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Andrew J. Quantock, Keith M. Meek, Shukti Chakravarti; An X-ray Diffraction Investigation of Corneal Structure in Lumican-Deficient Mice. Invest. Ophthalmol. Vis. Sci. 2001;42(8):1750-1756.
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purpose. The corneas of mice homozygous for a null mutation in lumican, a
keratan sulfate–containing proteoglycan, are not as clear as normal.
In the present study, mutant corneas were examined by synchrotron x-ray
diffraction to see what structural changes might lie behind the loss of
methods. X-ray diffraction patterns were obtained from the corneas of
6-month-old and 2-month-old lumican-null and wild-type mice. Measured
in each cornea were the average collagen fibril diameter, average
collagen fibril spacing, and the level of order in the collagen array.
results. The x-ray reflection arising from regularly packed collagen was
well-defined on all x-ray patterns from 6-month-old wild-type corneas.
Patterns from 6-month-old lumican-deficient corneas, however, contained
interfibrillar reflections that were measurably more diffuse, a fact
that points to a widespread alteration in the way the collagen fibrils
are configured. The same distinction between mutant and wild-type
corneas was also noted at 2-months of age. Average collagen fibril
spacing was marginally higher in corneas of 6-month-old lumican-null
mice than in corneas of normal animals. Unlike x-ray patterns from
wild-type corneas, patterns from lumican-deficient corneas of both ages
registered no measurable subsidiary x-ray reflection, evidence of a
wider than normal range of fibril diameters.
conclusions. The spatial arrangement of stromal collagen in the corneas of
lumican-deficient mice is in disarray. There is also a considerable
variation in the diameter of the hydrated collagen fibrils. These
abnormalities, seen at 2 months as well as 6 months of age, probably
contribute to the reduced transparency.
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