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Background. Enterotoxigenic E. coli (ETEC) is a principal cause of diarrhea in travelers, deployed military personnel, and children living in low to middle-income countries. ETEC expresses a variety of virulence factors including colonization factors (CF) that facilitate adherence to the intestinal mucosa. We assessed the protective efficacy of a tip-localized subunit of CF antigen I (CFA/I), CfaE, delivered intradermally with the mutant E. coli heat-labile enterotoxin, LTR192G, in a controlled human infection model (CHIM). Methods. Three cohorts of healthy adult subjects were enrolled and given three doses of 25 μg CfaE + 100 ng LTR192G vaccine intradermally at 3-week intervals. Approximately 28 days after the last vaccination, vaccinated and unvaccinated subjects were admitted as inpatients and challenged with approximately 2 × 107 cfu of CFA/I+ ETEC strain H10407 following an overnight fast. Subjects were assessed for moderate-to-severe diarrhea for 5 days post-challenge. Results. A total of 52 volunteers received all three vaccinations; 41 vaccinated and 43 unvaccinated subjects were challenged and assessed for moderate-to-severe diarrhea. Naïve attack rates varied from 45.5% to 64.7% across the cohorts yielding an overall efficacy estimate of 27.8% (95% confidence intervals: −7.5–51.6%). In addition to reducing moderate–severe diarrhea rates, the vaccine significantly reduced loose stool output and overall ETEC disease severity. Conclusions. This is the first study to demonstrate protection against ETEC challenge after intradermal vaccination with an ETEC adhesin. Further examination of the challenge methodology is necessary to address the variability in naïve attack rate observed among the three cohorts in the present study. [ABSTRACT FROM AUTHOR]

Few studies have examined how avian life-history traits vary within populations as elevation increases and climate becomes more severe. We compared egg and clutch sizes of Mountain Bluebirds (Sialia currucoides) nesting at two elevations (1500 m and 2500 m above sea level) in the Bighorn Mountains of Wyoming over two years. Eggs laid by females at the high-elevation site were, on average, significantly (6%) smaller in volume than eggs laid by their lower-elevation counterparts. Across elevations, egg size showed a significant positive correlation with female body condition (weight relative to size), and high-elevation females had significantly lower indices of condition than low-elevation females. Temperatures during clutch formation were colder at the high-elevation site, and egg size was negatively related to temperature after controlling for the effects of female condition. Clutches of females at high elevations were, on average, marginally smaller (by 5%, ~0.3 eggs) than clutches of low-elevation females. Unlike egg size, clutch size was unrelated to either female condition or temperature during clutch formation. This suggests that, when under energetic or nutritional stress at high elevations, females sacrifice egg size before sacrificing clutch size. Key words: clutch size, egg size, elevation, female condition, Mountain Bluebird, Sialia currucoides, temperature. Pocos estudios han examinado como los caracteres de historia de vida cambian dentro de poblaciones a medida que la elevacion aumenta y el clima se torna mas severo. Comparamos el tamano de los huevos y de la nidada de individuos de Sialia currucoides que se encontraban nidificando a dos altitudes (1500 m y 2500 m sobre el nivel del mar) en las Montanas Bighorn de Wyoming durante dos anos. Los huevos puestos por hembras del sitio a mayor altitud fueron, en promedio, significativamente (6%) menores en volumen que los huevos puestos por hembras en los sitios de baja altitud. A traves del rango de elevacion, el tamano de los huevos mostro una relacion positiva y significativa con la condicion corporal (peso en relacion con el tamano). Las hembras del sitio de mayor altitud tuvieron indices de condicion significativamente menores que las hembras del sitio de baja altitud. Las temperaturas durante la formacion de la nidada en el sitio de mayor altitud fueron, en promedio, marginalmente menores (en un 5%, ~0.3 huevos) que las nidadas de las hembras del sitio de menor elevacion. De modo contrario al tamano del huevo, el tamano de la nidada no se relaciono con la condicion de las hembras ni con la temperatura durante la formacion de la nidada. Esto sugiere que cuando las hembras se encuentran bajo estres energetico o nutricional a altitudes altas, estas sacrifican el tamafio del huevo antes de sacrificar el tamano de la nidada.

The article presents research which assessed the evidence for the heterozygote instability in house wrens microsatellite loci. The researchers analyzed 20 microsatellite loci of Troglodytes aedon also called as the songbird. They found the difference between the homologue and the allele affects the mutation rate of this species. The authors argue that instability in the bird's heterozygote is possible at microsatellite loci.

Female birds are hypothesized to mate outside the pairbond to secure alleles that enhance the fitness potential of their offspring. To test this, researchers typically compare fitness-related attributes of extra-pair (EP) and within-pair (WP) half-siblings. Often neglected, however, is the possibility that females may provide EP offspring with certain non-genetic advantages. For example, in species in which eggs hatch asynchronously, females may place EP offspring amongst earlier-laid eggs in the clutch. Because they tend to hatch first, chicks from earlier-laid eggs are often larger and more developed than their nestmates and thus have a competitive advantage. We tested for an association between offspring paternity and position in the laying/hatching sequence in a Wyoming population of the house wren Troglodytes aedon. Eggs in this population always hatch asynchronously, usually in the order laid, over 24–48 h, setting up a stair-step-like size hierarchy within broods early in the nestling stage. This suggested that we could thus use a chick's mass relative to that of its nestmates as an index of the chick's position in the laying sequence. We first confirmed this, showing that position in the laying sequence explains 70% of the variance in chick size relative to nestmates. We then compared masses of EP and WP offspring shortly after hatching in 27 broods with mixed paternity. On average, EP offspring weighed 14% more than their WP counterparts, a highly significant difference. Our results therefore suggest that EP offspring are more likely than WP offspring to occur in earlier-laid eggs, thus gaining a size-based competitive advantage. We recommend that, when comparing EP and WP half-siblings in species in which eggs hatch asynchronously, researchers test for this potential maternally derived effect on offspring performance. [ABSTRACT FROM AUTHOR]

In many bird species that conceal nests within cavities or burrows, only females incubate eggs, but both sexes feed young after hatching. How males in such species discover that eggs have hatched and start provisioning offspring is unknown. We video-taped 26 house wren (Troglodytes aedon) nests continuously before, during, and after hatching began to test four hypotheses as to how males might learn of hatching: (i) females signal hatching to males; (ii) males hear hatchlings vocalizing; (iii) males observe changes in their mate's behaviour (e.g., entering and exiting nests more frequently and/or carrying eggshells or food); and (iv) males enter the nest cavity and encounter hatchlings directly. We did not detect any unique visual or vocal displays by females immediately post-hatching and so could not support the first hypothesis. At only three of 26 nests did it appear that males might have been stimulated to begin feeding solely as a result of either hearing offspring from outside the nest or observing changes in their mate's behaviour. Rather, males at most nests did not begin delivering food until after they had entered nest cavities and presumably had direct visual and/or tactile contact with hatchlings, even though most of these males previously had the opportunity to hear offspring from outside nests and/or see their mates acting parentally. Our finding that most males do not start delivering food until they have had direct exposure to young is consistent with recent neurological studies in mammals and birds that suggest direct exposure to young triggers a cascade of gene expression in the brain that induces nurturing behaviour. [ABSTRACT FROM AUTHOR]

Polymerase chain reaction (PCR)-based methods to determine the sex of birds are well established and have seen few modifications since they were first introduced in the 1990s. Although these methods allowed for sex determination in species that were previously difficult to analyse, they were not conducive to high-throughput analysis because of the laboriousness of DNA extraction and gel electrophoresis. We developed a high-throughput real-time PCR-based method for analysis of sex in birds, which uses noninvasive sample collection and avoids DNA extraction and gel electrophoresis. [ABSTRACT FROM AUTHOR]