References of "Balthazart, Jacques"
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See detailRapid changes in production and behavioral action of estrogens.
Balthazart, Jacques ULg; Cornil, Charlotte ULg; Taziaux, Mélanie ULg et al

in Neuroscience (2006), 138(3), 783-91

It is well established that sex steroid hormones bind to nuclear receptors, which then act as transcription factors to control brain sexual differentiation and the activation of sexual behaviors ... [more ▼]

It is well established that sex steroid hormones bind to nuclear receptors, which then act as transcription factors to control brain sexual differentiation and the activation of sexual behaviors. Estrogens locally produced in the brain exert their behavioral effects in this way but mounting evidence indicates that estrogens also can influence brain functioning more rapidly via non-genomic mechanisms. We recently reported that, in Japanese quail, the activity of preoptic estrogen synthase (aromatase) can be modulated quite rapidly (within minutes) by non-genomic mechanisms, including calcium-dependent phosphorylations. Behavioral studies further demonstrated that rapid changes in estrogen bioavailability, resulting either from a single injection of a high dose of estradiol or from the acute inhibition of aromatase activity, significantly affect the expression of both appetitive and consummatory aspects of male sexual behavior with latencies ranging between 15 and 30 min. Together these data indicate that the bioavailability of estrogens in the brain can change on different time-scales (long- and short-term) that match well with the genomic and non-genomic actions of this steroid and underlie two complementary mechanisms through which estrogens modulate behavior. Estrogens produced locally in the brain should therefore be considered not only as neuroactive steroids but they also display many (if not all) functional characteristics of neuromodulators and perhaps neurotransmitters. [less ▲]

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See detailRapid testosterone-induced apparent diffusion coefficient (ADC) changes in the sexually dimorphic medial preoptic nucleus of male Japanese quail.
Van Der Linden, Annemie; De Groof, Geert; Charlier, Thierry ULg et al

Poster (2006)

Testosterone (T) influences the volume and cellular characteristics of a variety of steroid-dependent brain nuclei in many vertebrates. In castrated quail, the volume of the sexually dimorphic (males ... [more ▼]

Testosterone (T) influences the volume and cellular characteristics of a variety of steroid-dependent brain nuclei in many vertebrates. In castrated quail, the volume of the sexually dimorphic (males > females) medial preoptic nucleus (POM), a key area in the control of male sexual behavior, is markedly increased by T but previous studies always assessed this effect after a period of 8-14 days and its specific time-course was unknown. We recently found that following treatment with T, the POM volume increases in a time-dependent fashion: a significant increase was already detected after only one day and the response reached it maximum (volume doubling) after 14 days of treatment. This however raised the question of the cellular mechanism underlying such a rapid brain plasticity (increase in cell size, neuropil volume, dendritic branching, extracellular space?). To research whether a change in extra- vs. intra-cellular space could be responsible for the rapid T-induced increase in POM volume, we repeatedly analyzed by in vivo diffusion-weighted magnetic resonance imaging (DW-MRI) the brain of castrated male quail before as well as after 1, 2, 7 and 14 days of T implantation. MRI was performed on a 7T-system (Bruker) using a multislice diffusion weighted-spin echo sequence. Coronal slices with an image resolution of 100*100*500µm³ were obtained covering the whole telencephalon. Images were accurately coregistered allowing voxel-wise paired comparisons of the ADC data between the different time periods. The ADC significantly increased after one day of T treatment (696±16 vs 758±30 µm²/s, p=0.011, N=5) in POM and this effect apparently persisted during the whole experiment. By contrast, T insensitive regions like the nucleus rotundus (586±170 vs 511±26 µm²/s, p-value=0.24) and nucleus mesencephalicus lateralis, pars dorsalis (934±107 vs 911±64 µm²/s, p=0.68) were not affected after the first day nor later in the experiment. These data indicate that T increases the extracellular water volume in POM specifically, either as a result of cell shrinkage or of an increase in the space between cells, and that changes in the ratio of extra- to intra-cellular water mediate, at least in part, the fast plasticity of the POM volume observed after exposure to T. [less ▲]

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See detailPlasticity in the expression of the steroid receptor coactivator 1 in the Japanese quail brain: effect of sex, testosterone, stress and time of the day.
Charlier, Thierry ULg; Ball, G. F.; Balthazart, Jacques ULg

in Neuroscience (2006), 140(4), 1381-94

Analysis of nuclear receptor action on the eukaryotic genome highlights the importance of coactivators on gene transcription. The steroid receptor coactivator-1 in particular is the focus of an intense ... [more ▼]

Analysis of nuclear receptor action on the eukaryotic genome highlights the importance of coactivators on gene transcription. The steroid receptor coactivator-1 in particular is the focus of an intense research and physiological or behavioral studies have confirmed that it plays a major role in the modulation of steroid and thyroid receptors activity. However, little is known about the regulation of steroid receptor coactivator-1 expression the brain. The goal of this study was to determine the potential factors modulating steroid receptor coactivator-1 synthesis in Japanese quail by quantification of its mRNA with real time quantitative polymerase chain reaction and of the corresponding protein via Western blotting. Contrary to previously published results from our laboratory [Charlier TD, Lakaye B, Ball GF, Balthazart J (2002) The steroid receptor coactivator SRC-1 exhibits high expression in steroid-sensitive brain areas regulating reproductive behaviors in the quail brain. Neuroendocrinology 76:297-315], we found here that sexually mature females had a higher concentration of steroid receptor coactivator-1 in the preoptic area/hypothalamus compared with males. Steroid receptor coactivator-1 expression in the male preoptic area/hypothalamus was up-regulated by testosterone and tended to be decreased by stress. We also identified a significant correlation between the time of the day and the expression of the coactivator in the optic lobes, hippocampus, telencephalon and hindbrain but the pattern of changes in expression as a function of the time of the day varied from one brain area to another. Together, these data support the idea that steroid receptor coactivator-1 is not constitutively expressed but rather is finely regulated by steroids, stress and possibly other unidentified factors. [less ▲]

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See detailTargeting steroid receptor coactivator-1 expression with locked nucleic acids antisense reveals different thresholds for the hormonal regulation of male sexual behavior in relation to aromatase activity and protein expression.
Charlier, Thierry ULg; Harada, Nobuhiro; Ball, Gregory F et al

in Behavioural Brain Research (2006), 172(2), 333-43

Steroid receptors such as the androgen and estrogen receptors require the presence of several proteins, known as coactivators, to enhance the transcription of target genes. The first goal of the present ... [more ▼]

Steroid receptors such as the androgen and estrogen receptors require the presence of several proteins, known as coactivators, to enhance the transcription of target genes. The first goal of the present study was to define the role of SRC-1 on the steroid-dependent expression of the aromatase protein and its activity in male Japanese quail. The second goal was to analyze the rapid plasticity of the POM following antisense treatment interruption. We confirm here that the inhibition of SRC-1 expression by daily intracerebroventricular injections of locked nucleic acid antisense oligonucleotides in the third ventricle at the level of the preoptic area-hypothalamus (HPOA) significantly reduces testosterone-dependent male sexual behavior. In the first experiment, aromatase protein expression in HPOA was inhibited in SRC-1-depleted males but the enzymatic activity remained at the level measured in controls. We observed in the second experiment a recovery of the behavioral response to testosterone treatment after interruption of the antisense injection. However, several morphological characteristics of the POM were not different between the control group, the antisense-treated birds and antisense-treated birds in which treatment had been discontinued 3 days earlier. Antisense was also less effective in knocking-down SRC-1 in the present experiments as compared to our previous study. An analysis of this variation in the degree of knock-down of SRC-1 expression suggests dissociation among different aspects of steroid action on brain and behavior presumably resulting from the differential sensitivity of behavioral and neurochemical responses to the activation by testosterone and/or its estrogenic metabolites. [less ▲]

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See detailSocially induced and rapid increases in aggression are inversely related to brain aromatase activity in a sex-changing fish, Lythrypnus dalli
Black, M. P.; Balthazart, Jacques ULg; Baillien, M. et al

in Proceedings of the Royal Society B : Biological Sciences (2005), 272(1579), 2435-2440

Social interactions can generate rapid and dramatic changes in behaviour and neuroendocrine activity. We investigated the effects of a changing social environment on aggressive behaviour and brain ... [more ▼]

Social interactions can generate rapid and dramatic changes in behaviour and neuroendocrine activity. We investigated the effects of a changing social environment on aggressive behaviour and brain aromatase activity (bAA) in a sex-changing fish, Lythrypnus dalli. Aromatase is responsible for the conversion of androgen into oestradiol. Male removal from a socially stable group resulted in rapid and dramatic (>= 200%) increases in aggression in the dominant female, which will become male usually 7-10 days later. These dominant females and recently sex-changed individuals had lower bAA but similar gonadal aromatase activity (gAA) compared to control females, while established males had lower bAA than all groups and lower gAA than all groups except dominant females. Within hours of male removal, dominant females' aggressive behaviour was inversely related to bAA but not gAA. These results are novel because they are the first to: (i) demonstrate socially induced decreases in bAA levels corresponding with increased aggression, (ii) identify this process as a possible neurochemical mechanism regulating the induction of behavioural, and subsequently gonadal, sex change and (iii) show differential regulation of bAA versus gAA resulting from social manipulations. Combined with other studies, this suggests that aromatase activity may modulate fast changes in vertebrate social behaviour. [less ▲]

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See detailMale aromatase-knockout mice exhibit normal levels of activity, anxiety and "depressive-like" symptomatology
Dalla, C.; Antoniou, K.; Papadopoulou-Daifoti, Z. et al

in Behavioural Brain Research (2005), 163(2), 186-193

It is well known that estradiol derived from neural aromatization of testosterone plays a crucial role in the development of the male brain and the display of sexual behaviors in adulthood. It was ... [more ▼]

It is well known that estradiol derived from neural aromatization of testosterone plays a crucial role in the development of the male brain and the display of sexual behaviors in adulthood. It was recently found that male aromatase knockout mice (ArKO) deficient in estradiol due to a mutation in the aromatase gene have general deficits in coital behavior and are sexually less motivated. We wondered whether these behavioral deficits of ArKO males could be related to changes in activity, exploration, anxiety and "depressive-like" symptomatology. ArKO and wild type (WT) males were subjected to open field (OF), elevated plus maze (EPM), and forced swim tests (FST), after being exposed or not to chronic mild stress (CMS). CNIS was used to evaluate the impact of chronic stressful procedures and to unveil possible differences between genotypes. There was no effect of genotype on OF, EPM and FST behavioral parameters. WT and ArKO mice exposed to CMS or not exhibited the same behavioral profile during these three types of tests. However, all CMS-exposed mice (ArKO and WT) spent less time in the center of the EPM. Additionally, floating duration measured in the FST increased between two tests in both WT and ArKO mice, though that increase was less prominent in mice previously subjected to CNIS than in controls. Therefore, both ArKO and WT males displayed the same behavior and had the same response to CMS however CMS exposure slightly modified the behavior displayed by mice of both genotypes in the FST and EPM paradigms. These results show that ArKO males display normal levels of activity, exploration, anxiety and "depressive-like" symptomatology and thus their deficits in sexual behavior are specific in nature and do not result indirectly from other behavioral changes. (c) 2005 Published by Elsevier B.V. [less ▲]

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See detailRapid decreases in preoptic aromatase activity and brain monoamine concentrations after engaging in male sexual behavior
Cornil, Charlotte ULg; Dalla, C.; Papadopoulou-Daifoti, Z. et al

in Endocrinology (2005), 146(9), 3809-3820

In Japanese quail, as in rats, the expression of male sexual behavior over relatively long time periods (days to weeks) is dependent on the local production of estradiol in the preoptic area via the ... [more ▼]

In Japanese quail, as in rats, the expression of male sexual behavior over relatively long time periods (days to weeks) is dependent on the local production of estradiol in the preoptic area via the aromatization of testosterone. On a short-term basis (minutes to hours), central actions of dopamine as well as locally produced estrogens modulate behavioral expression. In rats, a view of and sexual interaction with a female increase dopamine release in the preoptic area. In quail, in vitro brain aromatase activity (AA) is rapidly modulated by calcium-dependent phosphorylations that are likely to occur in vivo as a result of changes in neurotransmitter activity. Furthermore, an acute estradiol injection rapidly stimulates copulation in quail, whereas a single injection of the aromatase inhibitor vorozole rapidly inhibits this behavior. We hypothesized that brain aromatase and dopaminergic activities are regulated in quail in association with the expression of male sexual behavior. Visual access as well as sexual interactions with a female produced a significant decrease in brain AA, which was maximal after 5 min. This expression of sexual behavior also resulted in a significant decrease in dopaminergic as well as serotonergic activity after 1 min, which returned to basal levels after 5 min. These results demonstrate for the first time that AA is rapidly modulated in vivo in parallel with changes in dopamine activity. Sexual interactions with the female decreased aromatase and dopamine activities. These data challenge established views about the causal relationships among dopamine, estrogen action, and male sexual behavior. [less ▲]

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See detailInteractions between kinases and phosphatases in the rapid control of brain aromatase
Balthazart, Jacques ULg; Baillien, M.; Ball, G. F.

in Journal of Neuroendocrinology (2005), 17(9), 553-559

Aromatization of testosterone into oestradiol plays a key role in the activation of male sexual behaviour in many vertebrate species. Rapid changes in brain aromatase activity have recently been ... [more ▼]

Aromatization of testosterone into oestradiol plays a key role in the activation of male sexual behaviour in many vertebrate species. Rapid changes in brain aromatase activity have recently been identified and the resulting changes in local oestrogen bioavailability could modulate fast behavioural responses to oestrogens. In quail hypothalamic homogenates, aromatase activity is down-regulated within minutes by calcium-dependent phosphorylations in the presence of ATP, MgCl2 and CaCl2 (ATP/Mg/Ca). Three kinases (protein kinases A and C and calmodulin kinase; PKA, PKC and CAMK) are potentially implicated in this process. If kinases decrease aromatase activity in a reversible manner, then it would be expected that the enzymatic activity would increase and/or return to baseline levels in the presence of phosphatases. We showed previously that 0.1 mM vanadate (a general inhibitor of protein phosphatases) significantly decreases aromatase activity but specific protein phosphatases that could up-regulate aromatase activity have not been identified to date. The reversibility of aromatase activity inhibition by phosphorylations was investigated in the present study using alkaline and acid phosphatase (Alk and Ac PPase). Unexpectedly, Alk PPase inhibited aromatase activity in a dose-dependent manner in the presence, as well as in the absence, of ATP/Mg/Ca. By contrast, Ac PPase completely blocked the inhibitory effects of ATP/Mg/Ca on aromatase activity, even if it moderately inhibited aromatase activity in the absence of ATP/Mg/Ca. However, the addition of Ac PPase was unable to restore aromatase activity after it had been inhibited by exposure to ATP/Mg/Ca. Taken together, these data suggest that, amongst the 15 potential consensus phosphorylation sites identified on the quail aromatase sequence, some must be constitutively phosphorylated for the enzyme to be active whereas phosphorylation of the others is involved in the rapid inhibition of aromatase activity by the competitive effects of protein kinases and phosphatases. Two out of these 15 putative phosphorylation sites occur in an environment corresponding to the consensus sites for PKC, PKA (and possibly a CAMK) and, in all probability, represent the sites whose phosphorylation rapidly blocks enzyme activity. [less ▲]

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See detailDopamine modulates male sexual behavior in Japanese quail in part via actions on noradrenergic receptors
Cornil, Charlotte ULg; Dejace, C.; Ball, G. F. et al

in Behavioural Brain Research (2005), 163(1), 42-57

In rats, dopamine (DA) facilitates male sexual behavior through its combined action on D1- and D2-like receptors, in the medial preoptic area (MPOA) as well as other brain areas. In Japanese quail ... [more ▼]

In rats, dopamine (DA) facilitates male sexual behavior through its combined action on D1- and D2-like receptors, in the medial preoptic area (MPOA) as well as other brain areas. In Japanese quail, systemic injections of dopaminergic drugs suggested a similar pharmacology but central injections have never been performed. Recent electrophysiological experiments demonstrated that DA effects in the MPOA of quail are mediated mainly through the activation of alpha(2)-noradrenergic receptors. Previous studies of DA action on behavior used specific dopaminergic agonists/antagonists and therefore unintentionally avoided the potential cross-reaction with a-receptors. The present study was thus designed to investigate directly the effects of DA on male sexual behavior and to test whether the interaction of DA with heterologous receptors affects this behavior. Intracerebroventricular (i.c.v.) injection of DA or NE inhibited copulation in a dose-dependent manner. Systemic injections of yohimbine, an alpha(2)-noradrenergic antagonist, modulated copulation in a bimodal manner depending on the dose injected. Interestingly, a behaviorally ineffective dose of yohimbine markedly reduced the inhibitory effects of DA when injected 15 min before. Together, these results show for the first time that i.c.v. injections of DA itself inhibit male sexual behavior in quail and suggest that the interaction of DA with alpha(2)-receptors has behavioral significance. (C) 2005 Elsevier B.V. All rights reserved. [less ▲]

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See detailThe effect of auditory distractors on song discrimination in male canaries (Serinus canaria)
Appeltants, D.; Gentner, T. Q.; Hulse, S. H. et al

in Behavioural Processes (2005), 69(3), 331-341

Male songbirds such as canaries produce complex learned vocalizations that are used in the context of mate attraction and territory defense. Successful mate attraction or territorial defense requires that ... [more ▼]

Male songbirds such as canaries produce complex learned vocalizations that are used in the context of mate attraction and territory defense. Successful mate attraction or territorial defense requires that a bird be able to recognize individuals based on their vocal performance and identify these songs in a noisy background. In order to learn more about how birds are able to solve this problem, we investigated, with a two-alternative choice procedure, the ability of adult male canaries to discriminate between conspecific song segments from two different birds and to maintain this discrimination when conspecific songs are superimposed with a variety of distractors. The results indicate that male canaries have the ability to discriminate, with a high level of accuracy song segments produced by two different conspecific birds. Song discrimination was partially maintained when the stimuli were masked by auditory distractors, but the accuracy of the discrimination progressively declined as a function of the number of masking distractors. The type of distractor used in the experiments (other conspecific songs or different types of artificial white noise) did not markedly affect the rate of deterioration of the song discrimination. These data indicate that adult male canaries have the perceptual abilities to discriminate and selectively attend to one ongoing sound that occurs simultaneously with one or more other sounds. The administration of a noradrenergic neurotoxin did not impair markedly the discrimination learning abilities although the number of subjects tested was too small to allow any firm conclusion. In these conditions, however, the noradrenergic lesion significantly increased the number failures to respond in the discrimination learning task suggesting a role, in canaries, of the noradrenergic system in some attentional processes underlying song learning and processing. (c) 2005 Elsevier B.V. All rights reserved. [less ▲]

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See detailTestosterone-induced singing is regulated by social status in male canaries (serinus canaria)
Carere, C.; Boseret, Géraldine ULg; Ball, G. F. et al

in Hormones & Behavior (2005, June), 48(1), 92

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See detailDistribution of Reelin and its cytoplasmic signaling protein, DAB-1 in the forebrain of male canaries
Boseret, Géraldine ULg; Ball, G. F.; Balthazart, Jacques ULg

in Hormones & Behavior (2005, June), 48(1), 90

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See detailDifferences in neural activation following expression of appetitive and consummatory male sexual behavior in the quail brain
Taziaux, Mélanie ULg; Cornil, Charlotte ULg; Dejace, C. et al

in Hormones & Behavior (2005, June), 48(1), 130

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See detailDaily changes in the expression of the steroid receptor coactivator SRC-1
Charlier, T. D.; Ball, G. F.; Balthazart, Jacques ULg

in Hormones & Behavior (2005, June), 48(1), 93

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See detailAlpha-fetoprotein (AFP) knock out mice demonstrate the protective role of AFP during brain sexual differentiation
Bakker, Julie ULg; de Mees, C.; Balthazart, Jacques ULg et al

in Hormones & Behavior (2005, June), 48(1), 87

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See detailSpatiotemporal properties of the BOLD response in the songbirds' auditory circuit during a variety of listening tasks
Van Meir, V.; Boumans, T.; De Groof, G. et al

in Neuroimage (2005), 25(4), 1242-1255

Auditory fMRI in humans has recently received increasing attention from cognitive neuroscientists as a tool to understand mental processing of learned acoustic sequences and analyzing speech recognition ... [more ▼]

Auditory fMRI in humans has recently received increasing attention from cognitive neuroscientists as a tool to understand mental processing of learned acoustic sequences and analyzing speech recognition and development of musical skills. The present study introduces this tool in a well-documented animal model for vocal learning, the songbird, and provides fundamental insight in the main technical issues associated with auditory fMRI in these songbirds. Stimulation protocols with various listening tasks lead to appropriate activation of successive relays in the songbirds' auditory pathway. The elicited BOLD response is also region and stimulus specific, and its temporal aspects provide accurate measures of the changes in brain physiology induced by the acoustic stimuli. Extensive repetition of an identical stimulus does not lead to habituation of the response in the primary or secondary telencephalic auditory regions of anesthetized subjects. The BOLD signal intensity changes during a stimulation and subsequent rest period have a very specific time course which shows a remarkable resemblance to auditory evoked BOLD responses commonly observed in human subjects. This observation indicates that auditory fMRI in the songbird may establish a link between auditory related neuro-imaging studies done in humans and the large body of neuro-ethological research on song learning and neuro-plasticity performed in songbirds. © 2005 Elsevier Inc. All rights reserved. [less ▲]

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See detailCoordinated and dissociated effects of testosterone on singing behavior and song control nuclei in canaries (Serinus canaria)
Sartor, Jennifer J.; Balthazart, Jacques ULg; Ball, Gregory F.

in Hormones & Behavior (2005), 47(4), 467-476

Temperate zone songbirds that breed seasonally exhibit pronounced differences in reproductive behaviors including song inside and outside the breeding season. Springlike long daylengths are associated ... [more ▼]

Temperate zone songbirds that breed seasonally exhibit pronounced differences in reproductive behaviors including song inside and outside the breeding season. Springlike long daylengths are associated with increases in plasma testosterone (T) concentrations, as well as with increases in singing and in the volume of several brain nuclei known to control this behavior. The mechanisms whereby T can induce changes in behavior and brain, and whether or not these effects are differentially regulated, have recently begun to be examined, as has the question of the relative contributions of T and its androgenic and estrogenic metabolites to the regulation of this seasonal behavioral and neural plasticity. In this experiment, we examined the effects of T, 5 alpha-dihydrotestosterone, or 17 beta-estradiol treatment on castrated male canaries housed on short days and compared neural and behavioral effects in these males to similarly-housed males given only blank implants. We observed that only T treatment was effective in eliciting significant increases in singing behavior after 11 days of hormone exposure. In addition, T alone was effective in increasing the volume of a key song production nucleus, HVC. However, at this time, none of the steroids had any effects on the volumes of two other song control nuclei, Area X of the medial striatum and the robust nucleus of the arcopallium (RA), that are efferent targets of HVC, known to be regulated by androgen in canaries and also to play a role in the control of adult song. T can thus enhance singing well before concomitant androgen-induced changes in the song control system are complete. (c) 2004 Elsevier Inc. All rights reserved. [less ▲]

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