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Biomedical subjects

G A James

Publications and source records attributed to G A James.

At least 19 recordsLinked to original sources
PubMed2005

Satiety dysfunction in Prader-Willi syndrome demonstrated by fMRI.

The neurobiology relating to the insatiable appetite observed in Prader-Willi syndrome (PWS) has not been fully characterised. Two functional magnetic resonance imaging (fMRI) scans were performed on each of three adults with PWS. The scans were carried out pre- and post-treatment with the antiepileptic topiramate, which had little effect on body weight and appetite in these subjects. Subjects fasted overnight and drank a 75 g dextrose solution prior to fMRI scans for measurement of brain activation levels during/after glucose ingestion. Following glucose administration, there was a significant delay in activation at the hypothalamus and other brain regions associated with satiety compared with previous data on obese volunteers. These regions include the insula, ventromedial prefrontal cortex, and nucleus accumbens. Individuals with PWS showed a mean latency of 24 min while in a previous study obese volunteers had shown a latency of 15 min and lean volunteers a latency of 10 min in the hypothalamus. Our results provide evidence towards a satiety dysfunction in the central nervous system of PWS patients.

Adult↗
PubMed2001

Imaging in vivo brain-hormone interaction in the control of eating and obesity.

The field of neuroimaging has made great progress in the mapping of human brain function. In this article, we present a functional magnetic resonance imaging (fMRI) study on the hypothalamic regulation of satiety and its relationship with obesity. The fMRI techniques have been proven invaluable for analyzing changes in brain activity that are associated with most sensorimotor and cognitive functions. However, few studies have been successful in the delineation of the interaction between the central nervous system and the endocrine system, due to the lack of suitable mapping methods which can pinpoint the onset of changes in neuronal activity (e.g., those following eating or drug intake). We have recently introduced a new fMRI method known as temporal clustering analysis (TCA) for dynamically tracking the time course of brain activation. Along with simultaneous blood sampling for the circulating hormone levels, the fMRI techniques with TCA may provide an integrated view of the nervous and endocrine systems in vivo, and thus greatly enhance our understanding of the complex interplay between neural events and hormonal signals.

Cluster Analysis↗
PubMed1995

Digital image analysis of growth and starvation responses of a surface-colonizing Acinetobacter sp.

Surface growth of an Acinetobacter sp. cultivated under several nutrient regimens was examined by using continuous-flow slide culture, phase-contrast microscopy, scanning confocal laser microscopy, and computer image analysis. Irrigation of attached coccoid stationary-phase Acinetobacter sp. cells with high-nutrient medium resulted in a transition from coccoid to bacillar morphology. Digital image analysis revealed that this transition was biphasic. During phase I, both the length and the width of cells increased. In contrast, cell width remained constant during phase II, while both cell length and cell area increased at a rate greater than in phase I. Cells were capable of growth and division without morphological transition when irrigated with a low-nutrient medium. Rod-shaped cells reverted to cocci by reduction-division when irrigated with starvation medium. This resulted in conservation of cell area (biomass) with an increase in cell number. In addition, the changes in cell morphology were accompanied by changes in the stability of cell attachment. During phase I, coccoid cells remained firmly attached. Following transition in high-nutrient medium, bacillar cells displayed detachment, transient attachment, and drifting behaviors, resulting in a spreading colonization pattern. In contrast, cells irrigated with a low-nutrient medium remained firmly attached to the surface and eventually formed tightly packed microcolonies. It is hypothesized that the coccoid and bacillar Acinetobacter sp. morphotypes and associated behavior represent specialized physiological adaptations for attachment and colonization in low-nutrient systems (coccoid morphotype) or dispersion under high-nutrient conditions (bacillar morphotype).

Acinetobacter↗
PubMed1994

Evaluation of Fleroxacin Activity against Established Pseudomonas fluorescens Biofilms.

Scanning confocal laser microscopy (SCLM) and fluorescent molecular probes were used to evaluate the effect of the fluoroquinolone fleroxacin on the architecture of established Pseudomonas fluorescens biofilms. Control P. fluorescens biofilms were heterogeneous, consisting of cell aggregates extending from the attachment surface to maximum measured depths of approximately 90 mum (mean biofilm depth at 72 h, 42 +/- 28 mum) and penetrated by an array of channels. In contrast, fleroxacin-treated biofilms were less deep (mean biofilm depth at 72 h, 29 +/- 8 mum), varied little in depth over large areas, and consisted of a homogeneous distribution of cells. Fleroxacin also caused cells to elongate, with cells located near the biofilm-liquid interface lengthening significantly more than cells located at the attachment surface. By using SCLM, acridine orange, and image analysis it was found that approximately 59% of cells within fleroxacin-treated biofilms emitted red fluorescence whereas >99% of cells from control biofilms emitted green fluorescence. The fleroxacin-treated cells which emitted red fluorescence were observed to be the population of cells which elongated.

Journal Article↗
PubMed1985

Replantation of avulsed teeth with immature root development.

Successful treatment of the avulsed tooth with immature root development is dependent on both pulpal and periodontal responses. The pulpal reaction is often one of revascularization with subsequent replacement of the necrotic pulp tissue. Continued root development and further calcification of the existing root structure are often seen with revitalization. The periodontal response to avulsion is dependent on the vitality of the periodontal ligament cells on the root surface. Normal healing occurs when the vitality is maintained, while replacement resorption results when the vitality is lost. Replantation after a short extra-alveolar period appears to provide the best prognosis for long-term retention of the avulsed tooth.

Child↗
PubMed1983

The effect of autoclave sterilization on endodontic files.

This study evaluates the effect of cyclic autoclave sterilization and simulated clinical usage on a mechanical property of one brand of stainless steel endodontic files. The angular deflection moments were measured by a torque apparatus approved by the American Dental Association for such purposes. Comparisons of values for sterilized and nonsterilized files were made. 1. A significant decrease in angular deflection values exists for stainless steel endodontic files having undergone ten cycles of autoclave sterilization versus files having undergone only two or five similar cyclings. 2. All file sizes (15, 20, 25, 30, 35, 40) tested in torsion were detrimentally affected by the autoclave sterilization. 3. Of the files investigated, sizes 35 and 40 were the most adversely affected by the steam-under-pressure sterilization. 4. The angular deflection values of those files subjected to repeated autoclavings were not decreased below the minimum value accepted by the American Dental Association for resistance to torquing forces. It can therefore be concluded that repeated sterilization of a stainless steel endodontic file does result in a significant reduction in the torque resistance of that file. This reduction of the metal property is not significant clinically, however.

Endodontics↗
PubMed1979

The necessity of updating dental examining boards.

Though state boards may be necessary, let them be less anachronistic in the expectations they have for current graduates. Let us hope that the state and regional boards will change and keep pace with the current literature. The boards can have an influence on upgrading dentistry but only if they are progressive, and if they do not hold back the profession by demanding antiquated means of looking at dental care for the patients.

Curriculum↗