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Biomedical subjects

A Towle

Publications and source records attributed to A Towle.

16 recordsLinked to original sources
PubMed1996

Self directed learning.

The ability to acquire skills in self directed learning may be the key link between undergraduate education, postgraduate training, and continuing professional development. If future and current practitioners are to adopt an ongoing reflective and critical approach to practice, we should aim to provide learning opportunities that promote self confidence, question asking and reflection, openness and risk taking, uncertainty and surprise. Teaching techniques that encourage these skills are being introduced widely and have been shown to be at least as effective as traditional methods of education while promoting more enjoyment and enthusiasm among both staff and students.

Education, Medical, Continuing↗
PubMed1995

Doctors' continuing education in Tanzania: distance learning.

A distance learning programme for medical officers and their assistants at the district level has produced some valuable lessons for future activities in continuing education. Besides correspondence and study materials, face-to-face contact between students and their tutors is a particularly important ingredient, as it provides the guidance, flexibility and motivation that are essential for an effective programme.

Curriculum↗
PubMed1992

Loss of hippocampal CA1 pyramidal neurons correlates with memory impairment in rats with ischemic or neurotoxin lesions.

Rats were trained for 20 days in a modified T maze to perform an invariant, tactile discrimination and a variable, delayed spatial discrimination, and then were exposed either to 30 min of transient forebrain ischemia or to low- or high-dose ibotenic acid to damage the dorsal hippocampus bilaterally. Only rats exposed to ischemia or high-dose ibotenic acid demonstrated impaired performance during 30 postoperative test days on both aspects of the task (p less than .05). Volume of hippocampal damage did not predict performance. However, the extent of CA1 pyramidal neuron loss correlated significantly with performance on the delayed spatial discrimination (p less than .01). Damage to the dentate gyrus and CA2-3 did not correlate with performance. These results support the view that the hippocampus, in particular the CA1 region, is crucial for certain types of memory performance.

Animals↗
PubMed1992

Problem-based learning in distance education: a first exploration in continuing medical education.

The Wellcome Tropical Institute has assisted countries in the tropics to establish viable systems of continuing medical education, particularly for young doctors practising in rural areas. As part of this strategy the Institute has developed material for use in distance learning. The first attempt to apply the problem-based learning approach to written material for use by an individual learner in the absence of a tutor led to a trial in Ghana, Kenya and Pakistan to compare a conventionally designed module with a problem-based learning module on the same topic for their respective acceptability, effectiveness and efficiency. The design, implementation and results of these three comparative trials are presented.

Education, Medical, Continuing↗
PubMed1989

Neuronal and glial elements of fetal neostriatal grafts in the adult neostriatum.

The cellular components of striatal grafts into the host striatum of rats were studied using [3H]thymidine autoradiography, histochemistry, immunocytochemistry and Golgi-staining. Autoradiography revealed that a layer of glial cells, somas smaller than 8 microns in diameter, stained positive with glial fibrillary acidic protein, and demarcating transplant from host, is derived mainly from the donor. Golgi studies revealed that many neuronal fibers fail to cross the glial layer to reach the host striatum. Migration of transplanted striatal cells into the host milieu was evident. The density of migrated cells decreased linearly as a function of distance from the transplant. Most of the far-migrated cells were glial cells. Neuronal migration was limited. In the transplant, donor cells marked by [3H]thymidine constituted at least 70% of the population. Neurons which stained positively for GABA, substance P, and acetylcholinesterase were identified in the transplant. Fibers of two of these three neuronal types, substance P and acetylcholinesterase, formed patchy patterns in the transplant. Detailed morphology on GABAergic fiber is not available to date, because of the limited antibodies or the method used. GABA is the highest population in the striatal transplant. Two types of GABA-positive cells were clearly distinguishable according to cell size. A majority resembled the medium-sized cell commonly found in striatum, while those of the other type resembled the larger GABA cells usually found in the globus pallidus.

Animals↗
PubMed1989

Serotonin-immunoreactive neurons in the brain of Manduca sexta during larval development and larval-pupal metamorphosis.

The developing serotonergic system of the tobacco hornworm, Manduca sexta, has been studied immunocytochemically in whole mount preparations of brain-retrocerebral complexes. The distribution of serotonin-immunoreactive cell bodies, fibers and terminal fields has been analysed during larval and larval-pupal development using a specific rabbit antiserum against serotonin-hemocyanin conjugates. The serotonergic system was conserved from the fourth to the fifth larval stadium, with minimal changes occurring until the onset of pupal development. At this time, alterations in the distribution of serotonin-immunoreactive cells and processes were observed, including the apparent disappearance of some cell bodies and terminals. Nevertheless, the overall appearance of this system in the pupal brain was not significantly different from that in the larva. The larval pattern was characterized by eight bilateral groups of cell bodies which sent thick bridges of fibers across the midline, a feature strikingly similar to the serotonergic system in vertebrate embryos. In addition, three bilateral immunoreactive fields of arborization were observed around and ventral to these cell groups, together with regions of serotonin immunoreactivity in the medial and lateral protocerebral lobes. The central body, larval antennal centers, larval accessory lobes, and the tritocerebrum were also immunoreactive. Fibrous networks of serotonergic processes were usually observed around nerves emanating from the brain, including the connectives from the brain to the corpus cardiacum and corpus allatum. Smaller varicosities were observed in the interior of these neurohemal and glandular organs, and a network of 5-HT fibers was occasionally found around the corpus cardiacum and corpus allatum. The possible relationship of serotonin to cerebral neuroendocrine functions during the postembryonic development of M. sexta is discussed.

Animals↗
PubMed1987

Changes in plasma atrial natriuretic peptide--immunoreactivity in patients undergoing coronary artery bypass graft placements.

Plasma atrial natriuretic peptide immunoreactivity (IrANP) was measured before, during, and after cardiopulmonary bypass for coronary artery bypass graft placement. Eight subjects scheduled for elective operation had in the premedicated preoperative state slightly elevated IrANP compared to controls. Neither induction of anesthesia with a high dose narcotic/non-depolarising relaxant/diazepam technique nor cardiopulmonary bypass changed IrANP significantly. Mixed venous and arterial IrANP increased immediately after discontinuing bypass, and remained elevated 1 h later. Because ANPs affect peripheral resistance as well as urinary sodium loss, the post-bypass elevations in these peptides may contribute to cardiovascular and diuretic effects after cardiopulmonary bypass.

Anesthesia↗
PubMed1986

On the role of atrial natriuretic peptide in cardiovascular regulation in the spontaneously hypertensive rat.

Atrial natriuretic peptide ANP(1-23) reduced mean arterial pressure (MAP), cardiac output (CO), central blood volume (CBV) and stroke volume (SV) when given i.v. (100 pmol/min) to spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY). In SHR, total peripheral resistance (TPR) was significantly lowered. The major cause of the fall in blood pressure in WKY was reduction in CO and in SHR reduction in TPR. Acute 20% volume expansion increased plasma immunoreactive ANP (IR-ANP) in WKY as well as in SHR. However, the ANP release in SHR was blunted compared with WKY. After chronic high salt intake, ANP release in SHR was even further reduced in relation to an acute volume load. We conclude that the release of ANP as well as the haemodynamic responses to exogenous ANP is altered in SHR.

Animals↗
PubMed1985

Serotonin turnover and supersensitivity after neonatal 5,7-dihydroxytryptamine.

Adult awake rats which received neonatal pargyline and 5,7-dihydroxytryptamine to severely reduce CNS serotonin terminals and perikarya have a reduced rate of accumulation of brain stem 5-hydroxytryptophan after Ro-44602. The rate of accumulation in the cerebral cortex and spinal cord were near normal when adult, even though serotonin and 5-hydroxyindoleacetic acid were sharply reduced in these regions. The respiratory response to 5-methoxy N,N-dimethyl-tryptamine was much more pronounced in pargyline-5,7-dihydroxytryptamine treated rats than in controls. If supersensitivity in serotonin receptors only develops in areas with decreased transmitter turnover, the site of action of serotonin agonists to depress respiration would seem to reside in the brain stem region. The results also suggest that compensatory changes in turnover do not develop to a similar degree in all CNS areas with altered serotonin content.

5,7-Dihydroxytryptamine↗
PubMed1985

Plasma atrial natriuretic peptide and haemodynamics in conscious normotensive and spontaneously hypertensive rats after acute blood volume expansion.

The atrial natriuretic peptides (ANP) are a family of newly discovered peptides which are released from atrial tissue and have potent diuretic/natriuretic, vasodilating and aldosterone inhibitory properties. Plasma concentration of ANP was measured and related to haemodynamic changes after acute blood volume expansion (10 and 20%) in normotensive Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHR). Acute blood volume expansion resulted in an increase in central (CBV) and peripheral blood volume (PBV), central venous pressure (CVP), stroke volume (SV) and cardiac output (CO), while total peripheral resistance (TPR) and heart rate (HR) were decreased. Mean arterial pressure (MAP) was unchanged. There were larger increases in CBV, CVP and CO in SHR than in WKY rats. In contrast, the increase in PBV and the decrease in HR were more marked in the WKY rats. Basal plasma ANP concentrations were similar in both groups. Blood volume expansion caused a linear increase in plasma ANP in the WKY rats, while the increase in plasma ANP concentration was attenuated in the SHR. It is concluded that acute blood volume expansion is more centralized in the SHR than in the WKY rats. Interestingly, the ANP release in response to blood volume expansion seems to be attenuated in SHR compared with WKY rats, as maximal plasma ANP concentrations were found at 10% volume load.

Animals↗
PubMed1985

Fluid homeostasis and haemodynamics during sodium restriction in hypertensive men.

To investigate the antihypertensive effect of moderate sodium restriction, the sodium intake of 11 male outpatients was reduced by 120 mmol/day for 4-6 weeks. These patients and an untreated control group were slightly obese and had mild untreated hypertension (WHO 1-2). All subjects were examined before and at the end of the experiment. Diastolic blood pressure fell significantly in the diet group in comparison with the control group. Invasive haemodynamic examinations in the diet group showed an unchanged mean cardiac output and a reduction of mean total peripheral resistance. Plasma volume (Evan's Blue) did not change, neither did extracellular volume as calculated from determinations of tritiated water, total body potassium and body mass. During sodium restriction, plasma renin activity and urinary aldosterone excretion significantly increased. Noradrenaline and dopamine excretion in urine showed no significant changes during sodium restriction, neither did the plasma concentrations of atrial natriuretic peptides. The reduction in mean arterial blood pressure was correlated significantly with a decrease in 24-h sodium excretion and an increase in urinary aldosterone excretion. In conclusion, moderate dietary sodium restriction seems to lower blood pressure by diminishing the total peripheral resistance while cardiac output, extracellular and intravascular volumes are maintained.

Body Fluids↗