Allostasis, Homeostasis, and the Costs of Physiological Adaptation

Sarah Coste reviews Allostasis, Homeostasis, and the Costs of Physiological Adaptation (edited by Jay Schulkin) for the Quarterly Review of Biology

The Effects of Social Stress on Voluntary Running Behavior in Female Mice

Regular physical activity (PA) positively impacts physical and mental health outcomes. However, there is a reciprocal relationship wherein stress significantly reduces healthy levels of routine PA. We showed previously that voluntary running behavior of male mice essentially ceases following exposure to a resident-intruder social stress. Here we examined female mice. Female mice were divided into four groups (n=8/group): sedentary/control, voluntary running/control, sedentary/stress, and voluntary running/stress. Running groups were given unlimited access to a running wheel in the home cage for 9 weeks with a nightly average of 6.86 ± 2.5 km. During the ninth week, stress groups were exposed to a single, 6-hour bout of a female-specific, resident-intruder social stress. Plasma corticosterone significantly increased following stress (34.56 ± 13 ng/ml basal to 330.5 ± 95 ng/ml immediately post-stress). Nightly running dropped significantly to 1.72 ± 0.9 km. Unlike male mice where running levels were slow to recover, voluntary running in these female mice returned to normal levels by the second night (5.01 ± 2.5 km). This study shows the sensitivity of habitual running behavior to stress exposure and suggests the utility of this mouse model in exploring the means by which stress negatively impacts routine PA

The Effects of Physical Activity on Stress-induced Cardiac Fibrosis

Purpose: This study examined whether routine physical activity limits stress-induced tissue remodeling processes that lead to cardiac fibrosis. The study also explored whether the cardiac urocortin 2/corticotropin releasing factor receptor 2β pathway was activated during physical activity and involved in reducing fibrotic processes. Methods: C67BL/6J male mice were divided into four groups (n=8/group): sedentary/control, voluntary running/control, sedentary/stress and voluntary running/stress. Voluntary running groups were given 24-hour access to a running wheel in the home cage for 9 weeks. During the 9th week, stress groups were exposed to a 5-day resident-intruder stress paradigm that models human post-traumatic stress outcomes. Ventricular cardiac tissue was collected for analysis. Results: Mice ran an average of 4.75 ± 1 km each night. Interestingly, running behavior essentially ceased following stress. Running distance dropped to 0.31 km following the 1st stress day. Some habituation to stress occurred, as running distance increased to 1.12 km by the 5th day of stress but remained significantly lower than pre-stress running distances and distances recorded in non-stressed mice. Quantitative RT-PCR showed small changes in ventricular urocortin 2 and CRF-R2β expression in the running groups. TGF-β, a signaling molecule known to induce fibrosis, had comparable expression levels across groups over controls. Conclusion: Further work is planned to fully characterize urocortin 2/ CRF-R2β and fibrotic processes. Our running data lead us in a new direction, as we have stumbled upon a paradigm that will be useful to study underlying mechanisms by which stress exposure impairs physical activity behavior

Comments on the Links between su(3) Modular Invariants, Simple Factors in the Jacobian of Fermat Curves, and Rational Triangular Billiards

We examine the proposal made recently that the su(3) modular invariant partition functions could be related to the geometry of the complex Fermat curves. Although a number of coincidences and similarities emerge between them and certain algebraic curves related to triangular billiards, their meaning remains obscure. In an attempt to go beyond the su(3) case, we show that any rational conformal field theory determines canonically a Riemann surface.Comment: 56 pages, 4 eps figures, LaTeX, uses eps

Cessation of Nightly Voluntary Wheel Running Activity Following Exposure to a Mouse Model of Posttraumatic Stress

Regular physical activity (PA) is well known to positively impact physical and mental health outcomes. In our work to examine cardiovascular benefits of PA in a mouse model of posttraumatic stress, we stumbled upon the reciprocal relationship between PA and stress exposure, wherein stress significantly reduced healthy levels of routine PA. The aim of the present studies was to define the parameters of our paradigm. C67BL/6J male mice were divided into four groups (n=8/group): sedentary/control, voluntary running/control, sedentary/stress, and voluntary running/stress. Voluntary running groups were given unlimited access to a running wheel for 9 weeks. Stress groups were then exposed to a 5-day resident-intruder social stress that models human posttraumatic stress. Running behavior essentially ceased following stress. Habituation to stress occurred, as running distance increased by the 5th day of stress but remained significantly low. A separate study examined a single exposure to resident-intruder social stress. Plasma corticosterone significantly increased while nightly running dropped significantly but returned to normal by the 3rd night post-stress. These studies show the sensitivity of habitual running behavior to stress exposure and suggest the utility of this mouse model in exploring the means by which stress negatively impacts routine PA

Scattering of dislocated wavefronts by vertical vorticity and the Aharonov-Bohm effect II: Dispersive waves

Previous results on the scattering of surface waves by vertical vorticity on shallow water are generalized to the case of dispersive water waves. Dispersion effects are treated perturbatively around the shallow water limit, to first order in the ratio of depth to wavelength. The dislocation of the incident wavefront, analogous to the Aharonov-Bohm effect, is still observed. At short wavelengths the scattering is qualitatively similar to the nondispersive case. At moderate wavelengths, however, there are two markedly different scattering regimes according to wether the capillary length is smaller or larger than $\sqrt{3}$ times depth. The dislocation is characterized by a parameter that depends both on phase and group velocity. The validity range of the calculation is the same as in the shallow water case: wavelengths small compared to vortex radius, and low Mach number. The implications of these limitations are carefully considered.Comment: 30 pages, 11 figure

Velocity, Distance and Shoulder Range of Motion in Two Throwing Programs

Success in baseball pitching is determined by throwing velocity and accuracy. Strength conditioning, as well as repetitive throwing programs, are used to improve the pitch. Recently, a weighted ball program has been developed and is believed to increase ball velocity with less potential injury. However, there is limited research examining the impact of this program on performance. The purpose of this study was to compare a traditional long toss program versus a weighted ball program. Baseline throwing velocity and distance as well as shoulder range of motion (ROM) were measured in collegiate baseball players. Participants were then randomized to either a six-week-long toss throwing program or weighted ball program. Following training, throwing velocity, distance, and shoulder ROM were measured again. Both training methods significantly improved throwing distance. However, throwing velocity did not change from pre-training measurements. All measurements of shoulder ROM (flexion, abduction, and external rotation) significantly improved in both groups, with abduction showing the greatest improvement in the long toss group. Our results suggest both training programs are beneficial for baseball performance

Sensitivity of freshwater periphytic diatoms to agricultural herbicides

The biomonitoring of pesticide pollution in streams and rivers using algae such as diatoms remains difficult. The responses of diatomcommunities to toxic stress in streamwater are disturbed by the variations of environmental parameters. In this study, periphytic algae collected in situwere exposed under controlled conditions to two major herbicides used in French agriculture (isoproturon and s-metolachlor). Three exposure regimes were tested: 5 and 30gL−1 for 6 days and 30gL−1 for 3 days followed by a recovery period of 3 days. The algal biomasses were assessed from pigment concentrations (chlorophyll a and c) and from live cell density. The highest concentration (30gL−1) of isoproturon inhibited the biomass increase statistically significantly. In periphyton exposed to 5 and 30gL−1 of s-metolachlor, chlorophyll c concentration and live cell densitywere also statistically significantly lower than in the control. Periphyton left to recover after reduced exposure duration (3 days) showed higher growth rates after treatment with s-metolachlor than with isoproturon. Taxonomic identifications showed that species like Melosira varians, Nitzschia dissipata and Cocconeis placentula were not affected by the herbicide exposure. Other species like Eolimna minima and Navicula reichardtiana were more sensitive. Studying diatoms according to their trophic mode showed that facultative heterotroph specieswere statistically significantly favoured by isoproturon exposure at the highest concentration. Results obtained with s-metolachlor exposure showed a disturbance of cell multiplication rather than that of photosynthesis. These results suggest that photosynthesis inhibitors like isoproturon favour species able to survive when the autotroph mode is inhibited

Resonant Magnetic Vortices

By using the complex angular momentum method, we provide a semiclassical analysis of electron scattering by a magnetic vortex of Aharonov-Bohm-type. Regge poles of the $S$-matrix are associated with surface waves orbiting around the vortex and supported by a magnetic field discontinuity. Rapid variations of sharp characteristic shapes can be observed on scattering cross sections. They correspond to quasibound states which are Breit-Wigner-type resonances associated with surface waves and which can be considered as quantum analogues of acoustic whispering-gallery modes. Such a resonant magnetic vortex could provide a new kind of artificial atom while the semiclassical approach developed here could be profitably extended in various areas of the physics of vortices.Comment: 6 pages, 7 figure

IL-1α and TNF-α Down-Regulate CRH Receptor-2 mRNA Expression in the Mouse Heart

Two receptors (CRH receptor type 1 and CRH receptor type 2) have been identified for the stress-induced neuropeptide, CRH and related peptides, urocortin, and urocortin II. We previously found marked down-regulation of cardiac CRH receptor type 2 expression following administration of bacterial endotoxin, lipopolysaccharide, a model of systemic immune activation, and inflammation. We postulated that inflammatory cytokines may regulate CRH receptor type 2. We show that systemic IL-1α administration significantly down-regulates CRH receptor type 2 mRNA in mouse heart. In addition, TNFα treatment also reduces CRH receptor type 2 mRNA expression, although the effect was not as marked as with IL-1α. However, CRH receptor type 2 mRNA expression is not altered in adult mouse ventricular cardiomyocytes stimulated in vitro with TNFα or IL-1α. Thus, cytokine regulation may be indirect. Exogenous administration of corticosterone in vivo or acute restraint stress also reduces cardiac CRH receptor type 2 mRNA expression, but like cytokines, in vitro corticosterone treatment does not modulate expression in cardiomyocytes. Interestingly, treatment with urocortin significantly decreases CRH receptor type 2 mRNA in cultured cardiomyocytes. We speculate that in vivo, inflammatory mediators such as lipopolysaccharide and/or cytokines may increase urocortin, which in turn down-regulates CRH receptor type 2 expression in the heart. Because CRH and urocortin increase cardiac contractility and coronary blood flow, impaired CRH receptor type 2 function during systemic inflammation may ultimately diminish the adaptive cardiac response to adverse conditions