表面粗糙度对牙科银汞合金抗折力的影响

目的比较不同表面粗糙度的牙科银汞合金试件的断裂载荷,探讨试件表面状况对脆性牙科材料抗折力的影响。方法制作直径10mm、厚2mm的圆盘形银汞试件48个．随机分成4组,其中3组分别以220、400、1200号SiC砂纸双面磨平．另一组不经打磨．表面保持试件制作完毕后的自然状态。每组随机抽取5个试件,置于粗糙度测试仪上测量表面粗糙度。试件于（23±1）。C空气中保存7d后置于30％玻璃纤维加强尼龙6．6基底上以20mm直径不锈钢球加载进行赫兹压痕试验,记录初始断裂载荷值并进行统计分析。结果未经打磨、220号、400号、1200号SiC砂纸打磨的试件的表面粗糙度平均值分别为1．77、1．99、1．28、0．66μm,断裂载荷值分别为（656．1±44．1）、（644．9±57．9）、（678.3±40．4）、（721．1±60．1）N。随着粗糙度的降低,初始断裂载荷值逐渐增加,1200号砂纸打磨组与未经打磨组和220号砂纸打磨组之间差异有统计学意义（P〈0．05）。结论脆性材料试件的表面粗糙度对其抗折能力有一定影响．     

Fate of the aortic root after arterial switch operation.

OBJECTIVE: Concerns have been voiced about possible dilation and insufficiency of the neo-aortic valve after the arterial switch operation (ASO). AIMS: To determine growth of the neo-aortic valve and the aortic anastomosis after ASO and the prevalence of insufficiency or stenosis. PATIENTS AND METHODS: Since 1977, 144 consecutive patients (pts) underwent ASO for transposition of the great arteries (TGA). Median follow-up was 8.65 years (0.1--22.5 years). Simple TGA was present in 97 pts and 47 had TGA with ventricular septal defect (VSD). Detailed echocardiography included measurements of aortic diameter at four levels. The 608 measurements were compared with published normal values. RESULTS: The mean aortic valve z-score was 1.5, without significant change with age (P=0.75). Under 4 months, mean valve z-score was 0.63+/-2.20, between 5 and 12 months 2.56+/-2.30 (P<0.0001). Gradual growth occurs thereafter. The aortic sinus follows an identical growth pattern. The aorta at the anastomosis, is initially smaller than normal (z-score -0.64). After 4 months the z-score is 0.83, followed by continued growth of 0.1 z-score per year. At the last visit, the aortic valve z-score was above 2 in 51 patients, between -2 and 2 in 72 and less than -2 in six patients, none of whom had a flow velocity above 2 m/s. z-score of patients with VSD remained above those without VSD (P<0.0001).Aortic insufficiency was grade 2/4 in three patients, grade 3/4 in one and grade 4/4 in one. No patient developed aortic stenosis. CONCLUSION: After ASO the neo-aortic valve and sinus are larger than normal, representing the natural size difference in the prenatal situation and influence of associated cardiac malformations. In the first year of life, rapid dilatation of the new aorta is observed, followed by growth towards normalization of the valve and sinus size. Stenosis at the anastomosis was not observed. Aortic dilatation by itself is rarely associated with significant insufficiency.     

“In-house” pharmacological management for computed tomography coronary angiography: heart rate reduction, timing and safety of different drugs used during patient preparation

We retrospectively evaluated the effect, timing and safety of different pharmacological strategies during 64-slice CT coronary angiography (CT-CA). From the institutional database of CT-CA we enrolled 560 consecutive patients with suspected coronary artery disease. The type of drug preparation (group 1 = no treatment; group 2 = oral metoprolol; group 3 = other; group 4?=?intravenous (IV) atenolol; group 5?=?IV atenolol + nitrates; NR = non-responders), timing, and adverse effects were recorded. Heart rate (HR) during different preparation phases was recorded. Four adverse effects were recorded, none of which was attributable to pharmacological treatment. In all groups, except group 1, the HR on arrival was significantly reduced by the pharmacological treatment (p?<?0.01). Group 4 showed the best (?16?±?8 bpm) HR reduction. There was no significant effect on HR due to nitrates (p?=?0.49), while a slight increase due to contrast material was noted (p?<?0.05). Average time required for preparation was 44?±?25 min. Groups 4 and 5 showed the most effective timing (8?±?9 min and 8?±?8 min, respectively; p?<?0.01). Pharmacological preparation in patients undergoing CT-CA is safe and effective. Best results in terms of HR reduction and fast preparation are obtained with IV administration of beta-blockers.     

Potential Additional Indicators for Pacemaker Requirement in Isolated Congenital Atrioventricular Block

Low heart rate is the predominantly used indication for pacemaker intervention in patients with isolated congenital atrioventricular block (CAVB). The aim of this study was to compare the difference in heart rates recorded with ECG and Holter monitoring between paced (PM) and nonpaced (NPM) patients with isolated CAVB before pacemaker implantation to identify additional predictors for future PM need. Retrospective evaluation of atrial and ventricular rates (electrocardiography) and minimal and maximal (Holter) heart rates in 129 CAVB patients prior to PM implantation (n = 93) was performed, and results are expressed in V adjusted for age and sex. The average V score for the atrial rate was 0.51 (n = 50) in the PM group and 0.60 (n = 22) in the NPM group (not-significant). The average z score for the ventricular (average) rate was −0.91 (n = 83) in the PM group and −0.93 (n = 33) in the NPM group (not-significant). Minimal heart rate was −0.94 (n = 61) in the PM group and −0.86 (n = 25) in the NPM group (not significant). Maximal heart rate was −0.96 (n = 61) in the PM group and −0.95 (n = 26) in the NPM group (not significant). Initial recordings of the average heart rate and the minimal and maximal heart rate recorded during Holter monitoring do not seem to predict future pacemaker need in patients with CAVB. Studies with exercise stress tests are needed to confirm these findings.     

Diagnostic accuracy of multislice computed tomography coronary angiography is improved at low heart rates

Purpose: Assess the effect of heart rate on diagnostic accuracy for the detection of significant coronary artery stenosis using 16-row multislice computed tomography (MSCT). Material and methods: About 120 patients (105 males; 59±11 years) with suspected coronary artery disease who underwent conventional coronary angiography (CA) and MSCT-CA were retrospectively enrolled for the study. Patients underwent a MSCT-CA (Sensation 16, Siemens, Germany), with the following protocol: collimation 16×0.75 mm, gantry rotation time 420 ms, feed/rotation 3.0 mm, kV 120, mAs 400–500. The protocol for contrast material administration was 100 ml of Iodixanol (Visipaque 320 mg l/ml, Amersham, UK) at 4 ml/s and the delay was defined with a bolus tracking technique. In all patients the mean heart rate (HR) during the scan was used as a criteria to divide the population in two groups of 60 patients each. In one group (Low HR) the 60 patients with lower heart rates, and in the other group (High HR) the patients with higher heart rates. In the two groups diagnostic accuracy (per coronary segment) for the detection of significant stenosis (≥50% lumen reduction) was evaluated in vessels ≥2 mm of diameter using quantitative CA as reference standard. The difference in diagnostic accuracy were compared with a Chi² test and a p<0.05 was considered significant. Results: There was no significant difference between the two groups regarding age, gender, weight, mean intravascular attenuation, and calcium score. Overall 1310 (652 for Low HR and 658 for High HR) segments with 219 (105 for Low HR and 114 for High HR) significant lesions were available for the analysis. The average heart rate was 52±4HU and 63±5HU for Low HR and High HR, respectively (p<0.001). The sensitivity and specificity were 92 and 96% for Low HR and 90 and 92% for High HR (p<0.05). There were 22 vs. 44 false positives, and 8 vs. 12 false negatives in the Low HR and High HR, respectively. Conclusion: Increasing HR significantly deteriorates diagnostic accuracy in MSCT-CA.     

妥卡尼对豚鼠心室肌细胞钙电流和钾电流的抑制作用

利用酶分散的成年豚鼠心室肌细胞和全细胞电压钳技术,研究了妥卡尼(tocainide)对心室肌细胞钙电流(I_ca)、延迟整流钾电流(I_k)和ATP敏感性钾电流(Ik,ATP)的作用。结果表明,妥卡尼对I_ca和I_k均显示浓度相关的抑制作用,妥卡尼50umol·L^-1对I_ca和I_k的抑制率分别为16%和3%。这可能是妥卡尼有效抑制室上性心动过速和缩短心肌动作电位平台期的重要机制。     

Interleukin-6 is not involved in the interleukin-1-induced production of colony-stimulating factors by human bone marrow stromal cells and fibroblasts

Interleukin-6 (IL-6) is a multifunctional cytokine that plays a role in regulation of hematopoiesis. Because IL-6 is coinduced with colony- stimulating factors (CSFs) by various cell types in response to stimulation with IL-1, we investigated whether IL-6 is involved in the IL-1-induced production of CSF by human bone marrow (BM) cells in long- term culture or human fibroblasts. We showed that IL-6 does not induce CSF production by these cells. Neither addition of exogenous IL-6 nor neutralization of endogenous production of IL-6 by an anti-IL-6 monoclonal antibody (MoAb) diminished the IL-1-induced colony- stimulating activity (CSA), indicating that IL-6 did not act synergistically with IL-1. Finally, IL-6 did not influence the kinetics of IL-1-induced CSA production by human fibroblasts. We conclude that IL-6, either alone or in combination with IL-1, does not induce CSF production by human BM stromal cells or fibroblasts.     

Beta-blocking therapy in patients with the Marfan syndrome and entire aortic replacement.

OBJECTIVE: Beta-blocking therapy is the standard therapy in non-operated Marfan patients, however its efficacy after entire aortic replacement is unknown. The aim of this study was to describe the influence of (nearly) entire aortic replacement and beta-blocking therapy on blood pressure and wave reflections in Marfan patients. METHODS: Four Marfan patients (mean age 31+/-3 years) and 8 age matched control subjects were studied. Blood pressure and wave reflections (reflection coefficient and augmentation index) were studied by means of magnetic resonance imaging, continuous non-invasive blood pressure measurements and applanation tonometry. Patients were studied with atenolol, labetalol and without beta-blocking therapy. RESULTS: In Marfan patients, aortic systolic pressure (129+/-13 vs 114+/-10 mmHg), pulse pressure (58+/-13 vs 40+/-5 mmHg), wave speed (11+/-3 vs 4+/-0.4 m s(-1)) and reflection coefficient (65+/-22 vs 41+/-5%) were significantly increased compared to controls. There was no difference in aortic pressure between various medications in Marfan patients (atenolol 129/76 mmHg, labetalol 121/75 mmHg and without beta-blocking therapy 129/71 mmHg). Higher reflection coefficients were seen in patients with atenolol compared to discontinued medication (73+/-18 vs 65+/-22%), and also the augmentation index was higher with atenolol compared to labetalol and discontinued medication (24+/-22 vs 17+/-17 vs 22+/-22%, respectively). CONCLUSION: Our results describe increased pulse pressure, systolic pressure, wave speed and wave reflections in four Marfan patients after entire aortic replacement. The use of atenolol or labetalol did not decrease aortic pressure and with atenolol increased wave reflections were observed. Therefore, the beneficial effect of atenolol in these patients is doubtful.