Synthesis of Cytoplasmic Membrane-associated DNA in Lymphocyte Nucleus

The unique species of DNA associated with the cytoplasmic membranes of human lymphocytes in culture is synthesized in the nucleus during the S growth phase and then transported to the plasma membrane.     

A Developmental Window for Salt-Adaptation in Sorghum bicolor

Following exposure to specific NaCl treatments, certain Sorghumbicolor genotypes developed increased salinity tolerance, ‘adaptation’,which was accompanied by a morphological modification in thedevelopment of one or several leaves. Adaptation differed fromthe more common response of the plant to salinity, ‘pre–existingresistance’, which rested on the prevalent tolerance mechanismsexisting prior to the salinization treatment. Induction of adaptationwas possible only during a specific time period of plant development.This time-limited capacity for adjustment to a changing environmentalparameter, developmental window, resembled similar processesoccurring in animal development. Key words: Sorghum, adaptation, resistance, salinity, developmental window     

A Rapid Quantitative Bioassay for Evaluating the Effects of Ligands Upon Receptors That Modulate cAMP Levels in a Melanophore Cell Line

A new method for rapidly evaluating the effects of drugs on receptors that regulate intracellular cAMP in a cell line derived from Xenopus laevis melanophores has been developed. Melanophores were plated into sterile 96 well microtiter plates, and 3 days later the cells were treated with melatonin for 30 min to induce melanosome aggregation. Subsequent exposure to MSH or adrenergic agonists caused dose dependent pigment dispersion that peaked within 30 min. The cumulative pigment displacement from cells could be quantitated by using a microplate reader to measure changes in transmittance of light through the wells. The acquired data enabled detailed and reproducible dose response curves and time course analyses to be generated. In addition, the assay followed for the rapid characterization of the effects of antagonists upon the (β adrenergic receptor (β AR). The assay has the potential to test the effects of ligands upon any receptor capable of mediating pigment translocation in the melanophore cell line.