bluuebunny/crossref_metadata_2025 huggingface dataset:
Smooth Muscle Contraction: Recent Advances
Authors: Stephens Newman L.
Published: April 2011

Research in smooth muscle contraction has shown remarkable progress over the last 5 years. Striking advances have been made in the areas of biochemical regulation of contraction, centering on myosin light chain kinase activity, and of biophysical delineation of the contractile process at the actomyosin level by use of the newly developed motility assay. The purpose of the symposium held at Minaki, Ont., was to obtain a comprehensive reporting of the recent advances made in the area of smooth muscle contraction. Specifically, advances in the areas of biophysics of contraction, energetics, and contractile and regulator proteins (including the interesting newcomers caldesmon and calponin) and the changes that occur in pathophysiological entities such as asthma, hypertension, anaphylactic shock, high-altitude hypoxia, and persistent pulmonary hypertension of the newborn were presented.Key words: smooth muscle biophysics, smooth muscle biochemistry, energetics of smooth muscle, pathophysiology of smooth muscle.
Smooth muscle protein kinase C
Authors: Walsh Michael P. , Andrea Jacquelyn E. , Allen Bruce G. , Clément-Chomienne Odile , Collins Elizabeth M. , Morgan Kathleen G.
Published: April 2011

Protein kinase C (PKC) was first implicated in the regulation of smooth muscle contraction with the observation that phorbol esters induce slowly developing, sustained contractions. In some vascular smooth muscles, e.g., ferret aorta, phorbol ester induced contractions occur without an increase in sarcoplasmic free-Ca2+ concentration ([Ca]i) or myosin light chain phosphorylation. This response appears to be mediated by a Ca2+-independent isoenzyme of PKC (probably PKCε), since saponin-permeabilized single ferret aortic smooth muscle cells, which retain receptor coupling, developed force in response to phenylephrine at low free [Ca2+] (pCa 7.0–8.6) and the constitutively active proteolytic fragment of PKC (PKM) elicited a contraction at pCa 7 comparable with the phenylephrine-induced contraction. Both contractions were reversed by a pseudo-substrate peptide inhibitor of PKC. These observations suggest a mechanism whereby α-adrenergic agonists may elicit a contractile response without a Ca2+ signal: α-adrenergic stimulation of phosphatidylcholine-specific phosphoiipase C or D (the latter in conjunction with phosphatidate phosphohydrolase) generates diacylglycerol. In the absence of an increase in [Ca2+]i, diacylglycerol specifically activates so-called novel PKCs, of which ε is the only isoenzyme known to be expressed in vascular smooth muscle. Recent evidence suggests that PKC may trigger a cascade of phosphorylation reactions, resulting in activation of mitogen-activated protein kinase and phosphorylation of the thin filament associated protein caldesmon. Alternatively, or additionally, PKC may directly phosphorylate calponin, another thin filament associated protein. These phosphorylations are predicted to alleviate inhibition of the cross-bridge cycling rate by these thin-filament proteins. The slow development of force would then result from a slow rate of cross-bridge cycling due to the low basal level of myosin phosphorylation.Key words: protein kinase C, smooth muscle, calcium, caldesmon, calponin.
Smooth muscle phosphatases: structure, regulation, and function
Authors: Pato M. D. , Tulloch A. G. , Walsh M. P. , Kerc E.
Published: April 2011

Smooth muscle contraction is regulated primarily by the reversible phosphorylation of myosin by myosin light chain kinase. Secondary mechanisms that might modulate contractility are phosphorylation–dephosphorylation of myosin light chain kinase and thin-filament proteins, caldesmon and calponin. Purification of several protein phosphatases that are active toward myosin light chains and (or) myosin and heavy meromyosin from smooth muscles has been reported. All the cytosolic turkey gizzard smooth muscle phosphatases, termed SMP-I, -II, -III, and -IV, dephosphorylate myosin light chains rapidly, but only SMP-III and -IV are active toward myosin and heavy meromyosin, suggesting that SMP-III and -IV might be directly involved in the relaxation of smooth muscle. SMP-III and -IV exhibit properties typical of type 1 protein phosphatases following tryptic digestion. These enzymes appear to share structural similarity with myofibrillar phosphatase PP1M. Purified calponin phosphatase and caldesmon phosphatase from chicken gizzards are structurally and immunologically identical with SMP-I, a type 2A protein phosphatase. SMP-I dephosphorylates calponin faster than it does caldesmon, and has much higher activity toward these substrates than SMP-II, -III, and -IV. Thus, one role for SMP-I might be to regulate the activities of caldesmon and calponin. Since SMP-I is active toward myosin light chain kinase, it might also modulate this enzyme.Key words: smooth muscle, contractility, protein phosphatases, smooth muscle phosphatases.
Changes of activation and inactivation gating of the transient potassium current of rat pituitary melanotrophs caused by micromolar Cd2+and Zn2+
Authors: Davidson Jana-Lea , Kehl Steven F.
Published: April 2011

We studied the effects of Zn2+and Cd2+on the behaviour of IK(f), a transient outward potassium current in acutely dissociated melanotrophs of the pars intermedia of the rat pituitary gland. Micromolar concentrations of external Cd2+or Zn2+caused parallel and nearly equal rightward shifts along the voltage axis of the activation and steady-state inactivation curves for IK(f). The KDfor the half-maximal shift of the activation curve was 278 μM for Cd2+and 93 μM for Zn2+; the maximal shifts of the activation curve were 32.5 and 34 mV, for Cd2+and Zn2+, respectively. The times to half-activation and half-inactivation were shifted rightward by 30–60 mV in both 500 μM Cd2+and 500 μM Zn2+. We suggest that Cd2+and Zn2+interact specifically with a binding site on or electrically close to the IK(f) channel and in so doing modify the electric field "seen" by the voltage sensors.Key words: fast transient K+current, melanotrophs, divalent cations, activation gating, inactivation gating.
Inotropic effect of low extracellular sodium on perfused perinatal rat heart
Authors: Oštádalová Ivana , Kolář František , Oštádal Bohuslav
Published: April 2011

The purpose of the present study was to estimate the development of the inotropic response to low extracellular sodium (LES) during the perinatal period. The effect of LES (35 mmol∙L−1) was measured in isolated perfused control and ryanodine-pretreated rat hearts on prenatal day 20 and postnatal days 1, 2, 4, and 7. The effect of LES on the developed force (DF) of control hearts changes significantly day by day: whereas a persisting increase of magnitude of contractions was recorded in the prenatal hearts, this increase was only transient on postnatal day 1 and 2. Starting from day 4, the initial signs of a triphasic response, typical for adult hearts, appeared (an initial increase of DF, followed by a decrease of DF and a rise of resting force, and finally a delayed increase of DF); this trend was more pronounced on day 7. The LES-induced increase of resting force was recorded only in 2-, 4-, and 7-day-old hearts. The negative inotropic effect of ryanodine (10−6 mol∙L−1) was observed already prenatally (60% of the controls) and continued during the whole period of investigation; in contrast, a ryanodine-induced increase of resting force was recorded only postnatally. However, pretreatment with ryanodine abolished the day-by-day changes in the response to LES: in all the hearts studied, the first phase (initial increase of DF) was followed by a severe depression of the magnitude of contractions, together with increased resting force. Our data show significant age-dependent differences in the cardiac contractile response to LES. This response changes rapidly during the perinatal development, and it attains the adult pattern by the end of the 1st postnatal week in rats.Key words: low extracellular sodium, ryanodine, inotropic effect, contractile function, perinatal ontogeny, rat heart, Na+–Ca2+ exchange.
Comparison of the glucose-lowering properties of vanadyl sulfate and bis(maltolato)oxovanadium(IV) following acute and chronic administration
Authors: Yuen Violet G. , McNeill J. H. , Orvig C.
Published: April 2011

Numerous studies, both in vitro and in vivo, have demonstrated the insulin-mimetic properties of vanadium. Chronic oral administration of inorganic and organic compounds of both vanadium(IV) and vanadium(V) reduced plasma glucose levels and restored plasma lipid levels in streptozotocin-diabetic rats. We investigated the acute effects of both vanadyl sulfate and bis(maltolato)oxovanadium(IV) (BMOV), an organic vanadium compound, on plasma glucose levels by several routes of administration. Previous studies have shown that chronic administration of vanadyl sulfate has resulted in a sustained euglycemia following withdrawal of the drug. This effect was not observed following the chronic administration of BMOV; therefore, we investigated the effect of increasing the concentration of BMOV on the production of a sustained euglycemic response. An acute plasma glucose lowering effect was obtained with both vanadyl sulfate and BMOV when administered as a single dose by either oral gavage or intraperitoneal injection. In those animals that responded to vanadium treatment, plasma glucose levels were within the normal range within 2 to 6 h when given by i.p. injection or within 4 to 8 h when given by oral gavage. BMOV-treated rats that responded to treatment maintained the euglycemic effect for extended periods, ranging from 1 to 14 weeks following administration. However, vanadyl sulfate treated rats reverted to hyperglycemia within 12 to 24 h, depending on the route of administration. Intravenous administration of BMOV was effective in lowering plasma glucose levels only when administered by continuous infusion. An oral dose – response curve showed that BMOV was 2 to 3 times as potent as vanadyl sulfate. This difference in potency was observed with both oral and intraperitoneal administration, which suggests that the increase in potency with BMOV cannot be totally attributed to increased gastrointestinal absorption. Organic chelation of vanadium may facilitate uptake into vanadium-sensitive tissues. Chronic oral administration of higher concentrations of BMOV did not result in a sustained reduction in plasma glucose following withdrawal of the drug. All diabetic rats eventually responded to increased concentrations of BMOV with a restoration of plasma glucose levels to normal values; however, reversion to the hyperglycemic state occurred within 2 days of withdrawal of treatment. Chronic oral administration of BMOV did not produce a sustained euglycemic effect following withdrawal, but acute administrations of the compound by either oral gavage or intraperitoneal injection did produce a long-term reduction in plasma glucose levels. Rats treated chronically with vanadyl sulfate remained euglycemic even after the drug was withdrawn. However, acute treatment produced only a transient euglycemia.Key words: streptozotocin diabetic, acute, bis(maltolato)oxovanadium(IV), vanadyl sulfate, dose response.
Otenzepad shows two populations of binding sites in human gastric smooth muscle
Authors: Bellido I. , Gómez A. , Cuesta F. Sánchez de la , Fernández J. L.
Published: April 2011

Cholinergic agonists and antagonists frequently used for gastrointestinal motility disorders often produce adverse effects. A possible explanation for this is the presence of similar muscarinic receptor subtypes on smooth muscle from different gastrointestinal organs. The aim of this study was to characterize muscarinic receptor subtypes in human gastric smooth muscle with receptor binding methods. N-[3H]Methylscopolamine ([3H]NMS) saturation experiments showed a homogeneous population of noninteracting binding sites (KD = 0.76 ± 0.07 nM, Bmax = 46.94 ± 3.69 fmol/mg of tissue protein, nH = 0.99 ± 0.01). The rank order of inhibition of [3H]NMS binding by nonlabelled compounds was atropine [Formula: see text] otenzepad [Formula: see text] pirenzepine. Atropine and pirenzepine bound to a homogeneous population of binding sites. The inhibition of [3H]NMS binding by otenzepad showed two populations of receptors (nH < 1, p < 0.01), whose apparent Ki1of 298 ± 40 nM and apparent Ki2of 3.463 ± 0.62 mM were similar to those reported for the M2and M3muscarinic receptor subtypes. The M2subtype was the more abundant of the two, representing 79.12 ± 5.48% of the total population. We conclude that two muscarinic receptor subpopulations similar to the M2and M3subtypes are present in human gastric smooth muscle and that the M2-like receptor is the more abundant of the two.Key words: human stomach, muscarinic receptor subtypes, smooth muscle.
Could cytoplasmic concentration gradients for sodium and ATP exist in intact renal cells?
Authors: Ammann H. , Noël J. , Tejedor A. , Boulanger Y. , Gougoux A. , Vinay P.
Published: April 2011

In renal cells, the Na+ pump maintains a transmembrane concentration gradient for sodium ensuring the net reabsorption of sodium with or without cotransported species. This process requires a significant fraction of the ATP turnover of proximal tubules and thick ascending limbs. To understand the potential regulatory influences of Na+ and ATP on the activity of the Na+ pump in these nephron segments, the apparent kinetics of the membrane-bound Na+–K+ ATPase and of the cellular Na+ pump were studied in different preparations of dog proximal tubules and thick ascending limbs (tubular suspensions, tissue homogenates, and basolateral membrane vesicles) obtained from dog kidney cortex and red medulla. Two determinant kinetic parameters, i.e., the apparent Michaelis constant (Km) and the saturating concentrations for sodium and ATP, were compared with the intracellular concentrations of Na+ and ATP measured under physiological conditions. In both types of tubules, the apparent Km value for Na+ (5–15 mM) is set well below the measured mean intracellular concentration of sodium (50–60 mM), suggesting that the Na+ pump should be saturated by sodium ions under normal conditions. Nevertheless, a modest increment of the Na concentration in the vicinity of the pump, obtained by equilibrating the intra- and extra-cellular sodium concentrations at various extracellular [Na+] with nystatin, increases the activity of the Na+ pump in intact cortical tubules and thick ascending limbs, even when the extracellular [Na+] is set at the estimated intracellular [Na+], demonstrating that the pump is not saturated by sodium in situ. Similarly, the kinetics of the renal Na+ pump as a function of the ATP concentration suggested that the pump should be saturated by ATP in physiological conditions, since in both tissues the cellular ATP level (3–6 mM) is higher than the concentration required to achieve saturation of this activity (<2.5 mM). However, in renal cortical tubules, the steady-state intracellular [Na+] is affected by modest changes of ATP concentration, suggesting that the Na+ pump is not functionally saturated by ATP. Our data suggest that concentration gradients for Na+ and ATP may exist in the cytosol of renal cells. These gradients would be related to the polarity of sodium transport and of the ATP-consuming and ATP-regenerating processes in intact cells. According to this scheme, the intracellular concentration of both Na+ and ATP would be lower in the vicinity of the Na+ pump, the site of active extrusion of sodium and ATP utilization, than the mean cellular concentrations measured using classical techniques. Such an organization would amplify the signals given to the cell membranes by changes in ATP concentration.Key words: sodium, ATP, gradients, Na–K ATPase, regulation, mitochondria.
Inhibition by BMS 186295, a selective nonpeptide AT1 antagonist, of adrenal catecholamine release induced by angiotensin II in the dog in vivo
Authors: Martineau Daniel , Yamaguchi Nobuharu , Briand Richard
Published: April 2011

The aim of the present study was to investigate whether a novel nonpeptide AT1 selective antagonist, BMS 186295 (BMS), can antagonize adrenal catecholamine release induced by local administration of angiotensin II (AII) in anesthetized dogs. Plasma catecholamine concentrations in adrenal venous and aortic blood were determined by an HPLC–electrochemical method. AII was locally administered to the left adrenal gland in the absence and presence of BMS. In the first group (n = 7), local infusion (0.5 mL/min, 1 min) of AII (0.001 – 1.0 μg/mL) resulted in a significant dose-dependent increase in the basal secretion of adrenal catecholamines. Aortic catecholamine levels and mean aortic pressure remained unchanged at all doses tested. In the second group (control, n = 10), four repeated infusions (at intervals of 15 min) of AII at 0.1 μg/mL resulted in significant increases of adrenal catecholamine secretion compared with the baseline. In the third group receiving BMS given locally to the gland (n = 8), the basal adrenal catecholamine secretion was not significantly altered by BMS itself at any dose tested. However, the net catecholamine response to AII (0.1 μg/mL) was significantly and dose dependency attenuated by approximately 40, 60, and 80% in the presence of BMS at doses of 0.1, 1.0, and 10 μg/mL, respectively, compared with the control group. The study indicates that BMS dose dependency blocks AII-induced catecholamine secretion in the dog adrenal gland in vivo.Key words: adrenal gland, angiotensin II, AT1 antagonist, BMS 186295, catecholamine, dog, in vivo.
Increased glucose phosphorylating activity correlates with insulin secretory capacity of male JCR:LA-corpulent rat islets
Authors: Chan C. B. , MacPhail R. M. , Kibenge M. T. , Russell J. C.
Published: April 2011

In this study the glucose responsiveness of isolated, overnight-cultured islets of obese LA/N-corpulent (cp/cp) rats was compared with glucose phosphorylating activity to determine whether changes in the function of glucokinase could be identified. Islets from both male and female cp/cp rats showed a left-shifted concentration response to glucose, with EC50values of 1.5 and 4.6 mM, respectively, compared with 9.2 mM for lean control islets. Islets from cp/cp rats were partially resistant to inhibition by mannoheptulose, a glucokinase inhibitor. Minimum inhibitory concentrations were 10 mM in cp/cp vs. 3 mM in lean rat islets. Glucose phosphorylating potential was markedly increased in islets of male cp/cp, but not female cp/cp, compared with lean rats. The maximal velocity (Vmax) of hexokinase was increased 5-fold, while the Kmof glucokinase was significantly decreased, in male cp/cp compared with the lean control islets (3.6 vs. 35.2 mM). The Kmfor glucokinase was also decreased in female cp/cp rat islets (17.2 mM). The data from male cp/cp rat islets are consistent with the idea that increased glucose phosphorylation capacity can contribute to insulin hypersecretion and an extreme leftward shift in the concentration–response curve. However, other factors must also be considered because female cp/cp rats have moderately increased insulin secretory capacity without marked changes in total glucose phosphorylating capacity.Key words: obesity, glucokinase, insulin secretion, islets of Langerhans.
Regulation of vascular tone
Authors: Rossitti Sandro , Frangos John , Girard Peggy R. , Bevan John
Published: April 2011

The intimal surface of the blood vessel in vivo is subject to shear stress resulting from blood flow, which in most of the circulation, at least at rest, is laminar. Turbulence can occur at bifurcations, especially those of the large arteries, and where vessels curve significantly. Shear stress is a frictional tangential force exerted at the fluid–intimal interface in the long axis of the vessel. It is now known that hemodynamic shear stress can influence a large variety of biological processes in endothelial cells, which vary from those with a short response time, just a few milliseconds, such as the opening of ion channels, to those that change over a period of minutes to several hours, for example, endocytosis and cytoskeleton rearrangement, and those features that alter much more slowly, such as cell shape and stiffness. In addition to these types of changes, there are suggestions that flow acting through shear stress may be responsible for several basic attributes of the vasculature, including the relative size and diameter of the components of a branching vascular system. In this symposium on the flow regulation of the blood vessel, the first presentation dealt with optimality principles that appear to govern the dimensions of the vasculature, in particular the geometry of the arterial branching and the role of shear stress. An optimally designed system is one that requires the least metabolic work to perform its function. The subsequent three presentations focussed on the effect of shear stress on three different aspects of the artery wall, the composition and organization of the extracellular matrix, the production of vasoactive factors by the endothelium, and the regulation of vascular tone.Key words: endothelial cells, extracellular matrix, shear stress, vascular smooth muscle, vascular tone.
Specific [3H]spiperone binding sites in the pituitary of rainbow trout (Oncorhynchus mykiss) and goldfish (Carassius auratus)
Authors: Omeljaniuk Robert J.
Published: April 2011

Dopamine, a catecholamine neurohormone, modulates pituitary hormone release in teleost fishes and other vertebrates. The existence and binding parameters of a pituitary dopamine–neuroleptic receptor from trout were examined and compared with those from goldfish. Pituitary homogenate was incubated with [3H]spiperone (D2 antagonist) under several experimental paradigms; incubations were terminated by filtration and bound 3H radioactivity was assessed by liquid scintillation spectroscopy. Specific binding of [3H]spiperone was tissue dependent. Equilibrium displacement analyses using domperidone (D2 antagonist) indicated a single class of binding site (LIGAND) with Kd = 2.49 ± 0.89 μM and a capacity of 3.10 ± 0.45 nmol/mg protein; the goldfish Kd and capacity were both significantly (p < 0.05) larger: Kd = 4.63 ± 0.30 μM and capacity = 20.66 ± 2.03 nmol/mg protein. The Kd and capacity for the trout pars distalis (2.45 ± 0.33 μM and 3.27 ± 0.24 nmol/mg protein, respectively) did not differ significantly (p < 0.05) from that of the neurointermediate lobe (2.50 ± 0.08 μM and 3.58 ± 0.56 nmol/mg protein, respectively). Dopamine D2 receptor ligands differentially displaced [3H]spiperone from the trout pituitary, while D1 ligands, a D4 ligand, and a 5-hydroxytryptamine (5HT2) receptor antagonist had only small nonspecific effects. Comparison of the trout and goldfish pituitary dopamine–neuroleptic receptor indicates conservation of receptor affinity (Kd); however, differences in receptor numbers and in the distribution of receptors between the pars distalis and neurointermediate lobe in the two species may be due in part to species or developmental differences, and may reflect differences in the role(s) and degrees of influence of dopamine in these fishes.Key words: pituitary, dopamine, receptor, rainbow trout, goldfish.
Effects of angiotensin II on plasma atrial natriuretic factor in nonpregnant and pregnant ewes
Authors: Fan L. , Javeshghani D. , Mukaddam-Daher S. , Guan Z. , Nuwayhid B. S. , Quillen Jr. E. W. , Gutkowska J.
Published: April 2011

The release of atrial natriuretic factor (ANF) is primarily determined by atrial stretch, but may also be modulated by circulating angiotensin II (AngII). During pregnancy, the circulating concentrations of both ANF and AngII are increased. To further define possible effects of AngII on ANF release, four doses of AngII (0.5, 5, 20, 40 ng∙kg−1∙min−1) were intravenously infused into five nonpregnant and five pregnant (105–140 days of gestation) ewes alone and during the simultaneous infusion of sodium nitroprusside at doses sufficient to abolish the pressor effects of AngII. Mean arterial pressure (MAP) was increased from 80 ± 2 to a maximum of 121 ± 5 mmHg (1 mmHg = 133.3 Pa) in nonpregnant ewes (p < 0.01) and from 79 ± 2 to 116 ± 4 mmHg in pregnant ewes (p < 0.01) over the range of AngII infusion. MAP was unaltered during AngII plus nitroprusside infusion, averaging 78 ± 3 mmHg in nonpregnant ewes and 80 ± 2 mmHg in pregnant ewes. Basal ANF was higher (p < 0.01) in pregnant sheep than in nonpregnant sheep. With AngII infusion alone, plasma ANF was increased from 13 ± 2 to 42 ± 4 fmol/mL in nonpregnant ewes (p < 0.01) and from 23 ± 5 to 72 ± 16 fmol/mL in pregnant ewes (p < 0.01). However, during AngII plus nitroprusside infusion, the increases in plasma ANF observed were completely abolished in both nonpregnant and pregnant ewes. These results suggest that AngII does not have a direct stimulatory effect on ANF release but rather that the increase in plasma ANF is a consequence of the pressor effects of AngII. This response does not appear to be altered during ovine pregnancy.Key words: angiotensin II, atrial natriuretic factor, nitroprusside, mean arterial pressure.
Similar distribution oftransfatty acid isomers in partially hydrogenated vegetable oils and adipose tissue of Canadians
Authors: Chen Z. Y. , Ratnayake W. M. N. , Fortier L. , Ross R. , Cunnane S. C.
Published: April 2011

The objective of this study was to evaluate the composition of trans fatty acids in the subcutaneous fat of Canadians relative to the composition of dietary sources of trans fatty acids. The fatty acid composition, total trans fatty acid content, and the geometric and positional isomer distribution of unsaturated fatty acids of subcutaneous adipose tissue of Canadians were determined using a combination of capillary gas–liquid chromatography and silver nitrate thin-layer chromatography. The mean total trans fatty acid content was 6.80% at the abdominal site and 5.80% at the lateral thigh site. Total trans isomers of linoleic acid (18:2n−6) were present at 1.17% in abdominal and 1.59% in thigh adipose tissue, with 9c,12t-18:2 being the most prevalent isomer followed by 9c-13t-18:2 and 9t,12c,-18:2. The oleic acid (18:1) trans isomer distribution in adipose tissue differed from that in butter fat, but it was similar to that in partially hydrogenated vegetable oils. The reverse was true for the 18:1 cis isomers. Total 18:1 trans isomers were inversely related to 18:2n−6 content in adipose tissue, suggesting the trans fatty acid intake is inversely related to the intake of linoleic acid. Partially hydrogenated vegetable oils appear to be the major source of trans fatty acids in adipose tissue of Canadians.Key words: trans fatty acids, adipose tissue, partially hydrogenated vegetable oil, linoleic acid.
Myocardial metabolic and functional responses to acetylcholine are altered in thyroxine-induced cardiac hypertrophy
Authors: Weiss Harvey R. , Tse James
Published: April 2011

We tested the hypothesis that acetylcholine would reduce myocardial O2consumption and function, and that thyroxine (T4, 0.5 mg/kg for 16 days) induced cardiac hypertrophy would change this relationship. Anesthetized open-chest New Zealand white rabbits were divided into four groups: control–vehicle (CV, n = 8), control–acetylcholine (CA, n = 10), T4–vehicle (T4V, n = 9), and T4-acetylcholine (T4A, n = 10). Either vehicle or acetylcholine (10−3 M) was topically applied to the left ventricular surface. Coronary blood flow (radioactive microspheres) and O2extraction (microspectrophotometry) were used to determine O2consumption, and muscarinic receptor density and affinity were also determined. T4increased the heart weight/body weight ratio from 2.6 ± 0.1 to 3.4 ± 0.1. T4-treated animals had higher heart rates, blood pressures, and left ventricular dP/dtmaxthan control rabbits. Topical acetylcholine depressed hemodynamic parameters with a greater decrement in pressures and cardiac output in the T4A group (CA, −25%, T4A, −40%). Myocardial O2consumption and coronary blood flow were higher in the T4-treated hearts. Myocardial O2consumption significantly declined in both groups during acetylcholine, but the reduction was greater in the T4-treated hearts (CV 7.9 ± 0.4 to CA 5.8 ± 0.6 and T4V 18.8 ± 3.0 to T4A 7.3 ± 1.0 mL O2∙min−1∙100 g−1). Muscarinic receptor density (Bmax) was elevated by 41% in the T4-treated hearts, but affinity (Kd) was not altered. Thus, the T4-treated hearts responded to acetylcholine to a greater extent than control hearts in terms of functional and O2consumption decrements. This may, in part, be related to the elevated number of muscarinic receptors in the T4-treated rabbit hearts.Key words: thyroxine, cardiac hypertrophy, acetylcholine, muscarinic receptors, coronary blood flow, myocardial O2consumption, rabbit.
Evaluating food use by Canadian Aboriginal Peoples
Authors: Wein Eleanor E.
Published: April 2011

Canadian Aboriginal people encompass diverse cultural groups, whose daily food patterns vary in regard to the kinds and proportions of indigenous foods. Standard dietary methods of assessing food consumption sometimes require modification to be understandable and acceptable to Aboriginal communities. Depending upon the purpose of the research, food frequency methods, repeated 24-h recalls of individual food consumption, and (or) examination of food preferences and food health beliefs may be used. Consultation with Aboriginal community leaders in planning the research is essential, to ensure collaboration and support. Explaining the purpose and methods to community members requires assistance of a respected local Aboriginal person, fluent in the language. Extra time is required for becoming acquainted with local foods, for translation, and for training community members as interviewers. Examples of these principles are discussed from the author's experience in the Yukon, the Northwest Territories, and northern Alberta.Key words: evaluating food use, Aboriginal Canadians.
Expression of B1 kinin receptors mediating paw edema and Formalin-induced nociception. Modulation by glucocorticoids
Authors: Campos Maria M. , Mata Luciana V. , Callxto João B.
Published: April 2011

Bradykinin (BK) and Tyr8-BK induced graded rat paw edema with EC50 values of 1.9 and 1.1 nmol/paw, while des-Arg9-BK (DABK, up to 300 nmol/paw) was marginally effective. Tyr8-BK, but not DABK, also caused a dose-related increase in mouse paw edema, with an EC50 of 1.3 nmol/paw. The response to Tyr8-BK (10 nmol/paw) in rat paw edema was antagonized by B2 receptor antagonists (HOE-140 or NPC 17731, 30 nmol/paw) but not by the B1 antagonist des-Arg9[Leu8]BK (DALBK, 100 nmol/paw). Daily intraplantar injections of Tyr8-BK (10 nmol/paw) for 7 days caused progressive desensitization (D) of edema in sham-operated and adrenalectomized Wistar rats. DABK (100 nmol/paw) caused marked paw edema in D paws from both groups, which was inhibited by DALBK (100 nmol/paw) and by dexamethasone (0.5 mg/kg, s.c). Systemic injection of lipopolysaccharide (10 μg/mouse, 24 h prior) potentiated the first and second phases of Formalin-induced pain but had no effect on paw edema. Coinjection of DABK (2–22 nmol/paw) with low doses of Formalin in lipopolysaccharide-treated mice, which had no effect on naive animals, dose dependently potentiated both phases of Formalin-induced pain but did not modify paw edema. These effects were antagonized by DALBK with ID50 values of 21.9 (first phase) and 64.1 (second phase) nmol/paw. Thus, both progressive desensitization of B2 receptors and systemic treatment with lipopolysaccharide induce a glucocorticoid-sensitive upregulation of B1 receptors mediating paw edema in the rat and Formalin-induced nociception in mice. These results suggest that induction of upregulation of B1 receptors may play important roles in controlling inflammatory processes and hyperalgesia.Key words: paw edema, rat, mouse, pain, Formalin test, bradykinin, B1 and B2 agonists and antagonists, lipopolysaccharide, dexamethasone.
Role of bradykinin in the antihypertensive and cardioprotective actions of converting enzyme inhibitors
Authors: Zhu Yï-Chun , Stauss Harald M. , Bao Gang , Gohlke Peter , Zhu Yi-Zhun , Redlich Thomas , Unger Thomas
Published: April 2011

Angiotensin converting enzyme inhibitors (ACEIs) not only reduce angiotensin II synthesis but also potentiate endogenous kinins. In addition to their antihypertensive actions, accumulated evidence has demonstrated an improvement by ACEIs of cardiac function, cardiac structural and metabolic status, and myocardial blood flow in conditions such as cardiac ischemia, left ventricular hypertrophy, and myocardial infarction. The mechanisms underlying the antihypertensive and cardioprotective actions of ACEIs are under intensive investigation. A reduction of angiotensin II synthesis is undoubtedly responsible for a major part of the antihypertensive effects of ACEIs. However, in experimental renal hypertension but not in genetic hypertension, bradykinin potentiation has been shown to partially mediate the acute and chronic antihypertensive actions of these drugs. In addition, experimental observations suggest that bradykinin potentiation plays a pivotal role in the cardioprotective effects of ACEIs.Key words: angiotensin converting enzyme inhibitors, antihypertension, cardiac function, myocardial infarction, tissue blood flow, bradykinin, angiotensin II.
Bradykinin B1 and B2 receptor mechanisms and cytokine-induced hyperalgesia in the rat
Authors: Perkins M. N. , Kelly D. , Davis A. J.
Published: April 2011

The involvement of bradykinin (BK) B1 and B2 receptors in cytokine-induced hyperalgesia has been studied in the rat. Intraplantar injections of interleukin (IL) 1β and tumor necrosis factor α (TNFα) induced thermal hyperalgesia, with in the the case of IL-1β, contralateral hyperalgesia also present. Subsequent to administration of IL-1β, but not after TNFα, des-Arg9-BK reduced the withdrawal latency in both ipsi- and contra-lateral paws. Mechanical hyperalgesia was also induced by IL-1β, IL-2, and IL-8 when injected into rat knee joints, whereas IL-6 and TNFα were without effect. Coadministration of des-Arg9,Leu8-BK prevented the development of the cytokine-induced hyperalgesia for the duration of the experiment (6 h), but HOE-140 only reversed the hyperalgesia for the 1st h. At 3.5 h after IL-1β, IL-2, or IL-8, administration of des-Arg9,Leu8-BK or HOE-140 (iv) completely reversed the hyperalgesia. Twenty-four hours after pretreatment with IL-1β, injection of des-Arg9-BK into the joint produced opposite effects, depending on the dose: at 50 pmol the hyperalgesia was reversed, but at 0.5 nmol there was further hyperalgesia. Both responses were blocked by B1 but not B2 receptor antagonists. These data suggest that both B1 and B2 receptors are involved in the induction and maintenance of cytokine-induced hyperalgesia. B1 receptors appear to play a more important role than B2 receptors in the development of mechanical hyperalgesia.Key words: interleukin 1β, interleukin 2, interleukin 6, interleukin 8, tumor necrosis factor α, bradykinin, des-Arg9-bradykinin, bradykinin receptors, hyperalgesia, inflammation.
Tachykinin NK2 receptors further characterized in the lung with nonpeptide receptor antagonists
Authors: Advenier Charles
Published: April 2011

Two nonpeptide tackykinin NK2 receptor antagonists have now been described, SR 48968 and GR 159897. These drugs are highly specific and very potent antagonists with affinity (binding and in vitro study) for NK2 receptors in the subnanomolar range (pKi = 9–10), without intrinsic activity. They act preferentially on the human NK2A receptor subtype. These drugs exert potent and long-acting antagonism by both i.v. and oral administration. Their use has first confirmed the preponderant role of NK2 receptors in airway smooth muscle contraction, especially in human bronchi. A role for NK2 receptor stimulation has also been clearly demonstrated in bronchoconstriction induced by various agents known to induce the release of tachykinins (capsaicin, resiniferatoxin, citric acid, sodium metabisulfite diethyl ether, serotonin, and bradykinin), in allergen-induced airway constriction in the guinea pig sensitized to ovalbumin, and in hyperpnea-induced bronchoconstriction. Inhibition of neurokinin A mediated or capsaicin-mediated dyspnea by SR 48968 has also been demonstrated in the guinea pig. SR 48968 also is very efficient in inhibiting cough induced by citric acid or capsaicin. Finally, SR 48968 is able to abolish in guinea pigs in vivo the bronchial hyperreactivity induced after 24 or 48 h by a citric acid challenge or an ovalbumin challenge, respectively. Thus, nonpeptide, long-acting NK2 receptor antagonists can be regarded as suitable tools for investigations in humans. They may shortly allow a precise determination of the role of tachykinins in asthmatic patients.Key words: tachykinins, neurokinins, NK2 receptor antagonists, SR 48968, airways.
Transcriptional control of neuropeptide gene expression in sensory neurons, using the preprotachykinin-A gene as a model
Authors: Quinn J. P. , Mendelson S. C. , Paterson J. M. , McAllister J. , Morrison C. F.
Published: April 2011

Control of neuropeptide gene expression in sensory neurons is determined in part by a variety of tissue-specific, developmental, and stimulus-induced transcription factors that interact with the promoters of these genes. We have analysed the regulation of the rat preprotachykinin-A (rPPT) gene, which is expressed in a subset of dorsal root ganglia neurons. A region of the promoter encompassing approximately 1300 base pairs spanning the transcriptional start site has been analysed in detail both by functional analysis of promoter activity in clonal cell lines and dorsal root ganglia neurons grown in culture and by in vitro characterisation of transcription factor interaction with this region. Interestingly our analysis indicates an important role in rPPT gene expression for the E box transcription factor family. This class of transcription factor has been demonstrated to be a major determinant of calcitonin gene related peptide (CGRP) expression, which is also expressed in dorsal root ganglia neurons often under similar conditions as rPPT. In addition, multiple regulatory domains have been identified in the rPPT promoter, which act as activators in a variety of cell types. These elements are silenced in the context of the rPPT promoter in many non-neuronal cells. Therefore, tissue-specific expression of reporter genes directed by the rPPT promoter in transient transfection is determined in part by a variety of silencer elements, which act to repress the function of several domains that act as constitutive enhancers of expression in a wide range of cells. Removal or modulation of silencer elements in the rPPT promoter allows activity in a wider variety of cell types. We postulate that control of rPPT gene expression is the result of dynamic interplay of both positive and negative regulatory elements, a phenomenon observed in several other neuronal-specific genes, including that encoding CGRP.Key words: preprotachykinin, substance P, transcription, basic helix–loop–helix protein, activator protein 1.
Differential antagonism of amylin's metabolic and vascular actions with amylin receptor antagonists
Authors: Beaumont K. , Moore C. X. , Pittner R. A. , Prickett K. S. , Gaeta L. S. L. , Rink T. J. , Young A. A.
Published: April 2011

High affinity amylin binding sites are present in the rat nucleus accumbens. These sites bind [125I]amylin with an affinity of 27 pM and have high affinity for salmon calcitonin (sCT) and moderately high affinity for calcitonin gene related peptide (CGRP). N-terminally truncated peptides were tested for their ability to compete for [125I]amylin binding to these sites and to antagonize the metabolic and vascular actions of amylin. CGRP(8–37), sCT(8–32), and ac-[Asn30,Tyr32]sCT(8–32) (AC187) inhibited [125I]amylin binding to rat nucleus accumbens. Order of potency at inhibiting amylin binding (AC187 > sCT(8–32) > CGRP(8–37)) differed from the order of potency at inhibiting [125I]CGRP binding to SK-N-MC neuroblastoma cells (CGRP(8–37) > AC187 > sCT(8–32)). AC187 was the most potent antagonist of amylin's effects on isolated rat soleus muscle glycogen metabolism, and it was more effective than either sCT(8–32) or CGRP(8–37) at reducing amylin-stimulated hyperlactemia in rats. In contrast, CGRP(8–37) was the most potent peptide at antagonizing amylin-induced hypotension in rats. Amylin's hypotensive actions appear to be mediated by a weak action at CGRP receptors, while its metabolic actions are mediated by receptors with a distinct antagonist profile. AC187 is a potent antagonist of amylin binding sites in nucleus accumbens and of amylin's metabolic actions.Key words: amylin, calcitonin gene related peptide, diabetes, skeletal muscle, peptide receptors.
Comparative distribution off receptors for amylin and the related peptides calcitonin gene related peptide and calcitonin in rat and monkey brain
Authors: Christopoulos George , Sexton Patrick M. , Paxinos George , Huang Xu-Feng , Beaumont Kevin , Toga Arthur W.
Published: April 2011

The distribution of amylin receptors (125I-labelled rat amylin) in brains of rat and monkey were mapped and compared with the distribution of receptors for calcitonin (CT) (125I-labelled salmon CT) and calcitonin gene related peptide (CGRP) (rat, 125I-labelled rat CGRPα; monkey, 125-labelled human CGRPα). In rat, amylin receptors were discretely distributed with the highest receptor densities found in mid-caudal accumbens nucleus, parts of the bed nucleus of the stria terminalis, amygdala, and hypothalamus. Moderate to high densities of binding also occurred in the area postrema, subfornical organ, vascular organ of the lamina terminalis, locus ceruleus, dorsal raphe, and caudal solitary tract nucleus. In monkey, the distribution of amylin binding sites was similar, although the highest densities of receptors were in the hypothalamus, with relatively fewer sites present in the accumbens nucleus. In rat, the distribution of amylin receptors formed a subset of the receptor distributions for 125I-labelled salmon CT and 125I-labelled rat CGRPα. In contrast, in monkey, although the amyiin receptors again formed a subset of the binding sites identified with 125I-labelled salmon CT, mere was very little overlap with the pattern of CGRP receptor distribution. This suggests that the specificity profile of amylin receptors in primates differs from that of amylin receptors in the rat, with CGRPα having relatively lower affinity for the primate amylin receptors.Key words: amylin, calcitonin, calcitonin gene related peptide, receptor, rat, monkey.
Effects of amylin on appetite regulation and memory
Authors: Flood J. F. , Farr S. A. , Perry III H. J. , Kaiser F. E. , Morley P. M. K. , Morley J. E.
Published: April 2011

Amylin has been demonstrated to decrease food intake in mice and rats. Amylin is effective when delivered both peripherally and directly into the central nervous system. Amylin's effect on food intake is not aversive. Amylin may produce its effect on food intake by modulating nitric oxide synthesis. Calcitonin gene related peptide also decreases food intake after peripheral and central administration. In addition, amylin has been demonstrated to modulate memory at both peripheral and central sites.Key words: appetite, retention, satiety, memory, amylin.
Alteration of calcitonin gene related peptide and its receptor binding sites during the development of tolerance to μ and δ opioids
Authors: Ménard D. P. , Rossum D. van , Kar S. , Quirion R.
Published: April 2011

Calcitonin gene related peptide (CGRP), one of the most abundant peptides in the spinal cord, is localized in primary afferents and released following nociceptive stimuli. Its colocalization and corelease with substance P, a well-known nociceptive neuropeptide, support the importance of CGRP in pain mechanisms. However, its distinctive function in that regard remains to be fully established. Recently, we reported that increases in CGRP-like immunostaining and decrements in specific 125I-labelled human CGRPα ([125I]hCGRPα) binding sites in the spinal cord were correlated with the development of tolerance to the spinal antinociceptive action of a μ opioid agonist, morphine. The goal of the present study was to investigate whether the development of tolerance to other classes of opioids, namely, δ and κ agonists, can also alter CGRP-like immunostaining and receptors in the rat spinal cord. The antinociceptive effects of all opioids were monitored by the tail-immersion test. Tolerance to their antinociceptive properties was induced by the infusion for 7 days of μ (morphine sulfate, 7.5 μg/h), δ ([D-Pen2,D-Pen5]enkephalin (DPDPE), 2.0 μg/h), and κ (U-50488H, 10.0 μg/h) related agonists at the spinal level (L4), using osmotic minipumps. We confirmed that rats chronically treated with morphine showed significant decreases in [125I]CGRPα binding in laminae I, II, and III of the L4 spinal cord, while CGRP-like immunostaining was increased in these same laminae. Similar effects were observed following a treatment with the δ agonist, DPDPE, while the κ agonist, U-50488H, apparently only slightly decreased [125I]CGRPα binding in lamina II. Binding in other laminae and CGRP-like immunostaining were not affected. These results suggest a specific interaction between spinal CGRP systems and the development of tolerance to the spinal antinociceptive effects of μ- and δ-related agonists.Key words: opioid tolerance, calcitonin gene related peptide, sensory neurons, immunostaining, receptor autoradiography.
Effect of taurine deficiency on tissue taurine concentrations and pregnancy outcome in the rat
Authors: Gottschall-Pass K. T. , Gorecki D. K. J. , Paterson P. G.
Published: April 2011

Taurine status and pregnancy outcome were assessed in rats fed low dietary taurine and varying doses of guanidinoethyl sulfonate (GES), a structural analogue of taurine. Female Sprague–Dawley rats (225–270 g) were mated overnight and assigned to one of four groups from day 0 to 20 of gestation. Taurine-deficient animals were fed a basal diet containing <0.001 μmol taurine/g and 0.5 (n = 7), 1.0 (n = 8), or 2.0% (n = 7) GES in their drinking water, ad libitum. Control animals (n = 8) received similar treatment, with 2 μmol taurine/g added to the diet and no GES in their water. Taurine was analyzed by reverse-phase HPLC, using electrochemical detection after precolumn derivatization with ortho-phthalaldehyde. Treatment of rats with varying doses of GES produced a sharp decline in maternal liver and brain taurine to 15 and 55% of that of control levels, and in fetal liver and brain taurine to 75 and 50% of that of control levels, respectively (p = 0.0001; one-way ANOVA). The 2% group had a smaller mean (±SEM) litter weight than the control group (35.8 ± 6.1 vs. 51.9 ± 2.8 g; p = 0.042) as a result of a smaller litter size. The decrease in litter size was associated with confinement of implantation sites to either the left or right uterine horn in four of seven dams. Taurine deficiency did not result in intrauterine growth retardation or significant external, visceral, or skeletal malformations. Developmental defects were not found in any of the taurine-deficient groups, but reproductive abnormalities were present at the highest dose of the analogue.Key words: taurine deficiency, guanidinoethyl sulfonate, pregnancy outcome, congenital malformations, unilateral pregnancy.