bluuebunny/crossref_metadata_2025 huggingface dataset:
Selective large coronary endothelial dysfunction in conscious dogs with chronic coronary pressure overload
Authors: Ghaleh Bijan , Hittinger Luc , Kim Song-Jung , Kudej Raymond K. , Iwase Mitsunori , Uechi Masami , Berdeaux Alain , Bishop Sanford P. , Vatner Stephen F.
Published: December 2017

Coronary vascular responses to acetylcholine (ACh, 3 μg/kg iv), nitroglycerin (NTG, 25 μg/kg iv), and a 20-s coronary artery occlusion (reactive hyperemia, RH) were investigated in seven conscious dogs with severe left ventricular (LV) hypertrophy and chronic coronary pressure overload (CCPO) due to supravalvular aortic banding and in seven control dogs. All dogs were instrumented for measurement of ultrasonic coronary diameter (CD) and Doppler coronary blood flow (CBF). LV-to-body weight ratio was increased by 82% in CCPO dogs. In control dogs, ACh increased CD (+5.9 ± 1.7%). This response was reduced ( P < 0.05) in CCPO dogs (+1.9 ± 0.9%). Similarly, flow-mediated increases in CD after RH were blunted ( P < 0.01) in CCPO (+2.1 ± 0.8) vs. control dogs (+6.8 ± 1.8%). In contrast, ACh and RH increased CBF similarly in both groups. Increases in both CD and CBF to NTG were not different between control dogs and CCPO. Peak systolic CBF velocity was greater, P< 0.01, in CCPO (94 ± 17 cm/s) compared with control (35 ± 7 cm/s) dogs, most likely secondary to the increased systolic coronary perfusion pressure (215 vs. 130 mmHg). Histological analyses of large coronary arteries in CCPO revealed medial thickening, intimal thickening, and disruption of the internal elastic lamina and endothelium. In contrast, small intramyocardial arterioles failed to show the intimal and endothelial lesions. Thus, in CCPO selective to the coronary arteries, i.e., a model independent from systemic hypertension and enhanced levels of plasma renin activity, endothelial control was impaired for both flow-mediated and receptor-mediated large coronary artery function, which could be accounted for by the major morphological changes in the large coronary arteries sparing the resistance vessels. The mechanism may involve chronically elevated systolic coronary perfusion pressure, CBF velocity, and potential disruption of laminar flow patterns.
Endotoxemia-induced myocardial dysfunction is not associated with changes in myofilament Ca2+responsiveness
Authors: Rigby Sherri L. , Hofmann Polly A. , Zhong Juming , Adams H. Richard , Rubin Leona J.
Published: December 2017

Myocardial contractile function is depressed after onset of endotoxemia and is intrinsic to the ventricular myocyte. We tested the hypothesis that decreased Ca2+ responsiveness of the contractile myofilaments underlies this inotropic depression. Specifically, we evaluated the relationship between Ca2+ and unloaded cell shortening and isometric tension development of skinned guinea pig ventricular myocytes. Myocytes were isolated 4 h after intraperitoneal injection of 4 mg/kg Escherichia colilipopolysaccharide (LPS) or saline (control; Ctl). Myofilament Ca2+ responsiveness assessed by image analysis of shortening of skinned myocytes at pH 7.0 was not different between Ctl [pCa value that resulted in half-maximal shortening (pCa50): 5.78 ± 0.04] and LPS (pCa50: 5.72 ± 0.02). Similarly, myofilament Ca2+ responsiveness measured by isometric tension of skinned myocytes was not different between Ctl (pCa50: 5.73 ± 0.02) and LPS (pCa50: 5.76 ± 0.02). Maximal tension generated by LPS myocytes (2.89 ± 0.23 g/mm2) was significantly less ( P < 0.05) than Ctl (3.75 ± 0.34 g/mm2). However, when myocytes were isolated and skinned in the presence of protease inhibitors, maximal tension generated by LPS myocytes (3.53 ± 0.98 g/mm2) was similar to Ctl (3.01 ± 0.80 g/mm2). We conclude that in vivo administration of LPS resulting in endotoxemia without shock does not alter myofilament Ca2+ responsiveness of ventricular myocytes. Rather, reduced contractility is more likely a result of decreased Ca2+ availability because systolic Ca2+ transients of fura 2-loaded LPS myocytes were significantly decreased ( P < 0.05) compared with Ctl myocytes.
Acute blood stasis reduces interstitial uptake of albumin from intestinal microcirculatory networks
Authors: Merkle Carrie J. , Wilson Lisa M. , Baldwin Ann L.
Published: December 2017

Temporary blood flow stoppage occurs in a greater percentage of the capillaries when blood flow to organs is reduced. Previous studies on the small intestine have suggested that acute blood stasis (≤10 min) results in expression of negative charge, not present when blood flow is brisk, on the luminal surface of mucosal capillaries. Negative surface charge would tend to reduce transcapillary passage of albumin from blood to interstitium, since albumin is also negatively charged. Here we test the hypothesis that acute blood stasis reduces the interstitial uptake of albumin from mucosal capillary networks in rat small intestine in situ. Animals were subjected to two treatments, which included intestinal blood flow and acute stasis. After each treatment, fluorescent albumins were perfused into the intestinal circulation, and then interstitial fluorescence was recorded using fluorescence microscopy. Images were later quantified by computer analysis. After brisk blood flow, but not after acute blood stasis, fluorescence rapidly appeared in the interstitium and resulted in higher interstitial fluorescence intensity values. These results may have relevance to the mechanisms by which albumin flux in the small intestine is synchronized with digestion and fasting, which are associated with high and low intestinal blood flow, respectively.
Attenuation of ANG II actions by adenovirus delivery of AT1receptor antisense in neurons and SMC
Authors: Lu Di , Yang Hong , Raizada Mohan K.
Published: December 2017

Both central and peripheral renin-angiotensin systems (RAS) are important in the development and establishment of hypertension. Thus, introducing genes relevant to RAS into neuronal and vascular smooth muscle (VSM) cells, two major targets for angiotensin (ANG) II action, is a prerequisite in considering a gene therapy approach for the control of ANG-dependent hypertension. In this study, we explored the use of adenoviral (Ad) vector to transfer AT1receptor antisense cDNA (AT1R-AS) into neuronal and VSM cells with the anticipation of attenuation of ANG II-mediated cellular actions. Incubation of neurons and VSM cells with viral particles containing AT1R-AS (Ad-AT1R-AS) resulted in a robust expression of AT1R-AS in a majority (∼80%) of the cells. The expression was persistent for at least 28 days and was associated with decreases in the immunoreactive AT1receptor protein and the maximal binding for AT1receptor in a time- and dose-dependent manner in both cell types. ANG II stimulation of [3H]thymidine incorporation in VSM cells and norepinephrine transporter gene expression in neuronal cells were attenuated by Ad-AT1R-AS infection. Uninfected cells or cells infected with adenovirus particles containing a mutant AT1receptor sense cDNA showed no effects on either AT1receptor or on attenuation of ANG II’s cellular affects. These observations show, for the first time, that adenovirus can be used to deliver AT1receptor mutant sense and antisense cDNAs into two major ANG II target tissues. This consequently influences AT1receptor-mediated cellular actions of ANG II.
Peroxynitrite-mediated vasorelaxation: evidence against the formation of circulatingS-nitrosothiols
Authors: Graves Jonathan E. , Lewis Stephen J. , Kooy Neil W.
Published: December 2017

Peroxynitrite-induced relaxation of isolated vessels may involve the formation of S-nitrosothiols. This study characterized the hemodynamic effects of systemically injected peroxynitrite in pentobarbital sodium-anesthetized rats and determined whether these effects were due to the formation of S-nitrosothiols. We utilizedl-penicillamine, which attenuates the hemodynamic effects of systemically injected S-nitrosothiols. The hemodynamic effects of peroxynitrite and the S-nitrosothiolsl- S-nitrosocysteine,l- S-nitrosoglutathione, and S-nitrosoalbumin were determined before and 25 min after the administration ofl-penicillamine or saline. Peroxynitrite and the S-nitrosothiols produced dose-dependent reductions in mean arterial pressure and mesenteric and hindquarter vascular resistances. The hypotensive and vasodilator effects of the S-nitrosothiols were significantly reduced by l-penicillamine. In contrast, the hemodynamic actions of peroxynitrite were unaffected byl-penicillamine. Therefore, peroxynitrite produces hypotensive and vasodilator responses in anesthetized rats that are unlikely to be due to the formation of circulating S-nitrosothiols. The mechanisms by which peroxynitrite produces vasodilatation in vivo remain to be determined.
Basal metabolism does not account for high O2consumption in stunned myocardium
Authors: Schipke J. D. , Korbmacher B. , Schwanke U. , Frehen D. , Schmidt T. , Arnold G.
Published: December 2017

Myocardial O2consumption (MV˙o2) in stunned myocardium is relatively high compared with the reduced ventricular function. The mechanism of this “oxygen paradox” could occur at different levels: basal metabolism, excitation-contraction coupling, and energy production. In one previously reported series on 12 isolated, blood-perfused rabbit hearts, left ventricular systolic and diastolic function in stunned myocardium were significantly decreased compared with control, whereas total MV˙o2was not. The MV˙o2for the unloaded contraction was overproportionately high for the decreased function in stunned myocardium, and contractile efficiency was clearly deteriorated. To assess whether the basal metabolism specifically is elevated in stunned myocardium, a second series ( n =14) with a similar protocol was performed in this study. Basal MV˙o2after KCl arrest (0.5 ± 0.3 ml ⋅ min−1⋅ 100 g−1) was significantly lower than that measured after KCl arrest (1.2 ± 0.5 ml ⋅ min−1⋅ 100 g−1) in an additional series on nonischemic hearts ( n = 8). Our conclusion is that basal MV˙o2in stunned myocardium is not elevated. Thus this O2-consuming portion of total MV˙o2is not responsible for the inefficiency in stunned myocardium. Instead, a “metabolic stunning” occurs at the level of both excitation-contraction coupling and force development by the contractile apparatus.
Response of isolated rat descending vasa recta to bradykinin
Authors: Pallone Thomas L. , Silldorff Erik P. , Cheung Joseph Y.
Published: December 2017

Outer medullary descending vasa recta (OMDVR) were dissected from the outer medullary vascular bundles of young rats, perfused in vitro, and loaded with fura 2 for measurement of intracellular calcium concentration ([Ca2+]i) by fluorescent ratio imaging. Fluorescent video images revealed that fura 2 selectively loads into endothelial cells but not pericytes. Bradykinin (BK), at concentrations >10−11M, elicited an increase in [Ca2+]ifrom baseline values in the range from 50 to 100 nM to peak values of 600–800 nM followed by a sustained plateau of 150–250 nM. The vasopressin V1-receptor agonist [Phe2,Ile3,Orn8]vasopressin constricted OMDVR but yielded no observable [Ca2+]iresponse, a finding that is consistent with an endothelial cell origin for the fura 2 fluorescent signal. The BK [Ca2+]iresponse was blocked by the selective BK B2-receptor antagonistsd-Arg-[Hyp3,Thi5,8, d-Phe7]BK andd-Arg-[Hyp3,d-Phe7,Leu8]BK but not the B1antagonist des-Arg9-[Leu8]BK. BK vasodilated microperfused OMDVR that had been preconstricted with 10−8M angiotensin II. We conclude that the [Ca2+]iresponse of OMDVR endothelia can be selectively studied with fura 2, that BK increases endothelial [Ca2+]ivia the B2receptor, and that BK can vasodilate descending vasa recta.
Hypothermia preserves function and signaling for mitochondrial biogenesis during subsequent ischemia
Authors: Ning Xue-Han , Xu Cheng-Su , Song Ying C. , Xiao Yun , Hu Ying-Jia , Lupinetti Flavian Mark , Portman Michael A.
Published: December 2017

Hypothermia is known to protect myocardium during ischemia, but its role in induction of a protective stress response before ischemia has not been evaluated. As cold incites stress responses in other tissues, including heat shock protein induction and signaling mitochondrial biogenesis, we postulated that hypothermia in perfused hearts would produce similar phenomena while reducing injury during subsequent ischemia. Studies were performed in isolated perfused rabbit hearts ( n = 77): a control group (C) and a hypothermic group (H) subjected to decreasing infusate temperature from 37 to 31°C over 20 min. Subsequent ischemia during cardioplegic arrest at 34°C for 120 min was followed by reperfusion. At 15 min of reperfusion, recovery of left ventricular developed pressure (LVDP), maximum first derivative of left ventricular pressure (LV dP/d tmax), LV −dP/d tmax, and the product of heart rate and LVDP was significantly increased in H ( P < 0.01) compared with C hearts. Ischemic contracture started later in H (97.5 ± 3.6 min) than in C (67.3 ± 3.3 min) hearts. Myocardial ATP preservation and repletion during ischemia and reperfusion were higher in H than in C hearts. mRNA levels of the nuclear-encoded mitochondrial proteins adenine nucleotide translocase isoform 1 (ANT1) and β-F1-adenosinetriphosphatase (β-F1-ATPase) normalized to 28S RNA decreased in C hearts but were preserved in H hearts after reperfusion. Inducible heat shock protein (HSP70–1) mRNA was elevated nearly 4-fold after ischemia in C hearts and 12-fold in H hearts. These data indicate that hypothermia preserves myocardial function and ATP stores during subsequent ischemia and reperfusion. Signaling for mitochondrial biogenesis indexed by ANT1and β-F1-ATPase mRNA levels is also preserved during a marked increase in HSP70–1 mRNA.
TAN-67, a δ1-opioid receptor agonist, reduces infarct size via activation of Gi/oproteins and KATPchannels
Authors: Schultz Jo El J. , Hsu Anna K. , Nagase Hiroshi , Gross Garrett J.
Published: December 2017

We have previously shown that delta (δ)-opioid receptors, most notably δ1, are involved in the cardioprotective effect of ischemic preconditioning (PC) in rats; however, the mechanism by which δ-opioid receptor-induced cardioprotection is mediated remains unknown. Therefore, we hypothesized that several of the known mediators of ischemic PC such as the ATP-sensitive potassium (KATP) channel and Gi/oproteins are involved in the cardioprotective effect produced by δ1-opioid receptor activation. To address these possibilities, anesthetized, open-chest Wistar rats were randomly assigned to five groups. Control animals were subjected to 30 min of coronary artery occlusion and 2 h of reperfusion. To demonstrate that stimulating δ1-opioid receptors produces cardioprotection, TAN-67, a new selective δ1-agonist, was infused for 15 min before the long occlusion and reperfusion periods. In addition, one group received 7-benzylidenenaltrexone (BNTX), a selective δ1-antagonist, before TAN-67. To study the involvement of KATPchannels or Gi/oproteins in δ1-opioid receptor-induced cardioprotection, glibenclamide (Glib), a KATPchannel antagonist, or pertussis toxin (PTX), an inhibitor of Gi/oproteins, was administered before TAN-67. Infarct size (IS) as a percentage of the area at risk (IS/AAR) was determined by tetrazolium stain. TAN-67 significantly reduced IS/AAR as compared with control (56 ± 2 to 27 ± 5%, n = 5, P < 0.05). The cardioprotective effect of TAN-67 was completely abolished by BNTX, Glib, and PTX (51 ± 3, 53 ± 5, and 61 ± 4%, n = 6 for each group, respectively). These results are the first to suggest that stimulating the δ1-opioid receptor elicits a cardioprotective effect that is mediated via Gi/oproteins and KATPchannels in the intact rat heart.
Effects of hypoproteinemia-induced myocardial edema on left ventricular function
Authors: Miyamoto M. , McClure D. E. , Schertel E. R. , Andrews P. J. , Jones G. A. , Pratt J. W. , Ross P. , Myerowitz P. D.
Published: December 2017

In previous studies, we observed left ventricular (LV) systolic and diastolic dysfunction in association with interstitial myocardial edema (IME) induced by either coronary venous hypertension (CVH) or lymphatic obstruction. In the present study, we examined the effects of myocardial edema induced by acute hypoproteinemia (HP) on LV systolic and diastolic function. We also combined the methods of HP and CVH (HP-CVH) to determine their combined effects on LV function and myocardial water content (MWC). We used a cell-saving device to lower plasma protein concentration in HP and HP-CVH groups. CVH was induced by inflating the balloon in the coronary sinus. Six control dogs were treated to sham HP. Conductance and micromanometer catheters were used to assess LV function. Contractility, as measured by preload recruitable stroke work, did not change in control or HP groups but declined significantly (14.5%) in the HP-CVH group. The time constant of isovolumic LV pressure decline (τ) increased significantly from baseline by 3 h in the HP (24.8%) and HP-CVH (27.1%) groups. The end-diastolic pressure-volume relationship (stiffness) also increased significantly from baseline by 3 h in the HP (78.6%) and HP-CVH (42.6%) groups. Total plasma protein concentration decreased from 5.2 ± 0.2 g/dl at baseline to 2.5 ± 0.0 g/dl by 3 h in the HP and HP-CVH groups. MWC of the HP (79.8 ± 0.25%) and HP-CVH groups (79.8 ±0.2%) were significantly greater than that of the control group (77.8 ± 0.3%) but not different from one another. In conclusion, hypoproteinemia-induced myocardial edema was associated with diastolic LV dysfunction but not systolic dysfunction. The edema caused by hypoproteinemia was more than twice that produced by our previous models, yet it was not associated with systolic dysfunction. CVH had a negative inotropic effect and no significant influence on MWC. IME may not have the inverse causal relationship with LV contractility that has been previously postulated but appears to have a direct causal association with diastolic stiffness as has been previously demonstrated.
Entropy measures of heart rate variation in conscious dogs
Authors: Palazzolo James A. , Estafanous Fawzy G. , Murray Paul A.
Published: December 2017

Our goal was to determine the contributions of sympathetic and parasympathetic activity to entropy measures of heart rate variability (HRV). We compared our results with two commonly used methods to analyze HRV: standard deviation (SDNN) and power spectral analysis (HF norm). Beat-by-beat analysis of R-R intervals was performed in conscious dogs. The R-R intervals were analyzed with approximate entropy (ApEn) and entropy of symbolic dynamics (SymDyn) to assess the effects of reducing system complexity. This was achieved by pharmacologically inhibiting sympathetic, parasympathetic, and total autonomic nervous system regulation of heart rate. Three conditions were examined: rest, standing, and systemic hypotension. At rest or standing, sympathetic inhibition (propranolol) had no effect on ApEn or SymDyn, whereas parasympathetic (atropine) and combined (propranolol + atropine) inhibition reduced both entropy measures to near zero. Systemic hypotension reduced both entropy measures in intact dogs. When hypotension was induced after sympathetic inhibition, ApEn was increased compared with hypotension alone, whereas parasympathetic inhibition with hypotension resulted in near-zero ApEn. Changes in the entropy measures of HRV were directionally similar to changes in SDNN and HF norm. These results indicate that the entropy of R-R intervals reflects parasympathetic modulation of heart rate.
Opposing effects of α1-adrenergic receptor subtypes on Ca2+and pH homeostasis in rat cardiac myocytes
Authors: Gambassi Giovanni , Spurgeon Harold A. , Ziman Bruce D. , Lakatta Edward G. , Capogrossi Maurizio C.
Published: December 2017

We examined the effect of α1-adrenergic receptor (AR) subtypes on contraction, cytosolic Ca2+concentration ([Ca2+]i), and cytosolic pH (pHi) of rat ventricular myocytes loaded with the Ca2+indicator indo 1 or the pH indicator carboxy-seminaphthorhodafluor-1. Nonselective α1-AR stimulation was effected with phenylephrine plus nadolol. α1-AR subtype stimulation was achieved with α1-AR and chloroethylclonidine (CEC) or with α1-AR and WB-4101. Cells were in bicarbonate buffer with 0.5 mM Ca2+and were electrically stimulated at 0.5 Hz. Results show that 1) nonselective α1-AR stimulation increased twitch and [Ca2+]itransient amplitudes, myofilament response to Ca2+, and pHi; 2) α1-AR plus CEC increased twitch and [Ca2+]itransient amplitudes and also enhanced myofilament response to Ca2+via cytosolic alkalinization; 3) α1-AR plus WB-4101 decreased twitch and [Ca2+]itransient amplitudes and also pHi; and 4) cytosolic acidification due to α1-AR plus WB-4101 was abolished by protein kinase C inhibition (staurosporine pretreatment) or downregulation (prolonged exposure to phorbol esters). In summary, the net effects of α1-adrenergic stimulation on contraction, [Ca2+]i, and pHiare due to opposing WB-4101- and CEC-sensitive α1-AR subtype signaling pathways.
Low-frequency arterial pressure fluctuations do not reflect sympathetic outflow: gender and age differences
Authors: Taylor J. Andrew , Williams Todd D. , Seals Douglas R. , Davy Kevin P.
Published: December 2017

Low-frequency arterial pressure oscillations (Mayer waves) have been proposed as an index of vascular sympathetic outflow. However, cross-sectional differences in these pressure oscillations may not reflect different levels of sympathetic nervous outflow in humans. Three groups of healthy subjects with characteristically different sympathetic nervous outflow were studied: young females ( n = 10, 18–28 yr), young males ( n = 11, 18–29 yr), and older males ( n = 13, 60–72 yr). Average R-R interval, arterial pressures, and systolic pressure variability at the Mayer wave frequency (0.05–0.15 Hz) did not differ among the three groups. Diastolic pressure Mayer wave variability was similar in young females vs. young males (39 ± 10 vs. 34 ± 5 mmHg2) and lower in older males vs. young males (14 ± 2 mmHg2; P < 0.05). In contrast, muscle sympathetic activity was lowest in young females (892 ± 249 total activity/min) and highest in older males (3,616 ± 528 total activity/min; both P < 0.05 vs. young males: 2,505 ± 285 total activity/min). Across the three groups, arterial pressure Mayer wave variability did not correlate with any index of sympathetic activity. Our results demonstrate that arterial pressure Mayer wave amplitude is not a surrogate measure of vascular sympathetic outflow.
Analysis of responses to adrenomedullin-(13—52) in the pulmonary vascular bed of rats
Authors: Gumusel Bulent , Hao Quingzhong , Hyman Albert L. , Kadowitz Philip J. , Champion Hunter C. , Chang Jaw K. , Mehta Jawahar L. , Lippton Howard
Published: December 2017

The effects of human adrenomedullin-(13—52) [hADM-(13—52)] were investigated in the rat pulmonary vascular bed and in isolated rings from the rat pulmonary artery (PA). Under conditions of controlled blood flow and constant left atrial pressure when tone was increased with U-46619, injections of hADM-(13—52) produced dose-related decreases in lobar arterial pressure. Pulmonary vasodilator responses in the intact rat and vasorelaxant responses to hADM-(13—52) in rat PA rings were inhibited by N G-nitro-l-arginine methyl ester (l-NAME) andl- N 5-(1-iminoethyl)ornithine hydrochloride (l-NIO). Vasorelaxant responses to hADM-(13—52) were also inhibited by methylene blue, endothelium removal, hADM-(26—52), and iberiotoxin, whereas meclofenamate, calcitonin gene-related peptide-(8—37) [CGRP-(8—37)], glibenclamide, and apamin were without effect. Because vasorelaxant responses to NS-1619, a large-conductance Ca2+-activated K+ channel agonist, were not altered by l-NAME and vasorelaxant responses to acetylcholine and CGRP were not altered by hADM-(26—52), the present data suggest that ADM-(13—52) acts on a receptor in the pulmonary vascular bed that is coupled to endothelial nitric oxide release. These data suggest that this nitric oxide release may lead to guanosine 3′,5′-cyclic monophosphate-dependent K+ channel activation, which produces a pulmonary vasorelaxant response through hyperpolarization of vascular smooth muscle cells. The present data suggest that ADM-(13—52) modulates receptor-mediated, but not voltage-dependent, pulmonary vascular contraction by influencing Ca2+influx. These results suggest that the ADM fragment, hADM-(13—52), acts as an endothelium-dependent vasodilator agent in the pulmonary vascular bed of the rat.
Locall-NAME decreases blood flow and increases leukocyte adhesion via CD18
Authors: Mitchell Debra J. , Yu Jingcheng , Tyml Karel
Published: December 2017

Local inhibition of nitric oxide (NO) synthesis withl-arginine analogs such as NG-nitro-l-arginine methyl ester (l-NAME) decreased red blood cell velocity ( VRBC) in capillaries and increased leukocyte adhesion in postcapillary venules in rat skeletal muscle. The goal of the present study was to determine the mechanism of this response tol-NAME. Using intravital videomicroscopy, we examined blood flow in the surface microvasculature of rat extensor digitorum longus muscle.l-NAME (30 mM in the pipette) locally applied to capillaries (300 μm from feeding arteriole) reduced VRBC[control VRBC= 244 ± 53 (SE) μm/s; Δ VRBC= −52 ± 8%] and increased leukocyte adhesion (from 0.2 ± 0.01 to 1.3 ± 0.3 cells/100 μm) in control animals. Systemic pretreatment with fucoidan (selectin binder), superoxide dismutase and catalase (extracellular antioxidants), dimethylthiourea (intracellular antioxidant), or ketotifen (mast cell stabilizer) did not alter this response. Pretreatment with CL26, an anti-CD18 antibody, abolished the l-NAME response. Our results suggest that l-NAME increased leukocyte-endothelial interactions via an effect on CD11/CD18 or its ligand, intercellular adhesion molecule.
Pressure-permeability relationships in basement membrane: effects of static and dynamic pressures
Authors: Klaentschi Karel , Brown J. Anne , Niblett Philip G. , Shore Angela C. , Tooke John E.
Published: December 2017

The glomerular basement membrane (GBM) is an important component of the filtration barrier that is the glomerular capillary wall. Previously GBM permeability has been investigated only under static pressures and often within a supraphysiological range. We used Matrigel as a model of GBM and formed membranes at the base of a filtration chamber. We measured membrane permeability under static and dynamic pressures. Matrigel membranes were size and charge selective toward neutrally and negatively charged dextrans. Their permeability (as measured by hydraulic conductivity) was found to decrease from 1.61 ± 0.06 to 0.75 ± 0.07 × 10−6cm ⋅ s−1⋅ cmH2O−1as static pressure increased from 6 to 78 cmH2O, an effect attributed to membrane compression. In comparison to static pressure, sinusoidal pressure waves with a mean pressure of 50 cmH2O decreased membrane permeability, e.g., fluid flux was reduced by a maximum of 2% to a value of 5.47 ± 0.38 × 10−5cm/s; albumin clearance was reduced by a maximum of 5.2% to a value of 9.63 ± 1.06 × 10−6ml ⋅ cm−2⋅ s−1. Such changes were affected by the frequency of pressure wave application and could be attributed to a switching on and off of the membrane compression effect.
Ca flux, contractility, and excitation-contraction coupling in hypertrophic rat ventricular myocytes
Authors: McCall Eileen , Ginsburg Kenneth S. , Bassani Rosana A. , Shannon Thomas R. , Qi Ming , Samarel Allen M. , Bers Donald M.
Published: December 2017

Left ventricular hypertrophy (∼40%) was induced in rats by banding of the abdominal aorta. After 16 wk, ventricular homogenates were prepared for biochemical measurements and ventricular myocytes were isolated for functional studies. In myocytes, the effects of banding on intracellular Ca handling, contraction, and excitation-contraction (E-C) coupling were determined using indo 1 fluorescence and whole cell voltage clamp. After steady-state field or voltage-clamp stimulation to load the sarcoplasmic reticulum (SR), SR Ca content assessed by caffeine-induced Ca transients was the same in sham and banded groups. Despite this, cell shortening amplitudes were significantly depressed in the banded group, suggesting altered contractile properties. In banded rats, the SR Ca-adenosinetriphosphatase (Ca-ATPase) mRNA level was reduced, as was homogenate thapsigargin-sensitive SR Ca-ATPase, but cytosolic free Ca concentration ([Ca]i) decline attributed to SR Ca-ATPase activity in intact cells was not slowed. Banding also reduced Na/Ca exchange mRNA level but did not affect either Na-dependent sarcolemmal45Ca transport in homogenate or the rate of [Ca]idecline in intact cells attributed to Na/Ca exchange (during caffeine-induced contractures). Banding also did not change the rate of [Ca]idecline mediated by the combined function of the mitochondrial Ca uptake and sarcolemmal Ca-ATPase in intact cells. Ca current ( ICa) density and voltage dependence were the same in sham and banded groups. Ryanodine receptor mRNA, protein content, and ryanodine affinity were also unchanged in the banded group. At 1 mM extracellular Ca concentration ([Ca]o), banding did not affect E-C coupling efficacy in intact cells under voltage clamp (i.e., same contraction for given ICaand SR Ca load). However, when [Ca]owas reduced to 0.5 mM, the efficacy of E-C coupling was greatly depressed in the banded group (even though ICaand SR Ca content were matched). In summary, unloaded myocyte contraction was depressed in these hypertrophic hearts, but Ca transport was little altered, at 1 mM [Ca]o. However, reduction of [Ca]oto 0.5 mM appears to unmask a depressed fractional SR Ca release in response to a given ICatrigger and SR Ca load.
Age-dependent responses of the mesenteric vasculature to ischemia-reperfusion
Authors: Harris Norman R. , Langlois Kimberly W.
Published: December 2017

The age-dependent responses of the mesenteric vasculature to ischemia-reperfusion (I/R) were compared in 2-mo-old and 2-yr-old rats. Measurements were made of leukocyte adherence, albumin leakage, and oxidative stress in postcapillary venules. In young rats I/R induced an increase in leukocyte adherence and albumin leakage, but in aged rats I/R induced an increase in albumin leakage without an increase in leukocyte adherence. Furthermore, I/R-induced oxidative stress was higher in the aged rats than in the young rats. To investigate whether the age-associated oxidative stress is related to a decrease in the role of nitric oxide, NG-nitro-l-arginine methyl ester (l-NAME) was superfused onto the mesentery of young and aged rats.l-NAME induced an increase in postcapillary protein leakage only in young rats; however, arteriolar constriction induced byl-NAME occurred in both age groups. These results suggest that different mechanisms contribute to the inflammatory responses and microvascular dysfunction elicited by I/R in young and aged rats.
Upregulation of the cardiac homeobox gene Nkx2–5 (CSX) in feline right ventricular pressure overload
Authors: Thompson Jerry T. , Rackley Mary S. , O’Brien Terrence X.
Published: December 2017

The recent characterization of the cardiac-specific homeobox gene Nkx2–5 (or CSX) and its detection in normal adult heart tissue raises the possibility of a role in adult hypertrophy. Using pressure overload as a primary stimulus, we used a feline pulmonary artery banding model to produce right ventricular hypertrophy (RVH). Total RNA was hybridized to a full-length murine Nkx2–5 cDNA probe that contained the NK family homeodomain. Nkx2–5 mRNA levels increased 5.1-fold ( P < 0.05) and 3.9-fold vs. the corresponding left ventricles at 2 and 7 days of RVH, respectively, during the period of maximal myocardial growth. By 2 wk, when the RVH response had been completed, Nkx2–5 mRNA levels were returning toward baseline. Hybridization with an Nkx2–5 probe not containing the NK homologous homeodomain demonstrated that upregulation was specific for the Nkx2–5 gene. Atrial natriuretic factor and α-cardiac actin, both activated in part by Nkx2–5 DNA binding elements, also increased with RVH. These data suggest that a cardiac homeobox gene may play a role in the induction of adult cardiac hypertrophy.
Differential atrial and ventricular expression of myocardial BNP during evolution of heart failure
Authors: Luchner Andreas , Stevens Tracy L. , Borgeson Daniel D. , Redfield Margaret , Wei Chi-Ming , Porter J. Gordon , Burnett John C.
Published: December 2017

Although brain natriuretic peptide (BNP) of myocardial origin is important in cardiovascular and renal function and as a marker of cardiac dysfunction, the expression of BNP in atrial and ventricular myocardium remains controversial both under normal conditions and in heart failure. We therefore determined left atrial and left ventricular (LV) gene expression and tissue concentration as well as circulating BNP during the evolution of rapid ventricular pacing-induced congestive heart failure (CHF) in the dog. Early LV dysfunction after 10 days of pacing was characterized by impaired LV function but maintained arterial pressure, and overt CHF after 38 days of pacing was characterized by further impaired LV function and decreased systemic arterial pressure. Under normal conditions, cardiac BNP mRNA and cardiac tissue BNP were of atrial origin. In early LV dysfunction, BNP mRNA and tissue BNP were markedly increased in the left atrium in association with an increase in circulating BNP but remained below or at the limit of detection in the LV. In overt CHF, BNP mRNA was further increased in the left atrium and first increased in the LV, together with an increase in LV tissue BNP and a further increase in circulating BNP. In the progression of CHF, early LV dysfunction is characterized by a selective increase in atrial BNP expression in association with increased circulating BNP. Overt CHF is characterized by an additional recruitment of ventricular BNP expression and a further increase in circulating BNP. These studies provide important new insight into the local and temporal regulation of cardiac BNP gene expression during the progression of heart failure and underscore the predominant endocrine role of atrial myocardium under normal conditions and in early LV dysfunction.
Intracellular calcium dynamics in mouse model of myocardial stunning
Authors: Hampton Thomas G. , Amende Ivo , Travers Kerry E. , Morgan James P.
Published: December 2017

Intracellular calcium ([Formula: see text]) and left ventricular (LV) function were determined in the coronary-perfused mouse heart to study[Formula: see text]-related mechanisms of injury from myocardial ischemia and reperfusion. Specifics for loading of the photoprotein aequorin into isovolumically contracting mouse hearts under constant-flow conditions are provided. The method allows detection of changes in [Formula: see text] on a beat-to-beat basis in a model of myocardial stunning and permits correlation of interventions that regulate Ca2+exchange with functional alterations. Twenty-three coronary-perfused mouse hearts were subjected to 15 min of ischemia followed by 20 min of reperfusion. In 13 hearts, the perfusate included the calmodulin antagonist W7 (10 μM) to inhibit Ca2+-calmodulin-regulated mechanisms. Peak [Formula: see text] was 0.77 ± 0.03 μM in the control group and was unaffected by W7 at baseline. Ischemia was characterized by a rapid decline in LV function, followed by ischemic contracture, accompanied by a gradual rise in[Formula: see text]. Reperfusion was characterized by an initial burst of [Formula: see text] and a gradual recovery to nearly normal systolic[Formula: see text] while LV pressure recovered to 55% after 20 min of reperfusion (stunned myocardium). These results in the mouse heart confirm that stunning does not result from deficiency of [Formula: see text] but rather from a decreased myofilament responsiveness to [Formula: see text] due to changes in the myofilaments themselves. In hearts perfused with W7, the rise in [Formula: see text] during ischemia was significantly attenuated, as was the magnitude of mean[Formula: see text] during early reflow. Ischemic contracture was abolished or delayed. Hearts perfused with W7 showed significantly improved recovery of LV pressure, rate of contraction, and rate of relaxation. Diastolic [Formula: see text]was increased in control hearts during stunning but returned to baseline in hearts perfused with W7. Simultaneous assessment of[Formula: see text] and LV function demonstrates that calmodulin-regulated mechanisms may contribute to the pathogenesis of myocardial stunning in the mouse heart.
Apolipoprotein AIV: a potent endogenous inhibitor of lipid oxidation
Authors: Qin Xiaofa , Swertfeger Debi K. , Zheng Shuqin , Hui David Y. , Tso Patrick
Published: December 2017

Overexpression of apolipoprotein (apo) AIV in transgenic mice confers significant protection against atherosclerosis in apoE knockout animals even in the presence of a more severe atherogenic lipid profile. Because lipoprotein oxidation has been recognized to be pivotal in development of atherosclerosis, the antioxidative activity of apoAIV was investigated. Fasting intestinal lymph was used to mimic conditions in the interstitial fluid, the potential site for lipoprotein oxidation in vivo. ApoAIV (10 μg/ml) significantly inhibited copper-mediated oxidation of lymph. This inhibitory effect was further evaluated using purified low-density lipoprotein. Addition of apoAIV (2.5 μg/ml) increased the time of 50% conjugated diene formation by 2.4-fold, whereas apoE or BSA did not show such a protection even at 20 μg/ml. Addition of apoAIV during the propagation phase also resulted in a dose-dependent inhibition. ApoAIV also protected macrophage-induced oxidation of fasting lymph. These results provide the first evidence that apoAIV is a potent endogenous antioxidant.
Effects of β-adrenoceptor stimulation on contractility, [Ca2+]i, and Ca2+ current in diabetic rat cardiomyocytes
Authors: Tamada Atsushi , Hattori Yuichi , Houzen Hideki , Yamada Yoichi , Sakuma Ichiro , Kitabatake Akira , Kanno Morio
Published: December 2017

The mechanism of the diminished inotropic response to β-adrenoceptor stimulation in diabetic hearts was studied in enzymatically isolated diabetic rat ventricular myocytes in comparison with age-matched controls. The increases in contractions and intracellular Ca2+ concentration ([Ca2+]i) transients produced by isoproterenol were markedly diminished in diabetic myocytes. The inotropic and [Ca2+]iresponses to forskolin and dibutyryl cAMP (DBcAMP) were also reduced. No significant difference was found in the stimulating effects of isoproterenol, forskolin, and DBcAMP on the L-type Ca2+ current ( I Ca) between control and diabetic myocytes. The rise of [Ca2+]iin response to rapid caffeine application, an index of sarcoplasmic reticulum (SR) Ca2+ content, was significantly decreased in diabetic myocytes. Isoproterenol, forskolin, and DBcAMP enhanced this [Ca2+]iresponse to caffeine in control myocytes more markedly than in diabetic myocytes. The changes in the isoproterenol responses observed in diabetic myocytes were prevented by insulin therapy. We conclude that 1) diabetes causes an impairment of the contractile and [Ca2+]iresponses of cardiac myocytes when stimulated at both β-adrenoceptors and the postreceptor level without affecting the I Ca response and 2) altered SR functions of uptake and/or release of Ca2+ may primarily contribute to the diminished β-adrenergic response.
Changes in the sympathetic nervous system induced by 42 days of head-down bed rest
Authors: Sigaudo Dominique , Fortrat Jacques-Olivier , Allevard Anne-Marie , Maillet Alain , Cottet-Emard Jean-Marie , Vouillarmet Annick , Hughson Richard L. , Gauquelin-Koch Guillemette , Gharib Claude
Published: December 2017

Changes in autonomic nervous system activity could be linked to the orthostatic intolerance (OI) that individuals suffer after a spaceflight or head-down bed rest (HDBR). We examined this possibility by assessing the sympathetic nervous system activity during 42 days of HDBR in seven healthy men. Heart rate variability was studied with the use of power spectral analysis, which provided indicators of the sympathetic (SNSi) and parasympathetic (PNSi) nervous system influences on the heart. Urinary catecholamines and the spontaneous baroreflex sensitivity were measured. Urinary catecholamines decreased by 21.3%, showing a decrease in SNSi. Heart rate variability was greatly reduced during 42 days of HDBR with a drop in PNSi but with no significant changes in SNSi. The baroreflex sensitivity was greatly reduced (30.7%) on day 42 of HDBR. These results suggest a dissociation between the catecholamine response and the SNSi of the heart rate. This dissociation could be the consequence of an increase in β-adrenergic receptor density and/or activity induced by a decrease in catecholamines during HDBR. The subjects who suffered from OI also had a greater sympathetic response and much lower baroreflex sensitivity when supine than those who finished the stand test. However, the mean response of all subjects indicated that the sympathetic activity (catecholamine excretion) was probably slightly inhibited during HDBR and could contribute to OI.
Microvascular permeability and number of tight junctions are modulated by cAMP
Authors: Adamson R. H. , Liu B. , Fry G. Nilson , Rubin L. L. , Curry F. E.
Published: December 2017

We tested the hypothesis that increased endothelial cell adenosine 3′,5′-cyclic monophosphate (cAMP) decreases microvascular permeability in vivo. The effects of cAMP-specific phosphodiesterase type IV inhibition and adenylate cyclase activation on microvascular hydraulic conductivity ( Lp) were investigated in intact individual capillaries and postcapillary venules in mesentery of pithed frogs ( Rana pipiens). Treatment with rolipram (10 μM) and forskolin (5 μM) for 25 min decreased Lpto 37% of control. Rolipram alone also significantly decreased Lp. Isoproterenol (10 μM) decreased Lpto 27% of control within 20 min. A subgroup of eight vessels treated with rolipram and forskolin, in which mean Lpfell to 25% of control, was examined with transmission electron microscopy. The mean number of tight junctions in the treated vessels was 2.2 per cleft (303 clefts), significantly higher than in a matched control group (192 clefts), which was 1.7 per cleft. The results indicate that microvascular Lpcan be modulated by intracellular cAMP and that one of the structural end points of stimulated cAMP levels is an increase in the mean number of tight-junction strands between endothelial cells.
Determinants of action potential initiation in isolated rabbit atrial and ventricular myocytes
Authors: Golod David A. , Kumar Rajiv , Joyner Ronald W.
Published: December 2017

Action potential conduction through the atrium and the ventricle of the heart depends on the membrane properties of the atrial and ventricular cells, particularly with respect to the determinants of the initiation of action potentials in each cell type. We have utilized both current- and voltage-clamp techniques on isolated cells to examine biophysical properties of the two cell types at physiological temperature. The resting membrane potential, action potential amplitude, current threshold, voltage threshold, and maximum rate of rise measured from atrial cells (−80 ± 1 mV, 109 ± 3 mV, 0.69 ± 0.05 nA, −59 ± 1 mV, and 206 ± 17 V/s, respectively; means ± SE) differed significantly ( P < 0.05) from those values measured from ventricular cells (−82.7 ± 0.4 mV, 127 ± 1 mV, 2.45 ± 0.13 nA, −46 ± 2 mV, and 395 ± 21 V/s, respectively). Input impedance, capacitance, time constant, and critical depolarization for activation also were significantly different between atrial (341 ± 41 MΩ, 70 ± 4 pF, 23.8 ± 2.3 ms, and 19 ± 1 mV, respectively) and ventricular (16.5 ± 5.4 MΩ, 99 ± 4.3 pF, 1.56 ± 0.32 ms, and 36 ± 1 mV, respectively) cells. The major mechanism of these differences is the much greater magnitude of the inward rectifying potassium current in ventricular cells compared with that in atrial cells, with an additional difference of an apparently lower availability of inward Na current in atrial cells. These differences in the two cell types may be important in allowing the atrial cells to be driven successfully by normal regions of automaticity (e.g., the sinoatrial node), whereas ventricular cells would suppress action potential initiation from a region of automaticity (e.g., an ectopic focus).
Microvascular transport is associated with TNF plasma levels and protein synthesis in postischemic muscle
Authors: Takenaka Hiroaki , Oshiro Hidemi , Kim David D. , Thompson Peter N. , Seyama Atsushi , Hobson Robert W. , Durán Walter N.
Published: December 2017

To better understand the mechanisms of ischemia-reperfusion (I/R) injury, we tested the hypothesis that protein synthesis is involved in the production of tumor necrosis factor (TNF) and in the microvascular transport changes in I/R. To evaluate the hypothesis, we inhibited protein synthesis with topically applied actinomycin D (AMD), measured I/R-induced changes in microvascular transport, and bioassayed the venous plasma levels of TNF. The rat cremaster muscle I/R model consisted of 4 h of ischemia followed by 2 h of reperfusion. Changes in transport were determined by integrated optical intensity (IOI) using FITC-Dextran 150 as tracer. Animals were separated into four groups: 1) control (C), 2) control treated with AMD (C + AMD), 3) I/R, and 4) I/R treated with AMD (I/R + AMD). The mean (±SE) maximal IOI in C and C + AMD were 3.0 ± 1.0 and 3.7 ± 0.7 units, respectively. I/R elevated mean maximal IOI to 21.8 ± 1.9 units ( P < 0.05 vs. C, C + AMD, I/R + AMD). Treatment with AMD reduced the I/R-induced mean maximal IOI to 9.7 ± 2.0 units ( P< 0.05 vs. I/R). In I/R group, plasma TNF levels increased (relative to preischemia baseline) immediately after the release of the vascular occlusion to 250 pg/ml and reached a peak value of 342 pg/ml at 60 min of reperfusion. In the I/R + AMD group, AMD reduced TNF increase to 44 pg/ml. The C and C + AMD groups showed no differences in TNF values during the 6 h of observation. We conclude that protein synthesis and TNF generation are at least partially involved in I/R-induced changes in microvascular transport.
Temperature and protein kinase C modulate myofilament Ca2+sensitivity in pressurized rat cerebral arteries
Authors: Gokina Natalia I. , Osol George
Published: December 2017

The effects of pharmacological activation and inhibition of protein kinase C (PKC) and temperature on the relationship between cytoplasmic Ca2+and lumen diameter were studied in pressurized (50 mmHg) rat posterior cerebral arteries permeabilized with α-toxin. Increasing Ca2+concentrations (30 nM–10 μM, 22°C) induced stable, concentration-dependent constrictions with a half-maximal effective concentration (EC50) of 112 nM. The maximal constriction was 80% of baseline diameter and 157% of that during depolarization of nonpermeabilized vessels with 124 mM KCl. Elevation of temperature to 37°C increased the EC50to 246 nM and enhanced the steepness of concentration-response curves. Exposure of permeabilized arteries to indolactam V, an activator of PKC, resulted in a significant myofilament Ca2+sensitization (e.g., EC50at 5 μM = 126 nM) without changing efficacy. The effects of calphostin C, a PKC inhibitor, on Ca2+sensitivity were minimal; however, the amplitude of Ca2+-induced constrictions in both control and indolactam-treated arteries was suppressed in a concentration-dependent manner. Thus 1) temperature is an important variable in studies of arterial Ca2+sensitivity, and 2) changes in PKC activity can significantly alter both myofilament sensitivity to and constrictor efficacy of cytosolic Ca2+.