Choice and use of standards for dynamic headspace trapping and application to the analysis of the volatiles of baked potato

When attempting to quantify the volatile components of a food isolated by dynamic headspace trapping onto an adsorbent, the analyst has to select the most appropriate compounds to use as standards and at which stage of the analysis to add them. Factors to be borne in mind include the volatility of the standard, the response of the GC detector, and whether to add the standard to the sample or to the adsorbent trap. This chapter considers the issues and describes the application of one chosen method to the quantitation of the volatile components of baked potato.

Responses to interactive playback predict future pairing success in nightingales

Birdsong is a sexually selected trait that serves in territory defence and mate choice. Individual song traits can be affected by the body condition of the male and thus may reflect his quality. Such relations between male quality and general singing performance raise the question whether differences in male quality also affect response strategies used in dyadic interactions. To address this question, we studied the relation between pairing success of male common nightingales, Luscinia megarhynchos, and their responses to rivals posing different levels of threat. Using interactive playback, we exposed males prior to mating to either aggressively or moderately singing rivals (by song overlapping and song alternating, respectively). Males that remained unpaired throughout the season (bachelors) interrupted their singing significantly more often after being overlapped than after alternating playback, whereas subsequently mated males kept the number of singing interruptions more constant across playback treatment. This suggests that subsequently paired males are less discriminative than are bachelors when challenged by rivals varying in aggressiveness. Regardless of playback treatment, males that later became paired responded significantly more strongly than did bachelor males. Thus, an increase in singing after a vocal interaction prior to mating predicted future mating success. (c) 2006 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.

Experimentally elevated plasma testosterone levels do not influence singing behaviour of male blue tits (Parus caeruleus) during the early breeding season

Sexual selection theory suggests that females might prefer males on the basis of testosterone (T)-dependent secondary sexual traits such as song. Correlational studies have linked high plasma T-levels to high diurnal song output. This has been confirmed in experiments where T-levels were kept high at times when natural T-levels have decreased. However, surprisingly little is known about the relation between T-levels during the early breeding season and song. In many passerine birds males sing at a high rate at dawn early in the breeding season, referred to as the dawn chorus. In blue tits (Parus caeruleus), the dawn chorus coincides with the fertile period of the female, whereas diurnal song occurs throughout the breeding season. Previous studies on blue tits showed that characteristics of the dawn chorus correlate with male reproductive success. We experimentally elevated plasma T-levels in male blue tits during the pre-fertile and fertile period. Our aim was to test whether increased plasma T-levels affect dawn song characteristics and increase the amount of diurnal song. Although T-implants successfully raised circulating T-levels, we did not find any difference between T- and control males in temporal performance measures of dawn song or in diurnal song output. Our results suggest that either there is no direct causal link between song output or quality and individual T-levels, or experimental manipulations of T-levels using implants do not permit detection of such effects during the early breeding season. Although we cannot exclude that individual T-levels are causally linked to other (e.g. structural) song parameters, our results cast doubt on T-dependence as the mechanisms that enforces honesty on song as a sexually selected trait.

Seasonal variation in dawn song characteristics in the common nightingale

Many male temperate zone passerines show a marked peak of singing activity before sunrise. The two main functions of this so-called dawn chorus are mate attraction and territory defence. We examined how seasonal patterns of different dawn song characteristics were related to mating status and to the breeding cycle of females in the common nightingale, Luscinia megarhynchos. We investigated two measures of song output: song rate and percentage performance time. We also calculated the proportion of 'whistle songs', a song category that is thought to be important in female choice. We predicted that if the main function of dawn singing in nightingales is to attract a social mate, then mated males should change their dawn singing behaviour after pair formation. In contrast, if dawn singing is mainly used in territory defence, we expected no difference in song traits between mated and unmated males throughout the season. We found that song rate and the proportion of whistle songs were low at the beginning of the season and did not predict future mating status. After arrival of females, all measures of dawn song performance remained largely constant throughout the breeding season, and we did not find significant differences in the seasonal variation between mated and unmated males. These findings are consistent with the hypothesis that song at dawn is important to defend a territory throughout the breeding season. (c) 2005 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.

The natural plasma testosterone profile of male blue tits during the breeding season and its relation to song output

In male birds, the gonadal hormone testosterone (T) is known to influence territorial and mating behaviour. Plasma levels of T show seasonal fluctuations which vary in relation to mating system and social instability. First, we determined the natural T profile of male blue tits Parus caeruleus during the breeding season. We found that plasma levels of T increased at the onset of nest building. Thus, the increase in circulating T was not associated with territory establishment, nor with the fertile period of the males' mates. In most individuals, T levels dropped to values close to zero during the period of chick feeding. Second, we investigated the relationship between plasma levels of T and male age, size, and singing behaviour. During the mating period, T levels did not differ between 1 yr old and older males and did not correlate with body size or condition. However, song output during the dawn chorus tended to be positively correlated with T levels. Therefore, if high T levels are costly, song output might be an honest indicator of male quality in blue tits. Finally, we show that plasma levels of T are significantly higher during the night than during the day. This pattern has also been observed in captive non-passerine birds, but its functional significance remains unknown.

Sequential extracellular matrix-focused and baited-global cluster analysis of serial transcriptomic profiles identifies candidate modulators of renal tubulointerstitial fibrosis in murine adriamycin-induced nephropathy

Transcriptome analysis using microarray technology represents a powerful unbiased approach for delineating pathogenic mechanisms in disease. Here molecular mechanisms of renal tubulointerstitial fibrosis (TIF) were probed by monitoring changes in the renal transcriptome in a glomerular disease-dependent model of TIF ( adriamycin nephropathy) using Affymetrix (mu74av2) microarray coupled with sequential primary biological function-focused and secondary