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  • Biochemistry and Biotechnology  (8)
  • Epithelia  (2)
  • Genetics  (2)
  • soils  (2)
  • 1995-1999  (14)
  • 1985-1989
  • 1995  (14)
  • 1
    Electronic Resource
    Electronic Resource
    Extractable chromium determination in soils by AAS (1995)
    Springer
    Microchimica acta 119 (1995), S. 251-258 
    Details
    ISSN: 1436-5073
    Keywords: extractable chromium ; soils ; EDTA extracts ; acetic acid extracts ; FAAS ; releasing agent oxine and ETAAS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The lixiviation of trace metals from soils using selective extractants gives valuable information, especially for agricultural purposes. The two reagents validated by a group of European researchers coordinated by the Measurements and Testing Program (MAT) of the Commission of the European Community, in single extraction procedures, are EDTA 0.05 moll−1 and CH3COOH 0.43 moll−1. This paper reports the effect of these extractants upon chromium determination in extracts by AAS. Matrix effects were studied in extracts of two soils of different origin: a terra rossa soil from a Mediterranean area and a sewage amended soil. For the FAAS technique, the matrix effects were studied for air-acetylene and nitrous oxide-acetylene flames and using Cr(VI) and Cr(III) as standard solutions. The interfering effects observed are circumvented by the use of 1% 8-hydroxyquinoline as suppressor agent. For the ETAAS technique, charring and atomization curves were obtained for extracts in each reagent and after setting up the graphite furnace program, matrix effects were studied. Different matrix modifiers (Mg(NO3)2, Pd and Triton X-100) were also tested. Once the analytical method had been established, single extraction procedures were applied in the two soils, determining the percentage of extractable chromium in relation to the total content.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01244004
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  • 2
    Electronic Resource
    Electronic Resource
    Preparation of candidate certified reference materials for the quality control of EDTA-and acetic acid-extractable trace metal determinations in sewage sludge-amended soil and terra rossa soil (1995)
    Springer
    Microchimica acta 120 (1995), S. 289-300 
    Details
    ISSN: 1436-5073
    Keywords: extraction ; soils ; trace elements ; candidate CRMs ; reference materials
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The determination of extractable trace metal contents in soil using single extraction procedures is currently performed in many laboratories to assess the bioavailable metal fraction (and related phytotoxic effects) and the accessability to the environment (e.g. contamination of ground waters). Owing to the need for validation of the extraction schemes used and of the analytical techniques, the EC Measurements and Testing Programme (formerly BCR) has organized a project for improving the quality of determination of extractable trace metal contents in soil, the first step being an interlaboratory study to adopt common extraction procedures and the second being a certification campaign to certify two soils for their extractable trace element contents following these procedures. This paper gives a brief overview of the project organisation and describes the preparation, homogeneity and stability studies of two soil candidate reference materials (sewage sludge-amended and terra rossa soils).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01244439
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  • 3
    Electronic Resource
    Electronic Resource
    Expression of potassium channels in epithelial cells depends on calcium-activated cell-cell contacts (1995)
    Springer
    The journal of membrane biology 143 (1995), S. 219-226 
    Details
    ISSN: 1432-1424
    Keywords: Epithelia ; K+ channels ; Expression of ion channels ; Ca2+ ; Membrane area ; Cell-cell contacts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Harvesting MDCK cells with trypsin-EDTA reduces potassium currents (I K) to a mere 10%, presumably by hydrolysis of K+ channels, but replating at confluence restores them in 12–18 hr, through a process that requires transcription, translation and exocytic fusion of intracellular membrane vesicles to the plasma membrane (Ponce & Cereijido, 1991; Ponce et al., 1991a). In the present work we find that this restoration of I K also requires cell-cell contacts and the presence of 1.8 mm Ca2+. The role of extracellular Ca2+ may be substituted by 2.0 μm TRH, 10 nm PMA or 200 μg/ml DiC8, drags that stimulate the system of phospholipase C (PLC) and protein kinase C (PKC). Conversely, the recovery of I K triggered by Ca-dependent contacts can be blocked by 110 μm neomycin, 2.0 μm H7, and 250 nm staurosporine, inhibitors of PLC and PKC. These results suggest that the expression of new K+ channels depends on Ca2+-activated contacts with neighboring cells and that the information is conveyed through PLC and PKC, a process in keeping with changes in its enzymatic activity and cellular distribution of PKC. Plasma membrane is also reduced and restored upon harvesting and replating, and depends on Ca2+-activated contracts. However, the effects of the chemicals tested on I K differ from the ones they elicit on the recovery of plasma membrane, suggesting that cells can independently regulate their population of K+ channels and the surface of their membrane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00233450
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  • 4
    Electronic Resource
    Electronic Resource
    A novel type of cell-cell cooperation between epithelial cells (1995)
    Springer
    The journal of membrane biology 145 (1995), S. 305-310 
    Details
    ISSN: 1432-1424
    Keywords: Ouabain-resistance ; Epithelia ; Ma104 cells ; MDCK cells ; Tight junctions ; Na+, K+-ATPase ; K+ content ; Metabolic cooperation ; Cell attachment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Ma104 cells (renal, epithelial) have a peculiar way of resisting ouabain: their Na+,K+-pumps bind the drug with high affinity, cellular K+ is lost and cell division arrested, but cells do not detach as most cell types do. Then, if up to 4 days later the drug is removed, Ma104 cells recover K+ and resume proliferation (Contreras et al., 1994). In the present work, we investigate whether Ma104 cells are able to protect ouabain-sensitive MDCK cells in co-culture. The main finding is that they do, but in this case protection is not elicited by the usual mechanism of maintaining the K+ content of neighboring cells through cell-cell communications. Ma104 cells treated with ouabain simply remain attached to the substrate and to their MDCK neighbors, and both cells lose K+. This attachment includes tight junctions, because the transepithelial electrical resistance of the monolayers is not abolished by ouabain. Although the β-subunit of the Na+,K+-ATPase is known to possess molecular characteristics of cell-cell attachment molecules, attachment between Ma104-MDCK cells does not seem to be mediated by this enzyme, as immunofluorescence analysis reveals that Na+,K+-ATPase is only inserted in the plasma membrane facing a neighboring cell of the same type.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00232722
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  • 5
    Electronic Resource
    Electronic Resource
    Enhancement and inhibition of luminol chemiluminescence by phenolic acids (1995)
    New York : Wiley-Blackwell
    Journal of Bioluminescence and Chemiluminescence 10 (1995), S. 175-184 
    Details
    ISSN: 0884-3996
    Keywords: Luminol ; enhanced chemiluminescence ; phenolic acid ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: We explored the behaviour of a series of phenolic acids used as enhancers or inhibitors of luminol chemiluminescence by three different methods to determine if behaviour was associated with phenolic acid structure and redox character. All the phenolic acids inhibited chemiluminescence when hexacyanoferrate(III) was reacted with the phenolic acids before adding luminol. The redox character of these compounds was clearly related to structure. When hexacyanoferrate(III)-luminol-O2 chemiluminescence was initiated by phenolic acid-luminol mixtures some phenolic acids behaved as enhancers of chemiluminescence, and others as inhibitors. We propose a mechanism to explain these findings. We found direct relationships between the redox character of the phenolic acids and the enhancement or inhibition of the chemiluminescence of the luminol-H2O2-peroxidase system and we propose mechanism to explain these phenomena.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bio.1170100306
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  • 6
    Electronic Resource
    Electronic Resource
    Characterization of the conformational domains of bradykinin by computational methods (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 1 (1995), S. 227-235 
    Details
    ISSN: 1075-2617
    Keywords: Bradykinin ; conformational domains ; conformational search ; molecular mechanics ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The AMBER 4.0 force field was used to perform a characterization of the conformational profile of the nonapeptide bradykinin. A thorough conformational search was carried out using molecular dynamics as sampling technique, by computing cycles of high (900 K) and low (300 K) temperature trajectories. A total of 2400 minima were generated and subsequently clustered using the root-mean-square of the backbone dihedral angles as criterium. After the use of a tolerance value of 20deg;, the conformations were clustered in 233 unique conformations with energies up to 40 kcal/mol above the lowest minimum. The analysis of the low-energy conformations indicate that the peptide exhibits a high tendency to adopt a β-turn at the C-terminus and a propensity to adopt a bent structure at the N-terminus. These results are in agreement with the experimental evidence reported in the literature and provide detailed information necessary to understand the conformational preferences of the peptide.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/psc.310010403
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  • 7
    Electronic Resource
    Electronic Resource
    Assay of cholinesterase using a proenhancer of the luminol-H2O2-horseradish peroxidase reaction (1995)
    New York : Wiley-Blackwell
    Journal of Bioluminescence and Chemiluminescence 10 (1995), S. 285-289 
    Details
    ISSN: 0884-3996
    Keywords: Cholinesterase ; luminol ; pro-enhancer ; chemiluminescence ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: 2-Naphthyl acetate acts as a pro-enhancer of the luminol-H2O2-horseradish peroxidase reaction. Cholinesterase hydrolyses the bound acetyl group and produces 2-naphthol, and this compound is an enhancer of the chemiluminescent reaction. We studied the kinetics of chemiluminescent emission and the influence of 2-naphthyl acetate and cholinesterase enzyme concentration. The cholinesterase concentration versus chemiluminescence intensity maximum was linear for cholinesterase between 0 and 181 μU/mL, with a detection limit of 8 μU/mL and a relative standard deviation of 9.5% (n = 3), for a sample containing 90.67 μU/mL of cholinesterase.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bio.1170100505
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  • 8
    Electronic Resource
    Electronic Resource
    Inside SWISS-2DPAGE database (1995)
    Weinheim : Wiley-Blackwell
    Electrophoresis 16 (1995), S. 1131-1151 
    Details
    ISSN: 0173-0835
    Keywords: SWISS-2DPAGE ; Two-dimensional gel electrophoresis ; Protein database ; Protein mapping ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Several two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) databases have been established and updated for more than 15 years. Only recently have developments of computer networks and high-speed transfer protocols provided the required tools for sharing comprehensive and hypermedia 2-D PAGE databases. This publication describes the SWISS-2DPAGE database structure. Proteins present in samples of human tissue, cells, cell lines and body fluids are assembled and described in an accessible uniform format. SWISS-2DPAGE can be freely accessed through the World-Wide Web (WWW) network on the ExPASy molecular biology server.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.11501601190
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  • 9
    Electronic Resource
    Electronic Resource
    Phenotyping of apolipoprotein E using immobilized pH gradient gels for one-dimensional and two-dimensional separations (1995)
    Weinheim : Wiley-Blackwell
    Electrophoresis 16 (1995), S. 1184-1186 
    Details
    ISSN: 0173-0835
    Keywords: Apolipoprotein E ; Immobilized pH gradient ; Phenotyping ; Immunoblotting ; Two-dimensional polyacrylamide gel electrophoresis ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Apolipoprotein E (apo E) is a normal component of several classes of plasma lipoproteins. Apo E phenotypes are closely related to total cholesterol, low density lipoprotein (LDL)-cholesterol and apo B concentration. The apo E 2/2 phenotype is related to the type III hyperlipoproteinemia due to the defective binding of apo E-2 to the hepatic receptors. The apo E 4/4 phenotype has been reported to be present in most elderly people suffering from the Alzheimer disease, and is associated with increased risk of coronary heart disease and Creutzfeld-Jakob disease. Therefore, apo E phenotyping is essential. The method described here uses a precast immobilized pH gradient, avoids time-consuming separation of lipoproteins from plasma, needs no pretreatment with neuraminidase and involves highly sensitive enhanced chemiluminescence for visualization. Therefore it has many advantages over previously published methods.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.11501601196
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  • 10
    Electronic Resource
    Electronic Resource
    Cloning and sequencing of the URA5 gene from the yeast Yarrowia lipolytica (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 11 (1995), S. 425-433 
    Details
    ISSN: 0749-503X
    Keywords: Yarrowia lipolytica ; orotate phosphoribosyl transferase ; nucleotide sequence ; transcription ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The URA5 gene of Yarrowia lipolytica encoding the orotate phosphoribosyl transferase (OPRTase, EC2.4.2.10) was isolated by target integration in a mutant strain originally named ura2.21. The nucleotide sequence of the gene predicts a protein with high similarities with the OPRTases from Saccharomyces cerevisiae, Podospora anserina and Escherichia coli and to a lesser extent with that of Dictyostelium discoideum. The transcription start point has been mapped by primer extension analysis and indicates the existence of a long leader sequence in the corresponding mRNA. Northern-blot hybridization revealed the URA5 transcript to be approximately 0·94 kb. Deletion of the URA5 gene in Y. lipolytica produced a leaky phenotype similar to the one described for the ura5 mutation in S. cerevisiae. The URA5 gene of Y. lipolytica was able to complement functionally the ura5 mutation of S. cerevisiae. The sequence presented here has been submitted to the EMBL data library under Accession Number Z22571.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/yea.320110505
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