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Demeekul K, Suthammarak W, Petchdee S. Bioactive Compounds from Germinated Brown Rice Protect Cardiomyocytes Against Simulated Ischemic/Reperfusion Injury by Ameliorating Mitochondrial Dysfunction. DRUG DESIGN DEVELOPMENT AND THERAPY 2021; 15:1055-1066. [PMID: 33727794 PMCID: PMC7955705 DOI: 10.2147/dddt.s294779] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/16/2020] [Accepted: 02/04/2021] [Indexed: 01/11/2023]
Abstract
Purpose Ischemic/reperfusion (I/R) injury is the principal mechanism during Ischemic Heart Disease (IHD). The key modulator of I/R injury is dysregulation of mitochondria function. Germinated Brown Rice (GBR) has been recommended as a bio-functional food and has clarified the potential properties in several effects. However, the effect of GBR mediated cardioprotective properties, focusing on mitochondrial function’s role, remains unexplored. Thus, this study aims to investigate the cardioprotective effects of GBR pretreatment against simulated I/R injury. Methods H9c2 cardiomyocytes were incubated with GBR at a five ƞg/mL concentration for 24 hours and simulated I/R (sI/R) for 40 minutes. Cell viability and cell apoptosis were assessed by 7-AAD staining and Annexin V/PI staining, respectively. The mitochondrial membrane potential was determined by JC-1 staining and mitochondrial respiration represented by oxygen consumption rate (OCR) using Seahorse Flux analyzer. Results The results revealed that the administration of GBR before sI/R significantly decreased the percentage of cell death and total cell apoptosis in H9c2 during stimulation of ischemic/reperfusion. Besides, pretreatment of cardiomyocytes with GBR remarkably stabilized mitochondrial membrane potential and improved impaired mitochondrial respiration in simulated-H9c2 injury. Conclusion The present research is the first study to report the effective cardioprotection of GBR. Pretreatment of GBR potentially protects H9c2 cardiomyocytes against sI/R injury through mitochondrial function. The underlying therapeutic activities are possibly associated with its bio-functional compounds. However, the underlying mechanism on the cardioprotective effects of GBR needs further studies.
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Affiliation(s)
- Kanokwan Demeekul
- Graduate School, Program of Bio-Veterinary Science, Kasetsart University, Kamphaeng Saen, Nakorn Pathom, Thailand
| | - Wichit Suthammarak
- Department of Biochemistry, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand
| | - Soontaree Petchdee
- Department of Large Animal and Wildlife Clinical Sciences, Faculty of Veterinary Medicine, Kasetsart University, Kamphaeng Saen Campus, Nakorn Pathom, Thailand
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van der Weg K, Prinzen FW, Gorgels AP. Editor's Choice- Reperfusion cardiac arrhythmias and their relation to reperfusion-induced cell death. EUROPEAN HEART JOURNAL-ACUTE CARDIOVASCULAR CARE 2018; 8:142-152. [PMID: 30421619 DOI: 10.1177/2048872618812148] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Reperfusion does not only salvage ischaemic myocardium but can also cause additional cell death which is called lethal reperfusion injury. The time of reperfusion is often accompanied by ventricular arrhythmias, i.e. reperfusion arrhythmias. While both conditions are seen as separate processes, recent research has shown that reperfusion arrhythmias are related to larger infarct size. The pathophysiology of fatal reperfusion injury revolves around intracellular calcium overload and reactive oxidative species inducing apoptosis by opening of the mitochondrial protein transition pore. The pathophysiological basis for reperfusion arrhythmias is the same intracellular calcium overload as that causing fatal reperfusion injury. Therefore both conditions should not be seen as separate entities but as one and the same process resulting in two different visible effects. Reperfusion arrhythmias could therefore be seen as a potential marker for fatal reperfusion injury.
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Affiliation(s)
- Kirian van der Weg
- 1 Department of Cardiology, Maastricht University Medical Center, The Netherlands
| | - Frits W Prinzen
- 2 Cardiovascular Research Institute Maastricht (CARIM), Maastricht University, The Netherlands
| | - Anton Pm Gorgels
- 1 Department of Cardiology, Maastricht University Medical Center, The Netherlands.,2 Cardiovascular Research Institute Maastricht (CARIM), Maastricht University, The Netherlands
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Kimura W, Muralidhar S, Canseco DC, Puente B, Zhang CC, Xiao F, Abderrahman YH, Sadek HA. Redox signaling in cardiac renewal. Antioxid Redox Signal 2014; 21:1660-73. [PMID: 25000143 PMCID: PMC4175032 DOI: 10.1089/ars.2014.6029] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
SIGNIFICANCE Utilizing oxygen (O2) through mitochondrial oxidative phosphorylation enables organisms to generate adenosine triphosphate (ATP) with a higher efficiency than glycolysis, but it results in increased reactive oxygen species production from mitochondria, which can result in stem cell dysfunction and senescence. RECENT ADVANCES In the postnatal organism, the hematopoietic system represents a classic example of the role of stem cells in cellular turnover and regeneration. However, in other organs such as the heart, both the degree and source of cellular turnover have been heavily contested. CRITICAL ISSUES Although recent evidence suggests that the major source of the limited cardiomyocyte turnover in the adult heart is cardiomyocyte proliferation, the identity and potential role of undifferentiated cardiac progenitor cells remain controversial. Several types of cardiac progenitor cells have been identified, and several studies have identified an important role of redox and metabolic regulation in survival and differentiation of cardiac progenitor cells. Perhaps a simple way to approach these controversies is to focus on the multipotentiality characteristics of a certain progenitor population, and not necessarily its ability to give rise to all cell types within the heart. In addition, it is important to note that cycling cells in the heart may express markers of differentiation or may be truly undifferentiated, and for the purpose of this review, we will refer to these cycling cells as progenitors. FUTURE DIRECTIONS We propose that hypoxia, redox signaling, and metabolic phenotypes are major regulators of cardiac renewal, and may prove to be important therapeutic targets for heart regeneration.
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Affiliation(s)
- Wataru Kimura
- 1 Division of Cardiology, Department of Internal Medicine, UT Southwestern Medical Center , Dallas, Texas
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Xu J, Dehaghani AR, Gao F, Wang L. Noninvasive transmural electrophysiological imaging based on minimization of total-variation functional. IEEE TRANSACTIONS ON MEDICAL IMAGING 2014; 33:1860-74. [PMID: 24846557 PMCID: PMC6476190 DOI: 10.1109/tmi.2014.2324900] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
While tomographic imaging of cardiac structure and kinetics has improved substantially, electrophysiological mapping of the heart is still restricted to the surface with little or no depth information beneath. The progress in reconstructing 3-D action potential from surface voltage data has been hindered by the intrinsic ill-posedness of the problem and the lack of a unique solution in the absence of prior assumptions. In this work, we propose a novel adaption of the total-variation (TV) prior to exploit the unique spatial property of transmural action potential of being piecewise smooth with a steep boundary (gradient) separating depolarized and repolarized regions. We present a variational TV-prior instead of a common discrete TV-prior for improved robustness to mesh resolution, and solve the TV-minimization by a sequence of weighted, first-order L2-norm minimization. In a large set of phantom experiments, the proposed method is shown to outperform existing quadratic methods in preserving the steep gradient of action potential along the border of infarcts, as well as in capturing the disruption to the normal path of electrical wavefronts. Real-data experiments also further demonstrate the potential of the proposed method in revealing the location and shape of infarcts when quadratic methods fail to do so.
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Affiliation(s)
- Jingjia Xu
- Computational Biomedicine Laboratory, Golisano College of Computing and Information Sciences, Rochester Institute of Technology, Rochester, NY 14623 USA ()
| | - Azar Rahimi Dehaghani
- Computational Biomedicine Laboratory, Golisano College of Computing and Information Sciences, Rochester Institute of Technology, Rochester, NY 14623 USA
| | - Fei Gao
- Molecular Imaging Division, Siemens Medical Solutions, Knoxville, TN 37932 USA
| | - Linwei Wang
- Computational Biomedicine Laboratory, Golisano College of Computing and Information Sciences, Rochester Institute of Technology, Rochester, NY 14623 USA
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Kimura W, Sadek HA. The cardiac hypoxic niche: emerging role of hypoxic microenvironment in cardiac progenitors. Cardiovasc Diagn Ther 2013; 2:278-89. [PMID: 24282728 DOI: 10.3978/j.issn.2223-3652.2012.12.02] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2012] [Accepted: 12/10/2012] [Indexed: 12/11/2022]
Abstract
Resident stem cells persist throughout the entire lifetime of an organism where they replenishing damaged cells. Numerous types of resident stem cells are housed in a low-oxygen tension (hypoxic) microenvironment, or niches, which seem to be critical for survival and maintenance of stem cells. Recently our group has identified the adult mammalian epicardium and subepicardium as a hypoxic niche for cardiac progenitor cells. Similar to hematopoietic stem cells (LT-HSCs), progenitor cells in the hypoxic epicardial niche utilize cytoplasmic glycolysis instead of mitochondrial oxidative phosphorylation, where hypoxia inducible factor 1α (Hif-1α) maintains them in glycolytic undifferentiated state. In this review we summarize the relationship between hypoxic signaling and stem cell function, and discuss potential roles of several cardiac stem/progenitor cells in cardiac homeostasis and regeneration.
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Affiliation(s)
- Wataru Kimura
- Department of Internal Medicine, Division of Cardiology, UT Southwestern Medical Center, Dallas, TX, USA
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Sharma V, Bell RM, Yellon DM. Targeting reperfusion injury in acute myocardial infarction: a review of reperfusion injury pharmacotherapy. Expert Opin Pharmacother 2012; 13:1153-75. [PMID: 22594845 DOI: 10.1517/14656566.2012.685163] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
INTRODUCTION Acute myocardial infarction (AMI) (secondary to lethal ischemia-reperfusion [IR]) contributes to much of the mortality and morbidity from ischemic heart disease. Currently, the treatment for AMI is early reperfusion; however, this itself contributes to the final myocardial infarct size, in the form of what has been termed 'lethal reperfusion injury'. Over the last few decades, the discovery of the phenomena of ischemic preconditioning and postconditioning, as well as remote preconditioning and remote postconditioning, along with significant advances in our understanding of the cardioprotective pathways underlying these phenomena, have provided the possibility of successful mechanical and pharmacological interventions against reperfusion injury. AREAS COVERED This review summarizes the evidence from clinical trials evaluating pharmacological agents as adjuncts to standard reperfusion therapy for ST-elevation AMI. EXPERT OPINION Reperfusion injury pharmacotherapy has moved from bench to bedside, with clinical evaluation and ongoing clinical trials providing us with valuable insights into the shortcomings of current research in establishing successful treatments for reducing reperfusion injury. There is a need to address some key issues that may be leading to lack of translation of cardioprotection seen in basic models to the clinical setting. These issues are discussed in the Expert opinion section.
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Affiliation(s)
- Vikram Sharma
- The Hatter Cardiovascular Institute, 67 Chenies Mews, London WC1E 6HX, UK
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Sahin MA, Yucel O, Guler A, Doganci S, Jahollari A, Cingoz F, Arslan S, Gamsizkan M, Yaman H, Demirkilic U. Is there any cardioprotective role of Taurine during cold ischemic period following global myocardial ischemia? J Cardiothorac Surg 2011; 6:31. [PMID: 21418563 PMCID: PMC3068941 DOI: 10.1186/1749-8090-6-31] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2010] [Accepted: 03/18/2011] [Indexed: 11/25/2022] Open
Abstract
Background The aim of the present study was to investigate the cardioprotective effect of Taurine on the donor hearts during cold ischemic period. Methods 32 rats were divided into four groups (sham, taurine, ischemia, treatment group, 8 rats in each). All rats were fed with rat food for three weeks. Taurine and treatment groups were given a 200 mg/kg/day dose of Taurine by oral gavage besides rat feed. Cardiectomy was performed in all rats after three weeks. In ischemia and treatment groups, harvested hearts were kept in 0.9% sodium chloride at +4 degrees C for 5 hours. Tissue samples were taken from left ventricle in all groups. These samples were evaluated by histopathologic and biochemical examination. Results In the present study results of the biochemical and histopathological examination reveals the protective effects of Taurine. As a marker of lipid peroxidation, Malondialdehyde (MDA) levels in ischemia group were significantly higher than both Sham and Taurine groups. MDA values were recorded; 3.62 ± 0.197 in the sham group, 2.07 ± 0.751 in the Taurine group, 9.71 ± 1.439 in the ischemia group and 7.68 ± 1.365 in the treatment group. MDA levels decreased in treatment group. (p < 0.05) In accordance with MDA findings, while superoxide dismutase and glutathione peroxidase levels decreased in ischemia group, they increased in treatment group. (p < 0.05) There was no differences in Catalase (CAT) enzyme level between treatment and ischemia group (p = 1.000). CAT level results were recorded; 7.08 ± 0.609 in the sham group, 6.15 ± 0.119 in the Taurine group, 5.02 ± 0.62 in the ischemia group, and 5.36 ± 0.384 in the treatment group. Less intracellular edema and inflammatory cell reaction were observed in histologic examination in favor of treatment group. (p < 0.01) Conclusion Taurine decreased myocardial damage during cold ischemic period following global myocardial ischemia.
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Affiliation(s)
- Mehmet A Sahin
- Gülhane Military Medical Academy, Department of Cardiovascular Surgery, 06010, Etlik, Ankara, Turkey.
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Veress AI, Segars WP, Weiss JA, Tsui BMW, Gullberg GT. Normal and pathological NCAT image and phantom data based on physiologically realistic left ventricle finite-element models. IEEE TRANSACTIONS ON MEDICAL IMAGING 2006; 25:1604-16. [PMID: 17167995 DOI: 10.1109/tmi.2006.884213] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
The four-dimensional (4-D) NURBS-based cardiac-torso (NCAT) phantom, which provides a realistic model of the normal human anatomy and cardiac and respiratory motions, is used in medical imaging research to evaluate and improve imaging devices and techniques, especially dynamic cardiac applications. One limitation of the phantom is that it lacks the ability to accurately simulate altered functions of the heart that result from cardiac pathologies such as coronary artery disease (CAD). The goal of this work was to enhance the 4-D NCAT phantom by incorporating a physiologically based, finite-element (FE) mechanical model of the left ventricle (LV) to simulate both normal and abnormal cardiac motions. The geometry of the FE mechanical model was based on gated high-resolution X-ray multislice computed tomography (MSCT) data of a healthy male subject. The myocardial wall was represented as a transversely isotropic hyperelastic material, with the fiber angle varying from -90 degrees at the epicardial surface, through 0 degrees at the midwall, to 90 degrees at the endocardial surface. A time-varying elastance model was used to simulate fiber contraction, and physiological intraventricular systolic pressure-time curves were applied to simulate the cardiac motion over the entire cardiac cycle. To demonstrate the ability of the FE mechanical model to accurately simulate the normal cardiac motion as well as the abnormal motions indicative of CAD, a normal case and two pathologic cases were simulated and analyzed. In the first pathologic model, a subendocardial anterior ischemic region was defined. A second model was created with a transmural ischemic region defined in the same location. The FE-based deformations were incorporated into the 4-D NCAT cardiac model through the control points that define the cardiac structures in the phantom which were set to move according to the predictions of the mechanical model. A simulation study was performed using the FE-NCAT combination to investigate how the differences in contractile function between the subendocardial and transmural infarcts manifest themselves in myocardial Single photon emission computed tomography (SPECT) images. The normal FE model produced strain distributions that were consistent with those reported in the literature and a motion consistent with that defined in the normal 4-D NCAT beating heart model based on tagged magnetic resonance imaging (MRI) data. The addition of a subendocardial ischemic region changed the average transmural circumferential strain from a contractile value of -0.09 to a tensile value of 0.02. The addition of a transmural ischemic region changed average circumferential strain to a value of 0.13, which is consistent with data reported in the literature. Model results demonstrated differences in contractile function between subendocardial and transmural infarcts and how these differences in function are documented in simulated myocardial SPECT images produced using the 4-D NCAT phantom. Compared with the original NCAT beating heart model, the FE mechanical model produced a more accurate simulation for the cardiac motion abnormalities. Such a model, when incorporated into the 4-D NCAT phantom, has great potential for use in cardiac imaging research. With its enhanced physiologically based cardiac model, the 4-D NCAT phantom can be used to simulate realistic, predictive imaging data of a patient population with varying whole-body anatomy and with varying healthy and diseased states of the heart that will provide a known truth from which to evaluate and improve existing and emerging 4-D imaging techniques used in the diagnosis of cardiac disease.
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MESH Headings
- Algorithms
- Artifacts
- Computer Simulation
- Finite Element Analysis
- Heart Ventricles/diagnostic imaging
- Heart Ventricles/pathology
- Heart Ventricles/physiopathology
- Humans
- Imaging, Three-Dimensional/methods
- Models, Anatomic
- Models, Cardiovascular
- Movement
- Phantoms, Imaging
- Radiographic Image Enhancement/methods
- Radiographic Image Interpretation, Computer-Assisted/methods
- Reproducibility of Results
- Sensitivity and Specificity
- Tomography, X-Ray Computed/instrumentation
- Tomography, X-Ray Computed/methods
- Ventricular Dysfunction, Left/diagnostic imaging
- Ventricular Dysfunction, Left/pathology
- Ventricular Dysfunction, Left/physiopathology
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Affiliation(s)
- Alexander I Veress
- Department of Bioengineering and the Scientific Computing and Imaging Institute, University of Utah, Salt Lake City, UT 84112-9202, USA.
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Yamamoto Y, Ikegaki I, Sasaki Y, Uchida T. The protein kinase inhibitor fasudil protects against ischemic myocardial injury induced by endothelin-1 in the rabbit. J Cardiovasc Pharmacol 2000; 35:203-11. [PMID: 10672851 DOI: 10.1097/00005344-200002000-00005] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Endothelin-1 (ET-1) induces severe pathologic conditions such as coronary spasm followed by vasospastic angina pectoris and acute myocardial infarction. The related pathophysiologic mechanisms have remained obscure. Endothelin-1 receptor (ET(A) and ET(B)) is reported to couple with several types of G protein-involved pathways that participate in phospholipase C activation and atrial myofibrils organization into sarcomeric units. Here we demonstrate that ET-1 induces histologic and pathologic dysfunction in the rabbit myocardium and that such pathologic events are prevented by the Rho-kinase inhibitor fasudil. Although the bolus injection of ET-1 (1.4 nmol/kg) via the auricular vein of the rabbit induced only transient T-wave elevation, irreversible, severe histologic changes were observed in papillary muscles of the ventricle, and multifocal myocardial necrosis with infiltration of neutrophils and macrophages in the left ventricle occurred. Oral administration of fasudil (10 mg/kg) significantly reduced the occurrence of myocardial injury determinants, whereas conventional Ca2+ channel blockers (nifedipine, diltiazem) and a K+ channel opener (nicorandil; 10 mg/kg, p.o. each) showed a lesser or no effect on such determinants. These results suggest that ET-1 induces severe myocardial dysfunction based not only on the occurrence of vasospastic ischemia but also on its direct effects on the myocardium.
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Affiliation(s)
- Y Yamamoto
- Institute for Life Science Research, Asahi Chemical Industry, Co., Ltd., Fuji, Shizuoka, Japan
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Hegstad AC, Ytrehus K, Lindal S, Jørgensen L. Ultrastructural alterations during the critical phase of reperfusion: a stereological study in buffer-perfused isolated rat hearts. Cardiovasc Pathol 1999; 8:279-89. [PMID: 10533960 DOI: 10.1016/s1054-8807(99)00011-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
The present study focuses on myocardial ultrastructural alterations during the early phase of reperfusion. Isolated buffer-perfused rat hearts were exposed to standard perfusion (control group,n = 10); 60 min of global ischemia (n = 10); 60 min of global ischemia followed by 2 min of reperfusion (n = 10); or 60 min of global ischemia followed by 10 min of reperfusion (n = 10). The hearts were perfusion-fixed for electron microscopy, and ultrastructural evaluation was performed using stereological technique in order to obtain an estimate of the volume fraction and absolute volume of different tissue components. EFFECT OF ISCHEMIA: Neither the ventricular nor the myocytic volume differed significantly from the respective control values. Both the myocytic mitochondrial volume (135+/-8 vs control 89+/-6 microl) and the volume of myocytic clear space (35+/-6 vs control 10+/-2 microl) were significantly increased. The capillary volume (22+/-4 vs control 58+/-6 microl) and the volume of the capillary lumen (15+/-3 vs control 48+/-5 microl) were significantly decreased. The volume of the capillary wall, however, was not altered after exposure to ischemia (7+/-3 vs control 10+/-1 microl). ADDITIVE EFFECT OF ISCHEMIA AND REPERFUSION: Both the ventricular volume (755+/-28 vs control 600+/-32 microl) and the myocytic volume (396+/-24 vs control 287+/-16 microl) were significantly increased after 10 min of reperfusion. EFFECT OF REPERFUSION: The ischemic-induced myocytic mitochondrial swelling and increase of clear space were not reinforced during reperfusion. Furthermore, the volume of the capillary lumen and the capillary wall did not alter significantly in the groups exposed to reperfusion compared to the ischemic hearts. In conclusion, stereological evaluation did not reveal significant aggravation of ischemic-induced myocardial injury during the early phase of reperfusion.
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Affiliation(s)
- A C Hegstad
- Department of Morphology, Institute of Medical Biology, University of Tromsø, Norway.
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Rogers MS, Ryan BB, Cashon RE, Alayash AI. Effects of polymerization on the oxygen carrying and redox properties of diaspirin cross-linked hemoglobin. BIOCHIMICA ET BIOPHYSICA ACTA 1995; 1248:135-42. [PMID: 7748895 DOI: 10.1016/0167-4838(95)00017-o] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Human hemoglobin site specifically cross-linked with bis(3,5-dibromosalicyl)fumarate results in a low oxygen affinity hemoglobin-based red cell substitute (alpha-DBBF). Polymerization of alpha-DBBF by bis(maleoylglycylamide) polyethylene glycol (BMAA-PEG) yields poly alpha-DBBF which offers the added benefits of reduced renal clearance and increased retention in the vascular circulation. Oxygen equilibrium curves for poly alpha-DBBF are slightly left-shifted (higher O2 affinity) compared to those of alpha-DBBF; with a diminished cooperativity and a reduced Bohr effect. In rapid mixing experiments (oxygen dissociation and carbon monoxide binding), poly alpha-DBBF exhibits a several fold increase in the overall rate of deoxygenation and carbon monoxide binding kinetics over its cross-linked counterpart. The rate of nitric oxide binding to the oxidized form of poly alpha-DBBF shows little or no change compared to the intramolecularly cross-linked derivative. The reduction of cyanomet poly alpha-DBBF by dithionite is several fold faster than that of HbA0 and alpha-DBBF whereas the slow subsequent cyanide dissociation from the ferrous iron remained unchanged among all proteins. The propensity of poly alpha-DBBF for auto-oxidation is slightly enhanced over alpha-DBBF whereas the extent of oxidative modification by hydrogen peroxide is very similar. Polymerization appears to selectively modify ligand interactions and redox kinetics of the tetrameric cross-linked form which reflects a possibly more open heme pocket. The data suggests that changes in oxygenation properties of hemoglobin brought about by a given modification are not necessarily predictive of other functional changes.
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Affiliation(s)
- M S Rogers
- Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, MD 20892, USA
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