[Hydrogen peroxide in the aqueous humor and cataract formation in human diabetes]. / Perossido di idrogeno nell'umore acqueo e catarattogenesi nel diabete umano.

Hydrogen peroxide in the aqueous humor was measured in cataractous eyes from normal subjects and in cataractous eyes from diabetic subjects. The level of H2O2 in the aqueous humor was significantly higher in diabetes than in the idiopathic forms. It is likely that in the eye, impaired enzymic defenses lead to the accumulation of reactive species of O2, such as H2O2, which induces lipid peroxidation. This mechanism may be involved, as a direct consequence of retinal damage, in the pathogenesis of cataract in diabetes.

Lipid peroxidation and human cataractogenesis in diabetes and severe myopia.

To investigate the role of lipid peroxidation in human cataract, malondialdehyde, a breakdown product of lipid peroxidation, was measured in clear and cataractous lenses from normal subjects, and in cataractous lenses from diabetics and from subjects with severe myopia. The cataractous lenses contained more malondialdehyde than did clear lenses and the level was higher in diabetes and severe myopia than in the idiopathic forms. This indicates that lipid peroxidation may be involved in the development of senile cataract and, as a direct consequence of retinal damage, also in the pathogenesis of cataract in diabetes and in severe myopia.

[Lipid peroxidation and cataract formation in experimental diabetes]. / Perossidazione lipidica e catarattogenesi nel diabete sperimentale.

To investigate the role of lipid peroxidation in diabetic cataractogenesis, malondialdehyde, a breakdown product of lipid peroxidation, was measured in lenses with incipient opacities and in retinas from diabetic rats and in clear lenses and in retinas from normal rats. The malondialdehyde mean values obtained in the transparent and cataractous lenses showed non-significant differences, while non-diabetic rat retinas had a significantly lower mean level of malondialdehyde compared with diabetic rat retinas (p less than 0.01). This indicates that, in streptozotocin-induced diabetic rats, lipid peroxidation is apparently not involved in the development of cataract, but it is quite probably involved in retinal damage. The retina, richer in polyunsaturated fatty acids than other ocular structures, is the elective site of lipid peroxidation and from this membrane peroxidation products might probably diffuse and damage other ocular tissues.

[Role of the non-enzymatic glycosylation of protein in the formation of human cataracts]. / Ruolo della glicosilazione non enzimatica delle proteine nella catarattogenesi umana.

We have measured the free epsilon amino groups in soluble and insoluble proteins of clear human lenses and diabetic and non-diabetic senile cataractous lenses. The free epsilon amino groups content of soluble and insoluble proteins was significantly lower in diabetic cataracts than in clear lenses and non diabetic senile cataracts. Our results seem to demonstrate that non-enzymatic glycosylation of lens protein could play a role in the pathogenesis of cataract in diabetes.

A novel archaebacterial NAD+-dependent alcohol dehydrogenase. Purification and properties.

An NAD+-dependent alcohol dehydrogenase (alcohol: NAD+ oxidoreductase, EC 1.1.1.1) was detected in cellular extracts of the extreme thermophilic archaebacterium Sulfolobus solfataricus. The enzyme was purified to homogeneity and shown to be a dimer with a native molecular mass of 71 kDa by sucrose gradient centrifugation and SDS electrophoresis. The enzyme has a broad substrate specificity that includes linear and branched primary alcohols, linear and cyclic secondary alcohols, linear and cyclic ketones and anisaldehyde. The enzyme has an extraordinary thermophilicity and a remarkable thermostability, and appears to have some properties and a structure different from those previously described for thermophilic alcohol dehydrogenases.