一种新的正交参数选优法及其在非线性回归分析中的应用

非线性回归分析是工程中经常采用的一种用来估计数学模型参数的方法，该方法能否顺利运用与参数初始值的选择有极大关系。本研究提出一种新的正交参数选优法——阻尼正交表法，它不仅可以保证非线性回归分析算法的顺利收敛，而且能够显著提高后者的收敛速度，进而极大改善非线性回归分析算法的应用性能。本研究的数值试验及心肌造影超声心动图定量分析应用实例表明，作为对传统正交参数选优法的一种改进，阻尼正交表法在科学与工程计算或信号与信息处理领域有着很好的应用前景。     

Effect of dietary protein on Masheri-induced drug metabolising enzymes

The modulation of drug metabolising enzymes by Masheri extract (ME) and Benzo(a)Pyrene [B(a)P] was studied in male Sprague Dawley rats fed different dietary protein levels. Two groups of 21 days old male Sprague Dawley rats were put on a high protein diet (SHP) with 20% Casein, and a low protein diet (SLP) with 3% Casein semisynthetic based diets for 12 weeks. The SLP fed animals showed lower basal levels of the Phase I activating enzymes viz. Cytochrome P450, Benzo(a)Pyrene hydroxylase, Benzphetamine demethylase and Phase II glutathione detoxification system viz. Glutathione (GSH) and Glutathione-S-transferase. ME and B(a)P treatment significantly depleted the glutathione detoxification system in the SLP group whereas an opposite effect was observed in the SHP group. Interstingly, ME and B(a)P treated rats in the SLP group showed a higher percent increase in the hepatic and pulmonary Phase I enzyme activities than those observed in the treated ME/B(a)P treated SHP rats. Furthermore, both ME and B(a)P significantly decreased the hepatic pool of vitamin A while a concomittant increase in that of vitamin C was observed.     

Effects of hydroxocobalamin on rat cardiac papillary muscle

Hydroxocobalamin is a rapid and powerful antidote in acute cyanide poisoning. The effects of hydroxocobalamin (0.1, 0.3, and 1 mM) on intrinsic myocardial contractility were studied on isolated rat cardiac papillary muscles (n=10). Whatever the concentration, hydroxocobalamin did not modify the active isometric force and a slight increase in maximum unloaded shortening velocity was noted at 1 mM. Only 0.3 mM significantly impaired contraction-relaxation coupling under low load, suggesting a slight decrease in sarcoplasmic reticulum function. No changes in contraction relaxation coupling under heavy load were noted, suggesting the lack of modification of myofilament calcium sensitivity. These results suggest that hydroxocobalamin does not induce noticeable changes in intrinsic myocardial contractility. An indirect mechanism might be involved in the previously reported decrease in cardiac function at supratherapeutic concentrations of hydroxocobalamin.     

高氧液对家兔心肌缺血再灌注损伤的保护作用

目的：观察高氧液对家兔心肌缺血再灌注损伤的保护作用。方法：结扎兔冠状动脉左室支段，40min后解除结扎，制成心肌急性缺血再灌注模型。于缺血前10min、再灌注前10min，静滴平衡盐液（对照组）、高氧平衡盐液（高氧液组），观察在急性缺血及再灌注状态下心电图、血浆肌酸磷酸激酶（CK）、丙二醛（MDA）和超氧化物歧化酶（SOD）的变化。结果：高氧平衡盐液能使抬高的心电图S－T段明显下降，缺血再灌注心肌CK活性明显降低；并能保护SOD的活性，降低脂质过氧化反应代谢产物MDA的含量。结论：高氧平衡盐液对家兔在体心肌缺血再灌注损伤具有保护作用。     

溶栓及经皮冠脉腔内成形术治疗急性心肌梗死的疗效分析

目的　对比直接冠状动脉腔内成形术 (PTCA)及静脉尿激酶 (UK)溶栓对急性心肌梗死 (AMI)治疗的临床疗效。方法　采用观察性队列研究的方法 ,对 97例AMI患者采用UK溶栓 ,60例AMI患者采用直接PTCA治疗 ,比较两组住院期及随访期的超声心动图 (UCG)和临床结果。结果　住院期间UCG检查室壁运动正常者在PTCA组为 (4 6.0 0 % ) ,高于UK组 (2 4.73 % ) (p =0 .0 2 1) ,矛盾运动发生率PTCA组为 0 ,而UK组为 11.83 %。LVEF在PTCA组为 5 6.88± 10 .47,高于UK组 (5 1.5 8± 10 .97) (p =0 .0 41)。住院期心衰发生率UK组为 3 2 .5 9% ,高于PTCA组 (18.3 3 % ) (p =0 .0 2 9)。随访 13 .3 2± 6.86个月累计心衰发生率UK组为 16.2 8% ,也高于PTCA组 (5 .19% ) (p =0 .0 0 1)。住院期间的病死率UK组为 10 .3 1% ,PTCA组为 5 .0 0 % (p =0 .10 0 )。累计病死率UK组为 15 .5 6% ,明显高于PTCA组 (5 .0 0 % ) (p =0 .0 2 1)。 60岁以上年龄组累计的病死率仍然是UK组 (2 8.99% )高于PTCA组 (10 .3 4% ) (p =0 .0 49)。在随访 3、6、12及 2 4个月时PTCA组的生活质量计分各自为 :5 9.90± 14 .67、74.40± 12 .86、73 .86± 9.70、82 .47± 10 .47均高于同时期UK组的计分 (分别是 5 2 .0 8± 14 .49、65 .0 0± 14 .72、67.0 2     

纤溶酶原激活物抑制物-1基因4G/5G基因型分布频率与心肌梗死和脑梗死相关性初步分析

目的研究我国汉族人纤溶酶原激活物抑制物-1基因启动子区-675位4G/5G(单鸟嘌呤核苷酸插入/缺失)基因多态性与心肌梗死和脑梗死的等位基因特异性的相关性.方法以等位基因特异性聚合酶链反应(AS-PCR)扩增56例心肌梗死患者,54例脑梗死患者,83例无关健康对照个体的基因组DNA,鉴定PAl-1 4G/5G基因型及分布频率,常规方法检验研究个体的主要临床和生化指标.结果PAI-1基因启动子区4G/5G基因多态性在心肌梗死,脑梗死患者组中的分布频率与对照组明显不同.在心肌梗死组中,4G/4G基因型分布频率(71.40%)比对照组(30.12%)显著增加(P＜0.001),杂合型4G/5G基因型分布频率(25.00%)比对照组(62.65%)明显降低;而在脑梗死组中,4G/4G,4G/5G基因型分布频率(分别为20.37%,55.56%)均比对照组(分别为30.12%,62.65%)低,5G/5G基因型明显增加(24.07%vs7.32%,P＜0.001).而且心梗组中血浆PAI-1活性水平随着4G等位基因的减少而降低;脑梗死组中,血浆PAI-1活性水平随着5G等位基因的升高而增加.心肌梗死、脑梗死患者组中的血浆PAI-1活性水平,甘油三酯水平和血糖水平都比对照组明显升高(分别为P＜0.001,P＜0.05,P＜0.001).结论本研究表明,中国汉族人PAI-1基因启动子区4G/5G基因多态性可能和心肌梗死、脑梗死发生的危险性相关,4G/5G基因多态性可能是一种重要的遗传性血栓性疾病的危险因子.     

表没食子儿茶素没食子酸酯对缺血再灌注损伤大鼠心肌脂质过氧化及心肌酶活性的影响

目的：观察表没食子儿茶表没食子酸酯（EGCG）对缺血再灌注损伤大鼠心肌脂质过氧化及心肌酶活性的影响。方法：雄性Wistar大鼠50只分为5组，假手术组、缺血再灌注组（IR），丹参（SM，100mg/kg）组，EGCG1（10mg/kg)组和EGCG2（20mg/kg）组，每组10只动物，采用结扎大鼠左冠状动脉前降支30min后再灌注60min的方法建立在体缺血再灌注损伤模型，分别测定心肌丙二醛（MDA）含量，超氧化物歧化酶（SOD）及ATP酶活性和血浆乳酸脱氢酶（LDH）水平。结果：与假手术组比，IR组大鼠心肌MDA及血浆LDH明显升高，SOD及ATP酶活性则显著降低（P＜0．01）；EGCG和SM均能显著，降低MDA与LDH，明显增加SOD与ATP酶活性（与IR组比，P＜0．01），并且EGCG（20mg/kg)，降低MDA与LDH的作用较SM（100mg/kg)更明显（P＜0．05）。结论：EGCG通过抑制脂过氧化反应和提高心肌SOD与ATP酶活性，对大鼠缺血再灌注损伤心肌有显著的保护作用。     

Detection of moderate and severe coronary artery stenosis with technetium-99m tetrofosmin myocardial single-photon emission tomography

The aim of this study was to determine the diagnostic accuracy of technetium-99m tetrofosmin myocardial imaging for the localization of coronary artery stenoses of different degrees of severity. Stress-rest single-photon emission tomography (SPET) was performed on separate days in 80 patients (64 males, 16 females; mean age 61 years; 43 patients with previous myocardial infarction; 18 patients with pharmacological stress), within 6 months of coronary angiography. Scintigraphic images were blindly and independently evaluated by three observers. Coronary stenosis was defined as a >50% narrowing in luminal diameter; severe stenosis was defined as a proximal stenosis of >75% or a peripheral stenosis of >90%. Coronary angiography revealed normal coronary arteries or insignificant coronary stenosis in 13 patients and significant coronary stenoses in 67 patients. The sensitivity and specificity of ^99mTc-tetrofosmin SPET in respect of severely stenosed vessels were, respectively, 80% and 65% for the left anterior descending artery (LAD), 100% and 46% for the right coronary artery (RCA) and 58 and 78% for the left circumflex artery (LCx) territories. Considering all the significantly stenosed vessels, a significant decrease in sensitivity was observed for LAD territories (to 59%, P=0.05), and a nonsignificant decrease for RCA (88%) and LCx (47%) territories while specificity values remained essentially unchanged. No significant changes in sensitivity or specificity were observed when regions with previous myocardial infarction were excluded. In conclusion, the sensitivity of ^99mTc-tetrofosmin SPET for the localization of individual stenosed vessels is only moderate when all significant stenoses are considered, but the ability of this technique to predict the location of severe coronary artery stenoses seems satisfactory, with the exception of the low specificity in respect of RCA territories. Received 26 April and in revised form 7 June 1997     

Postpartum acute myocardial infarction

We report a postpartum acute myocardial infarction that occurred during the first week after cesarean section delivery. We also calculated the rate of postpartum myocardial infarction as related to all women with myocardial infarctions seen in our hospital.(Am J Obstet Gynecol 1997;177:1553-5.)     

Effect of artifacts due to flowing blood on the reproducibility of phase-contrast measurements of myocardial motion

The reproducibility of myocardial motion trajectories calculated from cine phase-contrast (PC) velocity data is reduced by artifacts due to the inconsistent motion of intracardiac blood. Spatial presaturation reduces these artifacts but requires a longer sequence TR, with a potentially negative effect on trajectory accuracy and reproducibility. We investigated the effect of spatial presaturation on trajectory reproducibility. A midventricular transaxial slice was imaged in five normal volunteers. The same slice was imaged three times each with sequences using spatial presaturation or not. Because the most serious artifacts originate in the heart chambers and propagate in the phase-encoded direction, myocardial regions that were in line with the heart chambers (in the phase-encode direction) had the highest artifact level in the scans without spatial presaturation. The reproducibility of trajectories for regions placed in these areas (the anterior wall, septum and posterior wall in the transaxial scans with phase encoding in the anterior-posterior direction) improved by a factor of two when presaturation was used (P < .001). In areas that were not in line with the heart chambers (eg, the anterior aspect of the lateral wall in the transaxial scans), the effect of presaturation was not significant. These results correlate well with the measured reduction in artifact level. The reproducibility of myocardial motion trajectories over large areas of the heart is improved to approximately 1 mm when presaturation is used. Therefore, use of presaturation is recommended for myocardial motion studies using cine PC velocity data.