In vivo online monitoring of testosterone-induced neuroplasticity in a female songbird

Adult neuroplasticity in the song control system of seasonal songbirds is largely driven by photoperiod-induced increases in testosterone. Prior studies of the relationships between testosterone, song performance and neuroplasticity used invasive techniques, which prevent analyzing the dynamic changes over time and often focus on pre-defined regions-of-interest instead of examining the entire brain. Here, we combined (i) in vivo diffusion tensor imaging (DTI) to assess structural neuroplasticity with (ii) repeated monitoring of song and (iii) measures of plasma testosterone concentrations in thirteen female photosensitive starlings (Sturnus vulgaris) who received a testosterone implant for 3 weeks. We observed fast (days) and slower (weeks) effects of testosterone on song behavior and structural neuroplasticity and determined how these effects correlate on a within-subject level, which suggested separate contributions of the song motor and anterior forebrain pathways in the development of song performance. Specifically, the increase in testosterone correlated with a rapid increase of song rate and RA volume, and with changes in Area X microstructure. After implant removal, these variables rapidly reverted to baseline levels. In contrast, the more gradual improvement of song quality was positively correlated with the fractional anisotropy values (DTI metric sensitive to white matter changes) of the HVC-RA tract and of the lamina mesopallialis, which contains fibers connecting the song control nuclei. Thus, we confirmed many of the previously reported testosterone-induced effects, like the increase in song control nuclei volume, but identified for the first time a more global picture of the spatio-temporal changes in brain plasticity.

The placenta in fetal thyroid hormone delivery: from normal physiology to adaptive mechanisms in complicated pregnancies

Context: Thyroid hormones are indispensable for normal fetal development. Since the fetus depends to a large extent on maternal thyroid hormone supply through the placenta, this challenges maternal thyroid economy. Several molecular mechanisms are involved in placental thyroid hormone transport and metabolism. Chronic pregnancy complications, associated with utero-placental hypoxia, trigger the development of accelerated placental maturation in order to improve fetal-placental exchange to strengthen the offspring's chance of survival. This review provides an overview of normal maternal-fetal thyroid hormone supply and explores the presence of placental adaptive mechanisms in complicated pregnancies with chronical utero-placental hypoxia to improve the thyroid hormone supply to the fetus under pressure, to end with reflections about the long term health consequences.Evidence acquisition: This work is based on a comprehensive literature review of the PubMed and Embase database, including relevant articles from 1969 to June 2018.Conclusions: The placenta is actively involved in fetal thyroid hormone delivery through a combination of stimulatory and inhibitory mechanisms. Parallel with histological adaptations to improve transplacental fetal-maternal exchange, there are indications of placental adaptive mechanisms in thyroid hormone transport and metabolism in case of complicated pregnancies, from animal models and in-vitro experiments. Evidence from human in-vivo studies is limited due to heterogeneity in study populations, small study samples, and technical limitations. Further research is necessary to reveal the role of the placenta in pathological circumstances. The placenta might thus be considered as the infants' black box of pregnancy. Results will contribute to more insights in the concept of fetal programming, which lays the foundations of optimum health, growth, and neurodevelopment across the lifespan.

Influence of strain origin on osmoregulatory and endocrine parameters of two non-native strains of Atlantic salmon (Salmo salar L.)

Non-native strains of Atlantic salmon are used in reinstatement trials where populations are extinct. Environmental cues like photoperiod and temperature are known to influence the smolting process and there is evidence of strain-, stock- or population-specific differences associated with seaward migration or smoltification. The objective of this study was to compare morphological, osmoregulatory and endorcrine features between two strains, one originating from a cold and short river in Ireland (Cong) and another from a long and warm river in France (Loire-Allier), reared under Belgian conditions in order to highlight major differences in restocking adaptability. Comprehensive endocrine profiles, consistent with their interactive role of mediating changes associated with smolting, have been observed. Na⁺/K⁺ATPase activity (1.3-10.5 µmol ADP∗mg prot.^-1∗h^-1) and hormone plasma levels (e.g. 55-122 ng∗mL^-1 of cortisol and 4.5-6.4 ng∗mL^-1 of GH) were consistent with reported values. We observed strain-related differences of the influence of temperature and daylength on cortisol, GH and sodium plasma levels. These may be related to the respective environmental conditions prevailing in the river of origin, which have impacted the genetic background for smoltification. Using Na⁺/K⁺ATPase activity as an indicator, both strains smoltified successfully and simultaneously testifying a prevailing influence of environmental cues over genetic factors for smoltification.

Regioselective thioacetylation of chitosan end-groups for nanoparticle gene delivery systems

Chitosan (CS) end-group chemistry is a conjugation strategy that has been minimally exploited in the literature to date. Although the open-chain form of the CS reducing extremity bears a reactive aldehyde moiety, the most common method to generate a reactive end-group on CS is nitrous acid depolymerization, which produces a 2,5-anhydro-d-mannose unit (M-Unit) bearing also an aldehyde moiety. However, the availability of the latter might be low, since previous literature suggests that its hydrated and non-reactive form, namely the gem-diol form, is predominant in acidic aqueous conditions. Oxime-click chemistry has been used to react on such aldehydes with various degrees of success, but the use of a co-solvent and additional chemical reagents remain necessary to obtain the desired and stable covalent linkage. In this study, we have assessed the availability of the aldehyde reactive form on chitosan treated with nitrous acid. We have also assessed its reactivity towards thiol-bearing molecules in acidic conditions where CS amino groups are fully protonated and thus unreactive towards aldehyde. LC-MS and NMR spectroscopy methods (1H and DOSY, respectively) confirmed the regioselective thioacetylation of the reactive aldehyde with conversion rates between 55 and 70% depending on the thiol molecule engaged. The stabilization of the hemithioacetal intermediates into the corresponding thioacetals was also found to be facilitated upon freeze-drying of the reaction medium. The PEGylation of the CS M-Unit aldehyde by thioacetylation was also performed as a direct application of the proposed conjugation approach. CS-b-PEG2 block copolymers were successfully synthesized and were used to prepare block ionomer complexes with plasmid DNA, as revealed by their spherical morphology vs. the rod-like/globular/toroidal morphology observed for polyplexes prepared using native unmodified chitosan. This novel aqueous thiol-based conjugation strategy constitutes an alternative to the oxime-click pathway; it could be applicable to other polymers.

Plasma testosterone levels of male European starlings (Sturnus vulgaris) during the breeding cycle and in relation to song and paternal care

In temperate-zone birds, seasonal testosterone (T) profiles often vary among species with different mating systems. The trade-off hypothesis suggests that T levels in male birds represent a trade-off between additional mating effort, stimulated by high T, and paternal effort, inhibited by high T. To study the role of T in mediating the trade-off between paternal and mating effort in the facultatively polygynous European starling (

Sturnus vulgaris

), we monitored seasonal fluctuations in T levels and song activity, which functions mainly in mate attraction, and we investigated natural covariation between plasma T levels and male parental and song behaviour during the parental phase. T concentrations peaked during nest building, remained high during the fertile period, and then decreased gradually during the period of paternal care. This resembles the profile typically found in polygynous species with biparental care. Seasonal variation in song activity paralleled seasonal changes in T. The proportion of time spent incubating was significantly negatively correlated with T levels in individual males. There was a positive, but non-significant, correlation between song activity at an additional nest box and T levels during incubation. We suggest that this negative correlation between T and incubation behaviour may be partly explained by T increases in males responding to the presence of prospecting females with additional nestbox occupation and mate attraction song, rather than that high T levels stimulate mate attraction song. During the feeding period, characterized by a very low availability of unmated females, variation in T levels was low and there was no covariation between T and feeding. T levels during the parental phase reflect, but do not seem to directly regulate, the trade-off between parental and additional mating effort and other factors such as opportunities for additional matings may influence the resolution of this reproductive trade-off.

Effects of nestboxes and males on female song activity in the European starling: an experimental study

Abstract

Environmental, contextual or social factors influencing song in female songbirds have been little studied. Female European starlings Sturnus vulgaris sing robustly throughout most of the year, except during the breeding season when their song production dramatically decreases. Here we experimentally investigated the effect of the presence of males and/or nestboxes on song production in captive female starlings during the breeding season. Spontaneous song activity of two experimental groups and one control group (housed with nestboxes, but no males) was observed for one month from the end of March onwards. Additionally, we tested whether female song rate is related to oestradiol plasma levels. The experimental results showed that song rate significantly decreased with the progressing of the breeding season and this process seemed not to be regulated by oestradiol. Nestboxes clearly promoted song production, as previously found in male starlings, while the presence of males negatively affected female song rate. Taken together these results indicate that, in the course of the breeding period, the suppressive influence of the day length and the presence of males on female song production override the stimulating effect of nestboxes, and that engagement in breeding activities is largely incompatible with singing in female starlings.

Tissue deiodinase activity during prolonged critical illness: effects of exogenous thyrotropin-releasing hormone and its combination with growth hormone-releasing peptide-2

Prolonged critical illness is characterized by reduced pulsatile TSH secretion, causing reduced thyroid hormone release and profound changes in thyroid hormone metabolism, resulting in low circulating T(3) and elevated rT(3) levels. To further unravel the underlying mechanisms, we investigated the effects of exogenous TRH and GH-releasing peptide-2 (GHRP-2) in an in vivo model of prolonged critical illness. Burn-injured, parenterally fed rabbits were randomized to receive 4-d treatment with saline, 60 microg/kg.h GHRP-2, 60 microg/kg.h TRH, or 60 microg/kg.h TRH plus 60 microg/kg.h GHRP-2 started on d 4 of the illness (n = 8/group). The activities of the deiodinase 1 (D1), D2, and D3 in snap-frozen liver, kidney, and muscle as well as their impact on circulating thyroid hormone levels were studied. Compared with healthy controls, hepatic D1 activity in the saline-treated, ill animals was significantly down-regulated (P = 0.02), and D3 activity tended to be up-regulated (P = 0.06). Infusion of TRH and TRH plus GHRP-2 restored the catalytic activity of D1 (P = 0.02) and increased T(3) levels back within physiological range (P = 0.008). D3 activity was normalized by all three interventions, but only addition of GHRP-2 to TRH prevented the rise in rT(3) seen with TRH alone (P = 0.02). Liver D1 and D3 activity were correlated (respectively, positively and negatively) with the changes in circulating T(3) (r = 0.84 and r = -0.65) and the T(3)/rT(3) ratio (r = 0.71 and r = -0.60). We conclude that D1 activity during critical illness is suppressed and related to the alterations within the thyrotropic axis, whereas D3 activity tends to be increased and under the joint control of the somatotropic and thyrotropic axes.

Opposite Changes in Plasma Testosterone and Corticosterone Levels Following a Simulated Territorial Challenge in Male Great Tits

Abstract

The apparent ability of plasma testosterone (T) and corticosterone (B) levels to fluctuate rapidly in response to agonistic interactions, suggests that these hormones may play an important role in an animal's acute behavioural response during such interactions. In the present study, free-living male great tits, Parus major, were subjected to a simulated territorial intrusion (STI) during the egg laying, incubation and nestling stage of first broods. Plasma T and B levels of challenged males were compared to those of control males matched for breeding stage, day in breeding stage, and time of day. Plasma B levels were significantly higher in challenged males compared to control males during the egg laying and incubation stage but not during the nestling stage. On the other hand, challenged males had significantly lower plasma T levels than control males throughout the breeding cycle. While having low plasma T and elevated plasma B levels, challenged males showed a vigorous and unrelenting territorial response to the STI. Plasma T and B levels of challenged males did not correlate with the intensity of the behavioural response to the STI. These findings do not agree with the predictions of the 'challenge hypothesis' that males exposed to a territorial challenge while having breeding baseline T levels will respond with an increase in T or that T correlates with the intensity of aggression during a challenge. Together, our findings suggest a role for B rather than T in the regulation of territorial defence in male great tits.

Dexamethasone ester treatment alters insulin-like growth factor-I, its binding proteins and thyroid status in finishing calves

To improve carcass quality in finishing calves, some breeders use preparations containing corticoids alone or in association with other growth promoters. We have investigated the effects of dexamethasone treatment on insulin-like growth factor-I (IGF-I), IGF-binding proteins (IGFBP-2 and 3) and thyroid hormones (T3, T4, free T4). Limousine male calves were allocated to a control group (C) (n = 18) and a group (n = 18) that received dexamethasone esters (DEX). Blood and hepatic tissue samples were collected at slaughtering. Thyroid hormones and IGF-I plasma levels were measured by RIA and IGFBPs were evaluated by immunoblotting. Hepatic type I 5′deiodinase (5′D-I) activity was determined by enzyme assay and hepatic expression of mRNA for GH receptor, IGF-I, IGFBP-2, IGFBP-3 and type I deiodinase (D-I) was evaluated by dot blot analysis. Plasma IGF-I and IGFBP-3 levels were reduced by the DEX treatment (P < 0.001 and P < 0.01, respectively) while IGFBP-2 was unaffected. Significant plasma changes for IGF-I and IGFBP-3 were not corroborated by hepatic mRNA levels, for which only a slight non-significant decrease was noted. Growth hormone receptor mRNA expression was increased after treatment (P < 0.01). T3 plasma level was higher in DEX animals (P < 0.05) than in C calves. Finally, treatment increased 5′D-I activity in the hepatic tissue (P < 0.001) and seemed to also affect D-I mRNA expression (P = 0.1). In conclusion, dexamethasone ester injection in calves altered some of their endocrinological parameters; this could explain the catabolic action of corticoids in the bovine species. Key words: Calves, corticoids, IGF-I, IGFBPs, thyroid axis

New insights into the mechanism and actions of growth hormone (GH) in poultry

Despite well documented anabolic effects of GH in mammals, a clear demonstration of such responses in domestic poultry is lacking. Recently, comprehensive dose-response studies of GH have been conducted in broilers during late post-hatch development (8 to 9 weeks of age). GH reduced feed intake (FI) and body weight gain in a dose-dependent manner, whereas birds pair-fed to the level of voluntary FI of GH-infused birds did not differ from controls. The reduction in voluntary FI may involve centrally mediated mechanisms, as hypothalamic neuropeptide Y protein and mRNA were reduced with GH, coincident with the maximal depression in FI. Growth of breast muscle was also reduced in a dose-dependent manner. Circulating IGF-I was not enhanced by GH, despite evidence that early events in the GH signaling pathway were intact. A GH dose-dependent increase in circulating 3,3',5-triiodothyronine(T3) paralleled decreases in hepatic 5D-III monodeiodinase activity, whereas 5'D-I activity was not altered. This confirms that a marked hyperthyroid response to GH occurs in late posthatch chickens, resulting from a decrease in the degradative pathway of T3 metabolism. This secondary hyperthyroidism would account for the decreased skeletal muscle mass (52) and lack of enhanced IGF-I (53) in GH-treated birds. Based upon these studies, it is now evident that GH does in fact have significant effects in poultry, but metabolic responses may confound the anabolic potential of the hormone.

Comparative effects of neonatal and prepubertal castration on craniofacial growth in rats

The role of endogenous testosterone in the craniofacial growth of the young male rat was investigated. First, the effect of neonatal surgical castration was examined in a randomized, cross-sectional study in which male Wistar rats were allocated to be either castrated or sham-operated 4 h after birth. Then, the effect of prepubertal chemical castration was analysed in a second, randomized longitudinal study in which male Wistar rats were randomly allocated either to a control group or to two experimental groups, one injected with triptorelin at day 25 and the other injected on day 25 and on day 45. Every tenth day between 20 and 70 days of age for the first study, and between 30 and 110 days of age for the second, body length and weight were measured, cephalometric X-rays taken, and blood samples obtained. Neonatal and prepubertal castration resulted in decreased plasma concentrations of testosterone and in delayed growth of somatic and craniofacial components. The initiation, duration and magnitude of the effect was dependent on individual bones (cranial base, skull roof) and on the lower incisor, and related to the testosterone concentrations. These results suggest that testosterone effects participate in the process of normal craniofacial growth, particularly during puberty.

Effect of testosterone replacement after neonatal castration on craniofacial growth in rats

Neonatal castration precludes the pubertal increase in serum testosterone and reduces general and craniofacial growth in the male Wistar rat. This study aimed to determine whether exogenous testosterone given at an age beyond the normal pubertal peak restores general and craniofacial growth in male, neonatally castrated rats. The design was a randomized, double-controlled, cross-sectional trial. Male Wistar rats were assigned by weighted randomization to be either castrated early after birth (n = 35) or not (n = 15). On day 57, a 1.5-cm Silastic tube with testosterone was implanted in 18 of the castrated rats. On day 70 and day 110, body length, weight, and craniofacial growth were measured together with the weight of the prostate, and blood samples taken. The exogenous testosterone resulted in a significant increase in serum testosterone and prostate weight. All measures of general and craniofacial growth had higher mean values in the non-castrated control group than in the castrated group, while in the testosterone-implant group the mean values lay between these of the castrated animals and the non-castrated controls. Two-way ANOVA indicated a significant effect of the testosterone administration on lower-incisor growth and the size of the total skull vault.

Influence of long-term simmondsin administration on thyroid hormone levels in adult rats

Treatment of adult rats for 28 days with 0.50% of simmondsin induced a reduction of food intake of about 40%. The degree of emaciation was the same in simmondsin treated rats (SM) and pair-fed controls (PF). Diurnal variation of plasma thyroid hormone concentrations was determined. The reduction in food intake induced a decrease of mean 24 h plasma T3, T4 and TSH concentrations. Plasma T4 concentrations were decreased more in SM than in PF at almost all times of the day. No difference was seen between SM and PF for plasma T3 and TSH concentrations. Liver outer ring deiodinating activity (type I) remained unchanged compared to controls in PF and SM, but liver inner ring deiodinating activity (type III) was increased 4 fold in both SM and PF. It was concluded that the food intake reduction induced by simmondsin produced a decrease in plasma TSH concentrations which in turn reduced plasma T4 concentrations. Decreased plasma T4 concentrations together with an increased degradation of plasma T3 resulted in lower plasma T3 concentrations.

Rat monoclonal antibodies against Aspergillus galactomannan

Monoclonal antibodies (MAbs) against Aspergillus fumigatus galactomannan were produced in rats. Seven of them, EB-A1 through EB-A7, were characterized in more detail. They were all immunoglobulin M antibodies, reacting in an indirect enzyme-linked immunosorbent assay with purified A. fumigatus galactomannan, with avidity constants of between 2 x 10(9) and 5 x 10(9)/M. Enzyme-linked immunosorbent assay inhibition experiments with modified galactomannan and synthetic oligomers of beta (1----5)galactofuranose demonstrated that the MAbs bound to an epitope located on the beta(1----5)galactofuranose-containing side chains of the galactomannan molecule. An identical or similar epitope also seemed to be present in other fungi. Immunofluorescence and immunoelectron microscopy experiments with EB-A2 revealed the presence of the antigen in the fungal wall and inside the cell. Immunoblotting experiments demonstrated that the epitope recognized by the MAbs was a common oligosaccharide moiety of a wide range of intracellular and extracellular glycoproteins in A. fumigatus. The characteristics of the MAbs justify their use in the diagnosis of invasive aspergillosis by antigen detection.

Stimulation of thyroid function by several pituitary hormones results in an increase in plasma thyroxine and reverse triiodothyronine in tilapia (Tilapia nilotica)

In this study, intravenous injection of several doses of porcine follicle stimulating hormone (pFSH: 0.002, 0.01, 0.05, and 0.5 micrograms/g body wt), bovine TSH (bTSH: 0.5 micrograms/g body wt), and ovine growth hormone (oGH: 0.04, 0.02, and 0.4 microgram/g body wt) stimulated an increase in plasma thyroxine (T4) and reverse triiodothyronine (rT3) in tilapia. This effect occurred in a dose-dependent manner. pFSH was the most potent in stimulating thyroid function. The dose of 0.002 microgram pFSH/g body wt increased plasma levels of T4 over control levels (2.59 +/- 0.16 ng/ml) about 2.5-fold within 4 hr, whereas a concentration of 0.5 micrograms/g body wt caused a great and prolonged increase of T4 and rT3 levels. Control levels (2.59 +/- 0.16 ng/ml for T4 and 40.37 +/- 8.60 pg/ml for rT3) were increased 19- and 22-fold respectively, over 24 hr. An increase of T4 and rT3 levels occurred also after injection of total hypophyseal extract and Con A II glycoprotein fraction of a tilapia pituitary homogenate, whereas the protein fraction failed to alter plasma concentrations of T4 and rT3. rT3 levels were also significantly increased at 2 hr, but not at 1 hr, after injection of T4. Basal T3 levels (1.90 +/- 0.22 ng/ml) were reduced by half over 24 hr in all experiments. These results suggest the existence, in tilapia, of a 5-D pathway deiodination of T4 which is pituitary independent. Stimulation of T4 release is always followed by an increase in plasma rT3 levels.

Hypothalamic hormones that release growth hormone stimulate hepatic 5'-monodeiodination activity in the chick embryo

Plasma GH, tri-iodothyronine (T3), thyroxine (T4) and liver 5'-monodeiodination (5'-D) activity were measured in 18-day-old chick embryos injected with thyrotrophin-releasing hormone (TRH) and human pancreatic growth hormone releasing factor (hpGRF). Injections of 0.1 and 1 microgram TRH and 1.5 micrograms hpGRF increased the concentration of plasma GH while injection of 15 micrograms hpGRF had no effect. Concentrations of plasma T3 were raised after injection of TRH or hpGRF. Injections of TRH but not of hpGRF raised the concentration of plasma T4. The increases in concentration of plasma T3 after injection of TRH or hpGRF were parallelled by increases in liver 5'-D activity. An injection of 0.25 micrograms T4 significantly raised the concentration of T4 in plasma but had no effect on plasma T3 or liver 5'-D activity. It is concluded that the release of chicken GH by TRH or hpGRF is responsible for the observed increase in plasma concentration of T3 and liver 5'-D activity.

Measurement of urokinase-type plasminogen activator (u-PA) with an enzyme-linked immunosorbent assay (ELISA) based on three murine monoclonal antibodies

An enzyme-linked immunosorbent assay (ELISA) for the measurement of urokinase-type plasminogen activator (u-PA) was developed. Three murine monoclonal antibodies to single chain urokinase-type plasminogen activator (scu-PA) were isolated and shown to react with non-overlapping epitopes in scu-PA. Two of the three antibodies were coated onto microtiter plates and bound u-PA was quantitated with the third antibody conjugated to horseradish peroxidase. The assay was equally sensitive to Mr 54,000 u-PA in the single chain or two-chain form but did not respond to Mr 33,000 urokinase. The lower limit of sensitivity of the assay was 0.1 ng/ml in buffer and 1 ng/ml in plasma. Coefficients of variation of the assay at physiological levels of u-PA were 6.5 percent within assays and 13 percent between assays. The level of u-PA in normal resting plasma was 1.9 +/- 0.66 ng/ml (mean +/- SD, n = 54). The assay can be performed within one working day and provides an efficient, reproducible, and stable means for the measurement of u-PA in biological fluids. As such it may facilitate physiological and pharmacological studies of urokinase-type plasminogen activators in man.

Fetal growth inhibition and decreased thyroid activity after injection of oestradiol benzoate into pregnant rats

Pregnant rats were subcutaneously injected daily with 10 μg oestradiol benzoate (OB) and/or 1 mg bromocriptine starting on day 15 of gestation. After treatment with OB, but not bromocriptine, lower fetal body weight, fetal length and placental weight were observed. The administration of bromocriptine did not influence maternal plasma levels of prolactin, but fetal levels were decreased on day 22 of gestation. Oestradiol benzoate raised prolactin concentrations in maternal plasma on days 20 and 22, whereas fetal plasma levels were raised on day 22. This increase was counteracted by simultaneous administration of bromocriptine and OB, whereas impairment of fetal growth remained after treatment. A slight decline in fetal plasma levels of insulin was observed once, but thyroid content of triiodothyronine and thyroxine (T4) was decreased to a quarter and a third respectively of control levels in male and female fetuses of OB-treated rats, fetal circulating levels of T4 were also depressed. Maternal and fetal plasma glucose levels were decreased. A close correlation between T4 and placental or fetal weight was always present on day 22 of gestation. It was concluded that OB injected into pregnant rats will reach the fetal circulation as judged by increases in fetal plasma levels of prolactin. The observed fetal growth retardation after the OB injection was associated with thyroid deficiency, whereas plasma levels of prolactin and insulin were either not at all or only slightly altered. A direct effect of OB on placental blood flow and hence on the fetal food supply cannot, however, be excluded.