bluuebunny/crossref_metadata_2025 huggingface dataset:
Antinociceptive and morphine modulatory actions of spinal orphanin FQ
Authors: Jhamandas K H , Sutak M , Henderson G
Published: April 2011

Orphanin FQ (nociceptin, OFQ), a heptadecapeptide peptide, has been designated as an endogenous ligand at the orphan receptor ORL1, which lacks affinity for opioid receptor ligands. OFQ-like immunoreactivity has been localized in spinal cord areas that are involved in the processing of nociceptive signals. In this study, the effects of spinally administered OFQ on thermal and mechanical nociceptive stimuli were investigated following intrathecal (i.t.) injection in unanesthetized rats bearing chronic indwelling catheters in the subarachnoid space. Intrathecal OFQ produced two distinct acute actions: an opioid-like antinociceptive effect, and antagonism of morphine-induced antinociception. Chronic administration produces tolerance. Acute actions were as follows. First, injection of OFQ alone in the dose range 10-100 nmol produced sustained antinociceptive effects in the tail-flick (baseline latency 1.5-2 s) and paw-pressure tests. These effects peaked at 45-60 min post-injection, were fully reversible, and were observed in absence of discernable motor impairments. Intrathecal naloxone (5 nmol) significantly attenuated the antinociceptive effects of OFQ (50 nmol i.t.) in tail-flick and paw-pressure tests. A 24-h pretreatment with the irreversible opioid receptor antagonist, beta -flunatrexamine (2 nmol i.t.), also attenuated the antinociceptive effects of OFQ (50, 100 nmol i.t.) and of morphine (7.5 nmol i.t.) in both tests. Low doses (1, 5 nmol) of OFQ, which failed to produce antinociception in the tail-flick test involving a baseline latency of 1.5-2 s, produced a strong antinociceptive response when the baseline latency was increased to 5-6 s. Second, intrathecal OFQ, at doses (0.5, 1.0, and 5.0 nmol) that had no antinociceptive activity in the tail-flick (baseline latency 1.5-2 s) and paw-pressure tests, attenuated the antinociceptive effect of morphine (7.5 nmol i.t.) in these tests. However, a threshold OFQ dose (10 nmol) significantly extended the duration of antinociception induced by morphine (7.5 nmol i.t.) or deltorphin (20 nmol i.t.). Chronic actions were as follows. In rats that were rendered tolerant to spinal morphine, by a continuous intrathecal infusion (7.5 nmol/h) of the agonist for 5 days, the OFQ dose-response curves for its antinociceptive effect in the tail-flick and paw-pressure tests were significantly shifted to the right. In separate experiments, repeated intrathecal injection of OFQ (50 nmol) or morphine (7.5 nmol) produced a significant decline in their antinociceptive effects. Thus, intrathecally administered OFQ produces both development of tolerance to its antinociceptive actions and cross-tolerance to the action of morphine.Key words: orphanin FQ, nociceptin, spinal antinociception, opioid antagonism, tolerance, cross-tolerance.
Evidence that cannabinoid-induced inhibition of electrically evoked contractions of the myenteric plexus - longitudinal muscle preparation of guinea-pig small intestine can be modulated by Ca2+ and camp
Authors: Coutts Angela A , Pertwee Roger G
Published: April 2011

Cannabinoid receptor agonists inhibit electrically evoked isometric contractions of the myenteric plexus - longitudinal muscle preparation of the guinea-pig small intestine (MPLM), probably by reducing release of acetylcholine (ACh) through the activation of prejunctional CB1 receptors. As CB1 receptors are thought to be negatively coupled through Gi/o proteins to both N-type Ca2+ channels and adenylate cyclase, we have now further investigated the involvement of CB1 receptors by monitoring the effects of forskolin, 8-bromo-cAMP, 3-isobutyl-1-methylxanthine (IBMX), and extracellular Ca2+ on the ability of the cannabinoid agonist, (+)-WIN 55212 to inhibitelectrically evoked contractions of the MPLM (0.1 Hz, 0.5.ms, and 110% maximal voltage). Some experiments were performed with normorphine instead of (+)-WIN 55212. At 10-7 M, forskolin, 8-bromo-cAMP, and IBMX were found to reduce significantly the maximum inhibitory response to (+)-WIN 55212 by 49.4, 48.4, and 40.2%, respectively, without affecting control contractions or responses to exogenous ACh. Low external Ca2+ (0.64 mM) significantly increased the maximum response to (+)-WIN 55212 and shifted the curve slightly leftwards, whereas high external Ca2+ (5.08 mM) reduced the maximum response by 27.2%. The concentration-response curve to normorphine, which also reduces evoked contractions of this preparation as a result of a presynaptic inhibition of ACh release via opioid µ receptors, was affected similarly. These results support the hypothesis that cannabinoid-induced inhibition in the MPLM is mediated by CB1 receptors.Key words: cannabinoid, myenteric, calcium, cAMP, normorphine.
Mechanism of the acute pressor effect and bradycardia elicited by diaspirin crosslinked hemoglobin in anesthetized rats
Authors: Moisan Steve , Drapeau Guy , Burhop Kenneth E , Rioux Francis
Published: April 2011

Diaspirin crosslinked hemoglobin (DCLHb) is a chemically stabilizedhemoglobin (Hb) that induces an increase in blood pressure and a decrease of heart rate wheninjected intravenously in some animals. The mechanism by which DCLHb elicits thesehemodynamic effects was studied in pentobarbital-anesthetized, vagotomized rats using a varietyof drugs known for their inhibitory action towards endogenous hemodynamically active systems.The hypertensive episode elicited by DCLHb (100 or 400 mg·kg1) was attenuatedin animals pretreated with NG-nitro-L-arginine (inhibitor of nitric oxidesynthases) throughout the 30-min period of observation, but it was not reduced in thosepretreated with a variety of sympatholytic drugs (e.g., prazosin), atropine, BIBP-3226(neuropeptide Y antagonist), indomethacin,[1-(Beta-mercapto-Beta,Beta-cyclopentanemethylene propionic acid), 2-(0-methyl)tyrosine]-Arg8 vasopressin (vasopressin antagonist), losartan (angiotensin antagonist),bosentan (endothelin antagonist), or L-arginine- (nitric oxide precursor), compared withcontrol animals. With the exception of propranolol and BIBP-3226, none of the aforenamedinhibitors reduced the amplitude of the bradycardia associated with the pressor effect of DCLHb.These results suggest that: (i) the acute (<30 min) pressor activity of DCLHb inour animal model requires the presence of an endogenous nitric oxide generating system to beexpressed; (ii) the bradycardia elicited by DCLHb might involve the participation ofneuropeptide Y and (or) its NPY-1 receptors, but it is unlikely to involve abaroreceptor-mediated vagal reflex, at least in our animal model.Key words: hemoglobin, nitric oxide, blood pressure, heart rate,DCLHb.
The effect of storage time and repeated measurements on the elastic properties of isolated porcine aortas using high resolution x-ray CT
Authors: Medynsky Andrew O , Holdsworth David W , Sherebrin Marvin H , Rankin Richard N , Roach Margot R
Published: April 2011

A Laboratory CT scanner with a resolution of (0.1 mm)3 wasused to determine if storage up to 7 days in saline at 4°C and (or) repeated measurementswould alter the compliance, C, and incremental elastic modulus, Einc,of isolated porcine aortas. All specimens were obtained fresh, made pressure-tight, and thenmounted in the scanner, with humidified air used to produce adequate x-ray contrast. Thespecimens were imaged at pressures of 4, 8, 12, 16, 20, and 24 kPa, and vessel measurementswere then obtained with a computerized technique and analyzed. Seven thoracic aortas werestudied on days 0, 3, 5, and 7, with a significant change (p < 0.05) in compliance firstoccurring after three imaging studies (i.e., day 5). Compliance of the fresh thoracic aortas (mean± SD) was 0.90 ± 0.28 mm/kPa at 14.4 kPa and 0.85 ± 0.31 mm/kPa at 22.5 kPa.Six thoracic aortas were studied only on days 0 and 6 with no intermediate measurements. Theyshowed no change in either compliance (0.88 ± 0.07 mm/kPa at 14.4 kPa and 0.64 ±0.09 mm/kPa at 22.5 kPa) or Einc (0.46 ± 0.05 MPa at14.4 kPa and 0.88 ± 0.15 MPa at 22.5 kPa) from day 0 to day 6. Thus, number ofmeasurements rather than time appears to be the important factor. Six abdominal aortas werestudied similarly but on days 0, 3, and 6. No significant change occurred in compliance (0.15 ±0.06 mm/kPa at 14.4 kPa and 0.032 ± 0.026 mm/kPa at 22.5 kPa) butEinc showed a change, possibly due to their viscoelastic properties. Weconclude that this nondestructive CT measurement method is suitable for repeated studies onporcine thoracic aortas, but not abdominal aortas, if the measurement involves two consecutiveimaging sessions separated by no more than 6 days.Key words: compliance, incremental elastic modulus, porcine aorta,x-ray computed tomography.
Pancreatic islet transplantation, but not intensive insulin therapy, corrects the pulmonary vascular complications of streptozotocin diabetes
Authors: Russ Roy D , Tobin Brian W
Published: April 2011

We examined the effects of long-term streptozotocin (STZ) diabetes andits treatment by intensive insulin therapy (IIT) or pancreatic islet transplantation on pulmonarypressor and depressor responses and segmental resistance profiles in female WistarFurth rats.Pulmonary vascular reactivity was examined using isolated, salt-perfused lungs at a constantflow rate of 30 mL·min1·kg1 body weight. Baseline perfusion pressurewas significantly (p < 0.05) lower in lungs obtained from IIT animals compared with allother treatment groups. Following STZ administration, pressor responsiveness to 1.0 µg ofU-46619(9,11-dideoxy-9 alpha,11 alpha-methanoepoxy prostaglandinF2 alpha) was decreased in diabetic compared with IIT animals (9.33 ± 0.54 vs. 11.94 ±0.29 mmHg (1 mmHg = 133.3 Pa)). Diabetes caused a similar decrease in thevasodilatory response to arginine vasopressin when compared with IIT animals (39.25 ± 7.54vs. 68.24 ± 4.75%). Diabetes was also associated with a shift in the primary site of resistancefrom the pulmonary arterial to the pulmonary venous bed. This shift was restored to normalfollowing pancreatic islet transplantation, but not IIT. IIT was also associated with significantalterations in the pattern of constrictor and dilator responses to U-46619 and argininevasopressin. Pulmonary venous vasoconstrictor responses to U-46619 were augmented whencompared with either control or diabetic animals, but not transplant. In addition, pulmonaryvenous vasoconstrictor responses in IIT animals were significantly greater than pulmonaryarterial responses in the same group, a finding that was unique to IIT animals. Finally, IITsignificantly augmented the pulmonary venous vasodilatory response to arginine vasopressinwhen compared with all other treatment groups. These data demonstrate significant alterations inpulmonary hemodynamic status of STZ diabetic female animals and suggest that pancreatic islettransplantation may be more beneficial than intensive insulin therapy in ameliorating thesechanges.Key words: segmental vascular resistance,insulin-dependent diabetes mellitus, lungs, U-46619, pressor responsiveness, gender effects.
Isolation of angiotensin converting enzyme (ACE) binding protein from human serum with an ACE affinity column
Authors: Thevananther Sundararajah , Brecher Arthur S
Published: April 2011

Immobilized angiotensin-converting enzyme (ACE) was utilized as an affinity ligand to isolate a naturally occurring ACE binding protein from normal human serum. The enzyme was isolated from solubilized bovine lung membrane preparations by lisinopril affinity chromatography. It had an estimated molecular weight of 180 000 and was recognized by the anti-ACE antibody for the rabbit testicular ACE in immunoblots. ACE was immobilized onto epoxy Sepharose as well as Affi-Gel 15. Immobilized ACE on Affi-Gel 15 had higher catalytic activity (0.176 U/mL) compared with the enzyme immobilized on epoxy Sepharose (0.00005 U/mL). Immobilized ACE served as the affinity ligand for the identification of the ACE binding protein in human serum with an estimated molecular weight of 14 000 as observed by SDS polyacrylamide gel electrophoresis. The identification and further characterization of ACE binding proteins in serum and tissues may facilitate the greater understanding of the endogenous regulation of this key enzyme, which is involved in blood pressure homeostasis.Key words: angiotensin-converting enzyme (ACE), ACE binding protein, ACE affinity column, human serum protein.
Pharmacological uses and perspectives of heavy water and deuterated compounds
Authors: Kushner D J , Baker Alison , Dunstall T G
Published: April 2011

Since the discovery of D2O (heavy water) and its use as a moderator in nuclear reactors, its biological effects have been extensively, although seldom deeply, studied. This article reviews these effects on whole animals, animal cells, and microorganisms. Both "solvent isotope effects," those due to the special properties of D2O as a solvent, and "deuterium isotope effects" (DIE), which result when D replaces H in many biological molecules, are considered. The low toxicity of D2O toward mammals is reflected in its widespread use for measuring water spaces in humans and other animals. Higher concentrations (usually >20% of body weight) can be toxic to animals and animal cells. Effects on the nervous system and the liver and on formation of different blood cells have been noted. At the cellular level, D2O may affect mitosis and membrane function. Protozoa are able to withstand up to 70% D2O. Algae and bacteria can adapt to grow in 100% D2O and can serve as sources of a large number of deuterated molecules. D2O increases heat stability of macromolecules but may decrease cellular heat stability, possibly as a result of inhibition of chaperonin formation. High D2O concentrations can reduce salt- and ethanol-induced hypertension in rats and protect mice from gamma irradation. Such concentrations are also used in boron neutron capture therapy to increase neutron penetration to boron compounds bound to malignant cells. D2O is more toxic to malignant than normal animal cells, but at concentrations too high for regular therapeutic use. D2O and deuterated drugs are widely used in studies of metabolism of drugs and toxic substances in humans and other animals. The deuterated forms of drugs often have different actions than the protonated forms. Some deuterated drugs show different transport processes. Most are more resistant to metabolic changes, especially those changes mediated by cytochrome P450 systems. Deuteration may also change the pathway of drug metabolism (metabolic switching). Changed metabolism may lead to increased duration of action and lower toxicity. It may also lead to lower activity, if the drug is normally changed to the active form in vivo. Deuteration can also lower the genotoxicity of the anticancer drug tamoxifen and other compounds. Deuteration increases effectiveness of long-chain fatty acids and fluoro-D-phenylalanine by preventing their breakdown by target microorganisms. A few deuterated antibiotics have been prepared, and their antimicrobial activity was found to be little changed. Their action on resistant bacteria has not been studied, but there is no reason to believe that they would be more effective against such bacteria. Insect resistance to insecticides is very often due to insecticide destruction through the cytochrome P450 system. Deuterated insecticides might well be more effective against resistant insects, but this potentially valuable possibility has not yet been studied.Key words: deuterium, heavy water, D2O, deuterium isotope effects.
Incommensurate frequencies of major vascular regulatory mechanisms
Authors: Lessard Andrée , Salevsky Fred C , Bachelard Hélène , Cupples William A
Published: April 2011

The dynamic relationship among three major vascular control mechanisms that operate on large fractions of cardiac output: arterial baroreflex and renal and mesenteric autoregulation, was investigated in conscious rats. Wistar and spontaneously hypertensive rats were studied in their home cages 10 days after implantation of pulsed Doppler flow probes. There was an oscillation of blood pressure centered at 0.45 Hz that is associated with operation of arterial baroreflexes. Hindquarters blood flow displayed a featureless, "1/f " power spectrum, in which no autoregulatory or baroreflex signatures could be discerned, although active control of resistance over a wide range of frequencies was evident. The renal pressure - flow transfer function was dominated by an autoregulatory mechanism with a resonance peak at 0.25 ± 0.01 Hz. In the mesenteric circulation an autoregulatory mechanism was seen with a resonance peak at 0.15 ± 0.01 Hz and another active mechanism was seen above 0.2 Hz that appeared from its negative admittance phase to be a baroreflex. The center frequencies of mesenteric and renal autoregulation and of the arterial baroreflex were related in a ratio of 1 : 1.7 ± 0.1 : 3.0 ± 0.2 (approximately 4:7:12). Such relatively high order ratios can be expected to minimize the possibility of phase locking and (or) entrainment among the various control mechanisms.Key words: flow, pressure, blood, dynamics, Wistar, spontaneously hypertensive rat (SHR).
Response component analysis of simple and complex cells of area 18 during depression of area 17
Authors: Chabli A , Fortin S , Shumikhina S , Molotchnikoff S
Published: April 2011

Simple and complex cells of visual areas of cats may be reliably classified according to the modulatory index (MI) of their responses. This investigation is aimed at analysing the MI in area 18 when a small region (about 200-400 µm in diameter) of area 17 was inactivated with a microinjection of GABA, in anesthetized cats. Cells were stimulated with sine-wave gratings whose orientation, spatial, and temporal frequencies were optimal for the studied unit. The AC and DC response components, and the MI were computed along with fast Fourier transforms of evoked discharges recorded as peristimulus time histograms. Results showed that these response components were relatively unaffected in simple cells, whereas complex cells exhibited large changes when area 17 was silenced. In particular, a large proportion of complex cells showed a MI greater than 1, thereby adopting a response pattern resembling simple cells. It is suggested that this subpopulation of complex cells receives a direct input from geniculate X cells.Key words: simple cells, complex cells, visual cortex, corticocortical influences, cats.
Effect of α-phenyl-N-tert-butylnitrone on diabetes and lipid peroxidation in BB rats
Authors: Iovino Giugetta , Kubow Stan , Marliss Errol B
Published: April 2011

Oxygen free radicals have been shown to interfere with pancreatic islet beta cell function and integrity, and have been implicated in autoimmune type 1 diabetes. We hypothesized that the spontaneous autoimmune type 1 diabetes of the BB rat would be prevented by in vivo administration of a free-radical spin trap, α-phenyl-N-tert-butylnitrone (PBN). Twenty-eight diabetes-prone (BBdp) and 13 non-diabetes-prone (BBn) rats received PBN (10 mg/kg) subcutaneously twice daily, and 27 BBdp and 12 BBn rats received saline as controls. Rats were treated from age 47 ± 6 days until diabetes onset or age 118 ± 7 days. PBN caused no growth, biochemical, or hematological side effects. Sixteen control BBdp rats became diabetic (BBd, mean age 77 ± 6 days) and six demonstrated impaired glucose tolerance (IGT rats). The incidence of diabetes and IGT was not different in PBN-treated BBdp rats. Saline-treated rats showed no differences in pancreatic malondialdehyde (MDA) contents of BBd, IGT rats, and the BBdp that did not develop diabetes, versus BBn rats (2.38 ± 0.35 nmoL/g). Among rats receiving PBN, BBn had lower pancreatic MDA than BBd and IGT rats (1.38 ± 0.15 vs. 1.88 ± 0.15 and 2.02 ± 0.24 nmoL/g, p < 0.05), but not than BBdp rats (1.78 ± 0.12 nmoL/g, ns). BBn rats receiving PBN also had lower pancreatic MDA than the saline controls (p < 0.05). Thus, PBN is remarkably nontoxic and is able to decrease MDA in the absence of the autoimmune process, but does not prevent diabetes. A combination of PBN with other complementary antioxidant agents may hold better promise for disease prevention.Key words: α-phenyl-N-tert-butylnitrone, type 1 diabetes mellitus, BB rats, lipid peroxidation, malondialdehyde, spin traps.
Effects of adenosine and acadesine on interstitial nucleosides and myocardial stunning in the pig
Authors: Lasley Robert D , Randhawa, Jr. Mohinder PS , Hegge Julia O , Mentzer, Jr. Robert M
Published: April 2011

5-Amino-4-imidazolecarboxamide riboside (AICAr) or acadesine has been proposed to exert cardioprotection by enhancing adenosine production in ischemic myocardium. However, there are conflicting reports on acadesine's effects in ischemic myocardium and few studies in which myocardial adenosine levels have been measured. The purpose of this study was to determine whether acadesine increases interstitial fluid adenosine levels and attenuates myocardial stunning or potentiates the effects of adenosine in the intact pig. In pentobarbital-anesthetized pigs, myocardial stunning was induced by 10 min left anterior descending coronary artery occlusion and 90 min reperfusion. Regional ventricular function was assessed by measuring systolic wall thickening, and interstitial nucleosides were estimated by cardiac microdialysis. Control hearts were compared with hearts treated with acadesine, adenosine, and adenosine plus acadesine. Adenosine pretreatment (100 µg·kg-1·min-1, intracoronary) immediately prior to ischemia increased interstitial adenosine levels 9-fold and improved postischemic functional recovery from a control value of 17.6 ± 4.1% to 43.6 ± 3.4% of preischemic systolic wall thickening. In contrast, acadesine (20 mg/kg i.v. bolus 10 min prior to ischemia + 0.5 mg·kg-1·min-1, i.v. infusion through 60 min reperfusion) had no effect on interstitial fluid adenosine levels or the recovery of regional function (21.5 ± 5.9% recovery), nor were the functional effects of adenosine potentiated by acadesine. These findings indicate that acadesine does not enhance myocardial adenosine levels, attenuate myocardial stunning, or potentiate the cardioprotective effects of adenosine in the pig.Key words: adenosine, acadesine, interstitial fluid, microdialysis, myocardial stunning.
Postnatal changes in regional blood flow during cold-induced shivering in sow-reared piglets
Authors: Lossec Gaëlle , Duchamp Claude , Lebreton Yves , Herpin Patrick
Published: April 2011

To determine whether newborn pigs are able to display adequate cardiovascular adjustments favouring shivering thermogenesis in skeletal muscles soon after birth, regional blood flow and fractional distribution of cardiac output were determined in 1-day-old (n = 6) and 5-day-old (n = 6) conscious piglets at thermal neutrality and during cold exposure, using coloured microspheres. Five-day-old piglets stayed with the sow before the experiment. The cold challenge was designed to induce a similar increase (~+90%) in heat production at both ages. Skeletal muscle blood flow increased with both age (p < 0.05) and cold exposure (p < 0.001), with the effect of cold being more pronounced in 5-day-old piglets than in 1-day-old piglets (+60%, p < 0.05). The difference between individual muscles increased with age, with fractional blood flow being 41% higher in rhomboideus than in longissimus thoracis muscle during cold exposure in 5-day-old piglets (p < 0.05). Cardiac output was similar at both ages and increased by 23% in the cold (p < 0.001). At 1 day of age, there was no redistribution of cardiac output among the internal organs during the cold challenge, while at 5 days of age, the increase in muscle fractional blood flow was associated with a reduction (p < 0.05) in the fraction of cardiac output reaching the skin (-24%), the small intestine (-21%), and the liver (-20%). In conclusion, these results suggest that there is a rapid postnatal improvement of cardiovascular adjustments favouring blood perfusion and probably heat production during cold-induced shivering in the most oxidative muscles studied. This cardiovascular response may play a role in the postnatal enhancement of thermoregulation in piglets.Key words: skeletal muscle, blood distribution, shivering thermogenesis, piglet, age.
Cyclic GMP and cyclic AMP induced changes in control and hypertrophic cardiac myocyte function interact through cyclic GMP affected cyclic-AMP phosphodiesterases
Authors: Weiss Harvey R , Gong Gary X , Straznicka Michaela , Yan Lin , Tse James , Scholz Peter M
Published: April 2011

We tested the hypothesis that the negative functional effects of cyclic GMP (cGMP) would be greater after increasing cyclic AMP (cAMP), because of the action of cGMP-affected cAMP phosphodiesterases in cardiac myocytes and that this effect would be altered in left ventricular hypertrophy (LVH) produced by aortic valve plication. Myocyte shortening data were collected using a video edge detector, and O2 consumption was measured by O2 electrodes during stimulation (5 ms, 1 Hz, in 2 mM Ca2+) from control (n = 7) and LVH (n = 7) dog ventricular myocytes. cAMP and cGMP were determined by a competitive binding assay. cAMP was increased by forskolin and milrinone (10-6 M). cGMP was increased with zaprinast and decreased by 1H-[1,2,4]oxadiazolo[4,3-a]quinoxilin-1-one (ODQ) both at 10-6 and 10-4 M, with and without forskolin or forskolin + milrinone. Zaprinast significantly decreased percent shortening in control (9 ± 1 to 7 ± 1%) and LVH (10 ± 1 to 7 ± 1%) myocytes. It increased cGMP in control (36 ± 5 to 52 ± 7 fmol/105 myocytes) and from the significantly higher baseline value in LVH (71 ± 12 to 104 ± 18 fmol/105 myocytes). ODQ increased myocyte function and decreased cGMP levels in control and LVH myocytes. Forskolin + milrinone increased cAMP levels in control (6 ± 1 to 15 ± 2 pmol/105 myocytes) and LVH (8 ± 1 to 18 ± 2 pmol/105 myocytes) myocytes, as did forskolin alone. They also significantly increased percent shortening. There were significant negative functional effects of zaprinast after forskolin + milrinone in control (15 ± 2 to 9 ± 1%), which were greater than zaprinast alone, and LVH (12 ± 1 to 9 ± 1%). This was associated with an increase in cGMP and a reduction in the increased cAMP induced by forskolin or milrinone. ODQ did not further increase function after forskolin or milrinone in control myocytes, despite lowering cGMP. However, it prevented the forskolin and milrinone induced increase in cAMP. In hypertrophy, ODQ lowered cGMP and increased function after forskolin. ODQ did not affect cAMP after forskolin and milrinone in LVH. Thus, the level of cGMP was inversely correlated with myocyte function. When cAMP levels were elevated, cGMP was still inversely correlated with myocyte function. This was, in part, related to alterations in cAMP. The interaction between cGMP and cAMP was altered in LVH myocytes.Key words: second messengers, cyclic AMP, cyclic GMP, cardiac myocyte function, cyclic GMP dependent cyclic-AMP phosphodiesterases, left ventricular hypertrophy, dog.
Effect of saline infusion on kidney and collecting duct function in atrial natriuretic peptide (ANP) gene "knockout" mice
Authors: Honrath U , Chong C K , Melo L G , Sonnenberg Harald
Published: April 2011

Atrial natriuretic peptide (ANP) is thought to play a role in renal regulation of salt balance by reducing tubular reabsorption of sodium and chloride. Therefore, in the chronic absence of this hormone, a defect of salt excretion should be evident. We used an ANP gene deletion model to test this premise. F2 homozygous mutant mice (-/-) and their wild-type littermates (+/+) were fed an 8% NaCl diet prior to an acute infusion of isotonic saline. Arterial blood pressures, renal excretions of salt and water, as well as collecting duct transport of fluid and electrolytes were measured. Pressures were significantly higher in -/- compared with +/+ mice (139 ± 4 vs. 101 ± 2 mmHg; 1 mmHg = 133.3 Pa). There was no difference in glomerular filtration rate (-/- = 0.84 ± 0.06; +/+ = 0.81 ± 0.04 mL·min-1·g-1 kidney weight). In the collecting duct, sodium and chloride reabsorptions were significantly higher in the -/- group than in the +/+ group. As a result, natriuresis and chloruresis were relatively reduced (UNaV: -/- = 8.6 ± 1.1; +/+ = 14.0 ± 1.1; UClV: -/- = 10.1 ± 1.4; +/+ = 16.0 ± 1.1 µmol·min-1·g-1 kidney weight). We conclude that the absence of endogenous ANP activity in mice on a high-salt diet subjected to acute saline infusion causes inappropriately high reabsorption of sodium and chloride in the medullary collecting duct, resulting in a relative defect in renal excretory capacity for salt.Key words: high-salt diet; water, sodium, chloride, and potassium transport.
Changes in spine and radius bone density during long-term hormone replacement
Authors: Blake Jennifer M , Ryan Eamonn D , Beaumont Lesley F , Webber Colin E
Published: April 2011

Lumbar spine and mid-radius bone mineral density was measured repeatedly in 48 postmenopausal women who completed 7 years of taking either a 500 mg·day-1 calcium supplement (n = 22) or calcium supplementation with hormone replacement therapy. The hormone replacement was either a low dose (n = 15) or a moderate dose (n = 11) regime. The purpose of the measurements was to establish the long-term pattern of change in bone mineral mass produced by continued hormone replacement. The calcium-only group lost bone mineral mass at the radius, while at the spine, bone was preserved. Low dose hormone replacement preserved radius bone. Moderate dose replacement increased bone mineral mass at the spine and preserved radius bone.Key words: calcium supplementation, long-term hormone replacement, lumbar spine bone mineral density, radius bone mineral density.
Nitric oxide, atrial natriuretic factor, and dynamic renal autoregulation
Authors: Wang Xuemei , Salevsky Fred C , Cupples William A
Published: April 2011

Inhibition of nitric oxide (NO) synthase by Nω-nitro-L-arginine methyl ester (L-NAME) increases arterial pressure (PA) and profoundly reduces renal blood flow (RBF). Here we report that L-NAME causes changes in the PA-RBF transfer function which suggest augmentation of the approximately 0.2 Hz autoregulatory mechanism. Attenuation of PA fluctuations from 0.06 to 0.11 Hz was enhanced, indicating increased efficacy of autoregulation. Also, the rate of gain reduction between 0.1 and 0.2 Hz increased while the associated phase peak became >= π/2 radians, indicating emergence of a substantial rate-sensitive component in this system so that autoregulatory responses to rapid PA changes become more vigorous. Infusion of L-arginine partly reversed the pressor response to L-NAME, but not the renal vasoconstriction or the changes in the transfer function. The ability of atrial natriuretic factor (ANF), which also acts via cGMP, to replace NO was assessed. ANF dose dependently reversed but did not prevent the pressor response to L-NAME, indicating additive responses. ANF did not restore RBF or reverse the changes in the transfer function induced by L-NAME. The rate-sensitive component that was enhanced by L-NAME remained prominent, suggesting that either ANF did not adequately replace cGMP or provision of a basal level of cGMP was not able to replace cGMP generated in response to NO. It is concluded that NO synthase inhibition changes RBF dynamics with the most notable change being increased contribution by a rate-sensitive component of the myogenic system.Key words: Nω-nitro-L-arginine methyl ester (L-NAME), renal blood flow, rat, blood pressure, transfer function.
The human renin infused rat: use as an in vivo model for the biological evaluation of human renin inhibitors
Authors: Bolger Gordon , Vigeant Jean-Claude , Liard Francine , Simoneau Bruno , Thibeault Diane , Pilote Louise , Lamarre Daniel , Jung Grace , Anderson Paul , Jaramillo Jorge
Published: April 2011

The human renin infused rat model (HRIRM) was used as an in vivo small-animal model for evaluating the efficacy of a collection of inhibitors of human renin. The intravenous infusion of recombinant human renin (2.4 µg·kg-1·min-1) in the ganglion-blocked, nephrectomized rat produced a mean blood pressor response of 47 ± 3 mmHg (1 mmHg = 133.3 Pa), which was reduced by captopril, enalkiren, and losartan in a dose-dependent manner following oral administration, with ED50values of 0.3 ± 0.1, 2.5 ± 0.9, and 5.2 ± 1.6 mg/kg, respectively. A series of peptidomimetic P2-P3butanediamide renin inhibitors inhibited purified recombinant human renin in vitro in a concentration-dependent manner, with IC50values ranging from 0.4 to 20 nM at pH 6.0, with a higher range of IC50values (0.8-80 nM) observed at pH 7.4. Following i.v. administration of renin inhibitors, the pressor response to infused human renin in the HRIRM was inhibited in a dose-dependent manner, with ED50values ranging from 4 to 600 µg/kg. The in vivo inhibition of human renin following i.v. administration in the rat correlated significantly better with the in vitro inhibition of human renin at pH 7.4 (r = 0.8) compared with pH 6.0 (r = 0.5). Oral administration of renin inhibitors also resulted in a dose-dependent inhibition of the pressor response to infused human renin, with ED50values ranging from 0.4 to 6.0 mg/kg and the identification of six renin inhibitors with an oral potency of <1 mg/kg. The ED50of renin inhibitors for inhibition of angiotensin I formation in vivo was highly correlated (r = 0.9) with the ED50for inhibition of the pressor response. These results demonstrate the high potency, dose dependence, and availability following oral administration of the butanediamide series of renin inhibitors.Key words: renin-angiotensin system, recombinant human renin, rat, renin inhibitors.
Synaptic vesicle recruitment for release explored by Monte Carlo simulation at the crayfish neuromuscular junction
Authors: Kennedy K M , Piper S T , Atwood H L
Published: April 2011

Neurotransmission at chemically transmitting synapses requires calcium-mediated fusion of synaptic vesicles with the presynaptic membrane. Utilizing ultrastructural information available for the crustacean excitatory neuromuscular junction, we developed a model that employs the Monte Carlo simulation technique to follow the entry and movement of Ca2+ ions at a presynaptic active zone, where synaptic vesicles are preferentially docked for release. The model includes interaction of Ca2+ with an intracellular buffer, and variable separation between calcium channels and vesicle-associated Ca2+-binding targets that react with Ca2+ to trigger vesicle fusion. The end point for vesicle recruitment for release was binding of four Ca2+ ions to the target controlling release. The results of the modeling experiments showed that intracellular structures that interfere with Ca2+ diffusion (in particular synaptic vesicles) influence recruitment or priming of vesicles for release. Vesicular recruitment is strongly influenced by the separation distance between an opened calcium channel and the target controlling release, and by the concentration and binding properties of the intracellular buffers, as in previous models. When a single opened calcium channel is very close to the target, a single synaptic vesicle can be recruited. However, many of the single-channel openings actuated by a nerve impulse are likely to be ineffective for release, although they contribute to the buildup of total intracellular Ca2+. Thus, the overall effectiveness of single calcium channels in causing vesicles to undergo exocytosis is likely quite low.Key words: synapse, Monte Carlo simulation, synaptic vesicle, active zone, vesicle recruitment, crayfish, calcium, calcium buffer.
Mediatophore, a protein supporting quantal acetylcholine release
Authors: Israël Maurice , Dunant Yves
Published: April 2011

After having reconstituted in artificial membranes the calcium-dependent acetylcholine release step, and shown that essential properties of the mechanism were preserved, we purified from Torpedo electric organ nerve terminals a protein, the mediatophore, able to release acetylcholine upon calcium action. A plasmid encoding for Torpedo mediatophore was introduced into cells deficient for acetylcholine release and for the expression of the cholinergic genomic locus defined by the co-regulated choline acetyltransferase and vesicular transporter genes. The transfected cells became able to release acetylcholine in response to a calcium influx in the form of quanta. The cells had to be loaded with acetylcholine since they did not synthesize it, and without transporter they could not concentrate it in vesicles. We may then attribute the observed quanta to mediatophores. We know from previous works that like the release mechanism, mediatophore is activated at high calcium concentrations and desensitized at low calcium concentrations. Therefore only the mediatophores localized within the calcium microdomain would be activated synchronously. Synaptic vesicles have been shown to take up calcium and those of the active zone are well situated to control the diffusion of the calcium microdomain and consequently the synchronization of mediatophores. If this was the case, synchronization of mediatophores would depend on vesicular docking and on proteins ensuring this process.Key words: acetylcholine release, presynaptic proteins, quantal release, mediatophore, transfection.
Central benzodiazepine involvement in clonidine cardiovascular actions
Authors: Castro José Luis , Ricci Daniel , Taira Carlos Alberto , Ramirez Agustín
Published: April 2011

It is well known that the GABAergic and noradrenergic systems play an important role in blood pressure and heart rate regulation. Benzodiazepines and beta-carbolines, respectively, increase or decrease the probability of chloride-channel opening induced by GABA. The aim of this study was to determine, in conscious rats, the interaction existing between the central alpha2-adrenoceptor stimulation induced by clonidine and the facilitation or impairment of benzodiazepine receptor activity through the administration of either diazepam, a benzodiazepine receptor agonist, or methyl 6,7-dimethoxy-4-ethyl-beta-carboline-3-carboxylate (DMCM), an inverse benzodiazepine agonist. Clonidine (5-10 µg, intracerebroventricularly) reduced heart rate and increased mean blood pressure by activation of central alpha2-adrenoceptors. Diazepam (2 mg/kg, intravenously (i.v.)) induced an increase in heart rate, while DMCM (0.3 mg/kg, i.v.) elicited a bradycardic effect. The bradycardic effects induced by both clonidine and DMCM were antagonized by the prior administration of methylatropine (1.5 mg/kg, i.v.). DMCM (0.3 mg/kg, i.v.) prevented the clonidine effects on heart rate and mean blood pressure, while diazepam (2 mg/kg, i.v.) failed to modify these effects. Our results suggest that the bradycardic effects of clonidine are mediated by a vagal stimulation and are related to the activation of a GABAergic pathway.Key words: blood pressure, clonidine, diazepam, methyl 6,7-dimethoxy-4-ethyl-beta-carboline-3-carboxylate (DMCM), heart rate.
Human hypoxic ventilatory response with blood dopamine content under intermittent hypoxic training
Authors: Serebrovskaya T V , Karaban I N , Kolesnikova E E , Mishunina T M , Kuzminskaya L A , Serebrovsky A N , Swanson R J
Published: April 2011

Adaptation to intermittent hypoxia can enhance a hypoxic ventilatory response (HVR) in healthy humans. Naturally occurring oscillations in blood dopamine (DA) level may modulate these responses. We have measured ventilatory response to hypoxia relative to blood DA concentration and its precursor DOPA before and after a 2-week course of intermittent hypoxic training (IHT). Eighteen healthy male subjects (mean 22.8 ± 2.1 years old) participated in the study. HVRs to isocapnic, progressive, hypoxic rebreathing were recorded and analyzed using piecewise linear approximation. Rebreathing lasted for 5-6 min until inspired O2 reached 8 to 7%. IHT consisted of three identical daily rebreathing sessions separated by 5-min breaks for 14 consecutive days. Before and after the 2-week course of IHT, blood was sampled from the antecubital vein to measure DA and DOPA content. The investigation associated pretraining high blood DA and DOPA values with low HVR (r = -0.66 and -0.75, respectively), elevated tidal volume (r = 0.58 and 0.37) and vital capacity (r = 0.69 and 0.58), and reduced respiratory frequency (r = -0.89 and -0.82). IHT produced no significant change in ventilatory responses to mild hypoxic challenge (PetO2 from 110 to 70-80 mmHg; 1 mmHg = 133.3 Pa) but elicited a 96% increase in ventilatory response to severe hypoxia (from 70-80 to 45 mmHg). Changes in HVRs were not accompanied by statistically significant shifts in blood DA content (24% change), although a twofold increase in DOPA concentration was observed. Individual subject's changes in DA and DOPA content were not correlated with HVR changes when these two parameters were evaluated in relation to the IHT. We hypothesize that DA flowing to the carotid body through the blood may provoke DA autoreceptor-mediated inhibition of endogenous DA synthesis-release, as shown in our baseline data.Key words: hypoxic ventilatory response, dopamine, intermittent hypoxia.
Thiopental inhibits nitric oxide production in rat aorta
Authors: Castillo Carlos , Asbun Juan , Escalante Bruno , Villalón Carlos M , López Pedro , Castillo Enrique F
Published: April 2011

We studied whether thiopental affects endothelial nitric oxide dependent vasodilator responses and nitrite production (an indicator of nitric oxide production) elicited by acetylcholine, histamine, and A23187 in rat aorta (artery in which nitric oxide is the main endothelial relaxant factor). In addition, we evaluated the barbiturate effect on nitric oxide synthase (NOS) activity in both rat aorta and kidney homogenates. Thiopental (10-100 µg/mL) reversibly inhibited the endothelium-dependent relaxation elicited by acetylcholine, histamine, and A23187. On the contrary, this anesthetic did not modify the endothelium-independent but cGMP-dependent relaxation elicited by sodium nitroprusside (1 nM - 1 µM) and nitroglycerin (1 nM - 1 µM), thus excluding an effect of thiopental on guanylate cyclase of vascular smooth muscle. Thiopental (100 µg/mL) inhibited both basal (87.8 ± 14.3%) and acetylcholine- or A23187-stimulated (78.6 ± 3.9 and 39.7 ± 5.6%, respectively) production of nitrites in aortic rings. In addition the barbiturate inhibited (100 µg/mL) the NOS (45 ± 4 and 42.8 ± 9%) in aortic and kidney homogenates, respectively (measured as 14C-labeled citrulline production). In conclusion, thiopental inhibition of endothelium-dependent relaxation and nitrite production in aortic rings strongly suggests an inhibitory effect on NOS. Thiopental inhibition of the NOS provides further support to this contention.Key words: thiopental, rat aorta, endothelium-dependent relaxation, nitric oxide synthesis.
Modification of vasodilator response in streptozotocin-induced diabetic rat
Authors: Bouchard Jean-François , Dumont Éric C , Lamontagne Daniel
Published: April 2011

Functional dilatory response in streptozotocin-induced diabetic rats was investigated using thoracic aortas, isolated hearts, and mesenteric beds. Dose-response curves to the PGI2 analogue iloprost on phenylephrine-preconstricted rings of diabetic rats and controls were comparable. In contrast, decreased vasodilation in diabetic rats was observed when dose-response curves to iloprost were performed in hearts and on phenylephrine-preconstricted mesenteric beds. Dose-response curves to forskolin, an adenylyl cyclase activator, performed with hearts and phenylephrine-preconstricted aortic rings and isolated mesenteric beds of diabetic rats and controls were comparable. However, a decreased vasodilation to the ATP-sensitive potassium channel (KATP) activator lemakalim was observed in diabetic hearts, but not in aortic rings and mesenteric beds. In conclusion, under our experimental conditions, diabetes mellitus affects the vasodilation to iloprost in both coronary and mesenteric beds, but not in the aorta. In the heart, this modification of vascular reactivity may be due to a decrease in KATP channel mediated response and not to a decreased activity of adenylyl cyclase. At this time, in the isolated mesenteric bed, the mechanism of this modification in vascular reactivity remains unknown.Key words: diabetes mellitus, iloprost, KATP channels, adenylyl cyclase, aorta, coronary circulation, mesenteric bed.
Intra-atrial communication and control of atrial natriuretic factor (ANF) release
Authors: Deng Yiming , Zhang Yunlong , Lang Mia , Kaufman Susan
Published: April 2011

Atrial natriuretic factor (ANF) release was studied in isolated perfused atria prepared from rats. When the vein-atrial junction (VAJ) was distended with an inflatable balloon, ANF release into the perfusate was greater in intact atria than in appendectomized atria. It was concluded that distention of the VAJ causes ANF release from the atrial appendage. A cascade experiment was then prepared whereby buffer from one isolated atrium perfused a second atrium. Although the VAJ of the first atrium could be distended by balloon, the atrial appendage was ligated so ANF was not secreted into the perfusate. The second atrium was intact, but no balloon was inserted. Despite the fact that there were no changes in intraluminal pressure, ANF secretion from the second atrium increased when the VAJ of the first atrium was distended. This response was blocked by the endothelin (ET) A receptor antagonist BQ-123. However, no distention-induced changes in ET-1 levels could be found in the perfusate from the first atrium. It is proposed that, in response to changes in distention of the VAJ, ANF is released remotely from the atrial appendage. The mediator does not appear to be ET-1 itself, but rather some factor that stimulates ET-1-induced ANF release within the tissue of the atrial appendage.Key words: atrial natriuretic factor (ANF) secretion, endothelin, atrial distention, BQ-123, atrial appendectomy.
Potential interactions of zinc in the neuroendocrine-endocrine disturbances of diabetes mellitus type 2
Authors: Tallman Diana L , Taylor Carla G
Published: April 2011

An accumulation of evidence implicates leptin, insulin, glucocorticoids, proopiomelanocortin (POMC), and neuropeptide Y (NPY) interactions as being integral to metabolic control associated with neuroendocrine-endocrine functioning. Dysfunction of neuroendocrine-endocrine interactions contributes to the metabolic disturbances of diabetes mellitus type 2 (DM-2). Since Zn has a direct impact on the healthy functioning of hormonal and neuropeptide balance, it is possible that altered Zn status and metabolism in DM-2 are involved in some of the metabolic dysfunctions of DM-2.Key words: zinc, insulin, leptin, neuropeptide Y, glucocorticoids, proopiomelanocortin (POMC), diabetes, obesity.