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Biomedical subjects

B Brown

Publications and source records attributed to B Brown.

At least 127 records · Page 7Linked to original sources
PubMed1996

Contrast and luminance as parameters defining the output of the VERIS topographical ERG.

The Visual Evoked Response Imaging System (VERIS I) topographical electroretinogram system (EDI Associates, San Francisco, CA) allows measurement of the response of large numbers of retinal areas simultaneously. This paper examines ERG responses derived with the VERIS system to changes in target contrast and to local reductions in luminance. There is a linear reduction of response with reductions of target contrast. Neutral density filters were placed over part of the display, to mimic the localised reductions in response which occur in glaucoma, age-related maculopathy or diabetic retinopathy. There is a definite reduction in response seen with a 0.4 ND filter, indicating that the system should have similar sensitivity in detection of retinal lesions to the commonly used visual field analysis systems.

Adult↗
PubMed1996

Spatial interference with vertical pistol sight alignment.

When competition pistol shooters aim, they perform four basic visual alignment tasks. With optimal stimuli such tasks can be performed with exquisite sensitivity. However, pistol sights and the target may not constitute the optimal stimuli, and this may impose limits on how well shooters perform. By simulating pistol sights and targets on a computer monitor, we investigated how the vernier task of aligning the top edges of the front and rear pistol sights was affected by the proximity of the target aiming mark. Alignment random error in this task, an analogous measure to vernier acuity, was unaffected by the proximity of the aiming mark; however, alignment systematic error did change significantly as the proximity of the aiming mark changed. This effect was unlikely to significantly change pistol shooting performance as shooters can adjust their sights to compensate for systematic errors. Likewise, compared to the vertical spread of shots on the pistol target, alignment random error was extremely small (only 10 s arc), which implies that other sources of variation limit pistol shooting performance.

Adult↗
PubMed1996

A new stereotest: the double two rod test.

A new stereoacuity test, the double two rod test, uses a two-alternative forced-choice (2AFC) paradigm. The subject's task is to state which pair of rods, the left or the right, contains depth information. The test gives repeatable results; comparison between the depth threshold measured binocularly and monocularly suggests that monocular cues, if present, provide only poor depth information, compared to the depth information arising from binocular disparity. As part of an investigation of stereoacuity and ageing, we tested stereoacuity as a function of viewing time and the number of comparisons made between the two pairs of rods. Stereoacuity was significantly reduced for viewing times less than 3 s while longer viewing times did not improve stereoacuity. The number of comparisons made between the two pairs of rods had no effect on stereoacuity.

Adult↗
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

IOP in myopic children: the relationship between increases in IOP and the development of myopia.

Intraocular pressure (IOP) was measured at yearly intervals, from age 7 to 9 years, in 106 Chinese children. The sample had been selected from newborn children for participation in a growth and nutrition study, and all children remaining in this study took part in the myopia study. As part of an ongoing prospective study to examine factors which may be associated with the development of myopia, IOP was compared according to whether the subjects had become myopic or remained non-myopic during the time-frame of the study. During the course of the study 13 children became myopic. There was no difference in the IOP of the incident compared with control groups at age 7 years. The IOP of the incident group was higher following onset of myopia than it was prior to onset whereas there was no difference in the IOP of the control groups over the same period. A high IOP therefore follows the onset of myopia and cannot cause myopia. It is still unknown whether or how myopia causes a high IOP.

Analysis of Variance↗
PubMed1996

Visual and vestibular components of motion sickness.

BACKGROUND: The relative importance of visual and vestibular information in the etiology of motion sickness (MS) is not well understood, but these factors can be manipulated by inducing Coriolis and pseudo-Coriolis effects in experimental subjects. HYPOTHESIS: We hypothesized that visual and vestibular information are equivalent in producing MS. The experiments reported here aim, in part, to examine the relative influence of Coriolis and pseudo-Coriolis effects in inducing MS. METHODS: We induced MS symptoms by combinations of whole body rotation and tilt, and environment rotation and tilt, in 22 volunteer subjects. Subjects participated in all of the experiments with at least 2 d between each experiment to dissipate after-effects. We recorded MS signs and symptoms when only visual stimulation was applied, when only vestibular stimulation was applied, and when both visual and vestibular stimulation were applied under specific conditions of whole body and environmental tilt. RESULTS: Visual stimuli produced more symptoms of MS than vestibular stimuli when only visual or vestibular stimuli were used (ANOVA F = 7.94, df = 1, 21 p = 0.01), but there was no significant difference in MS production when combined visual and vestibular stimulation were used to produce the Coriolis effect or pseudo-Coriolis effect (ANOVA: F = 0.40, df = 1, 21 p = 0.53). This was further confirmed by examination of the order in which the symptoms occurred and the lack of a correlation between previous experience and visually induced MS. CONCLUSIONS: Visual information is more important than vestibular input in causing MS when these stimuli are presented in isolation. In conditions where both visual and vestibular information are present, cross-coupling appears to occur between the pseudo-Coriolis effect and the Coriolis effect, as these two conditions are not significantly different in producing MS symptoms.

Adolescent↗
PubMed1995

Genotypic variation in coxsackievirus B5 isolates from three different outbreaks in the United States.

Genomic sequences in VP1/2A and 5'-non-coding region of 10 isolates of Coxsackievirus B5 from three outbreaks were compared with published sequences of another Coxsackievirus B5, swine vesicular disease virus, Coxsackievirus B1, Coxsackievirus B3, and Coxsackievirus B4. Isolates of Coxsackievirus B5 from the same outbreak showed close relations, not exceeding 7.2% in nucleotide differences. Differences were greater between isolates from different outbreaks, varying between 8.4 and 16%. We have also shown that Coxsackie B5 viruses from an outbreak in 1967 are more similar to viruses from an outbreak in 1983 than to the viruses isolated from an intervening outbreak in 1972. The sequence comparison of Coxsackievirus B5 isolates with other Coxsackie B viruses and swine vesicular study, cDNA synthesis, polymerase chain reaction, and sequencing, are suitable for rapid Coxsackie B virus detection and identification of genotypic relations between viruses originating from different outbreaks.

Animals↗
PubMed1995

Exploring the lived experiences of psychiatric nursing students through self-reflective journals.

This study explores the use of journals to identify important issues facing nursing students when learning in a psychiatric setting. During a 13-week psychiatric clinical experience, 18 third-year students kept journals describing the most significant event that occurred each week, reflecting on the impact and accompanying attitudes of that event. Throughout the clinical experience, the nursing faculty read the students' journals and provided written feedback on a bi-weekly basis. Major themes that students wrote about in their journals were identified. These included: meaningful learning, issues of the novice, relationships, control, self-reflection, and identification with clients. Keeping a journal provided the students with an opportunity to become more self-reflective in their practice. The issues identified by students in their journals may assist nurse educators to anticipate the learning needs of their students in psychiatry.

Female↗
PubMed1995

Differences in visual acuity between the eyes: determination of normal limits in a clinical population.

We determined the difference in visual acuity between the right and left eyes of patients and also determined the maximal level of acuity expected in a group of visually normal individuals. Visual acuity was measured in the right and left eyes of 72 subjects aged from 16 to 67 years using Bailey-Lovie type charts. The chart was read until fewer than three letters were read on a line and acuities were based on each letter correct contributing -0.02 to the overall score. For 12 of these subjects, visual acuity was measured a further four times. Average visual acuities for right and left eyes were -0.137 and -0.126log MAR, respectively. The signed visual acuity difference was normally distributed and had a standard deviation of 0.050log MAR. The mean visual acuity difference for the 12 subjects for whom the measures were repeated was 0.033log MAR (SD of the signed visual acuity difference: 0.049log MAR). We conclude that if a patient has a difference in visual acuity between the two eyes of more than 5 letters on a Bailey-Lovie style chart, further investigation is indicated.

Adolescent↗
PubMed1995

Ethanolamine sclerotherapy of a renal cyst.

We report the effective use of 5% ethanolamine oleate to sclerose a large simple renal cyst. The comparative advantages of ethanolamine versus other sclerosants are discussed in terms of adverse effects, availability and convenience. Guidelines to optimize sclerotherapy with ethanolamine are provided.

Aged↗
PubMed1995

Production of immunoglobulins by human sIgD+ and sIgD- human blood B lymphocytes in response to stimulation with activated T cells and agonistic antibodies; effect of IL-10, IL-2 and mode of activation of T cells.

Production of IgM, IgG and IgA was induced from human blood B lymphocytes by culturing with a CD40 MoAb and IL-2 for 9 days. Replacement of IL-2 by IL-10 markedly enhanced production of all three isotypes. High levels of immunoglobulin production also occurred when activated irradiated autologous T cells replaced the CD40 MoAb, and when IL-10 replaced IL-2 in these cultures a spectacular increase in IgG production occurred. The effectiveness of the T cell stimulus depended on the mode of purification of the T cells and the nature of the stimulant used to activate them. Differences in the kinetics and level of expression of CD40L on the various T cell preparations were observed, but did not account for variations in immunoglobulin-inducing efficiency. Immunoglobulin production from sIgD+ and sIgD- B cells was investigated. IgG and IgA were found in sIgD+ cultures, indicating that some isotype switching had occurred, but the major part of the IgG and IgA secreted was from cells already committed to these isotypes. Anti-IgD or anti-IgM MoAbs enhanced the proliferation of B cells induced by anti-CD40 antibody, but immunoglobulin production was not enhanced. Factors affecting the balance of proliferation and differentiation are discussed.

Animals↗
PubMed1995

Linguistic entrapment: medico-nursing biographies as fictions.

This paper argues that in their trainings health professionals are encouraged to use language naively as if it were a transparent medium of scientific communication. We contend that language use, particularly in the field of mental health care, should be studied in terms of its social functions and attention should be paid to the inevitably constructive nature of language in patients' records, in order that a 'fictional distance' opens up between patients and their records. Recent developments in literary theory and narrative analysis can be deployed as theoretical frameworks to understand this process, and we suggest that more attention to the use of language should be included in the educational programmes for health care professionals to counteract the risk of 'linguistic entrapment' or 'incarceration'.

Linguistics↗
PubMed1995

Preservation of peristaltic reflex in hypertrophied ileum of guinea pig.

Chronic obstruction of the guinea pig ileum leads to distension and muscular hypertrophy, but how this affects passive biomechanical and nerve-mediated contractions and clearance known as peristaltic reflex is unclear. Ileum of controls had a diameter of 3.0 +/- 1.1 mm and a circular muscle thickness of 37.2 +/- 11.2 microns; 4 wk after placement of a nonconstricting Gore-Tex band, the ileum was distended to 10.0 +/- 0.19 mm, and its muscle had hypertrophied to 195.0 +/- 61.2 microns. Hypertrophied segments exceeded controls in capacity (e.g., 5.1 +/- 1.1 vs. 1.1 +/0 0.2 ml at 6 cm), compliance, and hysteresis. Threshold volumes and pressures that triggered the reflex were 3.3 +/- 1.3 ml and 3.1 +/- 0.01 mmHg in hypertrophied vs. 0.7 +/- 0.2 ml and 1.5 +/- 0.2 mmHg in controls. The diameter increase that triggered the reflex was 1.4 +/- 0.1 mm in hypertrophied segments and 0.6 +/- 0.1 mm in controls. Hypertrophied segments generated fewer contractions of virtually double the amplitude and failed to generate a pressure differential between up- and downstream sites as controls did. Hypertrophied segments generated larger stroke volumes and cumulative clearance than controls. The ratio of antegrade to retrograde clearance was similar in hypertrophied and control segments. The length of the occluding segment in hypertrophied preparations exceeded that of controls. Control contractions indented the antimesenteric border and propagated antegrade from their site of origin; bizarre writhing movements of hypertrophied segments made their contractions difficult to monitor. Thus distension and muscular hypertrophy do not interfere with the ability of the chronically obstructed guinea pig ileum to generate a peristaltic reflex at least as readily and as powerful and as effective in clearing the lumen as controls.

Animals↗
PubMed1995

Localisation of androgen receptors in dermal fibroblasts, grown in vitro, from normal subjects and from patients with androgen insensitivity syndrome.

Human genital skin fibroblasts show the androgen receptor (AR) as bright red granules (0.5 micron in diameter) after treatment with one (of 3) primary polyclonal antibody and a secondary antibody linked to alkaline phosphatase. Almost all AR were cytoplasmic in 12 normal strains and in 8 strains from patients with partial (PAIS) and 6 with complete androgen insensitivity syndrome (CAIS). When 25.8 nM 5-alpha-dihydrotestosterone (DHT) or methyltrienolone was added to the medium, some AR were translocated into the nucleus in 13 experiments with 8 strains of normal fibroblasts; of 8 strains of patients with PAIS 3 failed to translocate to a detectable extent in the presence of androgen in the medium and none of the 6 strains from patients with CAIS translocated.

Androgens↗