bluuebunny/crossref_metadata_2025 huggingface dataset:
Increasing myocardial contraction and blood pressure in C57BL/6 mice during early postnatal development
Authors: Tiemann Klaus , Weyer Dirk , Djoufack P. Chryso , Ghanem Alexander , Lewalter Thorsten , Dreiner Ulrike , Meyer Rainer , Grohé Christian , Fink Klaus B.
Published: March 2015

Knowledge of the developmental changes of cardiovascular parameters in the genetic background of a mouse strain is important for understanding phenotypic changes in transgenic or knockout mouse models for heart disease. We studied arterial blood pressure and myocardial contractility in mice of the common background strain C57BL/6, aged 21 days [postnatal day 21 (P21)] to 580 days. Heart rate increased during maturation from 396 beats/min at P21 to 551 beats/min at postnatal day 50 (P50), and mean arterial blood pressure increased in parallel from 86 to 110 mmHg and remained constant afterward. Echocardiographically determined left ventricular myocardial wall dimensions ( R = 0.79, P < 0.0001) and left ventricular mass calculated using the area-length algorithm correlated strongly with histomorphometrical measurements ( R = 0.93, P < 0.001). Sarcomere shortening records from isolated ventricular myocytes used as a measure for myocardial contractility revealed a negative shortening-frequency relation under a pacing frequency of 2 Hz and a positive relation above 2 Hz. Shortening amplitudes recorded from P21 myocytes were smaller, and the shortening-frequency relation was less steep than in adult myocytes. A stimulation pause was followed by a negative “staircase” at pacing frequency of ≤6 Hz and a positive staircase at ≥6 Hz. P21 myocytes developed positive staircases at 8 and 10 Hz, and adult myocytes also developed them at 6 Hz. Blood pressure increase during maturation until P50 may originate from increasing single cardiomyocyte contractility.
Different roles of PKC and MAP kinases in arteriolar constrictions to pressure and agonists
Authors: Massett Michael P. , Ungvari Zoltan , Csiszar Anna , Kaley Gabor , Koller Akos
Published: March 2015

Protein kinase C (PKC) and mitogen-activated protein (MAP) kinases have been implicated in the modulation of agonist-induced contractions of large vessels. However, their role in pressure- and agonist-induced constrictions of skeletal muscle arterioles, which have a major role in regulating peripheral resistance, is not clearly elucidated. Thus constrictions of isolated rat gracilis muscle arterioles (∼80 μm in diameter) to increases in intraluminal pressure and to norepinephrine (NE) or angiotensin II (ANG II) were assessed in the absence or presence of chelerythrine, PD-98058, and SB-203580 (inhibitors of PKC, p42/44 and p38 MAP kinase pathways, respectively). Arteriolar constriction to NE and ANG II were significantly reduced by chelerythrine (by ∼90%) and unaffected by SB-203580, whereas PD-98058 decreased only ANG II-induced constrictions (by ∼60%). Pressure-induced increases in wall tension (from 0.1 to 0.7 N/m) resulted in significant arteriolar constrictions (50% maximum) that were abolished by chelerythrine without altering smooth muscle intracellular Ca2+concentration ([Ca2+]i) (fura 2 microfluorimetry). PD-98058 and SB-203580 significantly decreased the magnitude of myogenic tone (by 20% and 60%, respectively) and reduced the sensitivity of the myogenic mechanism to wall tension, causing a significant rightward shift in the wall tension-myogenic tone relationship without affecting smooth muscle [Ca2+i]. MAP kinases were demonstrated with Western blotting. Thus in skeletal muscle arterioles 1) PKC is involved in both myogenic and agonist-induced constrictions , 2) PD-98058-sensitive p42/44 MAP kinases modulate both wall tension-dependent and ANG II-induced constrictions, whereas 3) a SB-203580-sensitive p38 MAP kinase pathway seems to be specifically involved in the mechanotransduction of wall tension.
Altered PYK2 phosphorylation by ANG II in hypertensive vascular smooth muscle
Authors: Rocic Petra , Griffin Tina M. , McRae Chastity N. , Lucchesi Pamela A.
Published: March 2015

10.1152/ajpheart 00546.2001.—Vascular smooth muscle cells (VSMC) from spontaneously hypertensive rats (SHR) exhibit increased cell growth compared with normotensive Wistar-Kyoto rats (WKY). ANG II stimulates growth via Gq-protein-coupled signaling that involves changes in cytosolic intracellular Ca2+concentration ([Ca2+]i) and activation of protein kinase C (PKC) and mitogen-activated protein kinases. This study examines the role of the proline-rich tyrosine kinase 2 (PYK2) in hypertensive VSMC. Basal PYK2 phosphorylation in SHR VSMC was increased compared with WKY (0.44 ± 0.02 vs. 0.20 ± 0.02-fold). ANG II-induced activation of PYK2 in SHR VSMC was of greater magnitude (2.2 ± 0.2-fold in SHR; 1.4 ± 0.1-fold in WKY) and occurred more rapidly (peak activation at 2 min in SHR vs. 5 min in WKY). This effect was blocked by pretreatment with the [Ca2+]ichelator 1,2-bis(2-aminophenoxy)ethane- N,N,N′,N′-tetraacetic acid or the PKC inhibitor chelerythrine. Basal and ANG II-stimulated c-Fos expression was increased in SHR versus WKY VSMC. PYK2 downregulation with antisense oligonucleotides blocked ANG II-induced c-Fos expression. Increased PYK2 activation may be altered signaling cascades that regulate cell growth in hypertensive VSMC.
Autologous bone marrow cell implantation as therapeutic angiogenesis for ischemic hindlimb in diabetic rat model
Authors: Hirata Ken , Li Tao-Sheng , Nishida Masahiko , Ito Hiroshi , Matsuzaki Masunori , Kasaoka Shunji , Hamano Kimikazu
Published: March 2015

The angiogenic effect induced by autologous bone marrow cell implantation (BMCI) was examined in the ischemic hindlimbs of diabetic and nondiabetic rats. Diabetes mellitus was induced by the systemic administration of streptozotocin. We investigated the production of angiogenic factors and endothelial differentiation from bone marrow cells and the native recovery of blood flow in the ischemic hindlimbs. To observe the angiogenic effect induced by BMCI treatment, 6 × 107 bone marrow cells were injected intramuscularly at six points into the ischemic limbs, and regional perfusion recovery was evaluated with colored microspheres 2 wk later. No difference was found between diabetic and nondiabetic rats in the release of angiogenic factors or endothelial differentiation from bone marrow cells in vitro. The levels of nitric oxide in plasma were significantly lower, and native perfusion recovery in the ischemic hindlimbs was significantly slower in the diabetic rats than in the nondiabetic rats. However, although perfusion recovery was achieved in the ischemic hindlimbs, there was no significant increase in systemic VEGF after BMCI treatment in either the diabetic or nondiabetic rats. Therefore, therapeutic angiogenesis induced by BMCI could be a safe and effective treatment for ischemic limb disease in diabetic patients.
Role of interleukin 12 in hypercholesterolemia-induced inflammation
Authors: Stokes Karen Y. , Clanton E. Chris , Gehrig John L. , Granger D. Neil
Published: March 2015

We have previously shown that T lymphocytes and interferon-γ are involved in hypercholesterolemia-induced leukocyte adhesion to vascular endothelium. This study assessed the contribution of interleukin 12 (IL-12) to these hypercholesterolemia-induced inflammatory responses. Intravital videomicroscopy was used to quantify leukocyte adhesion and emigration and oxidant stress (dihydrorhodamine oxidation) in unstimulated cremasteric venules (wall shear rate ≥500 s–1) of wild-type (WT) C57Bl/6, lymphocyte-deficient [recombinase-activating gene knockout (RAG1–/–)], and IL-12-deficient (p35–/–and p40–/–; p35 and p40 are the two subunits of active IL-12) mice on either a normal (ND) or high-cholesterol (HC) diet for 2 wk. RAG1–/–-HC mice received splenocytes from WT-HC (WT → RAG1–/–), p35–/–-HC (p35–/–→ RAG1–/–), or p40–/–-HC (p40–/–→ RAG1–/–) mice. Compared with WT-ND mice, WT-HC mice exhibited exaggerated leukocyte adherence and emigration as well as increased dihydrorhodamine oxidation. The enhanced leukocyte recruitment was absent in the RAG1–/–-ND, p35–/–-ND, and p40–/–-ND groups. Hypercholesterolemia-induced leukocyte adherence and emigration were attenuated in RAG1–/–-HC vs. WT-HC mice but were similar to ND mice. Furthermore, compared with WT-HC animals, p35–/–-HC and p40–/–-HC mice showed significantly lower leukocyte adhesion and tissue oxidant stress responses, but these values were comparable to ND mice. Leukocyte adherence and emigration in WT → RAG1–/–mice were similar to responses of WT-HC mice. However, p35–/–→ RAG1–/–mice had lower levels of adherence and emigration vs. the WT → RAG1–/–and WT-HC groups. Elevated levels of leukocyte adherence and emigration were restored by ∼50% toward WT-HC levels in p40–/–→ RAG1–/–mice. These findings implicate IL-12 in the inflammatory responses observed in the venules of hypercholesterolemic mice.
Ablation of PLB exacerbates ischemic injury to a lesser extent in female than male mice: protective role of NO
Authors: Cross Heather R. , Kranias Evangelia G. , Murphy Elizabeth , Steenbergen Charles
Published: March 2015

Recent studies suggest a role for phospholamban phosphorylation during ischemia and reperfusion. The role of phospholamban in ischemia was studied by subjecting hearts from male and female wild-type (MWT/FWT) and phospholamban-knockout (MKO/FKO) mice to 20 min of ischemia-40 min of reperfusion while31P NMR spectra were acquired. ATP and pH values fell lower during ischemia, and postischemic contractility was less, in MKO and FKO versus WT hearts. After shorter ischemia (15 min), recoveries of contraction, ATP, and pH were greater in FKO than MKO hearts. To examine the role of nitric oxide (NO) synthases (NOS) in the protection in FKO versus MKO hearts, we utilized 1 μMl-NAME, a NOS inhibitor, or 100 μM S-nitroso- N-acetylpenicillamine (SNAP), an NO donor. Recoveries of function, ATP, and pH were less inl-NAME-treated FKO than untreated FKO hearts and greater in SNAP-treated MKO than untreated MKO hearts. In conclusion, phospholamban ablation increased ischemic injury in both males and females; however, female hearts were less susceptible than male hearts. Protection in females was decreased by a NOS inhibitor and mimicked in males by an NO donor, implying that protection was NOS mediated.
Prostaglandin modulation of venoconstriction to physiological stress in normals and heart failure patients
Authors: Dzeka T. Nancy , Arnold J. Malcolm O.
Published: March 2015

Prostaglandins released from blood vessels modulate vascular tone, and inhibition of their production during exogenous infusions of catecholamines causes increased venoconstriction. To determine the influence of prostaglandin production on venoconstriction during physiological stimuli known to cause sympathetic activation, and to assess its importance in chronic heart failure (CHF), we studied 11 normal subjects (62 ± 4 yr) and 14 patients with CHF (64 ± 2 yr, left ventricular ejection fraction 23 ± 1%, New York Heart Association classes II and III) (means ± SE). Dorsal hand vein distension was measured during mental arithmetic (MA), cold pressor test (CPT), and lower body negative pressure (LBNP; −10 and −40 mmHg), with saline infusion in one hand and local indomethacin (cyclooxygenase inhibitor) infusion (3 μg/min) in the other. Acetylcholine (0.01–1 nmol/min) dilated veins preconstricted with PGF2αin normals but, consistent with endothelial dysfunction, barely did so in CHF patients ( P = 0.001). Nonendothelial venodilation to sodium nitroprusside (0.3–10 nmol/min) was not different between normals and CHF patients. Resting venous norepinephrine levels were higher in CHF patients (2,812 ± 420 pmol/l) than normals (1,418 ± 145 pmol/l, P = 0.007). In normals, indomethacin caused increased venoconstriction to MA (from 4.9 ± 1.5 to 19.2 ± 4.5%, P = 0.022) and CPT (from 2.9 ± 3.8 to 17.6 ± 4.2%, P = 0.007). In CHF, indomethacin caused increased venoconstriction to MA (from 6.6 ± 3.9% to 19.0 ± 4.5%, P = 0.014), CPT (from 9.6 ± 2.1% to 20.1 ± 3.7%, P = 0.001), and −40 mmHg LBNP (from 10.7 ± 3.0% to 23.2 ± 3.8%, P= 0.041). Control responses for all tests were not different between normals and CHF patients. The effects of indomethacin on venoconstriction to MA and CPT were not different between normals and CHF patients, but venoconstriction to −40 mmHg LBNP was accentuated in CHF patients ( P = 0.036). Inhibition of prostaglandins by indomethacin significantly enhances hand vein constriction to physiological stimuli in both normals and CHF patients, although a differential effect exists for LBNP.
Superoxide anion impairs contractility in cultured aortic smooth muscle cells
Authors: Kimura Chiwaka , Cheng Wei , Hisadome Kazunari , Wang Yi-Ping , Koyama Tetsuya , Karashima Yuji , Oike Masahiro , Ito Yushi
Published: March 2015

We examined the effects of superoxide anion (O[Formula: see text]) generated by xanthine plus xanthine oxidase (X/XO) on the intracellular Ca2+concentration ([Ca2+]i) and muscle contractility in cultured bovine aortic smooth muscle cells (BASMC). Cells were grown on collagen-coated dish for the measurement of [Ca2+]i. Pretreatment with X/XO inhibited ATP-induced Ca2+transient and Ca2+release-activated Ca2+entry (CRAC) after thapsigargin-induced store depletion, both of which were reversed by superoxide dismutase (SOD). In contrast, Ca2+transients induced by high-K+solution and Ca2+ionophore A-23187 were not affected by X/XO. BASMC-embedded collagen gel lattice, which was pretreated with xanthine alone, showed contraction in response to ATP, thapsigargin, high-K+solution, and A-23187. Pretreatment of the gel with X/XO impaired gel contraction not only by ATP and thapsigargin, but also by high-K+solution and A-23187. The X/XO-treated gel showed normal contraction; however, when SOD was present during the pretreatment period. These results indicate that O[Formula: see text] attenuates smooth muscle contraction by impairing CRAC, ATP-induced Ca2+transient, and Ca2+sensitivity in BASMC.
RV functional imaging: 3-D echo-derived dynamic geometry and flow field simulations
Authors: Pasipoularides Ares D. , Shu Ming , Womack Michael S. , Shah Ashish , von Ramm Olaf , Glower Donald D.
Published: March 2015

We describe a novel functional imaging approach for quantitative analysis of right ventricular (RV) blood flow patterns in specific experimental animals (or humans) using real-time, three-dimensional (3-D) echocardiography (RT3D). The method is independent of the digital imaging modality used. It comprises three parts. First, a semiautomated segmentation aided by intraluminal contrast medium locates the RV endocardial surface. Second, a geometric scheme for dynamic RV chamber reconstruction applies a time interpolation procedure to the RT3D data to quantify wall geometry and motion at 400 Hz. A volumetric prism method validated the dynamic geometric reconstruction against simultaneous sonomicrometric canine measurements. Finally, the RV endocardial border motion information is used for mesh generation on a computational fluid dynamics solver to simulate development of the early RV diastolic inflow field. Boundary conditions (tessellated endocardial surface nodal velocities) for the solver are directly derived from the endocardial geometry and motion information. The new functional imaging approach may yield important kinematic information on the distribution of instantaneous velocities in the RV diastolic flow field of specific normal or diseased hearts.
Carbamazepine increases atherogenic lipoproteins: mechanism of action in male adults
Authors: Brämswig Susanne , Kerksiek Anja , Sudhop Thomas , Luers Claus , Von Bergmann Klaus , Berthold Heiner K.
Published: March 2015

Treatment with carbamazepine (CBZ) affects cholesterol concentrations, but little is known about the precise nature and underlying mechanisms of changes in lipoprotein metabolism. We investigated prospectively the effects of CBZ on lipid metabolism in normolipemic adults. In 21 healthy males, lipoprotein and noncholesterol sterol concentrations were measured before and during treatment with CBZ for 70 ± 18 days. Thirteen subjects underwent kinetic studies of apolipoprotein-B (ApoB) metabolism with the use of endogenous stable isotope labeling. Lipoprotein kinetic parameters were calculated by multicompartmental modeling. Significant increases in total cholesterol, in ApoB-containing lipoproteins [very-low-density lipoprotein (VLDL), intermediate density lipoprotein (IDL), and low-density lipoprotein (LDL)], and in triglycerides, but not in high-density lipoprotein (HDL), were observed. Lipoprotein particle composition remained unchanged. Mean fractional catabolic and production rates of ApoB-containing lipoproteins were not significantly different, although mean production rates of VLDL and IDL were substantially increased (+46 ± 139% and +30 ± 97%, respectively), whereas mean production of LDL remained unchanged (+2.1 ± 45.6%). Cholestanol in serum increased significantly but not the concentrations of plant sterols (campesterol, sitosterol) and the cholesterol precursors (lathosterol, mevalonic acid). There was a significant correlation between the decrease in free thyroxine and the increase in IDL cholesterol. Treatment with CBZ increases mainly ApoB-containing lipoproteins. CBZ seems not to influence endogenous cholesterol synthesis or intestinal absorption directly. The increase is neither related to increased ApoB production nor to decreased catabolism but is rather due to changes in the conversion cascade of IDL particles, most likely as an indirect effect through a decrease in thyroid hormones.
Inhibition of NOS II prevents cardiac dysfunction in myocardial infarction and congestive heart failure
Authors: Saito Takayuki , Hu Fu , Tayara Lara , Fahas Linda , Shennib Hani , Giaid Adel
Published: March 2015

Strong expression of the inducible form of nitric oxide synthase (NOS II) has been shown in the myocardium of patients with myocardial infarction (MI). We hypothesized that NOS II plays an important role in the development of MI and subsequent heart failure and that inhibition of NOS II may beneficially alter the course of the disease. Long-term administration (2 mo) of the selective NOS II inhibitor S-methylisothiourea (SMT) to rats with MI significantly improved cardiac function. A significant drop in mortality, lung water content, infarct size, and cardiomyocyte hypertrophy was also associated with the use of SMT. Plasma concentration of nitrite and nitrate was also reduced by SMT. Short-term administration of SMT (first 2 wk only) significantly reduced infarct size; however, it did not improve cardiac dysfunction measured 2 mo after MI. These findings demonstrate that induction of NOS II during MI exerts negative effects on cardiac function and structure. Long-term administration of a selective NOS II inhibitor may prove to be beneficial in the treatment of MI and congestive heart failure.
Inhibitors of gap junctions attenuate myogenic tone in cerebral arteries
Authors: Lagaud Guy , Karicheti Venkateswarlu , Knot Harm. J. , Christ George J. , Laher Ismail
Published: March 2015

The effects of two structurally distinct inhibitors of gap junction communication were studied by using three different forms of vasoconstriction in pressurized rat middle cerebral arteries. The sensitivity of myogenic tone (at 60 mmHg), vasopressin-induced tone (10 nM, at 20 mmHg), and depolarizing solution-induced tone (80 mM K+, at 20 mmHg) to inhibition by heptanol (1.0 μM to 3.0 mM) or 18α-glycyrrhetinic acid (18α-GA, 1.0 to 50 μM) were determined. Pressure-induced myogenic tone was inhibited by heptanol (IC50 = 0.75 ± 0.09 mM) and 18α-GA (∼30 μM). Vasopressin-induced vasoconstriction was also inhibited by heptanol (IC50= 0.4 ± 0.3 mM) and 18α-GA (>1 μM). Depolarizing solution-induced vasoconstriction was less sensitive to inhibition by heptanol compared to vasopressin ( P < 0.01) or pressure-induced constriction ( P < 0.05). However, 18α-GA did not inhibit depolarization-induced constriction. Sharp microelectrode experiments on isolated arteries revealed stable membrane potentials, with no detectable effect of heptanol (1 mM) or 18α-GA (20–30 μM) on the average membrane potential at 20 mmHg. However, ≈20% of impaled cells (5 of 28) exhibited uncharacteristic oscillations in membrane potential after pharmacological uncoupling. At 60 mmHg a ≈7- to 9-mV hyperpolarization and corresponding vasodilation (≈50%) was observed, and the frequency of membrane potential oscillations doubled (9 of 23 cells). These data indicate that gap junctions play an important role in the maintenance and modulation of membrane potential and tone in cerebral resistance arteries.
Coronary artery myogenic response in a genetic model of hypertrophic cardiomyopathy
Authors: Petersen Henrik H. , Choy Jonathan , Stauffer Brian , Moien-Afshari Farzad , Aalkjaer Christian , Leinwand Leslie , McManus Bruce M. , Laher Ismail
Published: March 2015

Hypertrophic cardiac myopathy (HCM) is the leading cause of mortality in young athletes. Abnormalities in small intramural coronary arteries have been observed at autopsy in such subjects. The walls of these intramural vessels, especially in the ventricular septum, are thickened, and the lumen frequently appears narrowed. Whether these morphological characteristics have functional correlates is unknown. We studied coronary myogenic tone in a transgenic mouse model of HCM that has mutations in the cardiac α-myosin heavy chain gene. This transgenic mouse has a cardiac phenotype that resembles that occurring in humans. We examined the possible vascular contributions to the pathology of HCM. Septal arteries from 3- and 11-mo-old wild-type (WT) and transgenic (TG) mice were studied on a pressure myograph. The myogenic response to increased intravascular pressure in older animals was significantly reduced [maximal constriction: 32 ± 4% (TG) and 46 ± 4% (WT), P < 0.05]. After inhibition of endothelin receptors with bosentan, both WT and TG mice had similar increases in myogenic constriction. The sensitivity to exogenous endothelin was significantly reduced in TG mice, suggesting that the reduced myogenic constriction in HCM was due to reduced receptor sensitivity. In conclusion, we show for the first time that 1) myogenic tone in the coronary septal artery of the mouse is regulated by a basal release of endothelin, and 2) pressure-induced myogenic activation is attenuated in HCM, possibly consequent to a reduction in endothelin responsiveness. The associated reduction in coronary vasodilatory reserve may increase susceptibility to ischemia and arrhythmias.
Sildenafil-nitric oxide donor combination promotes ventricular tachyarrhythmias in the swine right ventricle
Authors: Swissa Moshe , Ohara Toshihiko , Lee Moon-Hyoung , Kaul Sanjay , Shah Prediman K. , Hayashi Hideki , Chen Peng-Sheng , Karagueuzian Hrayr S.
Published: March 2015

We tested the hypothesis that sildenafil, singly or in combination with nitric oxide (NO) donors, promotes ventricular tachycardia (VT) and ventricular fibrillation (VF). Vulnerability to VT/VF was tested by rapid pacing in eight isolated normal swine right ventricles (RV). The endocardial activation was optically mapped, and the dynamic action potential duration (APD) restitution curves were constructed with metal microelectrodes. At baseline, no VT/VF could be induced. Sildenafil (0.2 μg/ml) or NO donor singly or in combination did not alter VT/VF vulnerability. However, when 2 μg/ml sildenafil was combined with NO donors, the incidence of VT and VF rose significantly ( P < 0.01). VT with a single periodic wavefront was induced in five of eight RVs, and VF with multiple wavefronts was induced in all eight RVs. The sildenafil-NO donor pro-VT/VF combination significantly increased the maximum slope of the APD restitution curve and the amplitude of the APD alternans. The pro-VT/VF effects of sildenafil were reversible after drug-free Tyrode solution perfusion. We conclude that a sildenafil (2 μg/ml) and NO donor combination increases VT/VF vulnerability in the normal RV by a mechanism compatible with the restitution hypothesis.
Attenuation of neutrophil-mediated myocardial ischemia-reperfusion injury by a calpain inhibitor
Authors: Ikeda Yasuhiko , Young Lindon H. , Lefer Allan M.
Published: March 2015

Calpains are ubiquitous neutral cysteine proteases. Although their physiological role has yet to be clarified, calpains seem to be involved in the expression of cell adhesion molecules. Therefore, we hypothesized that a selective calpain inhibitor could attenuate polymorphonuclear (PMN) leukocyte-induced myocardial ischemia-reperfusion (I/R) injury. We examined the effects of the calpain inhibitor Z-Leu-Leu-CHO in isolated ischemic (20 min) and reperfused (45 min) rat hearts perfused with PMNs. Z-Leu-Leu-CHO (10 and 20 μM, respectively) significantly improved left ventricular developed pressure (LVDP) ( P< 0.01) and the maximal rate of development of LVDP ( P< 0.01) compared with I/R hearts perfused without Z-Leu-Leu-CHO. In addition, Z-Leu-Leu-CHO significantly reduced PMN adherence to the vascular endothelium and subsequent infiltration into the postischemic myocardium ( P < 0.01). Moreover, Z-Leu-Leu-CHO significantly inhibited expression of P-selectin on the rat coronary microvascular endothelium ( P < 0.01). These results provide evidence that Z-Leu-Leu-CHO significantly attenuates PMN-mediated I/R injury in the isolated perfused rat heart to a significant extent via downregulation of P-selectin expression.
Increased dietary sodium alters neural control of blood pressure during intravenous ANG II infusion
Authors: Bealer Steven L.
Published: March 2015

Increased dietary sodium enhances both excitatory and inhibitory blood pressure responses to stimulation of the central sympathetic nervous system (SNS) centers. In addition, long-term (hours to days) administration of ANG II increases blood pressure by activation of the SNS. These studies investigated the effects of increased dietary sodium on SNS control of blood pressure during 0- to 24-h infusion of ANG II in conscious, male rats consuming either tap water or isotonic saline (Iso) for 2 to 3 wk. The SNS component (evaluated by ganglionic blockade with trimetaphan) of both control blood pressure and the pressor response to intravenous ANG II was reduced in Iso animals. Furthermore, although the pressor response to intravenous ANG II infusion was similar between groups, the baroreflex-induced bradycardia during the initial 6 h of ANG II infusion was significantly greater, whereas the tachycardia accompanying longer infusion periods was significantly attenuated in Iso animals. These data suggest that in normal rats increased dietary sodium enhances sympathoinhibitory responses during intravenous ANG II.
Vascular smooth muscle cell stress as a determinant of cerebral artery myogenic tone
Authors: Brekke Johan Fredrik , Gokina Natalia I. , Osol George
Published: March 2015

Although the level of myogenic tone (MT) varies considerably from vessel to vessel, the regulatory mechanisms through which the actual diameter set point is determined are not known. We hypothesized that a unifying principle may be the equalization of active force at the contractile filament level, which would be reflected in a normalization of wall stress or, more specifically, media stress. Branched segments of rat cerebral arteries ranging from <50 μm to >200 μm in diameter were cannulated and held at 60 mmHg with the objectives of: 1) evaluating the relationship between arterial diameter and the extent of myogenic tone, 2) determining whether differences in MT correlate with changes in cytosolic calcium ([Ca2+]i), and 3) testing the hypothesis that a normalization of wall or media stress occurs during the process of tone development. The level of MT increased significantly as vessel size decreased. At 60 mmHg, vascular smooth muscle [Ca2+]iconcentrations were similar in all vessels studied (averaging 230 ± 9.2 nM) and not correlated with vessel size or the extent of tone. Wall tension increased with increasing arterial size, but wall stress and media stress were similar in large versus small arteries. Media stress, in particular, was quite uniform in all vessels studied. Both morphological and calcium data support the concept of equalization of media stress (and, hence, vascular smooth muscle cell stress and force) as an underlying mechanism in determining the level of tone present in any particular vessel. The equalization of active (vascular smooth muscle cell) stress may thus explain differences in MT observed in the different-sized vessels constituting the arterial network and provide a link between arterial structure and function, in both short- and long-term (hypertension) pressure adaptation.
Myogenic tone, reactivity, and forced dilatation: a three-phase model of in vitro arterial myogenic behavior
Authors: Osol George , Brekke Johan Fredrik , McElroy-Yaggy Keara , Gokina Natalia I.
Published: March 2015

Myogenic behavior, prevalent in resistance arteries and arterioles, involves arterial constriction in response to intravascular pressure. This process is often studied in vitro by using cannulated, pressurized arterial segments from different regional circulations. We propose a comprehensive model for myogenicity that consists of three interrelated but dissociable phases: 1) the initial development of myogenic tone (MT), 2) myogenic reactivity to subsequent changes in pressure (MR), and 3) forced dilatation at high transmural pressures (FD). The three phases span the physiological range of transmural pressures (e.g., MT, 40–60 mmHg; MR, 60–140 mmHg; FD, >140 mmHg in cerebral arteries) and are characterized by distinct changes in cytosolic calcium ([Ca2+]i), which do not parallel arterial diameter or wall tension, and therefore suggest the existence of additional regulatory mechanisms. Specifically, the development of MT is accompanied by a substantial (200%) elevation in [Ca2+]iand a reduction in lumen diameter and wall tension, whereas MR is associated with relatively small [Ca2+]iincrements (<20% over the entire pressure range) despite considerable increases in wall tension and force production but little or no change in diameter. FD is characterized by a significant additional elevation in [Ca2+]i(>50%), complete loss of force production, and a rapid increase in wall tension. The utility of this model is that it provides a framework for comparing myogenic behavior of vessels of different size and anatomic origin and for investigating the underlying cellular mechanisms that govern vascular smooth muscle mechanotransduction and contribute to the regulation of peripheral resistance.
Pressure-volume-based single-beat estimations cannot predict left ventricular contractility in vivo
Authors: Kjørstad Knut E. , Korvald Christian , Myrmel Truls
Published: March 2015

The end-systolic pressure-volume relationship is regarded as a useful index for assessing the contractile state of the heart. However, the need for preload alterations has been a serious limitation to its clinical applications, and there have been numerous attempts to develop a method for calculating contractility based on one single pressure-volume loop. We have evaluated four of these methods. Pressure-volume data were obtained by combined pressure and conductance catheters in 37 pigs. All four methods were applied to 88 steady-state pressure-volume files, including eight files sampled during dopamine infusions. Estimates of single-beat contractility (elastance) were compared with preload-varied multiple-beat elastance [ E es(MB)]. All methods had a low average bias (−0.3 to 0.5 mmHg/ml) but limits of agreement (±2 SD) were unacceptably high (±2.6 to ±3.8 mmHg/ml). In the dopamine group, E es(MB) showed an increase of 1.7 ± 0.8 mmHg/ml (mean ± SD) compared with baseline ( P < 0.001). None of the single-beat methods predicted this increase in contractility. It is therefore doubtful whether any of the methods allow for single-beat assessment of contractility.
Effects of dopamine on human retinal vessel diameter and its modulation during flicker stimulation
Authors: Huemer Karl-Heinz , Garhöfer Gerhard , Zawinka Claudia , Golestani Elisabeth , Litschauer Brigitte , Schmetterer Leopold , Dorner Guido T.
Published: March 2015

We performed a randomized, subject-blinded, placebo and time-controlled, two-way crossover study in 12 healthy male subjects. Placebo or dopamine was administered on two separate study days. After saline infusion, dopamine hydrochloride was infused in three consecutive doses (5, 10, and 15 μg · kg−1 · min−1). Plasma levels of dopamine were determined at each perfusion step. Arterial and venous retinal vessel diameters were measured with the use of a Zeiss retinal vessel analyzer. Diffuse luminance flicker stimuli of 8 Hz were applied for 60 s. Blood pressure and pulse rate were monitored continuously. Flicker stimulation (8 Hz) increased retinal vessel diameters under basal conditions. The response to 8-Hz flicker light was significantly reduced by dopamine administration. In addition, dopamine slightly but significantly increased retinal vessel diameters. Dopamine hydrochloride significantly increased systolic but not diastolic or mean arterial pressure. The present study indicates that dopamine has a distinct effect on retinal vessel diameters also attenuating the flicker-induced response reactivity of retinal vessels. This implies a role of dopamine in retinal blood flow hemodynamics.
ecNOS gene polymorphism is associated with endothelium-dependent vasodilation in Type 2 diabetes
Authors: Komatsu Miyoko , Kawagishi Takahiko , Emoto Masanori , Shoji Tetsuo , Yamada Atsuko , Sato Kyoko , Hosoi Masayuki , Nishizawa Yoshiki
Published: March 2015

The association between endothelial constitutive nitric oxide synthase (ecNOS) gene polymorphism and vascular endothelial function has not been clarified. We investigated the impact of ecNOS gene polymorphism on endothelial function in 95 patients with Type 2 diabetes (ecNOS genotype: 4b/b, n= 62; 4b/a, n = 30; 4a/a, n = 3). Flow-mediated (endothelium dependent, FMD) and nitroglycerin-induced (endothelium independent, NTG) vasodilations of the right brachial artery were studied using a phase-locked echotracking system. There were no significant differences in clinical characteristics among the ecNOS genotypes. The FMD was significantly lower in the patients with ecNOS4a allele than in those without ecNOS4a allele ( P< 0.05). Multiple regression analysis showed that ecNOS4a allele and mean blood pressure were significant independent determinants for reduced FMD in all patients ( R2 = 0.122, P = 0.0025). The ecNOS4a allele was an independent determinant for reduced FMD in smokers but not in nonsmokers. These results suggest that ecNOS4a allele is a genetic risk factor for endothelial dysfunction in diabetic patients, especially in smokers.
Echocardiographic measurement of cardiac output in rats
Authors: Slama Michel , Susic Dinko , Varagic Jasmina , Ahn Jwari , Frohlich Edward D.
Published: March 2015

The systematic evaluation of different transthoracic echocardiographic (TTE) methods to determine cardiac output (CO) and the effect of changes in intravascular volume on echocardiographically determined indexes of cardiovascular structure in the rat has not been documented. With the use of 11 Wistar rats, simultaneous echocardiographic and thermodilution measurements of CO were compared at baseline and after blood withdrawal or transfusion at 43 different levels of intravascular volume and using 10 different echocardiographic approaches. The best correlation ( r = 0.93; P < 0.0001), least bias (−3 ml/min), and best precision (16 ml/min) between thermodilution and echocardiographic methods were obtained at the level of aortic annulus using pulsed Doppler. In conclusion, CO could be accurately assessed in rats using TTE and pulsed Doppler at the level of the aortic annulus. This annulus was demonstrated to remain stable, but pulmonary annulus, thoracic aorta, mitral valve, and left ventricular diameters were found to be more modifiable during volumic changes.
Myogenic response of rat femoral small arteries in relation to wall structure and [Ca2+]i
Authors: Matchkov Vladimir V. , Tarasova Olga S. , Mulvany Michael J. , Nilsson Holger
Published: March 2015

The present study investigated the influence of media thickness on myogenic tone and intracellular calcium concentration ([Ca2+]i) in rat skeletal muscle small arteries. A ligature was loosely tied around one external iliac artery of 5-wk-old spontaneously hypertensive rats. At 18 wk of age, femoral artery blood pressure was 102 ± 11 mmHg ( n = 15) on the ligated side and 164 ± 6 mmHg ( n = 15) on the contralateral side. Small arteries feeding the gracilis muscle had a reduced media cross-sectional area and a reduced media-to-lumen ratio on the ligated side, where also the range of myogenic constriction was shifted to lower pressures. However, when expressed as a function of wall stress, diameter responses were nearly identical. [Ca2+]iwas higher in vessels from the ligated hindlimb at pressures above 10 mmHg, but vasoconstriction was not accompanied by changes in [Ca2+]i. Thus the myogenic constriction here seems due primarily to changes in intracellular calcium sensitivity, which are determined mainly by the force per cross-sectional area of the wall and therefore altered by changes in vascular structure.
Augmented adrenergic vasoconstriction in hypertensive diabetic obese Zucker rats
Authors: Stepp David W. , Frisbee Jefferson C.
Published: March 2015

This study examined skeletal muscle microvessel reactivity to constrictor stimuli in obese (OZR) versus lean Zucker rats (LZR). Gracilis arteries from both rat groups were isolated, cannulated with glass micropipettes, and viewed via television microscopy. Changes in vessel diameter were measured with a video micrometer. Arterial constriction to norepinephrine was elevated in OZR versus LZR, although vasoconstrictor reactivity to endothelin and angiotensin II was unaltered. Differences in reactivity between vessels of LZR and OZR were not explained by the loss of either endothelial nitric oxide synthase or β-adrenergic receptor function. Reactivity of in situ cremasteric arterioles of OZR to norepinephrine was elevated versus LZR. Treatment with prazosin increased the diameter of in vivo gracilis arteries of OZR to levels determined in LZR and also normalized blood pressure in OZR. These results suggest that the constrictor reactivity of skeletal muscle microvessels in OZR is heightened in response to α-adrenergic stimuli and that development of diabetes in OZR may be associated with impaired skeletal muscle perfusion and hypertension due to microvessel hyperreactivity in response to sympathetic stimulation.
Mechanism of cGMP contribution to the vasodilator response to NO in rat middle cerebral arteries
Authors: Yu Ming , Sun Cheng-Wen , Maier Kristopher G. , Harder David R. , Roman Richard J.
Published: March 2015

This study examined the mechanism by which cGMP contributes to the vasodilator response to nitric oxide (NO) in rat middle cerebral arteries (MCA). Administration of a NO donor, diethylaminodiazen-1-ium-1,2-dioate (DEA-NONOate), or 8-bromo-cGMP (8-BrcGMP) increased the diameter of serotonin-preconstricted MCA by 79 ± 3%. The response to DEA-NONOate, but not 8-BrcGMP, was attenuated by iberiotoxin (10−7M) or a 80 mM high-K+media, suggesting that activation of K+channels contributes to the vasodilator response to NO but not 8-BrcGMP. The effects of NO and cGMP on the vasoconstrictor response to Ca2+were also studied in MCA that were permeabilized with α-toxin and ionomycin. Elevations in bath Ca2+from 10−8to 10−5M decreased the diameter of permeabilized MCA by 76 ± 5%. DEA-NONOate (10−6M) and 8-BrcGMP (10−4M) blunted this response by 60%. Inhibition of guanylyl cyclase with 1 H-[1,2,4]oxadiazole[4,3-a] quinoxalin-1-one (10−5M) blocked the inhibitory effect of the NO donor, but not 8-BrcGMP, on Ca2+-induced vasoconstriction. 8-BrcGMP (10−4M) had no effect on intracellular Ca2+concentration ([Ca2+]i) in control, serotonin-stimulated, or α-toxin- and ionomycin-permeabilized vascular smooth muscle cells isolated from the MCA. These results indicate that the vasodilator response to NO in rat MCA is mediated by activation of Ca2+-activated K+channels via a cGMP-independent pathway and that cGMP also contributes to the vasodilator response to NO by decreasing the contractile response to elevations in [Ca2+]i.
Chronic hypoxia opposes pregnancy-induced increase in uterine artery vasodilator response to flow
Authors: Mateev Stephanie , Sillau A. Hugo , Mouser Rhonda , McCullough Robert E. , White Margueritte M. , Young David A. , Moore Lorna G.
Published: March 2015

We tested the hypotheses that pregnancy increases the uterine artery (UA) vasodilator response to flow and that this increase is impaired under conditions of chronic hypoxia (30 days, simulated elevation 3,960 m). UA were isolated from 24 normoxic or chronically hypoxic midpregnant guinea pigs and studied with the use of pressure myography. Normoxic pregnancy increased UA flow vasodilator response and protected against a rise in wall shear stress (WSS). Chronic hypoxia opposed these effects, prompting vasoconstriction at high flow and increasing WSS above levels seen in normoxic pregnant UA. The nitric oxide synthase inhibitor N G-nitro-l-arginine (l-NNA) eliminated the pregnancy-associated increase in flow vasodilation in normoxic UA, suggesting that increased nitric oxide production was responsible. The considerable residual vasodilation after nitric oxide synthase and cyclooxygenase inhibition implicated endothelial-derived hyperpolarizing factor (EDHF) as an additional contributor to flow vasodilation.l-NNA increased flow vasodilation in UA from chronically hypoxic animals, suggesting that chronic hypoxia may have lowered EDHF or elevated peroxynitrite production. In conclusion, flow is an important physiological vasodilator for the acute and more chronic UA dimensional changes required to increase uteroplacental blood flow during normal pregnancy. Chronic hypoxia may be a mechanism that opposes the pregnancy-associated rise in UA flow vasodilation, thereby increasing the incidence of preeclampsia and intrauterine growth restriction at a high altitude.
α-Adrenergic response and myofilament activity in mouse hearts lacking PKC phosphorylation sites on cardiac TnI
Authors: Montgomery David E. , Wolska Beata M. , Pyle W. Glen , Roman Brian B. , Dowell Jasmine C. , Buttrick Peter M. , Koretsky Alan P. , Del Nido Pedro , Solaro R. John
Published: March 2015

Protein kinase C (PKC)-mediated phosphorylation of cardiac myofilament (MF) proteins has been shown to depress the actomyosin interaction and may be important during heart failure. Biochemical studies indicate that phosphorylation of Ser43and Ser45of cardiac troponin I (cTnI) plays a substantial role in the PKC-mediated depression. We studied intact and detergent-extracted papillary muscles from nontransgenic (NTG) and transgenic (TG) mouse hearts that express a mutant cTnI (Ser43Ala, Ser45Ala) that lacks specific PKC-dependent phosphorylation sites. Treatment of NTG papillary muscles with phenylephrine (PE) resulted in a transient increase and a subsequent 62% reduction in peak twitch force. TG muscles showed no transient increase and only a 45% reduction in force. There was a similar difference in maximum tension between NTG and TG fiber bundles that had been treated with a phorbol ester and had received subsequent detergent extraction. Although levels of cTnI phosphorylation correlated with these differences, the TG fibers also demonstrated a decrease in phosphorylation of cardiac troponin T. The PKC-specific inhibitor chelerythrine inhibited these responses. Our data provide evidence that specific PKC-mediated phosphorylation of Ser43and Ser45of cTnI plays an important role in regulating force development in the intact myocardium.
Gender dimorphic tissue perfusion response after acute hemorrhage and resuscitation: role of vascular endothelial cell function
Authors: Ba Zheng F. , Kuebler Joachim F. , Rue Loring W. , Bland Kirby I. , Wang Ping , Chaudry Irshad H.
Published: March 2015

Proestrous female rodents are protected from the deleterious effects of trauma-hemorrhage that are observed in males. We hypothesized that the gender dimorphic outcome after trauma-hemorrhage might be related to gender differences in endothelial function and organ perfusion under such conditions. Male and cycle-matched proestrous female Sprague-Dawley rats underwent a midline laparotomy, hemorrhagic shock (40 mmHg for ∼90 min), and resuscitation (Ringer lactate, 4× shed blood volume over 60 min). Various parameters were measured 2 h after completion of resuscitation. In the first set of animals, the left ventricle was cannulated and heart performance (maximal rate of left ventricular pressure increase) as well as cardiac output and organ perfusion rates were determined with 85Sr microspheres. In the second set of animals, aortic vessel rings were harvested and relaxation in response to acetylcholine and nitroglycerin was measured. In the third set of animals, in situ isolated small intestine was perfused to measure the response of the splanchnic vessel bed to acetylcholine and nitroglycerin. After trauma-hemorrhage and resuscitation, females maintained cardiac output and demonstrated increased splanchnic and cardiac perfusion compared with males. Moreover, female intestines did not manifest the endothelial dysfunction that was observed in male intestines after hemorrhagic shock. We conclude that proestrous females show improved endothelial function and tissue perfusion patterns after hemorrhagic shock and that this gender-specific response might be a potential mechanism contributing to the beneficial effects of the proestrus stage under such conditions.
Palmitate-induced apoptosis in neonatal cardiomyocytes is not dependent on the generation of ROS
Authors: Hickson-Bick Diane L. M. , Sparagna Genevieve C. , Buja L. Maximilian , McMillin Jeanie B.
Published: March 2015

The saturated fatty acid palmitate induces apoptosis in neonatal rat cardiomyocytes. This apoptosis is associated with early mitochondrial release of cytochrome c and a subsequent loss of mitochondrial membrane potential. Recent reports implicate a role for reactive oxygen species (ROS) in palmitate-induced apoptosis. We studied the role of ROS in palmitate-induced apoptosis in the neonatal rat cardiomyocyte and report no evidence of ROS involvement. ROS production, nitric oxide production, and nuclear factor-κB activation were not increased above those observed using the nonapoptotic fatty acid oleate. Indeed, the production of ROS was significantly higher in cells treated with oleate. Furthermore, the presence of antioxidants and ROS scavengers did not attenuate the induction of apoptosis by palmitate. Variations in the fatty acid-to-albumin ratio from 2:1 to 7:1 had no effect on the absence of ROS production or on the extent of apoptosis. No evidence was found for an increase in oxidative protein modification in palmitate-treated cells. Our results lead us to conclude that oxidative stress does not play a role in palmitate-induced apoptosis.