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  • 1
    ISSN: 1432-0738
    Keywords: 2,4-D ; Biotransformation ; Urinary excretion ; Agent Orange
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The metabolic fate of 2,4-dichlorophenoxyacetic acid (2,4-D)-n-butyl ester in rats has not been extensively studied. Upon subcutaneous administration of a 100 mg/kg dose of 2,4-D butyl ester to four male Wistar rats, urine samples were analyzed by three analytical techniques for the presence of the butyl ester and metabolites. Thin layer chromatography (TLC), gas chromatography using an electron capture detector (GC-ECD), and gas chromatography-mass spectroscopy (GC-MS) were the techniques employed. 2,4-D butyl ester was rapidly hydrolyzed in the body to form 2,4-D acid. Ninety-five percent of the administered dose was excreted into the urine as the free acid within 48 h of injection, while only a small fraction (5%) was excreted over an additional 48 h. No amino acid conjugates or the parent 2,4-D butyl ester could be detected in the urine of treated rats. A minor metabolite (≤2% of dose) was detected by GC-MS analysis of urine samples. This compound appears to be a side chain metabolite of the 2,4-D butyl ester. Some chemical properties of the metabolite were characterized, and a 2,4-D hydroxyethyl ester structure proposed. The mechanism of this minor metabolic formation remains unknown.
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  • 2
    ISSN: 1573-904X
    Keywords: adenoviral vector ; Caco-2 ; gene transfer ; integrin ; intestinal epithelium ; vitronectin receptor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. Adenoviral (Ad) vectors have been used as efficient tools for gene therapy in various tissues, whereas in some differentiated epithelium transduction efficiency is almost abolished. Methods. Caco-2 cell monolayers were chosen as an in vitro model for the differentiated intestinal epithelium. Fluorescence-labeled adenoviral particles were used for binding studies to cell surfaces. Internalization receptors for adenoviral uptake were decteted by a fluorescence-labeled vitronectin antibody. Gene expression was studied by using the β-galactosidase reporter gene. All experiments were done on undifferentiated and differentiated Caco-2 cells. Furthermore, adenoviral particles were allowed to bind to differentiated Caco-2 monolayers followed by a trypsinization step that disintegrates the monolayers and result in a cell suspension. Gene expression was tested after reseeding the cells into dishes. Results. The results from adenoviral binding studies, vitronectin immunofluorescence detection and gene expression are in good agreement and indicate that virion binding as well as the expression of internalization receptors almost disappear in fully differentiated cells. Nonetheless, adenoviral binding to differentiated monolayers seems to be sufficient to cause up to 53% gene expression, but only if internalization of the vector can be induced by disintegrating the monolayers and releasing free vitronectin receptors. Conclusions. These findings indicate that gene transfer to the intestinal epithelium utilizing adenoviral vectors is poor and ineffective, because of the lack of sufficient internalization receptors. If these receptors can be exposed in differentiated epithelium, transduction can be made more efficicient. Alternatively, a viral vector must be developed whose uptake mechanism is independent of integrin receptor expression like the enteral virus Ad40, or Ad5 could be conjugated to ligands that trigger viral internalization by receptor-mediated endocytosis.
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  • 3
    ISSN: 1573-904X
    Keywords: gene expression ; hPepTl ; Caco-2 cells ; adenovirus ; drug screening
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. Our goals are to establish an in vitro screening system and to evaluate a new approach in improving oral absorption of peptides and peptide-like drugs by overexpression of the human intestinal oligo-peptide transporter (hPepTl). This study characterizes the expression of hPepTl in human intestinal Caco-2 cells, rat intestinal epithelial cells (IEC-18), and human cervix epithelial cells (Hela) after adenoviral transduction. Methods. A recombinant replication-deficient adenovirus carrying the hPepTl gene was made and used as a vector for the expression of hPepTl. The increase in the uptake permeability of cephalexin and Gly-Sar was determined. The effects of time, dose, apical pH, and substrate specificity were evaluated. Results. A significant increase in the uptake permeability of Gly-Sar and cephalexin was found in all three cell lines after viral transduction. The increase of Gly-Sar permeability in Hela, IEC-18, and Caco-2 cells was 85-, 46-, and 15-fold respectively. Immunoblotting using an antibody against hPepTl detected high levels of a 85-98-kDa protein in all three infected cell lines. Substrate permeability was dependent on time of infection, inward pH gradients, and multiplicity of infection (MOI). Decreased infectivity and lower hPepTl expression were observed in differentiated Caco-2 cells. The uptake was inhibited by dipeptides and β-lactam antibiotics but not amino acids. Conclusions. Adenoviral infected Hela cells displayed a pronounced level of hPepTl expression with a low background and high specificity to dipeptides. These features make this system a useful tool for screening of potential substrates. The success of overexpression of hPepTl in Caco-2 and IEC-18 cells may lead to a novel approach in improving oral absorption of peptides and peptidomimetic drugs.
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  • 4
    ISSN: 1573-904X
    Keywords: adenovirus ; intestine ; gene therapy ; cyclodextrins ; jejunum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. In general, the intestinal epithelium is quite refractory to viral and non-viral methods of gene transfer. In this report, various cyclodextrin formulations were tested for their ability to enhance adenoviral transduction efficiency in two models of the intestinal epithelium: differentiated Caco-2 cells and rat jejunum. Methods. Transduction efficiency of replication-deficient adenovirus type 5 vectors encoded with either the E. coli beta-galactosidase or the jellyfish green fluorescent protein gene was assessed by X-gal staining or visualization of fluorescence 48 hours after infection. In vivo experiments were performed using an intestinal loop ligation technique. Results. Several formulations of neutral and positively charged beta cyclodextrins significantly enhanced adenoviral-mediated gene transfer in the selected models. The cyclodextrin formulations studied increased adenoviral transduction in the intestine by enhancing both viral binding and internalization. Viral binding was significantly increased on cell membranes treated with positively charged cyclodextrins, as seen with confocal microscopy and rhodamine-labeled virus. Permeability studies and TEER readings revealed that the most successful formulations gently disrupt cell membranes. This enhances internalization of viral particles and results in increased levels of gene expression. Conclusions. These formulations can be of value in gene transfer to cells and tissues in which adenoviral infection is limited due to a lack of fiber and αv integrin receptors. They are simple to prepare and do not affect the ability of the virus to transduce target cells.
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  • 5
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this work the role of extended defects on the electrical performance of epitaxial silicon on substrates containing an insulating SiO2 layer has been examined. The buried SiO2 layers in the substrates were obtained by two techniques: implantation of oxygen and zone melt recrystallization. In order to make a thorough structural and electrical evaluation of silicon on the insulator substrates, 5-μm-thick epitaxial capping layers have been simultaneously deposited via chemical vapor deposition on representative insulating substrates and reference wafers. The average minority-carrier lifetime was found to vary from 2.5 to 242 μs depending on the density and distribution of dislocations emerging from the capping epitaxial layer.
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  • 6
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford [u.a.] : International Union of Crystallography (IUCr)
    Acta crystallographica 51 (1995), S. 1067-1069 
    ISSN: 1600-5759
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford [u.a.] : International Union of Crystallography (IUCr)
    Acta crystallographica 51 (1995), S. 2565-2567 
    ISSN: 1600-5759
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1520-5118
    Source: ACS Legacy Archives
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1365-2133
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: A small, but clinically significant proportion of acne patients fail to respond adequately to antibiotic therapy. All non-responding acne patients attending the Leeds General Infirmary between September 1985 and April 1986 (49 out of a total of 610 patients; 8%) were investigated with respect to changes in their acne grade, microbial flora and sebum excretion rate. They were compared with 22 age and sex matched untreated control subjects. It was found that in 65% of non-responding patients there was no microbiological abnormality, in 16% there was evidence of Gram-negative folliculitis and 20% carried predominantly antibiotic resistant propionibac teria compared with only 5% of untreated controls. There was a significant association between erythromycin therapy and the isolation of erythromycin resistant propionibacteria (P 〈 0·001). A causal link, however, has yet to be established between carriage of antibiotic resistant propionibacteria and failure to respond to antibiotic therapy. Our results show that for most patients with recalcitrant acne a non-microbiological explanation must be sought for the lack of therapeutic success. The mean sebum excretion rate (SER) of the non-responding patients was significantly higher than that of matched untreated acne patients (P 〈 0·001). A majority of non responders (69%) had an SER above the upper 95% confidence limit of the control mean. The SER may affect treatment efficacy by influencing the antibiotic concentration within the pilosebaceous ducts.
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