Search PubMed⌕ Search

Biomedical subjects

A Hughes

Publications and source records attributed to A Hughes.

286 records · Page 16Linked to original sources
PubMedDate not supplied

Processing of scotopic increments and decrements.

Rod and cone photoreceptors send their signals to ON- and OFF-retinal ganglion cells through different pathways in the primate retina. We hypothesized that increments and decrements of light may be processed differently by the rod-bipolar pathway because of the funneling of the rod signal through the rod bipolar cell. We tested this hypothesis using a psychophysical adaptation paradigm, which has provided evidence that photopic increments and decrements of light are processed by ON- and OFF-pathways in the human visual system. We had observers adapt to either a rapid-on or rapid-off sawtooth waveform, under both photopic and scotopic conditions. We then measured detection thresholds for one cycle of a rapid-on or rapid-off sawtooth stimulus. For photopic stimuli, sawtooth adaptation asymmetrically raised thresholds for test stimuli in a manner that depended on the polarity of the adaptation stimulus. For scotopic stimuli, thresholds were raised, but no significant selective adaptation effect was found. By repeating the photopic condition with sawtooth stimuli which had been filtered using an impulse response function derived for the rod system, we demonstrated that the lack of selective adaptation was not a consequence of the sluggish temporal response of the rod-bipolar pathway. We conclude instead that the reduced effectiveness of sawtooth adaptation is due to channeling of rod photoreceptor signals through the rod bipolar cell before reaching ON- and OFF-ganglion cells.

Adult↗
PubMedDate not supplied

Cone contributions to the photopic spectral sensitivity of the zebrafish ERG.

Microspectrophotometry studies show that zebrafish (Danio rerio) possess four cone photopigments. The purpose of this study was to determine the cone contributions to the zebrafish photopic increment threshold spectral-sensitivity function. Electroretinogram (ERG) b-wave responses to monochromatic lights presented on a broadband or chromatic background were obtained. It was found that under the broadband background condition, the zebrafish spectral-sensitivity function showed several peaks that were narrower in sensitivity compared to the cone spectra. The spectral-sensitivity function was modeled with L - M and M - S opponent interactions and nonopponent S- and U-cone mechanisms. Using chromatic adaptation designed to suppress the contribution of the S-cones, a strong U-cone contribution to the spectral-sensitivity function was revealed, and the contributions of the S-cones to the M - S mechanism were reduced. These results show that the b-wave component of the ERG receives input from all four cone types and appears to reflect color opponent mechanisms. Thus, zebrafish may possess the fundamental properties necessary for color vision.

Adaptation, Physiological↗
PubMedDate not supplied

Assessing the comprehension and production of language in young children: an account of the Reynell Developmental Language Scales III.

The Reynell Developmental Language Scales III have been designed to test the language abilities of children from 18 months to 7 years. They have been standardized on a large, representative sample of children in the United Kingdom and thereby provide a robust measure of language achievement. These Scales provide clinicians with the means of comparing the performance of children who have been referred for therapy, or who are in therapy, with the performance of a large group of normally developing children. The Scales reflect the developmental progression of normal child language in the early years, focusing on key features of child language acquisition at different stages as well as on features which are known to distinguish language impaired-children from language-normal children. While not claiming that the tests are fully comprehensive, the authors maintain that they afford the clinician with a means of looking at components of language while also gaining some insights into the child's ability to integrate vocabulary and grammar. It is recognized that no test can fully assess every aspect of language; essentially a test must be practical in terms of design and, for screening purposes, sufficiently comprehensive to be used with a large section of children referred. In addition to fulfilling these criteria, the Scales have been designed to provide some diagnostic indicators of areas of difficulty. The aims of the original Scales were to provide a measure of verbal ability that could be compared with mental age, and to provide separate scores for production and comprehension. These aims have also been realized in the new version. Additionally a test has been provided that is consonant with information gained from the intensive research in the field of child language that has taken place since the original Scales were devised. The Scales can reveal information about a child's language abilities not readily available from observation and serve a useful function in both identifying disorder and evaluating therapy. Clinicians are increasingly being asked to demonstrate effectiveness of therapy but are hampered by inappropriate outcome measures (Law 1997). It is hoped that the RDLS III provides a test that is valid and reliable and one that can contribute to both the characterization of speech and language disorders and the measurement of treatment efficacy.

Child↗
PubMedDate not supplied

Homocysteine and cognitive decline in healthy elderly.

Serum homocysteine is increased, and correlates inversely with cognitive scores, in Alzheimer's disease (AD), vascular dementia and "age-associated memory impairment". Elevated levels might signal accelerated cognitive decline, although this remains to be established. We therefore repeated Mini-Mental State Examinations, together with additional ADAS-Cog assessments, in 32 healthy elderly individuals to determine whether prior homocysteine levels predicted cognitive changes over a 5-year period. Homocysteine predicted follow-up cognitive scores and rate of decline in cognitive performance independently of age, sex, education, renal function, vitamin B status, smoking and hypertension (p < 0.001). Homocysteine predicted word recall (p = 0.01), orientation (p = 0.02) and constructional praxis scores (p < 0.0001). One subject, with the second highest initial homocysteine, had developed probable AD at follow-up. Fasting total serum homocysteine appears to be an independent predictor of cognitive decline in healthy elderly and exerts a maximal effect on spatial copying skills.

Aged↗
PubMedDate not supplied

Nutritional, respiratory, and psychological effects of recombinant human growth hormone in patients undergoing abdominal aortic aneurysm repair.

BACKGROUND: Recombinant human growth hormone (rhGH) has been shown to have powerful anabolic effects and to reduce or even prevent nitrogen catabolism in stressed patients. The effects of rhGH on functional parameters are less clearly defined. The aim of this study was to assess the effects of perioperative rhGH on nutritional markers, skeletal muscle function, and psychological well-being in patients undergoing infrarenal, abdominal aortic aneurysm repair. METHODS: Thirty-three patients undergoing elective infrarenal abdominal aortic aneurysm repair were randomized to one of three groups: (1) control (n = 12): placebo for 6 days before and after surgery; (2) preop + postop (n = 10): rhGH (Genotropin; Pharmacia Ltd, Uppsala, Sweden) 0.3 IU/kg/d for 6 days before and after surgery; and (3) postop (n = 11): placebo for 6 days before and rhGH 0.3 IU/kg/d for 6 days after surgery. Patients were assessed on days -7 and -1 before surgery and days 7, 14, and 60 after surgery. RESULTS: Administration of rhGH resulted in increased insulin-like growth factor 1 levels, the increase being significantly more marked in the group given rhGH preoperatively. Preoperative and postoperative rhGH reduced the postoperative decrease in both serum transferrin and grip strength at day 7 by 30% and 70%, respectively. Postoperative respiratory function and arterial oxygenation also were improved, with significant differences in arterial oxygenation between rhGH-treated and untreated groups. No difference in mood was seen between groups after surgery, nor was there any difference between subjective assessment of fatigue scores between groups. CONCLUSIONS: This pilot study indicates that rhGH administered preoperatively has beneficial effects on skeletal muscle and respiratory function and may be more useful than postoperative rhGH administration alone.

Aged↗
PubMedDate not supplied

L-dopa-resistant parkinsonism syndrome following cerebral radiation therapy for neoplasm.

A bradykinetic form of parkinsonism, unresponsive to levo-dopa therapy developed in four patients two to eight weeks after completion of external beam irradiation (39.2 Gy to 59.4 Gy) of their intracranial neoplasm. In the absence of other causative factors, we relate the movement disorder to radiation-induced changes within the basal ganglia. At post-mortem examination one patient had putamenal gliosis and thickened vessels with loss of nigral neurons.

Aged↗
PubMedDate not supplied

Life with a stoma.

Explore the source record for details and available documents.

Adaptation, Psychological↗
PubMedDate not supplied

Assessment and treatment of a suicidal patient.

This case study describes the nursing treatment of a suicidal patient in an interim secure unit. The authors describe the process of in-depth assessment using the clinic's own global nursing assessment schedule, incorporating a number of rating scales. They explain the design of a single-case methodology which enabled them to assess the effectiveness of different treatment interventions. The study describes how the consistent application of care plans and the use of cognitive counselling were more effective than psychotropic medication in reducing the patient's depression and suicidal urges. The authors demonstrate the importance of nursing assessment and highlight the need to evaluate response to treatment. They emphasise the way in which mental nursing has developed from a primarily caring role to that of a clinical specialty. This nursing care study was a runner-up in the NTS/Special Hospitals Service Authority forensic nursing study competition.

Adult↗