杭州湾潮滩表层沉积物中磷的分布、赋存形态及生态意义

对杭州湾潮滩表层沉积物样品中的磷进行了总量、形态分级提取及生物有效性分析.结果表明:沉积物中总磷的含量为595.5～1268.8μg·g-1,空间分布特征总体表现为杭州湾北岸＞钱塘江杭州河段＞杭州湾南岸.总磷中有89.3%以无机磷形式存在,钙磷、残留无机态磷、有机磷和铁铝结合态磷是沉积物中磷的主要赋存形态,平均分别占总磷的68.3%、14.6%、10.7%和5.3%.钙磷的分布受到盐度变化影响,自钱塘江河口向外海方向明显增加;铁铝结合态磷则相反,分布朝外海逐步递减.沉积物中的潜在生物有效磷(BAP)含量为43.62～177.84 μg·g-1,平均含量为94.13 μg·g-1.该地区与国内典型的河口和滨岸带潮滩比较,总磷处于相对较高水平.强烈的水动力作用及咸淡水交汇使得环境因子频繁变化,加大了沉积物中磷作为内源向上覆水体释放及造成水体富营养化的可能性.     

Assessment of a model for intron RNA secondary structure relevant to RNA self-splicing--a review

A widespread class of introns is characterized by a particular RNA secondary structure, based upon four conserved nucleotide sequences. Among such "class I" introns are found the majority of introns in fungal mitochondrial genes and the self-splicing intron of the large ribosomal RNA of several species of Tetrahymena. A model of the RNA secondary structure, which must underlie the self-splicing activity, is here evaluated in the light of data on 16 further introns. The main body or "core structure" of the intron always consists of the base-paired regions P3 to P9 with the associated single-stranded loops, with P2 present also in most cases. Two minority sub-classes of core structure occur, one of which is typical of introns in fungal ribosomal RNA. Introns in which the core structure is close to the 5' splice site all have an internal guide sequence (IGS) which can pair with exon sequences adjacent to the 5' and 3' splice sites to align them precisely, as proposed by Davies et al. [Nature 300 (1982) 719-724]. In these cases, the internal guide model allows us to predict correctly the exact location of splice sites. All other introns probably use other mechanisms of alignment. This analysis provides strong support for the RNA splicing model which we have developed.     

Effects of spring and autumn fires on the composition of Chionochloa rigida tussock grassland,New Zealand

Two areas of Chionochloa rigida tussock grassland on Flagstaff Hill were burnt in autumn and spring 1976, respectively. Plant species cover and frequency were recorded in 1977 and 1985. Initially, plant cover and frequency were lower, and the area of bare ground was greater, on the autumn burnt site. After nine years, cover and frequency values were similar for most species, and bare ground was rare, on both sites. Over this period, recovery in size of indigenous tussock-forming physiognomic dominants resulted in suppression of intertussock sub-shrubs, herbs and grasses that were initially favoured by reduction of competition after fire. Plant species most tolerant of fire have features that protect the meristem, for instance an underground perennating organ or dense tillering.     

大青沟自然保护区主要森林群落优势种的叶性状

植物功能性状是近年来生态学研究的热点。其中叶功能性状与植株生物量和植物对资源的获得、利用及利用效率的关系最为密切。大青沟森林植物群落分布于科尔沁沙地,生境条件非常特殊,在沙沟里存在着一片茂密的森林,与周围浩瀚无垠的沙坨景观形成极为鲜明的对照。从沟底到沟顶,虽然海拔高度仅相差六、七十米,但由于距离沟底水源不同,土壤条件差异大,形成了不同的森林植物群落类型。大果榆群落、蒙古栎群落和水曲柳群落分别分布在大青沟自然保护区的沟顶、沟中和沟底。为了对大青沟自然保护区,不同环境梯度下的森林植物群落叶片功能性状进行研究,以大青沟自然保护区大果榆、蒙古栎、水曲柳3种主要森林群落为研究对象,分别测定不同群落优势种的叶厚度、比叶面积、叶干物质含量、叶大小和叶干重等5项叶功能性状,研究叶功能性状之间的关系,并对不同生长型、不同群落叶功能性状进行比较。相关分析结果表明,叶厚度与比叶面积呈极显著负相关,与叶大小和叶干重呈极显著正相关;比叶面积与叶干物质含量、叶干重呈极显著负相关,与叶大小呈显著正相关;叶干物质含量与叶大小呈极显著负相关,与叶干重呈极显著正相关;叶大小与叶干重呈极显著正相关。不同生长型植物叶片性状的分析表明,草本植物的叶干物质含量比乔木和灌木低,而其比叶面积高于乔木和灌木;对不同群落叶功能性状进行比较发现,大果榆群落和蒙古栎群落乔木、灌木叶厚度与干物质含量显著高于水曲柳群落的叶厚度与干物质含量,二者比叶面积显著低于水曲柳群落。大果榆群落和蒙古栎群落从叶功能性状的角度,它们具有较高的叶干物质含量和较低的比叶面积,体现出适应干旱生境叶片的特征。水曲柳群落呈现出低叶干物质含量、高比叶面积的特征,体现出适应湿润、土壤水分较好生境的特征。不同群落通过调节自身的物种组成,形成不同的功能性状组合来适应环境。     

The obesity in bilateral ovariectomized rats is related to a decrease in the expression of leptin receptors in the brain.

We investigated the expression levels of leptin receptors in the brain of ovariectomized (OVX) rats. The mean expression level of ob mRNA in adipose tissues of OVX rats was significantly (P < 0.01) lower than that in the SHAM operation group rats, and the mean body weight of OVX rats was significantly (P < 0.01) greater than that in the SHAM group rats. However, there were no differences between serum leptin concentrations in these two groups. The mean level of leptin receptor (OB-R) mRNA expression in the brain tissue and the mean level of long form type OB-R (OB-RL) mRNA expression in the hypothalamus of the OVX rats were significantly (P < 0.05) lower than those in the SHAM group rats. These changes were cancelled by supplementation with 17 beta-estradiol in OVX rats. These results suggested that not only changes in the expression level of ob mRNA in adipose tissue and the serum leptin concentration but also changes in the OB-R mRNA in the brain are involved in the body weight increase in OVX rats and that a decrease in OB-R makes transmission of signals to suppress the amount of food intake difficult, thus leading to an increase in body weight.     

跨膜型肿瘤坏死因子α稳定表达细胞株的构建

目的：在体内,相对分子质量为26×103的跨膜型肿瘤坏死因子α（mTNF-α）可被TNF转化酶（TACE）酶解成相对分子质量为17×103的游离型TNF-α（sTNF-α）。为评价新研发的TNF-α全人源单克隆抗体与mTNF-α的结合能力,以及该单抗的ADCC作用,须构建只能稳定表达mTNF-α而不受TACE影响的Sp2/0细胞株。方法：PCR扩增缺失了TACE酶切位点的人TNF-α野生型基因序列,构建pcDNA3.1（＋）-dTNF-α重组质粒并测序鉴定;重组质粒转染Sp2/0细胞,构建只能稳定表达mTNF-α的细胞株,用流式细胞仪检测其表达情况。结果：pcDNA3.1（＋）-dTNF-α重组质粒测序结果与设计缺失基因的碱基序列完全一致,重组质粒构建成功;转染的阳性细胞株经流式细胞仪检测有表达,其中Clone11、15、16的表达量最高。结论：跨膜型TNF-α稳定表达细胞株构建成功,可用于TNF-α全人源单克隆抗体体外药效的评价。     

Natural incorporation of mercury in bone

Mercury (Hg) is a highly toxic element that causes bone defects and malformations. Structure and surface analyses using quantitative x-ray diffraction using the Rietveld method, High-Resolution Transmission Electron Microscopy and nanodiffraction analyses, and Fourier-Transformed Infrared spectroscopy showed that bone enriched naturally with Hg (≤ 2.3 %) contained Hg₃PO₄ [(Hg₂)₃(PO₄)₂] and HgO. Bone [mostly as apatite, verified as carboxyapatite Ca₁₀(PO₄)₄(CO₃)₃(OH)₂(s)] and cinnabar (HgS) dissolved releasing Hg⁺ (existing as dimer Hg₂²⁺) and PO₄³⁻, both of which became immobilized as (Hg₂)₃(PO₄)₂. Besides, released Hg²⁺ became oxidized to form HgO. The outcome of this work is novel, provided that only a handful of stable compounds of Hg₂²⁺ are found in nature.     

贵州省赤水县桫椤调查初报

国家一级重点保护植物桫椤,目前世界上少数国家尚存,国内除华南、西南地区及台湾等少数省份外亦不多见。其中贵州省赤水县桫椤不仅面积广,且数量多,生长旺。据不完全统计,全县35个乡中,有20个乡有分布,面积