Little is known about the mechanisms responsible for the adaptation and changes in the capillary network of hindlimb unweighting (HU)-induced atrophied skeletal muscle, especially the coupling between functional and structural alterations of intercapillary anastomoses and tortuosity of capillaries. We hypothesized that muscle atrophy by HU leads to the apoptotic regression of the capillaries and intercapillary anastomoses with their functional alteration in hemodynamics. To clarify the three-dimensional architecture of the capillary network, contrast medium-injected rat soleus muscles were visualized clearly using a confocal laser scanning microscope, and sections were stained by terminal deoxynucleotidyltransferase-mediated dUTP nick-end labeling (TUNEL) and with anti-von Willebrand factor. In vivo, the red blood cell velocity of soleus muscle capillaries were determined with a pencil-lens intravital microscope brought into direct contact with the soleus surface. After HU, the total muscle mass, myofibril protein mass, and slow-type myosin heavy chain content were significantly lower. The number of capillaries paralleling muscle fiber and red blood cells velocity were higher in atrophied soleus. However, the mean capillary volume and capillary luminal diameter were significantly smaller after HU than in the age-matched control group. In addition, we found that the number of anastomoses and the tortuosity were significantly lower and TUNEL-positive endothelial cells were observed in atrophied soleus muscles, especially the anastomoses and/or tortuous capillaries. These results indicate that muscle atrophy by HU generates structural alterations in the capillary network, and apoptosis appears to occur in the endothelial cell of the muscle capillaries. intercapllary anastomosis; tortuosity; capillary volume; capillary lumen; erythrocyte velocity; disuse atrophy; endothelial terminal deoxynucleotidyltransferase-mediated dUTP nick-end labeling SKELETAL MUSCLE CAPILLARIES run tortuously along muscle fibers in the relaxed resting state (2,4,18,20,33). These capillaries are connected with anastomoses, which run orthogonally to muscle fiber direction like parallel rungs of ladder (12, 33). Capillary-to-fiber (C/F) ratio is frequently used to evaluate O 2 supply capacity in skeletal muscle (27). In fact, the C/F ratio is higher in rat soleus muscle, which mainly contains slow oxidative fibers (type I), than in extensor digitorum longus, which is predominantly comprised of fast glycolytic fibers (type IIb) (1, 8, 13). C/F ratio was increased by the augmentation of muscle activity, e.g., exercise or electrical stimulation (9,14,20,25), and was decreased by disuse (14, 31, 33). Histological sections from earlier studies of capillary remodeling in skeletal muscle with disuse atrophy demonstrate a decrease in capillary luminal diameter (16,36) and in the C/F ratio (13, 31, 32) despite an increase in capillary density (13,31,32).Although the regression of anastomoses in atrophied skeletal muscle has not been well studied, it wa...

Objective-We tested the hypothesis that hydrogen peroxide (H 2 O 2 ), the dismutated product of superoxide (O 2 ⅐Ϫ ), couples myocardial oxygen consumption to coronary blood flow. Accordingly, we measured O 2 ⅐Ϫ and H 2 O 2 production by isolated cardiac myocytes, determined the role of mitochondrial electron transport in the production of these species, and determined the vasoactive properties of the produced H 2 O 2 . Methods and Results-The production of O 2⅐Ϫ is coupled to oxidative metabolism because inhibition of complex I (rotenone) or III (antimycin) enhanced the production of O 2 ⅐Ϫ during pacing by about 50% and 400%, respectively; whereas uncoupling oxidative phosphorylation by decreasing the protonmotive force with carbonylcyanide-ptrifluoromethoxyphenyl-hydrazone (FCCP) decreased pacing-induced O 2 ⅐Ϫ production. The inhibitor of cytosolic NAD(P)H oxidase assembly, apocynin, did not affect O 2 ⅐Ϫ production by pacing. Aliquots of buffer from paced myocytes produced vasodilation of isolated arterioles (peak response 67Ϯ8% percent of maximal dilation) that was significantly reduced by catalase (5Ϯ0.5%, PϽ0.05) or the antagonist of Kv channels, 4-aminopyridine (18Ϯ4%, PϽ0.05). In intact animals, tissue concentrations of H 2 O 2 are proportionate to myocardial oxygen consumption and directly correlated to coronary blood flow. Intracoronary infusion of catalase reduced tissue levels of H 2 O 2 by 30%, and reduced coronary flow by 26%. Intracoronary administration of 4-aminopyridine also shifted the relationship between myocardial oxygen consumption and coronary blood flow or coronary sinus pO 2 . Conclusions-Taken together, our results demonstrate that O 2⅐Ϫ is produced in proportion to cardiac metabolism, which leads to the production of the vasoactive reactive oxygen species, H 2 O 2 . Our results further suggest that the production of H 2 O 2 in proportion to metabolism couples coronary blood flow to myocardial oxygen consumption. Key Words: reactive oxygen species Ⅲ coronary circulation Ⅲ vasodilation Ⅲ microcirculation T he coupling of blood flow to metabolism is the most important vasomotor adjustment for the regulation of oxygen delivery to metabolically active organ systems. This matching, termed metabolic dilation, or metabolic or active hyperemia, is critical to ensure adequate oxygen delivery for aerobic metabolism and adequate organ function. 1 Although the factor or factors responsible for the coupling of flow to metabolism have been actively pursued for decades, no metabolite has been casually linked to the process of metabolic hyperemia or has withstood critical evaluation. 1-3 Most investigations have pursued the idea that the metabolic regulation of flow is a negative feedback pathway, in which an imbalance between oxygen supply (delivered via flow) and oxygen demands, ie, demands exceed supply, results in the production of a metabolic dilator. The adenosine hypothesis was such a scheme, in which oxygen demands, in excess of supply would increase the production of adenosine through hydro...

Neiguan ) is a traditional acupoint in the bilateral forearms, overlying the median nerve trunk. Acupuncture at some acupoints including Neiguan, has been believed to affect cardiovascular function and is used in traditional Chinese medicine to improve or treat a wide range of heart diseases [1-6]. However, physiological mechanisms of these circulatory effects remain to be established scientifically.Clinical evidence indicates that acupuncture at Neiguan acupoints has therapeutic effects on some types of hypertension, arrhythmias, angina pectoris, and myocardial infarction [1][2][3][4]. Studies in anesthetized animals (rabbit, cat, and dog) have also demonstrated beneficial effects of acupuncture and electroacupuncture at Neiguan acupoints (Neiguan EA) on myocardial ischemia, arrhythmias, hypertension, and hypotension [5]. However, no experiments have been done to assess the effects of Neiguan EA on hemodynamics and cardiac contractility under physiological conditions.The purpose of this study was to obtain basic physiological evidence of the effects of Neiguan EA on hemodynamics and cardiac contractility in anesthetized open-chest dogs. We successfully observed that Neiguan EA significantly improved hemodynamics and cardiac contractility. Key words: Chinese medicine, Neiguan acupoint, cardiac performance, ventricular contractility. METHODS Surgical preparation. Ten adult mongrel dogsAbstract: Neiguan (PC-6) is a traditional acupoint in the bilateral forearms, overlying the median nerve trunk. Neiguan electroacupuncture (EA) has been believed to affect cardiovascular function and used in traditional Chinese medicine to improve or treat a wide range of health conditions and diseases, including angina pectoris, myocardial infarction, hypertension, and hypotension. However, few physiological studies have assessed the beneficial effects of Neiguan EA on the cardiovascular function. In the present study, we investigated its effects on the cardiovascular function in normal open-chest dogs under pentobarbital and fentanyl anesthesia. We also obtained left ventricular (LV) pressure-volume (P-V) data with a micromanometer catheter and a volumetric conductance catheter. Mean arterial pressure, end-diastolic volume, heart rate, stroke volume, cardiac output, and end-systolic pressure gradually decreased by 5 to 10% over 1.5 h without Neiguan EA. Neiguan EA at 40 Hz, however, increased these cardiovascular variables by 10 to 15%, especially end-systolic elastance (Ees) by 40% (pϽ0.05) over 15 to 60 min. After Neiguan EA was stopped at 1 h, these facilitated cardiovascular variables decreased below the pre-EA level. This beneficial effect of electroacupuncture may contribute to the effectiveness of the acupuncture in Chinese medicine.

Aims To provide multi-national, multi-ethnic data on the clinical characteristics and prognosis of patients with microvascular angina (MVA). Methods and results The Coronary Vasomotor Disorders International Study Group proposed the diagnostic criteria for MVA. We prospectively evaluated the clinical characteristics of patients according to these criteria and their prognosis. The primary endpoint was the composite of major cardiovascular events (MACE), verified by institutional investigators, which included cardiovascular death, non-fatal myocardial infarction, non-fatal stroke, and hospitalization due to heart failure or unstable angina. During the period from 1 July 2015 to 31 December 2018, 686 patients with MVA were registered from 14 institutes in 7 countries from 4 continents. Among them, 64% were female and the main ethnic groups were Caucasians (61%) and Asians (29%). During follow-up of a median of 398 days (IQR 365–744), 78 MACE occurred (6.4% in men vs. 8.6% in women, P = 0.19). Multivariable Cox proportional hazard analysis disclosed that hypertension and previous history of coronary artery disease (CAD), including acute coronary syndrome and stable angina pectoris, were independent predictors of MACE. There was no sex or ethnic difference in prognosis, although women had lower Seattle Angina Questionnaire scores than men (P < 0.05). Conclusions This first international study provides novel evidence that MVA is an important health problem regardless of sex or ethnicity that a diagnosis of MVA portends a substantial risk for MACE associated with hypertension and previous history of CAD, and that women have a lower quality of life than men despite the comparable prognosis.

We have observed that hydrogen peroxide (H 2O2), the dismutated product of superoxide, is a coronary metabolic dilator and couples myocardial oxygen consumption to coronary blood flow. Because the chemical activity of H 2O2 favors its role as an oxidant, and thiol groups are susceptible to oxidation, we hypothesized that coronary metabolic dilation occurs via a redox mechanism involving thiol oxidation. To test this hypothesis, we studied the mechanisms of dilation of isolated coronary arterioles to metabolites released by metabolically active (paced at 400 min) isolated cardiac myocytes and directly compared these responses with authentic H2O2. Studies were performed under control conditions and using interventions designed to reduce oxidized thiols [0.1 M dithiothreitol (DTT) and 10 mM N-acetyl-L-cysteine (NAC)]. Aliquots of the conditioned buffer from paced myocytes produced vasodilation of isolated arterioles (peak response, 71% Ϯ 6% of maximal dilation), whereas H 2O2 produced complete dilation (92% Ϯ 7%). Dilation to either the conditioned buffer or to H 2O2 was significantly reduced by the administration of either NAC or DTT. The location of the thiols oxidized by the conditioned buffer or of H 2O2 was determined by the administration of the fluorochromes monochlorobimane (20 M) or monobromotrimethylammoniobimane (20 M), which covalently label the reduced total or extracellular-reduced thiols, respectively. H 2O2 or the conditioned buffer predominately oxidized intracellular thiols since the fluorescent signal from monochlorobimane was reduced more than that of monobromotrimethylammoniobimane. To determine whether one of the intracellular targets of thiol oxidation that leads to dilation is the redoxsensitive kinase p38 mitogen-activated protein (MAP) kinase, we evaluated dilation following the administration of the p38 inhibitor SB-203580 (10 M). The inhibition of p38 attenuated dilation to either H2O2 or to the conditioned buffer from stimulated myocytes by a similar degree, but SB-203580 did not attenuate dilation to nitroprusside. Western blot analysis for the activated form of p38 (phospho-p38) in the isolated aortae revealed robust activation of this enzyme by H2O2. Taken together, our results show that an active component of cardiac metabolic dilation, like that of H2O2, produces dilation by the oxidation of thiols, which are predominately intracellular and dependent activation on the p38 MAP kinase. Thus coronary metabolic dilation appears to be mediated by redox-dependent signals. coronary circulation; coronary microcirculation; reactive oxygen species; vasodilatation THE OXIDATION OF THIOL GROUPS is involved in many biological processes. Thiol oxidation induces protein conformation changes by converting the free thiols (-SH) into sulfenic acids (SO Ϫ ), sulfinic acids (SOO Ϫ ), sulfonic acids (SOOO Ϫ ), and disulfide bridges (S-S). Thiol oxidation is involved in many cellular processes, e.g., p38 mitogen-activating protein (MAP) kinase activation (2, 23), inhibition of p56 (lck) tyrosine kinase ...