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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Calcified tissue international 56 (1995), S. 118-122 
    ISSN: 1432-0827
    Schlagwort(e): Osteogenesis imperfecta ; Mineral ; Composition ; Microanalysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Abstract A semiquantitative electron probe X-ray microan-alytical (XRMA) technique, in conjunction with transmission electron microscopy, was used to compare the calcium to phosphorus (Ca/P) molar ratios in calcium phosphate standards of known composition, in normal bone and in bone from patients with osteogenesis imperfecta (OI). Using a modified routine processing and resin embedding schedule, the measured Ca/P molar ratio of calcium phosphates standards of known composition were found to correlate well with the Ca/P molar ratio based on their respective chemical formulae. This technique was then used to compare the Ca/P molar ratio in normal human bone and in OI bone. The Ca/P ratio values for normal bone (Ca/P=1.631) correlated well with those for chemically prepared hydroxyapatite (Ca/P=1.602), but in bone from OI patients, the Ca/P molar ratio was significantly lower (Ca/P=1.488). This study has shown that there is a lower Ca/P molar ratio in OI bone compared with normal, matched bone. This suggests that the mineral deviates from the carbanoapatite usually found in bone. Isomorphous substitutions in the carbanoapatite lattice could account for this although this study has neither proved nor disproved this. The altered bone mineral is an-other factor that could contribute to the increased fracture rate observed in OI.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    ISSN: 1432-0428
    Schlagwort(e): Key words Diabetic retinopathy ; rat model ; aminoguanidine ; glycation ; retinal basement membrane.
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary We have previously shown that long-term administration of aminoguanidine, an inhibitor of advanced glycosylation product formation, reduces the extent of experimental diabetic retinopathy in the rat by 85 %. In order to determine whether the residual retinopathy that developed despite aminoguanidine was attributable to advanced glycation endproduct formation, a time-course study was performed in three different groups of male Wistar rats: non-diabetic controls (NC), streptozotocin-diabetic controls (DC) and streptozotocin-diabetic rats treated with aminoguanidine HCL, 50 mg/100 ml drinking water (D-AG). Eyes were obtained at 24, 32, 44 and 56 weeks of diabetes/treatment duration and morphologic evaluation was done on retinal digest preparations. At 56 weeks, retinal basement membrane thickness was additionally measured. After 24 weeks of diabetes, the number of acellular capillaries was significantly elevated in DC (44.6 ± 5.7/mm2 of retinal area, NC 19.6 ± 4.9; p 〈 0.001) and increased continuously over time (DC 56 weeks 87.4 ± 15.1; p 〈 0.001 vs DC 24 weeks). In contrast, acellular capillaries in D-AG increased over the first 24 weeks and then remained constant for the rest of the study (D-AG 24 weeks 35.7 ± 5.18; p 〈 0.01 vs NC 24 weeks and NS vs DC 24 weeks; D-AG 56 weeks 42.0 ± 6.20; p NS vs D-AG 24 weeks). Diabetes-associated pericyte loss (DC 24 weeks 2310 ± 170/mm2 of capillary area; NC 24 weeks 3120 ± 190; p 〈 0.001; DC 56 weeks 1570 ± 230; NC 56 weeks 2960 ± 50; p 〈 0.001) was significantly prevented by aminoguanidine after diabetic-like changes over the initial 24 weeks (D-AG 24 weeks 2450 ± 75; p NS vs DC 24 weeks; D-AG 56 weeks 2350 ± 90; p 〈 0.001 vs DC 56 weeks). At 56 weeks, aminoguanidine treatment was associated with a 67.4 % reduction in retinal basement membrane thickening. This time-course study demonstrates that aminoguanidine prevents the progression of experimental diabetic retinopathy, and suggests that non AG-inhibitable mechanisms are involved in the initial phase of diabetic retinopathy. [Diabetologia (1995) 38: 269–273]
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    ISSN: 1432-0428
    Schlagwort(e): Diabetic retinopathy ; rat model ; aminoguanidine ; glycation ; retinal basement membrane
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary We have previously shown that long-term administration of aminoguanidine, an inhibitor of advanced glycosylation product formation, reduces the extent of experimental diabetic retinopathy in the rat by 85%. In order to determine whether the residual retinopathy that developed despite aminoguanidine was attributable to advanced glycation endproduct formation, a time-course study was performed in three different groups of male Wistar rats: non-diabetic controls (NC), streptozotocin-diabetic controls (DC) and streptozotocin-diabetic rats treated with aminoguanidine HCL, 50 mg/100 ml drinking water (D-AG). Eyes were obtained at 24, 32, 44 and 56 weeks of diabetes/treatment duration and morphologic evaluation was done on retinal digest preparations. At 56 weeks, retinal basement membrane thickness was additionally measured. After 24 weeks of diabetes, the number of acellular capillaries was significantly elevated in DC (44.6±5.7/mm2 of retinal area, NC 19.6±4.9; p〈0.001) and increased continuously over time (DC 56 weeks 87.4±15.1; p〈0.001 vs DC 24 weeks). In contrast, acellular capillaries in D-AG increased over the first 24 weeks and then remained constant for the rest of the study (D-AG 24 weeks 35.7±5.18; p〈0.01 vs NC 24 weeks and NS vs DC 24 weeks; D-AG 56 weeks 42.0±6.20; p NS vs D-AG 24 weeks). Diabetes-associated pericyte loss (DC 24 weeks 2310±170/mm2 of capillary area; NC 24 weeks 3120±190; p〈0.001; DC 56 weeks 1570±230; NC 56 weeks 2960±50; p〈0.001) was significantly prevented by aminoguanidine after diabetic-like changes over the initial 24 weeks (D-AG 24 weeks 2450±75; p NS vs DC 24 weeks; D-AG 56 weeks 2350±90; p〈0.001 vs DC 56 weeks). At 56 weeks, aminoguanidine treatment was associated with a 67.4% reduction in retinal basement membrane thickening. This time-course study demonstrates that aminoguanidine prevents the progression of experimental diabetic retinopathy, and suggests that non AG-inhibitable mechanisms are involved in the initial phase of diabetic retinopathy.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 4
    ISSN: 1435-5604
    Schlagwort(e): Key words Osteogenesis imperfecta ; Mineral ; Composition ; FTIR ; 31P-NMR
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Fourier transform infrared spectroscopy and 31P solid-state nuclear magnetic resonance spectroscopy were used to determine if any structural or compositional differences in osteogenesis imperfecta (OI) bone mineral could be detected that might help to explain the bone fragility observed in this disease. A previous study by Cassella et al. used an electron probe X-ray microanalytical technique to compare the calcium to phosphorus (Ca/P) molar ratios in normal bone and bone from patients with OI. It was demonstrated that bone from OI patients had a lower Ca/P molar ratio. This study demonstrated that OI bone mineral had a general hydroxyapatite structure and that isomorphous substitutions in the carbanoapatite lattice could account for the low Ca/P molar ratio.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Glycoconjugate journal 12 (1995), S. 618-621 
    ISSN: 1573-4986
    Schlagwort(e): glycation ; lens proteins ; diabetes ; ageing ; cataract
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Glycation (nonenzymatic glycosylation) in the human lens (cortex and nucleus) in senile (nondiabetic) and diabetic cataracts was studied by measuring the extent of early and late glycation products, the content of free ε-amino groups and the formation of disulfide bonds in the soluble lens proteins. There was a significant (p〈0.001) increase in early and late glycation in the lens nucleus compared to the cortex in both the senile and diabetic groups. Overall these changes were much larger in the diabetic group. The concentration of free ε-amino groups was decreased in the senile nucleus as well as in the diabetic nucleus when compared with the senile and diabetic cortex (p〈0.001). Disulfide bond content was in the order of diabetic nucleus 〉 diabetic cortex 〉 senile nucleus 〉 senile cortex. Glycation of the lens proteins is a generalized feature which is enhanced in the diabetic lens compared to senile lens proteins and is associated with a decrease in free ε-amino groups and an increase in disulfide bonds formation in the lens proteins.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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