Plasma steroids and immune measures vary with restraint duration in a toad (Rhinella icterica).

Immunoenhancing effects have been widely described following acute stressors in several vertebrates, and valuable contributions have been made from studies on acute stress to understand hormonal-immune interactions. However, most studies focus on hormonal and immune responses after standardized time lapses, neglecting potential influence of duration of exposition to stressor. Herein, we investigate fluctuations of plasma hormone concentrations (corticosterone and testosterone) and immunity (neutrophil to lymphocyte ratio, phagocytosis of blood cells, and plasma bacterial killing ability) in a toad species (Rhinella icterica) in response to six different periods of exposure to restraint stress. We observed increased plasma corticosterone concentrations following restraint in all sampled times (0.5 to 48 h), with the highest values being observed during the first hour (0.5 to 1 h). Restraint-induced increases in the neutrophil to lymphocyte ratio and phagocytosis percentage were observed from the first 0.5 h, gradually increasing after that with the time of restraint. We also observed decreased testosterone plasma concentrations in response to a more prolonged restraint (24 and 48 h). No changes were observed in plasma bacterial killing ability following restraint. Together, our results demonstrate dynamic time-related hormonal and immune changes. These results point to the fact that for some species measuring hormonal and immune variables at single time points following a stressor might work better when preceded by a study of the temporal changes of the response variables to the stimuli applied. Also, time of response needs to be considered when different variables are used as proxies of stress.

Corticosterone transdermal application in toads (Rhinella icterica): Effects on cellular and humoral immunity and steroid plasma levels.

Previous studies in a variety of vertebrates show stressed animals to exhibit acute increases in glucocorticoid levels, with consequences for immune modulation. Chronically elevated glucocorticoid levels are mostly associated with immunosuppression. However, there is still a paucity of knowledge regarding the amphibian physiological reaction to short- and long-term stress conditions, including glucocorticoid effects on the immune response. In order to better clarify the relationship between glucocorticoids and immune response, newly captured Brazilian toads (Rhinella icterica) (1 week in captivity) were subjected to a daily transdermal application (TA), of corticosterone or vehicle, for 30 consecutive days. Measures were made on the first day (acute stressor) and last day (chronic stressor), at timepoints 1, 6, and 12 hr post TA. A number of variables were analyzed: corticosterone plasma levels (CORT); neutrophil/lymphocyte ratio (N:L); testosterone plasma levels (T); innate immune response, as indicated by bacterial killing ability (BKA); and whole blood phagocytosis. The corticosterone TA only simulated hormonal changes associated with the acute stress response, even after 30 consecutive days of the treatment, with the increased CORT in response after corticosterone TA being evident only 1 hr postapplication and not thereafter. The general responses to corticosterone TA included increased CORT and N:L at first day of the treatment, and increased CORT and phagocytosis on the last day of the treatment. A decrease in T and BKA associated with the time in captivity was also evident, suggesting that captivity may be a chronic stressor for these toads.

Posterior Reversible Encephalopathy Syndrome and Anti-Angiogenic Agents: A Case Report.

Posterior reversible encephalopathy syndrome is an increasingly recognised clinico-radiological entity, associated with several medical conditions (such as systemic arterial hypertension) and characterised by seizures, altered mental status, headaches, and visual symptoms. Magnetic resonance imaging is a key component in this diagnosis, with hyperintense foci in T2-weighted images, corresponding to vasogenic oedema. The pathophysiology is not fully understood but probably involves loss of auto-regulation of cerebral vasculature or endothelial dysfunction or both. A 56-year-old male, suffering from a gastro-intestinal stromal tumour with hepatic metastasis resistant to imatinib, on therapy with sunitinib, came to the Emergency Department because of headaches, hallucinations, and loss of vision. There was no previous history of high blood pressure. A hypertensive crisis was diagnosed; ophthalmological examination on admission showed no light perception bilaterally. Brain imaging displayed bilateral parieto-occipital and frontal vasogenic oedema, consistent with the clinical diagnosis of posterior reversible encephalopathy syndrome. After treatment of hypertension and suspension of sunitinib, the patient recovered from his symptoms. Control imaging showed no oedema. Angiogenesis inhibitors, such as sunitinib and bevacizumab, can cause hypertension, one of the many medical conditions associated with the posterior reversible encephalopathy syndrome. This syndrome should be considered in cases of acute visual loss, particularly in view of its reversible nature when diagnosed and treated promptly.