Complex duplications in maize lines

Rp1 is a disease resistance complex and is the terminal morphological marker on the short arm of maize chromosome 10. Several restriction fragment length polymorphisms (RFLPs), which map within 5 map units of Rp1, were examined to determine if they are also complex in structure. Two RFLP loci, which mapped distally to Rp1, BNL3.04 and PIO200075, existed in a single copy in all maize lines examined. These two loci cosegregated perfectly in 130 test cross progeny. Two RFLP loci that map proximally to Rp1 had unusual structures, which have not yet been reported for maize RFLPs; the loci were complex, with variable numbers of copies in different maize lines. One of the loci, NPI285, occasionally recombined in meiosis to yield changes in the number of copies of sequences homologous to the probe. The other proximal locus, detected by the probes NPI422, KSU3, and KSU4, was relatively stable in meiosis and no changes in the number of restriction fragments were observed. The similarity in map position between Rp1 and the complex RFLP loci indicate there may be genomic areas where variable numbers of repeated sequences are common. The structure of these complex loci may provide insight into the structure and evolution of Rp1.     

Logistic曲线参数的一个最佳估计方法

本文提出用O．628优选法和SAS/STAT软件NLIN模块中的DUD法,对Logistic曲线中的参数k,a和b可得到最佳估计。     

零下低温对杂交杨树皮层膜脂组成的影响

以不耐寒的美洲黑杨（Ｐｏｐｕｌｕｓｄｅｌｔｏｉｄｅｓｃｖ．“Ｌｕｘ”Ｉ－６９／５５,父本）和耐寒性较强的欧美杨（Ｐ．ｅｕｒａｍｅｒｉｃａｎａｃｌｃｖ．Ｉ－４５／５１,母本）的４个杂交Ｆ＿１代无性系（９５杨、５５９杨、６００杨和１３８１杨）为材料,分析了零下低温寒潮前后枝条皮层的脂质组成。结果表明,寒潮影响下,皮层中磷脂含量增加而组成基本不变,膜脂脂肪酸组成的变化规律是：寒潮前脂肪酸不饱和指数（ＩＵＦＡ）值大的无性系,寒潮前后的ＩＵＦＡ值变化量小;寒潮前ＩＵＦＡ值较小的无性系,寒潮前后ＩＵＦＡ值变化量较大。本文借用力学概念,提出相对抗性概念,给出杨树无性系的相对抗性序列。序列表明Ｆ＿１代无性系的耐寒性已较不耐寒的父本提高,这与田间观察基本一致。     

三硝基甲苯对大鼠晶状体中可溶性蛋白质、巯基及二硫键含量的影响

我们采用三硝基甲苯（ＴＮＴ）与大鼠晶状体体外培养的方法,动态观察了晶状体中可溶性蛋白质、非蛋白质巯基、蛋白质巯基、蛋白质结合巯基及二硫键含量的变化,发现随着三硝基甲苯作用时间的延长,可溶性蛋白质、非蛋白质巯基及蛋白质巯基均减少,蛋白质结合巯基及二硫键交联的蛋白质含量增加,其中可溶性蛋白质、非蛋白质巯基及二硫键含量的变化皆达到了统计学上显著意义水平（Ｐ＜０．０５）。     

Absence of a direct role for RNase HI in initiation of DNA replication at the oriC site on the Escherichia coli chromosome.

On the basis of the experiments carried out with rnhA224 mutants, we previously concluded that RNase HI is not essential for initiation of Escherichia coli chromosome replication at oriC (T. Kogoma, N.L. Subia, and K. von Meyenburg, Mol. Gen. Genet. 200:103-109, 1985). In light of the recent finding that rnhA224 is a UGA nonsense mutation which can be leaky in certain genetic backgrounds, we reexamined this conclusion with the use of rnhA339 (Null)::cat mutants. The possibility that recB+ is required for initiation at the alternative origins (oriKs) of replication in rnhA mutants was also tested. The results clearly indicated that RNase HI is not essential for oriC initiation and that recB+ is not required for initiation at oriK sites.     

(蜓)类旋壁超微构造的研究——以麦(蜓)型旋壁为例

光学显微镜下的观察表明(蜒)类的旋壁属于钙质微粒壳类型,对它们的电镜观察揭示了组成旋壁的晶粒的大小、形态和排列方式.对具有致密层和蜂巢层型两层式旋壁的Triticites的电镜研究表明:其致密层由近等轴晶无定向排列而成;蜂巢层由短柱状晶定向排列组成板状复合体,进而组合成管状孔,镶嵌在不定向排列的近等轴品基质中构成.Pseudofusulina的致密层也由近等轴晶不定向排列构成,蜂巢层由粗柱晶定向排列组成纤状复合体,进而形成管状孔,镶嵌在近等轴晶基质中.     

Phase shifts of the adult locomotor activity rhythm in Calliphora vicina induced by non-steroidal ecdysteroid agonist RH 5849

RH 5849, a non-steroidal ecdysteroid mimic, was found to cause consistent phase shifts in the circadian rhythm of locomotor activity of the blowfly, Calliphora vicina. This compound causes phase advances in the early subjective night and phase delays in the late subjective night. This effect is the opposite, but not the mirror image of the phase response curve obtained for 1 h light pulses. This suggests that ecdysteroids might act as entraining agents via the output pathway by feedback to clock neurons in the brain. A computer model based on 12 pacemaker neurons with circadian periods ( values) from short to long without simulated feedback from the ecdysteroid system becomes arrhythmic; with feedback, the oscillators become synchronized to a common period. The possible role of ecdysteroids as endogenous synchronizing agents in the insect circadian system is discussed.     

Fine-scale mapping of physicochemical and microbial landscapes of the coral skeleton

The coral skeleton harbours a diverse community of bacteria and microeukaryotes exposed to light, O₂ and pH gradients, but how such physicochemical gradients affect the coral skeleton microbiome remains unclear. In this study, we employed chemical imaging of O₂ and pH, hyperspectral reflectance imaging and spatially resolved taxonomic and inferred functional microbiome characterization to explore links between the skeleton microenvironment and microbiome in the reef-building corals Porites lutea and Paragoniastrea benhami. The physicochemical environment was more stable in the deep skeleton, and the diversity and evenness of the bacterial community increased with skeletal depth, suggesting that the microbiome was stratified along the physicochemical gradients. The bulk of the coral skeleton was in a low O₂ habitat, whereas pH varied from pH 6–9 with depth. Physicochemical gradients of O₂ and pH of the coral skeleton explained the β-diversity of the bacterial communities, and skeletal layers that showed O₂ peaks had a higher relative abundance of endolithic algae, reflecting a link between the abiotic environment and the microbiome composition. Our study links the physicochemical, microbial and functional landscapes of the coral skeleton and provides new insights into the involvement of skeletal microbes in the coral holobiont metabolism.     

Terpenoids from Euphorbia helioscopia and Their Cytotoxic Activities against H1975 Cells

Three previously undescribed diterpenoids, helioscopnoids A–C, and eight known compounds were isolated from the whole plants of Euphorbia helioscopia. Their structures were established by extensive analysis of spectra and data comparison with previous literatures. Among them, compound 4 was identified as 24,24-dimethoxy-25,26,27-trinoreuphan-3β-ol with revised configurations of C-13, C-14, and C-17 (13R*, 14R*, 17R*). Cytotoxicity assays revealed that all compounds exhibited varying levels of cytotoxicity against H1975 cells, with compound 9 displaying the most potent activity, as indicated by cell viability rates of 18.13 % and 20.76 % at concentrations of 20 μM and 5 μM, respectively. This study expands the understanding of E. helioscopia terpenoids’ structural diversity and biological activities, contributing to the exploration of potential therapeutic applications.