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Biomedical subjects

M Edwards

Publications and source records attributed to M Edwards.

At least 91 records · Page 5Linked to original sources
PubMed1994

Comparison of cycloplegic and noncycloplegic retinoscopy in Chinese pre-school children.

Twenty-seven Hong Kong Chinese children, aged 3 to 5 1/2 years, were recruited in this study to evaluate the relation between refractive error as measured retinoscopically before and after cycloplegia using cyclopentolate 1%. The noncycloplegic spherical refractive error of these children ranged from -0.75 to +2.50 D and approximately 98% of the Hong Kong pre-school children have a manifest spherical error within this range. The cycloplegic refractive error can be approximated by multiplying the spherical component of the manifest error by 1.45 and adding +0.39 D to the product, while keeping the astigmatic power and axis unchanged. Cyclopentolate 1% requires more time to produce mydriasis and cycloplegia in eyes with heavily pigmented irides; however, its final effect on refractive error is apparently independent of iris pigmentation and depends on the amount of spherical refractive error present.

Accommodation, Ocular↗
PubMed1994

Refraction referral criteria for Hong Kong Chinese preschool children.

The major types of ametropia and visual problems for Hong Kong Chinese and Caucasian children are different. Consequently, the referral criteria developed for Caucasian children may not be applicable to Hong Kong children. Results of our study suggested that the referral criteria for Hong Kong children should be set as hyperopia of > or = +2.0 D, myopia of > or = 1.0 D, astigmatism of > or = 1.0 D and anisometropia of > or = 1.25 D. Sensitivity using only these criteria for abnormal refraction in identifying children with amblyopia, esotropia, exotropia and subnormal vision (< 6/12) was respectively 100%, 84.6%, 45.2% and 95.7%. The overall sensitivity for the identification of visual problems was 86.1% and the overall specificity was 76%. If a cover test or a Hirschberg test was introduced into the screening battery so that all the strabismic cases were identified. the overall sensitivity would increase to 98.6%.

Amblyopia↗
PubMed1994

Workload measurement: A survey of computerized data collection.

The results of a national survey which examined current computer usage and occupational therapist direct entry of Workload Measurement Data is presented. Results indicated an almost equal distribution of departments using computers versus not using computers. A variety of software packages are used for the purposes of collecting workload measurement data, but the majority of departments use customized in-house programmes. The most common method of data entry was a clerk in a central location, however, a number of departments are considering a switch to therapist direct entry. Advantages and disadvantages of both methods were described by survey respondents.

Canada↗
PubMed1993

Heat-shock gene expression and cell cycle changes during mammalian embryonic development.

Synchronized regulation of cell division during gastrulation is essential for the regional proliferation of cells and pattern formation of the early CNS. The neural plate and neuroectoderm cells are a rapidly dividing and differentiating population of cells with a unique and rapid heat-shock response. Heat shock and the heat-shock genes were studied during neural plate development in a whole rat embryo culture system at 9.5-11.5 days. A lethal shock can cause cell death and severe developmental defects to the forebrain and eye during organogenesis. Heat shock can also result in acquired thermotolerance whereby cell progression is delayed at the G1/S and S/G2 boundaries of the cell cycle. This delay in cell cycle progression caused an overall lengthening of the cell cycle time of at least 2 hr. The heat shock genes may therefore function as cell cycle regulators in neuroectoderm induction and differentiation. The kinetics and expression of the hsp genes were examined in neuroectodermal cells by flow cytometry and Northern analysis. The levels of hsp mRNA 27, 71, 73, and 88 were identified following exposure at 42 degrees C (nonlethal), 43 degrees C (lethal) and 42 degrees/43 degrees C (thermotolerant) heat shock. Examination of hsp gene expression in the neural plate showed tight regulation in the cell cycle phases. Hsp 88 expression was enhanced at Go and hsp71 induction at G2 + M of the cell cycle. Cells exposed to a thermotolerant heat shock of 42 degrees C induced hsp71 mRNA expression in all phases of the cell cycle with the mRNA levels of hsp27, 73, and 88 increased but relatively constant. Following a lethal heat shock, dramatic changes in hsp expression were seen especially enhanced hsp71 induction in late S phase. The regulated expression of hsps during the cell cycle at various phases could play a unique and important role in the fate and recovery of neuroectoderm cells during early mammalian embryo development.

Animals↗
PubMed1993

Glutamate uptake from the synaptic cleft does not shape the decay of the non-NMDA component of the synaptic current.

To study the role of glutamate uptake at central glutamatergic synapses, we used the uptake blocker L-transpyrrolidine-2,4-dicarboxylate (PDC). The effects of PDC on the glutamate uptake current in salamander retinal glia indicated that PDC competes with glutamate for transport on the uptake carrier and that 300 microM PDC should significantly reduce the uptake of glutamate during the synaptic current. In isolated rat hippocampal neurons, 300 microM PDC did not affect non-N-methyl-D-aspartate (NMDA) receptor currents, but reduced NMDA receptor currents by 30%. In hippocampal and cerebellar slices, whereas 300 microM PDC reduced the NMDA component of excitatory synaptic currents by 50%, it reduced the non-NMDA component only slightly with no change in its decay time constant. Thus, the decay rate of the non-NMDA component is not set by the rate of glutamate uptake from the synaptic cleft into the presynaptic terminal.

Animals↗
PubMed1993

Asymmetries in the sensitivity to motion in depth: a centripetal bias.

It is reasonable to ask whether observers are more sensitive to the pattern of image motion caused by forward locomotion through the environment than to the pattern caused by backward locomotion. The distribution of sensitivities of cells in MT does show such a bias, although this bias is minimal at small eccentricities. Additionally, both locomotion-induced stimulation and the sensitivities of MT cells suggest greater sensitivity should be obtained in the lower visual field. Previous research on this issue has usually employed frontoparallel motion in patterns presented to one side of the fixation point. Both centrifugal and centripetal biases have been obtained. In this study the stimuli present motion signals that travel radially from (or towards) the fixation point. These stimuli, which produce a strong percept of motion in depth, are an adaptation of the global-dot-motion stimulus employed by Newsome and Pare. With these stimuli we find that sensitivity to motion in depth is greater in the lower visual field than in the upper visual field, and that sensitivity is greater to centripetal motion than to either centrifugal or frontoparallel motion. This centrifugal bias in sensitivity decreases with eccentricity. The last two findings contradict the notion that the bias is produced by the visual experience induced by normal forward locomotion and also that the detection of motion in depth is subserved by MT.

Adult↗
PubMed1993

Expertise in expert systems: knowledge acquisition for biological expert systems.

In this paper it is argued that an expert system requires more than factual knowledge before it can display expertise in a given domain. The additional knowledge consists of the heuristics or 'rules of thumb' used by an expert to manipulate and interpret the factual knowledge. The knowledge acquisition phase of an expert system project involves determining the factual knowledge (which may be obtained from published sources) and the heuristics used by an expert to manipulate that knowledge--these heuristics can only be obtained from an expert. In reviewing existing biological expert systems it is apparent that many contain only the factual knowledge relating to the domain, and lack the heuristics that enable such systems to show expertise. This paper reviews a number of knowledge acquisition techniques which could be used for acquiring heuristic knowledge and discusses when their use is appropriate. The knowledge acquisition techniques discussed are those suitable for the development of small-scale expert systems as these are most likely to be of interest to biologists. The techniques include the use of questionnaires, interview techniques and protocol analysis; particular emphasis is placed on a modification to the 'twenty questions' interview technique which was developed specifically to elicit taxonomic knowledge relating to water mite identification.

Biology↗
PubMed1993

Variation in phenotypic expression of the Opa outer membrane protein and lipooligosaccharide of Neisseria meningitidis serogroup C causing periorbital cellulitis and bacteremia.

Expression of the Opa outer membrane protein varies widely among isolates of Neisseria meningitidis; the clinical significance of this variation is unclear. A sialic-acid acceptor is present in the lipooligosaccharide of some strains of Neisseria and has been shown to render Neisseria gonorrhoeae serum-resistant. We report the case of a patient who had an unusual clinical manifestation of infection due to N. meningitidis serogroup C, periorbital cellulitis with concomitant bacteremia. Clinical isolates from the blood and aspirate of the periorbital cellulitis were identical except for the phenotypic expression of the Opa outer membrane protein in the isolate from the periorbital cellulitis and in the lipooligosaccharide phenotype of the sialic-acid acceptor as defined by monoclonal antibodies. We discuss the laboratory and clinical implications of these findings.

Antigens, Bacterial↗
PubMed1993

Effects of skeletal fixation on craniofacial imaging.

The imaging effects of high-density scatter from different metal compositions of plate and screw fixation systems were assessed in cadaveric craniomaxillofacial skeletons with computed tomographic scanning. Differences in image clarity of three-dimensional reconstructions were observed between titanium, stainless steel, and cobalt-chromium-molybdenum alloy onlay fixation systems, which were not significantly altered with or without an overlying soft-tissue density (facial drape). These differences were reduced in a plaster model, in which the plates were in an intrabony location.

Artifacts↗
PubMed1993

Refractive errors in Hong Kong Chinese pre-school children.

Five hundred and seventy Chinese children aged between 36 and 65 months were recruited for refractive examination. The results show that both the spherical and cylindrical components of the refractive error tend to decrease with increasing age, although the changes were not statistically significant. The results of the present study, together with those of earlier studies carried out on Hong Kong Chinese children of different ages, show a pattern in the change of refractive errors in local children during the first 17 years of life. The combined results show that the average spherical refractive error decreases rapidly in hyperopic power during the 1st and the 6th to the 10th years of life; the astigmatic power decreases rapidly in the 1st year of life and remains thereafter rather constant until the age of 17 years.

Aging↗
PubMed1993

Evaluation of a breastfeeding protocol.

A breastfeeding protocol has been field-tested in three hospitals. A pre- and post-test design was utilized to measure breastfeeding knowledge of health professionals and mothers before and after implementation of a standard breastfeeding protocol. Although results demonstrated a statistically significant increase in knowledge scores for health professionals and mothers, actual change in score was less than two percent and one percent respectively, compared to preintervention scores. Scores of both groups were not high and indicated limited knowledge in the health professional group in particular. Despite the fact that protocol implementation did not significantly alter knowledge scores, it did initiate positive changes in policies and procedures which may continue to influence knowledge and practice of health professionals.

Breast Feeding↗
PubMed1992

Erythroid expression and DNAaseI-hypersensitive sites of the carbonic anhydrase 1 gene.

The carbonic anhydrase 1 gene is expressed in adult human and mouse erythroid cells and colon epithelia from two distinct promoters. We have explored the erythroid promoter for cis-acting sequences involved in transcription using DNAaseI as a probe. Two DNAaseI-hypersensitive sites (DHS-1 and DHS-2) have been identified in the distal erythroid promoter in CA1-expressing erythroleukaemic cells. These sites are present at low levels in K562 cells, which have a foetal/embryonic phenotype and do not express CA1. DHS-1 and DHS-2 are not present in non-erythroid cells, including colon cells, which express CA1 from the proximal colon promoter. DHS-1 and DHS-2 were also generated in an heterologous CA1 gene containing 5 kb of erythroid promoter sequence after transfection into erythroid cells, including K562 cells. These transfection studies showed that both this fragment, and an abbreviated 817 bp promoter fragment which contains only DHS-1, were sufficient to confer erythroid-specific expression to a reporter gene. These promoters were active in cell lines expressing CA1 and in K562 cells. This latter observation implies that a developmental repressor factor is both present in K562 cells and binds to a cis-acting sequence that is absent from the sequence 5 kb upstream of the erythroid transcription start site.

Base Sequence↗
PubMed1992

Neural tube and other developmental anomalies in the guinea pig following maternal hyperthermia during early neural tube development.

Guinea pigs were exposed to hyperthermia for 1 hr once or twice on day 11, 12, 13, or 14 (E11-E14) of pregnancy. The mean rectal temperatures were elevated by 3.4 degrees C-4.0 degrees C. This treatment resulted in a marked elevation of rates of resorption and developmental defects in embryos examined at day E23. The defects observed were those affecting the neural tube (NTD) (exencephaly, encephaloceles, and microphthalmia), kyphosis/scoliosis, branchial arch defects, and pericardial edema. Embryos with NTD and kyphosis/scoliosis have not been found among newborn guinea pigs to date following maternal heat exposure on days E12-E14. It appears that embryos with these defects are filtered out by resorption or abortion by days E30-E35.

Abortion, Spontaneous↗
PubMed1992

Gastroesophageal physiology after stapled gastroesophagostomy in dogs.

A stapled vertical gastroesophagostomy (VGE) has been proposed for benign esophageal stricture. The VGE involves performing an anastomosis using a linear cutting stapler inserted via a gastrotomy (one limb in the esophagus, the other in the proximal fundus). In phase I of the study, a 50-mm VGE was performed in 13 dogs; 7 received an additional fundoplication. Endoscopy with pinch biopsies, esophageal manometry, and 4-hour ambulatory pH recordings were performed in each dog prior to and 1 month after VGE. The only difference between groups postoperatively was a higher lower esophageal sphincter pressure in the group with the added fundoplication. The incidence of histologic esophagitis was low in both groups. In phase II of the study, a VGE was performed in six dogs using a 75-mm linear cutting stapler, accompanied by fundoplication in each dog. These dogs were then followed for 6 months to more completely assess the long-term risk of developing reflux esophagitis. At necropsy, no gross or histologic evidence of esophagitis was found. The performance of a VGE through the lower esophageal sphincter in normal dogs does not result in significant reflux esophagitis. VGE may be an alternative to resection for esophageal stricture.

Anastomosis, Surgical↗