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Nitric oxide (NO) was analysed in expired air from 27 healthy human subjects. At rest the NO concentration was 10.5 +/- 0.9 ng 1-1 (mean +/- SEM) corresponding to 8.6 +/- 0.7 parts per billion (ppb). The expired NO concentration did not change when the subjects were switched from breathing NO-free tank gas to room air which contained 7.7 ng l-1 NO. Repeated measurements of expired NO with an interval of 1 day showed a mean variation of 2.2 +/- 0.7 ng l-1 NO. The NO concentration in the first portion in the expired tidal volume (44%) was insignificantly higher than in the latter expired portion, 6.9 +/- 1.9 vs. 5.1 +/- 1.0 ng l-1 (n = 5). During moderately heavy exercise on an ergometer bicycle (90 W for women, n = 4, 150 W for men, n = 4) the expired concentration of NO decreased, however because of increased minute ventilation, the expired amount of NO almost doubled (from 111 +/- 12 to 209 +/- 30 ng min-1). The source of the expired NO is not clear and both the airways and the pulmonary circulation may contribute.

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Seventeen medicinal plants used popularly in Brazil for their reputed analgesic properties were tested in mice by the writhing and tail flick methods. All extractions were made in 50% aqueous ethanol at low temperatures. The oral dose administered was always 1 g extract/kg. Significant effects in both tests were produced by Lippia alba, Piper abutiloides, Piper cincinnatoris, Piper lindbergii and Tillandsia usneoides.

GABA levels of the whole mouse brain were studied after in vivo inhibition of GABA synthesis by 3-mercaptopropionic acid (3-MPA, 100 mg/kg i.p.) and of GABA degradation by aminooxyacetic acid (AOAA, 3.8-60 mg/kg i.v.). The influence of 3-MPA on GABA levels was investigated in brains where postmortal GABA accumulation was allowed to occur and in brains where this phenomenon was avoided by very rapid dissection and homogenization of the brain in acid (within 50 sec after decapitation). The post-mortal GABA increase was blocked by 86% after injection of 3-MPA and 3 min before decapitation. In the group where the postmortal accumulation was avoided by very rapid homogenization of the brain in acid, GABA levels decreased by 15% within 2 min after 3-MPA (mean turnover time = 14 min). From 2 to 4 min the GABA concentration remained stable at this decreased level. GABA accumulation after AOAA was maximal after a dose of 7.5 to 15 mg/kg. i.v. Doses higher than 60 mg/kg always produced convulsions. The phase of most rapid accumulation of GABA after AOAA indicates a mean turnover time of about 10 min. The first rapid phase of accumulation was followed by a slower phase. It is probable that the turnover time of whole mouse brain GABA is approximately 10-14 min. It is also concluded that AOAA in a dose of around 15 mg/kg i.v. hardly can inhibit GAD in vivo in the mouse brain and that this dose, by this route of administration, could be used for studies of GABA synthesis in vivo in the mouse.

A systematic search for solasodine, an important starting material for the partial synthesis of steroidal hormones as well as other potentially bioactive constituents of various Solanum species of Brazil has been undertaken. Thus, the fruits of S. paludosum, S. asperum, S. sessiliflorum and Solanum sp. were found to contain significant amounts of solasodine. The root bark of S. paludosum which showed curare like activity yielded tomatidenol and another yet unidentified alkaloid responsible for the biological activity. The fruits of S. asperum yielded a new spirosolane alkaloid, solaparnaine. The stem bark of S. pseudo-quina showed convulsive and excitatory activity from which (25S)-isosolafloridine was identified as the active principle. In addition, the latter alkaloid was also found to show antimicrobial activity.