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Fluid and glycosaminoglycan excretion by chick embryos treated with a beta-D-xyloside
Insights
Chick embryos treated with beta-xyloside showed increased uronic acid in embryos and excreted large amounts of chondroitin sulfate in allantoic fluid, with significantly reduced fluid accumulation.
Area of Science:
- Developmental Biology
- Biochemistry
Background:
- Glycosaminoglycans (GAGs) are crucial for embryonic development.
- Understanding GAG metabolism is key to developmental processes.
Purpose of the Study:
- To investigate the effects of 4-methylumbelliferyl beta-D-xyloside on GAG content and fluid balance in chick embryos.
- To analyze the composition and quantity of GAGs in different embryonic compartments.
Main Methods:
- Chick embryos were injected with 4-methylumbelliferyl beta-D-xyloside at nine days of age.
- Wet weights and glycosaminoglycan content (uronic acid) were measured in embryo, amnion, and allantois.
- GAGs in allantoic fluid were analyzed for composition and sulfation.
Main Results:
- Injected embryos showed increased total uronic acid in the embryo but not concentration.
- Allantoic fluid volume remained low in treated embryos compared to controls.
- Treated embryos accumulated significantly more uronic acid in allantoic fluid, primarily as chondroitin sulfate linked to methylumbelliferone.
Conclusions:
- Beta-xyloside treatment disrupts normal fluid balance in chick embryos.
- Embryos treated with beta-xyloside excrete substantial amounts of chondroitin sulfate.
- This suggests beta-xyloside interferes with GAG processing and excretion pathways during development.
Abstract:
Wet weights and glycosaminoglycan content were determined for embryo, amnion, and allantois of control chick embryos and embryos injected with 4-methylumbelliferyl beta-D-xyloside at nine days of age. There was an immediate increase in total uronic acid content, but not in uronic acid concentration, in the embryo. No difference could be detected either in fluid volume, nor in content or type of glycosaminoglycan, in the amnion of the two groups. The fluid content of the allantois fo control eggs increased steadily between nine and 14 days, but in treated embryos the fluid content of the allantois remained low for at least a week. Less than 2 mg of uronic acid was present in allantoic fluid of control 16-day-old embryos, while treated embryos had accumulated more than 8 mg. More than 95% of the latter uronic acid was accounted for as chondroitin sulfate linked to methylumbelliferone and with a degree of sulfation of 50-60%. Thus beta-xyloside-treated embryos excrete large amounts of chondroitin sulfate and very little fluid.