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Biomedical subjects

S A Margolis

Publications and source records attributed to S A Margolis.

At least 19 recordsLinked to original sources

Clinical simulators: applications and implications for rural medical education.

Medical education has undergone significant changes globally. Calls for the revitalisation of centuries old pathways of learning have resulted in innovative medical curricula. Didactic modes of teaching which involved the learning of copious amounts of facts have given way to curricula that focus on the horizontal and vertical integration of basic and clinical sciences. Increasing concern for patient care and safety has led to a 'gap' between the needs of medical students to acquire necessary psychomotor skills and the safety and wellbeing of the patient. This has resulted in alternate teaching methods that include non-patient based training for the acquisition of clinical skills. The use of computerised, full-sized human simulators provides medical students with the necessary psychomotor and clinical reasoning skills in a realistic learning environment, while remaining risk free to patients. These clinical simulators are powerful learning tools that have applications at all levels of medical education across multiple disciplines, emphasising the multidisciplinary approach required in many medical situations. This article reviews the literature on medical simulation and provides the contextual basis for the establishment of a Clinical Simulation Learning Centre (CSLC) in a rural clinical school in Australia. The educational program, as well as the design, layout and equipment of the CSLC are described, as well as implications for rural practitioners. The CSLC has been a major capital investment in a relatively under-resourced part of regional Australia and has provided opportunities for ongoing education across a range of healthcare professionals in the community.

Australia↗

How can experience in clinical and community settings contribute to early medical education? A BEME systematic review.

REVIEW DATE: Review period January 1992-December 2001. Final analysis July 2004-January 2005. BACKGROUND AND REVIEW CONTEXT: There has been no rigorous systematic review of the outcomes of early exposure to clinical and community settings in medical education. OBJECTIVES OF REVIEW: Identify published empirical evidence of the effects of early experience in medical education, analyse it, and synthesize conclusions from it. Identify the strengths and limitations of the research effort to date, and identify objectives for future research. SEARCH STRATEGY: Ovid search of: BEI, ERIC, Medline, CINAHL and EMBASE Additional electronic searches of: Psychinfo, Timelit, EBM reviews, SIGLE, and the Cochrane databases. Hand-searches of:Medical Education, Medical Teacher, Academic Medicine, Teaching and Learning in Medicine, Advances in Health Sciences Education, Journal of Educational Psychology. CRITERIA DEFINITIONS EXPERIENCE: Authentic (real as opposed to simulated) human contact in a social or clinical context that enhances learning of health, illness and/or disease, and the role of the health professional. Early: What would traditionally have been regarded as the preclinical phase, usually the first 2 years. Inclusions: All empirical studies (verifiable, observational data) of early experience in the basic education of health professionals, whatever their design or methodology, including papers not in English. Evidence from other health care professions that could be applied to medicine was included. EXCLUSIONS: Not empirical; not early; post-basic; simulated rather than 'authentic' experience. DATA COLLECTION: Careful validation of selection processes. Coding by two reviewers onto an extensively modified version of the standard BEME coding sheet. Accumulation into an Access database. Secondary coding and synthesis of an interpretation. HEADLINE RESULTS: A total of 73 studies met the selection criteria and yielded 277 educational outcomes; 116 of those outcomes (from 38 studies) were rated strong and important enough to include in a narrative synthesis of results; 76% of those outcomes were from descriptive studies and 24% from comparative studies. Early experience motivated and satisfied students of the health professions and helped them acclimatize to clinical environments, develop professionally, interact with patients with more confidence and less stress, develop self-reflection and appraisal skill, and develop a professional identity. It strengthened their learning and made it more real and relevant to clinical practice. It helped students learn about the structure and function of the healthcare system, and about preventive care and the role of health professionals. It supported the learning of both biomedical and behavioural/social sciences and helped students acquire communication and basic clinical skills. There were outcomes for beneficiaries other than students, including teachers, patients, populations, organizations and specialties. Early experience increased recruitment to primary care/rural medical practice, though mainly in US studies which introduced it for that specific purpose as part of a complex intervention. CONCLUSIONS: Early experience helps medical students socialize to their chosen profession. It helps them acquire a range of subject matter and makes their learning more real and relevant. It has potential benefits for other stakeholders, notably teachers and patients. It can influence career choices.

Attitude of Health Personnel↗

Preliminary application of liquid chromatography-electrospray-ionization mass spectrometry to the detection of 5-methyltetrahydrofolic acid monoglutamate in human plasma.

Liquid chromatography (LC) in direct combination with mass spectrometry (MS) has been shown to be a good analytical technique for the selective separation and detection of labile folate monoglutamates. Reversed-phase LC and electrospray-ionization MS conditions were developed and optimized for the separation and detection of 5-methyltetrahydrofolic acid, 5-formyl tetrahydrofolic acid, tetrahydrofolic acid, dihydrofolic acid and folic acid in aqueous samples. Representative and reproducible positive ion mass spectra were generated for each folate under mild MS conditions. The selective MS detection and identification of endogenous 5-methyltetrahydrofolic acid in human plasma was accomplished through the development of a straightforward C18-based solid-phase extraction procedure. This procedure allows for the qualitative assessment of 5-methyltetrahydrofolic acid in plasma. Based upon an isotope-dilution internal standard calibration study with standards, the LC-MS limit of quantitation for 5M-THF was estimated to be 0.39 ng/mnl.

Chromatography, Liquid↗

Systematic bias in the measurement of water in oils by tubular oven evaporation and azeotropic distillation.

Water in oil has been measured by tubular oven evaporation and by azeotropic distillation into a coulometric moisture analyzer. The results of these measurements were compared to the results obtained by volumetric titration of water in oil. The volumetric measurements were consistently higher than the measurements made by tubular oven evaporation or azeotropic distillation. A mass balance study was performed by volumetric Karl Fischer titration of the water in the oil that remained in the tubular oven and in the distillation apparatus. This study indicated that measurable amounts of water were not removed after exhaustive evaporation or distillation. The sum of the water removed by distillation from toluene and that remaining in the distillation chamber was equal to the amount of water measured in the oil by the volumetric method. The data are consistent with the existence of an oil-water azeotrope that does not release water upon evaporation at 160 degrees C or upon dissolution in toluene and distillation of the water-toluene azeotrope. These results were obtained for oils varying in viscosity from 8 to 850 m2/s, and the amount of water remaining associated with the oil appears to be dependent upon the composition of the oil and the method of analysis.

Journal Article↗

Analysis of anthocyanins in foods by liquid chromatography, liquid chromatography-mass spectrometry and capillary electrophoresis.

This article reviews recent developments in the methodology for the measurement of anthocyanins that offer several advantages over classical methods of analysis. The use of UV-diode array and mass spectrometric (MS) detectors, with improved methods of liquid chromatography analysis has facilitated identification of these analytes. The use of capillary electrophoresis (CE) analysis of the anthocyanins under acid conditions has significantly increased peak resolution and improved the detection limits by several orders of magnitude. CE offers the advantage of economies of very small sample size, very small solvent consumption, and short analysis times along with the future possibility of being combined with MS detection.

Anthocyanins↗

Characterization of prenylated xanthones and flavanones by liquid chromatography/atmospheric pressure chemical ionization mass spectrometry.

Reversed-phase liquid chromatography with atmospheric pressure chemical ionization mass spectrometry (LC/APCI-MS) in the positive-ion mode was utilized to analyze crude ether extracts from the root bark of Maclura pomifera, a tree known to have a high content of prenylated xanthones and flavanones. Identification of three xanthones and two flavanones was based on their unique mass spectra. Under optimum conditions peaks corresponding to the [MH](+) ion and characteristic fragments for each compound were observed. (1)H NMR data were used to confirm the identities of two xanthones that had the same molecular mass and similar fragmentation patterns. Fragmentation of the analytes was achieved by application of an electrostatic potential at the entrance of the single quadrupole mass spectrometer. The optimum voltage for fragmentation was found to be related to the class of compounds analyzed and, within each class, to be dependent on the structure of the prenyl moiety. Collision-induced pathways consistent with precedent literature describing the MS characterization of similar compounds and with the observed fragmentation patterns are tentatively proposed.

Chromatography, Liquid↗

Certification by the Karl Fischer method of the water content in SRM 2890, Water Saturated 1-Octanol, and the analysis of associated interlaboratory bias in the measurement process.

The calibration of Karl Fischer instruments and reagents and the compensation for instrumental bias are essential to the accurate measurement of trace levels of water in organic and inorganic chemicals. A stable, nonhygroscopic standard, Water Saturated Octanol, which is compatible with the Karl Fischer reagents, has been prepared. This material, Standard Reference Material (SRM) 2890, is homogeneous and is certified to contain 39.24 +/- 0.85 mg water/mL (expanded uncertainty) of solution (47.3 +/- 1.0 mg water/g solution, expanded uncertainty) at 21.5 degrees C. The solubility of water in -octanol has been shown to be nearly constant between 10 degrees C and 30 degrees C (i.e., within 1% of the value at 21.5 degrees C). The results of an interlaboratory comparison exercise illustrate the utility of SRM 2890 in assessing the accuracy and bias of Karl Fischer instruments and measurements.

Journal Article↗

Sources of systematic bias in the measurement of water by the coulometric and volumetric Karl Fischer methods.

The sources of systematic bias in the measurement of moisture by the volumetric and coulometric Karl Fischer methods were assessed. Using water-saturated octanol as a moisture standard, the measurement accuracy of five coulometric instruments was evaluated. Six possible sources of systematic bias were examined: accuracy of the moisture standard, nonadjustable instrumental bias, operator-adjustable instrumental bias, solvent composition, cell design, and sample composition. The published water content of water-saturated octanol was confirmed by the method of standard additions. The nonadjustable instrumental bias consisted of two types, one that was variable and was observed at water levels below 200 micrograms of water, and one that represented a constant percentage of the total water over the tested range from 40 to 400 micrograms of water. The adjustable instrumental parameters, if set incorrectly, may cause a small but significant negative bias (< 7%). Solvent composition as a function of both solvent type and titration vessel design can introduce a negative bias of up to 10%. Finally, the nature of the sample introduces a negative bias as demonstrated by the results obtained from titrating water in four different oil samples. Under optimum conditions, different amounts of water were measured in each oil using different Karl Fischer titration procedures and five different instruments.

Electrochemistry↗

Liquid chromatographic measurement of L-ascorbic acid and D-ascorbic acid in biological samples.

D- and L-Ascorbic acids have been separated using liquid chromatography (LC) on a polymer-coated silica-based NH2 column and the L-isomer has been quantified in human serum, rat serum, rat lung, rat lung perfusate, infant formula (SRM 1846) and mixed food sample (SRM 2383). The D-isomer was observed only in trace amounts in the mixed food sample. The results demonstrate that ascorbic acid was stable on the column and completely recovered from supplemented samples of human serum and that this method of analysis is accurate, precise and has broad application exhibiting no dependence on the nature of the matrices evaluated herein.

Animals↗

Measurement of ascorbic acid in human plasma and serum: stability, intralaboratory repeatability, and interlaboratory reproducibility.

We demonstrate that total ascorbic acid (TAA, the sum of ascorbic acid and dehydroascorbic acid) in properly prepared human plasma is stable at -70 degrees C for at least 6 years when preserved with dithiothreitol. TAA in human plasma or serum preserved with metaphosphoric acid degrades slowly, at the rate of no more than 1% per year. As assessed from our stability data and from data obtained from 23 laboratories over a period of > 2 years, the intralaboratory repeatability of TAA measurement is approximately 2 mumol/L, irrespective of TAA concentration. Nonchromatographic analytical methods involving dinitrophenylhydrazine and 0-phenylenediamine yield biased results relative to chromatographic methods. Within groups of laboratories that use roughly similar analytical methods, the interlaboratory measurement reproducibility CV for TAA is 15%.

Ascorbic Acid↗

Ascorbic and dehydroascorbic acid measurement in human serum and plasma.

Plasma supplemented with ascorbic acid was prepared; the stability of these samples was characterized and the accuracy of the supplementation was established. Studies on the accuracy, precision, and sources of methodological bias in the measurement of ascorbic acid were summarized. Measurements of the ratio of ascorbic acid to dehydroascorbic acid in clinical samples was evaluated and was shown to be relatively constant in plasma taken from blood stored at 12 degrees C for 6 h. These results imply that whole blood has the capacity to maintain a constant ascorbic-dehydroascorbic acid ratio and suggest that this ratio may be of physiological significance.

Ascorbic Acid↗

Ascorbic and dehydroascorbic acids measured in plasma preserved with dithiothreitol or metaphosphoric acid.

We describe a rapid method for accurately and precisely measuring ascorbic acid and dehydroascorbic acid in plasma. Total analysis time is less than 10 min, replicate analyses of a single pool provide precision less than or equal to 2%, and values measured in supplemented samples agree with known concentrations of 4.68 and 11.83 mg/L. The stability and homogeneity of lyophilized plasma samples supplemented with ascorbic acid and dithiothreitol are documented. We also describe a procedure in which metaphosphoric acid (50 g/L) is used to prepare a reference material for the measurement of ascorbic acid and dehydroascorbic acid. The procedure for both acids consists of first measuring the native ascorbic acid, then reducing the dehydroascorbic acid, at neutral pH, with dithiothreitol, and finally measuring the total ascorbic acid; dehydroascorbic acid is then determined by difference. The metaphosphoric-acid-treated samples were stable at -70 degrees C, but stability decreased with temperature over the range examined, 4-50 degrees C.

Ascorbic Acid↗

Chromatographic separations of serum proteins on immobilized metal ion stationary phases.

The separation of proteins on stationary phases consisting of a bound organic chelator and a chelated divalent transition metal has been studied as a function of (A) metal ion species; (B) mobile phase composition and pH; and (C) anion and cation concentration. Optimum separation was observed at alkaline pH on chelated nickel stationary phases. Ammonium and Tris salts reduced the affinity of the metal chelate packing for serum proteins. Halide ions caused the proteins to be more strongly bound to the stationary phase. High salt concentrations had only a small effect on the binding of serum proteins in the absence of amine containing buffers or salts. It was also observed that the ease of elution and the recovery of protein were dependent on pH and upon the presence of halides. The general order of elution of serum proteins, based on isoelectric focusing, was independent of metal ion species and elution conditions, suggesting that a single mechanism or a unique sequence of mechanisms was operative. The results suggest that ligand exchange is the major mechanism of separation under basic conditions and that hydrophobic effects are the result of the competition of nonnitrogen ions with ammonium ions or amines for ligand binding sites modifying or participating in protein binding. Protein binding studies under weak acidic conditions are also presented although the mechanism responsible for protein binding is unclear.

Blood Protein Electrophoresis↗

Structure of a hydroxyl radical induced DNA-protein cross-link involving thymine and tyrosine in nucleohistone.

Hydroxyl radical induced formation of a DNA-protein cross-link involving thymine and tyrosine in nucleohistone is described. Hydroxyl radicals were generated in N2O-saturated aqueous solution by ionizing radiation. Samples of nucleohistone were hydrolyzed with HCl and trimethylsilylated. Analysis of irradiated samples by gas chromatography-mass spectrometry with selected-ion monitoring showed the presence of a thymine-tyrosine cross-link on the basis of typical fragment ions from the previously known mass spectrum of its trimethylsilyl derivative. The yield of this DNA-protein cross-link in nucleohistone was measured at incrementing doses of radiation and found to be a linear function of radiation dose between 14 and 300 Gy (J.kg-1). This yield amounted to 0.003 mumol.J-1. The mechanism of formation of this DNA-protein cross-link is thought to result from H atom abstraction by hydroxyl radicals from the methyl group of thymine followed by the addition of the resultant thymine radical to the carbon 3 position of the tyrosine ring and subsequent oxidation of the adduct radical.

Animals↗

Structure of a hydroxyl radical induced cross-link of thymine and tyrosine.

DNA-protein cross-links are formed when living cells or isolated chromatin is exposed to ionizing radiation. Little is known about the actual cross-linked products of DNA and proteins. In this work, a novel hydroxyl radical induced cross-link of thymine and tyrosine has been isolated along with a tyrosine dimer by high-performance liquid chromatography of aqueous mixtures of tyrosine and thymine that had been exposed to hydroxyl radicals generated by ionizing radiation. The isolated compounds have been examined by gas chromatography-mass spectrometry, high-resolution mass spectrometry, and 1H and 13C nuclear magnetic resonance spectroscopy. The structure of the thymine-tyrosine cross-link has been identified as the product from the formation of a covalent bond between the methyl group of the thymine and carbon 3 of the tyrosine ring. In addition, the 3,3' tyrosine dimer was isolated and characterized. The mechanism of the formation of these compounds is discussed. This work presents the first complete chemical characterization of a hydroxyl radical induced DNA base-amino acid cross-link.

Chromatography, High Pressure Liquid↗

Stabilization of ascorbic acid in human plasma, and its liquid-chromatographic measurement.

We describe two independent HPLC procedures for the rapid, accurate analysis for ascorbic acid in human plasma. No sample extraction or phase separation is required. We also describe a procedure for preparing a human plasma reference material for use in clinical laboratory analysis for ascorbic acid. The ascorbic acid in plasma can be determined in 15 min, with as little as 50 microL of sample. Analytical recoveries are near 100% with direct injection of deproteinized plasma. Extensive stability data under several conditions, with dithiothreitol as a preservative (antioxidant), indicate that ascorbic acid remains stable in stored plasma for as long as 57 weeks. CVs for round-robin analysis of 11 normal human blood samples by two independent methods were between 0.1% and 5.3%. These clinical samples appear to be stable for at least 50 days under the described conditions of stabilization and sample treatment. Finally, because ascorbic acid prepared by the described procedures is stable at room temperature for at least 18 h, these methods can be readily adapted to clinical laboratory automation at room temperature.

Ascorbic Acid↗