Invasive alien plant species in China: regional distribution patterns

Plant invasions have been attracting increasing attention from ecologists because of their worldwide environmental impacts and huge economic costs. Research on the characteristics of the recipient regions is essential for understanding the process of plant invasion. However, few previous studies on invasibility of habitats include social factors, although human activities are critical in the process of plant invasion. China is a vast country with high plant species diversity and a long history of introduction of exotic plant species and is particularly vulnerable to invasive plant species. Alien plant species are widespread in the country. Therefore, the study of invasive plants in China is urgent in practice and theoretically important for developing invasion ecology. For the present study, 126 species were selected to represent the major invasive plant species in China. We then collected data on their species richness in 31 provincial administrative units of China and performed Spearman rank correlations between species richness and possible natural and socio‐economic factors. We found that socio‐economic factors, such as human density and GDP, correlated positively with the species richness of invasive plants in China. In conjunction with the natural and socio‐economic correlations in the study of regional distribution pattern of the major invasive plants, we discussed the factors influencing the regional distribution pattern of the major invasive plants in China. We suggest that native plant species richness was mainly determined by the natural conditions of the regions, while invasive species richness was influenced by natural conditions and human disturbance together.     

Generation and Analysis of ESTs from the Grass Carp,Ctenopharyngodon idellus

Grass carp, Ctenopharyngodon idellus (Valenciennes, 1844), is an economically important species widely cultured in the world, but its genome research resources are largely lacking. The objectives of this study were to construct normalized cDNA libraries for efficient EST analysis, to generate ESTs from these libraries, and to identify EST-related molecular markers such as microsatellites and single nucleotide polymorphisms (SNPs) for genetic analysis of this species. A total of 6,269 ESTs were generated representing 4,815 unique sequences, from which 105 putative microsatellites and 5,228 SNPs were identified. These genome resources provide the material basis for future genetic and functional analyses in this species.     

Contraction of fibroblast-containing collagen gels: Initial collagen concentration regulates the degree of contraction and cell survival

Remodeling of extracellular matrix involves a number of steps including the recruitment, accumulation, and eventual apoptosis of parenchymal cells as well as the production, organization, and rearrangement of extracellular matrix produced by these cells. The culture of fibroblasts in three-dimensional gels made of type I collagen has been used as a model of tissue contraction which characterizes both wound repair and fibrosis. The current study was designed to determine the effect of initial collagen concentration on the ability of fibroblasts to contract collagen gels and on cell survival. Native type I collagen was extracted from rat tail tendons and used to prepare collagen gels with varying collagen concentrations (0.75-2.0 mg/ml). Human lung fibroblasts (HFL-1) were cast into the gels and cultured in Dulbecco modified Eagle medium with 0.1% fetal calf serum for 2 wk. The gel size, collagen content, and deoxyribonucleic acid (DNA) content were determined. Gels prepared with an initial concentration of 0.75 mg/ml contracted more rapidly and to a smaller final size than gels prepared from 2 mg/ml initial collagen concentration (final size 7.1 versus 36.4% of initial size, P < 0.01). There was no significant degradation of the collagen in the gels under either condition. Hence, the dramatically increased contraction of the lower density gels resulted in a higher final density (P < 0.01). Cell density was estimated from DNA content. In low initial density gels, the final DNA content was significantly less than that in higher initial density gels (0.73 versus 1.88 microg/gel, P < 0.05). This was accompanied by an increased percentage of apoptotic cells at day 14 (43.3 versus 34.1%, P < 0.05). If the gels were maintained in the attached state which largely prevents contraction, apoptosis was significantly reduced, suggesting that contraction rather than matrix composition was a requirement for the increased apoptosis. In summary, these findings indicate that the initial matrix composition can lead to differing outcomes during fibroblast-mediated wound contraction.     

PNAS-4 expression and its relationship to p53 in colorectal cancer

PNAS-4 is a novel pro-apoptotic protein activated during the early response to DNA damage; however, the molecular mechanisms and pathways regulating PNAS-4 expression in tumors are not well understood. We hypothesized that PNAS-4 is a p53 down-stream target gene and designed this study. We searched online for putative p53-binding sites in the entire PNAS-4 gene and did not find any corresponding information. In HCT116 colon cancer cells, after being transfected with small interfering RNA to silence p53, the expressions of PNAS-4 and other known p53 target gene (Apaf1, Bax, Fas and Dr5) were determined by real-time PCR. We found that PNAS-4 was up-regulated while Apaf1, Bax, Fas and Dr5 were down-regulated. We then examined the expression of PNAS-4 and p53 mutation in colorectal cancer patients. PNAS-4 expressed both in colorectal cancers and normal tissues, but compared with paired control, PNAS-4 was up-regulated in cancers (P = 0.018). PNAS-4 overexpression ratios were correlated to the p53 mutant status (P = 0.001). The mean PNAS-4 expression levels of p53 mutant homozygote group and heterozygote group were higher than that of p53 wild type group (P = 0.013). The expression ratios of PNAS-4 (every sample in relative to its paired normal mucosa) were different between negative lymph node metastasis (66% up-regulated, 34% down-regulated) and positive metastasis (42% up-regulated, 58% down-regulated). Taken together, these findings suggested that PNAS-4 was not a p53 target, but overexpression of PNAS-4 was correlated to p53 inactivity in colorectal cancer.     

Fatty-acid-binding protein in locust flight muscle. Developmental changes of expression, concentration and intracellular distribution.

Fatty-acid-binding protein (FABP) from the flight muscle of the locust, Schistocerca gregaria, is similar to mammalian heart FABP in its primary structure and biochemical characteristics. We have studied developmental changes using enzyme-linked immunosorbent assays, RNA hybridization and electron microscopy of immunogold-labeled sections. Locust muscle FABP is the most abundant soluble muscle protein in fully developed adult locusts, comprising 18% of the total cytosolic protein. At the beginning of the adult stage, however, no FABP is detectable. Its concentration rises during the following 10 days, after which it reaches its maximal value. FABP mRNA is present shortly after adult ecdysis; its concentration increases for 10 days, before it diminishes and reaches a constant, low level, probably needed to maintain the established FABP level. The protein is abundant in cytosol and nuclei, but virtually absent in mitochondria.     

两种类型聚半乳糖醛酸酶的提纯及性质

黑曲霉(AspergilluS niger)AS 3.3883所产果胶酶经DEAE Sephadex A50及Sephadex G100柱层析分离出电泳纯的两种聚半乳糖醛酸酶(PG1,PG2),并对它们的性质及结构进行了比较研究。结果证明两种酶作用的最适条件、动力学性质、分子量、氨基酸组成及金属离子对酶活力影响等方面有很大差异,但二者的每个摩尔的活力及酶的构象很相似。     

病毒衣壳结构亚单位的种类数与三角形剖分数关系的研究和探讨

本文报道了在正廿面体病毒衣壳中,当蛋白结构亚单位以“三聚体”的形式聚集在单位三角形(?)时,其亚单位的种类数应等于该病毒的三角形剖分数值。