bluuebunny/crossref_metadata_2025 huggingface dataset:
Design of potent and selective dynorphin A related peptides devoid of supraspinal motor effects in mice
Authors: Shukla Vijay K. , Lemaire Simon , Ibrahim Ibrahim H. , Cyr Terry D. , Chen Yanmin , Michelot Robert
Published: April 2011

Dynorphin A-(1 – 13)-Tyr-Leu-Phe-Asn-Gly-Pro (Dyn Ia) was previously shown to be a highly potent and selective κ opioid peptide. Four analogs of Dyn Ia are synthesized by the solid-phase procedure, introducing pseudo CH2NH linkage between positions 6 and 7 as follows: analog 1, [6ψ7 (CH2NH)]Dyn Ia; analog 2, [6ψ7 (CH2NH), D-Leu8]Dyn Ia; analog 3, [N(Me)-Tyr1, 6ψ7 (CH2NH)]Dyn Ia; and analog 4, [N(Me)-Tyr1, 6ψ7 (CH2NH), D-Leu8]Dyn Ia. The purified peptides are compared in vitro with Dyn Ia for their ability to compete with the binding of selective κ, μ, and δ opioid ligands using membrane preparations of guinea pig cerebellum (κ) and rat brain (μ and δ). The synthetic compounds are also compared in vivo in mice (intracerebroventricularly administered) for their analgesic activity against acetic acid induced writhing and their ability to produce motor dysfunction. All compounds display a high affinity (Ki = 0.5 – 1.8 nM) and a good selectivity for the κ opioid receptor, and their rank order of potency on the κ site (analog 2 > analog 1 > analog 3 > analog 4) closely parallels their potency (AD50 = 1.57–5 nmol/mouse) in inhibiting acetic acid induced writhing in mice (analog 2 > analog 1 > analog 4 > analog 3). On the other hand, all the synthetic analogs are less potent than Dyn Ia in producing motor effects, analog 2 being the least potent (CD50 = 15.4 nM as compared with 2.9 nM for Dyn Ia). Thus, analog 2 is a good model for developing Dyn A related peptides with selective antinociceptive activity.Key words: dynorphin, opioid receptors, analgesia, motor effects.
Site specificity of fat cell lipolysis during pregnancy in two strains of rats
Authors: Savard R. , Greenwood M. R. C.
Published: April 2011

The response to energy intake and expenditure is thought to be influenced by the genetic background. In the present study the metabolic response to pregnancy and to exercise training during pregnancy was investigated in two strains of rats. Lean Zucker and Wistar rats were divided into three groups: control pregnant (CP), exercise-trained pregnant (TRP), and not trained and not pregnant control (CNP). Trained rats swam 3 h per day, 6 days per week, throughout pregnancy. Body weight and food intake increased similarly during pregnancy in both strains (p ≤ 0.05). However, only Wistar rats had a further increase of food intake and body weight during the second half of pregnancy: TRP weighed 29.1 more grams and ate 4.5 more grams of food per day than CP at the end of pregnancy (p ≤ 0.05). Inguinal and parametrial fat cell sizes were unchanged during pregnancy. In both strains training induced a decrease of inguinal fat cell size at the beginning of pregnancy (p ≤ 0.05), which was rapidly counteracted to reach CP values on day 20 of pregnancy. Parametrial fat cell size was also decreased by training (p ≤ 0.05), but no values returned to control levels during pregnancy. In both strains, pregnancy increased fat cell lipolysis in the inguinal depot only (p ≤ 0.05). Training during pregnancy inhibited fat cell lipolysis in inguinal and parametrial depots, especially in Zucker (p ≤ 0.05), TRP reaching values similar to control values on day 20 of pregnancy. These results suggest that the effects of exercise training on the morphology of adipose tissue are similar in different strains of rats. They also show that the mobilization of fatty acids during pregnancy could respond to training in a strain-specific manner.Key words: adipose tissue, lipolysis, rat strain differences, pregnancy.
Chloride and depolarization by acetylcholine in canine airway smooth muscle
Authors: Daniel E. E. , Jury J. , Bourreau J.-P. , Jager L.
Published: April 2011

The role of chloride channels has been examined in canine tracheal smooth muscle by recording mechanical responses to field stimulation and to acetylcholine (ACh) and by sucrose gap recording of excitatory junction potentials and ACh-induced electrical changes. The results of substitution studies using isethionate for chloride provided evidence that a chloride conductance contributes to the resting potential. The extrapolated reversal potential for ACh-induced depolarization was positive to the resting potential. Isethionate substitution inhibited ACh-induced depolarization, consistent with a contribution from increased Cl− conductance to the depolarization induced by ACh. However, closure of K+ channels and opening of a nonspecific cation channel could also contribute to depolarization. Further study of the effects of isethionate substitution during prolonged tissue exposure to chloride-free medium showed that retention or the accumulation of Ca2+ in intracellular stores was impaired. We conclude that effects of chloride deprivation on responses to ACh may reflect an early increase in Cl− conductance, but longer term changes reflect the requirement for this anion to maintain internal Ca2+ stores.Key words: chloride ion, airway smooth muscle, ion channels, release of intracellular Ca2+.
Hypometabolic and hypothermic factors from small intestine of hibernating ground squirrels (Citellus undulatus)
Authors: Kramarova L. I. , Kolaeva S. G. , Bronnikov G. E. , Ignatiev A. D. , Krasts I. V.
Published: April 2011

Low molecular mass components of the acetic acid extract from the small intestine of hibernating ground squirrels (Citellus undulatus) produced a decrease in oxygen consumption and body temperature of white mice and a dose-dependent delay in embryonic development of sea urchin (Strongylocentrotus intermedius). Equivalent doses of low molecular mass components obtained by the same method from active (summer) animals did not have such an effect.Key words: hibernation, hypometabolic factors, hypothermic factors, sea urchin.
Impairment of endothelium-dependent relaxation of superior mesenteric artery in genetically diabetic WBN/Kob rats
Authors: Miyata Noriyuki , Yamaura Hiroko , Tsuchida Katsuharu , Okuyama Shigeru , Otomo Susumu , Kamata Katsuo , Kasuya Yutaka
Published: April 2011

The endothelium-dependent relaxation of superior mesenteric arteries of Wistar and genetically diabetic WBN/Kob rats was compared. Endothelium-dependent relaxation induced by acetylcholine (ACh) and A23187 was depressed in WBN/Kob rats. Relaxation induced by sodium nitroprusside, an endothelium-independent agent, in strips from WBN/Kob rats was similar to that in strips from Wistar rats. Indomethacin (5 × 10−6 M) enhanced the relaxation responses to ACh in strips from both WBN/Kob and Wistar rats; however, endothelium-dependent relaxation induced by ACh remained attenuated in WBN/Kob rats. These results show that endothelium-dependent relaxation is impaired not only in thoracic aorta but also in superior mesenteric arteries in genetically diabetic rats.Key words: acetylcholine, A23187, sodium nitroprusside, indomethacin, genetically diabetic rats, endothelium-derived relaxing factor.
Hemin inhibits protein synthesis and degradation in isolated brown adipose tissue mitochondria
Authors: Desautels M. , Dulos R. A.
Published: April 2011

The primary objectives of this work were to evaluate the effects of hemin on protein synthesis and degradation in isolated brown adipose tissue (BAT) mitochondria. Exposure of mice to a cold environment (4 °C) caused a significant increase in 5′-aminolevulinate synthase (ALV synthase) activity in BAT coincident with an increase in the tissue mitochondrial protein content. Hemin caused significant inhibition of protein synthesis and of ATP-stimulated proteolysis in isolated BAT mitochondria. These effects were specific, as protoporphyrin IX, a precursor of heme, increased protein synthesis and had no effect on ATP-stimulated degradation of mitochondrial translation products. The end products of degradation of proteins synthesized within isolated mitochondria were amino acids released to the outside of the organelles. Hemin appeared to inhibit an early step of the degradation pathway, as it caused a significant reduction in labelled methionine release from the organelles but no accumulation of peptides. Hemin caused significant inhibition of ATP-stimulated hydrolysis of labelled casein by soluble mitochondrial fractions, while addition of protoporphyrin IX was much less effective. In contrast, protease activity associated with mitochondrial membranes was almost equally sensitive to inhibition by hemin and protoporphyrin IX. These results suggest that heme may play a role in BAT mitochondriogenesis by its action on protein synthesis and degradation within the organelles.Key words: thermoregulation, body weight, heme, 5′-aminolevulinate synthase, ATP-dependent proteolysis, protease, protoporphyrin IX.
Plasma endothelin-1 response to acute hypotension induced by vasodilating agents
Authors: Cernacek Peter , Stewart Duncan J. , Levy Mortimer
Published: April 2011

Cyclic GMP (cGMP) dependent vasodilating agents (natriuretic peptides, nitric oxide) inhibit secretion of endothelin-1 (ET-1) in cultured endothelial cells. However, in circulatory conditions associated with acute hypotension, a marked increase in plasma ET-1 has repeatedly been observed. Therefore, after administration of cGMP-dependent agents in hypotensive dose, the net effect of these opposing influences on ET-1 release may shed light on the mechanisms determining circulating levels of this peptide. We have studied the effect of a hypotensive dose of atrial natriuretic peptide (n = 16), 8-Br-cGMP (n = 5), and papaverin (n = 7) on plasma ET-1 in anesthetized dogs. All agents produced marked increases in the peptide level at the end of infusion (178, 280, and 240% of the last preinfusion level, respectively) and a mean arterial blood pressure (MAP) decrease of 19, 18, and 42 mmHg (1 mmHg = 133.3 Pa), respectively. In all three protocols, plasma ET-1 continued to rise when the hypotensive agent was discontinued and remained elevated for 2–3 h postinfusion, even though MAP was normalized. There was a close positive correlation between the maximal increment in plasma ET-1 and the maximal decrease in MAP (r = 0.67, p < 0.001). These results show that acute hypotension due to directly acting vasodilators is a potent stimulus for systemic release of ET-1, even when due to agents known to inhibit ET-1 production in cultured endothelial cells. The discrepancy between the previous in vitro data and the present in vivo data can be explained either by non-endothelial origin of circulating ET-1, at least during acute hypotension, or by substantial differences in the production of ET-1 in the intact organism as opposed to endothelial cells in culture.Key words: endothelin secretion, big endothelin, atrial natriuretic peptide, cyclic GMP, papaverin.
Triacylglycerol turnover in isolated working hearts of acutely diabetic rats
Authors: Saddik Maruf , Lopaschuk Gary D.
Published: April 2011

Although myocardial triacylglycerol may be a potentially important source of fatty acids for β-oxidation in diabetes, few studies have measured triacylglycerol turnover directly in hearts from diabetic animals. In this study, myocardial triacylglycerol turnover was directly measured in isolated working hearts from streptozotocin-induced acutely diabetic rats. Hearts were initially perfused in the presence of 1.2 mM [14C]palmitate and 11 mM glucose for 1 h (pulse) to label the endogenous lipid pools, followed by a 10-min washout perfusion. Hearts were then perfused for another hour (chase) with buffer containing 11 mM glucose ± 1.2 mM [3H]palmitate. During the chase, both 14CO2 and 3H2O production (measures of endogenous and exogenous fatty acid oxidation, respectively) were determined. A second series of hearts were perfused using the same protocol, except that unlabeled palmitate was used during the pulse and 11 mM [14C(U),5-3H]glucose ± unlabeled palmitate was present during the chase. Both glycolysis (3H2O production) and glucose oxidation (14CO2 production) rates were measured in this series. Myocardial triacylglycerol levels were significantly higher in the diabetic rat hearts (77.5 ± 4.6 vs. 33.7 ± 4.1 μmol fatty acid/g dry mass in control hearts). In diabetic rat hearts chased with 1.2 mM palmitate, triacylglycerol lipolysis was increased, although endogenous [14C]palmitate oxidation rates were similar to control hearts and contributed 10.1% of overall ATP production. The majority of fatty acids derived from triacylglycerol lipolysis were released into the perfusate. In the absence of palmitate, both triacylglycerol lipolysis and endogenous [14C]palmitate oxidation rates were significantly increased in diabetic rat hearts, compared with control. Under these conditions, triacylglycerol fatty acid oxidation contributed 70% of steady-state ATP production in diabetic rat hearts, compared with 34% in control hearts. These results demonstrate that in diabetic rat hearts myocardial triacylglycerol lipolysis is significantly increased and can readily be used as a source of fatty acids for mitochondrial β-oxidation.Key words: heart, triacylglycerols, fatty acid oxidation, glucose oxidation, glycolysis.
meta-Iodobenzylguanidine uptake in the hypertensive–diabetic rat heart: a marker for myocardial dysfunction?
Authors: Herman Lynda M. , Dai Soter , Hartman Neil G. , McNeill John H.
Published: April 2011

The purpose of this study was to investigate the cardiac adrenergic neuronal changes induced by diabetes and hypertension by using an analogue of norepinephrine, meta-iodobenzylguanidine (MIBG), and to compare these changes with the contractile state of ventricular papillary muscle. The tissue concentration of norepinephrine in the cardiac apex was also measured for direct comparison with [123I]MIBG uptake. One week following the induction of diabetes by streptozotocin injection (55 mg/kg, i.v.), male Sprague – Dawley rats were given subcutaneous injections of a hypertension-inducing agent, deoxycorticosterone acetate (DOC A, 25 mg/kg), or DOCA vehicle twice weekly for 3, 6, 9, or 12 weeks. At the end of each time point, the animals were injected intravenously (15 mCi/mg; 1 Ci = 37 GBq) with [123I]MIBG. The results showed a progressive decrease in MIBG uptake into the hearts of diabetic, hypertensive, and diabetic–hypertensive rats during the 12-week observation period, compared with the control group. However, length–tension papillary muscle studies at 12 weeks indicated that only the diabetic group had a diminished performance compared with control. Furthermore, an inverse relationship was observed between MIBG uptake and norepinephrine levels in the cardiac apex of the diabetic and diabetic–hypertensive groups. Therefore, we concluded that either MIBG does not provide an accurate indication of adrenergic integrity or that there is no relationship between sympathetic activity and myocardial function at the time points measured. MIBG did not prove to be a useful marker for myocardial dysfunction in diabetic rats.Key words: diabetes, deoxycorticosterone acetate hypertension, meta-iodobenzylguanidine, adrenergic function, heart.
The endothelium contributes to the contractile responses of the human umbilical artery to 5-hydroxytryptamine and endothelin-1 under low but not high conditions
Authors: Xie Hui , Triggle Christopher R.
Published: April 2011

To determine the influences of both [Formula: see text] and the presence of the endothelium on contractile responses of the human umbilical artery (HUA), the effects of a series of vasoconstrictors were compared in ring preparations with and without endothelium at low (2.5% O2, [Formula: see text] (1 mmHg = 133.3 Pa)) and high [Formula: see text] (95% O2, [Formula: see text]). The results demonstrate the following. (i) 5-Hydroxytryptamine (5-HT) and endothelin-1 (ET-1) contracted the HUA at either low or high [Formula: see text]. At low [Formula: see text], removal of the endothelium significantly reduced receptor-mediated responses, (ii) The nitric oxide synthase inhibitor Nω–nitro-L-arginine methyl ester (L-NAME, 100 μM) did not modulate 5-HT-initiated contractions at either level of [Formula: see text]. (iii) α-Methyl-5-hydroxytryptamine (α-Me-5-HT) and 5-carboxamidotryptamine (5-CT), relatively selective 5-HT1C/5-HT2 and 5-HT1-like receptor agonists, respectively, elicited contractions in the HUA, and the responses were reduced at low [Formula: see text] but unaffected by removal of the endothelium, (iv) Responses of the HUA to high potassium (hK+) were unaffected by either changes in [Formula: see text] or removal of the endothelium, (v) The 5-HT2 receptor antagonist ketanserin at low concentration (10 nM) inhibited contractile responses to 5-HT in an apparently competitive manner. However, with 100 nM ketanserin and at low [Formula: see text], inhibition became noncompetitive. Removal of the endothelium did not influence the action of ketanserin. (vi) Regardless of [Formula: see text], the Ca2+ channel antagonist nifedipine (1 μM) significantly inhibited 5-HT- and ET-1-mediated contractions. Depletion of extracellular Ca2+ also greatly reduced 5-HT-induced contractions. We conclude that, in the HUA, endothelial cells and changes in [Formula: see text] differentially modulate contractions initiated by 5-HT agonists and ET-1, possibly via the release of an endothelium-derived contracting factor (EDCF).Key words: endothelium, contracting factors, vascular smooth muscle, oxygen tension.
Effect of the calcium channel agonist Bay K8644 on mechanical and electrical responses of frog skeletal muscle
Authors: Oz Murat , Frank George B.
Published: April 2011

The effects of Bay K8644, a Ca2+ channel agonist, on the mechanical and electrical properties of frog skeletal muscle fibers were investigated. At relatively low concentrations, such as 10−6 and 10−5 M, Bay K8644 significantly potentiated the maximum amplitudes of twitch responses, and this effect was not reversed in the presence of the calcium channel antagonist nitrendipine. At higher concentrations, such as 10−4 M, Bay K8644 depressed the amplitudes of twitch responses, and nitrendipine did not change this effect. At all concentrations, Bay K8644 greatly reduced the area under the tetanic force versus time curve, and this effect was not modified by the concomitant application of Bay K8644 and nitrendipine. Intracellular recordings revealed that the depressing effect of Bay K8644 on tetanic contractions was due to the blockade of sodium action potentials. In conclusion, the present results suggest that the modulation of twitch responses by calcium channel agonist and antagonists, at the concentration range used, is not related to the expected modulation of voltage-sensitive slow calcium channels in frog skeletal muscle fibers, and tetanic contractions are depressed by the calcium channel agonist Bay K8644 through its effect on sodium channels.Key words: Bay K8644, calcium channels, sodium channels, muscle contraction.
Lipid esterification and synthesis by the IEC-6 intestinal epithelial crypt cell line: effect of transforming growth factor β
Authors: Mehran M. , Seidman E. , Gurbindo C. , Levy E.
Published: April 2011

The capacity of immature intestinal epithelial crypt cells to synthesize lipids and the factors that promote their differentiation remain largely unknown. We examined the profile of lipids synthesized by a normal rat intestinal epithelial crypt cell line (IEC-6) and determined the effects of transforming growth factor β (TGFβ), a putative crypt cell differentiating factor, on their lipid handling. Incubation of IEC-6 cells with [14C]oleic acid (20 h) resulted in lipid esterification and synthesis, mainly as triglycerides (TGs, 57 ± 0.6%) and phospholipids (PLs, 30 ± 0.6%), with a PL/TG ratio of 0.53. When cells were pulsed (2.5 h) with [14C]oleic acid and then maintained 20 h in medium alone, a significant elevation of the PL/TG ratio (10.2 ± 1.3, p < 0.01) was observed, primarily accounted for by a significant decrease of the TG fraction (p < 0.01). IEC-6 cells secreted only trace amounts of lipids under the latter experimental condition. Incubation with TGFβ (20 h) significantly inhibited IEC-6 cell proliferation but did not promote the expression of cell sucrase activity. TGFβ induced a significant increase in the cellular composition of PL (p < 0.05) and a decrease in the TG fraction (p < 0.02), after a 2.5-h pulse of [14C]oleic acid. Lipid production was unaffected by TGFβ during the 20-h incubation with [14C]oleic acid. Lipid secretion into the medium remained negligible in the presence of TGFβ, after 2.5 h of incubation with substrate as above. Our findings suggest that immature crypt IEC-6 cells are capable of lipid esterification and synthesis but secrete minute amounts of lipoproteins. The predominant lipid fraction synthesized depended upon the availability of fatty acid substrate, with longer incubations favoring TG synthesis and brief cultures generating mainly PLs. The latter tendency was enhanced by TGFβ, which did not induce crypt cell maturation under the conditions tested.Key words: intestinal crypt epithelial cells, transforming growth factor β, triglycerides, phospholipids, enterocyte differentiation.
Plasticity in smooth muscle, a hypothesis
Authors: Ford Lincoln E. , Seow Chun Y. , Pratusevich Victor R.
Published: April 2011

The controversial finding that the thick filaments of smooth muscle can be evanescent leads to the hypothesis that the large functional range of this muscle is accommodated by plastic rearrangements that place more thick filaments in series at longer lengths. Our preliminary finding that the shortening velocity and compliance of dog tracheal muscle were strongly dependent on adapted muscle length, while force was much less length dependent, supports this hypothesis (V.R. Pratusevich, C.Y. Seow, and L.E. Ford. Biophys. J. 66: A139, 1994). The hypothesis leads to two further corollaries. The first is that the lengthening of the thick filaments that must accompany their reformation will cause a series to parallel transition: fewer long filaments span the muscle length, but the longer filaments have more cross bridges acting in parallel. The second is that there is more than one activating mechanism in smooth muscle. It is known that myosin light chain phosphorylation activates the actomyosin ATPase, but this same phosphorylation also causes a structural change that facilitates filament formation. The consideration that the unaggregated, phosphorylated myosin must be prevented from competing with myosin in thick filaments and hydrolyzing ATP suggests that there must be a second mechanism that must allow the thin filaments to interact selectively with filamentous myosin. This need for a second activating mechanism may explain the presence of tropomyosin, calponin, and caldesmon on thin filaments. Although the two corollaries follow from the initial hypothesis, it should be emphasized that the three are not mutually dependent, and that the proof or disproof of any one of them would not prove or disprove the others.Key words: smooth muscle, myosin, thick filaments, contraction.
Smooth muscle contraction kinetics at different calcium concentrations
Authors: Peiper Ulrich , Dee Jürgen
Published: April 2011

Actin–myosin interaction kinetics of the intact rat portal vein were studied by analyzing force recovery after cessation of force-inhibiting length vibration. The time constant of postvibration force recovery averaged 0.86 ± 0.04 s during short-term activation (< 12 s), and increased up to 1.59 ± 0.02 s (cross-bridge downregulation) during sustained activation of more than 10 min. After the depletion of intracellular calcium stores, the depolarized preparation developed maximum force at an extracellular calcium concentration in excess of 50 mM CaCl2. The time constant of postvibration force recovery rose to 12.31 ± 1.35 s after an activation period of 30 min. These retarded contraction kinetics may be caused either by low activation of the 20-kDa myosin light chain kinase or by high activity of the 20-kDa myosin light chain phosphatase. Addition of the phosphatase inhibitor okadaic acid (10 μM) during high calcium activation decreases the time constant to 8.04 ± 0.86 s and appears to prevent the distinct retardation of the contraction kinetics. During submaximum activation (2.5 mM CaCl2), the time constant of postvibration force recovery stabilizes at 1.56 ± 0.07 s, indicating downregulated cross-bridge kinetics, and is unaffected by phosphatase inhibition. For maximum barium activation, instead of calcium, 19.5 mM BaCl2 is required, which produced time constants of postvibration force recovery of 8.38 ± 0.32 s. The addition of okadaic did not affect contraction kinetics during barium activation. The pronounced retardation of contraction kinetics that was observed after the maximum calcium activation of the previously calcium depleted, depolarized preparation is probably due to high phosphatase activity. High phosphatase activity, on the other hand, does not seem to be involved in the process of cross-bridge downregulation or during barium activation.Key words: smooth muscle, portal vein, contraction kinetics, calcium, barium, phosphatase.
Protein tyrosine phosphorylation, cellular Ca2+, and Ca2+ sensitivity for contraction of smooth muscle
Authors: Salvo Joseph Di , Pfitzer Gabrielle , Semenchuk Lori A.
Published: April 2011

Our studies are guided by the novel hypothesis that protein tyrosine phosphorylation is an important mechanism for regulating contraction of smooth muscle. Several lines of evidence are reviewed which suggest that enhanced tyrosine phosphorylation participates in mechanisms that regulate cytosolic Ca2+ and Ca2+ sensitivity for contraction. First, vanadate-induced contraction of guinea-pig taenia coli is functionally linked to enhanced protein tyrosine phosphorylation of at least three substrates, apparently resulting from vanadate-mediated inhibition of protein tyrosine phosphatase activity. Second, vanadate-induced contraction is dependent on extracellular Ca2+. Third, increases in cytosolic Ca2+ resulting from stimulation of αi-adrenergic receptors in cultured canine vascular smooth muscle cells are associated with enhanced tyrosine phosphorylation and are inhibited by genistein, a potent inhibitor of tyrosine kinase activity. Fourth, genistein markedly and reversibly suppresses Ca2+ sensitivity for contraction in ileal longitudinal smooth muscle permeabilized with staphylococcal α-toxin. Moreover, the same or similar substrates (e.g., 42–45, 70, 80–85, 95, 100, 110, 116, and 205 kDa) are tyrosine phosphorylated in response to Ca2+ or stimulation of muscarinic or αi-adrenergic receptors. Collectively, these data strongly suggest that tyrosine phosphorylation is an important mechanism for regulation of smooth muscle contraction.Key words: actin–myosin interaction, calcium sensitivity, genistein, permeabilized smooth muscle, tyrosine kinase activity, tyrosine phosphatase activity, vascular smooth muscle cells, vanadate.
Characterization of polyclonal antibodies to the aromatic hydrocarbon receptor
Authors: Giannone John V. , Okey Allan B. , Harper Patricia A.
Published: April 2011

The aromatic hydrocarbon receptor (AHR) is a soluble intracellular protein that mediates most, if not all, the toxic effects of polycyclic aromatic hydrocarbons, such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and 3-methylcholanthrene. Initial binding of specific AHR ligands occurs in the cytoplasm; after a "transformation" step the ligand∙receptor complex translocates to the cell nucleus and binds to specific DNA sequences, which act as transcriptional enhancers. We used a synthetic peptide – KLH conjugate corresponding to a 20 amino acid sequence at the N-terminal of the AHR to generate rabbit polyclonal anti-AHR antibodies. The antiserum was affinity purified, using the synthetic peptide conjugated to ovalbumin, and screened by western blot analyses, using [3H]TCDD photoaffinity labeled AHR. Specificity of the antiserum was confirmed by co-migration of photolabeled AHR with the major immunoreactive band identified by western blot. Further characterization showed that the antipeptide antibodies recognized equally both mouse and human AHR, which differ significantly in molecular mass (mouse Hepa-1 cells ≈ 95 kDa; human LS180 cells ≈ 110 kDa). The affinity-purified antibodies also recognized undenatured TCDD∙AHR complexes, as determined by a shift in sedimentation of the [3H]TCDD∙AHR complex on a sucrose gradient. The high specificity and sensitivity of this antibody were used to determine the fate of the AHR in cells exposed to [3H]TCDD. Western blot analysis revealed that TCDD exposure caused a dramatic decrease in total cellular AHR to about 20% pre-TCDD levels within 2 h after TCDD, which persisted up to 20 h after initial TCDD exposure. However, in the presence of actinomycin D or cycloheximide, nuclear AHR remained elevated in cells exposed to TCDD, at levels similar to or greater than the maximum previously observed after 1-h incubations. These data suggest that ligand-dependent downregulation of the AHR is the result of protein degradation by a short-lived protease.Key words: aromatic hydrocarbon receptor, polyclonal antibody, downregulation, 2,3,7,8-tetrachlorodibenzo-p-dioxin.
Synthesis and biological activity of histogranin and related peptides
Authors: Prasad Jyoti A. , Shukla Vijay K. , Lemaire Simon
Published: April 2011

Histogranin (HN) was first isolated from bovine adrenal medulla and shown to be a pentadecapeptide displaying N-methyl-D-aspartate (NMDA) receptor antagonist activity. To determine the active pharmacophore of HN, fragments of the peptide were synthesized and their structure–activity relationships studied by measuring their ability to displace the binding of [125I][Ser1]HN to rat brain membrane preparations and to block NMDA-induced convulsions in mice. In the binding assay, only the full length peptide HN and HN(1–10) displayed a high affinity (Kiof 72 and 162 nM, respectively). All other tested fragments with deletions at the N- and (or) C-terminals of the molecule showed large (16- to 2500-fold) decreases in potency. The least active peptide fragment tested was HN(6–10) (Kiof 164 μM). In vivo, HN and HN(2–15) (100 nmol; i.c.v.) produced 94 and 40% protection against NMDA-induced convulsions in mice, respectively. None of the other peptide fragments displayed significant anticonvulsant activity. The protective activity of HN (60 and 100 nmol) was markedly antagonized by coadministration of HN(1–10) (100 nmol). The results indicate that the in vivo anti-NMDA and in vitro binding activities of HN and related peptides, with the exception of HN(1–10), depend upon the integrity of the molecule. On the other hand, the high affinity of HN(1–10) for HN binding sites correlates well with its antagonist effects towards the activity of the parent peptide.Key words: histogranin, peptide receptor, N-methyl-D-aspartate receptor, anticonvulsant.
Reorganisation in human motor cortex
Authors: Ridding M. C. , Rothwell J. C
Published: April 2011

Transcranial magnetic stimulation over the motor cortex was used to construct a map of the effective sites on the scalp from which short-latency electromyogram responses could be evoked in muscles proximal to either an amputation stump (two subjects) or an ischemically anesthetized forearm (two subjects). At rest, the maps were larger and the responses bigger when stimulating contralateral to the amputated arm or after anesthesia than they were in the intact arm or before anesthesia. However, this difference disappeared when the maps were constructed during a small tonic voluntary contraction of the target muscle. We conclude that reorganisation of the corticospinal projection to a muscle at rest may no longer be present during activity. If so, this calls into question the possible functional benefits of such reorganisation in the control of movement after peripheral damage.Key words: motor cortex, magnetic stimulation, amputation, ischemia.
Evoked potentials in a subject with a large-fibre sensory neuropathy below the neck
Authors: Cole J. D. , Merton W. L. , Barrett G. , Katifi H. A. , Treede R.-D.
Published: April 2011

The results from experiments in various modalities of evoked potentials are described in a subject with a complete large peripheral neuropathy below the neck. He has no tactile or position sensitivity below that level, but has retained fatigue, pain, and temperature sensation. Percutaneous electrical stimulation of peripheral nerves led to scalp recorded evoked potentials with thresholds and propagation velocities compatible with conduction along A-δ peripheral pathways. CO2 laser evoked potentials were similar to those seen in controls, further support for intact A-δ peripheral fibres. Movement-related cortical potentials (MRCPs) were recorded associated with active and passive movement of the middle finger. The former were normal, evidence that the termination of the MRCP is not dependent on peripheral feedback. By comparing passive MRCPs between controls and the subject it was possible to establish which parts of the potentials are visual and which are proprioceptive and to gain evidence of central reorganisation in the subject. Magnetic brain stimulation was used to show that the subject did not perceive induced movement, had a normal centrally originating silent period, and could focus his attention during real and imagined movement of the finger more successfully than could normal controls.Key words: sensory and motor evoked potentials, sensory neuropathy.
Proprioceptive sensory codes mediating movement trajectory perception: human hand vibration-induced drawing illusions
Authors: Roll J. P. , Gilhodes J. C.
Published: April 2011

To study the organization of the proprioceptive sensory codes subserving movement trajectory perception, complex hand drawing illusions were elicited using various vibration patterns applied to the wrist muscles of nine human subjects. It was established that it is possible to elicit kinesthetic illusions involving spatially oriented lines and geometrical shapes such as rectilinear or curvilinear figures by activating four groups of muscle tendons at the wrist level. The vibration sequences specifically evoking each shape were determined by varying the vibration frequency, the duration of each stimulus applied, and the vibrator onsets, and by applying the vibrations either successively or simultaneously. The proprioceptive coding of a trajectory can be modelled in terms of a series of vectors, the direction of which depends on the anatomical sites of the muscles that are stretched and shortened during the movement. The vector giving the spatial path of a movement is the sum vector of the vectors determined on the basis of the proprioceptive inputs originating from each muscle, and the modulus of the resulting vector is the instantaneous velocity of the movement. In line with previous cortical data, our results suggest that the perception of the spatial paths of limb segment movements is coded in joint space kinematic coordinates on the basis of the relevant ongoing proprioceptive information. It therefore emerges from the results of this study that muscle proprioception is able to generate spatiotemporal afferent patterns that may mediate complex cognitive operations such as those involved in the memorizing and recognition of motor forms.Key words: kinesthesia, proprioception, vibration, hand drawing, motor images.
New aspects of the role of histamine in cardiovascular function: identification, characterization, and potential pathophysiological importance of H3receptors
Authors: Göthert M. , Schlicker E. , Garbarg M. , Schwartz J.-C. , Hey J. A. , Levi R.
Published: April 2011

As a result of intensive research during several decades, the distribution, function, and pathophysiological role of cardiovascular H1and H2receptors are well known, whereas reports on the occurrence and function of H3receptors in blood vessels and the heart have not become available before the last 7 years (i.e., 4 years after the first description of these receptors in the central nervous system in 1983). The development of selective and potent H3receptor agonists and antagonists was a prerequisite for convenient investigations of cardiovascular H3receptors, which like H1and H2receptors are G-protein coupled but unlike them have not yet been cloned. Both in blood vessels and the heart, H3receptors are located on noradrenergic nerve endings and upon stimulation mediate an inhibition of noradrenaline release. Whereas it remains to be clarified under which conditions the vascular H3receptors may be stimulated by endogenous histamine, those in the heart become activated in the early phases of myocardial ischemia characterized by an increased histamine spillover. The H3receptors in the central nervous system also appear to be of importance for the control of vascular function. Inhibitory presynaptic H3receptors occur on trigeminal sensory C fibres supplying blood vessels in the dura mater. Release of neuropeptides from these fibres induces a neurogenic inflammation, which has been suggested to be involved in the pathogenesis of migraine. An interaction, involving presynaptic H3receptors, between sensory C fibres and mast ceils in close apposition to these fibres plays a role in the control of histamine synthesis in the dura mater. By influencing this regulatory process, H3receptor agonists may limit the extent of the neurogenic inflammation involved in the pathophysiology of migraine.Key words: histamine receptors, H3receptors, presynaptic receptors, noradrenaline release, migraine.
Pharmacological investigation of signaling mechanisms contributing to phasic and tonic components of the contractile response of rat arteries to noradrenaline
Authors: Weber Lynn P. , Chow Wing L. , Moshenko Janice , Belsher Slavica , MacLeod Kathleen M.
Published: April 2011

The mechanisms contributing to the contractile responses to two different concentrations of noradrenaline (NA) in rat aorta and mesenteric artery were compared using nifedipine, which inhibits calcium influx through dihydropyridine-sensitive channels, ryanodine, which depletes intracellular calcium stores, and calphostin C, which inhibits protein kinase C (PKC). Both submaximal and maximal concentrations of NA induced a biphasic response in aorta and mesenteric artery, with an early fast phase and a later sustained tonic component. Calcium release from intracellular stores contributed to the phasic component of contraction to both concentrations of NA in aorta, although to a greater extent to the submaximal concentration. In aorta, inhibiting both intracellular calcium release and calcium influx through dihydropyridine-sensitive channels simultaneously or inhibiting PKC activity alone significantly reduced the tonic response to a maximal concentration of NA. However, the tonic response to a submaximal concentration of NA in aorta was significantly inhibited only when intracellular calcium stores were depleted with ryanodine. In mesenteric artery, the phasic response to a maximal concentration of NA was significantly depressed only when both calcium influx and intracellular calcium release were inhibited simultaneously. However, the phasic response to a submaximal concentration of NA was significantly inhibited by blocking calcium influx alone, but not by blocking intracellular calcium release alone. The tonic component of the contractile response to both concentrations of NA in mesenteric artery appeared to be mediated in part by calcium from both intracellular and extracellular sources. However, the submaximal concentration relied on calcium influx to a greater extent than the maximal concentration, while PKC contributed to a greater extent to the response to the maximal concentration of NA in this artery. These results indicate that the relative contributions of the signaling mechanisms activated by NA differ between maximal and submaximal concentrations of the agonist as well as between different arteries.Key words: noradrenaline, vasoconstriction, ryanodine, nifedipine, calphostin C.
Hemostatic profile of bovine ovarian follicular fluid
Authors: Yamada Manabu , Gentry Patricia A.
Published: April 2011

The hemostatic profile of bovine ovarian follicular fluid was evaluated and the levels of procoagulant, fibrinolytic, and inhibitory activity compared with plasma. The results of the prothrombin time assay and the presence of fibrinogen along with factor VII and factor X activity indicate that bovine follicular fluid possesses components of the "extrinsic" or "tissue factor" coagulation system. The absence of factor VIII:C activity, along with the extremely low levels of factors IX and XI, indicates that there is not a functional "intrinsic" coagulation pathway. The fluid derived from large follicles exhibited increased levels of factors VII and X activity and a shorter prothrombin time compared with fluid obtained from the less mature small follicles. Similar alterations in the levels of the inhibitory proteins antithrombin III and α2-macroglobulin were observed. Overall the amount of antithrombin III was similar to that in plasma, the levels of fibrinogen and factor X were approximately 2-fold lower, and the levels of factor VII and factor X were approximately 10-fold lower than in plasma. The fibrinolytic activity in follicular fluid was greater than the procoagulant or inhibitory activity. Plasminogen activator activity was 5-foid higher, while both plasminogen and antiplasmin values were similar to plasma levels.Key words: hemostasis, follicular fluid, bovine.
Direct depressant effect of phosphodiesterase inhibitors on ATPase activity of rat cardiac myofibrils
Authors: Polla B. , Cappelli V. , Canepari M. , Zanardi M. C. , Reggiani C.
Published: April 2011

The aim of this study was to determine (i) whether phosphodiesterase inhibitors influenced ATPase activity of maximally calcium activated cardiac myofibrils and (ii) whether this effect varied in relation to isomyosin composition. Myofibrils were prepared from ventricular myocardium of 2- to 3-month-old rats. ATPase activity was determined at low ionic strength at high (>7.5) and low (4.4) pCa. Five compounds (amrinone, milrinone, enoximone, piroximone, and rolipram) were examined at concentrations between 10 μM and 1 mM. The results obtained showed that only milrinone and amrinone inhibited ATPase activity; inhibition was dose dependent, and milrinone was more potent than amrinone. To assess whether isomyosin composition might influence the responsiveness of myofibrils to phosphodiesterase inhibitors, the effect of 1 mM milrinone was also determined in myofibrils from hypothyroid rats. According to previous observations hypothyroidism caused an isomyosin shift from VI to V3 in rat ventricular myocardium. The inhibitory effect of milrinone was lower in myofibrils prepared from hypothyroid rats than in myofibrils from euthyroid rats.Key words: cardiac muscle, myofibrillar ATPase, phosphodiesterase inhibitors.
In vivo pharmacological evaluation off two novel type II (inducible) nitric oxide synthase inhibitors
Authors: Tracey W. Ross , Nakane Masaki , Basha Fatima , Carter George
Published: April 2011

Selective type II (inducible) nitric oxide synthase (NOS) inhibitors have several potential therapeutic applications, including treatment of sepsis, diabetes, and autoimmune diseases. The ability of two novel, selective inhibitors of type II NOS, S-ethylisothiourea (EIT) and 2-amino-5,6-dihydro-6-methyl-4H-1,3-thiazine (AMT), to inhibit type II NOS function in vivo was studied in lipopolysaccharide (LPS) treated rats. Type II NOS activity was assessed by measuring changes in plasma nitrite and nitrate concentrations ([NOx]). Both EIT and AMT elicited a dose-dependent and >95% inhibition of the LPS-induced increase in plasma [NOx]. The ED50 values for EIT and AMT were 0.4 and 0.2 mg/kg, respectively. In addition, the administration of LPS and either NOS inhibitor resulted in a dose-dependent increase in animal mortality; neither compound was lethal when administered alone. Pretreatment with L-arginine (but not D-arginine) prevented the mortality, while not affecting the type II NOS-dependent NO production, suggesting the toxicity may be due to inhibition of one of the other NOS isoforms (endothelial or neuronal). Thus, although EIT and AMT are potent inhibitors of type II NOS function in vivo, type II NOS inhibitors of even greater selectivity may need to be developed for therapeutic applications.Key words: nitric oxide, nitrite, nitrate, sepsis, lipopolysaccharide.
Ontogeny of 2-[125I]iodomelatonin binding sites in the chicken (Gallus domesticus) kidney and spleen
Authors: Song Y. , Pang S. F. , Poon A. M. S. , Brown G. M.
Published: April 2011

To understand the possible role of melatonin receptors in the development of renal and immune functions, age-related variations of 2-[125I]iodomelatonin binding sites in the chicken kidney and spleen were investigated by radioreceptor assay. Chickens at embryonic day 20, as well as 2 days, 9 days, 2 weeks, 6 weeks, 12 weeks, and 16 weeks after hatching, were kept under a 12 h light: 12 h dark photoperiod and killed at the middle of the light period. Binding sites for 2-[125I]iodomelatonin in membrane preparations of the chicken kidney and spleen were present on embryonic day 20. The maximum binding densities (Bmax) in the kidney increased to a peak between 9 days and 2 weeks of age, then progressively decreased. Bmaxvalues of 2-[125I]iodomelatonin binding sites in the chicken spleen were lower than in the kidney. The peak density in the chicken spleen was recorded at day 2 after hatching and decreased significantly after 6 weeks of age. There were no significant differences in binding affinities (Kd) in kidney and spleen of chicken in the different age groups studied. The unity of Hill coefficients of 2-[125I]iodomelatonin binding sites of the chicken kidney and spleen in all age groups tested suggested that only a single class of binding sites was present in these tissues during development. It is proposed that the developmental changes in 2-[125I]iodomelatonin binding sites in the chicken kidney and spleen may be pertinent to the development of diurnal rhythms of kidney functions and the post-pubertal decline in immune functions of the chicken.Key words: melatonin receptor, renal system, immune system, pineal gland, development, age-related change.
Current status of nutritional deficiencies in Canadian Aboriginal people
Authors: Moffatt Michael E. K.
Published: April 2011

Since the Nutrition Canada Survey (1973) there has been clear evidence that Aboriginal people have low intakes of many nutrients such as iron, vitamin D, calcium, folate, vitamin A, and fluoride. Recent surveys suggest that the situation has not changed. Children are most likely to be affected clinically. More than half of Aboriginal children in some subpopulations in Manitoba suffer a period of iron deficiency, which may affect development. Nutritional rickets is still a common problem in Manitoba. We have seen cases of megaloblastic anemia due to folate deficiency. The relationship of the well-described low folate intake in pregnancy and birth defects has received no attention for the Aboriginal population. In a recent survey of Inuit children, dental caries of the primary teeth were present in over 70% of children, with a mean DMF (decayed, missing, and filled) index of 1.8 teeth in children under 2 and 9.5 in children 6 to 8 years. Although clinical vitamin A deficiency is not seen, there is now good evidence that subclinical deficiency increases susceptibility to infections. Although not all Aboriginal populations suffer all of these deficiencies, the problems are sufficiently widespread to suggest this is an urgent problem. It will not be solved simply by education. There must be a political will and a coordinated effort to make a balanced diet available to all at an affordable cost.Key words: North American Indian, nutrition, iron deficiency, rickets.