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Biomedical subjects

R L Harris

Publications and source records attributed to R L Harris.

At least 73 records · Page 4Linked to original sources
PubMed1984

Reconstruction of silica exposure in the North Carolina dusty trades.

The current occupational standard for quartz exposure is largely drawn from studies of the granite workers at Barre, Vermont. Since 1935, the North Carolina Dusty Trades program has accumulated data on work-place environmental conditions, occupational history and health status for persons exposed to silica in a broad range of mineral industries, including granite dimension stone. The environmental data have been collected with Greenburg-Smith and midget impingers and the respirable mass dust sampler. A procedure is presented to combine the results of these sampling methods and estimate exposure at the various jobs at each dusty trades plant. From an individual's occupational history, the environmental exposure estimates are used to formulate personal lifetime exposure summaries. The results of this procedure in the North Carolina granite industry compared well with historical data from Vermont granite sheds.

Air Pollutants, Occupational↗
PubMed1984

Villus atrophy and malabsorption in a rhesus monkey.

Villus atrophy involving the proximal small intestine was diagnosed in a rhesus monkey (Macaca mulatta) at necropsy. A juvenile, male, captive-born monkey exhibited weight loss, hypoalbuminemia, patchy alopecia, eosinophilia, and vomiting. D-xylose absorption was impaired. Contrast radiography revealed thickening of the gastric and intestinal walls, gaseous distension of intestines and a rapid transit rate. There was no clinicopathologic evidence of involvement of organs other than the gastrointestinal tract. The intestinal villus atrophy was similar in distribution and morphology to that of human celiac disease.

Animals↗
PubMed1983

Exposures and mortality among chrysotile asbestos workers. Part I: exposure estimates.

A detailed study of plant processes and dust control methods over the period 1930-1975 was conducted in an asbestos textile plant processing chrysotile. Linear statistical models for reconstructing historic dust exposure levels, taking into account textile processes, dust control measures, and job assignments, were developed. Parameters of these statistical models were estimated using 5,952 industrial hygiene sampling measurements covering the period 1930-1975. For most textile operations, exposure levels were significantly reduced by about 1940, when most engineering dust control measures were in place. Results of the exposure estimates indicated "precontrol" exposure levels to range from 3 to 78 fibers/cc with typical levels well above 10 fibers/cc. After textile operations were provided with dust control measures, estimated exposure levels ranged from 3 to 17 fibers/cc and were usually in the range of 5 to 10 fibers/cc. These exposure estimates were combined with an assessment of mortality among workers at this plant to investigate exposure-response relationships. Exposure-response results are presented in the companion manuscript in this volume.

Asbestos↗
PubMed1983

Exposures and mortality among chrysotile asbestos workers. Part II: mortality.

A retrospective cohort mortality study was conducted among a cohort of 1,261 white males employed one or more months in chrysotile asbestos textile operations and followed between 1940 and 1975. Statistically significant excess mortality was observed for all causes combined (standardized mortality ratio [SMR] = 150), lung cancer (SMR = 135), diseases of the circulatory system (SMR = 125), nonmalignant respiratory diseases (SMR = 294), and accidents (SMR = 134). Using estimated fiber exposure levels in conjunction with detailed worker job histories, exposure-response relationships were investigated. Strong exposure-response relationships for lung cancer and asbestos related non-malignant respiratory diseases were observed. Compared with data for chrysotile miners and millers, chrysotile textile workers were found to experience significantly greater lung cancer mortality at lower lifetime cumulative exposure levels. Factors such as differences in airborne fiber characteristics may partially account for the large differences in exposure response between textile workers and miners and millers.

Asbestos↗
PubMed1982

Lipid mobilization and metabolism after thermal trauma.

Lipid mobilization following thermal injury was studied in 25 patients with burns of between 35 and 95% TBSA for 30 to 50 days postinjury. The concentration of free fatty acids and glycerol in the plasma was elevated. The concentration of plasma triglycerides was elevated, while the concentration of ketone bodies remained normal. Thus it is suggested that the free fatty acids are primarily being re-esterified to triglycerides rather than being utilized for ketone body production. During the first 10 days postinjury, the plasma carnitine level was slightly decreased, while the concentration of carnitine in liver and muscle was elevated. The level of carnitine in burn wound fluid was similar to that in plasma. Therefore, the early decrease in plasma carnitine appeared to result from wound losses, as well as the sustained increased uptake by liver and muscle throughout the burn course.

Burns↗
PubMed1982

Visual scanning behavior and mental workload in aircraft pilots.

This paper describes an experimental paradigm and a set of preliminary results which demonstrate a relationship between the level of performance on a skilled man-machine control task, the skill of the operator, the level of mental difficulty induced by an additional task imposed on the basic control task, and visual scanning performance. During a constant, simulated piloting task, visual scanning of instruments was found to vary as a function of the level of difficulty of a verbal loading task. The average dwell time of each fixation on the pilot's primary instrument increased as a function of the loading. The scanning behavior was also a function of the estimated skill level of the pilots, with novices being affected by the loading task much more than experts. The results suggest that visual scanning of instruments in a controlled task may be an indicator of both workload and skill.

Aerospace Medicine↗
PubMed1982

Visual scanning behavior and pilot workload.

This paper describes an experimental paradigm and a set of results which demonstrate a relationship between the level of performance on a skilled man-machine control task, the skill of the operator, the level of mental difficulty induced by an additional task imposed on the basic control task, and visual scanning performance. During a constant, simulated piloting task, visual scanning of instruments was found to vary with the difficulty of a verbal mental loading task. The average dwell time of each fixation on the pilot's primary instrument increased with the estimated skill level of the pilot, with novices being affected by the loading task much more than experts. The results suggest that visual scanning of instruments in a controlled task may be an indicator of both workload and skill.

Aerospace Medicine↗
PubMed1981

The pathogenesis of abnormal erythrocyte morphology in burns.

The anemia of thermal injury is characterized by a decreased RBC half-life and abnormal RBC morphology (predominantly echinocytes). These changes are reversible in crossover studies with normal recipients, suggesting an extrinsic mechanism unrelated to initial heat or mechanical damage. Since alterations in plasma lipids, which are freely exchangeable with red cell lipids, produce similar changes, plasma and erythrocyte membrane lipid composition in 30 patients (mean 60% TBSA) was determined and related to RBC morphology in vivo and in vitro. Total cholesterol (TC) and phospholipids (PL) were decreased in plasma and plasma lipoproteins (LP) but remained normal in red blood cell membranes. The deficit in TC and LP cholesterol resulted from decreased cholesterol esters. Plasma phospholipids contained increased phosphatidylcholine (PC) and low lysophosphatidylcholine (LPC) and sphingomyelin levels. The essential fatty acid (EFA) composition of total plasma lipids rapidly decreased, with a more gradual decrease in EFA in red cell lipids. The ratio of free fatty acids to albumin in the plasma was greatly increased throughout and may have a primary role in the abnormal erythrocyte morphology and decreased half-life in burned patients.

Adult↗
PubMed1980

Worker exposure to chemical agents in the manufacture of rubber tires and tubes: particulates.

The Occupational Health Studies Group industrial hygiene studies at a group of 14 tire and tube manufacturing plants chosen to represent a cross-section of the industry include numerous evaluations of potential exposure to airborne particulate matter. Results of these environmental particulate sampling studies are reported by plant and by occupational groups within plants. High volume, open face and cyclone samplers were employed to evaluate both personnel and area particulate concentrations. The concentrations of particulates yielded by high volume and open face total particulate samplers are compared with those of comparison samples of respirable material. Personnel samples of particulates are compared with general air samples taken in the same work areas. An overall review and comparison is given of particulate exposures to workers in various occupational title groups where particulate materials are released to the air from processes or operations.

Air↗
PubMed1980

Worker exposures to chemical agents in the manufacture of rubber tires: solvent vapor studies.

Environmental sampling surveys have been conducted in ten large tire manufacturing plants across the U.S. to characterize the nature and intensity of current exposure to solvent vapors. These plants were chosen to represent a cross-section of the industry and include both old and new plants, plants of four different companies and plants with wide geographic distributions. A variety of organic solvents is used in the manufacture of tires and tubes; accordingly solvent vapors comprise one category of exposure for workers in specific Occupational Title Groups (OTGs). Approximately 1000 determinations of various solvent vapor components in air samples have been made with special emphasis on pentane, hexane, heptane, benzene and toluene vapor levels. Exposures stem from the widespread use of bulk materials including petroleum naphthas, gasoline and aliphatic and rubber solvents in various tire manufacturing operations.

Air↗
PubMed1980

Macaca mulatta--a new host for Choanotaenia cestodes.

A juvenile Macacca mulatta that died following a peracute illness was found to be harboring about 25 mature Choanotaenia infundibulum tapeworms. These cestodes commonly infest birds, occasionally insectivores and rodents but have never been reported in nonhuman primates.

Animals↗
PubMed1978

Multiple antibiotic allergies.

A case of an 18-year-old woman with postoperative infectious complications and multiple antibiotic allergies is discussed. The case poses several problems: the selection of an appropriate antibiotic to combat the infection, the persistence of the infection, and the treatment of multiple allergic responses to each of the antibiotic agents chosen.

Adolescent↗