Morphological aspects of human lens capsules

Lens capsules of patients of advanced age, obtained after extracapsular cataract surgery, were carefully prepared for a combined LM, TEM and SEM investigation, after preliminary washing and mounting onto a holder in a buffer solution. After pre-fixation with GA, samples were postfixed for LM/TEM and OsO₄/K₄Fe(CN)₆ and stained with toluidineblue/basic fuchsine for LM and with uranyl acetate/lead citrate for TEM; for SEM the GA-pre-fixed samples were post-fixed by the Tannine Arginine-OsO₄ non-coating technique. At LM-level discrimination between healthy and degenerating cells was possible after toluidine staining. At SEM-level protrusion of the cell nucleus and fibrillation and blebbing of the cell membrane as the result of capsular degeneration could be observed with the TAO-method. At TEM-level protrusion of the cell nucleus, degeneration of the cytoplasm, ballooning of the mitochondria, the presence of microfilaments and the occurrence of vacuoles were visible as the result of capsular degeneration on cataract formation.     

Relative contributions of epithelial cells and fibers to rabbit lens ATP content and glycolysis

The adenosine triphosphate (ATP) content was measured independently in separated capsule-epithelium and fibers from whole rabbit lenses, both fresh and after incubation under various combinations of glucose and oxygen deprivation. Lactate production was also measured during aerobic and anaerobic incubations of whole lenses and of monolayers of cultured epithelial cells. The fresh capsule-epithelium contained 3.3 nmoles ATP, whereas the decapsulated lens contained 410 nmoles ATP, a value that was indistinguishable from that of the whole, intact lens. In the presence of glucose, the fibers and epithelium each maintained their respective ATP content under aerobic and anaerobic conditions. In the absence of glucose, the ATP content in each fraction declined with time, but only in the epithelium was the rate of decline of ATP significantly faster in nitrogen than in oxygen. In whole lens, the rates of anaerobic and aerobic lactate production were similar, whereas in the cultured epithelial monolayers, the anaerobic rate was two-fold greater than in oxygen. From this it is concluded that approximately 50% of the ATP of the epithelial cells is derived from oxidative metabolism. A Pasteur response shown here for the first time with the cultured epithelium allows these cells to compensate for the loss of ATP production when mitochondrial oxidation is curtailed. The epithelium does not contribute to the ATP content of the lens fibers under aerobic or anaerobic conditions.     

Biochmical aspects of contact lens wear.

Glycogen, adenosine triphosphate, and hydration were measured in rabbit corneal epithelium to determine whether the corneal epithelium glycogen decrease, increase in epithelial hydration, and decrease in epithelial adenosine triphosphate stores, seen as a result of contact lens wear, were secondary only to anoxia or may also have resulted from mild trauma, with no interference to oxygenation. Conventional contact lens wear, trauma, and oxygen-permeable contact lens wear caused metabolic changes, showing trauma as well as anoxia may play an important role in the corneal epithelial response to contact lens wear.     

Yellowing of the human lens: nuclear and cortical contributions

The geometry of the cortex and nucleus of excised human lenses was determined by photography and dissection. Samples of the cortex and nucleus were measured spectrophotometrically to allow determination of light loss through the whole lens and the light loss per unit pathlength. It was concluded that the reduction of short wavelength light transmission with increasing age is due to two processes; first, the nuclear pathlength remains constant but there is increased pigment deposition; second, the pigment concentration does not change in the cortex but the pathlength increases.     

Some aspects of amblyopia

Some of the recently suggested methods for treating amblyopes are reviewed. A survey of the success rate in 50 young amblyopes, using conventional methods, is described. Whilst 26% did not improve at all in visual acuity, 50% improved by at least two Snellen lines. The suggestion is made that the success rate in the clinic described is similar to that found elsewhere.     

Some aspects of radiant energy damage to the retina

Summary The retinae of anaesthetised Dutch rabbits were exposed to white light of various intensities^* (^* 67–235 mW/cm² measured at 2.5 cms from the end plate of the light guide) for a period of one h. After this period the animals were killed and tissue taken for investigation by light and electron microscopy. The higher intensities produced marked disruption of the visual cell outer and inner segments as well as a variety of morphological changes in the pigment epithelium. The highest intensity produced severe disruption of the visual cells and pigment epithelium in addition to a general disruption of the other retinal layers. Accompanying the retinal damage there was an inflammatory response in the choroid of the experimental eyes and surprisingly, at some intensities, a similar inflammatory response in the choroid of the control eye.This paper was presented in part at the Sixth Annual Meeting of the European Club for Opthalmic Fine Structure in Paris, France on March 31 and April 1, 1978     

Molecular and cellular aspects of amphibian lens regeneration

Lens regeneration among vertebrates is basically restricted to some amphibians. The most notable cases are the ones that occur in premetamorphic frogs and in adult newts. Frogs and newts regenerate their lens in very different ways. In frogs the lens is regenerated by transdifferentiation of the cornea and is limited only to a time before metamorphosis. On the other hand, regeneration in newts is mediated by transdifferentiation of the pigment epithelial cells of the dorsal iris and is possible in adult animals as well. Thus, the study of both systems could provide important information about the process. Molecular tools have been developed in frogs and recently also in newts. Thus, the process has been studied at the molecular and cellular levels. A synthesis describing both systems was long due. In this review we describe the process in both Xenopus and the newt. The known molecular mechanisms are described and compared.