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1.  Condition-dependence, developmental plasticity, and cognition: implications for ecology and evolution 
Trends in ecology & evolution  2013;28(5):290-296.
Across taxa, both neural growth and cognitive function show considerable developmental plasticity. Data from studies of decision-making, learning and discrimination demonstrate that early life conditions have an impact on subsequent neural growth, maintenance and cognition, with important ecological and evolutionary implications. We provide a synthesis of the evidence that spatial and vocal learning are condition-dependent, addressing what is known about their physiological control and the functional explanations. Neural investment is predicted to be affected by environmental conditions, but the shape of the response should depend on the fitness benefits of the cognitive traits under control. From an evolutionary perspective, traits promoting resistance to environmental perturbations should be favoured when the cognitive trait is a crucial determinant of fitness.
PMCID: PMC3640828  PMID: 23518414
2.  Developmental stress, social rank and song complexity in the European starling (Sturnus vulgaris). 
Bird song is a sexually selected trait and females have been shown to prefer males that sing more complex songs. However, for repertoire size to be an honest signal of male quality it must be associated with some form of cost. This experiment investigates the effects of food restriction and social status during development on song complexity in the European starling (Sturnus vulgaris). Birds that experienced an unpredictable food supply early in life produced a significantly smaller repertoire of song phrases than those with a constant food supply. Social status during development was also significantly correlated with repertoire size, with dominant birds producing more phrase types. This study therefore provides novel evidence that social as well as nutritional history may be important in shaping the song signal in this species.
PMCID: PMC1809993  PMID: 15101438
3.  Song as an honest signal of past developmental stress in the European starling (Sturnus vulgaris). 
Bird song is a sexually selected male trait where females select males on the basis of song quality. It has recently been suggested that the quality of the adult male song may be determined by nutritional stress during early development. Here, we test the 'nutritional-stress hypothesis' using the complex song of the European starling. Fledgling starlings were kept under experimental treatment (unpredictable short-term food deprivations) or control conditions (ad libitum food supply), for three months immediately after independence. We measured their physiological and immune responses during the treatment and recorded song production during the following spring. Birds in the experimental group showed increased mass during the treatment and also a significantly suppressed humoral response compared with birds in the control group. There was no difference between the groups in the cell-mediated response. Next spring, males in the experimental group spent less time singing, sang fewer song bouts, took longer to start singing and also sang significantly shorter song bouts. These data support the hypothesis that both the quality and quantity of song produced by individual birds reflect past developmental stress. The results also suggest the 'nutritional-stress hypothesis' is best considered as a more general 'developmental-stress hypothesis'.
PMCID: PMC1691349  PMID: 12816653
4.  A549 Lung Epithelial Cells Grown as Three-Dimensional Aggregates: Alternative Tissue Culture Model for Pseudomonas aeruginosa Pathogenesis  
Infection and Immunity  2005;73(2):1129-1140.
A three-dimensional (3-D) lung aggregate model was developed from A549 human lung epithelial cells by using a rotating-wall vessel bioreactor to study the interactions between Pseudomonas aeruginosa and lung epithelial cells. The suitability of the 3-D aggregates as an infection model was examined by immunohistochemistry, adherence and invasion assays, scanning electron microscopy, and cytokine and mucoglycoprotein production. Immunohistochemical characterization of the 3-D A549 aggregates showed increased expression of epithelial cell-specific markers and decreased expression of cancer-specific markers compared to their monolayer counterparts. Immunohistochemistry of junctional markers on A549 3-D cells revealed that these cells formed tight junctions and polarity, in contrast to the cells grown as monolayers. Additionally, the 3-D aggregates stained positively for the production of mucoglycoprotein while the monolayers showed no indication of staining. Moreover, mucin-specific antibodies to MUC1 and MUC5A bound with greater affinity to 3-D aggregates than to the monolayers. P. aeruginosa attached to and penetrated A549 monolayers significantly more than the same cells grown as 3-D aggregates. Scanning electron microscopy of A549 cells grown as monolayers and 3-D aggregates infected with P. aeruginosa showed that monolayers detached from the surface of the culture plate postinfection, in contrast to the 3-D aggregates, which remained attached to the microcarrier beads. In response to infection, proinflammatory cytokine levels were elevated for the 3-D A549 aggregates compared to monolayer controls. These findings suggest that A549 lung cells grown as 3-D aggregates may represent a more physiologically relevant model to examine the interactions between P. aeruginosa and the lung epithelium during infection.
PMCID: PMC547019  PMID: 15664956
5.  Testosterone influences basal metabolic rate in male house sparrows: a new cost of dominance signalling? 
Sexually selected signals of individual dominance have profound effects on access to resources, mate choice and gene flow. However, why such signals should honestly reflect individual quality is poorly understood. Many such signals are known to develop under the influence of testosterone. We conducted an experiment in male house sparrows in which testosterone was manipulated independently during two periods: before the onset of the breeding season and prior to the autumn moult. We then measured the effects of these manipulations on basal metabolic rate and on the size of the chest bib, a sexually selected signal. The results demonstrate that testosterone simultaneously affects both signal development and basal metabolic rate in the house sparrow (Passer domesticus). This evidence, therefore, supports a novel conclusion: that testosterone-dependent signals act as honest indicators of male quality possibly because only high-quality individuals can sustain the energetic costs associated with signal development.
PMCID: PMC1088746  PMID: 11429132
6.  Song as an indicator of male parental effort in the sedge warbler. 
Repertoire size has been found to be a sexually selected trait in a number of bird species, although the advantages of mating with a male who possesses a complex song remain unclear. We studied the potential role of song as an indicator of male parental effort in the sedge warbler Acrocephalus schoenobaenus. The male provisioning rate was used as a measure of male parental effort and was found to increase with nestling age and brood size. When controlling for chick age, brood size and other variables, we found a highly significant positive correlation between a measure of song complexity (repertoire size) and male parental effort. Both male parental effort and repertoire size were found to be positively correlated with chick weight when controlling for chick age. We found no correlation between a measure of song output (amount of song flighting) or territory size and parental effort. Repertoire size is known to be the most important cue in female choice amongst sedge warblers and we discuss the possible reasons for this. We suggest that, in choosing a male with a large repertoire, a female obtains not only indirect benefits but also direct benefits in the form of increased parental effort.
PMCID: PMC1690544  PMID: 10722211
7.  Female choice in the sedge warbler Acrocephalus schoenobaenus: multiple cues from song and territory quality 
Recent models of animal signalling emphasize the evolution of complex displays containing 'multiple messages'. A variety of potential cues used in female choice were investigated during a three-year field study of the sedge warbler, Acrocephalus schoenobaenus. Twelve possible cues were investigated, and three were found to have a significant influence upon pairing date. Two were different measures of song (repertoire size and song flighting) and one a measure of territory (territory size). Repertoire and territory size had a significant influence on pairing date in all three years, and song-flighting in two. The three cues were not intercorrelated and so had independent effects upon pairing date. We suggest that females select males upon multiple cues as these reflect different aspects of male and territory quality.
PMCID: PMC1688389
Female Choice Sexual Selection Multiple Cues Song Quality Territory Quality
8.  What makes Cryptococcus neoformans a pathogen? 
Emerging Infectious Diseases  1998;4(1):71-83.
Life-threatening infections caused by the encapsulated fungal pathogen Cryptococcus neoformans have been increasing steadily over the past 10 years because of the onset of AIDS and the expanded use of immunosuppressive drugs. Intricate host-organism interactions make the full understanding of pathogenicity and virulence of C. neoformans difficult. We discuss the current knowledge of the characteristics C. neoformans must possess to enter the host and establish progressive disease: basic growth requirements and virulence factors, such as the polysaccharide capsule; shed products of the organism; melanin production; mannitol secretion; superoxide dismutase; proteases; and phospholipases.
PMCID: PMC2627665  PMID: 9452400
9.  Regulation of cytokine production during the expression phase of the anticryptococcal delayed-type hypersensitivity response. 
Infection and Immunity  1994;62(7):2930-2939.
Effects of both positive and negative regulatory T cells on cellular infiltration and cytokine production during the expression phase of the anticryptococcal immune response were examined. Tamp cells, which are induced by cryptococcal antigen, significantly amplify the anticryptococcal delayed-type hypersensitivity response, whereas a cascade of T suppressor (Ts) cells inhibits the response and decreases the clearance of Cryptococcus neoformans during an infection. By using the gelatin sponge implantation model, we found that Tamp cells do not stimulate a significant increase in cellular infiltration into the sponges in response to cryptococcal antigen compared with that into delayed-type hypersensitivity-reactive sponges in immune control mice. However, Tamp cells do stimulate significant increases in the production of gamma interferon and interleukin-2 (IL-2) in the antigen-injected sponges over the level of the representative cytokine in antigen-injected sponges from the immune control mice. Likewise, Ts1 cells, induced with cryptococcal antigen, do not significantly affect antigen-induced cellular infiltration into sponges in immune mice. In contrast, decreased levels of gamma interferon and IL-2 are observed in antigen-injected sponges from Ts1-cell-recipient, immunized mice compared with those of the positive immune controls. The presence of either Tamp or Ts1 cells in immunized mice stimulates increased production of IL-5 but not IL-4 over that of the positive immune controls.
PMCID: PMC302900  PMID: 7911788
10.  Characterization of cellular infiltrates and cytokine production during the expression phase of the anticryptococcal delayed-type hypersensitivity response. 
Infection and Immunity  1993;61(7):2854-2865.
Cryptococcosis, an increasingly important opportunistic infection caused by the encapsulated yeast-like organism Cryptococcus neoformans, is limited by an anticryptococcal cell-mediated immune (CMI) response. Gaining a thorough understanding of the complex anticryptococcal CMI response is essential for developing means of controlling infections with C. neoformans. The murine cryptococcosis model utilizing footpad swelling to cryptococcal antigen (delayed-type hypersensitivity [DTH]) has proven to be a valuable tool for studying the induction and regulation of the anticryptococcal CMI response, but this technique has limitations with regard to evaluating the role of the final effector cells recruited by an ongoing CMI response. The purpose of this study was to assess the types of cells and cytokines induced into the site of cryptococcal antigen deposition in C. neoformans-infected and -immunized mice compared with those for control mice. We used a gelatin sponge implant model to examine the cells and cytokines present at the site of an anticryptococcal DTH response. Sponges implanted in infected mice and injected with cryptococcal culture filtrate antigen (CneF) 24 h before assessment had significantly increased numbers of infiltrating leukocytes compared with saline-injected sponges in the same animals. Exaggerated influxes of neutrophils and mononuclear cells were the major contributors to the increase in total numbers of cells in the DTH-reactive sponges. The numbers of CD4+ and LFA-1+ cells were found to be significantly increased in the CneF-injected sponges of infected and immunized mice over the numbers in control sponges. The numbers of large granular lymphocytes were also increased in DTH-reactive sponges compared with control sponges. Gamma interferon, interleukin 2 (IL-2), and IL-5 are clearly relevant cytokines in the anticryptococcal CMI response, since they were produced in greater amounts in the CneF-injected sponges from C. neoformans-infected and -immunized mice than in control sponges. IL-4 was not associated with the expression of DTH to cryptococcal antigen. The gelatin sponge model is an excellent tool for studying cells and cytokines involved in specific CMI responses.
PMCID: PMC280931  PMID: 8514388
11.  Effects of Cryptococcus neoformans-specific suppressor T cells on the amplified anticryptococcal delayed-type hypersensitivity response. 
Infection and Immunity  1991;59(1):29-35.
Cell-mediated immunity is an important host resistance mechanism against Cryptococcus neoformans, the etiological agent of cryptococcosis. Previous studies from our laboratory have shown that the anticryptococcal cell-mediated immune response as measured by delayed-type hypersensitivity (DTH) is down-regulated by a cascade of antigen-specific T suppressor (Ts) cells. Recently, we have identified a population of CD4 T cells that up-regulate the anticryptococcal DTH response (Tamp cells). The Tamp cells are found in the spleens of donor mice at 6 days after immunization with cryptococcal antigen, and they amplify the anticryptococcal DTH response when transferred to syngeneic recipients at the time of immunization of the recipients. In this study, we determined the effects of C. neoformans-specific Ts cells on the induction of the Tamp cells in the Tamp cell-donor mice and on the induction and expression of the amplified anticryptococcal DTH response in the Tamp cell-recipient mice. When cryptococcal-specific Ts1 cells were given at the time of immunization of the Tamp cell-donor mice, induction of Tamp cells was inhibited. In contrast, when Ts1 cells were given at the time of adoptive transfer of Tamp cells, the recipients displayed amplified DTH responses, indicating that Ts1 cells do not affect the Tamp cells' function once the Tamp cells have been produced. C. neoformans-specific Ts2 cells given at the time of either immunization or footpad challenge of the Tamp cell-recipient mice did not alter, to any measurable extent, the amplified DTH response. These results indicate that in addition to amplifying the anticryptococcal DTH response, Tamp cells may protect the anticryptococcal TDH cells from suppression by C. neoformans-specific Ts cells, much like contrasuppressor cells do in other systems. However, further characterization of the Tamp cells revealed that they are not adherent to Viscia villosa lectin, indicating that the anticryptococcal Tamp cells do not have this characteristic in common with contrasuppressor cells of other antigen systems.
PMCID: PMC257701  PMID: 1824761

Results 1-11 (11)