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  • 1
    Electronic Resource
    Electronic Resource
    Terpenoids From Viguiera excelsa and Viguiera oaxacana (1984)
    s.l. : American Chemical Society
    Journal of natural products 47 (1984), S. 1042-1045 
    Details
    ISSN: 1520-6025
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/np50036a028
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  • 2
    Electronic Resource
    Electronic Resource
    Reef facies, dolomitization and stratified mineralization (1972)
    Springer
    Mineralium deposita 7 (1972), S. 89-99 
    Details
    ISSN: 1432-1866
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Résumé La sédimentation cyclique de type récifal, particulièrement bien développée dans le Givetien du Synclinorium de Dinant (Belgique), fait l'objet d'une description détaillée des différents faciès, de leurs caractéristiques faunistiques et physico-chimiques et de leur ordonnance. Les phénomènes récifaux plus récents de l'Aptien supérieur de la Province de Santander (Nord de l'Espagne), exception faite d'une dolomitisation plus intense, s'apparentent aux précédents par une même ordonnance de faciès identiques et d'une manière générale par une même sédimentation cyclique. L'étude comparative des deux étages met en évidence la similitude de milieu ayant favorisé, au cours de l'Aptien supérieur, le dépôt des minéralisations plombo-zincifères de Reocin confinées à certains horizons récifaux dolomitisés. Il apparaît ainsi des relations étroites entre récifs, processus de dolomitisation et gisements stratiformes.
    Notes: Abstract The particularly well developed reef-type cyclical sedimentation seen in the Givetian stage of the Dinant synclinorium (Belgium), is discussed in detail with respect to the various facies, their faunal and physicochemical characteristics and their sequence. More recent (Upper Aptian) reef phenomena in the Province of Santander in northern Spain are similar to the Givetian complex (except for their more marked dolomitization) in that they have the same sequence of identical facies and, generally speaking, the same cyclical sedimentation. A comparative study underscores the similarity of environment between the two stages. This environment, during the Upper Aptian, facilitated the deposition of lead-zinc ores at Reocin, which are limited to certain dolomitized reef levels. A close relationship thus emerges between reefs, the process of dolomitization and stratiform ore deposits.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00206898
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  • 3
    Electronic Resource
    Electronic Resource
    Efficient expression of tum− antigen P91A by transfected subgenic fragments (1992)
    Springer
    Immunogenetics 35 (1992), S. 241-252 
    Details
    ISSN: 1432-1211
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Mutagen treatment of mouse P815 tumor cells produces immunogenic mutants that express new transplantation antigens (tum− antigens) recognized by cytolytic T cells. The gene encoding tum− antigen P91A comprises 12 exons and a mutation located in exon 4 is responsible for the production of a new antigenic peptide. Transfection experiments showed that the expression of the antigen could be transferred not only by the entire gene but also by gene segments comprising only the mutated exon and parts of the surrounding introns. This was observed with subgenic regions that were not cloned in expression vectors. Antigen expression did not require the integration of the transfected gene segment into a resident P91A gene by homologous recombination. It also occurred when the subgenic segment was transfected without the usual selective gene, which comprises an eucaryotic promoter, and also without plasmid sequences, which are known to contain weak promoters. When a stop codon was introduced at the beginning of exon 4, the expression of the antigen was maintained and evidence was obtained that an ATG codon located in this region served as initiation site for the translation of the antigenic peptide. But we have not obtained evidence indicating that antigenic peptides are direct translation products rather than degradation products of entire proteins.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00166829
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  • 4
    Electronic Resource
    Electronic Resource
    Immunogenic (tum−) variants obtained by mutagenesis of mouse mastocytoma P815 (1987)
    Springer
    Immunogenetics 26 (1987), S. 178-187 
    Details
    ISSN: 1432-1211
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Mutagen treatment of mouse mastocytoma P815 produces highly inununogenic “tum−” variants. Most of these variants express potent transplantation antigens which are not present on the original P815 tumor cells. These tum− antigens, which appear to be specific for each variant, elicit a strong cytolytic T lymphocyte (CTL) response, but do not seem to induce a specific antibody response. As a first step in the isolation of the gene of a tum− antigen, we attempted DNA-mediated gene transfer. As a DNA recipient cell we used P1.HTR, a highly transfectable P815 cell line, whose selection has been previously described. For the detection of antigen-expressing cells in transfected populations we developed a procedure that relies on the ability of these cells to stimulate the proliferation of the relevant CTL. Using DNA from tum− variant P91 mixed with a plasmid carrying an antibiotic resistance gene, we obtained several independent transfectants expressing a tum− antigen, at a frequency of approximately 1 in 13 000 antibiotic-resistant transfectants. These transfectants express only one of the two tum− antigens that were identified on P91, suggesting that these tum− antigens correspond to different genes. We expect that the detection procedure described here will be-suitable for the identification of transfectants for any gene that determines the expression of an antigen recognized by CTL.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00365909
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  • 5
    Electronic Resource
    Electronic Resource
    T cell-recognized antigenic peptides derived from the cellular genome are not protein degradation products but can be generated directly by transcription and translation of short subgenic regions. A hypothesis (1989)
    Springer
    Immunogenetics 29 (1989), S. 75-79 
    Details
    ISSN: 1432-1211
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract It is now widely accepted that cytolytic T cells recognize their antigens in the form of small peptides bound to major histocompatibility complex molecules at the surface of the target cells. We present here the hypothesis that, when these antigenic peptides are derived from the cellular genome, they are not degradation products of cellular proteins but can be generated directly by the autonomous transcription and translation of short subgenic regions that we propose to name “peptons”. We discuss some consequences of the notion that antigenic peptides can be produced in the absence of synthesis of messenger RNA and protein from the corresponding genes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00395854
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  • 6
    Electronic Resource
    Electronic Resource
    Tum—mutation P35B generates the MHC-binding site of a new antigenic peptide (1993)
    Springer
    Immunogenetics 37 (1993), S. 135-138 
    Details
    ISSN: 1432-1211
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Immunogenic tumor cell variant P35 was obtained by mutagen treatment of mouse mastocytoma P815. It express a potent new antigen recognized by syngeneic cytolytic T lymphocytes (CTL). This antigen is the result of a point mutation in a gene that is expressed by most healthy cells. A decapeptide encoded by the region spanning the mutation sensitized P815 cells to the relevant CTL, whereas the homologous decapeptide corresponding to the normal sequence did not. Only the mutant decapeptide was capable of enhancing the expression of the Dd-presenting molecule at the cell surface, indicating that the mutation generates a motif which enables the antigenic peptide to bind to Dd.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00216837
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  • 7
    Electronic Resource
    Electronic Resource
    The nuclear Kluyveromyces lactis MRF1 gene encodes a mitochondrial class I peptide chain release factor that is important for cell viability (1996)
    Springer
    Current genetics 30 (1996), S. 19-28 
    Details
    ISSN: 1432-0983
    Keywords: Keywords Kluyveromyces lactis ; Mitochondrial release factor ; MRF1 ; Peptide chain termination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  We report the isolation and characterization of the Kluyveromyces lactis MRF1 gene encoding mitochondrial peptide chain release factor mRF-1. Over-expression of the KlMRF1 gene has a strong antisuppressive effect in a Saccharomyces cerevisiae mitochondrial nonsense suppressor strain. Inactivation of KlMRF1 results in a dual phenotype: most cells die after about 10–13 generations, while a small number of cells exceed this limit. We propose that the lethality is related to a loss of mitochondrial genome integrity. Surviving Klmrf1 cells are able to grow slowly on the non-fermentable substrate glycerol, indicating the existence of a second mitochondrial release factor activity. Our previous comparative analysis of class I release factors is refined by the incorporation of KlmRF-1 and ten recently identified prokaryotic release factor sequences.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002940050095
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  • 8
    Electronic Resource
    Electronic Resource
    Space-charge-limited currents in a synthetic semiconducting diamond (2000)
    Springer
    Semiconductors 34 (2000), S. 1116-1119 
    Details
    ISSN: 1063-7826
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The electrical properties of single crystals of synthetic semiconducting diamonds of p-and n-types with B and As impurities were studied. The method of space-charge-limited currents revealed As-related monoenergetic carrier traps and traps with exponential distribution of the density of states. The possibility of using the crystals of a synthetic semiconducting diamond in alpha-particle detectors and temperature-sensitive elements is demonstrated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.1317566
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  • 9
    Electronic Resource
    Electronic Resource
    Interspecies interaction based on transfer of a thioredoxin-like compound in anaerobic chitin-degrading mixed cultures (1989)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 62 (1989), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Fermentation of chitin by mixed cultures of the chitinolytic Clostridium sp. strain 9.1 and various non-chitinolytic bacteria proceeded up to eight times faster than in pure cultures. The addition of spent media of such mixed cultures also resulted in a marked stimulation of chitinolysis in pure cultures of strain 9.1. Pure cultures fermented chitin much faster if supplemented with either spent media or cell-free extracts of the non-chitinolytic bacteria. The compound responsible for this stimulation was thermostable (10 min at 85° C) and could not be removed by passage over Sephadex G-25, indicating a molecular weight of more than 1500. The heat stable enzyme thioredoxin (from Saccharomyces cerevisiae) was shown to stimulate the chitin fermentation in a similar manner. Alkylation of this enzyme reduced its stimulatory action significantly indicating its (di)thiol: disulfide interchanging activity.It is hypothesized that essential sulfhydryl groups in the chitinolytic system of strain 9.1 are reduced by thioredoxin and/or similar thiol: disulfide transhydrogenases present in the cell-free extracts and spent media, resulting in an acceleration of chitin hydrolysis and fermentation. This stimulation may thus be the result of a new type of interspecies interaction in anaerobic mixed cultures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1989.tb03390.x
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  • 10
    Electronic Resource
    Electronic Resource
    Chitin degradation by Clostridium sp. strain 9.1 in mixed cultures with saccharolytic and sulfate-reducing bacteria (1989)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 62 (1989), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract The fermentation of chitin was studied in pure and cocultures of the chitinolytic Clostridium strain 9.1 and various non-hydrolytic sugar-fermenting and sulfate-reducing bacteria. A 5- to 8-fold enhancement of the rate of chitin degradation was observed, which was not due to the alleviation of inhibition of the chitinolytic enzyme system by polymer hydrolysis products. This was concluded from the observation that rates of chitinolysis and fermentation were unaffected by the addition of N-acetylglucosamine (NAG) or NAG-oligomers to pure cultures of strain 9.1, and from the absence of an unequivocal relation between the ability of a secondary bacterium to consume potentially inhibitory hydrolysis products and its capacity to stimulate chitin degradation. The acceleration of chitin fermentation in the presence of sugar-fermenting bacteria was the result of a release by these secondary populations of growth factors essential to strain 9.1. These factors comprised a high molecular, thioredoxin-like compound responsible for enhanced chitinolytic activity [10], and various low molecular compounds necessary for optimal growth. The sulfate reducers (except Desulfovibrio sp. strain 20028) released primarily the high molecular growth factor in coculture with strain 9.1. NAG-fermenting bacteria consumed approximately 10% of the hydrolysis products, whereas species capable of utilizing both mono- and oligomeric sugars fermented at least 50% of the sugars produced by strain 9.1. Nevertheless, the rate of chitinolysis in these cocultures proceeded at very similar rates.The observed interactions between Clostridium sp. strain 9.1 and the secondary populations are discussed in relation to the results from studies on mixed culture fermentations of cellulosic substrates reported in the literature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1989.tb03693.x
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