Cardioprotective effects of exogenous and endogenous hydrocortisone in the rabbit model of ischemia-reperfusion Efectos cardioprotectores de la hidrocortisona exógena y endógena en el modelo isquemia-reperfusión de conejo

Reducing the infarct size in acute myocardial infarction is one of the most important goals driving new drug research and development. During the last two decades, many clinical studies have found cardioprotective effects of corticosteroids, but their exact role in ischemic preconditioning remains questionable. The aim of the present study was to determine the protective effects of hydrocortisone sodium succinate on myocardial preconditioning in rabbit hearts. Twenty-four male New Zealand rabbits were divided randomly & equally in four groups: 1) control, 2) Infarct, 3) Ischemic preconditioning (IP) and 4) Hydrocortisone (HYD). The HYD group received 50mg/kg Hydrocortisone 45min before major ischemia. Serum levels of cardiac troponin-T(cTNT) and cortisole were measured before and after the protocols. Triphenyl-tetrazolium chloride staining was used to determine the infarcted area. In the present study, exogenous hydrocortisone decreased infarct size by 53 in comparison to the infarct group. Serum level of cortisole was increased in the IP and HYD groups, and was significant in the HYD group (p0.01). In conclusion, we showed that hydrocortisone has cardioprotective effects when injected before the onset of myocardial infarction. In addition, we have proposed for the first time that endogenous hydrocortisone may play a role in ischemic preconditioning phenomena

Role of slow pathway after nodal fast pathway ablation on the basic and rate-dependent properties of the isolated rabbit atrioventricular node

Introduction: The aim of this study was to obtain new insights into the possible relations between functional properties of slow concealed pathway and rate-dependent properties of the AV-node. Methods: Rate-dependent nodal properties of recovery, facilitation, and fatigue were characterized by stimulation protocols in one group of isolated superfused AV-Nodal rabbits (n=7). Small miniature lesions were made by delivering constant voltage (110 V-100 s) with unipolar silver electrode. Results: Fast pathway ablation significantly decreased facilitation and had no effect on fatigue and nodal refractoriness. The most important effect of fast pathway ablation was prolongation of the minimum conduction time. Conclusion: The FP-ablation revealed the presence of the concealed SP. Rate-dependent property of the node is dependent to dynamic interaction between concealed slow with slow pathway. The fast pathway was involved in the mechanism of facilitation

A study of the role of nitric oxide in the mechanism of action of hydroalcoholic extract of saffron (Crocus sativus) on the electrophysiological properties of the rabbit atrioventricular node

Biologically active substances of plant origin represent an essential branch of modern cardiovascular pharmacotherapy. Furthermore, drugs of plant origin have the advantage of weaker adverse effects and lower prices than synthetic drugs. Pharmacological studies and traditional medical literature point to the anti-ischemic and hypotensive effects of the Crocus sativus L. (Iridacea). The major goals of the present study were: (1) to determine the negative dormotrophic properties of a hydroalcoholic extract of saffron on an isolated AV node and (2) to establish the role of nitric oxide in the mediating effects of saffron on the electrophysiological properties of the AV node. This was an experimental study. Selective stimulation protocols were used to independently quantify AV nodal recovery, facilitation and fatigue. We used isolated perfused rabbit AV node preparation, in three groups (N=32); in each group, we assessed the plant's effect in comparison with the control. In the pilot study, we used different concentrations (A=9 x 10-2 mg/L, B=19 x 10-2 mg/L and C=27 x 10-2 mg/L) to select the optimum concentration (19 x 10-2 mg/L) of the hydroalcoholic extract of saffron. Saffron has a depressant effect on basic and rate-dependent properties of the AV node. We observed an increasing AVCT (38.8 ±4 to 41.7 ±4 msec) and FRP (157.6 ±3 to 163.7 ±4 msec). Also saffron increased the amount of facilitation and the magnitude of fatigue (5.9 ±0.3 to 11.1 ±1 msec). The NOS inhibitor (L-NAME) has a preventative effect on the depressant effect of saffron on AVCT and FRP

Effect of Achillea santolina on mice spermatogenesis

Achillea santolina, a common variety of Achillea in Golestan province of Iran has been used in traditional medicine for its anti - inflammatory properties. The effect of hydroalcoholic extract (300 mg/kg/day Intraperitoneally, for 20 days) of Achillea santolina on the spermatogenesis of mice was studied by the evaluation of morphologic characteristics by light microscope. The alterations observed were disorganized germ epithelium, exfoliation of immature germ cells, germ cell necrosis and increased number of metaphasfis in germinal epithelium of seminiferous tubules. We concluded that hydroalcoholic extract of Achillea santolina 300 mg/kg/day intraperitoneally for 20 days as a different variety of Achillea has antispermatogenic effect similar to Achillea millefolium on mice

Prolongation of AV nodal refractoriness by Ruta graveolens in isolated rat hearts

Objectives: To evaluate concentration-dependent effects of total extract of Rusta graveolens and its purified alkaloid fraction on the nodal basic and functional properties. Methods: In the present experimental study, we used the Langendorff model for perfusion of isolated rat hearts to determine the effects of various concentrations of methanolic extract of Rue (1.25 × 10-6 weight per volume percent W/V; 2.5 × 10-6% W/V; 3.7 × 10-6 % W/ V) and total alkaloid of Rue (0.25 × 10-6% W/V; 0.5 × 10-6% W/V) on electrophysiological properties of cardiac tissue. Selective stimulation protocols were used to independently quantify atrioventricular (AV) nodal recovery, facilitation, and fatigue. We used 3 groups (N=24) of isolated perfused rat AV nodal preparations to assess the effect of Rue extracts. The study was carried out in October 2006 in the electrophysiology laboratory of the Cardiovascular Research Center of Golestan University of Medical Sciences, Golestan, Gorgan, Iran. Results: Our results showed that both the total plant extract and the alkaloid fraction of Ruta graveolens had a similar trend of action on nodal conduction time and refractorines. Furthermore, we observed increased atrioventricular conduction time (83±4 to 108±5 msec) and functional refractory period (157.6±3 to 163.7±4 msec) at a maximum concentration of 3.75 × 10-6% W/V. Conclusion: The above results indicated a potential antiarrhythmic effect of Ruta graveolens in treating supra ventricular tachyarrhythmia

The effect of aqueous extract of Crocus sativus on the electrophysiological properties of isolated perfused rabbit AV-node

In the present study we used isolated perfused AV-node of rabbit as an experimental model to determine the effect of various concentrations of extract of C. sativus (A = 9×10⁻², B = 19×10⁻², C = 28×10⁻², D = 37×10⁻² mg L⁻¹) on electrophysiological properties of isolated heart. Selective stimulation protocols were used to independently quantify AV nodal recovery, facilitation and fatigue in 12 rabbits. Our results showed concentration dependent depressant effects of aqueous extract of C. sativus on Wenchebach Cycle Length (WBCL), AV Conduction Time (AVCT), Functional Refractory Periods (FRP). C. sativus (28×10-2 mg L-1) prolonged AVCT from 44.4±5 (control) to 52.2±4 m sec, Rate-dependent properties such as Facilitation and fatigue significantly increased by 19×10⁻² mg L ⁻¹ of C. sativus. In control group magnitude of fatigue was 6.7±0.6 and increased by Saffron to 20±11.5 (p< 0.05). The effect of extract was prominent on fast pathway. The above results indicated differential effects of C. sativus on slow and fast pathways which has a dominant role on the fast pathway. This research for the first time has explained the role of saffron on the protective mechanism of artrioventricular node against supraventricular arrhythmia. These results showed the non-specific effect of saffron on the transitional cells of fast nodal pathway which was manifested as a rate-independent increase of basic and functional (facilitation and fatigue) parameters of artrioventricular node. © 2006 Asian Network for Scientific Information

Altered levels of nodal excitability by rate-dependent inhibitory effects of essential oil of Citrus aurantium on the electrophysiological properties of isolated perfused rabbit AV-Node. Protective role in the prevention of ouabain toxicity [Alteración de los niveles de excitabilidad nodal por efectos inhibitorios velocidad-dependiente del aceite esencial de Citrus aurantium sobre las propiedades electrofisiológicas del nodo AV aislado y perfundido de conejo. Papel protector en la prevención de toxicidad por ouabaína]

Treatment of supraventricular arrhythmia includes a wide range of medical interventions. Herbal remedies are suitable alternatives to synthetic drugs due to their availability, minimal side effects and lower price. Pharmacological studies and traditional medical literature point to the cardiovascular effects of Citrus aurantium L. (Rutaceae) in many instances. In the present study we used isolated perfused AV-node of rabbit as an experimental model to determine the effect of various concentrations of essential oil of C. aurantium (0.1-0.3 v/v) on the nodal conduction time and refractoriness of an isolated rabbit AV-nodal preparations. Selective stimulation protocols were used to independently quantify AV nodal recovery, facilitation and fatigue in 18 rabbits. Our results showed concentration-dependent and rate-independent suppressive effects of essence of C. aurantium on the Wenchebach cycle length (WBCL), AV Conduction Time (AVCT) and effective and functional refractory periods (ERP & FRP). Functional properties such as facilitation and fatigue were significantly increased by this plant. Citrus aurantium plays a protective role against the toxic effects of ouabaine by increasing AV nodal conduction time and refractoriness. The above results indicated differential effects of C. aurantium on slow and fast pathways, with a dominant role on fast pathways. This research has explained the protective role of C. aurantium on ouabaine toxicity. All results indicated the potential anti-arrhythmic effects of C. aurantium in treating supraventricular tachyarrhythmia

Age-dependent dynamic electrophysiological field potential behavior of atrioventricular node during experimental AF in rabbit

Introduction: Electrophysiological studies have demonstrated a relationship between aging and atrioventricular (AV) nodal conduction and refractoriness. The aim of the present study was to determine the effects of nodal aging on dynamic AV nodal field potential recording during atrial fibrillation (AF) in rabbit. Methods: Two groups of male New Zealand rabbits (neonatal 2-week-olds and adult 12-week-olds, n=14 each group) were used in this study. Field potential recordings were executed by silver electrodes with a diameter of 100 μM. Pre-defined stimulation protocols of AF, zone of concealment (ZOC) and concealed conduction for determination of the electrophysiological properties of the AV-node were separately applied in each group. Results: Results of the study showed that mean ventricular rate (HH) during atrial fibrillation was smaller in the neonatal compared to the adult group (229.1 ± 8.3 versus 198.6 ± 13.1 msec, respectively). Also ventricular distribution conduction pattern showed two peaks in the adult and one peak in the neonatal group. Analyzing the zone of concealment in different rates and after concealed beat indicated that the zone of concealment in neonates were significantly smaller compared with adult rabbits and increasing zone of concealment, which is accompanied with increasing ventricular rate is abrogated in the neonatal group (5 ± 3.3, 12.2 ± 6.3 msec). Conclusion: The results of this study showed that the electrophysiological protective dynamic behavior of the AV node during atrial fibrillation is smaller in neonates compared to adults. Narrower zone of concealment, abrogation rate dependent trend of the zone of concealment and shorter nodal refractoriness can account for the specific nodal electrophysiological properties of neonatal rabbits

Frequency-dependent anti arrhythmic effects of crataegus monogyna on the extracellular field potential recordings in the rabbit atrioventricular node, an experimental model of AF

Introduction: Despite extensive studies that have been performed on the effects of Crataegus monogyna in cardiovascular diseases, only few investigations have addressed the antiarrhythmic properties of this plant. Aims of the present study were: 1) To determine the protective role of methanolic extract of C. monogyna on the rate-dependent model and the concealed conduction of the AV node. 2) To explore the role of Na+-K+ ATPase in the protective role of C. monogyna Methods: Male New Zealand rabbits (1.5-2kg) were used in all experiments. Stimulation protocols were used to measure basic and rate-dependent AV nodal properties (recovery, atrial fibrilation and zone of concealment) in two groups (N=14). In the first group, all the stimulation protocols were performed before and after the administration of different concentrations of C. monogyna extract (n=7), while in the second group (n=7), all stimulation protocols were carried out in the presence of ouabaine (0.05 μM) and the plant extract. Results: Basic and rate-dependent properties of the AV node were inhibited after the addition of the extract of C. monogyna to Kerebs Henselite solution. At the maximum concentration of C. monogyna (30 mg/l), WBCL cycle length was significantly increased from 156.5±3.4 to 173±5.8 ms and the nodal functional refractory period was prolonged from 164.4±4.1 to 182.7±3.8 ms (P&lt;0.05). Significant decreases of ventricular rhythm were recorded in both selective concentrations of the plant extract. The depressant electrophysiological effect of C. monogyna on the AV node was not abolished by ouabaine, a selective inhibitor of Na+-K+ ATPase enzyme. Conclusion: The results showed a potential anti-arrhythmic and protective effect for C. monogyna. The effect of the plant extract in increasing nodal refractory period and widening of the concealment zone might be the major mechanisms involved. The protective role of C. monogyna was not related to the Na+-K+ ATPase activity

A Likelihood Ratio Test Approach to Profile Monitoring in Tourism Industry

A new statistical profile monitoring technique to monitor and detect changes in logistic profiles with an application in the tourism industry is presented in this paper. In the statistical process control literature, profile is usually referred to as a relationship between a response variable and one or more explanatory variables. In the tourism case study presented in this paper, time is considered as the explanatory variable and tourism satisfaction as the response variable. The Likelihood ratio test is used as a vehicle to detect any changes in the satisfaction profile in phase II of profile monitoring. The performance of the proposed method is evaluated using the average run length criterion. The numerical data indicate satisfactory results for the proposed approach