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PubMed1993

High-performance liquid chromatography of amino acids, peptides, and proteins. 123. Dynamics of peptides in reversed-phase high-performance liquid chromatography.

The dynamics of several peptides in reversed-phase high-performance liquid chromatography (RP-HPLC) have been investigated on both n-octadecyl (C18) silica and n-butyl (C4) silica sorbents. In particular, the conformational interconversions and the relative rates of chromatographic relaxation of bombesin, glucagon, and beta-endorphin on both C18 and C4 n-alkylsilicas were monitored by examining changes in the experimental bandwidths of these peptides as a function of temperature and column residence time under linear gradient elution RP-HPLC conditions. The observed band-broadening trends were correlated with previously derived retention parameters and thermodynamic descriptors of the association process determined for bombesin, beta-endorphin, glucagon, and a control peptide, penta-L-phenylalanine. This study confirms that bandwidth measurements can be used as an integral experimental component to study the effect of the secondary structure of peptidic solutes on their RP-HPLC retention behavior. Further, the data demonstrate the utility of RP-HPLC as a tool to examine peptide conformational dynamics at hydrophobic surfaces. The relevance of these results to the general phenomenon of peptide-lipid interactions is discussed in terms of the associated evidence for lipid-induced changes in the conformation of these three bioactive peptides.

Amino Acid Sequence↗

PubMed2005

Effect of dielectric roughness on performance of pentacene TFTs and restoration of performance with a polymeric smoothing layer.

The morphology, structure, and transport properties of pentacene thin film transistors (TFTs) are reported showing the influence of the gate dielectric surface roughness. Upon roughening of the amorphous SiO2 gate dielectric prior to pentacene deposition, dramatic reductions in pentacene grain size and crystallinity were observed. The TFT performance of pentacene films deposited on roughened substrates showed reduced free carrier mobility, larger transport activation energies, and larger trap distribution widths. Spin coating roughened dielectrics with polystyrene produced surfaces with 2 A root-mean-square (rms) roughness. The pentacene films deposited on these coated surfaces had grain sizes, crystallinities, mobilities, and trap distributions that were comparable to the range of values observed for pentacene films deposited on thermally grown SiO2 (roughness also approximately 2 A rms).

Journal Article↗

PubMed2006

Density functional for spectroscopy: no long-range self-interaction error, good performance for Rydberg and charge-transfer states, and better performance on average than B3LYP for ground states.

We present a new density functional called M06-HF. The new functional has full Hartree-Fock exchange, and therefore it eliminates self-exchange interactions at long range. This leads to good performance in TDDFT calculations of both Rydberg and charge-transfer states. In addition, the functional satisfies the uniform electron gas limit, and it is better than the popular B3LYP functional, on average, for ground-electronic-state energetics.

Journal Article↗

PubMed2002

Family-based and association studies of monoamine oxidase A and attention deficit hyperactivity disorder (ADHD): preferential transmission of the long promoter-region repeat and its association with impaired performance on a continuous performance test (TOVA).

Monoamine oxidase A (MAO A) is located on the X chromosome and metabolizes biogenic amines including dopamine, norepinephrine and serotonin. A functional promoter-region polymorphism of this gene has been described that has been studied in a number of mental illnesses but not in attention deficit hyperactivity disorder (ADHD). In the current study, we examined the MAO A promoter-region polymorphism initially in 133 triads and observed preferential transmission of the long alleles from 74 heterozygote mothers to ADHD probands (chi(2) = 4.37, P = 0.036, df = 1). We also examined the role of this polymorphism in a computerized continuous performance test, the TOVA. Significant differences were observed on errors of commission (chi(2) = 7.021, P = 0.008) and patients carrying the long MAO A allele made significantly more such errors. Errors of commission are a measure of impulsivity. However, following Ritalin (methylphenidate) administration the association between this polymorphism and errors of commission was markedly attenuated and no longer significant at the P < 0.05 level. We also analyzed the provisional association by the case-control design. A significant difference in allele frequency was observed between 110 male probands vs 202 male controls (Pearson chi(2) = 7.94, P = 0.047). Similarly results were obtained when 19 female probands were compared to female controls (genotype chi(2) = 21.28; P = 0.0032, 3 df and allele chi(2) = 30.88, P= 0.0007, 2 df). All three complementary approaches employed (family-based, case-control and quantitative trait design) suggest a role for the MAO A promoter-region polymorphism in conferring risk for ADHD in our patient population.

Attention Deficit Disorder with Hyperactivity↗

PubMed2001

The General Medical Council's Performance Procedures: peer review of performance in the workplace.

The General Medical Council procedures to assess the performance of doctors who may be seriously deficient include peer review of the doctor's practice at the workplace and tests of competence and skills. Peer reviews are conducted by three trained assessors, two from the same speciality as the doctor being assessed, with one lay assessor. The doctor completes a portfolio to describe his/her training, experience, the circumstances of practice and self rate his/her competence and familiarity in dealing with the common problems of his/her own discipline. The assessment includes a review of the doctor's medical records; discussion of cases selected from these records; observation of consultations for clinicians, or of relevant activities in non-clinicians; a tour of the doctor's workplace; interviews with at least 12 third parties (five nominated by the doctor); and structured interviews with the doctor. The content and structure of the peer review are designed to assess the doctor against the standards defined in Good Medical Practice, as applied to the doctor's speciality. The assessment methods are based on validated instruments and gather 700-1000 judgements on each doctor. Early experience of the peer review visits has confirmed their feasibility and effectiveness.

Clinical Competence↗

PubMed1988

[Performance training in pregnancy. Report of respiratory and cardiovascular physiologic changes in a pregnant high-performance athlete in comparison with a sample of normal pregnant patients].

Against the background of dramatic changes that took place in the history of sports during the past one hundred years, we are today discussing with regard to the compatibility of sport and pregnancy whether the extent of sports activities before pregnancy contributes to the amount of stress tolerated during pregnancy. Animal experimental studies on the effect of physical stress on the foetus cannot always be transferred to man, and hence recommendations made to pregnant women are often purely empirical. The article reports on the results of an examination of a professional woman athlete during pregnancy: Various maternal circulatory and respiratory parameters were recorded in this primigravida of 25 years of age, who had been regularly active as a competitive runner for 12 years, during the 24th week of pregnancy and from the 28th week of pregnancy onwards, at intervals of 14 days and post partum, at rest and during steady-state load on a bicycle ergometer (6 minutes each at 40 and 70 watts load, respectively) and a step-by-step load increasing every minute by 15 watts until attainment of a maternal heart rate of 150 beats per minute. The results were compared with those in a group of pregnant women who had not been competitive sportswomen. During continued training as per schedule up to the 36th week of pregnancy of the athlete, there was hardly any change in performance, and there was a marked difference against the other women. The pulse at rest was lower by a mean of 30 beats in the athlete during pregnancy, clearly indicating maintenance of the economic cardiac mechanism known to occur in trained persons, which produces a greater cardiac output via an increased stroke volume at a lower heart rate. This difference was impressively demonstrated under different loads. Another example of more economic management of an identical load is also seen, for instance, in the lower oxygen uptake and lower respiratory rate. Even at a maternal heart rate of 150 beats per minute the foetus of the athlete did not show any signs of stress under test conditions. In a measurement "at site" during the 38th week of pregnancy under routine and training conditions with relevant sprints and a maternal heart rate increase to more than 170 beats per minute, however, foetal behaviour displaying bradycardia clearly showed the existence of tolerance limits for foetal supply.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗

PubMed2006

Grape variety affects larval performance and also female reproductive performance of the European grapevine moth Lobesia botrana (Lepidoptera: Tortricidae).

For insect herbivores, the quality of the larval host plant is a key determinant of fitness. Therefore, insect populations are supposed to be positively correlated with the nutritional quality of their host plant. This study aimed to determine if and how different varieties of grapes (including the wild grape Lambrusque) affect both larval and adult performance of the polyphagous European grapevine moth Lobesia botrana (Denis & Schiffermüller). Significant differences were found in larval development time, but not in pupal mass, adult emergence rate, or sex ratio. Although the fecundity of females is not different among varieties, females fed on some varieties produced eggs of different sizes which are correlated to their fertility. Thus, females adapt resource allocation to eggs depending on their diet as larvae. Using a fitness index, the average reproductive output was found to be highest for females reared on cv. Chardonnay. Females reared on wild grape produced a fitness index identical to the cultivated grapes. However, Lambrusque and Gewurztraminer separate themselves from the cultivated varieties according to our discriminant analyses. It is emphasized, through this study, that cultivars fed on by larvae should be considered in the population dynamics of L. botrana and that egg number is insufficient to determine host plant quality.

Analysis of Variance↗

PubMed2005

Application of accelerated solvent extraction followed by gel performance chromatography and high-performance liquid chromatography for the determination of polycyclic aromatic hydrocarbons in mussel tissue.

Accelerated solvent extraction (ASE) has been evaluated as a fast alternative to methanolic saponification for the extraction of 12 polycyclic aromatic hydrocarbons (PAHs) from mussel tissue. Several solvent systems and different operating conditions were investigated. The mixture dichloromethane-acetone (1:1, v/v) gave the best recoveries at 125 degrees C and 1500 psi, in a total time of 10 min. No yield difference was found between freeze-drying (Fd) or drying the wet mussel with diatomaceous earth (Ded) prior to extraction. The ASE method was validated using the standard reference material SRM 2977, a freeze-dried mussel tissue with naturally present organic contaminants. The performance characteristics of the ASE method (trueness: 70-110%; precision: 4-14% and limit of quantification (LOQ): 0.1-0.25 microg/kg) meet the criteria established by the European Union for quantitative methods of analysis for official control of organic residues and contaminants. ASE provides a 24 times faster extraction than MSE and reduces 12 times the volume of solvent required.

Animals↗

PubMed2004

Cross-cultural effects on IQ test performance: a review and preliminary normative indications on WAIS-III test performance.

This article presents a review of cross-cultural influences on Wechsler IQ tests, together with a preliminary investigation into WAIS-III test performance (English administration) for a southern African sample (age range 19-30) stratified for white English first language and black African first language, level and quality of education. ('African language' is the term used to denote the indigenous languages of black populations in southern Africa). A two-way ANOVA revealed highly significant effects for both level and quality of education within the black African first language group. Scores for the white English and black African first language groups with advantaged education were comparable with the US standardization, whereas scores for black African first language participants with disadvantaged education were significantly lower than this. Thus indications from this research are that normative studies should take account of the influential variable of quality of education, in addition to level of education. Alternatively faulty conclusions may be drawn about the effects of ethnicity, with the potential for neuropsychological misdiagnosis.

Acculturation↗

PubMed1981

[Effect of the copper status on the reproduction performance and the milk yield of cows in 2 copper-deficient locations. 2. Effect of copper deficiency on the reproduction performance and the milk yield of cows].

The influence of copper deficiency on the reproduction performance of cows has not often been investigated. In two habitats feeding cows with mineral mixtures rich in copper resulted in a significant reduction of the aperiodically extended sexual cycles. The beginning of the first visible symptoms of heat, the period between gravidities, the duration of gravidity, the birth weight of the calves and the Cu-content of the colostrum remained uninfluenced by Cu-supply. The liver weight increase of the calves from cows without Cu-supplement during gravidity was by 5% lower during the first 90 days of life than that of the offspring of cows with additional intrauterine Cu-supply (p greater than 0.05). The mineral mixture increased the milk yield by 0.4 resp. 0.5 kg and the milk fat content by 0.10 resp. 0.13%. This resulted in an excess production of 32 resp. 62 g milk fat per cow and day of the experiment (p greater than 0,05).

Animals↗

PubMed2003

An examination of the relationship between clinical skills examination performance and performance on USMLE Step 2.

PURPOSE: To examine the relationship between performance on a large-scale clinical skills examination (CSE) and a high-stakes multiple-choice examination. METHOD: Two samples were used: (1) 6,372 first-taker international medical graduates (IMGs); and (2) 858 fourth-year U.S. medical students. Ninety-seven percent of IMGs and 70% of U.S. students had completed Step 2. Correlations were calculated, scatter plots produced, and regression lines estimated. RESULTS: Correlations between CSE and Step 2 ranged from .16 to .38. The observed relationship between scores confirms that CSE score information is not redundant with MCQ score information. This result was consistent across samples. CONCLUSIONS: Results suggest that the CSE assesses proficiencies distinct from those assessed by current USMLE components and therefore provides evidence justifying its inclusion in the medical licensure process.

Clinical Competence↗

PubMed1986

Delayed feedback of physician performance versus immediate reminders to perform preventive care. Effects on physician compliance.

In an academic general medicine clinic, we performed a randomized, controlled trial to compare (1) the effects of supplying monthly feedback reports of compliance with preventive care protocols by 135 internal medicine house staff with (2) the effects of specific reminders given to them at the time of patient visits. The protocols were randomly divided into two groups, A and B, and half the house staff were given feedback for Group A and half for Group B. Thus, each group served as a control for the other. Each feedback group was also randomly assigned to receive reminders for either Group A or B protocols. House staff receiving feedback more often complied with fecal occult blood testing, mammography, pneumococcal vaccination, use of metronidazole, and combined Group A and B protocols than did controls (P less than 0.01). There was also significantly more compliance with the same protocols by house staff receiving reminders, but the increase for fecal occult blood testing, pneumococcal vaccination, and combined Group A protocols was twice that seen in physicians given feedback alone. In addition, reminders alone increased compliance with oral calcium supplementation. Overall compliance with the preventive care protocols was low: 10-15% in physicians receiving neither feedback nor reminders, increasing to 15-30% in those receiving reminders. Physician compliance with suggested preventive care protocols can be increased by both delayed feedback and immediate reminders, but reminders have a greater effect.

Clinical Competence↗

PubMed1990

Measurement of vancomycin in renally impaired patient samples using a new high-performance liquid chromatography method with vitamin B12 internal standard: comparison of high-performance liquid chromatography, emit, and fluorescence polarization immunoassay methods.

A new reverse-phase high-performance liquid chromatographic (HPLC) procedure has been developed for the quantitation of vancomycin and its crystalline degradation product, CDP-1. The new HPLC procedure involves a liquid-liquid extraction pretreatment procedure and an HPLC internal standard, vitamin B12. The new HPLC procedure was used to measure 50 renally impaired patient samples. Samples were than analyzed by the monoclonal antibody Emit vancomycin assay, and the polyclonal antibody fluorescence polarization immunoassay (FPIA) vancomycin assay, and the results were compared. The Emit vancomycin assay correlated well with HPLC, but FPIA quantitated higher than Emit and HPLC. We conclude that the polyclonal antibody FPIA assay detects CDP-1 in the samples of renally impaired patients, accounting for an average of 10% of the FPIA/Emit bias, and should therefore be used with caution when monitoring vancomycin levels in renally impaired patients.

Chromatography, High Pressure Liquid↗

PubMed1993

Recent advances in high-performance liquid chromatography/mass spectrometry and high-performance liquid chromatography/tandem mass spectrometry: detection of cyclosporine and metabolites in kidney and liver tissue.

Recent advances in both ionization methods and mass spectrometers have resulted in powerful new techniques for the study of drug metabolism and disposition. The interest in high-performance liquid chromatography/mass spectrometry (HPLC/MS) is the result of the lack of a sensitive universal detector for HPLC. Although it is not the ideal detector, HPLC/MS has become a reliable technique for xenobiotic analysis. The application of HPLC/MS to studies of the pharmacology and toxicology of molecules of mass < 1,500 daltons is most advantageous in three areas: development of specific methods for trace analysis, detection and characterization of metabolites, and studies of interactions between drug molecules and peptides/proteins. We have used HPLC/MS to study the deposition of cyclosporine and its metabolites in needle biopsy samples from kidney and liver in which sample size is severely limited. The limit of detection in the single-ion monitoring mode was 500 fg (450 amol), which is about a thousandfold lower than UV limits of detection.

Chromatography, High Pressure Liquid↗

PubMed2002

Temperature-mediated heteroduplex analysis performed by using denaturing high-performance liquid chromatography to identify sequence polymorphisms in Mycobacterium tuberculosis complex organisms.

PCR products containing sequence polymorphisms were prepared from six mycobacterial genes, denatured, mixed with reference PCR products, and reannealed; the mixtures were then examined with a denaturing high-performance liquid chromatography system (WAVE) equipped with a temperature-controlled alkalated polystyrene divinyl benzene column. Mismatching of bases in heteroduplexes of the PCR products causes elution patterns of the DNA from the column to be altered. The six mycobacterial genes studied were oxyR, in which a specific polymorphism (G(1031)A) is found only in certain species of the Mycobacterium tuberculosis complex, and five genes in which mutations associated with antituberculosis drug resistance have been found. The resistance genes (with affected drug and PCR product sizes given parenthetically) were rpoB (rifampin; 258 bp), katG (isoniazid; 205 bp), pncA (pyrazinamide; 579 bp); rpsL (streptomycin; 196 bp), and embB (ethambutol; 185 bp). Elution patterns of heteroduplexes of all 20 polymorphisms studied shifted detectably at column temperatures ranging from 65.3 to 68 degrees C and elution times of 3.5 to 6 min. These results show that temperature-mediated heteroduplex analysis is a potentially useful genotypic screen for mutations associated with antituberculosis drug resistance and for the G(1031)A polymorphism in oxyR. The method may allow users to detect novel as well as heterogeneous mutations without using expensive kits or detection labels.

Antitubercular Agents↗

PubMed2005

Evaluation of student performance: clinical and professional performance.

In 1999, the Accreditation Council for Graduate Medical Education (ACGME) endorsed six general competencies for residents as part of an ongoing attempt to emphasize educational outcomes as part of residency program assessment and accreditation. Although the focus of these reforms has been on postgraduate training, the competencies are applicable to medical students who aspire to become excellent clinicians and can help guide the development of assessment tools to measure clinical and professional performance of students in the emergency department. This article reviews the definitions of clinical competence and briefly addresses the issues of evaluation tool validity, reliability, and feasibility as they relate to the assessment of medical students. Several assessment tools are outlined, with an eye to the ACGME competencies and the ACGME Toolbox of Assessment Methods. The pros and cons of global rating scales, direct observation, simulations, and oral examinations are reviewed. Multiple assessment tools are often necessary to provide a true evaluation of a student's clinical and professional skills. Their application in the setting of an emergency medicine rotation is described and discussed.

Accreditation↗

PubMed2004

The relationship between performance in a dental school and performance on a clinical examination for licensure: a nine-year study.

BACKGROUND: Licensure examinations in dentistry have become an increasing concern, owing to ethical issues in the use of patients, difficulties in seeing relationships between outcomes of licensure examinations and performance in educational programs, and questions on the reliability of "one-shot" clinical examinations. Using data from a nine-year period, the authors compared the results of clinical licensing tests and the academic class ranks of the candidates. METHODS: The authors studied data for 835 dental school graduates of one school from 1994 through 2002. They compared the dental graduates' results from the North East Regional Board, or NERB, of Dental Examiners examinations with their class ranks. The authors used analysis of variance to analyze the differences among passing, failing and "no data" groups, kappa statistic and logistic regression for variation, and receiver operating characteristic, or ROC, curves for diagnostic utility. RESULTS: The class rank of graduates who passed and failed NERB's restorative section of the examination did not differ. Differences for other sections of the examination were statistically significant but small. The variation in restorative and manikin exercises over time was highly significant. No consistency existed between these tests, and their ROC curves indicated no utility for diagnosing class rank. CONCLUSIONS: The authors' analysis of nine years' data called into question the reliability and validity of initial licensure examinations based on certain of the one-time tests used by NERB. Future study should determine if the results generalize to other schools and clinical testing agencies. PRACTICE IMPLICATIONS: If the results of this study can be generalized to all U.S. licensure examinations, basing licensing decisions on clinical licensure examination alone risks licensure decisions of low validity. Use of patients in examinations of questionable validity may be unethical because they may have been subjected to risk of irreversible damage without contribution to a valid decision-making process by the licensing authority.

Analysis of Variance↗

PubMed1992

The effect of body condition, live weight, breed, age, calf performance, and calving date on reproductive performance of spring-calving beef cows.

Data from 321 spring-calving cows (mean calving date March 27) were used to assess the effects of body condition, live weight, cow age (from 4 to 13 yr), and breed (237 Hereford x Friesians and 84 Blue-Greys) and time of calving on the proportion of cows that became pregnant, the number of days from the start of mating to pregnancy, and calving interval. Mating started at turn-out to pasture in mid-May and lasted 9 to 10 wk. Body condition at calving and breed were the most significant animal factors affecting reproductive performance. Cows calving in higher body condition had shorter (P less than .001) calving intervals (11.2 d per unit of body condition at calving). Blue-Grey cows became pregnant in a higher proportion (90%) and calving interval was shorter (364 d) than in Hereford x Friesians (83%; 374 d). Body condition at the start of mating was less important and body condition at the end of mating had no effect. Live weight at calving and changes in live weight from calving to the start of mating and during the mating period had no significant effect. The proportion of cows becoming pregnant decreased significantly with age in Hereford x Friesian cows older than 7 yr. The variance in calving interval accounted for by calving date, body condition at calving, breed, and age was 42%.

Aging↗