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Biomedical subjects

D R Reed

Publications and source records attributed to D R Reed.

43 records · Page 3Linked to original sources
PubMed1986

Tolerance to hypothermia induced by ethanol depends on specific drug effects.

Two experiments were conducted to test the hypothesis that tolerance to the hypothermic effect of ethanol fails to develop if rats are denied the unconditional stimulus represented by hypothermia. In both experiments, rats were injected with either ethanol (1.9 or 2.5 g/kg) or saline and given microwave hyperthermia (MHT) to offset the hypothermic effect of the drug or sham-MHT. In one experiment, rats no longer demonstrated a hyperthermic response to a saline challenge after hypothermia was offset during 5 MHT treatment sessions. In a second experiment, rats prevented from becoming hypothermic did not develop tolerance to the hypothermic effect of ethanol due to MHT treatment, but did become tolerant to the ataxic effects of ethanol, which were unaffected by MHT. Results suggest that rats must experience the specific consequences of a drug to become tolerant to that effect.

Adaptation, Physiological↗
PubMedDate not supplied

Flip angle dependence of experimentally determined T1sat and apparent magnetization transfer rate constants.

The purpose of this work was to develop a method for determining the T1sat and magnetization transfer (MT) rate constants by analyzing the slice-select flip angle dependent MT behavior of normal white and gray matter. The technique uses a high MT power, three-dimensional (3D) gradient-recalled echo (GRE) sequence, with a well chosen MT pulse frequency offset, such that the experimental conditions closely satisfy requisite assumptions for invoking a first order rate process for MT. Integral to this method is that the T1sat and MT ratio values are obtained under explicitly identical MT saturation conditions. The T1sat of white matter was found to be approximately 300 msec, and the MT rate constant was approximately 2.0 sec(-1). The T1sat of gray matter was approximately 500 msec, and the MT rate constant was 1.1 sec(-1). We also found a strong dependence of the MT rate constant on the slice-select flip angle used for the imaging sequence, independent of the MT saturation parameters. Strongly T1-weighted imaging sequences can result in the underestimation of the MT rate constant by 50%. Practical technical suggestions for quantitative MT experiments are put forth.

Adult↗
PubMedDate not supplied

The genetics of phenylthiocarbamide perception.

The ability to taste the bitter compound phenylthiocarbamide (PTC) and related chemicals is bimodal, and all human populations tested to date contain some people who can and some people who cannot taste PTC. Why this trait has been maintained in the population is uncertain but this polymorphism may influence food selection, nutritional status or thyroid metabolism. The gene product that gives rise to this phenotype is unknown, and its characterization would provide insight into the mechanism of bitter taste perception. Although this trait is often considered a simple Mendelian trait, i.e. one gene two alleles, a recent linkage study found a major locus on chromosome 5p15 and evidence for an additional locus on chromosome 7. The development of methods to identify these genes will provide a good stepping-stone between single-gene disorders and polygenic traits.

Antimetabolites↗