百合花朵不同发育期乙烯释放量与膜脂过氧化作用的研究

以百合（lilium)“精萃”为材料,研究了百合花朵的不同发育期与乙烯释放量,呼吸强度变化情况,发现百合花朵的乙烯释放量和呼吸强度变化趋势基本一致,属于乙烯末期上升型花卉,并发现随着花朵的发育,不饱合脂肪酸指数（IuFA)逐渐下降,丙二醛（MDA）上升,细胞膜相对透性增加。     

Detection of G-quadruplex DNA in mammalian cells

It has been proposed that guanine-rich DNA forms four-stranded structures in vivo called G-quadruplexes or G4 DNA. G4 DNA has been implicated in several biological processes, but tools to study G4 DNA structures in cells are limited. Here we report the development of novel murine monoclonal antibodies specific for different G4 DNA structures. We show that one of these antibodies designated 1H6 exhibits strong nuclear staining in most human and murine cells. Staining intensity increased on treatment of cells with agents that stabilize G4 DNA and, strikingly, cells deficient in FANCJ, a G4 DNA-specific helicase, showed stronger nuclear staining than controls. Our data strongly support the existence of G4 DNA structures in mammalian cells and indicate that the abundance of such structures is increased in the absence of FANCJ. We conclude that monoclonal antibody 1H6 is a valuable tool for further studies on the role of G4 DNA in cell and molecular biology.     

Phylogeny,phenotypic and nutritional characteristics of estuarine soil actinomycetes having broad-spectrum antimicrobial activity derived from an ecologically guided bioprospecting programme

No investigation has been done to identify ecological factors selecting for broad-spectrum antimicrobial activity of actinomycetes in the estuaries. Previously, we established that, in the Sundarbans (the world’s largest tidal mangrove forest), high antagonistic potential (AP) sampling sites were influenced by tides, while the low AP sites were not. We now report molecular phylogenetic analysis, morphological, physiological and biochemical characteristics of actinomycetes of high AP sites. The effects of soil organic carbon, nitrogen and ionic content (which strongly influenced AP) on the strength and spectrum of activity of the isolates were also studied in shake flasks. Molecular phylogenetic analysis showed sequences of our strains to be 96–99% similar to the 16S rDNA sequences of Streptomyces. Results showed variation among sporophore sizes, ornamentation and number of spores. Jaccard’s similarity coefficients of the isolates varied from 0.512 to 0.884 indicating disparity in the biochemical and physiological characteristics, possibly due to spatial separation of the sampling sites. Top soil in the intertidal zone of estuaries is generated from settling and consolidation of fluid mud and Streptomyces would be expected to produce broad-spectrum antimicrobials in such virgin soil. Isolates should be collected from the narrow band between the mean high and low tide marks to maximize chances of finding broad-spectrum activity. Considering the study on nutritional requirements vis-à-vis the field studies, it was concluded that results of this investigation corroborated the field observations where soil nitrogen, rather than organic carbon or ionic concentration, played a major role in determining the antimicrobial spectrum.     

多功能磁共振造影剂研究进展

磁共振成像技术因对人体无创、任意方向断层扫描三维图像且分辨率较高、提供形态与功能两方面诊断评价等突出优点,成为了临床上用于疾病诊断的重要手段之一。临床上使用磁共振造影剂可以提高成像的分辨率和灵敏度,提高图像质量,增强对比度和可读性。但是,各种成像技术由于实现原理不同,具有各自的优势和缺陷,靠传统单一的诊断模式无法提供疾病的全面信息,因而在对各种复杂疾病进行诊断时会受到一定的限制。因此,将磁共振成像与其他成像技术如CT成像、超声成像等联合起来使用,则可以达到优势互补的效果,能为疾病的临床诊断提供更快捷精确的信息,同时可将磁共振成像与各种治疗方式结合在一起,即开发基于磁共振成像的诊断治疗一体化试剂,以实现对疾病的即时治疗和实时监控。本文主要介绍了磁共振成像造影剂的原理和种类,并且综述了目前国内外在基于磁共振成像的多功能造影剂/诊疗制剂这一领域的研究进展,最后就未来可能的研究方向进行了展望。     

Pattern Association and Consolidation Emerges from Connectivity Properties between Cortex and Hippocampus

The basic structure of the cortico-hippocampal system is highly conserved across mammalian species. Comparatively few hippocampal neurons can represent and address a multitude of cortical patterns, establish associations between cortical patterns and consolidate these associations in the cortex. In this study, we investigate how elementary anatomical properties in the cortex-hippocampus loop along with synaptic plasticity contribute to these functions. Specifically, we focus on the high degree of connectivity between cortex and hippocampus leading to converging and diverging forward and backward projections and heterogenous synaptic transmission delays that result from the detached location of the hippocampus and its multiple loops. We found that in a model incorporating these concepts, each cortical pattern can evoke a unique spatio-temporal spiking pattern in hippocampal neurons. This hippocampal response facilitates a reliable disambiguation of learned associations and a bridging of a time interval larger than the time window of spike-timing dependent plasticity in the cortex. Moreover, we found that repeated retrieval of a stored association leads to a compression of the interval between cue presentation and retrieval of the associated pattern from the cortex. Neither a high degree of connectivity nor heterogenous synaptic delays alone is sufficient for this behavior. We conclude that basic anatomical properties between cortex and hippocampus implement mechanisms for representing and consolidating temporal information. Since our model reveals the observed functions for a range of parameters, we suggest that these functions are robust to evolutionary changes consistent with the preserved function of the hippocampal loop across different species.     

Functional expression of an acyl carrier protein (ACP) from Azospirillum brasilense alters fatty acid profiles in Escherichia coli and Brassica juncea.

Acyl carrier protein (ACP) is a central cofactor for de novo fatty acid synthesis, acyl chain modification and chain-length termination during lipid biosynthesis in living organisms. Although the structural and functional organization of the ACPs in bacteria and plant are highly conserved, the individual ACP is engaged in the generation of sets of signature fatty acids required for specific purpose in bacterial cells and plant tissues. Realizing the fact that the bacterial ACP being originated early in molecular evolution is characteristically different from the plant's counterpart, we explored the property of an ACP from Azospirillum brasilense (Ab), a plant-associative aerobic bacterium, to find its role in changing the fatty acid profile in heterologous systems. Functional expression of Ab-ACP in Escherichia coli, an enteric bacterium, and Brassica juncea, an oil-seed crop plant, altered the fatty acid composition having predominantly 18-carbon acyl pool, reflecting the intrinsic nature of the ACP from A. brasilense which usually has C18:1 rich membrane lipid. In transgenic Brassica the prime increment was found for C18:3 in leaves; and C18:1 and C8:2 in seeds. Interestingly, the seed oil quality of the transgenic Brassica potentially improved for edible purposes, particularly with respect to the enhancement in the ratio of monounsaturated (C18:1)/saturated fatty acids, increment in the ratio of linoleic (C18:2)/linolenic (C18:3) and reduction of erucic acid (C22:1).