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Biomedical subjects

K D White

Publications and source records attributed to K D White.

45 records · Page 3Linked to original sources
PubMedDate not supplied

Mobility, extraversion, and neuroticism.

Mobility, a property of Pavlovian higher nervous activity, was measured using an induction task. Negative induction, following presentation of an excitatory stimulus, is an index of mobility of excitation and positive induction, following presentation of an inhibitory stimulus is an index of mobility of inhibition. Mobility scores from 27 male and 37 female first-year psychology students, age 17 to 42 years were related to extraversion and neuroticism derived from Eysenck's Personality Inventory (Form A). Mobility of excitation and mobility of inhibition were found to be unrelated. Individual differences in the magnitude and latency of induction indicate that individuals can be typed according to low, medium, or high mobility of either nervous process. No relationship was found between neuroticism and mobility, and no relationship was found between extraversion and mobility of excitation. However, a significant negative relationship was found between extraversion and mobility of inhibition, providing a link between Pavlovian properties of the nervous system and Eysenck's personality dimension of extraversion.

Adolescent↗
PubMedDate not supplied

Determination and survey of ochratoxin A in wheat, barley, and coffee--1997.

Ochratoxin A (OA) is a nephrotoxic and nephrocarcinogenic mycotoxin produced by Aspergillus and Penicillium species. It has been found mainly in cereal grains and coffee beans. The purpose of this study was to investigate the occurrence of OA in cereal grains and in coffee imported to the United States. A modified liquid chromatographic (LC) method for determining OA in green coffee was applied to wheat, barley, green coffee, and roasted coffee. The test sample was extracted with methanol-1% NaHCO3 (7 + 3), and the extract was filtered. The filtrate was diluted with phosphate-buffered saline (PBS), filtered, and passed through an immunoaffinity column. After the column was washed with PBS and then with water, OA was eluted with methanol. The eluate was evaporated to dryness, and the residue was dissolved in acetonitrile-water (1 + 1). OA was separated on a reversed-phase C18 LC column with acetonitrile-water-acetic acid (55 + 45 + 1) as eluant and quantitated with a fluorescence detector. Recoveries of OA from the 4 commodities spiked over the range 1-4 ng/g were 71-96%. The limit of detection was about 0.03 ng/g. OA contamination at > 0.03 ng/g was found in 56 of 383 wheat samples, 11 of 103 barley samples, 9 of 19 green coffee samples, and 9 of 13 roasted coffee samples. None of the coffee samples contained OA at > 5 ng/g; only 4 samples of wheat and 1 sample of barley were contaminated above this level.

Carcinogens↗
PubMedDate not supplied

Capillary gas chromatography/mass spectrometry with chemical ionization and negative ion detection for confirmation of identity of patulin in apple juice.

Gas chromatography/mass spectrometry (GC/MS) with negative ion chemical ionization permits detection of underivatized patulin in apple juice extracts while minimizing co-extractive responses. The technique has been used with a variety of capillary columns in quadrupole, ion trap, and magnetic sector GC/MS instruments to confirm presumptive findings of patulin in apple juice at concentrations ranging from 68 to 3700 micrograms/L. The demonstrated ability to use any of these 3 mass spectrometers and several capillary columns to confirm the identity of patulin are significant strengths of the technique.

Beverages↗
PubMedDate not supplied

Gas chromatographic determination of yohimbine in commercial yohimbe products.

The bark of Pausinystalia yohimbe [K. Schumann] Pierre (Rubiaceae), long valued as an aphrodisiac in West Africa, recently has been promoted in the United States as a dietary supplement alternative to anabolic steroids for enhancement of athletic performance. As the number of yohimbe products on the retail market increases, concerns about their safety are raised because of the reported toxicity of yohimbine (the major alkaloid of the plant). Although plant materials are usually identified microscopically, we were unable to identify them in many of the products, because as their labels indicated, the products were mixtures of various botanicals or were bark extracts and contained little or no plant material. A method for extraction and capillary gas chromatographic (GC) separation of the alkaloids of P. yohimbe was, therefore, developed and used to analyze a number of commercial yohimbe products. The method involved solvent extraction and partitioning in chloroform-water followed by separation on a methyl silicone capillary GC column (N-P detection). Comparisons of chromatograms of extracts of authentic bark with those of commercial products indicated that, although many products contained measurable quantities of the alkaloid yohimbine, they were largely devoid of the other alkaloids previously reported in this species. Concentrations of yohimbine in the commercial products ranged from < 0.1 to 489 ppm, compared with 7089 ppm in the authentic material. Authentic bark has been reported to contain up to 6% total alkaloids, 10-15% of which are yohimbine. The possible presence of undeclared diluents in the products was indicated by peaks in product chromatograms but not in those of authentic bark.

Chloroform↗
PubMedDate not supplied

Validated method for quantitation and identification of 4,4-desmethylsterols and triterpene diols in plant oils by thin-layer chromatography-high resolution gas chromatography-mass spectrometry.

Alkaline hydrolysis was performed on a series of different vegetable oils. The unsaponifiable lipid matter was extracted with ethyl ether, and the class of 4,4-desmethylsterols (sterols) plus the triterpene diols (diols) erythrodiol, uvaol, and betulinol were isolated by thin-layer chromatography. A validated method using the acetate derivatives of sterols instead of their silyl ethers is presented. The acetate derivatives were analyzed by high resolution gas chromatography (HRGC). Retention time, precision, recovery studies, and absolute response factors were calculated for these esters, and GC/mass spectrometric structure of the assigned retention times was confirmed for the sterols and triterpene diols.

Chromatography, Thin Layer↗