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Biomedical subjects

L MacLean

Publications and source records attributed to L MacLean.

At least 19 recordsLinked to original sources
PubMed1992

Sulphydryl reactivity of the HLA-B27 epitope: accessibility of the free cysteine studied by flow cytometry.

HLA-B27 has an unpaired cysteine on or near its serologically defined spondylitis associated epitope, and it has been argued that its sulphydryl side chain may be chemically reactive. In a previous study it was shown that chemical treatment of HLA-B27 cells with the sulphydryl binding agent p-chloromercuriphenylsulphonic acid (pCMPSA) specifically reduced binding of antibodies to HLA-B27 by up to 80%, as measured in a cellular enzyme linked immunosorbent assay (CELISA). The effect of sulphydryl blockade on intact B27 cells was investigated using flow cytometry. Compared with the CELISA, inhibition required higher concentrations of pCMPSA, and the degree of inhibition produced by a greater than or equal to 30 microM solution of pCMPSA as measured by flow cytometry (median 28.9%) was significantly lower than that measured by CELISA (median 73.6%; p = 1.6 x 10(-6)). Analysis of unfixed, cell surface HLA-B27 by flow cytometry suggests that on most B27 molecules the unpaired sulphydryl site is not available. On the basis of this evidence for modification after translation, a new 'altered self' hypothesis is proposed for the part which HLA-B27 plays in inflammatory disease.

4-Chloromercuribenzenesulfonate↗
PubMed1988

Respiratory health in chrysotile asbestos miners in British Columbia: a longitudinal study.

A respiratory survey was undertaken in chrysotile asbestos miners in British Columbia consisting of a questionnaire, spirometry, chest radiography, and physical examination. The tests were performed in 1977 and again in 1983. The population groups studied included 63 "exposed" (working in the plant more than nine years), 52 "controls" (working in the plant less than five years), and 38 residents of the village at the minesite. A subset of 39 was identified with high exposure (worked in the mill more than five years). Measured levels of environmental particulates were similar over the entire period of operation of the plant (1.4 to 14.0 million particles per cubic foot and 0.7-88.0 fibres/cc in the mill; 0.2 to 2.7 mpcf and 0.6 to 9.3 f/cc in the mine). The exposed groups were more likely to report cough and breathlessness than the two other groups and were also more likely to have abnormal FVC and chest x ray films (the latter not significant, p greater than 0.05) and to be more likely to have a combination of these abnormalities. There was no trend to progression in the combination of abnormalities associated with exposure on follow up. The heavily exposed group showed a significantly worse trend in FVC. This adverse trend was confined to those with initial abnormalities. Tobacco smoking did not increase the trend to progression in this group.

Adult↗
PubMed1987

Follow-up study of 232 patients with occupational asthma caused by western red cedar (Thuja plicata).

A total of 232 patients with red cedar asthma diagnosed by inhalation provocation tests were observed an average of 4 years after the initial diagnosis. The status during the follow-up examination was as follows: 96 patients continued to work with red cedar, and 136 left the industry and had no further exposure to red cedar in their jobs or hobbies. Of the 136 patients who left the industry, only 55 (40.4%) recovered completely, whereas the remaining 81 (59.6%) continued to experience attacks of asthma of varying severity. The initial pulmonary function tests were significantly higher among the asymptomatic group compared to the symptomatic group (FEV1 99.3 +/- 2.7% versus 90.5 +/- 2.2% predicted, respectively). Methacholine PC20 during the initial examination was higher among the asymptomatic group than in the symptomatic group (1.46 +/- 3.96 mg/ml versus 0.77 +/- 4.52 mg/ml, respectively). These findings indicate that the patients in the asymptomatic group were diagnosed at an earlier stage of the disease. This observation was confirmed by the significantly shorter duration of symptoms before diagnosis among the asymptomatic patients compared to the symptomatic patients (1.6 +/- 1.9 versus 2.6 +/- 4.3 years). Race, smoking status, immediate skin reactivity, and presence of plicatic acid-specific IgE antibodies did not influence the outcome of these patients. Of the 96 patients who continued to work with red cedar, 47 were exposed daily, whereas 41 were exposed intermittently.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Adaptive decisions in the use of hospital beds.

This article investigates the manner by which a physician adapts his decision on referral to hospital and length of hospital stay to variations in the pressure (access) to hospital beds. An index of adaptation is developed which measures the adaptation to pressure from standard bed-use statistics. An example of the index is given for psychiatric bed use in Canada.

Bed Occupancy↗
PubMed1986

The structure of the antigenic lipopolysaccharide O-chains produced by Salmonella urbana and Salmonella godesberg.

The lipopolysaccharides of Salmonella urbana and Salmonella godesberg, which belong in group N (O:30) of the Kauffmann-White system, were shown by SDS-PAGE electrophoresis, glycose analysis, periodate oxidation, methylation, and 1H- and 13C-n.m.r. analyses to have identical O-chains composed of repeating, branched pentasaccharide units having the structure: [----4)-beta-D-Glcp-(1----3)-alpha-D-GalNAcp-(1----2)-alpha-D-P erNAcp-(1----3)-alpha-L-Fucp-(1----]n 4 increases 1 beta-D-Glcp. The serological cross-reactivity of S. urbana and S. godesberg with Brucella abortus and Yersinia enterocolitica (O:9) can now be related to the presence of a 1,2-glycosylated N-acyl derivative of 4-amino-4,6-dideoxy-alpha-D-mannopyranosyl residues in their respective lipopolysaccharide O-chains.

Carbohydrate Conformation↗
PubMed1986

Structure of the O-chain polysaccharide of the phenol-phase soluble lipopolysaccharide of Escherichia coli 0:157:H7.

The phenol-phase soluble lipopolysaccharide isolated from Escherichia coli 0:157 by the hot phenol-water extraction procedure was shown by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, periodate oxidation, methylation, and 13C and 1H nuclear magnetic resonance studies to be an unbranched linear polysaccharide with a tetrasaccharide repeating unit having the structure: (formula; see text) The serological cross-reactivity of E. coli 0:157 with Brucella abortus, Yersinia enterocolitica (serotype 0:9), group N Salmonella, and some other E. coli species can be related immunochemically to the presence of 1,2-glycosylated N-acylated 4-amino-4, 6-dideoxy-alpha-D-mannopyranosyl residues in the O-chains of their respective lipopolysaccharides.

Carbohydrate Conformation↗
PubMed1985

Respiratory abnormalities among workers in an iron and steel foundry.

A study of the health of 78 workers in an iron and steel foundry in Vancouver, British Columbia, was carried out and the results compared with those found in 372 railway repair yard workers who were not significantly exposed to air contaminants at work. The foundry workers were exposed to PepSet, which consists of diphenyl methane diisocyanate (MDI) and phenol formaldehyde and their decomposition products as well as to silica containing particulates. A questionnaire was administered by trained interviewers, and chest radiography, allergy skin tests, pulmonary function tests, and methacholine inhalation tests were carried out as well as measurement levels of dust and MDI. Compared with the controls, the foundry workers had more respiratory symptoms and a significantly lower mean FEV1 and FEF25-75% after adjustments had been made for differences in age, height, and smoking habit. Three workers (4.8%) had radiographic evidence of pneumoconiosis and 12 (18.2%) had asthma defined as presence of bronchial hyperreactivity, cough, and additional respiratory symptoms such as wheeze, chest tightness, or breathlessness. Sensitisation to MDI is probably the cause of asthma in these workers.

Adult↗
PubMed1984

Symptoms, pulmonary function, and bronchial hyperreactivity in western red cedar workers compared with those in office workers.

An epidemiologic health study was carried out on 652 cedar mill workers and a control group of 440 male office workers not exposed to air contaminants. Participants completed a medical-occupational questionnaire with trained interviewers, had allergy skin tests, performed spirometry, and had bronchial reactivity assessed by methacholine inhalation testing. After adjusting for differences in age, race, and smoking, cedar workers were found to have significantly higher prevalences of cough, phlegm, and dyspnea than did office workers. Symptoms of asthma and work-related asthma, but not persistent wheeze or doctor-diagnosed asthma, were reported in a significantly higher proportion of cedar workers than of office workers. Cedar workers also had significantly lower lung function test results than did office workers after controlling for height, age, race, and smoking. Bronchial hyperreactivity, defined by a methacholine PC20 less than 8 mg/ml, was more prevalent among cedar workers than among office workers, with the increase being limited to the nonatopic subgroup of workers. The prevalence of bronchial hyperreactivity increased with duration of employment among cedar workers but not among office workers. We conclude that exposure to western red cedar dust is harmful to the respiratory health of the workers, causing asthma and other respiratory symptoms, bronchial hyperreactivity, and lower levels of lung function.

Adult↗
PubMed1984

Host factors affecting longitudinal decline in lung spirometry among grain elevator workers.

The host factors affecting the longitudinal decline in lung function among 267 white male grain elevator workers who were still working in the industry and did not change their smoking habits over a period of six years were studied. Spirometric measures declined more rapidly in older grain handlers as compared with younger workers. Smokers had slightly greater decline in spirometry compared to nonsmokers, but the differences failed to reach the level of statistical significance. Acute changes in lung function over the course of one work week during the initial study were also positively correlated with subsequent decline in lung function, as was bronchial hyperreactivity determined during the follow-up study. Positive immediate skin reactivity to common allergens, presence and absence of respiratory symptoms, and initial lung function did not appear to influence the subsequent decline in lung function in this group.

Adult↗
PubMed1983

Epidemiologic health study of workers in an aluminum smelter in British Columbia. Effects on the respiratory system.

A health survey was carried out on all white males in an aluminum smelter in British Columbia. The survey consisted of a medical-occupational questionnaire, spirometry, chest radiography, and environmental monitoring. We have compared the results of a respiratory survey in 713 workers in the office and casting department with no significant exposure to air contaminants (control workers) with those of 797 potroom workers: 495 who spent more than 50% of their working time in the potroom (high exposure) and 302 workers who spent less than 50% of their working time in the potroom (medium exposure). Potroom workers (high) had a significantly greater prevalence of cough and wheeze than did those in the control group, and they had significantly lower mean forced expiratory volume in one second and maximal midexpiratory flow rate than did those in the control group after adjustment had been made for differences in age, height, and smoking habits. Potroom workers (medium) had a slightly greater prevalence of respiratory symptoms and lower lung function than did workers in the control group, but the differences were not significant. We were unable to demonstrate potroom asthma. The levels of total fluoride, gaseous fluoride, particulate fluoride, sulphur dioxide, and total particulates found in the potroom at the time of the study were below the currently accepted threshold limit values, but the levels of benzo-alpha-pyrene were high.

Adult↗
PubMed1979

Respiratory abnormalities among grain elevator workers.

Twenty-two grain workers with respiratory symptoms and lung function abnormalities were studied. Our findings suggest that grain dust asthma probably has an allergic basis, even though skin tests and precipitin studies were negative using extracts of grain dust. Hypersensitivity pneumonitis and grain dust fever were not found in any of the subjects. We found that grain dust can cause airflow obstruction in two ways: first by inducing asthma, probably through immunologic mechanisms, and second, by causing industrial chronic bronchitis.

Adult↗
PubMed1978

A respiratory survey of cedar mill workers. II. Influence of work-related and host factors on the prevalence of symptoms and pulmonary function abnormalities.

The influence of certain work-related and host factors on the prevalence of respiratory symptoms and pulmonary function abnormalities in 405 red cedar workers and 187 control workers was examined. In cedar workers, but not in controls, the prevalence of chest symptoms increased with duration of exposure. The decline in pulmonary function with increasing duration of exposure was also more marked in cedar workers, but in both groups smoking was a more important determinant. Substantial proportions of cedar workers and, to a lesser extent, controls noted improvement of cough and wheeze, and particularly of conjunctivitis and rhinitis, when away from work. No deterioration, however, was found in pulmonary function during the work week in either exposure group. Atopic status was unrelated to the prevalence of chest symptoms or pulmonary function abnormalities; it was more common in workers with conjunctivitis and rhinitis, particularly in the cedar group. Similarly, Pi phenotype did not appear to influence the occurrence of either symptoms or lung function abnormalities.

Adult↗
PubMed1975

Beclomethasone dipropionate in asthma.

Beclomethasone dipropionate aerosol therapy can replace or diminish systemic corticosteroid therapy in the majority of asthmatics. In a clinical trial of 41 patients with perennial asthma, the 10 who had not required long-term corticosteroid therapy improved symptomatically and in pulmonary function. Of the 31 who had required prolonged systemic corticosteroid therapy 12 were able to discontinue oral prednisone therapy, 15 were able to decrease the maintenance dose of prednisone and only 4 were unable to decrease the dose; all maintained satisfactory lung function and some showed improvement. Discontinuation of systemic corticosteroid therapy was accomplished more readily in patients whose daily maintenance dose was less than 15 mg and who had been taking the drug for less than 3 years. Side effects consisted of a "dry throat" in seven patients, two of whom had throat infections with Candida albicans. Recurrence of rhinitis after discontinuation or reduction of systemic corticosteroid therapy was noted in 11 patients.

Administration, Oral↗