Cataract Research Research Articles

Calcium content and distribution in human cataract

The calcium content and distribution was measured in brunescent cataracts from India and cataracts from the United States classified according to guidelines of the Cooperative Cataract Research Group (CCRG). The severity and extent of opacification correlates well with the increase in Ca 2+ bound to membranes and insoluble proteins separated by differential centrifugation. Thus, bound Ca 2+ is approximately 30 ng/mg for the immature cataract. 100 ng/mg for the pale yellow. 200 ng/mg for the mature cataract and 300 ng/mg for the brown brunescent. These values can be compared to 16 ng/mg (0·2 m m) for a freshly excised rabbit lens. To the extent that the mature cataract represents an advanced stage and the immature cataract an early stage of development, and likewise for the brown and pale yellow cataract, results of this study suggest that cataract development is not accompanied by, or the result of, a redistribution of ‘free’ and bound calcium. We find that the fraction of total calcium bound to membranes and insoluble proteins is the same in the early and advanced stages of U.S. and Indian cataracts. It appears that as calcium accumulates in the developing cataract, an increasing amount becomes membrane or protein bound while the level of diffusible Ca 2+ continues to increase. In the advanced stage as much as 85% of the calcium in the 10 000 g supernatant is dialyzable or diffusible. The remaining 15% is bound to watersoluble proteins and represents a sixfold to 15-fold increase in the mature and brown cataract, respectively. There is also a considerable increase in the amount of calcium found in the 1000 g pellet containing insoluble proteins and membrane fragments.

Direct measurement of Raman spectra of intact lens in a whole eyeball.

The Raman spectrum of an intact rabbit and rat lens was measured intraocularly without taking it out of a whole eyeball. The Raman spectrum was identical to that of an excised lens. There was no evidence for Raman bands from cornea, aqueous humor, or other ocular tissue in the spectrum of intact lens in the eyeball. The result is an important step toward the clinical application of Raman spectroscopy in the field of cataract research.

Mechanism of cataract production by 3- β(2-diethylaminoethoxy) androst-5-en-17-one hydrochloride, U18666A: An inhibitor of cholesterol biosynthesis

The present report describes a new model for cataract research induced by a compound (3-β(2-diethylaminoethoxy) androst-5-en-17-one hydrochloride; i.e. U18666A) which inhibits the enzymatic reduction of desmosterol to cholesterol and provides information on the possible mechanism of cataractogenesis. Treatment of the new born rat with U18666A results in nuclear cataracts appearing between 15 and 25 days of age. This cataract is apparently unrelated to accumulation of desmosterol, since this sterol was not detected in opaque lenses until long after their first appearance. Rather, development of this opacity could involve a selective reduction in the concentrations of γ-crystallin, the smallest of the four classes of water-soluble crystallins and the single major constituent of the rat lens after water. The observed lowering of γ-crystallin levels in opaque lens is apparently explained by a differential reduction in protein synthesis measured from [ 3H]leucine injected intraocularly. This differential effect could be explained by marked changes in the intracellular concentration of Na + and K + ions in opaque lens; Na + levels greatly increased and K + decreased. Recent reports indicate that decreasing the intracellular ratio of K + Na + in lens results in a shift of protein synthesis from lower to higher molecular weight species. In view of this information and the results of the present study, we suggest that the development and/or progression of the cataracts induced by U18666A could be related to a selective block in formation of γ-crystallin secondary to alteration in the levels of Na + and K + ions in lens.

Use of Guinea Pigs as Model to Study Galactose-Induced Cataract Formation

Because the dietary requirement for ascorbic acid is similar in humans and guinea pigs, galactose-induced cataract research with the guinea pig as an experimental model instead of the rat might be appropriate and may represent a closer analogy to galactosemic cataract formation in humans. In this study, dietary ascorbic acid was found in all guinea pigs to have a retarding or delaying effect on the development of galactose-induced cataracts.

Classification of human cataracts.

A stereoscopic system of lens photography was developed and was applied in the classification of different forms of cataract. Lenses, after surgical extraction, can be classified by a technician, independent of ophthalmological collaboration. This system meets the needs of the laboratory scientist and has been adopted by the Cooperative Cataract Research Group.

Microwave Induced Temperature Rises in Rabbit Eyes in Cataract Research

Microwave power deposition patterns and temperature distributions were measured for rabbit eyes exposed to localized near zone 2450 MHz radiation and good agreement was obtained between the measured and predicted transient temperature fields. The lenses were biomicroscopically examined to determine the minimum exposure times necessary to produce posterior lens opacity (cataracts) and these times are correlated with the temperature calculations to suggest that a threshold temperature level exists.

The Human Lens: In Relation to Cataract

This is a superb book! In 313 pages, there are 18 articles that clearly and concisely present an overview of, as well as abundant detail about, the present field of lens metabolism and cataract research. The Symposium was broadly international with authors from England, several European countries, India, and the United States participating. Each paper was well written with the authors taking pains to present a newcomer to this field of study with sufficient background and basic information to tempt him to finish the chapter. Background information and new advances are skillfully blended to provide an in-depth view of each area. Once embarked on reading this book, it is hard to put down. The entire book is minutely indexed and referenced. Practically every statement is supported by the reference source. For those interested in acquiring a resource text on cataract formation, this book is unsurpassed. It is only fitting that

Problems in Cataract Research

A general review concerning human senile cataract makes many unsolved problems obvious. Future research on these problems requires a generally accepted classification of these cataracts and well-organized co-operation between the ophthalmologist and the biologist. If research groups are established fulfilling these necessities in their studies of special problems, great progress can be achieved in a relatively short period of time.