bluuebunny/crossref_metadata_2025 huggingface dataset:
External pH dependency of delayed afterdepolarization in rabbit myocardium
Authors: Kano T. , Nishi K.
Published: December 2017

Effects of changing external pH on delayed afterdepolarization (DAD) induced by a train of electrical stimuli in the rabbit ventricular papillary muscle fibers were examined using a conventional microelectrode technique in vitro. Preparations were superfused with Tyrode solution containing norepinephrine (3 X 10(-6) M), and the external pH was decreased. After a train of driven action potentials, DAD was induced at pH 7.0 in the presence of norepinephrine. The amplitude of the DAD induced by norepinephrine at pH 7.0 increased as the stimulus cycle length was shortened and as the number of applied stimuli increased. The increase in the amplitude of DAD resulted in yielding one or multiple nondriven action potentials. DAD, thus initiated, was completely suppressed by a further decrease of external pH to 6.7-6.0. Lidocaine and adriamycin depressed the amplitude of DAD, but verapamil did not. The results imply that only slight lowering of the external pH induced by ischemic conditions or by other means would provoke DAD which, in turn, would result in triggered activity in situ.
Characterization of a sodium pump-induced hyperpolarization in isolated human atrium
Authors: Rasmussen H. H. , Singer D. H. , Ten Eick R. E.
Published: December 2017

Specimens of right atrial appendage from 106 patients were incubated in cold Tyrode solution, and transmembrane resting potentials (Em) were recorded during rewarming at selected temperatures. Rewarming caused a transient hyperpolarization to develop. The hyperpolarization had a temperature threshold between 17 and 22 degrees C and was inhibited by acetylstrophanthidin. Acetylcholine (ACh) induced a depolarization during early rewarming in 7, 10, 20, and 40 mM K+, indicating that Em hyperpolarized to a potential negative to the equilibrium potential for K+. ACh had no effect after some decline of Em, and hyperpolarization was induced by ACh when Em had reached steady state. The relationship between [K+] in the bulk phase of the superfusate [( K]b) and the "reversal potentials" for the ACh effect was log linear and had a slope of 61.7 mV per tenfold change in [K]b. The relationship between [K]b and hyperpolarization was studied in the presence of 0.5 mM Ba2+. The apparent [K]b resulting in half-maximal pump-induced hyperpolarization was 1.3 mM. The data indicate that human atrium can pump Na+ electrogenically and that the characteristics of the Na+ pump-induced hyperpolarization resemble those described for cardiac tissue from several other mammalian species.
Endogenous adenosine inhibits catecholamine contractile responses in normoxic hearts
Authors: Dobson J. G. , Ordway R. W. , Fenton R. A.
Published: December 2017

The importance of endogenous myocardial adenosine in attenuating catecholamine-elicited contractile responses was investigated in perfused oxygenated rat hearts. Perfusion of the isolated hearts with adenosine deaminase potentiated the isoproterenol-induced increases of three contractile variables (left ventricular pressure development and rates of both left ventricular pressure development and relaxation). The peak (maximal, within 30 s) and maintained (after 1 min) increases of the contractile variables caused by 10(-8) M isoproterenol were enhanced by 15-22 and 31-43%, respectively. Adenosine deaminase appeared in epicardial surface transudates of similarly perfused hearts, indicating that the enzyme had entered the myocardial interstitial space. Isoproterenol alone elevated the release of adenosine into coronary effluents of isoproterenol-stimulated hearts, and adenosine deaminase prevented the release of the nucleoside. The higher the level of adenosine in the effluent, the greater the reduction of the peak contractile variables. Phenylisopropyladenosine at 10(-8) M prevented the adenosine deaminase potentiation of 10(-9) M isoproterenol-induced contractile responses. The adenosine analogue at 10(-6) M blocked completely the isoproterenol-produced increases in the contractile variables. These results suggest that endogenous adenosine prevents full mechanical responsiveness to beta-adrenoceptor stimulation in the oxygenated myocardium. In addition, the findings support the notion that adenosine serves as an important negative feedback modulator in the oxygenated heart.
Modulation of endothelium-dependent responses by chronic alterations of blood flow
Authors: Miller V. M. , Aarhus L. L. , Vanhoutte P. M.
Published: December 2017

To determine whether the blood flow and O2 tension to which a blood vessel is chronically exposed could modulate endothelium-dependent responses, these parameters were altered in the dog either by causing partial occlusion of the femoral artery or by creating a fistula between the femoral artery and vein. Blood flow was reduced by 75% in the clamped artery; mean arterial pressure was unchanged. In the vessels proximal to the fistula, blood flow was elevated and O2 tensions were similar in the vein and artery. After 6 wk the femoral arteries and veins were excised, and their endothelium-dependent responses were studied in vitro. The endothelium-dependent relaxations to acetylcholine, adenosine diphosphate, and alpha 2-adrenergic stimulation were augmented in fistula-operated compared with sham-operated arteries. The responses to these agents in the clamp-operated vessels were not different from those of the sham-operated ones. Relaxation to arachidonic acid in the arteries showed an inverse relationship to blood flow. In the veins proximal to the fistula, the endothelium-dependent relaxations to acetylcholine were augmented and an endothelium-dependent relaxation to alpha 2-adrenergic stimulation was present; only a contractile response was observed in veins from the sham-operated limb in response to the latter. These studies suggest a pattern of increased endothelium-dependent relaxation in vessels exposed to chronically elevated blood flow.
Responses of ACTH, epinephrine, norepinephrine, and cardiovascular system to hemorrhage
Authors: Darlington D. N. , Shinsako J. , Dallman M. F.
Published: December 2017

Hemorrhages of various magnitudes were performed on conscious rats, and arterial pressure, heart rate, and plasma levels of adrenocorticotropin hormone (ACTH), epinephrine, and norepinephrine were measured. Eight rats were prepared with chronic femoral arterial cannulas and received a 10, 15, or 20 ml/kg X 3 min hemorrhage in random order on day 4, 7, or 10 after surgery. Mean arterial blood pressure, heart rate, and plasma ACTH, epinephrine, and norepinephrine concentrations were determined before and 20 min after hemorrhage. Arterial blood pressure decreased significantly immediately after each hemorrhage and slowly recovered over the next 20 min. Heart rate did not change during the 10 ml/kg X 3 min hemorrhage but decreased significantly after 15 and 20 ml/kg X 3 min hemorrhages. Plasma ACTH and epinephrine levels increased significantly 20 min after the 15 and 20 ml/kg X 3 min hemorrhages but not after 10 ml/kg X 3 min hemorrhage. Norepinephrine increased significantly 20 min after the 20 ml/kg X 3 min hemorrhage but not after the 10 or 15 ml/kg X 3 min hemorrhage. There was no significant effect of time and repeated hemorrhages on resting levels of plasma ACTH, epinephrine, norepinephrine, osmolality, or proteins. Since hemorrhage leads to a fall in arterial pressure and a subsequent rise in plasma ACTH, the relationship between plasma ACTH and mean arterial blood pressure during hemorrhage was examined in both conscious and acutely prepared pentobarbital sodium-anesthetized rats.(ABSTRACT TRUNCATED AT 250 WORDS)
Validation of a single crystal for measurement of transmural and epicardial thickening
Authors: Zhu W. X. , Myers M. L. , Hartley C. J. , Roberts R. , Bolli R.
Published: December 2017

Conventional measurement of wall thickening with two transit-time crystals requires considerable skill, is associated with myocardial trauma, and does not discern the function of different layers of the left ventricular (LV) wall. To overcome these limitations, we have developed a 10 MHz pulsed Doppler technique that measures thickening at any depth of the LV wall from a single crystal sutured to the epicardium. To verify its accuracy, we compared measurements of thickening fraction (TF) by pulsed Doppler and transit-time methods in 25 open-chest dogs. The epicardial Doppler crystal was placed over an intramyocardial crystal positioned either in the subendocardium or midwall. The epicardial crystal acted as both the Doppler transducer and the transit-time transmitter, so that TF was measured by each technique at the same site. A wide range of regional function (transmural TF:-28-42%, epicardial TF:-20-28%) was produced by coronary occlusion followed by reperfusion, and by isoproterenol and phenylephrine infusions. There was a good correlation between the two methods, both for transmural TF (r = 0.98, 107 paired measurements) and epicardial TF (r = 0.99, 70 paired measurements). Despite marked changes in function, the two techniques yielded similar measurements under all of the conditions tested (base line, ischemia, 5, 15, 30, 60, 120, and 180 min of reperfusion, isoproterenol and phenylephrine). One-millimeter errors in selecting the depth of the Doppler sample volume did not significantly affect the accuracy of TF measurements. Thus the single pulsed Doppler crystal provides a simple, atraumatic, and accurate means for measuring myocardial function, both transmurally and in selected layers of the LV wall.
Renal vasodilatation after inhibition of renin or converting enzyme in marmoset
Authors: Neisius D. , Wood J. M. , Hofbauer K. G.
Published: December 2017

The relative importance of angiotensin II for the renal vasodilatory response after converting-enzyme inhibition was evaluated by a comparison of the effects of converting-enzyme and renin inhibition on renal vascular resistance. Renal, mesenteric, and hindquarter blood flows were measured with chronically implanted ultrasonic-pulsed Doppler flow probes in conscious, mildly volume-depleted marmosets after administration of a converting-enzyme inhibitor (enalaprilat, 2 mg/kg iv), a synthetic renin inhibitor (CGP 29,287, 1 mg/kg iv), or a renin-inhibitory monoclonal antibody (R-3-36-16, 0.1 mg/kg iv). Enalaprilat reduced blood pressure (-16 +/- 4 mmHg, n = 6) and induced a selective increase in renal blood flow (27 +/- 8%, n = 6). CGP 29,287 and R-3-36-16 induced comparable reductions in blood pressure (-16 +/- 4 mmHg, n = 6 and -20 +/- 4 mmHg, n = 5, respectively) and selective increases in renal blood flow (36 +/- 12%, n = 6 and 34 +/- 16%, n = 4, respectively). The decrease in renal vascular resistance was of similar magnitude for all of the inhibitors (enalaprilat -28 +/- 3%, CGP 29,287 -32 +/- 6%; and R-3-36-16 -33 +/- 7%). These results indicate that the renal vasodilatation induced after converting-enzyme or renin inhibition is mainly due to decreased formation of angiotensin II.
Aminophylline and interstitial adenosine during sustained exercise hyperemia
Authors: Thompson L. P. , Gorman M. W. , Sparks H. V.
Published: December 2017

We tested the hypothesis that an increase in interstitial fluid (ISF) adenosine concentration contributes to vasodilation of high oxidative skeletal muscle during sustained free-flow exercise. Canine calf muscles were stimulated at 3 Hz for 10 min before and after the infusion of the adenosine receptor antagonist aminophylline (10 mg/kg). The vasodilation that occurred during aminophylline infusion was allowed to decay before the postaminophylline exercise period was begun. This dose of aminophylline shifted the response to infused adenosine 20-fold during rest and reduced the response to a standard dose by 90% during exercise. Aminophylline had no significant effect on blood flow or on O2 consumption at rest or during exercise. Adenosine release (venous minus arterial plasma concentration times plasma flow) increased during 3-Hz exercise both before and after aminophylline infusion, but venous plasma adenosine concentration did not increase in either case. We developed a mathematical model of adenosine movement between ISF and plasma to help us judge whether to use adenosine release or venous concentration as an index of ISF adenosine and decided that venous concentration should be used. We conclude that aminophylline has no effect on sustained 3-Hz exercise hyperemia because under these conditions ISF adenosine concentration does not increase.
Activation of mesenteric arteries and veins by preganglionic and postganglionic nerves
Authors: Kreulen D. L.
Published: December 2017

Intracellular recordings were made from inferior mesenteric artery and vein and their primary and secondary branches. The major nerve trunks associated with the inferior mesenteric ganglion were stimulated with single shocks and repetitively. Excitatory junction potentials (EJPs) were recorded in arterial cells but not in veins. Stimulation of the postganglionic lumbar colonic nerves elicited the largest EJPs; stimulation of preganglionic lumbar splanchnic nerves or the interganglionic intermesenteric nerves elicited EJPs that were 40 and 44%, respectively, of the amplitude of the EJPs elicited with lumbar colonic nerve stimulation. In response to repetitive stimulation, the membranes of both artery and vein cells depolarized by an amount dependent on the frequency and duration of stimulation. At a given frequency of stimulation, the vein cells depolarized more rapidly and constricted sooner than the arterial cells. The depolarizations and the associated constrictions were attenuated by phentolamine (10(-6) M) or prazosin (10(-6) M). In 70% of arterial cells tested, repetitive nerve stimulation at 1-5 Hz resulted in a long-lasting hyperpolarization. At 2 Hz the hyperpolarizations averaged 2.0 +/- 0.4 mV. These hyperpolarizations were not blocked by either alpha- or beta-adrenergic antagonists. These studies demonstrate that the innervation of mesenteric arteries and veins can be activated by stimulating preganglionic, interganglionic, and postganglionic nerves and that there are fundamental differences between the electrical responses of adjacent arteries and veins to nerve stimulation.
Failure of prolonged exercise training to increase red cell mass in humans
Authors: Shoemaker J. K. , Green H. J. , Coates J. , Ali M. , Grant S.
Published: December 2017

The purpose of this study was to investigate the time-dependent effects of long-term prolonged exercise training on vascular volumes and hematological status. Training using seven untrained males [age 21.1 +/- 1.4 (SE) yr] initially consisted of cycling at 68% of peak aerobic power (VO2peak) for 2 h/day, 4-5 days/wk, for 11 wk. Absolute training intensity was increased every 3 wk. Red cell mass (RCM), obtained using 51Cr, was unchanged (P > 0.05) with training (2,142 +/- 95, 2,168 +/- 86, 2,003 +/- 112, and 2,080 +/- 116 ml at 0, 3, 6, and 11 wk, respectively) as were serum erythropoietin levels (17.1 +/- 4.3, 13.9 +/- 3.5, and 17.0 +/- 2.0 U/l at 0, 6, and 11 wk, respectively). Plasma volume measured with 125I-labeled albumin and total blood volume (TBV) were also not significantly altered. The increase in mean cell volume that occurred with training (89.7 +/- 0.95 vs. 91.0 +/- 1.0 fl, 0 vs. 6 wk, P < 0.05) was not accompanied by changes in either mean cell hemoglobin or mean cell hemoglobin concentration. Serum ferritin was reduced 73% with training (67.4 +/- 13 to 17.9 +/- 1 microgram/l, 0 vs. 11 wk, P < 0.05). Total hemoglobin (HbTot) calculated as the product of hemoglobin concentration and TBV was unaltered (P > 0.05) at both 6 and 11 wk of training. The 15% increase in VO2peak (3.39 +/- 0.16 to 3.87 +/- 0.14 l/min, 0 vs. 11 wk, P < 0.05) with training occurred despite a failure of training to change TBV, RCM, or HbTot.
Endothelin-1 constricts fetoplacental microcirculation and decreases fetal O2 consumption in sheep
Authors: Adamson S. L. , Whiteley K. J. , Langille B. L.
Published: December 2017

Endothelin-1 produced by umbilicoplacental tissues may regulate fetal placental perfusion. To investigate its site of action, we measured segmental resistance in this bed in unanesthetized fetal sheep near term during fetal endothelin-1 infusion. A 15-min intravenous infusion of endothelin-1 at 1 micrograms/min significantly increased fetal blood pressure in the aorta (+33%), cotyledon artery and vein, and inferior vena cava, and endothelin-1 decreased fetal heart rate (-40%). Vascular resistance in the placental microcirculation increased significantly (+332%), but smaller increases in resistance of the umbilical artery and vein were not significant. Nevertheless, the stiffness of the umbilical arterial wall appeared to increase because vascular input impedance increased significantly both at the heart rate frequency (+85%) and when averaged > 2 Hz (characteristic impedance; +138%). Mean blood flow in the umbilical artery decreased by 64%, and the flow pulsatility index increased 137% (P < 0.05 for both). Despite the large decrease in placental perfusion, there was no significant change in descending aortic oxygen tension or oxygen content, because fetal oxygen consumption was reduced by 40%. We conclude that endothelin-1 is a potent constrictor of the placental microcirculation in sheep. Endothelin-1 also decreases fetal oxygen consumption by an unknown mechanism.
Metabolic compartmentation of lactate in the glucose-perfused rat heart
Authors: Chatham J. C. , Forder J. R.
Published: December 2017

Several studies using exogenous pyruvate as substrate have suggested that there are separate intracellular pyruvate pools in cardiac cells. Such heterogeneity in intracellular pyruvate has important implications for our understanding of both oxidative and nonoxidative glucose metabolism. Because pyruvate is not a major substrate for the heart in vivo, we wished to determine if there was pyruvate compartmentation with glucose as substrate. Hearts were isolated from male Sprague-Dawley rats and retrogradely perfused (Langendorff) with a modified Krebs-Henseleit buffer containing [1-13C[glucose for 5-115 min. At the end of each experiment, hearts were freeze-clamped and extracted for determination of the fractional enrichment of alanine, lactate, and acetyl CoA using 1H- and 13C-nuclear magnetic resonance spectroscopy. The fractional enrichment of alanine at the C-3 position was significantly higher than that for lactate at 55 min [43.6 +/- 2.8 vs. 27.2 +/- 4.6% (SD), n = 5, P < 0.003]. The differences in steady-state enrichment between lactate and alanine were not due to differences in the rate of labeling of these metabolites. The mean steady-state lactate enrichment was higher in the perfusate samples compared with the tissue samples from the same experiments (46.6 +/- 2.2 vs. 30.5 +/- 2.5%, n = 3, P < 0.005). Because fractional enrichment of alanine, acetyl CoA, and perfusate lactate are similar, we suggest that there is a separate nonexchanging pool of lactate rather than cytosolic compartmentation of pyruvate that has been previously proposed.
Regional myocardial interstitial norepinephrine kinetics during coronary occlusion and reperfusion
Authors: Shindo T. , Akiyama T. , Yamazaki T. , Ninomiya I.
Published: December 2017

We investigated myocardial interstitial norepinephrine kinetics in both the ischemic and nonischemic regions during reperfusion after 40 min of coronary occlusion in anesthetized cats. By use of a cardiac dialysis technique, dialysate norepinephrine contents from both regions were monitored as an index of myocardial interstitial norepinephrine levels. For vehicle perfusate (n = 8), the accumulated dialysate norepinephrine level in the postischemic region decreased from 3,010 +/- 923 pg/ml at 30-40 min of occlusion to 957 +/- 178 pg/ml at 0-10 min of reperfusion and returned to near control level at 30-40 min of reperfusion. After 40 min of reperfusion, there were no significant differences in tyramine (100 micrograms/ml, norepinephrine-releasing sympathomimetic amine)-induced norepinephrine release between both regions. For perfusate containing 100 microM desipramine (neural uptake inhibitor, n = 6), at 0-10 min of reperfusion, the dialysate norepinephrine in the postischemic region did not significantly decrease. The dialysate norepinephrine then returned to near preocclusion level at 30-40 min of reperfusion. These data suggest that reperfusion rapidly returns accumulated myocardial norepinephrine to the preischemic level and neuronal norepinephrine uptake greatly contributes to this return in the early phase of reperfusion. Forty minutes of coronary occlusion cause neither norepinephrine exhaustion nor irreversible impairment of norepinephrine uptake function in nerve terminals.
Effect of nitric oxide inhibition on secretion of atrial natriuretic factor in isolated rat heart
Authors: Melo L. G. , Sonnenberg H.
Published: December 2017

In addition to stretch, some hormones and neurotransmitters influence atrial natriuretic factor (ANF) secretion from the mammalian heart. In the present study, we investigated the effect of specific inhibition of nitric oxide/endothelium-derived relaxing factor (NO/ EDRF) on release of ANF from the isolated spontaneously beating heart during basal conditions and in response to arginine vasopressin (AVP; 3 x 10(-8) M), acetylcholine (ACh; 10(-6) M), and angiotensin II (ANG II; 4 x 10(-7) M) to determine whether NO is involved as a mediator of basal and hormone-modulated secretion of ANF. Basal secretion from control hearts remained stable for the duration of the experiment. Intracoronary perfusion of the heart with AVP, ACh, and ANG II reduced ANF secretion significantly by 58 +/- 4, 51 +/- 6, and 26 +/- 8%, respectively, independently of concomitant changes in coronary flow and heart rate. The NO donor sodium nitroprusside (SNP, 10(-4) M) inhibited ANF secretion comparably to AVP and ACh. The effect of SNP was not affected by inhibition of NO synthase activity with NG-nitro-L-arginine methyl ester (L-NAME; 3 x 10(-5) M). Similarly, L-arginine, (3 x 10(-4) M) but not its stereoisomer D-arginine (3 x 10(-4) M), significantly reduced ANF secretion. Subsequent perfusion with AVP singly or in combination with L-arginine or D-arginine did not affect ANF secretion further. The inhibitor of NO synthase NG-monomethyl-L-arginine (L-NMMA, 3 x 10(-5) M) did not affect basal secretion, but prevented the inhibitory effect of AVP and ACh. The effect of ANG II was not changed by L-NMMA. These results indicate that AVP and ACh inhibit ANF secretion in the isolated heart indirectly by stimulating NO/EDRF and suggest a novel function of NO/EDRF as a negative modulator of ANF secretion.
Pharmacological coupling and functional role for CGRP receptors in the vasodilation of rat pial arterioles
Authors: Hong K. W. , Yoo S. E. , Yu S. S. , Lee J. Y. , Rhim B. Y.
Published: December 2017

In this study, we investigated the signal transduction underlying the vasodilator action of calcitonin gene-related peptide (CGRP) in the rat pial arterioles. In an in vivo experiment, changes in pial arterial diameters (20.2 +/- 1.9 microns) were observed under suffusion with mock cerebrospinal fluid containing CGRP (10(-9)-10(-7) M) directly through a closed cranial window. Changes in intracellular adenosine 3',5'-cyclic monophosphate (cAMP) accumulation in response to CGRP and levcromakalim were measured in the pial arterioles in an in vitro experiment. CGRP-induced vasodilation and cAMP production were significantly inhibited by specific CGRP antibody serum and CGRP-(8-37) fragment, suggesting involvement of the CGRP1 receptor subtype. Vasodilation and increase in cAMP production evoked by CGRP were inhibited not only by glibenclamide (ATP-sensitive K+ channel blocker) but also by charybdotoxin (large-conductance Ca(2+)-activated K+ channel blocker), but this was not the case for the isoproterenol-induced vasodilation and cAMP production. These findings implicate the ATP-sensitive K+ channels and the large-conductance Ca(2+)-activated K+ channels in the CGRP receptor-coupled cAMP production for vasodilation. Further study is required to identify whether the cAMP-dependent K+ channel activation is related to CGRP-induced vasorelaxation of the rat pial arterioles.
Factors modifying protective effect of anti-CD18 antibodies on myocardial reperfusion injury in dogs
Authors: Perez R. G. , Arai M. , Richardson C. , DiPaula A. , Siu C. , Matsumoto N. , Hildreth J. E. , Mariscalco M. M. , Smith C. W. , Becker L. C.
Published: December 2017

Anti-CD18 monoclonal antibodies (MAb) have demonstrated variable protection against neutrophil (PMN)-mediated myocardial reperfusion injury. To identify factors contributing to this variability, open-chest dogs underwent coronary artery occlusion for 90 min followed by reperfusion for 3.5 h. Ten minutes before reperfusion the dogs received saline (n = 18) or one of three anti-CD18 MAb: MHM.23, R15.7, or PLM-2 (2, 1, and 1 mg/kg and n = 19, 8, and 4, respectively). Collateral flow was measured with radioactive microspheres, area at risk was assessed with monastral blue dye, and infarct size was measured postmortem by triphenyltetrazolium chloride. In vitro, all three MAb bound to canine PMNs, but only MHM.23 and R15.7 inhibited their adherence to keyhole limpet hemocyanin-coated plastic. In vivo, only MHM.23 and R15.7 significantly reduced infarct size after adjusting for the effect of collateral flow. MHM.23 afforded protection in dogs with moderate ischemia (epicardial collateral flow > 0.1 ml.min-1.g-1, infarct size reduced 46%) but not in dogs with more severe ischemia. Only R15.7 was effective in dogs with severe ischemia. Although MHM.23 and R15.7 produced similar inhibition of tissue PMN accumulation, as reflected by myeloperoxidase activity. R15.7 markedly inhibited H2O2 production by PMNs after exposure to platelet-activating factor, whereas MHM.23 had only a minimal effect. The effectiveness of different anti-CD18 MAb in preventing reperfusion injury appears to be 1) highly dependent on the specific anti-CD18 MAb employed, 2) predicted only partially by in vitro binding to PMNs, static in vitro tests of PMN adherence, or the extent of inhibition of PMN accumulation in vivo, 3) related more to their ability to inhibit oxidant release from activated PMNs, and 4) strongly influenced by the severity of myocardial ischemia before reperfusion.
THE ISOLATION OF A SUBSTANCE FROM URINE HAVING PROPERTIES OF CITRIC ACID: DESCRIPTION OF AN APPARATUS FACILITATING THE WORKING WITH SMALL VOLUMES OF GAS
Authors: Amberg Samuel , Mayer Mary E.
Published: December 2017

By an oversight in proof-reading, the name of the joint author of the article on "The Isolation of a Substance from Urine Having Properties of Citric Acid" etc., page 564 of Volume LX, was misspelled. The name should read "Mary E. Maver."
OXYGEN TRANSPORT AND UTILIZATION IN DOGS AT LOW BODY TEMPERATURES
Authors: Bigelow W. G. , Lindsay W. K. , Harrison R. C. , Gordon R. A. , Greenwood W. F.
Published: December 2017

Pages 131, 132: Legends for figures 8 and 9 should be transposed.
Participation of H1 and H2 histamine receptors in physiological vasodilator responses
Authors: Powell  , Brody MJ
Published: December 2017

Histamine causes vasodilation in the dog by activation of H1 and H2 receptors blocked by mepyramine and metiamide, respectively. Experiments were conducted in anesthetized dogs to determine the participation of H1 and H2 receptors in several forms of physiological dilatation. Mepyramine attenuated both histamine-induced and active-reflex dilatation in the hindlimb. Metiamide caused a further reduction in both sets of dilatation. Neither single nor combined antihistamines reduced dilatation due to exercise or after temporary occlusion of the circulation in the hindlimb. Poststimulation dilatation in the gracilis muscle was partially attenuated by metiamide or mepyramine. Neither dilatation caused by sympathetic nerve stimulation in the hindpaw nor dilatation in the gracilis muscle caused by compound 48/80 was reduced by mepyramine. Following combined H1- and H2-receptor blockade, portions of both types of dilatation were reduced. These data provide evidence for the participation of both types of histamine receptor in active reflex dilatation, low-frequency neurogenic dilatation, dilatation caused by compound 48/80, and poststimulation dilatation. Neither type of histamine receptor appears to be involved in reactive hyperemia or dilatation caused by exercise.
Lithium administration and phosphate excretion
Authors: Arruda JA , Richardson JM , Wolfson JA , Nascimento L , Rademacher DR , Kurtzman NA
Published: December 2017

The phosphaturic effect of parathyroid hormone (PTH), cyclic adenosine monophosphate (cAMP), acetazolamide (Az), and HCO3 loading was studied in normal, thyroparathyroidectomized (TPTX), and Li-treated dogs. PTH administration to normal animals markedly increased fractional excretion (F) of PO4 but had a blunted effect on FPO4 in the Li-treated animals. Cyclic AMP likewise markedly increased FPO4 in the normal animals but had a markedly blunted effect in the Li-treated animals. Az led to a significant increase in FNa, FHCO3, and FPO4 in the normal animals. In the Li-treated dogs, Az induced a significant natriuresis and bicarbonaturia but failed to increase phosphaturia. HCO3 loading in normal dogs caused a significant phosphaturia while having little effect on FPO4 in Li-treated dogs. HCO3 loading to TPTX dogs was associated with a lower FPO4 as compared to normal HCO3-loaded animals. These data suggest that Li administration not only blocks the adenyl cyclase-cAMP system in the renal cortex, but it may also interfere with a step distal to the formation of cAMP, since the phosphaturic effect of both PTH and cAMP was markedly diminished in Li-treated animals.
Potassium secretion by colonic mucosal cells after potassium adaptation
Authors: Fisher KA , Binder HJ , Hayslett JP
Published: December 2017

Recent studies have demonstrated that chronic potassium loading increases Na-K-ATPase specific activity in kidney tissue and suggest that this enzyme plays a role in renal potassium adaptation. Studies of fluid and electrolyte movement, potential difference (PD), AND Na-K-ATPase were performed in colon and jejunum of the rat in order to further characterize the relationship of Na-K-ATPase to potassium secretion. Experimental rats fed 2.6 meq K/gm diet for 7 days were compared to a control group fed 0.13 meq K/gm. In the colon, chronic potassium loading increased potassium secretion from 0.8 +/- 0.2 to 3.9 +/- 0.9 mueq/min per g tissue (P less than 0.01) and PD from 27 +/- 5.0 to 54 +/- 2.6 mV (P less than 0.001), lumen negative, as Na-K-ATPase increased from 5.0 +/- 0.5 to 11.4 +/- 1.0 muM Pi/mg protein per h (P less than 0.001). In contrast, there was no change in PD, potassium movement, or Na-K-ATPase in the jejunum of potassium-loaded rats. Colonic movement of water, sodium, and chloride was similar in the control and potassium-loaded rats. These results indicate that increased Na-K-ATPase is associated with both increased PD and increased potassium secretion in the colon and provide additional evidence suggesting that Na-K-ATPase may be important in the control of transepithelial potassium movement.
Effect of temperature of resistance to stretch of tortoise muscle
Authors: Fowler WS , Crowe A
Published: December 2017

The effects of temperature over the range 5-30 degrees on isometric contraction and resistance to mechanical stretches of the ramp and hold type applied to active muscle have been studied in isolated tortoise gastrocnemius muscles. The isometric tension decreases as the temperature is lowered but, when expressed as a proportion of the isometric tension, the change in tension at the end of the ramp phase of the stretch is increased at the lower temperatures. The proportionate tension change at the end of the hold phase of the stretch could not be directly related to the temperature. An attempt is made to interpret the results in terms of current opinions on the mechanism of the generation of muscular tension.
Plasma glucagon in pups, decreased by fasting, unaffected by somatostatin or hypoglycemia
Authors: Hetenyi G , Kovacevic N , Hall SE , Vranic M
Published: December 2017

In pups less than 4 days old, the mean basal plasma immunoreactive glucagon (IRG) level was about 3 times higher than in adult dogs. This high level decreased with age, and in pups older than 12 days the mean plasma IRG level did not differ from that in adults. Insulin-induced hypoglycemia did not raise plasma IRG concentration in young pups. Fasting decreased plasma IRG in young, but not in older pups. This decrease is consistent with the decrease in gluconeogenesis and in contrast to the metabolic adjustments observed in the adult organism. In pups less than 7 days old, both the pancreas and gastric mucosa contained considerably more IRG than the normal value reported for adult dogs. Gastroduodenal IRG was immunologically indistinguishable from pancreatic glucagon. In pups, somatostatin did not decrease the plasma concentration of either IRG or immunoreactive insulin (IRI) and caused no change in plasma glucose or in the rates of glucose production and utilization calculated from experiments with tracers. The experiments indicate that in pups the pancreatic and gastric alpha-cells are unresponsive to stimuli normally effective in grown dogs.
Effect of ethyl adenosine on myocardial flow after coronary artery occlusion
Authors: Hellmann DB , Pitt B
Published: December 2017

The effect of ethyl adenosine-5'-carboxylate hydrochloride (EA) was determined in 17 dogs by the radioactive microsphere technique. In both experimental and control animals, microspheres were injected 5 min before (preocclusion period), 60 min after (occlusion period), and 75 min after (saline or vasodilation period) ligation of the left anterior descending coronary artery (LAD). Ten seconds prior to the third microsphere injection, saline was administered to five control animals, and saline with 0.5 mg/kg of EA was given to 12 experimental animals. There was no significant change in myocardial blood flow after saline injection. After EA, mean arterial pressure fell 10% (P less than .001); myocardial blood flow increased 275% (P less than .001) in the nonischemic left circumflex artery (CIRC) area and increased 82% (P less than .01) in the occluded LAD area. In addition, those animals with extensive collateral development showed a significantly greater increase in collateral blood flow than those with minimal collateral development (P less than .05). Thus, EA may increase flow to ischemic areas of myocardium dependent upon the extent of preexistent collateral supply.
Ornithine decarboxylase in rat small intestine: stimulation with food or insulin
Authors: Maudsley DV , Leif J , Kobayashi Y
Published: December 2017

Ornithine decarboxylase in the small intestine of starved rats was stimulated 3- to 10-fold by refeeding or administration of insulin. A peak is observed 3-5 h following treatment after which the enzyme activity rapidly declines. The rise in ornithine decarboxylase is reduced by actinomycin D or cycloheximide. The increase in enzyme activity occurs mainly in the duodenum and jejunum with less than a twofold change being observed in the ileum. A small (twofold) increase in S-adenosylmethionine decarboxylase activity in the small intestine was observed after food, but there was no change in diamine oxidase activity. Whereas pentagastrin and metiamide administration markedly stimulated histidine decarbosylase in the gastric mucosa, no consistent effect of these agents on ornithine decarboxylase in the small intestine was observed. The similarities and differences between histidine decarboxylase and ornithine decarboxylase are discussed.
Basis for synchronization of sympathetic and phrenic nerve discharges
Authors: Barman SM , Gebber GL
Published: December 2017

The basis for the relationship between the discharges in the external cartized cats that were vagotomized, paralyzed, and artificially ventilated. Ive discharge (with the period of the cycle of phrenic nerve activity) is extrinsically imposed on central sympathetic networks by elements of the brainstem respiratory oscillator. However, a number of observations made in the present study contradict this view. First, changes in respiratory rate were accompanied by dramatic shifts in the phase relations between sympathetic and phrenic nerve discharge. Second, slow oscillations of sympathetic and phrenic nerve discharge were not always locked in a 1:1 relation. Third, the slow sympathetic rhythm persisted when respiratory rhythmicity disappeic components of sympathetic and phrenic nerve activity are generated by in
Ionic pathways of secretory membrane of frog gastric mucosa in Cl--free media
Authors: Holloman TL , Schwartz M , Dinno MA , Carrasquer G
Published: December 2017

Experiments were performed to determine the return ionic pathways of the secretory membrane of frog gastric mucosa associated with the electrogenic H+ pump in Cl--free media. The replacement of a 52 mM Na2SO4 secretory solution with a 52 mM K2SO4 secretory solution led to a decrease of resistance, an increase of the H+ secretory rate, and a reversal of the PD. The replacement of 52 mM Na2SO4 with 52 mM MgSO4 led to an increase of resistance and a decrease of the H+ rate. These results provided evidence for the existence of K+ and Na+ pathways, the former having a lower resistance than the latter. Short-circuiting the mucosa in Mg2+ solutions increased the H+ rate to the value in Na+ solutions, hence ruling out the possibility that Mg2+ might interfere with the H+ pump. The fact that the Mg2+ secretory solution, without K+ or Na+, did not abolish the H+ rate suggested the presence of at least a third ionic pathway. presumably SO42-, providing that Mg2+ does not penetrate the mucosa.
Endothelial cells internalize monoclonal antibody to angiotensin-converting enzyme
Authors: Muzykantov V. R. , Atochina E. N. , Kuo A. , Barnathan E. S. , Notarfrancesco K. , Shuman H. , Dodia C. , Fisher A. B.
Published: December 2017

We investigated the fate of MAb 9B9, a monoclonal antibody to angiotensin-converting enzyme (ACE), which binds to endothelium both in vitro and in vivo. Using cultured human umbilical vein endothelial cells (HUVEC) and isolated perfused rat lungs (IPL), we demonstrated specific and saturable binding of 125I-labeled MAb 9B9 at 4 degrees C [affinity constant (Kd) = 20-50 nM, maximal number of binding sites (Bmax) = 1.5-3.0 x 10(5) sites/cell]. When 125I-MAb 9B9 was bound to HUVEC at 37 degrees C, only 40% of cell-associated radioactivity was acid elutable, suggesting antibody internalization. This was confirmed by finding that 1) the amount of MAb 9B9 uptake at 37 degrees C was higher than at 4 degrees C both in HUVEC and IPL; 2) binding of 125I-labeled streptavidin with HUVEC and IPL pretreated with biotinylated MAb 9B9 (b-MAb 9B9) was diminished in a temperature- and time-dependent fashion at 37 degrees C; and 3) b-MAb 9B9 bound to HUVEC at 37 degrees C was found intracellularly by ultrastructural analysis using streptavidin gold. Intracellular 125I-MAb 9B9 was found in microsomal fractions of lung homogenate from IPL and after intravenous (iv) injections in rats. Degradation of internalized MAb 9B9 was minimal, since > 90% of cell-associated 125I label remained precipitable by trichloracetic acid in HUVEC, IPL, and in vivo. Autoradiography of sodium dodecyl sulfate-polyacrylamide gel electrophoresis of lung homogenates made as late as several days after iv injections of 125I-MAb 9B9 in rats demonstrated a predominant band above 140 kDa. These data indicate that endothelial cells either in vitro or in vivo internalize the ACE ligand MAb 9B9 without significant intracellular degradation. Therefore MAb 9B9 may be useful for selective intracellular delivery of drugs to the pulmonary vascular endothelium after systemic administration.
Dinucleotide-binding site of bovine liver catalase mimics a catalase mRNA-binding protein domain
Authors: Clerch L. B. , Wright A. , Massaro D.
Published: December 2017

Rat lung contains protein that interacts with catalase mRNA to form specific, redox-sensitive RNA-protein complexes. The studies in this report were aimed at determining whether catalase protein binds its own RNA. We found that rat catalase RNA binds NADPH-depleted bovine liver catalase (Sigma) but does not bind bovine liver catalase in the presence of NADPH. Complex formation between liver catalase and catalase RNA is competitively eliminated by a CA dinucleotide repeat. These data suggest the dinucleotide binding site of catalase mimics or is homologous to a catalase RNA-binding protein domain. These findings support the hypothesis that a class of RNA-binding proteins may have evolved from (di)nucleotide binding enzymes (M. W. Hentze. Trends Biol. Sci. 19: 101, 1994). When bovine liver catalase from two other commercial sources (Calbiochem and Boehringer) was used, we could not detect binding to catalase RNA. We have not yet been able to identify the basis for this difference. Thus the physiological importance of our observation of the NADPH-sensitive protein binding to catalase RNA cannot be assessed at this time.
Regulation of MUC5 and MUC1 gene expression: correlation with airway mucous differentiation
Authors: Guzman K. , Bader T. , Nettesheim P.
Published: December 2017

The purpose of this paper was to obtain probes to study the structure and function of mucins in rat models of airway cell differentiation and disease. We report the isolation and characterization of the rat cDNA homologue of the human airway secretory mucin, MUC5. Furthermore, we demonstrate the coordinate regulation of the expression of MUC5 and MUC1 (a membrane-bound mucin) and mucous differentiation. The rat MUC5 was cloned by the RT-PCR using motifs conserved in the secretory mucins, MUC2 and MUC5. The rat cDNA revealed a high degree of sequence similarity to human MUC5 (73% at the amino acid level). Alignments with three other secretory mucins (human MUC5, human MUC2, rat MUC2), indicated a conservation of the cysteines and of the octapeptide motifs, but a lack of conservation of a short tandem repeat sequence that is found only in the human MUC5. Northern analysis of MUC1 and MUC5 indicated a specific tissue-restricted pattern of expression. Surprisingly, rat MUC5 exhibited a monodisperse signal, a characteristic that is unusual for most secretory mucins, including the human MUC5. Expression of MUC1 and MUC5 correlated with mucous differentiation. Both genes were expressed at undetectable or very low levels in undifferentiated cultures, but both mucins became strongly expressed during mucous differentiation. Furthermore, neither mucin gene was expressed in retinoid-deficient cultures that undergo squamous instead of mucous differentiation. These studies demonstrate that expression of MUC1 and MUC5 is coordinately regulated with airway mucous cell differentiation. These cDNAs should provide useful tools to study mucin synthesis during differentiation and disease.
Retinoid-induced differentiation regulates prostaglandin H synthase and cPLA2 expression in tracheal epithelium
Authors: Hill E. M. , Bader T. , Nettesheim P. , Eling T. E.
Published: December 2017

Rat tracheal epithelial cells cultured in vitro at an air-liquid interface can differentiate into a mucociliary or squamous phenotype depending on the presence or absence of retinoic acid (RA). The airway epithelium is known to produce a number of eicosanoids. We propose that eicosanoid biosynthesis is dependent on the differentiation status of the epithelium. Therefore, prostaglandin production and the expression of cytosolic phospholipase A2 (cPLA2) and the prostaglandin H synthase (PGHS) isoforms were investigated during differentiation to these two phenotypes. The major eicosanoid produced by both phenotypes was prostaglandin E2 (PGE2). Proliferating undifferentiated cultures produced low levels of PGE2 regardless of retinoid status. Differentiated mucociliary cultures produced high levels of PGE2 (50 ng/10(6) cells), whereas differentiated squamous cultures produced low levels of PGE2 (< 5 ng/10(6) cells). Mucociliary cultures expressed high levels of cPLA2 and PGHS-2 isoform mRNA and protein. In contrast squamous cultures expressed very low levels of cPLA2 and PGHS-2 transcript and protein. The PGHS-1 isoform was expressed in squamous but not in mucociliary cultures. We investigated changes in expression of these enzymes during retinoid treatment of established squamous cultures. Treatment with RA resulted in a rapid (24 h) downregulation of PGHS-1 mRNA expression. However, the cPLA2 and PGHS-2 genes were expressed in squamous cultures only after 3 days of RA treatment coincident with redifferentiation of the culture to a mucociliary phenotype. These studies reveal that retinoid-induced differentiation of airway epithelium into either a mucociliary or squamous phenotype results in profound changes in the expression of cPLA2 and PGHS isozymes that regulate prostaglandin formation.
β-Adrenergic agonist modulation of monocyte adhesion to airway epithelial cells in vitro
Authors: Romberger Debra J. , Heires Peggy , Rennard Stephen I. , Wyatt Todd A.
Published: December 2017

β-Adrenergic agonists are commonly used in the treatment of obstructive airway diseases and are known to modulate cAMP-dependent processes of airway epithelial cells. However, little is known regarding the ability of cAMP-dependent mechanisms to influence cell-cell interactions within the airway. Thus we investigated the role of the β-adrenergic agonist isoproterenol in modulating the ability of human bronchial epithelial cells to support the adhesion of THP-1 cells, a monocyte/macrophage cell line, in vitro. We demonstrated that pretreatment of human bronchial epithelial cells (HBECs) with 10 μM isoproterenol or 100 μM salbutamol augments the adhesion of fluorescently labeled THP-1 cells to HBEC monolayers by ∼40–60%. The increase in THP-1 cell adhesion occurred with 10 min of isoproterenol pretreatment of HBECs and gradually declined but persisted with up to 24 h of isoproterenol exposure. Exposure of THP-1 cells to isoproterenol or salbutamol before the adhesion assays did not result in an increase in adhesion to HBECs, suggesting that the isoproterenol modulation was primarily via changes in epithelial cells. A specific protein kinase A inhibitor, KT-5720, inhibited subsequent isoproterenol augmentation of THP-1 cell adhesion, further supporting the role of cAMP-dependent mechanisms in modulating THP-1 cell adhesion to HBECs.
Mobilization of intracellular Ca2+by endothelin-1 in rat intrapulmonary arterial smooth muscle cells
Authors: Shimoda Larissa A. , Sylvester J. T. , Sham James S. K.
Published: December 2017

Endothelin-1 (ET-1) increases intracellular Ca2+concentration ([Ca2+]i) in pulmonary arterial smooth muscle cells (PASMCs); however, the mechanisms for Ca2+mobilization are not clear. We determined the contributions of extracellular influx and intracellular release to the ET-1-induced Ca2+response using Indo 1 fluorescence and electrophysiological techniques. Application of ET-1 (10−10to 10−8M) to transiently (24–48 h) cultured rat PASMCs caused concentration-dependent increases in [Ca2+]i. At 10−8M, ET-1 caused a large, transient increase in [Ca2+]i(>1 μM) followed by a sustained elevation in [Ca2+]i(<200 nM). The ET-1-induced increase in [Ca2+]iwas attenuated (<80%) by extracellular Ca2+removal; by verapamil, a voltage-gated Ca2+-channel antagonist; and by ryanodine, an inhibitor of Ca2+release from caffeine-sensitive stores. Depleting intracellular stores with thapsigargin abolished the peak in [Ca2+]i, but the sustained phase was unaffected. Simultaneously measuring membrane potential and [Ca2+]iindicated that depolarization preceded the rise in [Ca2+]i. These results suggest that ET-1 initiates depolarization in PASMCs, leading to Ca2+influx through voltage-gated Ca2+channels and Ca2+release from ryanodine- and inositol 1,4,5-trisphosphate-sensitive stores.