bluuebunny/crossref_metadata_2025 huggingface dataset:
Short-term hibernation in adult cardiomyocytes is Po2dependent and Ca2+mediated
Authors: Stumpe Thomas , Schrader Jürgen
Published: December 2017

The mechanism of myocardial hibernation, the reversible downregulation of contractile activity on reduction of coronary flow with unchanged cardiac energetics, is presently not understood. The oxygen consumption (V˙o2), shortening fraction (Δ L), energy status [phosphocreatine (PCr), ATP, and adenosine and lactate release], and free intracellular Ca2+concentration ([Ca2+]i) were measured in isolated rat cardiomyocytes at precisely controlled ambient Po2(Oxystat). When Po2was reduced from 25 to 6 mmHg, V˙o2decreased by 50%, while Δ L was downregulated from 11.2 ± 4.1 to 7.6 ± 4.0%, and energy status was unchanged in the steady state (observation time 12 min). Only transiently PCr decreased, and lactate and adenosine release increased. Further reduction of Po2(to 3 mmHg) reducedV˙o2by 80%, decreased PCr by 35%, moderately increased adenosine and lactate release, and progressively reduced Δ L by 50% (to 5.6 ± 3.3%). All parameters fully recovered during reoxygenation. Po2-dependent downregulation of Δ Lwas accompanied by a progressive reduction in systolic [Ca2+]i(from 512 ± 110 to 357 ± 91 nmol/l at 6 mmHg and to 251 ± 69 nmol/l at 3 mmHg), whereas diastolic free [Ca2+]iremained unchanged. Therefore, the mechanism of the reversible, Po2-dependent downregulation of contractile activity (myocardial hibernation) involves a substantial reduction of systolic calcium.
Activation of the heat shock response: relationship to energy metabolites. A31P NMR study in rat hearts
Authors: Chang J. , Knowlton A. A. , Xu F. , Wasser J. S.
Published: December 2017

Heat shock factor (HSF), the transcription factor for the heat shock proteins, is activated by cardiac ischemia, but the mechanism of activation is unknown. Ischemia is accompanied by changes in the energy state and acid-base conditions. We hypothesized that decreased ATP and/or intracellular pH (pHi) might activate HSF. To test this hypothesis, we perfused rat hearts within an NMR spectrometer. NMR data showed that after 6.5, 13, and 20 min of ischemia, ATP dropped to 62.7, 23.1, and 6.9% of the control level, and pHiwas 6.16, 5.94, and 5.79, respectively. Reperfusion after ischemia partially restored ATP levels, and this was associated with greater activation of HSF1. HSF1 was also activated after 6.5 min of ischemia. Activation of HSF1 was less after 13 min of ischemia and barely detectable after 20 min of ischemia. In conclusion, 1) a moderate decrease in intracellular ATP correlates with activation of HSF1 in the heart; and 2) a severe depletion in ATP correlates with an attenuation in HSF1 activation, and the restoration of ATP leads to greater activation of HSF1, suggesting that a critical ATP level is required for activation of HSF1.
New double-tracer digital radiography for analysis of spatial and temporal myocardial flow heterogeneity
Authors: Matsumoto Takeshi , Tachibana Hiroyuki , Ogasawara Yasuo , Kajiya Fumihiko
Published: December 2017

A new high-resolution digital radiographic technique based on the deposition of125I- and3H-labeled desmethylimipramine (IDMI and HDMI, respectively) was developed for the assessment of spatial and temporal myocardial flow heterogeneity at a microvascular level. The density distributions of two tracers, or relative flow distributions, were determined by subtraction digital radiography using two imaging plates of different sensitivity. The regions resolved are comparable in size to vascular regulatory units (400 × 400 μm2). This method was applied to the measurement of within-layer myocardial flow distributions in Langendorff-perfused rabbit hearts. The validity of this method was confirmed by the strong correlation between regional densities of two tracers injected simultaneously ( r = 0.89 ± 0.03, n = 8). The temporal flow stability was evaluated by a 90-s continuous IDMI injection and subsequent bolus HDMI injection ( n = 8). Regional densities of the two tracers were fairly correlated ( r = 0.86 ± 0.03), indicating that the spatial pattern of flow distribution was stable even at a microvascular level over a 90-s period. The effect of microsphere embolization on the flow distribution was also investigated by the sequential injections of IDMI, 15-μm microspheres, and HDMI at 20-s intervals ( n = 8). Microembolization increased the coefficient of variation of tracer density from 19 to 25% ( P < 0.05), whereas the regional densities of two tracers were still correlated substantially, as in the case of no embolization ( r = 0.84 ± 0.06). Thus the microsphere embolization enhanced flow heterogeneity with increasing flow differences between control high-flow and control low-flow regions but rather maintained the pattern of flow distribution. In conclusion, double-tracer digital radiography will be a promising method for the spatial and temporal myocardial flow analysis at microvascular levels.
Adenosine A2A receptors mediate cardiovascular responses to hypoxia in fetal sheep
Authors: Koos Brian J. , Maeda Takatsugu
Published: December 2017

Nonselective adenosine (ADO) receptor antagonists block hypoxia-induced bradycardia and hypertension in fetal sheep. This study was designed to determine the ADO receptor subtype that is involved in these cardiovascular responses. In chronically catheterized fetal sheep (>0.8 term), fetal hypoxemia was induced by having the ewe breathe a hypoxic gas mixture (9% O2-3% CO2-88% N2) for 1 h. Intra-arterial infusion of ZM-241385, an antagonist highly selective for ADO A2A receptors, to eight fetuses during normoxia significantly increased mean arterial pressure (MAP) from 42.5 ± 2.0 to 46.1 ± 2.0 mmHg without altering heart rate (HR). Infusion of a selective antagonist of ADO A1receptors [1,3-dipropyl-8-cyclopentylxanthine (DPCPX)] elevated MAP and HR only after the infusion was terminated, although administration of the vehicle for ZM-241385 or DPCPX had no effect on MAP or HR. Isocapnic hypoxia with infusion of DPCPX or the vehicle for DPCPX or ZM-241385 produced a transient fall in HR, a rise in MAP, and a decrease in plasma volume. In contrast, ADO A2A receptor blockade abolished the hypoxia-induced bradycardia and hypertension and blunted the decline in plasma volume. We conclude that fetal ADO A2A receptors: 1) modulate AP during normoxia, and 2) mediate cardiovascular responses during acute O2 deficiency.
Vascular NAD(P)H oxidase is distinct from the phagocytic enzyme and modulates vascular reactivity control
Authors: Souza Heraldo P. , Laurindo Francisco R. M. , Ziegelstein Roy C. , Berlowitz Carlos O. , Zweier Jay L.
Published: December 2017

An NAD(P)H oxidase has been hypothesized to be the main source of reactive oxygen species (ROS) in vessels; however, questions remain about its function and similarity with the neutrophil oxidase. Therefore, vascular superoxide generation was measured by electron paramagnetic resonance spectroscopy using the spin-trap 5,5′-dimethly-pyrroline- N-oxide in aortas from wild-type (WT) and gp91phox-deficient mice (gp91phox−/−), which do not have a functioning neutrophil NADPH oxidase. There was no significant difference between radical adduct formation by WT or gp91phox−/− mouse aortas either at baseline or after stimulation with NADPH or NADH. Also, spin-adduct formation was identical in the 100,000- g pellets obtained from WT and gp91phox−/− mouse aortas. SOD mimetics and the flavoenzyme inhibitor diphenyleneiodonium blocked spin-adduct formation from both intact vessels and particulate fractions. Other pharmacological inhibitors of metabolic pathways involved in ROS generation had no effect on this phenomenon. To examine the role of this enzyme in vascular tone control, aortic rings were suspended in organ chambers and preconstricted with phenylephrine to reach half-maximal contraction. Exposure to NADPH elicited a 20% increase in vascular tone, which was decreased by SOD mimetics in a concentration-dependent manner, suggesting that superoxide was responsible for this phenomenon. NADH had no effect on vascular tone. Thus superoxide is generated in the vessel wall by an NAD(P)H-dependent oxidase, which modulates vascular contractile tone. This enzyme is structurally and genetically distinct from the neutrophil NADPH oxidase.
Role of protein kinase C-ε in hypertrophy of cultured neonatal rat ventricular myocytes
Authors: Strait James B. , Martin Jody L. , Bayer Allison , Mestril Ruben , Eble Diane M. , Samarel Allen M.
Published: December 2017

Using adenovirus (Adv)-mediated overexpression of constitutively active (ca) and dominant-negative (dn) mutants, we examined whether protein kinase C (PKC)-ε, the major novel PKC isoenzyme expressed in the adult heart, was necessary and/or sufficient to induce specific aspects of the hypertrophic phenotype in low-density, neonatal rat ventricular myocytes (NRVM) in serum-free culture. Adv-caPKC-ε did not increase cell surface area or the total protein-to-DNA ratio. However, cell shape was markedly affected, as evidenced by a 67% increase in the cell length-to-width ratio and a 17% increase in the perimeter-to-area ratio. Adv-caPKC-ε also increased atrial natriuretic factor (ANF) and β-myosin heavy chain (MHC) mRNA levels 2.5 ± 0.3- and 2.1 ± 0.2-fold, respectively, compared with NRVM infected with an empty, parent vector ( P < 0.05 for both). Conversely, Adv-dnPKC-ε did not block endothelin-induced increases in cell surface area, the total protein-to-DNA ratio, or upregulation of β-MHC and ANF gene expression. However, the dominant-negative inhibitor markedly suppressed endothelin-induced extracellular signal-regulated kinase (ERK) 1/2 activation. Taken together, these results indicate that caPKC-ε overexpression alters cell geometry, producing cellular elongation and remodeling without a significant, overall increase in cell surface area or total protein accumulation. Furthermore, PKC-ε activation and downstream signaling via the ERK cascade may not be necessary for cell growth, protein accumulation, and gene expression changes induced by endothelin.
HOE-642 (cariporide) alters pHi and diastolic function after ischemia during reperfusion in pig hearts in situ
Authors: Portman Michael A. , Panos Anthony L. , Xiao Yun , Anderson David L. , Ning Xue-Han
Published: December 2017

The specific Na+/H+ exchange inhibitor HOE-642 prevents ischemic and reperfusion injury in the myocardium. Although this inhibitor alters H+ ion flux during reperfusion in vitro, this action has not been confirmed during complex conditions in situ. Myocardial intracellular pH (pHi) and high-energy phosphates were monitored using 31P magnetic resonance spectroscopy in open-chest pigs supported by cardiopulmonary bypass during 10 min of ischemia and reperfusion. Intravenous HOE-642 (2 mg/kg; n = 8) administered before ischemia prevented the increases in diastolic stiffness noted in control pigs ( n = 8), although it did not alter the postischemic peak-elastance or pressure-rate product measured using a distensible balloon within the left ventricle. HOE-642 induced no change in pHi during ischemia but caused significant delays in intracellular realkalinization during reperfusion. HOE-642 did not alter phosphocreatine depletion and repletion but did improve ATP preservation. Na+/H+ exchange inhibition through HOE-642 delays intracellular alkalinization in the myocardium in situ during reperfusion in association with improved diastolic function and high-energy phosphate preservation.
Cardiac sympathetic overactivity and decreased baroreflex sensitivity in l-NAME hypertensive rats
Authors: Souza Hugo C. D. , Ballejo Gustavo , Salgado Maria Cristina O. , Dias Da Silva Valdo J. , Salgado Helio C.
Published: December 2017

The present study evaluated the possible changes in the autonomic control of heart rate in the hypertensive model induced by the inhibition of nitric oxide synthase. Rats were treated with N G-nitro-l-arginine methyl ester (l-NAME group) in the drinking water during 7 days, whereas control groups were treated with tap water (control group) or with the N G-nitro-d-arginine methyl ester (d-NAME group), an inactive isomer of thel-NAME molecule. The l-NAME group developed hypertension and tachycardia. The sequential blockade of the autonomic influences with propranolol and methylatropine indicated that the intrinsic heart rate did not differ among groups and revealed a sympathetic overactivity in the control of heart rate in thel-NAME group. The spectral density power of heart rate, calculated using fast-Fourier transformation, indicated a reduced variability in the low-frequency band (0.20–0.60 Hz) for thel-NAME group. The baroreflex sensitivity was also attenuated in these animals when compared with the normotensive control or d-NAME group. Overall, these data indicate cardiac sympathetic overactivity associated with a decreased baroreflex sensitivity in l-NAME hypertensive rats.
Potent vasodilator responses to human urotensin-II in human pulmonary and abdominal resistance arteries
Authors: Stirrat Alison , Gallagher Marie , Douglas Stephen A. , Ohlstein Eliot H. , Berry Colin , Kirk A. , Richardson M. , MacLean Margaret R.
Published: December 2017

The peptide human urotensin-II (hUT-II) and its receptor have recently been cloned. The vascular function of this peptide in humans, however, has yet to be determined. Vasoconstrictor and vasodilator responses to hUT-II were investigated in human small muscular pulmonary arteries [∼170 μm internal diameter (ID)] and human abdominal resistance arteries (∼200 μm ID). Vasodilator responses were investigated in endothelin-1 (3 nM) precontracted vessels and, in the small pulmonary vessels, compared with the known vasodilators adrenomedullin, sodium nitroprusside, and acetylcholine. In human small pulmonary arteries, hUT-II did not induce vasoconstriction but was a potent vasodilator [−log M concentration causing 50% of the maximum vasodilator effect (pIC50) 10.4 ± 0.5; percentage of reduction in tone ( E max) 81 ± 8% (vs. 23 ± 11% in time controls), n = 5]. The order of potency for vasodilation was human urotensin-II = adrenomedullin (pIC50 10.1 ± 0.4, n = 6) > sodium nitroprusside (pIC50 7.4 ± 0.2, n = 6) = acetylcholine (pIC50 6.8 ± 0.3, n = 6). In human abdominal arteries, hUT-II did not induce vasoconstriction but was a potent vasodilator [pIC50 10.3 ± 0.7; E max96 ± 8% (vs. 43 ± 16% in time controls), n = 4]. This is the first report that hUT-II is a potent vasodilator but not a vasoconstrictor of human small pulmonary arteries and systemic resistance arteries.
Modulation of early [Ca2+]irise in metabolically inhibited endothelial cells by xestospongin C
Authors: Schäfer M. , Bahde D. , Bosche B. , Ladilov Y. , Schäfer C. , Piper H. M. , Noll T.
Published: December 2017

When energy metabolism is disrupted, endothelial cells lose Ca2+from endoplasmic reticulum (ER) and the cytosolic Ca2+concentration ([Ca2+]i) increases. The importance of glycolytic energy production and the mechanism of Ca2+loss from the ER were analyzed. Endothelial cells from porcine aorta in culture and in situ were used as models. 2-Deoxy-d-glucose (2-DG, 10 mM), an inhibitor of glycolysis, caused an increase in [Ca2+]i(measured with fura 2) within 1 min when total cellular ATP contents were not yet affected. Stimulation of oxidative energy production with pyruvate (5 mM) did not attenuate this 2-DG-induced rise of [Ca2+]i, while this maneuver preserved cellular ATP contents. The inhibitor of ER-Ca2+-ATPase, thapsigargin (10 nM), augmented the 2-DG-induced rise of [Ca2+]i. Xestospongin C (3 μM), an inhibitor of d- myo-inositol 3-phosphate [Ins(3) P]-sensitive ER-Ca2+release, abolished the rise. The results demonstrate that the ER of endothelial cells is very sensitive to glycolytic metabolic inhibition. When this occurs, the ER Ca2+store is discharged by opening of the Ins(3) P-sensitive release channel. Xestospongin C can effectively suppress the early [Ca2+]irise in metabolically inhibited endothelial cells.
Slow delayed rectifier current and repolarization in canine cardiac Purkinje cells
Authors: Han Wei , Wang Zhiguo , Nattel Stanley
Published: December 2017

Although cardiac Purkinje cells (PCs) are believed to be the source of early afterdepolarizations generating ventricular tachyarrhythmias in long Q-T syndromes (LQTS), the ionic determinants of PC repolarization are incompletely known. To evaluate the role of the slow delayed rectifier current ( I Ks) in PC repolarization, we studied PCs from canine ventricular false tendons with whole cell patch clamp (37°C). Typical I Ks voltage- and time-dependent properties were noted. Isoproterenol enhanced I Ks in a concentration-dependent fashion (EC50 ∼ 30 nM), negatively shifted I Ks activation voltage dependence, and accelerated I Ks activation. Block of I Ks with 293B did not alter PC action potential duration (APD) in the absence of isoproterenol; however, in the presence of isoproterenol, 293B significantly prolonged APD. We conclude that, without β-adrenergic stimulation, I Ks contributes little to PC repolarization; however, β-adrenergic stimulation increases the contribution of I Ks by increasing current amplitude, accelerating I Ks activation, and shifting activation voltage toward the PC plateau voltage range. I Ks may therefore provide an important “braking” function to limit PC APD prolongation in the presence of β-adrenergic stimulation.
Inflammatory pain alters blood-brain barrier permeability and tight junctional protein expression
Authors: Huber J. D. , Witt K. A. , Hom S. , Egleton R. D. , Mark K. S. , Davis T. P.
Published: December 2017

Effects of inflammatory pain states on functional and molecular properties of the rat blood-brain barrier (BBB) were investigated. Inflammation was produced by subcutaneous injection of formalin, λ-carrageenan, or complete Freund's adjuvant (CFA) into the right hind paw. In situ perfusion and Western blot analyses were performed to assess BBB integrity after inflammatory insult. In situ brain perfusion determined that peripheral inflammation significantly increased the uptake of sucrose into the cerebral hemispheres. Capillary depletion and cerebral blood flow analyses indicated the perturbations were due to increased paracellular permeability rather than vascular volume changes. Western blot analyses showed altered tight junctional protein expression during peripheral inflammation. Occludin significantly decreased in the λ-carrageenan- and CFA-treated groups. Zonula occluden-1 expression was significantly increased in all pain models. Claudin-1 protein expression was present at the BBB and remained unchanged during inflammation. Actin expression was significantly increased in the λ-carrageenan- and CFA-treated groups. We have shown that inflammatory-mediated pain alters both the functional and molecular properties of the BBB. Inflammatory-induced changes may significantly alter delivery of therapeutic agents to the brain, thus affecting dosing regimens during chronic pain.
Keratinocyte growth factor attenuates hydrostatic pulmonary edema in an isolated, perfused rat lung model
Authors: Welsh David A. , Guery Benoit P. H. , Deboisblanc Bennett P. , Dobard Elizabeth P. , Creusy Colette , Mercante Donald , Nelson Steve , Summer Warren R. , Mason Carol M.
Published: December 2017

Hydrostatic pulmonary edema is a common complication of congestive heart failure, resulting in substantial morbidity and mortality. Keratinocyte growth factor (KGF) is a mitogen for type II alveolar epithelial and microvascular cells. We utilized the isolated perfused rat lung model to produce hydrostatic pulmonary edema by varying the left atrial and pulmonary capillary pressure. Pretreatment with KGF attenuated hydrostatic edema formation. This was demonstrated by lower wet-to-dry lung weight ratios, histological evidence of less alveolar edema formation, and reduced alveolar accumulation of intravascularly administered FITC-labeled large-molecular-weight dextran in rats pretreated with KGF. Thus KGF attenuates injury in this ex vivo model of hydrostatic pulmonary edema via mechanisms that prevent increases in alveolar-capillary permeability.
Heterogeneity of laser Doppler flowmetry in perfused muscle indicative of nutritive and nonnutritive flow
Authors: Clark Andrew D. H. , Youd Joanne M. , Rattigan Stephen , Barrett Eugene J. , Clark Michael G.
Published: December 2017

Laser Doppler flowmetry (LDF) signal responses have been compared with metabolic changes using both a surface macroprobe and randomly placed implantable microprobes in muscles of the constant-flow-perfused rat hindlimb. Changes in response to total flow and to vasoconstrictors that are known to increase (norepinephrine, NE) or decrease (serotonin, 5-HT) hindlimb oxygen uptake were assessed. The surface macroprobe (anterior end of biceps femoris) identified only one type of LDF response characterized by increased signal in response to NE and decreased signal in response to 5-HT. Implanted microprobes (tibialis, gastrocnemius, vastus, or bicep femoris) identified sites that gave three LDF responses of differing character. These responses were where the LDF signal increased with NE and decreased with 5-HT (56.7%), where the LDF signal decreased with NE and increased with 5-HT (16.5%), or where there was no net response to either vasoconstrictor (24.7%). The data are consistent with discrete regions of nutritive and nonnutritive flow in muscle where flow in each as controlled by vasoconstrictors relates directly to the metabolic behavior of the tissue.
Endogenous estrogen mediates vascular reactivity and distensibility in pregnant rat mesenteric arteries
Authors: Zhang Yunlong , Stewart Ken G. , Davidge Sandra T.
Published: December 2017

The role of estrogen in the maternal systemic cardiovascular adaptations during pregnancy is still controversial. Female Sprague-Dawley rats were implanted at day 14 of pregnancy with either a 50-mg tamoxifen pellet (estrogen receptor blocker, n = 10) or placebo pellet ( n = 10). Virgin female rats were a nonpregnant control ( n = 7). At days 20–22 of pregnancy, resistance-sized mesenteric arteries were mounted onto a dual-chamber arteriograph system. Pregnancy significantly blunted the pressor response to phenylephrine [measurement of the effective concentration that yielded 50% maximum response (EC50) values were 1.5 ± 0.22 vs. 0.69 ± 0.16 μM ( P < 0.05)] and enhanced vasodilation to ACh [EC50 = 1.13 ± 2.53 vs. 3.13 ± 6.04 nM ( P < 0.05)] compared with nonpregnant rats. However, tamoxifen treatment during pregnancy reversed these effects. Inhibition of nitric oxide (NO) synthase with N G-monomethyl-l-arginine (250 μM) shifted only the responses of the placebo-treated pregnant group to both phenylephrine and ACh. Arterial distensibility in the placebo-treated pregnant group was also significantly increased ( P < 0.05) compared with nonpregnant and tamoxifen-treated pregnant animals. In summary, endogenous estrogen during pregnancy increases NO-dependent modulation of vessel tone and arterial distensibility.
RI in central retinal artery as assessed by CDI does not correspond to retinal vascular resistance
Authors: Polska Elzbieta , Kircher Karl , Ehrlich Paulina , Vecsei Pia V. , Schmetterer Leopold
Published: December 2017

The aim of the present study was to investigate the association between ultrasound Doppler measurements of resistive index (RI) in the central retinal artery and retinal vascular resistance ( R) assessed with laser Doppler velocimetry, vessel size measurement, and calculation of ocular perfusion pressure (PP) in healthy subjects. An increase in vascular resistance was induced by inhalation of 100% O2. During hyperoxia no significant changes in PP were observed. Mean flow velocity in main retinal veins was reduced by −27.5 ± 2.0%. The average decrease in diameter was −11.5 ± 1.0%. R, which was calculated as the ratio of PP to flow rate, increased by 97.6 ± 7.7%. RI increased as well, but the effect was much smaller (6.6 ± 2.2%). In addition, a negative correlation was found between baseline values of R and RI ( r = −0.83). During hyperoxia R and RI were not associated. In conclusion, our data indicate that RI as assessed with color Doppler imaging in the central retinal artery is not an adequate measure of R.
Infinite number of solutions to the hemodynamic inverse problem
Authors: Quick Christopher M. , Young William L. , Noordergraaf Abraham
Published: December 2017

Investigators have had much success solving the “hemodynamic forward problem,” i.e., predicting pressure and flow at the entrance of an arterial system given knowledge of specific arterial properties and arterial system topology. Recently, the focus has turned to solving the “hemodynamic inverse problem,” i.e., inferring mechanical properties of an arterial system from measured input pressure and flow. Conventional methods to solve the inverse problem rely on fitting to data simple models with parameters that represent specific mechanical properties. Controversies have arisen, because different models ascribe pressure and flow to different properties. However, an inherent assumption common to all model-based methods is the existence of a unique set of mechanical properties that yield a particular pressure and flow. The present work illustrates that there are, in fact, an infinite number of solutions to the hemodynamic inverse problem. Thus a measured pressure-flow pair can result from an infinite number of different arterial systems. Except for a few critical properties, conventional approaches to solve the inverse problem for specific arterial properties are futile.
Interstitial exclusion of positively and negatively charged IgG in rat skin and muscle
Authors: Wiig Helge , Tenstad Olav
Published: December 2017

Volume exclusion, i.e., the space not available for a specific probe, may be dependant on the probe charge. Therefore, interstitial exclusion was measured for positively and negatively charged immunoglobulin (IgG) in skin and muscle of rats by using a continuous infusion method (30). Steady-state concentration of125I-labeled IgG 1 (pI = 8.7) and131I- labeled IgG 4 (pI = 6.6) was maintained by infusion of tracer for 120–168 h with an implanted osmotic pump. At the end of the infusion period and before tissue sampling, the rat was anesthetized and nephrectomized, and51Cr-labeled EDTA was injected and allowed 4 h for equilibration to measure interstitial fluid volume (Vi). Interstitial fluid was isolated from skin and muscle by using nylon wicks implanted post mortem. The relative IgG available space was measured as the ratio between labeled IgG and51Cr-labeled EDTA wick fluid equivalent spaces, and relative excluded volume fraction (Ve/Vi) was calculated as 1 − Va/Vi. Ve/Viin hindlimb skin averaged 0.37 ± 0.05 (SE) and 0.65 ± 0.06 ( P < 0.01) for IgG 1 and 4, respectively, with corresponding figures of 0.24 ± 0.05 and 0.51 ± 0.04 ( P < 0.01) in hindlimb muscle ( n = 9 for both tissues). These experiments suggest that fixed negative charges, most likely glycosaminoglycans, influence distribution of macromolecules in the interstitium and therefore affect interstitial fluid balance.
Remodeling of the zero-stress state of femoral arteries in response to flow overload
Authors: Lu X. , Zhao J. B. , Wang G. R. , Gregersen H. , Kassab G. S.
Published: December 2017

The goal of this study is to quantitatively describe the remodeling of the zero-stress state of the femoral artery in flow overload. Increased blood flow, approximately as a unit step change, was imposed on the femoral artery by making an arteriovenous (a-v) fistula with the epigastric vein. The a-v fistula was created in the right leg of 36 rats, which were divided equally into six groups (2 days and 1, 2, 4, 8, and 12 wk after the fistula). The vessels in the left leg were used as controls without operative trauma. The in vivo blood pressure, flow, and femoral outer diameter and the in vitro zero-stress state geometry were measured. The in vivo shear rate at the endothelial surface increased approximately as a step function by ∼83%, after 2 days, compared with the control artery. The arterial luminal and wall area significantly increased postsurgically from 0.15 ± 0.02 and 0.22 ± 0.02 mm2 to 0.28 ± 0.04 and 0.31 ± 0.05 mm2, respectively, after 12 wk. The wall thickness did not change significantly over time ( P > 0.1). The opening angle decreased to 82 ± 4.2 degrees postsurgically when compared with controls (102 ± 4.4) after 12 wk and correlated linearly with the thickness-to-radius ratio. Histological analysis revealed vascular smooth muscle cell growth. The remodeling data are expressed mathematically in terms of indicial functions, i.e., change of a particular feature of a blood vessel in response to a unit step change of blood flow. The indicial function approach provides a quantitative description of the remodeling process in the blood vessel wall.
Effect of NO donors on protein phosphorylation in intact vascular and nonvascular smooth muscles
Authors: Hennan James K. , Diamond Jack
Published: December 2017

It is generally well accepted that nitrovasodilator-induced relaxation of vascular smooth muscle involves elevation of cGMP and activation of a specific cGMP-dependent protein kinase [protein kinase G (PKG)]. However, the protein targets of PKG and the underlying mechanisms by which this kinase leads to a relaxant response have not been elucidated. Several types of smooth muscle, including rat myometrium and vas deferens, are not relaxed by sodium nitroprusside, even at concentrations that produce marked elevation of cGMP and activation of PKG. The main objective of our studies was to compare PKG-mediated protein phosphorylation in intact rat aorta, rat myometrium, and rat vas deferens using two-dimensional gel electrophoresis. In intact rat aorta, seven PKG substrates were detected during relaxation of the tissue. None of the PKG substrates identified in the rat aorta appeared to be phosphorylated in the myometrium or vas deferens after administration of various cGMP-elevating agents. Thus the failure of the rat myometrium and rat vas deferens to relax in the face of cGMP elevation and PKG activation may be due to a lack of PKG substrate phosphorylation.
Detection of regional temporal abnormalities in left ventricular function during acute myocardial ischemia
Authors: Mor-Avi Victor , Collins Keith A. , Korcarz Claudia E. , Shah Milind , Spencer Kirk T. , Lang Roberto M.
Published: December 2017

Echocardiographic diagnosis of myocardial ischemia is based on visualizing hypokinesis, which occurs late in the ischemic cascade. We hypothesized that temporal changes in endocardial motion may constitute sensitive early markers of ischemia. Two protocols were performed in 19 anesthetized pigs. Protocol 1 included 54 intracoronary balloon occlusions. Transthoracic images were acquired at baseline and every 15 s during 5 min of occlusion and reperfusion. In protocol 2, ischemia was induced in 12 animals by use of graded dobutamine infusion, after creating significant partial occlusions without a resting wall motion abnormality. Systolic and diastolic endocardial motion was color encoded using color kinesis and analyzed using custom software. All ischemic episodes caused detectable and reversible changes. The earliest sign of ischemia was tardokinesis in 31/54 occlusions, whereas hypokinesis appeared first in 23/54 cases. Dobutamine-induced ischemia caused tardokinesis first in 9/12 and hypokinesis in 3/12 animals. Reversible ischemic changes in regional left ventricular performance can be objectively detected using analysis of echocardiographic images and will likely improve the early noninvasive diagnosis of acute ischemia.
Carbon monoxide wash-in method to determine gas transfer in vascular beds: application to rat hindlimb
Authors: Cho Carolyn S. L. , McLean Allan J. , Rivory Laurent P. , Gatenby Paul A. , Hardman David T. A. , Le Couteur David G.
Published: December 2017

The vascular barrier to gas transfer is an important physiological parameter; however, no readily applicable technique exists to quantitate the process. A simple technique to measure the permeability-surface area ( PS) product for gas transfer in vascular beds is proposed using wash in of carbon monoxide (CO) and Crone-Renkin analysis. Wash-in experiments were performed on the perfused hindlimbs of male Wistar rats ( n = 15) by using CO as a surrogate marker for oxygen and technetium-99m-labeled albumin as the vascular marker. The use of CO and erythrocyte-free perfusate and the collection of outflow samples into tubes preloaded with erythrocytes obviated the need for an anaerobic collection device or consideration of Hb binding in the analysis. The PS product for CO was determined from the early extraction as 0.013 ± 0.006 ml · s−1 · g−1. Compartmental analysis revealed that the fractional recovery of CO was 0.45 ± 0.14 and the volume of distribution was 2.31 ± 0.76 ml/g. This technique detected a small measurable barrier to the transfer of CO across the hindlimb vasculature and is potentially applicable to other vascular beds in health and disease.
Localized injury in cardiomyocyte network: a new experimental model of ischemia-reperfusion arrhythmias
Authors: Arutunyan Ara , Webster Daniel R. , Swift Luther M. , Sarvazyan Narine
Published: December 2017

We developed a new experimental approach to study the effects of local injury in a multicellular preparation and tested the ability of the method to induce reperfusion arrhythmias in cardiomyocyte monolayers. A small region of injury was created using geometrically defined flows of control and ischemia-like solutions. Calcium transients were acquired simultaneously from injured, control, and border zone cells using fluo 4. Superfusion with the injury solution rapidly diminished the amplitude of calcium transients within the injury zone, followed by cessation of cell beating. Reperfusion caused an immediate tachyarrhythmic response in ∼17% of experiments, with a wave front propagating from a single cell or small cell cluster within the former injury zone. Inclusion of a gap junction uncoupler (1 mM heptanol) in the injury solution narrowed the functional border and sharply increased the number of ectopic foci and the incidence of reperfusion arrhythmias. The model holds a potential to reveal both micro- and macroscopic features of propagation, conduction, and cell coupling in the normal and diseased myocardium and to serve as a new tool to test antiarrhythmic protocols in vitro.
Cardiac excitation-contraction coupling: role of membrane potential in regulation of contraction
Authors: Ferrier Gregory R. , Howlett Susan E.
Published: December 2017

The steps that couple depolarization of the cardiac cell membrane to initiation of contraction remain controversial. Depolarization triggers a rise in intracellular free Ca2+which activates contractile myofilaments. Most of this Ca2+is released from the sarcoplasmic reticulum (SR). Two fundamentally different mechanisms have been proposed for SR Ca2+release: Ca2+-induced Ca2+release (CICR) and a voltage-sensitive release mechanism (VSRM). Both mechanisms operate in the same cell and may contribute to contraction. CICR couples the release of SR Ca2+closely to the magnitude of the L-type Ca2+current. In contrast, the VSRM is graded by membrane potential rather than Ca2+current. The electrophysiological and pharmacological characteristics of the VSRM are strikingly different from CICR. Furthermore, the VSRM is strongly modulated by phosphorylation and provides a new regulatory mechanism for cardiac contraction. The VSRM is depressed in heart failure and may play an important role in contractile dysfunction. This review explores the operation and characteristics of the VSRM and CICR and discusses the impact of the VSRM on our understanding of cardiac excitation-contraction coupling.
Progressive loss of perfusion-contraction matching during sustained moderate ischemia in pigs
Authors: Schulz Rainer , Post Heiner , Neumann Till , Gres Petra , Lüss Hartmut , Heusch Gerd
Published: December 2017

It is unclear whether perfusion-contraction matching (PCM) is maintained during prolonged myocardial ischemia. In 27 anesthetized pigs, left anterior descending coronary arterial inflow was reduced to decrease an anterior work index (WI) at 5 min of hypoperfusion by 40% and then maintained at this level for 12 or 24 h. With 12 h of hypoperfusion, the myocardium remained viable in 6 of 7 pigs (with triphenyltetrazolium chloride; TTC) and with 24 h of hypoperfusion in 5 of 11 pigs (TTC, histology). The reduction in WI to 62 ± 4 and 62 ± 3% of baseline in the two groups was matched to the reduction of transmural blood flow (TBF; microspheres) at 5 min of hypoperfusion, averaging 59 ± 4 and 60 ± 2% of baseline. With prolonged hypoperfusion, WI decreased to 30 ± 5% at 12 h and 18 ± 3% at 24 h; TBF remained unchanged (53 ± 4 and 54 ± 4%). The added calcium concentration required for the half-maximal increase in WI increased from 121 ± 25 μg/ml blood at baseline to 192 ± 26 μg/ml blood at 12 h of hypoperfusion. Thus, with hypoperfusion for 24 h, PCM is progressively lost, and calcium responsiveness is reduced.
Direct biologically based biosensing of dynamic physiological function
Authors: Christini David J. , Walden Jeff , Edelberg Jay M.
Published: December 2017

Dynamic regulation of biological systems requires real-time assessment of relevant physiological needs. Biosensors, which transduce biological actions or reactions into signals amenable to processing, are well suited for such monitoring. Typically, in vivo biosensors approximate physiological function via the measurement of surrogate signals. The alternative approach presented here would be to use biologically based biosensors for the direct measurement of physiological activity via functional integration of relevant governing inputs. We show that an implanted excitable-tissue biosensor (excitable cardiac tissue) can be used as a real-time, integrated bioprocessor to analyze the complex inputs regulating a dynamic physiological variable (heart rate). This approach offers the potential for long-term biologically tuned quantification of endogenous physiological function.
Importance of PKC and PI3Ks in ethanol-induced contraction of cerebral arterial smooth muscle
Authors: Yang Zhi-Wei , Wang Jun , Zheng Tao , Altura Bella T. , Altura Burton M.
Published: December 2017

We investigated the relationships of two potential intracellular signaling pathways, protein kinase C (PKC) and phosphatidylinositol 3-kinases (PI3Ks), to ethanol-induced contractions in cerebral arteries. Ethanol (20–200 mM) induces concentration-dependent constriction in isolated canine basilar arteries that is inhibited in a concentration-dependent manner by pretreatment of these vessels with 10−9–10−3M Gö-6976 (an antagonist selective for PKC-α and PKC-βI), 10−10–10−4M bisindolylmaleimide I (a specific antagonist of PKC), and 10−10–10−4M wortmannin or 10−8–10−2M LY-294002 (selective antagonists of PI3Ks). Ethanol-induced increases in intracellular Ca2+concentration (from ∼100 to ∼500 nM) in canine basilar smooth muscle cells are also suppressed markedly (∼20–70%) in the presence of a similar concentration range of Gö-6976, bisindolymaleimide I, wortmannin, or LY-294002. This study suggests that activation of PKC isoforms and PI3Ks appears to be an important signaling pathway in ethanol-induced vasoconstriction of cerebral blood vessels.
Cerebral blood flow velocity response to induced and spontaneous sudden changes in arterial blood pressure
Authors: Panerai Ronney B. , Dawson Suzanne L. , Eames Penelope J. , Potter John F.
Published: December 2017

The influence of different types of maneuvers that can induce sudden changes of arterial blood pressure (ABP) on the cerebral blood flow velocity (CBFV) response was studied in 56 normal subjects (mean age 62 yr, range 23–80). ABP was recorded in the finger with a Finapres device, and bilateral recordings of CBFV were performed with Doppler ultrasound of the middle cerebral arteries. Recordings were performed at rest (baseline) and during the thigh cuff test, lower body negative pressure, cold pressor test, hand grip, and Valsalva maneuver. From baseline recordings, positive and negative spontaneous transients were also selected. Stability of Pco 2 was monitored with transcutaneous measurements. Dynamic autoregulatory index (ARI), impulse, and step responses were obtained for 1-min segments of data for the eight conditions by fitting a mathematical model to the ABP-CBFV baseline and transient data (Aaslid's model) and by the Wiener-Laguerre moving-average method. Impulse responses were similar for the right- and left-side recordings, and their temporal pattern was not influenced by type of maneuver. Step responses showed a sudden rise at time 0 and then started to fall back to their original level, indicating an active autoregulation. ARI was also independent of the type of maneuver, giving an overall mean of 4.7 ± 2.9 ( n = 602 recordings). Amplitudes of the impulse and step responses, however, were significantly influenced by type of maneuver and were highly correlated with the resistance-area product before the sudden change in ABP ( r = −0.93, P < 0.0004). These results suggest that amplitude of the CBFV step response is sensitive to the point of operation of the instantaneous ABP-CBFV relationship, which can be shifted by different maneuvers. Various degrees of sympathetic nervous system activation resulting from different ABP-stimulating maneuvers were not reflected by CBFV dynamic autoregulatory responses within the physiological range of ABP.
Role of endogenous opioids in ischemic preconditioning but not in short-term hibernation in pigs
Authors: Schulz Rainer , Gres Petra , Heusch Gerd
Published: December 2017

Endogenous opioids are involved in ischemic preconditioning (IP) in several species. Whether or not opioids are important for IP and short-term myocardial hibernation (STMH) in pigs is currently unknown. In 34 enflurane-anesthetized pigs, the left anterior descending coronary artery was flow constantly perfused. Subendocardial blood flow (Endo), infarct size (IS; percent area at risk), and the free energy change of ATP hydrolysis (Δ G) were determined. After 90-min severe ischemia and 120-min reperfusion, IS averaged 28.3 ± 5.4% (means ± SE) ( n = 8; Endo: 0.047 ± 0.009 ml · min−1· g−1). IP by 10-min ischemia and 15-min reperfusion reduced IS to 9.9 ± 3.8% ( P < 0.05, n = 8; Endo: 0.044 ± 0.009 ml · min−1· g−1). After naloxone (1 mg/kg iv followed by 2 μg · kg−1· min−1), IS averaged 25.8 ± 7.0% ( n = 6; Endo: 0.039 ± 0.008 ml · min−1· g−1) without and 24.7 ± 4.7% ( n = 6; Endo: 0.044 ± 0.006 ml · min−1· g−1) with IP. At 5-min moderate ischemia in the presence of naloxone, Endo decreased from 0.90 ± 0.07 to 0.28 ± 0.03 ml · min−1· g−1and Δ G decreased from −58.6 ± 1.0 to −52.6 ± 0.4 kJ/mol. Prolongation of ischemia to 90 min did not alter Endo, but Δ G recovered toward control values (57.7 ± 1.1 kJ/mol), and the myocardium remained viable. These responses are identical to those of nonnaloxone-treated pigs. Endogenous opioids are involved in IP but not in STMH in pigs.
Postischemic Na+-K+-ATPase reactivation is delayed in the absence of glycolytic ATP in isolated rat hearts
Authors: Van Emous Jan G. , Vleggeert-Lankamp Carmen L. A. M. , Nederhoff Marcel G. J. , Ruigrok Tom J. C. , Van Echteld Cees J. A.
Published: December 2017

Normalization of intracellular sodium (Na[Formula: see text]) after postischemic reperfusion depends on reactivation of the sarcolemmal Na+-K+-ATPase. To evaluate the requirement of glycolytic ATP for Na+-K+-ATPase function during postischemic reperfusion, 5-s time-resolution23Na NMR was performed in isolated perfused rat hearts. During 20 min of ischemia, Na[Formula: see text] increased approximately twofold. In glucose-reperfused hearts with or without prior preischemic glycogen depletion, Na[Formula: see text]decreased immediately upon postischemic reperfusion. In glycogen-depleted pyruvate-reperfused hearts, however, the decrease of Na[Formula: see text] was delayed by ∼25 s, and application of the pyruvate dehydrogenase (PDH) activator dichloroacetate (DA) did not shorten this delay. After 30 min of reperfusion, Na[Formula: see text]had almost normalized in all groups and contractile recovery was highest in the DA-treated hearts. In conclusion, some degree of functional coupling of glycolytic ATP and Na+-K+-ATPase activity exists, but glycolysis is not essential for recovery of Na[Formula: see text] homeostasis and contractility after prolonged reperfusion. Furthermore, the delayed Na+-K+-ATPase reactivation observed in pyruvate-reperfused hearts is not due to inhibition of PDH.
Augmentation of respiratory sinus arrhythmia in response to progressive hypercapnia in conscious dogs
Authors: Yasuma Fumihiko , Hayano Jun-Ichiro
Published: December 2017

Respiratory sinus arrhythmia (RSA) may serve to enhance pulmonary gas exchange efficiency by matching pulmonary blood flow with lung volume within each respiratory cycle. We examined the hypothesis that RSA is augmented as an active physiological response to hypercapnia. We measured electrocardiograms and arterial blood pressure during progressive hypercapnia in conscious dogs that were prepared with a permanent tracheostomy and an implanted blood pressure telemetry unit. The intensity of RSA was assessed continuously as the amplitude of respiratory fluctuation of heart rate using complex demodulation. In a total of 39 runs of hypercapnia in 3 dogs, RSA increased by 38 and 43% of the control level when minute ventilation reached 10 and 15 l/min, respectively ( P < 0.0001 for both), and heart rate and mean arterial pressure showed no significant change. The increases in RSA were significant even after adjustment for the effects of increased tidal volume, respiratory rate, and respiratory fluctuation of arterial blood pressure ( P < 0.001). These observations indicate that increased RSA during hypercapnia is not the consequence of altered autonomic balance or respiratory patterns and support the hypothesis that RSA is augmented as an active physiological response to hypercapnia.
Chemical preconditioning with 3-nitropropionic acid in hearts: role of mitochondrial KATPchannel
Authors: Ockaili Ramzi A. , Bhargava Peeyush , Kukreja Rakesh C.
Published: December 2017

We investigated the cardioprotective effect of 3-nitropropionic acid (3-NPA), an inhibitior of mitochondrial succinate dehydrogenase, and we wanted to show whether this protection is mediated by of opening mitochondrial ATP-sensitive potassium (KATP) channels. Adult rabbits were treated with either 3-NPA (3 mg/kg iv) or saline ( n = 6 rabbits/group). After 30 min (for early phase) or 24 h (for late phase) of the treatment, the animals were subjected to 30 min of ischemia and 3 h of reperfusion (ischemia-reperfusion). 5-Hydroxydecanoate (5-HD, 5 mg/kg iv),the mitochondrial KATPchannel blocker, was administered 10 min before ischemia-reperfusion in the saline- and 3-NPA-treated rabbits. 3-NPA caused a decrease in the infarct size from 27.8 ± 4.2% in the saline group to 16.5 ± 1.0% in the 3-NPA-treated rabbits during early phase and from 30.4 ± 4.2% in the saline group to 17.6 ± 1.05 in the 3-NPA group during delayed phase ( P < 0.05, % of risk area). The anti-infarct effect of 3-NPA was blocked by 5-HD as shown by an increase in infarct size to 33 ± 2.7% (early phase) and 31 ± 2.4% (delayed phase) ( P < 0.05 vs. 3-NPA groups). 5-HD had no proischemic effect in control animals. Also, 3-NPA had no effect on systemic hemodynamics. We conclude that 3-NPA induces long-lasting anti-ischemic effects via opening of mitochondrial KATPchannels.