Exogenous and endogenous corticosterone alter feather quality

We investigated how exogenous and endogenous glucocorticoids affect feather replacement in European starlings (Sturnus vulgaris) after approximately 56% of flight feathers were removed. We hypothesized that corticosterone would retard feather regrowth and decrease feather quality. After feather regrowth began, birds were treated with exogenous corticosterone or sham implants, or endogenous corticosterone by applying psychological or physical (food restriction) stressors. Exogenous corticosterone had no impact on feather length and vane area, but rectrices were lighter than controls. Exogenous corticosterone also decreased inter-barb distance for all feathers and increased barbule number for secondaries and rectrices. Although exogenous corticosterone had no affect on rachis tensile strength and stiffness, barbicel hooking strength was reduced. Finally, exogenous corticosterone did not alter the ability of Bacillus licheniformis to degrade feathers or affect the number of feathers that failed to regrow. In contrast, endogenous corticosterone via food restriction resulted in greater inter-barb distances in primaries and secondaries, and acute and chronic stress resulted in greater inter-barb distances in rectrices. Food-restricted birds had significantly fewer barbules in primaries than chronic stress birds and weaker feathers compared to controls. We conclude that, although exogenous and endogenous corticosterone had slightly different effects, some flight feathers grown in the presence of high circulating corticosterone are lighter, potentially weaker, and with altered feather micro-structure.     

Nutritional stress affects corticosterone deposition in feathers of Caspian tern chicks

Stressful environmental conditions affect the adrenocortical function of developing animals, which can have consequences for their fitness. Discovery of the avian stress hormone corticosterone (CORT) in feathers has the potential to broaden the application of endocrine research in ecological and evolutionary studies of wild birds by providing a long‐term measure of CORT secretion. Mechanisms of CORT deposition in feathers are not well known and few studies have related feather CORT to circulating plasma CORT during feather growth. Our objective was to experimentally test the validity of using feather CORT as a measure of CORT secretion in developing birds experiencing nutritional stress. Caspian tern Hydroprogne caspia chicks were fed ad libitum or restricted (35% less than ad libitum) diets for four weeks. We measured CORT in feathers from these chicks to examine the relationship between feather CORT concentrations and nutritional limitation, circulating plasma CORT, and feather development. We found that feather CORT was higher in controls fed ad libitum than in restricted individuals, despite higher levels of plasma CORT in restricted chicks compared to controls. Feather mass and growth rates were strongly and positively related to feather CORT concentrations in both treatments. This is the first experimental study to show that feather CORT concentrations can be lower in response to nutritional stress, even when plasma CORT concentrations are elevated. Our results indicate that CORT deposition in feathers may be confounded when feather mass and growth rates are compromised by nutritional stress. We conclude that feather CORT can be used for assessing nutritional stress in growing birds, but the direction of response depends on how strongly stress affects feather development.     

Exogenous and endogenous fluctuations of thermoregulatory activity in the honeybee

Thermovision and thermometric methods were used to study temperature variations in honeybee nests and in aggregations of honeybees isolated from their families. Endogenous and exogenous circadian rhythms of thermoregulatory activity and their physiological mechanisms were revealed. The magnitude of changes in this activity in response to ambient temperature decreased from the beginning to the end of wintering, which was due to the existence of a genetically determined self-regulation program in honeybees. The improvement of this program in the course of the species evolution contributed to transformation of a honeybee family into a reproducible biological unit.     

Exogenous and endogenous ghrelin in gastroprotection against stress-induced gastric damage

Ghrelin, identified in the gastric mucosa has been involved in control of food intake and growth hormone (GH) release but little is known about its influence on gastric secretion and mucosal integrity. The effects of ghrelin on gastric secretion, plasma gastrin and gastric lesions induced in rats by 75% ethanol or 3.5 h of water immersion and restraint stress (WRS) were determined. Exogenous ghrelin (5, 10, 20, 40 and 80 microg/kg i.p.) increased gastric acid secretion and attenuated gastric lesions induced by ethanol and WRS and this was accompanied by the significant rise in plasma ghrelin level, gastric mucosal blood flow (GBF) and luminal NO concentrations. Ghrelin-induced protection was abolished by vagotomy and attenuated by suppression of COX, deactivation of afferent nerves with neurotoxic dose of capsaicin or CGRP(8-37) and by inhibition of NOS with L-NNA but not influenced by medullectomy and administration of 6-hydroxydopamine. We conclude that ghrelin exerts a potent protective action on the stomach of rats exposed to ethanol and WRS, and these effects depend upon vagal activity, sensory nerves and hyperemia mediated by NOS-NO and COX-PG systems.     

Serine proteinase inhibitor proteins: Exogenous and endogenous functions

Summary Proteinase inhibitor II (PIN2) proteins from the Solanaceae family have been previously used in plant transformation to acquire protection against caterpillars. Some of these PIN2 proteins have been shown to exhibit exogenous activities against trypsin and/or chymotrypsin in vitro. Despite their application in conferring insect resistance in transgenic plants, the endogenous roles of this family of proteins in various plant species have not been well defined. To investigate the exogenous and endogenous functions of PIN2 proteins, cDNAs encoding PIN2 proteins from the weed Solanum americanum (American black nightshade), designated SaPIN2a and SaPIN2b, were cloned and characterized. The localization of S. americanum SaPIN2a and SaPIN2b mRNAs and proteins in the reproductive tissues destined to undergo developmental programmed cell death subsequently led to investigations into their function during seed development. Using plant transformation of lettuce and S. americanum, it was evident that: (1) the expression of SaPIN2a in transgenic lettuce conferred resistance to cabbage looper (Trichoplusia ni) caterpillars; and (2) the expression of siRNAs from a PIN2-RNAi construct resulted in transgenic S. americanum that were impaired in seed development. These results suggest that S. americanum PIN2 proteins not only enhance resistance to caterpillars (when expressed exogenously) but they function in inhibiting endogenous proteases that are expressed during seed development. Specifically, the aborted seeds of PIN2-RNAi lines showed abnormal endothelium that subsequently affected endosperm and embryo development.     

Measuring corticosterone in feathers using an acetonitrile/hexane extraction and enzyme immunoassay: feather corticosterone levels of food‐supplemented Atlantic Puffin chicks

Glucocorticoid levels measured in the blood of animals reflect hypothalamic‐pituitary‐adrenal (HPA) activity in response to predictable and unpredictable changes. In birds, circulating corticosterone is incorporated into growing feathers and provides an integrated measure of HPA activity over the period of feather growth. Measuring corticosterone in feathers can provide insight into the physiological state of birds during times when they are unavailable for blood sampling (e.g., during migratory or non‐breeding periods of the annual cycle). Building upon studies that used radioimmunoassay or liquid chromatography, we used a commercially available enzyme immunoassay kit to measure corticosterone in feathers of nestling Atlantic Puffins (Fratercula arctica) on Gull Island, Newfoundland, Canada, in 2012, and demonstrate the benefits of sample preparation via acetonitrile/hexane purification. We used this method to measure corticosterone in feathers of Atlantic Puffin chicks that experienced differences in mass gain in a supplementary feeding study. We found a positive relationship between feather corticosterone and mass gain, and a negative relationship between feather corticosterone and pre‐treatment body condition. Because feathers were growing prior to and during the supplementary feeding period, our results also suggest that extracting seabird feather samples with acetonitrile/hexane (in addition to methanol) prior to measuring corticosterone with enzyme immunoassay is beneficial, and, as reported in previous studies, blood and feather corticosterone values reflect different measures.     

Levels and subcellular distribution of endogenous corticosterone in rat liver during development

The concentration of corticosterone in liver homogenates, liver cytosol and purified nuclear fractions, and in plasma of fetal, newborn, immature and adult rats has been measured by radioimmunoassay.Highest plasma corticosterone levels were found in fetal rats, decreasing close to the levels observed in the adrenalectomized rat by the 6th day of postnatal life followed by a rise in the adult rat. The concentration of corticosterone in liver during development paralleled the plasma levels, the liver to plasma corticosterone ratio ranging between 0.09 and 0.17 suggesting that the corticosterone retained by the tissue is related to the unbound fraction of the hormone in plasma.Both plasma and tissue corticosterone levels declined after adrenalectomy and they were elevated after ether stress.Fractionation of liver homogenates showed that the major fraction of liver corticosterone is localized in the cytosol. Purified liver nuclei contained between 9 and 16% of the total liver corticosterone. The amount of corticosterone in the nuclei seems to be related to the plasma and tissue hormone levels rather than the concentration of cytoplasmic glucocorticoid receptors. Since most of the nuclear corticosterone appears to be bound to receptors, it has been calculated that close to 60% of the cellular receptors in fetal liver are localized in the nucleus. In adult rat liver, only about 10% of the cellular receptors appear to be associated with nuclei. Changes in the concentration of glucocorticoid receptors in liver during development and after adrenalectomy are inversely related to changes in plasma corticosterone levels. It is suggested that corticosterone may regulate the levels of its own receptors in liver.     

Exogenous and endogenous force regulation of endothelial cell behavior

Endothelial cells live in a dynamic environment where they are constantly exposed to external hemodynamic forces and generate cytoskeletal-based endogenous forces. These exogenous and endogenous forces are critical regulators of endothelial cell health and blood vessel maintenance at all generations of the vascular system, from large arteries to capillary beds. The first part of this review highlights the role of the primary exogenous hemodynamic forces of shear, cyclic strain, and pressure forces in mediating endothelial cell response. We then discuss the emergent role of the mechanical properties of the extracellular matrix and of cellular endogenous force generation on endothelial cell function, implicating substrate stiffness and cellular traction stresses as important mediators of endothelial cell health. The intersection of exogenous and endogenous forces on endothelial cell function is discussed, suggesting some of the many remaining questions in the field of endothelial mechanobiology.     

The effects of acute corticosterone administration on anxiety, endogenous corticosterone, and c-Fos expression in the rat brain

The effects of acute pretreatment of rats with corticosterone (5 and 20 mg/kg, s.c.) on emotional behavior, expression of c-Fos protein in brain structures, and serum concentration of corticosterone were studied to model the short-term glucocorticoid-dependent changes in brain functions. Corticosterone was administered 90 min before training of a conditioned fear reaction (a freezing response), and behavioral, hormonal and immunocytochemical effects were examined 1 day later, on the test day. Pretreatment of rats with corticosterone significantly attenuated the freezing reaction in the conditioned fear test. The effect of the corticosterone was accompanied by a selective enhancement of the aversive context-induced c-Fos expression in some brain structures: the parvocellular and magnocellular neurons of the paraventricular hypothalamic nucleus (pPVN and mPVN), the medial amygdala nucleus (MeA), and the cingulate cortex, area 1 (Cg1), as well as an increase in the concentration of aversive context-induced endogenous serum glucocorticoid, 1.5 h and 10 min after the test session, respectively. It is suggested that the behavioral effects of acute pretreatment of rats with corticosterone could be due to changes in the mnemonic processes in the brain, inhibition of brain corticotropin releasing factor (CRF) synthesis, or stimulation of GABA-A receptor modulating neurosteroids synthesis. It is hypothesized that the enhanced activity of Cg1, MeA, pPVN, and mPVN, and the hypothalamic-pituitary-adrenal axis with concomitant increased serum glucocorticoid concentration, might serve to facilitate active coping behavior in a threatening situation.     

Exogenous versus endogenous acceptors in photosystem ii in inhibited chloroplasts

The conditions for steady-state Signal IIf formation in response to single turnover flashes in Tris-treated, 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU)-inhibited chloroplasts have been investigated. DCMU inhibits Signal IIf generation as the photoinactive state, Z P680 Q-A, accumulates. Potassium ferricyanide relieves this inhibition so that Signal IIf can be fully developed on each flash in a flash series. The effectiveness of ferricyanide in stimulating Signal IIf formation is dependent on its concentration, the flash repetition rate, and the salt composition of the chloroplast suspension. There are two models in the literature for Q-A oxidation under these inhibitory conditions: direct oxidation of Q-A by exogenous acceptors like ferricyanide or oxidation of Q-A by an endogenous acceptor, AH, which has a midpoint potential of approximately 400 mV. It is found that the direct exogenous acceptor model accounts well for these data, whereas the AH model does not explain several of these results. The apparent rate constant for the direct oxidation of Q-A by ferricyanide at various concentrations of salt has been calculated from our electron paramagnetic resonance (EPR) data and compared with the corresponding rate constant determined by S. Itoh from fluorescence data (Biochim, Biophys. Acta 504, 324-340, 1978); good agreement is found for the two different experimental approaches.     

Exogenous and endogenous increase in fungal GGPP increased fungal Taxol production

Applied Microbiology and Biotechnology - Taxol is an anticancer identified in both endophytic fungus and its host plant. Plant Taxol is a diterpenoid with geranylgeranyl diphosphate (GGPP) mediates...     

Elevated corticosterone in feathers correlates with corticosterone‐induced decreased feather quality: a validation study

The newly described technique of extracting corticosterone (CORT) from bird feathers may serve as a less invasive, more integrated measure of a bird's stress response. Previous work indicated that elevated plasma CORT resulted in poorer quality feathers during molt. We tested the hypothesis that a direct link exists between plasma and feather CORT concentrations. We experimentally increased plasma CORT concentrations using implants and found that the corresponding rise in CORT could be detected in feathers grown during implantation. Furthermore, CORT levels in two feathers grown at the same time from the same bird were very consistent. These results provide evidence that elevated CORT is a causative factor in decreasing feather quality during molt. However, there remain technical details that suggest caution when interpreting data from CORT extracted from feathers. Different portions of a growing feather did not necessarily reflect changes in plasma CORT at the time different parts of the feather were forming, a standard pool of homogenized feathers indicated that sample mass affects measured feather CORT concentration, and different antibodies produced different measured CORT concentrations, leaving in doubt the exact steroid being assayed.     

Exogenous and endogenous corticosteroids modulate blood-brain barrier development in the ovine fetus

We previously reported decreases in blood-brain barrier permeability in the ovine fetus at 80% of gestation after antenatal corticosteroids and shown that permeability is not reduced in newborn lambs after postnatal corticosteroids. We now test the hypotheses that exogenous antenatal corticosteroids decrease blood-brain barrier permeability at 60% but not 90% of gestation in ovine fetuses and that endogenous increases in plasma cortisol concentrations are associated with ontogenic decreases in barrier permeability during gestation. Chronically instrumented ovine fetuses were studied 12 h after the last of four 6-mg dexamethasone or placebo injections were given 12 h apart over 48 h to ewes. Fetuses at 80% of gestation from placebo-treated ewes studied under the same protocol were also included. Blood-brain barrier function was quantified with the blood-to-brain transfer constant (K(i)) to alpha-aminoisobutyric acid. K(i) values were lower in cerebral cortex, caudate nucleus, hippocampus, superior colliculus, thalamus, medulla, and cervical spinal cord in fetuses of dexamethasone- than placebo-treated ewes at 60% but not 90% of gestation. Regional brain K(i) values demonstrated inverse correlations with increases in gestation and plasma cortisol concentrations in most brain regions. We conclude that maternal treatment with exogenous corticosteroids was associated with decreases in blood-brain barrier permeability at 60% but not 90% of gestation and that increases in gestation and endogenous cortisol concentrations were associated with ontogenic decreases in barrier permeability during fetal development.     

Exogenous and endogenous TLR ligands activate anti-chromatin and polyreactive B cells

Autoreactive B cells may become activated in a T-independent manner via synergistic engagement of the BCR and TLRs. Using the VH3H9 Ig H chain transgene to track anti-chromatin B cells, we demonstrate that VH3H9/Vlambda1 anti-chromatin B cells proliferate in response to stimulatory oligodeoxynucleotides containing CpG motifs, suggesting that these autoreactive B cells are responsive to TLR9 signaling. Strikingly, some VH3H9 B cells, but not the well-characterized VH3H9/Vlambda1 B cells, proliferate spontaneously in culture medium. This proliferation is blocked by inhibitory CpG oligodeoxynucleotides, implicating the TLR9 (or possibly TLR7) pathway. Most hybridomas generated from the proliferating cells are polyreactive, and one exhibits binding to nuclear Ags but not to the other Ags tested. Thus, B cells carrying autoreactive and/or polyreactive specificities may be susceptible to T cell-independent activation via dual engagement of the BCR and TLRs.     

Isotopic evidence for endogenous protein contributions to greylag goose Anser anser flight feathers

Feather stable isotope composition may not reflect local isoscapes in which they were grown if supplemented with protein of endogenous origin. Thus, feather isotope analysis, combined with knowledge of local isoscapes can be used to infer endogenous nutrient composition to feathers in cases where birds travel to moult. We investigated this possibility in a study of flightless moulting greylag geese Anser anser on the Danish island of Saltholm, which are known to mobilise endogenous protein stores (acquired at previous terrestrial staging locations in Sweden) to reconstitute muscle blocks and organs whilst feeding on a saltmarsh (i.e. marine-influenced) diet with contrasting stable isotope ratios. We used stable isotope (δ¹³C, δ¹⁵N) measurements to test the prediction that new-grown flight feathers would have stable isotope values intermediate between those derived from a purely terrestrial C₃ diet and one composed purely of saltmarsh plants. Feather δ¹³C and δ¹⁵N values were intermediate between those expected for feather material derived from local saltmarsh (i.e. exogenous) food items and Swedish terrestrial (endogenous muscle) sources, suggesting a mixing of endogenous and exogenous sources. These results confirm that moult migrant Anatidae exploit body stores to meet specific protein needs during the flightless period of remige regrowth and caution against the use of feather stable isotope ratios as direct indicators of the isotopic environment in which they were regrown, where endogenous contributions may occur.     

Sex and migratory strategy influence corticosterone levels in winter-grown feathers,with positive breeding effects in a migratory pelagic seabird

To overcome unpredictable stressful transitory events, animals trigger an allostatic response involving the hypothalamic–pituitary–adrenal cortex. This hormonal response, which involves the release of glucocorticoids which in turn mediate between the main physiological mechanisms that regulate the energetic demands and resource allocation trade-off with behavioural responses to environmental perturbations and may ultimately lead to variation in fitness. We have used the Cory’s shearwater Calonectris borealis, a sexually dimorphic pelagic seabird with a partial migratory strategy, as a model bird species to analyse a number of traits related to the stress response. We investigated whether the activation of a stressful response, mediated by corticosterone, during the wintering period (1) correlated with the previous breeding success, (2) was affected by the migratory behaviour of male birds and (3) had consequences in the fitness of the birds. Corticosterone levels in feathers grown overwinter were analysed in 61 adult birds during three consecutive migratory periods (2009–2012) and in 14 immature birds in the wintering period 2010–2011. Moreover, the levels of corticosterone were analysed in experimental birds which were freed from their reproductive duties and compared with control birds which raised fledglings to the end of the breeding period. The results show that the levels of corticosterone were sex dependent, differed between years and were affected by the migratory strategy performed by the birds. The activation of the stressful response over the wintering period generated residual carry-over effects that positively affected the reproductive output in the subsequent breeding stage, a phenomenon previously undescribed in a long-lived pelagic seabird. Our study provides evidence that the analysis of corticosterone from feathers is a useful tool to evaluate carry-over effects in birds far away from breeding sites, opening new possibilities for future studies in this field.