bluuebunny/crossref_metadata_2025 huggingface dataset:
Modulation of left ventricular relaxation in isolated ejecting heart by endogenous nitric oxide
Authors: Grocott-Mason R. , Anning P. , Evans H. , Lewis M. J. , Shah A. M.
Published: December 2017

Nitric oxide (NO) modulates myocardial contractile behavior in several isolated preparations, e.g., cardiac myocytes and papillary muscles, via elevation of intracellular guanosine 3',5'-cyclic monophosphate (cGMP). We have recently reported that the exogenous NO donor, sodium nitroprusside, selectively modulates left ventricular (LV) relaxation in the isolated ejecting guinea pig heart, independent of coronary flow. We now report the effects of endogenously released NO on LV performance in this preparation (constant heart rate and loading). Both bradykinin (1 nM, n = 6) and substance P (100 nM, n = 6) accelerated early LV relaxation (maximum change in time constant, tE, -10.5 +/- 1.6 and -13.4 +/- 2.1%, respectively; both P < 0.05), without significantly altering early systolic parameters (e.g., rate of LV pressure development). These effects were inhibited by hemoglobin (P < 0.05; n > or = 6), which inactivates NO. Bradykinin (100 nM, n = 10) had an additional negative inotropic effect, which was not inhibited by hemoglobin. Neither agonist altered relaxation in isolated papillary muscles. These data suggest that endogenous NO, probably released from coronary microvascular endothelial cells, modulates LV relaxation in the intact heart.
CGRP enhances induction of NO synthase in vascular smooth muscle cells via a cAMP-dependent mechanism
Authors: Schini-Kerth V. B. , Fisslthaler B. , Busse R.
Published: December 2017

Experiments were designed to examine whether calcitonin gene-related peptide (CGRP), a potent adenosine 3',5'-cyclic monophosphate (cAMP)-dependent vasodilator, affects the production of NO evoked by interleukin-1 beta) (IL-1 beta) in cultured rat aortic smooth muscle cells (SMC). CGRP, in a concentration-dependent manner, enhanced the release of nitrite (a stable oxidation product of NO) and the formation of L-citrulline from L-arginine caused by IL-1 beta. Two cAMP-dependent vasodilators, forskolin and isoproterenol, and the activator of the cAMP-dependent protein kinase, Sp-cAMPS, also enhanced the release of nitrite and the formation of L-citrulline evoked by IL-1 beta. The enhancing effect of isoproterenol required the presence of the vasodilator during the induction of NO synthase (NOS). IL-1 beta-treated vascular SMC inhibited the aggregation of indomethacin-treated platelets. Inhibition of platelet aggregation was more marked with SMC exposed to a combination of IL-1 beta and either CGRP or isoproterenol than with cells exposed to IL-1 beta alone. This inhibition was prevented by methylene blue and oxyhemoglobin. IL-1 beta induced the expression of inducible NOS mRNA in vascular SMC, which was enhanced by coincubation of IL-1 beta with either CGRP, isoproterenol, or forskolin. These observations indicate that CGRP via a cAMP-dependent mechanism potentiates the IL-1-beta-induced production of NO by enhancing the expression of inducible NOS. Therefore CGRP may contribute to the substantial production of NO in the vasculature during septic shock, which accounts, at least in part, for the collapse of the vascular system.
Does protein kinase C play a role in ischemic preconditioning in rat hearts?
Authors: Li Y. , Kloner R. A.
Published: December 2017

Protein kinase C (PKC) has been implicated in the cardioprotective effects of ischemic preconditioning in rabbits, but whether it plays a role in rats is unknown. We tested this preconditioning PKC theory by assessing whether the inhibition of PKC with calphostin C, a potent and specific inhibitor of PKC, can block the preconditioning effects in this model. Four groups of rats were studied: 1) control + vehicle, 2) control + calphostin C, 3) preconditioning + vehicle, and 4) preconditioning + calphostin C. All rats underwent 90 min of coronary occlusion followed by 4 h of reperfusion; in addition, preconditioned rats underwent three 3-min episodes of ischemia and 5 min of reperfusion before the 90 min of ischemia. Two injections of vehicle or calphostin C (0.1 mg/kg) were administered in intravenous boluses 29 min and 3 min before the 90-min coronary occlusion, i.e., one dose was given 5 min before preconditioning, and another dose was given between preconditioning and the sustained 90 min of ischemia in preconditioned rats. After 4 h of reperfusion, the area at risk (AR) was delineated by dye injection and area of necrosis was assessed by triphenyltetrazolium chloride staining. The electrocardiogram was recorded for the incidence of ventricular tachycardia (VT) and ventricular fibrillation. AR was similar in all four groups. In the nonpreconditioned control rats receiving vehicle, myocardial infarct size expressed as a percentage of the AR averaged 45.7 +/- 1.7%. Pretreatment with calphostin C had no effect on infarct size (48.9 +/- 3.4%) in nonpreconditioned control rats.(ABSTRACT TRUNCATED AT 250 WORDS)
Soluble TNF binding proteins modulate the negative inotropic properties of TNF-alpha in vitro
Authors: Kapadia S. , Torre-Amione G. , Yokoyama T. , Mann D. L.
Published: December 2017

Soluble tumor necrosis factor (TNF) binding proteins (TNF-BPs) were characterized with respect to their capacity to modulate the negative inotropic properties of TNF-alpha in isolated contracting cardiac myocytes. Three TNF-BPs were evaluated: two natural monomeric human TNF monomeric binding proteins, TNF-BP1 and TNF-BP2, and sTNFR:Fc, a dimer of two molecules of human TNF-BP2 linked by the Fc portion of the human immunoglobulin G1 molecule. When TNF-alpha (25 pM) was allowed to form TNF-BP-TNF-alpha complexes, the negative inotropic effects of TNF-alpha were completely prevented by “neutralizing concentrations” of TNF-BPs, whereas lesser concentrations of TNF-BPs only partially attenuated the negative inotropic effects of TNF-alpha. The dimeric binding protein sTNFR:Fc was more effective on a molar basis than either of the monomeric binding proteins (TNF-BP1 or TNF-BP2) with respect to blocking the negative inotropic effects of TNF-alpha. When cardiac myocytes that had been treated with TNF-alpha (25 pM) were exposed to neutralizing concentrations of TNF-BP1, TNF-BP2, and sTNFR:Fc, the negative inotropic effects were completely reversed within 30 min. Thus these studies show for the first time that TNF-BPs are sufficient to prevent, as well as reverse, the negative inotropic properties of TNF-alpha in vitro.
Palmitoyl-L-carnitine acts like ouabain on voltage, current, and contraction in guinea pig ventricular cells
Authors: Shen J. B. , Pappano A. J.
Published: December 2017

We previously showed that palmitoyl-L-carnitine (L-PC) inhibits the Na/K pump current (INa/K). In the present report, we test the hypothesis that L-PC, like ouabain, should increase myocyte shortening. Membrane potentials or ionic currents were recorded simultaneously with cell shortening in single guinea pig ventricular myocytes at room temperature (22 degrees C). Like ouabain, L-PC (1 microM) reversibly depolarized the resting membrane, decreased action potential duration, and increased the amplitude of myocyte contractions. Neither L-PC nor ouabain had a significant effect on Ca current (ICa). When L-PC increased cell shortening during ramp voltage clamp, membrane current shifted inward at voltages negative to -20 mV and shifted outward at more positive voltages. Similar to toxic concentrations of ouabain, L-PC induced transient inward currents and aftercontractions. At concentrations that inhibit INa/K, L-PC acted like ouabain to produce characteristic effects on membrane potentials, currents, and cell contractions that were unrelated to significant changes in ICa. L-PC reduces surface negative charge of erythrocytes and myocytes (C. Gruver and A. J. Pappano, J. Mol. Cell. Cardiol. 25: 1275–1284, 1993), and we speculate that L-PC inhibits INa/K by this mechanism.
Effects of anoxia on intracellular Ca2+ and contraction in isolated guinea pig cardiac myocytes
Authors: Seki S. , MacLeod K. T.
Published: December 2017

Single, enzymatically isolated guinea pig ventricular myocytes were exposed to 3-min periods of anoxia with glucose-free Tyrode solution containing 1 mM sodium dithionite (Na2S2O4) and were then reoxygenated for 10 min. The myocytes were exposed to rapid applications of 10 mM caffeine during the control, anoxic, and reoxygenation periods. Intracellular Ca2+ concentration ([Ca2+]i) was measured ratiometrically using indo 1 with simultaneous measurements of cell length. The effects of anoxia on Ca2+ were compared with those of hypoxia and metabolic inhibition. The amplitude of the electrically stimulated (Ca transient) and caffeine-evoked Ca2+ (Caff-Ca) transients decreased during anoxia and recovered after reoxygenation. Diastolic [Ca2+]i did not change during 3 min of anoxia but rose progressively after prolonged anoxia and remained at this higher level on reoxygenation. During metabolic inhibition the Ca transients decreased, while the Caff-Ca transients showed no change in amplitude. During hypoxia the Ca transients decreased. Anoxia slowed the time to peak of the Ca transient, the time to 50% relaxation, and the time to 90% relaxation. The decline of indo 1 fluorescence on rapid caffeine application was slowed during anoxia, metabolic inhibition, and hypoxia and partially recovered after reoxygenation.
Critical intracellular O2 in myocardium as determined by 1H nuclear magnetic resonance signal of myoglobin
Authors: Kreutzer U. , Jue T.
Published: December 2017

The 1H nuclear magnetic resonance (NMR) signal of tissue myoglobin has provided an opportunity to determine the critical O2 level in saline-perfused myocardium at room temperature. Above the intracellular PO2 of 4 mmHg, the myocardium exhibits no sign of hypoxia. At 4 mmHg, the rate pressure product (RPP) decreases, and the lactate formation rate, measured enzymatically, increases. However, O2 consumption and the 31P-NMR signal of phosphocreatine level remain relatively constant until the cellular PO2 reaches 2 mmHg. The ATP signal intensity dips only when cellular O2 reaches 0.8 mmHg, while pH remains unchanged at 7.2. The sequential nature of the cellular response to limiting O2, starting with alterations in the lactate formation rate and RPP, indicates that NADH, rather than ADP, signals tissue hypoxia. Moreover, the study suggests that the O2 gradient from capillary to cell is larger than that from cytosol to mitochondria.
Na+/Ca2+ exchange current density in cardiac myocytes from rabbits and guinea pigs during postnatal development
Authors: Artman M. , Ichikawa H. , Avkiran M. , Coetzee W. A.
Published: December 2017

It has been proposed that the activity of the cardiac sarcolemmal Na+/Ca2+ exchanger may be greatest in developing animals before the sarcoplasmic reticulum (SR) reaches functional maturity. Experiments were performed in rabbits, which have a sparse SR at birth, and in newborn guinea pigs, which exhibit a more extensive SR. Whole cell voltage clamp techniques were used to characterize the Ni(2+)-sensitive Na+/Ca2+ exchange current in single freshly isolated cardiac myocytes. Na+/Ca2+ exchange current was measured from a holding potential of -40 mV by using a slow-ramp voltage protocol (-120 to +60 mV, 0.09 V/s) in the presence of Ba2+, Cs+, tetraethylammonia, D-600, and ouabain to block Ca2+, Na+, and K+ currents. Experiments in developing rabbits (1–22 days old) demonstrated that Na+/Ca2+ exchange current density was greatest at 1–4 days and declined rapidly over the first 3 wk of age. In contrast, Na+/Ca2+ exchange current density in newborn guinea pig myocytes did not differ from that recorded in adults. These results confirm that Na+/Ca2+ exchange is functional at birth in both rabbits and guinea pigs. The species-related difference in the ontogeny of Na+/Ca2+ exchange is consistent with the concept that Na+/Ca2+ exchange assumes a relatively greater role in newborn animals with a sparse SR.
Palmitoylcarnitine increases [Na+]i and initiates transient inward current in adult ventricular myocytes
Authors: Wu J. , Corr P. B.
Published: December 2017

This study was performed to determine whether long-chain acylcarnitines, specifically palmitoylcarnitine, could account for the increase in intracellular Na+ ([Na+]i) during ischemia eliciting a secondary increase in intracellular Ca2+ ([Ca2+]i). Accordingly, whole cell voltage-clamp procedures and Na(+)-sensitive electrode recordings were employed simultaneously in isolated adult rabbit ventricular myocytes to assess the relationship between activation of a slow-inactivating Na+ current [INa(s)] and a potential increase in [Na+]i. The [Na+]i increased progressively from 8.4 +/- 1.2 to 22.5 +/- 1.8 mM (n = 8, P < 0.01) on exposure to palmitoylcarnitine (10 microM) accompanied by the activation of INa(s); both effects were reversible. Inhibition of INa(s) by tetrodotoxin (TTX, 10 microM) inhibited the increase in [Na+]i. Increasing [Na+]i to 20 mM without ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) to mimic effects measured with palmitoylcarnitine consistently elicited the transient inward current (Iti) and delayed afterdepolarizations (DADs). The percent inhibition (12.9 +/- 2.8%) of the Na(+)-K(+)-adenosinetriphosphatase pump activity by palmitoylcarnitine (10 microM) was much smaller than that induced by ouabain (10 microM, 90.5 +/- 2.5%), suggesting that this modest effect of palmitoylcarnitine on the pump is unlikely to account for the increase in [Na+]i induced by palmitoylcarnitine. Thus palmitoylcarnitine induces the INa(s) leading to an increase in [Na+]i, which elicits an increase in [Ca2+]i probably via the Na+/Ca2+ exchanger, thereby leading to the development of Iti and DADs.
Agonist and membrane depolarization induced activation of MAP kinase in the swine carotid artery
Authors: Katoch S. S. , Moreland R. S.
Published: December 2017

Caldesmon phosphorylation has been proposed to be involved in regulation of smooth muscle contraction. Mitogen-activated protein (MAP) kinase has been suggested to be the caldesmon kinase; stimulation-induced MAP kinase activation in intact vascular smooth muscle, however, has not been demonstrated. We measured temporal profiles of MAP kinase activation in response to histamine stimulation and membrane depolarization in intact swine carotid artery. Phosphotyrosine levels of 42- and 44-kDa MAP kinases were elevated during contraction in response to histamine or KCl. The temporal profile of MAP kinase activation/inactivation was similar to that for contraction/relaxation of the vascular tissue in response to KCl or histamine stimulation. MAP kinase activated during contractile stimulation phosphorylates caldesmon with a specific activity significantly greater than that for myelin basic protein-(95-98). We propose that MAP kinase is activated in response to all forms of contractile stimulation. We also suggest that activated MAP kinase phosphorylates and disinhibits the effects of caldesmon on actin-myosin interactions. This disinhibition allows an inherent level of myosin ATPase activity to be expressed.
Modulation of cardiac Na(+)-K+ pump current: role of protein and nonprotein sulfhydryl redox status
Authors: Haddock P. S. , Shattock M. J. , Hearse D. J.
Published: December 2017

Oxidant stress alters protein structure and function, possibly through the modification of the redox status of regulatory protein sulfhydryl groups. We used the sulfhydryl-blocking reagent p-chloromercuriphenylsulfonic acid (pCMPSA), applied selectively and independently to either the intracellular or extracellular environment, to study the relationship between blocking protein sulfhydryl groups and Na(+)-K+ pump current (i.p.). In guinea pig ventricular myocytes voltage clamped at -30 mV, extracellular pCMPSA (50, 100, and 400 microM) caused a concentration-dependent reduction in holding current. The selective intracellular administration of pCMPSA (100 microM) induced a similar inhibition of i.p., albeit over a longer time course. The inhibition of ip resulting from either the intracellular or extracellular application of pCMPSA (100 microM) was reversed, in part, by the extracellular application of dithiothreitol (3 mM). An intracellular oxidant stress was also imposed by using diethyl maleate to deplete the intracellular nonprotein sulfhydryl content [represented by reduced glutathione (GSH)]. In myocytes isolated from diethyl maleate-treated guinea pigs *860 mg/kg i.p., 30 min before study), intracellular GSH was depleted by 93% and i.p. was depressed by 38% at all membrane potentials tested. We propose that Na(+)-K+ pump function may be related to protein and nonprotein sulfhydryl status. Protein sulfhydryl oxidation and glutathione depletion may account, in part, for a depression in Na(+)-K+ pump activity during reperfusion-induced oxidant stress.
4-Aminopyridine block of the noninactivating cloned K+ channel Kv1.5 expressed in Xenopus oocytes
Authors: Yamane T. , Furukawa T. , Hiraoka M.
Published: December 2017

The blocking action of 4-aminopyridine (4-AP) on the cloned K+ channel Kv1.5 expressed in Xenopus oocytes was studied using the two-microelectrode voltage-clamp method. Application of 4-AP to the bath solution reversibly suppressed the expressed current in a voltage- and concentration-dependent manner decreasing with membrane depolarization and with a half-maximal inhibitory concentration of 0.14 mM (at +40 mV). Both block and unblock occurred mainly during a depolarization when channels were activated. With successive depolarizations, 4-AP decreased not only the peak amplitudes of the current in successive pulses, but also the current during a depolarization. Upon washout of 4-AP, the current recovered with successive depolarizations, whereas no recovery of the current was noted in the absence of depolarizations. The extent of block markedly increased with alkalization of the external solution and decreased with acidification. External application of 4-amino-pyridine methiodide, a charged form of a quaternary 4-AP derivative, did not affect the current, but internal application markedly suppressed the current, indicating the drug gained access to the channel from the cytoplasmic side. These data suggest that 4-AP crosses the membrane in its uncharged form and acts from inside of the cell in its charged form, resulting in block of the channels with higher affinity to the open state.
Effects of indomethacin on brain blood flow, cerebral metabolism, and sagittal sinus prostanoids after hypoxia
Authors: Coyle M. G. , Oh W. , Petersson K. H. , Stonestreet B. S.
Published: December 2017

We tested the hypotheses that during recovery from hypoxia, newborn piglets exhibit a posthypoxic cerebral hyperemia, indomethacin-pretreated piglets exhibit a posthypoxic cerebral hypoperfusion, and that the changes caused by indomethacin are dose dependent and related to the loss of prostanoids. We studied piglets exposed to 40 min of hypoxia after pretreatment with high (5 mg/kg, n = 9) or low (0.3 mg/kg, n = 8) doses of indomethacin or placebo (n = 9) and allowed to recover for 120 min. In the placebo and low-dose pretreatment groups, total and regional brain blood flow increased during hypoxia but returned to baseline 10 min after hypoxia. High-dose indomethacin pretreatment was associated with a posthypoxic hypoperfusion to certain brain regions at 10 min of recovery to values similar to those after indomethacin treatment before the onset of hypoxia. During and after hypoxia, the cerebral metabolic rate of oxygen was preserved in both the placebo and low-dose groups and decreased significantly during hypoxia in the high-dose group. Sagittal sinus prostacyclin was reduced significantly in both indomethacin-treated groups throughout the study. We conclude that a posthypoxic hyperemia is not observed in newborn piglets. This finding was not altered by pretreatment with a therapeutic dose of indomethacin, whereas a pharmacological dose was associated with selective hypoperfusion to certain brain regions both before hypoxia and during recovery from hypoxia.
Phorbol 12-myristate 13-acetate alters SR Ca(2+)-ATPase gene expression in cultured neonatal rat heart cells
Authors: Qi M. , Bassani J. W. , Bers D. M. , Samarel A. M.
Published: December 2017

Primary cultures of neonatal rat ventricular myocytes were used to examine how the cardiac myocyte cytoplasmic Ca2+ ([Ca2+]i) transient and sarcoplasmic reticulum Ca(2+)-ATPase (SERCA2) gene expression change in response to treatment with the protein kinase C activator phorbol 12-myristate 13-acetate (PMA). Exposure of neonatal myocytes to PMA (200 nM, 48-72 h) produced myocyte growth and a 70% prolongation of the half-time for [Ca2+]i decline induced by potassium depolarization in the absence of extracellular Na+ (in which the sarcoplasmic reticulum Ca2+ pump is the main mechanism responsible for [Ca2+]i decline). The reduced rate of [Ca2+]i transient decline corresponded to a 53% reduction in SERCA2 protein levels and a 43% reduction in SERCA2 mRNA levels as compared with control myocytes. Exposure to PMA for as little as 30 min or for as long as 48 h produced a similar degree of SERCA2 mRNA downregulation over time. PMA-induced downregulation of SERCA2 mRNA levels was blocked by either 10 nM staurosporine or 4 microM chelerythrine, whereas treatment with either agent alone increased SERCA2 mRNA levels as compared with control cells. Actinomycin D mRNA stability assays revealed that PMA treatment appeared to markedly destabilize the relatively long-lived SERCA2 mRNA transcript. Taken together, these results indicate that downregulation of SERCA2 gene by PMA in cultured neonatal myocytes occurs at least in part by alterations in mRNA stability and results in functional alterations in [Ca2+]i decline that are similar to that observed in the hypertrophied and failing adult myocardium.
Early collateral and microvascular adaptations to intestinal artery occlusion in rat
Authors: Unthank J. L. , Nixon J. C. , Burkhart H. M. , Fath S. W. , Dalsing M. C.
Published: December 2017

The technique to repeatedly observe exactly the same vessels in the rat intestine was used to investigate vascular compensation during the 1st wk after abrupt arterial ligation. A collateral-dependent tissue region was created by ligation of three to four sequential intestinal arteries. At the center of the collateral-dependent region, arterial pressure decreased from 96 +/- 3.7 to 29 +/- 2.5 mmHg, and intestinal blood flow fell approximately 80% during maximal dilation initially postligation. One week later, pressure and blood flow at the center had increased 31 and 250%, respectively. Relative to preligation values, the only compensatory adaptation was an enlargement (31 +/- 11%) of the collateral arteries located between normal tissue and the center; no increase was observed in the diameter or numbers of arterioles or collateral arteries at the center. Wall shear rate was increased 173 +/- 35% initially postligation at the site where luminal enlargement occurred. The selective enlargement of collateral arteries away from the center region is consistent with the hypothesis that collateral enlargement is induced by chronic increases in wall shear rate and can occur independently of tissue ischemia.
Inhibition of nitric oxide synthase augments myocardial contractile responses to beta-adrenergic stimulation
Authors: Keaney J. F. , Hare J. M. , Balligand J. L. , Loscalzo J. , Smith T. W. , Colucci W. S.
Published: December 2017

Recent in vitro evidence suggests a role for nitric oxide (NO) in the modulation of myocardial contractility. The specific role of NO in the control of cardiac function in vivo, however, remains unclear. We investigated the effect of NO synthase (NOS) inhibition on myocardial contractility in response to beta-adrenergic stimulation in autonomically blocked dogs. Intracoronary infusions of dobutamine (1-50 micrograms/min) and isoproterenol (0.1 and 0.5 microgram/min) were performed before and after the intracoronary administration of the specific NOS inhibitor NG-nitro-L-arginine methyl ester (L-NAME). Intracoronary dobutamine resulted in a dose-dependent increase in peak first derivative of pressure (dP/dtmax) to a maximum of 195 +/- 10% (P < 0.001). After inhibition of NOS with intracoronary L-NAME at rates of 0.1 and 1 mg/min, the response to dobutamine was significantly enhanced with dP/dtmax, increasing 276 +/- 17 and 317 +/- 26%, respectively (P < 0.001). Intracoronary isoproterenol resulted in a maximum increase in dP/dtmax of 116 +/- 15% (P < 0.001) that further increased to 154 +/- 17 and 157 +/- 18% after NOS inhibition with 0.1 and 1 mg/min L-NAME, respectively (both P < 0.002). L-NAME had no effect on baseline dP/dtmax but did produce a reduction in myocardial guanosine 3',5'-cyclic monophosphate content. These results suggest a role for NO in the control of myocardial contractility in response to beta-adrenergic stimulation in vivo.
Neutrophil recruitment as a factor limiting injury or promoting recovery from acute lung injury
Authors: Carey L. A. , Perkowski S. Z. , Lipsky C. L. , Cirelli R. A. , Spath J. A. , Gee M. H.
Published: December 2017

We studied 1) neutrophil mobilization in sheep given endotoxin (10 ng.kg-1.min-1, n = 5) for 4 h, 2) surviving (n = 17) and nonsurviving sheep (n = 8) during a 12-h infusion of endotoxin, and 3) adult sheep (n = 8) or lambs (n = 8) infused with endotoxin for 12 h. Bone marrow cells of sheep declined from a baseline value of 10,533 +/- 1,784 to 5,966 +/- 1,980 cells/microliter (P < 0.05) 4 h after endotoxin. After 12 h of endotoxin infusion, circulating neutrophils remained reduced from baseline values of 2,000-4,000 cells/microliter to 343 +/- 70 in lambs and 484 +/- 236 in nonsurviving sheep, while beginning to recover in surviving sheep to 1,838 +/- 467 cells/microliter. In lambs and nonsurviving sheep, a 12-h infusion of endotoxin increased lung lymph protein clearance tenfold compared with a fivefold increase in surviving sheep. Neutrophils cultured from sheep bone marrow exposed to lamb postendotoxin plasma failed to increase in cell number (609 +/- 229 to 610 +/- 182 cells/microliter), whereas similar cells exposed to adult sheep postendotoxic plasma showed a significant increase in cell number (1,069 +/- 101 to 2,293 +/- 448 cells/microliter, P <0.05). Our results are consistent with the hypothesis that the ability to recruit neutrophils to the circulation during periods of inflammation is important in limiting the severity of acute lung injury.
In vivo determination of left ventricular wall stress-shortening relationship in normal mice
Authors: Hoit B. D. , Khan Z. U. , Pawloski-Dahm C. M. , Walsh R. A.
Published: December 2017

Although targeted alterations of the mouse genome are used increasingly to identify the mechanisms underlying cardiac function, the methods used to study the phenotypic expression of these alterations in vivo are limited. To derive a relatively noninvasive, load-independent measure of left ventricular (LV) contractility in mice, we cannulated the femoral artery and performed two-dimensional directed M-mode echo studies in 28 anesthetized FVB/N mice, using a 9-MHz transducer. Loading conditions were altered by intraarterial methoxamine (3-12 microg/g), and LV shortening fraction was determined at several steady states, both before and after myocardial contractility was altered by either 4 microg/g intraperitoneal dobutamine (n = 16) or 1-2 microg/g verapamil (n = 12). The relation between LV systolic meridional stress and fractional shortening derived from pooled baseline data was inverse and linear [r = 0.80, slope = -0.19, intercept = 48%, standard error of estimate (SEE) = 5.5%, P < 0.001]. Dobutamine produced a parallel upward shift of the relation (r = 0.87, slope = -0.21, intercept = 61%, SEE = 4.5%, P < 0.001), and verapamil produced a downward shift of the relation (r = 0.48, slope = -0.05, intercept = 24%, SEE = 3.7%, P < 0.05). At matched levels of end-systolic stress, dobutamine increased and verapamil decreased the LV shortening fraction. We conclude that 1) inverse stress-shortening relations can be assessed noninvasively in mice; and 2) these relations are sensitive to alterations in inotropic state, independent of loading conditions.
Membrane currents evoked by histamine in rabbit basilar artery
Authors: Kamouchi M. , Ogata R. , Fujishima M. , Ito Y. , Kitamura K.
Published: December 2017

The membrane current evoked by histamine in isolated smooth muscle cells from rabbit basilar artery was investigated using the perforated-patch technique. When 10 microM histamine was applied in the bath at a holding potential of -60 mV, an inward current (79.2 +/- 55.8 pA) was transiently activated. An outward current was additionally evoked by 10 microM histamine when the membrane was held at -40 mV or less negative potentials. The outward but not the inward current was completely blocked by 100 nM charybdotoxin. A higher concentration of histamine (30 microM) failed to produce the inward current (3.4 +/- 4.8 pA) when Cl- concentration in the pipette was reduced. The apparent reversal potential of the inward current induced by histamine in physiological salt solution, in high-tetraethylammonium (TEA+) solution (bath), or in low-Cl- solution (pipette) was -6.3 +/- 4.4, -7.5 +/- 4.9, or -45.8 +/- 8.5 mV, respectively. Niflumic acid (100 microM) reversibly blocked the inward current, which was also blocked by 10 microM pyrilamine but not by 10 microM cimetidine. When histamine was continuously applied in the bath, spontaneous transient inward currents were generated. Removal of external Ca2+ or addition of 1 microM nicardipine or 2 mM caffeine reduced the amplitude of the histamine-induced inward current. These results suggest that histamine induces an inward current via H1 receptors at the resting membrane potential, possibly due to activation of Cl- currents. The Cl- inward current might be generated by elevation of intracellular Ca2+ via histamine receptors. The inward current may also contribute to control of the Ca2+ influx via a change in the membrane potential.
Modulation of baroreflex sensitivity and spectral power of blood pressure by heat stress and aging
Authors: Stauss H. M. , Morgan D. A. , Anderson K. E. , Massett M. P. , Kregel K. C.
Published: December 2017

To investigate the effects of hyperthermia and aging on baroreceptor-heart rate reflex sensitivity (BRS), cardiovascular parameters were recorded during a progressive rise in core temperature in conscious mature and senescent Fischer 344 rats. BRS was calculated from spontaneous changes in blood pressure and interbeat interval. Low- (LF, 0.01-0.20 Hz) and mid- (MF, 0.2-0.5 Hz) frequency blood pressure power were also determined. In both age groups, hyperthermia caused an increase in blood pressure, renal resistance, and LF but no changes in renal nerve activity, whereas a tachycardia was only observed in the older rats. Increases in BRS (0.80 +/- 0.14 vs. 1.72 +/- 0.34 ms/mmHg, P < 0.05) and MF (3.10 +/- 0.55 vs. 7.81 +/- 1.89 mmHg2, P < 0.05) and a positive correlation between BRS and MF (r = 0.50, P < 0.01) were observed with heating in mature but not senescent rats. These results indicate that LF, which increased with elevated core temperature, may be modulated by thermal stimuli. The augmented BRS in the mature group may contribute to the hemodynamic adjustments that occur with hyperthermia, whereas the lack of an increase in BRS during heat stress in the senescent group suggests that baroreceptor reflex modulation is impaired with aging. The positive correlation between BRS and MF in mature rats, together with the lack of an increase in renal sympathetic nerve activity, indicates that MF may reflect the modulating influence of the efferent sympathetic portion of the baroreceptor reflex loop on arterial blood pressure rather than merely the activity of the peripheral sympathetic nervous system.
Arterial expansive remodeling induced by high flow rates
Authors: Ben Driss A. , Benessiano J. , Poitevin P. , Levy B. I. , Michel J. B.
Published: December 2017

The effects of chronic increase in aortic blood flow on arterial wall remodeling were investigated in vivo with the use of an aortocaval fistula (ACF) model in rats. Phasic hemodynamics and aortic wall structure upstream and downstream in 30 male Wistar rats with ACF and 30 sham-operated rats were compared immediately and 2 mo after the ACF was opened in anesthetized rats. Opening the ACF upstream acutely decreased aortic pressure (-30%, P < 0.001) and increased aortic blood velocity (x12, P < 0.001), blood flow (x9, P < 0.001), wall shear stress (x10, P < 0.001) and guanosine 3',5'-cyclic monophosphate (cGMP) wall content (+50%, P < 0.01). After 2 mo, aortic pressure decreased (-22%, P < 0.001) and aortic blood velocity, diameter, and blood flow increased (+114%, P < 0.001; +60%, P < 0.001; and +250%, P < 0.001; respectively) compared with the control group. Aortic wall shear stress and cGMP wall content dropped over time and tended to recover control values; aortic wall tensile stress was higher than in the control group (P < 0.05). Medial cross-sectional area and elastin and collagen contents increased (+38%, P < 0.01; +50%, P < 0.01; and +30%, P < 0.05, respectively) and were associated with smooth muscle cell hypertrophy) (+23%, P < 0.05), despite a decrease in arterial wall thickness (-13%, P < 0.01). Opening the ACF downstream acutely decreased aortic pressure (-30%, P < 0.001) without any change in aortic blood velocity, diameter, blood flow, shear stress, and cGMP wall content. After 2 mo, pressure, blood velocity, shear stress, and cGMP wall content decreased (-22%, P < 0.001; -31%, P < 0.01; -46%, P < 0.02; and -50%, P < 0.05; respectively) and diameter and blood flow were unchanged; smooth muscle cell hypertrophy and hypoplasia were the only observed changes in the aortic wall structure. These results suggest that both shear and tensile stresses are involved in the aortic wall remodeling. Increase in shear stress likely induces expansive remodeling in relation to flow-dependent vasodilation, whereas increase in tensile stress is responsible for medial hypertrophy and fibrosis.
Compression of intramyocardial arterioles during cardiac contraction is attenuated by accompanying venules
Authors: Vis M. A. , Sipkema P. , Westerhof N.
Published: December 2017

It was calculated how cardiac contraction influences the luminal cross-sectional area of a maximally dilated coronary arteriole (37-micron inner diameter at a pressure of 35 mmHg) that is accompanied by two equal venules (45-micron inner diameter at a pressure of 17 mmHg), forming a so-called "triad." It was found that, during a contraction with 14% cardiac muscle shortening, arteriolar area is virtually unaffected (increase of 4%) at the expense of a large (55%) decrease in venular area. For comparison, the areas of an unaccompanied arteriole and an unaccompanied venule were calculated to be reduced by 45 and 36%, respectively, demonstrating the "protective effect" on accompanied arterioles in a triad. During contraction, the overall resistance of a system consisting of one arteriole in series with two parallel venules of equal length was calculated to increase about twice as much for nonaccompanied vessels (resistance increases by a factor of 2.8) than for vessels in a triad arrangement (resistance increased by a factor of 1.4). The calculations show that the extravascular (intramyocardial) pressure, which determines vascular area, is not an independent variable as in the intramyocardial pump and waterfall models but depends on the vascular "loading" conditions. Thus the small venular pressure together with the large venular compliance causes the extravascular pressure to remain low during contraction, thereby protecting the stiff arteriole at high pressure. We conclude that the triad arrangement of intramyocardial coronary vessels attenuates the increase in coronary resistance during cardiac contraction and thus has an important functional advantage.
Role of the renin-angiotensin system in cardiac hypertrophy induced in rats by hyperthyroidism
Authors: Kobori H. , Ichihara A. , Suzuki H. , Takenaka T. , Miyashita Y. , Hayashi M. , Saruta T.
Published: December 2017

This study was conducted to examine whether the renin-angiotensin system contributes to hyperthyroidism-induced cardiac hypertrophy without involving the sympathetic nervous system. Sprague-Dawley rats were divided into control-innervated, control-denervated, hyperthyroid-innervated, and hyperthyroid-denervated groups using intraperitoneal injections of thyroxine and 6-hydroxydopamine. After 8 wk, the heart-to-body weight ratio increased in hyperthyroid groups (63%), and this increase was only partially inhibited by sympathetic denervation. Radioimmunoassays and reverse transcription-polymerase chain reaction revealed increased cardiac levels of renin (33%) and angiotensin II (53%) and enhanced cardiac expression of renin mRNA (225%) in the hyperthyroid groups. These increases were unaffected by sympathetic denervation or 24-h bilateral nephrectomy. In addition, losartan and nicardipine decreased systolic blood pressure to the same extent, but only losartan caused regression of thyroxine-induced cardiac hypertrophy. These results suggest that thyroid hormone activates the cardiac renin-angiotensin system without involving the sympathetic nervous system or the circulating renin-angiotensin system; the activated renin-angiotensin system contributes to cardiac hypertrophy in hyperthyroidism.
Induction of tetrahydrobiopterin synthesis in rat cardiac myocytes: impact on cytokine-induced NO generation
Authors: Kasai K. , Hattori Y. , Banba N. , Hattori S. , Motohashi S. , Shimoda S. , Nakanishi N. , Gross S. S.
Published: December 2017

Because tetra-hydrobiopterin (BH4) is an essential cofactor for nitric oxide (NO) formation, we investigated whether BH4 synthesis is required for cytokine-induced NO production in cultured rat cardiac myocytes. The total biopterin content of untreated cardiac myocytes was below our limit of detection. However, treatment with interleukin-1 alpha (IL-1 alpha) + interferon-gamma (IFN-gamma) caused a significant rise in biopterin levels and induced NO synthesis. 2,4-Diamino-6-hydroxypyrimidine (DAHP), a selective inhibitor of GTP cyclohydrolase I (the rate-limiting enzyme for de novo BH4 synthesis), completely abolished the elevation in biopterin levels induced by IL-1 alpha + IFN-gamma. DAHP also caused a concentration-dependent inhibition of (IL-1 alpha + IFN-gamma)-induced NO synthesis. Similarly, N-acetylserotonin, an inhibitor of the BH4 synthetic enzyme sepiapterin reductase, blocked increases in biopterin levels as well as NO synthesis induced by IL-1 alpha + IFN-gamma. Sepiapterin, substrate for BH4 synthesis via the pterin salvage pathway, prevented this inhibition by DAHP or N-acetylserotonin, and this effect was blocked by methotrexate. Sepiapterin and, to a lesser extent, BH4 dose dependently enhanced (IL-1 alpha + IFN-gamma)-induced NO synthesis, suggesting that the concentration of BH4 limits the rate of NO production. Inducible NO synthase mRNA and GTP cyclohydrolase I mRNA were induced by IL-1 alpha + IFN-gamma in parallel. We thus demonstrate that BH4 synthesis is an absolute requirement for induction of NO synthesis by cytokines in cardiac myocytes.
Regulation of P-selectin expression in human endothelial cells by nitric oxide
Authors: Armstead V. E. , Minchenko A. G. , Schuhl R. A. , Hayward R. , Nossuli T. O. , Lefer A. M.
Published: December 2017

P-selectin translocation to the surface of endothelial cells is increased after exposure to the nitric oxide (NO) synthase inhibitor NG-nitro-L-arginine methyl ester (L-NAME), resulting in increased endothelial adhesiveness. L-NAME (3 mM) was added to human cultured iliac vein endothelial cells for 1, 2, 4, and 6 h, and P-selectin mRNA expression was quantified by a ribonuclease protection assay. In parallel experiments, the NO donor, SPM-5185 (10 microM), was added to human iliac venous endothelial cells, and P-selectin mRNA expression quantified. P-selectin protein synthesis was quantified by Western blot analysis. L-NAME caused increased expression of P-selection RNA at 2-4 h, whereas D-NAME, the stereoisomer lacking NO synthase-inhibitory activity, had no effect. The stimulatory effect of L-NAME was reversed by addition of 3 mM L-arginine. SPM-5185 decreased P-selectin mRNA over the same time period (P < 0.02). The increased P-selectin mRNA expression induced by L-NAME was paralleled by an increase in P-selectin protein synthesis. The effects of SPM-5185 and L-arginine were also paralleled by decreases in P-selectin protein synthesis and in decreased adherence of human neutrophils to human iliac venous endothelial cells. The peak effect of inhibition of NO synthesis or addition of exogenous NO occurred at 2-4 h. These results suggest a regulatory effect of NO on endothelial P-selectin expression that modulates early leukocyte-endothelial cell interactions to preserve vascular homeostasis.
Catalase-overexpressing transgenic mouse heart is resistant to ischemia-reperfusion injury
Authors: Li G. , Chen Y. , Saari J. T. , Kang Y. J.
Published: December 2017

Myocardial ischemia-reperfusion injury is at least partially mediated by oxygen-derived free radicals. Catalase is a major enzyme involved in the detoxification of hydrogen peroxide. The activity of catalase in the heart is very low, which may be a factor responsible for the high sensitivity of the heart to ischemia-reperfusion injury. The present study was undertaken to determine whether elevation of catalase specifically in the heart of transgenic mice can provide protection against ischemia-reperfusion injury. Hearts isolated from transgenic mice in which catalase in the heart was elevated approximately 60-fold higher than that in nontransgenic heart and from the non-transgenic littermates were subjected to 50 min of warm (37 degrees C) zero-flow ischemia followed by 90 min reflow. Compared with nontransgenic controls, transgenic hearts showed significantly improved recovery of contractile force (75 vs. 25% at the end of 90 min reperfusion, P < 0.01). Efflux of creatine kinase was reduced by approximately 50%, and the zone of myocardial infarction as demarcated by triphenyltetrazolium at the end of reperfusion was reduced by approximately 40% in transgenic hearts compared with nontransgenic controls. These findings support the view that hydrogen peroxide is an important cause of ischemia-reperfusion damage and suggest that protection may be provided by elevation of catalase activity.
Complexes of apoA-1 with phosphatidylcholine suppress dysregulation of arterial tone by oxidized LDL
Authors: Ota Y. , Kugiyama K. , Sugiyama S. , Matsumura T. , Terano T. , Yasue H.
Published: December 2017

The aim of this study was to determine whether apolipoprotein A-1 (apoA-1) may suppress the vasomotor dysregulation by oxidized low-density lipoprotein (ox-LDL), which is known to be an atherogenic lipoprotein. The isolated porcine coronary arterial rings and the cultured endothelial cells from the porcine coronary arteries were exposed to ox-LDL in the presence or absence of complexes of apoA-1 with dimyristoylphosphatidylcholine (DMPC/apoA-1), apoA-1 alone, or DMPC alone. DMPC/apoA-1 but not apoA-1 alone or DMPC alone was found to suppress both impairment of endothelium-dependent arterial relaxation and vasocontraction caused by ox-LDL in the isolated porcine coronary arterial rings suspended in organ chambers. DMPC/apoA-1 absorbed lysophosphatidylcholine (LPC) from ox-LDL and decreased the transfer of LPC from ox-LDL to the surface membrane of the cultured endothelial cells, but apoA-1 alone and DMPC alone had no effect. High-density lipoprotein exerted the protective actions mimicking those observed in DMPC/apoA-1. Thus DMPC/apoA-1 decreased the transfer of LPC from ox-LDL to surface membrane by absorbing LPC, leading to the suppression of ox-LDL-induced dysregulation of endothelium-dependent arterial tone. Therefore, apoA-1 appears to require formation of the complexes with phospholipids to prevent the endothelial dysfunction caused by ox-LDL.
Hemodynamic effects of intracoronary VEGF delivery: evidence of tachyphylaxis and NO dependence of response
Authors: Lopez J. J. , Laham R. J. , Carrozza J. P. , Tofukuji M. , Sellke F. W. , Bunting S. , Simons M.
Published: December 2017

Vascular endothelial growth factor (VEGF) has been utilized to improve blood flow in the setting of myocardial or peripheral vascular ischemia. In this investigation we studied the hemodynamic effects of intracoronary VEGF administration. Hemodynamic parameters and Doppler flow wire recordings from the left anterior descending coronary artery were measured after intracoronary infusion of VEGF (1, 10, and 100 micrograms) in 28 intubated pigs. Additional studies were performed using an in vitro isolated microvessel preparation. VEGF produced a highly significant dose-dependent increase in coronary blood flow (maximal 3.51 +/- 0.85-fold) in the absence of significant changes in epicardial artery diameter, a decline in mean arterial pressure (maximal 43%), and a decrease in left ventricular end-diastolic pressure (maximal 52%), all of which could be inhibited by pretreatment with NG-nitro-L-arginine. The increase in coronary flow seen with 10 or 100 micrograms VEGF was significantly greater than the maximal vasodilation achieved with serotonin or nitroglycerin and was equivalent to a maximal adenosine response. In summary, VEGF stimulates nitric oxide (NO)-dependent dilation of coronary microvessels, and repeat administrations of VEGF resulted in rapid development of tachyphylaxis to VEGF as well as serotonin, but not to nitroglycerin or adenosine, which appeared to be secondary to impaired NO production.
Microstructural model of perimysial collagen fibers for resting myocardial mechanics during ventricular filling
Authors: MacKenna D. A. , Vaplon S. M. , McCulloch A. D.
Published: December 2017

To study the structural contribution of perimysial collagen fibers to the passive mechanics of ventricular myocardium, we modeled the coiled fibers as helical springs using elastica theory to represent the fibers as initially curved, inextensible rods that could bend and twist. The extensional behavior in the physiological range of left ventricular (LV) pressures was dependent on structural parameters that were estimated histologically for rat and dog: collagen fiber diameter, coil period, collagen fiber tortuosity (fiber length in 2 dimensions/midline length), and number density (Nd) of collagen fibers per cross-sectional area of tissue. The difference in each geometric parameter was not great (27% maximal difference for Nd). However, the combined effect of all parameters accounted for a 102% difference in tissue stiffness. The only other model parameter was the Young's modulus (E) for bending of collagen, which was calculated from a linear regression of stress and strain scaled according to the geometric parameters. Despite an approximately fivefold difference in tissue stiffness, the resulting E was only 18.5% different (135 vs. 160 MPa for rat and dog, respectively). With the mean values from each species, the model was able to predict the stress-strain behavior of both rat and dog myocardium in the physiological range of LV pressures, suggesting that the perimysial collagen fibers may be the most important contributors to passive stiffness of the myocardium in the direction of the muscle fibers. It also appears that these large collagen fibers are not stretching to generate stress in the normal range of ventricular pressures, but rather stress gradually increases as collagen fibers straighten through bending and twisting. Finally, to understand the importance of differences in collagen architecture, one should measure the detailed collagen structure, not simply collagen density.