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排序方式: 共有182条查询结果,搜索用时 15 毫秒
91.
Fantin A Schwarz Q Davidson K Normando EM Denti L Ruhrberg C 《Development (Cambridge, England)》2011,138(19):4185-4191
Neuropilin 1 (NRP1) is a transmembrane glycoprotein that is essential for blood vessel development in vertebrates. Best known for its ability to bind members of the vascular endothelial growth factor (VEGF) and class 3 semaphorin families through its extracellular domain, it also has a highly conserved cytoplasmic domain, which terminates in a SEA motif that binds the PDZ protein synectin/GIPC1/NIP. Previous studies in zebrafish embryos and tissue culture models raised the possibility that the SEA motif of NRP1 is essential for angiogenesis. Here, we describe the generation of mice that express a form of NRP1 that lacks the cytoplasmic domain and, therefore, the SEA motif (Nrp1(cyto)(Δ)(/)(Δ) mice). Our analysis of pre- and perinatal vascular development revealed that vasculogenesis and angiogenesis proceed normally in these mutants, demonstrating that the membrane-anchored extracellular domain is sufficient for vessel growth. By contrast, the NRP1 cytoplasmic domain is required for normal arteriovenous patterning, because arteries and veins crossed each other at an abnormally high frequency in the Nrp1(cyto)(Δ)(/)(Δ) retina, as previously reported for mice with haploinsufficient expression of VEGF in neural progenitors. At crossing sites, the artery was positioned anteriorly to the vein, and both vessels were embedded in a shared collagen sleeve. In human eyes, similar arteriovenous crossings are risk factors for branch retinal vein occlusion (BRVO), an eye disease in which compression of the vein by the artery disrupts retinal blood flow, causing local tissue hypoxia and impairing vision. Nrp1(cyto)(Δ)(/)(Δ) mice may therefore provide a suitable genetic model to study the aetiology of BRVO. 相似文献
92.
93.
Vascular endothelial growth factor A (VEGF-A) is best known for its essential roles in blood vessel growth. However, evidence has emerged that VEGF-A also promotes a wide range of neuronal functions, both in vitro and in vivo, including neurogenesis, neuronal migration, neuronal survival and axon guidance. Recent studies have employed mouse models to distinguish the direct effects of VEGF on neurons from its indirect, vessel-mediated effects. Ultimately, refining our knowledge of VEGF signalling pathways in neurons should help us to understand how the current use of therapeutics targeting the VEGF pathway in cancer and eye disease might be expanded to promote neuronal health and nerve repair. 相似文献
94.
Christiana Iwuagwu Dalton King Ivar M. McDonald James Cook F. Christopher Zusi Matthew D. Hill Robert A. Mate Haiquan Fang Ronald Knox Lizbeth Gallagher Debra Post-Munson Amy Easton Regina Miller Yulia Benitex Judy Siuciak Nicholas Lodge Robert Zaczek Daniel Morgan Linda Bristow Richard E. Olson 《Bioorganic & medicinal chemistry letters》2017,27(5):1261-1266
Quinuclidine-containing spirooxazolines, as described in the previous report in this series, were demonstrated to have utility as α7 nicotinic acetylcholine receptor (α7 nAChR) partial agonists. In this work, the SAR of this chemotype was expanded to include an array of diazine heterocyclic substitutions. Many of the heterocyclic analogs were potent partial agonists of the α7 receptor, selective against other nicotinic receptors and the serotinergic 5HT3A receptor. (1′S,3′R,4′S)-N-(6-phenylpyrimidin-4-yl)-4H-1′-azaspiro[oxazole-5,3′-bicyclo[2.2.2]octan]-2-amine, a potent and selective α7 nAChR partial agonist, was demonstrated to improve cognition in the mouse novel object recognition (NOR) model of episodic memory. 相似文献
95.
Disparity between levels of in vitro neutralization of vaccinia virus by antibody to the A27 protein and protection of mice against intranasal challenge 下载免费PDF全文
Fogg CN Americo JL Earl PL Resch W Aldaz-Carroll L Eisenberg RJ Cohen GH Moss B 《Journal of virology》2008,82(16):8022-8029
Immunization with recombinant proteins may provide a safer alternative to live vaccinia virus for prophylaxis of poxvirus infections. Although antibody protects against vaccinia virus infection, the mechanism is not understood and the selection of immunogens is daunting as there are dozens of surface proteins and two infectious forms known as the mature virion (MV) and the enveloped virion (EV). Our previous studies showed that mice immunized with soluble forms of EV membrane proteins A33 and B5 and MV membrane protein L1 or passively immunized with antibodies to these proteins survived an intranasal challenge with vaccinia virus. The present study compared MV protein A27, which has a role in virus attachment to glycosaminoglycans on the cell surface, to L1 with respect to immunogenicity and protection. Although mice developed similar levels of neutralizing antibody after immunizations with A27 or L1, A27-immunized mice exhibited more severe disease upon an intranasal challenge with vaccinia virus. In addition, mice immunized with A27 and A33 were not as well protected as mice receiving L1 and A33. Polyclonal rabbit anti-A27 and anti-L1 IgG had equivalent MV-neutralizing activities when measured by the prevention of infection of human or mouse cells or cells deficient in glycosaminoglycans or by adding antibody prior to or after virus adsorption. Nevertheless, the passive administration of antibody to A27 was poorly protective compared to the antibody to L1. These studies raise questions regarding the basis for antibody protection against poxvirus disease and highlight the importance of animal models for the early evaluation of vaccine candidates. 相似文献
96.
Stute C Schimmelpfeng K Renkawitz-Pohl R Palmer RH Holz A 《Development (Cambridge, England)》2004,131(4):743-754
The visceral muscles of the Drosophila midgut consist of syncytia and arise by fusion of founder and fusion-competent myoblasts, as described for the somatic muscles. A single-step fusion results in the formation of binucleate circular midgut muscles, whereas a multiple-step fusion process produces the longitudinal muscles. A prerequisite for muscle fusion is the establishment of myoblast diversity in the mesoderm prior to the fusion process itself. We provide evidence for a role of Notch signalling during establishment of the different cell types in the visceral mesoderm, demonstrating that the basic mechanism underlying the segregation of somatic muscle founder cells is also conserved during visceral founder cell determination. Searching for genes involved in the determination and differentiation of the different visceral cell types, we identified two independent mutations causing loss of visceral midgut muscles. In both of these mutants visceral muscle founder cells are missing and the visceral mesoderm consists of fusion-competent myoblasts only. Thus, no fusion occurs resulting in a complete disruption of visceral myogenesis. Subsequent characterisation of the mutations revealed that they are novel alleles of jelly belly (jeb) and the Drosophila Alk homologue named milliways (mili(Alk)). We show that the process of founder cell determination in the visceral mesoderm depends on Jeb signalling via the Milliways/Alk receptor. Moreover, we demonstrate that in the somatic mesoderm determination of the opposite cell type, the fusion-competent myoblasts, also depends on Jeb and Alk, revealing different roles for Jeb signalling in specifying myoblast diversity. This novel mechanism uncovers a crosstalk between somatic and visceral mesoderm leading not only to the determination of different cell types but also maintains the separation of mesodermal tissues, the somatic and splanchnic mesoderm. 相似文献
97.
Neuronal defects in the hindbrain of Hoxa1, Hoxb1 and Hoxb2 mutants reflect regulatory interactions among these Hox genes 总被引:4,自引:0,他引:4
Gavalas A Ruhrberg C Livet J Henderson CE Krumlauf R 《Development (Cambridge, England)》2003,130(23):5663-5679
Hox genes are instrumental in assigning segmental identity in the developing hindbrain. Auto-, cross- and para-regulatory interactions help establish and maintain their expression. To understand to what extent such regulatory interactions shape neuronal patterning in the hindbrain, we analysed neurogenesis, neuronal differentiation and motoneuron migration in Hoxa1, Hoxb1 and Hoxb2 mutant mice. This comparison revealed that neurogenesis and differentiation of specific neuronal subpopulations in r4 was impaired in a similar fashion in all three mutants, but with different degrees of severity. In the Hoxb1 mutants, neurons derived from the presumptive r4 territory were re-specified towards an r2-like identity. Motoneurons derived from that territory resembled trigeminal motoneurons in both their migration patterns and the expression of molecular markers. Both migrating motoneurons and the resident territory underwent changes consistent with a switch from an r4 to r2 identity. Abnormally migrating motoneurons initially formed ectopic nuclei that were subsequently cleared. Their survival could be prolonged through the introduction of a block in the apoptotic pathway. The Hoxa1 mutant phenotype is consistent with a partial misspecification of the presumptive r4 territory that results from partial Hoxb1 activation. The Hoxb2 mutant phenotype is a hypomorph of the Hoxb1 mutant phenotype, consistent with the overlapping roles of these genes in facial motoneuron specification. Therefore, we have delineated the functional requirements in hindbrain neuronal patterning that follow the establishment of the genetic regulatory hierarchy between Hoxa1, Hoxb1 and Hoxb2. 相似文献
98.
Dimitropoulou C Han G Miller AW Molero M Fuchs LC White RE Carrier GO 《American journal of physiology. Heart and circulatory physiology》2002,282(3):H908-H917
Insulin resistance (IR) syndrome is associated with impaired vascular relaxation; however, the underlying pathophysiology is unknown. Potassium channel activation causes vascular smooth muscle hyperpolarization and relaxation. The present study determined whether a reduction in large conductance calcium- and voltage-activated potassium (BK(Ca)) channel activity contributes to impaired vascular relaxation in IR rats. BK(Ca) channels were characterized in mesenteric microvessels from IR and control rats. Macroscopic current density was reduced in myocytes from IR animals compared with controls. In addition, inhibition of BK(Ca) channels with tetraethylammonium (1 mM) or iberiotoxin (100 nM) was greater in myocytes from control (70%) compared with IR animals (approximately 20%). Furthermore, activation of BK(Ca) channels with NS-1619 was three times more effective at increasing outward current in cells from control versus IR animals. Single channel and Western blot analysis of BK(Ca) channels revealed similar conductance, amplitude, voltage sensitivity, Ca2+ sensitivity, and expression density between the two groups. These data provide the first direct evidence that microvascular potassium currents are reduced in IR and suggest a molecular mechanism that could account for impaired vascular relaxation in IR. 相似文献
99.
Christiana A. Dietzen Klaus Steenberg Larsen Per L. Ambus Anders Michelsen Marie Frost Arndal Claus Beier Sabine Reinsch Inger Kappel Schmidt 《Global Change Biology》2019,25(9):2970-2977
Elevated atmospheric CO2 concentration and climate change may substantially alter soil carbon (C) dynamics, which in turn may impact future climate through feedback cycles. However, only very few field experiments worldwide have combined elevated CO2 (eCO2) with both warming and changes in precipitation in order to study the potential combined effects of changes in these fundamental drivers of C cycling in ecosystems. We exposed a temperate heath/grassland to eCO2, warming, and drought, in all combinations for 8 years. At the end of the study, soil C stocks were on average 0.927 kg C/m2 higher across all treatment combinations with eCO2 compared to ambient CO2 treatments (equal to an increase of 0.120 ± 0.043 kg C m?2 year?1), and showed no sign of slowed accumulation over time. However, if observed pretreatment differences in soil C are taken into account, the annual rate of increase caused by eCO2 may be as high as 0.177 ± 0.070 kg C m?2 year?1. Furthermore, the response to eCO2 was not affected by simultaneous exposure to warming and drought. The robust increase in soil C under eCO2 observed here, even when combined with other climate change factors, suggests that there is continued and strong potential for enhanced soil carbon sequestration in some ecosystems to mitigate increasing atmospheric CO2 concentrations under future climate conditions. The feedback between land C and climate remains one of the largest sources of uncertainty in future climate projections, yet experimental data under simulated future climate, and especially including combined changes, are still scarce. Globally coordinated and distributed experiments with long‐term measurements of changes in soil C in response to the three major climate change‐related global changes, eCO2, warming, and changes in precipitation patterns, are, therefore, urgently needed. 相似文献
100.
Maria G. Kakkoura Christiana A. Demetriou Maria A. Loizidou Giorgos Loucaides Ioanna Neophytou Yiola Marcou Andreas Hadjisavvas Kyriacos Kyriacou 《Genes & nutrition》2015,10(2)
Single-nucleotide polymorphisms (SNPs) within genes of the one-carbon metabolism pathway have been shown to interact with dietary folate intake to modify breast cancer (BC) risk. Our group has previously demonstrated that the Mediterranean dietary pattern, rich in beneficial one-carbon metabolism micronutrients, protects against BC in Greek-Cypriot women. We aimed to investigate whether SNPs in the MTHFR (rs1801133 and rs1801131) and MTR (rs1805087) genes modify the effect of the Mediterranean dietary pattern on BC risk. Dietary intake data were obtained using a 32-item food-frequency questionnaire. A dietary pattern specific to the Greek-Cypriot population, which closely resembles the Mediterranean diet, was derived using principal component analysis (PCA) and used as our dietary variable. Genotyping was performed on subjects from the MASTOS study, a case–control study of BC in Cyprus, using TaqMan assays. Adjusted odds ratios (ORs) were estimated using logistic regression analyses. High adherence to the PCA-derived Mediterranean dietary pattern further reduced BC risk with increasing number of variant MTHFR 677T alleles (ORQ4vs.Q1 for 677TT = 0.37, 95 % CI 0.20–0.69, for 677 CT = 0.60, 95 % CI 0.42–0.86). Additionally, high adherence to the Mediterranean dietary pattern decreased BC risk in subjects with at least one MTR 2756A allele (ORQ4vs.Q1 for 2756AA = 0.59, 95 % CI 0.43–0.81, for 2756AG = 0.59, 95 % CI 0.39–0.91) and in subjects with the MTHFR 1298CC genotype (ORQ4vs.Q1 0.44, 95 % CI 0.30–0.65). Overall P-interaction values, however, were not statistically significant. Our study suggests that these MTHFR and MTR SNPs may act as effect modifiers, highlighting their biological significance in the association between Mediterranean diet, the one-carbon metabolism pathway and BC.