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71.
72.
Schaap FG Nierman MC Berbée JF Hattori H Talmud PJ Vaessen SF Rensen PC Chamuleau RA Kuivenhoven JA Groen AK 《Journal of lipid research》2006,47(10):2333-2339
The relevance of apolipoprotein A-V (apoA-V) for human lipid homeostasis is underscored by genetic association studies and the identification of truncation-causing mutations in the APOA5 gene as a cause of type V hyperlipidemia, compatible with an LPL-activating role of apoA-V. An inverse correlation between plasma apoA-V and triglyceride (TG) levels has been surmised from animal data. Recent studies in human subjects using (semi)quantitative immunoassays, however, do not provide unambiguous support for such a relationship. Here, we used a novel, validated ELISA to measure plasma apoA-V levels in patients (n = 28) with hypertriglyceridemia (HTG; 1.8-78.7 mmol TG/l) and normolipidemic controls (n = 42). Unexpectedly, plasma apoA-V levels were markedly increased in the HTG subjects compared with controls (1,987 vs. 258 ng/ml; P < 0.001). In the HTG group, apoA-V and TG were positively correlated (r = +0.44, P = 0.02). In addition, we noted an increased level of the LPL-inhibitory protein apoC-III in the HTG group (45.8 vs. 10.6 mg/dl in controls; P < 0.001). The correlation between apoA-V and TG levels in the HTG group disappeared (partial r = +0.09, P = 0.65) when controlling for apoC-III levels. In contrast, apoC-III and TG remained positively correlated in this group when controlling for apoA-V (partial r = +0.43, P = 0.025). Our findings suggest that in HTG patients, increased TG levels are accompanied by high plasma levels of apoA-V and apoC-III, apolipoproteins with opposite modes of action. This study provides evidence for a complex interaction between apoA-V and apoC-III in patients with severe HTG. 相似文献
73.
A single lineage of r2 retrotransposable elements is an active, evolutionarily stable component of the Drosophila rDNA locus 总被引:1,自引:0,他引:1
R2 elements are non-long-terminal-repeat (non-LTR) retrotransposons that
insert specifically in the 28S rRNA genes of many insects. Previous reports
concerning this element in the genus Drosophila have suggested that R2
elements are absent from many species of this genus, particularly those
species from the subgenus Drosophila. In this report, we present an
extensive study of the distribution and evolution of R2 elements in
Drosophila. A PCR survey of 59 species from 23 species groups of the two
major Drosophila subgenera found that R2 elements are present in all but
two species of the melanogaster species subgroup. Phylogenetic analysis
based on partial nucleotide sequences of R2 elements from 23 species
demonstrates that the relationships of R2 elements are congruent with those
of the Drosophila species phylogeny, suggesting that these elements have
been vertically inherited since the divergence of this genus some 60 MYA.
Sequence variation between different copies of R2 elements within each
species was less than 0.16%, indicating that these elements are undergoing
concerted evolution similar to that of the 28S genes. Several properties of
the R2 sequences suggest that these elements depend on retrotransposition
in addition to simple recombination to remain within the rDNA locus: the
rates of synonymous substitutions averaged 4.8 times the rate of
replacement substitutions, 82 of 83 R2 copies partially sequenced contained
intact open reading frames, and, finally, length variation associated with
the poly(A) 3' tails indicated that many R2 copies are the direct result of
retrotransposition.
相似文献
74.
Listeria spp. found on fresh market produce 总被引:5,自引:0,他引:5
J E Heisick D E Wagner M L Nierman J T Peeler 《Applied and environmental microbiology》1989,55(8):1925-1927
From October 1987 to August 1988, 1,000 tests were conducted on 10 types of fresh produce from two Minneapolis area supermarkets to detect Listeria spp. The produce included broccoli, cabbage, carrots, cauliflower, cucumbers, lettuce, mushrooms, potatoes, radishes, and tomatoes. The vegetables were tested by the Food and Drug Administration method for isolation of Listeria spp., with the addition of LiCl-phenylethanol-moxalactam agar in the last 280 tests; 8.6 and 11.4% of these tests were positive by modified McBride and LiCl-phenylethanol-moxalactam agars, respectively. Listeria monocytogenes was isolated from cabbage, cucumbers, potatoes, and radishes; L. innocua was isolated from cucumbers, lettuce, mushrooms, potatoes, and radishes; L. seeligeri was isolated from cabbage and radishes; and L. welshimeri was isolated from cucumbers, potatoes, and radishes. The isolates were of various serotypes; however, the L. monocytogenes isolates were predominantly serotype 1 (82%). Only potatoes (25.8% positive) and radishes (30.3% positive) showed significant amounts of L. monocytogenes contamination. 相似文献
75.
Lathe WC rd; Burke WD; Eickbush DG; Eickbush TH 《Molecular biology and evolution》1995,12(6):1094-1105
R1 is a non-long terminal repeat (non-LTR) retrotransposable element that
inserts into a specific sequence of insect 28S ribosomal RNA genes. We have
previously shown that this element has been maintained through vertical
transmission in the melanogaster species subgroup of Drosophila. To address
whether R1 elements have been vertically transmitted for longer periods of
evolutionary time, the analysis has been extended to 11 other species from
four species groups of the genus Drosophila (melanogaster, obscura,
testecea, and repleta). All sequenced elements appeared functional on the
basis of the preservation of their open-reading frames and consistently
higher rate of substitution at synonymous sites relative to replacement
sites. The phylogenetic relationships of the R1 elements from all species
analyzed were congruent with the species phylogenies, suggesting that the
R1 elements have been vertically transmitted since the inception of the
Drosophila genus, an estimated 50-70 Mya. The stable maintenance of R1
through the germ line appears to be the major mechanism for the widespread
distribution of these elements in Drosophila. In two species, D.
neotestecea of the testecea group and D. takahashii of the melanogaster
group, a second family of R1 elements was also present that differed in
sequence by 46% and 31%, respectively, from the family that was congruent
with the species phylogeny. These second families may represent occasional
horizontal transfers or, alternatively, they could reflect the ability of
R1 elements to diverge into new families within a species and evolve
independently.
相似文献
76.
Schrettl M Kim HS Eisendle M Kragl C Nierman WC Heinekamp T Werner ER Jacobsen I Illmer P Yi H Brakhage AA Haas H 《Molecular microbiology》2008,70(1):27-43
Aspergillus fumigatus, the most common airborne fungal pathogen of humans, employs two high-affinity iron uptake systems: iron uptake mediated by the extracellular siderophore triacetylfusarinine C and reductive iron assimilation. Furthermore, A. fumigatus utilizes two intracellular siderophores, ferricrocin and hydroxyferricrocin, to store iron. Siderophore biosynthesis, which is essential for virulence, is repressed by iron. Here we show that this control is mediated by the GATA factor SreA. During iron-replete conditions, SreA deficiency partially derepressed synthesis of triacetylfusarinine C and uptake of iron resulting in increased cellular accumulation of both iron and ferricrocin. Genome-wide DNA microarray analysis identified 49 genes that are repressed by iron in an SreA-dependent manner. This gene set, termed SreA regulon, includes all known genes involved in iron acquisition, putative novel siderophore biosynthetic genes, and also genes not directly linked to iron metabolism. SreA deficiency also caused upregulation of iron-dependent and antioxidative pathways, probably due to the increased iron content and iron-mediated oxidative stress. Consistently, the sreA disruption mutant displayed increased sensitivity to iron, menadion and phleomycin but retained wild-type virulence in a mouse model. As all detrimental effects of sreA disruption are restricted to iron-replete conditions these data underscore that A. fumigatus faces iron-depleted conditions during infection. 相似文献
77.
78.
79.
80.
Wilkinson JR Yu J Bland JM Nierman WC Bhatnagar D Cleveland TE 《Applied microbiology and biotechnology》2007,74(6):1308-1319
Aflatoxins are toxic and carcinogenic secondary metabolites produced by the fungi Aspergillus flavus and Aspergillus parasiticus. To better understand the molecular mechanisms that regulate aflatoxin production, the biosynthesis of the toxin in A. flavus and A. parasticus grown in yeast extract sucrose media supplemented with 50 mM tryptophan (Trp) were examined. Aspergillus flavus grown in the presence of 50 mM tryptophan was found to have significantly reduced aflatoxin B1 and B2 biosynthesis, while A. parasiticus cultures had significantly increased B1 and G1 biosynthesis. Microarray analysis of RNA extracted from fungi grown under these conditions revealed 77 genes that are expressed
significantly different between A. flavus and A. parasiticus, including the aflatoxin biosynthetic genes aflD (nor-1), aflE (norA), and aflO (omtB). It is clear that the regulatory mechanisms of aflatoxin biosynthesis in response to Trp in A. flavus and A. parasiticus are different. These candidate genes may serve as regulatory factors of aflatoxin biosynthesis. 相似文献