Pituitary adrenocortical response to chronic intermittent stress

Two experiments were conducted to investigate the pituitary adrenocortical response to stress. In the first experiment, rats received chronic and/or acute cold stress over a period of three weeks or three months. Plasma corticosterone, adrenal wet weight, and body weight were assessed. Three month chronically stressed rats had large adrenals, weighed less, and secreted less corticosterone in response to an acute stressor than did control rats stressed for the first time. Furthermore, their basal level of plasma corticosterone equalled the level secreted after acute stress. In Experiment two, repeated ACTH measures were taken in rats chronically stressed for three weeks. Plasma ACTH was significantly elevated after stress with no change in baseline levels. Taken together, these experiments suggested that rats adapt to stress and that a decreased hormonal stress response reflects conditioning and metabolic conservation rather than exhaustion of resources.     

Hypothalamic multiunit activity correlates of the adrenocortical response to stress

The corticotropic response to stress was studied by means of multiple unit activity (MUA) recording from the adrenocorticotropic region of the hypothalamus, and plasma corticosterone (B) determination. MUA was permanently obtained and B was measured at 2, then 5 and 10 min intervals before and after neurogenic (electrical shocks) or systemic (ether inhalation) stress was applied. Experiments were made on steady unanesthetized, unrestrained thalamic pigeons. Post-stress alterations of MUA and B were closely in parallel, exhibiting a rapid and sustained increase in firing rate and shifting by 5-10 min, in corticosteronemia. Three successive and progressively decreasing peaks of MUA and B could be observed. Basal resting values were restored by approximately 90 min. Adrenocorticotropic responses to stress appear to be modulated through neural thalamic and/or rhombencephalic mechanisms.     

Effect of stressor intensity on habituation of the adrenocortical stress response

Although it is known that the number of presentations of a stressor can influence the adrenocortical stress response, relatively little information exists on how stressor intensity affects this process. To evaluate this, we repeatedly presented rats with stressors of 3 different intensities and sampled blood for corticosterone. The first major finding was that the rat's initial adrenocortical responsiveness regardless of the stressor employed was a critical variable. Rats that showed a small corticosterone response showed no evidence of habituation or of differences due to stressor intensity. Rats that showed an initial robust response all showed partial habituation of their corticosterone response over time but the patterns varied with stressor intensity. Handled and prone restrained rats showed the same pattern but rats subjected to the more intense stressor of supine restraint showed delay in habituation and tonically elevated responses. These data indicate that individual differences in reactivity to stressors as well as stressor intensity can influence the pattern of the stress response over the course of repeated administration of the stressor.     

Some aspects of metabolism following a 35 km road run

Summary The metabolism of eight men (mean: age, 26.0 years; maximal oxygen consumption, 65.0 ml·kg^–1 · min^–1; body fat, 10.3%) was measured on counterbalanced control (baseline values for 8h) and experimental (post 35 km run values for 8 h) days. The excess postexercise volume of oxygen consumed of 32.37 1 and increase in energy used of 594 kJ during the 8 h after completion of the run were equivalent to average increases of 23.7 and 21.1%, respectively, when compared with time-matched controls. Furthermore, the oxygen uptake and energy expenditure were still elevated by 12.7 (P<0.0005) and 9.7% (P=0.001), respectively, at the mod, of this period but the fact that they had returned seline 24 h after the 35 km road run contrasts with some reports in the literature that metabolism is still elevated at this time following less demanding exercise intensities. Rectal temperature was elevated by 2.3° C at the end of the run but the difference had decreased to 0.2°C by 7 h postexercise. The respiratory exchange ratio and changes in blood metabolites (nonesterified fatty acids, glycerol and ketone bodies) indicated a greater postexercise utilisation of fat notwithstanding a 6300 kJ meal ingested on both control and experimental days. The highest measured serum creatine kinase enzyme activity of 1151 U.l^–1 (P< 0.05) occurred 24 h postexercise, as compared with the control value of 145 U · 1^–1, and indicates the possibility of skeletal muscle damage.     

Effects of repeated maternal separations on the adrenocortical response to stress of preweanling rats.

Previous data indicate that the infant rat shows a marked increase in adrenocortical responsiveness to stress immediately following prolonged maternal separation. In Experiment 1 we studied the immediate effects of repeated maternal deprivation. Our results indicate that the increase in basal as well as stress-induced corticosterone levels is a direct function of the length of the deprivation period immediately preceding testing, and is not cumulative. In Experiment 2 we examined the long-term consequences of maternal deprivation on adrenal responsivity. Four days following a single 24-h period of maternal deprivation, pups remained hyperresponsive to stress, although their basal levels of corticosterone had returned to control values. Shorter periods of deprivation (which did result in increased responsivity immediately following deprivation) did not have persistent effects. Our data suggest: 1) short periods of deprivation do not have a cumulative effect, and 2) there is a critical length of deprivation beyond which persistent changes in adrenocortical responsivity ensue.     

Fast positive feedback between the adrenocortical stress response and a brain mechanism involved in aggressive behavior

Aggressive behavior induces an adrenocortical stress response, and sudden stressors often precipitate violent behavior. Experiments in rats revealed a fast, mutual, positive feedback between the adrenocortical stress response and a brain mechanism controlling aggression. Stimulation of the aggressive area in the hypothalamus rapidly activated the adrenocortical response, even in the absence of an opponent and fighting. Hypothalamic aggression, in turn, was rapidly facilitated by a corticosterone injection in rats in which the natural adrenocortical stress response was prevented by adrenalectomy. The rapidity of both effects points to a fast, mutual, positive feedback of the controlling mechanisms within the time frame of a single conflict. Such a mutual facilitation may contribute to the precipitation and escalation of violent behavior under stressful conditions.     

Lack of stability in neonatal adrenocortical reactivity because of rapid habituation of the adrenocortical response

The purpose of the study was to examine the stability of the adrenocortical response to stimulation in the human neonate. Forty-nine healthy newborns were examined twice responding to discharge examinations performed on two consecutive days. The dependent measures were salivary and plasma cortisol and behavioral state. Little evidence of stability was obtained. Instead, the results showed significant elevations in cortisol only in response to the first discharge examination. No significant elevation in cortisol was noted to the second discharge examination although the newborns continued to exhibit behavioral distress. Time since delivery was not a significant factor in producing these results. The findings are discussed with regard to neonatal coping processes and the importance of novelty in regulating increases in adrenocortical activity.     

Failure to alter sympathoadrenal response to psychosocial stress following aerobic training

This experiment assessed the impact of aerobic training on sympathoadrenal, heart rate and subjective responses to psychosocial stress. Subjects were six previously sedentary males who demonstrated marked improvement in fitness level following 10 weeks of training. Plasma samples, heart rate and subjective arousal ratings were obtained prior to, during, and following exposure to stressful mental tasks within a laboratory session. With the exception of training-related bradycardia which was manifest throughout the session, no changes in plasma epinephrine and norepinephrine concentrations, heart rate or subjective reactivity or recovery were seen. These findings are inconsistent with the hypothesized beneficial effects of aerobic training on stress-response. Methodological factors such as self-selection inherent in previous correlation work or the duration of the training program should be considered in this context. The potential contribution of training-related bradycardia to enhanced coping with challenging situations is explored.     

几种血管活性因子与脑卒中

脑卒中是由于脑动脉或支配脑的颈动脉发生功能性或结构性病变，引起脑局灶性血流障碍，所导致的急性或亚急性脑损害，分出血性和缺血性两大类。其病因主要涉及血管的舒缩功能，所以调节血管舒张和收缩的血管活性因子在其中起着不可忽视的作用。血管活性因子包括肽类和非肽类物质，按其作用可分为血管收缩活性因子和血管舒张活性因子两种，前者包括：内皮素（ｅｎｄｏｔｈｅｌｉｎ，ＥＴ），血管紧张素（ａｎｇｉｏｔｅｎｓｉｎ，ＡＮＧ），精氨酸加压素（ａｒｇｉｎｉｎｅｖａｓｏｐｒｅｓｓｉｎ，ＡＶＰ）等；后者包括：一氧化氮（ｎｉｔ…     

Some aspects of occupational asthma

The behaviour of forty-four patients, taken from a group of 133 cases of extrinsic pulmonary granulomatoses (EPG), who before developing the disease had no history of atopy and after being affected presented asthma-like symptoms, is analysed. Some of these patients had simultaneously clinical signs of rhinitis which proved to be due to lesions identical to those found in the bronchial mucosa. From the presented results, the author concludes that the clinical manifestations of these patients are not of the classical allergic type but bronchial and nasal reactions of the EPG in which, at least, a type III hypersensitivity reaction is involved. This is supported by the results of bronchial provocation tests performed on twenty-three patients with suberosis.