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排序方式: 共有151条查询结果,搜索用时 0 毫秒
91.
Sean P. Keenan Tasnim Sinuff Karen E.A. Burns John Muscedere Jim Kutsogiannis Sangeeta Mehta Deborah J. Cook Najib Ayas Neill K.J. Adhikari Lori Hand Damon C. Scales Rose Pagnotta Lynda Lazosky Graeme Rocker Sandra Dial Kevin Laupland Kevin Sanders Peter Dodek as the Canadian Critical Care Trials Group/Canadian Critical Care Society Noninvasive Ventilation Guidelines Group 《CMAJ》2011,183(3):E195-E214
92.
Patterns of chloroplast DNA (cpDNA) and mitochondrial DNA (mtDNA) variation
were studied in 378 populations of oak trees sampled throughout the
southern half of France. Six cpDNA haplotypes detected in a previous
European survey and three new cpDNA haplotypes were found in this region.
Two mitochondrial polymorphisms detected earlier by restriction analysis of
PCR-amplified fragments alone, or in combination with single-strand
conformation polymorphism (SSCP), were compared with the cpDNA data.
Sequencing revealed the nature of the two mitochondrial mutations: a
single-base substitution and a 4-bp inversion associated with a 22-bp
hairpin secondary structure. The single-base substitution was then analyzed
by allele-specific amplification. Results for the two cytoplasmic genomes
were combined, which allowed the identification of 12 cpDNA-mtDNA
haplotypes. The 4-bp mtDNA inversion has appeared independently in
different cpDNA lineages. Given the peculiar nature of this mtDNA mutation,
we suggest that intramolecular recombination leading to repeated inversions
of the 4-bp sequence (rather than paternal leakage of one of the two
genomes) is responsible for this pattern. Furthermore, the geographic
locations of the unusual cpDNA-mtDNA associations (due to the inversion)
usually do not match the zones of contact between divergent haplotypes. In
addition, in southern France, the groupings of populations based on the
mtDNA substitution were strictly congruent with those based on cpDNA.
Because many populations that are polymorphic for both cpDNA and mtDNA have
remained in contact since postglacial recolonization in this area without
producing any new combination of cytoplasms involving the mitochondrial
substitution, we conclude that paternal leakage is not a significant factor
at this timescale. Such results confirm and expand our earlier conclusions
based on controlled crosses.
相似文献
93.
Cytosolic isocitrate dehydrogenase in humans, mice, and voles and phylogenetic analysis of the enzyme family 总被引:3,自引:0,他引:3
Nekrutenko A; Hillis DM; Patton JC; Bradley RD; Baker RJ 《Molecular biology and evolution》1998,15(12):1674-1684
In this study, we report cDNA sequences of the cytosolic NADP-dependent
isocitrate dehydrogenase for humans, mice, and two species of voles
(Microtus mexicanus and Microtus ochrogaster). Inferred amino acid
sequences from these taxa display a high level of amino acid sequence
conservation, comparable to that of myosin beta heavy chain, and share
known structural features. A Caenorhabditis elegans enzyme that was
previously identified as a protein similar to isocitrate dehydrogenase is
most likely the NADP-dependent cytosolic isocitrate dehydrogenase enzyme
equivalent, based on amino acid similarity to mammalian enzymes and
phylogenetic analysis. We also suggest that NADP-dependent isocitrate
dehydrogenases characterized from alfalfa, soybean, and eucalyptus are most
likely cytosolic enzymes. The phylogenetic tree of various isocitrate
dehydrogenases from eukaryotic sources revealed that independent gene
duplications may have given rise to the cytosolic and mitochondrial forms
of NADP-dependent isocitrate dehydrogenase in animals and fungi. There
appears to be no statistical support for a hypothesis that the
mitochondrial and cytosolic forms of the enzyme are orthologous in these
groups. A possible scenario of the evolution of NADP-dependent isocitrate
dehydrogenases is proposed.
相似文献
94.
95.
Matthew N Ward Allison M Churcher Kevin J Dick Chris RJ Laver Greg L Owens Megan D Polack Pam R Ward Felix Breden John S Taylor 《BMC evolutionary biology》2008,8(1):210
Background
Comparisons of functionally important changes at the molecular level in model systems have identified key adaptations driving isolation and speciation. In cichlids, for example, long wavelength-sensitive (LWS) opsins appear to play a role in mate choice and male color variation within and among species. To test the hypothesis that the evolution of elaborate coloration in male guppies (Poecilia reticulata) is also associated with opsin gene diversity, we sequenced long wavelength-sensitive (LWS) opsin genes in six species of the family Poeciliidae. 相似文献96.
Roman J. Dial Martin D. F. Ellwood Edward C. Turner William A. Foster 《Biotropica》2006,38(5):643-652
This study applies a novel, vertically stratified fogging protocol to document arthropod abundance, density, and biomass across a vertical gradient in a primary, lowland dipterocarp forest canopy in Borneo. We fogged arthropods at 5 m vertical intervals and 20 m horizontal intervals along six full‐canopy transects and measured leaf surface areas along the same transects. The results show that arthropod biomass in the aboveground regions was 23.6 kg/ha, the abundance was 23.9 million individuals/ha, and the density on leaf surfaces was 280 individuals/m2 leaf area. All three numbers are five to ten times higher than estimated by previous surveys of tropical lowland rain forest canopies using mass‐collection techniques. Arthropod abundance and biomass were analyzed in relation to canopy structure, composition, vapor pressure deficit (VPD), photosynthetic photon flux density (PPFD), and height. Using stepwise regression we found that 13 of 14 arthropod groups had significant positive relationships with one‐sided leaf area, 11 had significant negative relationships with VPD, 3 had significant relationships with height, and none showed positive relationships with light. Classifying the 14 taxa based on their responses to leaf area and VPD created three groups that corresponded roughly to the biology of these taxa. This study suggests that the biomass and abundance, and perhaps therefore—by extrapolation—the biodiversity, of tropical canopy arthropods may be very much higher than previously estimated. 相似文献
97.
A 4000 sow farm in the US using early weaning and a computerized record system was recruited. Farrowed sows were assigned into two experimental treatments: prostaglandin F2alpha injection or control. Sows were assigned by a farm worker to obtain even parity distributions between two groups in each farrowing group. A single i.m. injection of 2 ml of prostaglandin F2alpha between 24 and 48 h after farrowing was administered in the muscle immediately lateral to the vulva. Control sows received no treatment. Of 3562 farrowed sows, 1592 were administered with prostaglandin F2alpha. Parity distributions were not different between control and treatment groups. Parity was categorized into two groups: parity 1-2 or > or = 3. Mean lactation length was 18 days and there was no difference between the control and treatment groups. No main effects of prostaglandin F2alpha administration were found in either parity group on adjusted 21-day litter weight, weaning-to-first-mating interval or weaning-to-conception interval. In parity > or = 3 sows, a two-way interaction between the association of lactation length and treatment with pigs born alive at subsequent farrowing was found (P = 0.044), while no such interaction was found in parity 1-2 sows (P = 0.14). The prediction line for subsequent pigs born alive indicates that prostaglandin F2alpha administration alters the relationship between lactation length and subsequent litter size on mid- or old-parity sows. 相似文献
98.
Molecular phylogenetics of Stenodermatini bat genera: congruence of data from nuclear and mitochondrial DNA 总被引:2,自引:1,他引:1
Van den Bussche RA; Baker RJ; Wichman HA; Hamilton MJ 《Molecular biology and evolution》1993,10(5):944-959
Within the tribe Stenodermatini the systematics of the complex of species
allied with the genus Artibeus has generated several alternative
phylogenetic hypotheses. The most recent treatment recognized four genera
(Artibeus, Dermanura, Enchisthenes, and Koopmania) and suggested that the
most recent common ancestor of these four genera would include the common
ancestor of all other currently recognized Stenodermatini genera except
Sturnira. To test this hypothesis, we examined an EcoRI-defined nuclear
satellite DNA repeat and 402 bp of DNA sequence variation from the
mitochondrial cytochrome b gene. Phylogenetic conclusions based on Southern
blot analyses, in situ hybridization, and mitochondrial DNA sequence data
indicate that Enchisthenes is not closely related to Dermanura, Artibeus,
or Koopmania and that Dermanura, Artibeus, and Koopmania shared a common
ancestor after diverging from the remainder of the Stenodermatini. If our
conclusions are correct, then justification for recognizing Dermanura and
Koopmania as generically distinct from Artibeus must be based on the
magnitude of difference that distinguishes each rather than on the
conclusion that to place them as congeneric with Artibeus creates a
paraphyletic taxon.
相似文献
99.
100.