Comparison of anamnestic responses to rabies vaccination in dogs and cats with current and out-of-date vaccination status.

OBJECTIVE: To compare anamnestic antibody responses of dogs and cats with current versus out-of-date vaccination status. DESIGN: Cross-sectional study. ANIMALS: 74 dogs and 33 cats. PROCEDURES: Serum samples were obtained from dogs and cats that had been exposed to rabies and brought to a veterinarian for proactive serologic monitoring or that had been brought to a veterinarian for booster rabies vaccination. Blood samples were collected on the day of initial evaluation (day 0) and then again 5 to 15 days later. On day 0, a rabies vaccine was administered according to label recommendations. Paired serum samples were analyzed for antirabies antibodies by means of a rapid fluorescent focus inhibition test. RESULTS: All animals had an antirabies antibody titer ≥ 0.5 IU/mL 5 to 15 days after booster vaccination. Dogs with an out-of-date vaccination status had a higher median increase in titer, higher median fold increase in titer, and higher median titer following booster vaccination, compared with dogs with current vaccination status. Most (26/33) cats, regardless of rabies vaccination status, had a titer ≥ 12 IU/mL 5 to 15 days after booster vaccination. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that dogs with out-of-date vaccination status were not inferior in their antibody response following booster rabies vaccination, compared with dogs with current vaccination status. Findings supported immediate booster vaccination followed by observation for 45 days of dogs and cats with an out-of-date vaccination status that are exposed to rabies, as is the current practice for dogs and cats with current vaccination status.

Infrared spectra of CF(2)=CHD and CF(2)=CD(2): scaled quantum-chemical force fields and an equilibrium structure for 1,1-difluoroethylene.

Infrared (IR) spectra in the gas phase are reported for CF(2)=CHD and CF(2)=CD(2) in the region 350-4000 cm(-1). Ab initio calculations of an harmonic force-field and anharmonicity constants have been made with an MP2/aug-cc-pVTZ model. These enable a number of Fermi resonances in each species to be analyzed and a complete set of "observed" harmonic frequencies to be derived. The latter are combined with similar data for CF(2)=CH(2) in a scaling of the model harmonic force field to both anharmonic and harmonic frequencies. Inspection of the scale factors reveals minor defects of the model, evident in the out-of-plane wagging modes and in the CF stretch/CF stretch interaction force constant. Fermi resonance treatments involved in all isotopomers studied are compatible with the overall force-field refinement results. The treatment leaves a small anomaly in the (13)C shift on nu(1). Improved microwave spectra are reported for five isotopic species, and a semiexperimental equilibrium structure for F(2)C=CH(2) is determined and compared favorably with the structure obtained from new high-level ab initio calculations. Centrifugal distortion constants are predicted for the five isotopic species, and those for F(2)C=CH(2) are compared with values fit to microwave spectra.

Whispering gallery mode lasing from zinc oxide hexagonal nanodisks.

Disk-shaped semiconductor nanostructures provide enhanced architectures for low-threshold whispering gallery mode (WGM) lasing with the potential for on-chip nanophotonic integration. Unlike cavities that lase via Fabry-Perot modes, WGM structures utilize low-loss, total internal reflection of the optical mode along the circumference of the structure, which effectively reduces the volume of gain material required for lasing. As a result, circularly resonant cavities provide much higher quality (Q) factors than lower reflection linear cavities, which makes nanodisks an ideal platform to investigate lasing nanostructures smaller than the free-space wavelength of light (i.e., subwavelength laser). Here we report the bottom-up synthesis and single-mode lasing properties of individual ZnO disks with diameters from 280 to 900 nm and show finite difference time domain (FDTD) simulations of the whispering gallery mode inside subwavelength diameter disks. These results demonstrate ultraviolet WGM lasing in chemically synthesized, isolated nanostructures with subwavelength diameters.

Ecological immunology: The organism in context.

A major challenge in integrative biology is understanding the mechanisms by which organisms regulate trade-offs among various functions competing for limiting resources. Key among these competing processes is the maintenance of health and the production of offspring. Optimizing both, given limited resources, can prove challenging. The physiological and behavioral changes that occur during reproduction have been shown to greatly influence an organism's immune system, which can have consequences for susceptibility to disease. Likewise, investing in costly immunological defenses can impair reproductive function. However, the precise nature of these physiological and behavioral interactions appears to be greatly dependent upon the environmental context in which they occur. Here we take a comparative look at interactions between the reproductive and immune systems, including current immunological approaches, and discuss how similar studies can reveal vastly disparate results. Specifically, we highlight results from the ornate tree lizard (Urosuarus ornatus) and the Siberian hamster (Phodopus sungorus) model systems, which provide an example of current research in the field. Collectively, these results emphasize the importance of resource availability and an individual's energy stores for the existence of life-history trade-offs and the efficiency of physiological processes in general. Akin to Dobzhansky's famous line, like other aspects of biology, nothing in ecoimmunology seems to make sense except in the context of an organism's environment.

Arginine vasotocin (AVT) immunoreactivity relates to testosterone but not territorial aggression in the tree lizard, Urosaurus ornatus.

The neuropeptide arginine vasotocin (AVT) and its mammalian homologue arginine vasopressin (AVP) are neuromodulators known to be steroid sensitive and associated with social behaviors in a number of vertebrate taxa. However, the role of AVT/P in the regulation of aggression remains unclear and contrasting effects of this peptide on aggression are seen in differing species and contexts. In this study, we used immunohistochemistry to examine the effects of testosterone on the AVT system in male and female tree lizards, Urosaurus ornatus, and to determine whether AVT is related to territorial aggression in this species. Tree lizards are a free-living species that exhibit natural hormonal fluctuations across breeding seasons. We detected a male-biased sexual dimorphism in centrally projecting AVT fibers within the limbic system. Furthermore, changes with season, reproductive state, and hormonal treatment suggest that testosterone regulates AVT immunoreactivity in limbic brain regions, especially in the bed nucleus of the stria terminalis. Testosterone also affects AVT immunoreactivity in peripherally projecting cell clusters, as well as the size of AVT cell bodies in the paraventricular nucleus. Although higher testosterone levels alter AVT immunoreactivity, and are known to increase the frequency and intensity of male-male aggression in this species, no individual correlations between AVT immunoreactivity and aggression were detected.

Variation in stress and innate immunity in the tree lizard (Urosaurus ornatus) across an urban-rural gradient.

The urban environment presents new and different challenges to wildlife, but also potential opportunities depending on the species. As urban encroachment onto native habitats continues, understanding the impact of this expansion on native species is vital to conservation. A key physiological indicator of environmental disturbance is the vertebrate stress response, involving increases in circulating glucocorticoids (i.e. corticosterone), which exert influence on numerous physiological parameters including energy storage, reproduction, and immunity. We examined how urbanization in Phoenix, Arizona influences corticosterone levels, blood parasitism, and innate immunity in populations of tree lizards (Urosaurus ornatus) to determine whether urbanization may be detrimental or beneficial to this species. Both baseline and stress-induced corticosterone concentrations were significantly lower in urban lizards relative to the rural ones, however, the magnitude of the increase in corticosterone with stress did not differ across populations. Urban lizards also had a lower ratio of heterophils to lymphocytes, but elevated overall leukocyte count, as compared to lizards from the natural site. Urban and rural lizards did not differ in their prevalence of the blood parasite, Plasmodium mexicanum. Taken together, these results suggest that urban tree lizards may have suppressed overall corticosterone concentrations possibly from down-regulation as a result of frequent exposure to stressors, or increased access to urban resources. Also, urban lizards may have bolstered immunocompetence possibly from increased immune challenges, such as wounding, in the urban environment, or from greater energetic reserves being available as a result of access to urban resources.

Toward a dynamic model of deposition and utilization of yolk steroids.

The discovery by Schwabl that maternal steroid hormones are transferred to the egg yolk and have effects on the phenotype of offspring revealed a new pathway for non-genetic maternal effects. The initial model relied on passive transfer. The thinking was that steroids passively entered the lipophillic yolk during yolk deposition and then were deposited in the yolk until they were passively delivered to the embryo as the yolk was used. Subsequent studies revealed that the system is much more dynamic than that. Here, we explore questions about how dynamic the system really is and look at questions like: Is transfer of maternal steroids to the yolk passive or is it actively regulated? At what stages of the maternal reproductive cycle are steroids transferred? During reproduction, how dynamic are the levels of yolk steroids? Especially in the case of potentially deleterious steroids (e.g., androgens in female offspring; glucocorticoids), once deposited can they come out of the yolk over time? Can they be metabolized by the yolk or by the embryo? During incubation, how much do steroid levels in the yolk change? Can steroids diffuse from the yolk to the embryo prior to yolk utilization? Does the embryo contribute to yolk steroid levels as it develops? We believe that comprehensive answers to questions like these will eventually allow us to generate a much more accurate and complete model of the transfer and utilization of yolk steroids and that this model will be much more dynamic and active than the one initially proposed.

Steroid hormones alter neuroanatomy and aggression independently in the tree lizard.

Steroid hormones effect changes in both neuroanatomy and aggressive behavior in animals of various taxa. However, whether changes in neuroanatomy directly underlie changes in aggression is unknown. We investigate this relationship among steroid hormones, neuroanatomy, and aggression in a free-living vertebrate with a relatively simple nervous system, the tree lizard (Urosaurus ornatus). Weiss and Moore [1] manipulated testosterone and progesterone levels in adult male tree lizards and found that both hormones facilitated aggressive behavior toward a conspecific. In this study, we examined the brains of a subset of these animals to determine whether changes in limbic morphology were associated with hormone-induced changes in aggressive behavior. Specifically, we tested the hypothesis that testosterone and/or progesterone cause changes in neural morphology that are necessary for the expression of testosterone's effects on aggressive behavior. We found that both hormones increased aggression; however, only testosterone induced changes in neuroanatomy. Testosterone increased the size of both the amygdala and nucleus sphericus. However, we could detect no individual correlations between neuroanatomy and aggression levels suggesting that the observed large-scale changes in neuroanatomy are not precisely reflective of changes in mechanisms underlying aggression.

Immune function varies with reproductive stage and context in female and male tree lizards, Urosaurus ornatus.

Competition among physiological processes for limited resources often results in trade-offs. Key among these processes is reproduction and immune function, and optimizing both appears to be difficult. To test the hypothesis that the resource demands of reproduction compromise immune function, we measured rates of wound healing, an integrated measure of innate immunity, across different reproductive stages in female and male tree lizards (Urosaurus ornatus) in both the field and the laboratory. The hypothesis predicted that immune function would be lowest when resource demands of reproduction are highest, i.e., vitellogenic females and reproductive males. In the field, vitellogenic females had significantly slower healing rate than females in other reproductive stages. However, in the laboratory, vitellogenic females had a healing rate similar to that of other females. Conversely, males showed suppression of healing in the laboratory but not in the field during the reproductive season. The results of this study support a trade-off between reproduction and immune function, and suggest that reproduction is given priority. However, the results also indicate that this trade-off is not fixed in the reproductive process and that it may instead be dependent on the context, sex or resource balance of the individual.

Aggression frequency and intensity, independent of testosterone levels, relate to neural activation within the dorsolateral subdivision of the ventromedial hypothalamus in the tree lizard Urosaurus ornatus.

The mechanisms by which testosterone regulates aggression are unclear and may involve changes that alter the activity levels of one or more brain nuclei. We estimate neural activity by counting immunopositive cells against phosphorylated cyclic AMP response element binding protein (pCREB). We demonstrate increased pCREB immunoreactivity within the dorsolateral subdivision of the ventromedial hypothalamus (VMHdl) following an aggressive encounter in male tree lizards Urosaurus ornatus. This immunoreactivity is induced both by exposure to and performance of aggressive behaviors. This dual activation of the VMHdl suggests its possible role as an integration center for assessment and expression of aggressive behavior. Furthermore, pCREB induction was greater in encounters involving higher frequency and intensity of aggressive display, demonstrating a direct relationship between neural activation and behavior. The VMHdl is also rich in steroid receptors. In a second experiment involving hormone manipulations, testosterone treatment increased aggression levels, though it did not increase the number of pCREB positive cells within the VMHdl. This lack of an effect of testosterone on pCREB induction within the VMHdl may be due to induction arising from the behaviors of conspecifics (especially in low-testosterone, low-aggression individuals), variation in aggression mediated by other variables, or regulation of aggression by circuits outside of the VMHdl. Together, these findings support a notion of the VMHdl as a nucleus involved in integrating afferent and efferent information within the neural aggression-control circuit.

Trade-offs between the reproductive and immune systems: facultative responses to resources or obligate responses to reproduction?

A major challenge in biology is understanding how organisms partition limited resources among physiological processes. For example, offspring production and self-maintenance are important for fitness and survival, yet these critical processes often compete for resources. While physiological trade-offs between reproduction and immune function have been documented, their regulation remains unclear. Most current evidence suggests that physiological changes during specific reproductive states directly suppress various components of the immune system; however, some studies have not found this clear relationship. We performed two experiments in female tree lizards (Urosaurus ornatus) that demonstrate the presence of trade-offs between the reproductive and immune systems under controlled laboratory conditions. These results also support the hypothesis that these trade-offs are a facultative response to resource availability and are not obligatory responses to physiological changes during reproduction. We found that (1) experimentally increasing reproductive investment under limited resources resulted in suppressed immune function and (2) experimentally limiting resources resulted in immunosuppression but only during resource costly reproductive activities. There seems to be a critical balance of resources that is maintained between multiple processes, and changes in the balance between energy intake and output can have major consequences for immune function.

Corticosterone modulation of reproductive and immune systems trade-offs in female tree lizards: long-term corticosterone manipulations via injectable gelling material.

Physiological trade-offs arise because multiple processes compete for the same limiting resources. While competition for resources has been demonstrated between reproduction and immune function, the regulation of this competition remains unclear. Corticosterone (CORT) is a likely mediator due to its dual role in mobilizing energy stores throughout the body and regulating physiological responses to stressors. We manipulated CORT concentrations and resources in pre-reproductive and reproductive female tree lizards (Urosaurus ornatus) to test the hypothesis that CORT regulates the distribution of limiting resources between the reproductive and immune systems. To manipulate circulating concentrations of CORT we utilized a novel method of hormone implantation, in which a polymeric compound is mixed with hormone and injected in liquid form into the animal. After injection, the liquid quickly gels in situ forming a slow release hormone implant. This method of hormone delivery eliminated the need for substantial wounds to the animal or repeated handling required by other methods. In this study, the hormone-treated animals had plasma CORT concentrations comparable to high physiological concentrations. We found that CORT treatment suppressed immune function, but only when animals were energetically compromised. We assessed immune function by measuring the healing rate of a cutaneous biopsy. Healing was suppressed in all CORT-treated reproductive animals and in all CORT-treated animals (pre-reproductive and reproductive) undergoing food restriction, but CORT had no effect in ad libitum non-reproductive females. The context-dependent action of CORT renders its response adjustable to changing environmental conditions and may allow for the suppression of specific functions depending on resource availability.

Corticosterone stimulates hatching of late-term tree lizard embryos.

The regulation of hatching in oviparous animals is important for successful reproduction and survival, but is poorly understood. We unexpectedly found that RU-486, a progesterone and glucocorticoid antagonist, interferes with hatching of viable tree lizard (Urosaurus ornatus) embryos in a dose-dependent manner and hypothesized that embryonic glucocorticoids regulate hatching. To test this hypothesis, we treated eggs with corticosterone (CORT) or vehicle on Day 30 (85%) of incubation, left other eggs untreated, and observed relative hatch order and hatch time. In one study, the CORT egg hatched first in 9 of 11 clutches. In a second study, the CORT egg hatched first in 9 of 12 clutches, before vehicle-treated eggs in 10 of 12 clutches, and before untreated eggs in 7 of 9 clutches. On average, CORT eggs hatched 18.2 h before vehicle-treated eggs and 11.6 h before untreated eggs. Thus, CORT accelerates hatching of near-term embryos and RU-486 appears to block this effect. CORT may mobilize energy substrates that fuel hatching and/or accelerate lung development, and may provide a mechanism by which stressed embryos escape environmental stressors.

Steroid hormone mediation of limbic brain plasticity and aggression in free-living tree lizards, Urosaurus ornatus.

The neural mechanisms by which steroid hormones regulate aggression are unclear. Although testosterone and its metabolites are involved in both the regulation of aggression and the maintenance of neural morphology, it is unknown whether these changes are functionally related. We addressed the hypothesis that parallel changes in steroid levels and brain volumes are involved in the regulation of adult aggression. We examined the relationships between seasonal hormone changes, aggressive behavior, and the volumes of limbic brain regions in free-living male and female tree lizards (Urosaurus ornatus). The brain nuclei that we examined included the lateral septum (LS), preoptic area (POA), amygdala (AMY), and ventromedial hypothalamus (VMH). We showed that the volumes of the POA and AMY in males and the POA in females vary with season. However, reproductive state (and thus hormonal state) was incompletely predictive of these seasonal changes in males and completely unrelated to changes in females. We also detected male-biased dimorphisms in volume of the POA, AMY, and a dorsolateral subnucleus of the VMH but did not detect a dimorphism between alternate male morphological phenotypes. Finally, we showed that circulating testosterone levels were higher in males exhibiting higher frequency and intensity of aggressive display to a conspecific, though brain nucleus volumes were unrelated to behavior. Our findings fail to support our hypothesis and suggest instead that plasma testosterone level covaries with aggression level and in a limited capacity with brain nucleus volumes but that these are largely unrelated relationships.

The effects of stress on wound healing in male tree lizards (Urosaurus ornatus).

Exposure to stress can affect an organism's partitioning of resources among immune function and other organismal functions. However, measuring immune function is often difficult. Recent studies show that the rate of cutaneous wound healing in laboratory rodents is a simple, integrated measure of stress-sensitive immune function. We investigated the use of this technique in tree lizards to test the hypotheses (1) that stress compromises wound healing and (2) that this effect is at least partially mediated by corticosterone. Laboratory-housed male tree lizards randomly assigned to the experimental and control treatment groups received a 3.5 mm cutaneous biopsy on the dorsal surface of the pelvis. Experimental group males were restrained in cloth bags for 60 min every day for 21 days during the healing profile, whereas control males were left in their cages. Wound sizes were measured every other day by image analysis. Control animals healed faster than stressed animals. The difference in wound surface area between the groups was most pronounced early in the healing profile. Stressed animals also had higher corticosterone levels and corticosterone was negatively correlated with healing rate in the stressed animals. These observations support both hypotheses that stress compromises healing and that corticosterone may act to mediate the effects of stress.

Steroid hormone metabolism by the chorioallantoic placenta of the mountain spiny lizard Sceloporus jarrovi as a possible mechanism for buffering maternal-fetal hormone exchange.

The placenta provides a maternal-fetal exchange interface that maximizes the diffusion of gases, nutrients, and wastes. However, the placenta also may permit diffusion of lipid-soluble steroid hormones that influence processes such as sex-specific fetal development and maternal pregnancy maintenance. In mammals, placental steroid metabolism contributes to regulation of maternal and fetal hormone levels. Such mechanisms may be less highly developed in species that have recently evolved placentation, such as many reptiles. We therefore chose to investigate placental metabolism of steroids in the viviparous lizard Sceloporus jarrovi. In vitro tissue incubations tested the abilities of the chorioallantoic placenta to clear progesterone and corticosterone by converting them to other metabolites and to synthesize progesterone. Placental tissue rapidly cleared progesterone and corticosterone added to the incubation media, indicating that the tissue had converted the steroids to other products. Placental tissue also synthesized substantial concentrations of progesterone from the prohormone pregnenolone. Thus, even in a species with a simple, recently evolved placenta, steroid metabolism appears to be highly developed and could be critical for regulation of maternal and fetal hormone levels. This finding suggests that placental hormone metabolism may be critical to the successful evolution of placentation.

Historical contributions of research on reptiles to behavioral neuroendocrinology.

Some of the first experiments in behavioral endocrinology in the 1930s were conducted with lizards, but events led to a hiatus that lasted for 30 years. In the 1960s, research resumed using techniques current at the time, but it was not until the mid-1970s that behavioral neuroendocrinology "discovered" reptiles as animal model systems. This historical review summarizes this period of work, illustrating an enormous increase in research that have led to conclusions such as (1) the phenomenon of dissociated reproductive strategies and hormone-independent behaviors, which have aided our understanding of how the "memory" of sex steroid actions is maintained. (2) Progesterone plays an important role in the organization and activation of sexual behavior in males. Progesterone also synergizes with T to control male courtship much as does estrogen and progesterone to control sexual receptivity in females. Thus, progesterone is as much a "male" hormone as it is a "female" hormone. (3) Use of cytochrome oxidase histochemistry to study the role of experience over the long term in modifying brain activity. (4) Hormone manipulations as a powerful tool to test hypotheses about the evolution of behavior in free-living animals.

Role of the adrenal gland in early post-hatching differentiation of alternative male phenotypes in the tree lezard (Urosaurus ornatus).

During development, sex steroids are important in establishing differences between males and females. However, sex steroids also are involved in the development and maintenance of individual differences in morphology and behavior within each sex. As adults, male tree lizards (Urosaurus ornatus) exhibit alternative reproductive tactics correlated with dewlap (throat fan) coloration. Males with orange-blue dewlaps are aggressive and territorial, whereas males with orange dewlaps are less aggressive and employ a satellite strategy. Dewlap coloration develops within the first 90 days after hatching and remains fixed throughout life. Recent work demonstrates that individual males differ in progesterone and testosterone secretion during development, suggesting that these hormones regulate the development of alternative male phenotypes. The current work uses in vitro incubation of adrenal and gonadal tissues to identify the source of progesterone and testosterone during the period of male differentiation and to follow ontogenetic changes in hormone release. The results indicate that, in all developmental stages sampled, adrenal incubations primarily contain progesterone and corticosterone whereas gonadal incubations contain primarily testosterone. These data indicate that the hatchling adrenal is the primary source of progesterone during early post-hatching development. Since progesterone has been demonstrated to play a role in the establishment of individual differences in morphology and behavior in male tree lizards, our results suggest that the hatchling adrenal gland plays an important role in post-hatching development of alternative male phenotypes.

Effect of tidal cycle and food intake on the baseline plasma corticosterone rhythm in intertidally foraging marine iguanas.

In most species, plasma levels of baseline glucocorticoids such as corticosterone (B) have a circadian rhythm. This rhythm can be entrained by both photoperiod and food intake and is related to aspects of energy intake and metabolism. Marine iguanas (Amblyrhynchus cristatus) offer a unique opportunity to better understand the relative importance of the light:dark cycle versus food intake in influencing the rhythm in baseline B in a natural system. Compared to other species, food intake is not as strictly determined by the phase of the light:dark cycle. Animals feed in the intertidal zone so feeding activity is heavily influenced by the tidal cycle. We measured baseline plasma B levels in free-living iguanas over several 24-h periods that varied in the timing of low tide/foraging activity. We found that baseline B levels were higher during the day relative to night. However, when low tide occurred during the day, baseline B levels dropped coincident with the timing of low tide. Whether the baseline B rhythm (including the drop during foraging) is an endogenous rhythm with a circatidal component, or is simply a result of feeding and associated physiological changes needs to be tested. Together, these data suggest that the baseline B rhythm in marine iguanas is influenced by the tidal cycle/food intake as well as the light:dark cycle.

Environmental and endocrine correlates of tactic switching by nonterritorial male tree lizards (Urosaurus ornatus).

Animals often exhibit individual variation in their behavioral responses to the same stimuli in the biotic or abiotic environment. To elucidate the endocrine mechanisms mediating such behavioral variation, we have been studying a species of lizard with two distinct male phenotypes. Here we document behavioral variation across years in one of the two male phenotypes of the tree lizard, Urosaurus ornatus, and present hormone data that support an endocrine mechanism underlying this behavioral variation. Nonterritorial male tree lizards appear to be nomadic rovers in some years and sedentary satellites in others, whereas territorial males are always territorial. This behavioral variation by nonterritorial males was correlated with environmental conditions. In environmentally harsher years (as assessed by rainfall), nonterritorial males appear to behave as nomads, whereas in more benign years they are more site-faithful. A between-year comparison of levels of corticosterone and testosterone for the two male phenotypes supports a model for how hormones underlie the males' reproductive tactics, particularly the nonterritorial males' behavioral plasticity. In an environmentally harsher (drier) year, both types of males had higher corticosterone levels than in a milder (wetter) year, but only nonterritorial males had lower testosterone in the relatively harsher year. We propose that disruptive selection for individual variation in hormonal responses to environmental cues may be a common mechanism underlying the evolution of alternative male reproductive tactics in this and other species.