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Biomedical subjects

C M O'Donnell

Publications and source records attributed to C M O'Donnell.

At least 19 recordsLinked to original sources
PubMed1992

Nitrosating activity in Escherichia coli.

Nitrosation activity was measured in Escherichia coli isolates and a range of nitrite reductase (nir) mutants. Activity was only detected in intact cells and could be inhibited by a number of treatments such as sonication and osmotic shock. Aerobically-grown cells had highest nitrosation activity compared to oxygen-limited ones. Inclusion of nitrite in growth media induced high activities of nitrite reductase and for some isolates, nitrosation. Analysis of nir mutants identified two which were unable to nitrosate. This result suggested that NADH-dependent nitrite reductase was implicated either directly or indirectly in nitrosation.

Aerobiosis↗
PubMed1990

Industrial employee drug screening: a blind study of laboratory performance using commercially prepared controls.

Reference laboratories are an integral component of any industrial employee drug screening program. We evaluated the performance and accuracy of the reference laboratories used by Rockwell International, a large industrial employer with an active drug screening program. A total of 829 commercially prepared control samples containing drugs of abuse, over-the-counter drugs, and analytes found in the normal employee population were disguised as routine submissions to reference laboratories used by nine Rockwell facilities. Analyses of results included compilation of false-positive and false-negative errors per drug per laboratory and a correlation of errors with preliminary and confirmation methods. Error rates of 2% false-positive results and 20% false-negative results were found for all laboratories. The errors were not limited to any one technique nor to any particular drug. The error rates observed suggest the need for routine blind testing programs and increased interaction between industry and laboratories.

Animals↗
PubMed1989

A rapid sample-preparation technique for thin-layer chromatographic analysis for 11-nor-delta 9-tetrahydrocannabinol-9-carboxylic acid in human urine.

In this rapid TLC method of analysis for the urinary cannabinoid metabolite, 11-nor-delta 9-tetrahydrocannabinol-9-carboxylic acid (THC-COOH), hydrolyzed urine specimens are aspirated through a porous, alkyl-silica extraction layer located along the lower edge of a biphasic thin-layer chromatogram; THC-COOH is simultaneously extracted from the sample and concentrated on the TLC plate for subsequent migration and detection. The method, evaluated in a blind study, identified all samples containing THC-COOH greater than or equal to 20 micrograms/L. The technique increases samples throughput, sensitivity, and specificity as compared with conventional TLC methods and is applicable to a wide variety of compounds.

Chromatography, Thin Layer↗
PubMed1988

Nanomelic chondrocytes synthesize a glycoprotein related to chondroitin sulfate proteoglycan core protein.

Chicken embryos homozygous for the autosomal recessive gene nanomelia exhibit cartilage defects, synthesize low levels of cartilage chondroitin sulfate proteoglycan (CSPG), and are missing the CSPG core protein (Argraves, W. S., McKeown-Longo, P. J., and Goetinck, P. F. (1981) FEBS Lett. 131, 265). In our studies of nanomelic chondrocytes in culture, we detected neither sulfate-labeled CSPG nor its Mr 370,000 core protein. However, in immunoprecipitation reactions using both polyclonal and monoclonal antibodies directed against the cartilage CSPG core protein, we identified a protein of Mr 300,000 that contains an epitope found in the hyaluronic acid-binding region of the normal core protein. This protein was also detected among products synthesized by chondrocytes obtained from phenotypically normal embryos resulting from matings between parents heterozygous for nanomelia. Sensitivity to endoglycosidase H indicated that the product is a glycoprotein with attached mannose-rich oligosaccharides. Pulse-chase studies revealed the disappearance of the glycoprotein after 6 h of chase, but no detectable formation of proteoglycan. Our results suggest that although nanomelic chondrocytes are deficient in the production of normal CSPG and its core protein, they do synthesize a smaller, immunologically related glycoprotein that does not undergo the post-translational processing characteristic of the normal cartilage core protein.

Aggrecans↗
PubMed1988

Confirmation and certainty in toxicology screening.

Confirmation of presumptive positive urine drug screens, necessary to minimize the reporting of false-positive results, can be costly and time-consuming. The predictive value model can be used to select the confirming tests and to calculate the confidence of the result. The predictive value of a test result is the probability, based on the sensitivity and specificity of the test, that the result is a true positive or a true negative. The predictive value model applied to toxicology screening tests for drugs of abuse showed that prevalence, in addition to sensitivity and specificity, was the factor controlling the confidence level of a result. For example, the predictive value of a positive result for a screening test that has a sensitivity of 99% and a specificity of 99%, applied to screening in a population with a prevalence of 1% is 0.50; for a prevalence of 10%, it is 0.92. Confirmation with a second, chemically independent, test of equal sensitivity and specificity increases the predictive value to 0.99.

Algorithms↗
PubMed1987

Laboratory detection of cannabinoids.

Cannabis, or marijuana, has been known and used as a drug for many thousands of years. Recent interest in drug abuse and detection has spurred the development of several methodologies for cannabinoid detection. These methods include immunoassays and chromatography. Laboratories routinely performing cannabinoid testing use two or more methodologies; the accepted method is to screen with one methodology and confirm by a second. These methodologies vary widely in sensitivity, specificity, and time required for analysis. Although therapeutic applications of cannabis constituents often produce undesirable side effects, two cannabinoids, delta 9-THC and nabilone, have been approved for use as antiemetics in chemotherapy. Further investigations of cannabinoid pharmacology and structure-activity relationships may result in the development of promising new therapeutic agents.

Cannabinoids↗
PubMed1987

In-vitro production of nitrosamines by bacteria isolated from the operated stomach.

Evidence is presented of in-vitro catalysis of nitrosation by organisms isolated from the hypoacidic operated stomach. Subjects taking part in a prospective study of potential premalignancy after benign ulcer surgery underwent endoscopy, and samples of gastric juice were obtained aseptically. The organisms present were identified using the API system and tested for their ability to catalyse the nitrosation of the secondary amine, morpholine, at neutral pH and 37 degrees C. Four of the five species tested were found to be capable of the catalysis. Cellular disruption and denaturation of protein abolished the catalytic ability, suggesting that the catalysis is mediated by an enzymic system. Osmotic shock experiments indicate that the enzyme site may be on the inner membrane.

Female↗
PubMed1987

An investigation of possible risk factors associated with gastric cancer after benign ulcer operations.

The risk of developing gastric cancer has been investigated in a case-control study and in a prospective investigation. In the case-control study, 1495 cases of gastric cancer were identified in five city hospitals and matched with autopsy controls from the same hospitals. The frequency of operations for benign ulcer [partial gastrectomy (PG) and gastroenterostomy] was similar in the two groups. Thus, there was no increased risk for late gastric cancer after an ulcer operation. A total of 140 operated ulcer subjects [80 truncal vagotomy and drainage (TVD), 60 PG and 78 nonoperated cases attending with dyspepsia (C)] were examined by endoscopy, multiple gastric biopsy and analysis of gastric juice for nitrite. Biopsies were graded for gastritis and a gastritis index was derived (normal, 1; superficial gastritis, 2; chronic atrophic gastritis: mild, 3; moderate, 4; severe, 5). More atrophic gastritis was found in operated subjects than in controls: TVD, 2.3 +/- 0.08 (mean +/- SE); PG, 2.6 +/- 0.1 versus C, 1.8 +/- 0.08, p less than 0.01. The severity of atrophic gastritis increased after an operation interval of 20 years in PG subjects (p less than 0.05). Intestinal metaplasia was a common change, but unequivocal epithelial dysplasia was not observed. Two cases of operated stomach cancer were found. High levels of nitrite were positively correlated with pH and a high gastritis index. This evidence does not suggest that ulcer surgery leads to either an increased risk of cancer or a precancerous condition.

Gastrectomy↗
PubMed1979

Evaluation of the DuPont aca amylase method.

The dilution/activity curve for the DuPont aca kinetic amylase (EC 3.2.1.1) method is linear to approximately six times the upper limit of the expected range. Total reaction time on the aca is 4.3 min; however, there is a nonlinear rate of change in absorbance for at least the first 8 min, which is consistent with a lag phase. The within-run and day-to-day coefficients of variation were 2.4% at 100 U/L and 3.6% at 114 U/L, respectively. There was no interference by marked hemolysis (hemoglobin 4 g/L) or by glucose concentrations of 10--50 g/L. Comparisons by the split-sample method between the Amylochrome procedure and the aca procedure gave correlation coefficients of 0.992 for serum and 0.989 for urine. A second comparison, between the AutoAnalyzer I method and the aca, gave correlation coefficients of 0.998 for serum and 0.909 for urine. The expected range for serum was 18--106 U/L and for urine 2--33 U/2 h.

Amylases↗
PubMed1975

The potential of phosphorescence spectrometry in clinical chemistry--the new generation of instrumentation and methodology.

We review recent advances in instrumentation and methodology in phosphorimetry that should facilitate the use of phosphorimetry for clinical analyses and recent phosphorescence studies of interest to the clinical chemist. We indicate recent advances, particularly improvements in instrumentation, novel methodologies, and new chemical processes that result in either an increase in sensitivity or selectivity (or both) of measurement of compounds of clinical importance. The greatest use of phosphorimetry in the clinical laboratory will not be for the analysis of very large numbers of samples for one species via automatic instrumentation, but rather will be for the analysis of those molecular species difficult or impossible to measure by conventional methods (colorimetry, fluorometry, etc.). Although various instrumental and methodological advances are discussed separately here, the most important use of these advances in clinical chemistry will undoubtedly be when two or more of them are combined, for example, in the use of time- or frequency-resolved phosphorimetry for the selective measurement of the phosphorescence resulting with inorganic probes and the appropriate choice of solvent and pH (of course, the instrument could contain an image vidicon detector for rapid determination of the spectrum, the decay curve, or both).

Antimetabolites↗