Biomedical subjects

William C Adams

Publications and source records attributed to William C Adams.

11 recordsLinked to original sources

PubMed2006

Time course of ozone-induced changes in breathing pattern in healthy exercising humans.

We examined the time course of O3-induced changes in breathing pattern in 97 healthy human subjects (70 men and 27 women). One- to five-minute averages of breathing frequency (f(B)) and minute ventilation (Ve) were used to generate plots of cumulative breaths and cumulative exposure volume vs. time and cumulative exposure volume vs. cumulative breaths. Analysis revealed a three-phase response; delay, no response detected; onset, f(B) began to increase; response, f(B) stabilized. Regression analysis was used to identify four parameters: time to onset, number of breaths at onset, cumulative inhaled dose of ozone at onset of O3-induced tachypnea, and the percent change in f(B). The effect of altering O3 concentration, Ve, atropine treatment, and indomethacin treatment were examined. We found that the lower the O3 concentration, the greater the number of breaths at onset of tachypnea at a fixed ventilation, whereas number of breaths at onset of tachypnea remains unchanged when Ve is altered and O3 concentration is fixed. The cumulative inhaled dose of O3 at onset of tachypnea remained constant and showed no relationship with the magnitude of percent change in f(B). Atropine did not affect any of the derived parameters, whereas indomethacin did not affect time to onset, number of breaths at onset, or cumulative inhaled dose of O3 at onset of tachypnea but did attenuate percent change in f(B). The results are discussed in the context of dose response and intrinsic mechanisms of action.

Adolescent↗

PubMed2006

PD-1 is a regulator of virus-specific CD8+ T cell survival in HIV infection.

Here, we report on the expression of programmed death (PD)-1 on human virus-specific CD8(+) T cells and the effect of manipulating signaling through PD-1 on the survival, proliferation, and cytokine function of these cells. PD-1 expression was found to be low on naive CD8(+) T cells and increased on memory CD8(+) T cells according to antigen specificity. Memory CD8(+) T cells specific for poorly controlled chronic persistent virus (HIV) more frequently expressed PD-1 than memory CD8(+) T cells specific for well-controlled persistent virus (cytomegalovirus) or acute (vaccinia) viruses. PD-1 expression was independent of maturational markers on memory CD8(+) T cells and was not directly associated with an inability to produce cytokines. Importantly, the level of PD-1 surface expression was the primary determinant of apoptosis sensitivity of virus-specific CD8(+) T cells. Manipulation of PD-1 led to changes in the ability of the cells to survive and expand, which, over several days, affected the number of cells expressing cytokines. Therefore, PD-1 is a major regulator of apoptosis that can impact the frequency of antiviral T cells in chronic infections such as HIV, and could be manipulated to improve HIV-specific CD8(+) T cell numbers, but possibly not all functions in vivo.

Antigens, CD↗

PubMed2006

Comparison of chamber 6.6-h exposures to 0.04-0.08 PPM ozone via square-wave and triangular profiles on pulmonary responses.

It has become increasingly well realized that laboratory simulations of air pollution risk assessment need to employ O(3) concentration profiles that more accurately mimic those encountered during summer daylight ambient air pollution episodes. The present study was designed to compare the pulmonary function and symptoms of breathing discomfort responses to a 6.6-h square-wave 0.08-ppm O(3) chamber exposure to those observed in a triangular O(3) exposure profile (mean of 0.08 ppm), as well as to both a 0.06-ppm square-wave and triangular mean 0.06-ppm exposure, and to those observed during a triangular mean 0.04-ppm exposure and to a filtered air (FA) square-wave exposure. Thirty young adults (15 of each gender) served as subjects, each completing all exposures. While the 6.6-h postexposure responses to the acute triangular exposure to a mean O(3) concentration of 0.08 ppm did not differ significantly from those observed in the square-wave exposure, forced expiratory volume in 1 s (FEV)(1.0) and total symptoms severity (TSS) were significantly different from preexposure at 4.6 h (when O(3) concentration was 0.15 ppm) in the triangular exposure, but not until 6.6 h in the square-wave exposure. Thus, significant pulmonary function and symptoms responses were observed over a longer period in the triangular exposure protocol at a mean O(3) concentration of 0.08 ppm. These results support previous evidence that O(3) concentration has a greater singular effect in the total inhaled O(3) dose than do V(E) and exposure duration. Subtracting pulmonary function effects consequent to O(3) exposure to existent 8-h average background levels (e.g., approximately 0.04 ppm, rather than those observed in FA exposures) from those observed at higher concentrations (e.g., approximately 0.08 ppm) represents a means of focusing the regulatory effort on effects that can be controlled. The greatest pulmonary function and symptoms responses observed for a 0.04-ppm triangular exposure were nearly the same as those for the FA square-wave exposure. Thus, results of the present study show that calculating the net pulmonary function effect of exposure to 0.08 ppm with "correction" for FA response, or for that incurred for 0.04 ppm O(3), does not result in any statistically significant difference.

Adult↗

PubMed2006

Human pulmonary responses with 30-minute time intervals of exercise and rest when exposed for 8 hours to 0.12 ppm ozone via square-wave and acute triangular profiles.

Hazucha et al. (1992) compared pulmonary function responses during 8-h square-wave exposures to FA and to 0.12 ppm O3, as well as to an acute triangular exposure to a mean O3 concentration of 0.12 ppm. With 30 min of moderate exercise each hour during 8 h of continuous exposure, significantly greater pulmonary function responses were observed between 5 h and 7 h when O3 was varied in an acute triangular configuration from 0.00 ppm to 0.24 ppm over the first 4 h and back to 0.00 ppm during the last 4 h than when O3 concentration was maintained constant at 0.12 ppm throughout. These investigators employed equal periods of 30 min of exercise, in which mean VE was approximately 40 L/min, and 30 min of rest, with pulmonary function measurements taken at the end of each hour. This procedure (i.e., taking measurements at the end of each hour) could attenuate the full effect that would be observed very soon after exercise cessation, and permit some recovery to occur. Accordingly, in the present study, the primary objective was to determine what effect observations of pulmonary responses assessed immediately following repeated 30 min exercise bouts, as well as those at the end of each hour (following approximately 30 min rest) during 8-h square-wave exposures to FA and to 0.12 ppm O3, as well as to an acute triangular exposure to a mean O3 concentration of 0.12 ppm. During the last 4 h of the 8-h, 0.12-ppm square-wave exposure, the 30-min mean increases in FEV1.0 responses were consistently greater at the end of the first half hour immediately following exercise (-1.22%) than at the end of the second half-hour following 30 min of rest (+0.01%). Further, even though O3 concentration was steadily decreasing from 0.24 ppm to 0 ppm during the last 4 h of the triangular exposure, similar increases in FEV1.0 decrement (-1.38%) immediately after each 30 min exercise bout, and small recovery at the end of each 30 min rest (+0.56%) were observed. Symptom scores in both exposures during the last 4 h also showed this effect.

Adolescent↗

PubMed2003

Comparison of chamber and face mask 6.6-hour exposure to 0.08 ppm ozone via square-wave and triangular profiles on pulmonary responses.

Recently, a stainless-steel air pollution chamber was acquired in this laboratory, and data were obtained in a study that convincingly demonstrated that chamber and face-mask inhalation methods of exposing young adult subjects for 6.6 h to nearly identical total inhaled O(3) doses at 0.12 ppm produced very similar pulmonary function, symptoms, and exercise ventilatory pattern responses. However, the results of a 6.6-h face-mask exposure to 0.08 ppm O(3), compared to some previous chamber exposure study results, revealed several small incongruities that may be due primarily to high individual subject "noise" in responses to a relatively low O(3) exposure. To resolve these differences, it was the primary purpose of this study to compare chamber exposure responses to those elicited via face-mask exposure to 0.08 ppm O(3) for 6.6 h with subjects serving as their own controls. Two types of O(3) exposure patterns were used: (1) the usual square-wave profile, and (2) an acute triangular profile, in which O(3) concentration was increased each hour from 0.03 ppm to 0.15 ppm during h 4 and then decreased each hour to 0.05 ppm (mean = 0.08 ppm). Thirty young adults (15 of each gender) served as subjects. The two exposure methods (i.e., face mask and chamber) yielded near identical total inhaled O(3) doses in both the square-wave and triangular exposure profiles, and produced very similar postexposure pulmonary function, symptoms, and exercise ventilatory pattern responses. However, pulmonary function and symptoms responses became statistically significant from preexposure at the end of h 4 (when [O(3)] = 0.15 ppm) in the triangular protocols, but not until h 6 in the square-wave protocols. These results support previous evidence that O(3) concentration has a greater singular effect in the total inhaled O(3) dose than do V(E) and exposure duration.

Adult↗

PubMed2003

Relation of pulmonary responses induced by 6.6-h exposures to 0.08 ppm ozone and 2-h exposures to 0.30 ppm ozone via chamber and face-mask inhalation.

While direct comparison of pulmonary responses to 6.6-h exposures to 0.08 to 0.12 ppm ozone O3 have demonstrated that chamber and face-mask inhalation methods yield closely similar results, no comparative study of responses to 2-h intermittent exercise (IE) exposures to higher O3 concentrations have been reported. The present study was designed to achieve three primary objectives: (1) to compare pulmonary function and symptoms effects of a 2-h IE exposure to 0.30 ppm O3 via chamber and via face mask; (2) to compare the pulmonary effects of 6.6-h chamber exposure to 0.08 ppm O3 to those observed in 2-h IE 0.30 ppm O3 exposures via chamber and via face mask; and (3) to examine filtered air (FA) recovery pulmonary and symptoms responses following chamber exposures of 6.6 h to 0.08 ppm O3 and 2 h to 0.30 ppm O3. A simple regression of postexposure percent change in FEV(1.0) for the 2-h IE, 0.30-ppm O3 chamber exposure as a function of postexposure percent change in FEV(1.0) for the 2-h IE, 0.30-ppm O3 exposure with face mask yielded an R(2) of 0.83. Further, a regression of the postexposure FEV(1.0) response to the chamber 6.6-h, 0.08-ppm O3 exposure as a function of postexposure FEV(1.0) response to the face mask 2-h IE, 0.30-ppm O3 exposure (R(2) of 0.34) was similar to the 0.40 value obtained for the two chamber exposures FEV(1.0) response comparison. Results of the 1.4-h FA recovery following the two chamber O3 exposures showed different rates of FEV(1.0) and symptoms rectification that appeared related to the total O3 dose (product of O3 concentration, ventilation rate, and duration). More data are needed to clarify short-term recovery of O3-induced pulmonary effects and how they may be related to the more abundant data available on the delayed recovery of pulmonary function seen over longer time periods, such as 24 h.

Administration, Inhalation↗

PubMed2003

The size-independent oxygen cost of running.

PURPOSE: The purpose of this investigation was to determine whether differences in running economy among children, adolescents, and adults can be explained by differences in resting metabolism, mass, and stature. METHODS: Participants were 36 children, 23 adolescents, and 24 adults. Mass-specific gross oxygen cost per minute ([OV0312]O(2gross) x M-1), mass-specific gross oxygen cost per kilometer (VO(2gross) x M-1), mass-specific net oxygen cost per kilometer (VO(2net) x M-1), and a dimensionless index called the size-independent cost (SIC) were compared for level treadmill running at speeds ranging from 1.6 to 3.1 m.s-1. SIC was defined as the net oxygen cost to move a mass of 1 kg a distance equal to stature (mL x kg-1). RESULTS: Children generally had higher [OV0312]O(2gross).M-1, VO(2gross) x M-1, and VO(2net) x M-1 than adolescents who similarly had greater costs than adults. When SIC was used to control for size-related differences in resting metabolism, mass and stature the costs of children and adults were similar (0.323 +/- 0.034 and 0.338 +/- 0.035 mL x kg-1, respectively, P = 0.54). However, adolescents had significantly higher SIC (0.360 +/- 0.026 mL x kg-1, P < 0.001) than both children and adults. Analysis of data from the literature indicated SIC peaks around 15 yr of age and changes were parallel to changes in the ratio of leg length to stature. CONCLUSIONS: We conclude that when resting metabolism and the dimensional effects of mass and stature are controlled, the running economy of adolescents is greater than in children and adults, which are similar. Therefore, differences in [OV0312]O(2gross) x M-1, VO(2gross) x M-1, and VO(2net) x M-1 among children, adolescents, and adults do not solely reflect qualitative differences in running performance.

Adolescent↗

PubMed2002

Comparison of chamber and face-mask 6.6-hour exposures to ozone on pulmonary function and symptoms responses.

Because of increased interest in an 8-h ozone (O(3)) federal air quality standard, acute pulmonary function responses to prolonged square-wave O(3) exposure between 0.08 and 0.12 ppm have been examined in several U.S. Environmental Protection Agency (EPA) chamber studies. A low-cost face-mask O(3) exposure system was developed in this laboratory and found to produce closely similar pulmonary responses to those observed in prolonged exposures by U.S. EPA investigators. The primary purpose of the present study was to investigate the pulmonary function and subjective symptoms effects of 6.6-h square-wave exposure to 0.12 ppm O(3) by these two methods using the same group of subjects. In addition, further investigation of pulmonary function and symptoms responses upon 6.6-h exposures to lower levels of O(3) (0.04-0.08 ppm) were studied with the face-mask inhalation system. Thirty young adult subjects completed five 6.6-h exposures with six 50-min periods of exercise at an intensity requiring a minute ventilation rate (V(E)) of ~20 L/min/m2 of body surface area, each followed by 10 min of rest, except following 3 h when the rest period was lengthened for a lunch break. The total O(3) doses for the chamber and face-mask exposures to 0.12 ppm O(3) were not significantly different from each other, since the additional O(3) dose during the 35 min lunch break in the chamber exposure was offset by a slightly lower average exercise V(E) (i.e., 19.1 L/min/m2). The data convincingly demonstrated that the two methods of exposing young adults to nearly identical total inhaled O(3) doses at 0.12 ppm produce very similar pulmonary function, symptoms, and exercise ventilatory pattern responses. On the other hand, results of the 6.6-h face-mask exposures to 0.08 ppm O(3) in the present study, compared to similar U.S. EPA exposure study results, revealed several incongruities that may be due primarily to high individual subject variability in responses to a relatively low O(3) exposure. Thus, a comparison of chamber exposure responses to those elicited via face-mask exposure to 0.08 ppm O(3) in the same subject group seems warranted.

Adult↗

PubMed2002

A dimensional paradigm for identifying the size-independent cost of walking.

PURPOSE: The purpose of this investigation was to present an alternative paradigm to that of dividing the rate of oxygen consumption by body mass (VO2.M-1, mL.min-1kg-1) for comparing walking economy in humans. METHODS: The paradigm used dimensional analysis and similarity theory to derive a measure of size-independent cost (SIC), defined as the net oxygen cost to move a mass of one kilogram a distance equal to stature. Mass-specific gross oxygen cost per kilometer, mass-specific net oxygen cost per kilometer, and SIC were used to analyze results from 184 subjects who performed level treadmill walking. Subjects were 63 children, 40 adolescents, 42 adults, and 39 seniors (approximately equal numbers of male and female subjects) walking at treadmill speeds from 0.9 to 1.8 m.s-1. RESULTS: Comparisons of metabolic cost between children and the older groups were dependent on the measure of metabolic cost and speed. At each speed, VO2gross.M-1 was higher in children than in older groups, whereas VO2net.M-1 of children was higher at 1.1 and 1.3, but similar at 0.9 m.s-1. SIC of children was similar at 1.1 and 1.3 m.s-1 but lower than the older groups at 0.9 m.s-1. CONCLUSIONS: Higher mass-specific metabolic costs of children were explained by differences in standing metabolism and stature. When these variables were considered, children had similar or lower metabolic costs than older subjects. Alternatives to using mass alone to normalize locomotor economy are warranted.

Adolescent↗

PubMed2002

A theory for normalizing resting .VO(2) for differences in body size.

PURPOSE: The purpose of this paper was two-fold: 1) to present a method of normalizing data for differences in body size that is consistent with the dimensional relationship between mass and power, and can be universally applied to subjects of any age, sex, or size without statistical cross-validation; and 2) to apply the model to data gathered from boys, girls, men, and women to determine whether or not age- and sex-dependent differences in resting .VO(2) exist. METHODS: Mass, percent body fat, and resting .VO(2) were measured in 39 boys, 40 girls, 40 men, and 40 women. RESULTS: Dimensional analysis predicted .VO(2) = a fat-free mass (FFM)2/3, with a defined as the size-independent metabolism of FFM. Bivariate correlation revealed the association between .VO(2) and FFM in children was consistent with biological similarity but not in men and women. Group mean .VO(2).FFM(-2/3) (mL.min(-1).kg(-2/3)) was significantly greater in children (21.7 +/- 2.62) than adults (16.7 +/- 2.30). Also, .VO(2).FFM(-2/3) of female subjects was significantly lower than male subjects in children (girls: 21.0 +/- 2.46; boys: 22.5 +/- 2.61) and adults (women: 15.0 +/- 2.39; men: 16.5 +/- 2.21). CONCLUSIONS: The dimensional paradigm indicated that mass exponents not equal to 2/3 simultaneously factor out size-dependent and size-independent differences that accompany differences in size. Therefore, size-independent comparisons can only be made using the theoretical mass exponent of 2/3. Also, the experimental results indicated that structural changes accompanying growth must be different from those hypothesized to be the cause of 3/4 scaling in adult animals of different size and species.

Adult↗

PubMed2002

Upper-limb bone mineral density of female collegiate gymnasts versus controls.

PURPOSE: We examined bilateral bone mineral density (BMD) in the arms of female college gymnasts to assess the relative contribution of high-impact loading forces versus daily activities on bone plasticity. METHODS: Twenty-five female collegiate gymnasts and 25 controls were studied. BMD of the lumbar spine, proximal femur, and whole body were assessed via dual energy x-ray absorptiometry. Upper-limb BMD was determined by custom analyses of the whole-body scans to examine arms individually. RESULTS: BMD of gymnasts was significantly (P < 0.0001) greater than controls at all sites. Whole-body BMD was 8% higher in gymnasts (1.270 +/- 0.078 vs 1.175 +/- 0.073 g x cm(-2)), with 18-19% differences in the lumbar spine (1.427 +/- 0.144 vs 1.212 +/- 0.106 g x cm(-2), right proximal femur (1.298 +/- 0.101 vs 1.100 +/- 0.129 g x cm(-2)), and left proximal femur (1.293 +/- 0.111 vs 1.104 +/- 0.133 g x cm(-2)). Arm BMD was 17% greater in gymnasts, with higher values in both dominant (1.013 + 0.067 vs 0.875 + 0.066 g x cm(-2)) and nondominant (1.002 + 0.060 vs 0.849 + 0.062 g x cm(-2)) arms. Intragroup comparisons revealed a significantly (P < 0.0001) greater BMD in the dominant arm of the controls but no side-to-side difference in the arms of the gymnasts. CONCLUSIONS: Upper-limb BMD followed use patterns in both gymnasts and controls, demonstrating that the forces imposed on the arms with gymnastics training enhanced BMD and resulted in no bilateral differences. These findings illustrate the association between gymnastics training and increased BMD throughout the body, suggesting that the high BMD values observed in gymnasts are due primarily to the activity itself rather than selection bias.

Absorptiometry, Photon↗