Increases in aldosterone precede those of cortisol during graded exercise.

The purpose of this study was to determine the intensity threshold needed to elicit increases in plasma aldosterone and cortisol during graded exercise in humans. Seven male volunteers performed a maximal oxygen uptake (VO2max) test on a cycle ergometer. Plasma levels of aldosterone, cortisol, angiotensin II, ACTH, and potassium were measured at rest and at each 50 W workload of the exercise test. The results showed that aldosterone significantly (p less than or equal to 0.05) increased from a mean (+/- SE) of 231 +/- 22 pmol/L at rest to 464 +/- 22 pmol/L at exhaustion. Cortisol significantly (p less than or equal to 0.05) increased from 284 +/- 38 nmol/L at rest to 311 +/- 39 nmol/L at exhaustion. More importantly, however, was the fact that aldosterone was significantly increased above the resting level at exercise intensities greater than or equal to 60% VO2max. Cortisol, on the other hand, was only significantly increased at exhaustion (i.e. 100% VO2max). These results clearly show that increases in aldosterone precede those of cortisol during graded exercise in humans. Interestingly, potassium (r = 0.79), ACTH (r = 0.55), and angiotensin II (r = 0.54) were all significantly correlated with aldosterone during exercise. Such a finding seems to suggest that all 3 variables may be important stimuli for aldosterone secretion during graded exercise.

Effect of aerobic training on the plasma ACTH response to exercise.

The purpose of this study was to reexamine the effect of training on plasma adrenocorticotropin (ACTH) levels during exercise. Ten adult volunteers were split into a control and an experimental group. The experimental group participated in a 12-wk training program that resulted in a significant 11% increase in their mean maximal O2 uptake. The plasma ACTH response to a 150-W work rate was measured in both groups before and after the training program. The experimental group demonstrated a significant reduction in the ACTH response (11 vs. 4 pg/ml) to the work rate, whereas the control group demonstrated an unchanged response (16 vs. 13 pg/ml) over the course of the study. These data suggest that the ACTH response to an absolute submaximal work rate is blunted after training.

Plasma adrenocorticotropin and cortisol responses to brief high-intensity exercise in humans.

The purpose of this study is to examine plasma cortisol and adrenocorticotropin (ACTH) levels following a brief high-intensity bout of exercise. Each subject (n = 6) performed a 1-min bout of exercise on a cycle ergometer at 120% of his maximum O2 uptake. Blood samples were collected at rest, immediately following the exercise bout, and at 5, 15, and 30 min postexercise. Mean (+/- SE) plasma ACTH levels increased significantly (P less than 0.05) from 2.2 +/- 0.4 pmol/l at rest to 6.2 +/- 1.7 pmol/l immediately following exercise. Mean (+/- SE) plasma cortisol levels increased significantly from 0.40 +/- 0.04 mumol/l at rest to 0.52 +/- 0.04 mumol/l at 15 min postexercise. These data show that brief high-intensity exercise results in significant increases in plasma cortisol and ACTH levels. Furthermore, the temporal sequence between the two hormones suggests that the increase in plasma cortisol levels following brief high-intensity exercise is the result of ACTH-induced steroidogenesis in the adrenal cortex.

Intraerythrocyte and plasma lactate concentrations during exercise in humans.

The purpose of this study was to examine plasma and intraerythrocyte lactate concentrations during graded exercise in humans. Seven adult volunteers performed a maximum O2 uptake (VO2max) test on a cycle ergometer. Plasma and intraerythrocyte lactate concentrations (mmol . L-1 of plasma or cell water) were determined at rest, during exercise, and at 15-min post-exercise. The results show that plasma and intraerythrocyte lactate concentrations were not significantly different from each other at rest or moderate (less than or equal to 50% VO2max) exercise. However, the plasma concentrations were significantly increased over the intraerythrocyte levels at 75% and 100% VO2max. The plasma to red cell lactate gradient reached a mean (+/- SE) 1.7 +/- 0.4 mmol . L-1 of H2O at exhaustion, and was linearly (r = 0.84) related to the plasma lactate concentration during exercise. Interestingly, at 15-min post-exercise the direction of the lactate gradient was reversed, with the mean intraerythrocyte concentration now being significantly increased over that found in the plasma. These results suggest that the erythrocyte membrane provides a barrier to the flux of lactate between plasma and red cells during rapidly changing blood lactate levels. Furthermore, these data add to the growing body of research that indicates that lactate is not evenly distributed in the various water compartments of the body during non-steady state exercise.

Rejection of skin grafts after orthotopic tooth transplantation between RhLA-paired monkeys.

Statistical analysis of paired observations indicated that RhLA-A,B disparate teeth caused the accelerated rejection of tooth-donor skin grafts placed 21 to 24 mo after tooth allotransplantation, but not at 30 to 34 mo. Teeth transplanted between matched monkeys did not cause the accelerated rejection of skin grafts.

The healing of gingival wounds in miniature swine.

Standard wounds of simple incision and partial excision of the dentogingival junction were made in miniature swine. The healing from the 1st to the 14th day were described clinically and histologically, and the standardization of the wounds permitted quantitative and statistical analysis. In wounds that are closely adapted to the tooth, the epithelium of the new dentogingival junction contributes primarily to early wound strength recovery. This functional achievement probably would not occur with thick clots or hematomas, or with any displacement of the gingiva away from the tooth.