BDNF mediates the effects of testosterone on the survival of new neurons in an adult brain.
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New neurons are incorporated into the high vocal center (HVC), a nucleus of the adult canary (Serinus canaria) brain that plays a critical role in the acquisition and production of learned song. Recruitment of new neurons in the HVC is seasonally regulated and depends upon testosterone levels. We show here that brain-derived neurotrophic factor (BDNF) is present in the HVC of adult males but is not detectable in that of females, though the HVC of both sexes has BDNF receptors (TrkB). Testosterone treatment increases the levels of BDNF protein in the female HVC, and BDNF infused into the HVC of adult females triples the number of new neurons. Infusion of a neutralizing antibody to BDNF blocks the testosterone-induced increase in new neurons. Our results demonstrate that BDNF is involved in the regulation of neuronal replacement in the adult canary brain and suggest that the effects of testosterone are mediated through BDNF. (+info)
Streptococcus pluranimalium sp. nov., from cattle and other animals.
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Strains from subclinical mastitis, from the genital tract and tonsils of cattle, from tonsils of a goat and a cat and from the crop and the respiratory tract of canaries were found to constitute a new streptococcal species, for which the name Streptococcus pluranimalium sp. nov. is proposed. Sequencing of 16S rRNA showed that Streptococcus thoraltensis and Streptococcus hyovaginalis were its closest known phylogenetic relatives. The new species showed some phenotypic resemblance to the poorly described species Streptococcus acidominimus, but whole-cell protein analysis and 16S rRNA sequencing revealed that the new species was only distantly related to the type strain of S. acidominimus. Identification of these bacteria, which showed heterogeneous biochemical reaction patterns, was most reliably made by whole-cell protein analysis. Nevertheless, a number of biochemical reactions can be used to differentiate S. pluranimalium from other animal streptococci. Strain LMG 14177T, isolated from mastitic milk of a dairy cow, was designated as the type strain of S. pluranimalium sp. nov. (+info)
Associative learning and stimulus novelty influence the song-induced expression of an immediate early gene in the canary forebrain.
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To identify variables that affect immediate early gene (IEG) expression in the auditory telencephalon of songbirds, we developed a conditioning paradigm that trained adult male canaries to associate song with a mild shock. Learning of the association was measured by a bird's fear and avoidance responses. Birds exposed to paired song and shock were compared to yoked controls exposed to each stimulus alone or to both unpaired. Additional groups examined the effects of attention and stress, and of the novelty of the stimulus situation. In situ hybridization analysis of brain sections revealed an enhancement of ZENK expression in birds learning the association between song and shock above levels induced by song alone or yoked-unpaired song and shock. This effect was specifically seen in the caudomedial auditory telencephalon (NCM-HVCM). A comparison of the several control groups indicated that novelty of the song stimulus or of its pairing with shock were the main variables that predicted ZENK levels in NCM-HVCM. These observations are compatible with ZENK playing a role in the formation of song perceptual memories. (+info)
A relationship between behavior, neurotrophin expression, and new neuron survival.
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The high vocal center (HVC) controls song production in songbirds and sends a projection to the robust nucleus of the archistriatum (RA) of the descending vocal pathway. HVC receives new neurons in adulthood. Most of the new neurons project to RA and replace other neurons of the same kind. We show here that singing enhances mRNA and protein expression of brain-derived neurotrophic factor (BDNF) in the HVC of adult male canaries, Serinus canaria. The increased BDNF expression is proportional to the number of songs produced per unit time. Singing-induced BDNF expression in HVC occurs mainly in the RA-projecting neurons. Neuronal survival was compared among birds that did or did not sing during days 31-38 after BrdUrd injection. Survival of new HVC neurons is greater in the singing birds than in the nonsinging birds. A positive causal link between pathway use, neurotrophin expression, and new neuron survival may be common among systems that recruit new neurons in adulthood. (+info)
Hair cell death in a hearing-deficient canary.
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Cell death has been documented in bird auditory inner ear epithelia after induced damage. This cell death is quickly followed by an increase in supporting cell division and regeneration of the epithelium, thereby suggesting a possible relationship between these two processes. However, aspects of this relationship still need to be better understood. The Belgian Waterslager (BWS) canary is an ideal system in which to study cell death and subsequent cell division. In contrast to mixed breed (MB) canaries, cell division normally occurs in the auditory end organ of the BWS without any external manipulation. In addition, some of the cells in the auditory epithelium may be dying through an apoptotic-like process. In the present study two methods were used to quantify dying cells in the BWS and MB canary auditory epithelia: morphological criteria and TUNEL. Results confirm that some of the abnormal hair cells in the BWS auditory epithelium are apoptotic-like. The presence of both cell death and cell division indicates that these processes act concurrently in the adult end organ. Future studies are needed to determine if cell death is a stimulus for the observed cell division. (+info)
A monoclonal antibody specific to a song system nuclear antigen in estrildine finches.
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This paper describes a monoclonal antibody that recognizes a molecule whose expression is mostly restricted to some of the forebrain areas that control singing behavior in adult estrildine species studied, including the zebra, Bengalese, and spice finches. When the song system displays extreme sexual dimorphism, as in these species, antibody staining occurs only in the male's song nuclei. However, protein expression is identical in both sexes of estrildine finches, in which females also have a well-developed song system. Canaries appear to lack the protein, but it can be induced in female zebra finches by early estrogen treatment. Antibody staining patterns in the zebra finch show that the protein's expression is developmentally regulated to coincide with the abrupt increase in the volume and cell size of the male's or the estrogen-treated female's song system. (+info)
A growth cost of begging in captive canary chicks.
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Nestling birds solicit food from adults by using begging displays that appear paradoxically costly and wasteful. Theoretical work suggests that the evolution of such exuberant offspring behavior reflects parent-offspring conflict over the supply of parental investment. Originally, extravagant begging was seen as a means of psychological trickery by which offspring could wheedle additional resources from resistant parents. Subsequently, costly begging came to be viewed as the hallmark of resolved parent-offspring conflict, serving either to prevent escalated scramble competition or to enforce honest signaling. However, the theoretical assumption of costly solicitation has been called into question by the low level of energy expenditure measured empirically during begging. This finding has prompted new theoretical work that shows that begging can be cost-free and yet still resolve parent-offspring conflict. Here, I report that begging is more costly than recent work suggests. My experimental evidence from captive canaries demonstrates a marginal cost of begging through impaired growth. Furthermore, I argue that previous studies of energy expenditure during solicitation do not measure the cost of begging, as defined theoretically. More generally, my results may account for the evolution of nestling growth rates, as well as the observation that begging is typically most flamboyant in older offspring. (+info)
Nucleotide sequence analysis of a novel circovirus of canaries and its relationship to other members of the genus Circovirus of the family Circoviridae.
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The circular, single-stranded DNA genome of a novel circovirus of canaries, tentatively named canary circovirus (CaCV), was cloned and sequenced. Sequence analysis indicated that the genome was 1952 nucleotides (nt) in size and had the potential to encode three viral proteins, including the putative capsid and replication-associated (Rep) proteins. The CaCV genome shared greatest sequence similarity (58.3% nt identity) with the newly characterized columbid circovirus (CoCV) and was more distantly related to the two porcine circovirus strains, PCV1 and PCV2, beak and feather disease virus (BFDV) and a recently isolated goose circovirus (GCV) isolate (46.8-50.9% nt identity). In common with other members of the Circovirus genus, several nt structures and amino acid motifs thought to be implicated in virus replication were identified on the putative viral strand. Phylogenetic analysis of both the capsid and Rep protein-coding regions provided further evidence that CaCV is more closely related to CoCV and BFDV and more distantly related to GCV, PCV1 and PCV2. (+info)