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21.
The African Black Oystercatcher Haematopus moquini is a charismatic, southern African near-endemic, wader species, that is often seen as a flagship species for coastal bird conservation, as it was recently down-listed regionally to Least Concern on the IUCN Red List of Threatened Species. To celebrate this rare conservation success story, BirdLife South Africa named it the 2018 Bird of the Year and ran a year-long programme in collaboration with the Nature’s Valley Trust highlighting aspects of the species’ biology, current threats, and conservation success. We used data collected by the Southern African Bird Atlas Project (SABAP1 and SABAP2) to examine changes in the species’ range and relative abundance, both in the records between the two projects, as well as trends within the SABAP2 sampling period (2008–2017). This case study enabled us to assess whether such metrics can accurately reflect abundance and distributional changes in a species. We found increases in the reported range and the reporting rates between the two Atlas projects, and that the SABAP2 reporting rate was stable. Regionally, across four coastal categories, the reporting rate was lowest in KwaZulu-Natal, though this region also showed an increase in the probability of reporting during the SABAP2 period. While corroborating the recent change in the species’ conservation status, we also provide good evidence that the long-term SABAP data can be used successfully to assess population trends and range changes over time. 相似文献
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Long-range interphase chromosome organization in Drosophila: a study using color barcoded fluorescence in situ hybridization and structural clustering analysis 下载免费PDF全文
We have developed a color barcode labeling strategy for use with fluorescence in situ hybridization that enables the discrimination of multiple, identically labeled loci. Barcode labeling of chromosomes provides long-range path information and allows structural analysis at a scale and resolution beyond what was previously possible. Here, we demonstrate the use of a three-color, 13-probe barcode for the structural analysis of Drosophila chromosome 2L in blastoderm stage embryos. We observe the chromosome to be strongly polarized in the Rabl orientation and for some loci to assume defined positions relative to the nuclear envelope. Our analysis indicates packing approximately 15- to 28-fold above the 30-nm fiber, which varies along the chromosome in a pattern conserved across embryos. Using a clustering implementation based on rigid body alignment, our analysis suggests that structures within each embryo represent a single population and are effectively modeled as oriented random coils confined within nuclear boundaries. We also found an increased similarity between homologous chromosomes that have begun to pair. Chromosomes in embryos at equivalent developmental stages were found to share structural features and nuclear localization, although size-related differences that correlate with the cell cycle also were observed. The methodology and tools we describe provide a direct means for identifying developmental and cell type-specific features of higher order chromosome and nuclear organization. 相似文献
25.
Neuropilin-2 regulates the development of selective cranial and sensory nerves and hippocampal mossy fiber projections 总被引:12,自引:0,他引:12
Chen H Bagri A Zupicich JA Zou Y Stoeckli E Pleasure SJ Lowenstein DH Skarnes WC Chédotal A Tessier-Lavigne M 《Neuron》2000,25(1):43-56
Neuropilin-1 and neuropilin-2 bind differentially to different class 3 semaphorins and are thought to provide the ligand-binding moieties in receptor complexes mediating repulsive responses to these semaphorins. Here, we have studied the function of neuropilin-2 through analysis of a neuropilin-2 mutant mouse, which is viable and fertile. Repulsive responses of sympathetic and hippocampal neurons to Sema3F but not to Sema3A are abolished in the mutant. Marked defects are observed in the development of several cranial nerves, in the initial central projections of spinal sensory axons, and in the anterior commissure, habenulo-interpeduncular tract, and the projections of hippocampal mossyfiber axons in the infrapyramidal bundle. Our results show that neuropilin-2 is an essential component of the Sema3F receptor and identify key roles for neuropilin-2 in axon guidance in the PNS and CNS. 相似文献
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López-Ongil S Senchak V Saura M Zaragoza C Ames M Ballermann B Rodríguez-Puyol M Rodríguez-Puyol D Lowenstein CJ 《The Journal of biological chemistry》2000,275(34):26423-26427
Reactive oxygen species (ROS) act as signaling molecules in the cardiovascular system, regulating cellular proliferation and migration. However, an excess of ROS can damage cells and alter endothelial cell function. We hypothesized that endogenous mechanisms protect the vasculature from excess levels of ROS. We now show that superoxide can inhibit endothelin-converting enzyme activity (ECE) and decrease endothelin-1 synthesis. Superoxide inhibits ECE but hydrogen peroxide and nitric oxide do not. Superoxide inhibits ECE by ejecting zinc from the enzyme, and the addition of exogenous zinc restores enzymatic activity. Superoxide may inhibit other zinc metalloproteinases by a similar mechanism and may thus play an important role in regulating the biology of blood vessels. 相似文献
27.
German Z Chambliss KL Pace MC Arnet UA Lowenstein CJ Shaul PW 《The Journal of biological chemistry》2000,275(11):8183-8189
Nitric oxide (NO) plays an important role in airway function, and endothelial NO synthase (eNOS) is expressed in airway epithelium. To determine the basis of cell-specific eNOS expression in airway epithelium, studies were performed in NCI-H441 human bronchiolar epithelial cells transfected with the human eNOS promoter fused to luciferase. Transfection with 1624 base pairs of sequence 5' to the initiation ATG (position -1624) yielded a 19-fold increase in promoter activity versus vector alone. No activity was found in lung fibroblasts, which do not express eNOS. 5' deletions from -1624 to -279 had modest effects on promoter activity in H441 cells. Further deletion to -248 reduced activity by 65%, and activity was lost with deletion to -79. Point mutations revealed that the GATA binding motif at -254 is mandatory for promoter activity and that the positive regulatory element between -248 and -79 is the Sp1 binding motif at -125. Electrophoretic mobility shift assays yielded two complexes with the GATA site and three with the Sp1 site. Immunodepletion with antiserum to GATA-2 prevented formation of the slowest migrating GATA complex, and antiserum to Sp1 supershifted the slowest migrating Sp1 complex. An electrophoretic mobility shift assay with H441 versus fibroblast nuclei revealed that the slowest migrating GATA complex is unique to airway epithelium. Thus, cell-specific eNOS expression in airway epithelium is dependent on the interaction of GATA-2 with the core eNOS promoter, and the proximal Sp1 binding site is also an important positive regulatory element. 相似文献
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Out of Africa and back again: nested cladistic analysis of human Y chromosome variation 总被引:18,自引:3,他引:15
Hammer MF; Karafet T; Rasanayagam A; Wood ET; Altheide TK; Jenkins T; Griffiths RC; Templeton AR; Zegura SL 《Molecular biology and evolution》1998,15(4):427-441
We surveyed nine diallelic polymorphic sites on the Y chromosomes of 1,544
individuals from Africa, Asia, Europe, Oceania, and the New World.
Phylogenetic analyses of these nine sites resulted in a tree for 10
distinct Y haplotypes with a coalescence time of approximately 150,000
years. The 10 haplotypes were unevenly distributed among human populations:
5 were restricted to a particular continent, 2 were shared between Africa
and Europe, 1 was present only in the Old World, and 2 were found in all
geographic regions surveyed. The ancestral haplotype was limited to African
populations. Random permutation procedures revealed statistically
significant patterns of geographical structuring of this paternal genetic
variation. The results of a nested cladistic analysis indicated that these
geographical associations arose through a combination of processes,
including restricted, recurrent gene flow (isolation by distance) and range
expansions. We inferred that one of the oldest events in the nested
cladistic analysis was a range expansion out of Africa which resulted in
the complete replacement of Y chromosomes throughout the Old World, a
finding consistent with many versions of the Out of Africa Replacement
Model. A second and more recent range expansion brought Asian Y chromosomes
back to Africa without replacing the indigenous African male gene pool.
Thus, the previously observed high levels of Y chromosomal genetic
diversity in Africa may be due in part to bidirectional population
movements. Finally, a comparison of our results with those from nested
cladistic analyses of human mtDNA and beta-globin data revealed different
patterns of inferences for males and females concerning the relative roles
of population history (range expansions) and population structure
(recurrent gene flow), thereby adding a new sex-specific component to
models of human evolution.
相似文献
30.
Nassima Chikhi-Chorfi Chuong Pham-Huy Hervé Galons Nathalie Manuel William Lowenstein Jean-Michel Warnet Jean-Roger Claude 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1998,718(2):98
A rapid gas–liquid chromatographic assay is developed for the quantification of methadone (Mtd) and its major metabolite, 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP), in biological fluids of opiate addicts. After alkaline extraction from samples with lidocaine hydrochloride as internal standard, Mtd and EDDP are separated on SP-2250 column at 220°C and detected with a thermionic detector. The chromatographic time is about 6 min. The relative standard deviations (R.S.D.) of Mtd and EDDP standards are between 1.5 and 5.5%. Most drugs of abuse (morphine, codeine, narcotine, cocaine, benzoylecgonine, cocaethylene, dextropropoxyphene etc) are shown not to interfere with this technique. The method has been applied to study the levels of Mtd and EDDP metabolite in serum, saliva and urine of patients under maintenance treatment for opiate dependence. EDDP levels were found higher than those of Mtd in urine samples from four treated patients, but lower in serum and undetectable in saliva. However, Mtd concentrations were higher in saliva than in serum. 相似文献