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Biomedical subjects

W A Burgess

Publications and source records attributed to W A Burgess.

At least 19 recordsLinked to original sources
PubMed1993

Effects of intracranial self-stimulation on selected physiological variables in rats.

The purpose of this investigation was to characterize selected metabolic, cardiovascular, and hormonal responses to reinforcing intracranial self-stimulation (ICSS) of the ventral tegmental area (VTA) in rats. Twenty male Sprague-Dawley rats were stereotaxically implanted with bipolar electrodes aimed at the VTA of the brain. Rats were trained to lever-press for ICSS for 1 wk. While they adapted to the experimental environment by sitting in a metabolic operant chamber, they were connected to the electrode cable but did not lever-press. All animals were instrumented with arterial catheters. Rats receiving contingent stimulation (C-St; n = 10) performed 30 min of lever pressing in the metabolic operant chamber for reinforcing brain stimulation. Oxygen consumption (VO2), heart rate (HR), mean arterial pressure (MAP), and rectal temperature (Trec) increased with the onset and continuation of contingent brain stimulation over 30 min (P < 0.05). In addition, plasma norepinephrine (NE), epinephrine (Epi), and corticosterone increased significantly above resting values in C-St rats (P < 0.05). Five animals received investigator-delivered reinforcing brain stimulation (noncontingent stimulation; NC-St), with MAP, HR, VO2, NE, and Epi increasing significantly above resting values (P < 0.05). Trec and corticosterone were not responsive to noncontingent brain stimulation. With the exception of HR, nonstimulated controls (n = 5) did not experience increases above resting values in any of the variables measured. The responses suggest that contingent brain stimulation reward elicits heightened sympathetic arousal.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Exercise training alters cardiovascular and hormonal responses to intracranial self-stimulation.

Both reinforcing intracranial self-stimulation (ICSS) and physical exercise result in heightened cardiovascular and endocrine responses. This study compared the cardiovascular and endocrine responses to ICSS in rats after either chronic ICSS or treadmill running. Male rats (n = 35) were implanted with bipolar electrodes aimed at the ventral tegmental area of the brain, and those that performed vigorous lever pressing for ICSS (> 50 presses/min; n = 30) were counter balanced into three groups: chronic ICSS (PRESS), chronic run training (RUN), or sedentary controls (CONT). PRESS, RUN, and CONT rats performed ICSS, ran on a motorized treadmill, or sat quietly in cages for 30 min/day, 5 day/wk, for 12 wk, respectively. All animals then performed 30 min of lever pressing for ICSS and were immediately killed. Oxygen consumption, heart rate, blood pressure, rectal temperature, and plasma norepinephrine, epinephrine, and corticosterone increased (P < 0.05) for all groups during lever pressing. PRESS rats did not differ from CONT rats for any variable studied. However, heart rate was lower and oxygen consumption, norepinephrine, and corticosterone were higher in RUN than in CONT rats. Heart and ventricle weights were higher in PRESS and RUN than in CONT rats; body weights were not different. These data suggest that chronic treadmill running results in adaptations that influence cardiovascular and hormonal responses to ICSS.

Animals↗
PubMed1991

Failure of low dose carbohydrate feeding to attenuate glucoregulatory hormone responses and improve endurance performance.

The effects of ingesting a low dose of CHO on plasma glucose, glucoregulatory hormone responses, and performance during prolonged cycling were investigated. Nine male subjects cycled for 165 min at approximately 67% peak VO2 followed by a two-stage performance ride to exhaustion on two occasions in the laboratory. Every 20 min during exercise, subjects consumed either a flavored water placebo (P) or a dilute carbohydrate beverage (C). Blood samples were collected immediately before, every 20 min throughout, and immediately after exercise. Plasma was analyzed for glucose, lactate, free fatty acids (FFA), and various glucoregulatory hormones. VO2, RER, heart rate, perceived exertion, and exercise performance were also measured. Lactate, FFA, epinephrine, norepinephrine, ACTH, cortisol, and glucagon increased with exercise whereas glucose and insulin decreased (p < or = .05). Except for a small difference in glucose at 158 min of exercise and at exhaustion, no significant differences were found between drinks for any of the variables studied (P > or = .05). Ingestion of 13 g carbohydrate per hour is not sufficient to maintain plasma glucose, attenuate the glucoregulatory hormone response, and improve performance during prolonged moderate intensity cycling.

Adrenocorticotropic Hormone↗
PubMed1990

Fluid availability of sports drinks differing in carbohydrate type and concentration.

Plasma D2O-accumulation profiles (qualitative indices of fluid-absorption rates) were determined in eight subjects after ingestion of 275 mL of five D2O-labeled beverages: a water placebo (W), 6% maltodextrin (6% M), and three solutions containing a 6%, 8%, and 10% glucose-fructose mix (6% GF, 8% GF, and 10% GF). Except for W all beverages contained 20 mmol sodium/L and 3 mmol potassium/L. No differences in plasma D2O accumulation were found. Plasma glucose increased at 20 and 30 min after ingestion of the carbohydrate drinks and returned to baseline (6% GF and 6% M) or below (8% GF and 10% GF) by 60 min. Insulin responded similarly and, except for a slightly lower value at 30 min for 6% GF, no differences were detected. It appears that fluids in drinks containing less than or equal to 8-10% carbohydrate (simple sugars or maltodextrins) are made available for dilution in body fluids at similar rates and should be similar in replenishing body fluids lost in sweat during exercise.

Adult↗
PubMed1988

Effects of ingesting 6% and 12% glucose/electrolyte beverages during prolonged intermittent cycling in the heat.

This study compared the effects of ingesting 6% (MC) and 12% (HC) glucose/electrolyte beverages, and a flavored water placebo (P) on markers of fluid absorption, palatability, and physiological function during prolonged intermittent cycling in the heat. On three occasions, 15 trained male cyclists performed two 60 min cycling bouts at 65% VO2max (E1 and E2). A brief exhaustive performance ride (approximately 3 min) was completed after E1 and E2, and after 20 min recovery (P1, P2, P3). Every 20 min, subjects consumed 275 mL of P, MC or HC. The first drink contained 20 mL of D2O, a tracer of fluid entry into blood plasma. Plasma D2O accumulation was slower for HC than for P and MC (P less than 0.001). HC caused more nausea (P less than 0.01) and fullness (P less than 0.05) than MC or P, and subjects said they would be less likely to consume HC during training or competition (P less than 0.10). Sweat rates, HR, Tre, Tsk, VO2, and PV were similar for all drinks. Performance of P1, P2, P3 were not different among drinks. However, four cyclists failed to maintain the prescribed work rate during E2 for HC but only one failed for MC and P. These data suggest that the slow absorption of a 12% glucose/electrolyte beverage during prolonged intermittent exercise in the heat may increase the risk of gastrointestinal distress and thereby limit performance.

Adult↗
PubMed1988

Carbohydrate-electrolyte drinks: effects on endurance cycling in the heat.

On three occasions cyclists completed, as fast as possible, two exercise tasks (T1 and T2) separated by 30 min rest. T1 and T2 were equivalent to the work performed during 2 h cycling at 75% VO2max and 30 min at 75% VO2max, respectively. Every 20 min subjects drank 275 mL of a 6% (MC) or 2.5% (LC) carbohydrate-electrolyte beverage or a water placebo (P). The initial drink during both T1 and the rest period contained 20 g D2O as a marker for entry of ingested fluid into blood. No differences in drink effects were found for heart rate, sweat rate, change in plasma volume, rectal temperature, or D2O accumulation in blood. Blood glucose and respiratory exchange ratios were higher and T2 was performed faster with MC than with P. Ingestion of MC can help maintain blood glucose and enhance performance of prolonged cycling exercise without compromising fluid replenishment.

Adolescent↗
PubMed1987

Accumulation of deuterium oxide in body fluids after ingestion of D2O-labeled beverages.

A simple low-cost procedure was developed to compare the temporal profiles of deuterium oxide (D2O) accumulation in body fluids after ingestion of D2O-labeled solutions. D2O concentration was measured in plasma and saliva samples taken at various intervals after ingestion of 20 ml of D2O mixed with five solutions differing in carbohydrate and electrolyte concentrations. An infrared spectrometer was used to measure D2O in purified samples obtained after a 48-h incubation period during which the water (D2O and H2O) in the sample was equilibrated with an equal volume of distilled water in a sealed diffusion dish. The procedure yields 100% recoveries of 60-500 ppm D2O with an average precision of 5%. When compared with values for distilled water, D2O accumulation in serial samples of plasma and saliva was slower for ingested solutions containing 40 and 15% glucose and faster for hypotonic saline and a 6% carbohydrate-electrolyte solution. These differences appear to reflect known differences in gastric emptying and intestinal absorption of these beverages. Therefore this technique may provide a useful index of the rate of water uptake from ingested beverages into the body fluids.

Adult↗
PubMed1983

Capture efficiency of local exhaust ventilation systems.

A new technique to measure the performance of local exhaust ventilation systems has been developed and tested in both the laboratory and the field. The technique involves the measurement of the capture efficiency of exterior hoods, defined to be the fraction of contaminants given off by a process captured by the exhaust system serving that process. Capture efficiency measurement can be a powerful tool in the evaluation of local exhaust systems, since it is a direct, quantitative measure of system performance; in contrast, indices of performance now in use are either qualitative or measure quantities which may not be related directly to system performance. A basic theory for capture efficiency has been developed, and a prototype system for measuring capture efficiency has been constructed and tested. Preliminary laboratory and field measurements using the system have demonstrated the power of the method, which should find widespread use in the design of new ventilation systems and the evaluation of existing ones.

Air Pollutants, Occupational↗
PubMed1980

Air contaminants encountered by firefighters.

The concentrations of eight air contaminants suspected of causing acute and chronic health problems for firefighters were measured in over 200 fires in the City of Boston using a personal air sampler. Threatening concentrations of both carbon monoxide and acrolein were found in a small proportion of the fires. Less hazardous levels of hydrogen chloride, hydrogen cyanide, nitrogen dioxide and carbon dioxide were also noted. Benzene was found in most fires, but at concentrations well below those expected to cause acute injury. The air sampling data have application in treatment of smoke inhalation victims, development of firefighting strategies and selection of respiratory protection devices.

Air Pollutants↗
PubMed1978

Exposure of firefighters to toxic air contaminants.

A personal sampling apparatus for firefighters was developed to sample the fire atmosphere for CO, CO2, O2, NO2, HCI, HCN and pariculate content. Two fire companies made ninety successful sample runs during structural fires. CO presented a potential acute hazard and particulate concentrations were high. HCN was detected at low levels in half the samples. HCI was detected in only eight samples but on two occasions exceeded 100 ppm. CO2 and NO2 levels and O2 depression do not appear to represent significant hazards.

Air Pollutants↗
PubMed1978

Teaching occupational health to physicians.

A comprehensive training program for physicians interested in occupational health is presented. The objectives are to prepare students to identify and prevent occupational disease, with an emphasis on the development of a public health perspective. Seven content areas are described: epidemiology and biostatistics, toxicology, industrial hygiene, safety and ergonomics, policy issues, administration, and clinical aspects. These are organized in a matrix to provide appropriate levels of training for medical students, resident physicians, and general practioners as well as physicians seeking specialty training.

Curriculum↗
PubMed1977

Minimum protection factors for respiratory protective devices for firefighters.

Carbon monoxide and oxygen concentrations were measured in seventy-two structural fires using a personal air sampler carried by working firefighters. In a total sampling time of 1329 minutes the carbon monoxide concentration exceeded 500 ppm approximately 29 percent of the time. The maximum carbon monoxide concentration was 27,000 ppm and in 10 percent of the fires, the maximum concentration exceeded 5500 ppm. Only six runs indicated oxygen concentrations less than 18 percent. On the basis of these exposure data, a minimum protection factor of 100 is proposed for breathing apparatus for structural firefighting.

Air↗
PubMed1977

Health effects of exposure to automobile exhaust--V. exposure of toll booth operators to automobile exhaust.

The exposures of automobile toll booth collectors in the Boston area to selected air contaminants were monitored during the four seasons from 1972 to 1974. The highest carbon monoxide concentrations were found at the in-city toll booths and the highest lead levels at the surburban booths. Biological monitoring for carbon monoxide and lead exposure were closely related to airborne contaminant levels. The study supports the need for environmental control for toll booths located at busy highway and tunnels.

Air↗
PubMed1977

Apparent effect of an azodicarbonamide on the lungs. A preliminary report.

This preliminary study calls attention to the possible pulmonary reactivity of inhaled finely ground azodicarbonamide to which small numbers of workers may be exposed. The conditions in this particular plant involving significant exposure to respirable dust in the mg/m3 range may occur in other plants handling these fine powders. Engineering controls are indicated to protect the workers. We hope that this report will stimulate more detailed studies to validate or refute these observations.

Azo Compounds↗
PubMed1976

Evaluation of hoods for low volume-high velocity exhaust systems.

Current practice in the design of exhaust hoods for low volume-high velocity exhaust systems is empirical and evaluation of performance is conducted at the completed installation. A procedure is described for laboratory evaluation of prototype hoods using a simulator in conjunction with a tracer aerosol.

Air Pollution↗
PubMed1976

Occupational disease in the rubber industry.

We have studied mortality patterns in a large cohort of rubber workers. We have examined workers exposed to curing fumes, processing dusts, and industrial talc and have begun to evaluate exposures of these workers in detail. Gastrointestinal (especially stomach) cancer appears in excess in processing workers. Lung cancer is excessive in curing workers. Leukemia is increased generally. All three groups studied for respiratory disease have an increase in disease prevalence which is related to intensity and duration of exposure. Since both an increase in stomach cancer and respiratory disease is seen in processing workers, exposures in this area must be controlled. Since both lung cancer and chronic respiratory disease is excessive in curing rooms, this exposure must be controlled. The leukemia risk is probably related to solvents. Whether this is all explainable by past benzene exposure is unknown. Further studies are planned to refine our knowledge concerning these risks so that occupational disease in the rubber industry can be prevented.

Adult↗