In rats the duration of diabetes influences its impact on cardiac autonomic innervations and electrophysiology.

Diabetic cardiac autonomic neuropathy (DCAN) may cause fatal ventricular arrhythmias and increase mortality in diabetics. However, limited data are available with regard to the precise changes in cardiac autonomic denervation after diabetes onset. In this study, we dynamically observed the progression of DCAN and its relationship with the inducibility of ventricular arrhythmias in diabetic rats. Rats were randomly divided into normal control and diabetes mellitus (DM) groups. The rats were sacrificed at 3 or 6 months post-treatment. Heart rate variability and programmed electrical stimulation were used to assess the electrophysiological characteristics and the inducibility of ventricular arrhythmias in the animals. Immunohistochemistry and real-time RT-PCR were used to measure choline acetyltransferase and tyrosine hydroxylase-positive nerve fibers and the corresponding mRNA expression levels in the proximal and distal regions of the left ventricle. Short-term diabetes resulted in distal myocardial parasympathetic denervation with sparing of the proximal myocardium. By 6 months, both parasympathetic and sympathetic denervation were further aggravated. Moreover, electrophysiological experiments demonstrated a sympatho-parasympathetic imbalance and an increase in ventricular arrhythmia inducibility in the diabetic rats. These results suggest that DM causes cardiac nerve denervation, relative sympathetic hyperinnervation and inhomogeneous neural innervations, which may be associated with an increase in the induction of ventricular arrhythmia in diabetic rats.

Size-dependent biological effects on vascular endothelial cells induced by different particulate matters.

The contribution of particles to cardiovascular mortality and morbidity has been enlightened by epidemiologic and experimental studies. However, adverse biological effects of the particles with different sizes on cardiovascular cells have not been well recognized. In this study, sub-cultured human umbilical vein endothelial cells (HUVECs) were exposed to increasing concentrations of pure quartz particles (DQ) of three sizes (DQPM1, <1 µm; DQPM3-5, 3-5 µm; DQPM5, 5 µm) and carbon black particles of two sizes (CB0.1, <0.1 µm; CB1, <1 µm) for 24 h. Cytotoxicity was estimated by measuring the activity of lactate dehydrogenase (LDH) and cell viability. Nitric oxide (NO) generation and cytokines (TNF-α and IL-1ß) releases were analyzed by using NO assay and enzyme-linked immunoabsorbent assay (ELISA), respectively. It was found that both particles induced adverse biological effects on HUVECs in a dose-dependent manner. The size of particle directly influenced the biological activity. For quartz, the smaller particles induced stronger cytotoxicity and higher levels of cytokine responses than those particles of big size. For carbon black particles, CB0.1 was more capable of inducing adverse responses on HUVECs than CB1 only at lower particle concentrations, in contrast to those at higher concentrations. Meanwhile, our data also revealed that quartz particles performed stronger cell damage and produced higher levels of TNF-α than carbon black particles, even if particles size was similar. In conclusion, particle size as well as particle composition should be both considered in assessing vascular endothelial cells injury and inflammation responses induced by particles.

Exogenous nerve growth factor promotes the repair of cardiac sympathetic heterogeneity and electrophysiological instability in diabetic rats.

OBJECTIVES: Diabetic cardiac autonomic neuropathy can lead to an increased incidence of ventricular arrhythmias (VAs). However, few data are available regarding the pathogenesis and therapy of the VAs accompanying diabetic cardiac autonomic neuropathy. We aimed to explore whether or not exogenous nerve growth factor (NGF) can reduce the sympathetic heterogeneity and the incidence of VAs in diabetes mellitus (DM). METHODS: Male Wistar rats were randomly divided into 3 groups: controls, rats with DM with saline infused into the left stellate ganglion (LSG), i.e. the DS group and rats with DM with NGF infused into the LSG, i.e. the DN group. After 28 weeks, all rats were subjected to electrophysiological experiments. Sympathetic innervations and NGF were studied by immunostaining, RT-PCR or Western blot analysis. RESULTS: The incidence of inducible VAs was significantly higher in the DS group than in the control group, but was markedly decreased in the DN group. In the DS group, the tyrosine hydroxylase (TH) and NGF expression were significantly lower than in the other groups, and significant proximal-distal heterogeneities existed regarding the TH and NGF expression in the left ventricle, but were markedly repaired in the DN group. CONCLUSIONS: NGF intervention in the LSG can reduce the heterogeneity of cardiac sympathetic innervations and the incidence of VAs in diabetic rats.

Metoprolol-mediated amelioration of sympathetic nerve sprouting after myocardial infarction.

OBJECTIVES: Systemic or local inflammation causes cardiac nerve sprouting and consequent arrhythmia. Metoprolol can prevent sympathetic nerve remodeling after myocardial infarction (MI), but the underlying mechanism is unclear. In this study, we evaluated the role of metoprolol in ameliorating sympathetic sprouting. METHODS: Rabbits underwent ligation of the coronary artery for MI. MI rabbits received metoprolol or saline for 7 days. Immunohistochemistry was used to measure cardiac nerve sprouting and sympathetic innervations. Nuclear factor-κB (NF-κB) DNA binding activity was analyzed by electrophoretic mobility shift assay. The protein levels of NF-κB p65, inhibitor κBα (IκBα) and nerve growth factor (NGF) were detected by Western blot analysis. The mRNA levels of NGF, interleukin-1ß (IL-1ß) and tumor necrosis factor-α (TNF-α) were examined by quantitative real-time PCR. RESULTS: MI rabbits showed nerve sprouting and sympathetic hyperinnervation. In MI rabbits, as compared with saline treatment, metoprolol reduced NF-κB DNA binding activity and NF-κB p65 level, and increased IκBα level. Moreover, metoprolol downregulated IL-1ß, TNF-α and NGF levels, and reduced the density of sympathetic nerve fibers. CONCLUSIONS: Metoprolol ameliorates sympathetic nerve sprouting in rabbits after MI and is associated in part with inhibiting NF-κB activity.

Mesenchymal stem cell therapy improves diabetic cardiac autonomic neuropathy and decreases the inducibility of ventricular arrhythmias.

BACKGROUND: Diabetic cardiac autonomic neuropathy (DCAN) may cause fatal ventricular arrhythmias and increase mortality in diabetics. Mesenchymal stem cells (MSCs) can secrete various cytokines and growth factors exerting neurosupportive effects. In this study, we investigated the effect of MSC on DCAN in diabetic rats. METHODS: Forty rats were divided into normal control, diabetes mellitus (DM) control, MSC treatment (6 × 10(6) MSCs via direct myocardial injection) and MSC-conditioned medium group (100 µl via direct myocardial injection). Immunohistochemistry was used to measure choline acetyltransferase (ChAT, a marker for parasympathetic nerves) and tyrosine hydroxylase (TH, a marker for sympathetic nerves) positive nerve fibres in the ventricular myocardium. Heart rate variability and programmed electrical stimulation was used to assess the inducibility of ventricular arrhythmias in the animals. RESULTS: Two weeks after MSC treatment, the density of ChAT- and TH-positive nerve fibres in MSCs and MSC-conditioned medium group was higher than in DM control group (P < 0.05 or P < 0.01). The ChAT/TH ratio in MSC group was higher than in DM control group (0.37 ± 0.014 vs. 0.27 ± 0.020, P < 0.01). The standard deviation of normal-to-normal R-R intervals in MSCs (5.13 ± 0.69) and MSC-conditioned medium group (4.30 ± 0.56) was higher than in DM control group (3.45 ± 0.60, P < 0.05). The inducibility of VAs in the MSC group was lower than in the DM control group. CONCLUSIONS: MSC therapy may promote cardiac nerve sprouting and increase the ratio of parasympathetic to sympathetic nerve fibres. It may also suppress the inducibility of ventricular arrhythmias in the diabetic rats.

[The relationship between fit characteristics of two kinds of self-inhalation air-purifying dust respirators and head-face dimensions of subjects].

OBJECTIVE: To investigate the fitness characteristics of self-inhalation air-purifying dust respirators for representative subjects and to explore the influencing factors on fitness characteristics of respirators. METHODS: According to the Chinese new bivariate fit test panel, 50 representative subjects were studied for using 2 kinds of self-inhalation air-purifying dust respirators. The N95 Companion from TSI was used to test the Fit factor (FF), and five representative facial dimensions (face width, bigonial breadth, nasal root breadth, face length and nose protrusion) were measured. Then chi-square test was used to compare the qualified rates of 2 kinds of respirators. The t-test was utilized to analyze the differences of facial dimensions between qualified samples and unqualified samples. Multiple linear regression models were also established to analyze the effects of facial dimensions on FF. RESULTS: The qualified rate (86%) of folding respirators was significantly higher than that (68%) of cup respirators (P < 0.05). There were no significant differences of facial dimensions between qualified subjects and unqualified subjects for folding respirators. However, the face width, bigonial breadth and face length of qualified subjects were significantly larger than those of unqualified subjects for cup respirators (P < 0.01). The regression coefficient (0.31846) demonstrated that the positive effects of face length on mean log-transformed fit factor (MLFF) for all subjects with cup respirators (P < 0.05). CONCLUSION: There were significant effects of respirator styles and head-face dimensions on the respirator fitness. There was a significant correlation between the respirator fitness and the facial dimensions for cup respirators.

[Fit test and improvement of self-inhalation air-purifying dust respirator].

OBJECTIVE: To investigate the fit of self-inhalation air-purifying dust respirator for Chinese workers, to improve the respirators according to Chinese facial features and to evaluate the protective effects of improved respirators. METHODS: Two types of self-inhalation air-purifying dust respirators (cup respirators A1 and folding respirators B1) were tested by Condensation Nuclei Counting method (CNC) in 25 representative subjects (15 males and 10 females). According to the Chinese facial features and fit factors, A1 and B1 respirators were improved. The fit tests were performed for the improved A1 and B1 respirators. RESULTS: The fit factors ≥ 100 served as the qualified standard of self-inhalation air-purifying dust respirators. The qualified rate for cup respirator A1 was 0.0%. Its geometric mean fit factor was 20.7 (6.9 ∼ 46.9). The qualified rate for cup respirator B1 was 4.0%. Its geometric mean fit factor was 26.0 (6.8 ∼ 154.9). After improvement, the qualified rates and fit factors significantly increased. The qualified rate for cup respirator A2 was 72.0% and geometric mean fit factor was 223.5 (2.2 ∼ 5932.7). There were significantly differences between respirator A1 and A2 (χ(2) = 25.09, P < 0.05). The qualified rate for cup respirator B2 was 88.0 % and geometric mean fit factor was 429.8 (41.5 ∼ 3692.9). The significant differences (χ(2) = 32.21, P < 0.05) between B1 and B2 were found. CONCLUSION: To ensure the protective effects, the self-inhalation air-purifying dust respirators were designed according to Chinese facial features. The respirator fit test must be conducted when workers choose respirators.

Risk of ventricular arrhythmias after myocardial infarction with diabetes associated with sympathetic neural remodeling in rabbits.

BACKGROUND: Abnormal sympathetic innervation underlies both long-term hyperglycemia and myocardial infarction (MI). The incidence of ventricular arrhythmias (VAs) after MI is higher in diabetic than in nondiabetic patients. However, the exact mechanism remains unclear. In this study, we aimed to explore sympathetic neural remodeling after MI in diabetic rabbits and its relationship with VAs. METHODS: Rabbits were randomly assigned to 4 groups: control, diabetes mellitus (DM), MI and diabetic myocardial infarction (DI). After electrophysiological experiments in vivo, immunohistochemistry and real-time RT-PCR were used to measure sympathetic innervations. To test the function of sympathetic nerve fibers, norepinephrine levels were measured by high-performance liquid chromatography. RESULTS: The corrected QT interval and QT dispersion were significantly more prolonged with DI than other conditions. The density of tyrosine hydroxylase-positive fibers and corresponding mRNA abundance was significantly higher with DI than with DM and under control conditions, but was lower than with the MI group. Moreover, the distribution and structure of regenerated nerve was heterogeneous in DI rabbits. Norepinephrine content was higher in the DI group, and accompanied by an increased quantity of tyrosine hydroxylase-positive fibers. CONCLUSION: MI results in sympathetic neural remodeling in diabetic rabbits, which may be responsible in part for the increased occurrence of VAs.

[Study on the injury of vascular endothelial cells affected by dust particles from workplaces in pottery factories and tungsten mines].

OBJECTIVE: to assess direct adverse effects of occupational dusts from pottery factories and tungsten mines on vascular endothelial cells in vitro test. METHODS: human umbilical vein endothelial cell (HUVEC) line HUV-EC-C were used as target cells. HUVEC were then treated with respirable dust particles from workplaces in pottery factories and tungsten mines in concentrations of 25, 50, 100, 200 and 400 microg/ml for 24 h. Standard quartz was used as control. LDH activity, cell viability, the release of NO and TNF-α levels were determined to assess the biological responses of the dust particles. RESULTS: dose-response relationships between the dust concentrations and the enhancement of the LDH activity, the release of NO and TNF-α were found in both dust particles from pottery factories and tungsten mines. The cell viability decreased with the increase of dust concentration from 25 to 400 microg/ml. Compared with the dust particles from workplaces, the quartz dust induced significantly higher LDH activity (P < 0.05) after cultured with HUVEC. No significant difference of releases of NO were observed among the dust particles from workplaces and standard quartz. However, significantly higher levels of TNF-α were induced by standard quartz compared with dust samples from workplaces at concentrations of 200, 400 microg/ml. CONCLUSION: occupational dust particles from workplaces and quartz could induce the injury and the releases of TNF-α from HUVEC.

Evaluation of the surface ECG in detecting isthmus conduction block after ablation of typical atrial flutter.

OBJECTIVES: To investigate the value of changes in P wave morphology and duration detected by surface electrocardiogram (ECG) during proximal coronary sinus (PCS) and low lateral right atrial (LLRA) stimulation as a marker for complete bidirectional isthmus conduction block in the procedure of typical atrial flutter ablation. METHODS: Morphology, duration, and ratio of a positive terminal P wave were estimated in 52 typical atrial flutter patients before and after radiofrequency catheter ablation (RFCA). RESULTS: Atrial flutter ablation resulted in a complete bidirectional isthmus block in all 52 patients. The terminal portion of the P wave towards a positive morphology was detected in 90.7% (47/52) patients both during PCS and LLRA stimulation. These changes were predominantly observed in the inferior leads. Positive morphological changes of the terminal P wave portion and the measured P wave ratio (40% +/- 12%) in the inferior leads indicating bidirectional isthmus conduction block with a sensitivity of 87.5% and a specificity of 91.7% were observed. An increment of 20 ms or more in P wave duration during the PCS stimulation and 10 ms or more during the LLRA stimulation indicating the conduction block with a sensitivity of 90% and a specificity of 100%. CONCLUSIONS: The variation of P wave morphology and duration in inferior leads of the surface ECG is a helpful technique to assess the complete bidirectional isthmus conduction block in the procedure of typical atrial flutter ablation.

[Two new anthropometric panels of respirator fit test for Chinese adult workers].

OBJECTIVE: To develop two new respirator fit test panels using data from anthropometric survey of Chinese adult workers: bivariate panel and principal component analysis (PCA) panel for meeting the requirements of respirator fit design and testing and evaluate the applicability of the two different fit test panels for current Chinese workers. METHODS: An anthropometric database based upon anthropometric data of current Chinese workers was used for panel design. The bivariate panel was based upon the bivariate distribution of the face length and face width measurements, and the PCA panel was developed using principal components analysis of 10 stable facial dimensions (minimum frontal breadth, face width, bigonial breadth, face length, interpupillary distance, head breadth, nose protrusion, nose breadth, nasal root breadth, subnasale-sellion length). The distribution of Chinese workers across the panels was used to analyze the panels' applicability for Chinese workers. RESULTS: The bivariate panel and PCA panel developed in this study consisted of 10 cells and 8 cells respectively, covered 96.9% (male 95.4%, female 98.4%) and 96.5% (male 95.1%, female 98.1%) of the current Chinese workers, respectively. The distribution of workers across both panels was uniform. Each cell contained 4.6% - 21.7% of the population in the bivariate panel and 10.4% - 14.6% of the population in the PCA panel. The LANL full-face piece respirator fit test panel covered only 70.9% of the Chinese workers, It was thought to be no longer adequate for the Chinese adult workers. CONCLUSION: New respirator fit test panels based on updated anthropometric database and distributions specific to Chinese workers may be more beneficial for applications in China.

Mechanisms of atypical flutter wave morphology in patients with isthmus-dependent atrial flutter.

Sixty-three episodes of isthmus-dependent atrial flutter (AFL) in 55 patients were studied to characterize variations in flutter wave morphology and to investigate the mechanisms of the atypical flutter waves on surface ECG. The activation patterns of coronary sinus (CS) and their relationship with flutter wave morphology on the ECG were analyzed. In 46 episodes of counterclockwise AFL (CCW-AFL), there were four types of flutter waves on ECG. Typical and atypical flutter waves were found in 47.8% and 13.0% of the episodes, respectively. Atypical flutter waves had broad positive terminal portion or entirely positive wave in the inferior leads and in V(1), with a distal-to-proximal or fused activation pattern in the CS, and an average activation time of 21.3 +/- 11.4 ms. In 17 episodes of clockwise AFL (CW-AFL), typical and atypical flutter waves were identified in 41.2% and 41.2%, respectively. Atypical flutter waves had negative waves in the inferior ECG leads and in V1, a proximal-to-distal activation pattern in the CS, and an average activation time of 42.4 +/- 14.4 ms. We conclude that atypical flutter waves are common in the isthmus-dependent AFL. The clockwise or counterclockwise conduction in the right atrium, and the activation patterns or conduction sequences between the right and the left atrium, are associated with the variations in the flutter wave morphology on body surface ECG.

Effects of angiotensin converting enzyme inhibition on cardiac innervation and ventricular arrhythmias after myocardial infarction.

PURPOSE: To investigate the influence of angiotensin-converting enzyme inhibitor (ACEI) on cardiac innervation and inducible ventricular arrhythmias (VAs) in healed myocardial infarction (MI). METHODS: Left anterior descending coronary artery was ligated to induce MI in 30 rabbits. After oral captopril (10mg/kg/d) for 8 weeks, electrophysiological study was performed to evaluate the incidence of inducible VAs. RT-PCR and immunohistochemistry were used to measure the cardiac innervation. RESULTS: Eight weeks after the operation, the incidence of inducible VAs in the MI-placebo group was higher (58.3%, 7/12) than in the sham operation group (16.7%, 2/12, P < 0.05). However, the incidence of inducible VAs in the MI-captopril group was lower (27.2%, 3/11) than in the MI-placebo group (P < 0.05). Proliferation and growth of nerve fibres in the MI-placebo group were mainly distributed at the periphery of the infarcted and perivascular regions of the myocardium. The density of nerve fibres increased in the MI-placebo group (3889+/-521 microm2/mm2) compared with the sham group (1727+/-304 microm2/mm2, P < 0.01) at the infarct border. In the MI-captopril group, the density of nerve fibres (3507+/-433 microm2/mm2) at the infarct border did not differ from that in the MI-placebo group (P=0.07). MI-induced abnormal nerve fibre distribution was partly restored by captopril treatment. CONCLUSION: In this study, prolonged captopril treatment was effective in preventing VAs in healed MI, partly by attenuating the spatial heterogeneity of cardiac innervation.

Effects of prolonged metoprolol treatment on neural remodeling and inducible ventricular arrhythmias after myocardial infarction in rabbits.

BACKGROUND: Neural remodeling is part of the pathophysiology of ventricular arrhythmias after myocardial infarction (MI). In this study, we developed a rabbit model of MI to investigate the effect of the beta-blocker metoprolol on ventricular neural remodeling and susceptibility to ventricular arrhythmias. METHODS: MI was induced by ligation of the left anterior descending coronary artery in 30 rabbits, and sham operations were performed in 12 control animals. Metoprolol was then administered to 15 of the MI animals. After electrophysiological recordings, the expression of nerve markers was studied at the infarct border and the non-infarct left ventricle free wall (LVFW) by immunostaining or RT-PCR. RESULTS: Eight weeks after MI, the incidence of inducible ventricular arrhythmias was significantly (P<0.01) higher in the MI group than in the sham group. However, metoprolol treatment decreased incidence of post-MI ventricular arrhythmias (8.3%) compared to those without treatment (58.3%, P<0.001). The density of nerve fibers was increased in MI group (3889+/-521 microm(2)/mm(2)) compared to the sham group (1727+/-304 microm(2)/mm(2)). Treatment of MI rabbits with metoprolol resulted in a partial reduction (2725+/-283 microm(2)/mm(2)). However, the shape and imbalance of nerve fibers appeared to be normalized by the metoprolol treatment. The expression levels of TH mRNA were reduced (P<0.01) by metoprolol treatment. CONCLUSION: Metoprolol reduces post-MI ventricular arrhythmias, partly by altering the neural remodeling process.

[Fluorescence emission properties of Ni-doped ZnO films].

Ni-doped ZnO films were deposited on Si(100) by pulsed laser deposition(PLD) at room temperature. Fluorescence emission properties of the films were measured using VARAIN Cary-Eclips 500 fluorescence spectrum analyzer. Two peaks centered respectively at about 360 and 380 nm were observed. The origin of the ultraviolet peak at 360 nm was investigated through doping Ni into the ZnO films. It was found that the intensity of this ultraviolet peak changed with Ni content while its position remained stable. The fluorescence emission of the samples was optimal when Ni:ZnO was 5 mol%, indicating that the peak centered at 360 nm might originate from the composite transition between the splitting valence band and conduction band, not from the entrance of the impurity energy level into the conduction band after doping.