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21.
Nichola A. Strandberg Mary Edwards Joanna C. Ellison Manuel J. Steinbauer Anna Walentowitz Patricia L. Fall David Sear Peter Langdon Shane Cronin Alvaro Castilla-Beltrán Ian W. Croudace Matiu Prebble William D. Gosling Sandra Nogué 《Biotropica》2023,55(4):816-827
Here, we investigate Mid- to Late-Holocene vegetation changes in low-lying coastal areas in Tonga and how changing sea levels and recurrent volcanic eruptions have influenced vegetation dynamics on four islands of the Tongan archipelago (South Pacific). To investigate past vegetation and environmental change at Ngofe Marsh (‘Uta Vava’u), we examined palynomorphs (pollen and spores), charcoal (fire), and sediment characteristics (volcanic activity) from a 6.7-m-long sediment core. Radiocarbon dating indicated the sediments were deposited over the last 7700 years. We integrated the Ngofe Marsh data with similar previously published data from Avai’o’vuna Swamp on Pangaimotu Island, Lotofoa Swamp on Foa Island, and Finemui Swamp on Ha’afeva Island. Plant taxa were categorized as littoral, mangrove, rainforest, successional/ disturbance, and wetland groups, and linear models were used to examine relationships between vegetation, relative sea level change, and volcanic eruptions (tephra). We found that relative sea level change has impacted vegetation on three of the four islands investigated. Volcanic eruptions were not identified as a driver of vegetation change. Rainforest decline does not appear to be driven by sea level changes or volcanic eruptions. From all sites analyzed, vegetation at Finemui Swamp was most sensitive to changes in relative sea level. While vegetation on low-lying Pacific islands is sensitive to changing sea levels, island characteristics, such as area and elevation, are also likely to be important factors that mediate specific island responses to drivers of change. 相似文献
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Beata Bartodziejska Joanna Radziejewska-Lebrecht Maria Lipinska Yuriy A. Knirel Leonid O. Kononov Anatoly Y. Chernyak Hubert Mayer Antoni Rozalski 《FEMS immunology and medical microbiology》1996,13(2):113-121
Abstract In DOC-PAGE, lipopolysaccharide (LPS) of Proteus mirabilis R14/1959 (Rb-type) mutant showed a ladder-like migration pattern indicating the presence of a high molecular weight polysaccharide chain. The isolated polysaccharide, called T-antigen because of similarity with the T1 chain of Salmonella friedenau LPS, contained d -glucose, d -galacturonic acid ( d -GalA), and d -GlcNAc in molar ratios 2:1:1 and was structurally different from the O-antigen of the parental S-strain P. mirabilis S1959 but identical to the O-antigen of another S-strain Proteus penneri 42. The importance of a d -GalA( l -Lys)-containing epitope, most likely present in the core region of LPS, and of GalA present in the T-antigen chain in manifesting the serological specificity of P. mirabilis R14/1959 were revealed using rabbit polyclonal homologous and heterologous R- and O-specific antisera and the appropriate antigens, including synthetic antigens which represent partial structures of various Proteus LPS. 相似文献
25.
Comparative mapping in Arabidopsis and Brassica, fine scale genome collinearity and congruence of genes controlling flowering time 总被引:6,自引:0,他引:6
Ulf Lagercrantz Joanna Putterill George Coupland Derek Lydiate 《The Plant journal : for cell and molecular biology》1996,9(1):13-20
The model dicotyledonous plant, Arabidopsis thaliana , is closely related to Brassica crop species. It is intended that information concerning the genetic control of basic biological processes in Arabidopsis will be transferable to other species. Genome collinearity and its potential to facilitate the identification of candidate genes in Arabidopsis homologous to genes controlling important agronomic traits in Brassica was investigated. Genetic mapping in B. nigra identified two loci influencing flowering time (FT), with loci on linkage groups 2 and 8 explaining 53% and 12% of the total variation in FT, respectively. The CO gene exerts an important control over FT in A. thaliana , and B. nigra homologues of CO probably also play an important role in regulating FT. B. nigra homologues of CO were identified on linkage groups 2 and 8, the homologue on group 2 was coincident with the major locus controlling FT while the homologue on group 8 was within the 90% confidence interval of the weaker FT gene. The CO homologue on group 2 exhibits abundant allelic variation suggesting that it naturally controls a wide range of flowering times. Fine-scale A. thaliana/B. nigra comparative mapping demonstrated short-range collinearity between the genomes of Arabidopsis and Brassica . Eleven DNA fragments spaced over a 1.5 Mb contig in A. thaliana were used as RFLP probes in B. nigra . Three collinear representations of the A. thaliana contig were identified in B. nigra , with one interrupted by a large chromosomal inversion. Collinearity over this range will allow the resources generated by the Arabidopsis genome project to facilitate map-based cloning in Brassica crops. 相似文献
26.
A unique transgenic mouse line has undergone transgene integration in a very precise fashion. The phenotype displayed by mice of the line followed the predicted inheritance patterns for X-linked transgene insertion which has been confirmed. In order to investigate the mechanism of integration the DNA sequence of the transgene and cellular junctions have been determined. A comparison between wild type and transgenic mutant sequences at the site of insertion revealed that there was no loss or rearrangement of cellular DNA upon integration of the transgene. The cellular sequences at the transgene 5 and 3 joins are contiguous in the wild type. The integrant exists as a head to tail tandem dimer with minimal loss of sequence compared with the injected monomer. Analysis of the site of insertion has revealed a 5 bp homology between the 5 end of the transgene and the cellular sequences. In addition, adjacent to the site of insertion within the cellular sequences, there are several sequence motifs implicated in recombination events including a clustering of strong consensus sites for DNA topoisomerase type I and a region of homology to the human minisatellite consensus core sequence, theEscherichia coli Chi site and the meiotic recombination hotspot within the E gene of the murine major histocompatibility complex. This clustering of features is likely to have been factorial in the integrity of the insertion event. A model depicting the mechanism of this precise integration is proposed. 相似文献
27.
Chang WC Shyu WJ Shi GY Lin MT Jen CJ Wing LY Tang MJ Wu HL 《Journal of biomedical science》1996,3(1):59-66
Treatment of cultured bovine carotid artery endothelial cells with 0.1 µM human plasmin has been reported to induce a receptor-mediated short burst of arachidonate release, which is a pertussis toxin-sensitive and extracellular calcium-dependent reaction. Plasmin-induced calcium influx in cells was significantly inhibited by pretreatment with pertussis toxin, indicating that the former was coupled with a pertussis toxin-sensitive guanosine 5-triphosphate (GTP)-binding protein. Plasmin significantly induced the formation of lysophosphatidylcholine but not lysophosphatidylethanolamine. A cellular phospholipase A2 with an arachidonyl specificity at the sn-2 position of phosphatidylcholine, which required submicromolar calcium, was identified as a cytosolic phospholipase A2 by immunoblot analysis. By a cell-free enzyme activity assay and immunoblot analysis, plasmin was found to induce a translocation of the cytosolic phospholipase A2 from the cytosol to the membrane. Taken together, the results suggest that plasmin bound to its putative receptor and activated a GTP-binding protein coupled to calcium influx channel, followed by translocation and activation of cytosolic phospholipase A2 in endothelial cells. 相似文献
28.
Human Microtubule-Associated Protein-2c Localizes to Dendrites and Axons in Fetal Spinal Motor Neurons 总被引:2,自引:0,他引:2
Joanna S. Albala Yvonne Kress Wan-Kyng Liu Karen Weidenheim Shu-Hui C. Yen Bridget Shafit-Zagardo 《Journal of neurochemistry》1995,64(6):2480-2490
Abstract: Microtubule-associated protein-2 (MAP-2) functions to maintain neuronal morphology by promoting the assembly of microtubules. MAP-2c is an alternately spliced form of MAP-2, containing the first 151 amino acids of high-molecular-weight (HMW) MAP-2 joined to the last 321 amino acids, eliminating 1,352 amino acids specific to HMW MAP-2. A polyclonal antibody generated to the splice site of human MAP-2c was used to determine its cellular localization. The MAP-2c antiserum was depleted of any HMW MAP-2 reactivity by absorption with HMW MAP-2 fusion protein. Western blot analysis of human fetal spinal cord homogenates demonstrated that the antibody is specific for human MAP-2c. MAP-2c immunoreactivity was found in the perinuclear cytoplasm and processes of anterior motor neurons and large processes of the posterior column in sections from 22–24-week human fetal spinal cord. Double-label confocal microscopy was performed using the MAP-2c polyclonal antibody and either a HMW MAP-2 or a neurofilament protein (highly phosphorylated 160- and 200-kDa protein) monoclonal antibody to identify these processes as dendrites or axons, respectively. HMW MAP-2 and MAP-2c colocalized in cell bodies and dendrites of anterior motor neurons, demonstrating for the first time the presence of native MAP-2c within dendrites. In addition, immunoelectron microscopy showed MAP-2c associated with microtubules in dendrites of motor neurons. MAP-2c and the neurofilament proteins were found in axons of the dorsal and ventral roots. The presence of MAP-2c within axons and dendrites suggests that MAP-2c contributes to neuronal plasticity during human fetal development. 相似文献
29.
Expression of Biologically Active Basic Fibroblast Growth Factor by Genetically Modified Rat Primary Skin Fibroblasts 总被引:1,自引:0,他引:1
Jasodhara Ray Joanna Hogg reas S. Beutler Hideichi Takayama Andrew Baird Fred H. Gage 《Journal of neurochemistry》1995,64(2):503-513
Abstract: Basic fibroblast growth factor (FGF-2) is normally expressed as a cell-associated protein, and accordingly it is not clear how it exerts its action on target cells in vivo. It has been proposed that cells release, by death or other mechanisms, small amounts of FGF-2 that then acts in an autocrine manner. To address the question of whether it is necessary that FGF-2 remain cell associated or needs to be secreted from cells to have biological activity, we expressed the 18-kDa form of FGF-2 in primary fibroblasts as a cell-associated (FGF-2-B) or as a secreted (FGF-2-S) protein. FGF-2 protein is detected in cell lysates and membrane fractions of both cell types, whereas it is present in significant amounts only in the conditioned medium of FGF-2-S cells. No FGF-2 is detected in control (untransfected) cells. FGF-2-S cells also grow faster than the control or FGF-2-B cells. Yet, when evaluated for their ability to promote the survival of embryonic hippocampal neurons in vitro, both the cell types are active, establishing the activity of the transgene product. We conclude that FGF-2 is active when engineered to be expressed as a cell-associated form or secreted from cells. 相似文献
30.