Trichinella spiralis: selective intestinal immune deviation in the rat

In rats, infections with 100-2000 Trichinella spiralis muscle larvae lead to a prompt immunity that is expressed in parasite expulsion within 14 days. Rats infected with more than 2000 larvae display impaired immunity with rejection delayed by 50% (7 days) or more. Suppression is selective for expulsive immunity as the antifecundity response of rats is directly proportional to dose and is expressed sooner in heavily infected subjects. Suppression of intestinal expulsive immunity was suggested by the fact that, with low doses (2000 larvae or less), worm rejection was inhibited by cortisone, whereas cortisone inhibited antifecundity but had no discernable effect on worm rejection in high-dose infections. Evidence for local immune deviation as opposed to systemic immunosuppression was obtained in experiments using parabiotic rats. When one partner was infected with 6000 worms and the other with 200, the rat infected with 200 parasites showed earlier rejection than was seen in single controls infected with 200 worms. The prolonged survival of high-dose adults was not accompanied by a change in the site of worm residence in the gut. Immunological parameters such as serum antibody levels, the number of activated cells or specific anti-T. spiralis lymphocytes in thoracic duct lymph were all increased in a dose-dependent manner. These experiments therefore demonstrate a novel autoprotective mechanism by which adult T. spiralis selectively reduce the expression of expulsive immunity in the gut.     

A model for radiation-induced bystander effects, with allowance for spatial position and the effects of cell turnover

Bystander effects, whereby cells that are not directly exposed to ionizing radiation exhibit adverse biological effects, have been observed in a number of experimental systems. A novel stochastic model of the radiation-induced bystander effect is developed that takes account of spatial location, cell killing and repopulation. The ionizing radiation dose- and time-responses of this model are explored, and it is shown to exhibit pronounced downward curvature in the high dose-rate region, similar to that observed in many experimental systems, reviewed in the paper. It is also shown to predict the augmentation of effect after fractionated delivery of dose that has been observed in certain experimental systems. It is shown that the generally intractable solution of the full stochastic system can be considerably simplified by assumption of pairwise conditional dependence that varies exponentially over time.     

Convergence to stationary distributions in two-species stochastic competition models

Two sets of sufficient conditions are given for convergence to stationary distributions, for some general models of two species competing in a randomly varying environment. The models are nonlinear stochastic difference equations which define Markov chains. One set of sufficient conditions involves strong continuity and -irreducibility of the transition probability for the chain. The second set has a much weaker irreducibility condition, but is only applicable to monotonic models. The results are applied to a stochastic two-species Ricker model, and to Chesson's lottery model with vacant space, to illustrate how the assumptions can be checked in specific models.     

蛇床的生物学特性及资源分布

本文通过实地调查和异地栽培试验研究了蛇床的生物学特性及资源分布,为蛇床子药材的生产、收购提供了科学依据。     

Placing empirical limits on metapopulation models for terrestrial plants

Both island-biogeographic (dynamic) and niche-based (static) metapopulation models make predictions about the distribution and abundance of species assemblages. We tested the utility of these models concerning such predictions for terrestrial vascular plants using data from 74 landscapes across the globe. We examined correlations between species frequency and local abundance and shapes of the species frequency distribution. No data set met all of the predictions of any single island-biogeographic metapopulation model. In contrast, all data sets met the predictions of the niche-based model. We conclude that in predicting the distribution of species assemblages of plants over scales greater than 10–1 km, niche-based models are robust while current metapopulation models are insufficient. We discuss limitations in the assumptions of the various models and the types of empirical observations that they will each have to deal with in further developments.     

小剂量阿替普酶治疗急性脑梗死患者的临床疗效及安全性评价

目的:探讨急性脑梗死患者静脉溶栓使用小剂量(0.6 mg/kg)阿替普酶的临床疗效及安全性。方法:将2016年1月至2019年12月我院神经内科收治的溶栓时间窗内40例急性脑梗死患者随机分为标准剂量组(0.9 mg/kg)和小剂量组(0.6 mg/kg),每组20例,分别在溶栓前、溶栓后1小时对患者进行美国国立卫生研究院卒中量表(NIHSS)评分,溶栓前和溶栓后24小时做头颅CT排除脑出血,密切监测不良反应。结果:标准剂量组有效率为80.00%,小剂量组有效率为75.00%,两组比较差异无统计学意义(P0.05)。治疗前两组NIHSS评分比较差异无统计学意义(P0.05),治疗后两组NIHSS评分均降低,与治疗前相比差异有统计学意义(P0.05),治疗后两组NIHSS评分差异无统计学意义(P0.05)。标准剂量组总不良反应发生率为40.00%,高于小剂量组的20.00%,差异无统计学意义(P0.05)。结论:阿替普酶可有效改善急性脑梗死患者的神经功能,小剂量(0.6 mg/kg)与标准剂量(0.9 mg/kg)溶栓效果相当,安全性较好,出血事件发生率较低,可根据患者情况酌情选用小剂量。     

keV离子辐照固态腺嘌呤与胞嘧啶的剂量效应研究

研究了经20keV的氮离子、氩离子辐照后,腺嘌呤与胞嘧啶的残存率与注入剂理的关系。结果表明,在相同的剂量下,氮离子对碱基的损伤比氩离子高,而对同种离子而言,胞嘧啶比腺嘌呤表现出较高的辐射敏感性。计算了碱基分子损伤的G值,比较它们随剂量的增大呈减小的趋势。考察了加入自由基清除剂后,碱基损伤剂量效应的变化。并对上述结果提出了初步的解释。     

不同剂量甲泼尼龙治疗老年AECOPD的疗效及其对炎症因子水平的影响比较

目的:观察和比较不同剂量甲泼尼龙治疗老年慢性阻塞性肺疾病急性加重(AECOPD)的疗效及其对炎症因子的影响。方法:选取2014年1月到2017年1月收治的114例老年AECOPD患者,随机将患者分为A组、B组和C组各38例。A组采用甲泼尼龙40 mg/d静脉推注,B组采用甲泼尼龙80 mg/d静脉推注,C组不使用甲泼尼龙。对比三组患者的临床疗效以及治疗前后的改良版英国医学研究委员会呼吸问卷(mMRC)评分、动脉血氧分压(PaO_2)、动脉二氧化碳分压(PaCO_2)、下去白细胞介素-6(IL-6)、白细胞介素-8(IL-8)、肿瘤坏死因子-α(TNF-α)以及C反应蛋白(CRP)水平的变化。结果:治疗后,A组的总有效率为89.47%,B组的总有效率为92.11%,均显著高于C组(均P0.05)。A组和B组治疗后的mMRC评分、PaCO_2水平均显著低于C组,而PaO_2水平显著高于C组(均P0.05);B组治疗后的m MRC评分、PaCO_2均显著低于A组,而PaO_2显著高于A组(均P0.05);A组和B组治疗后的血清IL-6、IL-8、TNF-α以及CRP水平均显著低于C组(均P0.05);B组治疗后的血清IL-6、IL-8、TNF-α、CRP水平均显著低于A组(均P0.05)。三组患者不良反应发生率的对比差异均无统计学意义(均P0.05)。结论:与40 mg/d甲泼尼龙相比,短期80 mg/d甲泼尼龙静脉推注可更显著减轻AECOPD患者的炎症反应,提高临床疗效,同时具有良好的安全性。     

Dosimetric effect of intrafraction motion and different localization strategies in prostate SBRT

The aim of this study was to evaluate the dosimetric effect of continuous motion monitoring based localization (Calypso, Varian Medical Systems), gating and intrafraction motion correction in prostate SBRT. Delivered doses were modelled by reconstructing motion inclusive dose distributions for different localization strategies. Actually delivered dose (strategy A) utilized initial Calypso localization, CBCT and additional pre-treatment motion correction by kV-imaging and Calypso, and gating during the irradiation. The effect of gating was investigated by simulating non-gated treatments (strategy B). Additionally, non-gated and single image-guided (CBCT) localization was simulated (strategy C). A total of 308 fractions from 22 patients were reconstructed. The dosimetric effect was evaluated by comparing motion inclusive target and risk organ dose-volume parameters to planned values. Motion induced dose deficits were seen mainly in PTV and CTV to PTV margin regions, whereas CTV dose deficits were small in all strategies: mean ± SD difference in CTVD99% was –0.3 ± 0.4%, −0.4 ± 0.6% and –0.7 ± 1.2% in strategies A, B and C, respectively. Largest dose deficits were seen in individual fractions for strategy C (maximum dose reductions were −29.0% and –7.1% for PTVD95% and CTVD99%, respectively). The benefit of gating was minor, if additional motion correction was applied immediately prior to irradiation. Continuous motion monitoring based localization and motion correction ensured the target coverage and minimized the OAR exposure for every fraction and is recommended to use in prostate SBRT. The study is part of clinical trial NCT02319239.