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Brain receptors and zopiclone.

Zopiclone (ZPC; RP 27,267), which is chemically unrelated to benzodiazepines (BZD), was found to have a similar pharmacological profile and to possess in man hypnotic activity similar to that of some BZD such as nitrazepam. It was, therefore, interesting to study the interaction of ZPC with rat brain receptors and specially with the so-called 'BZD receptors'. ZPC possesses in three rat brain regions a high affinity for BZD receptors: its Ki values measured against [3H]-flunitrazepam are 24 nM in the cerebral cortex, 31 nM in the cerebellum, and 36 nM in the hippocampus. No other brain receptors such as gamma-aminobutyric acid receptor, dopamine receptor, serotonin and noradrenergic receptors are reached by ZPC. Moreover, ZPC seems to bind only to brain BZD receptors and, contrarily to some BZD such as flunitrazepam, it does not reach the peripheral renal BZD-binding sites. The synthesis of [3H]-ZPC has permitted a more in-depth study of the interaction of ZPC with brain receptors. The high affinity of ZPC has been confirmed by equilibrium-binding studies (KD = 13 +/- 4 nM in rat hippocampus) and the study of the modulating effect of gamma-aminobutyric acid and barbiturates on ZPC binding has revealed some differences between ZPC and BZD. It could, therefore, be postulated that ZPC might bind in rat brain to sites which do not correspond exactly to BZD sites.

Animals↗

Spectrophotometric determination of cyanoglucosides in cassava.

A new method is reported for determination of cyanoglucosides in cassava. The method is simple, rapid, and sensitive. Ten g cassava tuber is homogenized with warm (65-70 degrees C) 80% ethanol (1 + 6, w/v) to extract cyanoglucosides (CNG). The ethanol is evaporated, and an aliquot of the extract (0.1-0.2 mL) is incubated with added linamarase in pH 6.0 phosphate buffer for 15 min at 30 degrees C. The reaction is stopped by adding 0.2 N sodium hydroxide, the solution is neutralized, and cyanide is estimated by adding chloramine T and barbituric acid-pyridine reagent and measuring the absorbance at 570 nm. Complete CNG extraction and rapid inactivation of endogenous linamarase is possible with 80% ethanol. There is no interference from extractives in the linamarase reaction or in the estimation of cyanide. Recovery of added linamarin (as cyanide) is 98% by this assay. The minimum detection limit of cyanide in the assay is 0.1 micrograms/mL.

Glycosides↗

Environmental and drug factors in hepatic porphyria.

Numerous drugs and environmental chemicals are capable of influencing the clinical expression of human hepatic porphyria primarily by interfering with the orderly regulation of heme synthesis in the liver. Some agents trigger the disease in otherwise normal individuals whereas others exacerbate an underlying genetic abnormality leading to disease expression. In both instances careful avoidance of exposure to these drugs and chemicals can largely prevent the development of manifest disease. The mechanisms whereby these agents impair the normal regulation of hepatic heme synthesis have been carefully studied in recent years and have provided valuable new insights into this form of drug-induced hepatotoxicity.

5-Aminolevulinate Synthetase↗

Effect of divicine and isouramil on red cell metabolism in normal and G6PD-deficient (Mediterranean variant) subjects. Possible role in the genesis of favism.

Fava beans contain high amounts (up to 6.7 g/100 g dry weight) vicine and convicine. Their active aglycones divicine and isouramil have equivalent metabolic effects. They rapidly oxidize GSH to GSSG in normal and G6PD-deficient red cells. No regeneration of GSH occurs in deficient cells. The stoichiometry of the divicine oxidation of GSH is 1:1. Ascorbic acid is quickly oxidized by isouramil in both normal and deficient cells but regenerates only in normal cells. Isouramil oxidizes NADH at a much lesser extent than NADPH. Glycolysis is activated at the glyceraldehyde 3-phosphate dehydrogenase step. Divicine strongly stimulates hexone monophosphate shunt only in normal red cells. Divicine alone or associated with ascorbic acid has almost no effect in deficient red cells. Malonyl dialdehyde production is slight and virtually the same in normal and deficient cells treated with 5 mM isouramil. Large polypeptide aggregates are formed after 12 and 24 hours incubation with 1 mM divicine in deficient cells only. Divicine (0.25 mM) markedly decreases the filterability of deficient cells. The results are consistent with a causal role of divicine/isouramil in the genesis of the hemolytic crisis occurring in G6PD-deficient subjects after fava bean ingestion.

Ascorbic Acid↗

Computerized axial tomography in the detection of brain damage: 1. Alcohol, nutritional deficiency and drugs of addiction.

The severity and extent of cerebral atrophy was assessed on cranial computerized axial tomographic (CAT) scans in 240 alcoholics in whom this investigation had been performed for diagnostic purposes, and in a group of 59 male heavy social drinkers who were studied prospectively. Findings were compared with those in a group of 115 normal volunteers who were either total abstainers or light infrequent drinkers. Only 12 (5%) of the 240 alcoholics and 20 (33%) of the 59 social drinkers had a normal CAT scan. The remainder all showed a degree of cerebral and/or cerebellar atrophy in excess of that found in the normal subjects in a comparable age bracket. Atrophy was most frequent and most severe in the frontal lobes and superior vermis of the cerebellum, but, in most cases, there was more widespread cerebral and cerebellar cortical atrophy. The CAT scans of four patients with anorexia nervosa, two of whom showed an excessive degree of cerebral cortical atrophy for the patient's age, and of eight young people addicted to heroin, cannabis, lysergic acid or barbiturates, six of whom showed varying degrees of premature cerebral atrophy, were also studied.

Adolescent↗