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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 101 (1997), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Metabolic responses to water deficit that lead to an accumulation of cyclitols, have been examined in rice bean (Vigna umbellata [Thunb.] Ohwi et Ohashi). Imposition of drought stress by withholding water from the soil for 9 days led to an accumulation of D-ononitol (lD-4-O-methyl-myo-inositol) which was most pronounced in leaves (from 33 to 88 umol g−1 dry mass). However, the activity of the enzyme myo-inositol 6-O-methyltransferase (m6OMT, EC 2.1.1.X), which catalyzes the synthesis of ononitol from myo-inositol and S-adenosyl-L-methionine (AdoMet), increased in stems but not in leaves during the drought stress experiment. Detailed analysis of different plant parts revealed that the accumulation of ononitol in leaves was linearly related to stem m6OMT activity during drought stress, indicating that m6OMT may control the in vivo biosynthetic rate of this cyclitol. The availability of myo-inositol, required for enhanced rates of ononitol synthesis by m6OMT, increased during the stress experiment, while the capacity to synthezise AdoMet by S-adenosyl-L-methionine synthetase (SMS, EC 2.5.1.6) decreased. However, the high capacity for degradation of S-adenosyl-L-homocysteine (AdoHcy; a potent competitive inhibitor of m6OMT) by the enzyme S-adenosyl-L-homocysteine hydrolase (SHH, EC 3.3.1.1) provided favourable conditions for ononitol biosynthesis during the whole stress treatment.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1433-0423
    Keywords: Schlüsselwörter Hornhaut ; Hornhautepithel ; Hornhautstroma ; Chloroquin ; Konfokale Mikroskopie ; Key words Cornea ; Corneal epithelium ; Corneal stroma ; Chloroquine ; Confocal microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Background: Chloroquine keratopathy is known as a disease with epithelial deposits in the cornea. The appearance of corneal changes does not seem to be related to dose and duration of treatment. Chloroquine accumulates in lysosomes. The purpose of this study was to investigate microscopic changes of corneal morphology in patients treated with chloroquine in vivo. Patients and methods: Using the confocal slit scanning microscope, we examined 16 patients during chloroquine treatment and 4 patients after treatment. The patients' age was between 33 and 75 years. They were treated with chloroquine over a minimum period of 2 months up to a maximum period of 10 years. Results: In 12 of 20 patients, corneal changes were visible. An atypical inverse reflectivity of basal cells in comparison to healthy volunteers was found. There were also deposits in the wing cell layer. We saw a higher density in the anterior stroma before the appearance of epithelial opacities, as well as in cases of keratopathy on slit-lamp examination and also after the cessation of chloroquine treatment. In one patient with long-term therapy, there were atypically shaped and branched nerves in the anterior stroma. Conclusions: Using confocal microscopy, it was in some cases possible to detect changes in the corneal morphology before these changes could be detected by slit-lamp examination. As a result of this study we found that chloroquine keratopathy is not limited to the epithelium but can affect the anterior stroma and possibly neural structures.
    Notes: Hintergrund: Die Chloroquinkeratopathie ist als eine reversible epitheliale Hornhauteinlagerung bekannt, die ohne direkten Zusammenhang mit der Dauer und Dosierung der Behandlung auftritt. Dabei kommt es zu einer Anreicherung von Chloroquin in den Lysosomen der Zellen. Ziel unserer Untersuchungen war es, mikroskopische Veränderungen der Hornhaut bei Patienten infolge einer Chloroquintherapie in vivo zu erfassen. Patienten und Methode: Wir untersuchten mit dem konfokalen Spaltscanningmikroskop 16 Patienten während und 4 Patienten nach einer Chloroquintherapie. Die Patienten waren zwischen 33 und 75 Jahre alt und wurden über einen Zeitraum von 2 Monaten bis zu 10 Jahren mit Chloroquin therapiert. Ergebnisse: Bei 12 der untersuchten 20 Patienten fanden wir Hornhautveränderungen. Die Basalzellen zeigten ein inverses Reflektivitätsverhalten. Desweiteren konnten Ablagerungen in der Intermediärzellschicht nachgewiesen werden. Verdichtungen im vorderen Stroma waren einerseits vor dem Auftreten epithelialer Veränderungen, andererseits beim Vorhandensein einer Keratopathie und auch noch nach Absetzen der Therapie darstellbar. Atypisch geformte und verzweigte Nerven im vorderen Stroma konnten bei 1 Patientin unter langjähriger Chloroquintherapie gefunden werden. Schlußfolgerungen: Es waren in einigen Fällen spaltlampenmikroskopisch noch nicht sichtbare Hornhautveränderungen mit der konfokalen Mikroskopie zu erfassen. Obwohl sich aus den Untersuchungen klinisch keine Konsequenzen ergeben, können aber mikromorphologische Veränderungen dieser Arzneimittelnebenwirkung aufgezeigt und lokalisiert werden. Die Chloroquinkeratopathie ist nach den vorliegenden Ergebnissen nicht auf das Epithel beschränkt, sondern kann auch das vordere Stroma und möglicherweise neurale Strukturen einbeziehen.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1433-0423
    Keywords: Schlüsselwörter In-vivo-Hornhautmikroskopie ; Konfokale Mikroskopie ; Hornhautinnervation ; Menschliche Hornhaut ; Keratoplastik ; Key words In vivo corneal microscopy ; Confocal microscopy ; Corneal innervation ; Human cornea ; Keratoplasty
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: To date, descriptions of the structure of corneal innervation have only been possible on the basis of histological techniques. Confocal microscopy represents a new method for the structural examination of the cornea in vivo. Through our examinations we first defined the control group and then proceeded to record the reinnervation of donor tissue after perforating keratoplasty. We used the confocal slit-scanning video-microscope Microphthal® to examine 40 corneas from 20 normal volunteers, 15 donor corneas and 5 eyes after enucleation for ocular tumors. These results were compared to our findings from postoperative checks on 14 patients after perforating keratoplasty (from 1 month to 2 years). With this system we were able to see nerves in the middle and in the superficial stroma. The course of these nerves can be followed, as well as their branching in the subepithelial plexus. Nerve fibers from superficial stromal nerves penetrate Bowman's membrane and create the basal epithelial plexus in the region of the basal epithelium. Seven months after perforating keratoplasty the first stromal nerves could be seen in the central corneal area. The first central reinnervation in the region of Bowman's membrane as well as in the basal epithelium was not detected until 15 months after operation. With confocal microscopy we have the potential to study the morphology of corneal innervation in vivo and in fresh donor tissue. For the first time it is possible to perform non-invasive morphological studies of reinnervation of the human cornea after surgical treatment.
    Notes: Aussagen über die Struktur der Hornhautinnervation waren bisher nur mit Hilfe histologischer Techniken möglich. Die konfokale Mikroskopie stellt eine neue Methode für strukturelle Untersuchungen der Hornhaut in vivo dar. Anliegen unserer Untersuchung war die Erfassung von Normalbefunden und davon ausgehend die Untersuchung der Reinnervation des Spendergewebes nach perforierender Keratoplastik. Wir verwendeten das konfokale Spalt-Scanning-Video-Mikroskop Microphthal® und untersuchten 40 Hornhäute von 20 Normalprobanden, 15 Spenderhornhäute sowie 5 wegen intraokularer Tumoren enukleierte Augen. Vergleichend wurden 14 Patienten nach perforierender Keratoplastik untersucht (1 Monat bis 2 Jahre postoperativ). Mit dem eingesetzten System gelingt bei Normalprobanden sowie an Spenderbulbi die Darstellung von Nerven in mittleren und oberflächlichen Stromaanteilen. Diese können in ihrem Verlauf sowie ihrer Verzweigung im subepithelialen Plexus verfolgt werden. Von Nerven des oberen Stromas ausgehende Äste penetrieren senkrecht oder schräg die Bowman-Membran und bilden im Bereich des basalen Epithels den basalen epithelialen Plexus. Nach perforierender Keratoplastik waren im zentralen Transplantat 7 Monate postoperativ vereinzelte stromale Nerven nachweisbar. Eine beginnende Reinnervation des basalen Epithels fand sich im zentralen Transplantatanteil 15 Monate postoperativ. Die konfokale Mikroskopie ermöglicht die Darstellung der Nerven der menschlichen Hornhaut einschließlich ihrer Aufzweigungen und Plexusbildungen in vivo ebenso wie in frischem Spendergewebe. Mit diesem Verfahren ist erstmals eine morphologische Erfassung der Reinnervation der menschlichen Hornhaut in ihrer dreidimensionalen Struktur nach chirurgischen Eingriffen möglich.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-2285
    Keywords: Parasitic angiosperm ; Succulence ; Cations ; Organic osmolytes ; Cyclitols
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The inorganic ion and organic solute composition of Tapinanthus oleifolius (Loranthaceae) and Viscum rotundifolium (Viscaceae) growing on various host trees in Namibia were investigated. Organic osmolytes accounted for 22.8–45.1% of the total solutes determined in leaves of the mistletoes parasitizing Acacia nebrownii, Catophractes alexandri, Grewia flava and Ziziphus mucronata. On other hosts (Acacia karroo, Euphorbia virosa, Salvadora persica and Tamarix usneoides) T. oleifolius showed distinct succulence with increasing leaf age, with leaves more than 3 mm thick on E. virosa. In the more succulent leaves (〉 1.1 kg H2O m−2 leaf area) organic solutes were only of minor importance. Water content per leaf area was significantly correlated with chloride content per leaf area, suggesting that succulence served as a means to keep ion concentration at a physiological tolerable level. At whole plant levels 93.7% of the total sodium of the mistletoe bush was located in leaves thicker than 1 mm for T. oleifolius parasitizing Tamarix usneoides. This pronounced sequestration of sodium in older leaves as well as the high variability of the K/Na ratio in various parts of the parasite-host system point to highly selective ion distribution processes in this association.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-2048
    Keywords: Cyclitol biosynthesis ; myo-Inositol 6-O-methyltransferase ; Ononitol ; Vigna
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The cyclitol 1d-4-O-methyl-myo-inositol (d-ononitol) is accumulated in certain legumes in response to abiotic stresses. S-Adenosyl-l-methionine:myo-inositol 6-O-methyltransferase (m6OMT), the enzyme which catalyses the synthesis of d-ononitol, was extracted from stems of Vigna umbellata Ohwi et Ohashi and purified to apparent homogeneity by a combination of conventional chromatographic techniques and by affinity chromatography on immobilized S-adenosyl-l-homocysteine (SAH). The purified m6OMT was photoaffinity labelled with S-adenosyl-l-[14C-methyl]methionine. The native molecular weight was determined to be 106 kDa, with a subunit molecular weight of 40 kDa. Substrate-saturation kinetics of m6OMT for myo-inositol and S-adenosyl-l-methionine (SAM) were Michaelis-Menten type with K m values of 2.92 mM and 63 μM, respectively. The SAH competitively inhibited the enzyme with respect to SAM (K i of 1.63 μM). The enzyme did not require divalent cations for activity, but was strongly inhibited by Mn2+, Zn2+ and Cu2+ and sulfhydryl group inhibitors. The purified m6OMT was found to be highly specific for the 6-hydroxyl group of myo-inositol and showed no activity on other naturally occurring isomeric inositols and inositol O-methyl-ethers. Neither d-ononitol, nor d-3-O-methyl-chiro-inositol, d-1-O-methyl-muco-inositol or d-chiro-inositol (end products of the biosynthetic pathway in which m6OMT catalyses the first step), inhibited the activity of the enzyme.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-2048
    Keywords: Key words: Carbohydrate metabolism ; CO2 exchange ; Crassulacean acid metabolism (elevated CO2) ; Kalanchoë (elevated CO2) ; Organic acid metabolism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract.  Kalanchoë pinnata (Lam.) Pers. (Crassulaceae), a succulent-leaved crassulacean-acid-metabolism plant, was grown in open-top chambers at ambient and elevated (two times ambient) CO2 concentrations under natural conditions at the Smithsonian Tropical Research Institute, Republic of Panama. Nocturnal increase in titratable acidity and nocturnal carbon gain were linearly related, increased with leaf age, and were unaffected by CO2 treatments. However, under elevated CO2, dry matter accumulation increased by 42–51%. Thus, the increased growth at elevated CO2 was attributable entirely to increased net CO2 uptake during daytime in the light. Malic acid was the major organic acid accumulated overnight. Nocturnal malate accumulation exceeded nocturnal citrate accumulation by six-to eightfold at both CO2 concentrations. Basal (predawn) starch levels were higher in leaves of plants grown at elevated CO2 but diurnal fluctuations of starch were of similar magnitude under both ambient and elevated CO2. In both treatments, nocturnal starch degradation accounted for between 78 and 89% of the nocturnal accumulation of malate and citrate. Glucose, fructose, and sucrose were not found to exhibit marked day-night fluctuations.
    Type of Medium: Electronic Resource
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