Regulation of glucose and maltose transport in strains ofSaccharomyces

Summary Growth of yeast cells on glucose resulted in complete inactivation of maltose transport and repression of the high affinity glucose transport system. When the cells were grown on maltose or subjected to substrate starvation, an increase in glucose and maltose transport was observed in both brewing and non-brewing yeast strains. The concentration of glucose employed in the growth medium was also observed to affect sugar transport activity. The higher the glucose concentration, the more pronounced the repressive effect. In addition, the time of growth of yeast on glucose or maltose also intermining the rate of sugar transport. These results are consistent with the repressive effect of glucose on the high affinity glucose and maltose transport systems.     

Separate and shared lysosomal transport of branched and aromatic dipolar amino acids

Transport systems analogous to the T and L carriers for aromatic and bulky dipolar amino acids in plasma membranes have been characterized in the membranes of intact lysosomes isolated from human fetal skin fibroblasts. While system L appears ubiquitous in plasma membranes, system T has previously been discriminated only in the plasmalemma of human red blood cells and freshly isolated rat hepatocytes. Our findings with the lysosomal systems, provisionally designated t and l, reveal both shared and dissimilar properties with the plasma membrane systems. These properties include a lack of dependency on extralysosomal Na+, differential sensitivities to the classical system L analog, 2-aminobicyclo[2.2.1]heptane-2-carboxylic acid (BCH), and the system T analog, D-tryptophan, as well as susceptibility to thiol modification at the membrane by reactivity with N-ethylmaleimide. A transport system in lysosomes from the FRTL-5 rat thyroid cell line has been described by Bernar et al. ((1986) J. Biol. Chem. 261, 17107-17112) resembles a composite of both carrier systems reported in this work.     

The taste characteristics of sodium-saccharin in the rat: a re-examination of the dual taste hypothesis

A conditioned flavor aversion (CFA) was used to measure thetaste characteristics of 0.005 and 0.025 M Na-saccharin in therat. At neither concentration did the rats show generalizationto NaCl, quinine HCl or SO₄, sucrose octa-acetate or HCl, whereasgeneralization to sucrose was found at both concentrations.When the CFA was formed to 0.0001 M quinine HCl, no direct evidencewas found for generalization of the aversion to either saccharinconcentration. Thus at the two concentrations used Na-saccharinwould appear to be primarily sucrose-like in the rat taste systemwhen behavioral criteria are used.