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51.
Franken C Haase G Brandt C Weber-Heynemann J Martin S Lämmler C Podbielski A Lütticken R Spellerberg B 《Molecular microbiology》2001,41(4):925-935
Beta-haemolytic streptococci are important human and animal pathogens: their genetic traits that are associated with the ability to infect human hosts remain, however, unclear. The surface protein, Lmb, mediates the adherence of Streptococcus agalactiae to human laminin. For further analysis of the corresponding gene, the adjacent genomic regions were sequenced. Lmb is localized on a putative composite transposon of 16 kb and is flanked by two copies of a novel insertion sequence element (ISSag2). It harbours the genes scpB and lmb, which are 98% identical with the respective genes of Streptococcus pyogenes. Analysis of the distribution of these genes and ISSag2 among 131 streptococcal strains revealed that all of the human isolates, but only 20% (12 of 61) of the animal isolates, contained scpB and lmb or their homologues. To investigate if the putative transposon can be mobilized, an erythromycin resistance marker was incorporated into the lmb gene of S. agalactiae. Screening for mutant strains with a regained susceptibility for erythromycin identified strains with a deletion of scpB, lmb, and one copy of ISSag2. We hypothesize that a horizontal gene transfer caused the exchange of scpB and lmb and that the ability of S. pyogenes, S. agalactiae and group C and G streptococcal strains to colonize or infect human hosts is dependent on their presence. 相似文献
52.
Organelles called centrosomes in metazoans or spindle pole bodies (SPBs) in yeast direct the assembly of a bipolar spindle that is essential for faithful segregation of chromosomes during mitosis. Abnormal accumulation of multiple centrosomes leads to genome instability, and has been observed in both tumour cells and cells with targeted mutations in tumour-suppressor genes. The defects that lead to centrosome amplification are not understood. We have recapitulated the multiple-centrosome phenotype in budding yeast by disrupting the activity of specific cyclin-dependent kinase (CDK) complexes. Our observations are reminiscent of mechanisms that govern DNA replication, and show that specific cyclin/CDK activities function both to promote SPB duplication and to prevent SPB reduplication. 相似文献
53.
Wiesmann F Frydrychowicz A Rautenberg J Illinger R Rommel E Haase A Neubauer S 《American journal of physiology. Heart and circulatory physiology》2002,283(3):H1065-H1071
Because of its complex geometry, assessment of right ventricular (RV) function is more difficult than it is for the left ventricle (LV). Because gene-targeted mouse models of cardiomyopathy may involve remodeling of the right heart, the purpose of this study was to develop high-resolution functional magnetic resonance imaging (MRI) for in vivo quantification of RV volumes and global function in mice. Thirty-three mice of various age were studied under isoflurane anesthesia by electrocardiogram-triggered cine-MRI at 7 T. MRI revealed close correlations between RV and LV stroke volume and cardiac output (r = 0.97, P < 0.0001 each). Consistent with human physiology, murine RV end-diastolic and end-systolic volumes were significantly higher compared with LV volumes (P < 0.05 each). MRI in mice with LV heart failure due to myocardial infarction revealed significant structural and functional changes of the RV, indicating RV dysfunction. Hence, MRI allows for the quantification of RV volumes and global systolic function with high accuracy and bears the potential to evaluate mechanisms of RV remodeling in mouse models of heart failure. 相似文献
54.
55.
Chalisova NI Pennijainen VA Haase G 《Rossi?skii fiziologicheski? zhurnal imeni I.M. Sechenova / Rossi?skaia akademiia nauk》2002,88(5):627-633
The effect of aminoacids L-arginin, L-lysine, L-asparagin was investigated in organotypic tissue culture of brain cortex and spleen of 1-day old rats. The aminoacids in concentrations 0.05 and 0.1 ng/ml are active, inducing a less intensive growth zone as compared to the control, excluding the effect of asparagin on lymphoid tissue. Method of fluorescent staining shows a negative correlation between growth zone size and apoptotic cell number. The nerve and lymphoid tissue express apoptosis in response to aminoacids. 相似文献
56.
Apoplasmic barriers and oxygen transport properties of hypodermal cell walls in roots from four amazonian tree species 总被引:1,自引:0,他引:1
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De Simone O Haase K Müller E Junk WJ Hartmann K Schreiber L Schmidt W 《Plant physiology》2003,132(1):206-217
The formation of suberized and lignified barriers in the exodermis is suggested to be part of a suite of adaptations to flooded or waterlogged conditions, adjusting transport of solutes and gases in and out of roots. In this study, the composition of apoplasmic barriers in hypodermal cell walls and oxygen profiles in roots and the surrounding medium of four Amazon tree species that are subjected to long-term flooding at their habitat was analyzed. In hypodermal cell walls of the deciduous tree Crateva benthami, suberization is very weak and dominated by monoacids, 2-hydroxy acids, and omega-hydroxycarboxylic acids. This species does not show any morphological adaptations to flooding and overcomes the aquatic period in a dormant state. Hypodermal cells of Tabernaemontana juruana, a tree which is able to maintain its leaf system during the aquatic phase, are characterized by extensively suberized walls, incrusted mainly by the unsaturated C(18) omega-hydroxycarboxylic acid and the alpha,omega-dicarboxylic acid analogon, known as typical suberin markers. Two other evergreen species, Laetia corymbulosa and Salix martiana, contained 3- to 4-fold less aliphatic suberin in the exodermis, but more than 85% of the aromatic moiety of suberin are composed of para-hydroxybenzoic acid, suggesting a function of suberin in pathogen defense. No major differences in the lignin content among the species were observed. Determination of oxygen distribution in the roots and rhizosphere of the four species revealed that radial loss of oxygen can be effectively restricted by the formation of suberized barriers but not by lignification of exodermal cell walls. 相似文献
57.
Langfelder K Streibel M Jahn B Haase G Brakhage AA 《Fungal genetics and biology : FG & B》2003,38(2):143-158
For more than 40 years fungi have been known to produce pigments known as melanins. Predominantly these have been dihydroxyphenylalanine (DOPA)-melanin and dihydroxynaphthalene (DHN)-melanin. The biochemical and genetical analysis of the biosynthesis pathways have led to the identification of the genes and corresponding enzymes of the pathways. Only recently have both these types of melanin been linked to virulence in some human pathogenic and phytopathogenic fungi. The absence of melanin in human pathogenic and phytopathogenic fungi often leads to a decrease in virulence. In phytopathogenic fungi such as Magnaporthe grisea and Colletotrichum lagenarium, besides other possible functions in pathogenicity, DHN-melanin plays an essential role in generating turgor for plant appressoria to penetrate plant leaves. While the function of melanin in human pathogenic fungi such as Cryptococcus neoformans, Wangiella dermatitidis, Sporothrix schenckii, and Aspergillus fumigatus is less well defined, its role in protecting fungal cells has clearly been shown. Specifically, the ability of both DOPA- and DHN-melanins to quench free radicals is thought to be an important factor in virulence. In addition, in several fungi the production of fungal virulence factors, such as melanin, has been linked to a cAMP-dependent signaling pathway. Many of the components involved in the signaling pathway have been identified. 相似文献
58.
In a previous paper, we have reported on a new, troglobiticspecies of Georissa and its possible parapatric origin fromGeorissa saulae Benthem-Jutting, 1966, which occurs outsidethe cave system of Batu Sanaron, a limestone outcrop in Sabah,Malaysian Borneo. These analyses were based on genetic and morphometricdata. Here, we formally describe the new species adding anatomicaldata derived from dissections and histological serial sectionsas well as fine structural data of shell, operculum and radula,and compare it with its stem species. The two species differin shell and radular morphology as well as genital characters.Since we found anatomical differences between very closely relatedspecies, we assume that dissections would be of general usefor the taxonomy of Georissa and the remaining nominal genus-grouptaxa of the poorly known Hydrocenidae. 相似文献
59.
M. Haase A. Bisenberger 《Journal of Zoological Systematics and Evolutionary Research》2003,41(3):175-185
The intraspecific genetic differentiation depends to a large part on historical factors. The mode of dispersal is an important determinant of the genetic diversity especially of newly founded populations. Fast long-distance colonization of formerly unsuitable habitats results in reduced genetic diversity and lineages originating from different glacial refugia form well-defined hybrid zones, where they meet. Slow dispersers, on the other hand, preserve their refugial genetic diversity. Paleontological findings and a previous analysis of mtDNA suggest that the land snail Arianta arbustorum, which today is widely spread across Europe, has survived the Pleistocene glaciations within the boundaries of permafrost. In the present paper, we asked, whether the differentiation of nuclear markers, i.e. allozymes, supports these results. We investigated the allozymic differentiation at 15 polymorphic loci in 14 Alpine and one English populations of the land snail A. arbustorum. Various tests of genetic population differentiation yielded ambiguous results. Allele frequencies differed significantly across populations and all but five pairwise FST values were significant. Genetic distances between populations were comparatively high. On the other hand, an exact test of population differentiation found no differences and the assignment of individuals to their populations of origin was poor. This indicates that allozymic differentiation is constrained. Whether these constraints are of natural or methodological nature remains open. Matrices of genetic and geographical distances were correlated only after removal of the English population from the analysis. Similarly, with one exception FST values increased as the number of regions included in the calculations increased. Thus, on a regional scale, we largely observed a pattern of isolation by distance, which does no longer hold on a larger scale. This is well in accordance with the previous findings based on mtDNA. Mitochondrial lineages were widely distributed across Europe and overlapped extensively. Considering the low potential for dispersal of a land snail, the patchy distribution of lineages, and the high genetic diversity also found in the present study suggests that A. arbustorum has survived the Pleistocene within the boundaries of permafrost. 相似文献
60.
Mohamed Abd El Rahman Denise Haase Axel Rentzsch Julia Olchvary Hans-Joachim Sch?fers Wolfram Henn Stefan Wagenpfeil Hashim Abdul-Khaliq 《PloS one》2015,10(4)