Pertussis toxin blocks the outward currents evoked by opiate and alpha 2-agonists in locus coeruleus neurons

Pertussis toxin, a substance known to inactivate the inhibitory guanine nucleotide regulatory unit of adenylate cyclase, was injected into the lateral cerebral ventricle of rats; intracellular recordings were made from locus coeruleus neurons in brain slices 1-3 days later. Morphine (an opiate agonist) and clonidine (an alpha 2-agonist) produced the expected outward currents (and associated hyperpolarization and inhibition of firing) in controls whereas the effects of both agonists were blocked in animals pretreated with pertussis toxin. These results are consistent with the hypothesis that opiate and alpha 2-agonists may depress the firing of locus coeruleus neurons by inhibiting adenylate cyclase via a guanine nucleotide regulatory protein.

Structure-activity relationships of nitro and methyl-nitro derivatives of indoline, indole, indazole and benzimidazole in Salmonella typhimurium

The mutagenic activities of eleven nitro derivatives and eleven N-methyl-nitro derivatives of indoline, indole, indazole and benzimidazole were investigated in Salmonella TA98 and TA100. The presence of a nitro group at C4 or C7 resulted in only weakly or nonmutagenic compounds, while a nitro group at C2, C5 or C6 usually resulted in measurable mutagenic activity in the non-N-methylated compounds. Methylation of a ring nitrogen usually reduced the mutagenic activity of these nitroheterocyclics except 2-nitro-benzimidazole, which resulted in a better than 300-fold increase in mutagenic activity. A proposed mechanism for the increased mutagenic activity obtained by methylation of imidazole nitrogens may provide insights into the reasons for the potent mutagenicities observed for several similarly methylated cooked-food mutagens.

Improvement in hearing among otherwise normal schoolchildren in iodine-deficient areas of Guizhou, China, following use of iodized salt

According to a survey in Guizhou province of China, the average hearing level of otherwise normal schoolchildren in an area of endemic iodine-deficient goitre and cretinism was significantly poorer than in a non-endemic control area. After iodine prophylaxis for three years, audiometric tests showed that the average hearing level had improved and approached that of the non-endemic controls. In addition, mean values for thyroid function tests were restored to within the normal range. It is suggested that the most likely cause of the poorer hearing level among the ostensibly normal schoolchildren in endemic areas is subclinical hypothyroidism due to prolonged severe iodine deficiency.

Formation of mutagens in cooked foods. V. The mutagen reducing effect of soy protein concentrates and antioxidants during frying of beef

Cooking beef patties results in the formation of mutagens detectable by Salmonella typhimurium TA98 with metabolic activation. Decreased mutagenic activity results when frying beef with added soy protein concentrates (SPC). The reduction in mutagenicity takes place during the cooking process. Whereas fried beef hamburgers show high mutagenic activity, by comparison, similarly fried soy-hamburgers have much less mutagenic activity. Volumetric effects are responsible partly for the reduction on mutagenicity by SPC. Naturally occurring antioxidants in SPC, such as chlorogenic acid, also play a role. Also, a commonly used antioxidant, butylated hydroxyanisole (BHA), has been found effective in reducing the mutagenicity of fried beef. Thus, the addition of SPC or BHA in beef patties may provide a practical way of reducing mutagen formation during frying of beef.

Enhancement of formation of the esophageal carcinogen benzylmethylnitrosamine from its precursors by Candida albicans

Previous studies in Linxian, an area of China with a high incidence of esophageal carcinoma, showed that fungal infections are common in the esophageal epithelium of patients with either premalignant changes or early esophageal carcinoma. Fungi of the genus Candida were the most frequent invaders. In these areas nitrate and nitrite are often present in high concentrations in drinking water and staple grains. The present studies have established the ability of Candida albicans to augment the nitrosative formation of the esophagus-specific carcinogen, benzylmethylnitrosamine (NBMA; N-nitroso-N-methylbenzylamine). Stationary C. albicans cultures, with pH held at 6.8, were incubated with the precursors of NBMA, benzylmethylamine (BMA; N-methylbenzylamine) and NaNO(2). There was a significant increase in the amount of NBMA formed in these cultures, compared to precursors-only controls. The amount of NBMA synthesized depended on fungal cell number. Exponentially growing cultures were also able to cause NBMA formation. The identity of the NBMA was confirmed by high-performance liquid chromatographic coelution with authentic NBMA in three solvent systems and by mass spectroscopy. Boiled cells and conditioned medium in which cells had been incubated were not effective in enhancing nitrosation. Cultured Candida released acidic metabolites that reduced the pH of the medium when only a low concentration of buffer was present. Spontaneous nitrosation of BMA was enhanced under these acidic conditions. Thus, C. albicans infecting the esophageal epithelium could cause local formation of NBMA by both cell-mediated catalysis and extracellular decrease in pH.

Antimutagenic properties of liver homogenates, proteins and glutathione on diesel exhaust particulates

Diesel exhaust particulates contain mutagens which are active in the Ames Salmonella typhimurium assay. The mutagens do not require liver enzymes for activation and, in fact, the addition of liver homogenates (S-9) to the Ames system decreases the mutagenicity of diesel exhaust samples. We have examined here the properties and components of S-9 that account for its antimutagenic effect. The antimutagenic effect of S-9 is not changed by heating S-9 in a boiling water bath for 5 min or by omission of the NADPH-generating system in the cofactor mixture. These experiments showed that the antimutagenic effect on S-9 is not enzymatic. The antimutagenicity of S-9 disappeared after the protein component of S-9 was removed by filtration. Exogenous albumin added to the Ames system mimicked the antimutagenic effect. Analysis of the albumin content of liver cytosol showed that 90% of the antimutagenic effect could be accounted for by the amount of albumin present. Glutathione added to diesel exhausts reduced mutagenicity, but the qualities of glutathione present in S-9 are too small to account for the antimutagenic effect of S-9. We conclude that the antimutagenic effect of S-9 is non-enzymatic and is most likely the result of non-specific protein binding of mutagens to liver albumin. The antimutagenic effect of glutathione on diesel exhausts suggests that the mutagens present are electrophiles.

Seizure disorders and trace metals: manganese tissue levels in treated epileptics

We determined the concentrations of manganese in whole blood and hair in 52 epileptics, 6 blood relatives, and 24 normal controls. Blood, and possibly hair manganese content, was significantly lower in treated epileptics than in controls (p less than 0.002). Although not all patients showed reduced tissue manganese levels, most of those with frequent seizures had manganese levels falling below the lowest control level, suggesting a relationship between manganese tissue levels and high seizure activity. These differences in manganese levels were not correlated with the type, dose, or plasma levels of anticonvulsant medication. Reduced manganese availability at the neuronal level, where Mn++ stabilizes membrane excitability, may affect epileptogenic lesions to increase the likelihood of seizure activity.

Protein quality of several multi-component, commercially prepared foods

Eleven commercial food products that may be considered by consumers to be major sources of protein were evaluated. Most of these items contained significant amounts of carbohydrate in the form of cereal products or purified sugars. Seven of the products were at least equal to casein in protein efficiency ratio (PER). Canned spaghetti and meat balls, the TV dinner, canned chicken-and-vegetable baby food, and food bars had PER values between 91 and 73 per cent of that of casein, while PER values for ground beef and high-protein cereal were significantly higher than casein.

On the correlation between rast and the allergy intradermal test

RAST and intradermal testing correlated reasonably well for untreated patients for ragweed and molds and in treated patients for trees. Capillary blood was found to be comparable to venous blood as a source for RAST for ragweed and mixed grasses.

Plasma DOPA and growth hormone in parkinsonism: oscillations in symptoms

In 19 patients with Parkinson disease, we studied the relationship of the therapeutic effect of levodopa, or dyskinesia, to the plasma content of DOPA and growth hormone (GH). Those with stable responses to levodopa, individually or as a group, showed stable and lower plasma DOPA levels than those with unstable symptomatic responses. These results show that stable and oscillating clinical responses in Parkinson disease parallel plasma DOPA levels, suggesting that there are different mechanisms in peripheral levodopa metabolism and that extracerebral mechanisms are important in regulating the availability of levodopa to the brain. Plasma GH did not differ in the two groups, suggesting that the secretion of GH is independent of the effects of levodopa in parkinsonism.

Direct-acting mutagens in automobile exhaust

Particulate matter in city air contains chemicals which are mutagenic in the Ames Salmonella typhimurium assay. In residential urban areas, the principal mutagens in air do not require liver enzymes to be activated. The source of these liver independent (direct-acting) mutagens may be automobile exhaust because (1) the mutagenic activities were correlated to the lead content or air, (2) the mutagens were found exhaust samples from automobiles and from an experimental CFR single-cylinder gasoline engine, and (3) these mutagens were not found in fuel or unused motor oil, but were found in used motor oil. The strain specificity and the fact that liver enzymes were not required for activation indicated that the exhaust and airborne mutagens were not unsubstituted polycyclic aromatic hydrocarbons (PAH), aromatic amines, alkylnitrosamines or aliphatic epoxides, peroxides and hydroepoxides. A number of nitro-substituted aromatic compounds are direct-acting mutagens in the Ames test, and it is possible that nitration of PAH in exhaust may form the compounds observed here. We synthesized 6-nitrobenzo [a] pyrene and found it to be a potent, direct-acting mutagen with activity comparable to that of benzo-[a] pyrene.