bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of cardiac contraction and coronary vasomotor tone on regional myocardial blood flow
Authors: Austin R. E. , Smedira N. G. , Squiers T. M. , Hoffman J. I.
Published: December 2017

We analyzed patterns of left ventricular perfusion in arrested hearts without coronary tone and in the same hearts while beating with and without coronary tone. We used microspheres in anesthetized dogs to measure blood flow in 384 regions (averaging 140 mg wet wt) from the subendocardium, midwall, and subepicardium before and during intracoronary infusions of adenosine (beating without tone) or lidocaine and adenosine (arrest without tone). Mean coronary pressure was held constant at 80 mmHg. Changes in regional flow with arrest (vs. beating without tone) were surprisingly variable (range -28 to +124%) and exhibited substantial within-layer heterogeneity, suggesting that local differences in contractility, stresses, or strains limit maximum coronary flow. Regional flows in beating hearts with tone did not correlate with flows in the same hearts without tone, beating or not (r2 < or = 0.03; not significant). Flow patterns during beating with tone also demonstrated significantly shorter (i.e., the distance at which autocorrelation has decreased to 0.5) within-layer spatial autocorrelations as well as a complete loss of radial flow correlation (e.g., between corresponding subendocardial and subepicardial regions; r2 = 0.01). Thus neither coronary anatomy (assessed during arrest without tone) nor the mechanical effects of contraction (beating without tone) appear to influence myocardial perfusion when vasomotor tone is present.
Compensation for changes in tissue light absorption in fluorometry of hypoxic perfused rat hearts
Authors: Brandes R. , Figueredo V. M. , Camacho S. A. , Weiner M. W.
Published: December 2017

Fluorescence studies of NADH and various dyes in tissue are complicated by changes in light absorption, causing spurious results. Methods were developed to reduce and compensate for changes in light absorption in perfused rat hearts, subjected to normoxia and hypoxia. Isosbestic wavelengths were determined (i.e., absorption independent of oxygenation) in the whole ventricular wall and in the epicardium using transmitted and reflected light, respectively. Isosbestic wavelengths were found at approximately 385, 427, 455, 510, and 525 nm, similar in the epicardium, throughout the ventricle, in beating and arrested hearts, although the exact wavelengths varied among experiments. Furthermore, absolute light absorption was identical in the epicardium and endocardium. At nonisosbestic wavelengths, the effect of changing light absorption on fluorescence was quantified at various detection wavelengths using a reference dye. New correction methods were also developed and used to correct indo 1 fluorescence ratios for changing absorption so that results were independent of detection wavelengths. These methods can be used to greatly reduce artifacts due to changing tissue light absorption in a variety of fluorescence experiments.
Computer model of membrane current and intracellular Ca2+ flux in the isolated guinea pig ventricular myocyte
Authors: Nordin Charles
Published: December 2017

Pages H2117–H2136: Nordin, Charles. “Computer model of membrane current and intracellular Ca2+ flux in the isolated guinea pig ventricular myocyte.”

Figure 13: Units of time in Fig. 13B are seconds (not milliseconds). The output for concentration, using the equations of the appendix, is in units of 10-3 mol/l (millimolar). Equation A29 should read (See PDF) Equations A30a and A31a should read (See PDF)

Note: All errors in equations, except for the term with asterisk in Eq. A31a and removal of the term (0.1 x iCa) from Eq. A30a, were made in transcribing the computer program to the set of printed equations and therefore do not involve any simulations of the paper. The other changes are refinements of the program that slightly reduce the rise in [Na+]myo and fall in [K+]myo with increasing stimulation rate (Fig. 5A) but do not affect other aspects of the behavior of the model in any significant way.
Venoconstriction of hepatic capacitance vessels during hemorrhage in cats: afferent mechanisms
Authors: Greenway C. V. , Innes I. R. , Scott G. D.
Published: December 2017

Cats anesthetized with pentobarbital sodium were hemorrhaged (1 ml.min-1.kg body wt-1) until arterial pressure declined to 55 mmHg. Hepatic volume was recorded by plethysmography. Hemorrhage volume was 21.1 +/- 4.7 (SD) ml/kg, and hepatic volume declined by 4.0 +/- 1.7 ml/kg. These responses were markedly reduced by four procedures that prevented decreases in carotid arterial and central venous pressures and eliminated vagal conduction. When any three of these four procedures were carried out, the remaining stimulus caused a significant increase in the size of the hepatic volume decrease. The results suggest that arterial receptors (baro- and/or chemoreceptors) in the carotid arterial bed or brain and venous baroreceptors in the right atrium and superior and inferior venae cavae are involved in hepatic capacitance responses to hemorrhage. The responses were linearly related to the stimuli, and hepatic blood volume changed by 1.7 +/- 1.1 and 0.030 +/- 0.016 ml/kg for each 1-mmHg change in venous and carotid arterial pressures, respectively. The maximal responses to these afferent stimuli applied individually were not significantly different (-4.2 +/- 1.8 ml/kg) and were not additive, suggesting overlapping redundant systems. The possibility of baroreceptors in superior vena cava has not previously been documented.
Cerebral blood flow is reduced by N omega-nitro-L-arginine methyl ester during delayed hypoperfusion in cats
Authors: Clavier N. , Kirsch J. R. , Hurn P. D. , Traystman R. J.
Published: December 2017

We tested the hypothesis that decreased tonic release of nitric oxide (NO) or a NO-containing compound, during postischemic delayed hypoperfusion, would result in an impaired response of cerebral blood flow (CBF) to NO synthase inhibition. We measured CBF (microspheres), cerebral oxygen consumption, and physiological variables in 30 halothane-anesthetized cats. In 12 animals, complete cerebral ischemia (verified by midischemic CBF measurement) was produced for 12 min by brachiocephalic and left subclavian artery occlusion with hemorrhagic hypotension (mean arterial blood pressure = 40 mmHg). Steady-state hypoperfusion was present by 120 min of reperfusion (30 +/- 4% of baseline). Nonischemic animals (n = 12) were submitted to the same surgical procedures and anesthetic duration. N omega-nitro-L-arginine methyl ester (L-NAME, 10 mg/kg iv) or saline was administered 160 min after baseline measurements, equivalent to 140 min of reperfusion for animals treated with ischemia (n = 6 in each group). Blood pressure was controlled (aortic ligature) so that there was no change following L-NAME administration both in the ischemic and nonischemic groups. L-NAME reduced CBF during reperfusion in ischemic animals (from 37 +/- 2 to 24 +/- 2 ml.min-1 x 100 g-1) and in nonischemic animals (from 122 +/- 15 to 68 +/- 8 ml.min-1 x 100 g-1) with no change in cerebral oxygen consumption. In six additional cats, administration of L-arginine (250 mg/kg iv) reversed the effect of L-NAME. We conclude that tonic NO-mediated cerebral vasodilation occurs following transient global ischemia despite delayed hypoperfusion.
Role of EDRFs in the control of arteriolar diameter during increased metabolism of striated muscle
Authors: Saito Y. , Eraslan A. , Hester R. L.
Published: December 2017

This experiment was designed to determine the role that the release of endothelium-derived relaxing factors (EDRFs), endothelium-derived nitric oxide (EDNO), or prostaglandins have in the control of arteriolar vasodilation during an increased metabolic rate in striated muscle. A silicone stopcock grease dam was placed across the distal portion of the cremaster muscle of pentobarbital-anesthetized hamsters to localize the application of the metabolic stimulator 2,4-dinitrophenol (DNP). Application of DNP (10 mM) to the distal region resulted in significant increases in red cell velocity (from 6 +/- 1 to 10 +/- 2 mm/s) and arteriolar diameter (from 75 +/- 3 to 91 +/- 5 microns) (P < 0.05; n = 6) in the first-order arterioles located approximately 11 mm upstream from the silicone dam. Administration of N omega-nitro-L-arginine methyl ester (L-NAME; 2 mg iv) resulted in significant vasoconstriction of the first-order arterioles and a significant decrease in the vasodilator response to acetylcholine (1 microM). Addition of sodium nitroprusside (380 microM) to the superfusion solution during L-NAME treatment resulted in a return of arteriolar diameter to control levels. DNP treatment during L-NAME and sodium nitroprusside treatment did not inhibit the arteriolar vasodilation [75 +/- 3 to 87 +/- 4 microns (P > 0.05)] after a significant increase in red cell velocity from 7 +/- 1 to 11 +/- 1 mm/s. Before indomethacin treatment, DNP treatment resulted in an increase in arteriolar diameter from 72 +/- 3 to 90 +/- 3 microns, preceded by an increase in red cell velocity from 6 +/- 1 to 10 +/- 1 mm/s. (ABSTRACT TRUNCATED AT 250 WORDS)
Mechanisms of angiotensin-induced hypotension and bradycardia in the medial solitary tract nucleus
Authors: Fow J. E. , Averill D. B. , Barnes K. L.
Published: December 2017

The selective angiotensin (ANG) II antagonists losartan (AT1) and CGP-42112A (AT2) were used to determine the receptor subtype and neuronal pathways that mediate the hypotension and bradycardia produced by 200 fmol of ANG II microinjected into the dorsal medial nucleus tractus solitarii (NTS) or dorsal motor nucleus of the vagus (dmnX) in anesthetized rats. At dorsal medial NTS sites (0.3 mm below the surface) where L-glutamate microinjections produced maximal decreases in mean arterial pressure (MAP) and heart rate (HR), ANG II (200 fmol, 50 nl, n = 16) elicited hypotension (-22 +/- 1 mmHg) and bradycardia (-26 +/- 2 beats/min). Although L-glutamate also suppressed respiration, ANG II injections in the medial NTS did not alter respiration. Losartan injected at the medial NTS site caused a dose-dependent reduction of ANG II-induced decreases in MAP and HR. At 2 pmol, the AT1 antagonist attenuated the response to ANG II, whereas 100 pmol abolished the effects of ANG II microinjections. In contrast, the AT2 antagonist CGP-42112A (100 pmol) had no effect on the responses to ANG II. Neither ANG II antagonist altered the cardiovascular effects of L-glutamate injections. Losartan injected into the dmnX blocked hypotension and bradycardia produced by ANG II at that site but did not prevent responses to subsequent ANG II injections in the medial NTS.(ABSTRACT TRUNCATED AT 250 WORDS)
Dual effects of L-NAME during transient focal cerebral ischemia in spontaneously hypertensive rats
Authors: Ashwal S. , Cole D. J. , Osborne T. N. , Pearce W. J.
Published: December 2017

The role of nitric oxide (NO) in ischemic neuronal injury is unclear. In permanent focal ischemia models, NO release has been reported to be both neuroprotective, by virtue of actions to improve cerebral blood flow (CBF) within ischemic tissue, and neurotoxic. Very little attention has been given to determining the role of NO in transient focal ischemia. In the present studies, low-dose NO inhibition using NG-nitro-L-arginine methyl ester (L-NAME; 0.1 mg/kg bolus, 0.01 mg.kg-1.min-1 iv) reduced infarct volume after 180 min of middle cerebral arterial occlusion (MCAO) and 120 min of reperfusion as measured via 2,3,5-triphenyltetrazolium chloride by 55% (P < 0.0001). Similar reductions occurred whether L-NAME was given throughout MCAO-reperfusion or just 30 or 60 min before reperfusion. L-NAME reduced CBF in the area of infarction at 30 and 180 min of MCAO by 36 and 33% (P < 0.02). In contrast, 15 min into reperfusion, L-NAME increased CBF in the area of infarction by 69% (P < 0.03) and by 27% in the contralateral homologous right hemisphere. Although vascular effects are present, these findings suggest a neurotoxic role for NO primarily during reperfusion after transient focal ischemic injury.
Deficient noradrenergic response to oral glucose in hypertensives
Authors: Ziegler M. G. , Mills P. J. , Nelesen R. , Dimsdale J. E.
Published: December 2017

The blood pressures of hypertensives lower more following a meal than those of normotensives; the reason for this difference is not known. We gave an oral glucose tolerance test to 33 normotensives and 16 hypertensives matched for age, sex, race, height, and weight. The hypertensives had slightly higher glucose levels and similar insulin levels. The diastolic blood pressures of hypertensives decreased by approximately 10 mmHg, more than twice as much as those of normotensives, but their heart rates did not change. Glucose increased the normotensives' heart rates by approximately 5 beats/min. The hypertensives' plasma norepinephrine responses to a glucose meal were less than one-half of normal. These findings suggest that hypertensives have a large drop in blood pressure following glucose because of a deficient sympathetic nervous response to eating. This may reflect both impaired baroreflexes and deficient insulin-mediated stimulation of the sympathetic nervous system.
Left ventricular systolic dysfunction precedes diastolic dysfunction during myocardial ischemia in conscious dogs
Authors: Ihara T. , Komamura K. , Shen Y. T. , Patrick T. A. , Mirsky I. , Shannon R. P. , Vatner S. F.
Published: December 2017

We studied the initial effects of regional and global left ventricular (LV) ischemia induced by left circumflex and left main coronary artery occlusion (CAO), respectively, on indexes of systolic and diastolic LV function in conscious dogs to determine whether diastolic abnormalities precede systolic dysfunction or vice versa during the onset of either regional or global myocardial ischemia. With regional myocardial ischemia, within four beats after left circumflex CAO, there was a significant decrease in end-systolic wall thickness in the ischemic zone followed by significantly enhanced postsystolic wall thickening in the nonischemic zone at beat 6. Both peak negative first derivative of left ventricular pressure (LV dP/dt) and the isovolumic relaxation half-time (T 1/2) were prolonged, but later (i.e., by the 9th beat). During sustained CAO T1/2 was normalized shortly after postsystolic thickening in the nonischemic zone had disappeared despite persistent regional systolic asynchrony and shortened ejection time. Thus postsystolic thickening in the nonischemic zone played a major role in the early, transient changes in isovolumic relaxation after acute induction of regional ischemia. With global myocardial ischemia, induced by left main coronary occlusion, indexes of systolic function (e.g., LV dP/dt, ejection fraction, and velocity of circumferential endocardial fiber shortening) were also depressed significantly before (by 5–15 beats) indexes of LV diastolic function [e.g., time constant of isovolumic relaxation and LV myocardial and chamber stiffness (by 35–45 beats)]. Similar results were observed in the presence of autonomic blockade, when heart rate did not change with CAO. Thus, during the induction of either acute regional or acute global LV ischemia in conscious dogs, LV systolic dysfunction occurs before diastolic dysfunction.
Left atrial pressure-clamp servomechanism demonstrates LV suction in canine hearts with normal mitral valves
Authors: Ingels N. B. , Daughters G. T. , Nikolic S. D. , DeAnda A. , Moon M. R. , Bolger A. F. , Komeda M. , Derby G. C. , Yellin E. L. , Miller D. C.
Published: December 2017

A novel technique is presented to study suction of the in situ left ventricle in open-chest experimental animals without requiring cardiopulmonary bypass or disturbing the native mitral valvular apparatus. In 17 dogs, left ventricular pressure (LVP) and left atrial pressure (LAP) were measured, the left atrium was cannulated and connected to a servo pump, and LAP was controlled to a setpoint near 0 mmHg by withdrawing blood from the left atrium. Heart rate [103 +/- 17 (SD) min-1], peak pressure (100 +/- 13 mmHg), minimum pressure (1.4 +/- 0.8 mmHg), and maximum rate of change of pressure with respect to time during isovolumic contraction and relaxation (2,506 +/- 775 and -1,761 +/- 855 mmHg/s, respectively) were normal. Servo control of LAP was possible to +/- 1 mmHg. LV suction was demonstrated in each heart (mean negative LVP -2.3 +/- 1.1 mmHg; P < 0.0001). This new technique demonstrates that the left ventricle can generate negative diastolic suction pressures when examined in vivo and in situ with an undisturbed mitral valve and physiologically normal preload and afterload. This adds to a growing body of evidence that, under appropriate circumstances, the heart can suck blood into itself and thereby aid in its own filling.
Flow-induced release of EDRF in the pulmonary vasculature: site of release and action
Authors: Hakim T. S.
Published: December 2017

Pulsatile flow is thought to lower pulmonary vascular resistance by passive recruitment of capillaries and by active vasodilation. This study was undertaken to investigate the role of endothelium-derived relaxing factor (EDRF) during pulsatile flow in isolated canine left lower lobes pretreated with indomethacin. The lobes were perfused in situ with autologous blood (approximately 500 ml/min) using a nonpulsatile pump (Masterflex) or a pulsatile pump (Harvard). With the occlusion techniques, vascular resistance was partitioned into four segments: arterial (Ra), small arterial (R'a), small venous, and venous (Rv). Pulsatile flow (frequency = 70 min-1) did not lower total vascular resistance during baseline or during vasoconstriction. Distribution of vascular resistance among the four segments was not altered significantly by pulsatile flow during normoxia and angiotensin. In contrast, switching to pulsatile flow during hypoxia was associated with an increase in Ra and a decrease in R'a and Rv. N omega-nitro-L-arginine (L-NNA) had no effect on total or segmental resistance during baseline conditions but potentiated the hypoxic pressor response and prevented its recovery by 50%. In addition, the reduction in R'a by pulsatile flow was attenuated by L-NNA, suggesting that EDRF is released by pulsatile flow in this segment. We conclude that a shear stress-induced EDRF release from the small arteries is present in canine lungs and is experimentally demonstrable during pulsatile flow and hypoxia.
Comparison of methods for removal of ectopy in measurement of heart rate variability
Authors: Lippman N. , Stein K. M. , Lerman B. B.
Published: December 2017

Heart rate variability (HRV) analysis uses variations in heart rate to assess activity of the autonomic nervous system. Ectopic beats can affect HRV by introducing mathematical artifact into the computations of time- and frequency-domain measures. Exclusion of ectopy-containing segments of data from analysis has been used to correct for ectopy, but this technique eliminates data and may bias HRV measurements if ectopic beats are causally associated with changes in autonomic tone. We have assessed algorithms for correcting for ectopy: deletion, in which ectopic beats are removed from the R-R sequence; linear and cubic spline interpolation; and nonlinear predictive interpolation, in which ectopy-free R-R sequences are used as templates for replacing ectopic beats. The null method (no ectopy correction) was evaluated to determine the importance of ectopy correction. These methods were applied to computer-generated sequences created by adding simulated ventricular premature depolarizations to 5-min ectopy-free R-R sequences. The null method resulted in significant alterations in HRV. Deletion and nonlinear predictive interpolation performed superiorly to linear or cubic spline interpolation, which overestimated low-frequency power and underestimated high-frequency power. Thus ectopy correction is necessary for HRV analysis; deletion of ectopic beats performs as well as or better than more complicated methods for these relatively short data samples.
Na-independent Cl(-)-HCO3- exchange mediates recovery of pHi from alkalosis in guinea pig ventricular myocytes
Authors: Xu P. , Spitzer K. W.
Published: December 2017

The pH-sensitive fluorescent indicator, carboxy-seminaphthorhodafluor 1 (SNARF 1) was used to assess the contribution of forward Na-independent Cl(-)-HCO3- exchange (1 external Cl- exchanged for 1 internal HCO3-) to intracellular pH (pHi) recovery from alkalosis in adult ventricular myocytes (guinea pig). Intracellular alkalosis was elicited by external application of the weak base, trimethylamine. In the absence of CO2-HCO3- (N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid-buffered solution) the initial rate of pHi recovery from alkalosis (pHi = 7.25-7.75) was slow and independent of pHi, yielding an apparent net HCO3- efflux of 0.36 +/- 0.11 mM/min. In CO2-HCO3(-)-buffered solution, the initial rate of pHi recovery and net HCO3- efflux were much faster and markedly increased by raising pHi. At pHi approximately 7.25, net HCO3- efflux was approximately 2 mM/min and rose to 9 mM/min at pHi approximately 7.6. 4,4'-Diisothiocyanostilbene-2,2'-disulfonic acid (0.4 mM) decreased net HCO3- efflux by 78.1 +/- 8.9% in CO2-HCO3(-)-buffered solution. Reduction in extracellular Cl- concentration from 135 to 20 mM markedly slowed the rate of pHi recovery from alkalosis and reduced net HCO3- efflux. pHi recovery from alkalosis was unaffected by removal of external sodium or exposure to 1 mM amiloride. These results indicate that forward Na-independent Cl(-)-HCO3- exchange mediates pHi recovery from alkalosis in guinea pig ventricular myocytes.
Role of P-selectin in microvascular leukocyte-endothelial interaction in splanchnic ischemia-reperfusion
Authors: Davenpeck K. L. , Gauthier T. W. , Albertine K. H. , Lefer A. M.
Published: December 2017

The role of P-selectin in leukocyte-endothelial interaction after splanchnic arterial occlusion and reperfusion (SAO/R) in pentobarbital-anesthetized rats was investigated employing a P-selectin-neutralizing monoclonal antibody (i.e., MAb PB1.3). MAb PB1.3 (1 mg/kg) given intravenously to SAO/R rats just before reperfusion significantly attenuated leukocyte rolling and adherence in mesenteric postcapillary venules as observed via intravital microscopy. Likewise, ileal myeloperoxidase (MPO) activity was decreased from 4.6 +/- 0.6 in nontreated ischemic rats to 2.0 +/- 0.2 U/100 mg (P < 0.01), indicating a lesser degree of polymorphonuclear leukocyte (PMN) accumulation. A significantly lower plasma free amino-nitrogen concentration was observed in MAb PB1.3-treated rats vs. untreated (P < 0.01), suggesting decreased tissue injury after reperfusion. Immunohistochemical localization demonstrated significant expression of P-selectin in endothelial cells lining ileal postcapillary venules 30 min after reperfusion of the ischemic splanchnic circulation. Thus P-selectin appears to plays an important role in leukocyte accumulation after splanchnic ischemia-reperfusion, and the MAb PB1.3 attenuates the accumulation of PMNs in the ischemic-reperfused small bowel, resulting in reduced tissue injury.
Response of extraparenchymal resistance arteries of rat skeletal muscle to reduced PO2
Authors: Fredricks K. T. , Liu Y. , Lombard J. H.
Published: December 2017

Isolated resistance arteries from the gracilis muscle of rats were simultaneously perfused and superfused with physiological salt solution (PSS) equilibrated with control (21% O2) and reduced (15, 10, 5, or 0% O2) concentrations of O2. The vessels exhibited a significant dilation in response to reduced PO2, which could be inhibited by selective perfusion of the lumen with 21% O2 PSS, endothelial removal, and 1 microM indomethacin, but was unaffected by the nitric oxide synthase inhibitor N omega-nitro-L-arginine (10 microM). Contraction of the arteries in response to 50 mM K+ was inhibited by 0% O2, whereas agonist (norepinephrine and serotonin)-induced contractions and pressure-induced myogenic responses were insensitive to reduced PO2. These results suggest that 1) skeletal muscle resistance arteries are intrinsically sensitive to reduced PO2 independent of parenchymal cell influences, 2) inhibition of resting tone in these vessels is mediated by an endothelium-derived product of the cyclooxygenase pathway, and 3) various forms of contractile activation are not equally sensitive to inhibition by reduced PO2 in extraparenchymal resistance arteries of skeletal muscle.
Regulation of Ca(2+)-dependent ATPase activity in detergent-skinned vascular smooth muscle
Authors: Zhang Y. , Moreland R. S.
Published: December 2017

We measured force, actin-activated myosin adenosinetriphosphatase (ATPase) activity, and myosin light-chain (MLC) phosphorylation levels in Triton X-100 detergent-skinned media of swine carotid arteries. Pseudo-ATPase activity composed of MLC kinase and phosphatase activities contributed maximally 12% to steady-state tissue ATPase activity. An increase in the Ca2+ concentration ([Ca2+]) induced an increase in force, MLC phosphorylation, and actin-activated myosin ATPase activity; this protocol was defined as the force development phase of contraction. Force maintenance was defined as the state induced by decreasing the [Ca2+] after a maximal contraction. Lowering the [Ca2+] decreased MLC phosphorylation to levels similar to those measured during force development at each [Ca2+]. In contrast, force remained at elevated levels while actin-activated myosin ATPase activity fell to significantly lower levels than those measured during the development phase for each [Ca2+]. We suggest that the significantly lower actin-activated myosin ATPase activity observed during a state of elevated force, compared with the development phase of a contraction, is evidence of slowly cycling latch bridges.
Thrombin receptor peptide-mediated leukocyte rolling in rat mesenteric venules: roles of P-selectin and sialyl Lewis X
Authors: Zimmerman B. J. , Paulson J. C. , Arrhenius T. S. , Gaeta F. C. , Granger D. N.
Published: December 2017

Neutrophil adhesion to monolayers of cultured endothelial cells is enhanced, via a P-selectin-mediated mechanism, by a 14-amino acid peptide fragment (TRP-14) of the thrombin receptor. The objective of this study was to determine whether TRP-14 promotes P-selectin-mediated sialyl Lewis X-dependent leukocyte rolling in postcapillary venules. Superfusion of the rat mesentery with TRP-14 for 30 min resulted in the recruitment of rolling leukocytes and a concomitant reduction in leukocyte rolling velocity. Analogues of TRP-14 were largely ineffective in promoting leukocyte-endothelial cell adhesion. Treatment with either a monoclonal antibody directed against rat P-selectin or soluble sialyl Lewis X oligosaccharide (the carbohydrate ligand to P-selectin found on leukocytes) significantly attenuated the TRP-14-induced recruitment of rolling leukocytes. However, no effect was observed with a nonbinding antibody or a control fucose-deficient oligosaccharide. These results indicate that TRP-14 elicits the recruitment of rolling leukocytes in postcapillary venules via a P-selectin-dependent mechanism. The results also support the view that sialyl Lewis X participates in P-selectin-mediated leukocyte-endothelial cell adhesion.
Ryanodine and dihydropyridine binding patterns and ryanodine receptor mRNA levels in myopathic hamster heart
Authors: Lachnit W. G. , Phillips M. , Gayman K. J. , Pessah I. N.
Published: December 2017

We have determined the densities of sarcolemmal voltage-dependent Ca2+ channels (VDCC) and Ca(2+)-induced Ca2+ release channels (CICR) of sarcoplasmic reticulum (SR) in the cardiomyopathic hamster heart using [3H]PN-200 and [3H]ryanodine, respectively. Partially purified cardiac membrane preparations from myopathic animals exhibit a twofold higher capacity to bind both [3H]PN-200 and [3H]ryanodine. Crude particulate membrane fractions from normal and cardiomyopathic animals reveal no significant difference in receptor densities for [3H]PN-200, whereas densities for [3H]ryanodine binding sites and mRNA levels are significantly (P < 0.05) diminished in cardiomyopathic animals. Inhibition of [3H]ryanodine binding by either Ca2+ or Mg2+ (in mM) as well as temperature dependence for receptor activation for [3H]ryanodine (Q10) is not significantly different, whereas membranes isolated from cardiomyopathic hearts are 1.4-fold and threefold more sensitive to activation by doxorubicin and Ca2+ (in microM), respectively. Vesicles isolated from myopathic hearts are more sensitive to inhibition of Ca2+ uptake by doxorubicin. The higher densities of binding sites for [3H]PN-200 and [3H]ryanodine observed in partially purified membrane fractions from cardiomyopathic hearts are more likely the result of altered patterns with which T-tubule and CICR channels fractionate in preparations from cardiomyopathic hamster heart rather than transcriptional upregulation and may be a consequence of the deficiency in a dystrophin-associated glycoprotein recently identified. Downregulation and functional changes in CICR channels may alter SR Ca2+ transport and contribute to the progression of cardiomyopathy in the hamster.
Role of venular endothelium in control of arteriolar diameter during functional hyperemia
Authors: Saito Y. , Eraslan A. , Lockard V. , Hester R. L.
Published: December 2017

This study was designed to determine the importance of the venular endothelium in the vasodilation of adjacent arterioles during functional hyperemia. The hamster cremaster muscle was prepared for in vivo microscopy. Two silver-silver chloride electrodes were placed across the pedicle of the cremaster muscle, and a square-wave pulse (10 V amplitude, 1 ms duration, and 1 Hz frequency) was used to elicit muscle contraction. Muscle stimulation for 1 min resulted in a vasodilation of the first-order arterioles from 74 +/- 2 to 91 +/- 2 microns (n = 9, P < 0.05). After perfusion of the venule with air to disrupt the venular endothelium, there was no significant effect on the resting diameter, 73 +/- 3 microns, but the vasodilation associated with the muscle stimulation was significantly attenuated to 82 +/- 3 microns (P < 0.01). After completion of these experiments, the disruption of venular endothelium was confirmed by electron microscopy. The functional vasodilation of arterioles adjacent to venules with an intact endothelium (venules in which air did not enter) was retained after air perfusion (n = 6). These results suggest that the presence of the venular endothelium is important for the arteriolar vasodilation during functional hyperemia. We propose that the venular endothelium releases a relaxing factor responsible for a portion of the functional arteriolar vasodilation.
Effect of hypoxia on adherence of granulocytes to endothelial cells in vitro
Authors: Pietersma A. , De Jong N. , Koster J. F. , Sluiter W.
Published: December 2017

The objective of this study was to investigate the effect of hypoxia on the adhesiveness of endothelial cells for granulocytes. Human umbilical vein endothelial cells (HUVEC) were exposed to a PO2 of 7.5 mmHg (1.0 kPa), and the adherence of granulocytes was assessed under continuous hypoxia by means of a hypoxic incubator room. After 2 h of hypoxia the adherence of granulocytes decreased to 50% of the normoxic control, which was not due to a decreased viability of the endothelial cells nor to an increased generation of the antiadhesive factors nitric oxide, prostacyclin, and adenosine. Hypoxia also had no effect on the expression of intercellular adhesion molecule (ICAM)-1 or ICAM-2 on the endothelium. Although the mechanism of the action of hypoxia on the adhesiveness of endothelial cells remains unclear as yet, our data suggest that HUVEC possess a protective mechanism that prevents granulocyte adherence to endothelial cells under extreme hypoxic conditions. The decreased adherence seems paradoxical to the in vivo situation for which the increased margination of granulocytes within the vascular compartment of the ischemic tissue has been observed. However, hypoxia did not impair the potential adhesiveness of HUVEC, since stimulation of endothelial cells under hypoxic conditions with calcium ionophore or lipopolysaccharide increased the adherence of granulocytes in a similar fashion as under normoxic conditions. We therefore conclude that the increased margination of granulocytes during ischemia may be accomplished by the additional stimulation of hypoxic endothelial cells.
Inhibition of nitric oxide synthesis augments centrally induced sympathetic coronary vasoconstriction in cats
Authors: Goodson A. R. , Leibold J. M. , Gutterman D. D.
Published: December 2017

The principal effect of sympathetic activation on the coronary circulation is an alpha-adrenergic coronary vasoconstriction in the presence of beta-receptor blockade. Secondary effects include vasodilation due to beta-adrenoceptor stimulation and alpha 2-mediated release of endothelium-derived relaxing factor (EDRF) from the coronary vascular endothelium. We hypothesized that blockade of nitric oxide synthesis (nitro-L-arginine methyl ester, L-NAME) would augment coronary vasoconstriction to sympathetic stimulation as a result of a decrease in alpha 2-mediated EDRF release. In chloralose-anesthetized cats, hypothalamic stimulation produced increases in coronary vascular resistance [maximum 26 +/- 9% (SE)] and arterial pressure (41 +/- 7%) and a decrease in coronary blood flow velocity (15 +/- 6%). L-NAME (3 mg/kg iv) increased baseline arterial pressure from 69 +/- to 92 +/- 7 mmHg (P < 0.05). After L-NAME, a greater increase in coronary vascular resistance (55 +/- 20%, P < 0.05), a decrease in coronary blood flow velocity (24 +/- 7%, P < 0.05), and a similar pressor response (34 +/- 7%) were observed in response to hypothalamic stimulation. L-Arginine reversed the effect of L-NAME on coronary vasoconstriction to hypothalamic stimulation. Similar increases in arterial pressure (from 73 +/- 3 to 91 +/- 5 mmHg, P < 0.05) with vasopressin (0.01-0.05 U/min) failed to enhance coronary vasoconstriction to activation in anterior hypothalamus. We conclude that inhibition of EDRF synthesis augments centrally induced sympathetic coronary vasoconstriction in the cat.
Cloning and characterization of an Ito-like potassium channel from ferret ventricle
Authors: Comer M. B. , Campbell D. L. , Rasmusson R. L. , Lamson D. R. , Morales M. J. , Zhang Y. , Strauss H. C.
Published: December 2017

FK1, a ferret ventricular full-length cDNA clone, encodes a 654-amino acid protein with 98% identity to human K+ transient outward current (Ito)-like HK1 (Tamkun et al. FASEB J.5: 331-337, 1991). FK1 is detectable in ferret brain, atrium, left and right ventricle, and kidney but not in skeletal muscle, endothelial cells, aorta, and liver. In Xenopus oocytes, FK1 cRNA gives rise to a rapidly activating and inactivating Ito-like current, which is highly K+ selective (Na(+)-to-K+ permeability ratio = 0.003). Activation occurs over an approximately 50-mV range (-40 to +10 mV) and displays a sigmoid delay in onset with potential-dependent time constants that decrease with depolarization. Steady-state activation can be described with either a simple Boltzmann relationship [half-activation potential (V1/2) = -25 mV, slope (k) = 10 mV] or a Boltzmann relationship raised to either the third or fourth power (alpha 3: V1/2 = -43 mV, kappa = 13.1 mV; alpha 4: V1/2 = -48 mV, kappa = 13.6 mV, where alpha is the activation variable). Inactivation kinetics are biexponential, with the main fast time constant becoming independent of membrane potential depolarized to 0 mV. Steady-state inactivation can be described with a single Boltzmann relationship (V1/2 = -57 mV, kappa = 5.0 mV). Fast inactivation is removed by NH2-terminal deletions. Recovery from inactivation (-90 mV) is quite slow (half-time = 4.8 +/- 2.5 s). In 2 mM extracellular K+ concentration ([K+]o), FK1 tail currents display conventional deactivation behavior; however, in 98 mM [K+]o the tail currents display "reopening" behavior. These results suggest a molecular basis for the electrophysiological similarities between ferret and human ventricular Ito (Campbell et al. J. Gen. Physiol. 101: 571-601, 1993; Nabauer et al. Circ. Res. 73: 386-394, 1993).
Angiotensin II maintains, but does not mediate, isoproterenol-induced cardiac hypertrophy in rats
Authors: Golomb E. , Abassi Z. A. , Cuda G. , Stylianou M. , Panchal V. R. , Trachewsky D. , Keiser H. R.
Published: December 2017

The role of angiotensin II (ANG II) in the development of isoproterenol (Iso)-induced cardiac hypertrophy was examined in rats. Iso increased cardiac mass, left ventricular RNA-to-DNA ratio, and the cardiac content of both myosin heavy chain and hydroxyproline in a dose-dependent manner, indicating that Iso-induced cardiac hypertrophy involves growth of both muscle and connective tissue. Cardiac hypertrophy reverted within 11-14 days after cessation of Iso. Propranolol prevented development of Iso-induced cardiac hypertrophy but did not affect the rate of its reversal. The ANG II receptor blocker losartan (Los) did not significantly decrease the hypertrophic response to Iso. Los injected after cessation of Iso dramatically enhanced the reversal of cardiac hypertrophy, even in rats that received Los with Iso during the induction of Iso-induced cardiac hypertrophy. ANG II, injected continuously at a subpressor dose that did not affect heart weight when given alone, inhibited reversal of cardiac hypertrophy when given after cessation of Iso. Los did not significantly affect the induction of the protooncogene c-fos by Iso. We conclude that endogenous ANG II has a major function in maintaining Iso-induced cardiac hypertrophy but does not mediate its induction. This suggests that different interactive stimuli may be required for development of cardiac hypertrophy, i.e., for initiation and for maintenance.
Resonance in the kidney system of rats
Authors: Yu G. L. , Wang Y. L. , Wang W. K.
Published: December 2017

The pressure wave of the abdominal aorta and the flow wave of the renal artery were recorded simultaneously from a rat. The impedance of a kidney system that is derived by dividing the pressure of the corresponding frequency by that of the flow was studied in six rats. The data show that the system has two resonant frequencies, at the second and third harmonics. At the second harmonic, the pressure wave and fluid flow in a round trip through the branch of the kidney. Whereas it is difficult for the third harmonic flow to enter the kidney, it flows directly through the aorta. To obtain further proof, we compared the frequency components of the two flows measured simultaneously on the abdominal aorta and the renal artery and found the same result. The kidney, renal artery, and aorta combined show a coupled oscillation that is analogous to that of resonance circuits. The kidney vascular system exhibits a resonant frequency at the second harmonic of the heartbeat.
Loss of elastic recoil in postischemic myocardium induces rightward shift of the systolic pressure-volume relationship
Authors: Krams R. , Janssen M. , Van der Lee C. , Van Meegen J. , De Jong J. W. , Slager C. J. , Verdouw P. D.
Published: December 2017

Ischemia-induced systolic dysfunction has been ascribed to changes in cellular excitation-contraction coupling and diastolic dysfunction because of disruption of the extracellular collagen matrix. Therefore, systolic and diastolic pressure-volume relationships and O2 consumption were determined before and after 5 min of global ischemia in isolated blood-perfused porcine hearts. The slope of the systolic pressure-volume relationship was 7.2 +/- 0.6 (SE) mmHg.ml-1.100 g-1 (n = 18) at baseline and did not change during reperfusion, but the systolic volume intercept shifted from 1.0 +/- 0.4 ml/100 g at baseline to 3.7 +/- 1.4, 4.1 +/- 1.1, and 4.2 +/- 0.9 ml/100 g at 15, 30, and 60 min of reperfusion, respectively (all P < 0.05). The diastolic volume intercept was 8.2 +/- 0.7 ml/100 g at baseline and remained unchanged during reperfusion. Therefore, the difference of the systolic-diastolic volume intercepts, an index of elastic recoil forces, was decreased to 57 +/- 8, 49 +/- 7, and 47 +/- 9% of baseline values (P < 0.05). The shift of the systolic pressure-volume relationship was accompanied by a transient decrease of contractile efficiency (slope of O2 consumption-pressure-volume-area relationship) at 15 min of reperfusion (from 43 +/- 6 to 27 +/- 7%). We hypothesize that the rightward shift of the systolic pressure-volume relationship was compatible with a decrease of elastic-restoring forces, probably induced by alterations in the extracellular collagen matrix and/or the cytoskeleton, and thereby our data imply that left ventricular dysfunction of postischemic myocardium does not result solely from disturbances in excitation-contraction coupling.
Stretch-mediated activation of cardiac renin gene
Authors: Boer P. H. , Ruzicka M. , Lear W. , Harmsen E. , Rosenthal J. , Leenen F. H.
Published: December 2017

This study was designed to quantitate cardiac mRNA levels encoding components of the local renin-angiotensin system during the development of volume overload-induced cardiac hypertrophy. Changes in cardiac renin mRNA levels were measured in relation to renin activity in the left ventricle (LV) and in plasma after acute passive stretch of the heart caused by an aortovenocaval shunt in the rat. A quantitative reverse-transcriptase polymerase chain reaction method with competitive internal standards was used to measure mRNA levels in total RNA derived from cardiac tissues after shunt. Seven days after shunt surgery, LV weight was increased by 23%. Renin activities were elevated four- and twofold in plasma and LV, respectively. LV angiotensinogen mRNAs were not significantly increased by shunt surgery; they were twofold higher than phosphoglycerate kinase mRNA from the housekeeping gene PGK-1. By day 7, LV levels for renin mRNA were significantly increased from well below 0.25% to approximately 1% of PGK-1 mRNA. Identity between renin polymerase chain reaction products from kidney and heart cDNAs and absence of "reninlike" amplification products were supported by Southern blotting. Volume overload caused increased expression of the renin gene in the stretched myocardium. This finding is consistent with the concept of a myocardial renin-angiotensin system that can be activated by locally produced renin and contributes to the hypertrophy of cardiac muscle.
Leukocyte rolling in venules of striated muscle and skin is mediated by P-selectin, not by L-selectin
Authors: Nolte D. , Schmid P. , Jager U. , Botzlar A. , Roesken F. , Hecht R. , Uhl E. , Messmer K. , Vestweber D.
Published: December 2017

Leukocyte rolling in post-capillary venules is mediated by adhesion molecules of the selectin family expressed on both leukocytes (L-selectin) and endothelial cells (E- and P-selectin). With the use of intravital fluorescence microscopy, the effects of antibodies against these selectins were analyzed in the skinfold chamber model of BALB/c mice and the ear model of homozygous hairless mice (hr/hr) that permit chronic observation of striated muscle and skin microcirculation in awake animals, respectively. Mice were injected intravenously with monoclonal antibodies (MAb) to murine L-selectin and E-selectin and affinity-purified polyclonal antibodies to P-selectin. The antibodies, which are known to block cell adhesion, were tested by immunoprecipitation to selectively bind to L-, E-, or P-selectin. Leukocyte rolling was a constant finding in both microcirculation models in the absence of inflammatory stimuli. In both models, injection of anti-P-selectin antibodies completely prevented baseline leukocyte rolling over an observation period of 2 h (P < 0.01 vs. baseline), while no effects were seen after administration of either anti-L-selectin or anti-E-selectin MAb. Treatment with the isotype-matched control antibodies did not affect leukocyte rolling in either model. We conclude that leukocyte rolling in postcapillary venules of murine striated muscle and skin is a physiological process mediated via P-selectin, whereas L- and E-selectin appear not to play a significant role under these circumstances.
Kinetics of tension development in skinned cardiac myocytes measured by photorelease of Ca2+
Authors: Araujo A. , Walker J. W.
Published: December 2017

The rate of activation of tension development by free Ca2+ was examined in skinned rat ventricular myocytes. Pulse photolysis of the photosensitive Ca2+ chelator, Nitr-7, was used to rapidly elevate Ca2+ in the vicinity of the myofilaments. Tension increased exponentially with a first-order rate constant (kCa) that depended on the level of Ca2+ activation. kCa increased approximately linearly from 0.9 +/- 0.2 s-1 at 20% maximal Ca(2+)-activated tension (Po) to 4.0 +/- 0.9 s-1 at 85% Po, representing a fourfold increase in kCa with activation. Reducing free Mg2+ from 1 to 0.1 mM accelerated kCa by about twofold at all levels of Ca2+. Tension development kinetics were significantly different in skinned rabbit psoas fibers: kCa increased nonlinearly from 1.2 +/- 0.2 s-1 at 15% Po to a maximum of 17.5 +/- 1.3 s-1 at 85% Po, representing a 15-fold increase in kCa with activation. Moreover, lowering free Mg2+ increased kCa only at submaximal Ca2+ in psoas fibers. Extraction of troponin C (TNC) from psoas fibers and recombination with bovine cardiac TNC did not significantly alter any of these characteristics of tension development kinetics. We conclude that significant differences exist between cardiac and fast-twitch skeletal muscles in terms of the effects of Ca2+ and Mg2+ on contraction kinetics and that these differences cannot be attributed solely to differences in TNC isoforms.
Hypertension induced by high salt intake in absence of volume retention in reduced renal mass rats
Authors: Cowley A. W. , Skelton M. M. , Papanek P. E. , Greene A. S.
Published: December 2017

Reduction of renal mass (RRM) combined with a high-salt diet results in volume retention, a rise of cardiac output, and hypertension. The present studies were designed to determine whether prevention of volume retention would alter the rise of mean arterial pressure (MAP) in RRM rats given high salt. Rats were studied in a modified metabolic cage to permit continuous determination of total body weight (TBW). In group 1, NaCl was increased from 1 to 14.5 meq/day and delivered isotonically. In group 2, NaCl was increased while TBW was servo-controlled to a constant level. Group 3 was also servo-controlled, but rats received an intravenous infusion of an arginine vasopressin V1 antagonist throughout the study. MAP in group 1 rose 24 mmHg by day 4 of high salt with a parallel increase of TBW of 26 g. In group 2, MAP rose 48 mmHg by day 4 of high salt, while TBW was controlled to within 0.6% of control body weight. With inhibition of vasopressin V1 receptors (group 3), MAP rose 39 mmHg. Nearly equivalent amounts of NaCl were retained in all groups, which was associated with no change of plasma Na in group 1 but an increase of nearly 7 meq/ml in groups 2 and 3. Hematocrit fell nearly 9% in groups 2 and 3 compared with a 4% reduction in group 1. The results suggest that under conditions where net retention cannot occur, high salt intake increases MAP by an osmotically driven fluid transfer from cells, which results in an even greater expansion of blood volume.(ABSTRACT TRUNCATED AT 250 WORDS)