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Biomedical subjects

M Edwards

Publications and source records attributed to M Edwards.

At least 109 records · Page 6Linked to original sources
PubMed1996

Calibration and validity of an eccentric photorefractor.

A new graphical calibration method was developed to convert the photorefractive reflex into refractive error. With this graphical method, the refractive error can be obtained for pupil sizes and for photorefractive reflex sizes which have not been precalibrated. In the conventional method, the refractive error associated with non-precalibrated pupil and reflex sizes is obtained by interpolating between neighbouring precalibrated points. This introduces error because the relationship between refractive error and pupil and reflex size is not linear. Three hundred and sixty-one children aged between 36 and 65 months were clinically examined and photorefracted. The refractive error obtained using retinoscopy and the eccentric photorefractor agreed well with each other, although the photorefractor tended to under-estimate refractive error. Using the referral criteria developed by Chan, O.Y.C. and Edwards, L.M. (Refraction referral criteria for Hong Kong Chinese Children. Ophthal. Physiol. Opt. 14, 259-256, 1994), the photorefractor had a sensitivity of 74.6% and a specificity of 96.4%. All the under-referred cases were borderline, having just failed the referral criteria. All the cases with hyperopia of > + 2.0 D, astigmatism of > 1.25 D and visual acuity of worse than 6/18 were identified.

Calibration↗
PubMed1996

Obesity in primary care patients in Kelantan, Malaysia: prevalence, and patients' knowledge and attitudes.

This study measured the body mass index (BMI), and assessed attitudes and knowledge about obesity, of 197 male and 217 female patients aged 20-59 years attending the primary care clinic of the university hospital in Kelantan, Malaysia. There was no significant difference between the mean BMI of males (23.7) and females (24.2). In the overweight group (BMI 25-29.9) were 60 men (30%) and 66 women (30%). In the obese group (BMI 30 and above) were 12 men (6%) and 22 women (10%). Both diabetes mellitus and hypertension were associated with significantly higher BMI's. Knowledge about obesity was lacking. Sixty-three (15%) failed to recognize that obesity is bad for health. When asked the causes of obesity, 88 (21%) failed to mention either diet or lack of exercise. "Being happy" was suggested as a cause by 32 (8%). When asked if certain foods would cause obesity if eaten in excess, 45 (11%) said "No" for fatty foods, and 164 (40%) said "No" for sweet foods. Concerning appearance, 30 (15%) men regarded an obese man as normal or even handsome, while 49 (23%) women regarded an obese woman as normal or beautiful. Obesity is common among our adult patients, and is associated with some of their common health problems. However, a substantial minority do not regard obesity as unhealthy, do not relate it to diet or lack of exercise, do not recognize important groups of fattening foods, and do not regard obesity as unattractive.

Adult↗
PubMed1995

Molecular analysis at the NF1 locus in astrocytic brain tumors.

BACKGROUND: Patients with neurofibromatosis type 1 (NF1) are at increased risk for developing malignant neural crest tumors and juvenile myeloid leukemia. Although the normal allele of the NF1 tumor-suppressor gene is frequently deleted in some of the malignant tumors that arise in patients with NF1, the role of NF1 alterations in the sporadic forms of these cancers is unclear. METHODS: A series of intragenic sequence polymorphisms was used to investigate lymphocyte and tumor DNA samples from 22 adults with high grade malignant gliomas for loss of heterozygosity (LOH) at NF1. In addition, an assay based on the polymerase chain reaction was used to screen these tumors for point mutations at codon 1423. RESULTS: One recurrent anaplastic astrocytoma showed LOH within NF1 but not with a flanking marker located near the gene. Of 21 informative tumors, none showed point mutations affecting codon 1423 of NF1. CONCLUSION: These data suggest that LOH at NF1 is uncommon in sporadic high grade astrocytoma, and codon 1423 is not a "hot spot" for activating point mutations in these tumors.

Adult↗
PubMed1995

Constitutional p53 mutations associated with brain tumors in young adults.

Identification of patients at risk for developing brain tumors is important for the development of preventative strategies. Because individuals with germline p53 mutations may be at increased risk, we examined DNA from brain tumor-derived cell lines and malignant and normal nervous system tissue for p53 gene mutations using the single strand conformation polymorphism assay and direct sequencing of polymerase chain reaction-amplified DNA. We found mutations in the p53 gene in eight of 22 adult glioma tissue specimens and germline mutations in two of these eight patients. In contrast, mutation of the p53 gene was not detectable in either 16 glial tumors occurring in children, glial tumor tissue from three unrelated glioblastoma multiforme patients with a familial history of cancer, or in benign meningiomas. One constitutional p53 mutation was a G to T transversion at codon 154, and the second was a C to T transition at codon 256. Both patients with germline mutations developed glioblastoma multiforme before the age of 31, although the median age for glioma patients is above 50. These findings suggest that p53 germline mutations may identify a subset of young adults predisposed to the development of high-grade astrocytic tumors.

Adult↗
PubMed1995

Global motion perception: no interaction between the first- and second-order motion pathways.

The experiments reported here address the issue of whether the pathways which extract motion from first-order and second-order spatial patterns remain separate or whether they combine at some higher level in the motion system to form a single pathway. The question is addressed by investigating the interaction of first-order and second-order stimuli in the processing of a global-motion stimulus [a variant of the task introduced by Newsome & Pare (Journal of Neuroscience, 8, 2201-2211, (1988)]. Two experimental procedures were used. The first consisted of determining the effect of the addition of dots of one type (e.g. first order) undergoing purely random motion on the ability to extract the global-motion signal carried by dots of the other type (e.g. second order). The second experimental procedure consisted of determining the effect of maintaining a coherent-motion signal in one type of dot, moving in the opposite direction to the global-motion direction, on the ability to extract the global-motion signal carried by dots of the other type. The dots were matched for their effectiveness in producing a global motion percept and the results for both procedures were the same. First-order dots impaired the ability to extract second-order global-motion, and second-order dots had no effect on first-order global-motion extraction. It is argued that the sensitivity of the second-order global-motion system to the first-order dots is due to the ability of the second-order local-motion detectors to detect these dots. The present results are thus interpreted as indicating that the first-order and second-order motion pathways remain separate up to and including the level in the motion system at which global-motion signals are extracted.

Humans↗
PubMed1995

The function of visual search and memory in sequential looking tasks.

UNLABELLED: Eye and head movements were recorded as unrestrained subjects tapped or only looked at nearby targets. Scanning patterns were the same in both tasks: subjects looked at each target before tapping it; visual search had similar speeds and gaze-shift accuracies. Looking, however, took longer and, unlike tapping, benefitted little from practice. Looking speeded up more than tapping when memory load was reduced: memory was more efficient during tapping. CONCLUSION: eye movements made when only looking are different from those made when tapping. Visual search functions as a separate process, incorporated into both tasks: it can be used to improve performance when memory load is heavy.

Eye Movements↗
PubMed1995

CHILD syndrome: analysis of abnormal keratinization and ultrastructure.

A new patient with CHILD syndrome (congenital hemidysplasia, ichthyosiform erythroderma, and limb defects), the thirtieth in the literature, was observed for over three years. Initially, the right-sided lesion spared the breast area. At 10 months of age the trunk lesion extended to cover the entire area of the right chest. At age 20 months the patient developed linear, bandlike, keratotic, brown-black lesions on her left thigh that subsided within six weeks, leaving a slight hyperpigmentation. This patient was studied by routine histologic methods as well as with markers of keratinization and electron microscopy. In hematoxylin and eosinstained sections, parakeratosis and orthokeratosis alternated. In some parakeratotic areas, large granular cells, and in others, ghost granular cells, were present. The latter showed basophilic cytoplasm, and palestaining or vacuolated nucleus and were seen either above the normal granular layer or without it. Although regional variations existed, basal cell-type keratins as recognized by AE1 continued to be expressed in suprabasal layers. Filaggrin- and involucrin-positive layers were expanded, particularly the latter, down to the lower prickle cell layer. Ultrastructurally, numerous lamellar or membranous structures were found in upper layers of the epidermis, both intracellulary and intercellularly. Normal cementsomes coexisted with these abnormal lamellar structures, and it was thought that the latter represent modified cementsomes because the discharge of those from the cell periphery was often detected.

Arm↗
PubMed1995

Evaluation of the cost effectiveness of therapist computerized entry of occupational therapy workload measurement data.

A study was conducted to examine the cost effectiveness of two methods of managing occupational therapy workload measurement data. The computer entry of statistical data by a clerk in a central location was compared to multi-site direct input of data by therapists. Cost effectiveness, efficiency and accuracy of each method were the primary outcomes. Ease of coordination and level of computer comfort were secondary outcomes. It was clear that clerk entry of data was more cost effective, efficient and accurate than therapist entry of data. The monitoring of monthly data entry was best facilitated by clerk entry. Therapists had a positive attitude towards direct entry but were unable to approximate the speed and accuracy of the data entry clerk. Therapists' comfort with computers increased slightly during the study. Since the prime purpose of the study was to examine cost effectiveness, it was concluded that clerk entry of workload data is the best use of resources.

Canada↗
PubMed1995

The levels of reliability and validity of the Waterlow pressure sore risk calculator.

The Waterlow pressure sore risk calculator is widely used in the UK but has not been found to display high levels of reliability and validity. Few evaluative studies have been carried out in the community. This study aimed to evaluate the Waterlow score when used by district nurses to assess elderly patients. The score was not found to display high levels of reliability, and suffered from a lack of operational definitions within risk categories. In line with other studies, it was found to over-predict pressure sore formation. The findings of this small study suggest that the Waterlow score should not be used as the sole basis for decisions concerning the use of pressure sore prevention resources. High Waterlow scores may be a predictor of ill health in elderly people and this hypothesis requires further examination. The findings also indicate that clarification of the role of risk calculators in general is needed, as many mediating factors appear to affect the ability of a tool to predict pressure sore formation.

Aged↗
PubMed1994

Competitive binding of vascular cell adhesion molecule-1 and the HepII/IIICS domain of fibronectin to the integrin alpha 4 beta 1.

The integrin receptor alpha 4 beta 1 binds to two different ligands, the extracellular matrix glycoprotein fibronectin and the endothelial cell surface protein vascular cell adhesion molecule-1 (VCAM-1). Using probes derived from each ligand and a variety of cell adhesion and ligand-receptor binding assays, we have investigated the relationship between the mechanisms of fibronectin and VCAM-1 interaction with alpha 4 beta 1. CS1 peptide, which represents the dominant active site from the HepII/IIICS recognition domain in fibronectin, was found to inhibit VCAM-1-dependent adhesion in three different assays: MOLT-4 T lymphoblastic leukaemia cell attachment to immobilized recombinant soluble VCAM-1 (rsVCAM-1), MOLT-4 cell attachment to monolayers of VCAM-1-transfected COS-1 cells, and A375-SM melanoma cell spreading on immobilized rs VCAM-1. Half-maximal inhibition required CS1 concentrations of 1.7-3.0 mg/ml, some 3-7-fold higher than that needed to autoinhibit adhesion to CS1-IgG conjugate. Using a more sensitive solid-phase receptor-ligand binding assay, CS1 was found to be a potent inhibitor of the binding of rsVCAM-1 to alpha 4 beta 1 (half-maximal inhibition at 13 micrograms/ml). In agreement with cell-based assays, severalfold lower concentrations of CS1 were required to inhibit binding of recombinant HepII/IIICS region of fibronectin (half-maximal inhibition at 3 micrograms/ml). VCAM-1-alpha 4 beta 1 binding was blocked not only by CS1 peptide but also by the recombinant HepII/IIICS region of fibronectin. Kinetic analysis of CS1 inhibition of VCAM-1 binding revealed that it was directly competitive in nature, indicating that VCAM-1 and fibronectin recognize either identical or spatially overlapping binding sites on alpha 4 beta 1. The implications of these results for the future design of VCAM-1 antagonists are discussed.

Amino Acid Sequence↗
PubMed1994

Significant improvement to the catalytic properties of aspartate aminotransferase: role of hydrophobic and charged residues in the substrate binding pocket.

The substrate specificity of tyrosine aminotransferase (eTAT) from Escherichia coli has been tested by transferring the critically different residues Leu39, Glu141, and Arg293 into equivalent positions of aspartate aminotransferase (eAAT). These residues are not directly involved in the catalytic process. The single mutant eAAT V39L possesses greater values of kcat/KM not only for tyrosine but also for aspartate and glutamate. In contrast, the double mutant eAAT P141E,A293R and also the triple mutant eAAT V39L,P141E,A293R exhibit smaller changes of kcat/KM. The converse mutants of tyrosine aminotransferase, in which critical residues of eAAT (Val39) and of mitochondrial AAT (Ala39, Val37) were transferred into equivalent positions of eTAT, exhibited generally decreased values of kcat/KM for both dicarboxylic and aromatic substrates. On the basis of the known structures of eAAT and eAAT V39L as well as of a refined model of eTAT, these results indicate that the different substrate specificities of eAAT and eTAT are due to multiple side chain differences and minor rearrangements of the backbone. The generally improved catalytic efficiency of the mutant eAAT V39L appears to be due to an indirect effect, namely, the facilitated closure of the active site upon substrate binding.

Amino Acid Sequence↗
PubMed1994

Prolonged intragraft urokinase with a new infusion wire: improved short-term results.

Patients with aged saphenous vein grafts and recurrent symptoms of angina are being seen with increasing frequency [Bourassa: J Am Coll Cardiol 17:1081-1083, 1991]. The treatment of these patients remains a dilemma. Direct balloon angioplasty is frequently complicated by distal embolization and early restenosis [Aureran and Gruentzig: Am J Cardiol 53:953-954, 1984]. There is evidence that thrombus plays a significant role in this occlusive process [Hartmann et al.: J Am Coll Cardiol 18:1517-1523, 1991]. Prolonged intragraft urokinase infusion with a new multiside hole infusion catheter debulks thrombus and permits balloon angioplasty without the usual complications.

Angina Pectoris↗
PubMed1994

Growth hormone-releasing activity of hexarelin in humans. A dose-response study.

Hexarelin is a new hexapeptide (His-D-2-methyl-Trp-Ala-Trp-D-Phe-Lys-NH2) that stimulates the release of growth hormone both in vitro and in vivo. In this double-blind, placebo-controlled, rising-dose study we evaluated the growth hormone releasing activity of hexarelin in healthy human subjects. Twelve adult male volunteers received single intravenous boluses of 0.5, 1 and 2.micrograms.kg-1 hexarelin as well as placebo. For safety, drug doses were given in a rising-dose fashion with placebo randomly inserted into the sequence. Plasma growth hormone concentrations increased dose-dependently after the injection of the peptide, peaking at about 30 min and then decreasing to baseline values within 240 min with a half-life of about 55 min. The mean peak plasma growth hormone concentrations (Cmax) were 3.9, 26.9, 52.3, 55.0 ng.ml-1 after 0, 0.5, 1 and 2 micrograms.kg-1, respectively. The corresponding areas under the curve of growth hormone plasma levels from drug injection to 180 min (AUC0-180) were 0.135, 1.412, 2.918 and 3.695 micrograms.min.ml-1. The theoretical maximum response (Emax) and the dose that produces half of the maximum response (ED50) were estimated using logistic regression. The calculated ED50 values were 0.50 and 0.64 microgram.kg-1 for Cmax and AUC0-180, respectively. The corresponding Emaxs were 55.1 ng.ml-1 and 3936 ng.min.ml-1, thus indicating that the effect after the 2 micrograms.kg-1 dose is very close to the maximal response.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗