Clinical evaluation of the neuroprotective effect of alpha-tocopherol against glaucomatous damage.

PURPOSE: To evaluate the vasoregulatory effect of antioxidant alpha-tocopherol on retina via protein kinase C pathway. METHODS: Thirty glaucomatous patients (60 eyes) were included in this study. The patients were divided into three groups. For patients in Group A, tocopherol was not supplemented in their therapy. Patients in Groups B and C received 300 and 600 mg/day of oral alpha-tocopherol acetate, respectively. The ultimate blood tocopherol levels were confirmed via high-performance liquid chromatography assay. Progression of the disease for each subject was monitored via visual field measurements and color Doppler imaging of ophthalmic and posterior ciliary arteries at the beginning and at the 6th and 12th months of this study. RESULTS: The average differences between the pulsatility indexes (PI) and resistivity indexes (RI) of both ophthalmic arteries (OA) and posterior ciliary arteries (PCA) of Groups B and C were significantly lower than those of Group A at months 6 and 12. In trial groups, RI decreases observed in PCAs at months 6 and 12 and PI decreases observed in OAs at the 6th month were statistically significant. Differences of mean deviations with visual fields in Groups B and C were highly significantly lower than that of Group A. CONCLUSIONS: Alpha-tocopherol deserves attention beyond its antioxidant properties for protecting retina from glaucomatous damage.

Effects of ammonia on pentylenetetrazole-induced seizure threshold.

The effect of chronic perfusion of ammonia on the seizure threshold against pentylenetetrazol was studied. Ammonia plus sodium bicarbonate and saline (0.9%) was continuously administered to two groups of rats respectively. All animals were tested three times for seizure threshold, and were then decapitated and the brains removed for analysis of the amino acids. The results showed that the infusion of ammonia increased the seizure threshold, and this protective effect was accompanied by selective changes in brain glutamate and glutamine. Thus, continuous infusion of ammonia may cause an imbalance between excitatory and inhibitory systems in favor of inhibitory systems. These findings may provide insights into the basic mechanisms of seizures observed in hepatic failure, in other hyperammonemic states, and in epilepsy.

Age-dependent changes in liver ganglioside levels.

Gangliosides, sialic acid-containing glycosphingolipids, are found in the outer layer of the plasma membrane of all vertebrate tissue cells; the highest concentration is in the central nervous system. In recent years, there has been research on the distribution and quantity of gangliosides in extra-neuronal tissues, such as liver, kidney and intestine. Since liver is the main source of gangliosides that are carried by lipoproteins in the blood, we examined the effect of development and aging on gangliosides in liver tissue. The relationship was investigated between GM1, GD3, GD1a, GD1b, GT1b ganglioside fractions and the aging process in liver tissue of Wistar-Albino rats aged 3, 6, 12 and 24 months. HPLC analysis of liver gangliosides showed the following results: Compared to 3 month-old rats, the GM1 fraction was decreased by 50% in 6 month-old rats, increased in 12 month-old rats and decreased in 24 month-old rats. The GD3 and GD1b fractions increased until 12 months of age and were decreased significantly (p < 0.01) in 24 month-old rats. The GD1a ganglioside fraction was significantly increased in 6 and 24 month-old rats (p < 0.01). We concluded that the increment of the polar fractions, such as GD3 and GD1b, and the variations of the other fractions in the plasma membrane of the hydrophilic liver tissue during the first 12 months were important parameters.

Protective role of immobilization on ouabain-induced arrhythmias.

The effects of the opioid-type stressor, immobilization, on severity of ouabain-induced cardiac arrhythmias and the possible involvement of serum catecholamines were investigated in rats. Immobilization significantly reduced the number of ventricular premature beats and the incidence of ventricular tachycardia episodes. The arterial serum catecholamine levels (A, NA and DA), measured immediately after the stressor application, were increased significantly and were in negative correlation with the arrhythmia parameters. Both changes were reversed by naloxone (5 mg/kg) treatment after application of immobilization. The effects observed in this study may be attributed to the actions of endogenous opioid peptides released during stress.