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21.
D. Dartigues 《Entomologia Experimentalis et Applicata》1992,64(3):203-208
Résumé La fréquence des gouttelettes de miellat excrétées par Toxoptera aurantii (Boyer de F.) augmente en la présence de Tapinoma simrothi Krausse., mais le phénomène est seulement important quand les aphides sont familiarisés avec la visite des fourmis. En présence d'ouvrières pourvoyeuses âgées, le nombre de gouttelettes de miellat excrétées par une colonie d'aphides est multiplié par 4,9. Les meilleures performances sont obtenues avec les larves, qui défèquent plus vite que les adultes. Les jeunes ouvrières âgées de moins de deux semaines et isolées juste avant la naissance, sont capables d'augmenter la production de gouttelettes, et ceci sans apprentissage. Mais l'effet est plutôt faible. Dans tous les cas, le nombre de sollicitations pour la nourriture est plus élevé que le nombre des gouttelettes excrétées. Habituellement, les fourmis collectent le miellat directement sur les aphides. Néanmoins, le miellat restant sur les feuilles peut être ramassé, mais cette récolte n'est pas très importante.
Summary The frequency of honeydew droplets excreted by Toxoptera aurantii (Boyer de F.) increases in the presence of Tapinoma simrothi Krausse., but the phenomenon is only important when aphids are familiarized with ant-attendance. In presence of old foraging workers, the number of honeydew droplets excreted by an aphid colony is multiplied by 4.9. The best performances are obtained with larvae, which defecate faster than adults. Young workers less than two weeks old and isolated just before birth, are able to increase the droplets production, and this without apprenticeship. But the effect is rather slight. In all cases, the number of food sollicitations is higher than the number of excreted droplets. Usually, ants collect honeydew directly on aphids. Nevertheless, honeydew remaining on leaves can be picked up, but this gathering is not very important.相似文献
22.
Background
Host parasitism by Trichomonas vaginalis is complex. Adherence to vaginal epithelial cells (VECs) is mediated by surface proteins. We showed before that antisense down-regulation of expression of adhesin AP65 decreased amounts of protein, which lowered levels of T. vaginalis adherence to VECs. We now perform antisense down-regulation of expression of the ap33 gene to evaluate and confirm a role for AP33 in adherence by T. vaginalis. We also used an established transfection system for heterologous expression of AP33 in T. foetus as an additional confirmatory approach. 相似文献23.
Paul Blanche Jean‐François Dartigues Hélène Jacqmin‐Gadda 《Biometrical journal. Biometrische Zeitschrift》2013,55(5):687-704
To quantify the ability of a marker to predict the onset of a clinical outcome in the future, time‐dependent estimators of sensitivity, specificity, and ROC curve have been proposed accounting for censoring of the outcome. In this paper, we review these estimators, recall their assumptions about the censoring mechanism and highlight their relationships and properties. A simulation study shows that marker‐dependent censoring can lead to important biases for the ROC estimators not adapted to this case. A slight modification of the inverse probability of censoring weighting estimators proposed by Uno et al. (2007) and Hung and Chiang (2010a) performs as well as the nearest neighbor estimator of Heagerty et al. (2000) in the simulation study and has interesting practical properties. Finally, the estimators were used to evaluate abilities of a marker combining age and a cognitive test to predict dementia in the elderly. Data were obtained from the French PAQUID cohort. The censoring appears clearly marker‐dependent leading to appreciable differences between ROC curves estimated with the different methods. 相似文献
24.
25.
The murid rodent subfamily Sigmodontinae contains 79 genera which are
distributed throughout the New World. The time of arrival of the first
sigmodontines in South America and the estimated divergence time(s) of the
different lineages of South American sigmodontines have been controversial
due to the lack of a good fossil record and the immense number of extant
species. The "early-arrival hypothesis" states that the sigmodontines must
have arrived in South America no later than the early Miocene, at least 20
MYA, in order to account for their vast present-day diversity, whereas the
"late-arrival hypothesis" includes the sigmodontines as part of the
Plio-Pleistocene Great American Interchange, which occurred approximately
3.5 MYA. The phylogenetic relationships among 33 of these genera were
reconstructed using mitochondrial DNA (mtDNA) sequence data from the ND3,
ND4L, arginine tRNA, and ND4 genes, which we show to be evolving at the
same rate. A molecular clock was calibrated for these genes using published
fossil dates, and the genetic distances were estimated from the DNA
sequences in this study. The molecular clock was used to estimate the dates
of the South American sigmodontine origin and the main sigmodontine
radiation in order to evaluate the "early-" and "late-arrival" scenarios.
We estimate the time of the sigmodontine invasion of South America as
between approximately 5 and 9 MYA, supporting neither of the scenarios but
suggesting two possible models in which the invading lineage was either (1)
ancestral to the oryzomyines, akodonts, and phyllotines or (2) ancestral to
the akodonts and phyllotines and accompanied by the oryzomyines. The
sigmodontine invasion of South America provides an example of the advantage
afforded to a lineage by the fortuitous invasion of a previously
unexploited habitat, in this case an entire continent.
相似文献
26.
Previously, treatment of Tamm-Horsfall glycoprotein (THp) from different
donors with endo-beta-galactosidase has been shown to liberate a tetra- and
a Sd(a)-active pentasaccharide, concluding the presence of N-linked
carbohydrate chains containing additional N - acetyllactosamine units.
These type of oligosaccharides were not found in a detailed structure
elucidation of the carbohydrate moiety of THp of one male donor, suggesting
a donor-specific feature for these type of structures. Therefore, THp was
isolated from four healthy male donors and each subjected to
endo-beta-galactosidase treatment in order to release these tetra- and
Sd(a)-active pentasaccharide. Differences were observed in the total amount
of released tetra- and Sda-active pentasaccharide of the used donors (42,
470, 478, 718 microg/100 mg THp), indicating that the presence of repeating
N-acetyllactosamine units incorporated into the N-glycan moiety of THp is
donor specific. Furthermore, a higher expression of the Sd(a) determinant
on antennae which display N-acetyllactosamine elongation was observed,
suggesting a better accessibility for the
beta-N-acetylgalactosaminyltransferase. In order to characterize the
N-glycans containing repeating N- acetyllactosamine units, carbohydrate
chains were enzymatically released from THp and isolated. The
tetraantennary fraction, which accounts for more than 33% of the total
carbohydrate moiety of THp, was used to isolate oligosaccharides containing
additional N - acetyllactosamine units. Five N-linked tetraantennary
oligosaccharides containing a repeating N-acetyllactosamine unit were
identified, varying from structures bearing four Sd(a) determinants to
structures containing no Sd(a) determinant (see below). One compound was
used in order to specify the branch location of the additional N-
acetyllactosamine unit, and it appeared that only the Gal-6' and Gal-8'
residues were occupied by a repeating N -acetyllactosamine unit.
相似文献
27.
Wingfield BD; Grant WS; Wolfaardt JF; Wingfield MJ 《Molecular biology and evolution》1994,11(3):376-383
The genus Ceratocystis sensu stricto includes important fungal pathogens of
woody and herbaceous plants. This genus is distinguished from species in
Ceratocystis sensu lato by the presence of Chalara anamorphs. Ascospore
shape has been used extensively in delineating Ceratocystis taxa, which
show a large variety of ascospore shapes. Sequence analysis of one region
of he 18S ribosomal RNA subunit and two regions of the 28S ribosomal RNA
subunit showed that there was a majority of multiple substitutions at
nucleotide sites and that there was a low transition/transversion ratio, T
= 0.72. Both of these results suggest that these are well established, old
species. Ascospore morphology, for the most part, was not congruent with
the molecular phylogeny, and the use of morphological characters may be
misleading in the taxonomy of these species.
相似文献
28.
Membrane compartmentalized ATP and its preferential use by the Na, K-ATPase of human red cell ghosts
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This paper describes work which begins to define the molecular organization in the region of the membrane that comprises the functional domain of the Na:K pump. The membrane-bound phosphoglycerate kinase (PGK) and Na, K-ATPase appear to be directly linked via a compartmentalized form of ATP. Evidence for the membrane pool of ATP is based on the labeling characteristics of the phosphoproteins by [γ-(32)P]ATP of ghosts incubated under various conditions. Preincubation of ghosts in the presence of ATP at 37 degrees C, but not at 0 degrees C, completely obscures the formation of the Na-phosphoprotein in ghosts washed and subsequently incubated in the presence of [gamma-(32)P]ATP. In contrast to the Na component, the Mg component of phosphorylation is only slightly altered by preincubation with ATP. ATPase activity measured as (32)P(i) liberated during the subsequent incubation at 0 degrees C, reflects completely the differential effects of preincubation with ATP on (32)P incorporation into phosphoprotein. ATP placed within the pool by preincubation can be removed by operating the Na, K-ATPase or the PGK reaction in the reverse direction by use of exogenous substrates. Alternatively, the membrane pool of ATP can be formed also from exogenous substrates by running the PGK reaction in the forward direction. These results, while providing direct support for a membrane compartment of ATP, also indicate the location of this compartment in relation to the PGK and the Na, K-ATPase. In addition, these results also imply that the Mg and Na components are different enzymatic entities since substrate ATP can be derived from separate sources. 相似文献
29.
Epidemiological studies on aging in France: from the PAQUID study to the Three-City study 总被引:3,自引:0,他引:3
Alpérovitch A Amouyel P Dartigues JF Ducimetière P Mazoyer B Ritchie K Tzourio C 《Comptes rendus biologies》2002,325(6):665-672
Follow-up of cohorts recruited in general population with active screening and diagnosis of incident cases, is the most appropriate epidemiological design for studying incidence and risk factors of Alzheimer disease and other types of dementia. In France, people considered in the PAQUID study, then in the EVA study, have been the first cohorts on dementia. They have prepared the way for the Three-City (3C) study, conducted in Bordeaux, Dijon and Montpellier. About 9500 persons aged 65 years and over have been recruited in these three cities and will be followed-up during four years. The main objective of the 3C study is to investigate the relation between vascular risk and neurodegenerative diseases. The 3C study will provide essential data for defining strategies for dementia prevention. To measure the impact of the strategies on the incidence of dementia and the social burden of this disease will be an important public health objective in the near future. 相似文献
30.
Niels Reinmuth Nadine Payer Thomas Muley Hans Hoffmann Felix JF Herth Matthias Villalobos Michael Thomas 《Respiratory research》2013,14(1):139