Biomedical subjects
B McKenzie
Publications and source records attributed to B McKenzie.
Accuracy of peak flow meters. Don't interchange devices.
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Airway management for unilateral lung lavage in children.
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Race, socioeconomic status, and the subjective well-being of older Americans.
Causal examination of factors influencing life satisfaction among older Americans can provide knowledge important to social policy development. Using rotated factor analysis, this study isolates two dimensions of life satisfaction, labeled happiness and morale, using data from the 1981 Harris survey on aging. Race, SES characteristics, and the two intervening variables of self-assessed health status and problems experienced are tested through path analysis on the two attributes of life satisfaction. Most of the effects of race and SES are mediated by self-assessed health status and problems experienced, and these two intervening variables are the strongest direct predictors of happiness and morale. Of particular significance are results which demonstrate that racial background has a strong influence on problems experienced, and that education is more influential than income on the life satisfaction factors tested in this study.
Staphylococcus aureus: a common virulent cause of bacteremia.
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Sensitivity of cultured skin fibroblasts from patients with neurofibromatosis to DNA-damaging agents.
Neurofibromatosis (NF) is an autosomal dominant disorder associated with various constitutional abnormalities as well as a striking predisposition for malignant and nonmalignant neoplasms, both in cells originating in and not originating in the neural crest. We have examined the sensitivity of cultured skin fibroblasts from patients with neurofibromatosis to several types of DNA damage. Fibroblasts in Dulbecco's modified Eagle's medium were plated at 10(2) to 2 X 10(4) cells per 75 cm2 tissue culture plates, and exposed to various doses of gamma radiation (leads to DNA scission), actinomycin D (a DNA intercalating agent), or mitomycin C (a bifunctional alkylating agent leading to DNA cross-links). Cells were reincubated for 15 to 40 days until surviving colonies exhibited greater than 30-50 cells. Plates were then stained with 1% methylene blue and the colonies counted, with surviving fraction determined relative to plating efficiency. Nine skin fibroblast cell strains from normal individuals were studied as controls. One neurofibromatosis (NF) cell strain, SB23, exhibited normal sensitivity to all three DNA-damaging agents studied in early (7-8) and middle (12-13) in vitro passage. Strain GM0622, on the other hand, exhibited normal sensitivity to the three DNA-damaging agents studied at early passage, but showed a significant decrease in survival after exposure to both gamma radiation (D0 = 106 rad) and actinomycin D (D0 = 0.024 mcg/ml) with increasing passage. Strain GM1639 exhibited decreased survival after actinomycin D exposure at early passage (D0 = 0.017 mcg/ml), with normal survival after exposure to gamma radiation and mitomycin C at the same passage. Cell strains exhibited decreasing low density plating efficiencies and growth rates with increasing passage such that study of cytotoxicity was not feasible after middle passage in strains SB23 and GM0622, and after early passage in strain GM1639. The results suggest that cultured fibroblast cell strains from patients with NF exhibit early in vitro senescence which sometimes is associated with an inability to handle certain DNA-damaging agents.
Technical tips on the Crozat appliance: design and fabrication.
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Photography: the practicalities of a creative field.
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Preliminary report on ten patients with spinal cord injuries treated with hyperbaric oxygen.
A preliminary report is presented on 10 patients with spinal cord injuries who were treated with hyperbaric oxygen. The results suggest that by supporting injured spinal cord tissue with oxygen under pressure, improvement in nerve function may occur. No deterioration of motor power or sensation was evident during or after hyperbaric oxygen treatment in any of these patients. The possible contribution of ischaemia to the pathology of spinal cord injury should encourage further experimental research and clinical trials with hyperbaric oxygen.
Central and peripheral object distances as determinants of the effective visual field in early infancy.
While visually fixating on a central, coloured object, thirty-six infants aged between two and five months were presented with a peripheral target to the right or to the left of midline. Both objects were presented at two distances: either 30 or 90 cm from the infant. The extent of the effective visual field was measured by the presence and the latency of saccadic shifts of gaze from the fixation object toward the target object placed at varying degrees of eccentricity. The effective visual field expanded between two and four months. Near peripheral targets were detected at greater angles of eccentricity than those more distant, but this effect was modified both by age and by the distance of central fixation. For two- and three-month infants the effective visual field was most reduced when the central fixation object was placed at 30 cm and the target object at 90 cm. The ability to respond to peripheral objects more distant than the fixation object develops after three months.
A study of the effects of hyperbaric oxygen on the experimental spinal cord injury.
The degree of motor recovery in sheep with a controlled contusion to the thoracic spinal cord is compared with the recovery in sheep treated with hyperbaric oxygen and confirms the results of a preliminary series previously reported. The degree of central cord cystic necrosis and degeneration in the surrounding white matter is compared in the control and treated animals. The improvement in motor recovery and in the degree of cord degeneration after treatment with hyperbaric oxygen suggests that ischaemia plays a significant role in the experimental animal with a contusion injury to the spinal cord.
Rhythm perception in early infancy.
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Central necrosis following contusion to the sheep's spinal cord.
This paper presents the results of a study on the pathological changes associated with post traumatic central spinal cord necrosis.
Treatment of paraplegic sheep with hyperbaric oxygen.
The results of the use of hyperbaric oxygen therapy to control the onset of paraplegia after recent spinal cord injury in sheep are described. This preliminary report suggest that hyperbaric oxygen therapy instituted within two hours of the injury will result in improved motor recovery.
Orientation discrimination in infants: a comparison of visual fixation and operant training methods.
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Operant learning of visual pattern discrimination in young infants.
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Sinus barotrauma in divers.
Sinus barotrauma is a common occupational disease of divers, with the incidence of descent barotrauma approximately double that of ascent. Pain chronologically associated with the change of pressure is the most dominant symptom and is seen in 92% of the cases presented for treatment. The majority complain of a frontal distribution of pain, with ethmoidal and maxillary being much less significant. Epistaxis is the second commonest symptom, and may be the sole symptom in some ascent cases. A history of recent or past sinus barotrauma or upper respiratory tract pathology is very common. Clinical examination supports the evidence of upper respiratory tract pathology in many cases. The radiological signs of abnormality were present in over three quarters of the cases examined. Of these the maxillary sinus was affected in most cases, the frontal in approximately one quarter and the ethmoidal in less than a fifth. The pathology was more commonly that of mucosal thickening, but in 12% of cases there was a fluid level. It is noted that although symptoms were predominantly frontal, x-ray changes were most often present in the maxillary sinuses.