Methodological Considerations for Using Fecal Glucocorticoid Metabolite Concentrations as an Indicator of Physiological Stress in the Brown Bear (Ursus arctos).

Reliable methods to measure stress-related glucocorticoid responses in free-ranging animals are important for wildlife management and conservation. Such methods are also paramount for our ability to improve our knowledge of the ecological consequences of physiological processes. The brown bear (Ursus arctos) is a large carnivore of ecological and cultural importance and is important for management. Here, we provide a physiological validation for an enzyme immunoassay (EIA) to quantify glucocorticoid metabolites in brown bear feces. We also provide an evaluation of the effects of sample exposure to ambient temperature on measured fecal glucocorticoid metabolite (fGCM) concentrations. We evaluated three EIA systems: a cortisol assay, an 11-oxoetiocholanolone assay, and an 11ß-hydroxyetiocholanolone assay. Of these, the cortisol assay provided the best discrimination between peak fGCM concentrations detected 1-4 d after injections of synthetic adrenocorticotrophic hormone and preinjection baseline concentrations in four individual brown bears. The time of exposure to ambient temperature had substantial but variable effects on measured fGCM concentrations, including variation both between samples from the same individual and among samples from different bears. We propose that the validated EIA system for measuring fGCM concentrations in the brown bear could be a useful noninvasive method to monitor stress in this species. However, we highlight that this method requires that fecal samples be frozen immediately after defecation, which could be a limitation in many field situations.

Evaluación de la reperfusión tras angiogénesis terapéutica con fotopletismografía en un modelo murino de isquemia de miembros inferiores / Evaluation of the reperfusion after angiogenic therapy with photoplethysmography in a murine model of limb ischemia

INTRODUCCIÓN: a pesar del extendido uso de la fotopletismografía (PPG) en clínica como test diagnóstico no invasivo de la isquemia, su utilización en experimentación animal es escasa. OBJETIVO: evaluar el valor de la PPG en el seguimiento de la reperfusión angiogénica en un modelo murino de isquemia periférica. MATERIAL Y MÉTODOS: en ratas macho Sprague Dawley se excluyeron los sectores arteriales ilíaco y femoral de la pata trasera izquierda. Como control se utilizó la pata contralateral. Los animales se dividieron en tres grupos: GH (n = 8), placebo (n = 6) y sham (n = 2). La perfusión fue evaluada mediante escalas clínica y funcional y por PPG. Toda recuperación de la onda de PPG mayor del 5% fue considerada significativa. Se diseñaron controles basales, a los 10, 20 y 30 días. Se calculó el cociente de pulsatilidad pata/pata (rpp), así como los cambios morfológicos de la onda de pulso. La relación entre variables cualitativas fue evaluada por test Chi-cuadrado y la de las variables cuantitativas, mediante t de Student. RESULTADOS: los valores basales de rpp entre patas mostraron gran variabilidad, pero con una correlación significativa positiva: 0.9 (0,74-0,97, IC 95%, p < 0,001). La media de incremento de rpp a 30 días fue mayor en el grupo GH: 0,3 (0-1,1), p = 0,097 frente a 0,03 (0-0,2), p = 0,81. El 62,5% de animales GH presentó una recuperación significativa de la onda frente al 20% en el grupo placebo (recuperación media de la onda: 45% frente a 15,8% [p = 0,086], GH y placebo, respectivamente). CONCLUSIONES: la fotopletismografía ha mostrado una sensibilidad adecuada para detectar pequeños cambios de perfusión en el modelo de isquemia propuesto y tras la administración de GH. Dicha prueba podría ser de utilidad como complemento en el seguimiento de la reperfusión angiogénica tras isquemia en el modelo de tipo murino

INTRODUCTION: despite the widespread use of photoplethysmography (PPG) in clinical practice as a non-invasive diagnostic test for ischemia, it has been little used in animal experimentation. OBJECTIVE: to evaluate PPG for the follow-up of angiogenic reperfusion after growth hormone (GH) therapy in a murine model of limb ischemia. MATERIAL AND METHODS: in male Sprague Dawley rats, the iliac and femoral arterial sectors of the left hind limb were excluded. As a control, the contralateral limb was used. The rats were divided into three groups: GH (n = 8), placebo (n= 6) and sham (n = 2). Besides PPG, the perfusion was evaluated by clinical and functional scores. Any recovery of the PPG wave greater than 5% was considered as significant. Controls at baseline, 10, 20 and 30 days were planned. The paw/paw pulsatility ratio (rpp) was calculated, as well as the morphological changes of the pulse wave. The relationship between qualitative variables was evaluated by Chi-square test, and that of quantitative variables by Student's t-test. RESULTS: the baseline values of rpp between limbs showed great variability, but with a significant positive correlation: 0.9 (0.74-0.97, 95% CI, p < 0.001). The mean increase in rpp at 30 days was higher in the GH group: 0.3 (0-1.1), p = 0.097 vs. 0.03 (0-0.2), p = 0.81. Among GH animals, 62.5% presented a significant recovery of the wave as compared to 20% in placebo group (average recovery of the wave: 45% vs. 15.8% [p = 0.086], GH and placebo, respectively). CONCLUSIONS: photoplethysmography has shown a suitable sensitivity to detect small changes of perfusion in the proposed ischemic model and after GH administration. The aforementioned test could be useful as a supplementary tool during the identification of the angiogenic reperfusión process after ischemia in a murine model