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Biomedical subjects

A M Harris

Publications and source records attributed to A M Harris.

At least 19 recordsLinked to original sources
PubMed2003

Introduction, audit and review of guidelines for delegated authorization of nuclear medicine investigations in compliance with the Ionising Radiation (Medical Exposure) Regulations 2000.

The introduction of the Ionising Radiation (Medical Exposure) Regulations 2000 in Great Britain required every nuclear medicine investigation to be justified by a practitioner holding an appropriate Administration of Radioactive Substances Committee (ARSAC) certificate. The task of authorizing the radiation exposure may be performed by the practitioner (direct authorization) or delegated to an appropriately trained operator working to written guidelines approved by the practitioner (delegated authorization). In this study, we look at the process of implementation, audit and review of a set of Delegated Authorization Guidelines (DAG). The process of drafting the DAG is outlined. Following the introduction of the DAG, an audit of nuclear medicine referrals was performed at two sites for a period of 3 months. Each referral was compared with the DAG to determine whether it matched the criteria set out. If it did not match, it was further categorized as being due to: (1) insufficient referral information; or (2) clinical indication not included in the DAG. All non-matching requests were reviewed by the practitioner. Four hundred and thirty-seven of 632 (69%) referrals fitted the DAG, 12% (n=75) required clarification from the referrer before fitting with the criteria and 19% (n=120) were directly authorized by the practitioner. From those referrals that were directly authorized, some additional indications were identified and the DAG were subsequently revised. In conclusion, a delegated authorization procedure for nuclear medicine investigations can be implemented successfully. Regular audit is essential. This study identified the need to improve the format of the request card and to obtain additional referral information from the referrer.

Certification↗
PubMed2003

Outcome of women with inadequate cervical smears followed up for five years.

BACKGROUND: The clinical and prognostic significance of "inadequate" cervical smear is unknown, even though women with repeated inadequate smears are referred for colposcopy in the National Health Service (NHS) Cervical Screening Programme. AIM: To follow up a cohort of women with inadequate cervical smears over the following five years to examine outcomes, including detection of high grade cervical intraepithelial neoplasia (CIN). METHODS: The study comprised 1972 women with an inadequate cervical smear reported at Walsall Hospitals NHS Trust between 1 April 1995 and 31 March 1996. Results of cervical smears and biopsies taken over the following five years were reviewed to confirm the outcome. FINDINGS: Within five years, 2.2% of women with an inadequate cervical smear developed histologically confirmed high grade CIN, which was higher than the 1.3% seen among all women with cervical smear tests reported at the same laboratory over the same period, although the difference was not significant at the 95% level of confidence. Where inadequacy resulted from or was contributed to by "polymorphs obscuring", the risk of subsequent development/detection of high grade CIN was 2.6%. CONCLUSIONS: Women with inadequate cervical smears had an increased risk of detection of high grade CIN in the following five years compared with "all women". This increased risk was not significant, although if a larger number of women had been studied significance may have been reached, so that further studies are needed. The increased risk appeared to be at least partially dependent on the reason for inadequacy.

Adult↗
PubMed2001

Adrenal masses: the investigation and management of adrenal incidentalomas.

Most general surgeons will face at sometime in their career an 'incidentaloma' of the adrenal gland. How should a surgeon approach an incidentaloma found during routine investigation for other unrelated disease processes? This paper discusses the investigation and management of adrenal incidentalomas and includes guidelines for the non-specialist.

Adrenal Gland Neoplasms↗
PubMed2001

Does the lead apron and collar always reduce radiation dose?

The possibility that personal lead shielding devices can increase absorption of radiation has not been entertained. The purpose of the present investigation specifically was to determine whether pituitary dose might be increased when a leaded apron and thyroid collar are used. Thermoluminescent dosimeters (TLDs) were used to measure absorbed dose. They were calibrated at the kVp used in the clinical situation and a calibration curve relating light output to dose was generated. Lithium fluoride TLD discs were placed in the pituitary gland region of a Rando-Alderson female human phantom. The equivalent of 100 transpharyngeal exposures were delivered. The resultant light output from recovered dosimeters was converted to a uGy value using the calibration curve. The experiment was repeated using a 0.25 mm lead equivalent collar and apron fitted to the phantom in the customary manner. The entire process was repeated in order to have 30 dosimeters for the unshielded and 30 dosimeters for the shielded conditions. A further 30 dosimeters were sham irradiated and served as controls. A statistical comparison between unshielded and shielded conditions was performed. When the leaded apron and thyroid collar were used the absorbed dose to the pituitary gland was increased significantly (P < 0.05). Following this a second group, using a different dosimetry system and a male phantom repeated the experiment. In both cases, the shielded phantom received significantly higher dose to the pituitary region than the unshielded.

Absorption↗
PubMed2000

Endogenously expressed estrogen receptor and coactivator AIB1 interact in MCF-7 human breast cancer cells.

Coactivators are believed to mediate estrogen-induced gene responses via interaction with estrogen receptors (ER). Currently, a major challenge is to determine the importance of each coactivator in a specific cell type and promoter context in response to a particular ligand. The potential of ER to interact with a growing list of coactivators has been shown in a variety of in vitro and gene transfer assays, yet very few data have demonstrated the interaction of endogenous coactivators with ER in intact cells. We report here a ligand-specific interaction of endogenous human ER (hER) and the AIB1 coactivator in MCF-7 human breast cancer cells by using immunoprecipitation analyses. Complexes between endogenously expressed hER and AIB1 were detected in estradiol-treated cells and to a much lesser extent in cells treated with the partial agonist, monohydroxytamoxifen. We were unable to detect an hER-SRC-1 complex in our immunoprecipitations from MCF-7 cells. The in vitro-binding affinity for mouse ER interaction with AIB1 was estimated to be 40-120 nM. We conclude that AIB1 is a major coactivator for hER in MCF-7 human breast cancer cells.

Animals↗
PubMed2000

The structural failure of a multi-hole collimator.

During measurements of the extrinsic spatial resolution of a gamma camera, it was noted that there was a variation with the position in the field of view. The problem was traced to the collimator, and this was confirmed by inspection of the parallel hole structure. Removal of the cover showed that the lead foil honeycomb had become detached from its surround. The fault could have had serious implications for the quality of patient investigations and could also have caused damage to the crystal if it had gone undetected. As a result of this investigation, the quality assurance procedures within this department have been updated to include a visual check of all collimator cores.

Gamma Cameras↗
PubMed2000

Absorption, disposition, and metabolism of rosiglitazone, a potent thiazolidinedione insulin sensitizer, in humans.

Rosiglitazone is a potent peroxisome proliferator-activated receptor gamma agonist that decreases hyperglycemia by reducing insulin resistance in patients with type 2 diabetes mellitus. The disposition of (14)C-labeled rosiglitazone was determined after oral and i.v. dosing of rosiglitazone solution, and the disposition of nonradiolabeled rosiglitazone was determined after oral dosing of tablets in this open-label, three-part, semirandomized, crossover study. The absorption of rosiglitazone was rapid and essentially complete, with absolute bioavailability estimated to be approximately 99% after oral tablet dosing and approximately 95% after oral solution dosing, and clearance was primarily metabolic. The time to maximal concentration of radioactivity and the elimination half-life for two metabolites in plasma were significantly longer than for rosiglitazone itself (4-6 h versus 0. 5-1 h, and ca. 5 days versus 3-7 h). Radioactivity was excreted primarily via the urine ( approximately 65%) and was excreted similarly after oral and i.v. dosing. The major routes of metabolism were N-demethylation and hydroxylation with subsequent conjugation, of which neither was affected by the route of drug administration. The major metabolites, those of intermediate importance, and nearly all of the trace metabolites in humans have been identified previously in preclinical studies. Rosiglitazone was well tolerated in all formulations.

Adult↗
PubMed1999

Recruitment of house staff into anesthesiology: factors responsible for house staff selecting anesthesiology as a career and individual training program.

STUDY OBJECTIVE: To identify factors responsible in the selection of anesthesiology as a career by Mayo Clinic house staff (i.e., residents and clinical fellows); to evaluate their level of satisfaction with their choice of career and training program, and their perceptions of the future for anesthesiology trainees. DESIGN: Cross-sectional analysis using a questionnaire survey of 67 house staff enrolled in the anesthesiology training program during the 1995-1996 academic year. SETTING: Mayo Clinic, Rochester, MN. MEASUREMENTS AND MAIN RESULTS: Forty-eight (72%) of those surveyed responded to the questionnaire. Data were analyzed using the Chi-square and Mann-Whitney rank sum tests. A p-value less than or equal to 0.05 was considered statistically significant. The most frequently cited reasons for selecting anesthesiology as a career included the following: it is a "hands-on" specialty, it involves clinical application of physiology and pharmacology, and it provides immediate gratification in one's work. The most frequently cited reasons for selecting our training program were the diversity of training experience, prestige associated with Mayo Clinic, and employment opportunities following training. Forty-four (92%) felt downsizing of anesthesiology training programs was a national trend, 26 (54%) anticipated difficulty obtaining a job following training, and 16 (33%) felt they had future job security. Overall, 47 (98%) were happy with their career choice, and 40 (83%) would choose anesthesiology as a career if they were now graduating from medical school. All 1996 graduates found suitable employment without difficulty. CONCLUSIONS: Our data indicate that selection of a career in anesthesiology and training program are strongly associated with concerns regarding educational experiences and postgraduate employment opportunities.

Adult↗
PubMed1997

Differential premolar extractions.

The primary object of this research project was to establish the amount of incisor retraction to be expected during full fixed mechanotherapy and to generate regression models that could provide more accurate prediction of each of the three most popular combinations of symmetrical premolar extractions, where extraoral anchorage would not be used. Pretreatment and posttreatment records of 73 cases that had their four first premolars extracted (group 44), 74 cases with four second premolar extractions (group 55), and 59 cases with upper first and lower second premolar extractions (group 45) were selected. All these cases were treated by one orthodontist, who used the same edgewise technique throughout. The results indicate that, on average, maxillary retraction in relation to the facial plane (N Po) differed only slightly between group 55 (mean 4.2 +/- 2.4 mm) and group 44 (mean 4.7 +/- 2.3 mm), with relatively more retraction for group 45 (mean 6.6 +/- 2.5 mm; p < 0.05). In contrast, the mandibular incisors were retracted slightly more in group 44 than in the other two groups (p < 0.05). The regression models that were developed could be useful as an additional tool to assist the practitioner in the selection of which teeth to extract for a particular case.

Adolescent↗
PubMed1996

Dimensional differences in the craniofacial morphologies of groups with deep and shallow mandibular antegonial notching.

Certain craniofacial characteristics were identified on the lateral cephalograms of 40 untreated subjects with shallow mandibular antegonial notches and 40 subjects with deep notches. Subjects with shallow notches demonstrated more on the morphological characteristics usually associated with horizontal mandibular growth patterns than did subjects with deep notches, and their mandibles were positioned more protrusively. In general, the mandibles of the shallow notch subjects proved to be longer than mandibles of the deep notch subjects. On average, mandibles with deep notches showed greater gonial angles, deeper posterior ramus notch depths, and larger occlusal plane inclinations. The total anterior facial height of shallow notch subjects was much smaller than that of the deep notch subjects. The maxillae in deep notch subjects were more retrusive in relation to the cranial base when compared with the shallow notch subjects. A discriminant analysis was used to determine which combinations of variables were most consistently related to either deep or shallow mandibular antegonial notches. Eighty percent (80%) of the cases were classified correctly as deep or shallow notch cases by means of this discriminant function.

Adolescent↗
PubMed1996

Anterior arch circumference adjustment--how much?

A table is presented by means of which changes in arch length and arch circumference can be more accurately predicted, thereby simplifying treatment planning for cases with special problems, e.g. a Bolton discrepancy. A fundamental condition for the use of this table is that the anterior arch from canine to canine forms a parabolic curve.

Algorithms↗
PubMed1996

Biostereometric quantification of clinical denture tooth wear.

In this study the wear of mandibular acrylic resin teeth opposed by porcelain maxillary teeth arranged in a lingualized occlusal scheme over a period of 3 years was measured. Six edentulous subjects received complete dentures as above and with three baseline markers of amalgam. At yearly intervals casts were made of the mandibular occlusal surfaces, including markers, and plotted by stereophotogrammetry. Volumetric loss of material was quantifiable. Ranges of 0.62-3.33 mm3/mm2 on the left side and 0.71-1.64 mm3/mm2 on the right were recorded. Friedman two-way ANOVA test indicated significant wear on teeth 35, 36, 45 and 46 but not on 34 and 44. A one-sided chewer displayed greater wear on the contralateral side, a finding difficult to explain.

Acrylic Resins↗
PubMed1995

Last occurrence and survival during winter of the arbovirus vector Culicoides brevitarsis at the southern limits of its distribution.

Linear regression analysis was used to describe the decline in numbers of Culicoides brevitarsis Kieffer into winter with monthly maximum, average and minimum temperatures at the southern limits to its distribution in New South Wales. From this, low temperature thresholds were derived when C brevitarsis would be absent from the field. The low minimum threshold +/- 2 SE (95% Confidence Interval) of 8.1 +/- 0.3 degree C was used with historical temperature data to estimate the last month that the species should occur (March to June) and the mean number of months (2 to 6.5) below the threshold at 17 selected sites. Probability for survival during winter at these sites was estimated from years when the number of consecutive months below the threshold was < or = 2 months. This varied from zero to 51% depending on the location of the site. Last occurrence was 0.7 months later on average and absolute probabilities for survival ranged from zero to 100% when the temperatures were increased by an arbitrary 2 degrees C.

Animals↗
PubMed1994

Adaptive acid tolerance response by Salmonella typhi and candidate live oral typhoid vaccine strains.

The data presented here demonstrate that Salmonella typhi is capable of expressing an acid tolerance response (ATR) and that effective induction of this response (in nutrient-rich medium) occurs at pH 5.0 in anaerobic conditions. The candidate live oral S. typhi vaccine strains made by precise genetic methods and which carry auxotrophic mutations were CVD 906 (carries defined attenuating deletion mutations: delta aroC, delta aroD), CVD 908 (carries defined attenuating deletion mutations: delta aroC, delta aroD), 541Ty (carries attenuating deletion mutations: aroA, purA), and galE, Vi-negative (via) strain EX462. All generate an effective ATR. In contrast, nitrosoguanidine-derived live oral typhoid vaccine strain Ty21a only weakly expresses acid tolerance. This further demonstrates that the non-specific mutagenesis process used to produce Ty21a affects genetic loci outside the intended target genes for mutagenesis, galE and via, and further emphasizes the importance of using precise genetic techniques when developing live oral S. typhi vaccines.

Acids↗
PubMed1994

Construction and characterization of isogenic O-antigen variants of Salmonella typhi.

A 7.5 kb KpnI-generated fragment, from within the rfb cluster of Salmonella typhimurium LT2 that encodes abequose synthase (the rfbJ gene) which is necessary for O4 antigen synthesis, and flanking sequences, was inserted into a suicide vector. Using allelic exchange techniques, these rfb sequences of S. typhimurium were integrated into the rfb clusters of wild-type Salmonella typhi Vi-positive strain ISP 1820 (i.e. serotype O9,12; Vi+; H-d), S. typhi Vinegative strain H400 (i.e. serotype O9,12; Vi-; H-d), and a double aro mutant of S. typhi ISP 1820, strain CVD 906, resulting in the isolation of strains H325, H404 and CVD 906-O4, respectively. Immunoblot analysis of lipopolysaccharide (LPS) purified from H325, H404 and CVD 906-O4 demonstrated that these strains express the O4 antigen (an abequose residue) in place of the O9 antigen (a tyvelose residue) in the LPS molecule. Hence, the serotype of H325 is O4,12; Vi+; H-d and the serotype of H404 is O4,12; Vi-; H-d. DNA hybridization analysis of chromosomal DNA from H325, H404 and CVD 906-O4 confirmed that a precise recombination event within sequences flanking rfbSE of S. typhi (which encodes the enzymes necessary for cytidine diphosphate-tyvelose synthesis) resulted in replacement of rfbSE with rfbJ (which encodes abequose synthase and is necessary for O4 synthesis) of S. typhimurium in strains H325, H404 and CVD 906-O4. The resistance of each strain to the bactericidal effects of guinea-pig serum (GPC) was assessed. Whereas ISP 1820, H325 and H404 exhibit similar resistance patterns in GPC, strain H400 is sensitive to the bactericidal effects of GPC.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗