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Biomedical subjects

B Brown

Publications and source records attributed to B Brown.

At least 217 records · Page 12Linked to original sources
PubMed1989

Contrast sensitivity with contact lens corrections for presbyopia.

We measured contrast sensitivity at three distances (330 mm, 660 mm and 4 m) with six contact lens and two multifocal spectacle corrections for presbyopia. The two spectacle corrections were D-segment bifocals and trifocals and the contact lens corrections were distance contact lens with lookover spectacles, soft progressive bifocals, soft concentric bifocals, monovision, modified monovision, and hard crescent segment bifocals. The spectacle corrections in general gave better results for the contrast sensitivity function (CSF), than did the contact lens corrections. Distance contact lenses with lookover spectacles performed best of the contact lens corrections used. However, the differences in CSF between the various contact lens corrections were small and not statistically significant.

Adolescent↗
PubMed1989

Detection of change of size by young and old observers.

Thresholds for detecting change of angular size were determined for a range of angular separations in young and elderly observers. We found no differences in thresholds between these subjects groups. Thresholds for detection of change of visual angle increased with angular separation in a power function relationship. Angular size change judgements based on successive views of a target are apparently not significantly affected by age.

Adolescent↗
PubMed1989

Spatial summation in young and elderly observers.

We measured detection thresholds for targets over a range of sizes at both photopic and scotopic luminance levels in young and elderly observers, and used these data to estimate spatial summation areas 10 degrees in the retinal periphery. There were differences in detection thresholds between the young and old groups at photopic and scotopic luminances, but no differences in spatial summation areas at either background luminance level.

Adult↗
PubMed1989

Peripheral visual acuity and age.

We measured the peripheral visual acuity of a group of eleven older subjects (mean age 54.2 years) and a group of seventeen young subjects (mean age 22.1 years). Peripheral visual acuity was measured using Konig bars with critical detail subtending 2.4 and 4.8 minutes of arc. The older group showed a substantial reduction of peripheral visual acuity.

Adult↗
PubMed1989

Thermal resistance of Listeria monocytogenes in sausage meat.

The heat resistance of a mixture of 10 different strains of Listeria monocytogenes inoculated into ground meat and ground meat plus cure was examined. D-values for ground meat ranged from 1.01 min at 62 degrees C to 13.18 min at 56 degrees C. The D-values obtained for ground meat plus cure were approximately 5-8 fold times higher than those for ground meat alone. These results imply that rare meats and possibly some cooked fermented meats may not be heated adequately to inactivate Listeria.

Food Microbiology↗
PubMed1988

Gender differences in variables associated with psychosocial adjustment to a burn injury.

The purpose of this study was to determine whether variables associated with psychosocial adjustment to a burn injury vary by gender. Male and female burned subjects (N = 260) were compared on their functional disability, disfigurement, coping responses, social resources, and psychosocial adjustment to a burn injury. Both men and women had adjusted psychosocially to their burn injury. Less functional disability (r = .57, p less than .001) for men and greater problem-solving (r = .57, p less than .001) for women were the most important variables in explaining psychosocial adjustment to a burn injury. In the future, researchers need to be cognizant of gender differences and consider men and women as separate populations.

Adaptation, Psychological↗
PubMed1988

Characteristics of three- and four-wheeled all-terrain vehicle accidents in Quebec.

During a seven-month survey from May to November 1985, 624 victims injured from three- or four-wheeled all-terrain vehicles (ATVs) were observed in the emergency rooms of 10 regional hospitals in Quebec. A total of 1,100 injuries were identified, including 3 fatal and 104 serious to critical injuries (AIS greater than or equal to 3). These injuries were to the lower limb (29%), the upper limb (28%), the head, neck, and face (26%), and the thorax, abdomen, and pelvis (18%). Close to one-half (45%) of the victims were 19 years old and less; 54% reported wearing helmets. Ten percent of the victims were hospitalized for an average period of 8 days. In 70% of the cases, the vehicle overturned: half of these vehicles turned on the side, 27% toward the back, and 19% flipped forward. Two-thirds of persons injured were involved in accidents in which no external objects were hit by the vehicle; these accidents typically involved vehicle overturns, both on hills and on level ground. Ninety-five percent of the vehicles were in good mechanical condition. The use of these vehicles presents a danger whether used by a child or an adult, by an experienced or an inexperienced rider. The average user may not be aware that three- and four-wheel ATVs demand considerable skill and caution. We suggest the use of accident reconstruction studies for possible engineering solutions.

Accidents, Traffic↗
PubMed1988

Lesions of the MPO or AV3V: influences on fluid intake.

Electrolytic lesions in the MPO of rats had no significant effects on ad lib food and water intake, but impaired the drinking response to 1 M NaCl. Large MPO lesions also produced a persistent increase in plasma osmolality. In Experiment 2, we depleted neurons from the MPO of rats by iontophoretic application of the neurotoxin kainic acid (KA) which destroys nerve cell bodies without damage to fibers of passage. KA-induced neuron depletion in the MPO of rats significantly reduced the drinking response to 1.0 M saline, to 30% PG, and to 30 micrograms/kg isoproterenol. Ad lib water intake and drinking responses to food or water deprivation, to low concentrations (0.5 M) of hypertonic saline, to low concentrations (10% or 20%) of PG, and to systemic administration of 1.5 mg/kg angiotensin II were within the normal range. In Experiment 3, rats with electrolytic lesions that were strictly confined to the tissue immediately surrounding the wall of the anteroventral portion of the third ventricle (AV3V), without invading the MPO displayed normal ad lib food and water intake and plasma osmolality as well as drinking responses to water deprivation, hypertonic saline (0.5 or 1.0 M), angiotensin II (1.5 mg/kg) and isoproterenol (30 micrograms/kg).

Animals↗
PubMed1988

Depletion of neurons from preoptic area impairs drinking to various dipsogens.

We depleted neurons from the lateral preoptic region (LPO) of rats by iontophoretic application of the neurotoxin kainic acid (KA). Rats with KA-induced damage to LPO neurons drank less water than controls after subcutaneous (SC) administration of: (a) 5 ml of a 1.0 M saline solution or (b) 5 ml of a 30% polyethylene glycol (PG) solution. The drinking response to 1.5 mg/kg angiotensin II (AII) was significantly smaller than was that of controls 15 min but not 1 hour after the SC injection. The experimental animals drank as much water as controls under ad lib conditions and showed normal drinking responses to low concentrations of hypertonic saline (0.5 M) or PG (10% or 20%).

Angiotensin II↗
PubMed1988

Fluctuations in intra-ocular pressure with sleep: II. Time course of IOP decrease after waking from sleep.

Intra-ocular pressure (IOP) was measured immediately after normal subjects were woken from at least 5 hours sleep. Measurements were made at approximately 15 s intervals, for about 20 minutes. The IOP of all 14 subjects was elevated after sleep and returned to baseline levels with a time course which was approximately exponential; the longest time constant of return of IOP to baseline was 1056.9 s, and the shortest 133.5 s. Mean time constant of recovery was 404.8 s. The decrease in IOP may be related to melatonin levels which increase during sleep and decrease in the light, or be related to accommodation and eye movements which may act to 'pump' aqueous from the eye.

Adolescent↗
PubMed1988

Age-related changes in contrast sensitivity in central and peripheral retina.

Eight young (average age 20.4 years) and eight elderly (average age 64.4 years) observers took part in three experiments designed to study age-related changes in peripheral retinal function. A further eight young (average age 22.3 years) and eight elderly (average age 63.8 years) observers took part in a replication of experiment 3. All observers had normal or better-than-normal visual acuity and no evidence of ocular pathology. All testing was monocular and the eye with better visual acuity was used. In the first experiment contrast sensitivity was measured in central retina and 10 deg temporally, at spatial frequencies of 0.2, 0.8, 2.0, and 5.0 cycles deg-1. Young observers had better contrast sensitivities than older observers, but only at higher spatial frequencies (2.0 and 5.0 cycles deg-1). For both groups, contrast sensitivity was poorer with peripheral presentation of stimuli than with central presentation, but not for the lowest spatial frequency used (0.2 cycle deg-1). In the second experiment observers had to detect the presence of a sharp edge (square-wave luminance profile), while in the third and fourth experiments the target was a "fuzzy' edge (sine-wave profile). Edges were again presented centrally or 10 deg temporally. As expected from the data of experiment 1, young observers were better able to detect the sharp edge than were the older observers in both central and peripheral viewing conditions. For both age groups, edge detection was better during central viewing than during peripheral viewing. However, contrary to expectations based on the results of experiment 1, detection of the fuzzy edge was better for central than for peripheral viewing for both age groups in experiments 3 and 4. The apparent (and expected) equality of performance found in experiment 3 for young and elderly observers in detecting the fuzzy edge was shown to be due to the range of contrast values used. When appropriate contrast values were used in experiment 4, young observers detected fuzzy edges presented in central retina better than did elderly observers. The results of experiment 1 show sparing of the ability to process low spatial frequencies across (i) age and (ii) retinal location, and are discussed in terms of the notion of (i) models of age-related loss of visual function and (ii) cortical magnification. The results of experiments 2, 3, and 4 provide some support for the proposition that the contrast sensitivity of observers may be used to predict their performance on other visual tasks.(ABSTRACT TRUNCATED AT 400 WORDS)

Aging↗