视网膜神经节细胞感受野的一种新模型 I.含大周边的感受野模型

感受野是视觉系统信息处理的基本结构和功能单元。Ｘ、Ｙ细胞是两类主要的视网膜神经节细胞。生理实验发现,在经典感受野之外还存在一个大范围的在周边去抑制区。文中采用周边去抑制区对经典外周的去抑制非线性使用方式,建立一个二维的与实验结果联系紧密的Ｘ、Ｙ细胞统一的复合感受野模型。该模型不仅能模拟Ｘ细胞的ｎｕｌｌ－ｔｅｓｔ反应和Ｙ细胞的ｏｎ－ｏｆｆ反应,还模拟了Ｙ细胞在低空频刺激时的信频反应、圆面积空间的倍频     

Interspecific patterns for egg and clutch sizes of African Bufonidae (Amphibia: Anura)

Little is known about reproductive trade-offs in African amphibians, but such data, particularly in the form of quantitative measurements, are a key for investigating life history evolution. Here we compile and analyze known data on African bufonids from published material and new data from preserved museum specimens, to investigate interspecific patterns of egg and clutch sizes variation. Our data is a composite of mixed sources, including ova data from dissected females and laid clutches from observations in the field. Our study shows that, as body size increases, clutch size increases but egg size decreases, and when correcting for body size, egg size is inversely correlated with clutch size. These parameter interactions however, are different for different reproductive modes. In free-swimming larval developing species, the same trends are recovered, but for lecithotrophic viviparous species no significant correlations could be recovered for clutch size and body size nor for the trade-off between clutch size and egg size, and egg size is positively related to body size. The egg size of Nimbaphrynoides occidentalis (Angel, 1943) is a clear outlier, which may be due to its matrotrophic viviparous reproduction. In addition, we observed no statistical difference between ova data collected from dissections and laid clutch data from field observations, which suggests that such a mixed dataset has utility in comparative analyses.     

玉米转录因子zmCBF1的凝胶阻滞分析

凝胶阻滞试验是分析核酸与蛋白质相互作用的有效方法,在转录因子的功能分析中得到了广泛应用。以玉米转录因子zmCBF1与顺式元件CRT的结合为例,建立了用于转录因子分析的GRA/EMSA实验体系,并对其在应用中可能出现的问题进行了分析。     

转基因小麦“中间试验”与农艺性状评价

在湖北武汉对3个转基因小麦品系连续2次进行了"中间试验".结果表明在田间栽培条件下,转基因小麦植株个体生长发育正常,但转基因小麦主要农艺性状与对照间存在差异;特别是小区产量与本地小麦品种之间存在极显著差异;转基因小麦品系与其受体品系之间千粒重和小区产量上存在显著差异或极显著差异.组织化学和SDS-PAGE检测结果表明,外源基因能够稳定遗传,功能得到正确表达.     

The regulation of activity in populations of the terrestrial slugLimax maximus (Gastropoda; Limacidae)

The activity of the slug Limax maximus was studied in relation to weather. Three hundred-and-fifty-eight hourly observations of activity and weather were made on 21 nights from May until October, 1976. Factors causally important to molluscan activity were included in a step-down correlation-regression analysis of daily and seasonal behavior. The analysis was also performed using weather data from the previous hourly observation. Models using lag-weather did not explain as much variability as did concurrent weather. The regression models explained about 73% to 87% of the observed variation in activity. The most important factors included in the regression models were time of day (circadian rhythm), light intensity, changes in light intensity and surface temperature. Shelter temperature, temperature gradients, length of the night, and time of sunset were also included in some models. Age and hydration were shown to be key factors in other experiments. A model incorporating weather thresholds estimated from field data explained 83.06% of the variability in the activity of L. maximus over the season. The values predicted from the model did not differ significantly from those actually observed in the field (Kolmogorov-Smirnov test, p>0.50).     

Plant community composition steers grassland vegetation via soil legacy effects

Soil legacy effects are commonly highlighted as drivers of plant community dynamics and species co‐existence. However, experimental evidence for soil legacy effects of conditioning plant communities on responding plant communities under natural conditions is lacking. We conditioned 192 grassland plots using six different plant communities with different ratios of grasses and forbs and for different durations. Soil microbial legacies were evident for soil fungi, but not for soil bacteria, while soil abiotic parameters did not significantly change in response to conditioning. The soil legacies affected the composition of the succeeding vegetation. Plant communities with different ratios of grasses and forbs left soil legacies that negatively affected succeeding plants of the same functional type. We conclude that fungal‐mediated soil legacy effects play a significant role in vegetation assembly of natural plant communities.     

浙江省葡萄属野生葡萄资源调查与开发利用研究

浙江是中国野生葡萄属资源分布较广泛、种类较多的地区之一,但对野生葡萄属资源的深入研究和合理开发利用不多。我们在野外调查和民间走访的基础上,结合查询文献资料,分析浙江境内野生葡萄资源的特点,并提出野生葡萄资源创新利用的思路。     

Different effects of carbohydrate binding modules on the viscoelasticity of nanocellulose gels

Many cellulose degrading and modifying enzymes have distinct parts called carbohydrate binding modules (CBMs). The CBMs have been shown to increase the concentration of enzymes on the insoluble substrate and thereby enhance catalytic activity. It has been suggested that CBMs also have a role in disrupting or dispersing the insoluble cellulose substrate, but dispute remains and explicit evidence of such a mechanism is lacking. We produced the isolated CBMs from two major cellulases (Cel6A and Cel7A) from Trichoderma reesei as recombinant proteins in Escherichia coli. We then studied the viscoelastic properties of native unmodified cellulose nanofibrils (CNF) in combination with the highly purified CBMs to detect possible functional effects of the CBMs on the CNF. The two CBMs showed clearly different effects on the viscoelastic properties of CNF. The difference in effects is noteworthy, yet it was not possible to conclude for example disruptive effects. We discuss here the alternative explanations for viscoelastic effects on CNF caused by CBMs, including the effect of ionic cosolutes.     

Measurement verification of dose distributions in pulsed-dose rate brachytherapy in breast cancer

Aim

The aim of the study was to verify the dose distribution optimisation method in pulsed brachytherapy.

Background

The pulsed-dose rate brachytherapy is a very important method of breast tumour treatment using a standard brachytheraphy equipment. The appropriate dose distribution round an implant is an important issue in treatment planning. Advanced computer systems of treatment planning are equipped with algorithms optimising dose distribution.

Materials and methods

The wax-paraffin phantom was constructed and seven applicators were placed within it. Two treatment plans (non-optimised, optimised) were prepared. The reference points were located at a distance of 5 mm from the applicators’ axis. Thermoluminescent detectors were placed in the phantom at suitable 35 chosen reference points.

Results

The dosimetry verification was carried out in 35 reference points for the plans before and after optimisation. Percentage difference for the plan without optimisation ranged from −8.5% to 1.4% and after optimisation from −8.3% to 0.01%. In 16 reference points, the calculated percentage difference was negative (from −8.5% to 1.3% for the plan without optimisation and from −8.3% to 0.8% for the optimised plan). In the remaining 19 points percentage difference was from 9.1% to 1.4% for the plan without optimisation and from 7.5% to 0.01% for the optimised plan.No statistically significant differences were found between calculated doses and doses measured at reference points in both dose distribution non-optimised treatment plans and optimised treatment plans.

Conclusions

No statistically significant differences were found in dose values at reference points between doses calculated by the treatment planning system and those measured by TLDs. This proves the consistency between the measurements and the calculations.     

RELATIVE STABILITY OF QUADRUPLEXES CONTAINING DIFFERENT NUMBER OF G-TETRADS

The aim of this work is to compare the physicochemical properties of three oligonucleotidic sequences, d(TGGGT), d(TGGGGT) and d(TGGGGGT), which assemble to form quadruplex structures with the same molecularity, but containing three, four, and five G-quartets, respectively. The addition of one or two G-tetrads greatly increases both the enthalpy and T_m values of the quadruplex dissociation.