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Biomedical subjects

G D Byrd

Publications and source records attributed to G D Byrd.

18 recordsLinked to original sources
PubMed1995

Comparison of measured and FTC-predicted nicotine uptake in smokers.

Cigarette smokers have a wide variety of "tar" and nicotine yields to choose from in the current market, ranging from 0.5 mg "tar" and less than 0.05 mg nicotine to 27 mg "tar" and 1.8 mg nicotine by the Federal Trade Commission (FTC) method. To understand better the relationship between FTC nicotine yields and actual nicotine uptake in smokers, we have studied nicotine uptake in 33 smokers of self-selected products representing four "tar" groupings: 1 mg "tar" (1MG), ultra-low "tar" (ULT), full-flavor low "tar" (FFLT), and full flavor (FF) cigarettes. These cigarette categories had mean FTC nicotine yields of 0.14, 0.49, 0.67, and 1.13 mg/cigarette, respectively. The subjects smoked their usual brand of cigarette ad libitum and provided a 24-h urine sample for total nicotine uptake analysis over a period during which the number of cigarettes smoked was recorded. Nicotine uptake was determined by monitoring urinary nicotine and its metabolites, including the glucuronide conjugates. Daily nicotine uptake was 9.1 +/- 7.3 mg (range 1-21 mg) for 1MG, 19.2 +/- 10.0 mg (range 4-42 mg) for ULT, 21.8 +/- 9.4 mg (range 13-38 mg) for FFLT, and 37.1 +/- 14.4 mg (range 21-60 mg) for FF smokers. On a per cigarette basis, yields were 0.23 +/- 0.11, 0.56 +/- 0.23, 0.60 +/- 0.18, and 1.19 +/- 0.43 mg nicotine, respectively. Although individual variability was fairly large (CVs of 0.39-0.80), means for the different groups showed that lower FTC yield smokers not only absorb less nicotine per 24-h period, but also per cigarette smoked. These data suggest that nicotine uptake is a function of individual smoking behavior within product design limits. We conclude from these data that, while FTC yield cannot precisely predict nicotine uptake for an individual smoker, it is useful in predicting and comparing actual nicotine uptake by smokers who select cigarettes with a particular FTC yield.

Adult↗
PubMed1994

Direct determination of cotinine-N-glucuronide in urine using thermospray liquid chromatography/mass spectrometry.

A thermospray liquid chromatographic/mass spectrometric method has been developed for direct determination of cotinine-N-glucuronide in the urine of smokers. Quantification was performed using methyl-d3-cotinine-N-glucuronide as internal standard and monitoring the protonated aglycons. Using a simple preparation, urine samples from four smokers were analyzed and the results compared favorably with those from a previously reported method that quantifies aglycon release following beta-glucuronidase treatment. Amounts of cotinine-N-glucuronide found in urine from smokers ranged from less than 0.7 to 21 nmol ml-1, indicating wide inter-individual variability in the metabolic production of this metabolite. Cotinine-N-glucuronide was found to be the second most abundant urinary nicotine metabolite. A similar method was developed for trans-3'-hydroxycotinine-N-glucuronide but this compound was not detected in smokers' urine.

Adult↗
PubMed1991

The ethical implications of health sciences library economics.

The intersection of ethics and economics is rarely discussed in the library literature or at conferences. This may be due, in part, to what economists describe as a romantic value system, that is, the belief that resources are or should be unlimited and available for exploitation by every individual with a need. But recent changes in the national economy for libraries are forcing a realization that individualistic codes of ethics and value systems do not always result in socially desirable consequences. The problems of information management and access cannot be solved by ethical individuals acting alone. Instead, a new consensus is needed on collective ethical behaviors to ensure that health information resources are managed for the common good.

Civil Rights↗
PubMed1990

Isotope dilution gas chromatography-mass spectrometry in the determination of benzene, toluene, styrene and acrylonitrile in mainstream cigarette smoke.

A cryogenic trapping method with isotope dilution gas chromatography-mass spectrometry analysis has been developed for the determination of benzene, toluene, styrene and acrylonitrile in mainstream vapor phase cigarette smoke. The method is simple, direct, and quantitative. Vapor phase samples are collected cryogenically in a series of four traps following removal of the particulate phase with a Cambridge filter pad. For all four analytes, 75-85% of the total amounts recovered were found in the initial trap and less than 1% in the final trap. Assessment of instrumental precision by multiple injections of a sample gave relative standard deviations of less than 2%. Linear calibration for all analytes over the analysis range gave an r2 value greater than 0.99 with average relative standard deviations at the mean ranging from 1.4 to 8.2%. The cigarettes analyzed include a reference cigarette (Kentucky 1R4F), a commercial ultra-low "tar" mentholated cigarette, and two cigarettes that heat but do not burn tobacco. The values determined for the four analytes in the 1R4F samples are comparable to reported values of similar cigarettes. The cigarettes which heat rather than burn tobacco yield less of all four analytes compared to the other cigarettes in the study.

Acrylonitrile↗
PubMed1989

Preparation and certification of standard reference material 1507: 11-nor-delta 9-tetrahydrocannabinol-9-carboxylic acid in freeze-dried urine.

The National Institute of Standards and Technology (NIST) has prepared and certified SRM 1507, a freeze-dried urine fortified with 11-nor-delta 9-tetrahydrocannabinol-9-carboxylic acid (THC-9-COOH), the major urinary metabolite of marijuana. The certified concentration of 20 +/- 1 ng/mL for the analyte was obtained from the concordant results of analyses of the material by gas chromatography/mass spectrometry (GC/MS) and high-performance liquid chromatography with electrochemical detection (HPLC-EC). Solid-phase extraction was used to prepare the sample for GC/MS analyses, and liquid-liquid extraction was used for the HPLC-EC analyses. The multistep HPLC method was developed at NIST to circumvent interferences from urinary constituents. The results of a round robin test on this material among five Department of Defense laboratories involved in drug testing are reported.

Chromatography, High Pressure Liquid↗
PubMed1982

Collection development using interlibrary loan borrowing and acquisitions statistics.

Libraries, especially those supporting the sciences, continually face the problem of selecting appropriate new books for their users. Traditional collection development techniques include the use of librarian or user subject specialists, user recommendations, and approval plans. These methods of selection, however, are most effective in large libraries and do not systemically correlate new book purchases with the actual demands of users served. This paper describes a statistical method for determining subject strengths and weaknesses in a library book collection in relation to user demand. Using interlibrary loan borrowing and book acquisition statistics gathered for one fiscal year from three health sciences libraries, the authors developed a way to graph the broad and narrow subject fields of strength and potential weakness in a book collection. This method has the advantages of simplicity, speed of implementation, and clarity. It can also be used over a period of time to verify the success or failure of a collection development program. Finally, the method has potential as a tool for use by two or more libraries seeking to improve cooperative collection development in a network or consortium.

Interlibrary Loans↗
PubMed1981

Copyright compliance in health sciences libraries: a status report two years after the implementation of PL 94-553.

This paper briefly reviews developments since the implementation of the new Copyright Law (PL 94-553) and reports on a nationwide survey of academic, hospital, and special health sciences libraries. These libraries were asked to report anonymously on their current policies and the procedures used to comply with the new law. They were also asked to indicate any special concerns they have with the law or the guidelines which they have followed for compliance. The results show that with few exceptions United States health sciences libraries are complying with the specific provisions of the law and that compliance has not significantly affected library services.

Copyright↗
PubMed1979

Medical school graduates' retrospective evaluation of a clinical medical librarian program.

This paper reports on the results of a survey of sixty-six graduates of the University of Missouri-Kansas City (UMKC) School of Medicine conducted in the spring of 1977. The graduates were questioned about their present library use behavior and their restrospective perceptions of the clinical medical librarian (CML) services which they received as medical students at UMKC. The results show that these young physicians, after regular association with other, more tradional medical library services, hold very positive impressions of the CML program. The graduates also typically credit the CML'S with helping them to learn to use library resources effectively. These retrospective perceptions of the CML match the short-term benefits reported in other studies of similar programs.

Evaluation Studies as Topic↗
PubMed1978

Systematic serials selection analysis in a small academic health sciences library.

This paper describes the implementation of a straightforward quantitative technique to analyze the serials collection of the Medical Library at the University of Missouri-Kansas City (UMKC). Our simplified operations research approach resulted in a savings of nearly $1400 per year in subscriptions costs without reducing the net number of seven hundred titles or causing an imbalance in the subject distribution of our collection. By detailing both the rationale behind the process and the actual steps followed at UMKC, we hope to demonstrate that operations research techniques can be used practically and successfully even in small health sciences libraries. In the Appendix a more general and more rigorous operations research approach to the analysis of serials collections is also presented in a fashion that is, as far as possible, not mathematically forbidding.

Book Selection↗
PubMed1977

Reclassification in a small decentralized medical library.

This study describes procedures and indentifies problems in the reclassification of a small medical school library collection that is decentralized into five locations in three different communities. A total of 9,915 monographic titles (14,911 volumes) were reclassified in a nine-month period. The reclassification staff consisted of one professional, two nonprofessionals, and one partime student assistant.

Book Classification↗
PubMedDate not supplied

Characterization of the glucuronide conjugate of cotinine: a previously unidentified major metabolite of nicotine in smokers' urine.

Recent studies in our laboratories have confirmed that a major unidentified metabolite of nicotine in smokers' urine was susceptible to enzymatic degradation by beta-glucuronidase to afford (S)-(-)-cotinine. In order to establish the identity of this metabolite, the quaternary ammonium conjugate, viz., (S)-(-)-cotinine N-glucuronide, was synthesized. Reaction of methyl 2,3,4-tri-O-acetyl-1-bromo-1-deoxy-alpha-D-glucopyranuronate with (S)-(-)-cotinine at 60 degrees C for 3 days affords the fully protected conjugate as the bromide salt. Deprotection was accomplished in 1 M NaOH overnight at 25 degrees C. The deprotected inner salt was isolated by Dowex-50W cation-exchange chromatography. Electrospray mass spectra of the inner salt revealed the presence of ions with m/z 353 (M + H)+, 375 (M + Na)+, and 391 (M + K)+ as well as ions resulting from loss of water and cleavage of the glycosidic bond. Proton and carbon nuclear magnetic resonance spectra established that the position of glucuronidation was the pyridyl nitrogen. The magnitude of the coupling between H1" and H2" of the sugar ring (8.71 Hz) and nuclear Overhauser enhancements were consistent with the beta-isomer of the glucuronide conjugate. The synthetic (S)-(-)-cotinine N-glucuronide was susceptible to enzymatic hydrolysis by beta-glucuronidase to afford (S)-(-)-cotinine. Application of a cation-exchange high-performance liquid chromatographic method enabled the collection of a fraction containing (S)-(-)-cotinine N-glucuronide from a smoker's urine. The electrospray mass spectrum of this fraction contained ions consistent with the presence of (S)-(-)-cotinine N-glucuronide. The concentrated fraction was subjected to enzymatic hydrolysis by beta-glucuronidase to afford (S)-(-)-cotinine.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMedDate not supplied

Determination of 3-quinuclidinyl benzilate (QNB) and its major metabolites in urine by isotope dilution gas chromatography/mass spectrometry.

In response to the scheduled destruction of U.S. military stockpiles of the hallucinogenic agent 3-quinuclidinyl benzilate (QNB), a specific confirmatory test for human exposure to QNB was developed. The amount of the parent compound in the urine as well as the two major metabolites, 3-quinuclidinol (Q) and benzilic acid (BA), was determined because the relationship between QNB dose and levels of QNB and its metabolites in human urine is not known. QNB was determined in urine samples spiked at a target level of 0.5 ng/mL, and the metabolites BA and Q were determined at a target level of 5 ng/mL. The method uses solid-phase extraction to isolate each analyte from the urine and isotope dilution gas chromatography/mass spectrometry for quantitation. Each analyte is converted to its trimethylsilyl derivative for analysis. The analytical method was tested on eight different urine samples spiked with known amounts of the analytes near the target levels, at 10 times the target levels, and blank (unspiked) urine samples. The variabilities in the method are for the most part evenly distributed between three imprecision categories: GC/MS measurement, sample preparation, and the urine samples. The total imprecision (1 standard deviation) of a single measurement is about 15% of the value for each analyte.

Gas Chromatography-Mass Spectrometry↗
PubMedDate not supplied

Evidence for urinary excretion of glucuronide conjugates of nicotine, cotinine, and trans-3'-hydroxycotinine in smokers.

Urinary nicotine metabolic output was profiled for 11 smokers who smoked their regular cigarette brands ad libitum. Thermospray liquid chromatography/mass spectrometry was used to monitor nicotine and eight metabolites, including glucuronide conjugates of nicotine, cotinine, and trans-3'-hydroxycotinine that were determined indirectly using enzyme hydrolysis. These results were used to estimate an average, steady-state concentration in a 24-hr urine sample during ad libitum smoking and to assess interindividual variability in the excretion of these metabolites. The variability in absolute amount among the nine analytes ranged from 35 to 70% for these smokers. The glucuronide conjugates constituted an average of 29% of all urinary metabolites monitored in this study. trans-3'-Hydroxycotinine in the free form constitutes the largest single metabolite in smokers' urine, with an average of 35% of the total. The sums of nicotine metabolites determined here are very close to the Federal Trade Commission yields of nicotine for the total number of cigarettes smoked by these subjects during the urine collection interval. These results indicate that a large proportion of the nicotine absorbed while smoking can be accounted for as urinary metabolites of nicotine, including glucuronide conjugates of nicotine, cotinine, and trans-3'-hydroxycotinine.

Adult↗