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Biomedical subjects

J E Wilkerson

Publications and source records attributed to J E Wilkerson.

At least 19 recordsLinked to original sources
PubMed2001

Serotonin elicits long-lasting enhancement of rhythmic respiratory activity in turtle brain stems in vitro.

Brain stem preparations from adult turtles were used to determine how bath-applied serotonin (5-HT) alters respiration-related hypoglossal activity in a mature vertebrate. 5-HT (5-20 microM) reversibly decreased integrated burst amplitude by approximately 45% (P < 0.05); burst frequency decreased in a dose-dependent manner with 20 microM abolishing bursts in 9 of 13 preparations (P < 0.05). These 5-HT-dependent effects were mimicked by application of a 5-HT(1A) agonist, but not a 5-HT(1B) agonist, and were abolished by the broad-spectrum 5-HT antagonist, methiothepin. During 5-HT (20 microM) washout, frequency rebounded to levels above the original baseline for 40 min (P < 0.05) and remained above baseline for 2 h. A 5-HT(3) antagonist (tropesitron) blocked the post-5-HT rebound and persistent frequency increase. A 5-HT(3) agonist (phenylbiguanide) increased frequency during and after bath application (P < 0.05). When phenylbiguanide was applied to the brain stem of brain stem/spinal cord preparations, there was a persistent frequency increase (P < 0.05), but neither spinal-expiratory nor -inspiratory burst amplitude were altered. The 5-HT(3) receptor-dependent persistent frequency increase represents a unique model of plasticity in vertebrate rhythm generation.

Animals↗
PubMed1986

An association between aerobic fitness and lung closing volume.

This study was performed to determine whether an association exists between relative aerobic fitness (fitness index) and lung closing volume (CV). The subject population consisted of 100 healthy nonsmoking adults (50 males and 50 females) divided equally into five age groups; 20-29, 30-39, 40-49, 50-59, and over 60 years. Each subject underwent four to six closing volume and forced vital capacity (FVC) tests followed by a modified Balke maximal oxygen uptake test on a motor-driven treadmill with a constant treadmill speed. Relative VO2 maximum (VO2 max, mlO2 X kg-1 X min-1) was determined from the exercise test and was used to define subject rank on the fitness index. CV, as a % of slow vital capacity (SVC), had a negative linear correlation (r = -0.53, P less than 0.05) with the fitness index. Slope of phase III (%N2/L) and FEV1/FVC (forced expired volume in 1 s as a % of forced vital capacity) also had significant correlation coefficients (r = -0.31, r = 0.24, respectively; both P less than 0.05) with the fitness index. The correlation coefficients, with age partialled from the relationships, between FVC/body weight (kg) and VO2 max were r = 0.59 for females and r = 0.43 for males (P less than 0.05, both groups). We hypothesize that the effects of aerobic fitness on lung function may be the result of changes in autonomic nervous system activity and may represent a situation where a high level of aerobic fitness affects the aging process of the lung beta-adrenergic nervous system.

Adult↗
PubMed1986

Effect of prolonged bed rest on lung volume in normal individuals.

Pulmonary function was assessed in supine subjects before, during, and after three separate bed-rest studies of 11 and 12 days duration. Forced vital capacity (FVC) increased during bed rest in each subject. Total lung capacity (TLC) was measured by helium dilution in one bed-rest study and increased in each subject, while residual volume and functional residual capacity of the respiratory system did not change. No change in FVC was found in an ambulatory control group using identical measurement techniques. Maintaining base-line plasma volume during one bed rest by the use of exogenous estrogen did not prevent an increase in FVC, and decreasing plasma volume with diuretics in ambulatory subjects to the same degree as seen in the bed rests did not cause an increase in FVC. We conclude that prolonged bed rest results in a small significant increase in TLC and that this change is not dependent on alterations in plasma volume.

Adult↗
PubMed1986

Blood biochemical status of miniature swine during submaximal and exhaustive exercise.

Simultaneous arterial (left atrial) and mixed venous (right atrial) blood samples were anaerobically drawn from 14 miniature swine (mean weight = 25.0 +/- 1.7 [SE] kg) in order to examine the adequacy of these animals as a model for the exercising human. Samples were drawn: 1) at rest; 2) during exercise that elicited 80.4 +/- 1.2% of the animals' measured maximal heart rates; 3) at exhaustion; and 4) during the 4th min of a standing, resting recovery period. At rest, the animals were mildly alkalotic (pHa = 7.497 +/- 0.016) and hypocapnic (pCO2a = 29.6 +/- 1.2 torr), with low hematological values (arterial hemoglobin = 6.66 +/- 0.18 mmol X 1-1; arterial hematocrit = 32.0 +/- 0.9%) and slightly elevated catecholamine concentrations. During the submaximal exercise, there were no statistically significant changes in the arterial blood pH or in plasma sodium (Na+) and chloride (Cl-) concentrations, with significant decreases observed in Hcta, pCO2a, and increases in arterial plasma norepinephrine, total protein, and potassium (K+) concentrations. At exhaustion, pHa and pCO2a decreased further, with increases noted in the arterial plasma concentrations of K+, epinephrine, total protein, and the Hct but not in Na+ or Cl-. During recovery, arterial lactate averaged 20.54 +/- 0.71 mmol X 1-1. Venous changes were similar to those observed in arterial blood, with a mean pHv of 7.168 +/- 0.043 and arterial lactate = 21.08 +/- 0.90 mmol X 1-1 during recovery. Exercise-induced hemoconcentration was similar for both arterial and venous sample sites during both the submaximal and exhaustive exercise.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Effects of exercise and anabolic steroids on total and lipoprotein cholesterol concentrations in male and female rats.

Forty male and 40 female rats were randomly assigned to 1 of 4 experimental groups. Half of the animals of each gender were exercised by jumping (weighted by a vest with up to 70% body weight) to a height of 16 cm 20 times X d-1 (30 s between jumps) 5 d X wk-1 for 8 wk. Half of the exercised animals and half of the sedentary animals were injected with the anabolic steroid durabolin (0.2 mg in 0.1 ml sesame seed oil) 6 d X wk-1 for the last 3 wk of the 8-wk exercise program. The other animals were injected with 0.1 ml of sesame seed oil (as a placebo) on the same schedule. At the end of the 8-wk program, blood was drawn from the right atria of the anesthetized animals. Plasmas were analyzed for total cholesterol (TC) and high density lipoprotein cholesterol (HDL-C) concentrations. Low density lipoprotein cholesterol (LDL-C) concentration was estimated as the difference between these two parameters (TC - HDL-C). A three-factor analysis of variance (2 X 2 X 2) demonstrated that there was a significant (P less than 0.05) gender effect (males greater than females), but no steroid or exercise main effects for TC. There were significant (P less than 0.05) steroid and exercise main effects for both HDL-C and estimated LDL-C, as well as a significant gender main effect for estimated LDL-C (but not HDL-C).(ABSTRACT TRUNCATED AT 250 WORDS)

Anabolic Agents↗
PubMed1984

Effects of endurance exercise on metabolic water production and plasma volume.

Six endurance-trained and heat-acclimatized adult males ran for 1 h (or until exhaustion) at room temperature (23.8 degrees C) on three occasions. The work loads approximated 37, 56, and 74% of the subjects' aerobic capacities. Venous blood samples were drawn, and urine was collected before and immediately after each exercise bout. Metabolic cost was partitioned by energy substrate, and metabolic water production was quantified from urinary nitrogen, oxygen, and carbon dioxide production. Total body water loss was recorded as the decrease in body weight during the exercise. All subjects completed 1 h of exercise at the two lower exercise intensities but, due to exhaustion, averaged only 35.5 min at the highest work intensity. There were no significant changes in plasma volume after the exercise bouts. Metabolic water production increased with increasing work intensity as did the fraction of total caloric expenditure derived from carbohydrate metabolism. Plasma protein content significantly increased at all levels of exercise intensity. Metabolic water production alone would be of minimal help in plasma volume maintenance and thermoregulation during endurance exercise.

Adult↗
PubMed1982

Erythrocyte indices during a competitive marathon.

Three adult male volunteers ran a competitive marathon (42.2 km) during which there was an average ambient air (dry bulb) temperature of 19.4 degree C, with an average ambient water vapor pressure of 9.5 Toor. Prior to and at 4.8-km (3-mi) intervals throughout the race, venous blood samples were drawn from an indwelling catheter in a peripheral arm vein. In each blood sample the total erythrocyte count (EC) was made, and whole blood hemoglobin concentration, hematocrit, and plasma osmolality were determined. From these measurements, the standard red blood cell (RBC) indices of mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), and mean corpuscular hemoglobin concentration (MCHC) were calculated. The three subjects completed the race in 191, 240, and 310 min, with weight losses averaging 5.4% of prerace body weight. EC linearly decreased below the prerace control levels of 5.69 X 10(6) RBC/mm3 for the first 14.5 km of the race, so that EC was 4.7% below control levels by this point. Subsequently, EC rose back to control levels by 19.3 km, where it remained for the rest of the race. MCHC, MCH, and calculated total RBC volume did not significantly change during the race. Plasma osmolality related to plasma osmolality. These data indicate the dynamic nature of erythrocyte number and volume during long-duration submaximal exercise, and the extraordinary ability of the human body to maintain RBC indices within narrow limits when confronted with a severe stress such as the marathon.

Adult↗
PubMed1982

Plasma electrolyte content and concentration during treadmill exercise in humans.

Five healthy males volunteered to exercise for 20 min on a motor-driven treadmill at five submaximal intensities (30, 45, 60, 75, and 90% of VO2 max). Peripheral venous blood samples were drawn from an indwelling catheter prior to and at 9, 14, and 19 min of each exercise bout. Blood samples were assayed for whole-blood hemoglobin, total plasma protein concentrations, and hematocrit, with plasma water concentration calculated from these values. The plasma concentration of the electrolytes sodium (Na+), potassium (K+), total calcium (Catot), ionized calcium (Ca2+), chloride (Cl-), and inorganic phosphorus (Pi) were also determined. With plasma and blood volumes the total plasma contents of each of the measured constituents and the concentration of each electrolyte per liter of water were calculated. Statistically significant linear increases in plasma concentrations of Na+, K+, and Cl- relative to exercise intensity were observed, with linear decreases in plasma contents of Na+ and Cl- and linear increases in K+ content. Plasma Pi concentration decreased with a Pi increased content, with plasma Catot concentration elevated at the highest two work loads. Plasma Catot content increased linearly with exercise intensity and duration. Plasma water concentration and content decreased with exercise intensity, resulting in no change in electrolyte concentration per liter of water except at the highest two exercise intensities. These data suggest that extrapolation from plasma electrolyte concentration to muscle concentration and/or content is not supported. Changes in plasma volume and plasma water must be considered when postulating a role for electrolytes in the physiological responses of the human to exercise.

Adult↗
PubMed1982

Metabolic and thermoregulatory responses to exercise during the human menstrual cycle.

Metabolic and thermoregulatory responses to exercise during the human menstrual cycle. Med. Sci. Sports Exercise, Vol. 14, No. 4, pp. 270-275, 1982. Six healthy adult females with presumptively normal menstrual cycles volunteered to exercise on a bicycle ergometer on five separate days (days 2, 8, 14, 20, and 26 of the menstrual cycle; day 1 = onset of menstruation). On each experimental day each subject exercise at four submaximal exercise intensities and at an exercise intensity that elicited a peak oxygen uptake. At rest and at each exercise intensity metabolic and thermoregulatory measurements were made. There were no changes at rest or at any exercise intensity relative to cycle day in absolute oxygen uptake (l . min-1). Similarly, mean peak oxygen uptake and average work time to exhaustion were not different during the various phases of the menstrual cycle. The mean core temperature (Tre) at each exercise intensity was elevated on days 14 and 20 above that observed during flow (day 2) and the follicular phase (day 8). This implied a dissociation of metabolic responses from thermoregulatory responses to exercise during the human menstrual cycle similar to that previously observed in exercising febrile males.

Adult↗
PubMed1982

Judo nephropathy: trauma versus non-trauma.

Nine male judo players were studied to evaluate possible renal dysfunction after repeated falls. During a 15-second period a pair of subjects took two steps and one subject performed an arm throw upon his partner. The procedure was then reversed and he was thrown by his partner. This alternating exercise was continued for a total of hundred falls per subject. This protocol was carried out twice by each subject, once on a 10-cm mat, once on a 2.5-cm mat. The compressive forces after falling on both mats were 0 joules and 5,919 joules, respectively. Experimental blood and urine samples were collected at 1, 2, 4, 9, and 24 hours post-trauma. Twenty four-hour glomerular filtration rate (GFR) was significantly inhibited during the traumatic session (2.5-cm mat). For the non-traumatic session (10-cm mat) a 24-hour GFR increase of 73.88% was noted compared to control values. Both experimental sessions demonstrated significantly increased urinary protein. Electrophoretic analysis of the urine showed a marked predominance of albumin. Hematuria present after the traumatic session grossly discolored the urine. All non-traumatic samples failed to demonstrate the presence of red blood cells in pathologic numbers. In this investigation the precipitating factor for hematuria during exercise seemed to depend largely on the severity of the mechanical trauma, and not the exercise per se.

Athletic Injuries↗
PubMed1982

Perceived exertion and anaerobic threshold during the menstrual cycle.

Six adult females with normal menstrual cycles (28-31 d in length) volunteered to exercise on a bicycle ergometer on five different days of their menstrual cycles (days 2, 8, 14, 20, and 26; day 1 = onset of menstruation). Each day the subjects exercised at a maximum work load (184.4 W) and at four submaximal exercise intensities (45.0, 83.1, 121.4 and 154.4 W). Ratings of perceived exertion (RPE) were obtained during minute 4 of each 5-min submaximal exercise bout and at exhaustion each day. Overall, RPE was linearly correlated with heart rate (r = 0.87) when all exercise intensities and cycle days were considered. There was no statistically significant (P greater than 0.05) change in RPE at any exercise intensity related to cycle day. Factors (expired ventilatory volume, respiratory frequency, tidal volume, end-tidal CO2 tension, and heart rate) that may have affected RPE, maximal aerobic power, and anaerobic threshold (AT) were also statistically unchanged because of cycle day. Anaerobic threshold averaged 68.7% of the VO2max, or 1.592 l . min for all cycle days, as determined by the total expiratory volume/oxygen uptake "break point" method of Wasserman and co-workers (18). These data support the utilization of female subjects with normal menstrual cycles in psychophysiological studies without regard to menstrual cycle phase.

Anaerobiosis↗
PubMed1981

Dentin Apposition rates as markers of primate growth.

The incremental lines of von Ebner frequently have been described as ultradian markers of dentin calcification. To determine the relationship between these lines and the quantity of dentin formed, reference was made to an in vivo marker of calcification, tetracycline. These markers were produced by injecting four juvenile monkeys periodically over a period of 175 days. These animals had been subjects in the heat stress study and were exposed to a series of heat stresses and cortisone injections. At the end of the study, undecalcified thin sections of premolars and second molars were prepared by standard histological techniques. We found that linear apposition rates increased in a gradient toward the pulp chamber. These rates varied within each tooth but not in corresponding parts of different teeth. Also, we determined that dentin apposition can be temporarily depressed by certain metabolic stresses. Heat load and cortisone significantly slowed dentin formation. Each depression, however, was followed by a "catch-up" period. Incremental line distances also increased as a function of the distance from the dentoenamel junction. There was, however, no systematic relationship between apposition rates and incremental line distance; these distances did not deviate from the observed trends during periods of slowed apposition. Incremental lines may by interpreted, not as natural growth markers, but as structural phenomena which are a function of dentin geometry and tubule bending.

Animals↗
PubMed1981

Physiologic response to endurance work as a function of prior exercise.

Five male subjects performed an endurance task (ET) following 20 min of prior exercise (PE) at work loads corresponding to approximately 30%, 45%, 60% and 75% of VO2 max. There was a 1-min rest interval between the PE and ET. The ET consisted of 10 min of walking at a speed and slope corresponding to 75% of VO2 max after which time the speed was increased by 10 m/min each minute until the subject could no longer continue. Although endurance performance was not significantly influenced by the PE-30 and PE-45, performance following PE-60 and PE-75 was significantly impaired, as was the peak VO2 attained at the end of the ET. Although O2 deficits at the beginning of the ET were reduced by the higher intensities of PE, the plasma lactate levels at the 8th min of the ET were not significantly lower under those conditions since those levels of PE led to some lactate accumulation during the PE itself. VO2 during the last 5 min of the constant load part of the ET was similar in all conditions but PE-75, during which it was higher. It is suggested that although PE might be useful for tasks in which the initial work loads are maximal or supramaximal with respect to VO2, it is of questionable value in endurance tasks that begin at a high but submaximal intensity.

Adult↗
PubMed1980

Plasma testosterone during treadmill exercise.

Five male volunteers performed 20 min of steady-state submaximal exercise on a motor-driven treadmill at five intensities (30, 45, 60, 75, and 90% VO2 max) as well as several maximal aerobic capacity tests. Peripheral venous plasma testosterone concentrations increased above resting values in proportion to exercise intensity. However, this increase in plasma testosterone concentration was virtually equal in magnitude to the decrease in plasma volume observed consequent to the exercise bouts, resulting in no change in total testosterone contents. There was an unexpected anticipatory elevation in resting preexercise control testosterone concentration and content with increasing work intensity. The possibility that testosterone has a direct role in the organism's response to whole-body exercise is questioned.

Adult↗
PubMed1977

Exercise-induced changes in blood ammonia levels in humans.

Five male and two female subjects each performed a maximal aerobic capacity (VO2 max) test, and two to four submaximal aerobic exercise bouts (requiring approximately 50 and 80% of the individual's measured VO2 max) on a motor-driven treadmill. Pre-exercise resting oxygen uptakes (VO2) and heart rates were determined and a venous blood sample drawn prior to each work session. These same measurements were repeated at 4, 15, 30, and 45 min of the resting recovery period that followed each exercise experiment. Additionally, at the 30th min of each 45-min submaximal exercise, another peripheral venous blood sample was drawn following determination of VO2 and heart rate. In all blood samples, the hematocrit and concentrations of ammonia, lactate, pyruvate, glucose, hemoglobin, and total plasma proteins were measured. A significant exponential relationship was observed betwen blood ammonia levels and VO2 for all sample periods (pre-exercise rest, exercise, and post-exercise recovery). Peripheral venous blood ammonia levels were significantly correlated with levels of pyruvate and lactate, as these latter substrates exhibited a similar exponential relationship with VO2 as was observed with ammonia.

Adult↗
PubMed1977

Blood biochemical alterations during recovery from competitive marathon running.

The occurrence of possible prolonged alterations in plasma levels of cortisol, epinephrine, norepinephrine, selected energy metabolites, and water and electrolyte balance was assessed in six highly trained male marathon runners by measuring blood biochemical constituents on the 10th day before and for the three days following the running of a marathon. Post-race changes in hemoglobin, hematocrit, and protein levels indicated that a hemodilution had occurred, possibly as a result of elevated sodium levels. Epinephrine remained elevated until the second day. Cortisol was depressed on the first and third post-race days while variable levels were observed on the second day. No prolonged alterations were noted in norepinephrine, FFA, glycerol, triglycerides, glucose, lactate, and pyruvate.

Blood Glucose↗