情景模拟在“医学微生物学”翻转课堂教学中的应用

翻转课堂是实现以学生为中心、提升学生自主学习能力的重要教学方法。随着线上课程的开展和学习平台技术的成熟,学生已能在课前获得足够的资源。然而,习惯于灌输式教育的学生仍缺乏自主学习的动力和方法。为此,我们教研团队尝试采用情景模拟的课堂活动设计来突破翻转环节实施的难点。研究发现,参考临床案例撰写剧本的过程能有效提升学生的自学兴趣和能力。学生课前在线预习时长和章节访问次数,以及参考资料阅读率和小组讨论时长均显著增加。课堂上,学生将课前所学知识在模拟实践中进行练习,促进了师生互动,帮助学生加深对知识的理解,提升学习成绩和满意度,同时也培养了学生的团队合作精神,建立临床思维,提升职业兴趣和能力。因此,情景模拟的融入实现了翻转课堂教学中“课前学”和“课上习”的教学闭环,为进一步推进翻转课堂的开展提供参考。     

Topography and Nanomechanics of Live Neuronal Growth Cones Analyzed by Atomic Force Microscopy

Neuronal growth cones are motile structures located at the end of axons that translate extracellular guidance information into directional movements. Despite the important role of growth cones in neuronal development and regeneration, relatively little is known about the topography and mechanical properties of distinct subcellular growth cone regions under live conditions. In this study, we used the AFM to study the P domain, T zone, and C domain of live Aplysia growth cones. The average height of these regions was calculated from contact mode AFM images to be 183 ± 33, 690 ± 274, and 1322 ± 164 nm, respectively. These findings are consistent with data derived from dynamic mode images of live and contact mode images of fixed growth cones. Nano-indentation measurements indicate that the elastic moduli of the C domain and T zone ruffling region ranged between 3-7 and 7-23 kPa, respectively. The range of the measured elastic modulus of the P domain was 10-40 kPa. High resolution images of the P domain suggest its relatively high elastic modulus results from a dense meshwork of actin filaments in lamellipodia and from actin bundles in the filopodia. The increased mechanical stiffness of the P and T domains is likely important to support and transduce tension that develops during growth cone steering.     

Effect of betamethasone phosphate loaded polymeric nanoparticles on a murine asthma model

Although inhaled steroids are the treatment of first choice to control asthma, administration of systemic steroids is required for treatment of asthmatic exacerbation and intractable asthma. To improve efficacy and reduce side effects, we examine the effects of betamethasone disodium phosphate (BP) encapsulated in biocompatible, biodegradable blended nanoparticles (stealth nanosteroids) on a murine model of asthma. These stealth nanosteroids were found to accumulate at the site of airway inflammation and exhibit anti-inflammatory activity. Significant decreases in BALF eosinophil number were maintained for 7 days with a single injection of nanosteroids containing 40 μg BP. Airway responsiveness was also attenuated by the injection of stealth nanosteroids. A single injection of 40 μg of free BP and 8 μg of free BP once daily for 5 days did not show any significant effects. We conclude that stealth nanosteroids achieve prolonged and higher benefits at the site of airway inflammation compared to free steroids.     

野化培训大熊猫采食和人为砍伐对拐棍竹无性系种群更新的影响

亚高山竹类占据着野生大熊猫(Ailuropoda melanoleuca)食物组分的99%,竹子的生命周期与大熊猫的生活史密切相关,竹子的更新和生长直接影响着大熊猫的生存与保护.为了弄清大熊猫的采食利用和人为砍伐是否促进或制约竹子的繁殖更新,应用样方法、定位观察法,连续研究了卧龙自然保护区大熊猫栖息地内野化培训大熊猫采食、人为砍伐和对照样方中拐棍竹无性系种群的更新动态.结果表明,在相同种群数量和环境条件的基础上(p>0.05),被大熊猫采食竹子的比例为67.07%,致死率29.07%;人为砍伐竹子的比例为65.67%,致死率46.68%,可见与大熊猫采食相比,砍伐更为影响拐棍竹种群的生存.从出笋数量来看,不同处理方式有利于拐棍竹无性系种群的更新(p<0.05),尤其是人为砍伐措施大大提高了竹子的出笋率,但人为砍伐样方的竹笋质量(地径和株高生长)却远低于大熊猫采食和对照样方,未能达到大熊猫觅食的选择利用标准.不同年份之间,各种处理方式下的拐棍竹出笋数量波动较大(p=0.006～0.035),并随着恢复时间的延长,逐渐趋于相似(2007,p=0 825).不同处理方式之间,拐棍竹无性系种群的年补充率,各年份均具有显著性差异(p<0.05,除2007年外),年死亡率仅2003年和2004年有明显的差异(p<0.05),2005～2007年均不显著(p>0.05).拐棍竹无性系种群的年补充率与年死亡率之间表现出年补充率﹥年死亡率的格局(p<0.05),唯有大熊猫采食样方的2004年和2005年、人为砍伐和对照样方的2005年的年死亡率略高于年补充率(p>0.05),这表明拐棍竹无性系种群对大熊猫采食和人为砍伐具有无性系整合的补偿效应.     

Defining null expectations for animal site fidelity

Site fidelity—the tendency to return to previously visited locations—is widespread across taxa. Returns may be driven by several mechanisms, including memory, habitat selection, or chance; however, pattern-based definitions group different generating mechanisms under the same label of ‘site fidelity’, often assuming memory as the main driver. We propose an operational definition of site fidelity as patterns of return that deviate from a null expectation derived from a memory-free movement model. First, using agent-based simulations, we show that without memory, intrinsic movement characteristics and extrinsic landscape characteristics are key determinants of return patterns and that even random movements may generate substantial probabilities of return. Second, we illustrate how to implement our framework empirically to establish ecologically meaningful, system-specific null expectations for site fidelity. Our approach provides a conceptual and operational framework to test hypotheses on site fidelity across systems and scales.     

HFOV联合PS对治疗新生儿ALI/ARDS的疗效及对肺动态顺应性的影响

摘要 目的：探讨高频振荡通气（HFOV）联合肺表面活性物质（PS）对治疗新生儿急性肺损伤/急性呼吸窘迫综合征（ALI/ARDS）的疗效及对肺动态顺应性的影响。方法：选择2018年1月至2020年12月我院新生儿科收治的160例ALI/ARDS患儿进行研究,按照随机数表法分为观察组和对照组,每组80例。对照组患儿给予常频通气（CMV）模式联合PS治疗,观察组患儿给予HFOV模式联合PS治疗。比较两组患儿一般治疗情况、治疗前后肺动态顺应性、动脉血氧分压（PaO₂）、动脉二氧化氮分压（PaCO₂）、氧合指数（OI）、血清肿瘤坏死因子-α（TNF-α）、白细胞介素（IL）-6、IL-10的变化,以及治疗期间并发症发生情况。结果：观察组胸片恢复正常时间、机械通气时间、氧暴露时间、ICU停留时间、住院时间结果均明显短于对照组（P＜0.05）,两组患儿病死率相比较,无统计学意义（P＞0.05）;治疗后12 h、24 h、48 h时,观察组肺动态顺应性及PaO₂、OI结果明显高于对照组,PaCO₂明显比对照组低,差异有统计学意义（P＜0.05）;治疗后48 h时,观察组血清TNF-α、IL-6水平均明显低于对照组,IL-10明显比对照组高,差异有统计学意义（P＜0.05）;两组治疗期间,呼吸机相关性肺损伤、颅内出血、气漏、呼吸道感染的总发生率比较,无统计学意义（P＞0.05）。结论：HFOV联合PS治疗新生儿ALI/ARDS疗效明显,可有效改善患儿肺动态顺应性,促进血气分析指标恢复,且可降低炎症因子的表达,值得推广应用。     

The Dynamics of Microtubules in Cultured Cells

The behavior of microtubules in cultured cells in a cooled matrix after the microinjection of fluorescent tubulin was studied using a frame recording with a digital camcorder. In the cell lamella, the positive ends of individual microtubules extend and shorten at random. The histograms of rate distribution have an almost normal distribution with a mode close to 0. The maximum rate of lengthening and shortening reaches 30 and 50 m/min, respectively. The positive ends of microtubules in PtK cells were in an equilibrium state, while in murine embryonic fibroblasts and Vero cells, they were usually displaced to the cell edge. Free microtubules were present in the cells of all three cultures. In the epithelial cells, they were numerous and relatively stable, while in the fibroblasts, they occurred rarely and were depolymerized at the proximal end. Free microtubules in PtK cells appeared mostly due to spontaneous assembly in the cytoplasm (not in the relationship with the preexisting microtubules) and, more rarely, due to breakage of long microtubules. Separation of microtubules from the centrosome is a very rare event. Unlike positive ends that were characterized by dynamic instability, negative ends were stable and were sometimes depolymerized. When long microtubules were broken, new negative ends were formed that were, as a rule, stable, while in the lamella of fibroblasts (in murine embryonic fibroblasts and Vero cells), new negative ends were immediately depolymerized: free microtubules existed in these cells no more than 1–2 min. A diffusion model has been proposed where the behavior of microtubule ends is considered as unidimensional diffusion. The coefficient of diffusion of positive ends in the epithelial cells is several times less than in the fibroblasts, thus suggesting a higher rate of tubulin metabolism in the fibroblasts as compared to the epithelium. The results obtained indicate that for the exchange of long microtubules, the dynamic instability is not sufficient. In the fibroblasts, their exchange takes place mostly at the expense of depolymerization of the liberating negative ends, which agrees with the previously proposed conveyer hypothesis of microtubule assembly on the centrosome.     

福州地区桑白蚧发生动态和药剂防治试验

桑白蚧在福州地区一年发生4代．以雌成虫在寄主枝干上越冬．越冬代(第4代)一雌虫产卵量多的达278粒．少的36粒,平均171粒,比第2代产卵量多2．6倍．比第3代多4．5倍．药剂防治试验结果,在2龄幼蚧高峰期,用25％扑虱灵可温性粉剂1500倍液,40％氧化乐果乳油800-1000倍液和95%机油乳剂50—100倍液喷雾．防治效果可达90％左右．用25％扑虱是可湿性粉剂1000-1500倍液．喷酒幼蚕触杀试验和喷洒桑叶喂蚕胃毒试验结果．对幼蚕安全．用扑虱灵防治桑树上的桑白蚧,对养蚕业无不良影响。     

Site fidelity in predictable and unpredictable habitats

Summary Site fidelity, the tendency to return to a previously occupied location, has been observed in numerous species belonging to at least three phyla. In this paper I develop a general model using dynamic programming to investigate conditions under which fidelity to a previously occupied territory will be advantageous. The results predict that site fidelity should be inversely related to heterogeneity in territory quality and the animal's lifespan and positively related to the cost of changing territories, age and probability of mortality in the habitat. The predictability of reproductive outcome (defined as the probability that next period's outcome will be the same as this period's outcome) also affects site fidelity. In predictable habitats, changing territories may be favoured after a bad previous outcome. In contrast, settlement should be independent of the previous outcome in unpredictable habitats. Individuals should also be site-faithful in unpredictable habitats, as long as the mean territory quality is equal among available territories. I also investigate the success of two potential decision rules (always stay and win-stay: lose-switch) relative to the optimal settlement strategy. The results show that these rules may perform as well as the optimal strategy under certain conditions. The always stay strategy does well in unpredictable habitats, when the mean quality within a territory is equal among territories. In contrast, the win-stay: lose-switch strategy performs best in predictable habitats.     

The investigation of the G-quadruplex aptamer selectivity to Pb2+ ion: a joint molecular dynamics simulation and density functional theory study

Abstract

The aptamers with the ability to form a G-quadruplex structure can be stable in the presence of some ions. Hence, study of the interactions between such aptamers and ions can be beneficial to determine the highest selective aptamer toward an ion. In this article, molecular dynamics (MD) simulations and quantum mechanics (QM) calculations have been applied to investigate the selectivity of the T30695 aptamer toward Pb²⁺ in comparison with some ions. The Free Energy Landscape (FEL) analysis indicates that Pb²⁺ has remained inside the aptamer during the MD simulation, while the other ions have left it. The Molecular Mechanics Poisson-Boltzmann Surface Area (MM-PBSA) binding energies prove that the conformational stability of the aptamer is the highest in the presence of Pb²⁺. According to the compaction parameters, the greatest compressed ion-aptamer complex, and hence, the highest ion-aptamer interaction have been induced in the presence of Pb²⁺. The contact maps clarify the closer contacts between the nucleotides of the aptamer in the presence of Pb²⁺. The density functional theory (DFT) results show that Pb²⁺ forms the most stable complex with the aptamer, which is consistent with the MD results. The QM calculations reveal that the N-H bonds and the O…H distances are the longest and the shortest, respectively, in the presence of Pb²⁺. The obtained results verify that the strongest hydrogen bonds (HBs), and hence, the most compressed aptamer structure are induced by Pb²⁺. Besides, atoms in molecules (AIM) and natural bond orbital (NBO) analyses confirm the results.

Communicated by Ramaswamy H. Sarma