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Biomedical subjects

N A Saunders

Publications and source records attributed to N A Saunders.

At least 127 records · Page 7Linked to original sources
PubMed1989

Typing of Listeria monocytogenes for epidemiological studies using DNA probes.

We have investigated the possibility of using restriction fragment length polymorphisms (RFLPs) to distinguish different strains of Listeria monocytogenes. Cloned DNA fragments (probes) were selected from a bacteriophage lambda gene library of L. monocytogenes (L1428). DNAs from two lambda clones consisting of a total of approximately 20kb of probe DNA were labelled with biotinylated dUTP for use in these experiments. The criteria for probe selection were the ability both to hybridise with all strains of L. monocytogenes and to reveal RFLPs. Southern blots of restriction endonuclease (Nci I) digested DNAs from test strains of L. monocytogenes were hybridized to the probe. Following washing, biotinylated probe remaining bound to the filters was detected using the Blugene reagents (Gibco/BRL). Under these experimental conditions strain-specific restriction fragments were revealed. We have examined 64 strains of L. monocytogenes belonging to serogroup 1/2 which were not apparently epidemiologically associated and 19 patterns were observed. Epidemiologically related strains gave identical patterns of restriction fragments.

Bacterial Typing Techniques↗
PubMed1989

Effect of protriptyline on ventilatory responses to hypercapnia and asphyxia in normal subjects.

A double-blind crossover study was undertaken to assess the effect of protriptyline on ventilatory responses in normal subjects. Seven subjects received in random order placebo, 10 mg and 20 mg protriptyline daily for 2 weeks. Measurements of hypercapnic ventilatory response (HCVR) and asphyxial hypoxic ventilatory response (HVR) were made before treatment, 6-8 h after the first dose, and after 2 weeks treatment. Mean HCVR and HVR following 10 mg and 20 mg protriptyline did not differ significantly from measurements on placebo, neither for the single dose study or after 2 weeks.

Adult↗
PubMed1988

A study of intranasally administered interferon A (rIFN-alpha 2A) for the seasonal prophylaxis of natural viral infections of the upper respiratory tract in healthy volunteers.

The efficacy of interferon A (rIFN-alpha 2A), an Escherichia coli-derived interferon, in the prophylaxis of acute upper respiratory tract infection, was evaluated in a community-based double-blind placebo-controlled study in the Australian winter of 1985. The trial population of 412 healthy volunteers (190 males and 222 females, aged 18-65 years) self-administered 1.5, 3.0 and 6.0 megaunits (MU) of interferon A per day or a placebo, intranasally for 28 days. The period of study coincided with an outbreak of H3N2 influenza A (detected in 35 of the 107 acute specimens) as well as substantial numbers of respiratory syncytial virus and adenovirus infections. Rhinoviruses were isolated from only three specimens. In many cases, subjects had laboratory and clinical evidence of having had more than one respiratory tract infection during the period of the study. Viruses were detected in 54 or 107 acute specimens (49%). No statistically significant differences were noted between the various treatment groups in the incidence of laboratory-proven viral infection (virus isolation and/or antibody response). Analysis of reported symptoms indicated that blood-tinged mucus and nasal stuffiness occurred more frequently with higher doses of interferon. There appeared to be no clinical benefit from the use of interferon A in the amelioration of symptoms.

Administration, Intranasal↗
PubMed1988

Recognition of dementia in general practice: comparison of general practitioners' opinions with assessments using the mini-mental state examination and the Blessed dementia rating scale.

In a study of 226 elderly residents in a retirement village in Sydney, Australia, general practitioners' opinions about dementia status had high positive and negative predictive values and high specificity, but low sensitivity when evaluated against the mini-mental state examination and the Blessed dementia rating scale. General practitioners were found to disagree with these two measures more often when patients were in advanced old age, and when they considered the patients to be depressed. We conclude that the general practitioner can increase his or her sensitivity to dementia in the elderly by use of either measure.

Aged↗
PubMed1988

Sleep-related respiratory disturbance and dementia in elderly females.

Sleep-related respiratory disturbance was studied with a microprocessor-based portable monitoring system in female residents of a retirement village aged greater than or equal to 75 years. Comparisons were made between 29 demented subjects Mini-Mental State Examination Score (MMSE) less than 21 and 48 controls (MMSE greater than 25). Respiratory disturbance index (RDI, the number of episodes of apnea and hypopnea/hour of total sleep time) was higher in the demented subjects: mean RDI (+/- SD) 18.5 +/- 18.6 vs 7.3 +/- 10.8, p = .004. The number of minutes per hour of sleep spent with disturbed breathing was greater in demented subjects than in controls (p = .01). These differences between demented subjects and controls persisted after adjustment for age and relevant medical history. Other possible confounders, namely body mass index and use of sedatives, were not significant. We conclude that respiratory disturbance during sleep is more prevalent in elderly demented females than in controls.

Aged↗
PubMed1988

Identification of species of the genus Legionella using a cloned rRNA gene from Legionella pneumophila.

A cloned EcoRI fragment from Legionella pneumophila, which includes 16S and 23S rRNA genes, was used to identify bacteria belonging to the genus Legionella by hybridization to a series of species specific restriction fragments. Examination of the type strains of 28 species of legionellae gave different band patterns in every case. When further isolates of these species were tested the patterns obtained were usually either identical, or very similar, to those of the respective type strains. Thirty-one coded isolates were examined and of these 29 were allocated to the correct species. The remaining strains (a non-Legionella and a L. pneumophila) could not be identified using this technique. The rRNA gene probe method should be of great value in the identification of legionellae, particularly for those species which are at present very difficult to distinguish serologically.

Cloning, Molecular↗
PubMed1988

Serological diversity within the species Legionella spiritensis.

A strain of Legionella isolated from the environment which could not initially be identified was shown by restriction fragment length polymorphisms to be a Legionella spiritensis. This was confirmed by DNA homology studies, cell wall fatty acid composition and isoprenoid quinone analysis. This strain, which is only the second reported representative of the species, was shown to be serologically distinct from the type strain of L. spiritensis and all other serogroups of Legionella.

Antigenic Variation↗
PubMed1988

Identification of simulated patients by interns in a casualty setting.

Fifty-four interns agreed to a study in which their clinical performance in an out-patient unit with standardized patients was recorded on videotape. In order to examine whether they could distinguish standardized from real patients, the interns were asked to note any patients who they thought might be simulating their complaints and report these to the researchers at the end of each 2-day period of study. Thirty-two of the interns were assessed again at the end of their internship, using the same clinical problems presented by different simulators. The consultations took place in the casualty department of a large urban hospital. At the beginning of the year there were 152 consultations with standardized patients and 328 consultations with appropriate genuine patients. Standardized patients were identified definitely as 'not genuine' in only 12 of the 152 consultations (sensitivity 7.8%) whereas 320 of the 328 genuine consultations were accepted by the interns as genuine (specificity 97.8%). When the level of confidence required to distinguish the two groups was reduced from 'definite' to 'probable', the number of correctly identified simulator consultations increased to 36/152 (27%) but the rate of misclassification of genuine patients also increased from 8 to 37 out of 328 consultations (11%). At the end of the year there were 81 consultations with standardized patients and 149 consultations with genuine patients. Identification rates were only slightly changed. We conclude that simulator identification is not a problem in applying standardized patients to evaluate the quality of care provided in a hospital casualty.

Clinical Competence↗
PubMed1988

Effects of breathing supplemental oxygen before progressive exercise in patients with chronic obstructive lung disease.

A study was carried out to determine whether supplemental oxygen before exercise would improve maximum exercise performance and relieve exertional dyspnoea in 20 patients with chronic obstructive lung disease (mean FEV1 0.79 l; forced vital capacity 2.30 l). Patients performed two progressive treadmill exercise tests to a symptom limited maximum, with at least 30 minutes rest between tests. They received compressed air or supplemental oxygen from nasal prongs for 10 minutes before exercise in a double blind randomised trial with a crossover design. Heart rate and breathlessness score on a visual analogue scale were compared between tests at 75% of the maximum distance walked in the compressed air test. The mean arterial oxygen saturation (SaO2) after oxygen (93%) was significantly higher than after compressed air (91%). There was no significant change, however, in maximum distance walked or maximum heart rate, or in the breathlessness score or heart rate at 75% of maximum distance walked. The study had a power of 93% for detecting an increase of 50 metres in maximum distance walked. There was an order effect, with better performance on the second test; but the magnitude of the difference was small. It is concluded that administration of supplemental oxygen sufficient to raise SaO2 above 90% for 10 minutes before exercise is unlikely to improve maximum exercise performance or breathlessness on exertion in patients with chronic obstructive lung disease.

Adult↗
PubMed1988

Seasonal variation in non-specific bronchial reactivity: a study of wheat workers with a history of wheat associated asthma.

To investigate seasonal variation in non-specific bronchial reactivity in wheat workers, we carried out histamine inhalation tests in 29 workers (28 of them men) from a small farming community with symptoms of wheat associated asthma before, during and after the 1983-4 Australian wheat harvest season. Four were cigarette smokers, and the age range was 12-54 (mean (SD) 30 (10)) years. Twenty eight subjects were atopic (one positive skinprick test result in tests with 10 common antigens), 60% reacting to house dust mite and all to at least one of eight wheat antigens. Baseline spirometry gave normal results (mean FVC1 90% (SD 8%) predicted; FVC 91% (7%) predicted). Bronchial reactivity was tested by the method of Yan et al. The cumulative doses of histamine acid phosphate (up to 3.91 mumol) that caused a fall of 20% from baseline in FEV1 was determined (PD20) and expressed as the geometric mean. In the low exposure season, May 1983, nine subjects had a PD20 (mean 1.2, range 0.3-3.9 mumol). The number rose to 19 in the summer harvest season, December 1983 (mean 0.8, range 0.07-3.9 mumol) and returned to nine in the subsequent winter, July 1984 (mean 1.8, range 0.4-3.9 mumol). The change in the number of subjects with a PD20 was significant (p less than 0.01). Four additional subjects probably had increased bronchial reactivity in the harvest season: in two the post-saline FEV1 was too unstable to give them histamine challenge and in two the challenge was inadvertently discontinued prematurely. Baseline FEV1 and FVC fell by 8% between the first and second studies (p less than 0.001); values were intermediate in the third study (FEV1 3.74, 3.44, and 3.57; FVC 4.66, 4.28, and 4.41 litres respectively). Linear modelling analysis of log PD20, season, FEV1, FVC, age, seasonality of asthma symptoms and skin test data indicated that the harvest season was the only significant determinant of variation in log PD20. It is concluded that in these wheat workers there is a seasonal variation in bronchial reactivity that may reflect a response to allergens associated with grain.

Adolescent↗
PubMed1988

Prediction of oxygenation during sleep in patients with chronic obstructive lung disease.

The accuracy of a prediction equation for assessing the lowest arterial oxygen saturation (SaO2) during sleep was determined in 24 consecutive patients with chronic obstructive lung disease referred for assessment for home oxygen therapy. Subjects had a mean (SD) FEV1 of 0.81 (0.31) litre and an FEV1/FVC of 37% (12%). There was reasonable agreement between predicted and measured values (mean difference [predicted-measured] = -2.5%) but the prediction was not precise as the 95% confidence interval for the difference was +8% to -13%. The duration of arterial oxygen desaturation, defined as the percentage of total sleep time spent below a given SaO2, was not predicted accurately. It is concluded that nocturnal arterial oxygen desaturation in individual patients with chronic obstructive lung disease cannot be predicted from "awake" measurements with sufficient accuracy to be clinically useful.

Adult↗
PubMed1988

Biotyping respiratory Haemophilus species with the microbact system.

The biochemical characteristics of 114 respiratory Haemophilus isolates were examined by the Minitek and Microbact systems. The Microbact system was easy to use and read, although some of the less important reactions (glucose and xylose) were difficult to interpret on occasions. On the basis of the 3 crucial reactions--indole production, ornithine decarboxylase and urease activity--discrepancies between the two systems were minor. Given careful standardization of techniques the Microbact system is a suitable alternative to established techniques for the biotyping of H. influenzae and H. parainfluenzae.

Bacterial Typing Techniques↗
PubMed1988

Autoradiographic localization of putrescine uptake to type II pneumocytes of rabbit lung slices.

At low concentrations (0.4-5.0 microM), the polyamine, putrescine, is accumulated predominantly by a saturable process in rabbit lung slices. The question of why the lung should possess polyamine transport capabilities and the known cellular compartmentalization of various other pulmonary functions prompted us to investigate whether putrescine uptake was localized to a specific cell type(s) within rabbit lung. Localization of putrescine uptake in rabbit lung was investigated by frozen and plastic section autoradiography, combined with electron microscopy. Rabbit lung slices were incubated with [3H]putrescine at a concentration (0.4 microM) at which the saturable component of uptake predominates. Both frozen and plastic section autoradiograms revealed relatively minor amounts of radiolabel associated with either vascular or bronchiolar tissues, whereas a greater density of radiolabel was present over the alveolar epithelium. Highly localized areas of radiolabel were found at the junctions of adjacent alveoli and these labeled cells were identified by electron microscopy as type II pneumocytes. We conclude that the type II pneumocyte is a major site of putrescine uptake in rabbit lung slices. Our study also indicates that different rabbit lung cell types possess differing abilities to accumulate putrescine.

Animals↗
PubMed1987

Comparison of performance of final-year students from three Australian medical schools.

Between 1984 and 1986, 888 final-year medical students from The Universities of Sydney, Western Australia and Newcastle took part in trial examinations that comprised multiple-choice questions, modified essay questions and a patient management problem. Differences in student performance among the schools were small. In 1984 and 1985, Newcastle students performed less well than did Sydney students on multiple-choice questions that were prepared by The University of Sydney, but there was no difference between the schools in 1986. Sydney students performed better than did Newcastle students on the multiple-choice question paper that was prepared by The University of New South Wales in 1984, but in the last two years no differences have been detected between the schools in performance on this paper. The performance on modified essay questions in 1984 suggested that Newcastle students were stronger in behavioural sciences and weaker in pathological sciences than were Sydney students. Sydney students performed less well than did Newcastle students in the patient management problem in 1985, particularly in the area of the use of clinical investigations. On the one occasion of testing that involved students from The University of Western Australia (in 1985), these students performed best of the three schools in the patient management problem, and roughly equally with students from Sydney and Newcastle in the multiple-choice question papers. Differences among the schools usually amounted to less than 10% and might have been accounted for by differences in familiarity with test instruments. We conclude that medical students are likely to graduate from The University of Sydney, Western Australia and Newcastle with similar levels of knowledge of internal medicine. Possible differences in problem-solving ability require further study, particularly in the clinical setting.

Australia↗
PubMed1987

Uptake, efflux and metabolism of the polyamine putrescine in rabbit lung slices.

The herbicide paraquat is a selective pulmonary toxin in many mammals, including man, and its pulmonary toxicity has been attributed to selective uptake by a polyamine transport system in lung. In the present study, we investigated the characteristics of this transport process in rabbit lung slices. [14C]Putrescine was accumulated by both saturable and non-saturable processes and the accumulated putrescine was non-effluxable over 60 min. The saturable component was inhibited by spermine and paraquat. Moreover, uptake studies in Na+-deficient medium indicated that the lack of Na+ may selectively enhance uptake via the non-saturable process. The two components also differed in the metabolic fate of accumulated substrate. At 0.6 microM putrescine, where the saturable process predominated, 98% of the 14C in the perchloric acid-soluble fraction of tissue homogenates was present as putrescine, whilst 3% of the accumulated substrate was found in the acid-insoluble fraction. With 500 microM putrescine, where the non-saturable process predominated, 82% of the 14C in the acid-soluble fraction was present as putrescine and 15% of accumulated putrescine was found in the acid-insoluble fraction. The acid-insoluble 14C was localised mainly in the 700 g and 4500 g pellets obtained after homogenising the tissue. We conclude that there are two components to putrescine uptake in rabbit lung slices, both of an apparently irreversible nature. We suggest that the components represent compartmentalisation of putrescine in selective pulmonary cell-types or separate subcellular organelles. The observed metabolism and covalent binding of putrescine appeared to be associated with the non-saturable component only.

Animals↗
PubMed1987

Domiciliary oxygen: rationalization of supply in the Hunter region from 1982-1986.

In October 1982, a clinic was planned at The Royal Newcastle Hospital to review the usage of domiciliary oxygen that was funded by the Provision of Aids for Disabled Persons scheme in the Hunter Region of New South Wales. Patient review included an assessment of the indications for domiciliary oxygen, education in the use of oxygen, the efficiency of delivery arrangements and the transfer from cylinders to concentrators as indicated. Between January and June 1983, 111 patients who were receiving oxygen at home were reviewed: 84 (76%) of these patients had chronic obstructive pulmonary disease; their two-year survival was 80% (95% confidence interval, 69%-87%) and five-year survival was 36% (95% confidence interval, 25%-46%). In 66 (59%) patients, review led to a reduction in the usage of domiciliary oxygen which was estimated to save $40,000 each year in the Hunter Region. In the year from 1985-1986 the decrease in the usage of oxygen at home represented an actual cost saving of $60,000 for the region ($470 per person) which translated into a saving of $95,000 ($740 per person) when inflation was taken into account. If our experience is projected nation-wide, the potential exists for a considerable cost saving by means of programmes to rationalize the use of domiciliary oxygen.

Actuarial Analysis↗
PubMed1987

Effect of a dopamine antagonist on ventilation during sustained hypoxia in mice.

To test the hypothesis that dopamine accumulated in the carotid body limits hyperventilation during acclimatization to sustained hypoxia, we administered the dopamine antagonist droperidol to mice undergoing acclimatization to an inspired O2 fraction (FIo2) of 0.1. Twelve mice were exposed to hypoxia for 10 days and ventilation in 10% O2 and in 7% CO2 in air were measured daily by a plethysmographic method. Under both conditions ventilation increased during acclimatization to hypoxia: ventilation in 10% O2 increased from 39.4 +/- 3.8 (mean +/- SE) ml/min before exposure to sustained hypoxia to 72.2 +/- 4.2 ml/min after 3 days of continuous hypoxia, and ventilation in 7% CO2 in air at the same time increased from 113.2 +/- 5.4 ml/min to 140.0 +/- 5.6 ml/min. Twelve mice were exposed to FIo2 of 0.1 for 10 days and received droperidol (300 micrograms/kg intraperitoneally) before exposure to sustained hypoxia and on the 2nd, 4th, and 8th days of continuous hypoxia. Before exposure to sustained hypoxia, droperidol increased ventilation in 10% O2 from 40.1 +/- 2.5 ml/min to 72.5 +/- 5.2 ml/min, but after 2, 4, and 8 days of continuous hypoxia droperidol caused an acute fall in ventilation (ventilation in 10% O2 after droperidol on day 2: 49.1 +/- 3.1 ml/min, on day 4: 44.4 +/- 3.7 ml/min, and on day 8: 27.8 +/- 3.4 ml/min). Two days after the animals were returned to room air, ventilation in 10% O2 again increased in response to droperidol. We conclude that dopamine in the carotid body does not limit ventilatory responses to hypoxia during acclimatization to sustained hypoxia.

Animals↗