bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of [3H] desmethylimipramine binding in bovine adrenal medulla: interactions with σ- and (or) phencyclidine-receptor ligands
Authors: Rogers Cheryl , Lemaire Simon
Published: April 2011

High-affinity binding sites (apparent KD 2.87 nM) for [3H]desmethylimipramine ([3H]DMI), have been demonstrated and characterized in membrane preparations of bovine adrenal medulla. The binding of [3H]DMI improved upon pretreatment of the membrane with KCl and was saturable, sodium dependent, and potently inhibited by nisoxetine and imipramine. [3H]DMI binding was also inhibited by various phencyclidine (PCP)- and (or) σ-receptor ligands, with the following order of potency: haloperidol > rimcazole > (−)-butaclamol > dextromethorphan > MK-801 > (+)-3-(3-hydroxyphenyl)-N-(1-propyl)piperidine((+)-3-PPP) > PCP > N-(2-thienyl)cyclohexyl-3,4-piperidine (TCP) > (+)-SKF-10047 > (−)-SKF-10047. The inhibition produced by σ ligands was not attributed to stimulation of either σ1- or σ2-receptors, owing to inactivity of the selective σ-receptor ligands (+)-pentazocine and 1,3-di(2-tolyl)guanidine (DTG). The inhibition of [3H]DMI binding by σ- and PCP-receptor ligands was not attributed to PCP1- or PCP2-receptor stimulation, owing to the decreased potency (100-fold) of these ligands in [3H]DMI assays compared with the affinity for brain PCP1 sites, and the ineffectiveness of the PCP2-ligand N-(1-(2-benzo(b)thiophenyl)cyclohexyl)piperidine (BTCP). Scatchard analysis of the inhibition by the σ-ligands haloperidol and (+)-3-PPP, as well as the PCP1 receptor ligand MK-801, demonstrated noncompetitive interaction with the site bound by [3H]DMI. These studies indicate that bovine adrenomedullary membranes possess a specific receptor for the noradrenaline uptake inhibitor [3H]DMI, which is sensitive to allosteric modulation produced by PCP and σ-ligands.Key words: desmethylimipramine, σ-receptor, phencyclidine, noradrenaline uptake, adrenal medulla.
Reduced sensitivity to dexamethasone of pancreatic islets from obese (fa/fa) rats
Authors: Chan Catherine , Lejeune Jeffrey
Published: April 2011

The direct effects of dexamethasone exposure on insulin secretion from islets of fa/fa rats and their lean littermates (Fa/?) were compared. After 72 h culture in 1 nM dexamethasone, glucose (27.5 mM)-stimulated insulin secretion over 90 min from islets of lean rats was significantly decreased compared with islets cultured without dexamethasone (12.9 ± 1.4 vs. 5.7 ± 1.0% of total islet content, p < 0.05). Higher doses of dexamethasone for 24–48 h culture produced similar effects. For islets of fa/fa rats, the minimum inhibitory concentration of dexamethasone was 10-fold higher, and islets required at least 48 h exposure for inhibitory effects to be observed. Dexamethasone also decreased the insulin response by islets to glybenclamide, indicating that dexamethasone effects were not specific to glucose transport or metabolism. The results suggest that islets of fa/fa rats may be less sensitive to direct inhibitory effects of glucocorticoids on glucose-stimulated insulin release than islets of lean animals.Key words: obesity, glucocorticoid, insulin, Zucker rat.
Physiologic coupling of glial glycogen metabolism to neuronal activity in brain
Authors: Swanson Raymond A.
Published: April 2011

Brain glycogen is localized almost exclusively to glia, where it undergoes continuous utilization and resynthesis. We have shown that glycogen utilization increases during tactile stimulation of the rat face and vibrissae. Conversely, decreased neuronal activity during hibernation and anesthesia is accompanied by a marked increase in brain glycogen content. These observations support a link between neuronal activity and glial glycogen metabolism. The energetics of glycogen metabolism suggest that glial glycogen is mobilized to meet increased metabolic demands of glia rather than to serve as a substrate for neuronal activity. An advantage to the use of glycogen may be the potentially faster generation of ATP from glycogen than from glucose. Alternatively, glycogen could be utilized if glucose supply is transiently insufficient during the onset of increased metabolic activity. Brain glycogen may have a dynamic role as a buffer between the abrupt increases in focal metabolic demands that occur during normal brain activity and the compensatory changes in focal cerebral blood flow or oxidative metabolism.Key words: brain, glia, glycogen, glycolysis, hibernation.
Effect of elevated potassium on the ion content of mouse astrocytes and neurons
Authors: White H. Steve , Chow Sien Yao , Yen-Chow Y. C. , Woodbury Dixon M.
Published: April 2011

Potassium is tightly regulated within the extracellular compartment of the brain. Nonetheless, it can increase 3- to 4-fold during periods of intense seizure activity and 10- to 20-fold under certain pathological conditions such as spreading depression. Within the central nervous system, neurons and astrocytes are both affected by shifts in the extracellular concentration of potassium. Elevated potassium can lead to a redistribution of other ions (e.g., calcium, sodium, chloride, hydrogen, etc.) within the cellular compartment of the brain. Small shifts in the extracellular potassium concentration can markedly affect acid–base homeostasis, energy metabolism, and volume regulation of these two brain cells. Since normal neuronal function is tightly coupled to the ability of the surrounding glial cells to regulate ionic shifts within the brain and since both cell types can be affected by shifts in the extracellular potassium, it is important to characterize their individual response to an elevation of this ion. This review describes the results of side-by-side studies conducted on cortical neurons and astrocytes, which assessed the effect of elevated potassium on their resting membrane potential, intracellular volume, and their intracellular concentration of potassium, sodium, and chloride. The results obtained from these studies suggest that there exists a marked cellular heterogeneity between neurons and astrocytes in their response to an elevation in the extracellular potassium concentration.Key words: astrocytes, neurons, ion concentration, neuronal–glial interactions, mouse, cell culture.
Quantitative analysis of extracellular space using the method of TMA+ iontophoresis and the issue of TMA+ uptake
Authors: Nicholson Charles
Published: April 2011

The tetramethylammonium (TMA+) method for measuring the volume fraction and tortuosity of brain extracellular space is presented in detail. The temporal and spatial distribution of TMA+ in the extracellular space following iontophoresis or pressure microinjection is described by suitable equations and illustrated with graphs. By fitting the equations to the concentration versus time data obtained from measurements with ion-selective micropipettes, the volume fraction and tortuosity can be measured. In addition, the concentration-dependent uptake of TMA+ can be estimated from the given equations. The final section of the paper derives simple numerical estimates of TMA+ loss from the extracellular space by this mechanism.Key words: extracellular space, volume fraction, tortuosity, uptake, tetramethylammonium.
Use of cell cultures to differentiate among effects of various ischemia factors on astrocytic cell volume
Authors: Juurlink Bernhard H. J. , Chen Ye , Hertz Leif
Published: April 2011

Mouse astrocytes were subjected to in vitro models of ischemia (hypoxia with or without substrate deprivation, excess potassium, or elevated glutamate). Three hours of hypoxia alone or with substrate deprivation had little effect upon the morphology of astrocytes but did cause disaggregation of polyribosomes. Excess (12–50 mM) potassium added (as KCl) to a normal isotonic medium also caused no swelling; it did, however, cause a shrinkage of cell volume. When 50 mM potassium was substituted for a similar amount of sodium, marked swelling occurred. Swelling of astrocytes was also seen after addition of glutamate (50 μM to 1 mM) to the culture medium. These results show that ischemia per se does not result in astrocytic swelling; rather, microenvironmental alterations such as rising glutamate levels and changes in the sodium/potassium ratios result in astrocytic swelling. We conclude that one can use astrocytes in culture to dissect out the mechanisms that cause postischemic alterations in astrocytes in vivo.Key words: astrocytes, glutamate, ischemia, potassium, swelling.
Modification of excitation–contraction coupling in cat ventricular myocardium following endocardial damage
Authors: Bourreau Jean-Pierre , Banijamali Hamid S. , Challice Cyril E.
Published: April 2011

Damage to endocardial endothelium (denudation of the superficial tissue) by brief exposure to a 100-μL bolus of detergent (Triton X-100, 1% by volume stock) decreased the twitch force of papillary muscle (and trabeculae) by ~ 30% to a new but steady level without changes in resting tension. The decline in twitch force was evident immediately after the addition of Triton. Modification of the action potential measured from the contracting tissue appeared only later, when the change in contraction was already well established (i.e., after ~ 2 min). Action potential shortened in duration at 50% repolarization by ~ 100 ms and increased in plateau amplitude, although the latter increase was not always observed. A similar treatment procedure applied to strips of ventricular wall with the endocardium exposed to the superfusion solution resulted in a substantial decrease in action potential duration (~ 110 ms). In contrast, treatment of strips of epicardial layers of ventricular walls (with epicardial side facing the superfusion solution) did not produce a similar result. In β-stimulated (1 μM isoproterenol) and partially depolarized preparations (with 20 mM KCl), with intact endocardium, electrically evoked contractions were followed by aftercontractions, which were suppressed following Triton treatment. Action potentials in a depolarizing medium also shortened in duration (~ 50 ms), although following a delay (2–3 min). The decay to steady state of postextrasystolic potentiated beat was slower after endocardial damage than under control conditions. This suggested an increased Ca2+ recirculation through the sarcoplasmic reticulum between two consecutive beats (35% before Triton vs. 45% after Triton). Finally, in a medium containing 3 μM ryanodine, Triton treatment of the endocardial endothelium failed to induce any effect on either twitch force or action potential. Prolonged exposure to Triton X-100 (by a slow flow or high concentration) induced only deteriorating effects leading to substantial rise in the resting tension and generation of contractures and abbreviated action potentials with depressed plateau. These observations are consistent with the hypothesis that a modification in the sarcoplasmic reticulum function may, at least in part, be responsible for the observed changes in contractile function of the myocardium following endocardial damage with Triton treatment.Key words: endocardial endothelium, sarcoplasmic reticulum, ventricle, myocardial contraction.
Nitric oxide synthase inhibitors do not alter functional hyperemia in canine skeletal muscle
Authors: Barclay J. K. , Woodley N. E.
Published: April 2011

To test the hypothesis that endothelium-derived products contribute to functional hyperemia in skeletal muscle, we infused nitric oxide synthase inhibitors, either 200 μM Nω-nitro-L-arginine (NNA) (N = 4) or 1 mM Nγ-monomethyl-L-arginine (NMMA) (N = 4), before and during 6 min of 4 Hz stimulation of canine gastrocnemius in situ. We infused saline (N = 4) as a control. NNA significantly decreased steady-level resting flow by 3.8 ± 0.4 mL∙kg−1∙s−1. The increase in flow from rest to 5 min of stimulation was not changed by the nitric oxide synthase inhibitors. We also stimulated muscles for 60 min either with saline infusion (N = 4) or with the infusion of saline during the first 15 min and NNA for the remaining 45 min (N = 4). There was no difference in the flow during contractions. To clarify the effect of these inhibitors on canine vessels, we challenged rings of canine femoral artery with and without endothelium with acetylcholine and bradykinin (both 1 μM) before and after the addition of NNA and NMMA (both 10 μM). The nitric oxide synthase inhibitors decreased the relaxation accompanying acetylcholine. Both inhibitors caused only endothelium-intact rings to contract. Thus, the presence of a nitric oxide synthase inhibitor identified an endothelium-dependent contribution to the regulation of blood flow to skeletal muscle at rest but had no effect on functional hyperemia.Key words: vascular reactivity, functional hyperemia, steady-level blood flow, endothelium-derived factors, Nω-nitro-L-arginine, Nγ-monomethyl-L-arginine.
Potentiation by caffeine of the analgesic effect of aspirin in the pain-induced functional impairment model in the rat
Authors: Castañeda-Hernández Gilberto , Castillo-Méndez María Soledad , López-Muñoz Francisco J. , Granados-Soto Vinicio , Flores-Murrieta Francisco J.
Published: April 2011

The ability of caffeine to potentiate the analgesic effect of aspirin was studied in the pain-induced functional impairment model in the rat. Female Wistar rats received an intra-articular injection of 30% uric acid in the right hind limb, inducing its dysfunction. Once the dysfunction was complete, animals received aspirin oral doses of 0, 0.55, 0.98, and 1.74 mmol/kg with and without 0.17 mmol/kg of caffeine, and the recovery of functionality over time was considered as an expression of analgesia. Blood samples were drawn simultaneously with hind limb functionality determinations, and plasma concentrations of aspirin, salicylic acid, and gentisic acid were measured by high-performance liquid chromatography. Aspirin induced a dose-dependent analgesic effect. Caffeine alone was ineffective. However, caffeine significantly increased the analgesic effect of aspirin at all doses, without modifying aspirin, salicylic acid, or gentisic acid plasma levels. It is concluded that caffeine potentiates the analgesic effect of aspirin by a pharmacodynamic, but not by a pharmacokinetic mechanism.Key words: aspirin, caffeine, analgesia, potentiation, experimental pain models.
Endothelium-dependent relaxations in canine coronary arteries are enhanced in early heart failure and persist in recovery
Authors: Larosa Giulia , Armstrong Paul W. , Forster Christine
Published: April 2011

In vitro coronary artery responsiveness to noradrenaline, phenylephrine, and BHT-920 together with functional relaxation to acetylcholine was assessed in dogs at the early onset of pacing-induced heart failure (1 week) and in dogs recovered from heart failure (3 weeks paced, followed by 4 weeks discontinued pacing). α-Adrenoceptor stimulation produced contractile responses that were unaltered in early congestive heart failure and recovery. Contractions to noradrenaline and BHT-920 were always less than those produced by phenylephrine. Endothelium-intact arteries demonstrated relaxations in response to noradrenaline and BHT-920, but not phenylephrine. Relaxations to noradrenaline were enhanced 24% in early heart failure and 47% following recovery from heart failure, compared with control. BHT-920 produced relaxations that were augmented 21 and 76% in early heart failure and recovery, respectively. Contractile sensitivity to noradrenaline increased 5-fold in early heart failure and was not different in recovery, compared with control. Contractile sensitivity to BHT-920 and phenylephrine was unaltered throughout. Acetylcholine produced relaxations that were increased 21% in early heart failure and 13% after recovery from congestive heart failure. Furthermore, acetylcholine sensitivity was significantly enhanced in early heart failure and recovery. The current study reveals a progressive adaptation of the coronary endothelium in congestive heart failure, possibly directed towards protection against excessive vasoconstriction due to circulating catecholamines.Key words: endothelium, congestive heart failure, coronary arteries, α-adrenoceptors, noradrenaline, acetylcholine.
Quantitative measurements of dietary and [1-14C]linoleate metabolism in pregnant rats: specific influence of moderate zinc depletion independent of food intake
Authors: Yang Jilin , Cunnane Stephen C.
Published: April 2011

Our objective was to investigate whether the effects of moderate zinc deficiency on metabolism of linoleate during pregnancy could be distinguished from the effects of low food intake. Rats were force-fed an isoenergetic zinc-deficient (3.2 mg/kg) or control (26.4 mg/kg) semiliquid diet during the second half of pregnancy. Fatty acid quantity and composition in both maternal and fetal organs were analyzed at term. Recovery of 14C in lipid- and water-soluble metabolites from orally injected [1-14C]linoleate was also studied. After 10 days of gavaging identical amounts of the diet, zinc-deficient rats had lower serum zinc and lower uterus and placenta weights than controls, but body weights were similar. At term, zinc-deficient rats had a fatty acid composition in organs and carcass similar to that of the controls, but the zinc-deficient fetuses had lower long-chain n−6 and n−3 polyunsaturates in brain, liver, and carcasses. Lipids extracted from most organs of zinc-deficient rats contained lower 14C levels, but 14C was raised in the maternal carcass lipids and in water-soluble metabolites. We conclude that zinc deficiency during pregnancy increases oxidation of linoleate and decreases synthesis or transport of polyunsaturates to the fetuses and that these effects are independent of depressed food intake, i.e., they are specific to zinc depletion. Thus, zinc deficiency has distinct effects on fatty acid metabolism, which are readily observed using 14C tracer methods.Key words: fetus, linoleic acid, pregnancy, zinc deficiency.
In vivo correlation between liver and blood energy status as evidenced by chronic treatment of carbon tetrachloride and adenosine to rats
Authors: Hernández-Muñoz Rolando , Sánchez Victoria Chagoya de
Published: April 2011

Several tissues, such as red blood cells, depend on the liver supply of the purine ring for adenine nucleotide synthesis. We explored whether progressive liver damage, induced by carbon tetrachloride (CCl4), is accompanied by alterations in liver and blood energy status. After 4 weeks of CCl4 treatment, liver ATP, ATP/ADP, and energy status were decreased. Blood ATP remained normal, whereas the blood energy status was also diminished. After 8 weeks the changes were more evident, and a significant decrease of total liver nucleotides was also found. In the blood, the changes paralleled those in the liver. Simultaneous administration of adenosine counteracted the CCl4 effects. A good correlation (r = 0.79, p < 0.01) between the liver and blood ATP changes and a very significant relationship between liver and blood ATP/ADP ratio (r = 0.92, p < 0.001) were observed. Therefore, the data suggest that liver function could influence the energy availability in other tissues, such as red blood cells, perhaps as a result of its capacity to provide purine rings for extrahepatic synthesis of adenine nucleotides.Key words: liver–blood ATP interrelationship, cirrhotic rats, carbon tetrachloride, energy parameters, adenosine.
Protein kinase C stimulates Ca2+ current in pregnant rat myometrial cells
Authors: Shimamura Keiichi , Kusaka Masumi , Sperelakis Nicholas
Published: April 2011

The factors that regulate the voltage-dependent Ca2+ channels in pregnant uterine smooth muscle cells have not been elucidated, including any roles for protein kinase C (PKC). Therefore, the role of PKC in the regulation of the slow (L type) Ca2+ channels was examined in myometrial cells isolated from late pregnant (18–19 day) rat uterus, using the nystatin-perforated whole-cell voltage clamp. A PKC activator, phorbol 12, 13-dibutyrate (PDB), increased the L-type Ca2+ current (ICa(L)). Bath application of PDB (0.03 and 0.3 μM) increased the peak amplitude of ICa(L) by 21 ± 14% (n = 6) and 37 ± 8% (n = 9, p < 0.01), respectively. PDB did not change the holding current or shift the current–voltage relationship for ICa(L). The PKC inhibitors, H-7 (20 μM) or staurosporine (10 nM), reversed the effect of PDB. These results indicate that PKC may play a role in regulating Ca2+ channel function in pregnant rat myometrial cells and, therefore, may be involved in control of uterine contraction.Key words: protein kinase C, phorbol ester, calcium current, myometrial cell, nystatin-perforated patch, whole-cell voltage clamp.
Nitric oxide synthase induction and cytoprotection of rat gastric mucosa from injury by ethanol
Authors: Tepperman B. L. , Soper B. D.
Published: April 2011

The present study determined the effects of nitric oxide (NO) synthase induction on ethanol-mediated damage to rat gastric mucosa. NO synthase activity was determined by [14C]arginine conversion to radiolabeled citrulline. Ca2+-independent NO synthase activity was determined by citrulline formation in the presence of EGTA (1 mM) in the incubation mixture. Intraluminal ethanol administration (2 mL; 40% w/v) to control rats resulted in an increase in mucosal damage characterized as vasocongestion and hemorrhagic necrosis and a reduction in Ca2+-dependent NO synthase activity. Administration of Escherichia coli lipopolysaccharide (LPS; 3 mg/kg i.v.) augmented Ca2+-independent NO synthase activity (determined 4 h later) and reduced damage in response to intraluminal ethanol instillation. Ethanol treatment did not significantly affect induction of NO synthase activity. Dexamethasone pretreatment (1 mg/kg i.v. 2 h before LPS administration) reduced both Ca2+-independent NO synthase activity and the gastroprotective effect of LPS against ethanol-mediated mucosal injury. Likewise, concurrent administration of the NO synthase inhibitor NG-nitro-L-arginine methyl ester (10 mg/kg s.c.) inhibited the gastroprotection associated with LPS treatment, an effect abolished by pretreatment with the NO substrate L-arginine (300 mg/kg s.c.). Indomethacin (5 mg/kg i.v.) was ineffective in suppressing LPS-mediated gastroprotection. These results suggest that while Ca2+-dependent NO formation is inhibited by ethanol treatment, the inducible Ca2+-independent NO synthase plays a role in LPS-mediated gastroprotection against ethanol-mediated damage to the gastric mucosa.Key words: nitric oxide, lipopolysaccharide, ethanol, gastroprotection, dexamethasone.
Cyclic nucleotide dependent relaxation in vascular smooth muscle
Authors: McDaniel Nancy L. , Rembold Christopher M. , Murphy Richard A.
Published: April 2011

Although not without controversy, the mechanisms inducing contraction of vascular smooth muscle are relatively well defined. There is a stimulus-induced increase in myoplasmic [Ca2+] with activation of myosin light chain kinase by the Ca2+–calmodulin complex, phosphorylation of the 20-kDa regulatory light chain of myosin, with subsequent cross-bridge cycling and force development. Ca2+-dependent phosphorylation of the myosin regulatory light chain appears to be the primary mechanism responsible for regulating stress in vascular smooth muscle. The relationship between myoplasmic [Ca2+] and myosin phosphorylation (i.e., the calcium sensitivity of phosphorylation) is regulated. It is higher with agonist stimulation than in tissues depolarized with high potassium solutions or after skinning procedures. The relationship between myosin phosphorylation and stress appears to be invariant with physiologic stimulation. This suggests that cross-bridge phosphorylation normally determines contraction. The mechanisms of relaxation are less well defined. In the most simple scheme, reduction of myoplasmic [Ca2+] with a fall in myosin light chain kinase activity would suffice to account for dephosphorylation of the regulatory light chain and relaxation. However, other mechanisms have been implicated in cyclic nucleotide dependent relaxation in vascular and other smooth muscle tissues. The current hypotheses of the mechanism of cyclic nucleotide dependent relaxation in vascular smooth muscle are reviewed.Key words: calcium, cyclic adenosine 3′,5′-monophosphate, cyclic guanosine 3′,5′-monophosphate, myosin light chain phosphorylation, vasodilation.
A hypothesis for the mechanism of receptor and G-protein-dependent enhancement of vascular smooth muscle myofilament Ca2+ sensitivity
Authors: Rokolya Anikó , Ahn Hee Yul , Moreland Suzanne , Breemen Cornelis van , Moreland Robert S.
Published: April 2011

Agonist activation enhances smooth muscle myofilament Ca2+ sensitivity. The increased force accompanying receptor stimulation (over Ca2+ alone) requires GTP and is reversed by GDPβS, demonstrating a G-protein dependence. Protein kinase C (PKC) activators, such as phorbol esters, mimic and PKC inhibitors block the agonist-induced increase in Ca2+ sensitivity, suggesting a role for PKC in the regulation of Ca2+ sensitivity. Myosin light chain (MLC) phosphorylation levels are transiently increased by agonist stimulation, but steady-state levels of MLC phosphorylation are similar to those in response to Ca2+ alone. Thus, G-protein-mediated inhibition of MLC phosphatase may account for the initial increase in force development but not the increase in steady-state force. In contrast to MLC, calponin phosphorylation levels are maintained during agonist stimulation of intact vascular smooth muscle. We propose that stimulation of smooth muscle by membrane depolarization increases MLC phosphorylation, but as a result of inhibition by unphosphorylated calponin only a portion of the phosphorylated cross bridges attach to actin. Agonist stimulation produces the same steady-state level of MLC phosphorylation but also leads to calponin phosphorylation via a PKC-dependent pathway. Thus, during agonist stimulation, all phosphorylated cross bridges can interact with actin, thereby generating significantly greater levels of force.Key words: β-toxin, permeabilized smooth muscle, calcium, calponin, phosphorylation, sensitization, protein kinase C, mesenteric artery, endothelin.
Early changes in airway smooth muscle hyperresponsiveness
Authors: Jiang He , Rao Kang , Liu Xueliang , Halayko Andrew J. , Liu Gang , Stephens Newman L.
Published: April 2011

To study asthmatic airway smooth muscle we developed a canine model of ragweed pollen sensitized, airway hyperresponsiveness because of the difficulties in obtaining human tissue. Tracheal and bronchial smooth muscles from sensitized dogs were shown to possess greater ability to shorten and higher maximum shortening velocity (Vo), both of which contribute to the excessive narrowing of airways typical of human asthma. However, maximum force production remained normal, demonstrating the dissociation between the behaviour of shortening and force. Because we found no evidence of inflammation, hypertrophy, or hyperplasia in the sensitized airway smooth muscles, we felt this is a model of early disease and should provide insight into early and perhaps primary pathogenetic mechanisms. Vo is known to be determined by actornyosin ATPase, which in smooth muscle is activated via phosphorylation of the 20-kDa myosin light chain (MLC20) by myosin light chain kinase (MLCK). Therefore, ATPase activity, MLC20 phosphorylation, and MLCK were investigated. Sensitized tracheal and bronchial smooth muscles showed significantly higher ATPase activity, and a higher level of MLC20 phosphorylation, resulting from increased MLCK activity, a consequence of the measured increase in total quantity of MLCK rather than in specific activity. Since MLCK is activated by binding with Ca2+–calmodulin complex, intracellular Ca2+ concentration and calmodulin activity were also assessed, but no difference was found between sensitized and control animals. Our study suggests that increased MLCK quantity may be the cause of airway hyperresponsiveness found in sensitized animals, and future investigation should be focused on depicting the reason for the elevated MLCK.Key words: airway hyperresponsiveness, smooth muscle, biophysics, biochemistry, early asthmatic changes.
Large pulmonary arteries and the control of pulmonary vascular resistance in the newborn
Authors: Belik J.
Published: April 2011

In the immediate neonatal period the pulmonary vascular resistance is higher than later in life. The role of maturational differences in the smooth muscle mechanical properties of large capacitance vessels in this response has not been previously studied. To this end, we studied the smooth muscle isometric and isotonic mechanical properties, as well as the myogenic response of large extralobar pulmonary arteries in newborn and adult guinea pigs. Compared with the adult, the newborn pulmonary vascular smooth muscle generates less force and has a similar shortening capacity but longer isometric and isotonic relaxation half times. The myogenic response could be elicited in 80% of the newborn and 70% of the adult vessels. A 20% increase in vessel diameter resulted in force generation equivalent to 46 + 5.1 % of maximal isometric tension in the newborn. Such a response was significantly greater than observed for the adult vessels (14 ± 2.8%; p < 0.001). Our results showed significant maturational differences in the mechanical properties of the large pulmonary artery smooth muscle in the newborn. We speculate that the presence of myogenic response in large pulmonary capacitance vessels and the observed greater magnitude of stretch-induced force generation in the newborn may play an important role in the maintenance of a higher pulmonary vascular resistance in the neonatal period.Key words: myogenic response, pulmonary artery, newborn.
Properties of Ca2+-mediated inactivation of L-type Ca channel in smooth muscle cells of the guinea-pig urinary bladder
Authors: Yoshino M. , Matsufuji Y. , Yabu H.
Published: April 2011

The properties of Ca2+-mediated inactivation as revealed by a conventional double-pulse protocol were examined by using the whole-cell patch clamp technique. A U-shaped relationship between the conditioning potential and the Ca2+ current (ICa) inactivation was observed, with a maximum inactivation of 52 ± 4% (n = 5) at 10 mV with 0.5 mM EGTA in the patch pipettes. The maximum inactivation was reduced significantly, to 31 ± 5.7% (n = 12) and 32 ± 7.0% (n = 5), when a high concentration of EGTA (20 mM) or a more efficient Ca2+ chelator, BAPTA, was included in the patch pipettes, respectively. The same double-pulse protocol was applied under conditions where the stored Ca2+ was depleted by using caffeine or the stored Ca2+ release function was blocked by using ryanodine or procaine and heparin. No significant difference in the maximum ICa inactivation before (45%) and after (50%) application of 10 mM caffeine was observed. The maximum ICa inactivations of 48 ± 3.2% (n = 4) and 52 ± 8.4% (n = 6) were still observed after treatment of the cell with ryanodine (20 μM) or loading 10 mM procaine and 1 mg/mL heparin in the patch pipettes, respectively. These results suggest that Ca2+ mobilization from an internal Ca2+ store is not essential for the Ca2+-mediated inactivation observed in the double-pulse experiment, rather influx of Ca2+ through a voltage-dependent Ca channel seems to be important for ICa inactivation. Recovery from Ca2+-mediated inactivation could be fitted by the sum of two exponentials; the time constants of the fast and slow components were 210 and 810 ms, respectively, at a holding potential of −80 mV. By lowering the holding potential to −30 from −80 mV, the time constants of both fast and slow components were increased to 740 and 4820 ms, respectively, suggesting that the recovery of Ca2+ channels from Ca2+-mediated inactivation is voltage dependent.Key words: urinary bladder, smooth muscle, whole-cell patch clamp, Ca2+ current, double-pulse protocol, Ca2+-mediated inactivation.
Gastrointestinal motor inhibition by exogenous human, salmon, and eel calcitonin in conscious dogs
Authors: Nakamura Hiroyuki , Asano Tadashi , Haruta Koichi , Takeda Keisuke
Published: April 2011

Effects of synthetic eel (E-), salmon (S-), and human (H-) calcitonin (CT) on gastrointestinal motility were studied in conscious beagle dogs, which had been implanted with strain gauge force transducers. Intramuscular administration of E-, S-, or H-CT interrupted gastric migrating motor complexes, digestive pattern, and gastric emptying. The order of potency was E-CT = S-CT > H-CT. Motor inhibition induced by CT occurred independently of plasma immunoreactive motilin levels or hypocalcemia. In addition, E-CT and S-CT induced vomiting without a retrograde giant contraction (RGC) during the postprandial state. Apomorphine or CuSO4initiated RGC prior to vomiting. RGC induced by apomorphine was inhibited by pretreatment with E-CT as well as hexamethonium, atropine, or surgical vagotomy. E-CT showed no inhibitory effect on nicotine stimulated contraction of isolated guinea-pig ileum. These results suggest that peripherally administered CT inhibits canine gastrointestinal motility at the central nervous system level by lowering vagal activity.Key words: gastric emptying, motilin, retrograde giant contraction, vagus, vomiting.
Effect of renal denervation on elevation of blood pressure in cold-exposed rats
Authors: Sun Zhongjie , Fregly Melvin J. , Cade J. Robert
Published: April 2011

The objective of this experiment was to determine whether bilateral renal denervation (RD) prevents the elevation of blood pressure and cardiac hypertrophy characteristically induced by chronic exposure to cold. Four groups (nine male rats each) were used. The kidneys of two groups were bilaterally denervated, while the remaining two groups were sham operated. Systolic blood pressures of the four groups, measured indirectly from the tail, did not differ significantly during the control period and following RD. At this time, 1 RD and 1 sham-operated group was exposed to cold (5 °C, 41°F). The remaining RD and sham-operated groups were kept at 25 °C. Blood pressure of the cold-exposed, sham-operated group increased significantly during the 1st week of cold exposure (125 ± 2 mmHg; 1 mmHg = 133.3 Pa), and rose to 139 ± 4 mmHg by the 5th week, whereas the blood pressure of the RD group exposed to cold remained at the control level (116 ± 2 mmHg). Both RD and sham-operated cold-exposed groups developed cardiac hypertrophy with significantly increased resting heart rates compared with controls kept at 25 °C. Plasma renin activities and renal norepinephrine content of kidneys of both RD groups at 7 weeks after RD were significantly less than those of sham-operated controls, confirming that renal nerves had been severed. Thus, RD prevented the elevation of blood pressure induced by chronic exposure to cold but had no significant effect on cardiac hypertrophy.Key words: cold exposure, rats, blood pressure elevation, hypertension, renal denervation, plasma renin activity, renal norepinephrine content, cardiac hypertrophy.
Proinsulin mRNA and peptide are present in β-cells of diabetic BB rats
Authors: Curtis S. B. , Buchan A. M. J.
Published: April 2011

Previous studies have demonstrated that islets isolated from newly diabetic BB rat pancreata retain the ability to release insulin in culture, although in vivo the insulin response to stimulation is absent. The purpose of this study was to determine whether the β-cells in these newly diabetic animals were releasing stored insulin or whether they were still capable of insulin biosynthesis, since secretory defects may reflect abnormalities in insulin synthetic capacity. Insulin gene transcription was examined using in situ hybridization to detect preproinsulin mRNA (ppImRNA) at the level of the single cell since this technique provides a valid semiquantitative index of insulin biosynthesis. In situ hybridization with digoxigenin-labeled rat insulin probes resulted in strong labeling of β-cells in normal Wistar rat pancreata; other islet and acinar cells were negative. Double labeling of sections with an antibody to insulin confirmed that the labeled cells were β-cells only. The intensity of the staining was variable between different islets within the same section, and sometimes within an islet. Nondiabetic and diabetic BB islets were also positive for ppImRNA not only in normal islets but also in islets affected by insulitis. Islets that contained very few β-cells also contained ppImRNA. A consistent finding was that the intensity of the hybridization signal in many islets from the diabetic BB rats was stronger than in controls, suggesting that there is more ppImRNA in these islets. β-Cells that were positive for ppImRNA but negative for insulin peptide were also observed; these were in islets that were affected by insulitis. These results indicate that insulin biosynthesis was still present in islets of diabetic animals; therefore, a lack of insulin gene expression was not involved in the loss of glucose-stimulated insulin secretion.Key words: BB rat, in situ hybridization, preproinsulin mRNA.
Presence and actions of vasoactive intestinal peptide in the isolated rabbit heart
Authors: Accili Eric A. , Buchan Alison M. J. , Kwok Yin Nam , Ledsome John R. , Brown John C.
Published: April 2011

The objectives of these experiments were to localize vasoactive intestinal peptide immunoreactivity (VIP-IR) in the intracardiac ganglia of the interatrial septum of the rabbit heart and to examine the effects of vasoactive intestinal peptide (VIP) on the isolated perfused rabbit heart. Cell bodies of neurones containing VIP-IR were located in the interatrial septa of rabbit hearts by using immunocytochemistry. In addition, the effects of substance P (SP), neurokinin A (NKA), and neurokinin B (NKB) on the isolated rabbit heart were compared with those of VIP. Bolus injections of SP, NKA, VIP, and NKB caused dose-dependent decreases in the perfusion pressure of hearts perfused at constant flow with ED50 values of 2.73 ± 0.10 fmol (n = 6), 0.18 ± 0.01 pmol (n = 8), 93.75 ± 1.88 pmol (n = 6), and 75.00 ± 3.06 pmol (n = 6), respectively. The slope of the dose–response curve of VIP was much greater than those of SP and NKA, suggesting the presence of one receptor subtype for VIP and multiple receptor subtypes for the neurokinins on rabbit coronary vessels. Differences in the slopes of the dose–response curves and potency may reflect differences in the mechanism of vasodilatation. The maximal values of vasodilatation of all of the peptides did not differ. None of the peptides produced significant changes in heart rate, left ventricular pressure, or contractility. These results suggest that VIP found in the intracardiac neurones of the rabbit heart can mediate coronary vasodilatation.Key words: coronary vasodilatation, intracardiac ganglia, substance P, neurokinin A, neurokinin B.
Hypoxia abolishes the morning–night differences of metabolism and ventilation in 6-day-old rats
Authors: Saiki Chikako , Mortola Jacopo P.
Published: April 2011

Rat pups have a higher metabolic rate at night than in the morning; we questioned to what extent this was accompanied by changes in ventilation [Formula: see text] and the effect of hypoxia on the morning–night differences. From birth, the pups were mother reared under a 12 h light: 12 h dark cycle (light on from 07:00 to 19:00). At day 6, oxygen consumption ([Formula: see text], by a flow-through method) and [Formula: see text] (by airflow plethysmography) were measured at 07:30 and 19:30, and again at 07:30 of the next day. In normoxia, all values were higher at 19:30 than at 07:30. At all hours, [Formula: see text] remained constant (36.5 at 33 °C, 32 at 29 °C), because changes in [Formula: see text] matched those of [Formula: see text]. In acute hypoxia (inspired O2 = 10%), [Formula: see text] and [Formula: see text] dropped significantly from normoxia, and more so at 19:30 than at 07:30, resulting in no difference in [Formula: see text], [Formula: see text], or [Formula: see text] among hours. These results suggest that in the rat pup [Formula: see text] control is sufficiently developed to finely track changes in metabolic rate, and that hypoxia interferes with the metabolic and ventilatory morning–night differences.Key words: circadian rhythmicity, neonatal respiration, oxygen consumption, thermoregulation.
Functional and molecular aspects of prostaglandin E receptors in the cortical collecting duct
Authors: Hébert Richard L. , Breyer Richard M. , Jacobson Harry R. , Breyer Matthew D.
Published: April 2011

Endogenous prostaglandin (PG) E2production potently modulates salt and water transport in the kidney. Multiple direct effects of PGE2on epithelial water and sodium transport have been demonstrated in the rabbit cortical collecting duct (CCD). Both functional and molecular studies now suggest that these disparate effects of PGE2on CCD function are mediated by different EP receptors. When added in the presence of vasopressin, PGE2inhibits cyclic AMP generation and water absorption. These effects are mediated via an inhibitory G-protein (Gi). In situ hybridization demonstrates high levels of expression of the Gi-coupled EP3receptor in the rabbit collecting duct. However, by itself, PGE2also stimulates cyclic AMP generation and water permeability. These effects appear to be mediated via a distinct EP receptor (possibly an EP4receptor). PGE2also increases intracellular Ca2+in the CCD and inhibits Na+absorption via a Ca2+-dependent mechanism. The EP1receptor is postulated to be responsible for this action of PGE2. We suggest receptor-selective prostaglandin analogs may be used to selectively modulate sodium and water transport in the kidney.Key words: EP receptor subtypes, G-proteins, in situ hybridization, prostaglandin E2, phosphatidylinositol biphosphate hydrolysis.
The epithelial barrier and airway responsiveness
Authors: Sparrow M. P. , Mitchell H. W. , Omari T. I.
Published: April 2011

Epithelial injury and bronchial hyperresponsiveness are commonly associated with airway disease, and are widely considered to occur as the result of inflammatory changes in the airway wall. Mechanistically, the airway epithelium may influence the sensitivity of the airways to provocative stimuli through its primary function as a cellular barrier between the air and the interstitium, or by liberating a variety of bronchoactive mediators, e.g., lipoxygenase and cyclooxygenase products, nitric oxide, and an epithelium-derived relaxing factor (EpDIF). Much attention has focused on the latter function of the epithelium, particularly the putative EpDIF, which has an action considered to be analogous to that of endothelium-derived relaxing factor in blood vessels. The modulation of airway calibre by the epithelium has recently been investigated in vitro using tubular preparations of bronchi, where removal of, or damage to, the epithelium increases the sensitivity to agonists by several orders of magnitude. This contrasts with the effect of removing the epithelium on strips or rings of airway wall, where the increase in sensitivity is small and rather variable, but this has been the primary observation for proposing a putative EpDIF. This review evaluates the barrier or protective function of the airway epithelium and the major role it plays in the modulation of airway responsiveness. A role of a putative EpDIF seems, at best, to be of minor functional significance.Key words: epithelial barrier, bronchial hyprresponsiveness, airway smooth muscle, epithelial permeability, epithelium-derived inhibitory factor.
Pharmacology of montelukast sodium (Singulair™), a potent and selective leukotriene D4receptor antagonist
Authors: Jones T. R. , Labelle M. , Belley M. , Champion E. , Charette L. , Evans J. , Ford-Hutchinson A. W. , Gauthier J. -Y. , Lord A. , Masson P. , McAuliffe M. , McFarlane C. S. , Metters K. M. , Pickett C. , Piechuta H. , Rochette C. , Rodger I. W. , Sawyer N. , Yoyng R. N. , Zamboni R. , Abraham W. M.
Published: April 2011

Montelukast sodium (Singulair™), also known as MK-0476 (1-(((1(R)-(3-(2-(7-chloro-2-quinolinyl)-(E)-ethenyl)phenyl)(3-2-(1-hydroxy-1-methylethyl)phenyl)propyl)thio)methyl)cyclopropane) acetic acid sodium salt, is a potent and selective inhibitor of [3H]leukotriene D4specific binding in guinea pig lung (Ki0.18 ± 0.03 nM), sheep lung (Ki4 nM), and dimethylsulfoxide-differentiated U937 cell plasma membrane preparations (Ki0.52 ± 0.23 nM), but it was essentially inactive versus [3H]leukotriene C4specific binding in dimethylsulfoxide-differentiated U937 cell membranes (IC5010 μM) and [3H]leukotriene B4specific binding in THP-1 cell membranes (IC5040 μM). Montelukast also inhibited specific binding of [3H]leukotriene D4to guinea pig lung in the presence of human serum albumin, human plasma, and squirrel monkey plasma with Kivalues of 0.21 ± 0.08, 0.19 ± 0.02, and 0.26 ± 0.02 nM, respectively. Functionally, montelukast antagonized contractions of guinea pig trachea induced by leukotriene D4(pA2value 9.3; slope 0.8). In contrast, montelukast (16 μM) failed to antagonize contractions of guinea pig trachea induced by leukotriene C4(45 mM serine–borate), serotonin, acetylcholine, histamine, prostaglandin D2, or U-44069. Intravenous montelukast antagonized bronchoconstriction induced in anesthetized guinea pigs by i.v. leukotriene D4but did not block bronchoconstriction to arachidonic acid, histamine, serotonin, or acetylcholine. Oral administration of montelukast blocked leukotriene D4induced bronchoconstriction in conscious squirrel monkeys, ovalbumin-induced bronchoconstriction in conscious sensitized rats (ED500.03 ± 0.001 mg/kg; 4 h pretreatment), and also ascaris-induced early and late phase bronchoconstriction in conscious squirrel monkeys (0.03–0.1 mg/kg; 4 h pretreatment). A continuous i.v. infusion of montelukast (8 μg∙kg−1∙min−1) resulted in a 70% decrease in the peak early response and a 75% reduction of the late response to ascaris aerosol in allergic conscious sheep. Montelukast, a potent and selective leukotriene D4receptor antagonist with excellent in vivo activity is currently in clinical development for the treatment of asthma and related diseases.Key words: montelukast, MK-0476, Singulair™, leukotriene D4receptor antagonist, airway smooth muscle, antigen challenge.
Representation of hand position prior to movement and motor variability
Authors: Desmurget Michel , Rossetti Yves , Prablanc Claude , Jeannerod Marc , Stelmach George E.
Published: April 2011

Pointing accurary of six human subjects was measured in two blocked conditions where the hand was either never visible (T: target only) or only visible in static position prior to movement onset (H+T: hand + target). It was shown in condition H+T that, viewing the hand prior to movement greatly decreased end-point variability compared with condition T. This effect was associated with a significant modification of the movement kinematics: the H+T condition induced a shortened acceleration phase with a corresponding lengthened deceleration phase, compared with the T condition. These results led us to the hypothesis that viewing the hand prior to movement onset allowed a decrease of pointing variability through a feedback process. This hypothesis was further tested by turning the target off during the deceleration phase of the movement at half peak velocity. It was shown that turning the target off had no effect upon the T condition but induced a significant increase of pointing variability in the H+T condition. This result suggests that vision of the static hand enhances the proprioceptive localization of the limb and allows for a better visual to kinesthesic feedback.Key words: proprioception, vision, motor control, pointing, feedback, human.