Biomedical subjects

Xiong Zhang

Publications and source records attributed to Xiong Zhang.

26 records · Page 2Linked to original sources

PubMed2003

[Negative inotropic effect of meperidine in rat ventricular muscle and the underlying mechanism].

The purpose of the present study was to investigate the effect of meperidine on rat ventricular muscle. Cardiac function was assessed in Langendorff-perfused rat hearts and intracellular calcium level was recorded in enzymatically isolated rat ventricular myocytes using spectrofluorometric techniques. To explore the underlying mechanism, whole-cell configuration of patch-clamp technique was used to record L-type Ca(2+) current. The results showed that meperidine decreased the product of heart rate and left ventricular developed pressure (LVDP HR), maximal rate of the left ventricular pressure increase (LV +dP/dt(max)) and decrease (LV -dP/dt(max)), but increased left ventricular end-diastolic pressure in a dose-dependent manner (0-1000 micromol/L). Meperidine also produced a dose-dependent reduction in electrically induced [Ca(2+)](i) transient amplitude and an increase in diastolic [Ca(2+)](i) baseline level, but did not alter the caffeine (20 mmol/L) induced Ca(2+) release from intracellular ryanodine-sensitive Ca(2+) stores. Meperidine at 100 micromol/L inhibited L-type Ca(2+) current to 67.4 10.1% of control but did not affect the voltage dependency of activation and inactivation. The inhibitory effect of meperidine on Ca(2+) current could not be prevented by pretreatment with the opioid receptor antagonist naloxone. These data suggest that meperidine exerts a negative inotropic effect by inhibiting L-type Ca(2+) current. The lack of effect of naloxone implies that the action is independent of the opioid receptor.

Animals↗

PubMed2003

Salvia miltiorrhiza attenuates the changes in contraction and intracellular calcium induced by anoxia and reoxygenation in rat cardiomyocytes.

The aim of the present study is to investigate the effect of Salvia miltiorrhiza (SM) on contraction and the intracellular calcium of isolated ventricular myocytes during normoxia or anoxia and reoxygenation using a video tracking system and spectrofluorometry. Cardiac ventricular myocytes were isolated enzymatically by collagenase and exposed to 5 min of anoxia followed by 10 min of reoxygenation. SM (1-9 g/L) depressed both contraction and the [Ca(2+)](i) transient in a dose-dependent manner. SM did not affect the diastolic calcium level and the sarcolemmal Ca(2+) channel of myocytes but decreased the caffeine-induced calcium release. During anoxia, the +/-dL/dtmax, amplitudes of contraction (dL) of cell contraction and [Ca(2+)](i) transients were decreased, while the diastolic calcium level was increased. None of the parameters returned to the pre-anoxia level during reoxygenaton. However, SM (3 g/L) did attenuate the changes in cell contraction and intracellular calcium induced by anoxia and reoxygenation. It is concluded that SM has different effects on normoxic and anoxic cardiomyocytes. The SM-induced reduction of changes in contraction and intracellular calcium induced by anoxia/reoxygenation indicates that SM may be beneficial for cardiac tissue in recovery of mechanical function and intracellular calcium homeostasis.

Animals↗

PubMed2003

Age-related increase of plasma platelet-activating factor concentrations in Chinese.

BACKGROUND: Platelet-activating factor (PAF) is a potent bioactive phospholipid, which may be one of the determinants of atherogenesis. The purpose of this study was to investigate the relationship between the concentrations of plasma platelet-activating factor and age in a common Chinese population. METHODS: Two-hundred seventy-nine Han nation subjects (male: n=162; female: n=117) who had visited two hospitals for overall health survey, as an annual medical check-up or for other reasons by clinical examinations were recruited and divided into six age groups (21-30, 31-40, 41-50, 51-60, 61-70, 71-80 years). PAF was extracted from their plasma and purified by thin-layer chromatography (TLC). The PAF concentrations were detected by radioimmunoassay. RESULTS: The PAF concentrations (pg/ml) in plasma showed significantly age-related increase (r=0.3348, P<0.01, n=279). In the 21-30-year group, the PAF concentration was 338+/-96 pg/ml. Except for the 31-40-year group, the PAF concentrations in other four groups were all higher than that of the 21-30-year group (P<0.05, P<0.01, P<0.001 and P<0.001, respectively). CONCLUSIONS: Considering PAF is one of the key factors relevant to progression of atherogenesis, and the high concentrations of plasma PAF may therefore serve as a marker for the risk of atherosclerosis. Adjustment of the concentrations of plasma PAF correlated with aging may be helpful to reducing the prevalence rate of multi-senile arteriosclerosis occlusive diseases.

Adult↗

PubMed2003

[Improvement of cardiomyocyte isolation for different purposes].

OBJECTIVE: To improve the methods of isolating single ventricular myocytes for purposes of different experiments. METHODS: The cardiac ventricular myocytes were isolated enzymatically by Langendorff perfusion technique at constant flow rate. The patch clamp whole-cell recording, a spectrofluorometric method and a video tracking system were used to verify the basic electrophysiological properties, intracellular calcium transient and cell contraction of the single myocytes. RESULTS: The resting membrance potential of the myocyte was (-74.06+/-4.54)mV. The whole-cell sodium, potassium and calcium currents, intracellular calcium transients and contractile properties were stable and typical. CONCLUSION: The myocytes obtained by adjusting perfusion parameters are well suited for electrophysiological recording, intracellular calcium and single cell contraction measurements.

Action Potentials↗

PubMed2003

[Effects of pethidine on cardiac electrophysiological properties].

OBJECTIVE: To investigate the effects of pethidine on electrophysiological properties of the isolated ventricular myocytes and the underlying mechanism. METHODS: Langendorff was applied to perfuse rat heart model and whole-cell current clamp and voltage clamp techniques were used. RESULTS: Pethidine decreased heart rate (HR) in a concentration dependent manner and caused severe atrioventricular block (AVB) at >or=250 micromol/L. Pethidine reduced action potential amplitude and maximal rate of depolarization, prolonged action potential duration. Pethidine at 100 micromol/L decreased sodium currents (I(Na)), transient outward potassium currents (I(to)), delayed rectifier potassium currents (I(k)) and L-type calcium currents (I(Ca.L)) to (60.7+/-6.9)%, (55.4+/-5.6)%, (65.1+/-8.0)% and (67.4+/-10.1)% of control levels,respectively. These effects could be recovered by washout. Naloxone, an opioid receptor antagonist, could not abolish the effects of pethidine on ionic currents. CONCLUSION: Pethidine decreased HR and induced AVB, which may be related to the inhibition of I(Na), I(to), I(k) and I(Ca-L) of heart. The depression of cardiac currents is not mediated by opioid receptor.

Action Potentials↗

PubMed2003

[NO/cGMP signal pathway involved in the disturbance of calcium homeostasis in vascular smooth muscle during the late phase of sepsis].

OBJECTIVE: To evaluate the alterations in calcium metabolism of the vascular smooth muscle of rat thoracic aorta in the late phase of sepsis and to investigate the involvement of nitric oxide (NO)/cyclic-GMP(cGMP) signal transduction pathway in the sepsis-induced vascular hyporeactivity. METHODS: Male Sprague-Dawley rats were subjected to sepsis by cecal ligation and puncture (CLP). Eighteen hours post CLP, rat aortic rings were removed for measurement of contractile responses to vasoconstrictors by using organ bath technique. RESULT: In endothelium intact aortic rings from CLP rats, concentration-contraction curves to phenylephrine (PE) and high KCl were significantly decreased when compared with those from control rats. The transient contraction induced by PE in calcium-free Krebs solution and the concentration-dependent contraction to CaCl(2)in KCl-depolarized medium were also markedly reduced. The hyporeactivity to vasoconstrictors was completely reversed by pretreatment either with aminoguanidine (AMG), a selective inducible nitric oxide synthase inhibitor, or with 1H [1,2,4] oxadiazolo[4,3-a] quininoxalin-1-one(ODQ), an inhibitor of NO-sensitive guanylyl cyclase. CONCLUSION: A generalized impairment in calcium handling in vascular smooth muscle,including the calcium influx through the voltage-operated and receptor-operated channels and calcium release from intracellular calcium stores, is involved in vascular hyporeactivity during the late phase of sepsis. The NO/cGMP signal transduction pathway might be involved in this defect in vascular smooth muscle.

Animals↗

PubMed2002

Adding crumb rubber into exterior wall materials.

In Arizona US, most houses are built with walls covered by stuccos/coatings/mortars. This paper presents an explorative investigation of adding crumb rubber into stuccos/coatings/mortars. A series of experiments are conducted to examine the thermal and mechanical performance of the crumb rubber mixes. The results show that, the mixes with crumb rubber do exhibit more desirable performances like being high in crack-resistance and thermal insulation, and low in thermal expansion/contraction. The drawback for the crumb rubber mixes is the reduction in compressive strength, but which can be compensated by other means. As a site experiment, an area of 100 square-feet of crumb rubber coatings for two mix designs is sprayed on a tire-adobe wall. After being sprayed more than 14 months, the coatings apparently are in good condition. Significance of this study is that this practice, if accepted, will yield improved products that consume large quantities of crumb rubber.

Arizona↗

PubMed2001

Opioid receptor-mediated effects of interleukin-2 on the [Ca2+]i transient and contraction in isolated ventricular myocytes of the rat.

Cytokines play significant roles in some cardiovascular disorders, but direct myocardial effects of cytokines remain to be elucidated. In this study, we examined the effects and possible mechanisms of interleukin-2 (IL-2) on contraction and the [Ca2+]i transient of enzymatically isolated ventricular myocytes with spectrofluorometry and video tracking. IL-2 (2.5-200 U/ml) depressed both the contraction and the [Ca2+]i transient in a dose-dependent manner. Pretreatment with the universal opioid receptor antagonist naloxone (10 nM), or a specific kappa opioid receptor antagonist, nor-binaltorphimine (nor-BNI, 10 nM), abolished the inhibitory effect of IL-2 on contraction and the [Ca2+]i transient; the specific delta-opioid receptor antagonist naltrindole (1 microM) had no effect. The effect of IL-2 was also abolished after pretreatment with pertussis toxin (PTX, 5 mg/l), but not by genistein (100 microM). Pretreatment with the phospholipase C inhibitor U73122 (5 microM) significantly inhibited the IL-2-induced depression of contraction and the [Ca2+]i transient. It is concluded that the effects of IL-2 on contraction and the [Ca2+]i transient of ventricular myocytes are mediated via the cardiac kappa opioid receptor, and the postreceptor signal transduction pathway includes a PTX-sensitive G protein and phospholipase C.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗