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Biomedical subjects

A J Martin

Publications and source records attributed to A J Martin.

At least 55 records · Page 3Linked to original sources

Bcl-2 in LPS- and allergen-induced hyperplastic mucous cells in airway epithelia of Brown Norway rats.

Environmental toxins, infection, and allergens lead to a transient mucous cell hyperplasia (MCH) in airway epithelia; however, the mechanisms for reducing mucous cell numbers during recovery are largely unknown. This study investigated Bcl-2 expression in mucous cells induced by a neutrophilic or eosinophilic inflammatory response. Brown Norway rats intratracheally instilled with lipopolysaccharide (LPS) showed an inflammatory response characterized primarily by neutrophils. Secreted mucin was increased fourfold at 1 day, and the number of mucous cells was increased fivefold 2, 3, and 4 days post-LPS instillation compared with those in noninstilled rats. None of the mucous cells in non- or saline-instilled control animals expressed Bcl-2, whereas 20-30% of mucous cells were Bcl-2 positive 1 and 2 days post-LPS instillation. Brown Norway rats immunized and challenged with ovalbumin (OVA) for 2, 4, and 6 days showed an inflammatory response characterized primarily by eosinophils. Secreted mucin increased fivefold, and mucous cell number increased fivefold after 4 and 6 days of OVA exposure compared with water-immunized control rats challenged with OVA aerosols. Approximately 10-25% of mucous cells were Bcl-2 positive in OVA-immunized and -challenged rats. These data demonstrate Bcl-2 expression in hyperplastic mucous cells of Brown Norway rats regardless of the type of inflammatory response and indicate that apoptotic mechanisms may be involved in the resolution of MCHs.

Aerosols↗

Measurement of Gd-DTPA diffusion through PVA hydrogel using a novel magnetic resonance imaging method.

Polyvinyl alcohol-cryogel (PVA-C) is a hydrogel that is an excellent tissue mimic. In order to characterize mass transfer in this material, as well as to demonstrate in principle the ability to noninvasively measure solute diffusion in tissue, we measured the diffusion coefficient of the magnetic resonance (MR) contrast agent gadolinium diethylene triaminopentaacetic acid (Gd-DTPA) through PVA-C using a clinical MR imager. The method involved filling thick-walled rectangular PVA-C "cups" with known concentrations of Gd-DTPA solutions. Then by using a fast inversion recovery spin echo MR imaging protocol, a signal "null" contour was created in the MR image that corresponded to a second, known concentration of Gd-DTPA. By collecting a series of MR images through the PVA-C wall as a function of time, the displacement of this second known isoconcentration contour could be tracked. Application of Fick's second law of diffusion yielded the diffusion coefficient. Seven separate experiments were performed using various combinations of initial concentrations of Gd-DTPA within the PVA-C cups (3.2, 25.6, or 125 mM) and tracked isoconcentrations contours (0.096, 0.182, or 0.435 mM Gd-DTPA). The experimental results and the predictions of Fick's law were in excellent agreement. The diffusivity of Gd-DTPA through 10% PVA hydrogel was found to be (2.6 +/- 0.04) x 10(-10) m(2)/s (mean +/- s.e.m.). Separate permeability studies showed that the diffusion coefficient of Gd-DTPA through this hydrogel did not change with an applied pressure of up to 7.1 kPa. Accurate measurements could be made within 30 min if suitable Gd-DTPA concentrations were selected. Due to the excellent repeatability and fast data acquisition time, this technique is very promising for future in vivo studies of species transport in tissue.

Calibration↗

Repeated dose inhaled budesonide versus placebo in the treatment of croup.

OBJECTIVE: To investigate the efficacy and tolerance of 12-hourly dosing with 2 mg 4 mL-1 of inhaled budesonide versus placebo in patients admitted to hospital with moderate/severe croup. METHOD: Eighty-two children hospitalised with croup received either 2 mg 4 mL-1 of budesonide or placebo 12 hourly (maximum four doses) via Ventstream nebuliser in a randomised, double-blind manner. Croup scores were performed at 0, 2, 6, 12, 24, 36 and 48 h from initial nebulisation whilst the patient remained hospitalised. Follow-up assessments were made 1 and 3 days after discharge. RESULTS: Improvement was observed in the budesonide group over the 12-h dosing interval when compared to placebo (P = 0.04). Time to attain a significant clinical improvement was superior in the budesonide group (P = 0.01). Three days after discharge seven of 32 placebo-treated patients and one of 34 budesonide-treated patients had sought further medical follow-up (P = 0.02). CONCLUSION: Twelve-hourly dosing with inhaled budesonide significantly improved symptoms of croup as well as decreased relapse rates when compared with placebo.

Administration, Inhalation↗

Brain biopsy using high-field strength interventional magnetic resonance imaging.

OBJECTIVE: Lesions within the brain are commonly sampled using stereotactic techniques. The advent of interventional magnetic resonance imaging (MRI) now allows neurosurgeons to interactively investigate specific regions, with exquisite observational detail. We evaluated the safety and efficacy of this new surgical approach. METHODS: Between January 1997 and June 1998, 35 brain biopsies were performed in a high-field strength interventional MRI unit. All biopsies were performed using MRI-compatible instrumentation. Interactive scanning was used to confirm accurate positioning of the biopsy needle within the region of interest. Intraoperative pathological examination of the biopsy specimens was performed to verify the presence of diagnostic tissue, and intra- and postoperative imaging was performed to exclude the presence of intraoperative hemorrhage. Recently, magnetic resonance spectroscopic targeting was used for six patients. RESULTS: Diagnostic tissue was obtained in all 35 brain biopsies and was used in therapeutic decision-making. Histological diagnoses included 28 primary brain tumors (12 glioblastomas multiforme, 9 oligodendrogliomas, 2 anaplastic astrocytomas, 2 astrocytomas, 1 lymphoma, and 1 anaplastic oligodendroglioma), 1 melanoma brain metastasis, 1 cavernous sinus meningioma, 1 cerebral infarction, 1 demyelinating process, and 3 cases of radiation necrosis. In all cases, magnetic resonance spectroscopy was accurate in distinguishing recurrent tumors (five cases) from radiation necrosis (one case). No patient sustained clinically or radiologically significant hemorrhage, as determined by intraoperative imaging performed immediately after the biopsy. One patient (3%) suffered transient hemiparesis after a pontine biopsy for investigation of a brain stem glioma. Another patient developed scalp cellulitis, with possible intracranial extension, 3 weeks after the biopsy; this condition was effectively treated with antibiotic therapy. Three patients were discharged on the day of the biopsy. CONCLUSION: Interventional 1.5-T MRI is a safe and effective method for evaluating lesions of the brain. Magnetic resonance spectroscopic targeting is likely to augment the diagnostic yield of brain biopsies.

Adolescent↗

A cardiovascular extension of the Health Measurement Questionnaire.

OBJECTIVE: To investigate the psychometric properties of a cardiovascular extension of an existing utility-based quality of life questionnaire (Health Measurement Questionnaire). The new instrument has been named the Utility Based Quality of life--Heart questionnaire, or UBQ-H. DESIGN: Explored the test-retest reliability, construct validity, and responsiveness of the UBQ-H. PATIENTS: A sample of 322 patients attending cardiac outpatient clinics were recruited from two large metropolitan teaching hospitals. A second sample of 1112 patients taking part in the LIPID trial was also used to investigate the validity and responsiveness of the UBQ-H. RESULTS: Ninety per cent of all UBQ-H questionnaires were returned, and item completion rates were high (median of less than 1% missing or N/A answers). Cronbach's alpha measure of internal consistency for the scales ranged between 0.79-0.91, and each item was also most strongly correlated with its hypothesised domain than alternative domains. The intra-class test-retest reliability of the UBQ-H scales ranged from 0.65 to 0.81 for patients with stable health. Results supported the construct validity of the UBQ-H. The UBQ-H was significantly correlated with other information on quality of life (for example, General Health Questionnaire) as anticipated. The instrument was able to distinguish between contrasted groups of patients (for example, with versus without symptoms of dyspnoea, prior myocardial infarction versus none, etc), and was responsive to changes in health associated with adverse events requiring hospitalisation. CONCLUSIONS: The modifications made to the Health Measurement Questionnaire has resulted in an assessment designed for cardiovascular patients that has proved to be both reliable and valid.

Cardiovascular Diseases↗

Comparison of stereotactic brain biopsy to interventional magnetic-resonance-imaging-guided brain biopsy.

Lesions within the brain are commonly sampled using stereotactic techniques. The advent of interventional magnetic resonance (MR) imaging now allows neurosurgeons to interactively investigate specific regions with exquisite visualization. We compared the safety and efficacy of this new surgical approach with stereotaxis. From February 1991 to June 1998, 134 stereotactic and 35 interventional MR-guided brain biopsies were performed. Stereotactic biopsies utilized preoperative scanning. Interactive scanning was used to confirm accurate positioning of the biopsy needle within the region of interest. Intraoperative pathologic examination of biopsy material was performed to verify the presence of diagnostic tissue in both biopsy groups. Intra- and postoperative MR imaging was obtained to exclude the presence of intraoperative hemorrhage. Recently, MR spectroscopic targeting has been utilized in 6 patients. In the stereotactic group, 129/134 (96%) biopsies were diagnostic. One patient had a transient hemiparesis after a brain stem biopsy and another suffered a fatal hemorrhage for a morbidity rate of 0.7% and a mortality rate of 0.7%. In reviewing 7,471 stereotactic biopsies, the morbidity was 3.5%, mortality 0.7% and diagnostic yield 91%. All 35 MR-guided brain biopsies were diagnostic (100%). MR spectroscopy was accurate in all cases in distinguishing recurrent tumor (5 cases) from radiation necrosis (1 case). One patient (3%) suffered a transient hemiparesis following a pontine biopsy and another patient (3%) developed a postoperative scalp cellulitis. No patient sustained a clinically or radiologically significant hemorrhage as determined by the immediate postbiopsy, intraoperative MR imaging. Interventional MR-guided brain biopsy is a safe and effective technique for evaluating lesions of the brain with morbidity and mortality rates comparable to those of stereotaxis. MR-guided biopsy appears to have a higher diagnostic yield than stereotaxis, which may reflect the ability to perform interactive, intraoperative scanning with that technique.

Biopsy↗

Assessing the multidimensionality of the 12-item General Health Questionnaire.

The present study assessed a variety of factor structures identified by various authors as underlying the 12-item General Health Questionnaire and proposed an alternative structure based on an analysis of item content. Using confirmatory factor analytic techniques (LISREL), the data indicated that the presently proposed factor structure, comprising three factors (Self-esteem, Stress, and successful Coping), fits better than structures previously identified. The findings contribute to understanding of the 12-item General Health Questionnaire by separating Self-esteem and Stress, two dimensions often treated as one factor, and by identifying a third dimension of Successful Coping which is proposed to reflect individuals' perceived efficacy in interacting with the environment.

Adult↗

Effect of antenatal tracheal occlusion on lung development in the sheep model of congenital diaphragmatic hernia: a morphometric analysis of pulmonary structure and maturity.

The incidence of congenital diaphragmatic hernia (CDH) is 1:1,207-5,000, and the condition is associated with high mortality and morbidity, attributed principally to associated pulmonary hypoplasia. Repairing the diaphragmatic defect by antenatal surgery has high mortality, mainly due to premature labor. Antenatal tracheal occlusion, which is achievable by less invasive methods, stimulates lung growth (weight and DNA). However, its effectiveness in reversing structural and maturational abnormalities and its optimal timing requires further investigation. We hypothesized that (1) antenatal tracheal occlusion performed in the lamb model of congenital diaphragmatic hernia will stimulate lung growth and structural development and restore lung structure and maturity toward normal levels by term gestation; (2) effects will be detectable by morphometric measurements of the following parameters: lung volume, ratio of parenchyma to nonparenchyma, volume density of connective tissue within nonparenchyma, ratio of gas exchange tissue to airspace in parenchyma, gas exchange surface area, capillary loading, alveolar/airspace density and alveolar perimeter; (3) effects will be seen in all lobes of the lung; and (4) a greater effect will be observed when tracheal occlusion is performed early rather than late in gestation. Fourteen lambs underwent CDH creation at gestation day 72-74 followed by tracheal occlusion at day 101 (n = 7) or 129 (n = 7). They were delivered by Cesarean section at 143 days (term = 145-149). Lungs were obtained at autopsy, inflation fixed, divided into lobes, and sampled; morphometric analysis was performed. Comparisons were made with previously reported results from control lungs of normal lambs and lambs with untreated CDH. In comparison with untreated lungs, antenatal tracheal occlusion at both times resulted in increased volumes for total lung and lobes, increased volume density of parenchyma and of airspace within parenchyma, and increased gas exchange surface areas. Normal values for gas exchange surface area density, and alveolar density and perimeter were attained and the lungs appeared more mature than non-occluded lungs. Tracheal occlusion earlier in gestation produced a greater effect, achieving greater than normal values for lung volumes and volume densities, whereas the capillary loading value was similar to normal lung. Later occlusion achieved less than normal values for lung volumes and volume densities, with a reduced capillary loading value. We conclude that antenatal tracheal occlusion is capable of reversing structural total lung and lobar hypoplasia and immaturity caused by CDH as determined by morphometrically determined parameters. The effect is greater when tracheal occlusion is performed early rather than late in gestation. The results are encouraging for development of treatment methods for humans with antenatally diagnosed CDH.

Animals↗

Predicting patients' utilities from quality of life items: an improved scoring system for the UBQ-H.

The Utility-based Quality of Life--Heart Questionnaire (UBQ-H) is a cardiovascular extension of the Health Measurement Questionnaire. It is a multidimensional instrument that can be scored to yield a utility estimate using the Rosser Index and a classification algorithm developed for the Health Measurement Questionnaire. The aim of this study was to employ a statistical modelling approach to devise an improved scoring system. A sample of 201 cardiovascular patients completed the UBQ-H and assessed the utility of their own health state using standard gamble and time trade-off questions in an interview. Two new scoring methods were devised by regressing the UBQ-H data against patients' self-assessed utilities. The new methods gave utility estimates that correlated with angina/dyspnoea grades, life satisfaction scores and General Health Questionnaire (GHQ) scores. In a second sample of 1,112 cardiovascular patients, the UBQ-H utilities were able to distinguish between patients who had/had not experienced an adverse event (e.g. myocardial infarction) and were responsive to changes in health over time. The new scoring methods were not particularly more sensitive to quality of life effects than the original method based on the Rosser Index. However, they produced significantly lower estimates and more accurately reflected patients' self-assessed utilities.

Cardiovascular Diseases↗

Bowel dysfunction in cystic fibrosis: importance of breath testing.

OBJECTIVE: To investigate the prevalence of carbohydrate malabsorption and bacterial overgrowth in children with cystic fibrosis (CF) and abnormal stool pattern referred for breath hydrogen testing. METHODS: Results from 89 tests using lactose, sucrose and lactulose in 54 children with CF were compared with 5430 tests on children with non-CF-related stool abnormalities. RESULTS: Children with CF were more frequently unable to ferment lactulose to hydrogen (39% vs. 20%, P<0.03); they had significantly longer oro-caecal transit times (mean 99 vs. 68 min, P<0.0003); they had a higher incidence of bacterial overgrowth (32% vs. 7%, P<0.003) and sucrose malabsorption (47% vs. 14.5%, P<0.004); but they had no increase in lactose malabsorption (40% vs. 31%). Children with bacterial overgrowth in both groups had longer transit times (CF 123 min, non-CF 108 min) compared to the non-CF children without overgrowth (68 min) and reference normal children (69 min). CONCLUSIONS: Bacterial overgrowth and carbohydrate malabsorption, particularly of sucrose, should be considered when assessing children with CF and abnormal stool patterns.

Breath Tests↗

Investigation of intraoperative brain deformation using a 1.5-T interventional MR system: preliminary results.

All image-guided neurosurgical systems that we are aware of assume that the head and its contents behave as a rigid body. It is important to measure intraoperative brain deformation (brain shift) to provide some indication of the application accuracy of image-guided surgical systems, and also to provide data to develop and validate nonrigid registration algorithms to correct for such deformation. We are collecting data from patients undergoing neurosurgery in a high-field (1.5 T) interventional magnetic resonance (MR) scanner. High-contrast and high-resolution gradient-echo MR image volumes are collected immediately prior to surgery, during surgery, and at the end of surgery, with the patient intubated and lying on the operating table in the operative position. In this paper we report initial results from six patients: one freehand biopsy, one stereotactic functional procedure, and four resections. We investigate intraoperative brain deformation by examining threshold boundary overlays and difference images and by measuring ventricular volume. We also present preliminary results obtained using a nonrigid registration algorithm to quantify deformation. We found that some cases had much greater deformation than others, and also that, regardless of the procedure, there was very little deformation of the midline, the tentorium, the hemisphere contralateral to the procedure, and ipsilateral structures except those that are within 1 cm of the lesion or are gravitationally above the surgical site.

Adult↗

Self-reports of mathematics self-concept and educational outcomes: the roles of ego-dimensions and self-consciousness.

BACKGROUND: There is a need for research to (a) explore more fully the academic outcomes that follow from under-/over-rating of self-concept and (b) identify factors that predict the nature of self-reports of self-concept as well as under- and over-rating of this self-concept. AIMS: The study examines the link between students' self-appraisals of both mathematics self-concept and under-/over-rating of this self-concept and educational outcomes in mathematics such as achievement and motivation (future plans for mathematics). Ego-dimensions (ego-orientation and competence-valuation) and public self-consciousness were examined as two factors that might contribute to predicting these self-appraisals. SAMPLE: Findings are drawn from a sample of 382 male and female high school students ranging in age from 14 to 16 years. METHODS: Students responded to a questionnaire (at Time 1) that assessed self-concept, motivation orientation, competence-valuation, self-consciousness, and mathematics motivation. Teachers rated each student using a brief mathematics self-concept scale. RESULTS: Higher mathematics self-concept and over-rating of this self-concept were predictive of higher levels of mathematics motivation and later mathematics achievement (Time 2). Findings also indicate that ego-orientation and competence-valuation are positively associated with mathematics self-concept and over-rating, whilst public self-consciousness negatively predicts mathematics self-concept and is also associated with a tendency to under-rate oneself in this domain.

Achievement↗

High-field strength interventional magnetic resonance imaging for pediatric neurosurgery.

BACKGROUND: Interventional magnetic resonance (MR) imaging allows neurosurgeons to interactively perform surgery using MR guidance. High-field (1.5-Tesla) strength imaging provides exceptional visualization of intracranial and spinal pathology. The full capabilities of this technology for pediatric neurosurgery have not been defined or determined. MATERIALS AND METHODS: From January 1997 through June 1998, 10 of 85 cases performed in the interventional MR unit were in the pediatric population (mean age 8.3, median 8, range 2-15 years). Procedures included 2 brain biopsies, 5 craniotomies for tumor, 2 thoracic laminectomies for syringomyelia, and placement of a reservoir into a cystic brainstem tumor. The biopsies and reservoir placement were performed using MR-compatible equipment. Craniotomies and spinal surgery were performed with conventional instrumentation outside the 5-Gauss magnetic footprint. Interactive and intraoperative imaging was performed to assess the goals of surgery. RESULTS: Both brain biopsies were diagnostic for cerebral infarct and anaplastic astrocytoma and the reservoir was optimally placed within the tumor cyst. Of the 5 tumor resections, all were considered radiographically complete. One biopsy patient and 1 tumor resection patient experienced transient neurological deficits after surgery. The patient with the thoracic syrinx required reoperation when the syringosubarachnoid shunt migrated into the syrinx 3 months after initial placement. No patient sustained a postoperative hemorrhage. Tumor histologies found at craniotomy were craniopharyngioma, ganglioglioma, and 3 low-grade gliomas. No evidence of tumor progression has been seen in any of these patients at a mean follow-up of 5.3 (range 4-8) months. The goals of the procedure were achieved in all 10 cases. There were no untoward events experienced related to MR-compatible instrumentation or intraoperative patient monitoring, despite the present inability to monitor core body temperature. CONCLUSIONS: 1.5-Tesla interventional MR is a safe and effective technology for assisting neurosurgeons to achieve the goals of pediatric neurosurgery. Preliminary results suggest that surgical resection of histologically benign tumors is enhanced in the interventional MR unit. The incidence of surgically related morbidity is low.

Adolescent↗

Quality-of-life assessment in health care research and practice.

This article reviews the different ways in which quality-of-life assessment has been applied to and has affected health care research and practice. A schema that describes the steps involved in the ongoing challenge of improving health outcomes is used to structure the review. The role of quality-of-life assessment is addressed with regard to: the identification of health problems, the evaluation of new treatments, the formulation of treatment guidelines and health policies, the delivery of optimal care in practice, and the assessment of outcomes in the wider community. The benefit of quality-of-life assessment has been demonstrated in a number of these areas (e.g., in identifying problems and evaluating treatments). Its role in other applications (e.g., in clinical practice to assess patients' needs) shows great promise and requires additional evaluation.

Delivery of Health Care↗

Phonological short-term memory and new word learning in children.

Sixty-five 5-year old children participated in 4 experimental tasks of word learning that varied systematically in the amounts of phonological and nonphonological learning required. Measures of the children's performances on 2 measures of phonological memory (digit span and nonword repetition), vocabulary knowledge, and nonverbal ability were also obtained. Learning of the sound structures of new words was significantly, and to some degree independently, associated with aspects of both phonological memory skill and vocabulary knowledge. Learning of pairs of familiar words was linked with current vocabulary knowledge, although not with phonological memory scores. The findings suggest that both existing lexical knowledge and phonological short-term memory play significant roles in the long-term learning of the sounds of new words. The study also provides evidence of both shared and distinct processes contributing to nonword repetition and digit span tasks.

Child Development↗

The appropriateness of A&E attendances: a prospective study.

This prospective study was undertaken to establish the extent and source of appropriateness of attendances at the Accident & Emergency Department of University College Hospital Galway. All new attendees to the department within a two week period were surveyed and differences were observed between the sources of referral. Analysis of the results showed that general practitioner referrals were older, had a longer duration of complaint and required more investigations than self referred patients. Of requested admissions by general practitioners 82.7% were finally admitted. Self referred patients had a shorter duration of complaint, were more likely to present with fractures, dislocation or soft tissue injuries and less likely to require admission (9.8%). Within this region approximately 10% of attendances were inappropriate and were distributed equally between general practitioner and self referrals. This study found that reassessment by A&E staff of requested admissions is not beneficial. The level of abuse is low. There is no more abuse of A&E by patients who attend A&E without seeing their General Practitioner than by those who have.

Accidents↗

Improved MR images of arterial specimens by submersion in trichlorotrifluoroethane.

MR images of ex vivo arterial specimens immersed in 1,1,2-trichloro-1,2,2-trifluoroethane (R-113) have improved signal-to-noise ratio and contrast-to-noise ratio. R-113 has no hydrogen atoms, so it yields no proton signal; hence, the contrast between the specimen and its background is maximized. SNR is maximized because (i) R-113 is nonconductive so that coil loading and inductive noise are minimized, and (ii) the volume susceptibility of R-113 closely matches that of water and tissue so that T2* effects are minimized. Short-term submersion of porcine aortas in R-113 was found to have no significant effect on the artery's hydration level, relaxation time, tensile strength, and structure or quantity of elastin, collagen, or smooth muscle cells.

Animals↗

Near-fatal asthma in South Australia: descriptive features and medication use.

BACKGROUND: Self-reported prior morbidity levels and medication use among survivors of a near-fatal asthma attack (NFA) were studied. AIMS: To identify deficiencies in asthma management and opportunities for intervention. METHODS: A hundred and twenty-seven consecutive patients aged 15 years or more presenting with a NFA to accident and emergency departments of teaching hospitals were interviewed. RESULTS: High levels of morbidity due to asthma were reported. Most cases (79%) reported symptoms occurring at least weekly in the three months before their NFA. A mean of 20.8 days was reportedly lost from work, school or other usual daily activity in the 12 months before these events. Regular use of beta agonist as nebuliser solution was reported by 27% of cases, increasing to 34.5% in response to increased symptoms, while 41% reported use of nebulised beta agonist in response to the NFA event. Less than half of all cases (46%) reported using an inhaled corticosteroid on a regular basis. Oral corticosteroids were used by 33% of cases at times of increased symptoms in the preceding 12 months. However, only 7% of cases reported initiating or increasing oral corticosteroids at the time of the NFA. CONCLUSIONS: Despite high levels of prior asthma morbidity, regular preventive inhaled corticosteroid use was not widespread in this series of NFA asthmatics. By comparison, over-reliance on regular beta agonist medication was common. Oral corticosteroids were rarely commenced in response to the NFA.

Administration, Inhalation↗