PubMed Health⌕ Search

Biomedical subjects

Jeng Wei

Publications and source records attributed to Jeng Wei.

14 recordsLinked to original sources
PubMed2006

Cellular mechanisms responsible for the inotropic action of insulin on failing human myocardium.

BACKGROUND: An increase in intracellular calcium transients is responsible for the positive inotropic effect of insulin on human myocardium, but the mechanisms involved in this increase in [Ca2+]i remain unclear. METHODS: We studied isolated trabeculae or cardiomyocytes from end-stage failing hearts of 38 patients undergoing heart transplantation. The effect of insulin on isometric twitch force (37 degrees C, 0.5 Hz) and L-type Ca2+ current (whole-cell voltage clamp) was assessed. RESULTS: Crystalline insulin increased the contractile force in a dose-dependent manner (0.01 to 10 micromol/liter), with a maximum increase of 45 +/- 8% (p < 0.05) at 1 micromol/liter. It also increased L-type Ca2+ peak current density by 26 +/- 6% (p < 0.05). This insulin-mediated positive inotropic effect was unchanged in the presence of propranolol (1 micromol/liter). Positive inotropy was partially independent of glucose. L-type Ca2+ channel blockade (diltiazem, 5 micromol/liter), and sarcoplasmic reticulum (SR) Ca2+-release channel blockade (ryanodine, 0.1 micromol/liter) did not affect the inotropic response to insulin. However, blockade of SR Ca2+-ATPase (cyclopiazonic acid, 10 micromol/liter), inhibition of Na+-H+ exchange (HOE642, 10 micromol/liter), and inhibition of Na+-Ca2+ exchange (SEA0400, 1 micromol/liter) partially prevented the inotropic response to insulin. CONCLUSIONS: Positive inotropy of insulin was not related to catecholamine release and subsequent stimulation of beta-adrenergic receptor, but it may enhance the activity of SR Ca2+-ATPase and trans-sarcolemmal Ca2+ entry, mainly via reverse-mode Na+-Ca2+ exchange and insulin-mediated activation of Na+-H+ exchange. We hypothesize that these changes in [Ca2+]i might be secondary to the activation of reverse-mode Na+-Ca2+ exchange, presumably via elevated intracellular Na+ concentration.

Adult↗
PubMed2006

Cardiopulmonary resuscitation in prone position: a simplified method for outpatients.

BACKGROUND: The efficacy of cardiopulmonary resuscitation (CPR) is vital for saving lives of victims with sudden cardiac arrest. In 1960, Kuowenhoven and colleagues proposed the method that has become standard for CPR. Despite vast input of resources for public education and training of this procedure, its success rate outside hospitals remains poor to dismal. During CPR, restoration of respiration is as important as circulation. But opening the airway and giving effective mouth-to-mouth respiration is difficult for lay people to learn. Furthermore, most bystanders are reluctant to do mouth-to-mouth respiration because of the risk of infection. Therefore, the general population needs a more simplified CPR method for outpatients. The practice of CPR in the prone position, first proposed by McNeil in 1989, has not been adopted, despite the fact that it meets the desirable requirements of ideal resuscitation: simultaneous restoration of circulation and respiration with a very simple maneuver. METHODS: Part 1 (circulation test): Eleven patients who expired in the intensive care unit (ICU), with arterial lines attached, received standard pre-cordial cardiac massage, and the generated blood pressure (BP) was recorded. They were then turned to the prone position, with the head turned to one side. We compressed the patient's thoracic spine with the same force used in standard CPR (rhythm of approximately 60 per minute each time when the back bounces back), and the BP was also recorded. Part 2 (ventilation test): Ten healthy volunteers (5 doctors and 5 nurses) were enlisted for respiratory assessment during compression on the back. With the nose clipped and spontaneous breathing held, the volunteer's exhaled tidal volume upon compression was measured with a spirometer. RESULTS: Standard external cardiac massage of the cadavers generated BPs of 55 +/- 20/13 +/- 7 mmHg; however, external compression on the back of the cadavers generated higher BP of 79 +/- 20/17 +/- 10 mmHg (p = 0.028, Wilcoxon signed-rank analysis). External compression on the back of the volunteers generated mean tidal volumes of 399 +/- 110 mL. CONCLUSION: Our study revealed that prone CPR provides good respiratory and circulatory support at the same time. It is easy to perform and it may be a good alternative way for bystanders to perform CPR in public surroundings. We recommend that more investigators do further studies on this topic.

Adult↗
PubMed2006

Usefulness of live/real time three-dimensional transthoracic echocardiography in the identification of individual segment/scallop prolapse of the mitral valve.

In this report, we present 34 patients in whom surgical intervention was undertaken for severe mitral insufficiency due to mitral valve prolapse (MVP). Location and severity of MVP and regurgitation were assessed preoperatively by live/real time three-dimensional transthoracic echocardiography and closely agreed with the surgical findings.

Adult↗
PubMed2006

Long-term survival and prognostic implications after coronary artery bypass grafting in Chinese patients with coronary artery disease.

OBJECTIVES: This hospital-based study was conducted to determine the survival rates of patients after coronary artery bypass grafting (CABG) surgery and the associated prognostic factors related to all-cause mortality during a 7-year follow-up in Taiwan. METHODS AND RESULTS: Between January 1997 and December 2003, the medical records of 1877 patients who underwent primary, isolated CABG surgery were studied. The Kaplan-Meier method was used to estimate survival. Multiple Cox regression was used to investigate the independence of prognostic factors associated with all-cause mortality. Of the 1877 patients who underwent CABG surgery, 192 expired during the 7-year study period. The overall patient survival rate was 85.96% (95% CI: 83.74-88.16). Using multiple Cox regression analysis, in addition to female gender, older age at surgery, pulmonary oedema, longer ischaemic time, longer cardiopulmonary bypass time, and poorer postoperative left ventricular ejection fraction were significant factors associated with all-cause mortality for both men and women. Associated prognostic factors varied by gender. For men, smoking (RR = 2.82, 95% CI: 1.06-4.16), respiratory failure (RR = 6.88, 95% CI: 3.29-14.40) and cardiogenic shock (RR = 4.04, 95% CI: 2.13-7.67) were significantly related to all-cause mortality, but not for women. Sepsis (RR = 8.97,95% CI: 1.19-19.81) and ICU stay (RR = 1.03,95% CI: 1.01-1.05) were significantly related to all-cause mortality among female patients only. CONCLUSIONS: Several gender-related differences were noted pertaining to all-cause mortality and the relationships between smoking, sepsis, respiratory failure, cardiogenic shock, and ICU stay.

Age Factors↗
PubMed2005

An analysis of job satisfaction among physician assistants in Taiwan.

The physician assistant (PA) is a relatively new medical specialty that developed to manage the shortage of resident physicians and to ensure that patients receive high-quality health care in today's increasingly complex and demanding medical environment. PAs in Taiwan are not governed by laws and regulations, and the absence of legislation to define their roles and responsibilities can lead to confusion in the work environment and potential communication barriers with coworkers and supervising physicians. The purpose of this exploratory study was to examine the environmental and sociodemographic factors that influence job satisfaction and job-related communication among PAs in Taiwan. The data source, a self-administered mail survey, was sent to 196 PAs working within medical facilities in northern, central, and southern Taiwan. The response rate to the survey was 71.01%. There was a strong correlation between communication satisfaction and job satisfaction among respondents. The PAs' overall position in the hospital, relationships with coworkers (doctors, nurses, and other medical staff), and ability to perform his or her duties while working with the supervising physician were the major environmental factors that influenced job and communication satisfaction. In addition, the number of working years and marital status were important demographic factors influencing job satisfaction. Demographic and environmental factors influencing job satisfaction are analyzed, and ways in which the roles and responsibilities of PAs can be clarified, strengthened, and improved are discussed in an overall effort to provide management strategies for the current PA system in Taiwan.

Adult↗
PubMed2005

Mitral annular subvalvular left ventricular aneurysm.

Annular subvalvular left ventricular aneurysm was first reported in 1962. This type of aneurysm usually arises from the annular subaortic or submitral region of the left ventricle. It should be differentiated from the left ventricular false aneurysm, which was caused by myocardial necrosis. The etiology of subvalvular aneurysm remains unclear. We have presented a case of annular submitral left ventricular aneurysm. The patient had no history of coronary artery disease. Two-dimensional echocardiography and magnetic resonance image (MRI) showed a huge left ventricular aneurysm existed. An annular submitral left ventricular aneurysm was confirmed by an open heart surgery and pathological examination.

Aged↗
PubMed2004

Fish oil increases antioxidant enzyme activities in macrophages and reduces atherosclerotic lesions in apoE-knockout mice.

OBJECTIVES: The molecular and cellular mechanisms that fish oil (FO) exerts its physiological function are complicated. The present study brings evidence on the in vivo effect of FO on the development of atherosclerosis in apolipoprotein E knockout (apoE(-/-)) mice. We also test the hypothesis that the modulation of the cellular oxidative stress and antioxidant status contributes to the anti-atherosclerotic effect of FO. METHODS AND RESULTS: ApoE(-/-) mice were fed a diet rich either in FO or corn oil (CO) for 10 weeks. Both FO and CO had a plasma triacylglycerol-raising effect in apoE(-/-) mice, whereas aortic atherosclerotic lesions were significantly reduced in the mice that had consumed a high FO diet compared to those fed a high CO diet. The levels of hepatic superoxide dismutase (SOD) and catalase (CAT) activities were remarkably higher in the mice fed the FO diet than in mice fed the CO diet and the control diet. We then investigated the effects of FO and CO on the production of superoxide anion (O2*-)) and reactive oxygen species (ROS) in cultured J774 macrophages. Antioxidant status was assessed by the determination of antioxidant enzyme activities. Both FO and CO induced high levels of O2*-) and total ROS at a short time in macrophages. However, only the FO group restored the induction of O2*-) and ROS to near basal levels after oil treatment for 24 h. Throughout the time course experiments, antioxidant enzyme activities in the FO group mostly displayed a greater increase than in the corresponding CO group after the same time period of oil treatment. CONCLUSIONS: In the present study, FO reduced the formation of atherosclerotic lesions in the aortic arteries of apoE(-/-) mice not through any lipid-lowering effect. The protective role of FO in the development of atherosclerosis may result from its antioxidative defense mechanism through the induction of antioxidant enzyme activities.

Animals↗
PubMed2004

Electromechanical properties of Purkinje fiber strands isolated from human ventricular endocardium.

BACKGROUND: Abnormalities in the regulation of intracellular Ca2+ were observed in cardiac cells obtained from failing human hearts. However, the electromechanical properties and pharmacologic responses of human ventricular Purkinje fibers have not been well characterized. METHODS: Strands of free-running Purkinje fibers and/or trabecular muscle fibers with a diameter of around 1.5 mm were removed from the endocardial surface of ventricles obtained from 16 transplant recipient hearts. Action potential (AP) was detected by conventional microelectrode techniques and twitch force by a force-displacement transducer. RESULTS: The human Purkinje fiber strands as revealed by histologic examination were composed of Purkinje cells and the surrounding ventricular muscle cells. In well-polarized Purkinje fibers (mean +/- SE of maximum diastolic potential [MDP] = -85 +/- 1 mV) showing fast-response AP (Phase 0 Vmax >100 V/sec), the cardiotonic agents isoproterenol and strophanthidin (1 to 2 micromol/liter) accelerated the slope of diastolic depolarization and induced delayed afterdepolarization but not spontaneous APs. Steady-state contraction and the post-rest potentiation of contraction (PRPC) were similar in both Purkinje fibers and ventricular muscles, but inotropic agents induced tachyarrhythmia only in Purkinje fibers. In partially depolarized Purkinje fibers (MDP <-70 mV) with slow-response AP, isoproterenol and/or strophanthidin readily induced automatic and triggered rhythms. CONCLUSIONS: Accumulation of excessive cytosolic Ca2+ in the presence of cardiotonic agents could lead to tachyarrhythmias in Purkinje fibers, but rarely in ventricular muscles of failing human hearts.

Adult↗
PubMed2003

Role of the sarcoplasmic reticulum in altered action potential and contraction of myopathic human and hamster ventricle.

1. The present experiments were performed in order to study the role of the sarcoplasmic reticulum (SR) in the altered action potential and contraction of ventricular myocardium obtained from myopathic Syrian hamster and explanted human hearts (n = 8). The hamsters included age-matched healthy hamsters (F1B; n = 18), young myopathic hamsters (Bio 14.6; n = 8; aged 17-27 weeks) and older myopathic hamsters (n = 10; aged 39-43 weeks). 2. Action potentials were recorded by means of a microelectrode technique and force was recorded using a transducer. Post-rest potentiation of contraction (PRPC), a measure of the SR Ca2+-pumping activity, was determined after different rest intervals (2-60 s). Furthermore, cyclopiazonic acid (10 micro mol/L), a specific blocker of SR Ca2+-ATPase, was used to unmask abnormalities in the function of the SR. 3. The relationship between PRPC and rest interval was similar in younger healthy and myopathic hamsters, but the curve of the older myopathic muscle was obviously shifted downwards. Cyclopiazonic acid decreased predominantly the ascending part of the curve in both the healthy and myopathic hamster myocardium and could induce spontaneous action potentials during drug exposure or after washout. 4. In human myopathic myocardium, the curve of the PRPC-rest interval peaked at longer intervals (40-60 s) compared with that of the hamsters (10-20 s). Cyclopiazonic acid markedly depressed the relationship and increased the diastolic force (contracture) at high driving frequency, but did not induce action potentials during the rest interval. 5. We conclude that an impaired function of the SR contributes to the progressive deterioration of ventricular function in dilated cardiomyopathy and that the electromechanical behaviour of the ventricular myocardium of patients affected by dilated cardiomyopathy shows similarity and differences with the myopathic Syrian hamster model.

Action Potentials↗
PubMed2002

Hydrogen peroxide-induced intracellular acidosis and electromechanical inhibition in the diseased human ventricular myocardium.

Accumulation of oxygen free radicals is an important mediator of post-ischemia/reperfusion cardiac dysfunction. However, oxidative injury has not been well characterized in human cardiac tissues. In the present study, we superfused hydrogen peroxide (H(2)O(2)) into the diseased human ventricle in order to assess the effects of oxygen free radicals on the electromechanical parameters and the intracellular pH (pH(i)), and to test the ability of certain potential cardioprotective agents, including scavengers of hydrogen peroxide (dibenzamidostilbene disulfonic acid; DBDS), the.OH free radical (N-(mercaptopropionyl)-glycine; N-MPG), and the HOCl free radical (L-methionine), to protect against oxidative injury. Disease human ventricular tissues were obtained from patients undergoing heart transplantation. Electrophysiological experiments were performed using a traditional micropipette, while the pH(i) was measured by microspectrofluorimetry. We found that (a) H(2)O(2) (30 microM-3 mM) induced a significant dose-dependent intracellular acidosis, (b) H(2)O(2) (30 microM-3 mM) had a notable dose-dependent biphasic effect on the contractile force (an increase, followed by a decrease), while moderate concentrations of H(2)O(2) also inhibited the generation of action potential and increased the diastolic resting force significantly, and (c) N-MPG caused significant block of both the intracellular acidosis and the electromechanical inhibition induced by 3 mM H(2)O(2), whereas L-methionine and DBDS did not. Our data suggest that the toxic effects of H(2)O(2) are caused mainly through the generation of.OH, which is attributed to the intracellular acidosis seen in the diseased human ventricle.

Acidosis↗
PubMed2002

Development of an echocardiographic method for choosing the best fitting single-pass VDD lead.

To achieve stable single-lead VDD pacing, a selection of the electrode with the optimal distance between the lead tip and the floating atrial dipole (AV distance [AVD]) is important. The authors hypothesized that the size of the right heart chambers may affect atrial sensing, and that measurement of their internal dimension at end-diastole (RHIDd) in the apical four chamber view by transthoracic echocardiography may aid in choosing the proper AVD. Twenty-six consecutive cases that had undergone VDD pacer implantation using the conventional chest X ray were examined retrospectively by the echocardiographic method. The chest x-ray method properly selected a lead with optimal atrial sensing, defined as minimum P wave amplitude > or = 1.0 mV, for only 20 (77%) of 26 patients. By comparing these results with their respective RHIDd, a cut-off point of 13 cm was obtained that indicated a criterion for choosing the proper AVD. The indication was that if the RHIDd was > or = 13 cm, a lead with an AVD of 15.5/16 cm should have been used; if the RHIDd was < 13 cm, a lead with an AVD of 13/13.5 cm should have been chosen. Using the echocardiographic method, all six patients who had suboptimal atrial sensing could be identified and classified as having missized (four undersized; two oversized) permanent leads. In conclusion, the described method provides a promising preoperative assessment of the best fitting electrode length in single lead VDD pacing. A prospective study is ongoing to verify its applicability.

Adult↗
PubMed2002

Functional evidence for intracellular acid extruders in human ventricular myocardium.

Intracellular pH (pH(i)) is a major homeostatic system within the cell. Changes in pH(i) exert great influence on cardiac contractility and rhythm. Both the housekeeping Na+ - H+ exchanger (NHE) and the Na+ - HCO3- symporter (NHS) have been confirmed as major transporters for the active acid extrusion mechanism in animal cardiomyocytes. However, whether the NHE and NHS functionally coexist in human ventricular cardiomyocytes remains unclear. We therefore examined the mechanism of pH(i) recovery following an NH4Cl-induced intracellular acidosis in the human ventricular myocardium. The pH(i) was monitored by microspectrofluorimetry by the use of intracellular 2',7'-bis(2-carboxyethyl)-5(6)-carboxy-fluorescein (BCECF)-fluorescence. HOE 694 (30 microM), a specific NHE inhibitor could block pH(i) recovery from induced intracellular acidosis completely in nominally HCO3- -free HEPES Tyrode solution, but it only partially inhibited the pH(i) recovery in 5% CO2/HCO3- Tyrode solution. In 5% CO2/HCO3- Tyrode solution, the addition of HOE 694 together with DIDS (an NHS inhibitor) or the removal of [Na+](o) could entirely inhibit the acid extrusion. We conclude for the first time that two different acid extruders, HCO3- -independent and -dependent, were most likely the NHE and NHS, respectively, that functionally coexisted in the human ventricular cardiomyocytes.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗