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  • 1
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 29 (1977), S. 0 
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Abstract— —The uptake of the glucose analogue 2-deoxy-d-glucose by rat brain cortex slices was studied in order to compare the rate of membrane transport with the rate of phosphorylation in the concentration range 5–12 mM-glucose plus 0.5–15 mM-2-deoxy-glucose. The comparison was carried out by fitting a model of the brain slice to uptake data and by determination of 2-deoxy-glucose and 2-deoxy-glucose-6-phosphate by ion exchange chromatography.The rate of membrane transport exceeded the rate of phosphorylation by at least one order of magnitude. The membrane transport was so rapid that the extracellular diffusion became rate limiting for the uptake. The membrane transport could therefore only be determined as a minimum value and it was not possible to determine unidirectional flux across the cell membranes (initial rate). Accordingly, characterization of the membrane tranport with respect to maximal transport rate and affinity was not possible. The phosphorylation reaction, however, was so slow that it was accessible for exact determination and only the phosphorylation reaction was responsible for the fact that the cellular uptake of 2-deoxy-glucose was of the Michaelis-Menten type, thus emphasizing the importance of dissociation between membrane transport and metabolism when transport is studied of a substance which can undergo metabolism.The data indicate that glucose transport across glial and neuronal membranes is not rate limiting for glucose metabolism of brain tissue in vitro.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 27 (1976), S. 0 
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Abstract— In slice preparations the exchange of dissolved substances between cells and incubation medium is delayed by diffusion through the extracellular space. The delay may seriously interfere with the study of membrane transport in terms of unidirectional fluxes across the cell membranes. A three-compartment serial model has been developed to describe exchange between slice and incubation medium. By aid of this model it is shown that the diffusion delay prevents determination of unidirectional fluxes for the two non-metabolizable glucose analogues 3-O-methylglucose and α-methyl-glucosidc. The membrane transport of the slowly transported α-methylglucoside can however be examined by aid of the model whereas the transport of 3-O-methylglucose is so rapid that it can not be examined with respect to Vmax Km and Kr. An attempt to determine these parameters will result in falsely large values which reflect extracellular diffusion and not membrane transport.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 27 (1976), S. 0 
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Abstract— The glucose analogues 3-O-methyl-D-glucose and α-methyl-D-glucoside were not metabolized in brain tissue.The uptake of these two sugars into the intracellular compartment of brain cortex slices was investigated using media with normal and low Na+ concentration (replacement of all NaCl with choline Cl). The cellular transport was not Na+-dependent. The transport mechanism clearly distinguished between the two sugars in both normal and low Na+ media.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Amsterdam : Elsevier
    Bulletin of Mathematical Biology 45 (1983), S. 749-758 
    ISSN: 0092-8240
    Quelle: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Thema: Biologie , Mathematik
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Amsterdam : Elsevier
    Bulletin of Mathematical Biology 45 (1983), S. 749-758 
    ISSN: 0092-8240
    Quelle: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Thema: Biologie , Mathematik
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 6
    ISSN: 1432-0428
    Schlagwort(e): Arterial blood pressure ; antihypertensive treatment ; diabetic retinopathy ; diabetic nephropathy ; Type 1 (insulin-dependent) diabetes ; vitreous fluorometry
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The effect of antihypertensive treatment on blood-retinal barrier leakage of fluorescein in background retinopathy was studied in nine hypertensive Type 1 (insulin-dependent) diabetic patients suffering from nephropathy. The patients were investigated before and after 7 (3 to 13) months of treatment with captopril (n=8; 25 to 100 mg daily) and a diuretic, either frusemide (n=4; 80 to 200 mg daily) or bendrofluazide (n=2; 2.5 mg daily). Retinal function was assessed by fundus photography, fluorescein angiography, vitreous fluorometry, and renal function by glomerular filtration rate, and albuminuria. The antihypertensive treatment induced a significant reduction (p〈0.05) in: blood pressure from 152/97±14/8 mmHg to 134/82±11/6 mmHg; blood-retinal barrier leakage of fluorescein from 2.4 ±1.1 to 1.4±0.5·10−7 cm/second; albuminuria from 1391 (range: 168–4852) μg/min to 793 (range: 35–2081) ug/min. Glomerular filtration rate declined from 88±15 to 78±23 ml·min−1·1.73 m2 (0.05〈p〈0.10). The metabolic control of the patients as reflected by their blood glucose and HbA1c levels remained stable during the study. Our study suggests that systemic blood pressure elevation contributes to the abnormal blood-retinal barrier permeability to fluorescein characteristically found in diabetic background retinopathy and that this abnormality can be reversed during antihypertensive treatment.
    Materialart: Digitale Medien
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  • 7
    Digitale Medien
    Digitale Medien
    Springer
    Diabetologia 39 (1996), S. 1524-1527 
    ISSN: 1432-0428
    Schlagwort(e): Keywords Ocular fluorescence ; screening ; fluorometry ; lens ; cornea ; NIDDM ; hyperglycaemia ; non-enzymatic glycosylation.
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Lens and cornea autofluorescence has been shown to be increased in patients with insulin-dependent diabetes mellitus and to be positively correlated to glycaemic control and duration of diabetes. We have studied lens and cornea autofluorescence at the clinical onset of non-insulin-dependent diabetes mellitus (NIDDM), in comparison with age-matched subjects with normal glucose tolerance. Fourteen subjects with NIDDM diagnosed less than 6 months prior to the examination were characterised by ocular fluorometry, glycosylated hemoglobin A1c, plasma lipid status, arterial blood pressure, and an oral glucose tolerance test (OGTT). Eleven age- and gender-matched healthy subjects without a family history of diabetes and with a normal glucose tolerance underwent the same examinations. In 11 of the 14 diabetic patients lens autofluorescence was increased to levels higher than the age-related mean + 2 SD of healthy subjects. For the entire study population, control and diabetic subjects, lens fluorescence was positively correlated with HbA1c (p 〈 0.0001, r = 0.73), fasting plasma glucose (p = 0.002, r = 0.60) and the plasma glucose level 2 h after an OGTT (p = 0.004, r = 0.55). Cornea autofluorescence was also significantly increased in the group of newly diagnosed NIDDM patients, but only 9 patients had values above the mean + 2 SD of the healthy subjects. NIDDM could be detected by ocular fluorometry with a sensitivity of 79 % and a specificity of 100 %. We conclude that lens and cornea autofluorescence is abnormally increased in the majority of patients with newly diagnosed NIDDM. The sensitivity and specificity of the method indicate that lens fluorometry may potentially be useful for screening for undiagnosed NIDDM in the general population. Additionally, we propose that the method may be a clinically useful indicator of cumulative glycaemia and risk of development of secondary complications in patients with diabetes. [Diabetologia (1996) 39: 1524–1527]
    Materialart: Digitale Medien
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  • 8
    Digitale Medien
    Digitale Medien
    Springer
    Experimental brain research 11 (1970), S. 373-375 
    ISSN: 1432-1106
    Schlagwort(e): Cerebral cortex in vitro ; Slice holder
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary A new type of tissue holder is described in which the slices are freely floating. Rat brain-cortex slices incubated in this holder show a potassium concentration of 70.4 μmoles/g final wet wt. after incubation and transfer for 1 hr.
    Materialart: Digitale Medien
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  • 9
    Digitale Medien
    Digitale Medien
    Springer
    Experimental brain research 28 (1977), S. 37-50 
    ISSN: 1432-1106
    Schlagwort(e): Brain cortex slices ; Membrane transport of macromolecules ; Inulin space
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Light and electron microscope autoradiography indicated that 3H-labelled inulin was taken up by neurons and glia cells of rat brain cortex in vitro. The mechanism, by which inulin passed the cell membranes, was studied by comparing the transport of inulin (molecular weight 5000) with the transport of dextran (molecular weight 75000). The half-time for the cellular in- and efflux for the two molecules was the same although their diffusion coefficients differed by a factor of 4–5. The transport mechanism was therefore interpreted as bulk transport, and vesicular transport is suggested. Efflux of inulin from brain cortex exposed to inulin in vivo indicated that cellular uptake of inulin also occured in vivo.
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    Springer
    Experimental brain research 21 (1974), S. 299-314 
    ISSN: 1432-1106
    Schlagwort(e): Brain cortex slices ; Ultrastructure ; Fluid spaces ; Swelling
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary A comparison was made between morphological and biochemical estimates of extracellular and intracellular fluid spaces in rat brain cortex slices incubated under different conditions. By light microscopy the periphery of the slices was found to be more swollen than the center; this regional difference was verified biochemically in unfixed tissue. The electronmicroscopic evaluation of intra- and extracellular fluid spaces was accordingly based upon findings in a preselected area. Due to intracellular penetration of inulin in rat brain cortex slices the biochemically, determined extracellular and intracellular spaces were obtained by compartmental analysis of the inulin space. The concordance between the biochemical and the morphological findings was good: Both methods showed that the extracellular space increased during the incubation to a considerable magnitude after one hr. and that this extracellular space was reduced by excess potassium, glutamate, anoxia or incubation at 0°. Under the same conditions the biochemically determined intracellular space was increased. This cellular swelling was confirmed morphologically and found to comprise mainly glia cells after exposure to excess potassium, predominantly neurons after incubation at 0° and both cell types after anoxia or addition of glutamate.
    Materialart: Digitale Medien
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