Change in temperature in young and old rats exposed to emotional-noise and immobilization stress]

Experiments with rats have shown that thermoregulation under normal conditions and in response to stressful factors (immobilization, emotionally significant sound) is different in animals of different age. The effect of these stressful factors leads to more significant temperature changes in the group of young animals, as compared with the adult ones.     

Play behaviour in nonhuman animals and the animal welfare issue

The mission of defining animal welfare indicators is methodologically difficult, limited, and possibly impossible. A promising alternative, however, to evaluate suitable environmental conditions is the assessment of play behaviour. In the present review, we summarise the general aspects of play behaviour in nonhuman animals and propose its use as a potential indicator of animal welfare. Play behaviour probably occurs in most vertebrates and some invertebrates, but predominately in mammals. It is also more frequent in young males and is associated with the environmental context in which animals find themselves. Animals play if they are healthy and well-fed, but not if they are under stressful conditions or if they are in a stressful state. We can therefore use the prevalence of play behaviour as an indicator of suitable environmental conditions, considering the specificity associated with the above-mentioned modifying factors.     

Effect of thermal stress on physiological parameters, feed intake and plasma thyroid hormones concentration in Alentejana, Mertolenga, Frisian and Limousine cattle breeds

The aim of the present study was to assess the heat tolerance of animals of two Portuguese (Alentejana and Mertolenga) and two exotic (Frisian and Limousine) cattle breeds, through the monitoring of physiological acclimatization reactions in different thermal situations characterized by alternate periods of thermoneutrality and heat stress simulated in climatic chambers. In the experiment, six heifers of the Alentejana, Frisian and Mertolenga breeds and four heifers of the Limousine breed were used. The increase in chamber temperatures had different consequences on the animals of each breed. When submitted to heat stress, the Frisian animals developed high thermal polypnea (more than 105 breath movements per minute), which did not prevent an increase in the rectal temperature (from 38.7°C to 40.0°C). However, only a slight depression in food intake and in blood thyroid hormone concentrations was observed under thermal stressful conditions. Under the thermal stressful conditions, Limousine animals decreased food intake by 11.4% and blood triiodothyronine (T3) hormone concentration decreased to 76% of the level observed in thermoneutral conditions. Alentejana animals had similar reactions. The Mertolenga cattle exhibited the highest capacity for maintaining homeothermy: under heat stressful conditions, the mean thermal polypnea increased twofold, but mean rectal temperature did not increase. Mean food intake decreased by only 2% and mean T3 blood concentration was lowered to 85,6% of the concentration observed under thermoneutral conditions. These results lead to the conclusion that the Frisian animals had more difficulty in tolerating high temperatures, the Limousine and Alentejana ones had an intermediate difficulty, and the Mertolenga animals were by far the most heat tolerant.     

Testing the Effect of Medical Positive Reinforcement Training on Salivary Cortisol Levels in Bonobos and Orangutans

The management of captive animals has been improved by the establishment of positive reinforcement training as a tool to facilitate interactions between caretakers and animals. In great apes, positive reinforcement training has also been used to train individuals to participate in simple medical procedures to monitor physical health. One aim of positive reinforcement training is to establish a relaxed atmosphere for situations that, without training, might be very stressful. This is especially true for simple medical procedures that can require animals to engage in behaviours that are unusual or use unfamiliar medical devices that can be upsetting. Therefore, one cannot exclude the possibility that the training itself is a source of stress. In this study, we explored the effects of medical positive reinforcement training on salivary cortisol in two groups of captive ape species, orangutans and bonobos, which were familiar to this procedure. Furthermore, we successfully biologically validated the salivary cortisol assay, which had already been validated for bonobos, for orangutans. For the biological validation, we found that cortisol levels in orangutan saliva collected during baseline conditions were lower than in samples collected during three periods that were potentially stressful for the animals. However, we did not find significant changes in salivary cortisol during medical positive reinforcement training for either bonobos or orangutans. Therefore, for bonobos and orangutans with previous exposure to medical PRT, the procedure is not stressful. Thus, medical PRT provides a helpful tool for the captive management of the two species.     

Testing the threat-sensitive predator avoidance hypothesis: physiological responses and predator pressure in wild rabbits

Predation is a strong selective force with both direct and indirect effects on an animal’s fitness. In order to increase the chances of survival, animals have developed different antipredator strategies. However, these strategies have associated costs, so animals should assess their actual risk of predation and shape their antipredator effort accordingly. Under a stressful situation, such as the presence of predators, animals display a physiological stress response that might be proportional to the risk perceived. We tested this hypothesis in wild European rabbits (Oryctolagus cuniculus), subjected to different predator pressures, in Doñana National Park (Spain). We measured the concentrations of fecal corticosterone metabolites (FCM) in 20 rabbit populations. By means of track censuses we obtained indexes of mammalian predator presence for each rabbit population. Other factors that could modify the physiological stress response, such as breeding status, food availability and rabbit density, were also considered. Model selection based on information theory showed that predator pressure was the main factor triggering the glucocorticoid release and that the physiological stress response was positively correlated with the indexes of the presence of mammalian carnivore predators. Other factors, such as food availability and density of rabbits, were considerably less important. We conclude that rabbits are able to assess their actual risk of predation and show a threat-sensitive physiological response.     

Effects of maternal deprivation on adrenal and behavioural responses in rats with anterodorsal thalami nuclei lesions

There is evidence that repeated maternal isolation of neonatal rats may influence both emotional behavior and Hypothalamic-Pituitary Adrenal (HPA) activity. On the other hand the Anterodorsal Thalami Nuclei (ADTN) exerts an inhibitory influence on the hypophyso-adrenal system under basal and stressful conditions. In the present work we investigated whether neonatal maternal deprivation produces long term effects on the ADTN regulation of behavioral patterns (open field test) and on HPA axis activity. Specifically, we sought to determine whether adult female rats with ADTN lesions, previously isolated for 4.5 hours daily during the first 3 weeks of life, react in endocrinologically and behaviourally distinct manner as compared to controls. The examined groups were: non maternally deprived (NMD)/sham lesioned, NMD/lesioned, maternally deprived (MD)/sham lesioned, MD/lesioned with and without the open field test. At 3 months MD/sham lesioned animals showed a marked decrease in ambulation (P < 0.01), and with ADTN lesion, the rearing values were lower (P < 0.01) and grooming higher (P < 0.05) than NMD. This last data would indicate a high emotional index. Regarding the activity of the HPA axis, maternal deprivation induced a significant decrease in plasma ACTH concentration both in sham and lesioned animals (P < 0.001), and plasma Corticosterone (C) increased in sham animals (P < 0.001). This data would indicate a higher sensitivity of the adrenal glands. After the open field test ACTH and C were different between deprived and non-deprived animals depending on the ADTN lesion. Taking into consideration the increase of ACTH levels in sham lesioned MD animals exposed to the test, we could conclude that this new situation was a stressful situation. Finally in the present work, it was very difficult to relate the behavioral parameters with the endocrine data. It is known that depending on the context, corticosteroids may produce opposite effects on emotional behavior via different receptors in the brain.In summary, neonatal maternal deprivation induced alterations of behavioral patterns and affected the ADTN inhibitory influence on ACTH and C secretion.     

Comparison of stress induced by manual restraint and immobilisation in the estuarine crocodile,Crocodylus porosus

This study compared the stress induced in captive estuarine crocodiles, Crocodylus porosus, by two different handling methods: manual restraint (noosing with ropes) and immobilization by electro-stunning. To stun, a short charge (approx. 6 s) at 110 V was delivered to the back of the necks of C. porosus using a custom-built device, which immobilized the animals for 5-10 min. Immobilized and restrained animals were measured and sexed, and the condition of the skin assessed. Blood samples were taken from some animals immediately after restraint or immobilization. Other animals were returned to their pens to recover for periods of 30 min, 1, 4, 12, 24 or 48 hours after which they were stunned and blood samples taken. Individual animals (mean body length 1.96 m, N=99) were bled only once. Haematocrit and haemoglobin concentrations were measured and plasma samples were analysed for corticosterone, glucose and lactate levels. Following restraint, there were significant increases in haematocrit, haemoglobin, glucose, lactate and corticosterone concentrations in C. porosus. For restrained animals, recovery to baseline levels occurred after approximately 8 hours. The stress response of stunned animals was significantly reduced compared to manually captured and restrained crocodiles. Both groups showed a significant increase in haematocrit, haemoglobin concentration and lactate levels, however the magnitude of change was significantly reduced, and recovery was faster in stunned animals. No increase in either glucose or corticosterone levels occurred with immobilisation. The results imply that immobilization by electro-stunning is much less stressful.     

An environmental chamber system for prolonged metabolic studies on small animals

Measurement of metabolic adaptation to marginally stressful environments requires both precise regulation of a variety of atmospheric factors for extended periods of time and the capacity to employ sensitive parameters in an undisturbed subject. This paper describes a metabolic chamber system which can simultaneously maintain groups of small animals in two completely separate closed environments having different pressures, temperatures and gas compositions for an indefinite period. Oxygen consumption, carbon dioxide production, food and water consumption and animal activity cycles can be continuously monitored and quantified 24 h per day while the animals are in an unrestrained state. Each chamber can be serviced and the animals handled, injected and sacrificed without subjecting them to barometric stress. Several unique electrical and mechanical components allow semi-automated data collection on a continuous basis for indefinite periods of time.     

Stressful life events and co-occurring depression,substance abuse and suicidality among American Indian and Alaska Native adolescents

Depression, suicidality and substance abuse disorders are examined with special emphasis on the role of stressful life events in predicting severity and patterns of comorbidity among American Indian and Alaska Native adolescents in boarding school environments. Both amount and severity of comorbidity increase with age and specific patterns of comorbidity are associated with gender. Different types and amounts of stressful life events predict specific combinations of comorbidity. These outcomes are interpretable with respect to associated cultural dynamics and the ecology of mental health services delivery for Indian and Native adolescents. Theoretical and methodological issues are discussed in relation to the use of stressful life events in examining cultural factors related to comorbidity among culturally different populations.     

Changes in Ubiquitin Conjugates and Hsp72 Levels During Arm Regeneration in Echinoderms

All organisms show a common defensive mechanism that results in the expression of conserved heat shock proteins (Hsps). These proteins function in a wide range of stressful conditions. We have monitored their levels in species of regenerating echinoderms with different mechanisms of regeneration and from different geographical locations. The effect of an artificial higher temperature on expression of Hsps was also studied. Two stress proteins (Hsp72 and ubiquitin) that are important in processes such as development and protein degradation were investigated. Using Western blot analysis and immunocytochemistry, we found significant changes in the level (Hsp72) and pattern of conjugation (ubiquitin) that corresponded with the repair phase (early regenerative stages) and with the later growth and regeneration of new tissues. Animals from the intertidal environment showed a distinctly sustained expression pattern of Hsp72 compared with benthic animals which suggests a functionally adaptative and dynamic stress response program. Accepted March 1, 2000.     

Calcium-dependent proteolysis in the myocardium of rats subjected to stress

Activity of a calcium-dependent neutral protease (calpain II) and its specific endogenous inhibitor was investigated in the myocardium of rats subjected to different stressors: cold, anaesthesia, 24 and 48 h starvation and food restriction for 7 and 14 days. Enzyme and inhibitor activities were determined in the 37,200 g supernatant of homogenates prepared from the free left ventricular wall of the heart. The specific activity of the myocardial calcium-dependent proteinase increased in all rats exposed to stressful stimuli, reaching maximum values in animals starved for 48 hours. Decrease in the specific activity of the inhibitor accompanied the changes in enzyme activity. Differences from normal control values were statistically significant in the starved animals and in animals fed a restricted diet for 7 or 14 days. These observations suggest that interaction between calpain II and its specific inhibitor plays a role in the regulation of the enzyme activity and furthermore, that stressful stimuli lead to increased calcium-dependent proteolysis in the myocardium.     

Developmental and Evolutionary History Affect Survival in Stressful Environments

The world is increasingly impacted by a variety of stressors that have the potential to differentially influence life history stages of organisms. Organisms have evolved to cope with some stressors, while with others they have little capacity. It is thus important to understand the effects of both developmental and evolutionary history on survival in stressful environments. We present evidence of the effects of both developmental and evolutionary history on survival of a freshwater vertebrate, the rough-skinned newt (Taricha granulosa) in an osmotically stressful environment. We compared the survival of larvae in either NaCl or MgCl₂ that were exposed to salinity either as larvae only or as embryos as well. Embryonic exposure to salinity led to greater mortality of newt larvae than larval exposure alone, and this reduced survival probability was strongly linked to the carry-over effect of stunted embryonic growth in salts. Larval survival was also dependent on the type of salt (NaCl or MgCl₂) the larvae were exposed to, and was lowest in MgCl₂, a widely-used chemical deicer that, unlike NaCl, amphibian larvae do not have an evolutionary history of regulating at high levels. Both developmental and evolutionary history are critical factors in determining survival in this stressful environment, a pattern that may have widespread implications for the survival of animals increasingly impacted by substances with which they have little evolutionary history.     

The use of variance in enzyme activity as an indicator of long-term exposure to toxicant-stressed environments in Culex pipiens mosquitoes

1. The identification of easy to use and cheap biomarkers is important as a means of determining whether animals are developing under stressful environmental conditions. Previous studies have indicated that the variance about the mean esterase activity in toxic environments increases in the absence of a significant shift in the mean value, suggesting that variance levels may have potential as a biomarker of toxicant-stressed or otherwise stressful environments.
2. Several field and laboratory populations of the mosquito, Culex pipiens , were examined for esterase activities using a colorimetric assay and levels of polymorphism using polyacrylamide gel electrophoresis. Some of these populations had been exposed to environmental toxicants (organophosphorus (OP) insecticides).
3. The OP-stressed field population had lower levels of polymorphism as indicated by fewer electromorphs than the populations that had not been exposed to OPs. However, the mean level of esterase activity was higher in the OP-stressed populations.
4. Despite having lower genetic variation, the OP-stressed populations showed much higher levels of variation about the mean enzyme activity, at least two orders of magnitude higher, than the unstressed populations. Knowledge of the genetics of OP resistance in these populations confirmed that the increase in variance was not due to the general switching on of genes in response to stress.
5. One field population that had been exposed to heavy metal pollution had similar levels of esterase activity and variation about the mean as the unstressed populations, suggesting that variation only increases in characters directly affected by the environmental pollutant.
6. The probable factors causing the increase in variance and the potential of this type of variation as a biomarker of stressful environments are discussed.     

Serotonergic immunoreactivity in the pedal ganglia of the pulmonate snail Megalobulimus abbreviatus after thermal stimulus: A semi-quantitative analysis

Using an immunohistochemical procedure and optical densitometry, the distribution of neurons containing serotonin (5-HT) was investigated in the pedal ganglia of Megalobulimus abbreviatus after thermal "non-functional stimulus" (22 degrees C) and stressful thermal conditions (50 degrees C).The animals were sacrificed at different times (3 h, 6 h and 24 h) following these stimuli. In control animals, the results showed the location of these serotonergic immunoreactive elements (5HT-ir) in this ganglion to be similar to those shown in other studies, where the anterior region of ventral sections showed the largest number of 5HT-ir neurons. In the anterior neurons, significant differences (p < 0.01) were observed between the groups of animals stimulated at 50 degrees C and 22 degrees C and sacrificed after 6 h. In the medial neurons, significant differences (p < 0.05) were observed between the control group and the groups of animals stimulated at 50 degrees C and sacrificed after 6 and 24 h. Neuropilar area 1 showed differences (p < 0.01) in 5HT-ir between the control group and the groups of animals stimulated at 50 degrees C and sacrificed after 3 and 24 h. Neuropilar area 2 showed a significant difference (p < 0.05) between the groups of animals stimulated at 22 degrees C and sacrificed after 3 and 24 h. These results suggest the involvement of 5-HT in the nociceptive circuit of M. abbreviatus, mainly that of the medial neurons and neuropilar area 1, which showed increases in 5HT-ir after thermal aversive stimuli. These results could be helpful in drawing cellular homologies with other gastropods.     

Long-term ovariectomy enhances anxiety and depressive-like behaviors in mice submitted to chronic unpredictable stress

Ovarian hormones exert anti-depressive and anxiolytic actions. In this study we have analyzed the effects of ovariectomy on the development of anxiety and depression-like behaviors and on cell proliferation in the hippocampus of mice submitted to chronic unpredictable stress. Animals submitted to stress 4 months after ovariectomy showed a significant increase in immobility behavior in the forced swimming test compared to animals submitted to stress 2 weeks after ovariectomy. In addition, long-term ovariectomy resulted in a significant decrease on the time spent in the open arms in the elevated plus-maze test compared to control animals. Stress did not significantly affect cell proliferation in the hilus of the dentate gyrus. However, ovariectomy resulted in a significant decrease in cell proliferation. These results indicate that long-term deprivation of ovarian hormones enhances the effect of chronic unpredictable stress on depressive- and anxiety-like behaviors in mice. Therefore, a prolonged deprivation of ovarian hormones may represent a risk factor for the development of depressive and anxiety symptoms after the exposure to stressful experiences.     

Effects of a chronic stress treatment on vaccinal response in lambs

Farming systems can expose animals to chronic mild stress which is known to induce negative affective state. Affective state in animals, as in humans, can be assessed through behavioral cues. This study aimed to describe the effect of a chronic mild stress, known to induce a negative affective state, on sheep health through their response to vaccination. The study used 15 lambs subjected to a model of chronic mild stress for 15 weeks and 15 lambs reared under conventional farming as a control group. After 7 weeks of stressful treatment, the lambs were individually exposed to a judgment bias test to assess a putative stress-induced ‘pessimism.’ After 15 weeks of stressful treatment, antibody immune response was measured after an injection of a live vaccine challenge (Chlamydia abortus attenuated vaccine strain 1B). Stressed lambs displayed a pessimistic-like perception in the judgment bias test, revealing a negative affective state. Stressed and control animals showed different immunological reactions to vaccine challenge: stressed sheep had lower hemoglobin concentrations and higher platelet, granulocyte and acute-phase protein concentrations. Antibody response induced by the vaccine strain was not different between stressed and control sheep. Our results suggest that negative affective state induced by chronic stress treatment may induce a stronger inflammatory response to vaccine challenge in sheep. Improvement of animal health may be achieved through consideration of stressors that may affect the emotional and immunological state of sheep.     

Melanin-concentrating hormone (MCH) reverts the behavioral effects induced by inescapable stress

The aim of this work was to investigate if MCH modifies the feeding and freezing responses in rats exposed to stressful stimuli. We used a basic version of contextual fear, where one group of rats were placed in a novel environment and two different groups were exposed to footshock paradigms, one of them escapable and the other one inescapable. At the end of each treatment, freezing and feeding were measured. Only the animals exposed to inescapable footshock paradigm showed significant increase in the food intake and freezing behavior in comparison to the control animals. The MCH administration (intra-hippocampal or intra-amygdaline) reverted these effects elicited by inescapable footshock. Results presented in this paper lead us to the assumption that the anxiolytic effect of the peptide is responsible for the reversion of the IS effects.     

Body condition and ruminal morphology responses of free-ranging impala (Aepyceros melampus) to changes in diet

Variation of the intraruminal papillation pattern with diet quality has been described in many ruminant species, but the use of papillation measures as a proxy for habitat quality and nutritional status of animals has not been evaluated. We compared various measures of body condition (body mass, body condition score, kidney fat index, bone marrow fat index, adrenal mass, kidney to adrenal mass ratio), diet quality (%browse, protein and fibre content) and rumen papillation in 106 impalas (Aepyceros melampus) from four different locations in Zimbabwe. The various condition proxies indicated that periods of low diet quality are characterised by a high proportion of browse in the diet of this species. Animals with a high proportion of browse had more voluminous rumens, suggesting a compensation for lower diet quality by increased intake. Macroscopic papillation indices did not yield meaningful significant correlations with diet quality or body condition proxies, and hence, their use for estimating habitat or body condition cannot be advocated. In contrast to previous histological reports, ballooning cells of the Stratum corneum of the ruminal mucosa were more prominent in animals on lower-quality diets. There were significant correlations of the kidney to adrenal mass ratio with other body conditions and with diet quality indices, suggesting that poor body condition and low diet quality represent stressful situations.     

Transgenerational effects benefit offspring across diverse environments: a meta‐analysis in plants and animals

The adaptive value of transgenerational effects (the ancestor environmental effects on offspring) in changing environments has received much attention in recent years, but the related empirical evidence remains equivocal. Here, we conducted a meta‐analysis summarising 139 experimental studies in plants and animals with 1170 effect sizes to investigate the generality of transgenerational effects across taxa, traits, and environmental contexts. It was found that transgenerational effects generally enhanced offspring performance in response to both stressful and benign conditions. The strongest effects are in annual plants and invertebrates, whereas vertebrates appear to benefit mostly under benign conditions, and perennial plants show hardly any transgenerational responses at all. These differences among taxonomic/life‐history groups possibly reflect that vertebrates can avoid stressful conditions through their mobility, and longer‐lived plants have alternative strategies. In addition to environmental contexts and taxonomic/life‐history groups, transgenerational effects also varied among traits and developmental stages of ancestors and offspring, but the effects were similarly strong across three generations of offspring. By way of a more comprehensive data set and a different effect size, our results differ from those of a recent meta‐analysis, suggesting that transgenerational effects are widespread, strong and persistent and can substantially impact the responses of plants and animals to changing environments.     

The Association of Pet Ownership and Attachment with Perceived Stress among Chinese Adults

Pet ownership is associated with both positive and negative emotions. Given that not everyone responds to pet care in a stressful way, perceptions of companion animals may play a role in how owners respond to them. In this study, we explored the relationship between pet ownership and perceived stress among Chinese pet owners. We also examined the effect of care practices and perceptions of pets on perceived stress. A total of 288 Hong Kong Chinese, adult pet owners, aged 18 to 70 years, were recruited. Participants were surveyed using a self-administered questionnaire covering demographics, pet ownership background, pet attachment, and perceived stress. Regression analyses were performed to examine pet attachment in different demographic groups and its relationship with perceived stress. Moderation and mediation analyses were performed to elucidate their underlying mechanisms. After adjusting for demographics and pet ownership background, greater attachment to a pet was associated with lower stress in owners. The perception of pets as family members minimized the stressful burden of pet care. More time spent caring for a pet increased attachment to that animal which in turn reduced stress in owners. The findings suggest attachment to companion animals and the perception of them as family members can help manage and reduce stress in owners.