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Biomedical subjects

J S Levy

Publications and source records attributed to J S Levy.

28 records · Page 2Linked to original sources
PubMed1975

Inhibition of amino acid transport by ammonium ion in Saccharomyces cerevisiae.

The rate of transport of L-amino acids by Saccharomyces cerevisiae epsilon 1278b increased with time in response to nitrogen starvation. This increase could be prevented by the addition of ammonium sulfate or cycloheximide. A slow time-dependent loss of transport activity was observed when ammonium sulfate (or ammonium sulfate plus cycloheximide) was added to cells after 3 h of nitrogen starvation. This loss of activity was not observed in the presence of cycloheximide alone. In a mutant yeast strain which lacks the nicotinamide adenine dinucleotide phosphate-dependent (anabolic) glutamate dehydrogenase, no significant decrease in amino acid transport was observed when ammonium sulfate was added to nitrogen-starved cells. A double mutant, which lacks the nicotinamide adenine dinucleotide phosphate-dependent enzyme and in addition has a depressed level of the nicotinamide adenine dinucleotide-dependent (catabolic) glutamate dehydrogenase, shows the same sensitivity to ammonium ion as the wild-type strain. These data suggest that the inhibition of amino acid transport by ammonium ion results from the uptake of this metabolite into the cell and its subsequent incorporation into the alpha-amino groups of glutamate and other amino acids.

Amino Acids↗
PubMedDate not supplied

Enamel silicon and fluoride relationships demonstrating a surface silicon effect that facilitates fluoride uptake.

This study indicated that a clear relationship exists between silicon and fluoride. We have also demonstrated a probable surface enamel silicon effect that increases fluoride uptake. The complex set of relationships described in the surface chemistry of calcium, tin, and zirconium with fluoride, hydroxide, phosphate, and other surface-occurring ions need not be considered to confuse the specific silicon-fluoride relationship presented here because in this computation we are relating the changes in the silicon and fluoride ion values only. We have, however, considered the thermodynamics of such reactions and intend to elaborate on it in a later publication. We are aware of the small depth of fluoride penetration into enamel after topical treatment Health Foundation, Research Unit at the National Bureau of Standards, Washington, DC 20034, USA.

Composite Resins↗
PubMedDate not supplied

Marketing service guarantees for health care.

The author introduces the concept of service guarantees for application in health care and differentiates between explicit, implicit, and conditional vs. unconditional types of guarantees. An example of an unconditional guarantee of satisfaction is provided by the hospitality industry. Firms conveying an implicit guarantee are those with outstanding reputations for products such as luxury automobiles, or ultimate customer service, like Nordstrom. Federal Express and Domino's Pizza offer explicit guarantees of on-time delivery. Taking this concept into efforts to improve health care delivery involves a number of caveats. Customers invited to use exceptional service cards may use these to record either satisfaction or dissatisfaction. The cards need to provide enough specific information about issues so that "immediate action could be taken to improve processes." Front-line employees should be empowered to respond to complaints in a meaningful way to resolve the problem before the client leaves the premises.

Commerce↗