Attachment of p-benzophenone side chains at N1 was found to be one of the most effective modifications for enhancing the potency of 6-azauracil against a broad spectrum of coccidia in chickens. Compound 20 was about 1000-fold more potent than 6-azauracil. Structure-activity relationships paralleled those found in a previously reported series of related analogues containing diphenyl sulfide and sulfone side chains. Drug metabolism studies showed the ketones to be reduced rapidly to carbinols, which are the prevalent species in vivo.
The anticoccidial salinomycin has a cidal effect against chicken coccidia. Restricted and unrestricted medication studies and histopathological examinations of chicks infected with Eimeria acervulina, E. maxima, or E. tenella showed that parasites were destroyed within host cells during asexual development. Most sporozoites failed to become trophozoites and were destroyed 30--72 hr after ingestion of oocysts. The drug also affected schizonts during initial nuclear replication by either destroying or significantly delaying their maturation. Parasites affected by the drug were distorted grossly. Drug action against gametogony was not observed histologically, but when medication was restricted to this period of the life cycle, subsequent oocyst shedding of all 3 species was reduced by 20--70% compared to unmedicated controls. When drug was provided during the entire parasite life cycle, activity against asexual stages was so complete that only a limited number of parasites survived to form gamonts, and oocyst shedding was reduced by 80--90% relative to controls. As with other ionophores, salinomycin had no effect upon rate of oocyst sporulation.
An aspect of our work with quinoxaline 1,4-dioxides involved the synthesis and reactivity of (quinoxalin-2-yl)acrylonitrile 1,4-dioxide. We have found that treatment of a methanolic solution of this unsaturated nitrile (cis or trans) with primary alkylamines affords a novel series of pyrido[2,3-b]quinoxaline 5-oxides. These tricyclic pyridoquinoxalines represent a unique class of agents with oral activity against trichomoniasis.
The novel chlorine-containing acidic polycyclic ether antibiotic CP-54,883 (C41H61O12C12) is produced by the fermentation of Actinomadura routienii Huang sp. nov. This report presents the taxonomy and the fermentation conditions for the antibiotic-producing culture. The antibiotic is mainly active against Gram-positive bacteria. It protects chickens against Eimeria challenge in vivo and enhances rumen propionic acid in vitro. The physico-chemical properties are also characterized.
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