Using a photon phase-space source for convolution/superposition dose calculations in radiation therapy

For a given linac design, the dosimetric characteristics of a photon beam are determined uniquely by the energy and radial distributions of the electron beam striking the x-ray target. However, in the usual commissioning of a beam from measured data, a large number of variables can be independently tuned, making it difficult to derive a unique and self-consistent beam model. For example, the measured dosimetric penumbra in water may be attributed in various proportions to the lateral secondary electron range, the focal spot size and the transmission through the tips of a non-divergent collimator; the head-scatter component in the tails of the transverse profiles may not be easy to resolve from phantom scatter and head leakage; and the head-scatter tails corresponding to a certain extra-focal source model may not agree self-consistently with in-air output factors measured on the central axis. To reduce the number of adjustable variables in beam modelling, we replace the focal and extra-focal sources with a single phase-space plane scored just above the highest adjustable collimator in a EGS/BEAM simulation of the linac. The phase-space plane is then used as photon source in a stochastic convolution/superposition dose engine. A photon sampled from the uncollimated phase-space plane is first propagated through an arbitrary collimator arrangement and then interacted in the simulation phantom. Energy deposition kernel rays are then randomly issued from the interaction points and dose is deposited along these rays. The electrons in the phase-space file are used to account for electron contamination. 6 MV and 18 MV photon beams from an Elekta SL linac are used as representative examples. Except for small corrections for monitor backscatter and collimator forward scatter for large field sizes (<0.5% with <20 x 20 cm2 field size), we found that the use of a single phase-space photon source provides accurate and self-consistent results for both relative and absolute dose calculations.     

催经止孕药Ru-486的临床药代动力学

应用高效液相色谱法(HPLC)研究了抗孕激素药,Ru-486的临床药代动力学。六名志愿受试者,一次口服Ru-486 50毫克后测得该药的药代动力学各项参数,血药半寿期t 1/2 33.0小时,一级消除速率常数Kel 0.021 hr~(-1),血药表观容积Vd 120.1 Liter,体内血药总廓清率Cl2.5 Liter/hr,药-时曲线下面积Auc 19825.1 ng/ml/hr。实验表明,服药后一小时血药浓度迅即达高峰,随后转入消除期,血浆药物浓度在消除相的头4～8小时消除较快,而后逐渐减慢,持续24小时,到48小时血药浓度已较低(0.15±0.07μg/ml)。     

Sex-Dependent Effects of 7,8-Dihydroxyflavone on Metabolic Health Are Associated with Alterations in the Host Gut Microbiome

7,8-Dihydroxyflavone (DHF) is a naturally occurring flavonoid that has been reported to protect against a variety of pathologies. Chronic administration of DHF prevents high-fat diet (HFD)-induced obesity in female, but not male, mice. However, the mechanisms underlying this sexual dimorphism have not been elucidated. We have discovered that oral DHF supplementation significantly attenuates fat mass, hepatic lipid accumulation, and adipose tissue inflammation in female mice. In contrast, male mice were not protected from adiposity, and had a paradoxical worsening of hepatic lipid accumulation and adipose tissue inflammation upon DHF supplementation. Consistent with these sexually dimorphic effects on body weight and metabolic health, 7,8-DHF induced early and stable remodeling of the female intestinal microbiome. DHF supplementation significantly increased gut microbial diversity, and suppressed potentially detrimental bacteria, particularly Desulfovibrionaceae, which are pro-inflammatory and positively associated with obesity and inflammation. Changes in the female gut microbiome preceded alterations in body weights, and in silico analyses indicated that these early microbial changes were highly predictive of subsequent weight gain in female mice. While some alterations in the intestinal microbiome were also observed in male DHF-supplemented mice, these changes were distinct from those in females and, importantly, were not predictive of subsequent body weight changes in male animals. The temporality of microbial changes preceding alterations in body weight in female mice suggests a role for the gut microbiome in mediating the sexually dimorphic effects of DHF on body weight. Given the significant clinical interest in this flavonoid across a wide range of pathologies, further elucidation of these sexually dimorphic effects will aid the development of effective clinical therapies.     

活性氧对红细胞膜流动性影响的研究

目的 :研究活性氧诱导红细胞发生氧化溶血的机制。方法 :用不同浓度的 H2 O2 作用于离体正常红细胞 ,分别用比色法、硫代巴比妥酸荧光法、荧光偏振法测定红细胞溶血度、红细胞膜脂质过氧化物 (L PO)、红细胞膜微粘度。结果 :5 0 ,10 0 ,12 0 mm ol/ L 浓度的 H2 O2 作用于红细胞后 ,均引起红细胞发生氧化溶血 ,红细胞溶血度、红细胞膜 L PO、红细胞膜微粘度均明显增加 ;H2 O2 在 5 0～ 12 0 mm ol· L- 1浓度范围内 ,红细胞溶血度、红细胞膜 L PO、红细胞膜微粘度的增加与 H2 O2 有明显的量效关系 ;红细胞膜微粘度与红细胞溶血度呈明显正相关 ,红细胞膜 L PO与红细胞膜微粘度呈明显正关。结论 :活性氧引发红细胞膜脂质过氧化导致红细胞膜流动性降低在活性氧诱导红细胞发生氧化溶血的机制中起一定的作用     

胰岛的血液引流与胰腺外分泌的机能和临床意义

目的　研究胰岛的血液引流与胰腺外分泌的机能联系与临床意义。方法　运用微血管树脂 /墨汁灌注扫描电镜 /光镜观察法、保留动态及组织信息在静态样本的微循环观察法、FITC标记红细胞 (FITC- RBC)荧光活体显微镜观察法以及计算机图像处理微血管三维重建法 ,对 11例男性尸体、40只猴、2 4只狗、62只鼠、2 4只兔的胰岛血液引流通道与胰腺外分泌腺泡的关系进行了系统研究。结果　不同动物的内分泌胰岛血液主要经胰岛的三种类型输出血管引流至不同的外分泌腺泡区域 ,灵长类的部分胰岛血液还引流至邻近的小胰岛 ,研究者根据胰岛引流系统的特征对其进行了分类及命名 :1连续型引流系统 ,所有胰岛具有这类引流 (输出 )管道 ,其管径细 ,行程短、引流至胰岛周围的腺泡毛细血管区域。 2聚合型引流系统 ,为部分胰岛所有 ,其管径粗、行程长 ,引流至远离胰岛的腺泡毛细血管区域。 3跨越型引流系统 ,为部分胰岛所有 ,其输出管道越过小叶间隔引流至另一胰腺小叶的腺泡毛细血管区域 ,而这一小叶往往没有胰岛存在。 4胰岛 -胰岛型引流系统 ,灵长类部分胰岛的血液通过胰岛 -胰岛型引流通道回流至邻近的小胰岛。结论　胰岛具有完善联系外分泌腺泡的引流系统 ,提示含有高浓度胰岛内分泌激素的胰岛血液可能对外分泌腺泡的机能     

刺五加对豚鼠地高辛中毒的影响

豚鼠灌服地高辛复制地高辛中毒模型，研究五加对地高辛中毒的影响。结果发现，服刺五加组豚鼠发生心律失常较未给药组明显推迟，而血中地高辛浓度则显著高于未给药组，提未临床应用地高辛时同时给予刺五加有于减少减轻地高辛的毒性反应。     

前列腺癌与增生性病变的流式细胞分析

应用流式细胞分析术（ＦＣＭ）对２０例前列腺癌（ＰＣ）和１５例良性前列腺组织作了ＤＮＡ含量检测，着重分析了ＰＣ及增生性病变的细胞增殖指数（ＰＩ）与ＤＮＡ指数（ＤＩ）。结果表明在良恶性前列腺组织中有明显差异（Ｐ＜０．０１）。２０例ＰＣ的组织学分级与ＦＣＭ检测结果有关，ＰＣ－Ⅲ与ＰＣ１－Ⅰ、ＰＣ－Ⅱ与ＰＣ－Ⅰ、ＰＣ－Ⅲ与ＢＰＨ的ＰＩ、ＤＩ相差显著（Ｐ＜０．０１）。本研究结果提示良恶性前列腺病变的ＰＩ与ＤＩ能较客观地反应不同细胞的生物活性，并对分化低、分级高的ＰＣ的恶性程度判断及其预后的推测，以及癌前病变的分析有意义。     

MTT法检测极低频弱磁场对SY细胞的影响

本文采用 MTT 示踪法,检测极低频弱磁场对 SY 细胞有无影响。结果发现:频率固定为50Hz 时变化磁场幅值,在150uT、300uT 下细胞吸光度值有明显降低;幅值固定为150uT 时变化磁场频率,在25Hz、50Hz、75Hz 磁场照射下吸光度值均有不同程度下降,而在10Hz、60Hz、100Hz、300Hz、500Hz 磁场照射下没有变化;幅值固定为300uT 时变化磁场频率,在500Hz、75Hz、100Hz、300Hz、磁场照射下吸光度值均有不同程度下降,而在10Hz、25Hz、60Hz、500Hz 磁场照射下没有变化。