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Biomedical subjects

M G Stewart

Publications and source records attributed to M G Stewart.

At least 55 records · Page 3Linked to original sources
PubMed1999

Is parental perception an accurate predictor of childhood hearing loss? A prospective study.

OBJECTIVE: We performed this study to assess whether parental perception of hearing loss predicted the results of audiometric testing in children with recurrent otitis media or persistent otitis media with effusion. METHODS: As part of a larger prospective observational outcomes study of children undergoing tympanostomy tube placement, the child's parent completed a standardized questionnaire before and after tube placement. In addition, patients underwent age-appropriate audiologic threshold and tympanometry testing before and after tube placement. RESULTS: We enrolled 113 patients (median age, 2 years), and 93 (82%) completed follow-up. Before treatment, parental perception of hearing loss did not predict hearing threshold level. After tube placement, parental perception of hearing loss was also poorly correlated with change in threshold. CONCLUSIONS: Parental perception of their child's hearing loss is a poor predictor of objective audiologic findings both before and after treatment with tympanostomy tubes. These findings have important implications concerning the importance of screening for hearing loss in children with otitis media with effusion.

Attitude to Health↗
PubMed1999

Establishing the etiology of childhood hearing loss.

The cause of hearing loss in children is often difficult to identify. We evaluated a cohort of 114 children (47 boys, 67 girls) referred with newly diagnosed hearing loss (non-otitis media) to identify factors predictive of etiology and type of hearing loss. Clinical (history and physical examination), laboratory, and radiographic data were collected. One hundred children (87.7%) had sensorineural hearing loss, and 14 (12.3%) had conductive or mixed hearing loss. The cause of hearing loss was identified in 54 children (48%). Patients with isolated aural atresia (n = 7) or with a known diagnosis of congenital cytomegalovirus infection (n = 21) were excluded from further data analysis. We conducted statistical analysis to identify factors predictive of the cause and type of hearing loss. Clinical factors that aided in identifying a cause included abnormal physical examination findings (p = 0.001) and craniofacial anomalies (p = 0.006). Computed tomography of the temporal bones was the only diagnostic test predictive of cause (p < 0.001). Factors predictive of the type of hearing loss detected (sensorineural vs. conductive or mixed) were abnormal physical examination findings (p = 0.01) and craniofacial anomalies (p = 0.004). An exhaustive laboratory or radiographic workup did not prove beneficial in identifying the etiology of hearing loss in our series.

Audiometry↗
PubMed1999

Learning-induced plasticity of N-methyl-D-aspartate receptors is task and region specific.

Changes in binding of [3H]dizocilpine maleate to N-methyl-D-aspartate-sensitive ion channel receptors were evaluated after learning in order to specify brain regions which might be involved in memory formation. Rats were trained in a five-trial session of 40 min, to discriminate among three odours to obtain food reinforcement. Another group was trained in an eight-arm maze to choose always the same three arms to obtain food reinforcement (nine trials over 150 min). In rats killed 30 min after odour discrimination learning, dizocilpine maleate binding was significantly reduced in hippocampal sub-regions CA3, CA1 and fascia dentata and in frontal cortex. After spatial learning, changes in binding were limited to the amygdala, where a decrease was also observed. These results indicate that functional changes occur in specific brain regions after learning and suggest anatomical loci for further study of synaptic changes at a morphological level, after spatial learning or odour discrimination.

Amygdala↗
PubMed1999

Cost-effectiveness of the diagnostic evaluation of vertigo.

OBJECTIVE: To evaluate the cost-effectiveness of several diagnostic tests used in the evaluation of vertigo. STUDY DESIGN: Cost-effectiveness analysis, using data from retrospective case review. METHODS: Charts and test results were reviewed from 192 outpatients seen in an academic tertiary referral center for evaluation of vertigo. Cost-effectiveness analysis was performed using decision analysis software, data from office and hospital charges, and expert-based estimations of the utility of different test outcomes. Sensitivity analysis was performed using standard algorithms and wide variable ranges. RESULTS: We found that audiologic testing, posturography, and electronystagmography were the most cost-effective tests, and that magnetic resonance imaging and blood tests had the lowest cost-effectiveness. The analysis was sensitive to the effects of financial costs of tests but, with a few exceptions, was typically not sensitive to the utility of test outcomes or the distribution of test results. CONCLUSIONS: The use of cost-effectiveness analysis, the estimation of utility of test outcomes, and techniques of sensitivity analysis should help guide the clinician's decision making on appropriate testing for patients with vertigo.

Audiometry, Pure-Tone↗
PubMed1998

Passive avoidance learning involves alpha2-noradrenergic receptors in a day old chick.

Day-old chicks were trained on one-trial passive avoidance task, using methyl-anthranilate (MeA) as an aversive substance. Bilateral pharmacological manipulation of the intermediate hyperstriatum ventrale was performed by intracerebral application of an alpha2-noradrenergic agonist, clonidine (5 microM), or an antagonist, rauwolscine (300 microM). Only rauwolscine application (pre- or post-training) induced significant memory impairment. Quantitative receptor autoradiography was used to determine the kinetic properties of the binding sites for [3H]clonidine or [3H]rauwolscine in MeA-trained or water-trained (control) chicks, in forebrain areas known to be involved in avoidance learning. Scatchard analysis revealed that MeA-training resulted in a significant bilateral upregulation in the number of [3H]rauwolscine binding sites (Bmax) in the area of hyperstriatum ventrale. These findings suggest the importance of activation of alpha2-noradrenergic receptors in aversive learning in chicks.

Adrenergic alpha-Agonists↗
PubMed1998

Outcomes analysis of voice and quality of life in patients with laryngeal cancer.

OBJECTIVE: To assess relationships between voice satisfaction and global quality of life in patients who have been treated for laryngeal cancer. DESIGN: Cross-sectional survey study. SETTING: Veterans Affairs Medical Center. PATIENTS: Eighty patients who had completed treatment for laryngeal cancer with either total laryngectomy (n=17), radiotherapy (n=24), or both (n=39). MAIN OUTCOME MEASURES: Subscale scores on a general health status instrument (the Medical Outcomes Study 36-item short-form health survey), and a validated voice-specific functional status instrument (the Voice Handicap Index). RESULTS: Self-rated global health did not correlate significantly with emotional, functional, or physical voice handicap, although some subscales on the 36-item short-form health survey correlated with voice handicap scores. Global health status scores did not differ between patients who had undergone laryngectomy with a tracheoesophageal puncture and patients treated with radiotherapy only. Physical voice handicap scores did not differ significantly between those who underwent tracheoesophageal puncture and those who had radiotherapy, but emotional (P=.07) and functional (P=.01) handicap scores were lower in patients treated with radiotherapy. However, there was considerable overlap in voice handicap scores, with many patients who had had tracheoesophageal puncture showing less voice handicap than patients treated with radiotherapy. CONCLUSIONS: These data demonstrate that health status is affected by other factors than voice handicap in patients with laryngeal cancer. In addition, there is a large amount of individual variation in voice handicap after treatment. These findings illustrate the need for prospective studies assessing voice handicap and quality of life after treatment for laryngeal cancer.

Activities of Daily Living↗
PubMed1998

Searching the medical literature.

The widespread use of computers and the Internet have made searching the medical literature easier and more accessible to most physicians. The National Library of Medicine (NLM) maintains MEDLINE, a comprehensive, cross-referenced database of citations to the medical literature covering 1966 to the present. The NLM maintains several other literature databases that are also available online. In 1996, the NLM began providing free, unlimited access to MEDLINE to all Americans over the World Wide Web. This article discusses how to perform effective and efficient literature searches using MEDLINE and other databases.

Information Storage and Retrieval↗
PubMed1998

Increased immunogold labelling of neural cell adhesion molecule isoforms in synaptic active zones of the chick striatum 5-6 hours after one-trial passive avoidance training.

An area of the chick striatum, the lobus parolfactorius plays an important role in one-trial passive avoidance learning tasks. In the present study we report evidence that 5-6 h post-training, a significantly higher proportion of synaptic active zones in this area contain labelled epitopes of the neural cell adhesion molecule, with the greatest occurrence of labels at the edges of active zone profiles (in both control and trained groups). This suggests that there is a period after training when expression of the neural cell adhesion molecule in synaptic membranes almost doubles, and that events at active zone edges may play a specific role in mechanisms of synaptic adhesion. Cellular mechanisms of long-term memory formation are believed to include alterations in neural circuitry at the synaptic level. The involvement of the neural cell adhesion molecule (NCAM) in functional synaptic modifications has been demonstrated using a number of physiological models. Performance of rats in the Morris water maze, a spatial learning paradigm which requires the hippocampus, is impaired by either intraventricular injection of NCAM antibodies, or injection into the hippocampus of an enzyme which increases homophilic adhesion of the molecule, due to the removal of polysialic acid residuals from extracellular NCAM domains. In addition, intraventricular injections of anti-NCAM antibodies 6-8 h post-training were shown to impair memory for a one-trial passive avoidance task in the rat. An avoidance training model in the one-day-old chick indicates a similar time window, 5-6 h post-training during which memory for the task can be impaired by intraventricular injection of NCAM antibodies. In the hyperstriatum ventrale, a chick forebrain area involved in the passive avoidance task. subtle changes in the distribution pattern, but not density of NCAM molecules in synaptic membranes were revealed 5-6 h post-training. However, on the basis of studies of synaptic morphometry, a region of striatum, the lobus parolfactorius (LPO), appears to play a more important role in longer term memory storage for the task.

Animals↗
PubMed1998

Hippocampal synaptic density and glutamate immunoreactivity following transient cerebral ischaemia in the chick.

A transient ischaemic episode of 10 min duration was induced in 1-day-old chicks. After a 1-week survival period, synapse density was assessed in the ventral hippocampus using the 'disector' technique. A significant decrease was observed in asymmetric synapses, markedly greater than that observed previously in the dorsal hippocampus. Because the effect occurred mainly on excitatory synapses, the distribution of glutamate in the ventral hippocampus was also assessed by a postembedding immunogold labelling technique. The density of gold particles was significantly greater in both boutons and neuropil in the ischaemic group compared to controls, lending support to the theory of excitotoxicity as an explanation for ischaemic neural degeneration.

Animals↗
PubMed1998

Utilizing patient satisfaction data to assess quality improvement in community-based medical practices.

Our objective was to quantitatively measure the effect of quality improvement-based intervention on the improvement in patient satisfaction with physicians, office visits. A prospective nonrandomized case-control protocol was used at a multiple-site community-based medical and surgical office practices of members of Project Solo/Physicians Information Exchange. The study subjects were convenience samples of new and return patients seen between July 1996 and July 1997. One group of physicians (control group) surveyed patient satisfaction with office visits on two separate occasions with no intervention between the two occasions, except for seeing their own results after the first survey. A second group of physicians (intervention group) also surveyed patient satisfaction with office visits on two separate occasions, but were provided with a quality improvement poster between surveys. Changes in patient satisfaction between the two surveys were measured. The visit rating questionnaire, a nine-item patient-based questionnaire, was used to measure patient satisfaction; percentage excellent responses in the summary categories of patient access, physician attributes, and overall visit were used. Overall, 6088 patients from 59 physicians' offices participated; 3815 patients from 29 physicians in the control group, and 2273 patients from 30 physicians in the intervention group. The control group demonstrated small and nonsignificant changes in patient satisfaction between the two survey periods (0.6-1.4% increase, P = NS), and the intervention group demonstrated statistically significant improvements in patient satisfaction between the two survey periods (4.2-5.7% increase, P = 0.05-0.001). In addition, the two groups were compared directly using a stratified chi 2 analysis, and the differences were also statistically significant (chi 2 = 3.7-8.3, P = 0.05-0.004). We conclude that the use of a quality improvement-based intervention had a significant positive effect on patient satisfaction with office visits, when compared to a group of physicians who did not use any intervention.

Adolescent↗
PubMed1997

Exposure to light prior to hatching induces asymmetry of receptor binding in specific regions of the chick forebrain.

This paper describes neurochemical asymmetries present in forebrain regions of the newly hatched chick that result from environmental conditions; specifically from asymmetrical exposure of the chick embryo to light prior to hatching. Quantitative autoradiography was used to determine GABA and glutamate receptor subtype binding in a number of regions of the left and right forebrain hemispheres of chicks that had either the left (LES), or the right (RES), eye system exposed to light prior to hatching. On day 19 of incubation the embryo's head was withdrawn from the egg and the left or the right eye was occulded until hatching. [3H]MK-801, [3H]AMPA and [3H]muscimol binding assays were performed on frozen sections from 2 different coronal regions of the forebrain, sampled on day-1 posthatching. Significant [3H]MK-801, [3H]AMPA and [3H]muscimol binding asymmetries were determined in forebrain regions from chicks that had their RES exposed to light prior to hatching, particularly in forebrain regions which are known to receive afferent visual input. The reverse pattern of asymmetry was found for all 3 ligands in regions such as the ectostriatum of chicks that had their LES exposed to light, while asymmetry of muscimol and AMPA binding, present in many regions in right eye system chicks was not present in chicks that had the left eye system exposed to light during incubation. Thus, the presence and pattern of experience-dependent neurochemical asymmetries in the chick forebrain are specific to both region and receptor type.

Animals↗
PubMed1997

Synaptic terminals immunolabelled against glutamate in the lobus parolfactorius of domestic chicks (Gallus domesticus) in relation to afferents from the archistriatum.

The lobus parolfactorius (LPO) has been implicated in memory formation associated with passive avoidance training of young posthatch domestic chicks. The anatomical circuitry underlying memory formation in the chick is likely to involve the intermediate medial hyperstriatum ventrale-archistriatum-LPO arc. In the present work, we attempted to combine an ultrastructural characterisation of archistriatal afferent terminals in LPO with a description of the synaptic structure of LPO, in particular those elements that are immunoreactive to glutamate and GABA. Ventral archistriatal regions of 7-day-old domestic chicks were iontophoretically injected with Phaseolus vulgaris leucoagglutinin and the anterograde transport of the tracer was detected in the LPO. Selected samples from these birds, and also from other day-old chicks, were resin-embedded and reacted for L-glutamate or GABA, using the postembedding immunocytochemical method. Glutamate was abundant in the neuropil of LPO and typically seen in axodendritic or axospinous terminals with asymmetrical junctions, often multiple or perforated postsynaptic appositions. Conversely, GABA was often present in aspinous dendrites, probably representing GABAergic local circuit neurons or (putative striatonigral) projection neurons. Archistriatal efferents terminating in LPO formed small en passant or terminal varicosities, with infrequent asymmetrical axospinous synapses. Glutamate was not detected in these boutons. The findings imply that the functional state of LPO, based on powerful glutamatergic excitation, may be modified by a non-glutamatergic archistriatal input.

Afferent Pathways↗
PubMed1997

Baseline and post-treatment assessment of the general health status of head and neck cancer patients compared with United States population norms.

BACKGROUND: It is a common perception that the overall health of patients with head and neck cancer (HNC) is likely to be poor compared with the general population. This project was undertaken to investigate the pre- and post-treatment, global health status of HNC patients in comparison with age-matched, U.S. population norms using a self-administered general health status survey. METHODS: Between July 1, 1993, and May 1, 1996, 180 patients underwent pretreatment and 6 month follow-up evaluation with the standard version of the Medical Outcomes Study 36-Item Short-Form Health Survey (SF-36). The SF-36 scale scores, means, standard deviations, and 95% confidence intervals were calculated for each SF-36 scale as well as for physical-health-component summary scores (PCS) and mental-health-component summary scores (MCS). Comparisons of these scores were made to U.S. population normative data. Pretreatment and 6-month follow-up SF-36 scores were compared. RESULTS: In the 45-54-year age group, all 8 SF-36 scale scores, the PCS, and MCS scores were significantly worse for the HNC patients in comparison with age-matched norms (p < .05). In the 55-64-year age group, the HNC patients were worse in 5 of the 8 SF-36 scale scores and the MCS score in comparison with age-matched norms (p < .05). In the 65-74-year age group, the HNC patients scored significantly worse in the mental health scale. In the comparison of pretreatment and 6-month follow-up scores, the HNC patients had significant decreases in the physical functioning scale (p = .003) and the PCS score (p = .047). The HNC patients showed significant improvement in the mental health scale (p = .049) and improvement in the bodily-pain scale, which approached significance (p = .053) at 6-month follow-up. The HNC patients showed a marked decrease in general health status with increasing stage of HNC. CONCLUSIONS: This work provides objective support for the perception that many HNC patients are initially seen for treatment with baseline health status functioning significantly below their age-matched contemporaries in the general population. An educated evaluation of global health outcomes following treatment in the HNC patient population must begin with an accurate pretreatment assessment of these parameters. Self-reported health-status assessment (HSA) is a useful means of evaluating global health status in this patient population.

Adult↗
PubMed1997

Reduction in spine density associated with long-term potentiation in the dentate gyrus suggests a spine fusion-and-branching model of potentiation.

Approximately 2,700 dendritic spines in Golgi-impregnated hippocampal granule cells were quantified via image analysis 24 h after the unilateral induction of long-term potentiation in seven rats. Stereological corrections were made using a tilting disector and analytical unfolding technique. In the potentiated hemisphere the mean spine density along dendrites was reduced by approximately 20%. The relative frequency of shorter, thicker spines was increased in potentiated tissue. Physiological consequences of two morphological changes leading to a reduction in spine density (retraction or fusion of spines) were examined using a compartmental model of a simplified granule cell. The model was constructed in the NEURON modeling environment and included a realistic population of 60 dendritic spines (with dual-component synapses and active Ca(2+)-dependent mechanisms). Simulations demonstrated that potentiation of postsynaptic responses was compatible with fusion (with branching) of a proportion of spines with their neighbors but was not compatible with retraction of spines. This result held over wide variations of model parameters as long as dendritic membranes were assumed to be excitable.

Animals↗
PubMed1997

The effects of an outpatient practice guideline at a teaching hospital: a prospective pilot study.

Practice guidelines (PGs) are becoming increasingly important in modern medicine. To study the effects of a PG, we performed a pilot study at a large, urban, public teaching hospital according to a prospective, observational research design with both concurrent and historic controls. Specifically, we studied the effects of a multidisciplinary PG for pediatric outpatient tonsillectomy and adenoidectomy on the process of health-care delivery. Variables in the health-care process included patient compliance with clinic and surgery appointments, surgery time, operating room turnover, time in recovery room, unplanned admission rate, patient compliance with postoperative follow-up, provider compliance with guidelines, and hospital charges. Patients in the PG were found to have fewer preoperative laboratory tests, decreased duplication of services, and shorter operating room turnover times. Provider compliance with the PG varied by service and was intermittent at first but improved gradually. There was a trend toward improved compliance with postoperative follow-up in patients in the PG. Provider opinions concerning the guideline were positive. This pilot study demonstrates several advantages and disadvantages of the use of PGs in the outpatient setting and in a teaching hospital.

Adenoidectomy↗
PubMed1997

Factors predictive of poor compliance with follow-up care after facial trauma: a prospective study.

We performed a prospective study of 59 consecutive patients with facial trauma who were treated at an urban public hospital. We obtained demographic and clinical data before treatment, then recorded compliance with clinic follow-up care. As expected, young, minority male patients, victims of assault, and blunt mechanisms of injury predominated in our series, and midface fractures and soft tissue injuries were most commonly seen. Thirty-one (52%) patients were admitted, and 28 (48%) were treated as outpatients. Although 66% of patients kept their initial follow-up appointment, only 46% of patients were seen to completion of the follow-up period. We used univariate and multivariate analyses to identify factors predictive of poor compliance with follow-up care. Factors predictive of poor compliance with the initial follow-up appointment identified in the multivariate analysis were orbital injury site (p < 0.001), Caucasian race (p = 0.007), and not having a telephone at home (p = 0.043). Factors predictive of poor compliance with completion of follow-up were failure to keep initial appointment (p < 0.001), and treatment with observation, suture only, or open reduction internal fixation only (p = 0.018). Age, marital status, employment status, education level, and hospital admission of the patient were not predictive of compliance with follow-up care. Because compliance with follow-up care may be poor, patients with facial trauma should be managed aggressively initially. In particular, patients with orbital fractures, and those treated with watchful waiting only may have poorer long-term compliance with follow-up care.

Adolescent↗