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41.
Thurnher Martin; Wagner Ernst; Clausen Henrik; Mechtler Karl; Rusconi Sandro; Dinter Andre; Birnstiel Max L.; Berger Eric G.; Cotten Matt 《Glycobiology》1994,4(4):429-435
The mucin-type carbohydrate Tn cryptantigen (GalNAc1-O-Ser/Thr,where GalNAc is N-acetyl-D-galactosamine) is expressed in manycarcinomas, in haemopoietic disorders including the Tn syndrome,and on human immunodeficiency virus (HIV) coat glycoproteins,but is not expressed on normal, differentiated cells becauseof the expression of a Tn-processing galactosyltransferase.Using Jurkat T leukaemic cells which express high levels ofTn antigen due to deficient Tn galactosylation, we have establishedthe Tn antigen-mediated gene transfer and demonstrate the considerableefficiency of this approach. We used poly(L-lysine) conjugatesof the monoclonal antibody 1E3 directed against the Tn antigento deliver the luciferase and ß-galactosidase reportergenes to Jurkat cells by receptor-mediated endocytosis. Additionof unconjugated 1E3 reduced transfection efficiency in a concentration-dependentmanner and incubation with free GalNAc abolished DNA transfercompletely, indicating that gene delivery is indeed mediatedby the Tn antigen. Pre-treatment of Jurkat cells with Vibriocholerae sialidase, which uncovers additional Tn antigens, resultedin an improvement of gene transfection. Both human and chickenadenovirus particles attached to the DNA/polylysine complexstrongly augmented transgene expression. When the ß-galactosidase(lacZ) gene was delivered to Jurkat cells by Tn-mediated endocytosis,up to 60% of the cells were positive in the cytochemical stainusing 5-bromo-4-chloro-3-indolyl-ß-D-galactopyranoside(X-gal) as a chromogenic substrate. The efficiency of the transferrinreceptor-mediated DNA uptake into Jurkat cells was comparativelylow, although these cells were shown to express considerableamounts of transferrin receptor. We show here that a mucin-typecarbohydrate antigen mediates highly efficient DNA uptake byendocytosis into Jurkat T cells. This method represents a 50-foldimprovement of Jurkat cell transfection efficiency over otherphysical gene transfer techniques. Specific gene delivery toprimary cancer cells exhibiting Tn epitopes may especially bedesirable in immunotherapy protocols. adenovirus endocytosis gene transfer T cell Tn antigen 相似文献
42.
Bouchra Harraki Pascale Guiraud Marie-Hélène Rochat Henri Faure Marie-Jeanne Richard Michelle Fussellier Alain Favier 《Biometals》1994,7(3):237-243
Radioactive zinc was used to study the effect of a binary parenteral nutrient solution, composed of amino acids and glucose, on zinc uptake by fibroblasts. The influence of addition of taurine, l-glutamine and of the increase in l-histidine content of the admixture was assessed. The pure mixture was highly toxic for cells and so it was diluted 1/5 in tyrode buffer with 2% albumin. As compared with cells incubated in the buffer containing albumin, zinc absorption was significantly higher (P < 0.05) in the presence of the amino acids of the mixture. Amino acids thus increased bioavailability by displacing zinc bound to albumin. When the histidine concentration in the nutrient medium (4.2 mm) was doubled, inhibition was noted after 30 min of incubation and zinc uptake thereafter remained comparable to that in histidine-free medium. The addition of glutamine (4.2 mm), usually not present in binary mixtures, resulted in significant differences as compared with glutamine-free control medium. Taurine (0.8 mm), led to a constant increase in zinc uptake by fibroblasts as compared with that obtained with taurine-free mixture. However, ultrafiltration showed that taurine was not able to displace zinc from albumin. 相似文献
43.
Sites polluted with organic compounds frequently contain inorganic pollutants such as heavy metals. The latter might inhibit the biodegradation of the organics and impair bioremediation. Chromosomally located polychlorinated biphenyl (PCB) catabolic genes ofAlcaligenes eutrophus A5,Achromobacter sp. LBS1C1 andAlcaligenes denitrificans JB1 were introduced into the heavy metal resistantAlcaligenes eutrophus strain CH34 and related strains by means of natural conjugation. Mobile elements containing the PCB catabolic genes were transferred fromA. eutrophus A5 andAchromobacter sp. LB51C1 intoA. eutrophus CH34 after transposition onto their endogenous IncP plasmids pSS50 and pSS60, respectively. The PCB catabolic genes ofA. denitrificans JB1 were transferred intoA. eutrophus CH34 by means of RP4::Mu3A mediated prime plasmid formation. TheA. eutrophus CH34 transconjugant strains expressed both catabolic and metal resistance markers. Such constructs may be useful for the decontamination of sites polluted by both organics and heavy metals. 相似文献
44.
Paul Messner Max Wellan Wolfgang Kubelka Uwe B. Sleytr 《Applied microbiology and biotechnology》1993,40(1):7-11
After periodate oxidation and incubation with dithiodipropionic acid dihydrazide cross-linking of the crystalline surface layer (S-layer) glycoproteins of Clostridium thermohydrosulfuricum L111-69 and Bacillus alvei CCM 2051 was achieved specifically through the glycan chains. The cross-linked S-layers were used for the immobilization of chemically synthesized, spacer-linked, tumour-associated T-disaccharide [Gal(13)GalNAc]. Electron microscopical evaluation of the resulting conjugates showed densely packed, multilayered S-layer structures loaded with the immobilized ligand. After reductive cleavage of the disulphide bond of dithiodipropionic acid by dithiothreitol, monomeric haptenated S-layer conjugates could be obtained. Both the cross-linked and the monomeric type of conjugate might be useful for assessment of specific immune responses, which, in general, can be elicited by those artificial antigens.
Correspondence to: P. Messner 相似文献
45.
Marie J. Richard Veronique Ducros Michel Rorêt Josiane Arnaud Charles Coudray Michèle Fusselier Alain Favier 《Biological trace element research》1993,39(2-3):149-159
In six chronic dialyzed uremic patients, an intravenous sodium selenite (Se 50 μg during 5 wk and then 100 μg) and zinc gluconate
(Zn 5 mg) supplementation was performed during 20 wk at each dialysis session three times weekly. Before supplementation,
plasma Se and Zn, plasma and erythrocytes (RBC) antioxidant metalloenzymes glutathione peroxidase (GPX), and superoxide dismutase
(SOD) were significantly decreased, whereas lipid peroxidation (as thiobarbituric acid reactants TBARs) was increased. To
obtain a significative change in plasma selenium, we had to use an Se dose of 100 μg/dialysis session. Then, treatment-increased
plasma Se (from 0.58 ±0.09 to 0.89±0.16 μmol/L) led to a repletion of RBC-GPX (from 29.6±6 to 43±5.8 U/g Hb) and increased
plasma GPX levels (from 62±13 to 151±43 U/L). Plasma Zn and RBC-SOD did not vary significantly. The change of TBARs was not
observed between wk 1 and 4. They decreased significantly between wk 4 (4.80±0.21μmol/L) and wk 20 (4.16±0.26 μmol/L). We
noted a low correlation between TBARs and plasma GPX. A strong correlation was observed between Se and plasma GPX. The reversal
of Se deficiencies should reduce oxidative damage observed in these patients. 相似文献
46.
Max L. Bothwell Darren Sherbot Andre C. Roberge Ralph J. Daley 《Journal of phycology》1993,29(1):24-35
Growth rates, accumulation dynamics, and species succession of periphytic diatom communities were examined in the presence and absence of natural ultraviolet (UV) radiation using a series of outdoor, continuous-flow experimental flumes located on the South Thompson River, British Columbia. In a short-term experiment (2–3 wk), log-phase growth rates of naturally seeded diatom communities comprised of Tabellaria fenestrata (Lyngb.) Kütz., T. flocculosa (Roth) Kütz., Fragilaria crotonesis Kitton, and F. vaucheriae (Ehr.) Peter. exposed to 90% ambient photosynthetically active radiation (PAR) + UV were 30–40% lower than growth rates under 90% PAR alone. UV inhibition of growth rate was independent of the degree of P limitation within the range of relative specific growth rates (μ:μmax-P) of 0.5–1.0. In a long-term trial, inhibition of attached diatom accumulation under 90% PAR + UV during the first 2–3 wk was corroborated. Reduction of full sunlight to 50% PAR + UV prevented the initial inhibition phase. The initial inihibitory effect of 90% PAR + UV on algal accumulation was reversed after 3–4 wk, and by 5 wk total diatom abundance (chlorophyll a, cell numbers and cell biovolumes) in communities exposed to PAR + UV were 2–4-old greater than in communities protected from UV. Under 90% PAR + UV and 50% PAR + UV, a succession to stalked diatom genera (Cymbella and Gomphoneis) occurred. Species succession under UV radiation doubled the mean cell size of the diatom communities. The shift from inhibition to a long-term increase in the autotrophic community under PAR + UV compared to PAR alone provides further evidence against the use of short-term incubation experiments to define the long-term implications of increases in UVB. These results suggest that the ecological effects of present-day levels of UVB and UVB:UVA ratios on autotrophic communities are not well understood and might be mediated through complex trophic level interactions. 相似文献
47.
48.
Productivity is strongly associated with terrestrial species richness patterns, although the mechanisms underpinning such patterns have long been debated. Despite considerable consumption of primary productivity by fire, its influence on global diversity has received relatively little study. Here we examine the sensitivity of terrestrial vertebrate biodiversity (amphibians, birds and mammals) to fire, while accounting for other drivers. We analyse global data on terrestrial vertebrate richness, net primary productivity, fire occurrence (fraction of productivity consumed) and additional influences unrelated to productivity (i.e., historical phylogenetic and area effects) on species richness. For birds, fire is associated with higher diversity, rivalling the effects of productivity on richness, and for mammals, fire's positive association with diversity is even stronger than productivity; for amphibians, in contrast, there are few clear associations. Our findings suggest an underappreciated role for fire in the generation of animal species richness and the conservation of global biodiversity. 相似文献
49.
Max R. Brown Hannes Becher Sebastian Williams Alex D. Twyford 《American journal of botany》2023,110(1):e16100
Premise
Strong postzygotic reproductive isolating barriers are usually expected to limit the extent of natural hybridization between species with contrasting ploidy. However, genomic sequencing has revealed previously overlooked examples of natural cross-ploidy hybridization in some flowering plant genera, suggesting that the phenomenon may be more common than once thought. We investigated potential cross-ploidy hybridization in British eyebrights (Euphrasia, Orobanchaceae), a group from which 13 putative cross-ploidy hybrid combinations have been reported based on morphology.Methods
We analyzed a contact zone between diploid Euphrasia rostkoviana and tetraploid E. arctica in Wales. We sequenced part of the internal transcribed spacer (ITS) of nuclear ribosomal DNA and used genotyping by sequencing (GBS) to look for evidence of cross-ploidy hybridization and introgression.Results
Common variant sites in the ITS region were fixed between diploids and tetraploids, indicating a strong barrier to hybridization. Clustering analyses of 356 single-nucleotide polymorphisms (SNPs) generated using GBS clearly separated samples by ploidy and revealed strong genetic structure (FST = 0.44). However, the FST distribution across all SNPs was bimodal, indicating potential differential selection on loci between diploids and tetraploids. Demographic inference suggested potential gene flow, limited to around one or fewer migrants per generation.Conclusions
Our results suggest that recent cross-ploidy hybridization is rare or absent in a site of secondary contact in Euphrasia. While a strong ploidy barrier prevents hybridization over ecological timescales, such hybrids may form in stable populations over evolutionary timescales, potentially allowing cross-ploidy introgression to take place. 相似文献50.
Short-term (24–48 h) colonization dynamics of periphytic diatoms on artificial (styrofoam) substrata were examined using fast-flushing, continuous-flow troughs located on the North Thompson River, British Columbia. Two parallel troughs, one exposed to natural light and the other completely darkened, showed significant differences in periphyton biomass, chlorophyll a, and algal taxonomic composition with 24 h. Experiments which commenced at the onset of natural darkness demonstrated that rates of algal immigration during the night were the same in both troughs. Within 2–3 h of sunrise, however, certain diatom species (most notably Hannaea arcus (Ehr.) Pair, and Diatoma tenue Ag.) selectively emigrated from the artificially darkened trough but remained in the trough exposed to natural light. More closely adhering species such as Achnanthes minutissima Kütz, also showed significant emigration from the darkened trough after light deprivation for two photoperiods. Data from adhesion, emigration, and sinking rate experiments indicate that differential egress of cells from the darkened versus the lighted environments is the result of cellular regulation of buoyancy or form resistance. 相似文献