Does sex matter? Differential responses to corticosterone administration in the zebra finch

Because of potentially deleterious effects of chronic stress, physiological measurements of stress hormones (in birds, corticosterone (CORT)) are often used to determine the consequences of natural or human-induced change. Often, it is assumed that CORT levels will be similar between the sexes and the results are pooled. However, recent studies have reported sex differences in CORT concentrations in avian species. As zebra finches (Taeniopygia guttata) are one of the most widely used bird species in laboratory studies worldwide, potential sex-specific differences in hormone metabolism, as well as the clearance rate of oral doses of exogenous CORT, are highly relevant. The results of this study show that female zebra finches have a significantly higher baseline CORT than males, which could partially be a product of differential responses to semi-isolation. In addition, a single dose of exogenous CORT resulted in different blood profiles between the sexes over time, though exogenous CORT was cleared from blood within 90 min following treatment in both sexes. Interestingly, exposure to multiple doses of exogenous CORT resulted in elevated CORT levels 24 h after treatment in both sexes. These results highlight the need for further investigations into potential sex differences in hormone metabolism, as well as possible cumulative effects of repeated stress.     

The acoustic expression of stress in a songbird: Does corticosterone drive isolation-induced modifications of zebra finch calls?

Animal vocalizations convey multiple pieces of information about the sender. Some of them are stable, such as identity or sex, but others are labile like the emotional or motivational state. Only a few studies have examined the acoustic expression of emotional state in non-human animals and related vocal cues to physiological parameters. In this paper, we examined the vocal expression of isolation-induced stress in a songbird, the zebra finch (Taeniopygia guttata). Although songbirds use acoustic communication extensively, nothing is known to date on how they might encode physiological states in their vocalizations. We tested the hypothesis that social isolation in zebra finches induces a rise of plasma corticosterone that modifies the vocal behavior. We monitored plasma corticosterone, as well as call rate and acoustic structure of calls of males in response to the playback of female calls of varied saliences (familiar versus stranger) in two situations: social isolation and social housing. Social isolation induced both a rise in plasma corticosterone, and a range of modifications in males' vocal behavior. Isolated birds showed a lower vocal activity, an abolition of the difference of response between the two stimuli, and evoked calls with longer duration and higher pitch. Because some of these effects were mimicked after oral administration of corticosterone in socially housed subjects, we conclude that corticosterone could be partly responsible for the isolation-related modifications of calls in male zebra finches. To our knowledge, this is the first demonstration of the direct implication of glucocorticoids in the modulation of the structure of vocal sounds.     

Quantitative assessment of organism–environment couplings

The evolutionary implications of environmental change due to organismic action remain a controversial issue, after a decades—long debate on the subject. Much of this debate has been conducted in qualitative fashion, despite the availability of mathematical models for organism–environment interactions, and for gene frequencies when allele fitness can be related to exploitation of a particular environmental resource. In this article we focus on representative models dealing with niche construction, ecosystem engineering, the Gaia Hypothesis and community interactions of Lotka–Volterra type, and show that their quantitative character helps bring into sharper focus the similarities and differences among their respective theoretical contexts.     

Quantitative assessment of the association of the α-I fragment of spectrin with oligomers of intact spectrin

• 1.1. The α-I fragment of human spectrin that carries the binding site on the α-chain of spectrin for the β -chain has been purified from limited trypsin digests of spectrin by means of FPLC.
• 2.2. The self-association of spectrin and the binding of the α-I fragment to spectrin heterodimers and to tetramers have been quantified through the use of gel electrophoresis, staining with Coomassie Blue, and quantification of the bound dye following elution with pyridine.
• 3.3. The parameters of self-association were found to be consistent with those estimated from sedimentation equilibrium analysis.
• 4.4. The data were consistent with a model in which both self-association and the binding of the α-I fragment are considered to occur through an intermediate in which the α-β interface is initially dissociated. The α-β interface in the heterodimer was found to be less stable than that of higher oligomers by approx. 3 kJ/mol.

     

Neural response to bird’s own song and tutor song in the zebra finch field L and caudal mesopallium

Neurons in the song system nuclei of songbirds exhibit a strong preference for the sound of the birds own song relative to that of conspecific songs. This selectivity is observed in the high vocal center and the nucleus interface of the nidopallium, two song nuclei that receive input from the birds auditory system. To investigate the role of the auditory system in generating the selective responses observed in the song system, we recorded auditory responses in the zebra finch primary auditory forebrain, field L, and in a secondary auditory area, the caudal mesopallium. Field L and caudal mesopallium project directly or indirectly to the high vocal center and nucleus interface of the nidopallium and are presumed to provide substantial auditory input to the song system. We found that, on average, neurons in field L and caudal mesopallium did not show positive selective responses for the birds own song or tutor song relative to conspecific song. Moreover, there were no particular sub-areas in the auditory telencephalon that were relatively more selective than the average. The selectivity for the birds own song would therefore be restricted to song nuclei and would arise in one processing step, potentially found at the interface between the auditory and the song systems.Abbreviations BOS birds own song - CM caudal mesopallium (older term: caudal hyperstriatum ventrale or cHV) - Con conspecific song - HVC high vocal center - LMAN lateral magnocellular nucleus of the anterior nidopallium (older term: lateral magnocellular nucleus of the anterior neostriatum) - LPS pallial-subpallial lamina (older term: lamina medularis dorsalis or LMD) - NCM caudal medial nidopallium (older term: caudo-medial neostriatum) - NIf nucleus interface of the nidopallium (older term: nucleus interface of the neostriatum) - RA robust nucleus of arcopallium (older term: robust nucleus of the archistriatum) - Rev reverse BOS - Revorder reverse order of BOS - Uva nucleus uvaeformis of the thalamusNew avian brain terminology has been used in this paper (). Older terms are given in parentheses in the list of abbreviations     

Post-hatching syrinx development in the zebra finch: an analysis of androgen receptor,aromatase, estrogen receptor α and estrogen receptor β mRNAs

In zebra finches, the vocal organ (syrinx) is larger in males than in females. Specific details about the mechanisms responsible for this dimorphism are not known, but may involve sex differences in steroid hormone action early in post-hatching development. The distribution of androgen receptor (AR), aromatase (AROM), estrogen receptor (ER), and estrogen receptor (ER) mRNAs was examined at post-hatching days 3, 10 and 17. A low level of AR was equivalently expressed in the syrinx muscles of both sexes at all three ages. We detected no specific expression of AROM or ER mRNAs. In contrast, ER mRNA was detected in chondrocytes of the forming bone. The density of this expression increased with age as the chondrocytes hypertrophied, but did not differ between the sexes. Taken together, these data suggest that estrogens may act on cartilage/bone, and androgens may act on muscle fibers in early post-hatching development to influence syrinx morphology. However, the lack of a sex difference in steroid receptor mRNA expression in the syrinx suggests that, similar to the forebrain regions that control song, the interaction of androgens and estrogens with their receptors is not sufficient to induce full sexual differentiation of this organ.     

Quantitative assessment of the effect of ABCA1 gene polymorphism on the risk of Alzheimer’s disease

ATP-binding cassette transporter A1 (ABCA1) is a membrane-associated protein which has attracted considerable attention as a candidate gene for Alzheimer’s disease (AD) based on its function as a key factor in lipid metabolism by mediating cellular cholesterol efflux, the rate-limiting step in the production of nascent high-density lipoprotein (HDL) particles. The relationship between ABCA1 common variations (R219 K rs2230806, I883 M rs4149313 and R1587 K rs2230808) and AD has been reported in various ethnic groups; however, these studies have yielded contradictory results. To investigate this inconsistency, we performed a meta-analysis of 13 studies involving a total of 12,248 subjects to evaluate the effect of ABCA1 on genetic susceptibility for AD. Overall, the summary OR of AD was 1.01 (95 % CI: 0.93–1.10; P = 0.77), 1.10 (95 % CI: 0.96–1.26; P = 0.16), and 1.08 (95 % CI: 0.96–1.23; P = 0.21) for R219 K, I883 M and R1587 K polymorphism, respectively. No significant results were observed in dominant and recessive when compared with wild genotype for these polymorphisms. In the stratified analyses by ethnicity and sample size, no evidence of any gene-disease association was obtained. In conclusion, the present meta-analysis does not support the notion that common SNPs on ABCA1 is a major genetic risk factor for AD.     

Quantitative trends of zebra mussels in Lake Balaton (Hungary) in 2003–2005 at different water levels

During the extremely dry period between 2000 and 2003, the water level of Lake Balaton decreased by 82 cm and 80% of the stony littoral, an important habitat for the zebra mussel (Dreissena polymorpha), became dry. A recovery period started in 2004 due to intense precipitation, which increased water levels in the lake. Seasonal and spatial variations of the relative abundance, population density, population structure and biomass of the zebra mussel and the relative abundance of the amphipod Chelicorophium curvispinum were monitored in the period of 2003–2005 at four different shoreline sections and in two different portions (on the bottom and near the surface portion of the rip-rap) of Lake Balaton. Along with these studies, a quantitative survey of mussel larvae found in the plankton and of the abundance of mussel feeding diving ducks were made. As a consequence of the water level fall, on the dried part of the stony littoral, numerous zebra mussel druses perished. Following the dry period in early 2004, the relative abundance of the mussel on the bottom stones was smaller than in 2003 and the bottom community was dominated by C. curvispinum. By the end of 2004 and during 2005, the water level returned to normal and the surfaces of the reinundated stones were conducive to the successful colonization of zebra mussels. Hence, they returned as the dominant fauna in 2005. The stones near the surface might provide a new substrate for the recruitment of zebra mussels, probably offering more suitable substrata for the settlement in 2005 than in 2003. Therefore, the new substrata available in 2005 may have encouraged better and more rapid zebra mussel colonization than before. Zebra mussels may be better competitors for new space than C. curvispinum. A minor change of water-level fluctuation in 2005 and the reduction in population size of the mussel feeding waterfowl could have contributed to the intensive spread of zebra mussel by 2005.     

Female preference in the context of male–male interactions in Maylandia zebra of Lake Malawi

The mbuna cichlids of Lake Malawi are a diverse, monophyletic, and recently derived clade. Sexual selection is thought to have accelerated their rapid diversification, though the mechanism by which this has occurred remains unknown. In this study, we examine the effect that male–male interactions have on female preference. We first used a short interaction experiment as a proxy for male dominance. We then measured female preference for (1) a single, isolated male; (2) a group of three, highly ranked males, relative to a group of lower ranked males; and (3) a group of three, mixed-ranked males against a similar group of mixed-rank males. We found that male dominance was highly correlated with male standard length. Female preference for male standard length and for dominance rank was significant in both isolated and group interactions. However, females only showed preference for groups of interacting males when males were segregated by dominance rank, not when groups were composed of both dominant and subordinate males. The results suggest that male–male contests influence female mating decisions. By investigating the rules that dictate the outcomes of such interactions we can elucidate the role that behavior plays in the diversification of this species-rich lineage.     

Where did the finch go? Insights from radio telemetry of the medium ground finch (Geospiza fortis)

Movement patterns and habitat selection of animals have important implications for ecology and evolution. Darwin''s finches are a classic model system for ecological and evolutionary studies, yet their spatial ecology remains poorly studied. We tagged and radio‐tracked five (three females, two males) medium ground finches (Geospiza fortis) to examine the feasibility of telemetry for understanding their movement and habitat use. Based on 143 locations collected during a 3‐week period, we analyzed for the first time home‐range size and habitat selection patterns of finches at El Garrapatero, an arid coastal ecosystem on Santa Cruz Island (Galápagos). The average 95% home range and 50% core area for G. fortis in the breeding season was 20.54 ha ± 4.04 ha SE and 4.03 ha ± 1.11 ha SE, respectively. For most of the finches, their home range covered a diverse set of habitats. Three finches positively selected the dry‐forest habitat, while the other habitats seemed to be either negatively selected or simply neglected by the finches. In addition, we noted a communal roosting behavior in an area close to the ocean, where the vegetation is greener and denser than the more inland dry‐forest vegetation. We show that telemetry on Darwin''s finches provides valuable data to understand the movement ecology of the species. Based on our results, we propose a series of questions about the ecology and evolution of Darwin''s finches that can be addressed using telemetry.     

Quantitative analysis of extracted phycobilin pigments in cyanobacteria—an assessment of spectrophotometric and spectrofluorometric methods

Phycobilins are an important group of pigments that through complementary chromatic adaptation optimize the light-harvesting process in phytoplankton cells, exhibiting great potential as cyanobacteria species biomarkers. In their extracted form, concentrations of these water-soluble molecules are not easily determined using the chromatographic methods well suited to solvent-soluble pigments. Insights regarding the quantitative spectroscopic analysis of extracted phycobilins also remain limited. Here, we present an in-depth study of two methods that utilize the spectral properties of phycobilins in aqueous extracts. The technical work was carried out using high-purity standards of phycocyanin, phycoerythrin, and allophycocyanin. Calibration parameters for the spectrofluorometer and spectrophotometer were established. This analysis indicated the possibility of detecting pigments in concentrations ranging from 0.001 to 10 μg cm^?3. Fluorescence data revealed a reproducibility of 95 %. The differences in detection limits between the two methods enable the presence of phycobilins to be investigated and their amounts to be monitored from oligotrophic to eutrophic aquatic environments.     

Quantitative variation of “Mus musculus-like” constitutive heterochromatin and satellite DNA-sequences in the genus Mus

The extent of conservation of constitutive heterochromatin in three species of Mus viz. M. musculus, M. booduga and M. dunni, with shared cytological properties and homologous DNA sequences has been studied. The cytological properties were investigated by doing fluorescence staining and condensation inhibition of their chromosomes with Hoechst 33258. Both the parameters indicate the occurrence of a reduced quantum of M. musculus like heterochromatin at specific sites in the other two genomes. In situ hybridization of the nick translated ³H-labelled M. musculus satellite DNA with M. booduga and M. dunni chromosomes, also corroborates our Hoechst 33258 findings and comparable variation in the amount and site of occurrence of sequences homologous to M. musculus satellite DNA in these species are noticed. The study thus provides a good example of a gradual quantitative variation of a particular type of heterochromatin and in turn of the repetitive DNA constituting it in different related species. Further since the heterochromatin in M. booduga and M. dunni is expected to contain different repetitive DNA sequences in addition to those homologous to M. musculus satellite DNA, it is proposed that a change in the balance between two or more repetitive sequences in heterochromatin may be more crucial in its evolutionary consequences rather than a mere increase or decrease of a homogeneous repetitive sequence.     

Macrophytes in the anthropic constructions of the Venice littorals and their ecological assessment by an integration of the “CARLIT” index

A check-list of the macroalgae which colonize the artificial structures “dykes” formed by limestone blocks, placed between the northern Adriatic Sea and the Venice Lagoon to protect the wide sea inlets of Lido and Malamocco, the stone breakwaters and the submerged reefs parallel and perpendicular to the sea coastline of the Lido island “Murazzi” is presented. Macroalgae have been sampled monthly during one-year period (February 2007–January 2008) both in the lagoon inlets and along the marine coast. Flora was represented by 213 taxa: 61 Chlorophyta, 114 Rhodophyta, 38 Ochrophyta (37 Phaeophyceae, 1 Xanthophyceae), with the richest and luxuriant vegetation in the lagoon inlet areas. The application of the Rhodophyta/Chlorophyta (R/C) index and the Expert-Macrophyte Quality Index (E-MaQI) highlighted the “High” ecological status (EQR > 0.9) of the lagoon inlet areas.As E-MaQI is not applicable in marine areas, an adaptation of CARLIT to the anthropic structures of the north-western coasts of the northern Adriatic Sea and its integration with the dominant taxa is proposed.The application of the revised index to the Lido dykes and breakwaters placed along the marine littorals shows “Moderate” conditions.     

Symmetry-related mutants in the quinone binding sites of the bacterial reaction center – the effects of changes in charge distribution

To probe the structural elements that contribute to the functional asymmetries of the two ubiquinone₁₀ binding pockets in the reaction center of Rhodobacter capsulatus, we targeted the L212Glu–L213Asp (near Q_B) and the M246Ala-M247Ala (near Q_A) pairs of symmetry-related residues for site-specific mutagenesis. We have constructed site-specific mutants that eliminate the sequence differences at these positions (L212Glu–L213AspAla-Ala or M246Ala–M247AlaGlu-Asp), and have reversed that asymmetry by constructing a quadruple-mutant strain, RQ (L212Glu–L213Asp-M246Ala–M247AlaAla-Ala-Gl u-Asp). The mutations were designed to change the charge distribution in the quinone-binding region of the reaction center; none of the strains is capable of photosynthetic growth. In photocompetent phenotypic revertants of the RQ strain, second-site mutations which affect Q_B function are coupled to mutations in the Q_A site which restore an Ala or substitute a Tyr at the M247 site; one strain carries an additional MetLeu substitution at M260 near Q_A. All of the RQ revertants retain the engineered M246AlaGlu mutation in the Q_A site as well as the L212Ala–L213Ala mutations in the Q_B site. Kinetic characterization of the RQ revertants will give us an idea of what structural and functional elements are important for restoring efficiency to electron and proton transfer pathways in the RQ RC, which is far from native. To date, these preliminary results underscore the importance of an asymmetric distribution of polar amino acids in the quinone binding pockets and its influence on the functional properties of the reaction center.     

Plasma Propranolol Levels in the Quantitative Assessment of β-adrenergic Blockade in Man

Plasma propranolol levels associated with reductions in endogenous and exogenous cardiac β-stimulation were determined in normal people. The levels associated with a given degree of blockade of exercise-induced tachycardia were about three times greater after intravenous administration than after oral administration. This shows that an active metabolite of propranolol is formed only after the drug is taken by mouth. The greatest reduction in the tachycardia of strenuous exercise was associated with plasma levels of 40 ng./ml. with oral administration and 100 ng./ml. with intravenously administered propranolol.The effect on isoprenaline-induced tachycardia following intravenously administered propranolol showed that the dose ratio for isoprenaline was about 30 with plasma levels of 100 ng./ml. and 10 with levels of 10-20 ng./ml. These plasma levels give 100% and 20-30% blockade of exercise-induced tachycardia. These findings suggest that some of the therapeutic effects of propranolol may be unrelated to β-adrenergic blockade.