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131.
Soft tissue movement and stress shielding do not affect bone ingrowth in the bone conduction chamber
A variety of bone chambers are used in orthopedic research to study bone and tissue ingrowth in small and large animals. If different bone chambers are placed in one species, differences in bone ingrowth are observed. For instance, bone ingrowth in the bone conduction chamber (BCC) is high, but is low or absent in the repeated sampling bone chamber (RSBC). This difference may be explained by the design and fixation of these chambers. It is known that stress shielding and micromovement can influence bone formation. The objective of the study reported here was to determine whether stress shielding or soft tissue movement affected bone ingrowth in the BCC in the goat. Two types of caps were made, with fixation similar to that of the fixation plate of the RSBC. By placing the caps over the BCCs and fixating the caps directly to the tibial bone, the effect of stress shielding was studied. One cap was in direct contact with the bone chamber underneath, the other cap did not touch the chamber. This difference was used to observe whether movement of the soft tissue on top of the chamber and cap would affect bone ingrowth. Each limb received one control chamber without a cap and a chamber with a cap, either with or without contacting the BCC, yielding four implants per goat. After 12 weeks, bone and total tissue ingrowths were measured. Bone ingrowth was seen in 38 of 40 chambers. Total tissue and bone ingrowths were comparable between control chambers and BCCs with a cap, irrespective of type. Neither stress shielding, nor lack of movement of soft tissue affected bone ingrowth. Other factors in the design of the chambers were responsible for the difference in bone ingrowth between the BCC and the RSBC. 相似文献
132.
Completion of mitosis in budding yeast is triggered by activation of the protein phosphatase Cdc14, which is the ultimate effector of a signalling cascade, known as the mitotic exit network. Cdc14 activation leads to eradication of mitotic kinase activity, which is pivotal for mitotic exit and cytokinesis in all eukaryotes. The complexity in mitotic exit regulation is underscored by the recent discovery of a novel network, the so-called FEAR pathway that regulates early Cdc14 activation. Surprisingly, this has revealed an unexpected role for Spo12, a protein involved in meiosis, in Cdc14 activation. In this review, we will discuss these findings together with recent advances in deciphering the function of the FEAR circuit, which has unravelled an exciting new side of Cdc14. 相似文献
133.
The release of Cdc14 from the nucleolus occurs in two waves in early and late anaphase, controlled by the FEAR and MEN pathways, respectively. Two new papers report the localisation at the spindle pole body of the Cdc14 released in early anaphase and, surprisingly, show that the two pulses of released Cdc14 have opposite effects on MEN activation. 相似文献
134.
Lanzetti L Margaria V Melander F Virgili L Lee MH Bartek J Jensen S 《The Journal of biological chemistry》2007,282(20):15258-15270
The Cdc14 family of dual specificity phosphatases regulates key mitotic events in the eukaryotic cell cycle. Although extensively characterized in yeast, little is known about the function of mammalian Cdc14 family members. Here we report a genetic substrate-trapping system designed to identify substrates of the human Cdc14A (hCdc14A) phosphatase. Using this approach, we identify RN-tre, a GTPase-activating protein for the Rab5 GTPase, as a novel physiological target of hCdc14A. As a Rab5 GTPase-activating protein, RN-tre has previously been implicated in control of intracellular membrane trafficking. We find that RN-tre forms a stable complex with the catalytically inactive hCdc14A C278S mutant but not with the wild type protein in human cells, indicative of a substrate/enzyme interaction. In support, we show that RN-tre is regulated by cell cycle-dependent phosphorylation peaking at mitosis, which can be antagonized by hCdc14A activity in vitro as well as in vivo. Furthermore, we show that RN-tre phosphorylation is critical for efficient hCdc14A association and that RN-tre binding can be displaced by tungstate, a competitive inhibitor that binds to the active site of hCdc14A. Consistent with the preference of hCdc14A for phosphorylations mediated by proline-directed kinases, we find that RN-tre is a direct substrate of cyclin-dependent kinase. Finally, phosphorylation of RN-tre appears to finely modulate its catalytic activity. Our findings reveal a novel connection between the cell cycle machinery and the endocytic pathway. 相似文献
135.
Sanne Boessenkool Sabrina S. Taylor Carolyn K. Tepolt Jan Komdeur Ian G. Jamieson 《Conservation Genetics》2007,8(3):705-714
For conservation purposes islands are considered safe refuges for many species, particularly in regions where introduced predators
form a major threat to the native fauna, but island populations are also known to possess low levels of genetic diversity.
The New Zealand archipelago provides an ideal system to compare genetic diversity of large mainland populations where introduced
predators are common, to that of smaller offshore islands, which serve as predator-free refuges. We assessed microsatellite
variation in South Island robins (Petroica australis australis), and compared large mainland, small mainland, natural island and translocated island populations. Large mainland populations
exhibited more polymorphic loci and higher number of alleles than small mainland and natural island populations. Genetic variation
did not differ between natural and translocated island populations, even though one of the translocated populations was established
with five individuals. Hatching failure was recorded in a subset of the populations and found to be significantly higher in
translocated populations than in a large mainland population. Significant population differentiation was largely based on
heterogeneity in allele frequencies (including fixation of alleles), as few unique alleles were observed. This study shows
that large mainland populations retain higher levels of genetic diversity than natural and translocated island populations.
It highlights the importance of protecting these mainland populations and using them as a source for new translocations. In
the future, these populations may become extremely valuable for species conservation if existing island populations become
adversely affected by low levels of genetic variation and do not persist. 相似文献
136.
Sarah Noerklit Roed Anne Cathrine N?hr Pernille Wismann Helle Iversen Hans Br?uner-Osborne Sanne Moeller Knudsen Maria Waldhoer 《The Journal of biological chemistry》2015,290(2):1233-1243
The signaling capacity of seven-transmembrane/G-protein-coupled receptors (7TM/GPCRs) can be regulated through ligand-mediated receptor trafficking. Classically, the recycling of internalized receptors is associated with resensitization, whereas receptor degradation terminates signaling. We have shown previously that the incretin glucagon-like peptide-1 receptor (GLP-1R) internalizes fast and is primarily resensitized through recycling back to the cell surface. GLP-1R is expressed in pancreatic islets together with the closely related glucose-dependent insulinotropic polypeptide (GIPR) and glucagon (GCGR) receptors. The interaction and cross-talk between coexpressed receptors is a wide phenomenon of the 7TM/GPCR superfamily. Numerous reports show functional consequences for signaling and trafficking of the involved receptors. On the basis of the high structural similarity and tissue coexpression, we here investigated the potential cross-talk between GLP-1R and GIPR or GCGR in both trafficking and signaling pathways. Using a real-time time-resolved FRET-based internalization assay, we show that GLP-1R, GIPR, and GCGR internalize with differential properties. Remarkably, upon coexpression of the internalizing GLP-1R and the non-internalizing GIPR, GLP-1-mediated GLP-1R internalization was impaired in a GIPR concentration-dependent manner. As a functional consequence of such impaired internalization capability, GLP-1-mediated GLP-1R signaling was abrogated. A similar compromised signaling was found when GLP-1R internalization was abrogated by a dominant-negative version of dynamin (dynamin-1 K44E), which provides a mechanistic link between GLP-1R trafficking and signaling. This study highlights the importance of receptor internalization for full functionality of GLP-1R. Moreover, cross-talk between the two incretin receptors GLP-1R and GIPR is shown to alter receptor trafficking with functional consequences for GLP-1R signaling. 相似文献
137.
Sofie Symoens Aileen?M. Barnes Charlotte Gistelinck Fransiska Malfait Brecht Guillemyn Wouter Steyaert Delfien Syx Sanne D’hondt Martine Biervliet Julie De?Backer Eckhard?P. Witten Sergey Leikin Elena Makareeva Gabriele Gillessen-Kaesbach Ann Huysseune Kris Vleminckx Andy Willaert Anne De?Paepe Joan?C. Marini Paul?J. Coucke 《American journal of human genetics》2015,97(4):521-534
The evolutionarily conserved transmembrane anterior posterior transformation 1 protein, encoded by TAPT1, is involved in murine axial skeletal patterning, but its cellular function remains unknown. Our study demonstrates that TAPT1 mutations underlie a complex congenital syndrome, showing clinical overlap between lethal skeletal dysplasias and ciliopathies. This syndrome is characterized by fetal lethality, severe hypomineralization of the entire skeleton and intra-uterine fractures, and multiple congenital developmental anomalies affecting the brain, lungs, and kidneys. We establish that wild-type TAPT1 localizes to the centrosome and/or ciliary basal body, whereas defective TAPT1 mislocalizes to the cytoplasm and disrupts Golgi morphology and trafficking and normal primary cilium formation. Knockdown of tapt1b in zebrafish induces severe craniofacial cartilage malformations and delayed ossification, which is shown to be associated with aberrant differentiation of cranial neural crest cells. 相似文献
138.
Maarten?P.G. Massink Marijn?A. Créton Francesca Spanevello Willem?M.M. Fennis Marco?S. Cune Sanne?M.C. Savelberg Isa?c J. Nijman Madelon?M. Maurice Marie-José H. van?den?Boogaard Gijs van?Haaften 《American journal of human genetics》2015,97(4):621-626
Tooth agenesis is one of the most common developmental anomalies in man. Oligodontia, a severe form of tooth agenesis, occurs both as an isolated anomaly and as a syndromal feature. We performed exome sequencing on 20 unrelated individuals with apparent non-syndromic oligodontia and failed to detect mutations in genes previously associated with oligodontia. In three of the probands, we detected heterozygous variants in LRP6, and sequencing of additional oligodontia-affected individuals yielded one additional mutation in LRP6. Three mutations (c.1144_1145dupAG [p.Ala383Glyfs∗8], c.1779dupT [p.Glu594∗], and c.2224_2225dupTT [p.Leu742Phefs∗7]) are predicted to truncate the protein, whereas the fourth (c.56C>T [p.Ala19Val]) is a missense variant of a conserved residue located at the cleavage site of the protein’s signal peptide. All four affected individuals harboring a LRP6 mutation had a family history of tooth agenesis. LRP6 encodes a transmembrane cell-surface protein that functions as a co-receptor with members from the Frizzled protein family in the canonical Wnt/β-catenin signaling cascade. In this same pathway, WNT10A was recently identified as a major contributor in the etiology of non-syndromic oligodontia. We show that the LRP6 missense variant (c.56C>T) results in altered glycosylation and improper subcellular localization of the protein, resulting in abrogated activation of the Wnt pathway. Our results identify LRP6 variants as contributing to the etiology of non-syndromic autosomal-dominant oligodontia and suggest that this gene is a candidate for screening in DNA diagnostics. 相似文献
139.
Sanne Skov Jensen Anders Fomsgaard Tine Kochendorf Larsen Jeanette Linnea Tingstedt Jan Gerstoft Gitte Kronborg Court Pedersen Ingrid Karlsson 《PloS one》2015,10(10)
CD8+ T cell-restricted immunity is important in the control of HIV-1 infection, but continued immune activation results in CD8+ T cell dysfunction. Early initiation of antiretroviral treatment (ART) and the duration of ART have been associated with immune reconstitution. Here, we evaluated whether restoration of CD8+ T cell function in HIV-1-infected individuals was dependent on early initiation of ART. HIV-specific CD107a, IFNγ, IL-2, TNFα and MIP-1β expression by CD8+ T cells and the frequency of CD8+ T cells expressing PD-1, 2B4 and CD160 were measured by flow cytometry. The frequency of CD8+ T cells expressing the inhibitory markers PD-1, 2B4 and CD160 was lower in ART-treated individuals compared with ART-naïve individuals and similar to the frequency in HIV-uninfected controls. The expression of the three markers was similarly independent of when therapy was initiated. Individuals treated before seroconversion displayed an HIV-specific CD8+ T cell response that included all five functional markers; this was not observed in individuals treated after seroconversion or in ART-naïve individuals. In summary, ART appears to restore the total CD8+ T cell population to a less exhausted phenotype, independent of the time point of initiation. However, to preserve multifunctional, HIV-1-specific CD8+ T cells, ART might have to be initiated before seroconversion. 相似文献
140.
Evert van den Broek Maurits J. J. Dijkstra Oscar Krijgsman Daoud Sie Josien C. Haan Joleen J. H. Traets Mark A. van de Wiel Iris D. Nagtegaal Cornelis J. A. Punt Beatriz Carvalho Bauke Ylstra Sanne Abeln Gerrit A. Meijer Remond J. A. Fijneman 《PloS one》2015,10(9)