Many amyloid diseases are characterized by protein aggregations linked to oxidative stress. Such diseases including those of the brain, muscle, and blood vessels exhibit plaques containing beta-amyloid (Abeta). Here we demonstrate that Alzheimer's precursor protein (betaAPP) and A beta are present at low levels in normal lenses and increase in intact cultured monkey lenses treated with H2O2 or UV radiation (known cataractogenic agents), and with phorbol 12-myristate 13-acetate. AP-1 factor binding, shown by others to up-regulate betaAPP expression, increased in the monkey lenses treated with H2O2, UV radiation, or phorbol 12-myristate 13-acetate and paralleled the increase in betaAPP expression. Rat lenses exposed to oxidative stress showed increased betaAPP in the anterior epithelium and cortex. Incubation of cultured rabbit lens N/N1003A epithelial cells with Abeta induced inclusions and vacuoles and was cytotoxic. Abeta cross-reacting protein was readily detected in the cortex of a cataractous human lens. Our data show that betaAPP and Abeta increase in mammalian lenses as part of a response to H2O2 or UV radiation and suggest that they may contribute to the mechanism by which oxidative damage leads to lens opacification.

Alzheimer's disease (AD) is the major age-dependent disease of the brain, but what instigates late-onset AD is not yet clear. Epidemiological, animal model, and cell biology findings suggest links between AD and diabetes. Although AD pathology is accelerated by diabetes in mice engineered to accumulate human-sequence amyloid-β (Aβ) peptides, they do not adequately model non-inherited AD. We investigated AD-type pathology induced solely by diabetes in genetically unmodified rabbits which generate human-sequence Aβ peptides. After 15 weeks, alloxan-treated diabetic rabbits with expected high blood glucose showed ~5-fold increase in Aβ40/Aβ42 in cortex and hippocampus, and significantly, generated Aβ-derived assemblies found in human AD. Deposits of these putative pathogenic toxins were detected by Aβ/Aβ oligomer antibodies in brain parenchyma and surrounding vasculature, also co-localizing with markedly elevated levels of RAGE. Soluble brain extracts showed diabetes-induced buildup of Aβ oligomers on dot-blots. Phospho-tau also was clearly elevated, overlapping with βIII-tubulin along neuronal tracts. Indications of retina involvement in AD led to examination of AD-type pathology in diabetic retinas and showed Aβ accumulation in ganglion and inner nuclear cell layers using Aβ/oligomer antibodies, and RAGE again was elevated. Our study identifies emergence of AD pathology in brain and retina as a major consequence of diabetes; implicating dysfunctional insulin signaling in late-onset AD, and a potential relationship between Aβ-derived neurotoxins and retinal degeneration in aging and diabetes, as well as AD. AD-type pathology demonstrated in genetically unmodified rabbits calls attention to the considerable potential of the model for investigation of AD pathogenesis, diagnostics, and therapeutics.

Early-onset cataract and Alzheimer's disease occur with high frequency in Down syndrome (trisomy 21), the most common chromosome duplication in human live births. Previously, we used in vivo and lens organ culture models to demonstrate Alzheimer pathophysiology in oxidative stress-related lens degeneration. Currently, well-characterized Alzheimer transgenic mouse models are used to extend these findings. Here, we report on mice carrying a complete copy of a wild-type human AbetaPP (hAbetaPP) gene from the Down syndrome critical region on chromosome 21. hAbetaPP mice produce fiber cell membrane defects similar to those described in human cataracts and increased age-related lens degeneration. hAbetaPP expression and mRNA alternative splicing in human and mouse lens and cornea favor longer, potentially more amyloidogenic forms. Endogenous mouse AbetaPP expression is increased in transgenic lenses, consistent with the cycle of oxidative stress proposed in the mechanism of Alzheimer pathophysiology. Alternative splicing previously designated as neuron-specific occurs in human lens and cornea, and is maintained by hAbetaPP expressed in mouse tissues. These present data implicate AbetaPP in fiber cell formation and in early-onset cataracts in Down syndrome. Finally, our findings provide further support for our hypothesis that Alzheimer pathophysiology contributes to the cataract formation that is increasing in the aging population.

A capillary chemotaxis assay revealed that among a wide range of inorganic and organic chemicals, only ammonium ion (NH4+) could serve as an attractant for Chlamydomonas reinhardtii. NH4+ (10-2 M) gave the maximum response, with up to a 15-fold increase in accumulated algae being measured. No repellents for the chlorophyte were detected. The response to NH4+ was influenced by exogenous levels of calcium, but not by L-methionine. The optimal pH for positive chemotaxis was 7.0; however, attraction was measurable from pH 4.0 to 9.0. Positive chemotaxis was stimulated by performing the assay under fluorescent illumination rather than in the dark.Although there has been extensive work done on evaluating chemotactic responses induced by specific algal-produced sexual pheromones (3), relatively few quantitative studies have been applied to assess the abilities of motile algae to respond to a wide spectrum of inorganic and organic chemicals. Levandowsky et al. (6) A rapid, quantitative capillary assay in which algal numbers are determined with an electronic particle counter has shown that the motile, neritic, and littoral chlorophyte Dunaliella tertiolecta is attracted strongly by ammonium ion (NH4+) (11), L-tyrosine, L-tryptophan, and Lphenylalanine (12). The alga apparently possesses one chemoreceptor that binds only NH4', and another that binds NH4' and the three amino acids. In the present study, the same assay procedure was used to evaluate the chemotactic responses of C. reinhardtii to a wide range of chemicals. If future studies on the biochemical mechanisms or on the ecological significance of algal chemoreception are to be facilitated, it is essential that attention be given to factors that influence chemosensory behavior in these eucaryotes. Thus, we have evaluated some of these parameters with C. reinhardtii.MATERIALS AND METHODS C. reinhardtii Dangeard strain 90 was obtained from the Culture Collection of Algae (Austin, Tex.) and was cultivated in a modified Bold basal medium (1) containing urea (2 mM) as the sole nitrogen source and supplemented with thiamine (1.0 pg/liter), pyridoxine (10 ,ug/l), and cyanocobalamine (1.0 iLg/l). Cultures in 75 ml of growth medium were incubated at 21 ± 1°C in 250-ml Erlenmeyer flasks over continuous fluorescent illumination ("Gro'n Show," General Electric Co., Schenectady, N.Y.) at 4 klx. This lighting was also used in all subsequent studies. After a population density of 5 x 106 to 1 x 107 organisms per ml was attained, the culture was centrifuged at 270 x g for 10 min, and the algae were carefully resuspended in a medium composed of K2HPO4 (0.47 mM), KH2PO4 (1.29 mM), NaCl (0.43 mM), MgSO4.7H20 (0.3 mM), and CaCl2-2H20 (1 mM), in distilled water. This wash medium (pH 7.0) also served as the chemotaxis medium. Assays were done within 2 h after the suspension of the algae in the chemotaxis medium. Algal numbers were determined with an electronic particle counter (model Zb; Coulter Electronics, Inc., Hialeah, Fla.). Cultures of C. reinhardtii were maintained on agar slants...