bluuebunny/crossref_metadata_2025 huggingface dataset:
Vasodilation contributes to the rapid hyperemia with rhythmic contractions in humans
Authors: Shoemaker J K , Tschakovsky M E , Hughson R L
Published: April 2011

The hypothesis that the rapid increases in blood flow at the exercise onsetare exclusively due to the mechanical effects of the muscle pump was tested in six volunteersduring dynamic handgrip exercise. While supine, each subject completed a series of eightdifferent exercise tests in which brachial artery blood pressure (BP) was altered by2530 mmHg (1 mmHg = 133.3 Pa) by positioning the arm above or below the heart.Two different weights, corresponding to 4.9 and 9.7% of maximal voluntary isometriccontraction, were raised and lowered at two different contraction rate schedules (1s:1s and 2s:2sworkrest) each with a 50% duty cycle. Beat-by-beat measures of mean blood velocity (MBV)(pulsed Doppler) were obtained at rest and for 5 min following step increases in work ratewith emphasis on the first 24 s. MBV was increased 50100% above rest following the firstcontraction in both arm positions (p < 0.05). The increase in MBV from rest was greaterin the below position compared with above, and this effect was observed following the first andsubsequent contractions (p < 0.05). However, the positional effect on the increase inMBV could not be explained entirely by the ~40% greater BP in this position. Also, the greaterworkload resulted in greater increases in MBV as early as the first contraction, compared withthe light workload (p < 0.05) despite similar reductions in forearm volume followingsingle contractions. MBV was greater with faster contraction rate tests by 8 s of exercise. Itwas concluded that microvascular vasodilation must act in concert with a reduction in venouspressure to increase forearm blood flow within the initial 24 s of exercise.Key words: Doppler, mean blood velocity, arterial diameter,handgrip exercise, perfusion pressure.
Biochemical and molecular endothelin responses to morphine sulfate infusion in conscious newborn piglets
Authors: Modanlou Houchang D , Beharry Kay
Published: April 2011

The biochemical and molecular endothelin-1 (ET-1)responses to high dose morphine sulfate infusion were studied in conscious newborn piglets(n = 6) that received a loading dose of 100 µg/kg over 5 min followed by acontinuous i.v. infusion dose of 100 µg·kg1·h1 for 4 h. The controlgroup (n = 6) received equivalent volume loading and infusion doses of 5% dextrose.Blood samples were drawn serially from the femoral artery and sagittal sinus vein before (0),during (30 min, 1, 2, 3, and 4 h), and post (1 and 2 h) infusion. Five micrograms oftotal RNA obtained from brainstem tissue homogenates was analyzed by reverse transcriptase polymerase chain reaction (RT-PCR). The amounts of mRNA encoding ET-1, and endothelinreceptor subtypes ETA and ETB, were semiquantitated using densitometricscanning. Morphine infusion resulted in elevated respiratory rate and mean arterial bloodpressure, with no effect on arterial pH, PO2, and O2saturation. Compared with the control group, morphine induced significant elevations in plasmaET-1 levels following the bolus dose (systemic: 13.2 ± 3.6 vs. 8.6 ± 2.2 pg/mL, p < 0.05;sagittal sinus vein: 13.7 ± 3.4 vs. 8.2 ± 0.9 pg/mL, p < 0.01). These effects lasted up to2 h after discontinuation of morphine infusion (systemic: 14.5 ± 3.4 to 18.7 ± 5.7 pg/mL vs.7.5 ± 0.8 to 9.4 ± 3.2 pg/mL, p < 0.05 to p < 0.01; sagittal sinus vein: 14.8 ± 2.7to 17.6 ± 2.8 pg/mL vs. 7.5 ± 1.4 to 9.4 ± 3.4 pg/mL, p < 0.05 to p < 0.01). TheRT-PCR assay showed a twofold (p < 0.02) upregulation in ET-1 and a threefold(p < 0.007) upregulation in ETA receptor mRNA expression in the brainstemof morphine-treated animals. In contrast, there was a threefold (p < 0.0001)downregulation of the ETB receptor mRNA expression. The rapid and sustainedelevations in systemic arterial and sagittal sinus venous ET-1 levels suggest a role for ET-1 in themorphine-induced excitatory responses observed in newborn piglets. Upregulation ofETA receptors and downregulation of ETB receptors in the brainstem withhigh doses of morphine may indicate possible effects on cerebral vascular tone. Key words: morphine sulfate, endothelin-1, reverse transcriptase polymerase chain reaction.
Intracellular calcium stores modulation in lymph vessels depends on wall stretch
Authors: Atchison D J , Rodela H , Johnston M G
Published: April 2011

We studied the effect of intracellular calcium stores modulation on the ability of lymph vessels to propel fluid in a preparation of actively contracting isolated bovine mesenteric lymph vessels. Vessels were cannulated at each end, placed in a temperature-controlled organ bath, and circulated with oxygenated Krebs solution. Vessel wall tension (transmural pressure) was changed by raising the height of the fluid-filled reservoir and outflow catheters appropriately. When transmural pressure was set and maintained at 6 cmH2O (1 cmH2O = 98.1 Pa), caffeine (10-3M), ryanodine (10-7M), and cyclopiazonic acid (CPA; 7 x 10-6M) inhibited lymphatic pumping. We also studied the effect of these agents on the relationship between lymph pump activity and transmural pressure, a relationship normally described by a bell-shaped curve. When transmural pressure was increased at 5-min intervals, the magnitude of inhibition by caffeine (10-3M) and CPA (7 x 10-6M) was greater than when transmural pressure was held constant. Ryanodine, on the other hand, had no effect on lymphatic contractility when transmural pressure was manipulated. The ryanodine results suggest the existence of an interaction between vessel wall stretch and intracellular calcium stores modulation that is not seen with caffeine or CPA.Key words: caffeine, ryanodine,cyclopiazonic acid, calcium-induced calcium release.
Resting muscle sounds in anesthetized patients
Authors: McKay William P , Gregson Peter H , McKay Benjamin WS , Blanchet Travis
Published: April 2011

It is known that contracting muscle makes low frequency sound vibrations.Small vibrations of uncertain origin are found over resting muscle. These could be shown to beof muscle origin if they significantly diminish in response to agents expected to decrease muscleactivity. Thiopental, propofol, and neuromuscular-junction blocking muscle relaxants have suchproperties. Twenty-one subjects slated for elective surgery for which they would routinely beanesthetized and paralysed gave informed consent to having a small accelerometer taped upontheir supine biceps (9 subjects), or volar forearm (12 subjects). Recordings were made in fourstages while subjects: (i) lifted a 2-kg weight just off the sponge armrest on whichtheir outstretched arm lay; (ii) relaxed their arm in the awake state prior toanesthesia; (iii) had anesthesia induced with intravenous thiopental (n = 11)or propofol (n = 10); and (iv) were paralysed. Recordings were digitised at172-Hz and 6-s segments fast Fourier transformed (FFT). Total signal power, as determined bythe area under the power spectrum, was significantly different (p < 0.05) in all stages forthe biceps and in all but stages (iii) from (iv) in the forearm. It appearsthat resting muscle generates measurable vibrations.Key words: muscle sounds, accelerometer, anesthesia.
Erratum: Endothelial binding sites for lipoprotein lipase are not diminished in perfused hearts from diabetic rats
Authors: Liu Limin , Severson David L
Published: April 2011

This article was published with the wrong French abstract. The correct English and French abstracts are printed below in full. The Publisher regrets this error. Abstract : The possibility that diabetes reduces functional, heparin-releasable lipoprotein lipase (HR-LPL) activity on the coronary vasculature of perfused hearts by altering endothelial binding sites for the enzyme was examined by measuring the binding and subsequent heparin-induced release of exogenous lipoprotein lipase purified from bovine milk (mLPL). Rat hearts were first perfused with heparin (5 U/mL) for 5 min to displace endogenous HR-LPL into the perfusate. The subsequent perfusion of control hearts with 0.05-2 µg/mL mLPL resulted in a progressive increase in bound exogenous exzyme that could be released by a second heparin perfusion. Induction of an acute, insulin-deficient model of diabetes (100 mg/kg streptozotocin 4-5 days prior to heart perfusions) reduced endogenous HR-LPL activity, but the binding and heparin-induced release of mLPL (0.5 µg/mL) were the same as measured in control hearts. Therefore, diabetes does not alter low-affinity, high-capacity proteoglycan binding sites for mLPL on the endothelium of perfused hearts.Key words: diabetes, lipoprotein lipase, perfused hearts.
Nonadrenergic noncholinergic vasodilation of guinea pig pulmonary arteries is mediated by nitric oxide
Authors: Scott J A , McCormack D G
Published: April 2011

Nonadrenergic noncholinergic (NANC) mediated vasodilation may contribute to the maintenance of low pulmonary vascular tone. The NANC neurotransmitters, nitric oxide (NO) and the sensory neuropeptides, substance P and calcitonin gene related peptide (CGRP), were investigated as possible mediators of NANC vasodilation in guinea pig pulmonary arteries. Fresh guinea pig pulmonary artery rings, with and without an intact endothelium, were mounted in organ baths containing Krebs solution and precontracted with the prostaglandin F2α analogue U44069. In both endothelium-intact and denuded vessels, electrical field stimulation (1-12 Hz) in the presence of guanethidine and atropine resulted in a frequency-dependent vasodilation. The peptide fragment hCGRP8-37, a competitive antagonist of the CGRP receptors, the peptide fragment NK1 antagonist SP4-11, and the nonpeptide NK1 antagonist RP67580 had no effect on NANC vasodilation. In both endothelium-intact and denuded vessels, NG-nitro-L-arginine methyl ester (L-NAME), an inhibitor of NO synthesis, inhibited NANC vasodilation, an effect that was reversible with L-arginine. We conclude that NANC vasodilation in guinea pig pulmonary arteries is mediated predominantly through NO activity.Key words: nonadrenergic noncholinergic, pulmonary artery, nitric oxide, vasodilation.
Vascular, renal, and endocrine responses to low-dose atrial natriuretic peptide in the fluid-balanced New Zealand genetically hypertensive rats with and without endogenous arginine vasopressin
Authors: Abu-Amarah Isam , Balment Richard J
Published: April 2011

In hypertension, the relationship between atrial natriuretic peptide (ANP) and vasopressin (AVP) is not yet clear, although their renal actions are effectively autoregulation. To examine the possible interaction further, the responses to ANP infusion (75 ng·min-1, i.v.) have been investigated in both hypertensive and normotensive AVP-replete (HT and NT) and AVP-deficient (HTDI and NTDI) rats. This study aimed to assess the renal function and the plasma hormone concentrations of AVP, angiotensin II (AII), ANP, aldosterone, and corticosterone in the conscious, chronically catheterized, fluid-balanced rats, and to examine the cardiovascular, renal, and endocrine responses to a constant infusion of a low-dose ANP. Data gained from the present study showed, for the first time, the hormone profile, plasma electrolyte composition, and detailed renal function of the servo-controlled, fluid-balanced rats. The similarities of plasma electrolyte composition between servo-controlled and untreated rats indicated that the servo-controlled fluid replacement technique maintained the differences between the strains and maintained body fluid balance during the experimental periods. Following ANP administration, there were no changes in glomerular filtration rate (GFR) in all groups, but an enduring diuresis and natriuresis were observed in HT and NT, which were milder in HTDI rats. However, the hypotensive effect of ANP was of a similar magnitude in all rat strains. HTDI rats exhibited an inhibition of the renin-angiotensin system (RAS), which may have participated in the reduced mean arterial blood pressure (MAP) and natriuresis observed in these rats. The renal actions of ANP appear to rely upon renal tubular events, as indicated by increased fractional electrolyte excretions in the AVP-replete rats. This study highlights the importance of AVP to the profile of the renal actions of ANP in normal rats.Key words: atrial natriuretic peptide, arginine vasopressin, renal, hypertension.
Biochemical and pharmacological characteristics of a newly synthesized H+-K+ATPase inhibitor, YJA20379-1, 2-amino-4,5-dihydro-8-phenylimidazole [2,1-b]thiazolo[5,4-g]benzothiazole
Authors: Sohn Sang-Kwon , Chang Man-Sik , Choi Wahn-Soo , Kim Kyu-Bong , Woo Tae-Wook , Lee Seok-Bong , Chung Young-Kuk
Published: April 2011

The biochemical and pharmacological characteristics of a newly synthesized H+-K+ATPase inhibitor, 2-amino-4,5-dihydro-8-phenylimidazole[2,1-b]thiazolo[5,4-g]benzothiazole (YJA20379-1), were investigated. In the pig gastric microsomes, YJA20379-1 inhibited the gastric H+-K+ATPase regardless of pH condition, IC50values being 21 and 24 µM at pH 6.4 and 7.4, respectively. The inhibitory activity of YJA20379-1 was antagonized by dithiothreitol treatment but could not be reversed by dilution and washing of the enzyme preparation. In Sprague-Dawley rats, YJA20379-1, administered i.d., p.o, i.v., or s.c., significantly inhibited basal gastric acid secretion, with ED50values of 4.7, 20.2, 6.3, and 13.4 mg/kg, respectively. The antisecretory action of YJA20379-1 was short lasting (less than 7 h at an oral dosing of 30 mg/kg). Oral administration of YJA20379-1 also prevented the formation of ethanol, indomethacin, and water immersion stress induced gastric lesions and mepirizole-induced duodenal ulcers in rats. Furthermore, YJA20379-1 accelerated the healing of acetic acid induced chronic gastric ulcers in rats. In conclusion, these results suggest that YJA20379-1 has a potent inhibitory activity on the gastric H+-K+ATPase but much shorter duration of antisecretory action than omeprazole, thereby exerting its anti-ulcer effects partly with cytoprotective activity.Key words: proton pump inhibitor, acid secretion, anti-ulcer effects, cytoprotective activity.
Nitric oxide inhibits human and canine pulmonary vascular tone via a postjunctional, nonelectromechanical, cGMP-dependent pathway
Authors: Janssen Luke J , Mardi Kai , Netherton Stuart , Betti Pierre-A.
Published: April 2011

We examined nitric oxide mediated regulation of pulmonary arterial and venous smooth muscle (PASM and PVSM, respectively): whether this inhibition is mediated via prejunctional receptors on adrenergic nerve endings; whether NO is neuronally derived; the relationship between degree of inhibition and vessel size; and identification of the signalling mechanisms involved. Canine pulmonary vascular tissues were generally quiescent, while human PASM exhibited spontaneous phasic activity. The nitric oxide (NO) synthesis inhibitor Nω-nitro-L-arginine (L-NNA; 10-4M) increased tone and enhanced phasic activity. Electrical field stimulation (EFS) evoked contractions were markedly enhanced by L-NNA in an endothelium-dependent fashion, and antagonized by the NO donor S-nitroso-N-acetyl-penicillamine (SNAP; 10-7to 10-5M). 8-Bromo-cGMP mimicked the effects of SNAP on basal tone and EFS contractions, while an inhibitor of soluble guanylate cyclase mimicked those of L-NNA. While mechanical responses to exogenously added norepinephrine (10-9-10-4M) were also enhanced by L-NNA and suppressed by SNAP, EFS-evoked excitatory junction potentials were unaffected by SNAP. We conclude that, in human and canine PASM and PVSM, there is a tonic generation of NO originating within the endothelium that does not mediate a prejunctional effect, but which acts postjunctionally to activate a cGMP-dependent pathway within the smooth muscle.Key words: adrenergic neurotransmission, norepinephrine, regiospecificity, cGMP-dependent protein kinase.
Sodium-pump potentials and currents in guinea-pig ventricular muscles and myocytes
Authors: Kasamaki Yuji , Guo An Chi , Shuba Lesya M , Ogura Toshitsugu , McDonald Terence F
Published: April 2011

When guinea-pig papillary muscles were depolarized to ca. -30 mV by superfusion with K+-free Tyrode's solution supplemented with Ba2+, Ni2+, and D600, addition of Cs+ transiently hyperpolarized the membrane in a reproducible manner. The size of the hyperpolarization (pump potential) depended on the duration of the preceding K+-free exposure; peak amplitudes (Epmax) elicited by 10 mM Cs+ after 5-, 10-, and 15-min K+-free exposures were 12.9, 17.7, and 23.2 mV, respectively. Pump potentials were unaffected by external Cl- but suppressed by cardiac glycosides, hyperosmotic conditions, and low-Na+ solution. Using Epmax as an indicator of Na+ pump activation, the half-maximal concentration for activation by Cs+ was 12-16.3 mM. At 6 mM, Cs+ was three times less potent than Rb+ or K+ and five times more potent than Li+. From these findings, and correlative voltage-clamp data from myocytes, we calculate that (i) a pump current of 7.8 nA/cm2 generates an Epmax of 1 mV and (ii) resting pump current in normally polarized muscle (~0.16 µA/cm2) is five times smaller than previously estimated.Key words: sodium pump, cesium, rubidium, sodium pump current.
Ingestion of chilli pepper (Capsicum annuum) reduces salicylate bioavailability after oral aspirin administration in the rat
Authors: Cruz Leticia , Castañeda-Hernández Gilberto , Navarrete Andrés
Published: April 2011

The bioavailabilities of aspirin (acetylsalicylic acid) and of salicylic acid were studied in male Wistar rats after acute and chronic administration of a Capsicum annuum extract, containing 100 mg of capsaicin per gram. With a single administration of 100 mg/kg of the extract, aspirin blood levels remained unchanged, but salicylic acid bioavailability was reduced in 44% compared with control animals. With a single administration of 300 mg/kg of the extract, aspirin blood levels were undetectable while salicylic acid bioavailability was reduced in 59%. Chronic administration once daily for 4 weeks of 100 and 300 mg/kg of the extract resulted in undetectable aspirin blood levels, while salicylic acid bioavailability was reduced in 63 and 76%, respectively, compared with controls. Results show that Capsicum ingestion reduces oral drug bioavailability, likely as a result of the gastrointestinal effects of capsaicin.Key words: aspirin, Capsicum annuum, capsaicin, bioavailability, drug-food interaction.
Functional involvement of angiotensin AT2receptor in adrenal catecholamine secretion in vivo
Authors: Martineau Daniel , Lamouche Stéphane , Briand Richard , Yamaguchi Nobuharu
Published: April 2011

The aim of the present study was to analyse modulations of adrenal catecholamine secretion from the adrenal gland of anesthetized dogs in response to locally administered angiotensin II (AngII) in the presence of either PD 123319 or CGP 42112, both of which are highly specific and selective ligands to angiotensin AT2receptor. Plasma concentrations of epinephrine and norepinephrine in adrenal venous and aortic blood were quantified by a high performance liquid chromatography coupled with electrochemical detection (HPLC-EC) method. Adrenal venous blood flow was measured by gravimetry. Local administration of AngII (0.05 µg, 0.1 µM) to the left adrenal gland increased adrenal gland catecholamine output more than 30 times that found in nonstimulated states. Administration of either PD 123319 (0.085 µg (0.23 µM) to 8.5 µg (23 µM)) or CGP 42112 (0.005 µg (0.01 µM) to 5 µg (10 µM)) did not affect the basal catecholamine output significantly. The increase in adrenal catecholamine output in response to AngII was inhibited by ~80% following the largest dose of PD 123319. CGP 42112 significantly attenuated the catecholamine response to AngII by ~70%. PD 123319 and CGP 42112 were devoid of any agonist actions with respect to catecholamine output by the adrenal gland in vivo. Furthermore, both PD 123319 and CGP 42112 inhibited the increase in adrenal catecholamine secretion induced by local administration of AngII. The present study suggests that AT2receptors play a role in mediating catecholamine secretion by the adrenal medulla in response to AngII receptor agonist administration in vivo.Key words: AT1and AT2subtypes, PD 123319, CGP 42112, AT2antagonist, anesthetized dog.
Sulfated cholecystokinin octapeptide in the rat: pontomedullary distribution and modulation of the respiratory pattern
Authors: Ellenberger Howard H , Smith Frank M
Published: April 2011

We performed anatomical and physiological studies to determine the site and actions of sulfated cholecystokinin octapeptide (CCK8-S) on breathing. Peptide locations were determined by combined immunodetection of CCK8-S- containing synaptic varicosities and retrograde labeling of medullary neurons projecting to the ventral respiratory group. Retrogradely labeled neurons and CCK8-S immunolabeled varicosities overlapped within the nuclei of the solitary tract, ventral respiratory group, and the Kölliker-Fuse nucleus. Additional CCK8-S immunoreactive terminals were located in the rostroventrolateral medullary reticular nucleus, lateral paragigantocellular reticular nucleus, and the caudal pontine reticular nucleus. The respiratory effects of CCK8-S, which binds to CCKA and CCKB receptors, were examined by intravenous injection in adult rats and by bath application in the in vitro neonatal rat brainstem - spinal cord preparation. CCK8-S produced an increase in the mean amplitude of diaphragmatic electromyogram (EMG) of 28 ± 35% (SD) and a decrease in mean respiratory interval of 13 ± 4% in vivo. In vitro, CCK8-S significantly increased inspiratory duration and decreased respiratory interval, primarily by shortening expiratory duration. CCK8-unsulfated, a specific agonist for CCKB receptors, did not produce these effects. CCK8-S effects in the in vitro preparation were partially blocked by the CCK receptor antagonist lorglumide (final bath concentration 600 nM). These results suggest that CCK8-S modulates the respiratory rhythm via CCKA receptors within one or more medullary or pontine respiratory groups in both neonatal and adult rats.Key words: neuropeptide, ventral respiratory group, medulla, pons, respiratory network.
Inhibition of matrix metalloproteinase MMP-2 activates chloride current in human airway epithelial cells
Authors: Duszyk M , Shu Y , Sawicki G , Radomski A , Man SFP , Radomski M W
Published: April 2011

Matrix metalloproteinases (MMPs) are involved in the remodeling and degradation of the extracellular matrix. Recently, it has been found that MMPs also contribute to processes not directly related to tissue remodeling, such as platelet aggregation or degranulation of airway gland cells. Since mucus secretion is closely related to ion channel function, we investigated whether MMPs could also be involved in the regulation of ion channels. We used human airway submucosal cell line Calu-3 to study the effects of MMPs on whole-cell current and transepithelial short-circuit current (Isc). Phenanthroline, a specific inhibitor of MMPs, increased whole-cell current with the half-maximally effective dose of 5.2 µM, and reversibly activated Isc in transepithelial measurements. Current stimulated by phenanthroline displayed linear current-voltage relationships and had inhibitor pharmacology and ion selectivity consistent with cystic fibrosis transmembrane conductance regulator (CFTR) Cl- channel activity. Zymography and Western blot showed significant expression of MMP-2 in Calu-3 cells. Moreover, anti-MMP-2 antibodies (1 µg/mL) increased whole-cell current and Isc, whereas human recombinant MMP-2 (10 ng/mL) reduced it. We also studied the expression of MMPs and the effects of phenanthroline on whole-cell current in A549 cells, which are derived from airway surface epithelium and do not express CFTR Cl- channels. While these cells also showed significant expression of MMP-2, inhibition of this enzyme with phenanthroline exerted no significant effect on whole-cell current. It is concluded that MMP-2 is involved in the regulation of CFTR Cl- channels in human airways.Key words: matrix metalloproteinases, Cl- current, Calu-3 cells, zymography, phenanthroline.
Influence of some phospholipase A2and cytochrome P450 inhibitors on rat arterial smooth muscle K+currents
Authors: Vanheel Bert , Calders Patrick , Van den Bossche Isabelle , Van de Voorde Johan
Published: April 2011

The hyperpolarizing factor that is liberated by vascular endothelial cells in response to various agonists, and known to induce relaxation by opening of smooth muscle K+channels, has been suggested to be a product of cytochrome P450 dependent arachidonic acid metabolism. In this study, the direct influence of two phospholipase A2inhibitors and of five structurally and mechanistically different cytochrome P450 inhibitors on K+currents in freshly isolated vascular smooth muscle cells from the rat aorta was investigated. On stepping the cell membrane potential from -70 mV to a series of depolarized test potentials, a noisy outward current developed at test potentials > +10 mV, which showed no appreciable inactivation during the voltage pulse. It was largely abolished by 3 mM external tetraethylammonium chloride (TEA), suggesting that it predominantly consisted of current through large-conductance Ca2+-activated K+channels. The phospholipase A2inhibitor quinacrine considerably inhibited this TEA-sensitive current, while 4-bromophenacylbromide exerted no effect. The cytochrome P450 inhibitors proadifen and miconazole reversibly decreased the amplitude of IK, while clotrimazole and 1-aminobenzotriazole had no effect. Conversely, 17-octadecynoic acid increased whole-cell IK. These results show that some phospholipase A2and cytochrome P450 inhibitors may interfere with K+channel activation in the rat arterial smooth muscle cell. The relevance of these findings to studies on the involvement of cytochrome P450 dependent metabolism in the generation of the endothelium-derived hyperpolarizing factor in intact arteries is discussed.Key words: endothelial factors, smooth muscle, membrane currents, vasodilation, endothelium-derived hyperpolarizing factor (EDHF), arachidonic acid.
Slow wave and spike action potentials recorded in cell cultures from the muscularis externa of the guinea pig small intestine
Authors: Espinosa-Luna Rosa , Collins Stephen M , Montaño Luis M , Barajas-López Carlos
Published: April 2011

Intracellular recordings were obtained to investigate whether slow wave and spike type action potentials are present in cell cultures of the muscularis externa from the guinea pig small intestine. The muscularis externa of the small intestine was dissociated by using specific purified enzymes and gentle mechanical dissociation. Cells were plated on cover slips and maintained in culture for up to 4 weeks. Dissociated cells obtained in this way reorganized themselves in a few days to form small cell clumps showing spontaneous movements. Intracellular recordings of these clumps displayed both spike and slow wave type action potentials. Spikes were observed on top of some slow waves and were abolished by the addition of nifedipine or the removal of extracellular calcium. Slow waves, however, were nifedipine insensitive and temperature sensitive, and were abolished by octanol (a gap junction blocker) and forskolin (an adenyl cyclase activator). Slow waves were never observed in small clumps (<50 µm), suggesting that a critical mass of cells might be required for their generation. These observations demonstrated for the first time the presence of nifedipine-insensitive slow waves in cell cultures of the muscularis externa from the guinea pig small intestine. Cell cultures allow rigorous control of the immediate environment for the cells and this should facilitate future studies on the molecular and cellular mechanisms responsible for the slow waves in the gastrointestinal tract.Key words: smooth muscle, slow waves, spiking activity, gastrointestinal tract, gut, small intestine, electrophysiology, pacemaker activity, guinea pig.
Role of P-glycoprotein in the renal transport of dideoxynucleoside analog drugs
Authors: Leung Simon , Bendayan Reina
Published: April 2011

P-glycoprotein (P-gp), the MDR1 multidrug transporter, is known to be expressed in several human organs and tissues, including the apical membrane of the renal proximal tubular cells. It has been reported that human immunodeficiency virus 1 (HIV-1) can trigger the expression of P-gp in cultured cells (i.e., H9, a T-lymphocyte cell line, and U937, a monocyte cell line), which may render the cells resistant to antiretrovirals. Since multiple membrane transport systems (i.e., organic cation, organic anion, and nucleoside systems) can be involved in the renal tubular transport of dideoxynucleoside analog drugs (DADs) (i.e., zidovudine and zalcitabine), we have questioned if P-gp is involved in the renal transport of DADs. Chinese hamster ovary colchicine-resistant cells (CHRC5), a cell line that is well known to highly express P-gp, and continuous renal epithelial cell lines (LLC-PK1and OK), which have also been shown to express P-gp, were used. The accumulation of [3H]vinblastine (20 nM), an established P-gp substrate, by the monolayer cells was significantly enhanced in the presence of two P-gp inhibitors (i.e., verapamil and cyclosporin A) and nucleoside transport inhibitors (i.e., dipyridamole and dilazep). In contrast, DADs (i.e., zidovudine, lamivudine, didanosine, and zalcitabine) did not significantly affect vinblastine accumulation by these cell lines. These data suggest that P-gp does not play a significant role in the renal tubular transport of DADs. Dipyridamole and dilazep, two nucleoside membrane transport inhibitors, appear to be P-gp inhibitors.Key words: P-glycoprotein, dideoxynucleoside analogs, human immunodeficiency virus 1, transport, renal.
Role of angiotensin II in sympathetic nervous system induced left ventricular dysfunction
Authors: Bosso Frank J , Jarjoura David G , Pilati Charles F
Published: April 2011

Experiments were undertaken to determine whether angiotensin (Ang) II concentration increases during massive sympathetic nervous system (SNS) activation and whether such an increase plays a role in the pathogenesis of SNS-induced left ventricular (LV) dysfunction. We also sought to determine whether excessive Ca2+ uptake through L-type channels due to intense adrenoceptor activation is responsible for the LV dysfunction. AngII concentration was measured in the plasma and myocardium before and after massively activating the SNS with an intracisternal injection of veratrine. In separate experiments, rabbits were given losartan, enalaprilat, enalaprilat plus HOE-140, nifedipine, -Bay K 4866, or saline before massively activating the SNS. LV function was evaluated 2.5 h later. The intense SNS activity caused plasma and myocardial AngII to increase by 400 and 437%, respectively. AngII receptor blockade did not prevent LV dysfunction. In contrast, enalaprilat reduced the degree of dysfunction, but its cardioprotection was abolished by HOE-140. Although nifedipine prevented SNS-induced LV dysfunction, administration of the Ca2+ channel opener, -Bay K 4866, did not increase its severity. Our results indicate that AngII is not involved in the pathogenesis of SNS-induced LV dysfunction and that the cardioprotection provided by angiotensin converting enzyme (ACE) inhibition is due to activation of a bradykinin pathway. Furthermore, the finding that the magnitude of the LV dysfunction was reduced by enalaprilat, and not increased by -Bay K 4866, suggests that intense adrenoceptor activation of L-type Ca2+ channels is not the primary pathogenetic mechanism.Key words: converting-enzyme inhibitor, calcium channel opener-blocker, myocardial contractility, catecholamines, rabbits.
Structural changes and the storage of long-term memory inAplysia
Authors: Bailey Craig H
Published: April 2011

Long-term memory for sensitization of the gill-withdrawal reflex inAplysia is associated with the growth of new synaptic connections between sensory and motor neurons. The duration of this structural change parallels the behavioral retention of the memory. Such changes can be reconstituted in dissociated cell culture by repeated presentations of the modulatory neurotransmitter serotonin (5HT) and are associated with an activity-dependent downregulation of NCAM-related cell adhesion molecules thought to contribute to cell recognition and axonal outgrowth during development. Thus, aspects of the mechanisms utilized for learning-related synaptic growth initiated by experience in the adult may eventually be understood in the context of the molecular logic that shapes synaptic circuitry during the later stages of neuronal development.Key words: learning, synapse, invertebrate, habituation, sensitization.
Modulation of liver cell membrane NHE-1, Na+-K+ATPase, and GLUT-2 protein content after cold preservation and rewarming
Authors: Haddad Pierre , Noël Josette , Vadnais Julie , Mathé Laurence , Vallerand Diane
Published: April 2011

Liver cell pH and volume regulation are perturbed by prolonged cold storage in University of Wisconsin solution and subsequent rewarming, but the molecular basis of this effect remains unknown. We prepared membranes from hepatocytes subjected to variable periods of cold preservation with or without subsequent rewarming and probed them by Western blotting with specific antibodies against the Na+-H+exchanger isoform NHE-1 and the Na+-K+ATPase alpha subunit. Results were compared with the content of GLUT-2, an abundant basolateral protein. NHE-1 decreased significantly as cold preservation times exceeded 10 h. Subsequent rewarming by short-term culture at 37°C did not further reduce this parameter. On the other hand, expression of Na+-K+ATPase remained stable during cold storage times lasting up to 48 h, whereas rewarming resulted in a dramatic reduction in cells cold preserved beyond 10 h. In contrast, the membrane content of GLUT-2 was unaffected by cold preservation with or without subsequent rewarming. The results indicate that cold storage and rewarming respectively and selectively modulate the expression of specific hepatocellular membrane transport proteins.Key words: pH regulation, volume regulation, sodium-hydrogen antiport, cryopreservation, isolated rat hepatocytes.
Proteinase-activated receptor 4 (PAR4): action of PAR4-activating peptides in vascular and gastric tissue and lack of cross-reactivity with PAR1 and PAR2
Authors: Hollenberg Morley D , Saifeddine Mahmoud , Al-Ani Bahjat , Gui Yu
Published: April 2011

We studied the actions of the human and murine proteinase-activated receptor 4 (PAR4) derived receptor-activating peptides (APs), GYPGQV-NH2 (GQV-NH2) and GYPGKF-NH2 (GKF-NH2), (i) to activate-desensitize either PAR1 or PAR2 in cultured cell systems (calcium signalling in PAR1/PAR2-bearing human HEK cells and in rat KNRK cells expressing either rat or human PAR2) and (ii) to affect contractility in rat aorta (RA) and rat gastric longitudinal muscle (LM) preparations in vitro. We found that neither PAR1 nor PAR2 was affected by concentrations of the PAR4-APs (800 µM) that caused both an endothelium-dependent nitric oxide mediated relaxation of preconstricted RA tissue and a contractile response in the LM preparation. The potencies (EC50 values 300 to 400 µM) of GQV-NH2 and GKF-NH2 for causing a relaxant effect were identical and comparable with the potency of GQV-NH2 for causing a contractile effect in the LM. However, the potencies of the PAR4-APs in the RA and LM preparations were 20- to 150-fold lower than the potency of the receptor-selective PAR1-AP, TFLLR-NH2. We conclude that the PAR4-APs do not activate either PAR1 or PAR2, and we suggest that along with PAR1 and PAR2, PAR4 may also be present in rat vascular and gastric smooth muscle.Key words: proteinase-activated receptors, PAR4, calcium, vascular smooth muscle, gastric smooth muscle, thrombin.
Effect of blood flow and muscle contraction on noradrenaline spillover in the canine gracilis muscle
Authors: Lavoie Julie L , Trudeau François , Béliveau Louise
Published: April 2011

Many authors have reported that, during exercise, noradrenaline spillover increases and fractional extraction decreases. It has been suggested that the increase in blood flow to active muscles may contribute to these effects. Muscle contraction also causes changes in many factors that may affect noradrenaline spillover and fractional extraction. In this experiment, we studied the effect of muscle contraction and blood flow on noradrenaline and adrenaline spillover and fractional extraction in the in situ canine gracilis muscle. The low intensity stimulation protocol enabled us to have muscle contractions without any effect on the local concentration of noradrenaline, as measured by microdialysis, and noradrenaline spillover. Fractional extraction of both noradrenaline and adrenaline was unaffected by increasing blood flow three and four times its resting value. In addition, noradrenaline spillover was increased by the higher blood flow, from 188 to 452 pg·min-1 at rest and from 246 to 880 pg·min-1 during stimulation. Stimulation of muscle contraction caused a significant increase in fractional extraction of noradrenaline and a nonsignificant increase in adrenaline extraction. In addition, an adrenaline spillover was observed in certain conditions. In light of our results, it seems that blood flow may not be the main factor decreasing fractional extraction of noradrenaline during exercise. However, blood flow could contribute to the increase in noradrenaline spillover observed in the active muscles during exercise.Key words: skeletal muscle, spillover, fractional extraction, stimulation, adrenaline.
Baroreceptors, α1-adrenergic receptors, and regulation of mesenteric blood flow
Authors: Abu-Amarah Isam , Cupples William A
Published: April 2011

In the mesenteric circulation of the rat a myogenic autoregulatory system operates at 0.1-0.15 Hz. Negative admittance phase in the region above 0.2 Hz suggested operation of an arterial baroreflex. The present study was designed to test this interpretation and to identify the neurotransmitter involved. In rats anesthetized with isoflurane, blood pressure and mesenteric blood flow (transit time ultrasound) were measured with central mechanisms intact, after sinoaortic denervation, and after denervation of the mesenteric bed. Sinoaortic denervation abrogated the negative phase in the band from 0.3 to 0.6 Hz and increased admittance gain in this region. Subsequent mesenteric denervation had no further effect on the pressure-flow transfer function. In a separate experiment, α1-adrenergic blockade reduced, but did not remove, the negative admittance phase in the 0.2- to 0.5-Hz band without altering admittance gain. It is concluded that the baroreflex acting on the mesenteric circulation can be identified by admittance phase, but that admittance gain is uninformative. Part of the response is mediated by α1-adrenergic transmission.Key words: mesenteric, α1-adrenergic receptors, dynamic regulation.
Neuropeptide Y enhances potassium excretion by mechanisms distinct from those controlling sodium excretion
Authors: Bischoff Angela , Michel Martin C
Published: April 2011

Neuropeptide Y (NPY) is an established modulator of renal function. Although NPY reduces renal blood flow and does not alter glomerular filtration rate, it enhances diuresis and natriuresis. Although initial studies on natriuresis did not detect kaliuresis, we now report that a retrospective analysis of previous studies regarding natriuresis demonstrates NPY-induced kaliuresis under several experimental conditions. Kaliuresis was observed despite a marked reduction in urinary potassium concentrations, which may explain why it has not been noted in some initial studies. In a direct comparison of NPY-induced kaliuresis and natriuresis, both effects were slow in onset (requiring >45 min to develop fully) and blocked by the cyclooxygenase inhibitor indomethacin. While natriuresis occurred solely via a Y5 receptor, kaliuresis involved a Y1 receptor and an additional receptor subtype, possibly Y2. The L-type Ca2+ entry blocker nifedipine abolished natriuresis but did not inhibit kaliuresis. A combination of experiments with the bradykinin B2 receptor antagonist icatibant, the angiotensin II receptor antagonist losartan, and the converting enzyme inhibitor ramiprilat revealed that NPY-induced natriuresis involves bradykinin while kaliuresis involves angiotensin II. We conclude that NPY-induced kaliuresis is much less pronounced than natriuresis and is mediated by distinct mechanisms.Key words: neuropeptide Y, potassium excretion, sodium excretion, angiotensin II, cyclooxygenase.
Food intake regulation in rodents: Y5or Y1NPY receptors or both?
Authors: Duhault Jacques , Boulanger Michèle , Chamorro Susana , Boutin Jean A , Zuana Odile Della , Douillet Emmanuelle , Fauchère Jean-Luc , Félétou Michel , Germain Martine , Husson Bruno , Vega Antonio Monge , Renard Pierre , Tisserand Françoise
Published: April 2011

Neuropeptide Y (NPY), one of the most abundant peptides in rat and human brains, appears to act in the hypothalamus to stimulate feeding. It was first suggested that the NPY Y1receptor (Y1R) was involved in feeding stimulated by NPY. More recently a novel NPY receptor subtype (Y5R) was identified in rat and human as the NPY feeding receptor subtype. There is, however, no absolute consensus since selective Y1R antagonists also antagonize NPY-induced hyperphagia. Nevertheless, new anti-obesity drugs may emerge from further pharmacological characterization of the NPY receptors and their antagonists. A large panel of Y1R and Y5R antagonists (such as CGP71683A, BIBO3304, BIBP3226, 1229U91, and SYNAPTIC and BANYU derivatives but also patentable in-house-synthesized compounds) have been evaluated through in vitro and in vivo tests in an attempt to establish a predictive relationship between the binding selectivity for human receptors, the potency in isolated organs assays, and the inhibitory effect on food intake in both normal and obese hyperphagic rodents. Although these results do not allow one to conclude on the implication of a single receptor subtype at the molecular level, this approach is crucial for the design of novel NPY receptor antagonists with potential use as anti-obesity drugs and for evaluation of their possible adverse peripheral side effects, such as hypotension.Key words: obesity, weight reduction, food intake, neuropeptide Y, rodents.
Heterotrimeric G proteins in heart disease
Authors: Zolk Oliver , Kouchi Ichiro , Schnabel Petra , Böhm Michael
Published: April 2011

Guanine nucleotide binding proteins (G proteins) are largely grouped into three classes: heterotrimeric G proteins, ras-like or small molecular weight GTP binding proteins, and others like Gh. In the heart G proteins transduce signals from a variety of membrane receptors to generate diverse effects on contractility, heart rate, and myocyte growth. This central position of G proteins forming a switchboard between extracellular signals and intracellular effectors makes them candidates possibly involved in the pathogenesis of cardiac hypertrophy, heart failure, and arrhythmia. This review focuses primarily on discoveries of heterotrimeric G protein alterations in heart diseases that help us to understand the pathogenesis and pathophysiology. We also discuss the underlying molecular mechanisms of heterotrimeric G protein signalling.Key words: G proteins, signal transduction, adrenergic system, heart failure, hypertrophy.
Ion channel modifying agents influence the electrical activity generated by canine intrinsic cardiac neurons in situ
Authors: Thompson Gregory W , Horackova Magda , Armour J Andrew
Published: April 2011

This study was designed to establish whether agents known to modify neuronal ion channels influence the behavior of mammalian intrinsic cardiac neurons in situ and, if so, in a manner consistent with that found previously in vitro. The activity generated by right atrial neurons was recorded extracellularly in varying numbers of anesthetized dogs before and during continuous local arterial infusion of several neuronal ion channel modifying agents. Veratridine (7.5 µM), the specific modifier of Na+-selective channels, increased neuronal activity (95% above control) in 80% of dogs tested (n = 25). The membrane depolarizing agent potassium chloride (40 mM) reduced neuronal activity (43% below control) in 84% of dogs tested (n = 19). The inhibitor of voltage-sensitive K+channels, tetraethylammonium (10 mM), decreased neuronal activity (42% below control) in 73% of dogs tested (n = 11). The nonspecific potassium channel inhibitor barium chloride (5 mM) excited neurons (47% above control) in 13 of 19 animals tested. Cadmium chloride (200 µM), which inhibits Ca2+-selective channels and Ca2+-dependent K+channels, increased neuronal activity (65% above control) in 79% of dogs tested (n = 14). The specific L-type Ca2+channel blocking agent nifedipine (5 µM) reduced neuronal activity (52% blow control in 72% of 11 dogs tested), as did the nonspecific inhibitor of L-type Ca2+channels, nickel chloride (5 mM) (36% below control in 69% of 13 dogs tested). Each agent induced either excitatory or inhibitory responses, depending on the agent tested. It is concluded that specific ion channels (INa, ICaL, IKv, and IKCa) that have been associated with intrinsic cardiac neurons in vitro are involved in their capacity to generate action potentials in situ.Key words: calcium channels, intrinsic cardiac neuron, potassium channels, sodium channels.
Tissue distribution and antithrombotic activity of unlabeled or14C-labeled porcine intestinal mucosal heparin following administration to rats by the oral route
Authors: Hiebert Linda M , Wice Sandra M , Ping Tilly , Hileman Ronald E , Capila Ishan , Linhardt Robert J
Published: April 2011

Distribution and antithrombotic activity of orally administered unfractionated porcine heparin were studied. [14C]Heparin was prepared by de-N-acetylation of porcine mucosal heparin followed by re-N-acetylation, using [14C]acetic anhydride. [14C]Heparin and (or) cold heparin (60 mg/kg) were administered by stomach tube to male Wistar rats. Blood, all levels of gut and gut contents, liver, lung, spleen, kidney, and aortic and vena caval endothelium were collected under deep anesthesia at 3, 6, 15, 30, and 60 min and 4 and 24 h (6 rats/group) after administration. Urine and feces were collected at 24 h, using metabolic cages. In three additional rats, drugs were administered in gelatin capsules. Tissues listed above and tongue, esophagus, trachea, brain, heart, thymus, bile ducts, vena caval and aortic walls, ureters, bladder, samples of muscle, skin, hair, and bone marrow were collected at 24 h. Radioactivity and chemical heparin, measured by agarose gel electrophoresis, were observed in all tissues examined as well as gut washes, plasma, urine, and feces. Radiolabel recovered was confirmed to be heparin by autoradiograms of gradient polyacrylamide electrophoretic gels. [14C]Heparin and chemical heparin in gut tissue suggest a transit time of 4 h. Porcine or bovine heparin (7.5 mg/kg), administered by stomach tube, decreased the incidence of thrombosis induced by applying 10% formalin in 65% methanol to the exposed jugular vein of rats. Heparin isolation from non-gut tissue, endothelium, urine, and plasma and the observed antithrombotic effect are consistent with oral bioavailability.Key words: heparin, [14C]heparin, oral administration, distribution, radiolabel, thrombosis.