Age effect of deafening on stereotyped song maintenance in adult male bengalese finches Lonchura striata domestica

Birdsong is a complex learned vocal behavior that relies on auditory experience for development. However, it appears that among different species of close-ended songbirds, there are some variations in the necessity of auditory feedback for maintaining stereotyped adult song. In zebra finches, the deterioration of adult songs following deafness depends on the birds’ age. It is unknown whether this age effect is a general rule in other avian species as well. Therefore, we chose Bengalese finches, whose songs show more complexity and have much heavier dependency on auditory feedback than that of zebra finches, to compare the degree of song degradation after hearing loss in old (over 18 months old) and young adult birds (5–6 months old). We found that both syllable sequence and syllable phonology were much less severely affected by deafening in old adults than that in young ones. Moreover, young adults almost lost their capability to sing trills over 6 months following deafening, while old birds continued to sing plenty of trills and trilled syllables after the same period of deafening. Our results suggest that age plays an important role in affecting the dependency of adult song maintenance on auditory feedback in Bengalese finches. Furthermore, the age dependency may be a general phenomenon in different species of close-ended songbirds [Current Zoology 55(3):212–218, 2009]

Metabolic Study of Tetra-PEG-Based Hydrogel after Pelvic Implantation in Rats

In vivo metabolism of polyethylene glycol (PEG) hydrogels has rarely been studied. In this study, we prepared a chemically crosslinked hydrogel formulation using 14C-labeled tetra-armed poly (ethylene glycol) succinimidyl succinate (Tetra-PEG-SS) and 3H-labeled crosslinking agent for implantation into the pelvis of Sprague-Dawley (SD) rats. This radioactive labeling technique was used to investigate the radioactivity excretion rates in of feces and urine, the blood exposure time curve, and the radioactivity recovery rate in each tissue over time. We showed that the primary excretion route of the hydrogel was via urine (3H: about 86.4%, 14C: about 90.0%), with fewer portion through feces (3H: about 6.922%, 14C: about 8.16%). The hydrogel metabolites exhibited the highest distribution in the kidney, followed by the jejunal contents; The 3H and 14C radioactivity exposures in the remaining tissues were low. We also showed that the 3H and 14C radioactivity recovery rates in the blood were usually low (−1 at 12 h after implantation), even though, in theory, the hydrogel could be absorbed into the blood through the adjacent tissues. By using a combination of HPLC-MS/MS and offline radioactivity counting method, we established that the tetra-PEG-based hydrogel was mainly metabolized to lower-order PEG polymers and other low-molecular-weight substances in vivo

Sexual differences in cell proliferation in the ventricular zone, cell migration and differentiation in the HVC of juvenile Bengalese finch.

Song control nuclei have distinct sexual differences and thus are an ideal model to address how brain areas are sexually differentiated. Through a combination of histological analysis and electrical lesions, we first identified the ventricle site for HVC progenitor cells. We then found that there were significant sex differences in the cellular proliferation activity in the ventricular zone of the HVC, the number of migrating cells along the radial cells (positive immunoreactions to vimentin) and differentiation towards neurons. Through co-culturing of male and female slices containing the developing HVC in the same well, we found that the male slices could produce diffusible substances to masculinize the female HVC. By adding estrogen, an estrogen antagonist, brain-derived neurotrophic factor (BDNF) or its antibody into the culture medium, separately or in combination, we found that these diffusible substances may include estrogen and BDNF. Finally, we found that 1) estrogen-induced BDNF upregulation could be detected 48 hr after estrogen treatment and could not be blocked by a vascular endothelial growth factor (VEGF) receptor inhibitor and 2) the amount of VEGF mRNA expressed in the developing HVC and its adjacent area did not display any significant sex differences, as did the distribution of VEGF and laminin-expressing endothelial cells in the developing HVC. Because these findings are largely different from previous reports on the adult female HVC, it is suggested that our estrogen-induced BDNF up-regulation and the resultant sexual differentiation might not be mediated by VEGF and endothelial cells, but instead, may result from the direct effects of estrogen on BDNF

Soybean Bioactive Peptide Supplementation Affects the Intestinal Immune Antioxidant Function, Microbial Diversity, and Reproductive Organ Development in Roosters

Soybean is an important source of high-quality vegetable protein with various health-improving properties, and its main bioactive substances are small peptides produced by in vitro enzymatic hydrolytic processes. In traditional layer breeding, the nutritional health of roosters is frequently neglected, ultimately affecting the quality and quantity of offspring. This study investigated the effects of various quantities (0%, 0.15%, 0.30%, 0.45%, and 0.60%) of soybean bioactive peptide (SBP) feed additives on immunological and antioxidant functions, gut health, and reproductive performance of roosters. SBP supplementation significantly improved male growth and reproductive performance, including growth rate, feed conversion ratio, reproductive organ development, and semen quality. SBP also increased immune and antioxidant levels, boosted the integrity of the small intestinal physiological structure and barrier function, and diversity of cecal microbes, and decreased the apoptotic ratio of small intestinal epithelial cells. The effects of SBP on various functions of males showed a quadratic trend, with the optimal concentration determined to be 0.45%

Sexual Differences in Cell Loss during the Post-Hatch Development of Song Control Nuclei in the Bengalese Finch.

Birdsongs and the regions of their brain that control song exhibit obvious sexual differences. However, the mechanisms underlying these sexual dimorphisms remain unknown. To address this issue, we first examined apoptotic cells labeled with caspase-3 or TUNEL in Bengalese finch song control nuclei - the robust nucleus of the archopallium (RA), the lateral magnocellular nucleus of the anterior nidopallium (LMAN), the high vocal center (HVC) and Area X from post-hatch day (P) 15 to 120. Next, we investigated the expression dynamics of pro-apoptotic (Bid, Bad and Bax) and anti-apoptotic (Bcl-2 and Bcl-xL) genes in the aforementioned nuclei. Our results revealed that the female RA at P45 exhibited marked cell apoptosis, confirmed by low densities of Bcl-xL and Bcl-2. Both the male and female LMAN exhibited apoptotic peaks at P35 and P45, respectively, and the observed cell loss was more extensive in males. A corresponding sharp decrease in the density of Bcl-2 after P35 was observed in both sexes, and a greater density of Bid was noted at P45 in males. In addition, we observed that RA volume and the total number of BDNF-expressing cells decreased significantly after unilateral lesion of the LMAN or HVC (two areas that innervate the RA) and that greater numbers of RA-projecting cells were immunoreactive for BDNF in the LMAN than in the HVC. We reasoned that a decrease in the amount of BDNF transported via HVC afferent fibers might result in an increase in cell apoptosis in the female RA. Our data indicate that cell apoptosis resulting from different pro- and anti-apoptotic agents is involved in generating the differences between male and female song control nuclei

Distribution of VEGF-positive cells in the HVC.

<p>A–H: VEGF-positive cells at 15 post-hatching days (P15, A–D) or at adulthood (E–H). I: Comparison of the number of VEGF-positive cells in the developing HVC between the two sexes at P15 and adult. Scale bar = 200 µm (A and B), 500 µm (E, F), and 100 µm (C, D, G, H).</p

Summary of the assumed action routes of estradiol/testosterone on cell proliferation, migration and differentiation in adult (right) and juvenile (left) HVC.

<p>The action routes in adult HVC are discussed in a previous report (Louissaint et al., 2002). Note that there are substantial differences in the resources (shown by dashed brown arrows) of BDNF (from endothelial cells or not) and estradiol/testosterone (from capillary or from autonomous synthesis in local brain), and their actions during sexual differentiation of song control nucleus (shown by green arrows) between adult and juvenile birds. Curved arrows indicate some proliferating cells. Abbreviations: AR, androgen receptor; ER, estrogen receptor; Hu, Hu protein; VEGF, vascular endothelial growth factor; BDNF, brain-derived neurotrophic factor.</p

Alteration of CaBP Expression Pattern in the Nucleus Magnocellularis following Unilateral Cochlear Ablation in Adult Zebra Finches

<div><p>Songbirds have the rare ability of auditory-vocal learning and maintenance. Up to now, the organization and function of the nucleus magnocellularis (NM), the first relay of the avian ascending auditory pathway is largely based on studies in non-vocal learning species, such as chickens and owls. To investigate whether NM exhibits different histochemical properties associated with auditory processing in songbirds, we examined the expression patterns of three calcium-binding proteins (CaBPs), including calretinin (CR), parvalbumin (PV) and calbindin-D28k (CB), and their relations to auditory inputs in NM in adult zebra finches. We found enriched and co-localized immunostaining of CR, PV and CB in the majority of NM neurons, without neuronal population preference. Furthermore, they were sensitive to adult deafferentation with differential plasticity patterns. After unilateral cochlear removal, CR staining in the ipsilateral NM decreased appreciably at 3 days after surgery, and continued to decline thereafter. PV staining showed down-regulation first at 3 days, but subsequently recovered slightly. CB staining did not significantly decrease until 7 days after surgery. Our findings suggest that the three CaBPs might play distinct roles in association with auditory processing in zebra finches. These results are in contrast to the findings in the NM of chickens where CR is the predominant CaBP and deafferentation had no apparent effect on its expression. Further extended studies in other avian species are required to establish whether the difference in CaBP patterns in NM is functionally related to the different auditory-vocal behaviors.</p></div

Immunohistochemistry for caspase-3 in the RA, LMAN, HVC and Area X in the Bengalese finch.

<p>A1–D4: Labeled cells are observed in the RA (A1–A4), LMAN (B1–B4), HVC (C1–C4) and Area X (D1–D4) in males at post-hatching days P15 (A1–D1) and P45 (A3–D3) and in females at P15 (A2–D2) and P45 (A4–D4). E-H: Comparison of the densities of caspase-3-positive cells in the RA (E), LMAN (F), HVC (G) and Area X (H) between males and females. Borders of the song nuclei (dashed lines) were determined with the help of another set of Nissl-stained sections. The Nissl-defined border of the female Area X was difficult to identify clearly, and the dashed lines in D2 and D4 indicate the approximate region that corresponds to the male Area X. Dorsal is up and caudal is right. Scale bar = 200 μm in A1–C4 and 300 μm in D1–D4. The data are expressed as the mean ± SEM. **<i>P</i>< 0.01.</p