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  • Key wordsNeisseria meningitidis  (3)
  • Chlorophylls  (2)
  • Alkali-Resistenz  (1)
  • 1
    ISSN: 1432-2048
    Schlagwort(e): Carotenoids ; Chlorophylls ; Herbicides ; Phytochrome ; Plastid development ; Ribulosebisphosphate carboxylase
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Treatment of the mustard (Sinapis alba L.) seedling with the herbicide SAN 9789 inhibits synthesis of colored carotenoids and interferes with the formation of plastid membrane lipids without affecting growth and morphogenesis significantly. In farred light, which is hardly absorbed by chlorophyll, development of plastid ultrastructure, synthesis of ribulosebisphosphate carboxylase and synthesis of chlorophyll are not affected by SAN 9789. It is concluded that normal phytochrome actions on plastid structural development, protein and chlorophyll syntheses are not affected by the absence of carotenoids provided that there is no significant light absorption in chlorophyll. The findings show that the inhibition of synthesis of one set of plastid membrane components (the carotenoids) does not stop synthesis of other components such as chlorophyll and does not halt membrane assembly. Supplementary experiments with the closely related compound SAN 9785, which affects the amount and composition of plastid lipids but not carotenoid and chlorophyll syntheses, suggest that the effect of the herbicide SAN 9789 is due exclusively to its inhibition of synthesis of colored carotenoids. In the presence of SAN 9789 white or red light at high fluence rate causes photodestruction of chlorophyll and ribulosebisphosphate carboxylase and photodecomposition of thylakoids. These effects are interpreted as resulting exclusively from the self-photooxidation and photosensitizing action of chlorophyll once the protection by carotenoids of chlorophyll against self- and sensitized photooxidation is lost.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Planta 148 (1980), S. 279-286 
    ISSN: 1432-2048
    Schlagwort(e): Carotenoids ; Chlorophylls ; Light control ; Phytochrome ; Plastid development ; Sinapis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Carotenoid accumulation in the cotyledons of the mustard seedling (Sinapis alba L.) is controlled by light. Besides the stimulatory function of phytochrome in carotenogenesis the experiments reveal the significance of chlorophyll accumulation for the accumulation of larger amounts of acrotenoids. A specific blue light effect was not found. The data suggest that light exerts its control over carotenoid biogenesis through two separate mechanisms: A phytochrome regulation of enzyme levels before a postulated pool of free carotenoids, and a regulation by chlorophyll draining the pool by complex-formation.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    ISSN: 1432-1831
    Schlagwort(e): Key wordsNeisseria meningitidis ; Infant rat ; Sialic acid ; Capsule ; Lipooligosaccharide sialylation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract We investigated the contribution of the polysialic acid capsule and of terminal lipooligosaccharide (LOS) sialylation to the pathogenicity of Neisseria meningitidis in vivo using a set of defined isogenic mutants of the N. meningitidis strain B 1940 deficient in either capsule synthesis or LOS sialylation. Furthermore a spontaneous capsule-deficient variant was investigated, which was capable of switching on the capsule synthesis at a frequency of 3×10–3 in vitro. Infection of infant rats with the wild-type strain revealed a high potential to cause bacteremia. This potential was attenuated in the capsule-phase variable mutant (LOS sialylation+). However, using a mutant irreversibly deficient in capsule synthesis, but expressing a sialylated LOS, bacteremia could only be achieved using 106 times higher numbers of bacteria when compared to the wild-type. The unencapsulated bacteria were located extracellularly upon examination of blood smears, suggesting that defense mechanisms, i. e. phagocytosis, directed against unencapsulated meningococci were exhausted using very high infecting doses. Interestingly, when infant rats were infected with encapsulated meningococci which were unable to sialylate the LOS, bacteremia could never be achieved, even with an infective dose as high as 108 colony forming units (CFU). Despite the presence of capsular polysaccharide this mutant was phagocytosed by peritoneal phagocytes, as was the unencapsulated, LOS-sialylated mutant, suggesting that the inability to cause bacteremia was due to a higher susceptibility to the action of the complement system, which is virtually unsaturable. We conclude that in the infant rat model of meningococcal infection both forms of sialic acid on the bacterial cell surface are indispensable for systemic survival.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Archives of dermatological research 272 (1982), S. 269-278 
    ISSN: 1432-069X
    Schlagwort(e): Light sensitivity ; Cutaneous irritability ; Chamber testing ; DMSO test ; Alkali resistance ; Skin type ; Duhring chambers ; Lichtempfindlichkeit ; Hautirritabilität ; Kammer-Test ; DMSO-Test ; Alkali-Resistenz ; Haut-Typ ; Duhring-Kammern
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Das Ziel dieser Studie war die Untersuchung des Zusammenhanges zwischen der Sonnenempfindlichkeit menschlicher Haut und deren Reaktion auf chemische Irritantien. 44 weiße Probanden mit normaler Rückenhaut wurden getestet. Die minimale Erythemdosis (MED) wurde mit dem Sonnenbrandspektrum einer Quecksilberhochdrucklampe bestimmt. Die Hautirritabilität wurde quantifiziert durch eine Serie von sieben gut bekannten chemischen Irritantien von unterschiedlicher chemischer Struktur, Löslichkeit und Konzentration. Die Reaktion wurde entweder als Schwellenwert der Expositionszeit ausgedrückt (Ammoniaklösung, Natronlauge) oder nach einer Standardexposition bewertet hinsichtlich der Intensität der urticariellen Reaktion (Dimethylsulfoxid) bzw. des Erythems (Natriumlaurylsulfat, Quaternium 1, Krotonöl, Kerosin). Es wurde eine signifikante Korrelation zwischen der MED und allen sieben chemischen Irritantien festgestellt. Die Beziehung war enger für wasserlösliche Irritantien als für lipidlösliche. Trotz starker individueller Abweichungen wird die Bestimmung der MED empfohlen für die Erkennung von empfindlicher Haut. Die Hauttypisierung aufgrund äußerer Kriterien und der Sonnenbrandvorgeschichte erwies sich als weniger zuverlässig.
    Notizen: Summary This investigation examines the relationship between the sun sensitivity of human skin and its response to chemical irritants. Forty-four Caucasoid subjects with normal back skin were studied. The minimal erythema dose (MED) was determined with the sunburning spectrum of a high-pressure mercury lamp. Cutaneous irritability was quantified using a series of seven irritants of different chemical structure, solubility, and concentrations. The response was either expressed as a threshold value of exposure time (ammonium hydroxide, sodium hydroxide) or was graded after a standard exposure in intensity of whealing (dimethyl sulphoxide) or erythema (sodium lauryl sulphate, quaternium 1, croton oil, kerosene). A significant correlation between the MED and the response to all seven primary irritants was found. The relationship was better for water-soluble irritants than for lipid-soluble ones. Despite marked individual variations the determination of the MED is suggested as a valuable tool in identifying hyperirritable skin. Skin typing based on complexion and sunburn history proved to be less reliable.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Molecular genetics and genomics 259 (1998), S. 363-371 
    ISSN: 1617-4623
    Schlagwort(e): Key wordsNeisseria meningitidis ; Shuttle mutagenesis ; Signature-tagged mutagenesis ; Transformation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Shuttle mutagenesis using signature-tagged transposons was employed to generate a library of individually tagged mutants of the Neisseria meningitidis strain B1940, which belongs to serogroup B. The use of tagged transposons allowed us to monitor for enrichment for single mutants during the process of shuttle mutagenesis, by amplification of the tags and subsequent sequence determination. Enrichment of a single clone occurred during the transformation of the meningococci with transposon-containing plasmid DNA. Sequence determination around the site of transposon insertion revealed that the transposon had mutagenized a previously unknown locus, which was designated hrtA (high rate of transformation). hrtA-mediated transformation was independent of TnMax5 and tag sequences, and it most probably involved recombination events. The hrtA locus is restricted to meningococci and gonococci and is present in few apathogenic neisserial species. Chromosomal mapping of hrtA and six further hrt sites revealed a random distribution of highly transforming DNA fragments on the meningococcal chromosome. In conclusion, our data demonstrate that shuttle mutagenesis of naturally competent bacteria using signature-tagged transposons allows the isolation of chromosomal DNA fragments, which exhibit a high transformation efficiency, and which, therefore, are likely to be involved in horizontal gene transfer.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 6
    ISSN: 1617-4623
    Schlagwort(e): Key wordsNeisseria meningitidis ; Capsule synthesis ; Polysialyltransferase
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The serogroups B, C, W135 and Y of Neisseria meningitidis express chemically and immunologically distinct capsular polysaccharides containing sialic acid. In the case of serogroup B meningococci sialic acid is synthesized by the gene products of a locus termed sia and forms the homopolymers of the capsule. The organization of the genes required for sialic acid synthesis in serogroups B, C, W135 and Y was elucidated by PCR technology. Cloning, sequencing and the functional expression of the polysialyltransferase (PST) genes of serogroups B and C demonstrated that the difference in capsule composition derives from the presence of related, but distinct siaD genes coding for PSTs. Analysis of meningococci of serogroups W135 and Y expressing sialic acid heteropolymers revealed that the DNA sequences of the corresponding genetic loci in these serogroups were highly homologous, but differed completely from the siaD genes of serogroups B and C. This finding suggests that enzymes unrelated to those of serogroups B and C are required for the formation of sialic acid heteropolymers characteristic of the capsules of serogroups W135 and Y.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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