Reducing mitochondrial bound hexokinase II mediates transition from non-injurious into injurious ischemia/reperfusion of the intact heart

Ischemia/reperfusion (I/R) of the heart becomes injurious when duration of the ischemic insult exceeds a certain threshold (approximately ≥20 min). Mitochondrial bound hexokinase II (mtHKII) protects against I/R injury, with the amount of mtHKII correlating with injury. Here, we examine whether mtHKII can induce the transition from non-injurious to injurious I/R, by detaching HKII from mitochondria during a non-injurious I/R interval. Additionally, we examine possible underlying mechanisms (increased reactive oxygen species (ROS), increased oxygen consumption (MVO₂) and decreased cardiac energetics) associated with this transition. Langendorff perfused rat hearts were treated for 20 min with saline, TAT-only or 200 nM TAT-HKII, a peptide that translocates HKII from mitochondria. Then, hearts were exposed to non-injurious 15-min ischemia, followed by 30-min reperfusion. I/R injury was determined by necrosis (LDH release) and cardiac mechanical recovery. ROS were measured by DHE fluorescence. Changes in cardiac respiratory activity (cardiac MVO₂ and efficiency and mitochondrial oxygen tension (mitoPO₂) using protoporphyrin IX) and cardiac energetics (ATP, PCr, ?G_ATP) were determined following peptide treatment. When exposed to 15-min ischemia, control hearts had no necrosis and 85% recovery of function. Conversely, TAT-HKII treatment resulted in significant LDH release and reduced cardiac recovery (25%), indicating injurious I/R. This was associated with increased ROS during ischemia and reperfusion. TAT-HKII treatment reduced MVO₂ and improved energetics (increased PCr) before ischemia, without affecting MVO₂/RPP ratio or mitoPO₂. In conclusion, a reduction in mtHKII turns non-injurious I/R into injurious I/R. Loss of mtHKII was associated with increased ROS during ischemia and reperfusion, but not with increased MVO₂ or decreased cardiac energetics before damage occurs.     

A loss of heterozygosity,a loss in competition? The effects of inbreeding,pre‐ and postnatal conditions on nestling development

The early developmental trajectory is affected by genetic and environmental factors that co‐depend and interact often in a complex way. In order to distinguish their respective roles, we used canaries (Serinus canaria) of different genetic backgrounds (inbred and outbred birds). An artificial size hierarchy was created to provoke within‐nest competition, manipulating postnatal conditions. To this end, inbred birds were weight‐matched with outbred birds into duos, and each nest contained one duo of size‐advantaged, and one duo of size‐disadvantaged inbred and outbred nestlings. Prenatal (maternal) effects were taken into account also, enabling us to study the separate as well as the interactive effects of inbreeding, pre‐ and postnatal conditions on nestling development. We find that postnatal conditions were the most important determinant of early growth, with size‐advantaged nestlings growing faster and obtaining larger size/body mass at fledging in comparison with size‐disadvantaged nestlings. Prenatal conditions were important too, with birds that hatched from eggs that were laid late in the laying order obtaining a larger size at fledging than those hatched from early laid eggs. Inbreeding inhibited growth, but surprisingly this did not depend on (dis)advantageous pre‐ or postnatal conditions. Our findings imply that inbred individuals lose when they are in direct competition with same‐sized outbred individuals regardless of the rearing conditions, and we thus propose that reduced competitiveness is one of the driving forces of inbreeding depression.     

Hot or Not: The Effects of Exogenous Testosterone on Female Attractiveness to Male Conspecifics in the Budgerigar

An increasing number of studies indicate that not only females but also males can be selective when choosing a mate. In species exhibiting male or mutual mate choice, females may benefit from being attractive. While male attractiveness is often positively influenced by higher plasma levels of the androgenic hormone testosterone, it has been shown that testosterone can masculinise female behavior and morphology in several bird species, potentially rendering them less attractive. In this study, we investigated whether female budgerigars, Melopsittacusundulatus, suffer from increased plasma testosterone levels through a negative effect on their attractiveness to males. We experimentally increased plasma testosterone levels in testosterone-treated females (T-females) compared to controls (C-females) and allowed males to choose between a T- and a C-female in a two-way choice situation. Although testosterone treatment significantly affected female behavioral and morphological characteristics, males did not show a significant difference in preference between T- and C-females. These results suggest that experimentally increasing testosterone levels in females does not appear to influence male preference during initial mate choice. Our findings indicate that selection for higher levels of testosterone in male budgerigars is probably not constrained by a correlated response to selection causing negative effects on female attractiveness during initial mate choice. Evaluating whether or not a potential constraint may arise from negative testosterone-induced effects on other fitness related traits in females requires further work.     

Seasonal Changes in Courtship Song and the Medial Preoptic Area in Male European Starlings (Sturnus vulgaris)

In male starlings (Sturnus vulgaris) courtship song plays a critical role in mate attraction. During the breeding season courtship song occurs prior to copulation and appears to reflect male sexual arousal. Outside the breeding season starlings sing, but song appears unrelated to reproduction. The aromatization of testosterone (T), likely within the medial preoptic nucleus (POM), is critical for the expression of male sexual arousal. The present study was performed to determine whether seasonal changes in the POM might relate to seasonal changes in courtship singing behavior in male starlings. T concentrations, the volume of the POM, and aromatase within the POM were examined both during and outside of the breeding season in male starlings. Song was also recorded at these times both with and without a female present. The POM was largest and contained dense aromatase immunostaining only during the spring breeding season, when T concentrations were highest and males responded to a female with an increase in courtship song. Outside the breeding season the volume of the POM was small, T concentrations were low, and males displayed no changes in song expression in response to female conspecifics. Song bout length was positively related to POM volume, and males sang longer songs in spring. Only males with nestboxes in spring responded to a female, and the POM tended to be larger in these males, suggesting that nestbox possession might influence neuroplasticity within the POM. Overall, the findings suggest that T-dependent plasticity and aromatase activity within the POM might regulate courtship singing in a wild songbird.     

Corticosterone,Avoidance of Novelty,Risk‐Taking and Aggression in a Wild Bird: No Evidence for Pleiotropic Effects

Certain inherent characteristics of individuals can determine both physiological and behavioural responses to environmental challenges, which could drive a correlation between levels of corticosterone (CORT), the most important stress hormone and behavioural profiles. Therefore, CORT level may mediate consistent behaviours along the shy/bold continuum, and thus, it could serve as a pleiotropic basis for behavioural syndromes. Moreover, behavioural responses to environmental challenges may have consequences for CORT concentrations, which would also result in a correlation between physiology and behaviours even without requiring pleiotropic mechanisms. Accordingly, we investigated the relationship between CORT and behaviour in free‐living male collared flycatchers, Ficedula albicollis, using recently developed field assays. More specifically, we characterised novel object avoidance, intraspecific aggression and risk‐taking in males and related these correlated behaviours to the concentration of CORT metabolites in droppings measured by enzyme immunoassay. Individuals with higher levels of excreted CORT metabolites had no consistently higher or lower behavioural scores along the shy/bold spectrum, as avoidance of novelty, aggression and risk‐taking were not systematically related to CORT metabolite concentrations in the same direction. Moreover, environmental challenges owing to the presence of a novel object, territorial intruder and a potential predator caused no elevation in the level of CORT metabolites. Therefore, we did not find correlative evidence for CORT driving correlated behaviours through pleiotropic effects or for particular behaviours during courtship causing elevation in CORT levels.     

Intermediate clutches in the Starling (Sturnus vulgaris): replacement clutches, additional clutches of polygynous males or late first clutches?

Summary Literature on the breeding biology of the StarlingSturnus vulgaris refers to a sequence of egg-layings usually termed as first, intermediate and second broods. Egg-laying of first broods is highly synchronous. Accurate data concerning the identity of pairs producing the intermediate clutches, i.e. clutches that are laid in the period between the first and second brood layings, are lacking. These clutches are considered to be mainly replacement clutches of early clutches that failed. In this paper, we analyse the degree of synchronization of first layings during 5 breeding seasons and determine the identity of pairs producing intermediate clutches. The synchronized laying period of the first brood varied from 3 to 9 days. The percentage of intermediate clutches ranged from 14 % to 66 %. Only few intermediate clutches were replacement clutches of early clutches that failed. Most (95 %) were additional clutches of early breeding polygynous males or clutches of males that arrived only during the incubation or nestling period of the early breeding pairs (i.e. pairs being involved in a brood, initiated during the synchronized first brood period). The late arriving males and females may have been birds that migrated further than these being involved in a first brood, and consequently returned later in the season. The arrival of new males and females after the synchronized laying period of the first brood therefore may be a typical phenomenon for Continental Europe where starlings are mainly migratory.

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Zwischenbruten beim Star: Ersatzbruten, zusätzliche Bruten von polygynen Männchen oder späte Erstbruten?

Zusammenfassung In der Literatur zur Brutbiologie des Stars,Sturnus vulgaris, werden oft Erst-, Zwischen- und Zweitbruten unterschieden. Innerhalb einer Kolonie erfolgt die Eiablage bei der Erstbrut sehr synchron. Die Identität der Paare, die Zwischenbruten zeitigen, ist unbekannt. Oft wurde vermutet, Zwischenbruten ersetzten vorwiegend verlorene Erstbruten. Wir analysieren das Ausmaß der Synchronisation bei Erstgelegen aus 5 Brutperioden und bestimmen, welche Paare Zwischenbruten produzieren. Der Zeitraum der synchronen Eiablage zur Erstbrut dauerte 3–9 Tage. 14% bis 66% aller Bruten waren Zwischenbruten. Nur wenige Zwischenbruten ersetzten verlorene Erstbruten. Die meisten (95 %) waren zusätzliche Bruten von frühbrütenden polygynen Männchen oder Bruten von spät ankommenden Männchen. Solche Männchen trafen erst zu einer Zeit in der Kolonie ein, zu der frühbrütende Paare schon ihre Gelege bebrüteten oder Junge fütterten. Die spät ankommenden Männchen und Weibchen könnten Vögel gewesen sein, die weiter gewandert waren und deshalb später zurückkehrten als Vögel, die zur ersten Brut kamen. Es mag für kontinentaleuropäische Stare, die überwiegend Zugvögel sind, typisch sein, daß einige Männchen und Weibchen erst nach der Periode der synchronen Eiablage der Erstbrut ankommen.

     

Age-Dependent Expression of Song in the Collared Flycatcher, Ficedula albicollis

Theory suggests that male ornaments should be reliable signals of age, with more elaborated ornaments reflecting superior quality in terms of experience and/or viability. Bird song is immensely involved in sexual selection, thus not‐surprisingly, it usually shows age‐dependent variation. Although the collared flycatcher Ficedula albicollis has been intensively studied for its sexual traits, and female preference for male age is expected to be strong, there is no quantitative information on age‐dependent expression of song in this species. Here, we fill this gap and, based on phenotypic correlations, we report the relationship between age and several song features. Repertoire size was consistently smaller in yearlings than in older males, but it also tended to increase after the second year of breeding. In a meta‐analysis of effect sizes using data from the literature, we found that the strength of the relationship between age and repertoire size in the collared flycatcher is similar to patterns observed in other passerines. Song rate was inversely related to age, as yearlings sang at higher rates than older males. Generally, effect sizes for the relationship between age and other song traits were of medium level on average, and had broad confidence intervals. Song traits covaried with survival in a direction suggesting that differences in song between age categories are unlikely to result from phenotype dependent survival. Our results generally support the hypothesis that song holds the potential to function as a reliable indicator of male age in the collared flycatcher. However, it seems that not all song traits are unambiguously more expressed in older males than in yearlings.     

Effect of consumption of phenols from olives and extra virgin olive oil on LDL oxidizability in healthy humans

A high intake of olive oil has been proposed as an explanation for the low incidence of coronary heart disease in Mediterranean countries, but it is unclear whether olive oil offers specific benefits beyond a low content of saturated fat. Some types of extra virgin olive oil are rich in non-polar phenols, which might be taken up by plasma LDL particles and protect these from becoming atherogenic by oxidative modification. In a pilot study we found that consumption of 47 g fortified olive oil containing 31 mg phenols significantly increased the lag time of LDL oxidation from 112 ± 5 min before to 130 ± 7 min 2h after the meal. However, this study was not controlled, and in the current study we therefore investigated whether olive oil phenols increase the lag time of LDL oxidation in postprandial samples when compared with a control group.

Twelve healthy men and women consumed four different olive oil supplements with a meal on four separate occasions: one similar to the supplement in the pilot study (positive control); one containing mainly non-polar olive oil phenols; one containing mainly polar olive oil phenols; and one without phenols (placebo). Lag time significantly increased 2 h after the meals with the positive control (8 ± 2 min), the polar phenols (8 ± 2 min), and the placebo (8 ± 2 min), but not after the non-polar phenols (-0.4 ± 3 min). Increases were not statistically different between supplements.

These results indicate that the lag time of LDL-oxidation is increased after consumption of a meal. This increase is probably due to non-specific meal or time effects and not to phenols from olives or olive oil. Furthermore, these findings stress the need for adequate controlled studies to avoid misinterpretations of the data.