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The stromal ultrastructure of normal and pathologic human corneas
No full textSIGLEAvailable from British Library Document Supply Centre- DSC:DX96403 / BLDSC - British Library Document Supply CentreGBUnited Kingdo
Stromal Healing Following Explantation of an ICR (Intrastromal Corneal Ring) From a Nonfunctional Human Eye
No full textGarden of a Modern Prometheus:Fyne Court, Somerset
No full textBetween 1805 and 1855 the densely wooded grounds of Fyne Court on the Quantock slopes in Somerset were transformed by their owner, a brilliant experimental physicist, Andrew Crosse, into a scientific laboratory for the investigation of atmospheric electrical charges and the potential creative power of lightning strikes. Traces of Crosse’s garden laboratory survive today, confusingly superimposed upon an amateurish mid-eighteenth-century ‘Rococo’ garden layout, the creation of Crosse’s great uncle, also Andrew. While Crosse claimed to be a Christian, his revelations of the power of electricity would automatically challenge orthodox Creation theories, offering an alternative to divine creative power. The aetheist poet Percy Byshe Shelley and his equally talented mistress-wife, Mary, were present at one of Crosse’s London lectures in 1814. Mary Shelley’s Frankenstein; or, The Modern Prometheus, was published in 1818, and the connection between a ‘Modern Prometheus’, who defied the Gods by creating an electrical monster, and Crosse, who created, or claimed to have created, live beetles by passing electrical charges from his garden complex through an acid solution, is too close to be merely coincidental. Fyne Court has, therefore, a garden with Romantic literary associations and Crosse must, unwittingly, have challenged accepted notions of the divine and the human
Development of the corneal stroma, and the collagen–proteoglycan associations that help define its structure and function
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Limbal stem cell deficiencies and ocular surface reconstruction
No full textA smooth corneal surface of epithelial cells supporting an intact tear film is essential for good vision. In some diseased or injured eyes, however, not enough epithelial cells are generated to replace those lost due to natural turnover. Results can be devastating, and functional vision is often lost altogether. Reconstructing the ocular surface in situations such as these is one of the most serious challenges facing the eyecare profession today. This article describes a pioneering new strategy, which now makes this feasible
Collagen organization in the secondary chick cornea during development.
No full textPURPOSE. The latter stages of morphogenesis in the embryonic chick cornea are instrumental in the establishment of a properly formed corneal stroma. This study was designed to provide better appreciation of collagen reorganization in the avian corneal stroma during the latter stages of embryogenesis.
METHODS. High-angle synchrotron x-ray diffraction patterns were obtained from 47 developing chick corneas daily at developmental days 13 through 18 (n = 7 or 8 at each time point) and analyzed to establish collagen molecular spacing and fibril orientation.
RESULTS. Collagen intermolecular x-ray reflections were of approximately constant intensity between days 13 and 15 of development, but thereafter became progressively more intense, suggesting that extra collagen is deposited in embryonic chick corneas after day 16 of development. At all times, the mean collagen intermolecular spacing measured approximately 1.43 nm. X-ray intensity was not uniform around the intermolecular x-ray reflections at earlier time points. Rather, a fourfold symmetry was evident, indicative of an orthogonal array of collagen fibrils. An index of this symmetry was essentially unchanged between developmental days 13 and 15, but thereafter diminished considerably.
CONCLUSIONS. The lateral spacing of fibril-forming collagen molecules does not change as the chick cornea develops between days 13 and 18. An orthogonal array of collagen fibrils is present in the corneas of developmental day-13 to -18 chicks, but starting at developmental day 16, additional collagen is deposited in a less well-oriented manner and thus acts to obscure the overall orthogonality, with implications for the biomechanical strength and shape of the cornea
An X-ray diffraction investigation of corneal structure in lumican-deficient mice
No full textPURPOSE. 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 transparency.
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
Ultraviolet Light Transmission through the Human Corneal Stroma Is Reduced in the Periphery
No full textThis article investigates in vitro light transmission through the human cornea in the ultraviolet (UV) portion of the electromagnetic spectrum as a function of position across the cornea from center to periphery. Spectrophotometry was used to measure UV transmission in the wavelength range 310-400 nm, from the central cornea to its periphery. UV transmission decreases away from the center, and this is attributed to scattering and absorbance. Corneal endothelial cells, which line the back of the cornea and are more numerous in the periphery, therefore receive a lower dose of UV than do those in the central cornea. This is consistent with the recent observation that endothelial cells in the corneal periphery exhibit less nuclear oxidative DNA damage than those in the central cornea. © 2012, Cell Press
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