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1.
Claudia Raedig Carsten F. Dormann Anke Hildebrandt Sven Lautenbach 《Biodiversity and Conservation》2010,19(6):1523-1546
Monographic data rely on specimens deposited in herbaria and museums, which have been thoroughly revised by experts. However,
monographic data have been rarely used to map species richness at large scale, mainly because of the difficulties caused by
spatially heterogeneous sampling effort. In this paper we estimate patterns of species richness and narrow endemism, based
on monographic data of 4,055 Neotropical angiosperm species. We propose a geometric interpolation method to derive species
ranges at a 1° grid resolution. To this we apply an inverse distance-weighted summation scheme to derive maps of species richness
and endemism. In the latter we also adjust for heterogeneous sampling effort. Finally, we test the robustness of the interpolated
species ranges and derived species richness by applying the same method but using a leave-one-out-cross-validation (LOOCV).
The derived map shows four distinct regions of elevated species richness: (1) Central America, (2) the Northern Andes, (3)
Amazonia and (4) the Brazilian Atlantic coast (‘Mata Atlantica’). The region with the highest estimated species richness is
Amazonia, with Central America following closely behind. Centers of narrow endemism are located over the entire Neotropics,
several of them coinciding with regions of elevated species richness. Sampling effort has a minor influence on the interpolation
of overall species richness, but it substantially influences the estimation of regions of narrow endemism. Thus, in order
to improve maps of narrow endemism and resulting conservation efforts, more collection and identification activity is required. 相似文献
2.
Genetic complementation analysis of ataxia telangiectasia and Nijmegen breakage syndrome: a survey of 50 patients 总被引:21,自引:0,他引:21
N G Jaspers R A Gatti C Baan P C Linssen D Bootsma 《Cytogenetics and cell genetics》1988,49(4):259-263
Cultured cells from patients with ataxia telangiectasia (AT) or Nijmegen breakage syndrome (NBS) are hypersensitive to ionizing radiation. After radiation exposure, the rate of DNA replication is inhibited to a lesser extent than in normal cells, whereas the frequency of chromosomal aberrations is enhanced. Both of these features have been used in genetic complementation studies on a limited series of patients. Here we report the results of extended complementation studies on fibroblast strains from 50 patients from widely different origins, using the radioresistant DNA replication characteristic as a marker. Six different genetic complementation groups were identified. Four of these, called AB, C, D, and E (of which AB is the largest), represent patients with clinical signs of AT. Patients having NBS fall into two groups, V1 and V2. An individual with clinical symptoms of both AT and NBS was found in group V2, indicating that the two disorders are closely related. In AT, any group-specific patterns with respect to clinical characteristics or ethnic origin were not apparent. In addition to the radiosensitive ATs, a separate category of patients exists, characterized by a relatively mild clinical course and weak radiosensitivity. It is concluded that a defect in one of at least six different genes may underlie inherited radiosensitivity in humans. To facilitate research on defined defects, a complete list of genetically characterized fibroblast strains is presented. 相似文献
3.
Ralph Schröder Anke Maassen Andrea Lippoldt Thomas Börner Rüdiger von Baehr Peter Dobrowolski 《Applied microbiology and biotechnology》1991,35(5):631-637
Summary Using the broad-host-range promoter probe vector pRS201 for cloning of phage Acm1 promoters, we established a convenient vector system for expression of heterologous genes in different Gram-negative bacteria. The usefulness of this system was demonstrated by expression of the HBV core gene in Acetobacter methanolicus. Plasmids carrying the HBV core gene downstream of different Acm1-phage promoters were transferred to A. methanolicus, a new potential host for recombinant DNA expression. Using enzyme immunoassay and immunoblot techniques, the amount and composition of core antigen produced in A. methanolicus were compared with that derived from Escherichia coli. The expression of immunoreactive core antigen in A. methanolicus exceeds by sevenfold that in E. coli using an expression system with tandemly arranged promoters. Morphological observations by electron microscopy show that the HBV core gene products isolated from both hosts are assembled into regular spherical particles with a diameter of about 28 nm that are comparable to original viral nucleocapsids.
Offprint requests to: R. Schröder 相似文献
4.
Transfer and Expression of Lithoautotrophy and Denitrification in a Host Lacking These Metabolic Activities 总被引:3,自引:1,他引:2 下载免费PDF全文
The conjugative 450-kilobase-pair megaplasmid pHG1 from Alcaligenes eutrophus H16 was transferred to the herbicide-degrading soil bacterium A. eutrophus JMP134. This transfer was achieved by means of RP4 mobilization and a Tn5-Mob insertion provided in trans on the megaplasmid replicon. Although kanamycin-resistant transconjugants also occurred with other gram-negative species such as Rhizobium, Agrobacterium, and thiobacteria, A. eutrophus JMP134 was the only recipient which stably maintained the megaplasmid. pHG1-containing transconjugants derived from JMP134 expressed all metabolic functions associated with the plasmid: the ability to oxidize hydrogen through catalysis of two hydrogenases, to assimilate carbon dioxide via the Calvin cycle pathway, and to grow with nitrate anaerobically. All of these metabolic activities were absent in the original strain JMP134. 相似文献
5.
Development of flower buds in thin-layer cultures of floral stalk tissue from tobacco: Role of hormones in different stages 总被引:4,自引:0,他引:4
The in vitro development of flower buds was studied on tissue explants of epidermis and subepidermal cortex from the flower stalks of Nicotiana tabacum L. cv. Samsun. The number of flower buds formed depended mainly on cytokinin concentration. Auxin acted as a modifier in a complex way. In early development, NAA at 1 μ M decreased the number of buds initiated and delayed bud emergence. At a later stage, auxin promoted bud outgrowth at the same concentration. Optimal results were obtained when explants were first incubated at low auxin concentration for 3–5 days and subsequently transferred to an elevated auxin level. Physiological processes that lead to flower bud initiation start very soon after the onset of incubation. This was inferred from experiments whereby explants were first cultured at an inductive cytokinin concentration and then transferred to a non-inductive hormone level. 相似文献
6.
European Journal of Wildlife Research - Bei 30 Birkhühnern wurde nach kontrolliert durchgeführter Trinkwasservaccination gegen Newcastle Disease (ND) (Erstimpfung mit Hitchner B1,... 相似文献
7.
We studied recruitment behavior of the slavemaking ant Polyergus breviceps,which typically raids colonies of Formica gnava.The first test series demonstrated the importance of social context, by showing that recruitment was high during raiding, but virtually absent during preraid circling and during the return trip after a slave raid. The second test series showed that Formicapupae (alone or together with adults) must be present for workers of Polyegrusto recruit nestmates. The third test series demonstrated that panic alarm by raided Formicais caused by a pheromone, and we suggest that adults of Formicamay be the source of this secretion. Finally, the fourth test series showed that formic acid is lethal to adults of Formicabut has almost no adverse effect on Polyergus.This relative immunity by Polyergusmay enable them to remain organized while entering nests of Formicaduring slave raids. 相似文献
8.
Obst O. O. Linssen M. C. J. G. Vusse G. J. v. d. Kammermeier H. 《Molecular and cellular biochemistry》1996,163(1):173-180
Marked concentration differences of noradrenaline (NA) between the vascular and the interstitial compartment were detected by sampling interstitial transudate from isolated perfused rat hearts. The ratios of vascular/interstitial concentration amounted to 7.4 to 1.3 depending on the concentration of NA administered (3 × 10–9 to 10–6 M). These concentration differences were abolished by inhibitors of uptake1 desipramine (DMI) I and uptake, (O-methyl-isoprenaline (OMI)). Neuronal uptake, was characterized by a Km of 0.22 mol/l and a Vmax of 370 pmol × min–1 × gWWT–1, extraneuronal uptake2 by a KUPTAKE of = 0.313 min–4.The apparent permeability surface area (P×S)-product calculated from uptake rate and transcapillary concentration difference was significantly decreased by administrating 100 mol/l (NA) in presence of DMI. A presumed endothelial uptake mechanism contributing to catecholamine translocation was investigated in endothelial cells in culture. These cells showed a specific noradrenaline uptake with a Km of 4.35 mol/l and a Vmax of about 75 pmol × min–1 x gWWT–1. Any inhibiton by inhibitors of both of the two noradrenaline uptakes was lacking. The uptake rate of this mechanism is insufficient to contribute to the diffusive conductivity of the capillary wall (P × S-product). We conclude from our investigations on interstitial concentrations of catecholamines and transcapillary concentration differences, that the capillary wall, owing to its metabolic and diffusional characteristics, influences the exchange of catecholamines to a substantial and physiologically relevant extent. 相似文献
9.
10.
Two Rhodococcus strains, R. opacus strain AS2 and R. erythropolis strain AS3, that were able to use 4-nitroanisole as the sole source of carbon and energy, were isolated from environmental samples. The first step of the degradation involved the O-demethylation of 4-nitroanisole to 4-nitrophenol which accumulated transiently in the medium during growth. Oxygen uptake experiments indicated the transformation of 4-nitrophenol to 4-nitrocatechol and 1,2,4-trihydroxybenzene prior to ring cleavage and then subsequent mineralization. The nitro group was removed as nitrite, which accumulated in the medium in stoichiometric amounts. In R. opacus strain AS2 small amounts of hydroquinone were produced by a side reaction, but were not further degraded. 相似文献