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Biomedical subjects

P W Washko

Publications and source records attributed to P W Washko.

7 recordsLinked to original sources
PubMed1991

Ascorbic acid and in situ kinetics: a new approach to vitamin requirements.

Ascorbic acid requirements are based on preventing the deficiency disease scurvy and on urinary excretion of vitamin C. We proposed the first quantitative approach to determining optimal requirements for ascorbic acid and other vitamins, called in situ kinetics. In situ kinetics biochemically is based on the application of Michaelis-Menten reaction kinetics to ascorbic acid-dependent reactions in situ. Clinically in situ kinetics is based on determining vitamin availability to tissues so that cell-specific reactions can occur. The biochemical concepts of in situ kinetics are verified for the first time through studying ascorbic acid regulation of norepinephrine biosynthesis. The principles of in situ kinetics can now be applied to humans and human cells and for determining optimal requirements for ascorbic acid and for other vitamins.

Ascorbic Acid↗
PubMed1990

Determination of dehydroascorbic acid using high-performance liquid chromatography with coulometric electrochemical detection.

A method for the detection of dehydroascorbic acid using high-performance liquid chromatography with coulometric electrochemical detection is described. Samples were first assayed for ascorbic acid, then reduced with 2,3-dimercapto-1-propanol to convert dehydroascorbic acid in the sample to ascorbic acid, and subsequently reassayed for total ascorbic acid. The dehydroascorbic acid content was the difference between the two measurements. The dehydroascorbic acid assay provides complete recovery of dehydroascorbic acid, without affecting the ascorbic acid content present prior to reduction. The assay is highly sensitive and reproducible with both standards and biological samples, and was used for routine detection of less than or equal to 1 pmol per sample injection of dehydroascorbic acid. Prior to reduction, dehydroascorbic acid standards frozen at -80 degrees C were stable for at least 1 month; after reduction, stability was limited to 3 days. Dehydroascorbic acid was added to human neutrophil samples; the samples were reduced and ascorbic acid was measured. Ascorbic acid in these samples was stable for greater than or equal to 12 h in a refrigerated autosampler (0-2 degrees C). With a run time for each sample of only 4 min, multiple samples can be prepared and placed in the autosampler for unattended assaying.

Chromatography, High Pressure Liquid↗
PubMed1989

Ascorbic acid analysis using high-performance liquid chromatography with coulometric electrochemical detection.

A method for the detection of ascorbic acid using high-performance liquid chromatography with coulometric electrochemical detection and a technique for stabilization of the vitamin are described. Since less than 1 pmol of ascorbic acid can be detected, this assay provides significantly greater sensitivity than nearly all of the currently available procedures. Stabilization of 10 pmol or less of ascorbic acid at room temperature for up to 4 h and for several weeks at -70 degrees C facilitates storage of a large number of samples and measurement of ascorbic acid using an automated sampling device. This method was used to quantitate the amounts of ascorbic acid in human polymorphonuclear leukocytes and bovine adrenomedullary chromaffin granules. The calculated concentrations found for human neutrophils (1.35 mM) and bovine chromaffin granules (10.0 mM) are in agreement with previously published data. The assay is suitable for the determination of ascorbic acid in biological samples where only a small amount of tissue is available or very low amounts of ascorbic acid are found. This method is the first application of coulometric electrochemical detection to ascorbic acid HPLC analysis.

Animals↗
PubMed1988

Relationship of mandibular anterior tooth apices to genial muscle attachments.

Ten adult midsagittally sectioned cadaver heads were used to measure the distance between the apex of the central incisor or canine teeth and the attachment of the genioglossus or geniohyoid muscles. Measurements were made on both cadaver specimens and radiographs. The results of the two methods showed no statistically significant difference. The results indicate that there is a relatively small chance (5.6%) of including the genioglossus attachment in the lingual pedicle if an anterior mandibular subapical osteotomy is positioned 3 to 5 mm below the incisor apex but a large chance (65%) of including the genioglossus muscle when the osteotomy procedure includes the canine teeth.

Adult↗
PubMed1976

Metabolism of 109Cd in rats fed normal and low-calcium diets.

Growing male rats were fed purified diets that contained either 0.6% or 0.1% calcium to investigate the relationship of calcium intake to the uptake, tissue distribution, and excretion of 109Cd. An equal number of rats were fed either the 0.6 or 0.1% calcium diets for 4 wk before they were used for experiments. In the first experiment 11 rats from each dietary group were administered 5 muCi 109Cd by stomach tube and were then maintained in metabolism cages for 72 hr. Animals fed the low-calcium diet took up more 109Cd, as significantly higher levels of radioactivity were found in the intestinal mucosa, serum, lungs, liver, kidneys, and urine and a significantly lower level was found in the feces. Higher levels of 109Cd, associated with low-molecular-weight proteins that may be related to the absorption process, were found in the intestinal mucosa of the low-calcium group. In the second experiment 10 rats from each dietary group were administered 5 muCi 109Cd by subcutaneous injection and then maintained in a metabolism cage for 72 hr. No significant differences were found in the distribution or excretion of 109Cd except for the lungs where radioactivity was greater in the low-calcium group. The results of the study indicate that the enhanced cadmium toxicity observed in calcium-deficient animals exposed to the heavy metal is the result of an increased uptake from the small intestine.

Animals↗