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111.
112.
Abstract. The observed distribution of a species along an environmental gradient is strongly affected by environmental variability within a quadrat. Because a quadrat does not represent a point along an environmental gradient, but rather a range of conditions, it is likely to contain species not typically associated with the mean conditions in the quadrat. Systematic relationships exist between a species' true distribution, the observed distribution as a function of mean quadrat environment, and the frequency distribution of the environment within that quadrat. The observed species habitat breadth increases and the observed maximum abundance decreases as within-quadrat environmental heterogeneity increases. If species distributions or beta diversities are to be compared among species or coenoclines, they should be correctedforintra-quadratheterogeneity.Wederive simple corrections for environmental heterogeneity. The distributions of hardwood forest understory species along a soil acidity gradient in the North Carolina piedmont are presented as an example. 相似文献
113.
M Favrot R Capdeville V Combaret D C Zhou G Clapisson J Banchereau C R Franks S Chouaib J Y Blay T Philip 《European cytokine network》1990,1(3):141-147
The effect of human IL-4, used as a single agent or in combination with low or high dose IL-2, upon LAK-cell proliferation and activation has been tested on PBMC from patients treated with alpha 2-IFN and IL-2. Four days in vitro culture with IL-4 did not induce any LAK-cell activation; IL-4 induced the proliferation of CD3+ CD4+ T-cells, but decreased the percentage of NK cells in culture samples. When combined with high dose IL-2, IL-4 improved the recovery of MN cell without modification of T-cell subsets; however, IL-4 had no major effect on IL-2-induced NK or LAK cell activity. The combination of IL-4 and low dose IL-2 still significantly improved the total MN cell recovery but did not modify the distribution of T and NK lymphocytes; IL-4 inhibited low dose IL-2-induced NK and LAK cell activity, and increased the BL-esterase activity induced by high or low dose IL-2. The combination of IL-4 and IL-2 did not induce any large variation in the percentage of IL-2R (p55) expressing cells. In all tested conditions, IL-2R (p55) was mainly expressed on CD4+ T cells; less than 2% of the cells coexpressed the NK cell marker CD56 and IL-2R (p55). The effect of IL-4 upon IL-2-induced LAK cell expansion is thus very different on PBMC pre-activated in vivo by alpha IFN + IL-2 therapy than on PBMC pre-treated in vitro with IL-2.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
114.
115.
Keiko Tadano-Aritomi Harumi Kubo Philip Ireland Takeshi Kasama Shizuo Handa Ineo Ishizuka 《Glycoconjugate journal》1996,13(2):285-293
A novel mono-sulfated glycosphingolipid based on the gangliotriaose core structure was isolated from rat kidney. The isolation procedure involved extraction of lipids with chloroform/methanol, mild alkaline methanolysis, column chromatographies with anion exchangers and silica beads. The structure was characterized by compositional analysis, FTIR spectroscopy, methylation analysis,1H-NMR spectroscopy and negative-ion liquid secondary ion mass spectrometry (LSIMS) using the intact glycolipid and its desulfation product. The two dimensional chemical shift correlated spectroscopy provided information on the sugar sequence as well as anomeric configurations, and indicated the presence of a 3-O-sulfatedN-acetylgalactosamine within the molecule. Negative-ion LSIMS with high- and low-energy collision-induced dissociation defined the sugar sequence and ceramide composition, confirming the presence of a sulfatedN-acetylgalactosamine at the non-reducing terminus. From these results, the complete structure was proposed to be HSO3-3GalNAc1-4Gal1-4Glc1-1Cer (Gg3Cer III3-sulfate, SM2b).
Abbreviations: Abbreviations for sulfated glycolipids [17] follow the modifications of the nomenclature system of Svennerholm for gangliosides [37], and the designation of the other glycosphingolipids follows the IUPAC-IUB recommendations [38]. Cer, ceramide; LacCer, lactosylceramide, Gal1-4Glc1-1Cer; Gg3Cer, gangliotriaosylceramide, GalNAc1-4Gal1-4Glc1-1Cer; Gg4Cer, gangliotetraosylceramide, Gal1-3GalNAc1-4Gal1-4Glc1-1Cer; iGb4Cer, isoglobotetraosylceramide, GalNAc1-3Gal1-3Gal1-4Glc1-1Cer; Gb4Cer, globotetraosylceramide, GalNAc1-3Gal1-4Gal1-4Glc1-1Cer; SM4s, galactosylceramide sulfate, GalCer I3-sulfate; SM3, lactosylceramide sulfate, LacCer II3-sulfate; SM2a, Gg3Cer II3-sulfate; SM2b, Gg3Cer III3-sulfate; SB2, Gg3Cer II3,III3-bis-sulfate; SM1a, Gg4Cer II3-sulfate; SM1b, Gg4Cer IV3-sulfate; SB1a, Gg4Cer II3,IV3-bissulfate; GLC, gas-liquid chromatography; GC-MS, gas chromatography-mass spectrometry; DQF, double quantum filtered; COSY, chemical-shift-correlated spectroscopy; LSIMS, liquid secondary ion mass spectrometry; CID, collision-induced dissociation; MS/MS, tandem mass spectrometry. 相似文献
116.
Jonathan A. Lindquist Elisabeth Barofsky Philip N. McFadden 《Journal of Protein Chemistry》1996,15(1):115-122
Protein (d-aspartyl/l-isoaspartyl) carboxyl methyltransferase (PCM, E.C. 2.1.1.77) was previously shown to be enzymatically methyl esterified in an autocatalytic manner at altered aspartyl residues; methyl esters are observed in a subpopulation of the enzyme termed thePCM fraction [Lindquist and McFadden (1994),J. Protein Chem.
13, 23–30]. The altered aspartyl sites serving as methyl acceptors inPCM have now been localized by using proteolytic enzymes and chemical cleavage techniques in combination with matrix-assisted laser desorption/ionization (MALDI) mass spectrometry to identify fragments of the [3H]automethylated enzyme that contain a [3H]methyl ester. Methylation was positively identified at positions Asn188 and Asp217 in the enzyme sequence, a consequence of the spontaneous alteration of these sites tol-isoaspartyl ord-aspartyl sites and their methylation by active PCM molecules. The identification of more than one site of automethylation shows thatPCM is not a homogeneous population of damaged PCM molecules, but rather a complex population of molecules with a variety of age-altered damage sites.Abbreviations PCM
protein (d-aspartyl/l-isoaspartyl) carboxyl methyltransferase
- EDTA
disodium ethylenediaminetetraacetate
- PMSF
phenylmethylsulfonyl fluoride
- TEA
trifluoroacetic acid
- HPLC
high-pressure liquid chromatography 相似文献
117.
Arabidopsis consensus intron sequences 总被引:7,自引:0,他引:7
We have analysed 998 Arabidopsis intron sequences in the EMBL database. All Arabidopsis introns to adhere to the :GU...AG: rule with the exception of 1% of introns with :GC at their 5 ends. Virtually all of the introns contained a putative branchpoint sequence (YUNAN) 18 to 60 nt upstream of the 3 splice site. Although a polypyrimidine tract was much less apparent than in vertebrate introns, the most common nucleotide in the region upstream of the 3 splice site was uridine. Consensus sequences for 5 and 3 splice sites and branchpoint sequences for Arabidopsis introns are presented. 相似文献
118.
Kirsty Barr Henrik Moller Emma Christmas Philip Lyver Jacqueline Beggs 《Oecologia》1996,105(2):266-270
An introduced social wasp Vespula vulgaris may compete with native birds for honeydew and invertebrates in New Zealand forests. Experimentally hidden mealworms (Tenebrio molitor) persisted longer at two sites following wasp poisoning that at two sites where wasps were not poisoned. Mealworms persisted longer in the morning than in the afternoon within all study sites. An unusually low mealworm removal rate during a morning trial before wasp poisoning heavily influences the results of this experiment but we have no ecological reason to ignore it. Wasps may therefore be having a heavy impact on invertebrate abundance on very short time scales (within a day following dawn emergence). They may also remove cached food items that would otherwise be retrieved by the South Island robin (Petroica australis australis) during cold or dark feeding conditions. 相似文献
119.
Luke Olsen Jonathan A. Sherratt Philip K. Maini 《Bulletin of mathematical biology》1996,58(4):787-808
The normal process of dermal wound healing fails in some cases, due to fibro-proliferative disorders such as keloid and hypertrophic
scars. These types of abnormal healing may be regarded as pathologically excessive responses to wounding in terms of fibroblastic
cell profiles and their inflammatory growth-factor mediators. Biologically, these conditions are poorly understood and current
medical treatments are thus unreliable.
In this paper, the authors apply an existing deterministic mathematical model for fibroplasia and wound contraction in adult
mammalian dermis (Olsenet al., J. theor. Biol.
177, 113–128, 1995) to investigate key clinical problems concerning these healing disorders. A caricature model is proposed which
retains the fundamental cellular and chemical components of the full model, in order to analyse the spatiotemporal dynamics
of the initiation, progression, cessation and regression of fibro-contractive diseases in relation to normal healing. This
model accounts for fibroblastic cell migration, proliferation and death and growth-factor diffusion, production by cells and
tissue removal/decay.
Explicit results are obtained in terms of the model processes and parameters. The rate of cellular production of the chemical
is shown to be critical to the development of a stable pathological state. Further, cessation and/or regression of the disease
depend on appropriate spatiotemporally varying forms for this production rate, which can be understood in terms of the bistability
of the normal dermal and pathological steady states—a central property of the model, which is evident from stability and bifurcation
analyses.
The work predicts novel, biologically realistic and testable pathogenic and control mechanisms, the understanding of which
will lead toward more effective strategies for clinical therapy of fibro-proliferative disorders. 相似文献
120.
Ravindar Kaur-Sawhney Philip B. Applewhite Arthur W. Galston 《Plant Growth Regulation》1996,18(3):191-199
Thin longitudinal sections cut from pedicels of fifteen cultivars of tomato (Lycopersicon esculentum) were grown in vitro on Murashige-Skoog medium supplemented with various concentrations of different auxins and cytokinins. Isatin (an auxin precursor slowly converted to an active auxin) was the most effective source of auxin for the formation of buds without prior root formation, while zeatin was the most effective cytokinin for growth and development of the buds. Flower buds and ripe fruits developed consistently from explants of the cultivar Pixie Hybrid II treated with 10 M isatin plus 3 M zeatin as the cytokinin. Fruits developed parthenocarpically, grew to a diameter of about 15 mm, ripened promptly, and possessed normal color and flavor.Abbreviations BAP
benzylaminopurine
- IAA
indole-3-acetic acid
- IBA
indole-3-butyric acid
- IPA
isopentyladenosine
- NAA
-napthaleneacetic acid 相似文献