PubMed Health⌕ Search

Biomedical subjects

R M Douglas

Publications and source records attributed to R M Douglas.

At least 19 recordsLinked to original sources
PubMed1992

Indoor nitrogen dioxide and childhood respiratory illness.

Nitrogen dioxide is produced from the combustion of fossil fuels and as an emission from gas-fired appliances, and is also a component of tobacco smoke. Nitrogen dioxide has been shown in experimental animals to be toxic to the respiratory tract. A n number of recent studies have suggested that children exposed to significant levels of nitrogen dioxide in the home may be more susceptible to respiratory illness than children exposed to normal ambient levels. Respiratory illness is a major cause of morbidity in children everywhere. Here, we review the available evidence of this association and explore methodological issues in measurement of nitrogen dioxide exposure--misclassification of subjects, symptom bias and confounding. It has recently been shown that some New South Wales school rooms, where unflued gas heaters are often used as a source of warmth, have nitrogen dioxide levels which are above recommended ambient levels for outside air. This has underlined the need for setting standards for indoor levels of various pollutants, and cohort studies are suggested, to include personal monitoring and prospective data collection techniques.

Air Pollution, Indoor↗
PubMed1991

HIV prevalence and risk behaviours for HIV transmission in South Australian prisons.

During the latter half of 1989, HIV prevalence in South Australian prisoners was 1.4%. The prevalence of HIV infection across the prison system did not change significantly during 1989 but there was clustering of HIV-infected prisoners in some prisons. Almost half the prisoners from all of the South Australian prisons agreed to participate in our studies, from which we estimate that about 42% of prisoners engage in risk behaviours at least once while incarcerated. Prisoners estimated that 36% of all prisoners inject drugs intravenously at some stage during their stay and that 12% engage in anal intercourse at least once. Interviews with former prisoners who had a history of intravenous drug use revealed that about half had injected themselves while in prison, 60% shared needles and most did not clean shared needles adequately. Most of these prisoners injected themselves once a month or less frequently. The conditions for spread of HIV within the prison system exist but at the current prevalence of infection, transmission can be expected to be infrequent. The opportunity exists now to improve and expand preventive measures.

Adult↗
PubMed1991

The distribution of homologues of the Escherichia coli KefC K(+)-efflux system in other bacterial species.

Using a variety of techniques the distribution of the glutathione-regulated KefC K(+)-transport system among bacterial species was investigated. The presence of similar systems in a number of Gram-negative bacteria was demonstrated. In contrast, the system appeared to be absent from most Gram-positive bacteria tested with the exception of Staphylococcus aureus. Using the cloned Escherichia coli kefC gene as a probe for Southern hybridization it was shown that only limited DNA sequence homology exists with other bacteria, even when closely related members of the enteric group were examined.

Bacterial Proteins↗
PubMed1991

Corneal ulceration due to Nocardia asteroides.

A case of corneal ulceration due to infection with Nocardia asteroides is described. Microbiological examination of corneal scrapings permitted accurate diagnosis and suggested appropriate therapy. Nineteen other cases that have been described in the world literature are reviewed.

Adult↗
PubMed1991

Position-specific adaptation in simple cell receptive fields of the cat striate cortex.

1. Responses of simple cells in cat striate cortex were studied with flashed light-slit stimuli. The responses to bars flashed in different positions in the receptive field were assessed quantitatively before and after periods of prolonged stimulation of one small region. This type of prolonged stimulation resulted in reduced responsivity over a limited zone within the simple cell receptive field. 2. The adaptation-induced responsivity decrement was generally confined to the receptive-field subregion that was adapted (either ON or OFF). Prolonged stimulation within an ON region did not usually result in adaptation effects that spread into neighboring OFF regions. Furthermore, the adaptation-induced response decrement did not necessarily spread throughout the subregion in which the adapting stimulus was presented. The adaptation effects from prolonged stimulation at a single receptive-field position spread throughout the subregion in nearly one-half of the 25 cells examined for position-specific adaptation. Another subpopulation of neurons (n = 12) displayed adaptation effects that spread through only one-half of the subregion, whereas in two neurons the spread of the adaptation effect was even more restricted and encompassed only one-fourth of the subregion. 3. The spread of adaptation was not systematically related to the size of the stimulus presented, the size of the receptive field, or the magnitude of the adaptation-induced response decrements but was significantly correlated with the spatial wavelength of the cell (the reciprocal of the cell's preferred spatial frequency) and with the size of the subregion in which the adapting stimulus was presented. Cells with large receptive-field subregions and long wave-lengths showed adaptation effects that spread further than those of cells with small subregions. 4. The adaptation effects from repeated stimulation at a single receptive-field position did not spread symmetrically across the receptive field, and the preferred direction of motion for a given cell indicated the direction of the asymmetric spread of the adaptation. Receptive-field positions that would be stimulated by a light slit originating at the point of adaptation and moving in the preferred direction (preferred side) showed greater adaptation-induced response decrements than did receptive-field positions that would be stimulated by a light slit moving in the opposite direction from the point of adaptation (nonpreferred side). There was significant enhancement of responses at some receptive-field positions on the nonpreferred side of the point of adaptation.(ABSTRACT TRUNCATED AT 400 WORDS)

Acclimatization↗
PubMed1991

Acute respiratory infections in children in the developing world.

The profound decline in death rates from respiratory infections in recent decades in the developed countries of the world is a complex phenomenon that probably results from a combination of socioeconomic and environmental change and modern medical care. Death rates from respiratory infections in the developing world are very variable, and there is evidence that they can decrease dramatically when effective health services are engrafted onto a social environment in which mothers are literate and trained to observe their children's health. A worldwide case management program aimed at making lifesaving antibiotics and oxygen available for treatment of children in deprived areas is currently being spearheaded by the World Health Organization and rests on simplified approaches to diagnosis that are widely disseminated to parents and primary health workers. These guidelines have been shown in field studies to contribute to changes in child mortality. The epidemiology of pneumonia in childhood seems similar worldwide. Most children suffer five to eight respiratory infections annually if they live in the cities and fewer if they live in rural areas but, in deprived circumstances, pneumonia complicates the infection much more often and the principal organisms are pneumococcus and Haemophilus influenzae. A vaccine approach to these two organisms is attractive and needs further field testing. Meanwhile, a case management approach, making antibiotics available on a rational basis worldwide, is capable of saving lives. Until mothers in the developing world have confidence in the survival of their children, they are unlikely to be attracted to control of their fertility.

Bacterial Vaccines↗
PubMed1990

Could preventive intranasal interferon lower the morbidity in children prone to respiratory illness?

Recent studies have demonstrated that rhinovirus infections can be prevented in the family setting through use of intranasal interferon sprays which are commenced when another family member develops a cold. One hundred and twenty-seven children aged 4-9 years who had been hospitalized during their first year of life for severe infections caused by respiratory syncytial virus were studied virologically and epidemiologically during a seven-month period which included the winter months. The hypothesis was that a significant part of their respiratory morbidity would be preventable by a contact prophylaxis approach using intranasal interferon. However, the findings suggest that a preventive approach of this kind would not substantially reduce the burden of respiratory illness in these children because: the target children themselves more often introduced illness into the family than did other household members; rhinovirus infections preventable by interferon were associated with little lower respiratory morbidity; and rhinoviruses were minor contributors to the total respiratory illness burden in these respiratory illness-prone children.

Administration, Intranasal↗
PubMed1979

Pneumococcal disease and its prevention with polyvalent pneumococcal polysaccharide vaccines--a review.

Polyvalent pneumococcal polysaccharide vaccines have been shown to be safe, immunogenic and efficacious and are becoming available for use in patients at high risk of developing pneumococcal infections. Precise estimates of the role of the pneumococcus in human respiratory disease are difficult to obtain, as this organism is also a frequent commensal of the upper respiratory tract; and as the optimal techniques for the identification and proof of its role are not widely used. Nevertheless, the pneumococcus remains the principal cause of adult pneumonia and paediatric otitis media, and is also an important cause of death from bacteremia and meningitis. At present it seems likely that in Australia these vaccines will be most useful amongst people over the age of 50 years, those with chronic systemic disease, alcoholics, splenectomized individuals and disadvantaged groups such as Australian aborigines, all of whom are particularly susceptible to pneumo-coccal bacteremia which has a considerable mortality rate. The possibility of preventing pneumococcal otitis media in childhood is still being evaluated. Studies of the role played by the various pneumococcal serotypes in Australian populations are urgently needed.

Adult↗
PubMed1979

Symptoms and feeding patterns in the first year of life.

With the help of family doctors, mothers and infant welfare sisters, we report an analysis of symptom and food diaries maintained throughout the first twelve months of life on 482 infants. This reveals the existence of extensive symptomatology in the first year of life--most of which was clearly unrelated to ingestion of foods or cow's milk. Our efforts to define the true incidence of cow's milk allergy have been unsuccessful. Altogether, 77 of the 482 diaries have revealed symptomatology at some time in the year which could conceivably have been associated with cow's milk ingestion. But, in only one of these 77 children were withdrawal and challenge tests carried out to determine whether the symptomatology disappeared on withdrawal of cow's milk and reappeared on its reintroduction into the diet. Most of the remaining 76 children had long periods of complete freedom from symptoms whilst taking cow's milk, and the evidence of any association with cow's milk was generally very tenuous. Soya substitutes were introduced in 13 cases, and cow's milk was temporarily discontinued in another 11 cases. Only 16 of these 77 children continued to experience chronic symptoms during the last two weeks of their first year.

Animals↗
PubMed1978

Synaptic enhancement in fascia dentata: cooperativity among coactive afferents.

Evidence is presented that long-lasting enhancement of perforant path synapses following high-frequency activity is a cooperative process requiring coactivity of a considerable number of fibers. This was demonstrated in two ways: (1) A threshold stimulus intensity during high-frequency stimulation was required before any enhancement was observed. This threshold was considerably above the stimulus threshold for observing a minimal synaptic response in the fascia dentata. Above the enhancement threshold, the amount of enhancement increased as the intensity of high-frequency stimulation increased. (2) Concurrent high-frequency activation of fibres of the medial and lateral perforant path produced enhancement at intensities where identical but independent stimulation of the two pathways either failed or was less effective. Discharge of the granule cells during the high-frequency stimulation was independently manipulated and found not to be physically coupled to the enhancement generating mechanism.

Afferent Pathways↗
PubMed1978

Evaluation and peer review of the role of specialist and general medical units in a teaching hospital.

The trend toward increasing specialization in the medical wards of teaching hospitals has important implications for future health care delivery and student teaching. A study of the likely implications of a change to a specialty oriented medical admission system at the Royal Adelaide Hospital has shown that already the general physicians are seeing little renal and endocrine disease and, that work satisfaction is greater on the specialty units than on the general medical units. Patient satisfaction marginally favoured the specialty units. A peer review audit method was introduced to try and discern whether the quality of care was significantly different on the two types of units. Most physicians cooperated in at least one or two audits which involved them in judgements about adequacy of casenotes, management decisions, follow-up arrangements, length of stay and investigations in randomly assigned specialty pairs of patients (cared for by specialist or general units). No clear-cut trend was discerned favouring specialist or generalist care amongst 17 randomly selected pairs, but this part of the study was never completed, perhaps partly because of lack of enthusiasm for it by busy clinicians. The importance of maintaining a model of generalism for medical students on the teaching hospital campus is discussed discussed in the light of the decline of the role of general physicians.

Australia↗
PubMed1978

Evaluation of primary health and medical care: the current state of the art.

Evaluation is a subjective process which depends upon the perspective of the evaluator and the criteria he chooses. A review of past efforts at primary care evaluation indicates a preoccupation with the structure and process of care. Methods for the measurement of the outcome of primary care are at last being developed.

Australia↗
PubMed1977

Circadian rhythm of synaptic excitability in rat and monkey central nervous system.

Synaptic responses in hippocampal granule cells to stimulation of their afferent fibers from the entorhinal cortex fluctuate with a 24-hour period. The phase of this cycle for rats and monkeys depends on whether the animal is naturally nocturnal or diurnal. In a rat blinded by enucleation, the rhythm persists but drifts out of phase with the rhythm of sighted controls.

Action Potentials↗