[Analysis of trace elements in cataractous lenses and environmental samples in Tibet].

Trace elements of Cu, Fe, Zn, Mg, and Se in Tibetan cataractous lenses and also in local samples of earth, drinking water, and staple foods were analyzed to estimate the possible relationship between environmental factors and primary cataract formation in Tibet. The Fe, Mg and Se contents in Tibetan cataracts were significantly lower in comparison with levels in those of Chengdu area, particularly the Se contents were low in both cataracts and local environment, suggesting a probable correlation between cataract formation and low Se contents in food and water.

The cellular eye lens and crystallins of cubomedusan jellyfish.

The ultrastructure and major soluble proteins of the transparent eye lens of two cubomedusan jellyfish, Tripedalia cystophora and Carybdea marsupialis, have been examined. Each species has two complex eyes (one large and one small) on four sensory structures called rhopalia. The lenses consist of closely spaced cells with few organelles. The lens is situated next to the retina, with only an acellular layer separating it from the photoreceptors. SDS-PAGE showed that the large lens of C. marsupialis has only two crystallin polypeptide bands (with molecular masses of approximately 20,000 and 35,000 daltons), while that of T. cystophora has three bands (two with a molecular mass near 20,000 daltons and one with a molecular mass near 35,000 daltons). Interestingly, the small lens of T. cystophora appears to be markedly deficient in or lack the lower molecular weight proteins. The crystallins behaved as monomeric proteins by FPLC and showed no immunological reaction with antisera of the major squid crystallin, chicken delta-crystallin or mouse gamma-crystallin in western immunoblots. Very weak reactions were found with antimouse alpha- and beta-crystallin sera. The 35,000 dalton crystallin of T. cystophora was purified and called J1-crystallin. It contained relatively high leucine (13%) and tyrosine (9%) and low methionine (2%). Several tryptic peptides were sequenced. Weak sequence similarities were found with alpha- and beta-crystallins, which may account for some of the apparent weak immunological cross-reactivity with these vertebrate crystallins. A polyclonal antiserum made in rabbits from a synthetic peptide of J1-crystallin reacted strongly with J1-crystallin of T. cystophora and C. marsupialis in immunoblots; by contrast, no reaction was obtained with the lower molecular weight crystallins from these jellyfish, with the squid crystallin, or with any crystallins from the frog or human lens. Thus, despite the structural similarities between the cubomedusan, squid and vertebrate lenses, their crystallins appear very different.

Lenticular psoralen photoproducts and cataracts of a PUVA-treated psoriatic patient.

Psoralen photoproducts were identified in association with cataracts in a psoriatic patient several years after oral methoxsalen plus ultraviolet A light (PUVA) therapy. Patients should be required to wear adequate optical protection not only during PUVA therapy but 24 hours following ingestion of methoxsalen.

Zinc, cobalt and selenium concentrations in the premature and full-term newborn eye.

Zinc, cobalt and selenium concentrations were determined in tunics, vitreous and lens of the eyes of 17 infants who died during the neonatal period. Significantly higher concentrations of the measured elements were found in the vitreous. The tunics contained more zinc and cobalt than the lens, while the latter contained more selenium.

Nuclear magnetic resonance analyses of the cold cataract: whole lens studies.

Pulse nuclear magnetic resonance (NMR) magnetization decay studies were performed on normal and cold cataractous rat lenses. Computer analyses of the decay curves have been interpreted to reflect two types of water within the lens that do not exchange rapidly. Upon lowering the temperature in the presence and absence of 5% acrylamide (a known agent that prevents the cold cataract phenomenon), significant differences in the relaxation rates of one water fraction were noted. 2H (NMR) spectra on young rabbit and human lenses showed temperature-related linewidth changes, which are significantly diminished in lenses incubated in acrylamide. 31P spectra also showed similar inorganic phosphate linewidth changes and also reflected progressive alterations in the metabolic state of these lenses. These studies demonstrate the potential of NMR methods for monitoring physicochemical parameters in the normal and cataractous mammalian lens.

Alterations in the lenticular proteins of rats on riboflavin deficient diet.

Effect of feeding riboflavin deficient diet to rats on lens protein composition was investigated. Total proteins and profile of soluble and insoluble proteins in lenses from rats fed on a riboflavin deficient diet for seven weeks were found to be similar to that of the vitamin supplemented diet. Distribution of high molecular weight protein (above 4 X 10(6) daltons) isolated from the 9,900 g supernatant fraction was found to be significantly higher and gamma crystallin was significantly lower in riboflavin deficient group as compared to the normal lenses. However, the distribution of alpha and beta crystallins was not affected. Gel electrophoresis in sodium dodecyl sulfate of soluble lens proteins from riboflavin deficient animals had lower proportions of polypeptide species with molecular weight above 40,000 daltons while insoluble protein fraction had higher proportions of these polypeptide species as compared to control rats. These data suggest that the composition of lens proteins is altered in riboflavin deficiency.

Role of calcium in selenium cataract.

The purpose of this research was to test the role of certain minerals in the formation of cataract caused by an overdose of selenium. Several pieces of information indicated that lenticular calcium may play an important role in selenite cataractogenesis: 1) Lens calcium concentrations in selenite treated rats were increased more than 5-fold, and the increase in lens calcium was localized in the nucleus. 2) Lens calcium concentrations were elevated at least one full day before actual formation of nuclear cataract, but serum calcium levels were not changed. 3) In older rats not susceptible to selenite cataract, lens calcium was not significantly increased. 4) No evidence was found for a generalized disruption in lens permeability, since no major changes in lens water, sodium, and potassium levels were observed, and 5) when levels of calcium observed in selenite cataract were added to solutions of soluble proteins from rat lenses, light scattering was increased. Selenium-overdose cataracts may provide an important model for studies on the role of calcium in cataractogenesis.