The physiological consequences of crib-biting in horses in response to an ACTH challenge test

Stereotypies are repetitive and relatively invariant patterns of behavior, which are observed in a wide range of species in captivity. Stereotypic behavior occurs when environmental demands produce a physiological response that, if sustained for an extended period, exceeds the natural physiological regulatory capacity of the organism, particularly in situations that include unpredictability and uncontrollability. One hypothesis is that stereotypic behavior functions to cope with stressful environments, but the existing evidence is contradictory. To address the coping hypothesis of stereotypies, we triggered physiological reactions in 22 horses affected by stereotypic behavior (crib-biters) and 21 non-crib-biters (controls), using an ACTH challenge test. Following administration of an ACTH injection, we measured saliva cortisol every 30min and heart rate (HR) continuously for a period of 3h. We did not find any differences in HR or HR variability between the two groups, but crib-biters (Group CB) had significantly higher cortisol responses than controls (Group C; mean±SD: CB, 5.84±2.62ng/ml, C, 4.76±3.04ng/ml). Moreover, crib-biters that did not perform the stereotypic behavior during the 3-hour test period (Group B) had significantly higher cortisol levels than controls, which was not the case of crib-biters showing stereotypic behavior (Group A) (B, 6.44±2.38ng/ml A, 5.58±2.69ng/ml). Our results suggest that crib-biting is a coping strategy that helps stereotypic individuals to reduce cortisol levels caused by stressful situations. We conclude that preventing stereotypic horses from crib-biting could be an inappropriate strategy to control this abnormal behavior, as it prevents individuals from coping with situations that they perceive as stressful.

Growth at moderately elevated temperature alters the physiological response of the photosynthetic apparatus to heat stress in pea (Pisum sativum L.) leaves

The impact of heat stress on the functioning of the photosynthetic apparatus was examined in pea (Pisum sativum L.) plants grown at control (25 °C; 25 °C-plants) or moderately elevated temperature (35 °C; 35 °C-plants). In both types of plants net photosynthesis (Pn) decreased with increasing leaf temperature (LT) and was more than 80% reduced at 45 °C as compared to 25 °C. In the 25 °C-plants, LTs higher than 40 °C could result in a complete suppression of Pn. Short-term acclimation to heat stress did not alter the temperature response of Pn. Chlorophyll a fluorescence measurements revealed that photosynthetic electron transport (PET) started to decrease when LT increased above 35 °C and that growth at 35 °C improved the thermal stability of the thylakoid membranes. In the 25 °C-plants, but not in the 35 °C-plants, the maximum quantum yield of the photosystem II primary photochemistry, as judged by measuring the Fv/Fm ratio, decreased significantly at LTs higher than 38 °C. A post-illumination heat-induced reduction of the plastoquinone pool was observed in the 25 °C-plants, but not in the 35 °C-plants. Inhibition of Pn by heat stress correlated with a reduction of the activation state of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco). Western-blot analysis of Rubisco activase showed that heat stress resulted in a redistribution of activase polypeptides from the soluble to the insoluble fraction of extracts. Heat-dependent inhibition of Pn and PET could be reduced by increasing the intercellular CO2 concentration, but much more effectively so in the 35 °C-plants than in the 25 °C-plants. The 35 °C-plants recovered more efficiently from heat-dependent inhibition of Pn than the 25 °C-plants. The results show that growth at moderately high temperature hardly diminished inhibition of Pn by heat stress that originated from a reversible heat-dependent reduction of the Rubisco activation state. However, by improving the thermal stability of the thylakoid membranes it allowed the photosynthetic apparatus to preserve its functional potential at high LTs, thus minimizing the after-effects of heat stress.

Hypercoagulation and hyperkinetic blood pressure indicative of physiological loss-of-control despite behavioural control in Africans: The SABPA study.

OBJECTIVES A dissociation between behavioural (in-control) and physiological parameters (indicating loss-of-control) is associated with cardiovascular risk in defensive coping (DefS) Africans. We evaluated relationships between DefS, sub-clinical atherosclerosis, low-grade inflammation and hypercoagulation in a bi-ethnic sex cohort. METHODS Black (Africans) and white Africans (Caucasians) (n = 375; aged 44.6 ± 9.7 years) were included. Ambulatory BP, vascular structure (left carotid cross-sectional wall area (L-CSWA) and plaque counts), and markers of coagulation and inflammation were quantified. Ethnicity/coping style interaction was revealed only in DefS participants. RESULTS A hypertensive state, less plaque, low-grade inflammation, and hypercoagulation were more prevalent in DefS Africans (27-84%) than DefS Caucasians (18-41%). Regression analyses demonstrated associations between L-CSWA and 24 hour systolic BP (R(2) = 0.38; β = 0.78; p < 0.05) in DefS African men but not in DefS African women or Caucasians. No associations between L-CSWA and coagulation markers were evident. CONCLUSION Novel findings revealed hypercoagulation, low-grade inflammation and hyperkinetic BP (physiological loss-of-control responses) in DefS African men. Coupled to a self-reported in-control DefS behavioural profile, this reflects dissociation between behaviour and physiology. It may explain changes in vascular structure, increasing cerebrovascular disease risk in a state of hyper-vigilant coping.

A physiological and behavioral mechanism for leaf-herbivore induced systemic root resistance

Indirect plant-mediated interactions between herbivores are important drivers of community composition in terrestrial ecosystems. Among the most striking examples are the strong indirect interactions between spatially separated leaf- and root-feeding insects sharing a host plant. Although leaf feeders generally reduce the performance of root herbivores, little is known about the underlying systemic changes in root physiology and the associated behavioral responses of the root feeders. We investigated the consequences of maize (Zea mays) leaf infestation by Spodoptera littoralis caterpillars for the root-feeding larvae of the beetle Diabrotica virgifera virgifera, a major pest of maize. D. virgifera strongly avoided leaf-infested plants by recognizing systemic changes in soluble root components. The avoidance response occurred within 12 h and was induced by real and mimicked herbivory, but not wounding alone. Roots of leaf-infested plants showed altered patterns in soluble free and soluble conjugated phenolic acids. Biochemical inhibition and genetic manipulation of phenolic acid biosynthesis led to a complete disappearance of the avoidance response of D. virgifera. Furthermore, bioactivity-guided fractionation revealed a direct link between the avoidance response of D. virgifera and changes in soluble conjugated phenolic acids in the roots of leaf-attacked plants. Our study provides a physiological mechanism for a behavioral pattern that explains the negative effect of leaf attack on a root-feeding insect. Furthermore, it opens up the possibility to control D. virgifera in the field by genetically mimicking leaf herbivore-induced changes in root phenylpropanoid patterns.

The physiological roles of ICAM-1 and ICAM-2 in neutrophil migration into tissues

PURPOSE OF REVIEW Neutrophil extravasation from the blood into tissues is initiated by tethering and rolling of neutrophils on endothelial cells, followed by neutrophil integrin activation and shear resistant arrest, crawling, diapedesis and breaching the endothelial basement membrane harbouring pericytes. Endothelial intercellular cell adhesion molecule (ICAM)-1 and ICAM-2, in conjunction with ICAM-1 on pericytes, critically contribute to each step. In addition, epithelial ICAM-1 is involved in neutrophil migration to peri-epithelial sites. The most recent findings on the role of ICAM-1 and ICAM-2 for neutrophil migration into tissues will be reviewed here. RECENT FINDINGS Signalling via endothelial ICAM-1 and ICAM-2 contributes to stiffness of the endothelial cells at sites of chronic inflammation and junctional maturation, respectively. Endothelial ICAM-2 contributes to neutrophil crawling and initiation of paracellular diapedesis, which then proceeds independent of ICAM-2. Substantial transcellular neutrophil diapedesis across the blood-brain barrier is strictly dependent on endothelial ICAM-1 and ICAM-2. Endothelial ICAM-1 or ICAM-2 is involved in neutrophil-mediated plasma leakage. ICAM-1 on pericytes assists the final step of neutrophil extravasation. Epithelial ICAM-1 rather indirectly promotes neutrophil migration to peri-epithelial sites. SUMMARY ICAM-1 and ICAM-2 are involved in each step of neutrophil extravasation, and have redundant but also distinct functions. Analysis of the role of endothelial ICAM-1 requires simultaneous consideration of ICAM-2.

Physiological plasticity to water flow habitat in the damselfish, Acanthochromis polyacanthus: linking phenotype to performance

The relationships among animal form, function and performance are complex, and vary across environments. Therefore, it can be difficult to identify morphological and/or physiological traits responsible for enhancing performance in a given habitat. In fishes, differences in swimming performance across water flow gradients are related to morphological variation among and within species. However, physiological traits related to performance have been less well studied. We experimentally reared juvenile damselfish, Acanthochromis polyacanthus, under different water flow regimes to test 1) whether aspects of swimming physiology and morphology show plastic responses to water flow, 2) whether trait divergence correlates with swimming performance and 3) whether flow environment relates to performance differences observed in wild fish. We found that maximum metabolic rate, aerobic scope and blood haematocrit were higher in wave-reared fish compared to fish reared in low water flow. However, pectoral fin shape, which tends to correlate with sustained swimming performance, did not differ between rearing treatments or collection sites. Maximum metabolic rate was the best overall predictor of individual swimming performance; fin shape and fish total length were 3.3 and 3.7 times less likely than maximum metabolic rate to explain differences in critical swimming speed. Performance differences induced in fish reared in different flow environments were less pronounced than in wild fish but similar in direction. Our results suggest that exposure to water motion induces plastic physiological changes which enhance swimming performance in A. polyacanthus. Thus, functional relationships between fish morphology and performance across flow habitats should also consider differences in physiology.

Rapid divergence in physiological and life-history traits between northern and southern populations of the British introduced neo-species, Senecio squalidus

Alien plants provide a unique opportunity to study evolution in novel environments, but relatively little is known about the extent to which they become locally adapted to different environments across their new range. Here, we compare northern and southern populations of the introduced species Senecio squalidus in Britain; S. squalidus has been in southern Britain for approximately 200 years and reached Scotland only about 50 years ago. We conducted common garden experiments at sites in the north and south of the species’ range in Britain. We also conducted glasshouse and growth chamber experiments to test the hypothesis that southern genotypes flower later, are more drought-tolerant, germinate and establish better at warmer temperatures, and are less sensitive to cold stress than their more northern counterparts. Results from the common garden experiments are largely consistent with the hypothesis of rapid adaptive divergence of populations of the species within the introduced range, with genotypes typically showing a home-site advantage. Results from the glasshouse and growth chamber experiments demonstrate adaptive divergence in ability to tolerate drought stress and high temperatures, as well as in phenology. In particular, southern genotypes were more tolerant of dry conditions and high temperatures and they flowered later than northern genotypes. Our results show that rapid local adaptation can occur in alien species, and they have implications for our understanding of the ecological genetics of range expansion of introduced weeds.

Stable carbon and oxygen isotopes in tree rings show physiological responses of Pericopsis elata to precipitation in the Congo Basin

In equatorial regions, where tree rings are less distinct or even absent, the response of forests to high-frequency climate variability is poorly understood. We measured stable carbon and oxygen isotopes in anatomically distinct, annual growth rings of four Pericopsis elata trees from a plantation in the Congo Basin, to assess their sensitivity to recorded changes in precipitation over the last 50 y. Our results suggest that oxygen isotopes have high common signal strength (EPS = 0.74), and respond to multi-annual precipitation variability at the regional scale, with low δ18O values (28–29‰) during wetter conditions (1960–1970). Conversely, δ13C are mostly related to growth variation, which in a light-demanding species are driven by competition for light. Differences in δ13C values between fast- and slow-growing trees (c. 2‰), result in low common signal strength (EPS = 0.37) and are driven by micro-site conditions rather than by climate. This study highlights the potential for understanding the causes of growth variation in P. elata as well as past hydroclimatic changes, in a climatically complex region characterized by a bimodal distribution in precipitation.

Methodological and physiological test-retest reliability of (13) C-MRS glycogen measurements in liver and in skeletal muscle of patients with type 1 diabetes and matched healthy controls.

Glycogen is a major substrate in energy metabolism and particularly important to prevent hypoglycemia in pathologies of glucose homeostasis such as type 1 diabetes mellitus (T1DM). (13) C-MRS is increasingly used to determine glycogen in skeletal muscle and liver non-invasively; however, the low signal-to-noise ratio leads to long acquisition times, particularly when glycogen levels are determined before and after interventions. In order to ease the requirements for the subjects and to avoid systematic effects of the lengthy examination, we evaluated if a standardized preparation period would allow us to shift the baseline (pre-intervention) experiments to a preceding day. Based on natural abundance (13) C-MRS on a clinical 3 T MR system the present study investigated the test-retest reliability of glycogen measurements in patients with T1DM and matched controls (n = 10 each group) in quadriceps muscle and liver. Prior to the MR examination, participants followed a standardized diet and avoided strenuous exercise for two days. The average coefficient of variation (CV) of myocellular glycogen levels was 9.7% in patients with T1DM compared with 6.6% in controls after a 2 week period, while hepatic glycogen variability was 13.3% in patients with T1DM and 14.6% in controls. For comparison, a single-session test-retest variability in four healthy volunteers resulted in 9.5% for skeletal muscle and 14.3% for liver. Glycogen levels in muscle and liver were not statistically different between test and retest, except for hepatic glycogen, which decreased in T1DM patients in the retest examination, but without an increase of the group distribution. Since the CVs of glycogen levels determined in a "single session" versus "within weeks" are comparable, we conclude that the major source of uncertainty is the methodological error and that physiological variations can be minimized by a pre-study standardization. For hepatic glycogen examinations, familiarization sessions (MR and potentially strenuous interventions) are recommended. Copyright © 2016 John Wiley & Sons, Ltd.

Physiological Responses to Environmental Variation in Intertidal Red Algae: Does Thallus Morphology Matter?

Morphological variation within and among many species of algae show correlated life history traits. The trade-offs of Life history traits among different morphs are presumed to be determined by morphology. Form-function hypotheses also predict that algae of different morphological groups exhibit different tolerances to physiological stress, whereas algae within a morphological group respond similarly to stress. We tested this hypothesis by comparing photosynthetic and respiratory responses to variation in season, light, temperature, desiccation and freezing among the morphologically similar fronds of Chondrus crispus and Mastocarpus stellatus and the alternate stage crust of M. stellatus. Physiological differences between fronds of the 2 species and crusts and fronds were consistent with their patterns of distribution and abundance in the intertidal zone. However, there was no clear relationship between algal morphology and physiological response to environmental variation. These results suggest that among macroalgae the correlation between Life history traits and morphology is not always causal. Rather, the link between life history traits and morphology is constrained by the extent to which physiological characteristics codetermine these features.

Oxygen Supplementing, Biocompatible Outer Membranes for Enhanced Performance of Implantable Glucose Sensors

Lack of linearity and sensitivity, oxygen dependence, biofouling and tissue inflammation hinder the development of implantable biosensors for continuous monitoring of glucose. Herein, we report the development of stacked outer membranes based on LBL/PVA hydrogels that improve sensor sensitivity, linearity, oxygen independence and counter biofouling and inflammation. While the inner LBL membrane affords tunable diffusivity, the outer PVA is capable of releasing anti-inflammatory drugs/tissue response modifying agents to counter acute and chronic inflammation, and to induce neo-angiogenesis at the implant site. Sensors were fabricated by immobilizing GOx enzyme on top of 50 μm platinum wires, followed by deposition of stacked LBL/PVA hydrogel membranes. The response of the sensors at 0.7V to various glucose concentrations was studied. Michelis-Menten analysis was performed to quantify sensor performance in terms of linearity and oxygen dependence. The interplay between sensor performance and inward glucose diffusivity was elucidated using (i) various LBL membranes and (ii) various freeze-thaw (FT) cycles of PVA. Incorporation of LBL/PVA stacked membranes resulted in an 8 fold increase in sensor linearity and a 9 fold decrease in oxygen dependence compared to controls. The enhancement in the sensor performance is attributed to (i) the oxygen storing capability of PVA hydrogel due to the formation of hydrophobic domains during its freezing/ thawing employed for its physical crosslinking and (ii) regulation of glucose flux by the inner LBL membrane. Such membranes offer significant advantages over presently available outer membranes in lieu of (i) their ability to control inflammation, (ii) their modulus that closely matches that of subcutaneous human tissue, (iii) non-necessity of reactive chemical crosslinking agents, (iv) tunable sensitivity and (v) supplemental storage of oxygen.

Female-specific regulation of cytochrome P450 3As and their response to xenobiotic stress

Cytochrome P450 3As (CYP3As) are phase I enzymes responsible for metabolizing more than 50% of clinical drugs. Recent studies have revealed that expression of CYP3As is two-fold higher in women than in men leading to a faster metabolic clearance of therapeutic drugs in women. In this study, we analyzed the female specific rat CYP3A isoform, CYP3A9. We evaluated the effects of progesterone and estrogen on CYP3A9 regulation and showed a distinct role for estrogen in mediating female dominance of CYP3A9. We also observed changes in CYP3A9 expression at various stages of pregnancy which correlates well with varying physiological estradiol concentrations. In addition, by the in vitro data shows that estradiol mediated induction can be abrogated with estrogen receptor antagonist ICI182,780. We also identified three novel murine CYP3A isoforms CYP3A13, CYP3A41 and CYP3A44 and characterized their genomic structures and expression profiles. CYP3A41 and CYP3A44 show female specific expression but surprisingly this female dominance is not mediated via estrogen. Control male mice did not exhibit any CYP3A41 mRNA levels but showed minimal levels of CYP3A44. In order to gain insights into the governance ofαthe female specific genes, the hepatic regulation of CYP3A41 and CYP3A44 by the xeno-sensors PXR and CAR was examined. In female mice, pregnenolone-16α-carboxynitrile, suppressed CYP3A41 and CYP3A44 mRNA levels in PXR−/− background whereas dexamethasone-dependent suppression of CYP3A41 was mediated by PXR. In addition, phenobarbital challenge in PXR−/− revealed up-regulation of both CYP3A44, CYP3A41 levels only in males. No role for CAR was seen in the regulation of either CYP3A41 or CYP3A44 gene expression in female mice. Interestingly, PXR and CAR ligands induced male CYP3A44 levels in a receptor dependent fashion. This increase of CYP3A44 transcript in male mice is in contrast to the response seen in female mice, which clearly indicates an additional layer of regulation. Our findings suggest that gender plays a strategic role in directing the CAR/PXR mediated effects of CYP3A44/CYP3A41. This implies that differential regulation of female specific CYP3A isoforms may be the key to explain some of the gender differences observed in clearance of certain therapeutics like antidepressants and analgesics. ^

A physiological role of cytochromes P450 4Fs: Mouse model

Cytochromes P450 4Fs (CYP4F) are a subfamily of enzymes involved in arachidonic acid metabolism with highest catalytic activity towards leukotriene B 4 (LTB4), a potent chemoattractant involved in prompting inflammation. CYP4F-mediated metabolism of LTB4 leads to inactive ω-hydroxy products incapable of initiating chemotaxis and the inflammatory stimuli that result in the influx of inflammatory cells. Our hypothesis is based on the catalytic ability of CYP4Fs to inactivate pro-inflammatory LTB4 which assures these enzymes a pivotal role in the process of inflammation resolution. ^ To test this hypothesis and evaluate the changes in CYP4F expression under complex inflammatory conditions, we designed two mouse models, one challenged with lipopolysaccharide (LPS) as a sterile model of sepsis and the other challenged with a systemic live bacterial infection of Citrobacter rodentium, an equivalent of the human enterobacterium E. coli pathogen invasion. Based on the evidence that Peroxisome Proliferator Activated Receptors (PPARs) play an active role in inflammation regulation, we also examined PPARs as a regulation mechanism in CYP4F expression during inflammation using PPARα knockout mice under LPS challenge. Using the Citrobacter rodentium model of inflammation, we studied CYP4F levels to compare them to those in LPS challenged animals. LPS-triggered inflammation signal is mediated by Toll-like 4 (TLR4) receptors which specifically respond to LPS in association with several other proteins. Using TLR4 knockout mice challenged with Citrobacter rodentium we addressed possible mediation of CYP4F expression regulation via these receptors. ^ Our results show isoform- and tissue-specific CYP4F expression in all the tissues examined. The Citrobacter rodentium inflammation model revealed significant reduction in liver expression of CYP4F14 and CYP4F15 and an up-regulation of gene expression of CYP4F16 and CYP4F18. TLR4 knockout studies showed that the decrease in hepatic CYP4F15 expression is TLR4-dependent. CYP4F expression in kidney shows down-regulation of CYP4F14 and CYP4F15 and up-regulation of CYP4F18 expression. In the LPS inflammation model, we showed similar patterns of CYP4F changes as in Citrobacter rodentium -infected mice. The renal profile of CYP4Fs in PPARα knockout mice with LPS challenge showed CYP4F15 down-regulation to be PPARα dependent. Our study confirmed tissue- and isoform-specific regulation of CYP4F isoforms in the course of inflammation. ^