Effect of transverse gravitational loads on the vessels of the retinal membrane of the rabbit eyeball]

Changes in the eye ball retina were studied in 3 series of experiments in cleared preparations after exposure of the animal to gravitation stress of transversal direction. Prolonged single functionally endurable stress of ventro-dorsal direction (10 units/3 min) caused dilatation of the retina vessels, worse filling of peripheral parts of the circulatory bed, uneven staining of the vascular wall, constriction and dilatation along the course of the vessel. More continuous exposure to the same value of stresses (10 units up to the animal's death) resulted in a pressor effect; qualitative changes in the vessels increased. Within 1,5 hour after a 3-minute-long exposure to stress the vascular bed still remained unchanged. The diameter of vessels approached normal while the general quantity of vessels was decreased and qualitative changes were well pronounced.     

Effect of training for loads in the ventrodorsal direction on the blood vessels of the sympathetic trunk of the rabbit brain]

Thirty six rabbits underwent special training to get a state of being trained. In a centrifuge with a 1 m radius 18 animals got ventro-dorsal gravitation stress according to schedule N 1 (with limberung-up) and 18 animals according to schedule N 2 got gravitation stress without limbering-up. After training the animals had a 2, 3 and 4-week rest. Then a part of animals was killed and served as control and the others were subjected to a single exposure to stress of the same direction (10 units for 40 min). This stress was unendurable for untrained animals. By means of injection, clearing, measuring the vessels and histologically it was shown that the trained state was reached according to schedule N 2 and retained for 3 weeks. It was also confirmed by survival of animals and the state of the vessels of the sympathetic trunk. Training according to the 1st schedule resulted in cumulation.     

Effect of longitudinal gravitational loads on the structure of the wall of the vertebral artery]

A single exposure to the greatest endurable gravitation stress causes such changes in the wall of the vertebral artery as division into layers, oedema, vacuolization of smooth muscle cells. Repeated exposure according to a training schedule resulted in reconstruction of the vascular wall (division of the medial sheath of the artery into several muscular layers). Concentration of smooth muscle cells in "layers" increased when training was after a "cumulative" schedule. Under conditions of increasing cumulative effect the collagenization of the media and dystrophy of the muscular and elastic tissue began. The greatest changes in the arterial wall took place in the upper parts of the vertebral artery at the level of the 2nd and 3d cervical vertebra.     

Effect of hypokinesia and the combined action of gravitational load and hypokinesia on the structure of the hepatic portal system]

General hypokinesia during 1--6 weeks resulted in dilatation of the interlobular veins. sinusoids and central veins. The sequence of alterations corresponded to terms of hypokinesia. After exposure to "gravitation stress--hypokinesia for 1--6 weeks" stagnation in the portal system of the liver was less than after exposure to hypokinesia alone, but unevenness of lumens in the interlobular veins and sinusoids was more pronounced. The foci of the vessel spasm were determined. The signs of stagnation in the system of the portal vein and unevenness of the width of all the links of the portal bed were most pronounced after combination "hypokinesia for 1--6 weeks-- gravitation stress".     

The role of visual attention during the acquisition of differentiation in the northern fur seal

The role of visual attention during elaboration of visual differentiation (VD) of three stimuli, each of them signaled its own instrumental reaction directed to the certain object has been studied in experiments with two males of northern fur seal. In one of the fur seals VD formed by the standard motor and food methods, for the other the "blind" assertion of stimulus field (without stimulus demonstration) was introduced during VD formation in the accidental order. The animal's orientation to the stimulus field and the absence of any reaction to the objects during 15 s was confirmed. It has been shown that in this special training of visual attention mechanism the attainment of learning criteria realizes well quicker--more than twofold.     

Resistance factor in emotional stress in the brain of rats

The authors review the results of extraction from the brain of emotional stress-resistant donor rats of fractions containing "factor" that causes the increased resistance to stress in recipient rats predisposed to stress. Brain homogenates of donor rats were subjected to thermal treatment, gel filtration on Sephadex G-15 and lyophilization. The fractions extracted are low-molecular weight, thermostable, resistant to pronase hydrolysis and significantly (P less than 0.05) increase the resistance of recipient rats to stress.     

Pituitary-adrenocortical responses to the first dyadic encounters in male rhesus monkeys: effect of dominance relationship

Male rhesus monkeys unfamiliar with each other were paired in a cage, and blood samples were collected before and a few hours after pair formation. Adrenocorticotrophic hormone (ACTH) and cortisol levels in each blood sample were measured. Dominant-subordinate status was ascertained through two rank tests, the food competition test and the agonistic behavior test, which were performed immediately after pair formation. As a result, the dominance relationship was determined in seven pairs formed from five animals, and the differences in ACTH and cortisol values between the dominant and subordinate animal in these pairs were compared statistically. The day after the first encounter, a second encounter was conducted in randomly selected pairs of monkeys. In the first encounters, higher levels of both ACTH and cortisol were detected in dominant animals in comparison to subordinate animals. Changing the animal's partner altered the stress responses whenever the animal's dominant-subordinate status changed. The elevated levels of ACTH and cortisol in dominant animals disappeared on the day after the first encounter. In dominant animals, the pituitary-adrenocortical stress response reacts sharply to situational demands, whereas subordinate animals have a weaker response. This acute stress response is different from a chronic stress response. When the subordinate animal cannot escape, its hypothalamic-pituitary-adrenocortical axis appears to be suppressed.     

Trailer loading stress in horses: behavioral and physiological effects of nonaversive training (TTEAM)

Resistance in the horse to trailer loading is a common source of stress and injury to horses and their handlers. The objective of this study was to determine whether nonaversive training based on the Tellington-Touch Equine Awareness Method (TTEAM; Tellington-Jones &Bruns, 1988) would decrease loading time and reduce stress during loading for horses with a history of reluctance to load. Ten horses described by their owners as "problem loaders" were subjected to pretraining and posttraining assessments of loading. Each assessment involved two 7-min loading attempts during which heart rate and saliva cortisol were measured. The training consisted of six 30-min sessions over a 2-week period during which the horse and owner participated in basic leading exercises with obstacles simulating aspects of trailering. Assessment showed heart rate and saliva cortisol increased significantly during loading as compared to baseline (p <.001 and p <.05, respectively). Reassessment after training showed a decrease in loading time (p <.02), reduced heart rate during loading (p <.002), and reduced saliva cortisol as compared to pretraining assessments. Seven "good loaders" also were subject to loading assessment for physiological comparison. Increases in heart rate during loading were significantly higher in the good loaders (p <.001). Nonaversive training simulating aspects of loading may effectively reduce loading time and stress during loading for horses with a history of resistance to trailer loading.     

Stress and stress-induced neuroendocrine changes increase the susceptibility of juvenile oysters (Crassostrea gigas) to Vibrio splendidus

Oysters are permanently exposed to various microbes, and their defense system is continuously solicited to prevent accumulation of invading and pathogenic organisms. Therefore, impairment of the animal's defense system usually results in mass mortalities in cultured oyster stocks or increased bacterial loads in food products intended for human consumption. In the present study, experiments were conducted to examine the effects of stress on the juvenile oyster's resistance to the oyster pathogen Vibrio splendidus. Oysters (Crassostrea gigas) were challenged with a low dose of a pathogenic V. splendidus strain and subjected to a mechanical stress 3 days later. Both mortality and V. splendidus loads increased in stressed oysters, whereas they remained low in unstressed animals. Injection of noradrenaline or adrenocorticotropic hormone, two key components of the oyster neuroendocrine stress response system, also caused higher mortality and increased accumulation of V. splendidus in challenged oysters. These results suggest that the physiological changes imposed by stress, or stress hormones, influenced host-pathogen interactions in oysters and increased juvenile C. gigas vulnerability to Vibrio splendidus.     

Motor skill recovery in rats with various forelimb preference subjected to lesions in the caudate nucleus

Rats were trained for retrieving a sunflower seed from a tube using a forelimb. In the process of training, all the animals were divided in two groups: with the right- and left-limb preference. The period of learning was divided in two emotional (after the period of anxiety the animal takes a sunflower seed from the flow of a chamber) and three motor stages (different degrees of dexterity and precision in reaching a seed in the tube and grasping it). After a rat learned the skilled movement, the caudate nucleus was lesioned contralaterally to the preferred limb. After surgery, the animals were tested for recovery of the motor skill. The stages of recovery were the same as during learning. "Right-" and "left-handed" rats were compared in the percentage of animals performing each stage, duration of each stage, the depth of the tube reached by the animal's forelimb, and time required for obtaining the best results. The "right-handed" rats dominated in the percentage of animals performing the emotional stages and later began to recover the skilled movement (the crucial motor stage) but faster acquired their individual maximal depth of reaching a seed in the tube than the "left-handed" animals. The recovery of the skilled movement in the "left-handed" animals was a more gradual process than that in the "right-handed" ones.     

Influence of gravitational overload and hypokinesia on the structure of the vascular bed of the stomach]

Under study were effects of gravitation stresses, total hypokinesia and their combinations on blood vessels of the stomach. The work was carried out in 130 rabbits, 16 of them being used to study the normal structure of the gastric vascular bed. The vascular bed was injected with the Gerota's mass followed by clearing, making histological preparations and roentgenography. The investigation has revealed both quantitative and qualitative changes in the structure of the gastric blood vessels. The maximum endurable stress of the ventro-dorsal direction causes morphological shifts less pronounced than stresses of longitudinal directions. With prolonged terms of hypokinesia (1-12 weeks) morphological changes became more pronounced in all the layers of the stomach. A combination of successive gravitation stresses and hypokinesia during 4-12 weeks aggravated morphological changes which occurred after exposure to isolated above factors. The animals subjected to maximum endurable stresses before and after 4-week hypokinesia developed vascular changes more typical for the effects of gravitation. The pretraining of animals did not give a pronounced positive effect on the changes of the angioarchitectonics of all the gastric layers after a repeated stress following 4-week hypokinesia.     

State of Dogiel type II neurons in the wall of the cat small intestine following a single exposure to gravitational stress]

Under study was the nervous apparatus of the small intestine in 22 cats subjected to a single gravitation stress by rotation in a centrifuge of 1,5 m radius. The stress was equal to 10 units, duration from 2,5 to 3,5 min., and was of head-pelvis direction. The material was treated after Nissl and Gomori in Chilingarian's modification. Within 1-3 days after exposure to gravitation stresses in the Auerbach plexus there appeared changes in the shape of the body of the type II Dogiel cells, such as pericellular oedema, vacuoles in the cytoplasm, chromatolysis and varicous thickenings of nerve fibres. Terminal structures of the dendrites of the type II Dogiel cells are thickened. The changes are most pronounced within the 4th-7th days after exposure to gravitation and are observed as late as the 14th day, being sharply diminished by the 30th day.     

Strength gains after resistance training: the effect of stressful, negative life events

This study was designed to examine the effect of self-reported, stressful life events on strength gains after 12 weeks of resistance training. Participants were 135 undergraduates enrolled in weight training classes that met for 1.5 hours, two times per week. After a 2-week period to become familiar with weight training, participants completed the college version of the Adolescent Perceived Events Scale (APES), the Social Support Inventory, and one-repetition maximal lifts (1RM) for the bench press and squat. Maximal lifts were repeated after 12 weeks of training. Median splits for stress and social support were used to form groups. Results indicated that the low stress participants experienced a significantly greater increase in bench press and squat than their high stress counterparts. Strength gains were, however, unrelated to social support scores in either the low or high stress group. High life stress may lessen a person's ability to adapt to weight training. It may benefit coaches to monitor their athletes' stress both within and outside the training setting to maximize their recovery and adaptation.     

Deprivation and Enrichment in Laboratory Animal Environments

Resistance in the horse to trailer loading is a common source of stress and injury to horses and their handlers. The objective of this study was to determine whether nonaversive training based on the Tellington-Touch Equine Awareness Method (TTEAM; Tellington-Jones &; Bruns, 1988) would decrease loading time and reduce stress during loading for horses with a history of reluctance to load. Ten horses described by their owners as "problem loaders" were subjected to pretraining and posttraining assessments of loading. Each assessment involved two 7-min loading attempts during which heart rate and saliva cortisol were measured. The training consisted of six 30-min sessions over a 2-week period during which the horse and owner participated in basic leading exercises with obstacles simulating aspects of trailering. Assessment showed heart rate and saliva cortisol increased significantly during loading as compared to baseline (p < .001 and p < .05, respectively). Reassessment after training showed a decrease in loading time (p < .02), reduced heart rate during loading (p < .002), and reduced saliva cortisol as compared to pretraining assessments. Seven "good loaders" also were subject to loading assessment for physiological comparison. Increases in heart rate during loading were significantly higher in the good loaders (p < .001). Nonaversive training simulating aspects of loading may effectively reduce loading time and stress during loading for horses with a history of resistance to trailer loading.     

Dietary tyrosine suppresses the rise in plasma corticosterone following acute stress in rats

Acute, uncontrollable stress increases norepinephrine (NE) turnover in the rat's brain (depleting NE) and diminishes the animal's subsequent tendency to explore a novel environment. Pre-treatment with tyrosine can reverse these adverse effects of stress, presumably by preventing the depletion of NE in the hypothalamus. Numerous studies suggest that NE inhibits the release of adrenocorticotropic hormone (ACTH) by suppressing corticotropic releasing factor (CRF) secretion in the hypothalamus. In the present study, we found that pre-treatment with supplemental tyrosine not only prevented the behavioral depression and hypothalamic NE depletion observed after an acute stress, but also suppressed the rise in plasma corticosterone. These results support a role for brain NE in stress-induced corticosterone secretion and demonstrate that supplemental tyrosine can protect against several adverse consequences of such stress.     

Effect of long-term shock-avoidance training on certain biochemical constituents of rat brain

A few constituents of the brain of rats subjected to long-term shock avoidance training in the jump-box were investigated. The effects of training and that of the concomitant stress on these constituents were differentially examined. Brain DNA increased in both the trained rats and those subjected to stress. The total RNA showed a specific decrease in the trained rats. The total protein content remained unaffected, while the content of soluble protein showed a greater increase in the trained rats compared to that in animals subjected to stress. The Na⁺, K⁺-ATPase activity in the brain decreased in the trained rats, whereas the glial carbonic anhydrase activity increased in the stressed as well as the trained rats. No change was found in the activities of Mg⁺⁺-ATPase and pseudocholinesterase in the experimental groups.     

Stress induced biosynthesis of a 31 kd-glycoprotein in goldfish brain

The de novo protein synthesis in goldfish brain has been studied under defined stress conditions and after training in an active swimming task. One- and two-dimensional gel electrophoresis of the brain proteins previously labelled in vivo with 35S-methionine indicated that the synthesis of one distinct protein increases after stress but not after successful training. This protein is a glycoprotein with an apparent molecular weight of 31 kd and an isoelectric point of pH 5. It is discussed that the protein may be the ACTH precursor "pro-opiomelanocortin".     

Set Configuration in Resistance Exercise: Muscle Fatigue and Cardiovascular Effects

Purpose

Cardiovascular responses of traditional resistance (TS) training have been extensively explored. However, the fatigue mechanisms associated with an intra-set rest configuration (ISR) have not been investigated. This study compares two modalities of set configurations for resistance exercise that equates work to rest ratios and measures the central and peripheral fatigue in combination with cortical, hemodynamic and cardiovascular measures.

Methods

11 subjects performed two isometric knee extension training sessions using TS and ISR configurations. Voluntary activation (VA), single twitch amplitude, low frequency fatigue (LFF), Mwave, motor evoked potential (MEP), short intracortical inhibition (SICI), intracortical facilitation (ICF) and heart rate variability were evaluated before and after each training session. During each session beat to beat heart rate, blood pressure and rate pressure product (RPP) were also evaluated.

Results

After exercise VA decreased significantly for TS but not for ISR (P < 0.001), single twitch amplitude and LFF values were lower for TS than ISR (P < 0.004), and SICI was reduced only for the TS configuration (P = 0.049). During exercise RPP values were significantly higher for the TS than for ISR (P = 0.001). RPP correlated with VA for TS (r = -.85 P < 0.001) suggesting a relationship between central fatigue and cardiovascular stress.

Conclusions

We conclude that ISR induced lower central and peripheral fatigue as well as lower cardiovascular stress in comparison with TS configuration. Our study suggests that set configuration is a key factor in the regulation of the neuromuscular and cardiovascular responses of resistance training.     

Xenohormesis: health benefits from an eon of plant stress response evolution

Xenohormesis is a biological principle that explains how environmentally stressed plants produce bioactive compounds that can confer stress resistance and survival benefits to animals that consume them. Animals can piggyback off products of plants' sophisticated stress response which has evolved as a result of their stationary lifestyle. Factors eliciting the plant stress response can judiciously be employed to maximize yield of health-promoting plant compounds. The xenohormetic plant compounds can, when ingested, improve longevity and fitness by activating the animal's cellular stress response and can be applied in drug discovery, drug production, and nutritional enhancement of diet.     

Increased level of immunoreactive opioid peptides in the brain and adrenals of rats as affected by adaptation to physical loading

The effect of long-term (7 weeks) swimming training on the content of beta-endorphin, met- and leu-enkephalins in various brain regions and adrenal glands has been studied in Wistar rats. It has been shown that the adaptation to exercise induced an increase in the content of opioid peptides in most of the brain regions and in adrenal glands. This increase in the level of opioid peptides seems to play an important role in the increase of the resistance to stress.