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Biomedical subjects

J C Craig

Publications and source records attributed to J C Craig.

At least 145 records · Page 8Linked to original sources
PubMed1984

Stereochemistry of 1-(4'-hydroxyphenyl)ethanol produced by hydroxylation of 4-ethylphenol by p-cresol methylhydroxylase.

Enzymic hydroxylation of 4-ethylphenol by (a) Pseudomonas putida and (b) highly purified p-cresol methylhydroxylase gave optically active 1-(4'-hydroxyphenyl)-ethanol. The products were transformed into the phenolic methyl ethers and shown to contain 69.5% and 65.6%, respectively, of the (S)-(-)-isomer. The stereochemistry of the reaction is discussed in terms of three distinct steps occurring at the active site of the enzyme.

Ethanol↗
PubMed1984

Stable isotope dilution analysis of orotic acid and uracil in amniotic fluid.

Rapid, sensitive and accurate stable isotope dilution assays were developed for the measurement of orotic acid and uracil in amniotic fluid. The method utilizes [15N2]orotic acid and [15N2]uracil as internal standards, isolation by liquid partition chromatography and quantitation by chemical ionization selected ion monitoring gas chromatography-mass spectrometry. Orotic acid at a concentration of 0.26 +/- 0.05 mumol/l and uracil at a concentration of 0.55 +/- 0.13 mumol/l were detectable in normal amniotic fluid. As affected fetuses with argininosuccinate synthetase or ornithine carbamoyl transferase deficiency showed no significant elevation of orotic acid and/or uracil in their surrounding amniotic fluids, this method unfortunately seemed not to be useful for prenatal diagnosis of these inherited disorders. Nevertheless, it provides significant advantage over available methods for the quantitation of orotic acid and uracil in which the analysis of these compounds must be very accurate, highly specific and sensitive (e.g. detection of heterozygosity for ornithine carbamoyl transferase deficiency).

Amniotic Fluid↗
PubMed1983

A stable isotope technique for investigating lactate metabolism in humans.

A stable isotope tracer method has been developed for studying lactate metabolism in humans. The method uses lactic acid triple labeled with 13C as the tracer. The stable isotope is infused to attain a level of approximately 1.5% of that of the circulating unlabeled lactate. Following the isolation of lactic acid from the blood, the percentage of triple labeled (13C)lactate is measured using gas chromatography mas spectrometry. We compared this method with tracer methodology using [14C]lactate and found comparable results.

Carbon Isotopes↗
PubMed1983

Immunological control of Epstein-Barr virus-transformed lymphocytes in multiple sclerosis.

T-cell control of Epstein-Barr virus (EBV)-infected autologous lymphocytes was examined in 25 multiple sclerosis (MS) patients and in 25 healthy individuals, all seropositive for EBV. By assessing regression of cell transformation, 17 patients and all healthy subjects were scored as "regressors." Eight MS patients proved to be "nonregressors," indicating loss of cytotoxic T-cell control. In this group there was apparently a concurrent fall in the mean titer of antibody to Epstein-Barr nuclear antigen.

Antibodies, Viral↗
PubMed1983

Vibrotactile identification of vowels.

The ability of subjects to identify vowels in vibrotactile transformations of consonant-vowel syllables was measured for two types of displays: a spectral display (frequency by intensity), and a vocal tract area function display (vocal tract location by cross-sectional area). Both displays were presented to the fingertip via the tactile display of the Optacon transducer. In the first experiments the spectral display was effective for identifying vowels in /b/V/ context when as many as 24 or as few as eight spectral channels were presented to the skin. However, performance fell when the 12- and 8-channel displays were reduced in size to occupy 1/2 or 1/3 of the 24-row tactile matrix. The effect of reducing the size of the display was greater when the spectrum was represented as a solid histogram ("filled" patterns) than when it was represented as a simple spectral contour ("unfilled" patterns). Spatial masking within the filled pattern was postulated as the cause for this decline in performance. Another experiment measured the utility of the spectral display when the syllables were produced by multiple speakers. The resulting increase in response confusions was primarily attributable to variations in the tactile patterns caused by differences in vocal tract resonances among the speakers. The final experiment found an area function display to be inferior to the spectral display for identification of vowels. The results demonstrate that a two-dimensional spectral display is worthy of further development as a basic vibrotactile display for speech.

Communication Devices for People with Disabilities↗
PubMed1983

Some factors affecting tactile pattern recognition.

Tactile patterns were generated by means of a 6 X 24 array of vibrating pins. The ability of subjects to recognize these patterns presented to their fingertips was shown to be affected by a number of factors, including the display time of the pattern, the mode of generating the tactile patterns, the temporal relationship between the pattern to be identified and a masking stimulus, the type of masking stimulus, and temporal integration. Word recognition was also shown to be affected by some of these factors. Parallels are drawn between the factors that affect vibrotactile pattern recognition and visual pattern recognition.

Computers↗
PubMed1982

Simultaneous analysis of imipramine and its metabolite desipramine in biological fluids.

A method for the simultaneous quantitation of imipramine and its N-demethylated metabolite desipramine at the nanogram level in a single gas chromatograph peak is presented, utilizing gas chromatography-mass spectrometry with selected ion recording. The assay is specific and quantitation is achieved using [2H4]imipramine as the internal standard. The method involves the in situ methylation of desipramine with [2H2]formaldehyde and sodium borohydride to give [2H2]imipramine. Quantitation is then achieved by selected ion recording at m/z 280, 282 and 284, whence the ratio of the ion currents at 280/284 and at 282/284 gives the quantities of imipramine and desipramine respectively.

Desipramine↗
PubMed1981

Cholesterol and cholesterol epoxides in nipple aspirates of human breast fluid.

In nipple aspirates of breast fluid from nonpregnant healthy women, cholesterol and cholesterol epoxide levels were determined with gas-liquid chromatography and mass spectrophotometric techniques. Cholesterol levels were found to be elevated above plasma levels averaging 2200 +/- 1995 (S.D.) mg/dl and showing progressive increases in mean breast fluid cholesterol levels with advancing age, averaging 187, 1957, and 3554 mg/dl in women of age groups 20 to 29, 30 to 39, an 40 to 49 years, respectively. Cholesterol epoxide was detected in a significant number of women who yielded high levels of breast fluid cholesterol. Cholesterol epoxide has been reported by other workers to have transforming activity for embryo hamster cells and to be carcinogenic in animals. The findings lend support to our hypothesis and observation that the human breast secretes mutagenic and cancer-promoting substances which may have relevance in studies of the etiology of benign breast disease and cancer.

Adult↗