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  • 1
    ISSN: 1600-0757
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The autoxidation of dopa to melanin in culture media causes toxicity to retinal pigment epithelial (RPE) cells and endothelial cells. The damage is specific to cell type and to the ambient oxygen concentration. To determine whether RPE cells influence the oxidation of dopa to media, we compared light absorbing dopa derivatives in the media exposed to cells with those found in the media incubated without cells. Dopa was extensively oxidized in the presence of RPE cells, and more light absorbing substances were generated with higher dopa and oxygen concentrations. However, an increase in ambient oxygen concentration decreased the quantity of several dopa derivatives which had been formed. The data provided evidence that RPE modulated dopa metabolism. Quinolic derivatives produced from a tyrosinase reaction and dopa-melanin formation moved the peak absorbance wavelength of dopa into the visible range. The spectrum between the dopa-derived compounds in the media has an absorbance at 240–275 nm and a maximum around 300 nm wth a shoulder near 375 nm. Gaussian analysis (peak separation) resolved these spectra into five components: a sharp band at 248 nm, a band at 295 nm, a large band at 359 nm, and two broad bands at 459 and 585 nm.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-2568
    Keywords: arteriovenous malformation ; pancreas ; duodenal ulcer ; color Doppler ultrasonography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We report the color Doppler ultrasonography features of arteriovenous malformation (AVM) of the pancreas, a very rare disease. The patient was a 52-year-old man with congenital AVM of the pancreas and a duodenal ulcer that had been resistant to medication. Endoscopic color Doppler ultrasonography (color Doppler EUS) revealed many abnormal color signals showing pulsatile wave form at the portion of the duodenal wall involving the duodenal ulcer. Extracorporeal color Doppler ultrasonography revealed a mosaic-like color signal, caused by turbulent flow, in the portal trunk. Angiography demonstrated a vascular network with extensive proliferation at the pancreatic head and early portal filling. It is possible that the pancreatic AVM had caused the duodenal ulcer. Color Doppler EUS can be a useful modality for detection of vessel abnormalities of the gastrointestinal tract.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1435-702X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract • Purpose: To determine the mechanisms of vitreous changes during ocular inflammation. • Methods: We investigated vitreous changes, with special emphasis on collagen, in an experimental model of ocular inflammation induced by intravitreal injection of endotoxin (Escherichia coli) in rabbits. • Results: Inflammation caused gel contraction and loss of elasticity, accompanied by release of a water-like liquid from the gel, and increases in the amount of insoluble material and highmolecular-weight components of vitreous collagen, presumably due to extensive cross-links of the collagen molecules. Those changes were partially inhibited by intravitreal injection of superoxide dismutase. • Conclusions: The crosslinks of vitreous collagen may promote vitreous gel contraction and release of a water-like liquid from the gel. Superoxide anion may play a role in this process.
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  • 4
    ISSN: 1435-702X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract To determine a molecular mechanism for posterior vitreous detachment and contraction of vitreous gel, the effects of serum components on bovine vitreous were systematically studied. Incubation of vitreous gel with calf serum caused a contraction of the gel accompanied by the release of a waterlike liquid. The low molecular weight fraction (M r 〈 10000) of serum was ineffective in this process, whereas incubation of the vitreous with the high molecular weight fraction resulted in changes in the gel structure similar to those caused by serum alone. Individually, transglutaminase (factor XIIIa) was found to be most effective in inducing gel contraction. The effect was more pronounced when transglutaminase was used with fibronectin. Since transglutaminase is known to promote collagen-collagen or collagen-fibronectin-collagen cross-links, the contraction of the vitreous in this case can be attributed to the formation of similar cross-links.
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  • 5
    ISSN: 1435-702X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract • Purpose: To understand the molecular events underlying disease-related vitreous gel contraction, the effect of serum components on collagen was investigated. • Methods: Bovine vitreous or dermal collagen was incubated with a mixture of transglutaminase (TG; factor XIIIa) and fibronectin (FN), and the biochemical changes of collagen were monitored by gel electrophoresis. In addition, serum-induced changes in the volume of the collagen gel were monitored. • Results: Gel electrophoresis revealed a new high-molecular-weight band (Mr 240 000) presumably due to intermolecular cross-links of collagen peptides and FN. The serum components also were shown to cause a significant decrease in the volume of the collagen gel. • Conclusion. Collagen gel contraction could be attributed to the collagen-FN-collagen cross-links catalyzed by TG.
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  • 6
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 26 (1987), S. 1413-1420 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Changes in conformation of hyaluronate and chondroitin sulfates following periodate oxidation were studied by CD. We monitored the progressive oxidation of these polymers by periodic acid at 4°C in pH 5.6 buffer. The negative CD band of hyaluronate at 208 nm decreased in intensity upon oxidation and changed its sign after 16 h of oxidation. In contrast, the 208-nm CD band of chondroitin sulfates decreased, but showed no change in sign even after 48 h of oxidation. A specific difference in solution conformation between hyaluronate and chondroitins may be responsible for the difference in oxidation-induced dichroic behavior. The results are discussed in terms of available x-ray diffraction analyses of these polymers.
    Additional Material: 2 Ill.
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  • 7
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The release rates of 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU), an anticancer drug, from various kinds of silicone and silicone-nylon implantable and refillable devices were investigated in vitro. The devices were made with different surface areas and wall thicknesses. The relation of the release rate at steady state to the surface area and the relation of the release rate per unit surface area to the wall thickness were determined. The relationship among the release rate, the surface area, and the wall thickness was analyzed using the multiple regression method, and is represented on a three-dimensional graph. The multiple regression equation predicts the release rate from the surface area and the wall thickness; the release rate can also be read from a nomogram that is presented.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 28 (1989), S. 1891-1902 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The progressive periodate oxidation of glycosaminoglycans (GAG), including hyaluronate (HA), chondroitins (CH) (chondroitin, chondroitin 4- and 6-sulfate), dermatan sulfate (DS), and keratan sulfate (KS), were monitored by CD and high performance liquid chromatography (HPLC) using a size-exclusion column. The rate of oxidation also was measured and calculated using first- and second-order kinetics, and the data appear to fit better with first-order kinetics. In both HA and CH, the n - π* amide band at 208 nm decreases in intensity upon oxidation, but in HA it becomes positive after 16 h of periodate treatment. In CH, the band disappears, and the π - π* amide band below 200 nm becomes optically active. Concomitantly, a second negative band near 290 nm appears for these two oxidized GAG. Oxidation causes a slight change in the CD of DS. It ordinarily displays a very weak n - π* band at 210 nm, but instead shows an intense π - π* amide band near 190 nm. CD of KS remains unaffected by periodate. Kinetic studies, however, show a higher oxidation rate for DS than HA and CH. With the exception of KS, all other oxidized polymers shown an apparent decrease in molecular weight (higher peak retention time) in HPLC analysis. Both CD and HPLC results have been attributed to a major conformational cahange of HA and CH, and a minor one for DS. The ease and extent of periodate oxidation as well as the changes in molecular properties following periodate treatmenat are critically dependent on the changes in molecular properties following periodate treatment are critically dependent on the configuration of the individual GAG rather than the oxidation rate. There is a distinct difference in the conformational change between HA and CH, as manifested by their dichroic behavior, that was attributed to the equatorial disposition of C-4 hydroxyl group in HA and axial disposition CH.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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