bluuebunny/crossref_metadata_2025 huggingface dataset:
Receptor-activating peptides distinguish thrombin receptor (PAR-1) and protease activated receptor 2 (PAR-2) mediated hemodynamic responses in vivo
Authors: Cheung Wai-man , Andrade-Gordon Patricia , Derian Claudia K , Damiano Bruce P
Published: April 2011

Vascular expression and cellular functions of the thrombin receptor (PAR-1) and protease activated receptor 2 (PAR-2) suggest similar but distinct vascular regulatory roles. The vascular actions of PAR-1 and PAR-2 in vivo were differentiated by monitoring mean arterial pressure (MAP) and heart rate (HR) of anesthetized mice in response to intravenous SFLLRN (0.1, 0.3, and 1 µmol/kg) and SLIGRL (0.1, 0.3, and 1 µmol/kg), the respective receptor-activating sequences for PAR-1 and PAR-2, and TFLLRNPNDK (0.3, 1, and 3 µmol/kg), a synthetic peptide selective for PAR-1. All peptides dose dependently decreased MAP (order of potency: SLIGRL >> SFLLRN >> TFLLRNPNDK). SLIGRL induced a more prolonged hypotension with a slow return to baseline, whereas SFLLRN- and TFLLRNPNDK-induced hypotension was followed by a rapid return towards baseline and a sustained moderate hypotension. SFLLRN and TFLLRNPNDK, but not SLIGRL, decreased HR. Nomega-Nitro-L-arginine methyl ester HCl (L-NAME), an inhibitor of nitric oxide synthesis, attenuated the cumulative hypotensive response to SLIGRL but had no effect on the SFLLRN and TFLLRNPNDK hypotension. However, L-NAME revealed a rebound hypertension in response to SFLLRN and TFLLRNPNDK but not SLIGRL. In conclusion, activation of either PAR-1 or PAR-2 in vivo results in hypotension. In addition, only PAR-1 activation induced hypertension following L-NAME, reflecting concurrent PAR-1-mediated vasoconstriction. Thus, these different hemodynamic responses in vivo suggest distinct physiological or pathophysiological roles for PAR-1 and PAR-2 in local vascular regulation.

Key words: protease activated receptor, thrombin receptor, protease activated receptor 2 (PAR-2), arterial pressure.
Effects of propofol and pentobarbital on ligand binding to GABAA receptors suggest a similar mechanism of action
Authors: Davies Martin , Thuynsma Rick P , Dunn Susan M
Published: April 2011

The GABAA receptor is allosterically modulated by a number of anesthetics and barbiturates. We have examined the effects of propofol and pentobarbital on the binding of the receptor agonist [3H]muscimol and the benzodiazepine modulators [3H]flunitrazepam and [3H]Ro15-4513 to bovine brain membranes. Both agents potentiated the binding of [3H]muscimol (5 nM), with EC50 values of 18.7 and 276 µM, respectively. The binding of [3H]muscimol is heterogeneous, suggesting the presence of both high (Kd ~ 10 nM) and low (Kd ~ 0.1-1.0 µM) affinity sites. The major effect of both propofol and pentobarbital was to increase the affinity of the lower affinity sites without changing the total binding capacity. In contrast, the steroid anesthetic alphaxalone did not affect the affinity of these sites, suggesting that this drug has distinct effects on the GABAA receptor. Propofol and pentobarbital also increased the binding of the benzodiazepine agonist [3H]flunitrazepam and decreased the binding of the inverse agonist [3H]Ro15-4513. The results of these studies demonstrate that propofol and pentobarbital modulate the binding of ligands to the GABAA receptor in a similar manner, suggesting that these drugs may have a common mechanism of action.Key words: propofol, barbiturates, GABAA receptor, allosterism.
Scavestrogen sulfamates: correlation between estrone sulfatase inhibiting and antioxidant effects
Authors: Römer Wolfgang , Oettel Michael , Schwarz Sigfrid
Published: April 2011

In the present study estrone sulfatase (steryl-sulfatase; EC 3.1.6.2) and phenylsulfatase (arylsulfatase B; EC 3.1.6.1) inhibiting as well as antioxidant effects exerted by ring B,C unsaturated sulfamates of estrone (J 1025), 17 beta -estradiol (J 1054, J 1059, J 1067), and 17 alpha -estradiol (J 1051, J 1064, J 1065) were examined as compared with their parent compounds, J 994, J 995, and J 1050, using six different in vitro models: (i) estrone sulfatase activity in human placental microsomes, (ii) phenylsulfatase activity isolated from Helix pomatia, (iii) Fenton reaction driven lipid peroxidation in rat synaptosomes, (iv) Fe(II)-chelating activities, (v) formation of superoxide anion radicals, and (vi) total antioxidative activities. Ring B,C unsaturated estrogen (so-called scavestrogen) sulfamates were found to act as potent inhibitors of the following enzyme activities and generated radicals: estrone sulfatase, phenylsulfatase, lipid peroxyl, and superoxide anion. In addition, scavestrogen sulfamates were able to influence the iron redox chemistry and total antioxidative activities. These findings indicate that relatively minor modifications in the chemical structure of classical steroid sulfamates can preserve or enhance their estrone sulfatase inhibiting properties and, simultaneously, amplify their antioxidant capacity to a great extent. Taken together, our data suggest that scavestrogen sulfamates such as J 1025, J 1051, or J 1054 (17 beta -dihydroequilenin sulfamate) may serve as a very promising basis for the development of steroid-derived estrone sulfate - sulfatase inhibitors characterized by promising estrone sulfatase inhibiting activities in combination with a "good" antioxidant potency.Key words: estrogen 3-O-sulfamates, estrone sulfatase, phenylsulfatase, lipid peroxidation, iron redox chemistry, human placental microsomes, radical scavenging effects.
Opioid reward mechanisms: a key role in drug abuse?
Authors: Herz Albert
Published: April 2011

There is increasing evidence to implicate the mesolimbic dopamine system in the rewarding effects of drugs of abuse such as opioids, psychostimulants, and alcohol, and in addition endogenous opioids may play a key role in the underlying adaptive mechanisms. Opioid agonists with affinity for µ and delta opioid receptors are rewarding, whereas opioid agonists with affinity for kappa receptors are aversive. These opposing motivational effects are paralleled by an increase and decrease, respectively, of dopamine release in the nucleus accumbens. Opposite effects are induced in response to selective antagonists for these different receptor types, pointing to tonically active endogenous opioid reward mechanisms. Withdrawal from chronic morphine results in sensitization for opioid reward; an effect that is counteracted by kappa opioid agonists. The rewarding effects of psychostimulants such as cocaine and amphetamine, mediated by the mesolimbic dopamine pathway, are modulated by opioid mechanisms in both directions: sensitization by morphine pretreatment, inhibition by kappa receptor agonists. A modulatory role of endogenous opioids is also suggested from biochemical data, showing increased dynorphin and kappa receptor expression after chronic cocaine treatment. Alcohol reward involves the mesolimbic reward system also, and opioids modulate this behaviour. Naltrexone as well as selective µ and delta opioid receptor antagonists decrease alcohol consumption in operant conditioning models. Biochemical approaches point to a functional deficit of endogenous opioids in genetic models exhibiting high prevalence for alcohol intake. The therapeutic implications of these data are discussed.Key words: reward mechanisms, endogenouos opioid systems, psychostimulants, alcohol.
A tribute to the late Hans W. Kosterlitz: Ploughing the lone furrow
Authors: Lees Gordon M
Published: April 2011

Hans Kosterlitz was a quiet, rather modest man, who was greatly respected, both as a scientist and as a person of real courage, honour, judgement, polite manners, and inflexible integrity of conduct and consistency of principle. His deep sense of social responsibility and his concern about making a worthwhile contribution for the benefit of mankind were reflected in his choice of research topics, in a career spanning more than 65 years. His major research interests were also exceptionally wide ranging, in terms of both subject matter and methodology. His first focus was the biochemistry of carbohydrate metabolism in diabetes mellitus and influence of dietary protein intake on the liver, then the physiology and pharmacology of enteric reflexes. It is his pioneering work on pharmacology of the narcotic analgesics and multiple opioid receptors and his illuminating concept, and subsequent discovery (in his eighth decade of life), of the occurrence of endogenous opioid peptides with which his name will be forever most closely linked. His infectious enthusiasm and zest for life made a lasting impression on everyone who met him, no matter how briefly. He was an inspiring teacher with a particular rapport with young scientists.
Estrogen enhances baroreflex control of heart rate in conscious ovariectomized rats
Authors: El-Mas Mahmoud M , Abdel-Rahman Abdel A
Published: April 2011

In previous studies, we have shown that the baroreflex control of heart rate is significantly attenuated in females compared with age-matched males. This study investigated the role of estrogen in the modulation of baroreflex function in conscious unrestrained rats. Baroreflex-mediated decreases in heart rate in response to increments in blood pressure evoked by phenylephrine were evaluated in conscious freely moving male and female Sprague-Dawley rats as well as in ovariectomized rats. The effect of a 2-day 17 beta -estradiol (50 µg ·kg-1 ·day-1, s.c.) or vehicle treatment on baroreflex sensitivity was investigated in ovariectomized rats. Intravenous bolus doses of phenylephrine (1-16 µg/kg) elicited dose-dependent pressor and bradycardic responses in all groups of rats. Regression analysis of the baroreflex curves relating increments in blood pressure to the associated heart rate responses revealed a significantly (p < 0.05) smaller baroreflex sensitivity in female compared with male rats (-1.22 ± 0.07 and -1.85 ± 0.15 beats ·min-1 ·mmHg-1, respectively), suggesting an attenuated baroreflex function in females. In age-matched ovariectomized rats, baroreflex sensitivity showed further reduction (-0.93 ± 0.02 beats ·min-1 ·mmHg-1). Treatment of ovariectomized rats with 17 beta -estradiol significantly (p < 0.05) enhanced the baroreflex sensitivity (-1.41 ± 0.16 beats ·min-1 ·mmHg-1) to a level that was slightly higher than that of sham-operated female rats. Furthermore, baroreflex sensitivity of ovariectomized estradiol-treated rats was not significantly different from that of age-matched male rats. The vehicle, on the other hand, had no effect on baroreflex sensitivity of ovariectomized rats. These data support our earlier findings that sexual dimorphism exists in baroreflex control of heart rate. More importantly, the present study provides experimental evidence that suggests a facilitatory role for estrogen in the modulation of baroreflex function.Key words: rat, gender, baroreflex sensitivity, 17 beta -estradiol, ovariectomy.
Effect of pregnancy and steroid hormones on plasma adrenomedullin levels in the rat
Authors: Jerat Sandra , Kaufman Susan
Published: April 2011

Pregnancy is characterized by volumeexpansion and vasodilation. We investigated whether thehypotensive peptide adrenomedullin (ADM) might be a significantfactor in the cardiovascular adaptation to pregnancy. Rats wereprepared with indwelling cannulae. Plasma ADM levels weremeasured by RIA before mating, at 7, 14, and 21 days ofpregnancy, and at 7 days postpartum. We also investigated theeffects on plasma ADM levels of administering estrogen,progesterone, and the metabolite of progesterone3-OH-5-pregnan-20-one(3-OH-DHP); this last steroid has been implicated inaltering reflex control of blood pressure and volume duringpregnancy. Plasma ADM levels increased progressively duringpregnancy from 123 ± 27 pg/mL in virgin animals to 404 ± 50 pg/mLat 21 days of pregnancy. The levels returned to pre-pregnancyvalues postpartum.3-OH-DHP caused a significant rise in plasma ADM levels,whereas neither estrogen nor progesterone had any effect. Wesuggest that ADM may be an important contributing factor to thevasodilatation associated with normal pregnancy. Activemetabolites of progesterone, rather than progesterone itself, maybe at least partially responsible for stimulating the release ofADM.Key words: progesterone, estrogen,pregnanolone, cardiovascular system, nitric oxide.
Increased glucose synthesis in renal tubule fragments from hyperthyroid rats
Authors: Pimenta W P , Veiga JA Silva
Published: April 2011

Rates of glucose synthesis from several substrates were examined in renal tubule fragments from hyperthyroid rats. A hyperthyroid state was induced by daily intraperitoneal injections of thyroxine (T4) (100 µg/100 g body weight) for 14 days. At the end of the experimental period, plasma triiodothyronine and T4levels were six and eight times higher, respectively, than initial values. Hyperthyroid rats gained less weight and had lower blood glucose despite an increased food intake. In both control and hyperthyroid rats, rates of glucose production by renal tubule fragments were higher with glutamine and glycerol than with lactate, alanine, or glutamate. T4treatment induced a significant increase in the de novo glucose synthesis from all substrates, except glutamine. The highest percent increase was obtained with alanine (64%), compared with 31-40% for glutamate, lactate, and glycerol. The T4treatment induced increase in glucose synthesis by renal tubule fragments suggests that renal gluconeogenesis contributes to enhance glucose production in hyperthyroidism.Key words: hyperthyroidism, rat, renal gluconeogenesis, renal tubule fragments, glutamate, glutamine, lactate, alanine, glycerol.
The anion transport inhibitor DIDS activates a Ba2+-sensitive K+flux associated with hepatic exocrine secretion
Authors: Hill Ceredwyn Elizabeth
Published: April 2011

4,4'-Diisothiocyanatostilbene-2,2'-disulfonate (DIDS), an anion transport inhibitor and choleretic organic anion, was used to study the relationship between putative DIDS-sensitive K channels and exocrine secretion in the isolated and bile duct cannulated perfused rat liver. Bile flow, DIDS excretion, and effluent perfusate K+content were measured. DIDS (125 µM) caused a doubling in bile generation concomitant with its appearance in bile, confirming earlier reports. Furthermore, DIDS induced a transient increase in perfusate K+concentration that peaked prior to the biliary parameters and, after 10 min, reversed to net uptake that fully compensated for the initial release. The K channel blocker Ba2+(1 mM) strongly inhibited the release phase along with the accompanying choleresis and DIDS excretion. Ouabain (13.5 µM) alone was choleretic and hyperkalemic and, when applied in combination with DIDS, depressed DIDS excretion, choleresis, and DIDS-sensitive K+uptake. To obtain further evidence for the presence of DIDS-sensitive K channels K+flux was measured under the influence of different gradients of the cation. Perfusate K+at 26 and 80 mM changed the DIDS-activated K+flux from a transient outward to a sustained inward flux, and both DIDS excretion and bile flow decreased. Mean net K+flux over 20 min DIDS perfusion changed from -1.3 ± 1.1 µmol/g with 5.9 mM K+to -1304 ± 55 µmol/g with 80 mM K+in the perfusate. K+efflux was fully and reversibly blocked by Ba2+and influx was ouabain-insensitive, suggesting that the DIDS-activated K+flux was channel mediated. The results show that a significant fraction of DIDS-induced bile generation is associated with K+release that may be mediated by Ba2+-sensitive K channels, possibly of the inward rectifying type.Key words: hepatocyte, inward rectifier, 4,4'-diisothiocyanatostilbene-2,2'-disulfonate (DIDS), K+channel, bile formation.
Electrophysiologic properties and ventricular fibrillation in normal and myopathic hearts
Authors: Kavanagh Katherine M , Guerrero Patricia A , Jugdutt Bodh I , Witkowski Francis X , Saffitz Jeffrey E
Published: April 2011

This study tests the hypothesis that moderate myocardial dysfunction is associated with altered myocardial anisotropic properties and structurally altered ventricular fibrillation (VF). Mongrel dogs were randomized to either a control group or a group that was rapidly paced at 250 beats/min until the left ventricular ejection fraction was [Formula: see text] 40%. Changes in anisotropic properties and the electrical characteristics of VF associated with the development of moderate myocardial dysfunction were assessed by microminiature epicardial mapping studies. In vivo conduction, refractory periods, and repolarization times were prolonged in both longitudinal and transverse directions in myopathic animals versus controls. VF was different in myopathic versus control animals. There were significantly more conducted deflections during VF in normal hearts compared with myopathic hearts. Propagated deflection-to-deflection intervals during VF were significantly longer in myopathic hearts compared with controls (125.5 ± 49.06 versus 103.4 ± 32.9 ms, p = 0.009). There were no abnormalities in cell size, cell shape, or the number of intercellular gap junctions and there was no detectable change in the expression of the gap junction proteins Cx43 and Cx45. Moderate myocardial dysfunction is associated with significant electrophysiological abnormalities in the absence of changes in myocardial cell morphology or intercellular connections, suggesting a functional abnormality in cell-to-cell communication.Key words: cardiomyopathy, anisotropy, fibrillation, defibrillation.
"Rational hope" in the early treatment of Parkinson's disease
Authors: Sourkes Theodore L
Published: April 2011

The drug treatment of Parkinson's disease since the original description of the malady in 1817 is described. Consideration is given to the historic use of alkaloids of the belladonna, harmala, and aporphine families, and of amphetamine. The introduction of the L-dopa treatment is described. The modes of action of the various drugs employed in the past as well as those in current use are described in the context of knowledge of the functioning of the nigrostriatal tract.Key words: anticholinergic drugs, apomorphine, bulbocapnine, L-dopa, harmine.
cSrc is a major cytosolic tyrosine kinase in vascular tissue
Authors: Oda Yasuo , Renaux Bernard , Bjorge Jeff , Saifeddine Mahmoud , Fujita Donald J , Hollenberg Morley D
Published: April 2011

We are interested in identifying, in vascular tissue, nonreceptor tyrosine kinases that may be responsible for the contractile actions of G-protein-coupled agonists such as angiotensin II. By using a series of chromatographic steps, including ion exchange, hydrophobic, and affinity chromatography, we have isolated a major fraction of tyrosine kinase activity from the cytosolic fraction of porcine aorta tissue. According to (i) its immunologic cross-reactivity with the monoclonal anti-cSrc antibody, m327, and with the N-terminally directed monoclonal cSrc2-17 antibody, (ii) its inhibition by the C-terminal cSrc kinase, CSK, and (iii) its specificity for phosphorylating tyrosine 15 in the cdc2(6-20) peptide kinase substrate, we conclude that the kinase we have isolated represents porcine cSrc. A substantial proportion of the enzyme (>70%) was recovered in the cytoplasmic fraction from aorta tissue. The profile of inhibition of the human and porcine cSrc enzymes by a spectrum of tyrosine kinase inhibitors (PP1>> AG82 > AG490 congruent to genistein > AG10) was compared with the profile of inhibition of angiotensin II mediated contraction in a porcine coronary vascular preparation (AG10 >> genistein [Formula: see text] AG82 [Formula: see text] AG490; PP1inactive). The different inhibitory profiles indicated that cSrc does not represent the vascular tyrosine kinase responsible for the contractile actions of angiotensin II. We suggest, nonetheless, that cSrc plays a key role for other actions of angiotensin II in intact vascular tissue, such as the regulation of mitogen-activated protein kinase activity and gene transcription.Key words: tyrosine kinase, smooth muscle, cSrc.
ATP as a source of interstitial adenosine in the rat heart
Authors: Lorbar Mojca , Fenton Richard A , Dobson, Jr. James G
Published: April 2011

The contribution of neuronal ATP to interstitial adenosine levels was investigated in isolated perfused rat hearts. Ventricular surface transudates, representing interstitial fluid, were analyzed for norepinephrine, ATP, and adenosine. Exocytotic release of norepinephrine was induced by electrical stimulation of cardiac efferents emanating from the stellate ganglion. Ganglion stimulation increased contractility, interstitial norepinephrine, ATP, and adenosine. Interstitial adenosine was 11- to 27-fold higher than interstitial ATP, suggesting that the released ATP is unlikely the only source of adenosine. In the presence of AOPCP (α,β-methyleneadenosine 5'-diphosphate), an ecto-5'-nucleotidase inhibitor, the ganglion-stimulated increase in interstitial ATP and adenosine reached levels similar to those in the absence of AOPCP, also suggesting that adenosine does not derive from extracellular ATP. The perfusate Ca2+ was raised from 1 to 4 mM to determine the importance of the enhanced contractile function on the levels of norepinephrine, ATP, and adenosine. The results were increases in contractility and interstitial norepinephrine, ATP, and adenosine, which were not suppressed with atenolol, indicating a norepinephrine-independent release of ATP and adenosine. Reserpine treatment and administration of guanethidine depleted the catecholamine stores and diminished the catecholamine release, respectively. However, neither agent altered Ca2+-induced increases in ATP and adenosine. It is concluded that the amount of neuronal-derived ATP is low and most likely does not contribute significantly to interstitial levels of adenosine. Furthermore, elevations in interstitial norepinephrine, ATP, and adenosine are associated with neuronal-independent increases in contractile function.Key words: perfused heart, stellate ganglion, co-transmission, calcium, and contractility.
Scinderin and cortical F-actin are components of the secretory machinery
Authors: Trifaró J -M
Published: April 2011

Secretory vesicle exocytosis is the mechanism of release of neurotransmitters and neuropeptides. Secretory vesicles are localized in at least two morphologically and functionally distinct compartments: the reserve pool and the release-ready pool. Filamentous actin networks play an important role in this compartmentalization and in the trafficking of vesicles between these compartments. The cortical F-actin network constitutes a barrier (negative clamp) to the movement of secretory vesicles to release sites, and it must be locally disassembled to allow translocation of secretory vesicles in preparation for exocytosis. The disassembly of the cortical F-actin network is controlled by scinderin (a Ca2+-dependent F-actin severing protein) upon activation by Ca2+ entering the cells during stimulation. There are several factors that regulate scinderin activation (i.e., Ca2+ levels, phosphatidylinositol 4,5-bisphosphate (PIP2), etc.). The results suggest that scinderin and the cortical F-actin network are components of the secretory machinery.Key words: F-actin, scinderin, exocytosis, cytoskeleton, chromaffin cell.
Retention of cleaved synaptosome-associated protein of 25 kDa (SNAP-25) in neuromuscular junctions: a new hypothesis to explain persistence of botulinum A poisoning
Authors: Raciborska Dorota A , Charlton Milton P
Published: April 2011

Botulinum neurotoxins can block neurotransmitter release for several months. The molecular mechanism of these toxins' action is known, but the persistence of neuromuscular paralysis that they cause is unexplained. At frog neuromuscular junctions, application of botulinum toxin type A caused paralysis and reduced the C-terminus immunoreactivity of SNAP-25, but not that of the remaining N-terminus fragment. Botulinum toxin type C caused paralysis and reduced syntaxin immunoreactivity without affecting that of SNAP-25. Co-application of botulinum A and C reduced syntaxin immunoreactivity, and that of both C and N termini of SNAP-25. Application of hydroxylamine to de-palmitoylate SNAP-25 resulted in a slight reduction of the immunoreactivity of SNAP-25 N terminus, while it had no effect on immunoreactivity of botulinum A cleaved SNAP-25. In contrast, application of hydroxylamine to nerve terminals where syntaxin had been cleaved by botulinum C caused a considerable reduction in SNAP-25 N-terminus immunoreactivity. Hence the retention of immunoreactive SNAP-25 at the neuromuscular junction depends on its interactions with syntaxin and plasma membrane. Persistence of cleaved SNAP-25 in nerve terminals may prevent insertion of new SNAP-25 molecules, thereby contributing to the longevity of botulinum A effects.Key words: SNAP receptor, neurotoxin, dystonia, botulism, torticollis.
Parathyroid hypertensive factor inhibits voltage-gated K+ channels in vascular smooth muscle cells
Authors: Ren Jun , Zhang Lei , Benishin Christina G
Published: April 2011

Parathyroid hypertensive factor (PHF) has been implicated in regulation of vascular smooth muscle tone and pathogenesis of several forms of hypertension. Earlier studies have suggested that PHF enhances the actions of other vasoconstrictors, while it has no in vitro vasoconstrictor property of its own. PHF was previously found to enhance the L-type Ca channel currents and intracellular Ca responses to depolarization in vascular smooth muscle cells (VSMCs). The present study examined whether PHF might act on K channels in the plasma membrane of VSMCs. Primary cultured VSMCs from rat tail artery were used. The whole-cell version of the patch-clamp technique was used under conditions in which there was no contribution of Ca-activated K channels to the outward current. Both purified and semipurified PHF inhibited the delayed rectifier type potassium current in a dose-dependent manner. The effect was time dependent and was first significantly different from the control current after 30 min. The inhibition of the delayed rectifier K channel was associated with a time-dependent decrease in the resting membrane potential. Therefore, PHF may alter VSMC cellular Ca responses by reducing the membrane potential to a level closer to the activation potential of Ca channels.Key words: parathyroid hypertensive factor, hypertension, potassium channels, vascular smooth muscle, membrane potential.
Ligand-independent negative chronotropic responses of rat and mouse right atria to β-adrenoceptor antagonists
Authors: Varma Daya R
Published: April 2011

Negative chronotropic effects of β-adrenoceptor (βAR) antagonists on right atria from reserpine-treated rats and mice were determined as a test of their inverse agonist activities. β2AR antagonist ICI-118,551 and nonselective βAR antagonists alprenolol, propranolol, and timolol produced negative chronotropic effects. In contrast, nonselective βAR antagonists pindolol and nadolol as well as β1AR-selective antagonists atenolol, acebutolol, and metoprolol did not cause a significant decrease in atrial rates. The neutral antagonist pindolol but not the inverse agonist alprenolol inhibited the negative chronotropic activities of ICI-118,551. Isoprenaline, salbutamol, and noradrenaline produced positive chronotropic effects; the chronotropic effects of isoprenaline and salbutamol but not of noradrenaline were antagonized by ICI-118,551. It is concluded that both β1AR and β2AR mediate positive chronotropic effects of catecholamines on rat and mouse atria but only β2AR are constitutively active.Key words: inverse agonism, ICI-118,551, β1 adrenoceptor-selective antagonists, chronotropic responses, catecholamines.
Myocardial blood flow regulation relative to left ventricle pressure and volume in anesthetized dogs
Authors: Rouleau J R , Simard D , Kingma, Jr. J G
Published: April 2011

The influence of left ventricle pressure and volume changes on coronary blood flow was investigated in eight anesthetized dogs. Coronary artery pressure-flow relationships were determined at two levels of left ventricular pressure and volume. The distribution of blood flow within the myocardium was also determined when these relationships varied. Reducing left ventricle pressures and volumes increased heart rate. Rate-pressure product, diastolic coronary pressure, myocardial O2 consumption, total, subendocardial and subepicardial flow decreased. Hematocrit and blood gas data were unchanged. The pressure-flow relationships were shifted leftward (p = 0.001) but the range of autoregulation was not altered. At low left ventricle pressures and volumes, the lower coronary artery pressure limit was shifted leftward (from 75 to 45 mmHg (1 mmHg = 133.3 Pa)), while total, subendocardial, and subepicardial blood flow did not change compared with the control. Below the lower coronary artery pressure limit, subendocardial but not subepicardial flow decreased, resulting in maldistribution of flow across the left ventricular wall. When coronary pressure was reset between control and the lower coronary artery pressure limit, subendocardial flow was restored. These results show that the lower coronary artery pressure limit can be shifted leftward while the distribution of blood flow across the left ventricular wall is preserved.Key words: autoregulation, coronary artery pressure-flow relations, myocardial blood flow distribution, left ventricular pressure, left ventricular volume.
Increased tail artery vascular responsiveness to angiotensin II in cold-treated rats
Authors: Shechtman Orit , Sun Zhongjie , Fregly Melvin J , Katovich Michael J
Published: April 2011

Chronic exposure of rats to cold for 1-3 weeks results in a mild form of hypertension. The renin-angiotensin system (RAS) has been implicated in this model of cold-induced hypertension. Previously we have characterized the vascular responsiveness in cold-acclimated animals, using aortic tissue, and recent studies have focused on the thermoregulatory responses of angiotensin II (AngII), utilizing the tail artery of the rat. Therefore in the current study we evaluated the vascular responsiveness of cold-treated rats to AngII in both aorta and tail artery at 2 and 4 weeks of cold exposure (5 ± 2°C). Systolic blood pressures were significantly elevated in cold-treated animals compared with control animals at both 2 and 4 weeks of cold exposure. At both of these time points body weights were reduced and ventricular weights were increased in cold-treated animals. After 2 weeks of cold exposure the vascular responsiveness of the aorta to AngII was significantly lower than that of controls. This vascular responsiveness to AngII was elevated and returned to control levels after 5 weeks of cold exposure. However, this pattern was not observed in the tail artery. The vascular responsiveness of tail artery rings from cold-treated rats to AngII was significantly greater than that of control animals during both 2 and 5 weeks of exposure to cold. The vascular contractile responses of both the aorta and tail artery to KCl in the cold-treated animals was not different from that of the control animals maintained at ambient room temperature, suggesting that the vascular smooth muscle contractile components were not altered by the cold exposure. Thus, the in vitro vascular reactivity to the receptor-mediated vasoconstrictor AngII was decreased in the sparsely innervated aorta and increased in the more densely innervated tail artery of the cold-treated animals when compared with controls. These results suggest that the increased responsiveness of AngII on the smooth muscle of the tail artery may play a role in adaptation to the cold and the maintenance of cold-induced hypertension.Key words: cold exposure, hypertension, renin-angiotensin system, vascular responsiveness, angiotensin II.
Cloning and functional expression of the hNPY Y5 receptor in human endometrial cancer (HEC-1B) cells
Authors: Moser C , Bernhardt G , Michel J , Schwarz H , Buschauer A
Published: April 2011

Aiming to develop a functional assay for the human NPY Y5 receptor based on adenylyl cyclase activity, HEC-1B cells, in which cAMP synthesis can be efficiently stimulated with forskolin, were selected for the transfection with the pcDNA3-Y5-FLAG and the pcDEF3-Y5 vectors. After optimization of the transfection procedure, the binding of [3H]propionyl-NPY to transiently and stably expressed Y5 receptors was determined. The affinities of NPY, NPY derivatives, and rPP (pNPY >= p(Leu31Pro34)NPY = p(2-36)NPY >= p(D-Trp32)NPY > p(13-36)NPY > rPP) were in accordance with the NPY Y5 receptor subtype. For [3H]propionyl-pNPY approximately 1.7 × 105 and 1 × 106 binding sites per transiently and stably transfected cell, respectively, were determined. The KD values were 2.4 ± 0.4 and 1.7 ± 0.2 nM, respectively. Due to the high expression of the receptor protein, both stably and transiently transfected cells can be conveniently used in routine radioligand binding studies. By contrast, functional assays were only feasible with HEC-1B cells stably expressing the Y5 receptor. In these cells, 10 nM pNPY inhibited the forskolin-stimulated cAMP synthesis by 75%. This effect was partially antagonized by the Y5 antagonist N-{trans-[4-(2-naphthylmethylamino)- methyl]cyclohexylmethyl}naphthalene-2-sulfonamide. Although the genetic variability of cancer cells is in principle incompatible with a stable phenotype, both ligand binding characteristics and functionality of the Y5 receptor remained unchanged for more than 30 passages.Key words: human NPY Y5 receptor, HEC-1B cells, stable expression, radioligand binding, cAMP assay.
Neuropeptide Y induced increase of cytosolic and nuclear Ca2+in heart and vascular smooth muscle cells
Authors: Jacques Danielle , Sader Sawsan , El-Bizri Nesrine , Chouffani Sanaa , Hassan Ghada , Shbaklo Hadia
Published: April 2011

It was reported that neuropeptide Y (NPY) affects cardiac and vascular smooth muscle (VSM) function probably by increasing intracellular Ca2+. In this study, using fura-2 microfluorometry and fluo-3 confocal microscopy techniques for intracellular Ca2+measurement, we attempted to verify whether the action of NPY receptor's stimulation in heart and VSM cells modulates intracellular Ca2+and whether this effect is mediated via the Y1receptor type. Using spontaneously contracting single ventricular heart cells of 10-day-old embryonic chicks and the fluo-3 confocal microscopy Ca2+measurement technique to localize cytosolic ([Ca]c) and nuclear ([Ca]n) free Ca2+level and distribution, 10-10M of human (h) NPY significantly (P < 0.05) increased the frequency of cytosolic and nuclear Ca2+transients during spontaneous contraction. Increasing the concentration of hNPY (10-9M) did not further increase the frequency of Ca2+transients. The L-type Ca2+channel blocker, nifedipine (10-5M), significantly (P < 0.001) blocked the spontaneous rise of intracellular Ca2+in the absence and presence of hNPY (10-10and 10-9M). However, the selective Y1receptor antagonist, BIBP3226 (10-6M), significantly decreased the hNPY-induced (10-10and 10-9M) increase in the frequency of Ca2+transients back to near the control level (P < 0.05). In resting nonworking heart and human aortic VSM cells, hNPY induced a dose-dependent sustained increase of basal resting intracellular Ca2+with an EC50near 10-9M. This sustained increase was cytosolic and nuclear and was completely blocked by the Ca2+chelator EGTA, and was significantly decreased by the Y1receptor antagonist BIBP3226 in both heart (P < 0.05) and VSM (P < 0.01) cells. These results strongly suggest that NPY stimulates the resting basal steady-state Ca2+influx through the sarcolemma and induces sustained increases of cytosolic and nuclear calcium, in good part, via the activation of the sarcolemma membrane Y1receptor type in both resting heart and VSM cells. In addition, NPY also increased the frequency of Ca2+transients during spontaneous contraction of heart cells mainly via the activation of the Y1receptor type, which may explain in part the active cardiovascular action of this peptide.Key words: heart, vascular smooth muscle, neuropeptide Y, BIBP3226, calcium, nucleus.
Stable carbon and nitrogen isotopic fractionation between diet and tissue of captive red fox: implications for dietary reconstruction
Authors: Roth James D , Hobson Keith A
Published: April 2011

The amount of isotopic fractionation (change in isotope ratios) between diet and animal tissues is generally poorly known and may be affected by trophic position. Diet-tissue fractionation of stable-carbon and -nitrogen isotopes was measured in several tissues of red foxes (Vulpes vulpes) raised on a commercial pellet feed. Stable carbon isotopic fractionation in red fox was positive for all tissues and was greatest in fur (2.6), intermediate in muscle (1.1), and least in liver and blood fractions (0.4-0.6). These carbon isotope fractionation values were greater than those previously measured for mammalian herbivores but were similar to values for marine mammals in most tissues. Little variation in stable nitrogen isotopic fractionation occurred among tissues, except in the blood fractions. Nitrogen isotopic fractionation was much higher in blood serum (4.2) than in liver, muscle, and fur (3.3-3.5). Cellular fractions of blood had the lowest fractionation values (2.6). There was a significant age effect in nitrogen- but not in carbon-isotopic fractionation. Subadult foxes (<1 year) were significantly enriched in 15N compared with adult foxes for fur, muscle, and liver (no blood was collected from adults). The cause of this enrichment is unclear, but it may be related to the higher rate of protein synthesis and catabolism in growing animals. This study is the first to report isotopic fractionation values for a terrestrial mammalian carnivore. Such estimates are necessary to interpret stable-isotope patterns in wild carnivores.
Functions of perch relocations in a communal night roost of wintering bald eagles
Authors: Yackel Adams Amy A , Skagen Susan K , Knight Richard L
Published: April 2011

We investigated the functions of perch relocations within a communal night roost of wintering bald eagles (Haliaeetus leucocephalus) along the Nooksack River, Washington, during two winters. We tested seven predictions of two nonexclusive hypotheses: (1) bald eagles relocate within roosts to assess foraging success of conspecifics and (2) bald eagles relocate to obtain thermoregulatory benefits from an improved microclimate. Additionally, we gathered descriptive information to allow refinement of further alternative hypotheses. We rejected the hypothesis that relocations are a means of assessing foraging success. Contrary to our expectations, immature eagles did not relocate to be closer to adults, and relocations were less frequent when food was less abundant. Our data support the hypothesis that eagles relocate within night roosts to obtain a favorable microclimate during winters when they are subjected to cold stress and food stress. In both winters, relocations were more frequent in the evening than in the morning. In both winters, most evening relocations were to the center of the roost rather than to its edge, and the frequency of relocation to the center was greater when temperatures were low. The microclimate hypothesis, however, explains only a limited number of relocations. Based on our findings, it is likely that relocation has multiple functions, including establishing and (or) maintaining foraging associations, establishing and (or) maintaining social-dominance hierarchies when food is less abundant, and nonsocial activities.
Overwintering behavior and physiology of eastern painted turtles (Chrysemys picta picta) in Rhode Island
Authors: Crocker C E , Feldman R A , Ultsch G R , Jackson D C
Published: April 2011

We equipped 20 eastern painted turtles (Chrysemys picta picta) with radio transmitters and recovered them from a pond in Rhode Island during the winter of 1998-1999. Each month, three turtles were collected without permitting them to breathe. Blood was sampled by cardiac puncture and analyzed for pH, PCO2, PO2, and hematocrit; plasma was analyzed for [Na+], [K+], [Cl], total [Ca], total [Mg], [lactate], and osmolality. In December 1998, mean values for pH, PO2, PCO2, [HCO3], [lactate], total [Ca] and [Mg], hematocrit, and osmolality were 7.84 ± 0.02, 4.7 ± 1.9 mmHg (1 mmHg = 133.3 Pa), 10.2 ± 1.2 mmHg, 25.4 ± 2.6 mmol·L1, 2.78 ± 1.16 mmol·L1, 3.2 ± 0.4 mmol·L1, 2.5 ± 0.1 mmol·L1, 23% red blood cells, and 271 mosmol·kg1H2O, respectively, values similar to those for turtles submerged in normoxic water for 10 days at the prevailing water temperature (2-3°C). Throughout the winter, ice intermittently covered approximately 80% of the pond, water PO2was greater than 75% of air saturation, and blood PO2was maintained between 0.8 ± 0.3 and 10.1 ± 1.1 mmHg. Between December and February, there were no changes in most of the measured blood variables but, in March 1999, although the pond was largely free of ice, plasma [lactate], total [Ca], and total [Mg] averaged nearly 30, 8.1 ± 1.7, and 4.5 ± 0.8 mmol·L1, respectively, although with a large variation among individuals. The turtles did not bury in the substrate during the winter and, despite the increase in plasma lactate, there was no significant acidemia. However, the winter of 19981999 was relatively mild, and it is possible that more significant acid-base and ionic perturbations could occur during more severe winters, particularly in small ponds that cool sooner in late autumn and may have more prolonged ice cover than larger bodies of water.
Phylogeography of black bears (Ursus americanus) of the Pacific Northwest
Authors: Stone Karen D , Cook Joseph A
Published: April 2011

Phylogeographic study across codistributed taxa provides temporal and spatial perspectives on the assemblage of communities. A repeated pattern of intraspecific diversification within several taxa of the Pacific Northwest has been documented, and we contribute additional information to this growing data set. We analyzed variation in two mitochondrial genes (cytochrome b and control region) for the black bear (Ursus americanus) and expand previous analyses of phylogeographic variation. Two lineages (coastal and continental) exist; the coastal lineage extends along the Pacific coast from the Takhin River north of Glacier Bay National Park, southeast Alaska, to northern California, whereas the continental lineage is more widespread, occurring from central Alaska to the east coast. Both lineages occur along the coast of southeast Alaska, where interlineage divergence ranged from 3.1 to 3.6% (uncorrected p distances). Multiple lineages of other species have also been identified from southeast Alaska, indicating a complex history for the assembly of biotic communities along the North Pacific coast. The overlapping of the distributions of the black bear lineages with those of other birds and mammals suggests comparable routes of colonization.
Microsatellite analysis of North American pine marten (Martes americana) populations from the Yukon and Northwest Territories
Authors: Kyle C J , Davis C S , Strobeck C
Published: April 2011

Elucidating the population genetic structure of a species gives us insight into the levels of gene flow between geographic regions. Such data may have important implications for those trying to manage a heavily harvested wildlife species by determining the genetic connectivity of adjacent populations. In this study, the population structure of 12 North American pine marten (Martes americana) populations from the Yukon through to the central Northwest Territories was investigated using 11 microsatellite loci. Genetic variation within populations across the entire geographic range was relatively homogeneous as measured by: mean number of alleles (5.89 ± 0.45) and the average unbiased expected heterozygosity (He) (65.6 ± 1.7%). The overall unbiased probability of identity showed more variance between populations (1/10.25 ± 7.84 billion) than did the mean number of alleles and the Heestimates. Although some population structure was found among the populations, most regions were not strongly differentiated from one another. The low level of structure among the populations can, in part, be attributed to isolation by distance rather than to population fragmentation, as would be expected in more southerly regions in which suitable habitat is more disjunct. Furthermore, the low levels of population genetic structure were likely due to high levels of gene flow between regions and to large effective marten populations in the northern part of their distribution.
Localization and immunological characterization of insulin-like peptide(s) in the land snail Otala lactea (Mollusca: Pulmonata)
Authors: Abdraba A M , Saleuddin A SM
Published: April 2011

Insulin-like peptides were detected by means of immunological techniques in tissues of the land snail Otala lactea. Insulin-positive cells were detected in all the ganglia except the right parietal ganglion and visceral ganglion. In the digestive tract, insulin-positive cells were found in the muscle and connective tissue layer of the intestine. The amount of insulin-like peptide detected in acid-ethanol extract of brains and digestive tracts from active snails did not differ significantly from that in the corresponding tissues from estivating (dormant) ones. More insulin-like peptide was detected in hemolymph from active snails than in hemolymph from estivating ones. Brains from active snails released insulin-like peptide in vitro. Analysis of the cerebral ganglia or digestive tract extracts by size-exclusion chromatography and insulin RIA revealed more than one fraction with insulin immunoreactivity. Some of these fractions contained material with molecular masses close to those of mammalian insulin or its subunits. Further analysis of the extracts by reverse-phase chromatography also revealed more than one fraction with immunoreactivity. The immunoreactive material from the digestive tract was found to be less hydrophobic than insulin. Western blot analysis of the cerebral ganglia extract revealed more than one band with insulin immunoreactivity. Three of these bands had molecular masses very similar to those of vertebrate insulin, its subunits, and its precursor.
Phylogeny of theCrepidulaplana(Gastropoda: Calyptraeidae) cryptic species complex in North America
Authors: Collin Rachel
Published: April 2011

The taxonomy of Crepidula species with flat white shells is particularly difficult. These animals from the east coast of North America have generally been classified as a single species, Crepidula plana Say, 1822. Based on allozyme and developmental data, however, Hoagland (K.E. Hoagland. 1984. Malacologia, 25: 607-628; K.E. Hoagland. 1986. Am. Malacol. Bull. 4: 173-183) concluded that two species of flat white-shelled Crepidula live along the east coast of the United States, but she did not apply any name to the second species. Herein I use molecular techniques to characterize populations of flat white-shelled Crepidula species from Texas, Florida, Georgia, North Carolina, and |Massachusetts, and describe their morphology and development. DNA-sequence data support the existence of three species. One species is readily distinguished on the basis of morphology and development, but the other two are very similar. To clarify the nomenclature of these species, I designate neotypes for C. plana Say, 1822 and Crepidula depressa Say, 1822, and describe Crepidula atrasolea sp.nov.