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Biomedical subjects

R Ashton

Publications and source records attributed to R Ashton.

At least 55 records · Page 3Linked to original sources
PubMed1984

Animal assays for anti-psoriatic, retinoid and sun protective agents.

It is possible to evaluate different dermatological therapeutic agents intended for human use in a variety of animal assays. This review will discuss some of these assays, and attempt to correlate animal and human skin responses. Psoriasis is a disease where changes in epidermal proliferation may be an important factor. It is possible to assay potential anti-psoriatic agents by measuring their ability to suppress DNA synthesis in the epidermis of hairless mice. This assay is predictive of the anti-psoriatic effectiveness of numerous agents including a variety of anti-proliferative drugs and anthralin, and has been used to evaluate the potential efficacy of purified coal tar shampoos and body preparations. The activity of the polyamine biosynthesis enzyme ornithine decarboxylase (ODC) is elevated in psoriatic skin, and it is induced in mouse epidermis by tape stripping. Retinoids can inhibit the induction of ODC activity, and this inhibition may be used to evaluate novel synthetic retinoids. Retinoids have beneficial effects on the abnormal keratinization found in various diseases. Rhino mice have multiple keratin-filled epidermal utricles, and the size of these is reduced by retinoid treatment. Observing the changes in the size of the utricles can be utilized to evaluate the effects of retinoids on keratinization. Sunscreen agents are tested on human volunteers by observing their ability to inhibit the erythema induced by exposure to solar-simulated light, to obtain a sun protection factor (SPF). It is possible to utilize the ability of sunscreens to inhibit other actinic-induced changes in the skin using animals. Parameters that may be measured include changes in DNA synthesis and ODC activity in the epidermis following ultraviolet irradiation. Some of these assays correlate well with human SPF determinations.

Adolescent↗
PubMed1981

Motor performance and concurrent cognitive tasks.

Twenty students tapped between two targets while concurrently performing either a verbal or a visuospatial cognitive task. Speed of tapping and consistency revealed right- and left-hand disruption during solving either the con-current verbal or visuospatial task respectively. Accuracy of performance in terms of hitting the targets was not selectively disrupted by the cognitive activity. The results are discussed in terms of an attentional model of lateralization of cerebral function.

Journal Article↗
PubMed1980

Using ECT to study hemispheric specialization for sequential processes.

Two studies are reported, citing the effects of unilateral versus bilateral electroconvulsive shock therapy on the performance of short cognitive tests. In Study 1, seven tets were administered before and after three treatment sessions. The most interesting finding was that performance improved significantly on the Knox Cube Imitation test following right unilateral shock. Study 2 replicated this unexpected finding. These results were interpreted as demonstrating that the left cerebral hemisphere is specialized for the processing of sequential time-dependent information.

Adult↗
PubMed1978

The influence of brain lateralization of function on a manual skill.

The present study considers the predictions of the brain lateralization of function hypothesis for the concurrent-task situation where the subject is required, to perform simultaneously a manual and a cognitive task. The manual task required the subject to successively press two keys with either the right or left hand, this being done concurrently with one of twelve different cognitive tasks. The cognitive tasks varied in terms of their verbal (left hemisphere) and non-verbal (right hemisphere) attributes. The results indicate that, for the concurrent verbal task conditions, only right-hand performance was disrupted while left-hand performance remained unchanged. For the non-verbal conditions both left and right hand performance was disrupted. These findings were interpreted in terms of brain lateralization of cognitive functions and possible hemispheric processes controlling manual performance.

Adult↗
PubMed1978

Agenesis of the corpus callosum: report of two pre-school children and review of the literature.

The results of neuropsychological examinations of two patients with agenesis of the corpus callosum showed low intelligence-test performance, impared visuo-motor co-ordination and impaired bimanual co-ordination. The most striking deficits were observed in Case A, particularly in her inability to identify objects verbally when placed in the non-dominant hand, and in her ability to complete a task with the non-dominant hand without vision, when she was unable to complete the same task with vision. This patient is unusual insofar as she manifests deficits noted in acallosal patients, as well as some noted in split-brain patients but not previously ascribed to acallosal patients.

Agenesis of Corpus Callosum↗
PubMed1977

A method for producing synchronized audio signals.

An examination of the work dealing with dichotic listening reveals that technical problems prevent clear interpretation of the data. One of the most crucial problems is that of achieving simultaneity of output so that dichotic (simultaneous but different) material is introduced into the auditory system. A simple method for achieving such synchrony on stereotape is described together with a method for testing for degree of simultaneity, if possible.

Acoustic Stimulation↗