Gestagens and glucocorticoids in chicken eggs

Avian eggs contain a variety of steroid hormones, which have been attributed as a tool for maternal phenotypic engineering. The majority of studies focuses on androgens, but also significant amounts of progesterone as well as other steroid hormones have been measured. The question if corticosterone is also present in eggs of chickens is currently under debate. The only analytical validation performed so far has failed to demonstrate corticosterone in the yolk of chickens, suggesting that antibodies for corticosterone measurement cross-react with other steroids present in the yolk. In order to investigate this assumption and to characterise potential cross-reacting hormones in more detail, we performed high-performance liquid chromatographic (HPLC) analyses of chicken yolk extracts and determined the concentration of immunoreactive corticosterone, progesterone and cortisol. The progesterone antibody revealed several immunoreactive substances, including progesterone, pregnenolone and two substances with lower polarity. The corticosterone enzyme immunoassay detected immunoreactive substances at exactly the same elution positions as the progesterone assay and a very small peak at the elution position of corticosterone. Immunoreactive cortisol was not found. In addition, inner and outer regions of the yolk sphere were analysed separately via HPLC. We found different concentrations of immunoreactive substances between the inner and outer yolk regions, probably reflecting the steroidogenic activity of the follicle cells during oocyte growth. We conclude that in homogenised yolk extracts without previous clean-up, the measured corticosterone concentrations may actually reflect those of progesterone and its precursors, most probably being 5 alpha- and 5 beta-pregnanes and pregnenolone. (C) 2009 Elsevier Inc. All rights reserved

Wave reflection, assessed by use of the ARCSolver Algorithm for pulse wave separation, is reduced under acute µg conditions in parabolic flight

Weightlessness during long-term space flight over 6-12 months leads to complex individual cardiovascular adaptation. The initial central blood volume expansion followed by a loss of plasma volume is accompanied by changes in vascular mechanoreceptor loads and responsive-ness, altered autonomic reflex control of heart rate and blood pressure, and hormonal changes in the long run. Hence, function and structure of the heart and blood vessels may change. Hemodynamic data obtained during short- and long-term space flight may indicate that the adaptation process resembles ageing of the cardiovascular system characterized by decreased diastolic blood pressure, increased central sympathetic nerve traffic and increased arterial pulse wave velocity. Experiments during parabolic flights in supine position suggest, that stroke volume does not change during transitions between µ-g and 1-g. We tested a novel method of pulse wave separation based on simple oscillometric brachial cuff waveform reading to investigate pulse wave reflection during acute weightlessness in healthy subjects. We hypothesized that the wave reflection magnitude (RM) remains unaltered during parabolic flights in supine position

AORTIC VESSEL WALL PROPERTIES DURING 60 DAYS STRICT HEAD DOWN TILT BEDREST - PRELIMINARY RESULTS OF AGBRESA

Background Changes in large artery properties including increased arterial compliance and increased carotid artery stiffness have been described after space flight. Altered vascular structure, which heralds cardiovascular risk, and reversible changes in vascular function could contribute to the response. Compared with previous studies, which did not reproduce these findings, AGBRESA applied strict -6° head-down bedrest (HDT) mimicking chronic cephalad fluid shifts in space. In this study, we assessed aortic vessel wall properties using state-of-the art imaging methods and pulse wave analysis and tested for possible protective effects of artificial gravity training. Material and Methods We present preliminary data from 12 healthy subjects (8 men, 4 women) obtained during baseline data collection 9-6 days before bedrest (BDC, supine position) and towards the end of two months head down tilt bedrest (MRI on day 56 and echocardiography on day 60 of HDT). Subjects were assigned to 30 minutes per day continuous short arm centrifugation (cAG), 6 times for 5 minutes interval short arm centrifugation, iAG), or a control group (ctr). We assessed aortic pulse wave velocity using oscillometric upper arm and thigh cuffs (PWV-2C, CardioCube, AIT, Vienna, Austria) and 4D-flow cardiac velocity encoded phase contrast magnetic resonance imaging (PWV-4D-MRI). We also measured area, area changes, and distensibility (AoD) of the ascending aorta by 2D-phase contrast cardiac MRI and arterial compliance (Ca) using transthoracic echocardiography. Results Mean aortic area increased in all subjects after 60 days head down tilt bedrest (5.3±0.7 vs. 5.8±0.7 cm², p<0.05). Stroke volume decreased from 94±13 to 84±10 ml (p<0.05) and pulse pressure from 56±11 to 46±9 mmHg (p<0.05) in part through reductions in stroke volume. The figure illustrates individual data on aortic properties (red diamonds = women). In contrast to the more consistent changes in aortic area, stroke volume, and pulse pressure, aortic distensibility, compliance, and pulse wave velocity responses show substantial inter-individual variability. Conclusion The important finding of our study is that 60 days strict head down bedrest elicit consistent changes in ascending aortic area, pulse pressure, and stroke volume. The resulting changes in vascular loading conditions likely confound vascular function measurements, both, in head down bedrest studies and in space

PULSED DOPPLER FROM THE SUPRASTERNAL NOTCH SYSTEMATICALLY UNDERESTIMATES MEAN BLOOD FLOW VELOCITY IN THE ASCENDING AORTA COMPARED TO PHASE CONTRAST MRI

Background Continuous pulsed-wave Doppler readings of flow velocity in the ascending aorta from the suprasternal position (sCD) are widely used in estimating stroke volume, particularly during physiological challenge maneuvers such as head-up tilt testing. Stroke volume is derived from velocity time integrals and vessel area. We compared the sCD against an established gold standard. Methods In 12 healthy women and men, we obtained 2D cross sectional, velocity encoded phase contrast MRI of the ascending aorta (2DMRI) and sCD to measure mean blood flow velocity (Vmean) at the ascending aorta. We compared sCD insonation depth to the distance between Doppler probe and sinotubular junction measured by MRI. Within an aortic 4D-Flow dataset, allowing flow measurements in every anatomical point along the ascending aorta, Vmean was determined at the sCD measurement point for comparison. Results sCD significantly underestimated Vmean compared with 2DMRI at the sinotubular junction (Vmean 2DMRI – Vmean sCD = 24.42 cm/s ± 12.55 cm/s, p = <0.001). Moreover, sCD sampled flow velocities 21.8 mm ± 7mm (p = <0.001) or 26% off the sinotubular junction. Yet, depth and velocity differences between sCD and 2DMRI were not correlated with each other (Pearson r = -0.147; p = 0.648). When we applied 4DMRI to assess flow velocity at the sCD measurement site, the Vmean difference between methodologies was reduced to 9.1 cm/s ± 12.38 cm/s (p = 0.035). Conclusion sCD profoundly underestimates Vmean in the ascending aorta compared to 4DMRI. The methodology has important limitations in accessing the ideal position for aortic flow measurements and precise information regarding the position of data acquisition for vessel area quantification cannot be ascertained. Overall, sCD is of limited utility in measuring absolute stroke volum

Effects of 30days bed rest and exercise countermeasures on PBMC bioenergetics

Abstract Aim: Altered mitochondrial function across various tissues is a key determinant of spaceflight-induced physical deconditioning. In comparison to tissue biopsies, blood cell bioenergetics holds promise as a systemic and more readily accessible biomarker, which was evaluated during head-down tilt bed rest (HDTBR), an established ground-based analog for spaceflight-induced physiological changes in humans. More specifically, this study explored the effects of HDTBR and an exercise countermeasure on mitochondrial respiration in peripheral blood mononuclear cells (PBMCs). Methods: We subjected 24 healthy participants to a strict 30-day HDTBR protocol. The control group (n=12) underwent HDTBR only, while the countermeasure group (n=12) engaged in regular supine cycling exercise followed by veno-occlusive thigh cuffs post-exercise for 6h. We assessed routine blood parameters 14 days before bed rest, the respiratory capacity of PBMCs via highresolution respirometry, and citrate synthase activity 2days before and at day 30 of bed rest. We confirmed PBMC composition by flow cytometry. Results: The change of the PBMC maximal oxidative phosphorylation capacity (OXPHOS) amounted to an 11% increase in the countermeasure group, while it decreased by 10% in the control group (p=0.04). The limitation of OXPHOS increased in control only while other respiratory states were not affected by either intervention. Correlation analysis revealed positive associations between white blood cells, lymphocytes, and basophils with PBMC bioenergetics in both groups. Conclusion: This study reveals that a regular exercise countermeasure has a positive impact on PBMC mitochondrial function, confirming the potential application of blood cell bioenergetics for human spaceflight

Fecal corticosteroids in a territorial bird selected for different personalities:daily rhythm and the response to social stress

In this study we tested the hypothesis that in a passerine bird (great tit, Parus major) individuals differing for coping strategies differ in the magnitude of the adrenocortical response to social stress as well. Furthermore, we aimed at characterizing daily rhythms in corticosteroid release before and after social stress. We used 16 males from either of two lines bidirectionally selected for different coping strategies (fast and slow explorers). Social stress was induced by confrontation with an aggressive resident male. Corticosteroid metabolites were analyzed in feces collected at 90-min intervals from 900 to 1630 h on a baseline day, on the day of the social conflict, and on the following day. In both days and in both lines levels varied with time of day in a robust rhythm with a peak in the first sample of the morning and a trough at the end of the light phase. This rhythm correlates with activity (perch hopping). An overall increase in levels relative to baseline day was observed between 30 and 140 min after the challenge. Birds of the less aggressive and more cautious line (slow explorers) showed a trend for a higher response compared to birds of the more aggressive and bolder line (fast explorers), which showed almost no response. On the day after the challenge the birds of the slow line exhibited significantly reduced corticosteroid secretion, probably due to an increased negative feedback. The results provide evidence for a physiological basis of different coping strategies in birds, emerging in response to social stress and with a pattern similar to that in other vertebrates. (C) 2003 Elsevier Science (USA). All rights reserved

Corticosterone in bird eggs:The importance of analytical validation

<p>It was recently found that high concentrations of chicken yolk gestagens and gestagen metabolites hamper corticosterone quantification via immunoassays. However, the situation in chicken albumen is still unresolved. In addition, the ratio of steroid hormone in the yolk of wild birds might differ. To investigate these matters, corticosterone and gestagens were measured in individual fractions of high-performance liquid-chromatographic separations of chicken albumen and yolk of red jungle fowl. Similarly, yolk extracts of hens with corticosterone-releasing implants or placebos were analysed to assess the impact of elevated plasma corticosterone concentrations on authentic yolk corticosterone levels. We also compared the results of a previously used corticosterone enzyme immunoassay (EIA) to those from a commercial radioimmunoassay (RIA) kit. The analytical validations of chicken albumen, bankiva yolk and yolks from hens with or without artificially elevated plasma corticosterone levels indicated that the main share of the immunoreactivity measured via corticosterone immunoassays was caused by substances other than authentic corticosterone. In albumen, the concentration of authentic corticosterone was below the detection limit. Analysis of bankiva yolk revealed three major gestagen peaks with concentrations of up to 2000 ng per fraction and a corticosterone peak of about 0.8 ng per fraction. Both corticosterone assays found a slightly higher corticosterone peak in a corticosterone-implanted hen's yolk (EIA: 0.7 ng; RIA: 0.5 ng per fraction) compared to the sham-treated female (EIA: 0.5 ng; RIA: 0.2 ng per fraction) but both antibodies also bound to several other substances, presumably gestagens. Although a certain amount of circulating corticosterone might pass into the yolk, direct quantification of corticosterone in non-homogenized avian egg samples via immunoassays is not advisable.</p>