bluuebunny/crossref_metadata_2025 huggingface dataset:
Impaired endothelium-mediated vasodilation is not the principal cause of vasoconstriction in heart failure
Authors: Negrao Carlos E. , Hamilton Michele A. , Fonarow Gregg C. , Hage Antoine , Moriguchi Jaime D. , Middlekauff Holly R.
Published: December 2017

The extent to which abnormal endothelium-dependent vasodilator mechanisms contribute to abnormal resting vasoconstriction and blunted reflex vasodilation seen in heart failure is unknown. The purpose of this study was to test the hypothesis that the resting and reflex abnormalities in vascular tone that characterize heart failure are mediated by abnormal endothelium-mediated mechanisms. Thirteen advanced heart-failure patients (New York Heart Association III-IV) and 13 age-matched normal controls were studied. Saline, acetylcholine (20 μg/min), orl-arginine (10 mg/min) was infused into the brachial artery, and forearm blood flow was measured by venous plethysmography at rest and during mental stress. At rest, acetylcholine decreased forearm vascular resistance in normal subjects, but this response was blunted in heart failure. During mental stress with intra-arterial acetylcholine orl-arginine, the decrease in forearm vascular resistance was not greater than during saline control in heart failure [saline control vs. acetylcholine (7 ± 3 vs. 6 ± 3, P = NS) or vs.l-arginine (9 ± 2 units, P = NS)]. The increase in forearm blood flow was not greater than during saline control in heart failure [saline control vs. acetylcholine (1.2 ± 0.3 vs. 1.3 ± 0.3, P = NS), or vs.l-arginine (1.2 ± 0.2 ml ⋅ min−1 ⋅ 100 ml−1, P = NS)]. Furthermore, during mental stress with nitroprusside, the decrease in forearm vascular resistance was not greater than during saline control [saline control vs. nitroprusside (7 ± 3 vs. 5 ± 4 ml ⋅ min−1 ⋅ 100 g−1, P = NS)], and the increase in forearm blood flow was not greater than during saline control [saline control vs. nitroprusside (1.2 ± 0.3 vs. 1.3 ± 0.5 ml ⋅ min−1 ⋅ 100 g−1, P = NS)]. Because the endothelial-independent agent nitroprusside was unable to restore resting and reflex vasodilation to normal in heart failure, we conclude that impaired endothelium-mediated vasodilation with acetylholine-nitric oxide cannot be the principal cause of the attenuated resting- or reflex-mediated vasodilation in heart failure.
Increased myometrial contracture frequency at 96–140 days accelerates fetal cardiovascular maturation
Authors: Shinozuka Norio , Yen Andrew , Nathanielsz Peter W.
Published: December 2017

Fetal cardiovascular responses to an altered intrauterine environment of increased myometrial contractures induced by oxytocin (OT) pulses to the ewe over the final 50 days of gestation were studied in chronically instrumented sheep. Ewes received saline (Cntl) or long-term OT treatment (LTOT, 600 μU ⋅ kg−1 ⋅ min−1in 5-min pulses every 20 min) from 96 days gestational age. Fetal baroreflex responses to sodium nitroprusside (SNP) and phenylephrine (PE) were studied at 133 days gestation. OT increased contractures in LTOT ewes. Fetal blood pressure (FBP) was higher, and fetal heart rate (FHR) and slope of daily change in FBP and FHR were lower in LTOT fetuses. Fetal SNP-induced hypotension resulted in a narrow R-R interval variation range in LTOT fetuses; Cntl fetuses showed early breakdown in compensation. Baroreflex response slope during PE-induced fetal hypertension was lower in LTOT than in Cntl fetuses. Although the cortisol-to-ACTH ratio was lower in LTOT fetuses, fetal plasma ACTH and cortisol changes were similar in control and LTOT fetuses. We hypothesize that contracture-induced alterations in the intrauterine environment accelerate fetal cardiovascular development through mild hypoxemia, repetitive fetal pituitary-adrenal stimulation, and/or physical stimulation.
Adenosine is not responsible for local metabolic control of coronary blood flow in dogs during exercise
Authors: Tune Johnathan D. , Richmond Keith Neu , Gorman Mark W. , Olsson Ray A. , Feigl Eric O.
Published: December 2017

The purpose of this investigation was to quantitatively evaluate the role of adenosine in coronary exercise hyperemia. Dogs ( n = 10) were chronically instrumented with catheters in the aorta and coronary sinus, and a flow probe on the circumflex coronary artery. Cardiac interstitial adenosine concentration was estimated from arterial and coronary venous plasma concentrations using a previously tested mathematical model. Coronary blood flow, myocardial oxygen consumption, heart rate, and aortic pressure were measured at rest and during graded treadmill exercise with and without adenosine receptor blockade with either 8-phenyltheophylline (8-PT) or 8- p-sulfophenyltheophylline (8-PST). In control vehicle dogs, exercise increased myocardial oxygen consumption 4.2-fold, coronary blood flow 3.8-fold, and heart rate 2.5-fold, whereas mean aortic pressure was unchanged. Coronary venous plasma adenosine concentration was little changed with exercise, and the estimated interstitial adenosine concentration remained well below the threshold for coronary vasodilation. Adenosine receptor blockade did not significantly alter myocardial oxygen consumption or coronary blood flow at rest or during exercise. Coronary venous and estimated interstitial adenosine concentration did not increase to overcome the receptor blockade with either 8-PT or 8-PST as would be predicted if adenosine were part of a high-gain, negative-feedback, local metabolic control mechanism. These results demonstrate that adenosine is not responsible for local metabolic control of coronary blood flow in dogs during exercise.
Stroke volume during exercise: interaction of environment and hydration
Authors: González-Alonso José , Mora-Rodríguez Ricardo , Coyle Edward F.
Published: December 2017

Euhydrated and dehydrated subjects exercised in a hot and a cold environment with our aim to identify factors that relate to reductions in stroke volume (SV). We hypothesized that reductions in SV with heat stress are related to the interaction of several factors rather than the effect of elevated skin blood flow. Eight male endurance-trained cyclists [maximal O2 consumption (V˙o 2 max) 4.5 ± 0.1 l/min; means ± SE] cycled for 30 min (72%V˙o 2 max) in the heat (H; 35°C) or the cold (C; 8°C) when euhydrated or dehydrated by 1.5, 3.0, or 4.2% of their body weight. When euhydrated, SV and esophageal temperature (Tes 38.2–38.3°C) were similar in H and C, whereas skin blood flow was much higher in H vs. C (365 ± 64% higher; P < 0.05). With each 1% body weight loss, SV declined 6.4 ± 1.3 ml (4.8%) in H and 3.4 ± 0.4 ml (2.5%) in C, whereas Tes increased 0.21 ± 0.02 and 0.10 ± 0.02°C in H and C, respectively ( P < 0.05). However, reductions in SV were not associated with increases in skin blood flow. The reduced SV was highly associated with increased heart rate and reduced blood volume in both H ( R = 0.96; P < 0.01) and C ( R = 0.85; P < 0.01). In conclusion, these results suggest that SV is maintained in trained subjects during exercise in euhydrated conditions despite large differences in skin blood flow. Furthermore, the lowering of SV with dehydration appears largely related to increases in heart rate and reductions in blood volume.
Role of kinins in chronic heart failure and in the therapeutic effect of ACE inhibitors in kininogen-deficient rats
Authors: Liu Yun-He , Yang Xiao-Ping , Mehta Dharmesh , Bulagannawar Manohar , Scicli Gloria M. , Carretero Oscar A.
Published: December 2017

Using Brown Norway Katholiek (BNK) rats, which are deficient in kininogen (kinin precursor) due to a mutation in the kininogen gene, we examined the role of endogenous kinins in 1) normal cardiac function; 2) myocardial infarction (MI) caused by coronary artery ligation; 3) cardiac remodeling in the development of heart failure (HF) after MI; and 4) the cardioprotective effect of angiotensin-converting enzyme inhibitors (ACEI) on HF after MI. Two months after MI, rats were randomly treated with vehicle or the ACEI ramipril for 2 mo. Brown Norway rats (BN), which have normal kininogen, were used as controls. Left ventricular (LV) end-diastolic volume (EDV), end-systolic volume (ESV), end-diastolic pressure (EDP), and ejection fraction (EF) as well as myocardial infarct size (IS), interstitial collagen fraction (ICF), cardiomyocyte cross-sectional area (MCA), and oxygen diffusion distance (ODD) were measured. We found that 1) cardiac hemodynamics, function, and histology were the same in sham-ligated BN and BNK rats; 2) IS was similar in BN and BNK; 3) in rats with HF treated with vehicle, the decrease in LVEF and the increase in LVEDV, LVESV, LVEDP, ICF, MCA, and ODD did not differ between BNK and BN; and 4) ACEI increased EF, decreased LVEDV and LVESV, and improved cardiac remodeling in BN-HF rats, and these effects were partially blocked by the bradykinin B2 receptor antagonist icatibant (HOE-140). In BNK-HF rats, ACEI failed to produce these beneficial cardiac effects. We concluded that in rats, lack of kinins does not influence regulation of normal cardiac function, myocardial infarct size, or development of HF; however, kinins appear to play an important role in the cardioprotective effect of ACEI, since 1) this effect was significantly diminished in kininogen-deficient rats and 2) it was blocked by a B2 kinin receptor antagonist in BN rats.
Effects of autonomic disruption and inactivity on venous vascular function
Authors: Wecht Jill M. , de Meersman Ronald E. , Weir Joseph P. , Bauman William A. , Grimm David R.
Published: December 2017

The effects of autonomic disruption and inactivity were studied on the venous vascular system. Forty-eight subjects, 24 with spinal cord injury (SCI) and 12 sedentary and 12 active able-bodied controls, participated in this study. Peripheral autonomic data were obtained to estimate sympathetic vasomotor control [low-frequency component of systolic blood pressure (LFSBP)]. Vascular parameters were determined using strain-gauge venous occlusion plethysmography: venous capacitance (VC), venous emptying rate (VER), and total venous outflow (VOt). An additional vascular parameter was calculated: venous compliance [(VC/occlusion pressure) × 100]. VC and VOt were significantly different (SCI < sedentary < active). VER adjusted for VC was not different for any group comparison, whereas venous compliance was significantly lower in the SCI group than in the able-bodied groups and in the sedentary group compared with the active group. Regression analysis for the total group revealed a significant relationship between LFSBP and venous compliance ( r = 0.64, P < 0.0001). After controlling for LFSBP through analysis of covariance, we found that mean differences for all venous vascular parameters did not change from unadjusted mean values. Our findings suggest that in subjects with SCI, the loss of sympathetic vasomotor tone contributes more than inactivity to reductions in venous vascular function. Heightened VC, VOt, vasomotor tone, and venous compliance in the active group compared with the sedentary group imply that regular endurance training contributes to optimal venous vascular function and peripheral autonomic integrity.
Gene transfer of calcitonin gene-related peptide to cerebral arteries
Authors: Toyoda Kazunori , Faraci Frank M. , Russo Andrew F. , Davidson Beverly L. , Heistad Donald D.
Published: December 2017

Overexpression of calcitonin gene-related peptide (CGRP), an extremely potent vasodilator, to blood vessels is a possible strategy for prevention of vasospasm. We constructed an adenoviral vector that encodes prepro-CGRP (Adprepro-CGRP) and examined the effects of gene transfer on cultured cells and cerebral arteries. Transfection of Adprepro-CGRP to Cos-7 and NIH-3T3 cells increased CGRP-like immunoreactivity in media and produced an increase in cAMP in recipient cells. Five days after injection of Adprepro-CGRP into the cisterna magna of rabbits, the concentration of CGRP-like immunoreactivity increased by 93-fold in cerebrospinal fluid. In basilar artery, cAMP increased by 2.3-fold after Adprepro-CGRP compared with a control adenovirus. After transfection of Adprepro-CGRP, contraction of basilar artery in vitro to histamine and serotonin was attenuated, and relaxation to an inhibitor of cyclic nucleotide phosphodiesterase 3-isobutyl-1-methylxanthine was augmented compared with nontransduced arteries or arteries transfected with a control gene. Altered vascular responses were restored to normal by pretreatment with a CGRP1 receptor antagonist CGRP-(8–37). Thus gene transfer of prepro-CGRP in vivo overexpresses CGRP in cerebrospinal fluid and perivascular tissues and modulates vascular tone. We speculate that this approach may be useful in prevention of vasospasm after subarachnoid hemorrhage.
Tyrosine kinase and protein kinase C regulate L-type Ca2+current cooperatively in human atrial myocytes
Authors: Boixel Christophe , Tessier Sophie , Pansard Yves , Lang-Lazdunski Loïc , Mercadier Jean-Jacques , Hatem Stephane N.
Published: December 2017

The effects of tyrosine protein kinases (TK) on the L-type Ca2+current ( ICa) were examined in whole cell patch-clamped human atrial myocytes. The TK inhibitors genistein (50 μM), lavendustin A (50 μM), and tyrphostin 23 (50 μM) stimulated ICaby 132 ± 18% ( P < 0.001), 116 ± 18% ( P < 0.05), and 60 ± 6% ( P < 0.001), respectively. After ICastimulation by genistein, external application of isoproterenol (1 μM) caused an additional increase in ICa. Dialyzing the cells with a protein kinase A inhibitor suppressed the effect of isoproterenol on ICabut not that of genistein. Inhibition of protein kinase C (PKC) by pretreatment of cells with 100 nM staurosporine or 100 nM calphostin C prevented the effects of genistein on ICa. The PKC activator phorbol 12-myristate 13-acetate (PMA), after an initial stimulation (75 ± 17%, P < 0.05), decreased ICa(−36 ± 5%, P < 0.001). Once the inhibitory effect of PMA on ICahad stabilized, genistein strongly stimulated the current (323 ± 25%, P < 0.05). Pretreating myocytes with genistein reduced the inhibitory effect of PMA on ICa. We conclude that, in human atrial myocytes, TK inhibit ICavia a mechanism that involves PKC.
Altered LV inotropic reserve and mechanoenergetics early in the development of heart failure
Authors: Prabhu Sumanth D. , Freeman Gregory L.
Published: December 2017

To test the hypothesis that alterations in left ventricular (LV) mechanoenergetics and the LV inotropic response to afterload manifest early in the evolution of heart failure, we examined six anesthetized dogs instrumented with LV micromanometers, piezoelectric crystals, and coronary sinus catheters before and after 24 h of rapid ventricular pacing (RVP). After autonomic blockade, the end-systolic pressure-volume relation (ESPVR), myocardial O2 consumption (MV˙o 2), and LV pressure-volume area (PVA) were defined at several different afterloads produced by graded infusions of phenylephrine. Short-term RVP resulted in reduced preload with proportionate reductions in stroke work and the maximum first derivative of LV pressure but with no significant reduction in baseline LV contractile state. In response to increased afterload, the baseline ESPVR shifted to the left with maintained end-systolic elastance ( E es). In contrast, after short-term RVP, in response to comparable increases in afterload, the ESPVR displayed reduced E es ( P < 0.05) and significantly less leftward shift compared with control ( P< 0.05). Compared with the control MV˙o 2-PVA relation, short-term RVP significantly increased the MV˙o 2 intercept ( P< 0.05) with no change in slope. These results indicate that short-term RVP produces attenuation of afterload-induced enhancement of LV performance and increases energy consumption for nonmechanical processes with maintenance of contractile efficiency, suggesting that early in the development of tachycardia heart failure, there is blunting of length-dependent activation and increased O2requirements for excitation-contraction coupling, basal metabolism, or both. Rather than being adaptive mechanisms, these abnormalities may be primary defects involved in the progression of the heart failure phenotype.
Age-related changes in A1-adenosine receptor-mediated bradycardia
Authors: Hinschen Andrea K. , Rose'Meyer Roselyn B. , Headrick John P.
Published: December 2017

The impact of age on functional sensitivity to A1-adenosine receptor activation was studied in Langendorff-perfused hearts from young (1–2 mo) and old (12–18 mo) male Wistar rats. Adenosine mediated bradycardia in young and old hearts, with sensitivity enhanced ∼10-fold in old [negative logarithm of EC50(pEC50) = 4.56 ± 0.11] versus young hearts (pEC50 = 3.70 ± 0.09). Alternatively, the nonmetabolized A1 agonists N 6-cyclohexyladenosine and ( R)- N 6-phenylisopropyladenosine were equipotent in young (pEC50 = 7.43 ± 0.12 and 6.61 ± 0.19, respectively) and old hearts (pEC50 = 7.07 ± 0.10 and 6.80 ± 0.11, respectively), suggesting a role for uptake and/or catabolism in age-related changes in adenosine sensitivity. In support of this suggestion, [3H]-adenosine uptake was approximately twofold greater in young than in old hearts (from 3–100 μM adenosine). However, although inhibition of adenosine deaminase and adenosine transport with 10 μM erythro-9-(2-hydroxy-3-nonyl)adenine hydrochloride and 10 μM S-(4-nitrobenzyl)-6-thioinosine increased adenosine sensitivity three- to fourfold, it failed to abolish the sensitivity difference in old (pEC50 = 4.95 ± 0.08) versus young (pEC50= 4.29 ± 0.13) hearts. Data indicate that 1) age increases functional A1 receptor sensitivity to adenosine without altering the sensitivity of the A1 receptor itself, and 2) age impairs adenosine transport and/or catabolism, but this does not explain differing functional sensitivity to adenosine. This increased functional sensitivity to adenosine may have physiological significance in the older heart.
Altered molecular response to adrenoreceptor-induced cardiac hypertrophy in Egr-1-deficient mice
Authors: Saadane Nacéra , Alpert Lesley , Chalifour Lorraine E.
Published: December 2017

Unmanipulated early growth response-1 (Egr-1)-deficient −/− mice have similar heart-to-body weight ratios but express lower amounts of atrial natriuretic factor (ANF), β-myosin heavy chain (β-MHC), skeletal actin, NGF1-A binding protein (NAB)-2, Sp1, c- fos, c- jun, GATA-4, and Nkx2.5 than +/+ or +/− mice. α-MHC, tubulin, and NAB-1 expression was similar. Isoproterenol (Iso) and phenylephrine (PE) infusion into +/+ and −/− mice increased heart weight, ANF, β-MHC, skeletal actin, Sp1, NAB-2, c- fos, and c- jun expression, but induction in −/− mice was lower. Only Iso + PE-treated +/+ mice showed induction of NAB-1, GATA-4, and Nkx2.5. Foci of fibrosis were found in Iso + PE-treated −/− and +/+ mice. Surprisingly, vehicle-treated −/− mice displayed fibrosis and increased Sp1, skeletal actin, Nkx2.5, and GATA-4 expression without hypertrophy. Minipump removal caused the agonist-treated hearts and gene expression to regress to control or near-control levels. Thus Egr-1 deficiency caused a blunted catecholamine-induced hypertrophy response and increased sensitivity to stress.
Regional dysfunction correlates with myofiber disarray in transgenic mice with ventricular expression ofras
Authors: Karlon William J. , McCulloch Andrew D. , Covell James W. , Hunter John J. , Omens Jeffrey H.
Published: December 2017

A hallmark of certain cardiac diseases such as familial hypertrophic cardiomyopathy is focal myofiber disarray. Regional ventricular dysfunction occurs in human subjects with hypertrophic cardiomyopathy; however, no direct evidence exists to correlate regional dysfunction with myofiber disarray. We used a transgenic mouse, which exhibits regional myofiber disarray via ventricular expression of the human oncogene ras, to investigate the relationship between myofiber disarray and septal surface strain. An isolated ejecting mouse heart preparation was used to record deformation of markers on the septal surface and to determine nonhomogeneous septal surface strain maps. Myofiber disarray made in histological tissue sections was correlated with gradients in surface systolic shortening. Significantly smaller maximum principal shortening was associated with disarray located near the right ventricle (RV) septal surface. There was also significantly smaller surface shear strain associated with disarray located either near the RV surface or at the midwall. Because surface shear is a local indicator of torsion, we conclude that myofiber disarray is associated with reduced septal torsion and reduced surface shortening.
Differential ICP responses elicited by electrical stimulation of medial preoptic area
Authors: Sato Yoshikazu , Christ George J.
Published: December 2017

Recent findings indicate a complex role for the medial preoptic area (MPOA) in modulating penile erection. To further investigate this important area we measured changes in intracavernous pressure (ICP) elicited by electrical stimulation of the MPOA and evaluated the contribution of the cavernous nerve to the ICP responses after bilateral transection of the cavernous nerve (CN). In all experiments electrical stimulation was performed unilaterally in anesthetized male rats. Two distinct patterns of ICP response were seen after electrical stimulation of the MPOA: 1) increases in ICP during electrical stimulation ( pattern 1, n = 10 rats) and 2) increases in ICP after electrical stimulation was terminated ( pattern 2, n = 10 rats). For pattern 1, increases in ICP during stimulation exhibited a stable plateau without contraction of striated penile muscles, and bilateral transection of the CN eliminated the ICP responses. For pattern 2, increases in ICP observed after stimulation were lower, more variable, and accompanied by significant amplitude variations (“peaks”), caused by contraction of striated penile muscles. Bilateral transection of the CN eliminated the pattern 2 ICP response but did not alter striated muscle contraction. Histological studies documented that pattern 1 and pattern 2 responses occurred via electrical stimulation of the anterior and posterior areas of the MPOA, respectively. Thus both responses appear to result from activation of the CN, but the pattern 2 response apparently involves contraction of the striated penile muscles as well.
Temporal contribution of body movement to very long-term heart rate variability in humans
Authors: Aoyagi Naoko , Ohashi Kyoko , Tomono Shinji , Yamamoto Yoshiharu
Published: December 2017

A newly developed, very long-term (∼7 days) ambulatory monitoring system for assessing beat-to-beat heart rate variability (HRV) and body movements (BM) was used to study the mechanism(s) responsible for the long-period oscillation in human HRV. Data continuously collected from five healthy subjects were analyzed by 1) standard auto- and cross-spectral techniques, 2) a cross-Wigner distribution (WD; a time-frequency analysis) between BM and HRV for 10-s averaged data, and 3) coarse-graining spectral analysis for 600 successive cardiac cycles. The results showed 1) a clear circadian rhythm in HRV and BM, 2) a 1/ f β-type spectrum in HRV and BM at ultradian frequencies, and 3) coherent relationships between BM and HRV only at specific ultradian as well as circadian frequencies, indicated by significant ( P < 0.05) levels of the squared coherence and temporal localizations of the covariance between BM and HRV in the cross-WD. In a single subject, an instance in which the behavioral (mean BM) and autonomic [HRV power >0.15 Hz and mean heart rate (HR)] rhythmicities were dissociated occurred when the individual had an irregular daily life. It was concluded that the long-term HRV in normal humans contained persistent oscillations synchronized with those of BM at ultradian frequencies but could not be explained exclusively by activity levels of the subjects.
Age-associated arterial wall thickening is related to elevations in sympathetic activity in healthy humans
Authors: Dinenno Frank A. , Jones Pamela P. , Seals Douglas R. , Tanaka Hirofumi
Published: December 2017

Arterial wall hypertrophy occurs with age in humans and is a strong predictor of cardiovascular disease risk. The responsible mechanism is unknown, but data from studies in experimental animals suggest that elevated sympathetic-adrenergic tone may be involved. To test this hypothesis in humans we studied 11 young (29 ± 1 yr; means ± SE) and 13 older (63 ± 1) healthy normotensive men under supine resting conditions. Muscle sympathetic nerve activity (MSNA) burst frequency (peroneal microneurography) was 70% higher in the older men (39 ± 1 vs. 23 ± 2 bursts/min; P < 0.001). Femoral artery intima media thickness (IMT; B-mode ultrasound) and the femoral IMT-to-lumen diameter ratio (IMT/lumen) were ∼75% greater in the older men (both P < 0.001). Femoral IMT ( r = 0.82) and the femoral IMT/lumen ( r = 0.85) were strongly and positively related to MSNA (both P < 0.001). The significant age group differences in femoral IMT and the IMT/lumen were abolished when the influence of MSNA was removed. In contrast, the relationship between MSNA and femoral wall thickness remained significant after removing the influence of age. We conclude that 1) primary aging is associated with femoral artery hypertrophy in humans and 2) this is strongly related to elevations in sympathetic nerve activity to the vasculature. These results support the hypothesis that tonic elevations in sympathetic nerve activity may be an important mechanism in the arterial remodeling that occurs with human aging.
Organoid culture of cannulated rat resistance arteries: effect of serum factors on vasoactivity and remodeling
Authors: Bakker Erik N. T. P. , van der Meulen Esther T. , Spaan Jos A. E. , VanBavel Ed
Published: December 2017

We developed an organoid culture technique to study the mechanisms involved in arterial remodeling. Resistance arteries were isolated from rat cremaster muscle and mounted in a pressure myograph at 75 mmHg. Vessels were studied during a 4-day culture period in DMEM with either 2% albumin, 10% heat-inactivated FCS (HI-FCS) or 10% dialyzed HI-FCS (12 kDa cut off) added to the perfusate. The albumin group showed a gradual loss of endothelial function and integrity, whereas smooth muscle agonist and myogenic responses were retained. No remodeling was observed. Vessels cultured in the presence of serum showed a progressive constriction. Smooth muscle responses and substance P-induced endothelium-dependent dilation were maintained. An inward remodeling of 17 ± 4% in the HI-FCS group and 26 ± 3% in the dialyzed HI-FCS group was found, while media cross-sectional areas were unchanged. These data show that pressurized resistance arteries can be maintained in culture for several days and undergo eutrophic remodeling in vitro in the presence of high molecular weight serum factors.
Depressed tolerance to fluorocarbon-simulated ischemia in failing myocardium due to impaired [Ca2+]imodulation
Authors: Min Jiang-Yong , Hampton Thomas G. , Wang Ju-Feng , DeAngelis Joseph , Morgan James P.
Published: December 2017

The aim of this study was to investigate the tolerance of failing myocardium from postinfarction rats to simulated ischemia. Myocardial infarction (MI) was induced by ligation of the left coronary artery in male Wistar rats. Isometric force and free intracellular Ca2+concentration ([Ca2+]i) were measured in isolated left ventricular papillary muscles from sham-operated and post-MI animals 6 wk after surgery. Ischemia was simulated by using fluorocarbon immersion with hypoxia. Results showed that mechanical performance was depressed during the period of hypoxia in physiological salt solution (44 ± 7% of baseline in sham vs. 30 ± 6% of baseline in MI, P < 0.05) or ischemia (16 ± 2% of baseline in sham vs. 9 ± 1% of baseline in MI, P< 0.01) accompanied by no corresponding decrease of peak [Ca2+]i(hypoxia: 51 ± 8% of baseline in sham vs. 46 ± 7% of baseline in MI, P = NS; ischemia: 47 ± 5% of baseline in sham, 39 ± 7% of baseline in MI, P = NS). After reoxygenation, [Ca2+]irapidly returned to near preischemic basal levels, whereas developed tension in fluorocarbon remained significantly lower. This dissociation between peak [Ca2+]iand isometric contractility was more pronounced in the failing myocardium from postinfarction rats. In conclusion, more severe impairment of [Ca2+]ihomeostasis in the failing myocardium from postinfarction rats increases susceptibility to ischemia-reperfusion injury.
Myogenic reactivity and resistance distribution in the coronary arterial tree: a model study
Authors: Cornelissen Annemiek J. M. , Dankelman Jenny , VanBavel Ed , Stassen Henk G. , Spaan Jos A. E.
Published: December 2017

The objectives of this study were to evaluate the myogenic behavior of blood vessels and their interaction within the coronary arterial tree and to evaluate the possible role of the myogenic response in autoregulation. The model consists of 10 compartments in series, each representing a class of vessel sizes. Diameter and resistance in each class are determined by their value at full dilation ( d p, R p) and by the myogenic response. Three distributions of R p and three distributions of myogenic strength, M i (slope of pressure-diameter curve, range −0.05 to −0.4%/mmHg) were evaluated (9 cases). It was found that larger vessels attenuate the myogenic activity of smaller vessels and that myogenic responsiveness is sufficient to achieve autoregulation. When M i has a maximum in vessels of 84 μm, the maximum effect of perfusion pressure on active diameter occurs in vessels between 123 and 181 μm, depending on the distribution of R p. Distribution of resistance and control mechanisms in the coronary arterial tree are important for interpretation of individual vessel responses as observed in vivo.
Differential regulation of cardiac ANP and BNP mRNA in different stages of experimental heart failure
Authors: Langenickel Thomas , Pagel Ines , Höhnel Klaus , Dietz Rainer , Willenbrock Roland
Published: December 2017

Atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) are cardiac hormones that are involved in water and electrolyte homeostasis in heart failure. Although both hormones exert almost identical biological actions, the differential regulation of cardiac ANP and BNP mRNA in compensated and overt heart failure is not known. To study the hypothesis that cardiac BNP is more specifically induced in overt heart failure, a large aortocaval shunt of 30 days duration was produced in rats and compared with compensated heart failure. Compensated heart failure was induced either by a small shunt of 30 days duration or by a large shunt of 3 days duration. Both heart failure models were characterized by increased cardiac weight, which was significantly higher in the large-shunt model, and central venous pressure. Left ventricular end-diastolic pressure was elevated only in the overt heart failure group (control: 5.7 ± 0.7; small shunt: 8.6 ± 0.9; large shunt 3 days: 8.5 ± 1.7; large shunt 30 days: 15.9 ± 2.6 mmHg; P < 0.01). ANP and BNP plasma concentrations were elevated in both heart failure models. In compensated heart failure, ANP mRNA expression was induced in both ventricles. In contrast, ventricular BNP mRNA expression was not upregulated in any of the compensated heart failure models, whereas it increased in overt heart failure (left ventricle: 359 ± 104% of control, P < 0.001; right ventricle: 237 ± 33%, P < 0.01). A similar pattern of mRNA regulation was observed in the atria. These data indicate that, in contrast to ANP, cardiac BNP mRNA expression might be induced specifically in overt heart failure, pointing toward the possible role of BNP as a marker of the transition from compensated to overt heart failure.
Fluid flow activates a regulator of translation, p70/p85 S6 kinase, in human endothelial cells
Authors: Kraiss Larry W. , Weyrich Andrew S. , Alto Neal M. , Dixon Dan A. , Ennis Tina M. , Modur Vijayanand , McIntyre Thomas M. , Prescott Stephen M. , Zimmerman Guy A.
Published: December 2017

Cellular phenotype is determined not only by genetic transcription but also by subsequent translation of mRNA into protein. Extracellular signals trigger intracellular pathways that distinctly activate translation. The 70/85-kDa S6 kinase (pp70S6k) is a central enzyme in the signal-dependent control of translation, but its regulation in endothelial cells is largely unknown. Here we show that fluid flow (in the absence of an exogenous mitogen) as well as humoral agonists activate endothelial pp70S6k. Rapamycin, an inhibitor of the mammalian target of rapamycin (mTOR), and wortmannin, a phosphatidylinositol 3-kinase inhibitor, blocked flow-induced pp70S6kactivation; FK-506, a rapamycin analog with minimal mTOR inhibitory activity, and PD-98059, an inhibitor of the flow-sensitive mitogen-activated protein kinase pathway, had no effect. Synthesis of Bcl-3, a protein whose translation is controlled by an mTOR-dependent pathway, was induced by flow and inhibited by rapamycin and wortmannin. Transcriptional blockade did not abolish the flow-induced upregulation of Bcl-3. Fluid forces may therefore modify endothelial phenotype by specifically regulating translation of certain mRNA transcripts into protein.
Temporal gradient in shear-induced signaling pathway: involvement of MAP kinase, c-fos, and connexin43
Authors: Bao Xuping , Clark Craig B. , Frangos John A.
Published: December 2017

The effect of a temporal gradient in shear and steady shear on the activity of extracellular signal-regulated protein kinases 1 and 2 (ERK1/ERK2), c- fos, and connexin43 (Cx43) in human endothelial cells was investigated. Three laminar flow profiles (16 dyn/cm2), including impulse flow (shear stress abruptly applied for 3 s), ramp flow (shear stress smoothly transitioned at flow onset), and step flow (shear stress abruptly applied at flow onset) were utilized. Relative to static controls, impulse flow stimulated the phosphorylation of ERK1/ERK2 8.5- to 7.5-fold, respectively at 10 min, as well as the mRNA expression of c- fos 51-fold at 30 min, and Cx43 8-fold at 90 min. These high levels of mRNA expression were sustained for at least 4 h. In contrast, ramp flow was unable to significantly induce gene expression and even inhibited the activation of ERK1/ERK2. Step flow, which contains both a sharp temporal gradient in shear stress and a steady shear component, elicited only moderate and transient responses, indicating the distinct role of these fluid shear stimuli in endothelial signal transduction. The specific inhibitor of mitogen-activated protein kinase kinase PD-98059 inhibited impulse flow-induced c -fos and Cx43 mRNA expression. Thus these findings implicate the involvement of ERK1/ERK2, c -fos, and Cx43 in the signaling pathway induced by the temporal gradient in shear.
I NaCa contributes to electrical heterogeneity within the canine ventricle
Authors: Zygmunt Andrew C. , Goodrow Robert J. , Antzelevitch Charles
Published: December 2017

This study examines the amplitude of sodium-calcium exchange current ( I NaCa) in epicardial, midmyocardial, and endocardial canine ventricular myocytes. Whole cell currents were recorded at 37°C using standard or perforated-patch voltage-clamp techniques in the absence of potassium, calcium-activated chloride, and sodium-pump currents. I NaCa was triggered by release of calcium from the sarcoplasmic reticulum or by rapid removal of external sodium. I NaCa was large in midmyocardial myocytes and significantly smaller in endocardial myocytes, regardless of the method used to activate I NaCa. I NaCaat −80 mV was −0.316 ± 0.013, −0.293 ± 0.016, and −0.210 ± 0.007 pC/pF, respectively, in midmyocardial, epicardial, and endocardial myocytes when activated by the calcium transient. When triggered by sodium removal, peak I NaCa was 0.74 ± 0.04, 0.57 ± 0.04, and 0.50 ± 0.03 pA/pF, respectively, in midmyocardial, epicardial, and endocardial myocytes. Epicardial I NaCa was smaller than midmyocardial I NaCa when activated by removal of external sodium but was comparable to epicardial and midmyocardial I NaCa when activated by the normal calcium transient, implying possible transmural differences in excitation-contraction coupling. Our results suggest that I NaCa differences contribute to transmural electrical heterogeneity under normal and pathological states. A large midmyocardial I NaCa may contribute to the prolonged action potential of these cells as well as to the development of triggered activity under calcium-loading conditions.
Alterations in cardiac adrenergic terminal function and β-adrenoceptor density in pacing-induced heart failure
Authors: Kawai Hiroya , Mohan Amy , Hagen Jason , Dong Erdan , Armstrong Jacqueline , Stevens Suzanne Y. , Liang Chang-Seng
Published: December 2017

Congestive heart failure is associated with cardiac adrenergic nerve terminal changes and β-adrenoceptor density downregulation. To study the temporal sequence of these changes, we performed studies in rabbits at 2, 4, and 8 wk of cardiac pacing (360 beats/min) and at 1, 2, and 4 wk after cessation of pacing. Rapid pacing produced left ventricular (LV) dysfunction and an increase in plasma norepinephrine (NE) in 1–2 wk. At week 2, NE uptake activity, NE uptake-1 density, and adenylyl cyclase responses to isoproterenol, 5′-guanylyl imidodiphosphate [Gpp(NH)p], and forskolin reduced. However, immunostained tyrosine hydroxylase profile, β-adrenoceptor density, and NE histofluorescence did not reduce until 4–8 wk of pacing. After cessation of cardiac pacing, LV function normalized quickly, followed by return of tyrosine hydroxylase and NE profiles in 1 wk and adenylyl cyclase responses to agonists and NE uptake activity in 2 wk. Myocardial β-adrenoceptor density returned to normal by 4 wk after cessation of pacing. Our results suggest that there is no permanent structural neuronal damage in the myocardium within the first 8 wk of rapid cardiac pacing. Abnormal myocardial NE reuptake mechanism may play an important pathophysiological role in heart failure.
β1-Integrin and PI 3-kinase regulate RhoA-dependent activation of skeletal α-actin promoter in myoblasts
Authors: Wei Lei , Zhou Wei , Wang Lu , Schwartz Robert J.
Published: December 2017

RhoA GTPase, a regulator of actin cytoskeleton, is also involved in regulating c- fos gene expression through its effect on serum response factor (SRF) transcriptional activity. We have also shown that RhoA plays a critical role in myogenesis and regulates expression of SRF-dependent muscle genes, including skeletal α-actin. In the present study, we examined whether the RhoA signaling pathway cross talks with other myogenic signaling pathways to modulate skeletal α-actin promoter activity in myoblasts. We found that extracellular matrix proteins and the β1-integrin stimulated RhoA-dependent activation of the α-actin promoter. The muscle-specific isoform β1Dselectively activated the α-actin promoter in concert with RhoA but inhibited the c- fos promoter. In addition, focal adhesion kinase (FAK) and phosphatidylinositol (PI) 3-kinase were required for full activation of the α-actin promoter by RhoA. Expression of a dominant negative mutant of FAK, application of wortmannin to cultured myoblasts, or expression of a dominant negative mutant of PI 3-kinase inhibited α-actin promoter activity induced by RhoA. These results suggest that RhoA, β1-integrin, FAK, and PI 3-kinase serve together as an important signaling network in regulating muscle gene expression.
Histamine-induced depolarization: ionic mechanisms and role in sustained contraction of rabbit cerebral arteries
Authors: Gokina N. I. , Bevan J. A.
Published: December 2017

The role of membrane depolarization in the histamine-induced contraction of the rabbit middle cerebral artery was examined by simultaneous measurements of membrane potential and isometric force. Histamine (1–100 μM) induced a concentration-dependent sustained contraction associated with sustained depolarization. Action potentials were observed during depolarization caused by histamine but not by high-K+solution. K+-induced contraction was much smaller than sustained contraction associated with the same depolarization caused by histamine. Nifedipine attenuates histamine-induced sustained contraction by 80%, with no effect on depolarization. Inhibition of nonselective cation channels with Co2+(100–200 μM) reversed the histamine-induced depolarization and relaxed the arteries but induced only a minor change in K+-induced contraction. In the presence of Co2+and in low-Na+solution, histamine-evoked depolarization and contraction were transient. We conclude that nonselective cation channels contribute to histamine-induced sustained depolarization, which stimulates Ca2+influx through voltage-dependent Ca2+channels participating in contraction. The histamine-induced depolarization, although an important and necessary mechanism, cannot fully account for sustained contraction, which may be due in part to augmentation of currents through voltage-dependent Ca2+channels and Ca2+sensitization of the contractile process.
Cyclosporin A inhibits cardiac hypertrophy and enhances cardiac dysfunction during postinfarction failure in rats
Authors: Øie Erik , Bjørnerheim Reidar , Clausen Ole Petter F. , Attramadal Håvard
Published: December 2017

Calcineurin has recently been implicated as a mediator in the signaling pathways that transform intracellular calcium signals to the phenotype of myocardial hypertrophy. The present study was conducted to examine the effects of cyclosporin A (CsA), an inhibitor of calcineurin, on myocardial hypertrophy and remodeling during congestive heart failure (CHF) in rats. After ligation of the left coronary artery, rats were randomized to treatment with CsA or vehicle for 14 days. Compared with vehicle, CsA substantially attenuated myocardial hypertrophy in the CHF rats as assessed by alterations in ventricular weight-to-tibial length ratios ( P < 0.05). Myocardial gene expression of skeletal α-actin was also reduced in the failing left ventricle (LV) after treatment with CsA ( P < 0.05), although the mRNA levels were still substantially elevated relative to those of sham rats. CsA-induced inhibition of compensatory myocardial hypertrophy in the CHF rats led to increased dilatation of the LV cavity and reduced fractional shortening and peak positive and negative first derivatives of LV pressure ( P < 0.05). Plasma renin and endothelin-1 levels were increased in the CHF-CsA rats, providing humoral cues of aggravated cardiac function. Thus this study supports a crucial role of calcineurin-dependent pathways in the mechanisms of compensatory myocardial hypertrophy during CHF. In addition, our data indicate that inhibition of compensatory myocardial hypertrophy exerts detrimental effects on cardiac remodeling and function after myocardial infarction.
Nicotine increases ventricular vulnerability to fibrillation in hearts with healed myocardial infarction
Authors: Yashima Masaaki , Ohara Toshihiko , Cao Ji-Min , Kim Young-Hoon , Fishbein Michael C. , Mandel William J. , Chen Peng-Sheng , Karagueuzian Hrayr S.
Published: December 2017

The vulnerability of the infarcted hearts to ventricular fibrillation (VF) was tested in in situ canine hearts during nicotine infusion. The activation pattern was mapped with 477 bipolar electrodes in open-chest anesthetized dogs ( n = 8) 5–6 wk after permanent occlusion of the left anterior descending coronary artery. Nicotine (129 ± 76 ng/ml) lengthened ( P < 0.01) the pacing cycle length at which VF was induced from 171 ± 8.9 to 210 ± 14.7 ms. Nicotine selectively amplified the magnitude of conduction time and monophasic action potential (MAP) amplitude and duration (MAPA and MAPD, respectively) alternans in the epicardial border zone (EBZ) but not in the normal zone. With critical reduction of the MAPA and MAPD in the EBZ, conduction block occurred across the long axis of the EBZ cells. Block led immediately to reentry formation in the EBZ with a mean period of 105 ± 10 ms, which, after one to two rotations, degenerated to VF. Nicotine widened the range of diastolic intervals over which the dynamic MAPD restitution curve had a slope >1. We conclude that nicotine facilitates conduction block, reentry, and VF in hearts with healed myocardial infarction by increasing the magnitude of depolarization and repolarization alternans consistent with the restitution hypothesis of vulnerability to VF.
A custom confocal and two-photon digital laser scanning microscope
Authors: Wier W. Gil , Balke C. William , Michael Jeffrey A. , Mauban Joseph R. H.
Published: December 2017

We describe a custom one-photon (confocal) and two-photon all-digital (photon counting) laser scanning microscope. The confocal component uses two avalanche photodiodes (APDs) as the fluorescence detector to achieve high sensitivity and to overcome the limited photon counting rate of a single APD (∼5 MHz). The confocal component is approximately nine times more efficient than our commercial confocal microscope (fluorophore fluo 4). Switching from one-photon to two-photon excitation mode (Ti:sapphire laser) is accomplished by moving a single mirror beneath the objective lens. The pulse from the Ti:sapphire laser is 109 fs in duration at the specimen plane, and average power is ∼5 mW. Two-photon excited fluorescence is detected by a fast photomultiplier tube. With a ×63 1.4 NA oil-immersion objective, the resolution of the confocal system is 0.25 μm laterally and 0.52 μm axially. For the two-photon system, the corresponding values are 0.28 and 0.82 μm. The system is advantageous when excitation intensity must be limited, when fluorescence is low, or when thick, scattering specimens are being studied (with two-photon excitation).
Comparison of cerebrovascular effects of intravenous cocaine injection in fetal, newborn, and adult sheep
Authors: Robinson Roderick , Iida Hiroki , O'Brien Thomas P. , Pane Maria A. , Traystman Richard J. , Gleason Christine A.
Published: December 2017

Cocaine may cause stroke, intracranial hemorrhage, seizures, and neurobehavioral abnormalities in fetuses, newborns, and adults, and there could be developmental and/or species differences in mechanisms for these cocaine-induced cerebrovascular effects. To evaluate developmental differences in responses to cocaine, we compared the cerebrovascular and metabolic responses to a 2 mg/kg iv cocaine dose in unanesthetized fetal ( n = 8, previously reported, direct fetal injection), newborn ( n = 6), and adult ( n = 12) sheep. We measured cerebral blood flow, mean arterial blood pressure, and arterial and venous O2content, and we calculated cerebral O2consumption and cerebral vascular resistance at baseline and at 30 s and at 5, 15, and 60 min after cocaine injection. Cerebral blood flow increased 5 min after injection in the fetus and newborn, but not until 15 min in the adult. In the fetus, cocaine caused a transient cerebral vasoconstriction at 30 s; in all three groups, cocaine caused cerebral vasodilation, which was delayed in the adult. Cerebral metabolic O2consumption increased 5 min after injection in the fetus and newborn, but not until 15 min after injection in the adult. Arterial O2content decreased 5 min after injection in the fetus and 15 min after injection in the adult. We speculate that clinical differences in response to cocaine injection may be explained, in part, by these developmental differences in the cerebrovascular and metabolic responses to cocaine.