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RK Johnson

Publications and source records attributed to RK Johnson.

4 recordsLinked to original sources
PubMed1999

Amphibian Melanophore Technology as a Functional Screen for Antagonists of G-Protein Coupled 7-Transmembrane Receptors.

Xenopus laevis melanophores stably expressing 7-transmembrane G-protein-coupled receptors were established and evaluated, either as a primary screening utility for antagonists of the human calcium receptor, or as a screen to assign function to binding inhibitors of human cannabinoid receptors. Stably or transiently expressing melanophores responded selectively to respective effectors of the human calcium, cannabinoid, and neurokinin-1 receptors. Several selective cannabinoid receptor-binding inhibitors of known potency were characterized as agonists or antagonists of the human peripheral cannabinoid (CB(2)) receptor. The results were consistent with changes in cAMP content of hCB(2)-transfected human embryonic kidney (HEK) cells challenged with the same CB(2)-binding antagonists. A stable melanophore cell line expressing the human calcium receptor was used to screen a compound collection directly for functional antagonists, several of which were confirmed as antagonists in secondary screens by stimulating parathyroid hormone (PTH) secretion from bovine parathyroid cells. The percentage of hits in this cell-based screen was reasonably low (1.2%), indicating minimal interference due to toxic effects and validating melanophores as a primary screening modality. Also described is the development of a novel procedure for cryopreservation and reconstitution of cells retaining functional human receptors. ()

Journal Article↗
PubMed1998

Chemical mediation of egg dumping in the lace bug Gargaphia solani Heidemann (Heteroptera: Tingidae).

We tested the hypothesis that the proximate cue for egg dumping in the lace bug Gargaphia solani Heidemann is a chemical deposited by females on eggs during or shortly after oviposition. The results of this study show that: (1) dumping frequency declines as eggs age but can be elevated to its highest levels by exposure to chemical extracts from young egg masses; and (2) visual cues are not necessary to stimulate dumping. Further data support the hypothesis that the ovipositional chemical is used by egg dumpers as a long-distance signal of an appropriate oviposition site, and is not a mechanism by which guarding females relocate their eggs if separated from them. (c) 1998 The Association for the Study of Animal Behaviour.

Journal Article↗