Influence of fitness on the integrated neuroendocrine response to aerobic exercise until exhaustion.

A group of trained and sedentary men performed an incremental graded exercise-test to exhaustion in order to assess the organic response of the two main stress-activated systems: the sympathetic nervous system with its endocrine component (the adrenal medulla), and the hypothalamic-pituitary-adrenal (HPA) axis. Maximal plasma concentrations of ACTH, cortisol and endogenous opioids (beta-endorphins) were obtained at the end of the exercise-test in the trained group. Thus ACTH increased from basal value of 21.25 +/- 2.5 pg/ml to 88.78 +/- 11.8 pg/ml at the end of the exercise (p<0.01); cortisol, from 16.56 microg/dl +/- 4.94 microg/dl to 23.80 +/- 4.57 microg/dl in min 15 of the recovery period (p<0.001); and beta-endorphin from 21.80 +/- 8.33 pmol/ml to 64.36 +/- 9.8 pmol/ml in min 3 of the recovery period (p<0.05). Catecholamine levels were increased from initial values at the end of the effort test in both control and trained groups. Control subjects exhibited a higher responsiveness compared to trained and showed superior intrinsic stimulation of the sympathetic nervous system. These results reveal a different response according to fitness in a physical stress situation.

Metabolic and hormonal changes during aerobic exercise in distance runners.

A group of long-distance runners is studied in order to clarify aspects concerning neuroendocrine mechanisms regulating organic adaptation to maximum effort, with special interest in the function of the growth hormone in fat metabolism and the possible use of ketone bodies as an alternative source of energy. A test is designed on a treadmill with a gradient of 3% and progressive increases in speed of 2 Km/h every 10 min, starting at 6 Km/h, and continuing until exhaustion. Masks are worn to enable the breath by breath measurement of expired gases and the subjects are monitored electrocardiographically using V5. For blood sample collection an antecubital vein is catheterized with a system enabling the replacement of the blood volume extracted by means of perfusion with physiological saline solution, and the increasing concentration of hormones in the blood is evaluated. The results obtained, indicate that epinephrine as well as GH hormones increase significatively from 20 min of exercise in runners promoting changes from carbohydrates to lipids as fuels to carry out exercise. The concomitant variations in energy substrates support the former hypothesis of work. Moreover, the muscle could employ acetylCoA originating from acetoacetate as an alternative metabolic source of fuel during maximum effort.

Maintenance of the threshold/maximum heart rate quotient in swimmers.

The anaerobic threshold (AT) was calculated in 23 swimmers by field methods: MADER (MM) and modified exponential MADER (EM) and laboratory methods: SKINNER (SM), ROBERGS (RM), CONCONI (CM), and ventilatory (VM). Two types of test were designed. The first in a swimming pool (test 1), performing four series of increasing intensity swims, and the second on a cycle ergometer increasing until exhaustion (test 2). In both tests the heart rate (HR) was recorded in beats per minute by telemetry. Despite the different HR at the AT: 180.0 +/- 2.7 (MM), 179.1 +/- 2.4 (EM), 166.0 +/- 2.9 (SM), 157.0 +/- 2.8 (RM), 167.6 +/- 2.7 (VM) and 168.8 +/- 2.2 (CM), and the different maximum HR (HRmax) in the two tests: 201.6 +/- 2.0 in Test 1 and 188.5 +/- 1.6 in Test 2; the percentage HR in the AT/HRmax proved to be similar for all the methods except RM (88.0%-89.2%). The mechanism of organic control in progressive exercise can therefore have, in this test, a "threshold" zone at a given percentage of the maximum capacity of adaptation, both when the exercise is carried out in a pool and also on a cycle ergometer.

[Function of growth hormone in the human energy continuum during physical exertion]. / Función de la hormona del crecimiento en el continuum energético humano durante el ejercicio físico.

A study has been carried out in 18 healthy sedentary males (controls) and 15 trained handball players. It was programmed two different tests on cycle-ergometer: Test 1 aerobic of progressive increments of load (1 W/kg/3 min) and Test 2 (A) anaerobic (4 W/kg, during 1.5 min) and after resting 10 min., Test 2 (B) till exhaustion. The blood samples were 10 ml each collected by antecubital vein catheterization. Before, during and post-exercise recovery period HG hormone, glycemia, lactate, and FFA were measured. It was found a correlation between HGH levels and substances of the energetic metabolism. The only exception was trained subjects test-2 possibly due to slower response of HGH. However FFA variation levels are correlated at the beginning with the increasing levels (p less than 0.001). It is concluded that HGH can play an important role on the turn-over to get fuel to contractile process from carbohydrates to free fatty acids.

[Importance of changes in plasmatic volume in the evaluation of TSH, L-T3 and L-T4, during muscular activity]. / Importancia de los cambios de volumen plasmático en la valoración de la TSH, L-T3 y L-T4, durante la actividad muscular.

The changes in plasma concentrations of TSH and thyroid hormones (L-T3 and L-T4), lactate, proteins and FFA were studied in 8 male volunteers undergoing maximal exercise during 12 min on the bicycle ergometer from 1 to 4 w/kg. Serial blood samples were taken at -30, 0, 3, 6, 9, 12, +3, +15 and +30 min intervals. All samples for TSH, L-T3 and L-T4 measurements were processed by radioimmunoassay. The possibility of interference in the RIA determination, with protein and FFA, has been studied in this work. However, in men the available evidence suggests that protein and FFA do not play an important role of interference in the determination methodology of thyroid hormone levels. This interpretation is in accordance with the fact that in men, plasma concentrations of thyroid hormones are related to changes in plasmatic volume, the intensity and the extended duration of the exercise.

[L-thyroxine and triiodo-L-thyronine in the cerebrospinal fluid and hypothalamo-hypophyseal axis of hyper- or hypothyroid rats]. / L-tiroxina y triiodo-L-tironina en líquido cefalorraquídeo y eje hipotálamo hipofisario de ratas, hiper- e hipotiroideas.

L-thyroxine and triiodo-L-thyronine concentrations in cerebrospinal fluid (CSF), hypothalamus and pituitary gland are measured in male albino-Wistar rats under several experimental thyroid disfunction : including hyperthyroidism induced by L-T3 and L-T4 treatments and surgical hypothyroidism. Radioimmunoassay is carried out by Nejad's method modified in this work. The pattern of thyroid hormone concentrations in CSF is similar to that in serum, but the values obtained are lower. Thyroid hormone concentrations in adenohypophysis as opposed to hypothalamus or cerebral cortex, show an inverse change to functional thyroid status.

[Homologous radioimmunoanalysis of serum L-thyroxine and triiodo-L-thyronine in rats with hypo- and hyperthyroidism]. / Radioinmunoanálisis homólogo de L-tiroxina y triiodo-L-tironina séricas de rata en estados de hipo e hipertiroidismo.

Total L-thyroxine and triiodo-L-thyronine serum concentrations have been measured in 70-day-old male rats under normal conditions (controls) and in rats subjected to several experimental alterations of the thyroid function: hyperthyroidism, hypothyroidism and substitutive treatments. Since some problems appear when standard curves are performed with hormone serum, as consequence of differences in the affinity and inhibitory effects between heterologous proteins at the antigen-antibody reaction, RIA in this work has been carried out with standard curves performed with rat serum maintaining similar protein concentrations in standard and problems. This modification avoids errors by the use of extraction methods and shows a high degree of similarity between standard and problems.

[Measurement of total triiodo-L-thyronine in rat serum by homologous radioimmunoanalysis]. / Medida de la triiodo-L-tironina total en suero de rata mediante radioinmunoanálisis homólogo.

A radioimmunoanalysis comparative study of total tri-iodo-L-thyronine patterns in human and rat sera revealed a quantitative difference between the amounts of labelled antigen which associated with the specific antibody in each case. At the same time, in another experiment, three different protein concentrations were dissolved in rat serum standards producing the results that, at lower protein concentrations a larger quantity of antigen/antibody complex was formed. These changes must be kept in mind for the L-T3 measurement in rat serum.

[Changes in dehydrogenase glutamate in the rat brain caused by thyroid hormone deficiency]. / Alteraciones de la glutamato deshidrogenasa en áreas cerebrales de rata por deficiencia de hormonas tiroideas.

The dependent GDH-NADPH activity in adenohypophysis and other cerebral areas, has been studied in hypothyroid rats, in which hypothyroidism has been induced surgically. After thyroidectomy a decrease of GDH activity in limbic system (amygdala, septum and hippocampus), and an increase of this enzyme in cortex and hypothalamus have been found, with no changes in adenohypophysis. The alterations of GDH activity, induced by thyroidectomy, have been corrected, although not uniformly in the different brain areas after L-T3 treatment.