bluuebunny/crossref_metadata_2025 huggingface dataset:
Diverse interactions of calcitonin gene related peptide and nitric oxide in the gastric and cutaneous microcirculation
Authors: Holzer P. , Wachter Ch. , Jocič M. , Lippe I. Th. , Heinemann A. , Herbert M. K.
Published: April 2011

Calcitonin gene related peptide (CGRP) is the major mediator of afferent nerve mediated vasodilatation in the gastric mucosa and skin of the rat. Since receptors for CGRP occur on both the vascular endothelium and smooth muscle, it is conceivable that the vascular actions of CGRP involve multiple mechanisms. The vasodilator effect of rat CGRP-α in the rat gastric mucosa is indeed inhibited by blockade of nitric oxide (NO) synthesis, as is the gastric mucosal hyperemia in response to gastric acid challenge, which is mediated by CGRP release from afferent nerve fibres. In contrast, the vasodilator response to rat CGRP-α in the rat hind paw and the CGRP-mediated vasodilatation evoked by antidromic stimulation of afferent nerve fibres do not depend on the formation of NO. These data indicate that NO plays regionally different roles in the local vasodilator action of CGRP. NO is a secondary vasorelaxant messenger of CGRP in the gastric, but not in the cutaneous, microcirculation. However, this L-arginine-derived autacoid may have a role in the irritant-induced CGRP release from afferent vasodilator fibres in the skin.Key words: calcitonin gene related peptide, nitric oxide, microcirculation, gastric mucosa, skin, afferent nerve fibres, neurogenic vasodilatation.
Pharmacology of calcitonin gene related peptide release from sensory terminals in the rat trachea
Authors: Hua Xiao-Ying , Wong Sheila , Jinno Shigeharu , Yaksh Tony L.
Published: April 2011

In an intraluminally perfused rat trachea model, we have observed the following. (i) Capsaicin evoked a concentration-dependent calcitonin gene related peptide (CGRP) release from the trachea. Its effects were mimicked by the capsaicin analogue resiniferatoxin and blocked by capsazepine, a competitive antagonist of capsaicin. Capsazepine did not attenuate the peptide release evoked by bradykinin, nicotine, or prostaglandin E2. (ii) Elevation of extracellular H+ resulted in a proton concentration dependent increase in CGRP release, but this was not inhibited by capsazepine. (iii) Indomethacin treatment did not alter capsaicin- or proton-induced CGRP release; in contrast bradykinin- and nicotine-induced release were significantly reduced, (iv) Chemical destruction of sympathetic nerve fibers by systemic pretreatment with 6-hydroxydopamine reduced CGRP release evoked by nicotine, but the release produced by capsaicin or bradykinin remained unchanged. These results suggest that the effect of capsaicin on tracheal CGRP release occurs via activation of specific capsaicin receptors on primary sensory C-fibers, while protons act at a different site from that acted upon by capsaicin in the trachea. Cyclooxygenase products are likely involved in the effects of bradykinin and nicotine, but not those of capsaicin and protons. Sympathetic activation may mediate nicotine-, but not bradykinin- or capsaicin-induced CGRP release. These observations indicate that factors present in the extravascular–extracellular melieu of the trachea can evoke the release of CGRP from sensory C-fibers and that there are multiple mechanisms whereby these agents may interact with the afferent terminals.Key words: calcitonin gene related peptide, airway, primary sensory nerves, proton, sympathetic efferent nerves.
A role for calcitonin gene related peptide (CGRP) in the regulation of early B lymphocyte differentiation
Authors: McGillis Joseph P. , Rangnekar Vidya , Ciallella John R.
Published: April 2011

In previous studies we identified high affinity adenylyl cyclase linked receptors for calcitonin gene related peptide (CGRP) on rat T and B cells, on lymphocyte cell lines including the mouse pre-B cell line 70Z/3, and on cells in mouse bone marrow. The effect of CGRP on early B cell differentiation has been examined using the 70Z/3 cell line. CGRP inhibits the lipopolysaccharide (LPS) induction of surface immunoglobulin (sIg) protein expression in 70Z/3 cells, an effect that is associated with a decrease in the steady-state levels of Ig heavy (μ) and light (κ) chain mRNA. In this report, experiments are described that provide further information on the mechanism by which CGRP inhibits sIg expression. The kinetics of CGRP inhibition of LPS-induced sIg expression was examined in 70Z/3 cells. An optimal window for the inhibitory effect of CGRP on sIg induction occurs at least 24 h after the cells are treated with LPS. To determine whether the inhibitory effects of CGRP on sIg expression are mediated by an inhibition of NFκ-B translocation to the nucleus, electrophoretic mobility shift assays were performed using nuclear proteins from 70Z/3 cells. There was no difference in NFκ-B binding activity in cells that had been treated with LPS or LPS + CGRP, suggesting that the inhibitory effect of CGRP is not mediated by an inhibition of NFκ-B activity. These studies provide further evidence that CGRP plays an inhibitory role in early B cell differentiation. Finally, a model is proposed that describes an integrated role for CGRP in the homeostatic regulation of early B cell differentiation.Key words: neuropeptides, immune, immunoglobulin, neuroimmunology, calcitonin gene related peptides.
Effect of baroreceptor activation and systemic hypotension on plasma endothelin 1 and neuropeptide Y
Authors: Notarius C. F. , Erice F. , Stewart D. , Magder S.
Published: April 2011

To determine whether endothelin (ET-1) and neuropeptide Y (NPY) release are controlled by the carotid sinus (CS) baroreceptor or local endothelial mechanisms, we isolated and pump perfused the CS in eight chloralose-anesthetized dogs and controlled systemic arterial pressure (SAP) with an elevated reservoir connected to both femoral arteries. This allowed the SAP to be kept constant while CS pressure was varied from 55.8 ± 2.0 (low CS) to 192 ± 1.9 (high CS) mmHg (1 mmHg = 133.3 Pa) or CS pressure to be kept constant while SAP was lowered to 53.9 ± 1.8 mmHg (low SAP). There was no significant change in ET-1 when CS pressure was varied (control, 2.08 ± 0.50; low CS, 2.18 ± 0.51; high CS, 2.11 ± 0.38 pg/mL), but ET-1 was significantly higher during low SAP (2.93 ± 0.49 pg/mL, p < 0.05). This increase was not observed with vagi and CS intact in six dogs or with vagi intact and CS constant in four dogs. In contrast, plasma NPY was significantly higher in the low CS condition (619.13 ± 66.87 pg/mL) versus high CS condition (528.88 ± 45.19 pg/mL, p < 0.05) and did not change during hypotension. In conclusion, NPY, but not ET-1, is affected by CS baroreceptor manipulation, and plasma ET-1 increases in response to hemorrhagic hypotension when modulating reflexes are abolished.Key words: endothelin 1, neuropeptide Y, carotid sinus baroreceptor, hemorrhage, cardiac output.
Sulfhydryl involvement in nitric oxide sequestration and nitric oxide induced guanylyl cyclase activation in vascular smooth muscle
Authors: Liu Zhen-Guo , McLaughlin Brian E. , Marks Gerald S. , Brien James F. , Nakatsu Kanji
Published: April 2011

In the present study, the role of vascular smooth muscle sulhydryl groups was investigated with respect to sequestration of nitric oxide (NO) and activation of soluble guanylyl cyclase by NO. Vascular smooth muscle 100 000 × g supernatant (soluble) fraction was prepared in phosphate buffer, using the medial layer of bovine pulmonary artery. The soluble fraction was incubated with 100 pmol NO for 5 min in a sealed flask at 37 °C under anerobic conditions in the presence or absence of the sulfhydryl reagent, N-ethylmaleimide (NEM, 5 mM). NO sequestration by the soluble fraction was measured as an indicator of NO binding. Total thiol content was measured in the soluble fraction with and without exposure to NEM. Guanylyl cyclase activity was measured in the soluble fraction with and without exposure to NO and a combination of NO and NEM. NEM decreased total thiol content in the soluble fraction from 103.59 nmol/mL to undetectable levels, and decreased guanylyl cyclase activity to below basal levels. The percentage of NO sequestered by the soluble fraction was inhibited by NEM by approximately 25% from a control value of 26.52 ± 9.39 to 18.72 ± 8.52, n = 13, p < 0.05. The data indicate that sulfhydryl groups are essential for guanylyl cyclase activation by NO, and are also involved in the sequestration of NO by the vascular smooth muscle soluble fraction.Key words: nitric oxide, binding site, sulfhydryl, vascular smooth muscle, guanylyl cyclase, chemiluminescence – headspace gas analysis.
Reaotive oxygen generation by azomethine H: a new antimalarial drug
Authors: Novelli Ethel L. B. , Silva Assunta M. M. , Novell F. Jose L.V.B. , Curi Paulo R.
Published: April 2011

Superoxide radical [Formula: see text] is a free radical that may be involved in various toxic processes. Cu—Zn superoxide dismutase catalyzes the dismutation of the superoxide free radical and protects cells from oxidative damage. A rat bioassay validated for the identification of the toxic effects of azomethine H revealed increased serum activities of amylase, alanine transaminase, and alkaline phosphatase. The lipoperoxide and bilirubin concentrations were also increased in animals that received azomethine H (1 g/kg) from ascorbic or hydrochloric acid solutions. Azomethine H increased Cu–Zn superoxide dismutase activity. This elevation of Cu–Zn superoxide dismutase activity was highest on the 7th day and was at levels comparable with those of control rats from day 60 onwards. Superoxide is an important intermediate in the action and toxicity of azomethine H.Key words: azomethine H, superoxide radical, antimalarial, toxicity.
β-Adrenergic control of renin in sodium-deprived conscious dogs: renal versus extrarenal location
Authors: Blair M. L. , Gengo F. M
Published: April 2011

This study was designed to determine if tonic β-adrenergic control of plasma renin activity (PRA) during dietary sodium restriction is due to stimulation of renal β-adrenoceptors, extrarenal β-adrenoceptors, or both. Experiments were performed in six conscious resting uninephrectomized dogs with chronically indwelling catheters in the aorta, vena cava, and remaining renal artery. The dogs were fed a low-sodium diet of approximately 7 mequiv. Na/day. PRA decreased by 28 ± 4% of control (p < 0.01) when the β-adrenoceptor antagonist propranolol was infused directly into the renal artery (ira) at a rate of 0.25 μg ∙ kg−1 ∙ min−1 for 45 min, whereas iv propranolol infusion at the same rate had no effect on PRA. Propranolol infusion, 1 μg ∙ kg−1 ∙ min−1 iv, decreased PRA by 22 ± 8% of control (p < 0.05) and produced significantly greater systemic β-adrenoceptor blockade but a similar renal plasma propranolol concentration as with ira infusion, 0.25 μg ∙ kg−1 ∙ min−1. Thus blockade of extrarenal β-adrenoceptors produced no additional suppression of PRA beyond that which could be accounted for by blockade of renal β-adrenoceptors. Therefore, suppression of PRA by propranolol is due solely to blockade of renal β-adrenergic receptors in conscious sodium-deprived dogs.Key words: propranolol, sympathetic nervous system, plasma renin activity, dietary sodium restriction.
Regulatory peptides as modulators of vagal influence on cardiac rhythm
Authors: Pokrowsky Vladimir M. , Osadchiy Oleg E.
Published: April 2011

When the right vagus nerve of anesthetized cats was stimulated with repetitive bursts of pulses, decelerated heart rate became synchronized to the rhythm of the vagal bursts. Each burst applied to the vagus was followed by a single heart contraction. Within defined limits an increase in the frequency of vagal bursts evoked a proportional acceleration of the heart, whereas a decreased frequency diminished the heart rate. Therefore, over the range of synchronization the heart rate was precisely controlled by changing the vagal stimulation rate. We concluded that the chronotropic effect evoked by vagal bursts was composed of two functionally different types of influence, namely, inhibitory tonic and synchronizing. The vagotropic influence of intravenously injected regulatory peptides was found to be selective for either the tonic or synchronizing component. For instance, dalargin (D-Ala2-Leu5-Arg6-enkephalin) and neokyotorphin selectively diminished the inhibitory tonic vagal influence, whereas delta sleep inducing peptide and neurotensin potentiated it. The magnitude of synchronizing vagal influence was not modified by these peptides. In contrast, secretin selectively inhibited the synchronizing vagal effect, but the tonic one was not affected. Somatostatin potentiated the synchronizing effect but diminished the tonic one. These data support the hypothesis that certain regulatory peptides can modulate the effects of repetitive vagal bursts on pacemaker activity.Key words: vagus nerve, burst stimulation, controlled bradycardia, regulatory peptides.
Antiarrhythmic effects of ceruloplasmin during reperfusion in the ischemic isolated rat heart
Authors: Atanasiu Roxana , Chahine Ramez , Nadeau Réginald , Dumoulin Marie-Josée , Mateescu Mircea Alexandra
Published: April 2011

The ability of ceruloplasmin, an important serum antioxidant, to reduce the vulnerability of the isolated rat heart to reperfusion arrhythmias has been investigated. Bovine plasma ceruloplasmin was purified by chromatography on aminoethyl-agarose. Isolated rat hearts were submitted to 15 min of regional ischemia and 10 min of reperfusion. The dose–effect relationship and the role of ceruloplasmin conformational integrity in cardioprotection were established by treatment of ischemic hearts with ceruloplasmin at various concentrations (0.25, 0.5, 1, and 2 μM) and at different degrees of conformational integrity (A610/A280 = 0.02, 0.04, and 0.06), 5 min before reperfusion. Deferoxamine (20–500 μM) was used as a positive control. As negative controls we used chemically inactivated ceruloplasmin (1 μM), heat-denatured ceruloplasmin (1 μM), and albumin (1–4 μM). In the control group during the first 5 min of reperfusion, the incidence of total ventricular fibrillation was 100% and of irreversible ventricular fibrillation was 83%. The incidence of reversible and irreversible ventricular fibrillation was significantly decreased in the cerulopiasmin-treated groups in both a dose and molecular integrity dependent manner. Ceruloplasmin had no effect on the incidence of ventricular tachycardia. Deferoxamine reduced the incidence of ventricular fibrillation to the same degree as ceruloplasmin but at concentrations much higher than those of ceruloplasmin. Chemically inactivated ceruloplasmin, heat-denatured ceruloplasmin, and albumin had no protective effects on reperfusion-induced arrhythmias.Key words: ceruloplasmin, ischemic heart disease, oxygen free radicals, antioxidants, isolated rat heart.
Endothelial receptor subtypes in mesenteric wascular smooth muscle cells of spontaneously hypertensiwe rats
Authors: Touyz Rhian M. , Larivière Richard , Schiffrin Ernesto L.
Published: April 2011

Calcium responses to the endothelin B receptor (ETB) selective agonist IRL-1620 (IRL) and to endothelin 1 (ET-1) in the absence and presence of the endothelin A receptor (ETA) antagonist BQ-123 were determined in primary cultured unpassaged vascular smooth muscle cells derived from mesenteric resistance vessels of 3-, 9-, and 17-week-old spontaneously hypertensive rats (SHR), Wistar rats, and Wistar–Kyoto (WKY) rats. Intracellular free calcium concentration ([Ca2+]i) was measured microphotometrically and by digital imaging using fura 2 methodology. ET receptor affinity and density were determined in membrane preparations from the mesenteric vascular bed from these rats. Binding studies were performed using [125I]ET-1 in the presence of increasing concentrations of ET-1, BQ-123, or IRL. Basal [Ca2+]i was significantly greater (p < 0.01) in adult SHR compared with age-matched normotensive groups. IRL (10−7 mol/L) and ET-1 (10−9 mol/L) increased [Ca2+]i in cells from all strains of all age groups. Responses were significantly lower (p < 0.05) in vascular smooth muscle cells from 9- and 17-week SHR compared with cells from age-matched Wistar and WKY rats. Concentration–response curves for IRL were blunted in cells from 17-week SHR versus cells from WKY rats. The selective ETA receptor antagonist BQ-123 (10−7–10−5 mol/L) had no effect on IRL-induced [Ca2+]i but significantly reduced ET-1-induced [Ca2+]i by 135 ± 4, 80 ± 6, and 91 ± 4 nmol/L in cells from 17-week SHR, WKY, and Wistar groups, respectively. The selective ETB receptor antagonist BQ-788 (10−6 mol/L) significantly reduced ET-1-induced [Ca2+]i responses in 17-week rats. The Bmax for ET-1 binding was significantly lower in mesenteric artery membrane preparations from 17-week SHR (627 ± 163 fmol/mg protein) compared with WKY and Wistar rats (1190 ± 43 and 1059 ± 55 fmol/mg protein, respectively). These data demonstrate the presence of both ETA and ETB receptors in rat mesenteric vascular smooth muscle cells. In adult SHR, reduced responses of vascular smooth muscle cells to IRL, which represents ETB-mediated effects, and to ET-1, may be partly due, as demonstrated in the binding studies, to lower ET receptor density than in normotensive rats.Key words: small vessels, vascular smooth muscle cells, intracellular free calcium, endothelin 1, endothelin receptors, endothelin receptor agonists, endothelin receptor antagonists.
Glucagon increases medullary interstitial electrolyte concentration in rat kidney
Authors: Kompanowska-Jezierska E. , Sadowski J. , Walkowska A.
Published: April 2011

In anesthetized rats, tissue electrical admittance of the inner medulla (a measure of total ion concentration in the interstitium), medullary blood flow (laser Doppler technique), and renal clearances were measured simultaneously before and during i.v. infusion of glucagon at 110 and 330 ng∙min−1∙kg−1 body weight. Admittance increased modestly, 5.4% after a large glucagon dose (p < 0.01), whereas medullary blood flow was stable. Glomerular filtration rate increased transiently and then fell during high-dose glucagon infusion. The increase in tissue electrolyte (mostly NaCl) concentration in the medulla observed with stable medullary blood flow and decreasing glomerular filtration rate indicates that stimulation of NaCl reabsorption in the medullary ascending limb of Henle's loop by glucagon was the mechanism underlying augmentation of medullary ionic hypertonicity. This suggests that glucagon can contribute to the urine concentration process.Key words: glucagon, loop of Henle, tubular NaCl transport, medullary blood flow.
A method to study changes in eye-related columns in the visual cortex of kittens during and following early periods of monocular deprivation
Authors: Mitchell D. E. , Beaver C. J. , Ritchie P. J.
Published: April 2011

An immunohistochemical method that exploits the rapid light-evoked expression of Fos, the protein product of the immediate early gene, c-fos, to visualize eye-related columns in the visual cortex, has been used to provide preliminary data on the relative innervation of the cortex by the two eyes of monocularly deprived kittens and the speed of the changes that occur afterward during reverse occlusion. In contrast to conventional anatomical techniques, the method allows both cellular resolution and documentation of the dimensions of eye-related columns through the depth of the cortex. In kittens monocularly deprived from near birth, Fos-immunoreactive neurones were observed in oval or circular patches, the size of which decreased as the duration of deprivation was increased from 4 to 6 weeks. Following reverse occlusion at 5 weeks of age, the size of the patches increased rapidly so that after 4 days their area had approximately tripled. In addition to providing possible insights into the anatomical underpinnings of the puzzling behavioural effects that occur following termination of short periods of reverse occlusion, the method can be used to investigate the temporal order of the anatomical effects of monocular deprivation in different cortical layers.Key words: development, vision, visual cortex, amblyopia, deprivation.
Physiological studies of visual cortex reorganization following cortical deafferentation in neonatal cats
Authors: Yinon U. , Shemesh R. , Arda H. , Rosner M. , Jaros P. P.
Published: April 2011

Whether restoration takes place in the visual cortex of neonates was physiologically studied in cortical cells of cats following their deafferentation. Deafferentation was performed by a parasagittal incision made in the visual cortex, separating the medial part of it from the thalamocortical and other visual fibers. Responsiveness (percentage of responsive cells) in the middle zone (the middle sector along the cortical incision) of the deafferented region was 82.5%, compared with 91.7% in the afferented (lateral to the incision) region (p = 0.5). In comparison, the responsiveness level was 32.3 and 81.3% (p < 0.05) in the respective zones of the similarly deafferented adult controls. The ocular dominance distribution and binocularity were almost normal in the deafferented region of the neonatally operated cats, whereas binocularity was remarkably diminished in the adult controls. Recovery was also found in the specificity of the cells to orientation and direction in the neonatally operated cats, but not in the adult-operated cats. Thus, functional reorganization of the columnar organizations takes place in the neonatally deafferented but not in the adult-operated cats.Key words: visual cortex, neonatal cats, deafferentation, unit recording, responsiveness.
Binocular interactions and visual acuity loss in esotropic cats
Authors: Ptito M. , Bouchard P. , Lepore F. , Quessy S. , Stefano M. Di , Guillemot J.-P.
Published: April 2011

Visual acuity was measured behaviorally in various groups of cats by using a two-choice discrimination procedure. Cats in group 1 were rendered strabismic soon after birth by sectioning the tendon of the lateral rectus muscle (unilateral esotropia); at adulthood, their visual acuity (VA) was evaluated, after which the optic chiasm was sectioned and VA reassessed. Cats in group 2 were not only tenotomized but also chiasmatomized neonatally, while cats in group 3 underwent a neonatal section of the optic chiasm only. VA was measured at adulthood in the two latter groups. Group 4 consisted of adult cats whose VA was evaluated before and after an optic chiasm section. Stimuli consisted of square-wave gratings of various spatial frequencies. Results showed that in normal cats, the average threshold values under monocular viewing were identical for each eye (4.76 cycles/degree); however, following optic chiasm section, monocular VA was reduced to 1.23 cycles/degree. VA in early optic chiasm section cats was lower than that of the normal cats but higher than that of late-lesioned animals (2.33 cycles/degree). In strabismic cats, mean VA was 1.25 cycles/degree for the deviated eye and 2.8 cycles/degree for the normal eye. Following the optic chiasm section at adulthood, VA was lower not only for the deviated eye (<0.17 cycles/degree) but also for the normal eye (1.14 cycles/degree). Similar results were found when both the deviation and chiasmatomy were performed neonatally. The elimination of interocular interactions through chiasm transection failed to improve VA in the strabismic eye.Key words: visual acuity, esotropia, optic chiasm, corpus callosum, cats, development, behavior.
β-Cell stimulus–secretion coupling defects in rodent models of obesity
Authors: Chan Catherine B.
Published: April 2011

Hyperinsulinemia accompanies obesity in human patients and experimental rodent models and exacerbates insulin resistance, but the causes of increased insulin secretion remain obscure. This review examines progress in defining biochemical and molecular β-cell defects that have been elucidated in the past 5 years. Some defects, such as decreased glucose transport, decreased mitochondrial FAD-linked glycerophosphate dehydrogenase activity, and altered anomeric specificity for glucose, become evident only after onset of non-insulin-dependent diabetes mellitus. Thus, these defects are unlikely to play a role in the pathogenesis of hyperinsulinemia in obesity. Other biochemical changes, including increased glucokinase and (or) hexokinase function, increased glucose cycling, and altered regulation of intracellular Ca2+ are present in obese nondiabetic animals and may therefore contribute to development of hyperinsulinemia. Few developmental studies have been performed to correlate onset of defects with environmentally and genetically mediated control mechanisms of β-cell function. However, the availability of new molecular biology techniques should facilitate identification of factors causing hyperinsulinemia in obesity.Key words: obesity, insulin secretion, islets of Langerhans, rodent models, stimulus–secretion coupling.
Massive intestinal resection depresses circular smooth muscle contractility in the rat
Authors: Chin Beth C. , Tan Daimen T. M. , Scott R. Brent
Published: April 2011

To determine whether functional changes in in vitro contractility and in vivo gastrointestinal transit accompany the adaptive structural changes seen in jejunal circular muscle after massive intestinal resection, rats were subjected to either surgical resection of 75% of the mid-jejunoileum or a sham operation. Basal stress in response to stretch was similar for both groups on postoperative days 10, 20, 30, and 40. By day 10 after surgery, tissues from resected rats exhibited a significant reduction in bethanechol-stimulated tonic stress and in frequency of phasic contractions. The amplitude of spontaneous phasic activity was significantly increased; however, following cholinergic stimulation, the magnitude of the increase in the amplitude of phasic activity was significantly reduced. Experiments with tetrodotoxin (10−6 M) indicated a myogenic origin to the reduction in bethanechol-stimulated tonic stress and the reduced frequency and altered amplitude of phasic contractile activity in resected animals. The tonic stress developed in response to depolarization with KCl did not differ significantly between sham-operated and resected rats. Transit studies showed no change in the rate of gastric emptying after resection but did reveal a significant reduction in the velocity of intestinal transit. Thus, following massive intestinal resection the bethanechol-stimulated tonic stress response and phasic contractile activity of circular smooth muscle are significantly reduced, concomitant with altered intestinal transit. The reduction in contractility in the resected animals may be due to an alteration at the level of the smooth muscle receptor and (or) its signal transduction pathway.Key words: short gut, intestinal circular smooth muscle, contractility, adaptation.
Effects of uridine triphosphate on skinned skeletal muscle fibers of the rat
Authors: Suarez-Kurtz G. , Ponte C. G. , Catinot M.-P. , Mounier Y. , Vianna-Jorge R.
Published: April 2011

Chemically skinned muscle fibers from rat extensor digitorum longus muscle were used to study the effects of uridine triphosphate (UTP) on Ca2+uptake and release by the sarcoplasmic reticulum (SR) and on Ca2+-activated tensions. Total replacement (2.5 mM) of adenosine triphosphate (ATP) with UTP (i) increased submaximal Ca2+-induced tension (pCa 6.2–5.8) but diminished Po, the maximum tension elicited by pCa 4.2, by ca. 15%; (ii) markedly reduced Ca2+uptake by the SR (evaluated by caffeine-elicited tension); and (iii) induced tension in Ca2+-loaded fibers. The UTP-induced tension averaged 55% of Poand its rates of development and decay were considerably slower than those of caffeine-evoked tension. The UTP-induced tension (i) depended on the Ca2+-loading conditions; (ii) was reversibiy blocked by brief (15 s) exposures of Ca2+-loaded fibers to 5 mM EGTA or by pretreatment with caffeine; (iii) was abolished by functional disruption of the SR with the nonionic detergent Brij-58; and (iv) persisted after blockade of the SR Ca2+release channels with ruthenium red. Exposure of Ca2+-loaded fibers to UTP depressed the tension elicited subsequently by caffeine, and enhanced the rate of depletion of caffeine-sensitive Ca2+stores during soaking in relaxing solutions containing 5 mM EGTA. The UTP-induced tension is attributed to increased release of Ca2+from the SR, via a ruthenium red insensitive pathway(s), combined with reduced Ca2+uptake by the SR and increased Ca2+affinity of the contractile proteins.Key words: skinned muscle fiber, UTP-induced tension, tension–pCa relationship, sarcoplasmic reticulum, calcium transport.
Pyrogen–prostaglandin coupling in the pathogenesis of fever: evidence against a role for nitric oxide
Authors: Redford Jane , Bishai Isis , Coceani Flavio
Published: April 2011

There is much debate on the mechanism by which blood-borne pyrogens trigger prostaglandin E2(PGE2) synthesis in brain and fever. This investigation was undertaken to determine whether nitric oxide qualifies as a signal transducer for pyrogens at the interface between blood and brain. Experiments were carried out in vitro and in vivo using, respectively, preparations of cerebral tissue and microvessels from the rat, and the conscious, chronically instrumented cat. In vitro preparations produced PGE2and its production increased during a 30-min treatment with interleukin 1 (brain tissue) or endotoxin (microvessels). In addition, both pyrogens increased cyclic GMP levels in cerebral microvessels. In both brain tissue and microvessels, NG-nitro-L-arginine had no effect on basal PGE2release, while it curtailed the pyrogen-stimulated release. The same treatment reduced the cyclic GMP accumulation brought about by pyrogens in the microvessels. Conversely, in the conscious cat, inhibitors of nitric oxide synthesis (NG-monomethyl-L-argimne, NG-nitro-L-arginine) had no effect on fever and the concomitant elevation of PGE2in cerebrospinal fluid, regardless of the pyrogen used (endotoxin, interleukin 1) and the route of administration (intravenous, intracerebroventricular). We conclude that nitric oxide may serve as a pyrogen mediator in brain. This mediator function, however, is seemingly not important in the development of fever.Key words: pyrogen, fever mechanism, nitric oxide, prostaglandin E2, blood–brain barrier.
Developmental change in fast Na channel properties in embryonic chick ventricular heart cells
Authors: Sada Hideaki , Ban Takashi , Fujita Takeshi , Ebina Yoshio , Sperelakis Nicholas
Published: April 2011

To assess developmental changes in kinetic properties of the cardiac sodium current, whole-cell voltage-clamp experiments were conducted using 3-, 10-, and 17-day-old embryonic chick ventricular heart cells. Experimental data were quantified according to the Hodgkin–Huxley model. While the Na current density, as examined by the maximal conductance, drastically increased (six- to seven-fold) with development, other current–voltage parameters remained unchanged. Whereas the activation time constant and the steady-state activation characteristics were comparable among the three age groups, the voltage dependence of the inactivation time constant and the steady-state inactivation underwent a shift in the voltage dependence toward negative potentials during embryonic development. Consequently, the steady-state (window current) conductance, which was sufficient to induce automatic activity in the young embryos, was progressively reduced with age.Key words: cardiac electrophysiology, whole-cell voltage-clamp experiments, fast Na currents, heart, development, developmental changes.
Effects of endothelin 1 on calcium and sodium currents in isolated human cardiac myocytes
Authors: Cheng Tzu-Hurng , Chang Chung-Yi , Wei Jeng , Lin Cheng-I
Published: April 2011

We have used the whole-cell voltage-clamp technique to study the effects of endothelin 1 (ET-1, 10 nM) on L-type Ca2+currents and voltage-dependent Na+inward currents in human cardiac cells. Myocytes were enzymatically isolated from atrial specimens obtained during open-heart surgery and from human ventricular tissues of explanted hearts. Extracellular application of ET-1 decreased the peak amplitude of Ca2+currents by 26 ± 6% (n = 13) in atrial myocytes and by 19 ± 3% (n = 8) in ventricular myocytes. In three atrial cells, treatment with 1 μM BQ123 prevented the decrease in Ca2+currents induced by ET-1. When GTP (0.2 mM) was added to the dialyzing pipette solution, ET-1 still caused a small decline by 12 ± 5% (n = 16), in peak Ca2+currents, in atrial myocytes. When Ca2+currents were increased (+210 ± 19%) by a β-adrenoceptor agonist (0.1 μM isoproterenol) or by the phosphodiesterase inhibitor isobutylmethylxanthine (10 μM), ET-1 reduced Ca2+currents by 35 ± 6% (n = 4) and 30 ± 4% (n = 5), respectively. In human ventricular myocytes in the presence of 1 μM isoproterenol, which increased the peak Ca2+currents by 150 ± 30%, ET-1 also induced a drastic reduction in Ca2+currents, by 40 ± 11% (n = 5). The tetrodotoxin-sensitive Na+currents measured in the presence of 5 mM [Na]owere significantly enhanced (+28 ± 7%) by ET-1 in five atrial myocytes. The stimulatory effect of ET-1 on Na+currents was partially reversible. The present findings in human cardiac cells show that ET-1 did not enhance the Ca2+currents in the absence or presence of internal GTP. The positive inotropic actions induced by ET-1 in human heart may be mediated mainly by signal-transduction pathways other than the G-protein – adenylyl cyclase – cAMP system.Key words: endothelin 1, human cardiac myocytes, whole-cell voltage-clamp technique, calcium currents, sodium currents.
Specific cyclic nucleotide phosphodiesterase inhibitors differently modulate contractile kinetics in airway smooth muscle
Authors: Rousseau Eric , Dostie Josée , Beaudry Catherine , Taoudi-Benchekroun Majda , Cadieux Alain , Lugnier Claire
Published: April 2011

The involvement of various phosphodiesterases (PDEs) in controlling the time-dependent mechanical properties of guinea pig trachealis smooth muscles was determined by using different classes of PDE inhibitors as pharmacological tools. These drugs produced low amplitude and long-lasting dose-dependent relaxations on the resting tone with the following EC50values: rolipram, 3 nM; indolidan, 0.11 μM; and zaprinast, 0.5 nM and 1 μM. These PDE inhibitors were 50% less active than 1 μM norepinephrine. The effects of the drugs were also tested on carbachol-induced contractions and norepinephrine-evoked relaxations. Zaprinast, but not rolipram nor indolidan, decreased the rate of rise of contraction, thus prolonging the time to reach the plateau by 75% without modifying the magnitude of the responses. Zaprinast and rolipram significantly increased the total length of the norepinephrine effect by 25 and 35%, respectively. Similar results were obtained in a dose-dependent manner on isoproterenol-induced relaxations. In contrast, a higher concentration of indolidan was required to affect the amplitude, duration, and time to peak of isoproterenol- or norepinephrine-induced relaxations. These results indicate that PDE IV (rolipram sensitive) and PDE I, and less likely PDE V (both zaprinast sensitive), are involved in the control of guinea pig airway contractile kinetics, whereas PDE III (indolidan sensitive) is essentially involved in the modulation of the resting tone. Four cytosolic isozymes were identified in bovine airway smooth muscles (ASMs): PDE I (calmodulin-dependent PDE), PDE II (cGMP-stimulated PDE), PDE IV (cAMP-specific and rolipram-sensitive PDE), and PDE V (cGMP-specific and zaprinast-sensitive PDE). Characterization of PDE isoforms present in the microsomal fraction by HPLC showed the presence of PDE IV, PDE V, and to a lesser extent PDE III. However, PDE III was not detected in ASM cytosol. Using newly synthesized radioligands, binding studies confirmed the low level of expression of PDE III and the presence of PDE IV. We conclude that PDE I controls the rate of contraction, whereas PDE V and PDE IV prolong the time of relaxation induced by NE. PDE V would control the ASM responsiveness by regulating the intracellular cGMP concentration, which in turn would both activate PKG and stimulate PDE II (cGS-PDE). Since the various isozymes of PDE are differently involved in the kinetic control of the mechanical events in ASM, they represent physiologically relevant and important pharmacological targets.Key words: trachealis muscle, phosphodiesterase inhibitors, norepinephrine, carbamylcholine.
Strychnine-dependent allodynia in the urethane-anesthetized rat is segmentally distributed and prevented by intrathecal glycine and betaine
Authors: Sherman Stephen E. , Loomis Christopher W.
Published: April 2011

The blockade of spinal glycine receptors with intrathecal strychnine produces a reversible allodynia-like state in the rat. Thus, hair deflection, in the presence of intrathecal strychnine, induces cardiovascular and motor withdrawal responses comparable with those evoked by noxious thermal, mechanical, or chemical stimulation in the absence of strychnine. In the present study, we mapped the cutaneous sites of abnormal sensitivity to hair deflection throughout the strychnine time course to investigate the segmental distribution of strychnine-induced allodynia. The ability of intrathecal glycine and the glycine derivative betaine to reverse strychnine-induced allodynia was also determined using dose–response analysis. Following intrathecal strychnine (40 μg), stroking the legs, flanks, lower back, and tail with a cotton-tipped applicator evoked a pronounced increase in mean arterial pressure, tachycardia, and an abrupt motor withdrawal response in urethane-anesthetized rats. These abnormal responses were only evoked by hair deflection at discrete sites, corresponding to the cutaneous dermatomes innervated by spinal segments near the site of strychnine injection. In rats with intrathecal catheters lying laterally in the subarachnoid space, allodynic sites were observed unilaterally on the ipsilateral side of intrathecal strychnine injection. Recovery from strychnine was complete by 30 min in all affected dermatomes. The cardiovascular and motor withdrawal responses to hair deflection were dose dependently inhibited by intrathecal glycine and intrathecal betaine. The ED50 (95% confidence interval) for intrathecal glycine was 609 (429–865) μg for the heart rate response, 694 (548–878) μg for the pressor response, and 549 (458–658) μg for the motor withdrawal response. The corresponding values for intrathecal betaine were 981 (509–1889), 1045 (740–1476), and 1083 (843–1391) μg, respectively. There was no difference in the effect of betaine on sensory-evoked cardiovascular and motor responses. Cortical electroencephalographic activity was not affected by intrathecal glycine or betaine, consistent with a spinal locus of action in reversing strychnine-induced allodynia. These results support the hypothesis that removal of spinal glycinergic modulation from low threshold afferent input with intrathecal strychnine results in segmentally localized, tactile-evoked allodynia.Key words: intrathecal, glycine, allodynia, strychnine, rat.
Physiological characteristics of identified motor units in the mouse extensor digitorum longus muscle: an in vitro approach
Authors: Zardini D M , Parry D J
Published: April 2011

Physiological, histochemical, and morphometric properties of fast-twitch single motor units were studied in mouse extensor digitorum longus muscles in an in vitro ventral root - nerve - muscle preparation. Single motor units were functionally isolated by microdissection of the ventral root, and the glycogen depletion technique was used to demonstrate the component muscle fibers. Monoclonal antibodies were used to identify their myosin heavy chain composition. The technique allows one to correlate physiological characteristics of single motor units with fiber type but is less useful for morphological assessment of motor unit size as a result of failure to deplete glycogen from all fibers of motor units containing fibers with high oxidative capacity.Key words: fiber type, IIx motor units, fatigue index, glycogen depletion.
Inhibitory effects of candesartan on responses to angiotensin peptides in the hindquarters vascular bed of the cat
Authors: Lambert David G , Champion Hunter C , Kadowitz Philip J
Published: April 2011

The effects of the nonpeptide angiotensin II AT1 receptor antagonist candesartan on responses to angiotensin II were investigated in the hindquarters vascular bed of the cat. Under constant-flow conditions, injections of angiotensin II into the hindquarters perfusion circuit elicited dose-dependent increases in perfusion pressure. Candesartan in a dose of 3 µg/kg iv decreased vasoconstrictor responses to angiotensin II in a competitive manner. However, at doses of 10-1000 µg/kg iv, candesartan shifted the dose-response curve to angiotensin II to the right in a nonparallel manner, suggesting a noncompetitive blockade. The inhibitory effects of candesartan on responses to angiotensin II were long in duration, and the AT1 receptor antagonist had little effect on baseline pressures. Candesartan was without effect on vasoconstrictor responses to norepinephrine, U46619, PGF2 alpha , and BAY K8644; on biphasic responses to endothelin-1; and on vasodilator responses to acetylcholine. Candesartan significantly attenuated hindquarters vasoconstrictor responses to angiotensin III and IV with a parallel shift at the 3 µg/kg iv dose and a nonparallel shift to the right at the high dose of the AT1 receptor antagonist. The results of the present study indicate that candesartan is a potent angiotensin AT1 receptor antagonist that can induce both competitive and noncompetitive blockade of responses to angiotensin II, III, and IV in the hindquarters vascular bed of the cat.Key words: angiotensin, vasoconstrictor responses, angiotensin type 1 receptors, selective and competitive antagonist, U46619.
Extravascular adenosine influences endothelium-derived nitric oxide release from perfused dog semitendinosus artery
Authors: Woodley N , Barclay J K
Published: April 2011

We tested the hypothesis that extravascular adenosine induces the release of vasodilatory products from endothelial cells lining skeletal muscle vessels. Endothelium-intact (n = 35) and -denuded (n = 5) dog semitendinosus intramuscular arteries were isolated, cannulated, and placed in 100-mL baths containing Krebs-Henseleit bicarbonate buffer (Krebs) at 37°C and gassed with 95% O2- 5% CO2. Each vessel, as well as a parallel tubing segment (avascular control), was perfused at 3.5 ± 0.2 mL/min (inflow pressure 94 ± 2 mmHg; 1 mmHg = 133.3 Pa) with Krebs containing 100 µM phenylephrine, 6% dextran, and 15 units/mL superoxide dismutase. Perfusate from all segments dripped onto endothelium-denuded dog femoral artery rings. The addition of 10 µM acetylcholine to the perfusate to test the functional integrity of endothelium-intact donor segments did not alter resistance in vessel segments or change force in rings. The addition of 100 µM adenosine to the extravascular bath decreased resistance 1.5 ± 0.4 mmHg ·mL-1·min-1in vessel segments but was without effect on downstream rings. When acetylcholine was retested in the presence of extravascular adenosine, a relaxation (16 ± 6%) occurred in rings receiving perfusate from endothelium-intact segments but not endothelium-denuded or tubing segments. This relaxation was eliminated by Nomega-nitro-L-arginine (10 µM), a nitric oxide synthase inhibitor, and was attenuated to 4 ± 1% by 8-phenyltheophylline (10 µM), an adenosine receptor antagonist. Thus adenosine, in conjunction with acetylcholine, acting through a receptor-mediated event, resulted in the release of nitric oxide from the endothelium of perfused intramuscular arteries, indicating the potential for extravascular conditions to influence the release of endothelium-derived products.Key words: acetylcholine, adenosine, endothelium-dependent relaxation, nitric oxide, perfused intramuscular artery.
Antigen-induced responses in lung parenchymal strips during sinusoidal oscillation
Authors: Nagase T , Ludwig M S
Published: April 2011

We have recently demonstrated that tissue resistance increases during the early response to antigen challenge in sensitized Brown-Norway rats. The purpose of the present study was to investigate in vitro the dynamic tissue response to antigen challenge and the involvement of the mediators, i.e., serotonin (5HT) and leukotriene D4 (LTD4). In addition, we questioned whether strips from sensitized rats responded differently to nonspecific challenge compared with those of unsensitized controls. We sensitized Brown-Norway rats with ovalbumin and performed experiments using strips of subpleural parenchyma. Tissue strips were challenged with ovalbumin in the bath; in some experiments the tissues were exposed to methysergide (10-6 M), a 5HT antagonist, or MK-571 (10-6 M), a LTD4 receptor antagonist, or both, prior to challenge. At the end of the experiment all tissues were exposed to carbacholine (10-3 M). Oscillation mechanics of tissue strips were studied and values of resistance (R), elastance (E), and hysteresivity ( eta ) were obtained. During ovalbumin challenge in sensitized tissues, R, E, and eta increased significantly (% change in R, 12.1 ± 2.1%; % change in E, 3.8 ± 1.3%; % change in eta , 9.3 ± 2.8%). Both methysergide and MK-571 reduced the increase in R (3.0 ± 0.6 and 3.2 ± 0.8%, respectively, p < 0.05 vs. ovalbumin). There was no difference between sensitized and unsensitized strips in the response to carbacholine challenge. These data suggest that the oscillatory behaviour of tissue strips from sensitized rats is altered after ovalbumin challenge. The mechanism of that response is mediated by both 5HT and LTD4.Key words: tissue resistance, allergic asthma, serotonin, leukotrienes, hysteresis.
Functional significance of cysteine residues in the δ opioid receptor studied by site-directed mutagenesis
Authors: Ehrlich George K , Andria Matthew L , Zheng Xin , Kieffer Brigitte , Gioannini Theresa L , Hiller Jacob M , Rosenkranz Jeremy E , Veksler Boris M , Zukin R Suzanne , Simon Eric J
Published: April 2011

Previous work suggested that sulfhydryl groups and disulfide bridges have important functions in opioid binding to the delta opioid receptor. The question regarding which cysteines are essential for ligand binding was approached by replacement of cysteine residues in the cloned delta opioid receptor using site-directed mutagenesis. The wild-type and mutant receptors were expressed stably in Chinese hamster ovary cells. The two extracellular cysteine residues and the six located in transmembrane domains were mutated to serine or alanine, one at a time. Replacement of either of the extracellular cysteines produced a receptor devoid of delta agonist and antagonist binding activity. Immunofluorescence cytochemistry, performed with anti delta opioid receptor antibodies in washed cell monolayers in one of these mutants (Cys-Ser121), and immunoblots, performed on cell extracts, indicate that the receptor was expressed and seems to be associated with the cell membrane. The existence of an essential extracellular disulfide bridge, previously postulated by analogy to other G protein coupled receptors, is strongly supported by our results. Replacement of any one of the six transmembrane cysteines was virtually without effect on the ability of the receptor to bind delta agonists and antagonists. Since there is strong evidence that the transmembrane domains are involved in ligand binding, these results suggest that the cysteine residues, even those near or at the binding site, are not essential for receptor binding. Furthermore, these results support the idea that the striking effects of sulfhydryl reagents on ligand binding of opioid receptors are likely to be due to steric hindrance by the large moieties transferred to the sulfhydryl groups of cysteine residues by these reagents.Key words: opioid receptor, cysteine, sulfhydryl, site-directed mutagenesis.