Repeated assessment of changes in testes size in canaries by X-ray computer tomography

Photoperiodism, testosterone and adult neurogenesis in canaries (Serinus canaria)

Domestic strains of canaries (Serinus canaria) variably respond to photoperiod changes and apparently stay in breeding state for extended periods. Fife Fancy canaries are supposed to be similar to the native species living at 27-39° north where photoperiod significantly changes across the year. Our birds showed reproductive cycles when exposed to light regimes mimicking the annual cycle of photoperiod. However after 6 months in short days (SD: 8L:16D), males developed large testes, as observed by X-ray tomography, and intense singing. Switching to long days (LD: 16L:8D) did not further increase song rate nor testes size but increased song duration, number of syllables per song, and trill occurrence frequency. No sign of regression was observed after 12 weeks in LD but return to SD produced a rapid decrease in testes size and singing activity below values in birds maintained throughout in SD. Fife Fancy thus does not seem to develop absolute but only relative refractoriness. The relatively high singing activity expressed by SD-photosensitive males does not seem to depend on high testosterone (T) concentrations. Singing did not correlate with plasma testosterone (T). Treatment with ATD + Flutamide only marginally decreased song rate and did not affect song quality nor song control nuclei volume. These birds are either supersensitive to low T levels or their reproductive physiology is activated by other mechanisms. Neurogenesis is increased by T and by LD but the function of new neurons incorporated in HVC is poorly understood. We developed a procedure based on X-ray focal irradiation to deplete neural progenitors adjacent to HVC and study the functional consequences. The decrease in neurogenesis increased the variability of T-induced songs in females and decreased their bandwidth. Neurogenesis in HVC thus plays a role in song production and X-ray focal irradiation represents an excellent tool to analyze adult neurogenesis.

Radiotherapy Advances in Renal Disease-Focus on Renal Ischemic Preconditioning

Ionizing irradiation is widely applied as a fundamental therapeutic treatment in several diseases. Acute kidney injury (AKI) represents a global public health problem with major morbidity and mortality. Renal ischemia/reperfusion (I/R) is the main cause of AKI. I/R injury occurs when blood flow to the kidney is transiently interrupted and then restored. Such an ischemic insult significantly impairs renal function in the short and long terms. Renal ischemic preconditioning (IPC) corresponds to the maneuvers intended to prevent or attenuate the ischemic damage. In murine models, irradiation-induced preconditioning (IP) renders the renal parenchyma resistant to subsequent damage by activating defense pathways involved in oxidative stress, angiogenesis, and inflammation. Before envisioning translational applications in patients, safe irradiation modalities, including timing, dosage, and fractionation, need to be defined.

Photoperiodic control of singing behavior and reproductive physiology in male Fife fancy canaries

Temperate-zone birds display marked seasonal changes in reproductive behaviors and the underlying hormonal and neural mechanisms. These changes were extensively studied in canaries (Serinus canaria) but differ between strains. Fife fancy male canaries change their reproductive physiology in response to variations in day length but it remains unclear whether they become photorefractory (PR) when exposed to long days and what the consequences are for gonadal activity, singing behavior and the associated neural plasticity. Photosensitive (PS) male birds that had become reproductively competent (high song output, large testes) after being maintained on short days (SD, 8 L:16D) for 6 months were divided into two groups: control birds remained on SD (SD-PS group) and experimental birds were switched to long days (16 L:8D) and progressively developed photorefractoriness (LD-PR group). During the following 12 weeks, singing behavior (quantitatively analyzed for 3 × 2 hours every week) and gonadal size (repeatedly measured by CT X-ray scans) remained similar in both groups but there was an increase in plasma testosterone and trill numbers in the LD-PR group. Day length was then decreased back to 8 L:16D for LD-PR birds, which immediately induced a cessation of song, a decrease in plasma testosterone concentration, in the volume of song control nuclei (HVC, RA and Area X), in HVC neurogenesis and in aromatase expression in the medial preoptic area. These data demonstrate that Fife fancy canaries readily respond to changes in photoperiod and display a pattern of photorefractoriness following exposure to long days that is associated with marked changes in brain and behavior.