Sequence and analysis of chromosome 1 of the plant Arabidopsis thaliana

The genome of the flowering plant Arabidopsis thaliana has five chromosomes. Here we report the sequence of the largest, chromosome 1, in two contigs of around 14.2 and 14.6 megabases. The contigs extend from the telomeres to the centromeric borders, regions rich in transposons, retrotransposons and repetitive elements such as the 180-base-pair repeat. The chromosome represents 25% of the genome and contains about 6,850 open reading frames, 236 transfer RNAs (tRNAs) and 12 small nuclear RNAs. There are two clusters of tRNA genes at different places on the chromosome. One consists of 27 tRNA(Pro) genes and the other contains 27 tandem repeats of tRNA(Tyr)-tRNA(Tyr)-tRNA(Ser) genes. Chromosome 1 contains about 300 gene families with clustered duplications. There are also many repeat elements, representing 8% of the sequence.     

Controlled growth factor release from synthetic extracellular matrices

Polymeric matrices can be used to grow new tissues and organs, and the delivery of growth factors from these matrices is one method to regenerate tissues. A problem with engineering tissues that exist in a mechanically dynamic environment, such as bone, muscle and blood vessels, is that most drug delivery systems have been designed to operate under static conditions. We thought that polymeric matrices, which release growth factors in response to mechanical signals, might provide a new approach to guide tissue formation in mechanically stressed environments. Critical design features for this type of system include the ability to undergo repeated deformation, and a reversible binding of the protein growth factors to polymeric matrices to allow for responses to repeated stimuli. Here we report a model delivery system that can respond to mechanical signalling and upregulate the release of a growth factor to promote blood vessel formation. This approach may find a number of applications, including regeneration and engineering of new tissues and more general drug-delivery applications.     

The Pleistocene serpent Wonambi and the early evolution of snakes

The Madtsoiidae were medium sized to gigantic snakes with a fossil record extending from the mid-Cretaceous to the Pleistocene, and spanning Europe, Africa, Madagascar, South America and Australia. This widely distributed group survived for about 90 million years (70% of known ophidian history), and potentially provides important insights into the origin and early evolution of snakes. However, madtsoiids are known mostly from their vertebrae, and their skull morphology and phylogenetic affinities have been enigmatic. Here we report new Australian material of Wonambi, one of the last-surviving madtsoiids, that allows the first detailed assessment of madtsoiid cranial anatomy and relationships. Despite its recent age, which could have overlapped with human history in Australia, Wonambi is one of the most primitive snakes known--as basal as the Cretaceous forms Pachyrhachis and Dinilysia. None of these three primitive snake lineages shows features associated with burrowing, nor do any of the nearest lizard relatives of snakes (varanoids). These phylogenetic conclusions contradict the widely held 'subterranean' theory of snake origins, and instead imply that burrowing snakes (scolecophidians and anilioids) acquired their fossorial adaptations after the evolution of the snake body form and jaw apparatus in a large aquatic or (surface-active) terrestrial ancestor.     

光敏聚酰亚胺合成的新途径(Ⅰ)聚酰胺的氯甲基化反应

采用可溶性聚酰亚胺，经过氯甲基化反应，得到了聚酰亚胺改性的起始原料－氯甲基化聚酰亚胺。该聚合物的结构采用^1H-NMR和FT－IR得到了确认，最高氯甲基化率为181％，该聚合物溶于氯仿和四氢呋喃等溶剂。     

Dempster-Shafer证据推理在数据融合中的应用

介绍了Dempster-Shafer证据推理的基本概念和理论,并将数据融合思想引入到机械设备故障诊断中,采用Dempster-Shafer证据推理进行融合计算,验证了这一方法的有效性.     

Enzymatic formation of potential anticancer and antiviral inosine analogues

Theoretically, inosine analogues should act as effective inhibitors of tumor cell proliferation and viral replication. To acquire a broad spectrum of new candidate inosine analogues, a rapid, facile, quantitative and stereoselective method for deaminating potential antitumor and antiviral adenine analogues previously synthesized in our laboratory was developed. A novel 5-adenylic acid deaminase, with relaxed substrate requirements, fromAspergillus species was utilized to deaminate four hexofuranosyladenine nucleosides and five adenine nucleoside dialdehydes to their corresponding inosine analogues. The fastest rates of deamination for the hexofuranosyl nucleosides were for the compounds where the vicinal hydroxyl groups on the sugars are oriented in the erythro configuration. For rapid deamination of the adenine nucleoside dialdehydes, theR configuration at the proximal carbon atom is preferred, while the nature of the group on the distal carbon atom has no significant effect on the rate or extent of deamination.     

A possible chemical basis for the higher mutagenicity of marijuana smoke as compared to tobacco smoke

Summary The results of comparative analyses of polynuclear aromatic hydrocarbons in marijuana and tobacco smoke indicate a considerably higher content of potential carcinogens in the former. A model experiment involving ⁹-tetrahydrocannabinol suggests that the pyrolysis products of cannabinoids are major contributors to the polynuclear aromatic hydrocarbons.We thank Dr.John Benner and Ms.Carolyn Keene of the University of Kentucky for help with the smoking experiments. This work was supported by Grant No. R01-DA-00507-01 from the National Institute of Mental Health.