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Biomedical subjects

M B Evans

Publications and source records attributed to M B Evans.

18 recordsLinked to original sources
PubMed1995

Porous graphitic carbon shows promise for the rapid chromatographic analysis of polar drug metabolites.

A rapid and simple HPLC method has been developed and used to separate the polar metabolic conjugates of AZT, chloramphenicol, and beta-estradiol based upon the use of porous graphitic carbon. The HPLC system is sufficiently selective to resolve the polar drug conjugates from their parent compounds and from endogenous material present in urine. The compounds are separated, without the need for sample pretreatment or gradient elution, on a porous graphitic carbon (Hypercarb) column using aqueous trifluoroacetic acid modified with tetrahydrofuran as the mobile phase. Porous graphitic carbon exhibits a novel mechanism of retention towards these very polar substances, which are unretained under reversed-phase conditions on alkyl-bonded silica phases.

Animals↗
PubMed1995

The enantiomeric separation of metipranolol and desacetylmetipranolol on a cellulose tris-3,5-dimethylphenyl-carbamate chiral stationary phase.

A high-performance liquid chromatographic (HPLC) method is described for direct separation of the enantiomers of metipranolol and its principal degradation product and main metabolite, desacetylmetipranolol. Separations are performed on a chiral stationary phase of cellulose tris-3,5-dimethylphenyl carbamate (Chiralcel OD), with hexane-propan-2-ol-diethylamine elution and UV detection at 278 nm. The method affords identification and determination of the optical purity of the bulk drug and its formulated ophthalmic products.

1-Propanol↗
PubMed1995

Radioimmunoassay of drugs of abuse in hair. Part 2: The determination of methadone in the hair of known drug users.

This communication addresses the analytical problems associated with the analysis of hair specimens from known users and misusers of the synthetic opioid methadone. An adapted radioimmunoassay and a previously developed preanalytical decontamination procedure have been applied to samples from known drug users. The removal of drugs from the hair surface by washing and the effect of proprietary hair treatments on methadone entrapped in the hair have also been investigated. Pre-analytical washing reduced methadone levels by up to 29%, whilst hair colouration and peroxide bleaching were found to reduce levels by up to 21% and 50% respectively. Methadone assay of extracts from dated hair segments were shown to provide long-term histories of methadone intake, under controlled and non-controlled conditions. Evidence that a dose relationship between hair drug levels and intake may exist is presented. Results of hair analysis, expressed as ng methadone/mg hair, from drug users (range 0.20-10.63) are compared to a pre-determined cut-off of 0.1 ng methadone/mg hair, obtained from the analysis of a known drug free population (n = 23).

Chemistry Techniques, Analytical↗
PubMed1994

Capillary zone electrophoresis in pharmaceutical and biomedical analysis.

Capillary zone electrophoresis is a technique that is rapidly gaining popularity in the pharmaceutical industry because of the wide range of compounds applicable to the technique. These range from small biologically active molecules through to large nucleotides and proteins. This review outlines the historical development of the technique and some of the basic theory of capillary zone electrophoresis. This is followed by an explanation of some of the adaptations now being used to enable the separation of neutral molecules as well as charged species, and ways of achieving chiral selectivity.

Base Sequence↗
PubMed1994

Radioimmunoassay of drugs of abuse in hair. Part 1: Methadone in human hair, method adaptation and the evaluation of decontamination procedures.

A method suitable for the determination of methadone in human hair is presented. Adaptation and evaluation of a solid-phase I125 radioimmunoassay, designed for the quantitative measurement of methadone in urine, and development of a pre-analytical wash procedure has enabled a specific, sensitive and accurate analytical procedure to be developed. The specificity of the antiserum towards other drugs or biologically active compounds is evaluated up to a concentration of 100,000 ng ml-1 and accuracy covering a range of 0-450 ng ml-1 is found to be within 6% of expected methadone concentrations prepared in both drug free hair extract and urine. Inter-assay relative standard deviation (RSD) at concentrations of 5.1, 76.0 and 247 ng ml-1 methadone are 5.5, 2.5 and 3.6% respectively (n = 10) and intra-assay RSD at concentrations 2.3, 25.2 and 217 ng ml-1 are 5.3, 3.6 and 6.8% (n = 5). The limit of detection is 0.5 ng ml-1. Extraction of control drug free hair samples spiked with methadone at concentrations of 100, 250 and 400 ng ml-1 achieved recoveries of 86, 80 and 89%, respectively. Control hair samples contaminated with methadone are examined under differing wash procedures to assess their effectiveness in the removal of methadone contaminant. A suitable pre-analytical wash regime is proposed for removal of contaminant derived from external or environmental sources. The mechanics of the wash action and contaminant application to the hair is discussed. It is concluded that the adapted radioimmunoassay and developed pre-analytical decontamination procedure is a suitable technique to employ for the measurement of methadone in human hair, be it prescribed or abused, with concentrations expressed as ng methadone per mg hair.

Decontamination↗
PubMed1993

Challenging declarations of abstinence by the determination of morphine in hair by radioimmunoassay.

Morphine extracted from dated hair segments and analysed by adaptation of a specific solid-phase 125I radioimmunoassay for the measurement of morphine in urine has provided long term histories of the heroin usage of individual patients. Results expressed as ng morphine/mg hair are compared with a pre-determined cut-off level of 0.3 ng morphine/mg hair, from a known drug-free population (n = 21). Morphine concentrations in hair samples from known heroin abusers are found to be above the cut-off limit (range 0.6-9.4 ng morphine/mg hair), and suggest a possible correlation between heroin intake and concentration of morphine in hair. Intra-assay relative standard deviation (RSD), at morphine levels of 9.27 and 1.12 ng morphine/mg hair are 2.4 and 5.5%, respectively, and acceptable recoveries from drug-free hair spiked with morphine are also achieved. The developed segmental hair analysis regime has been used successfully to challenge a self-declaration of heroin abstinence. Routine cumulative urine screening was unable to provide such evidence. The potential for hair drug analysis is discussed.

Hair↗
PubMed1991

Comparison of in vitro replication and cytopathology caused by strains of canine distemper virus of vaccine and field origin.

Three biological properties of canine distemper virus were examined to determine if any would consistently differentiate field from vaccine strains of the virus. The properties were the ability to (1) infect macrophages and epithelial cells, (2) produce distinct cytopathologic effect in alveolar and peritoneal macrophages and Vero cells, and (3) produce pocks on the chorioallantoic membrane of embryonated chicken eggs. Four vaccine strains and 5 field isolates were used in the study. The 5 field isolates were obtained directly from canine tissues. Of the 3 properties studied, only the comparison of the ability of the viruses to infect macrophages and epithelial cells was a consistent marker of virus origin. Virulent field isolates would only infect macrophage cultures, whereas the vaccine strains infected both types of cells. One avirulent field isolate from a case of old dog encephalitis reacted more like a vaccine strain by infecting both cell types.

Allantois↗
PubMed1989

Chromatographic methods for determining the identity, strength and purity of ranitidine hydrochloride both in the drug substance and its dosage forms--an exercise in method selection, development, definition and validation.

The selection, development, definition and validation of selective stability-indicating procedures for high-performance liquid chromatographic and thin-layer chromatographic analyses of ranitidine hydrochloride are described. The procedures used in conjunction can be applied to the quality assurance and stability assessments of both the drug substance and its dosage forms and serve to establish the identity, strength and purity of this drug used in the treatment of peptic ulcer and related conditions.

Chromatography↗
PubMed1989

Serologic survey for infectious canine hepatitis virus in grizzly bears (Ursus arctos) from Alaska, 1973 to 1987.

Serum antibody prevalence of infectious canine hepatitis virus was 12% (90 of 725) for grizzly bears (Ursus arctos) from Alaska (USA) during the period 1973 to 1987. Prevalence was highest on Kodiak Island at 29% (37 of 127). Prevalence of exposure at individual collection areas did not change significantly over time. There were no significant sex-specific differences in prevalence. Prevalence was directly related to age, but it was 0% for bears less than 2-yr-old. Young bears which are exposed to the virus may develop clinical disease and die as a result of the infection. This disease may be a factor affecting grizzly bear population dynamics.

Adenoviridae Infections↗
PubMed1985

Emotional stress and diabetic control: a postulated model for the effect of emotional distress upon intermediary metabolism in the diabetic.

The findings of a number of clinical investigators across a wide variety of situations and using a wide variety of observational procedures agree on the disruptive effects of emotional distress upon diabetic control. An integrative model of coordinated neural and hormonal reactions to emotional stress and their additive and potentiating effects on intermediary metabolism is proposed. The end result of these effects, as part of a general fight/flight or defense-alarm reaction, is a strong energy mobilization response (namely, a sharp rise in blood glucose and free fatty acid levels resulting in increased levels of serum cholesterol, triglycerides, and ketone bodies), which the diabetic cannot readily counterregulate. It is further proposed that increased diabetic control, together with lower insulin requirements, may result from the inclusion of stress management procedures as an adjunct to traditional medical treatment. The findings of a large number of investigators supporting these propositions are presented and discussed.

Aldosterone↗
PubMed1969

A token reinforcement program in a public school: a replication and systematic analysis.

A base rate of disruptive behavior was obtained for seven children in a second-grade class of 21 children. Rules, Educational Structure, and Praising Appropriate Behavior while Ignoring Disruptive Behavior were introduced successively; none of these procedures consistently reduced disruptive behavior. However, a combination of Rules, Educational Structure, and Praise and Ignoring nearly eliminated disruptive behavior of one child. When the Token Reinforcement Program was introduced, the frequency of disruptive behavior declined in five of the six remaining children. Withdrawal of the Token Reinforcement Program increased disruptive behavior in these five children, and reinstatement of the Token Reinforcement Program reduced disruptive behavior in four of these five. Follow-up data indicated that the teacher was able to transfer control from the token and back-up reinforcers to the reinforcers existing within the educational setting, such as stars and occasional pieces of candy. Improvements in academic achievement during the year may have been related to the Token Program, and attendance records appeared to be enhanced during the Token phases. The Token Program was utilized only in the afternoon, and the data did not indicate any generalization of appropriate behavior from the afternoon to the morning.

Journal Article↗