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Biomedical subjects

C E Willis

Publications and source records attributed to C E Willis.

29 records · Page 2Linked to original sources
PubMed1979

High pressure liquid chromatography for simultaneous analysis of anticonvulsants: comparison with EMIT system.

We present a new high pressure liquid chromatography (HPLC) method for the simultaneous analysis of primidone, phenobarbital, phenytoin, and carbamazepine in serum. The chromatographic separation is carried out using an Altex model 110-A pump, a 250 times 4.6 mm column containing 5 mum Spherisorb ODS particles and a variable wavelength ultraviolet detector set at 197 nm. The mobile phase is a mixture of acetonitrile, distilled water, and 1.75 M phosphoric acid (27:72.8:0.2). The flow rate is 1.5 ml/min, and the analysis time is 17 min. A 200 mul aliquot of serum is buffered at pH 5 and extracted with dichloromethane. The extract is evaporated to dryness and dissolved in methanol for chromatographic analysis. Cyclopal is used as the internal standard and quantification is achieved using peak height ratios. This HPLC method is evaluated for precision and accuracy with reference to the EMIT system. The least-squares regression analysis of comparison data for the drugs shows a favorable correlation. Also, a paired t-test indicates no significant difference for the HPLC and EMIT values for primidone, phenobarbital, phenytoin, and carbamazepine. From this study we conclude that this HPLC method could be successfully used for the simultaneous therapeutic monitoring of the four anticonvulsants.

Anticonvulsants↗
PubMed1978

Enzymatic determination of plasma ammonia: evaluation of Sigma and BMC Kits.

We compared two kit methods for the enzymatic determination of plasma ammonia. The procedures involved measuring the decrease in absorbance at 340 nm resulting from the consumption of NADH in the Sigma kit, NADPH in the BMC kit. Both kits gave acceptable results for aqueous samples, but for plasma specimens values with the Sigma kit significantly exceeded those obtained with the BMC kit. In our hands, values with the BMC kit were more accurate and precise. On the basis of these results, we conclude that the BMC kit is the better choice.

Ammonia↗
PubMed1977

Malonaldehyde content of food.

Several types of commercially available food both cooked and uncooked were tested for the presence of the carcinogenic initiator and mutagen, malonaldehyde, which is a breakdown product of unsaturated fatty acids. The thiobarbituric acid derivative of malonaldehyde from meat extract was identified either by thin layer chromatography or by gas chromatography after silylation. Malonaldehyde was also identified directly by gas chromatography. Among the meats purchased from supermarkets, beef had the greatest amounts of malonaldehyde. Turkey and cooked chicken had high levels. Most cheeses had only small amounts of malonaldehyde. In contrast, many vegetables and fruits had either minute amounts or no malonaldehyde.

Animals↗
PubMed1973

The coma profile.

Explore the source record for details and available documents.

Barbiturates↗
PubMedDate not supplied

Antioxidants and cancer. Part VI. Selenium and age-adjusted human cancer mortality.

The possible epidemiologic relationship between selenium occurrence and cancer mortality was studied in cities and states located in areas with different levels of selenium bioavailability. Statistically significant differences were found in age-specific cancer death rates among states with high, medium, and low selenium levels. The death rates for specific types of cancer showed a larger difference in males than in females in the states with high selenium levels. The greater difference between males and females may be related to sex difference or to the fact that males are heavier smokers and are aslo more likely to be exposed to industrial pollution. In the states with high selenium levels, there was significantly lower mortality in both males and females from several types of cancer, particularly the environmental problem indicators, such as gastrointestinal and urogenital types of cancer.

Age Factors↗
PubMedDate not supplied

Logistic representation of the sensitometric response of screen-film systems: empirical validation.

An empirical logistic model that linearizes the sensitometric response data of screen-film systems over the entire dynamic range of exposures is presented. This linearization is evident when the net optical densities are scaled as fractions of the net saturation density and plotted on commercial logit, probit, or double-log paper, except under conditions of reciprocity law failure. Weighted linear regression analysis shows that the intercept, but not the slope, depends on the screen-film system used. Previous work indicates that the slope is also independent of development time and photon energy. The model is verified through an analysis of tabulated sensitometric data published by the Center for Devices and Radiological Health.

Logistic Models↗