Activity of phosphatidylethanolamine-N-methyltransferase in brain affected by Alzheimer's disease.

To determine whether phospholipid abnormality in Alzheimer's disease is associated with modification of phosphatidylethanolamine-N-methyltransferase, the activity of the enzyme was analysed in the frontal and occipital cortex of the brain from patients with Alzheimer's disease and from aged-matched control. The optimum pH for phosphatidylethanolamine-N-methyltransferase in human brain was 9.0. The enzyme activity was stimulated by detergent TWEEN 20 but inhibited by Triton X-100. Neither magnesium dependence nor chemical methylation was found. A decrease in activity of phosphatidylethanolamine-N-methyltransferase was observed in the frontal cortex of brain affected with Alzheimer's disease. The addition of exogenous phosphatidylethanolamine resulted in no modification in the methylation rate as compared with that of endogenous PE. The addition of phosphatidyl-N-monomethylethanolamine and phosphatidyl-N,N-dimethylethanolamine resulted in significantly increased rates of methylation in brain tissues. However, the increased rate of phosphatidylethanolamine-N-methyltransferase activity stimulated by exogenous phospholipids was lower in the frontal cortex of brains with Alzheimer's disease when compared to the normals and there was no difference in the occipital cortex between Alzheimer's disease and the control. It is plausible that the decreased activity of phosphatidylethanolamine-N-methyltransferase and its low compensating ability could relate to the modification of phosphatidylcholine in brain tissues from Alzheimer's disease patients.

Effect of long term fluoride exposure on lipid composition in rat liver.

Chronic fluorosis can severely damage many systems of human body, but its pathogenesis is unclear. Normal composition and structure of cellular membrane lipids are a basic factor to maintain cell function. In this investigation, cellular membrane lipids of the liver were analysed after a long term fluoride treatment for rats and the results are discussed in order to give an explanation for the pathogenesis of this disease. Wistar rats were supplied with drinking water containing either 30 or 100 ppm fluoride (NaF) for seven months. Contents of phospholipid and neutral lipid in rat liver were analyzed by high-performance liquid chromatography, and fatty acid composition from individual phospholipids was measured by gas chromatography. Results showed that the total liver phospholipid content decreased in the rats treated with high dose of fluoride due to a lower content of phosphatidylethanolamine (PE), phosphatidylcholine (PC) and phosphatidylserine (PS). Among the fatty acid compositions of PE and PC in the livers of fluoride poisoned animals, the proportion of polyunsaturated fatty acids (20:4 and 22:6) decreased, whereas saturated fatty acids (16:0 and 18:0) increased. No changes could be detected in the amounts of liver cholesterol and dolichol. Total ubiquinone contents in rat liver were reduced by 11% in the group treated with 30 ppm fluoride and by 42% in the group treated with 100 ppm fluoride. In the subclasses of ubiquinone, both ubiquinone-9 and ubiquinoine-10 amounts decreased after fluoride treatment. These modifications of membrane lipids might be induced by oxidative stress, which might be an important factor in the pathogenesis of chronic fluorosis.

Influence of chronic fluorosis on membrane lipids in rat brain.

Brain membrane lipid in rats were analyzed after being fed either 30 or 100 ppm fluoride for 3, 5, and 7 months. The protein content of brain with fluorosis decreased, whereas the DNA content remained stable during the entire period of investigation. After 7 months of fluoride treatment, the total brain phospholipid content decreased by 10% and 20% in the 30 and 100 ppm fluoride groups, respectively. The main species of phospholipid influenced by fluorosis were phosphatidylethanolamine, phosphatidylcholine, and phosphatidylserine. The fatty acid and aldehyde compositions of individual phospholipid classes were unchanged. No modifications could be detected in the amounts of cholesterol and dolichol. After 3 months of fluoride treatment, ubiquinone contents in brain were lower; however, at 7 months they were obviously increased in both groups of fluoride treatment. The results demonstrate that the contents of phospholipid and ubiquinone are modified in brains affected by chronic fluorosis and these changes of membrane lipids could be involved in the pathogenesis of this disease.

[Electron microscopy microanalysis and quantitative detection of trace elements in carcinoma of the colon].

The spectrum of trace elements was determined in 19 cases of colon carcinoma with analytical electron microscope. Besides, the quantities of trace elements in the cancerous tissue and the mucosa beyond the site of cancer were measured in 31 cases by flameless atomic absorption spectrophotometry. A reprocessing technique was applied to convert the paraffin sections directly to resin sections in order to recover the assessment of elements in these tissues. Fe, Al and macro elements Ca, S were recovered in 100% of the cases in both the cancer tissue and the mucosa taken beyond the site of cancer. The recovery rates of Ni and macro elements including K, Mg, P, Cl were 50%. The recovery rates of Si in poorly-differentiated adenocarcinoma were higher than that in the mucosa far from the cancer site. The levels of Cu, Zn and Ni in the cancerous tissue were lower than those detected in the mucosa (P < 0.01). No significant difference was noticed between the cancerous tissue and the mucosa beyond the site of cancer on Fe, Mn, Pb, Co and Cr contents.

[Radiological study of lumbosacral nerve root sheath cyst (analysis of 65 cases)].

65 cases of nerve root sheath cyst of lumbosacral region were found out of 544 cases of myelography, 43 were confirmed by operation. The main radiologic features were: round or oval in shape in 28 cases; cylindrical or fusiform in 14; and mixed form in 13. In 10 cases, the contrast medium was seen to extend in an irregular pattern along nerve root sheath.

Changed cellular membrane lipid composition and lipid peroxidation of kidney in rats with chronic fluorosis.

An animal model of chronic fluorosis was produced by subjecting Wistar rats to high doses of fluoride in drinking water for a prolonged period. Phospholipid and neutral lipid contents in rat kidney were then analyzed by high-performance liquid chromatography (HPLC), and fatty acid compositions from individual phospholipids were measured by gas chromatography. Lipid peroxidation was detected by the thiobarbituric-acid-reactive substance assay. Results showed that the total phospholipid content significantly decreased in the kidney of the rats treated with high doses of fluoride and the main species influenced were phosphatidylethanolamine (PE) and phosphatidylcholine (PC). Decreased proportions of polyunsaturated fatty acids were observed in PE and PC in kidney of fluoride-treated animals compared to controls. No changes could be detected in the amounts of cholesterol and dolichol in kidneys between the rats treated with fluoride and controls. A significant decrease of ubiquinone in rat kidney was observed in the groups treated with excessive fluoride. High levels of lipid peroxidation were detected in kidney of the rats with fluorosis. It is plausible that the specific modification of lipid composition results from lipid peroxidation. The oxidative stress and modification of cellular membrane lipids may be involved in the pathogenesis of chronic fluorosis and provide a possible explanation for the gross system damage observed in the body, especially in soft tissues and organs.