Summary. 

A fluorimetric method for the determination of dopamine is described. The principle is similar to that employed in the tri-hydroxyindole method for estimating adrenaline and noradrenaline. Utilizing differences in fluorescence characteristics at pH about 5.3, microquantities of dopainine can be determined in the presence of at least equal amounts of adrenaline or noradrenaline.

A fluorimetric method for the determination of dopamine (3-hydroxytyramine).

An imbalance between the overall strain experienced during exercise training and the athlete's tolerance of such effort may induce overreaching or overtraining syndrome. Overtraining syndrome is characterised by diminished sport-specific physical performance, accelerated fatiguability and subjective symptoms of stress. Overtraining is feared by athletes yet there is a lack of objective parameters suitable for its diagnosis and prevention. In addition to the determination of substrates (e.g. lactate, ammonia and urea) and enzymes (e.g. creatine kinase), the possibilities for monitoring of training by measuring hormonal levels in blood are currently being investigated. Endogenous hormones are essential for physiological reactions and adaptations during physical work and influence the recovery phase after exercise by modulating anabolic and catabolic processes. Testosterone and cortisol are playing a significant role in metabolism of protein as well as carbohydrate metabolism. Both are competitive agonists at the receptor level of muscular cells. The testosterone/cortisol ratio is used as an indication of the anabolic/catabolic balance. This ratio decreases in relation to the intensity and duration of physical exercise, as well as during periods of intense training or repetitive competition, and can be reversed by regenerative measures. Correlations have been noted with the training-induced changes of strength. However, it seems more likely that the testosterone/cortisol ratio indicates the actual physiological strain in training, rather than overtraining syndrome. The sympatho-adrenergic system might be involved in the pathogenesis of overtraining. Overtraining appears as a disturbed autonomic regulation, which in its parasympathicotonic form shows a diminished maximal secretion of catecholamines, combined with an impaired full mobilisation of anaerobic lactic reserves. This is supposed to lead to decreased maximal blood lactate levels and maximal performance. Free plasma adrenaline (epinephrine) and noradrenaline (norepinephrine) may provide additional information for the monitoring of endurance training. While prolonged aerobic exercise conducted at intensities below the individual anaerobic threshold lead to a moderate rise of sympathetic activity, workloads exceeding this threshold are characterised by a disproportionate increase in the levels of catecholamines. In addition, psychological stress during competitive events is characterised by a higher catecholamines to lactate ratio in comparison with training exercise sessions. Thus, the frequency of training sessions with higher anaerobic lactic demands or of competition, should be carefully limited in order to prevent overtraining syndrome. In the state of overtraining syndrome and overreaching, respectively, an intraindividually decreased maximum rise of pituitary hormones (corticotrophin, growth hormone), cortisol and insulin has been found after a standardised exhaustive exercise test performed with an intensity of 10% above the individual anaerobic threshold.(ABSTRACT TRUNCATED AT 400 WORDS)

Blood Hormones as Markers of Training Stress and Overtraining

Stress hormones, adrenaline (epinephrine) and noradrenaline (norepinephrine), are responsible for many adaptations both at rest and during exercise. Since their discovery, thousands of studies have focused on these two catecholamines and their importance in many adaptive processes to different stressors such as exercise, hypoglycaemia, hypoxia and heat exposure, and these studies are now well acknowledged. In fact, since adrenaline and noradrenaline are the main hormones whose concentrations increase markedly during exercise, many researchers have worked on the effect of exercise on these amines and reported 1.5 to >20 times basal concentrations depending on exercise characteristics (e.g. duration and intensity). Similarly, several studies have shown that adrenaline and noradrenaline are involved in cardiovascular and respiratory adjustments and in substrate mobilization and utilization. Thus, many studies have focused on physical training and gender effects on catecholamine response to exercise in an effort to verify if significant differences in catecholamine responses to exercise could be partly responsible for the different performances observed between trained and untrained subjects and/or men and women. In fact, previous studies conducted in men have used different types of exercise to compare trained and untrained subjects in response to exercise at the same absolute or relative intensity. Their results were conflicting for a while. As research progressed, parameters such as age, nutritional and emotional state have been found to influence catecholamine concentrations. As a result, most of the recent studies have taken into account all these parameters. Those studies also used very well trained subjects and/or more intense exercise, which is known to have a greater effect on catecholamine response so that differences between trained and untrained subjects are more likely to appear. Most findings then reported a higher adrenaline response to exercise in endurance-trained compared with untrained subjects in response to intense exercise at the same relative intensity as all-out exercise. This phenomenon is referred to as the 'sports adrenal medulla'. This higher capacity to secrete adrenaline was observed both in response to physical exercise and to other stimuli such as hypoglycaemia and hypoxia. For some authors, this phenomenon can partly explain the higher physical performance observed in trained compared with untrained subjects. More recently, these findings have also been reported in anaerobic-trained subjects in response to supramaximal exercise. In women, studies remain scarce; the results are more conflicting than in men and the physical training type (aerobic or anaerobic) effects on catecholamine response remain to be specified. Conversely, the works undertaken in animals are more unanimous and suggest that physical training can increase the capacity to secrete adrenaline via an increase of the adrenal gland volume and adrenaline content.

Catecholamines and the effects of exercise, training and gender.

The sections in this article are:


1
Reflex Cardiovascular Responses to Muscular Contraction in Anesthetized and Decerebrate Animals
1.1
Sensory Innervation of Skeletal Muscle

1.2
Reflex Autonomic Responses to Stimulation of Muscle Afferents in Anesthetized Animals

1.3
Discharge Properties of Group III and IV Muscle Afferents

1.4
The Site of the First Synapse—The Dorsal Horn

1.5
Role of Spinal Neurotransmitters and Neuromodulators in the Exercise Pressor Reflex

1.6
Pathways Ascending from the Dorsal Horn

1.7
The Ventrolateral Medulla

1.8
Other Central Neural Structures

1.9
Final Common Pathways

1.10
Interaction Between the Arterial Baroreflex and the Exercise Pressor Reflex in Anesthetized and Decerebrate Animals




2
Evidence for the Exercise Pressor Reflex in Humans and Conscious Animals
2.1
Feedback from Contracting Limb Skeletal Muscle in Humans and Conscious Animals

2.2
The Nature of the Stimulus Evoking the Exercise Pressor Reflex




3
Contribution of Peripheral Afferents to the Exercise Hyperpnea
3.1
Afferents from the Exercising limbs

3.2
The Carotid Chemoreceptor Afferents

3.3
Role in Hyperventilation During Heavy Exercise

3.4
The Pulmonary Afferents

3.5
Cardiac Afferents

3.6
Respiratory Muscle Afferents

3.7
Mediation of the Exercise Hyperpnea by Multiple Mechanisms




4
Summary and Conclusions
4.1
Peripheral Afferent Contribution to Circulatory Responses to Exercise

4.2
Peripheral Afferent Contribution to Ventilatory Responses to Exercise

Reflexes Controlling Circulatory, Ventilatory and Airway Responses to Exercise

There appears now to be no reasonable doubt that both epinephrine and norepinephrine belong to the category of hormones which are responsive to psychological influences.Catecholamine levels, furthermore, appear sensitively to reflect relatively common, psychological reactions associated with “everyd

A Review of Psychoendocrine Research on the Sympathetic-Adrenal Medullary System

Excretion of noradrenaline, adrenaline, and hydroxytyramine in urine.

Excretion of noradrenaline in urine in hypertension.

β-(3:4-dihydroxyphenyl)ethylamine (hydroxytyramine) in normal human urine

The mechanical properties of two-dimensional (2D) materials are important for a wide range of applications including composite materials, van der Waals materials and ﬂexible electronics. Several aspects are highly debated in the literature: For example, the theoretically predicted bending rigidity, κ ( T ) , of the most important 2D material, graphene, varies from 0.8 eV to 10 eV for predictions at 0 K and there are predictions that it could increase or decrease with temperature depending on the applied theory. Here we present the ﬁrst systematic experimental study of the temperature dependence κ ( T ) of graphene. Extracting values of κ from the ZA-phonon dispersion relation measured with helium atom scattering, we ﬁnd the value of κ ( T ) to increase with sample temperature. A linear ﬁt in the temperature range (120 K-480 K) gives a bending rigidity of κ ( T ) = (1 . 1 ± 0 . 1)[ eV ] + (0 . 0013 ± 0 . 0001)[ eV/K ] × T .

pdf/temperature-dependent-bending-rigidity-of-graphene-2qk9a3i0.pdf

Temperature Dependent Bending Rigidity of Graphene

Excretion of noradrenaline and adrenaline in muscular work.

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