典型草原大针茅种群空间格局及对长期过度放牧的响应

种群空间格局是生态学研究的基本问题之一。典型草原带由于过度放牧退化严重,原生群落罕见,探讨原生群落的种群空间格局具有重要生态学意义。大针茅(Stipagrandis)草原是典型草原区广泛分布的主要群落类型,1979年围封的大针茅样地,是目前保存完整的大针茅草原原生群落。本文选择大针茅草原原生群落和长期过度放牧群落,应用O-Ring函数结合不同零假设模型分析了大针茅种群的空间格局。结果表明:在原生群落中大针茅种群在小尺度范围内呈均匀分布,而在长期过度放牧群落中则表现为聚集分布。这说明在大针茅草原原生群落中竞争是主要的相互作用,而在长期过度放牧群落中正相互作用居主导,验证了胁迫梯度假说;同时证明长期过度放牧改变了种群空间格局。

Balance between facilitation and competition determines spatial patterns in a plant population

A considerable challenge in plant ecology is to understand how interactions,such as competition or facilitation,shape the spatial distribution of plants.The‘‘stress gradient hypothesis’’predicts that facilitation and competition will vary inversely across gradients of abiotic stress or consumer pressure.Surprisingly,few previous studies have explored how the balance between facilitation and competition affects spatial patterns along gradients of stress in a plant population based on field experiments.In order to investigate the effects of consumer pressure,facilitation,and competition on the spatial pattern of plant populations,we conducted a restoration succession series field experiment in the Inner Mongolian steppe in which sample sites of graded consumer pressure,specifically grazing stress,were established.We chose to examine the spatial patterns of Leymus chinensis,a dominant species in our experimental site.In order to test the‘‘stress gradient hypothesis,’’we applied the univariate O-ring statistic to analyze local neighborhood density at different spatial scales.We used the pair-correlation function to detect the characteristics of point patterns using complete spatial randomness,the Poisson cluster process,and the nested double-cluster process.We found that the local densities of L.chinensis were higher under high stress than lower stress environments.This demonstrated the‘‘stress gradient hypothesis’’in that facilitation and competition varied inversely across gradients of consumer pressure.However,we found nodifferences in the spatial patterns of L.chinensis based on complete spatial randomness when interactions shifted from facilitation to competition along gradients of consumer pressure.Furthermore,we detected the characteristics of point patterns using the Poisson cluster and nested doublecluster processes.The results showed the spatial patterns of L.chinensis to fit well with the nested double-cluster model under highly stressful conditions,while in lower stress environments they were best approximated by the Thomas process.Our results illustrate that a shift in interactions from facilitation to competition along gradients of consumer pressure can shape spatial patterns and that a combination of the Poisson cluster process and nested doublecluster process can detect spatial pattern characteristics which cannot be detected by complete spatial randomness.

Identification of p100 target promoters by chromatin immunoprecipitation-guided ligation and selection (ChIP-GLAS)

The multifunctional protein p100 is a vital transcriptional regulator that increases gene transcription by forming a physical bridge between promoter-specific transcription factors and the basal transcription machinery.To identify potential signal transduction pathways in which human p100 acts as a coregulator and to find target promoter regions that may interact with p100,we performed a promoter microarray assay called chromatin immunoprecipitation-guided ligation and selection(ChIP-GLAS).From this assay,we determined that a set of promoter fragments,including several factors in the transforming growth factor beta(TGF-β)signaling pathway,exhibited interaction with p100.The ChIP-GLAS data were validated by RT-PCR assessing the mRNA expression of various factors in the TGF-b signaling pathway in cell lines.

3D平视技术在玻璃体切割联合白内障手术中的应用

目的:比较3D平视技术与显微镜目镜下行玻璃体切割联合白内障手术的疗效和安全性。方法:回顾性系列病例研究。收集2018年9月至2021年6月于徐州市第一人民医院眼科行玻璃体切割联合白内障手术的患者48例(48眼)的临床资料。根据手术时观察系统不同分为3D平视技术组和显微镜目镜组,每组24例(24眼)。比较2组患者术眼手术持续时间及术中并发症等情况。术后随访3个月,评估术眼手术前后最佳矫正视力(BCVA)、术后解剖复位率和术后并发症发生率情况。数据采用t检验、卡方检验及Fisher确切概率法进行分析。结果:显微镜目镜组、3D平视技术组的手术时间依次为(64.4±19.8)min和(63.1±18.5)min,差异无统计学意义(t=-0.27,P=0.089)。术后1、3个月,显微镜目镜组和3D平视技术组术眼BCVA均较术前明显提高,且术后3个月BCVA均优于术后1个月,差异均有统计学意义(P<0.05)。术后1、3个月复查时,同一时间点2组BCVA比较差异均无统计学意义。2组术中出血率、后囊膜破裂率、气体注入率和硅油注入率及术后出现角膜水肿、前房反应、高眼压及低眼压率差异均无统计学意义。随访3个月时显微镜目镜组和3D平视技术组均未出现术后并发症。结论:3D平视技术下的玻璃体切割联合白内障手术可以达到与显微镜目镜下同样的治疗效果,且安全性好,可在临床上进行推广。