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121.
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
122.
Biotinyl-oligosaccharides are a relatively new generation of saccharide
probes that enable immobilization of desired oligosaccharides on
streptavidin matrices for studies of carbohydrate-protein interactions.
Here we describe the facile preparation of biotinyl-l-3-(2-naphthyl)-
alanine hydrazide (BNAH) derivatives of oligosaccharides, containing a
strong UV absorbing and fluorescent group, in which the ring of the
reducing-end monosaccharide is nonreduced. We evaluate reactivities of
immobilized BNAH- N -glycans with plant lectins that recognize aspects of
the oligosaccharide core or outer-arms. We make some comparisons with
2-amino-6-amidobiotinyl-pyridine (BAP) derivatives obtained by reductive
amination, and 6-(biotinyl)-aminocaproyl-hydrazide (BACH) derivatives which
have a longer spacer-arm. N -Glycan-BNAH and-BAP derivatives have, overall,
comparable reactivities with lectins which recognize N -glycan outer-arms
or the trimannosyl core, but only BNAH and BACH derivatives are bound by
lectins which recognize the non- reduced core. Moreover, with Pisum sativum
agglutinin (PSA) which additionally requires the fucosyl- N-
glycan-asparaginyl core for high affinity binding, the immobilized BNAH
derivative (which is an alanine hydrazide beta-glycoside) can substitute
for the natural beta- glycosylasparaginyl core, whereas the BACH derivative
(aminocaproyl- hydrazide-beta-glycoside) is less effective. BNAH is a
derivatization reagent of choice, therefore, for solid phase
carbohydrate-binding experiments with immobilized N -glycans.
相似文献
123.
Multidimensional heteronuclear NMR studies have been applied to the
resonance assignment and conformational analysis of 13C-enriched
Neu5Acalpha2-3Galbeta1-4Glc. It is demonstrated that three-dimensional
ROESY-HSQC experiments provide through-space distance restraints which
cannot be observed with conventional homonuclear 1H techniques due to
resonance overlap. In particular, connectivities demonstrating the
existence of the "anti" conformation about the Galbeta1-4Glc glycosidic
linkage are unambiguously observed. It is shown that 13C isotopic
enrichment of the trisaccharide at a level >95% enables straightforward
measurement of trans-glycosidic 1H-13C and 13C-13C coupling constants and a
Karplus-type relation is derived for the latter. In total 15 conformational
restraints were obtained for the trisaccharide in aqueous solution, all of
which were in excellent agreement with theoretical parameters computed from
a 5 ns molecular dynamics simulation of the glycan.
相似文献
124.
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126.
Wisdom M. Dlamini 《Ecosystems》2011,14(3):366-381
This study uses Bayesian networks (BNs) to simulate the spatial distribution of southern African biomes and bioregions using bioclimatic variables. Two Tree-Augmented Naïve (TAN) BN models were parameterized from 23 bioclimatic variables using the expectation-maximization (EM) algorithm. Using sensitivity analyses, the relative influence of each variable was determined using the mutual information from which six bioclimatic variables were selected for the final models. Precipitation of the warmest quarter and extra-terrestrial solar radiation was found to be the most influential variables on both bioregion and biome distributions. Isothermality was the least influential bioclimatic variable at both bioregion and biome levels. Overall correspondence was very high at 93.8 and 87.1% for biomes and bioregions, respectively, whereas classification errors were obtained in transition areas indicating the uncertainties associated with vegetation mapping around margins. The findings indicate that southern African bioregions and biomes can be classified and mapped according to key bioclimatic variables. Spatio-temporal, in particular, monthly and quarterly variations in both precipitation and temperature are found to be ecologically significant in determining the spatial distribution of biomes and bioregions. The findings also reflect the hierarchical relationship of biomes and bioregions as a function of local bioclimatic gradients and interactions. The results indicate the ecological significance of bioclimatic conditions in ecosystem science and offer the opportunity to utilize the models for predicting future responses and sensitivities to climatic changes. 相似文献
127.
128.
Garba Iliyasu Dimie Ogoina Akan A. Otu Farouq M. Dayyab Bassey Ebenso Daniel Otokpa Stella Rotifa Wisdom T. Olomo Abdulrazaq G. Habib 《PloS one》2015,10(8)
Background
The 2014 Ebola Virus Disease (EVD) outbreak was characterised by fear, misconceptions and irrational behaviours. We conducted a knowledge attitude and practice survey of EVD in Nigeria to inform implementation of effective control measures.Methods
Between July 30th and September 30th 2014, we undertook a cross sectional study on knowledge, attitude and practice (KAP) of Ebola Virus Disease (EVD) among adults of the general population and healthcare workers (HCW) in three states of Nigeria, namely Bayelsa, Cross River and Kano states. Demographic information and data on KAP were obtained using a self-administered standardized questionnaire. The percentage KAP scores were categorised as good and poor. Independent predictors of good knowledge of EVD were ascertained using a binary logistic regression model.Results
Out of 1035 study participants with median age of 32 years, 648 (62.6%) were males, 846 (81.7%) had tertiary education and 441 (42.6%) were HCW. There were 218, 239 and 578 respondents from Bayelsa, Cross River and Kano states respectively. The overall median percentage KAP scores and interquartile ranges (IQR) were 79.46% (15.07%), 95.0% (33.33%) and 49.95% (37.50%) respectively. Out of the 1035 respondents, 470 (45.4%), 544(52.56%) and 252 (24.35%) had good KAP of EVD defined using 80%, 90% and 70% score cut-offs respectively. Independent predictors of good knowledge of EVD were being a HCW (Odds Ratio-OR-2.89, 95% Confidence interval-CI of 1.41–5.90), reporting ‘moderate to high fear of EVD’ (OR-2.15, 95% CI-(1.47–3.13) and ‘willingness to modify habit’ (OR-1.68, 95% CI-1.23–2.30).Conclusion
Our results reveal suboptimal EVD-related knowledge, attitude and practice among adults in Nigeria. To effectively control future outbreaks of EVD in Nigeria, there is a need to implement public sensitization programmes that improve understanding of EVD and address EVD-related myths and misconceptions, especially among the general population. 相似文献129.
The replicative helicase MCM recruits cohesin acetyltransferase ESCO2 to mediate centromeric sister chromatid cohesion 下载免费PDF全文
Miroslav P Ivanov Rene Ladurner Ina Poser Rebecca Beveridge Evelyn Rampler Otto Hudecz Maria Novatchkova Jean‐Karim Hériché Gordana Wutz Petra van der Lelij Emanuel Kreidl James RA Hutchins Heinz Axelsson‐Ekker Jan Ellenberg Anthony A Hyman Karl Mechtler Jan‐Michael Peters 《The EMBO journal》2018,37(15)
Chromosome segregation depends on sister chromatid cohesion which is established by cohesin during DNA replication. Cohesive cohesin complexes become acetylated to prevent their precocious release by WAPL before cells have reached mitosis. To obtain insight into how DNA replication, cohesion establishment and cohesin acetylation are coordinated, we analysed the interaction partners of 55 human proteins implicated in these processes by mass spectrometry. This proteomic screen revealed that on chromatin the cohesin acetyltransferase ESCO2 associates with the MCM2‐7 subcomplex of the replicative Cdc45‐MCM‐GINS helicase. The analysis of ESCO2 mutants defective in MCM binding indicates that these interactions are required for proper recruitment of ESCO2 to chromatin, cohesin acetylation during DNA replication, and centromeric cohesion. We propose that MCM binding enables ESCO2 to travel with replisomes to acetylate cohesive cohesin complexes in the vicinity of replication forks so that these complexes can be protected from precocious release by WAPL. Our results also indicate that ESCO1 and ESCO2 have distinct functions in maintaining cohesion between chromosome arms and centromeres, respectively. 相似文献
130.
Priority Research and Management Issues for the Imperiled Great Basin of the Western United States 总被引:3,自引:0,他引:3
Like many arid and semiarid regions, the Great Basin of the western United States is undergoing major ecological, social, and economic changes that are having widespread detrimental effects on the structure, composition, and function of native ecosystems. The causes of change are highly interactive and include urban, suburban, and exurban growth, past and present land uses, climate change, altered fire regimes, and rapid expansion of invasive species. Cumulative effects include vegetation type conversions, loss of watershed functioning, loss of native species, and diminished economic potential. The diversity and magnitude of issues require consensus on priority issues, and new and innovative research and management approaches that address larger spatial scales and longer time scales than in the past. Primary research coupled with large-scale assessments and effective monitoring strategies is needed to understand and track the ongoing changes. Prediction and modeling of alternative futures are needed for incorporation into the planning process and use as a basis for adaptive management, and management tools are needed to aid decision-making and implementation. Historically, research and management in arid and semiarid regions such as the Great Basin have been severely under-funded and altering current trajectories will require financial resources, political support, and effective policies and institutional mechanisms. Sustaining the ecosystems, resources, and human populations of these regions will require strong collaborative partnerships among research and management organizations to reduce overlap, leverage funds, and increase efficiency. Close involvement of all stakeholders is needed to obtain the needed support for making necessary changes in policies and management activities. 相似文献