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Biomedical subjects

C J Mackenzie

Publications and source records attributed to C J Mackenzie.

At least 19 recordsLinked to original sources
PubMed1993

Incidence and classification of early embryonic mortality in broiler breeder chickens.

1. Unusually high early embryonic mortality (EEM) was observed in hatching eggs from broiler compared with white or brown table-egg breeders in Atlantic Canada. Broiler breeder EEM in Atlantic Canada was twice the EEM in broiler breeders from other areas of North America. 2. Comparisons of holding temperatures (18 and 30 degrees C) for 24 h after egg collection, in combination with a storage time of 0 or 7 d at 18 degrees C prior to incubation, were made using the criteria: embryo development (stage), and size at 0, 3, 6 and 9 d incubation, EEM, late embryonic mortality (LEM) and hatchability (HAT). 3. Stage of development of embryos, at 0 d incubation, was highest for eggs held for 24 h at 30 degrees C and stored for 7 d. Embryo stage, weight and length at 3, 6 and 9 d incubation were positively correlated. 4. Hatchability of fertile eggs was lowest (66.5%) for eggs held for 24 h at 30 degrees C and stored for 7 d and highest (87.2%) for eggs held for 24 h at 18 degrees C and stored for 0 d. Holding temperature and storage time significantly influenced EEM and LEM. 5. EEM classification differed for strain of breeder. In broiler breeders the majority of the EEM was at a relatively late stage of development (exhibiting an obvious blood ring with a visible embryo). In comparison, EEM from table egg breeders was distributed equally among three categories.

Abnormalities, Multiple↗
PubMed1987

Blood lead and carboxyhemoglobin levels in chainsaw operators.

Fallers in the British Columbia west coast lumber industry often work in climatic and local conditions where little ventilation in their immediate environment is possible. Under these conditions carbon monoxide (CO) and lead fumes from exhaust gases could build up and become a serious occupational hazard. This study monitored the environmental exposure of six fallers to carbon monoxide, nitrogen oxides, and lead under conditions where buildup of these agents would be expected. At the same time blood samples were taken to correlate these environmental concentrations to carboxyhemoglobin (COHb) and blood lead levels. Although there was a highly significant difference between the fallers and the controls regarding the exposure to CO and lead as well as their corresponding COHb and blood lead levels, the environmental and blood concentration of the agents in question did not exceed the maximum allowable concentrations. Temporary short fluctuations in carboxyhemoglobin levels were not monitored in this study and cannot be ruled out as a potential occupational hazard.

Adult↗
PubMed1987

Longitudinal study of vibration-induced white finger among coastal fallers in British Columbia.

Symptom-based vibration-induced white finger was determined longitudinally from a questionnaire administered to 71 full-time fallers exposed 2-4 h daily to generally heavy (greater than 11 kg), large displacement (greater than 95 cc) chain saws. The prevalence of Raynaud's phenomenon among 55 fallers (after 16 fallers were excluded because of possible confounders) was 51% in 1979-1980. This figure did not differ significantly from the prevalence in 1984-1985 (53%). Among the 28 fallers reporting symptoms in 1979-1980, seven reported no symptoms in 1984-1985, while four indicated improvement in the severity of symptoms resulting in a decreased stage assessment. Evidence for actual recovery was weak because of discrepancies in the symptom reporting. Reported recovery and improvement in the group with symptoms in 1979-1980 was counterbalanced by a significant 30% onset of new symptoms among fallers who were asymptomatic in 1979-1980. Six of the eight fallers reporting new symptoms were exposed only to antivibration saws, a finding suggesting that the type of saws used in the present investigation is not preventing the onset of new disease. Weighted 4-h equivalent acceleration levels from the handlebars of saws commonly used by the cohort group in 1984 ranged from 4.0 to 12.4 m/s2.

British Columbia↗
PubMed1986

Vibration-induced white finger among selected underground rock drillers in British Columbia.

Ninety-five rock drillers who used pneumatic hand-held drills were interviewed and tested. Thirty-seven were excluded because of factors predisposing to the appearance of white fingers other than exposure to industrial hand-drill vibration. Forty-five percent of the remaining 58 drillers suffered from periodic attacks of Raynaud's phenomenon. Symptoms were present in 25% of the drillers exposed for 1-5 years and in 80% of those exposed for greater than or equal to 16 years. Nine percent of the cases were classified as severe. The median latency for the onset of the blanching symptoms was 7.5 years. The prevalence of Raynaud's phenomenon was 4% among a reference group of 56 miners not exposed to hand vibration and corrected for possible predisposing factors. Objective evidence indicated delayed finger rewarming after a combination of digital ischemia and cooling in 75% of the drillers with blanching symptoms and 18% of the referents without symptoms. There was evidence of an increased frequency of vibration-induced white finger among current cigarette smokers. Weighted 4-h equivalent acceleration levels measured from the handles of 26 jack-leg and 13 stoper drills from the same mines as the miners ranged from 15 to 32 m/s2. These levels exceed recommended guidelines of the International Organization for Standardization.

British Columbia↗
PubMed1984

Two examples of environmental problems occurring in remote sparsely populated areas.

Studies in two widely separated remote areas are presented. Arsenic from gold mining contaminates the town of Yellowknife, North West Territories, Canada, An electromyographic study was carried out on 517 people in Yellowknife and a control population. Correlations between hair arsenic levels and nerve velocity, although not striking, are noted. Mercury contamination of fish in a pristine environment in Lake Murray, Western Province, Papua New Guinea, is reflected in elevated hair and urine levels in the local inhabitants. An attempt was made to determine the effects of mercury on the people and 40% of those tested had albumen in their urine. The conclusions drawn from these studies are given. The problems imposed on epidemiological studies by remote areas and harsh conditions are suggested.

Adult↗
PubMed1983

Vibration white finger disease among tree fellers in British columbia.

On the basis of symptomatology, 51% of 146 fellers from seven coastal lumber camps in British Columbia were found to be suffering from vibration white finger disease (VWFD). Symptoms were present in 70% of the men who had been engaged in felling for 11 to 15 years and in 75% of the men who had been employed in this occupation for more than 20 years. Prevalence rates were not changed by the exclusion of 57 fellers with a history of vibration exposure other than the chain saw, or with a history of other possible secondary causes. The prevalence of symptoms in an age-corrected control group was 2%. There was objective evidence of disease (delayed finger rewarming after cooling) in 31 of the 43 fellers with symptoms (72%) and in 13 of the 74 controls (18%) without symptoms. The median latency period for fellers with symptomatic VWFD was 7.3 years. There was no evidence that the condition was related to cigarette smoking.

Adult↗
PubMed1982

Albuminuria at Lake Murray due to high methylmercury intake.

A clinical examination of 24 subjects having a high intake of methylmercury through fish consumption showed no individual symptoms or signs that could be due to mercury poisoning. However, nearly 40% of the subjects (9) had significant amounts of albumin in the urine. The mean concentrations of mercury in hair and urine were 12.0 mg/kg (81% methylmercury) and 23 mg/kg (35% methylmercury) respectively. No correlation, however, was found between the incidence of albuminuria and mercury levels in hair or urine.

Albuminuria↗
PubMed1970

A two-year follow-up of persons with non-tuberculosis chest disease found at "operation doorstep", Vancouver 1964.

Eight hundred and fifty-four patients of 928 who had attended a mass radiographic tuberculosis survey and in whom the diagnosis of non-tuberculous lung disease had been made, were located two years after the survey. This was the second follow-up survey of this group, the first having been at four months. The majority of patients were well, but 247 were ill and 101 had died. Serious non-tuberculous chest disease can be diagnosed with accuracy at mass surveys but the benefit to the patient of having these conditions detected is less clear. Serious progressive conditions that lead to death or ill health within two years appear to become symptomatic and force the sufferer to seek medical advice at about the same time that they are detected at mass surveys. This fact, coupled with the low yield of previously unknown tuberculosis, makes the future use of general mass radiographic surveys questionable in areas with good medical services. Evidence is presented that suggests screening directed to specific age groups may be more productive.

Adult↗
PubMed1966

Non-tuberculous chest disease found in a mass x-ray survey in Vancouver, B.C.

In 1964, 219,085 persons were examined during a tuberculosis survey in Vancouver, B.C. One hundred and fifteen new cases of tuberculosis and 929 cases of significant non-tuberculous lung disease were found. In a four-month follow-up of the non-tuberculous cases it was found that of the 742 patients who had named a physician when examined 26.6% had not made contact with him. Of those who did contact the physician, the follow-up was considered "poor" in only 30 patients (2.1%). Seventeen patients had died in the four-month interval and 81 who could not be located after the initial survey were considered "lost". Rates were determined for 37 diagnoses per 1000 patients screened. The most common diagnosis was localized pulmonary fibrosis (1.69/1000). Carcinoma was found in 0.30/1000 and solitary lung density in 0.17/1000 population screened.

British Columbia↗