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1.
The single most difficult problem in phylogenetic analysis is deciding whether a shared taxonomic character is due to common ancestry or one that appeared independently due to convergence, parallelism, or reversion to an ancestral state. Mammalian L1 retrotransposons undergo periodic amplifications in which multiple copies of the elements are interspersed in the genome. Because these elements apparently are transmitted only by inheritance and are retained in the genome, a shared L1 amplification event can only be an inherited ancestral character. We propose that L1 amplification events can be an excellent tool for analyzing mammalian evolution and demonstrate here how we addressed several refractory problems in rodent systematics using L1 DNA as a taxonomic character.   相似文献   
2.
We identified a patient suffering from late-infantile metachromatic leukodystrophy (MLD) who has a residual arylsulfatase A (ARSA) activity of about 10%. Fibroblasts of the patient show significant sulfatide degradation activity exceeding that of adult MLD patients. Analysis of the ARSA gene in this patient revealed heterozygosity for two new mutant alleles: in one allele, deletion of C 447 in exon 2 leads to a frameshift and to a premature stop codon at amino acid position 105; in the second allele, a G-->A transition in exon 5 causes a Gly309-->Ser substitution. Transient expression of the mutant Ser309-ARSA resulted in only 13% enzyme activity of that observed in cells expressing normal ARSA. The mutant ARSA is correctly targeted to the lysosomes but is unstable. These findings are in contrast to previous results showing that the late-infantile type of MLD is always associated with the complete absence of ARSA activity. The expression of the mutant ARSA protein may be influenced by particular features of oligodendrocytes, such that the level of mutant enzyme is lower in these cells than in others.  相似文献   
3.
A new web tool, PDB2MultiGIF (http://www.dkfz-heidelberg.de/spec/pdb2mgif/),which converts the topological information (atom types, 3D coordinates, molecular connectivity) of molecules (given in PDB format [1]) to a series of animated images (in GIF Format) [2] is described. The molecular visualisation program RASMOL [3] is used to generate the images.Electronic Supplementary Material available.  相似文献   
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The 11 VirB proteins from Agrobacterium tumefaciens are predicted to form a membrane-bound complex that mediates the movement of DNA from the bacterium into plant cells. The studies reported here on the possible VirB protein interactions in such a complex demonstrate that VirB9 and VirB10 can each form high-molecular-weight complexes after treatment with a chemical cross-linker. Analysis of nonpolar virB mutants showed that the formation of the VirB10 complexes does not occur in a virB9 mutant and that VirB9 and VirB10 are not components of the same cross-linked complex. VirB9, when stabilized by the concurrent expression of VirB7, was shown to be sufficient to permit VirB10 to cross-link into its usual high-molecular-weight forms in the absence of other Vir proteins. Randomly introduced single point mutations in virB9 resulted in Agrobacterium strains with severely attenuated virulence. Although some of the mutants contained wild-type levels of VirB9 and displayed an unaltered VirB9 cross-linking pattern, VirB10 cross-linking was drastically reduced. We conclude that specific amino acid residues in VirB9 are necessary for interaction with VirB10 resulting in the capacity of VirB10 to participate in high-molecular-weight complexes that can be visualized by chemical cross-linking.  相似文献   
6.
Inflammatory bowel diseases (IBD) are emerging globally, indicating that environmental factors may be important in their pathogenesis. Colonic mucosal epigenetic changes, such as DNA methylation, can occur in response to the environment and have been implicated in IBD pathology. However, mucosal DNA methylation has not been examined in treatment-naïve patients. We studied DNA methylation in untreated, left sided colonic biopsy specimens using the Infinium HumanMethylation450 BeadChip array. We analyzed 22 control (C) patients, 15 untreated Crohn’s disease (CD) patients, and 9 untreated ulcerative colitis (UC) patients from two cohorts. Samples obtained at the time of clinical remission from two of the treatment-naïve UC patients were also included into the analysis. UC-specific gene expression was interrogated in a subset of adjacent samples (5 C and 5 UC) using the Affymetrix GeneChip PrimeView Human Gene Expression Arrays. Only treatment-naïve UC separated from control. One-hundred-and-twenty genes with significant expression change in UC (> 2-fold, P < 0.05) were associated with differentially methylated regions (DMRs). Epigenetically associated gene expression changes (including gene expression changes in the IFITM1, ITGB2, S100A9, SLPI, SAA1, and STAT3 genes) were linked to colonic mucosal immune and defense responses. These findings underscore the relationship between epigenetic changes and inflammation in pediatric treatment-naïve UC and may have potential etiologic, diagnostic, and therapeutic relevance for IBD.  相似文献   
7.
The work was focused on the investigation of possible dependencies between the development of viral infection in plants and the presence of high heavy metal concentrations in soil. Field experiments have been conducted in order to study the development of systemic tobacco mosaic virus (TMV) infection in Lycopersicon esculentum L. cv. Miliana plants under effect of separate salts of heavy metals Cu, Zn and Pb deposited in soil. As it is shown, simultaneous effect of viral infection and heavy metals in tenfold maximum permissible concentration leads to decrease of total chlorophyll content in experiment plants mainly due to the degradation of chlorophyll a. The reduction of chlorophyll concentration under the combined influence of both stress factors was more serious comparing to the separate effect of every single factor. Plants' treatment with toxic concentrations of lead and zinc leaded to slight delay in the development of systemic TMV infection together with more than twofold increase of virus content in plants that may be an evidence of synergism between these heavy metal's and virus' effects. Contrary, copper although decreased total chlorophyll content but showed protective properties and significantly reduced amount of virus in plants.  相似文献   
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9.
It has been established that the horseradish peroxidase/O2/isobutyraldehyde (IBAL) system leads to triplet acetone and formic acid formation followed by phosphorescence of the triplet acetone (see, for example, Bechara, E.J.H., Faria Oliveira, O.M.M., Durán, N., Casadei de Baptista, R., and Cilento, G. (1979) Photochem. Photobiol. 30, 101-110). In this paper many of the mechanistic details are established. The reaction is initiated by the autoxidation of IBAL to form the peracid (CH3)2CHC = O(OOH). The peracid converts horseradish peroxidase into compound I which in turn is converted into compound II by abstracting the alcoholic hydrogen atom from the enol form of IBAL. This creates a free radical with two resonance forms. (Formula: see text) Addition of molecular oxygen to the latter resonance form creates a peroxy radical which abstracts a hydrogen atom near the active site of the enzyme. The newly formed alpha-peroxide in turn forms a dioxetane-type of intermediate which rapidly decomposes into triplet acetone and formic acid. Compound II reacts with the enol by the same pathway as compound I. Thus native horseradish peroxidase is regenerated. The hydrogen atom abstraction near the enzyme active site may occur directly from ethanol, present to solubilize IBAL or from a group on the enzyme, in which case ethanol participates in a repair mechanism. Phosphate buffer is necessary because it catalyzes the keto-enol conversion of IBAL. Thus horseradish peroxidase participates in a normal peroxidatic cycle. The only chain reaction is the uncatalyzed autoxidation of IBAL, most of which occurs prior to the mixing of IBAL with the oxygenated horseradish peroxidase solution.  相似文献   
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