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Biomedical subjects

J Wingfield

Publications and source records attributed to J Wingfield.

10 recordsLinked to original sources
PubMed2003

Social competition, corticosterone and survival in female lizard morphs.

We examined the selective consequences of variation in behaviour and endocrine physiology in two female throat-colour morphs of the lizard, Uta stansburiana in the wild. Female morphs differed in home-range distribution patterns and corticosterone levels in relation to the density and frequency of their female neighbours. Levels of plasma corticosterone of yellow-throated females increased with increased density of both morphs. In contrast, orange-throated females had reduced levels of corticosterone in response to increased density of orange females. Additionally, females with lower corticosterone survived poorly, suggesting that social interactions and high local densities of orange females may be potentially costly for orange females. These results are consistent with decreased fitness effects and suppression of immune function previously reported for orange female morphs surrounded by more orange neighbours. These correlations, in conjunction with previous work in this system, indicate that corticosterone is likely to be an important physiological mechanism regulating female fitness in nature.

Animals↗
PubMed2001

A nuclear SH3 domain-binding protein that colocalizes with mRNA splicing factors and intermediate filament-containing perinuclear networks.

A protein (SNP70) has been isolated that binds to the Src homology domain 3 of p47(phox), p85alpha, and c-src. Cloning and sequencing of the polypeptide revealed it to be a 70-kDa protein that has a number of potential domains, including Src homology 3 binding motifs and several nuclear localization signals. Immunofluorescence using anti-peptide antibodies revealed SNP70 to be primarily concentrated in the nucleus but excluded from nucleoli, in interphase cells. However, it was distributed throughout the cytoplasm in dividing cells. Extraction and subfractionation experiments indicated that SNP70 did not bind directly to DNA but did bind to poly(G)-rich oligonucleotides and was resistant to extraction with non-ionic detergents but was solubilized by treatment with RNase, high salt, or ammonium sulfate. Double-immunofluorescence experiments showed that SNP70 co-localized with two pre-mRNA splicing factors SC35 and U2B" within the nucleus. A population of SNP70 was found outside the nucleus, and double-immunofluorescence and immunoelectron microscopy demonstrated that it associated with vimentin-containing intermediate filaments, particularly those surrounding the nucleus. The data suggest that SNP70 associates with nuclear or perinuclear filaments and may play a role in the regulation of pre-mRNA processing.

Amino Acid Sequence↗
PubMed1999

Effects of embryonic treatment with fadrozole on phenotype of gonads, syrinx, and neural song system in zebra finches.

Previous studies have found that treatment of zebra finch embryos with an aromatase inhibitor on Day 5 or 8 of incubation caused partial sex reversal of gonadal phenotype in females. These females possessed both testicular and ovarian tissue, and the development of the neural circuit for song remained feminine. The present study attempted more complete gonadal reversal by treating zebra finch embryos earlier, on Day 3 of incubation, with Fadrozole (CGS 16949A), an aromatase inhibitor, or with saline. We examined the phenotype of the syrinx (androgen-dependent vocal organ), the gonads, and the telencephallic neural song system in 100-day-old birds. Treated females typically possessed a left ovotestis and a right testis, and significantly larger syringes than control females. The histology and steroid synthetic enzyme activity of the testicular tissue in treated females were quite masculine and similar to that of control males. At the time of sacrifice, the plasma concentrations of testosterone and estradiol for fadrozole-treated females did not differ from those of control females, but dihydrotestosterone was lower in treated females. Despite the large amount of functional testicular tissue and a masculine syrinx, the volumes and soma sizes of song system nuclei (HVC, RA) in treated females remained feminine. These results suggest that testicular secretions masculinize the syrinx, but are not sufficient to masculinize the song system in zebra finches.

Animals↗
PubMed1999

Combined aromatase inhibitor and antiandrogen treatment decreases territorial aggression in a wild songbird during the nonbreeding season.

Male song sparrows (Melospiza melodia morphna) defend territories throughout the year in western Washington State. In the nonbreeding season (autumn and winter), aggression and song are robustly expressed but plasma testosterone (T) levels are basal. Also, castration does not decrease nonbreeding territoriality. In this field experiment, we asked whether nonbreeding aggression is independent of T. T can act via androgen receptors or T can be aromatized to 17beta-estradiol (E(2)) and act via estrogen receptors. We treated free-living nonbreeding birds with an aromatase inhibitor (ATD) and an androgen receptor antagonist (flutamide) in combination. We then challenged subjects with a live decoy and playback of tape-recorded songs. ATD+flutamide treatment decreased several aggressive behaviors. However, ATD+flutamide treatment did not affect body condition, suggesting that subjects were healthy and that foraging behavior was not reduced. As expected, ATD+flutamide treatment increased plasma T, probably by blocking negative feedback on luteinizing hormone. Surprisingly, ATD+flutamide treatment increased plasma E(2). Most other studies using aromatase inhibitors have not measured plasma E(2). However, it is possible that ATD+flutamide treatment decreased local E(2) levels in the brain but not in plasma. Finally, ATD+flutamide treatment increased plasma corticosterone, perhaps in response to increased plasma T or E(2). To our knowledge, these are the first data to suggest that nonbreeding territoriality is regulated by endogenous steroid hormones. Nongonadal production of sex steroids may support aggression in the nonbreeding season.

Aggression↗
PubMed1996

Identifying a species-specific region of yeast TF11B in vivo.

The general transcription factor IIB (TFIIB) is required for RNA polymerase II transcription in eukaryotes. It provides a physical link between the TATA-binding protein (TBP) and the RNA polymerase and is a component previously suggested to respond to transcriptional activators in vitro. In this report, we compare the yeast (Saccharomyces cerevisiae) and human forms of the protein in yeast cells to study their functional differences. We demonstrate that human TFIIB fails to functionally replace yeast TFIIB in yeast cells. By analyzing various human-yeast hybrid TFIIB molecules, we show that a 14-amino-acid region at the amino terminus of the first repeat of yeast TFIIB plays an important role in determining species specificity in vivo. In addition, we identify four amino acids in this region that are critical for an amphipathic helix unique to yeast TFIIB. By site-directed mutagenesis analyses we demonstrate that these four amino acids are important for yeast TFIIB's activity in vivo. Finally, we show that mutations in the species-specific region of yeast TFIIB can differentially affect the expression of genes activated by different activators in vivo. These results provide strong evidence suggesting that yeast TFIIB is involved in the process of transcriptional activation in living cells.

Amino Acid Sequence↗
PubMed1987

Correlations between song acquisition, song production, and plasma levels of testosterone and estradiol in sparrows.

Male birdsong is a sexually dimorphic behavior characterized by learned dialects. In a combined study of learning in relation to steroid levels in the plasma, changes in estradiol and testosterone levels were correlated with the timing of the sensitive period for song acquisition and with successive stages in song development. Male swamp sparrows were trained with a changing series of live singing tutors from 26 days to 1 year of age. Song acquisition was concentrated between 26 and 47 days of age (57%). By 85 days of age 71% of acquisition was completed; some occurred as late as 300 days. There were two major periods when testosterone levels were elevated. The first, from 30-80 days, encompassed most of the period of song acquisition. The second, from 260 to at least 360 days of age, coincided with song development. Estradiol levels were elevated from 18 to 170 days of age, encompassing almost all of the period of song acquisition. A marked estradiol peak between 40 and 50 days coincided with a trough in testosterone levels and a hiatus in song acquisition. The strong correlation between the second period of elevated testosterone and song motor development suggests a causal connection, with levels peaking in mid-development and declining during mature song production. Estradiol levels were elevated at the start of the study and remained so during early subsong production, from 30 to 165 days. They then fell to baseline, remaining there throughout the resumption of subsong and plastic song production at 250-326 days. Both estradiol and testosterone are candidates for possibly affecting song acquisition.

Aging↗
PubMed1983

Testosterone-binding protein in a seasonally breeding amphibian.

The concentration of testosterone and dihydrotestosterone (DHT) in the plasma of Taricha granulosa rises markedly during the season when androgen-dependent epigamic structures and behaviors recrudesce. During this season (June-October), the physiological characteristics of the testosterone-binding globulin (TeBG) remain unchanged. Competitive binding studies indicate that TeBG binds fairly specifically to testosterone and DHT. The dissociation constant (5 X 10(-8) M) and binding capacities (ranging from 6 to 12 ng androgen bound/ml plasma) were determined using the charcoal adsorption procedures. Because the binding capacity of TeBG remains unchanged when the concentrations of androgens increase, the proportion of testosterone and DHT bound to TeBG is drastically lower during the breeding season, compared to the nonbreeding season. Furthermore, bilateral castration of male newts apparently reduces the binding capacity of TeBG, but Silastic implants of androgen fail to restore the binding capacity.

Androgens↗