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Biomedical subjects

S Paxton

Publications and source records attributed to S Paxton.

6 recordsLinked to original sources
PubMed1993

Penetration of an aerosol, produced by film atomization, through the carinal bifurcation.

We have measured the size of spots produced by atomization of simulated biofilm particles from a tracheal tube. Draughtsman's ink was atomized from 8.5-mm i.d. Portex tracheal tubes, using an airflow of 1 litre s-1, and trapped on vertical acetate sheets. The spots produced by these particles were compared with the spot size after entrainment and dissemination from an ink-lined tracheal tube through a bifurcating tracheobronchial tube towards a glass plate. Spot dimensions were measured by computer-assisted image analysis of a video image. The smallest particles observed on the acetate sheets were 4-17 microns in size. In the bifurcating tube experiment, large particles were deposited around the carinal bifurcation, but smaller particles traversed the bend. The smallest spot size observed (7 microns minimum; 17 microns median) corresponds to particles small enough to penetrate further into the lower respiratory tract. Travel via a tube similar to the carinal bifurcation suggests that fragments of biofilm entrained in the tracheal tube could be propelled deeper into the respiratory tract during the inspiratory phase of mechanical ventilation.

Aerosols↗
PubMed1989

Secondary osteoporosis and the microanatomy of trabecular bone.

Osteoporosis is a generic term implying a decrease in bone mass which increases the risk of fracture. It is now becoming appreciated that decreases in bone mass alone are not the sole factor in increasing the risk of osteoporotic fracture, and that other skeletal and extraskeletal factors also contribute significantly to this risk. Extraskeletal factors include the propensity to falls and responses to falls, whereas additional skeletal factors include bone turnover, the ability to repair fatigue damage and the tertiary structure of bone, particularly trabecular tissue. There are a large number of causes of secondary osteoporosis each with their own specific pathophysiological mechanisms. It is therefore not surprising that they have heterogeneous effects on the skeleton. A good example is provided in corticosteroid osteoporosis which is characterised by thinning of trabecular elements, whereas postmenopausal osteoporosis is characterised less by thinning and more by destruction of trabecular elements which derange trabecular continuity. A variety of techniques are now being developed to address the heterogeneity of trabecular osteoporosis. These include direct histomorphometric techniques to assess trabecular continuity, and indirect techniques such as the attenuation of ultrasound. These different pathophysiological mechanisms in osteoporosis have important therapeutic implications, particularly with agents that affect bone remodelling. Since bone remodelling is a surface-based phenomenon, if trabecular surfaces are destroyed, the augmentation of bone mass may thicken remnant structures without restoring trabecular continuity. Since most treatments for osteoporosis affect bone remodelling they are likely to have a greater effect in restoring structural integrity of the skeleton in corticosteroid than in postmenopausal osteoporosis.

Adrenal Cortex Hormones↗
PubMed1988

Physical exercise and sleep: the effect of the age and sex of the subjects and type of exercise.

Exercise has generally been held to result in an increase in slow wave sleep (SWS) and sleep duration. We report the results of three experiments which assessed the effects of exercise on the sleep of young fit women as compared to young fit men; fit older men (aged 41 years) as compared to fit younger men (aged 22 years); and the effects of power exercise on the sleep of a group of trained power lifters. In each experiment physically fit subjects had their sleep assessed following both late afternoon exercise and no exercise conditions. In none of the experiments did exercise result in an increase in SWS or sleep duration. Instead the tendency was for exercise to affect sleep adversely.

Adult↗
PubMed1982

Contrast sensitivity functions and specific reading disability.

Contrast sensitivity functions for normal and specifically disabled readers were measured in two experiments. Each study showed that specifically disabled readers and controls differ in the pattern of relative sensitivity across spatial frequencies. Both studies provide evidence of differences between normal and disabled readers on measures of visual mechanisms fundamental to the reading process.

Child↗