Origin of ammonia excreted by trout gill (Salmo gairdneri)]

In the perfused head of Trout the gills are the site of ammonia clearance which corresponds exactly to the appearance rate of ammonia in the external medium. Thus metabolic production of ammonia by the gill apparently does not participate to its excretion. Under ammonia-free Ringer perfusion however, endogenous production is observed and ammonia is excreted in both external and internal media.     

Dominant effector genetics in mammalian cells

We have expressed libraries of peptides in mammalian cells to select for trans-dominant effects on intracellular signaling systems. As an example-and to reveal pharmacologically relevant points in pathways that lead to Taxol resistance-we selected for peptide motifs that confer resistance to Taxol-induced cell death. Of several peptides selected, one, termed RGP8.5, was linked to upregulation of expression of the gene ABCB1 (also known as MDR1, for multiple drug resistance) in HeLa cells. Our data indicate that trans-dominant effector peptides can point to potential mechanisms by which signaling systems operate. Such tools may be useful in functional genomic analysis of signaling pathways in mammalian disease processes.     

Evidence for a Na+/NH4+ exchange in the gill of trout adapted to sea water: adrenergic control]

A Na+/NH4+ exchange similar to that characterizing the fish gill in fresh water was shown to function in the trout adapted to sea water with the help of the head perfusion technique. This exchange stimulated by adrenaline through beta adrenoreceptors and inhibited by amiloride added to the external medium.     

Effect of adrenaline on the influx of Na+ and Cl- in trout (Salmo gairdneri) adapted to seawater]

The effects of adrenaline on the Na+ and Cl- influxes in the seawater adapted trout were studied with the perfused isolated head technique. With 10(-5) M adrenaline in the perfusion fluid, the lamellar influx of Na+ is increased by 60%, while the Cl- influx is inhibited by 90%. This catecholamine does not modify the extra-lamellar entry of NaCl which passes into the filamental sinus.