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Roth TM Chiang CY Inaba M Yuan H Salzmann V Roth CE Yamashita YM 《Molecular biology of the cell》2012,23(8):1524-1532
Drosophila male germline stem cells (GSCs) divide asymmetrically, balancing self-renewal and differentiation. Although asymmetric stem cell division balances between self-renewal and differentiation, it does not dictate how frequently differentiating cells must be produced. In male GSCs, asymmetric GSC division is achieved by stereotyped positioning of the centrosome with respect to the stem cell niche. Recently we showed that the centrosome orientation checkpoint monitors the correct centrosome orientation to ensure an asymmetric outcome of the GSC division. When GSC centrosomes are not correctly oriented with respect to the niche, GSC cell cycle is arrested/delayed until the correct centrosome orientation is reacquired. Here we show that induction of centrosome misorientation upon culture in poor nutrient conditions mediates slowing of GSC cell proliferation via activation of the centrosome orientation checkpoint. Consistently, inactivation of the centrosome orientation checkpoint leads to lack of cell cycle slowdown even under poor nutrient conditions. We propose that centrosome misorientation serves as a mediator that transduces nutrient information into stem cell proliferation, providing a previously unappreciated mechanism of stem cell regulation in response to nutrient conditions. 相似文献
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Viktoria Stelzhammer Bob Amess Daniel Martins‐de‐Souza Yishai Levin Susan E. Ozanne Malgorzata S. Martin‐Gronert Sebastian Urday Sabine Bahn Paul C. Guest 《Proteomics》2012,12(22):3386-3392
Studies of neuronal, endocrine, and metabolic disorders would be facilitated by characterization of the hypothalamus proteome. Protein extracts prepared from 16 whole rat hypothalami were measured by data‐independent label‐free nano LC‐MS/MS. Peptide features were detected, aligned, and searched against a rat Swiss‐Prot database using ProteinLynx Global Server v.2.5. The final combined dataset comprised 21 455 peptides, corresponding to 622 unique proteins, each identified by a minimum of two distinct peptides. The majority of the proteins (69%) were cytosolic, and 16% were membrane proteins. Important proteins involved in neurological and synaptic function were identified including several members of the Ras‐related protein family and proteins involved in glutamate biosynthesis. 相似文献
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The diversity and distribution of modern benthic foraminifera has been extensively studied in order to aid the paleoecological
interpretation of their fossil record. Traditionally, foraminiferal species are identified based on morphological characters
of their organic, agglutinated or calcareous tests. Recently, however, new molecular techniques based on analysis of DNA sequences
have been introduced to study the genetic variation in foraminifera. Although the number of species for which DNA sequence
data exist is still very limited, it appears that morphology-based studies largely underestimated foraminiferal diversity.
Here, we present two examples of the use of DNA sequences to examine the diversity of benthic foraminifera. The first case
deals with molecular and morphological variations in the well-known and common calcareous genus Ammonia. The second case presents molecular diversity in the poorly documented group of monothalamous (single-chambered) foraminifera.
Both examples perfectly illustrate high cryptic diversity revealed in almost all molecular studies. Molecular results also
confirm that the majority of foraminiferal species have a restricted geographic distribution and that globally distributed
species are rare. This is in opposition to the theory that biogeography has no impact on the diversity of small-sized eukaryotes.
At least in the case of foraminifera, size does not seem to have a main impact on dispersal capacities. However, the factors
responsible for the dispersal of foraminiferal species and the extension of their geographic ranges remain largely unknown.
Special Issue: Protist diversity and geographic distribution. Guest editor: W. Foissner. 相似文献
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Paternity in mallards: effects of sperm quality and female sperm selection for inbreeding avoidance 总被引:5,自引:0,他引:5
Denk Angelika G.; Holzmann Alois; Peters Anne; Vermeirssen Etienne L.M.; Kempenaers Bart 《Behavioral ecology》2005,16(5):825-833
Postcopulatory processes might play an important role in sexualselection. In theory, fertilization success could be controlledby females via selection of particular sperm within their reproductivetract, or it could be determined by sperm competition per se.In practice, these two mechanisms are difficult to disentangle.To assess the relative importance of both mechanisms we usedartificial insemination in combination with measurements ofsperm quality (swimming speed and motility) in mallards. Inthis species, females often lack behavioral control over copulationsand hence may use postcopulatory mechanisms to optimize theirreproductive output. One important factor affecting female fitnessmay be selection of genetically compatible males. To investigatethe influence of sperm quality and parental relatedness on paternitywe inseminated 12 groups of related females with a sperm mixturecontaining equal numbers of sperm from a brother and from anunrelated male. Paternity was independent of the relatednessof the siring male to the female but was significantly affectedby long-term sperm swimming speed and motility. No interactionbetween relatedness and sperm quality on paternity was observed.These results suggest that female mallards are not able to selectsperm on a purely genetic basis and emphasize the importanceof sperm quality in gaining paternity. 相似文献
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