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Biomedical subjects

G A Bell

Publications and source records attributed to G A Bell.

10 recordsLinked to original sources
PubMed1992

Metabolic activity in the hyperstriatum of 2-day-old chicks during optomotor and contrasting visual stimulation.

Our earlier report of differences in metabolic activity within the visual regions of the hyperstriatum and ectostriatum, in 2-day-old chicks compared with 23-day-old chicks, suggested that two visual pathways within the visual system develop at different rates. Here we have investigated whether the demands of varying visual environments will increase the activity of the hyperstriatum accessorium (HA) in 2-day-olds. Metabolic activity in the HA was monitored in 2-day-old chicks by the radioactive 2-deoxyglucose technique during monocular stimulation with three different visual environments: moving stripes in a rotating drum, which induced eye and head movements, a featureless white environment, and the complex visual environment of the home cage with other chicks. Although a small but significant level of activity was found in HA in the hemisphere opposite the open eye, the activity did not vary with the visual treatment. On the other hand, a raised level of activity in the hyperstriatum dorsale (HD) appeared in chicks viewing the rotating stripes, indicating that at this age the thalamo-hyperstriatal pathway may be involved in processing whole-field visual movement. The optomoter environment also produced high activity in the medial hyperstriatum ventrale (MHV), a region that has been implicated in memory formation of imprinting. We suggest that during the sensitive period for imprinting, HA may either have not developed its fully functional capacity, or that following or during imprinting it is actively shut down to protect itself and associated regions from interfering visual input. In contrast to the 2-day-olds, 17-day-old chicks in a visually rich cage environment, had high levels of activity in HA, demonstrating that the functional maturation of the HA, related to performance in the cage environment, is complete at least 6 days earlier than previously observed.

Aging↗
PubMed1990

Evaluation of analytical techniques for measurement of denture-base acrylic resin glass-transition temperature.

The glass-transition temperature of a range of acrylic resin materials used in prosthetic dentistry was determined. The techniques used to make the measurement included: thermal mechanical analysis, dynamic mechanical thermal analysis, and differential scanning calorimetry. It was found that the measuring techniques used yielded very similar results, and as a consequence it was concluded that: familiarity and easy availability of thermal mechanical analysis lead to the recommendation that this technique should be employed as the standard glass-transition evaluation technique for denture-base acrylic resins.

Acrylic Resins↗
PubMed1990

Two- and three-dimensional image reconstructions from stained and autoradiographed histological sections.

A complete system has been developed to utilize histological serial sections for two- and three-dimensional image reconstructions. Eighty to 120 sections are digitized using a personal computing system augmented with a imaging board and CCD camera. The image files are transmitted to a VAX computer for processing and image reconstruction, and the processed images are transmitted back to the personal computer for display and recording using a film recorder or PostScript printer. The software developed for the system allows serial sections to be placed into proper registration in a 256(3) array, 256 grey levels. Autoradiographs of the sections are obtained in the presence of appropriate standards which are used to recalibrate grey levels to represent linearly the radioactivity of each pixel in the sections and scale the values to allow maximum use of the grey scale. Starting from coronally sectioned material the system has been used to analyse and reconstruct rat nasal turbinates. In two dimensions horizontal and sagittal sections have been obtained while in three dimensions back-to-front and surface-rendered images have been constructed. Useful rendering of differential metabolic activity within an organ of complex geometry has been obtained, and there appears to be no reason why the system cannot be used for any material for which serial sectioning is appropriate.

Animals↗
PubMed1989

Odor-induced metabolic activity in the olfactory bulb of rats trained to detect propionic acid vapor.

The pattern of glucose metabolism in the glomerular layer of the main olfactory bulb was studied in rats trained to sample brief odor stimuli. After injection with [14C]2-deoxyglucose (2-DG). 5 rats were tested for discrimination of propionic acid from air. Over the 45 min test period rats sampled the stimulus for 0.5-0.8s during each trial and their total exposure to the stimulus was 53-147 s. A discrete focus of increased glucose metabolism was found in the central dorsomedial sector of the glomerular layer in each animal. The position of this focus and the overall pattern of glomerular layer activity was essentially identical to that obtained in 4 control rats which were exposed passively to alternating 5 min periods of the odor and clean air for 45 min. The size of the primary focus was only slightly smaller in the trained rats, despite the large difference in total exposure time. The absence of olfactory adaptation during the behavioral tests and the similar pattern of 2-DG uptake in controls and trained animals indicate that adaptation does not play a significant role in the patterns of glucose metabolism induced in the glomeruli of the olfactory bulb by extended exposure to an odor.

Animals↗
PubMed1989

Different rates of functional development in the two visual systems of the chicken revealed by [14C]2-deoxyglucose.

Age-dependent changes in neuronal metabolic activity in the visual systems of the male chicken were assessed using [14C]2-deoxyglucose (2-DG) autoradiography. Groups of 3 and 4 chicks aged either 2 or 23 days posthatching were injected with 2 DG and exposed for 30 min to a variety of visual stimuli in either the monocular or binocular condition. Control birds had both eyes occluded. All groups were subjected to the same auditory background. In the 2-day-old chicks high levels of metabolic activity occurred in the rotundal-ectostriatal system in a manner consistent with eye use and known neuro-anatomical connections, but very low levels of activity occurred in the thalamo-hyperstriatal visual system. In the 23-day-old chicks eye use resulted in high levels of metabolic activity in both visual systems. The distribution of higher activity within the rostral regions of the anterior hyperstriatum at this age was consistent with eye use and the known distribution of ipsilateral and contralateral projections to the region. Different rates of functional development in the hyperstriatal and ectostriatal systems may reflect a requirement for different visual information processing in young versus older chickens. This study indicates that the ectostriatal system subserves the majority of early visual behavior. Age-dependent changes in the regional arrangement of activity in the Field L auditory region were also noted.

Animals↗
PubMed1989

Function and quality of life results after ileal pouch surgery for chronic ulcerative colitis and familial polyposis.

The aim of this study was to assess gastrointestinal function and quality of life, including occupational, social, and sexual function, in 75 patients who underwent pelvic pouch construction between November 1984 and May 1988 at our institution. Complications occurred in 45 percent of patients after pouch construction and in 17 percent after ileostomy closure. One patient died from sepsis caused by an anastomotic leak after ileostomy closure. The most common complication was a pouch-anal anastomotic stricture (22 percent), and the complication with the greatest potential morbidity was pouch-anal dehiscence (8 percent), which was highly predictive of pouch failure. Functional results were assessed by questionnaire during the 3-month period after ileostomy closure in all 58 patients who successfully attained intestinal continuity. A second assessment was performed at 15 +/- 11 months after ileostomy closure in 52 patients whose continuity had been restored for longer than 3 months. In an overall assessment, 94 percent of all patients with restored intestinal continuity (73 percent of entire patient group) rated the pouch as being superior to a permanent ileostomy and 92 percent (71 percent of entire group) would go through another pouch procedure. These results support the continued recommendation of this procedure as an acceptable alternative to proctocolectomy and permanent ileostomy in patients with ulcerative colitis or familial polyposis.

Adenomatous Polyposis Coli↗
PubMed1985

Evaluation of the use of a protocol in the antimicrobial treatment of intra-abdominal sepsis.

A protocol was established aimed at limiting the duration of antimicrobial therapy in two patient groups with peritonitis. One group had perforated or gangrenous appendicitis and the other non-appendiceal disease. The duration of treatment given to patients treated according to the protocol was compared retrospectively to that of similar patients treated without the protocol. Patients with perforated or gangrenous appendicitis required significantly less antimicrobial therapy than those with peritonitis due to non-appendiceal disease. In non-appendiceal intra-abdominal sepsis the use of the protocol was associated with a significantly reduced duration of antimicrobial therapy, compared with that observed without the protocol.

Adult↗
PubMed1979

Interhemispheric engram transfer in chick.

Monocular training on a one-trial passive avoidance task in the young chick has been shown to establish an engram in the forebrain hemisphere contralateral to the trained eye, and hence interocular transfer of this task must involve the naive hemisphere making access to the engram in the opposite hemisphere. We have studied the consequences for the untrained hemisphere of accessing a unilateral engram during two short term stages of its consolidation, by conducting interocular transfer tests at 7.5 min and 30 min after learning, prior to onset of amnesia induced by intracranial injection of ouabain or cycloheximide. Testing the naive hemisphere 24 h later indicated that engram transfer had occurred in chicks receiving one access trial at 7.5 min, during the first stage of consolidation of the unilateral engram. At 30 min, during second consolidation stage, five access trials were required to achieve engram transfer. These experiments confirm the findings from the rat that engram transfer can follow from making access to the unilateral engram. However, it has not previously been recognised that interhemispheric memory transfer depends on the recency of formation of the unilateral engram.

Animals↗
PubMed1977

Unilateral storage of monocular engram in day-old chick.

Efficient interocular transfer of a one-trial passive avoidance task by the day-old domestic chicken, for whom the optic nerves decussate completely, raised the question of whether memory for the task was held in one or both sides of the forebrain. Intracranial injection of ouabain or cycloheximide to the trained hemisphere immediately after learning suppressed avoidance behaviour learned monocularly, while injection to the untrained side did not. Memory for the task was established in the side of the brain served by the eye used in learning. Interocular transfer was therefore achieved by the untrained hemisphere borrowing information from the other side's store. The presence of memories in the trained side was not sufficient to establish memory in the naive side.

Age Factors↗