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Biomedical subjects

R M Douglas

Publications and source records attributed to R M Douglas.

At least 127 records · Page 7Linked to original sources
PubMed1981

[A comparison between orienting rapid eye movements accompanying active or passive head movement in the cat].

Gaze is shifted by means of eye saccades which, in most instances, are synchronized with head rotations. During eye-head movements performed by cats in the dark, most of the rapid eye movements start after the head has begun to move (mean time lag was 45 msec). This pattern resembles that observed when the cat, as a whole, is suddenly rotated passively and consists of a short lasting vestibularly induced slow phase component followed by a rapid eye movement that takes the eye in the same direction as the head. We have compared the passively and actively induced eye-head movements. The rapid eye movements are similar in both cases in that they terminate at a fixed position ("goal") in the orbit irrespective of the eye's starting position. They differ primarily in the fact that the eccentricity of the "goal" during active head rotations increases much more rapidly with velocity than it does during the passive condition. The results suggest that the rapid eye movement that accompanies an active head movement in the dark is not simply a vestibularly induced quick phase.

Animals↗
PubMed1980

Microbiology of acute otitis media with particular reference to the feasibility of pneumococcal immunization.

Middle-ear fluid was aspirated in 103 episodes of acute otitis media occurring in 100 South Australian children aged from four months to 14 years in 1977, and in 1978. Bacteria were cultured from the middle-ear fluid in 66% of cases, and viruses were grown in three cases in conjunction with bacteria. The bacteria grown were pneumococci in 30 cases (29%), Haemophilus influenzae in 26 cases (25%), beta-haemolytic streptococci in 12 cases (12%) and Neisseria spp. in six cases (6%). Pneumococci and H. influenzae were cultured from children of all ages, whereas beta-haemolytic streptococci were more frequently isolated in children aged five years and older. Countercurrent immunoelectrophoresis yielded positive results in 35% of culture-positive pneumococcal infections and gave additionally the positive reaction for pneumococci in two cases where culture produced negative results. The pneumococci which were isolated belonged to 12 serotypes; 26 of the 30 isolates were serotypes for which pneumococcal vaccines are currently available. There were appreciable differences in the distribution of serotypes from that encountered in a study of nasal carriage amongst healthy schoolchildren living in the same district.

Acute Disease↗
PubMed1980

A radioimmunoassay for immunologic phenomena in pneumococcal disease and for the antibody response to pneumococcal vaccines. I. Method for the radioimmunoassay of anticapsular antibodies and comparison with other techniques.

A radioimmunossay is described which uses a 14C biosynthetically internally labeled antigen. This modified Farr technique has been standardized by quantitative precipitation and compared with hemagglutination and mouse protection. Specificity was established by use of heterologous hyperimmune sera and by use of unlabeled pneumococcal polysaccharides for inhibition. Reproducibility has been evaluated for different preparations of antigens and varying storage conditions of sera. The system has been applied to a wide variety of studies requiring analysis of human and animal sera.

Animals↗
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↗
PubMed1975

Long-term potentiation of the perforant path-granule cell synapse in the rat hippocampus.

When the entorhinal cortex is electrically stimulated, a monosynaptic evoked potential is produced in the ipsilateral hippocampus. Twenty-four hours after a 120-pulse stimulation train, the response to a single test pulse was found to be increased. Stimulation trains presented at a rate of 1/day had a cumulative effect on both the population EPSP and spike components of the evoked potential, and the potentiation so produced lasted at least 12 days. In a few cases, retested 2 months after the last stimulation train, the population EPSP was found to be still highly potentiated while the population spike had declined to initial levels. The most reliable results and largest potentiation were obtained with diphasic stimulation trains of 10 Hz or greater, though some changes were observed even with very low frequencies (0.2 Hz). The results imply that the efficiency of synaptic transmission in the perforant path-granule cell synapse can be modified.

Animals↗
PubMed1975

Does the engram of kindling model the engram of normal long term memory?

The kindling effect is a relatively permanent alteration in brain function which results from repeated electrical or chemical stimulation and culminates in the appearance of electrographic and behavioral convulsions whenever the original stimulus is reapplied. The effect results from tetanic activation in the anterior cortex, limbic system or associated areas of the adult mammalian brain, and the lasting alterations are transynaptic and quite widespread. They are based in part on synaptic facilitation, and they are accompanied by specific alterations in normal behavior. In these and other respects, kindling is analogous to normal learning. It is possible that the stored component (engram) of kindling involves the same physiological mechanism as the engram of normal long term memory. Morphological study of identified synapses has not provided conclusive evidence for an anatomical substrate of kindling, but physiological experiments demonstrate a lasting potentiation of the excitatory post-synaptic potential.

Amygdala↗