract:

    Abstract Objective Discrete morphologic, enzymatic and functional changes in skeletal muscle mitochondria have been demonstrated in patients with peripheral arterial disease (PAD). We examined mitochondrial respiration in the gastrocnemius muscle of nine patients (10 legs) with advanced PAD and in nine control patients (nine legs) without evidence of PAD. Methods Mitochondrial respiratory rates were determined with a Clark Electrode in an oxygraph cell containing saponin-skinned muscle bundles. Muscle samples were obtained from the anteromedial aspect of the gastrocnemius muscle, at a level 10 cm distal to the tibial tuberosity. Mitochondria respiratory rate, calculated as nanoatoms of oxygen consumed per minute per milligram of noncollagen protein, were measured at baseline (V 0 ), after addition of substrates (malate and glutamate; (V SUB ), after addition of adenosine diphosphate (ADP) (V ADP ), and finally, after adenine nucleotide translocase inhibition with atractyloside (V AT ). The acceptor control ratio, a sensitive indicator of overall mitochondrial function, was calculated as the ratio of the respiratory rate after the addition of ADP to the respiratory rate after adenine nucleotide translocase inhibition with atractyloside (V ADP / V AT ). Results Respiratory rate in muscle mitochondria from patients with PAD were not significantly different from control values at baseline (0.31 ± 0.06 vs 0.55 ± 0.12; P = .09), but V sub was significantly lower in patients with PAD compared with control subjects (0.43 ± 0.07 vs 0.89 ± 0.20; P ADP (0.69 ± 0.13 vs 1.24 ± 0.20; P P = .08). Compared with control values, mitochondria from patients with PAD had a significantly lower acceptor control ratio (1.41 ± 0.10 vs 2.90 ± 0.20; P Conclusion Mitochondrial respiratory activity is abnormal in lower extremity skeletal muscle in patients with PAD. When considered in concert with the ultrastructural and enzymatic abnormalities previously documented in mitochondria of chronically ischemic muscle, these data support the concept of defective mitochondrial function as a pathophysiologic component of PAD.

  • abnormal mitochondrial respiration in skeletal muscle in patients with peripheral arterial disease
    Annual Meeting of the Association for Academic Surgery, 2003
    Co-Authors: Iraklis I Pipinos, Victor G Sharov, Alexander D Shepard, Petros V Anagnostopoulos, Asterios N Katsamouris, Anastasia Todor, Konstantinos Filis, Hani N Sabbah
    Abstract:

    Objective: Discrete morphologic, enzymatic and functional changes in skeletal muscle mitochondria have been demonstrated in patients with peripheral arterial disease (PAD). We examined mitochondrial respiration in the gastrocnemius muscle of nine patients (10 legs) with advanced PAD and in nine control patients (nine legs) without evidence of PAD. Methods: Mitochondrial respiratory rates were determined with a Clark Electrode in an oxygraph cell containing saponin-skinned muscle bundles. Muscle samples were obtained from the anteromedial aspect of the gastrocnemius muscle, at a level 10 cm distal to the tibial tuberosity. Mitochondria respiratory rate, calculated as nanoatoms of oxygen consumed per minute per milligram of noncollagen protein, were measured at baseline (V 0 ), after addition of substrates (malate and glutamate; (V SUB ), after addition of adenosine diphosphate (ADP) (V ADP ), and finally, after adenine nucleotide translocase inhibition with atractyloside (V AT ). The acceptor control ratio, a sensitive indicator of overall mitochondrial function, was calculated as the ratio of the respiratory rate after the addition of ADP to the respiratory rate after adenine nucleotide translocase inhibition with atractyloside (V ADP /V AT ). Results: Respiratory rate in muscle mitochondria from patients with PAD were not significantly different from control values at baseline (0.31 ± 0.06 vs 0.55 ± 0.12; P = .09), but V sub was significantly lower in patients with PAD compared with control subjects (0.43 ± 0.07 vs 0.89 ± 0.20; P <.05), as was V ADP (0.69 ± 0.13 vs 1.24 ± 0.20; P <.05). Respiratory rates after atractyloside inhibition in patients with PAD were no different from those in control patients (0.47 ± 0.07 vs 0.45 ± P=.08). Compared with control values, mitochondria from patients with PAD had a significantly lower acceptor control ratio (1.41 ± 0.10 vs 2.90 ± 0.20; P <.001). Conclusion:Mitochondrial respiratory activity is abnormal in lower extremity skeletal muscle in patients with PAD. When considered in concert with the ultrastructural and enzymatic abnormalities previously documented in mitochondria of chronically ischemic muscle, these data support the concept of defective mitochondrial function as a pathophysiologic component of PAD.

  • abnormal mitochondrial respiration in failed human myocardium
    Journal of Molecular and Cellular Cardiology, 2000
    Co-Authors: Victor G Sharov, Anastassia Todor, Norman H Silverman, Sidney Goldstein, Hani N Sabbah
    Abstract:

    Chronic heart failure (HF) is associated with morphologic abnormalities of cardiac mitochondria including hyperplasia, reduced organelle size and compromised structural integrity. In this study, we examined whether functional abnormalities of mitochondrial respiration are also present in myocardium of patients with advanced HF. Mitochondrial respiration was examined using a Clark Electrode in an oxygraph cell containing saponin-skinned muscle bundles obtained from myocardium of failed explanted human hearts due to ischemic (ICM, n=9) or idiopathic dilated (IDC, n=9) cardiomyopathy. Myocardial specimens from five normal donor hearts served as controls (CON). Basal respiratory rate, respiratory rate after addition of the substrates glutamate and malate (V(SUB)), state 3 respiration (after addition of ADP, V(ADP)) and respiration after the addition of atractyloside (V(AT)) were measured in scar-free muscle bundles obtained from the subendocardial (ENDO) and subepicardial (EPI) thirds of the left ventricular (LV) free wall, interventricular septum and right ventricular (RV) free wall. There were no differences in basal and substrate-supported respiration between CON and HF regardless of etiology. V(ADP)was significantly depressed both in ICM and IDC compared to CON in all the regions studied. The respiratory control ratio, V(ADP)/V(AT), was also significantly decreased in HF compared to CON. In both ICM and IDC, V(ADP)was significantly lower in ENDO compared to EPI. The results indicate that mitochondrial respiration is abnormal in the failing human heart. The findings support the concept of low myocardial energy production in HF via oxidative phosphorylation, an abnormality with a potentially impact on global cardiac performance.

  • 965 49 abnormal mitochondrial respiration in myocardium of dogs with chronic heart failure
    Journal of the American College of Cardiology, 1995
    Co-Authors: Victor G Sharov, Norman H Silverman, Hani N Sabbah, Jane M Cook, Ramesh C Gupta, Michael Lesch, Sidney Goldstein
    Abstract:

    We previously showed that abnormalities of mitochondria (M IT) exist in the failing heart and include hyperplasia, reduced organelle size and structural injury. In the present study, we examined MIT respiration in LV tissue obtained from 11 normal (NL) dogs and 8 dogs with heart failure (HF) produced by intracoronary microembolizations (LV ejection fraction 23 ± 3%). Tissue specimen (30 mg) were obtained from the subendocardial (ENDO) and subepicardial (EPI) halves of the LV wall. Basal (V o ) and state 3 (maximal) respiration (V ADP , after addition of 1 mM ADP) were measured with an oxygraph and Clark Electrode using saponin skinned fiber bundles (0.2–0.3 mm). Respiratory rate was calculated in ngatoms of oxygen/min/mg of noncollagen protein. The respiration control ratio (RCR) was calculated as V ADP /V o . V o V ADP V ADP /V o ENDO EPI ENDO EPI ENDO EPI NL 9 ± 2 7 ± 1 46 ± 6 47 ± 1 6 ± 1 7 ± 1 HF 6 ± 1 6 ± 1 20 ± 5 22 ± 5 4 ± 1 4 ± 1 P-value l0.07 l0.5 l0.001 l0.005 l0.04 l0.004 MIT state 3 respiration is significantly reduced in myocardium of dogs with chronic HF. The observed reduction in the RCR confirms the presence of injury to inner MIT membrane. The abnormalities in MIT oxygen utilization support the concept of low energy production in the failing heart.

Klaus Ehrmann - One of the best experts on this subject based on the ideXlab platform.

  • in vivo corneal oxygen uptake during soft contact lens wear
    Investigative Ophthalmology & Visual Science, 2013
    Co-Authors: Sho C Takatori, Percy Lazon De La Jara, Brien A. Holden, Klaus Ehrmann, Clayton J. Radke
    Abstract:

    Purpose We develop a new method to compute in situ corneal oxygen uptake during soft-contact-lens (SCL) wear using a micro-polarographic Clark Electrode. Methods After steady SCL wear and subsequent removal, a membrane-covered polarographic microElectrode is immediately placed onto the cornea. The resulting polarographic signal is related to the steady-state corneal oxygen uptake rate during soft-contact-lens wear. We devise a new analysis to quantify oxygen uptake into the cornea during lens wear. The proposed procedure is applied to new polarographic data for 10 human subjects with 12 different commercial lenses during open eye. We compare our results with recent theory. Results Average corneal oxygen uptake rates at open eye during SCL wear for 10 subjects wearing 12 different commercial lenses vary from 2 to 10 μL(STP)/cm(2)/h. High oxygen permeability lenses have uptake rates of -10 μL(STP)/cm(2)/h, in close agreement with our previously obtained no-lens human uptake rates of 9 to 13 μL(STP)/cm(2)/h at open eye.(40) Application of the classical data-interpretation procedure to our experimental data gives corneal-uptake results that are approximately three to five times smaller than those obtained with our new interpretation scheme. Conclusions We provide a simple and reliable tool to quantify corneal-oxygen-uptake rates during in vivo soft-contact-lens wear. Comparison of our newly measured in vivo oxygen uptakes to model prediction for SCLs of varying oxygen transmissibility is in good agreement with available theory.