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treated animals were as follows: histamine, 0.22 zk 0.019 and 0.0098 f 0.0012; oxotremorine, 0.16 f 0.017 and 0.0062 f 0.0004; nicotine, 1.08 f 0.15 and 0.15 f 0.038; and serotonin, 12.8 f 0.29 and 0.12 =t 0.016. The toxicity of histamine was also increased by pretreatment with dichloroisoproterenol.
The resistance of the bronchiolar tree t o Krebs-Henseleit perfusion in lungs excised after intravenous injection of lethal doses of bronchoconstrictors was much higher than that of lungs from control animals.
Doses of oxotremorine, serotonin, and histamine which did not change the resistance to perfusion, resulted in pronounced postmortem bronchoconstriction when the animals had received an intravenous dose of 10 mg./kg. of propranolol 15 min. before the bronchoconstrictor. A similar phenomenon was observed when 1.5 mg./kg. of nicotine was injected i.v. with propranolol.
The results indicate that in toxicity tests in control guinea pigs endogenous catecholamines exert a powerful antagonistic action against the bronchoconstrictor effect of histamine, serotonin, and oxotremorine. In the case of these three substances this protective mechanism can be overwhelmed by larger doses; the mechanism of death is bronchoconstriction.
Nicotine, which is a bronchoconstrictor in the guinea pig pretreated with propranolol, does not kill untreated guinea pigs by producing bronchoconstriction.
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## Abstract For Abstract see ChemInform Abstract in Full Text.
Antibacterial activity of petroleum ether (PE), benzene (BE), chloroform (CE), acetone (AE) and ethanol (EE) extracts of dried Elaeocarpus sphaericus fruit was investigated against 28 gram-positive and gramnegative bacteria using the disc diffusion and plate dilution methods. The AE fraction showed