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Role of the non-enzymatic glycosylation of protein in the formation of human cataracts
No full textWe 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
Lipid peroxidation and cataract formation in experimental diabetes
No full textTo 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
Systemic human diseases as oxidative risk factors in cataractogenesis. I. Diabetes
No full textIn this study we have investigated the oxidative metabolism of red blood cells (RBC), plasma, serum, aqueous humor, and lens of healthy subjects and of age-matched cataractous patients with and without diabetes. Reduced and oxidized glutathione (GSH, GSSG) levels in RBC were similar among the three groups. Plasma levels of GSSG were higher in diabetics than in cataractous and control subjects. No differences in plasma content of GSH were noted among the three groups. The activity of the enzyme glucose-6-phosphate dehydrogenase was significantly diminished in diabetic patients. Controls and cataractous patients showed similar levels of malondialdehyde (MDA). Although not significant, the MDA content in RBC from diabetics was elevated. No differences in plasma levels of vitamin E were noted among the three groups. The biological liquid oxidant activity of serum in diabetic patients was significantly higher than in controls and cataractous patients. GSH levels in aqueous humor were similar in diabetic and nondiabetic cataractous patients. The content of GSSG in aqueous humor was highest in diabetic patients. Control clear lenses showed low levels of MDA. The MDA levels in cataractous lenses from nondiabetic patients were significantly higher than those of controls. In diabetic patients the content of MDA in the lens was approximately twice as high as the cataractous values. Our results seem to demonstrate that oxidative damages could play a role in the pathogenesis of cataract in diabetes
Possible role of altered levels of plasma docosahexaenoic acid in the pathogenesis of retinitis pigmentosa. Preliminary results
No full textPlasma samples obtained from Retinitis Pigmentosa (R.P.) patients and controls were assayed for docosahexaenoic acid (DXA), the major fatty acid in photoreceptor cells, in order to evaluate the possibility that abnormalities in PUFA metabolism could be involved in R.P. pathogenesis. Our preliminary results show levels of plasma DXA in dominantly inherited R.P. lower than in the recessive forms and controls
Hydrogen peroxide in the aqueous humor and cataract formation in human diabetes
No full textHydrogen 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
Systemic human diseases as oxidative risk factors in cataractogenesis. II. Chronic renal failure
No full textIn this study we have investigated the oxidative metabolism of red cells (RBC), plasma, serum and aqueous humour of healthy subjects and of age-matched cataractous patients with and without chronic renal failure (CRF). Reduced glutathione (GSH) levels in RBC were lower in CRF patients than in the other groups. Oxidized glutathione (GSSG) plasma levels in CRF patients were higher than those of controls and cataractous subjects. The activity of the enzyme glucose-6-phosphate dehydrogenase in RBC was significantly reduced in CRF patients with respect to the other two groups. The levels of malondialdehyde (MDA) in RBC and in lens were about twice in CRF patients compared with the other two groups. The plasma levels of vitamin E were diminished in CRF patients; on the contrary, the biological liquid oxidant activity (BLOA) of serum in CRF patients was significantly higher than in controls and in cataractous patients without CRF. Cataractous patients with and without CRF showed similar levels of GSH in aqueous humour; on the contrary, the content of GSSG was significantly higher in CRF patients. Our findings seem to demonstrate that CRF patients are exposed to oxidative stresses that could probably act synergistically with uraemia and carbamylation of lens proteins. This synergism could explain why CRF represents a relatively high risk factor for cataract. © 1990
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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