Luteinizing-hormone-releasing hormone, gonadotropins, and gonadal steroids in stress

Integrating Reference Intervals into Chimpanzee Welfare Research

Animal welfare researchers are committed to developing novel approaches to enhance the quality of life of chimpanzees living in professional care. To systematically monitor physical, mental, and emotional states, welfare scientists highlight the importance of integrating non-invasive, animal-based welfare indicators. This study aimed to create species-specific reference intervals for behavioral measures and physiological biomarkers. Specifically, we analyzed data from 40 adult chimpanzees (22 females, 18 males) residing at 16 zoological facilities to generate reference intervals for behavioral states and events, behavioral diversity, fecal glucocorticoid metabolites (GCMs), and fecal immunoglobulin-A (IgA). Comparisons of sex and age using linear regression models revealed significant differences for several behaviors. The proportion of time spent engaged in mutual/multiple social grooming significantly decreased as individuals aged. Furthermore, males spent a higher proportion of time performing aggressive contact behaviors and displaying to other chimpanzees when compared to females. Males also performed sexual examination behaviors at a higher rate than females. Behavioral diversity, fecal GCM, and fecal IgA did not vary by sex or age. In the future, values for individual chimpanzees can be compared to the ranges reported here for particular age/sex classes. Ultimately, animal care professionals can utilize reference intervals to make evidence-based decisions regarding management practices and environmental conditions.

VR for Pain Relief

The present chapter explores how immersive virtual reality (VR) systems can be used for pain research and treatment. Pain is a universal, yet entirely subjective and multifaceted unpleasant experience. One of the earliest VR studies on pain highlighted the role of attention in pain modulation. However, the role of body representation in pain modulation has also been described as a crucial factor. Through virtual reality systems, it is possible to modulate both attention to pain and body representation. In this chapter, first we define how immersive VR can be used to create the illusion of being present in immersive VR environments and argue why VR can be an effective tool for distracting patients from acute pain. However, distraction seems to be less useful in chronic pain treatment. Chronic pain can be highly disabling and can significantly impact not only the sufferer's quality of life, but also their perceptions of the bodily self. Close neural connections between the body matrix and pain open a chance for influencing pain through bodily illusions. This chapter explores approaches to inducing body ownership illusions in VR and discusses how they have been applied in pain research. The present chapter also covers a set of practical indications and methodological caveats of immersive VR and solutions for overcoming them. Finally, we outline several promising future research directions and highlight several yet unexplored areas.

Behavioural diversity as a potential welfare indicator for professionally managed chimpanzees (Pan troglodytes): Exploring variations in calculating diversity using species-specific behaviours

Behavioural diversity may serve as a positive indicator of animal welfare that can be applied in long-term monitoring schemes in managed settings (eg zoos, laboratories, farms). Behavioural diversity is often higher when animals live in stimulating environments and experience positive events. Unfortunately, welfare researchers have not adopted consistent, standardised approaches to measuring behavioural diversity. The goal of this exploratory study was to utilise data from 41 adult chimpanzees (Pan troglodytes) housed across 16 zoological institutions to examine various models of Shannon's Diversity Index. Specifically, we investigated the impact of: combining versus splitting behaviours, including only positive behaviours, including human interaction, and considering recipient behaviours. We evaluate how the inclusion or exclusion of different behaviours impacts the relationship of behavioural diversity with: (i) concentrations of faecal glucocorticoid metabolites (GCM), a common indicator of adrenal activity; (ii) concentrations of immunoglobulin-A (IgA), an indicator of immune function and potential indicator of positive welfare; and (iii) stereotypic behaviour, a validated indicator of poor welfare. Most indices had significant negative relationships with faecal GCM. Animals that express a variety of behaviours from their species-typical repertoire have lower average faecal GCM concentrations and are likely experiencing better welfare. We did not find significant relationships between the behavioural diversity indices and IgA concentrations. Two indices were inversely associated with stereotypic behaviour. Our findings provide additional support for using Shannon's Diversity Index to calculate behavioural diversity as a robust, valid measure of positive welfare. However, future publications must justify the process for including or excluding behaviours from calculations.

Irregular ovarian cyclicity is associated with adrenal activity in female eastern black rhinoceros (Diceros bicornis michaeli)

To achieve self-sustaining and genetically diverse populations ex situ, captive breeding programmes must ensure good overall rates of reproduction, and equal contribution across individuals. Previous research in the critically endangered eastern black rhinoceros (Diceros bicornis michaeli) revealed a high incidence of irregular oestrous cyclicity; in particular extended cycle duration among nulliparous females and acyclic periods in parous females that have not bred for several years. Irregular ovarian activity could play a role in reduced reproductive output; however, the mechanisms underlying these anomalies are poorly understood. The aim of this study was to measure faecal glucocorticoid metabolite (fGCM) concentrations and variability prior to and during periods of regular and irregular ovarian activity, and determine if adrenal activity influences the occurrence of different cycle types in this species. Faecal samples were collected every other day from parous (N = 6) and nulliparous (N = 12) females at eight European institutions for periods of 9-15 months. Concentration and variability in fGCM were compared between periods of regular and irregular cyclicity and between different cycle types (<20 days, 20-40 days, >40 days, acyclic) using generalized linear mixed models. Concentrations of fGCM were influenced by season and higher during the luteal than the follicular phase of the oestrous cycle. Taking this into account, fGCMs were increased during periods of irregular cyclicity (all types combined and during cycles >40 days in length) compared to 20-40 day cycles. This was predominantly driven by nulliparous females. The variation in fGCM concentration also differed between periods of regular and irregular cyclicity; higher standard deviation in fGCM preceded irregular cycles and >40 day cycles compared to 20-40 day cycles. These results suggest that although fGCM concentrations fluctuate across the oestrous cycle in this species, changes in adrenal activity at specific times could be one factor associated with irregular ovarian activity in the black rhinoceros.

Detrimental effects of endogenous oestrogens on primary acute myocardial infarction among postmenopausal women

OBJECTIVE

Traditionally, oestrogens were considered to be protective for the cardiovascular system for premenopausal women. Therefore, we conducted a retrospective case-control study to examine the association between endogenous oestrogens and acute myocardial infarction (AMI) risk among postmenopausal women.

METHODS

A case-control study was performed among 30 primary AMI patients and 60 control subjects. Baseline characteristics data was collected and endogenous sex hormones levels were determined using chemoluminescence and radioimmunoassay methods. Conditional logistic regression models were developed with adjustment for confounders.

RESULTS

Compared with controls, the circulating oestrone, oestradiol, androstenedione and testosterone levels were significantly higher in AMI patients (P < 0.05) while the sex hormone binding globulin (SHBG) level was lower (P < 0.05). Spearman correlation coefficients showed oestradiol was positively correlated with body mass index (BMI) and waist-to-hip ratio (WHR) in cases, but not in controls. In univariable conditional logistic regression models, oestrone, oestradiol, testosterone, WHR, BMI, diabetes and hypertension were all found to be positively associated with AMI (P < 0.05). After adjusting for these factors, oestradiol (odds ratio (OR) = 4.75; 95 % confidence interval (CI) = 1.07-21.10; P = 0.04) and WHR (OR = 6.46; 95 % CI = 1.09-38.39; P = 0.04) continued to demonstrate strong positive associations with AMI.

CONCLUSIONS

A higher level of oestradiol was potentially associated with primary AMI risk among postmenopausal women.

Influence of dominance status on adrenal activity and ovarian cyclicity status in captive African elephants

The North American African (Loxodonta africana) elephant population is not self-sustaining, in part because of a high rate of abnormal ovarian activity. About 12% of adult females exhibit irregular cycles and 31% do not cycle at all. Our earlier work revealed a relationship between dominance status and ovarian acyclicity, with dominant females being more likely to not cycle normally. One theory is that dominant females may be expending more energy to maintaining peace within the captive herd than for supporting reproduction. The goal of this study was to determine if there was a relationship among dominance status, serum cortisol concentrations, and ovarian acyclicity. We hypothesized that adrenal glucocorticoid activity would be increased in dominant, noncycling elephants as compared with subdominant individuals. Blood samples were collected weekly over a 2-year period in 81 females of known dominance and cyclicity status, and analyzed for cortisol. Based on a path analysis model (Reticular Action Model Or Near Approximation [RAMONA]), noncycling, dominant African elephant females did not have higher mean serum cortisol concentrations, or exhibit more variability (i.e., coefficient of variation, standard deviation) in cortisol secretion. This study suggests that alterations in adrenal activity are not related to dominance status nor contribute directly to acyclicity in captive African elephants.

Cortisol, estrogens and risk of ischaemic heart disease, cancer and all-cause mortality in postmenopausal women: a prospective cohort study

BACKGROUND

Chronic stress may affect morbidity and mortality through neuroendocrine changes, and the ratio of cortisol to sex steroid hormones has been suggested as a biomarker of stress. We aim to address a relation between the ratio of cortisol to estrogens (C/E) and risk of ischaemic heart disease (IHD), hormone-dependent cancers and all-cause mortality among postmenopausal women.

METHODS

Estradiol and cortisol were measured in a subset of 838 women randomly drawn from the second wave of the Copenhagen City Heart Study (n = 5297 examined in 1981-83) as well as among all women who developed hormone-dependent cancers after baseline. The participants were followed in nationwide registers until 2007, with < 0.1% loss to follow-up.

RESULTS

The C/E ratio was not associated with self-reported stress, and there were no clear associations with IHD (highest vs lowest quartile: HR = 1.23; 95% confidence interval 0.83-1.81), hormone-dependent cancers (0.69; 0.45-1.08) or all-cause mortality (1.10; 0.86-1.41).

CONCLUSIONS

The C/E ratio was not associated with morbidity and mortality in women, and we cannot replicate the robust findings of a relation between the cortisol to testosterone ratio and IHD previously reported in men. Whether the C/E ratio is a reasonable biomarker of stress is debatable.

Perceived stress and cause-specific mortality among men and women: results from a prospective cohort study

The authors assessed the effect of psychological stress on total and cause-specific mortality among men and women. In 1981-1983, the 12,128 Danish participants in the Copenhagen City Heart Study were asked two questions on stress intensity and frequency and were followed in a nationwide registry until 2004, with <0.1% loss to follow-up. Sex differences were found in the relations between stress and mortality (p = 0.02). After adjustments, men with high stress versus low stress had higher all-cause mortality (hazard ratio (HR) = 1.32, 95% confidence interval (CI): 1.15, 1.52). This finding was most pronounced for deaths due to respiratory diseases (high vs. low stress: HR = 1.79, 95% CI: 1.10, 2.91), external causes (HR = 3.07, 95% CI: 1.65, 5.71), and suicide (HR = 5.91, 95% CI: 2.47, 14.16). High stress was related to a 2.59 (95% CI: 1.20, 5.61) higher risk of ischemic heart disease mortality for younger, but not older, men. In general, the effects of stress were most pronounced among younger and healthier men. No associations were found between stress and mortality among women, except among younger women with high stress, who experienced lower cancer mortality (HR = 0.51, 95% CI: 0.28, 0.92). Future preventive strategies may be targeted toward stress as a risk factor for premature death among middle-aged, presumably healthy men.

Perceived stress and risk of colorectal cancer in men and women: a prospective cohort study

OBJECTIVE

We aim to assess the relationship between stress and risk of primary colorectal cancer in men and women.

DESIGN

A prospective cohort study.

SETTING

The Copenhagen City Heart Study, Denmark.

SUBJECTS

A total of 6488 women and 5426 men were included in the study. The participants were asked about intensity and frequency of stress at baseline in 1981-1983 and were followed until the end of 2000 in the Danish Cancer Registry. Less than 0.1% was lost to follow-up.

MAIN OUTCOME MEASURES

First time incidence of primary colorectal cancer.

RESULTS

During follow-up 162 women and 166 men were diagnosed with colorectal cancer. Women with moderate and high stress intensity had a hazard ratio of 0.60 (95% CI: 0.37-0.98) and 0.52 (0.23-1.14) for colorectal cancer, respectively, compared to women with no stress. For colon cancer, a one-unit increase on a seven-point stress-score was associated with an 11% lower incidence of the disease (HR = 0.89, 95% CI: 0.81-0.99) amongst women. There was no consistent evidence of an association between stress and colorectal cancer in men.

CONCLUSION

Perceived stress was associated with lower risk of particularly colon cancer in women, whilst there was no clear relationship between stress and colorectal cancer in men.

Self-reported stress and risk of endometrial cancer: a prospective cohort study

OBJECTIVES

To assess a possible relationship between perceived stress and first-time incidence of primary endometrial cancer. Psychological stress may affect the synthesis and metabolism of estrogens and thereby be related to risk of endometrial cancer.

METHODS

The 6760 women participating in the Copenhagen City Heart Study were asked about their stress level at baseline from 1981 to 1983. These women were prospectively followed up in the Danish nationwide cancer registry until 2000 and <0.1% were lost to follow-up. Cox proportional hazard models were used to analyze data.

RESULTS

During follow-up, 72 women were diagnosed with endometrial cancer. For each increase in stress level on a 7-point stress scale, there was a lower risk of primary endometrial cancer (hazard ratio (HR) = 0.88; 95% confidence interval (CI), 0.76-1.01). This inverse association was particularly strong in women who received hormone therapy (HR = 0.77; 95% CI, 0.61-0.96) and in normal-weight women (HR = 0.73; 95% CI, 0.58-0.91).

CONCLUSIONS

Stress may affect gonadal synthesis of estrogens and alter the sensitivity of the uterus toward estrogen stimulation. These mechanisms may explain the lower risk of endometrial cancer observed among stressed women in this study. Despite these results, stress may still be a risk factor for a range of other diseases and should therefore not be considered a healthy response.

Sociodemographic status, stress, and risk of prostate cancer. A prospective cohort study

PURPOSE

The social gradient in prostate cancer incidence observed in several studies may be a result of differential access to prostate cancer screening. We aim to assess if socioeconomic status, stress, and marital status are associated with prostate cancer risk in a population with free access to health care.

METHODS

The 5,496 men who participated in the Copenhagen City Heart Study were asked about their income, educational level, stress level, and marital status during 1981-1983. These men were prospectively followed up in the Danish Cancer Registry until the end of 2002 and fewer than 0.1 % were lost to follow-up.

RESULTS

During follow-up, 157 men were diagnosed with prostate cancer. Neither high income (HR = 1.17, 95% confidence interval [CI]: 0.78-1.76) nor high education (HR = 1.22; 95% CI: 0.76-1.96) were associated with risk of prostate cancer. There were also no differences in prostate cancer risk according to stress (HR = 0.99; 95% CI: 0.90-1.09) or marital status.

CONCLUSION

In a racially homogeneous population of Caucasians with free access to health care, we found no evidence of a relation between sociodemographic variables or stress and subsequent risk of prostate cancer.

Stress and breast cancer: a systematic update on the current knowledge

A vast body of research has been carried out to examine the relationship between psychological stress and the risk of breast cancer. Previous reviews on this issue have mainly focused on stressful life events and have included both prospective and retrospective studies. The results from these reviews have revealed conflicting data. We evaluate whether stressful life events, work-related stress, or perceived global stress are differentially associated with breast cancer incidence and breast cancer relapse in prospective studies. Systematic and explicit methods were used to identify, select, and critically appraise relevant studies. The substantial variability in the manner in which stress was conceptualized and measured did not allow for the calculation of a quantitative summary estimate for the association between stress and breast cancer. Despite the heterogeneity in the results obtained, it is concluded that stress does not seem to increase the risk of breast cancer incidence. Whether stress affects the progression of breast cancer is still unclear. Studies with more thorough adjustment for confounding factors and larger studies on stress and breast cancer relapse are required to address this issue.

Self reported stress and risk of breast cancer: prospective cohort study

OBJECTIVE

To assess the relation between self reported intensity and frequency of stress and first time incidence of primary breast cancer.

DESIGN

Prospective cohort study with 18 years of follow-up.

SETTING

Copenhagen City heart study, Denmark.

PARTICIPANTS

The 6689 women participating in the Copenhagen City heart study were asked about their perceived level of stress at baseline in 1981-3. These women were followed until 1999 in the Danish nationwide cancer registry, with < 0.1% loss to follow-up.

MAIN OUTCOME MEASURE

First time incidence of primary breast cancer.

RESULTS

During follow-up 251 women were diagnosed with breast cancer. After adjustment for confounders, women with high levels of stress had a hazard ratio of 0.60 (95% confidence interval 0.37 to 0.97) for breast cancer compared with women with low levels of stress. Furthermore, for each increase in stress level on a six point stress scale an 8% lower risk of primary breast cancer was found (hazard ratio 0.92, 0.85 to 0.99). This association seemed to be stable over time and was particularly pronounced in women receiving hormone therapy.

CONCLUSION

High endogenous concentrations of oestrogen are a known risk factor for breast cancer, and impairment of oestrogen synthesis induced by chronic stress may explain a lower incidence of breast cancer in women with high stress. Impairment of normal body function should not, however, be considered a healthy response, and the cumulative health consequences of stress may be disadvantageous.

A pain neuromatrix approach to patients with chronic pain

This paper presents an approach to rehabilitation of pain patients. The fundamental principles of the approach are (i) pain is an output of the brain that is produced whenever the brain concludes that body tissue is in danger and action is required, and (ii) pain is a multisystem output that is produced when an individual-specific cortical pain neuromatrix is activated. When pain becomes chronic, the efficacy of the pain neuromatrix is strengthened via nociceptive and non-nociceptive mechanisms, which means that less input, both nociceptive and non-nociceptive, is required to produce pain. The clinical approach focuses on decreasing all inputs that imply that body tissue is in danger and then on activating components of the pain neuromatrix without activating its output. Rehabilitation progresses to increase exposure to threatening input across sensory and non-sensory domains.

Differential effects of chronic escapable versus inescapable stress on male syrian hamster (Mesocricetus auratus) reproductive behavior

Stress decreases sexual activity, but it is uncertain which aspects of stress are detrimental to reproduction. This study used an escapable/inescapable stress paradigm to attempt to dissociate physical from psychological components of stress, and assess each component's impact on reproductive behavior in the male Syrian hamster (Mesocricetus auratus). Two experiments were completed using this protocol where two animals receive the same physical stressor (an electric footshock) but differ in the psychological aspect of control. One group (executive) could terminate the shock for themselves as well as a second group (yoked) by pressing a bar. Experiment 1 demonstrated a significant increase in plasma glucocorticoids at the end of a single 90-min stress session with no difference in glucocorticoid levels between the executive and yoked groups at any time point. Experiment 2 quantified male reproductive behavior prior to and immediately following 12 days of escapable or inescapable stress in executive, yoked, and no-stress control hamsters (n = 12/group). Repeated-measures analysis of variance revealed a number of significant changes in reproductive behavior before and after stress in the three treatment groups. The most striking difference was a decrease in hit rate observed only in the animals that could not control their stress (yoked group). Hit rate in the executive males that received the exact same physical stressor but could terminate the shock by pressing a bar was nearly identical to control animals that never received any foot shock. Therefore, we conclude that coping or control can ameliorate the negative effects of stress on male reproductive behavior.