Effect of Protein Intake on Strength, Body Composition and Endocrine Changes in Strength/Power Athletes

Comparison of protein intakes on strength, body composition and hormonal changes were examined in 23 experienced collegiate strength/power athletes participating in a 12-week resistance training program. Subjects were stratified into three groups depending upon their daily consumption of protein; below recommended levels (BL; 1.0 – 1.4 g·kg^-1·day^-1; n = 8), recommended levels (RL; 1.6 – 1.8 g·kg^-1·day^-1; n = 7) and above recommended levels (AL; > 2.0 g·kg^-1·day^-1; n = 8). Subjects were assessed for strength [one-repetition maximum (1-RM) bench press and squat] and body composition. Resting blood samples were analyzed for total testosterone, cortisol, growth hormone, and insulin-like growth factor. No differences were seen in energy intake (3,171 ± 577 kcal) between the groups, and the energy intake for all groups were also below the recommended levels for strength/power athletes. No significant changes were seen in body mass, lean body mass or fat mass in any group. Significant improvements in 1-RM bench press and 1-RM squat were seen in all three groups, however no differences between the groups were observed. Subjects in AL experienced a 22% and 42% greater change in Δ 1-RM squat and Δ 1-RM bench press than subjects in RL, however these differences were not significant. No significant changes were seen in any of the resting hormonal concentrations. The results of this study do not provide support for protein intakes greater than recommended levels in collegiate strength/power athletes for body composition improvements, or alterations in resting hormonal concentrations.     

Cortisol-Induced Impairments of Working Memory Require Acute Sympathetic Activation.

The present study assessed whether the effects of cortisol on working memory depend on the level of adrenergic activity (as measured by sympathetic activation) during memory performance. After exposure to a psychosocial stress task, participants were divided into cortisol responders and nonresponders. Cortisol responders showed working memory impairments during the psychosocial stress phase, when cortisol and adrenergic activity were enhanced, whereas nonresponders did not. During recovery, however, when cortisol levels were elevated but adrenergic activity was normalized, working memory of responders did not differ from that of nonresponders. Among several stress measures, cortisol was the only significant predictor for working memory performance during stress. These findings suggest that adrenergic activation is essential for the impairing effects of stress-induced cortisol on working memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

振动和噪声对动物ACTH和皮质醇的影响

研究了振动和噪声联合暴露作用大鼠引起的应激反应及垂体 肾上腺皮质系统的改变机制。结果表明 :在 1 30dB白噪声和 7Hz、0 .5g正弦振动信号实验条件下 ,暴露 45min ,引起大鼠血浆ACTH和血清皮质醇显著性变化 ,t检验p <0 .0 1。     

Examining infants' cortisol responses to laboratory tasks among children varying in attachment disorganization: Stress reactivity or return to baseline?

Cortisol is a hormone involved in mounting a stress response in humans. The evidence of stress reactivity among young children has been mixed, however. In the present study, the order of two laboratory tasks (i.e., Strange Situation and play) was counterbalanced, and home saliva samples were obtained. Saliva samples were also collected upon the children's arrival at the laboratory and at 40, 65, and 80 min after arrival. The authors examined changes in cortisol using piecewise hierarchical linear modeling, testing whether observed increases reflected a return to baseline or stress reactivity. An interaction between attachment disorganization and task emerged, such that disorganized infants showed increases in cortisol in response to the stressor compared with play, whereas organized infants did not show cortisol reactivity to either task. Implications for the buffering effects of maternal care on stress reactivity are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Children’s context inappropriate anger and salivary cortisol.

Some children show emotion that is not consistent with normative appraisal of the context and can therefore be defined as context inappropriate (CI). The authors used individual growth curve modeling and hierarchical multiple regression analyses to examine whether CI anger predicts differences in hypothalamic-pituitary-adrenal axis activity, as manifest in salivary cortisol measures. About 23% of the 360 children (ages 6–10 years, primarily 7–8) showed at least 1 expression of CI anger in situations designed to elicit positive affect. Expression of anger across 2 positive assessments was less common (around 4%). CI anger predicted the hypothesized lower levels of cortisol beyond that attributed to context appropriate anger. Boys’ CI anger predicted lower morning cortisol and flatter slopes. Results suggest that this novel approach to studying children’s emotion across varying contexts can provide insight into affective style. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Interindividual differences and intraindividual variability in the cortisol awakening response: An examination of age and gender.

This article shows age and gender differences in the magnitude and day-to-day variability of the cortisol awakening response (CAR) using a national sample of 1,143 adults who completed the second wave of the National Study of Daily Experiences, a part of the Midlife Development in the United States survey. Participants between the ages of 33 and 84 years completed 8 consecutive nightly interviews and provided 4 saliva samples (upon waking, 30 min after waking, before lunch, and before bed) on 4 consecutive interview days. Results revealed substantial day-to-day variability in the CAR as well as significant Age × Gender interactions, indicating that although no systematic age-related differences emerged for women, the magnitude and day-to-day variability of the CAR increased with age among men. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Interaction effect of D4 dopamine receptor gene and serotonin transporter promoter polymorphism on the cortisol stress response.

Genetic variation of the serotonin transporter (SCL6A4, 5-HTT) has been associated with fear- and anxiety-related behaviors, while a polymorphism in exon III of the D4 dopamine receptor gene (DRD4) has been linked to novelty seeking. The dopaminergic and the serotonergic neurotransmitter system have been found to modulate the amygdala-connected circuitries that are crucial in emotional modulation and response to fearful stimuli. Additionally, reactivity of amygdala-innervated effector systems is also essential for our understanding of anxiety-related behaviors. Here, we used the stress-induced activation of the hypothalamic-pituitary-adrenal axis to investigate the impact of 5-HTTLPR and DRD4 on the cortisol stress response in 84 healthy adults. Saliva cortisol was measured during and after the Trier Social Stress Test. We found a significant main effect of DRD4: Carriers of the 7R allele exhibited lower cortisol responses. Additionally, a DRD4 by 5-HTTLPR interaction emerged: 5-HTTLPR LA/LA homozygotes showed a lower cortisol response than did S or LG allele carriers but only if they possessed at least one copy of the DRD4 7R allele. The results point to independent and joint effects of these polymorphisms on stress responsivity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Evaluation of alternatives to cautery disbudding of dairy goat kids using physiological measures of immediate and longer-term pain

We evaluated alternatives to cautery disbudding of goat kids using physiological measures of immediate and longer-term pain. Fifty Saanen doe kids were randomly assigned to 1 of 5 treatments (n = 10/treatment): (1) cautery disbudding (CAUT), (2) caustic paste disbudding (CASP), (3) liquid nitrogen disbudding (CRYO), (4) clove oil injected into the horn bud (CLOV), or (5) sham disbudding (SHAM). Serum cortisol and haptoglobin concentrations were measured from blood samples collected immediately before treatment (baseline) and at 15, 30, 60, and 120 min and then again at 6 and 24 h post-treatment. An infrared thermography camera was used to take images of the horn buds 24 h pre- and 24, 48, and 72 h post-treatment to measure skin temperature. Body weight was measured daily for 1 wk to assess weight change post-treatment. Images of the horn buds were taken at d 1, 2, and 7 and at 6 wk post-treatment to assess tissue damage and wound healing. Mean cortisol concentrations were elevated in CASP kids 1 h post-treatment relative to CAUT kids. Cortisol concentrations of CRYO kids were higher than those of CAUT kids 30 min post-treatment; concentrations for CLOV kids were similar to CAUT kids post-treatment. Mean haptoglobin concentrations were similar across treatments over time; however, CLOV kids had higher concentrations at 24 h post-treatment than all other treatments. Skin temperatures of CASP and CLOV kids were elevated relative to CAUT kids at all time points post-treatment, and all disbudded kids had skin temperatures above those of SHAM kids at 72 h post-treatment. Treatment did not influence weight gain. The CAUT kids had large, open wounds exposing bone; small scabs were still evident 6 wk post-treatment. The CASP kids had red and open, raw wounds that generated large eschars, apparent for up to 6 wk. The CRYO kids had closed, dry wounds initially, but over time lesions appeared that caused open wounds; small scabs were present 6 wk post-treatment. The CLOV kids had closed, dry wounds with blackened skin; healed skin and minimal scabs were present 6 wk post-treatment. Caustic paste and cryosurgical disbudding appeared to cause more pain compared with cautery disbudding; thus, these methods may not provide good alternatives to cautery disbudding. Clove oil appeared to cause a similar pain response as cautery disbudding and smaller wounds with earlier tissue repair; this method shows promise as an alternative to cautery disbudding.     

Intimate partner violence moderates the association between mother–infant adrenocortical activity across an emotional challenge.

This study examined the relationship between mother and infant adrenocortical levels and reactivity to an emotion eliciting task. The impact of intimate partner violence (IPV) on these relationships was assessed as a moderator. The sample (n = 702 mother–infant dyads) was racially diverse and from predominantly low-income, rural communities. During a home visit, the dyad’s saliva was sampled before, 20 min, and 40 min after standardized tasks designed to elicit the infant’s emotional arousal and later assayed for cortisol. Mothers completed self-report measures of their partner’s violence, and parenting behaviors were assessed via structured interview and mother–child interactions. In response to the task, infants had positive, and mothers had negative, cortisol slopes. Contrary to expectations, there were no IPV-related differences in mean pretask cortisol levels or reactivity in the mothers or infants. Mother–infant dyads from households characterized by either (1) violence or (2) restrictive and punitive parenting behaviors exhibited correlated cortisol reactivity measured in response to the infant challenge task. The findings suggest that social contextual features of the early caregiving environment may influence individual differences in the coordination between maternal and infant adrenocortical reactivity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stress impairs retrieval of socially relevant information.

Several studies have reported that stress impairs memory retrieval, even though findings are not unequivocal. Moreover, memory for socially relevant information was not previously investigated. The present study aimed to test the effects of stress on the retrieval of social memory (e.g., memory concerning names, birthdays, or biographies). In a randomized cross-over experiment, the cognitive performance of 29 subjects (15 women) was tested twice. Social memory was tested in a stress session, in which participants were exposed to a brief standardized psychosocial laboratory stressor between encoding and retrieval. Performance was compared with a stress-free control session. Stress exposure caused an increase in cortisol concentrations and changes in several mood measures. Social memory retrieval was reduced in the stress compared with the control session. An association between the cortisol stress response and poorer retrieval was significant in responders, that is, those participants displaying a cortisol rise after stress onset. Thus, similar to other forms of declarative memory, the retrieval of declarative memory for socially relevant information learned from biographical notes is impaired after acute stress exposure. This effect is linked to the stress-induced cortisol increase. (PsycINFO Database Record (c) 2010 APA, all rights reserved)