MicroRNAs in avian influenza virus H9N2-infected and non-infected chicken embryo fibroblasts.

There is limited information about microRNAs (miR-NAs) in H9N2 subtype influenza virus-infected chicken cells or tissues. In this study, 10,487,469 and 13,119,795 reads were obtained from in-fected and non-infected chicken embryo fibroblasts, respectively. Seven hundred and thirty-six and 1004 miRNAs, including mature miRNAs and precursors, were obtained from the infected and non-infected fibro-blasts, respectively. Of those miRNAs, 48 were expressed differently between the groups: 37 had a low expression level in the infected chick-en embryo fibroblast, and the remaining 11 had a higher expression level. Every miRNA was predicted to target immune response-related genes. It has been found that some of the miRNAs, such as gga-miR-146c, gga-miR-181a, gga-miR-181b, gga-miR-30b, gga-miR-30c, gga-miR-30e, and gga-miR-455, are expressed differently in other types of influenza-infected chicken cells or tissues.

Naloxone inhibits arrhythmias induced by coronary artery occlusion and reperfusion in anaesthetized dogs.

The intravenous administration of naloxone 2 min before coronary artery occlusion in anaesthetized dogs reduced the incidence and severity of cardiac arrhythmias during coronary occlusion (20 min) and reperfusion (120 min) in a dose-related manner. It also reduced the mortality. At a dose of 1 mg kg-1 (the maximum dose used in this study) naloxone abolished the appearance of the life threatening ventricular fibrillation (VF) and ventricular tachycardia (VT) and as a consequence all dogs in this group survived. The results suggest a possible involvement of endogenous opioid peptides in arrhythmogenesis during coronary occlusion and reperfusion in the dog.

[Reduction of incidence of ischemia-reperfusion induced ventricular fibrillation by captopril].

To investigate the role of catecholamine and prostacyclin in ischemia reperfusion-induced ventricular fibrillation, experiments were performed in rat hearts using methods of radioimmunoassay and fluorohistochemistry. Regional myocardial ischemia was induced by ligation of the left coronary artery followed by reperfusion. In the ischemia reperfusion group, ventricular fibrillation during reperfusion took place in 78% of the hearts. In the group pretreated with captopril, the incidence of ventricular fibrillation decreased significantly (65.5%). In comparison with the ischemia reperfusion group, myocardial catecholamine content and 6-keto-PGF1 alpha of the captopril group were significantly increased (P < 0.01) while thromboxane B2 (TxB2) and TxB2/6-keto-PGF1 alpha were decreased (P < 0.01). In Ang II group, infusion of angiotensin II reversed the protective effect of captopril and restored the incidence of ventricular fibrillation (85%), while myocardial catecholamine content was not different from the ischemia reperfusion group (P > 0.05). Above results suggest that reduction of the incidence of ischemia reperfusion-induced ventricular fibrillation by captopril may be due to its inhibition on angiotensin II production with consequent reduction of the release of myocardial catecholamine, suppression of TxB2 and promotion of PGI2 synthesis.

[Different changes in renal sympathetic nerve activity and adrenal sympathetic nerve activity produced by hemorrhage].

The present study was undertaken to investigate the changes in renal sympathetic nerve activity (RSNA) and adrenal sympathetic nerve activity (AdSNA) due to acute hemorrhage in anesthetized rabbits. The animals were bled to a mean arterial pressure (MAP) of 5.3 kPa within 10 minutes from the femoral artery. Acute hemorrhage elicited a biphasic responses of RSNA with an initial excitation and a late inhibition during hemorrhage. But hemorrhage only induced a lasting excitation in AdSNA which could be abolished by sino-aortic denervation (SAD). Bilateral vagotomy either before or after hemorrhage could reverse the late inhibition in RSNA, but did not abolish the excitation in AdSNA. Intravenous injection of naloxone or microinjection of naloxone into rostral ventrolateral medulla (RVLM) could reverse the late inhibition in RSNA, but had no significant effect on the initial excitation in RSNA and AdSNA during hemorrhage. Hemorrhage-induced heart (HR) change was similar that in RSNA, but could not be reversed by naloxone. These results indicate that the late inhibition in RSNA is mediated by inputs from vagus nerves and opiate peptide, particularly that in RVLM, and the excitation in AdSNA during hemorrhage is related to arterial baroreceptor reflex.

[Effects of intracisternal injection of naloxone on the depressor response to stimulation of renal afferent nerve in rabbits].

The purpose of this study was to observe the effects of opioid receptor and alpha-adrenergic receptors in the lower brain stem on the depressor response to electrical stimulation of renal afferent nerve, using intracisternal injection of blockers of these receptors. Experiments were conducted in sodium pentobarbital-anesthetized rabbits. The intracisternal injection (ict) of artificial cerebrospinal fluid (CSF) did not greatly affect the depressor response to stimulation of renal afferent nerve (RAS) and of aortic nerve (ANS). Ict of 550 nmol naloxone significantly inhibited the depressor response to RAS (P less than 0.05) but enhanced the depressor response to ANS (P less than 0.05). Ict of 335 nmol phentolamine significantly inhibited the depressor response to both RAS and ANS. Ict of naloxone reversed the phentolamine inhibition of the depressor response to ANS but did not affect the phentolamine inhibition of the depressor response to RAS. Ict of both naloxone and phentolamine did not affect the inhibitory interaction between the RAS-induced depressor and aortic baroreflex. Ict of phentolamine significantly decreased MAP, and ict of naloxone did not decrease MAP but reversed the decrease in MAP by ict of phentolamine. These data suggest that the activation of opioid receptors in the lower brain stem enhances the depressor response to RAS and attenuates the depressor response to ANS. Moreover, activation of alpha-adrenergic receptors in the lower brain stem facilitates the depressor response to RAS and ANS.

[The role of G protein in Leu-enkephalin induced Ca2+ release from intracellular pool in myocytes].

The mechanism underlying Leu-enkephalin (LEK) induced increase of the intracellular concentration of free calcium ([Ca2+]i) in rat ventricular myocytes was investigated by using fura-2 AM as a calcium indicator. The results were as follows: LEK (60 mumol/L) elevated [Ca2+]i in ventricular myocytes no matter whether extracellular calcium was removed or not. However, the effect was no longer observed when the calcium in the intracellular pool was depleted by caffeine (5 mmol/L). The LEK effect could also be blocked by naloxone (100 mumol/L), pretreatment of the cells with PTX (200 ng/L) 8-10 h or procain (2 mmol/L). The results suggest that the LEK effect is mediated by coupling of G-protein with delta-receptor that induced Ca2+ release from the intracellular pool in myocytes.

[Effect of angiotensin II on c-fos expression and protein synthesis in cultured rat myocardial cells].

The present study was to investigate the effects of angiotensin II on c-fos mRNA expression and protein synthesis in cultured neonatal rat myocardial cells. The results showed that angiotensin II induced c-fos mRNA expression, increased protein content in a dose-dependent manner and stimulated 3H-leucine incorporation rate. All these effects were blocked by angiotensin II receptor antagonist saralasin. The angiotensin II-induced expression of c-fos gene was also blocked by Ca2+ channel antagonist nicardipine.

[The role of G protein, protein kinase C and Na(+)-H+ exchanger in endothelin-1-induced cardiomyocyte hypertrophic responses].

Endothelin-1 (ET-1) has been shown to be a potent growth factor and to induce cardiac hypertrophy. In the present study, we examined the role of G protein, protein kinase C (PKC) and Na(+)-H+ exchanger in ET-1-induced cardiac hypertrophy in cultured neonatal rat cardiac myocytes. ET-1 (10(-10)-10(-7) mol/L) induced promotion of 3H-leucine incorporation, increase in cell protein content and cell surface area in a dose-dependent manner with EC50 value of 5.2 x 10(-10), 5.2 x 10(-10) and 7.3 x 10(-10) mol/L respectively. All of these ET-1-induced cardiomyocyte hypertrophic responses were completely blocked by pretreatment with staurosporine (2 nmol/L), a protein kinase C inhibitor, and stimulated by 4-phorbol, 12-myristate, 13-acetate (PMA) (10(-8)-10(-6) mol/L), a protein kinase C activator, in a dose-dependent manner. Pretreatment of amiloride (10(-4) mol/L), a Na(+)-H+ exchange inhibitor completely inhibited the ET-1-induced, but not PMA-induced cardiomyocyte hypertrophic responses. The ET-1-induced increase in cardiomyocyte protein synthesis and cell surface area was significantly inhibited by pretreatment with pertussis toxin (150 ng/ml). These results suggest that ET-1-induced cardiomyocyte hypertrophy was linked with pertussis toxin sensitive G protein, and PKC and Na(+)-H+ exchange may be an important intracellular signaling transduction pathway during ET-1-induced cardiac hypertrophy in cultured neonatal rat cardiac myocytes.

[Effects of morphine of different concentrations on myocardial action potential].

The effects of morphine at different concentrations on myocardial action potential were studied in isolated right ventricular papillary muscles of the guinea pig. It was observed that morphine at low concentrations (0.2-1.6 mumol/L) shortened the action potential duration (ADP) and effective refractory period (ERP) in a concentration dependent manner. These effects could be abolished by naloxone (1 mumol/L), phentolamine, tetraethylammonium (TEA) and cesium chloride (Cs+), but not by verapamil. On the other hand, morphine at high concentrations (15-120 mumol/L) prolonged ADP and ERP in a concentration dependent manner. The effects were unaffected by low dose of naloxone (1.2 mumol/L) but were abolished by high dose of naloxone (10 mumol/L), phentolamine, TEA, Cs+ and verapamil. These results suggest that morphine at low and high concentrations might stimulate different subtypes of opioid receptors. The effects of morphine in low concentrations are associated with the activation of potassium channel, whereas the effects of morphine at high concentrations are associated with the activation of potassium channel, calcium channel or calcium activated potassium channel. The action of opioid receptor was closely related to alpha adrenoreceptors.

[Effect of hypertonic NaCl solution on arterial pressure compensation after hemorrhage in rats].

Rats were bled within 5 min in lowering mean arterial pressure (MAP) to 25 mmHg and were subsequently infused intravenously with hypertonic (7.5% NaCl) or normal saline in a volume equal to 10% of the amount of the lost blood. Intravenous infusion of hypertonic saline significantly facilitated posthemorrhagic recovery of MAP, which was markedly attenuated by 6-hydroxydopamine or Captopril. When these two drugs were used together, the attenuation effect was complete. While hypertonic saline significantly increased plasma Na+ concentration, normal saline only gave rise to a decrease. Intracerebroventricular injection of hypertonic NaCl solution also facilitated the recovery of MAP significantly. These results suggest that after hemorrhage increased plasma Na+ concentration following i.v. of a small amount of hypertonic saline may act on the central nervous system and activate sympathetic nervous system and renin angiotensin system to facilitate a rapid recovery of MAP.

Effects of beta-endorphin on the contraction and electrical activity of the isolated perfused rat heart.

beta-Endorphin at pharmacological doses reduced both the left ventricular systolic and diastolic pressures of the isolated rat heart. The reduction in the diastolic ventricular pressure was does dependent. Beta-Endorphin also altered the electrical activities of the isolated heart, disturbing the normal electrocardiogram pattern. The degree of disturbance was also dose dependent. Naloxone itself did not produce any effect. However it antagonized the depressant effects and completely abolished the effect of beta-endorphin on the electrical activity of the heart, indicating that beta-endorphin acts via the naloxone sensitive receptors. The results suggest a possible regulatory role of intracardiac endogenous opioid peptides in the cardiac functions.

Effects of reserpine treatment on arrhythmogenesis during ischaemia and reperfusion in the isolated rat heart.

1. The effects of reserpine treatment on the myocardial contents of catecholamines and enkephalins and the incidence of ventricular arrhythmias during ischaemia and reperfusion in the isolated rat heart were studied. 2. Reserpine treatment almost completely depleted the heart of noradrenaline (NA). It also significantly depleted the heart of adrenaline and dopamines. It did not, however, alter the myocardial contents of enkephalins. 3. Reserpine-treatment attenuated significantly, but did not abolish, cardiac arrhythmias induced by ischaemia and reperfusion in the isolated heart preparation. 4. The results of the present study indicate that myocardial catecholamines especially NA are a contributing factor to arrhythmogenesis during ischaemia and reperfusion.

A cardiac antiarrhythmic screening test using the isolated ischaemic perfused rat heart preparation.

Ventricular fibrillation was induced by myocardial ischaemia and reperfusion in the isolated perfused rat heart. The dose-response effectiveness for the prototype antiarrhythmic drugs, propranolol, quinidine and lidocaine in converting the induced ventricular fibrillation to sinus rhythm was determined. The test is easy to perform and does not require skillful surgical procedure and long time for observation. In addition, no arrhythmogenic drugs are used and the amount of substance needed for the test is very small. It is suggested that this simple test be used as a cardiac antiarrhythmic screening test for antiarrhythmic drugs.

Sequential external counterpulsation (SECP) in China.

A new SECP was developed and is currently successfully used in more than 120 clinics in China. This sequenced counterpulsation device has the effect of milking more blood as pressure is applied on the extremities in succession (first distally then proximally) and in decreasing values (265 to 200 mm Hg). In comparison of the 4 types of counterpulsation, namely nonsequenced leg and 4 limb counterpulsation, and sequenced 4 limb and 4 limb with buttock balloons, the SECP with buttock balloons method raised the DA to appreciably higher levels with respect to DA amplitude and area. DA was raised 43.9% higher than that obtained with 4 limb SECP alone. From our experimental and clinical results, we conclude that SECP with buttock balloons is a far more effective method providing greater diastolic augmentation than previously reported in the literature. Two hundred angina and 52 AMI patients who had undergone the SECP treatment constitute the basis of this report. The present work represents an analysis of 6 yrs experience with studies on the design, development and clinical evaluation of the SECP method. Ninety-seven percent of the angina patients obtained long-term symptomatic relief. Relapse was minimal. In 95.7% of the AMI patients chest pain or shock symptoms were rapidly relieved. SECP with high DA appears to be very effective in improving myocardial blood supply and ventricular function. Moreover, the simplicity and advantages of this noninvasive sequenced counterpulsation method have been reported (1063 cases) from 31 clinics in China. This method is convenient, safe, and far more effective than conventional drug therapy for patients with acute and chronic ischemic myocardial disease.