Early-Life Adversity Induces Epigenetically Regulated Changes in Hippocampal Dopaminergic Molecular Pathways

Early-life adversity (ELA) represents a major risk factor for the development of behavioral dysfunctions and mental disorders later in life. On the other hand, dependent on type, time point, and duration, ELA exposure can also induce adaptations, which result in better stress coping and resilience later in life. Guided by the hypothesis that chronic exposure to ELA results in dysfunctional brain and behavior, whereas short exposure to ELA may result in resilience, the behavioral and neurobiological consequences of long-term separation stress (LTSS) and short-term separation stress (STSS) were compared in a mouse model for ELA. In line with our hypothesis, we found that LTSS induced depressive-like behavior, whereas STSS reduced depressive-like behavioral symptoms. We then tested the hypothesis that the opposite behavioral outcomes of the two stress paradigms may be mediated by functional, epigenetically regulated changes of dopaminergic modulation in the hippocampal formation. We found that STSS exposure elevated dopamine receptor D1 (DRD1) gene expression and decreased gene expression of its downstream modulator DARPP-32 (32-kDa dopamine- and cAMP-regulated phosphoprotein), which was paralleled by decreased H3 acetylation at its gene promoter region. In contrast, LTSS elevated DARPP-32 gene expression, which was not paralleled by changes in histone acetylation and DRD1 gene expression. These findings indicate that short- and long-term neonatal exposure to ELA induces changes in dopaminergic molecular pathways, some of which are epigenetically regulated and which either alleviate or aggravate depressive-like symptoms later in life.

Comparing brain activity patterns during spontaneous exploratory and cue-instructed learning using single photon-emission computed tomography (SPECT) imaging of regional cerebral blood flow in freely behaving rats

Learning can be categorized into cue-instructed and spontaneous learning types; however, so far, there is no detailed comparative analysis of specific brain pathways involved in these learning types. The aim of this study was to compare brain activity patterns during these learning tasks using the in vivo imaging technique of single photon-emission computed tomography (SPECT) of regional cerebral blood flow (rCBF). During spontaneous exploratory learning, higher levels of rCBF compared to cue-instructed learning were observed in motor control regions, including specific subregions of the motor cortex and the striatum, as well as in regions of sensory pathways including olfactory, somatosensory, and visual modalities. In addition, elevated activity was found in limbic areas, including specific subregions of the hippocampal formation, the amygdala, and the insula. The main difference between the two learning paradigms analyzed in this study was the higher rCBF observed in prefrontal cortical regions during cue-instructed learning when compared to spontaneous learning. Higher rCBF during cue-instructed learning was also observed in the anterior insular cortex and in limbic areas, including the ectorhinal and entorhinal cortexes, subregions of the hippocampus, subnuclei of the amygdala, and the septum. Many of the rCBF changes showed hemispheric lateralization. Taken together, our study is the first to compare partly lateralized brain activity patterns during two different types of learning.

Early life stress induces attention-deficit hyperactivity disorder (ADHD)-like behavioral and brain metabolic dysfunctions: functional imaging of methylphenidate treatment in a novel rodent model

In a novel animal model Octodon degus we tested the hypothesis that, in addition to genetic predisposition, early life stress (ELS) contributes to the etiology of attention-deficit hyperactivity disorder-like behavioral symptoms and the associated brain functional deficits. Since previous neurochemical observations revealed that early life stress impairs dopaminergic functions, we predicted that these symptoms can be normalized by treatment with methylphenidate. In line with our hypothesis, the behavioral analysis revealed that repeated ELS induced locomotor hyperactivity and reduced attention towards an emotionally relevant acoustic stimulus. Functional imaging using (¹⁴C)-2-fluoro-deoxyglucose-autoradiography revealed that the behavioral symptoms are paralleled by metabolic hypoactivity of prefrontal, mesolimbic and subcortical brain areas. Finally, the pharmacological intervention provided further evidence that the behavioral and metabolic dysfunctions are due to impaired dopaminergic neurotransmission. Elevating dopamine in ELS animals by methylphenidate normalized locomotor hyperactivity and attention-deficit and ameliorated brain metabolic hypoactivity in a dose-dependent manner.

4D flow magnetic resonance imaging in bicuspid aortic valve disease demonstrates altered distribution of aortic blood flow helicity

PURPOSE

Changes in aortic geometry or presence of aortic valve (AoV) disease can result in substantially altered aortic hemodynamics. Dilatation of the ascending aorta or AoV abnormalities can result in an increase in helical flow.

METHODS

4D flow magnetic resonance imaging was used to test the feasibility of quantitative helicity analysis using equidistantly distributed 2D planes along the entire aorta. The evaluation of the method included three parts: (1) the quantification of helicity in 12 healthy subjects, (2) an evaluation of observer variability and test-retest reliability, and (3) the quantification of helical flow in 16 patients with congenitally altered bicuspid AoVs.

RESULTS

Helicity quantification in healthy subjects revealed consistent directions of flow rotation along the entire aorta with high clockwise helicity in the aortic arch and an opposite rotation sense in the ascending and descending aorta. The results demonstrated good scan-rescan and inter- and intraobserver agreement of the helicity parameters. Helicity quantification in patients revealed a significant increase in absolute peak relative helicity during systole and a considerably greater heterogeneous distribution of mean helicity in the aorta.

CONCLUSION

The method has the potential to serve as a reference distribution for comparisons of helical flow between healthy subjects and patients or between different patient groups.

Kinetics of maternally acquired anti-hepatitis A antibodies: prediction of waning based on maternal or cord blood antibody levels

BACKGROUND

Timing is critical for efficient hepatitis A vaccination in high endemic areas as high levels of maternal IgG antibodies against the hepatitis A virus (HAV) present in the first year of life may impede the vaccine response.

OBJECTIVES

To describe the kinetics of the decline of anti-HAV maternal antibodies, and to estimate the time of complete loss of maternal antibodies in infants in León, Nicaragua, a region in which almost all mothers are anti-HAV seropositive.

METHODS

We collected cord blood samples from 99 healthy newborns together with 49 corresponding maternal blood samples, as well as further blood samples at 2 and 7 months of age. Anti-HAV IgG antibody levels were measured by enzyme immunoassay (EIA). We predicted the time when antibodies would fall below 10 mIU/ml, the presumed lowest level of seroprotection.

RESULTS

Seroprevalence was 100% at birth (GMC 8392 mIU/ml); maternal and cord blood antibody concentrations were similar. The maternal antibody levels of the infants decreased exponentially with age and the half-life of the maternal antibody was estimated to be 40 days. The relationship between the antibody concentration at birth and time until full waning was described as: critical age (months)=3.355+1.969 × log(10)(Ab-level at birth). The survival model estimated that loss of passive immunity will have occurred in 95% of infants by the age of 13.2 months.

CONCLUSIONS

Complete waning of maternal anti-HAV antibodies may take until early in the second year of life. The here-derived formula relating maternal or cord blood antibody concentrations to the age at which passive immunity is lost may be used to determine the optimal age of childhood HAV vaccination.

Epicormic ontogeny in Quercus petraea constrains the highly plausible control of epicormic sprouting by water and carbohydrates

BACKGROUND AND AIMS

There is increasing evidence that suppressed bud burst and thus epicormic shoot emergence (sprouting) are controlled by water-carbohydrate supplies to entire trees and buds. This direct evidence is still lacking for oak. In other respects, recent studies focused on sessile oak, Quercus petraea, have confirmed the important constraints of sprouting by epicormic ontogeny. The main objective of this paper was thus to provide provisional confirmation of the water-carbohydrate control and direct evidence of the ontogenic constraints by bringing together results already published in separate studies on water status and distribution of carbohydrates, and on accompanying vegetation and epicormics, which also quantify epicormic ontogeny.

METHODS

This paper analyses results gained from a sessile oak experiment in which part of the site was free from fairly tall, dense accompanying vegetation. This experiment was initially focused on stand water status and more recently on the carbohydrate distribution of dominant trees. External observations of the epicormic composition and internal observations with X-ray computer tomography were undertaken on 60 and six trees, respectively.

KEY RESULTS

Sprouting was more intense in the part of the stand free from accompanying vegetation and on upper trunk segments. A clear effect of epicormic ontogeny was demonstrated as well: the more epicormics a trunk segment bears, the more chances it had to bear sprouts.

CONCLUSIONS

These results indirectly infer water-carbohydrate control and show direct evidence of constraints by epicormic ontogeny. These results have far-reaching consequences related to the quantification of all functions fulfilled by any type of epicormic structure in any part of the tree.

Dampening of blood-flow pulsatility along the carotid siphon: does form follow function?

BACKGROUND AND PURPOSE

The tortuous distal part of the ICA may have an attenuating effect on pulsatile arterial flow. We investigated local arterial blood flow patterns in the ICA proximal and distal to the carotid siphon to detect quantitative waveform changes.

MATERIALS AND METHODS

Arterial flow patterns were analyzed by using flow-sensitized 4D PC MR imaging (time-resolved 3D PCMR) at 3T in 17 healthy volunteers. Time-resolved blood flow velocities were extracted from the source data at the C4 and C7 segments of the ICA. PI, RI, and PA were calculated by using time-resolved flow volume. A linear mixed-effects model was applied to compare values at C4 and C7. Furthermore, 3D blood flow visualization was performed for all 34 ICAs.

RESULTS

PI, RI, and PA were significantly lower at the distal C7 segment compared with the proximal C4 segment of the ICA (P < .0001). Helical flow patterns were observed in 5 ICAs of 4 subjects.

CONCLUSIONS

Arterial flow patterns showed a significant reduction in PI, RI, and PA when compared distal to proximal to the carotid siphon. The observed attenuation of flow pulsatility is most likely related to the contorted shape of the distal ICA and may bear a protective effect for downstream cerebral vasculature.

Genome-wide screen reveals WNT11, a non-canonical WNT gene, as a direct target of ETS transcription factor ERG

E26 transforming sequence-related gene (ERG) is a transcription factor involved in normal hematopoiesis and is dysregulated in leukemia. ERG mRNA overexpression was associated with poor prognosis in a subset of patients with T-cell acute lymphoblastic leukemia (T-ALL) and acute myeloid leukemia (AML). Herein, a genome-wide screen of ERG target genes was conducted by chromatin immunoprecipitation-on-chip (ChIP-chip) in Jurkat cells. In this screen, 342 significant annotated genes were derived from this global approach. Notably, ERG-enriched targets included WNT signaling genes: WNT11, WNT2, WNT9A, CCND1 and FZD7. Furthermore, chromatin immunoprecipitation (ChIP) of normal and primary leukemia bone marrow material also confirmed WNT11 as a target of ERG in six of seven patient samples. A larger sampling of patient diagnostic material revealed that ERG and WNT11 mRNA were co-expressed in 80% of AML (n=30) and 40% in T-ALL (n=30) bone marrow samples. Small interfering RNA (siRNA)-mediated knockdown of ERG confirmed downregulation of WNT11 transcripts. Conversely, in a tet-on ERG-inducible assay, WNT11 transcripts were co-stimulated. A WNT pathway agonist, 6-bromoindirubin-3-oxime (BIO), was used to determine the effect of cell growth on the ERG-inducible cells. The addition of BIO resulted in an ERG-dependent proliferative growth advantage over ERG-uninduced cells. Finally, ERG induction prompted morphological transformation whereby round unpolarized K562 cells developed elongated protrusions and became polarized. This morphological transformation could effectively be inhibited with BIO and with siRNA knockdown of WNT11. In conclusion, ERG transcriptional networks in leukemia converge on WNT signaling targets. Specifically, WNT11 emerged as a direct target of ERG. Potent ERG induction promoted morphological transformation through WNT11 signals. The findings in this study unravel new ERG-directed molecular signals that may contribute to the resistance of current therapies in acute leukemia patients with poor prognosis characterized by high ERG mRNA expression.

Portable laser-heating system for diamond anvil cells

The diamond anvil cell (DAC) technique coupled with laser heating has become the most successful method for studying materials in the multimegabar pressure range at high temperatures. However, so far all DAC laser-heating systems have been stationary: they are linked either to certain equipment or to a beamline. Here, a portable laser-heating system for DACs has been developed which can be moved between various analytical facilities, including transfer from in-house to a synchrotron or between synchrotron beamlines. Application of the system is demonstrated in an example of nuclear inelastic scattering measurements of ferropericlase (Mg(0.88)Fe(0.12))O and h.c.p.-Fe(0.9)Ni(0.1) alloy, and X-ray absorption near-edge spectroscopy of (Mg(0.85)Fe(0.15))SiO(3) majorite at high pressures and temperatures. Our results indicate that sound velocities of h.c.p.-Fe(0.9)Ni(0.1) at pressures up to 50 GPa and high temperatures do not follow a linear relation with density.

Parity violation constraints using cosmic microwave background polarization spectra from 2006 and 2007 observations by the QUaD polarimeter

We constrain parity-violating interactions to the surface of last scattering using spectra from the QUaD experiment's second and third seasons of observations by searching for a possible systematic rotation of the polarization directions of cosmic microwave background photons. We measure the rotation angle due to such a possible "cosmological birefringence" to be 0.55 degrees +/-0.82 degrees (random) +/-0.5 degrees (systematic) using QUaD's 100 and 150 GHz temperature-curl and gradient-curl spectra over the spectra over the multipole range 200<l<2000, consistent with null, and constrain Lorentz-violating interactions to <2 x 10;{-43} GeV (68% confidence limit). This is the best constraint to date on electrodynamic parity violation on cosmological scales.

3D blood flow characteristics in the carotid artery bifurcation assessed by flow-sensitive 4D MRI at 3T

To determine three-dimensional (3D) blood flow patterns in the carotid bifurcation, 10 healthy volunteers and nine patients with internal carotid artery (ICA) stenosis > or =50% were examined by flow-sensitive 4D MRI at 3T. Absolute and mean blood velocities, pulsatility index (PI), and resistance index (RI) were measured in the common carotid arteries (CCAs) by duplex sonography (DS) and compared with flow-sensitive 4D MRI. Furthermore, 3D MRI blood flow patterns in the carotid bifurcation of volunteers and patients before and after recanalization were graded by two independent readers. Blood flow velocities measured by MRI were 31-39% lower than in DS. However, PI and RI differed by only 13-16%. Rating of 3D flow characteristics in the ICA revealed consistent patterns for filling and helical flow in volunteers. In patients with ICA stenosis, 3D blood flow visualization was successfully employed to detect markedly altered filling and helical flow patterns (forward-moving spiral flow) in the ICA bulb and to evaluate the effect of revascularization, which restored filling and helical flow. Our results demonstrate the feasibility of flow-sensitive 4D MRI for the quantification and 3D visualization of physiological and pathological flow patterns in the carotid artery bifurcation.

Quantitative 2D and 3D phase contrast MRI: optimized analysis of blood flow and vessel wall parameters

Quantification of CINE phase contrast (PC)-MRI data is a challenging task because of the limited spatiotemporal resolution and signal-to-noise ratio (SNR). The method presented in this work combines B-spline interpolation and Green's theorem to provide optimized quantification of blood flow and vessel wall parameters. The B-spline model provided optimal derivatives of the measured three-directional blood velocities onto the vessel contour, as required for vectorial wall shear stress (WSS) computation. Eight planes distributed along the entire thoracic aorta were evaluated in a 19-volunteer study using both high-spatiotemporal-resolution planar two-dimensional (2D)-CINE-PC ( approximately 1.4 x 1.4 mm(2)/24.4 ms) and lower-resolution 3D-CINE-PC ( approximately 2.8 x 1.6 x 3 mm(3)/48.6 ms) with three-directional velocity encoding. Synthetic data, error propagation, and interindividual, intermodality, and interobserver variability were used to evaluate the reliability and reproducibility of the method. While the impact of MR measurement noise was only minor, the limited resolution of PC-MRI introduced systematic WSS underestimations. In vivo data demonstrated close agreement for flow and WSS between 2D- and 3D-CINE-PC as well as observers, and confirmed the reliability of the method. WSS analysis along the aorta revealed the presence of a circumferential WSS component accounting for 10-20%. Initial results in a patient with atherosclerosis suggest the potential of the method for understanding the formation and progression of cardiovascular diseases.

3D MR flow analysis in realistic rapid-prototyping model systems of the thoracic aorta: comparison with in vivo data and computational fluid dynamics in identical vessel geometries

The knowledge of local vascular anatomy and function in the human body is of high interest for the diagnosis and treatment of cardiovascular disease. A comprehensive analysis of the hemodynamics in the thoracic aorta is presented based on the integration of flow-sensitive 4D MRI with state-of-the-art rapid prototyping technology and computational fluid dynamics (CFD). Rapid prototyping was used to transform aortic geometries as measured by contrast-enhanced MR angiography into realistic vascular models with large anatomical coverage. Integration into a flow circuit with patient-specific pulsatile in-flow conditions and application of flow-sensitive 4D MRI permitted detailed analysis of local and global 3D flow dynamics in a realistic vascular geometry. Visualization of characteristic 3D flow patterns and quantitative comparisons of the in vitro experiments with in vivo data and CFD simulations in identical vascular geometries were performed to evaluate the accuracy of vascular model systems. The results indicate the potential of such patient-specific model systems for detailed experimental simulation of realistic vascular hemodynamics. Further studies are warranted to examine the influence of refined boundary conditions of the human circulatory system such as fluid-wall interaction and their effect on normal and pathological blood flow characteristics associated with vascular geometry.

Weaning age, social isolation, and gender, interact to determine adult explorative and social behavior, and dendritic and spine morphology in prefrontal cortex of rats

We tested the effect of weaning at 21 or 30 days, followed by individual or group housing, on explorative and social behavior in adult male and female rats, and in males, on dendritic length and spine density in prefrontal cortex. In the open field, rats weaned early were the most active, while those weaned late and group housed were the most explorative. In the social interaction test, behavior in adult females was relatively impervious to weaning age or rearing condition. Isolated males sought out social interaction, whereas, group-reared males tended to avoid it. Social behaviors in males weaned early or group-reared correlated with decreased dendrite length and spine density, whereas, non-social behaviors correlated with increased dendritic length. Such changes are consistent with neural pruning in the development of social behavior. Although our experimental manipulations were mild, and serve as standard rearing conditions in many laboratories, their effects on brain and behavior were marked, and differed by gender. Early rearing conditions may have few appreciable effects when studied in isolation, but their interactive effects on adult social behavior are significant and varied.

Die Analyse aortaler Hämodynamik und Gefäßwandparameter mittels fluss-sensitiver in-vivo 4D-MRT bei 3 Tesla

Modern phase contrast MR imaging at 3 Tesla allows the depiction of 3D morphology as well as the acquisition of time-resolved blood flow velocities in 3 directions. In combination with state-of-the-art visualization and data processing software, the qualitative and quantitative analysis of hemodynamic changes associated with vascular pathologies is possible. The 4D nature of the acquired data permits free orientation within the vascular system of interest and offers the opportunity to quantify blood flow and derived vessel wall parameters at any desired location within the data volume without being dependent on predefined 2D slices. The technique has the potential of overcoming the limitations of current diagnostic strategies and of implementing new diagnostic parameters. In light of the recent discussions regarding the influence of the wall shear stress and the oscillatory shear index on the genesis of arteriosclerosis and dilatative vascular processes, flow-sensitive 4D MRI may provide the missing diagnostic link. Instead of relying on experience-based parameters such as aneurysm size, new hemodynamic considerations can deepen our understanding of vascular pathologies. This overview reviews the underlying methodology at 3T, the literature on time-resolved 3D MR velocity mapping, and presents case examples. By presenting the pre- and postoperative assessment of hemodynamics in a thoracic aortic aneurysm and the detailed analysis of blood flow in a patient with coarctation we underline the potential of time-resolved 3D phase contrast MR at 3T for hemodynamic assessment of vascular pathologies, especially in the thoracic aorta.

IL-15 protects intestinal epithelial cells

IL-15, a T-cell growth factor, has been shown to be increased in inflammatory bowel disease (IBD). It has been suggested that neutralization of IL-15 could protect from T cell-dependent autoimmune inflammation. On the other hand, an anti-apoptotic effect of IL-15 has been demonstrated in kidney epithelial cells during nephritis. We therefore tested the role of IL-15 in two different experimental models of colitis in vivo, and in models of intestinal epithelial cell (IEC) apoptosis in vitro. IL-15 blockade in chronic dextran sulphate sodium-induced colitis resulted in aggravation of the disease with a significantly 2.1-fold increased epithelial damage score compared to controls. TUNEL staining clearly revealed increased apoptosis. IL-6, TNF and IFN-gamma secretion by mesenteric lymph node cells were increased. In the T cell-dependent SCID transfer model of colitis IL-15 neutralization reduced the inflammatory infiltration and proinflammatory cytokine production. Despite that, the intestinal epithelial damage was not reduced. In vitro, IL-15 pre-incubation prevented up to 75% of CH11 antibody-induced apoptosis in SW-480 cells and reduced caspase-3 activity. According to this, endogenously produced IL-15 in chronic colitis does not only act as a proinflammatory cytokine but has at the same time the potential to reduce mucosal damage by preventing IEC apoptosis.

Regional and cellular distribution of the extracellular matrix protein tenascin-C in the chick forebrain and its role in neonatal learning

The juvenile brain's pronounced synaptic plasticity in response to early experience and learning events is related to the fact that the genetically pre-programmed molecular machinery mediating neuronal development and synapse formation, is activated throughout postnatal brain development and thereby can be recruited for learning and long-term memory formation. In situ hybridization and immunocytochemistry experiments revealed that tenascin-C, one candidate molecule which we suspect to be involved in neonatal learning, is expressed in the forebrain of domestic chicks around the sensitive period during which auditory filial imprinting takes place. The involvement of tenascin-C in this juvenile learning task was tested by injections of monoclonal antibodies directed to distinct domains of the tenascin-C molecule into the avian prefrontal cortex analog, the medio-rostral nidopallium/mesopallium (formerly termed medio-rostral neostriatum/hyperstriatum ventrale), a forebrain area which has been shown to be critically involved in auditory filial imprinting. Injections of monoclonal antibody Tn 68, which is directed against a cell-binding domain of the tenascin-C molecule, strongly reduced the imprinting rate, as opposed to injections of the monoclonal antibody Tn 578, which binds to a domain involved in neurite outgrowth. Double labeling immunohistochemistry revealed that tenascin-C is associated with neurons which express the Ca(2+)-binding protein parvalbumin, and displays a staining pattern highly reminiscent of perineuronal nets of the extracellular matrix. These results indicate that a distinct domain of tenascin-C is functionally involved in the juvenile learning process of filial imprinting and further suggest a critical role of a specific neuronal subpopulation.

Early neonatal and postweaning social emotional deprivation interferes with the maturation of serotonergic and tyrosine hydroxylase-immunoreactive afferent fiber systems in the rodent nucleus accumbens, hippocampus and amygdala

The impact of early emotional experience on the development of serotonergic and dopaminergic fiber innervation of the nucleus accumbens, hippocampal formation and the amygdala was quantitatively investigated in the precocious rodent Octodon degus. Two animal groups were compared: 1) degus which were repeatedly separated from their parents during the first three postnatal weeks, after weaning they were individually reared in chronic social isolation and 2) controls which were reared undisturbed with their families. In the deprived animals 5-hydroxytryptamine-immunoreactive fiber densities were increased in the core region of the nucleus accumbens (up to 126%), in the central nucleus of the amygdala (up to 112%) and in the outer subregion of the dentate gyrus stratum moleculare (up to 149%), whereas decreased fiber densities were detected in the dentate subgranular layer (down to 86%) and in the stratum lacunosum of the hippocampal cornu ammonis region 1 (down to 86%). Tyrosine hydroxylase-immunoreactive fiber densities were increased in the core (up to 115%) and shell region (up to 113%) of the nucleus accumbens of deprived animals, whereas decreased fiber densities (down to 84%) were observed in the hilus of the dentate gyrus. In the stratum granulosum and subgranular layer the fiber densities increased up to 168% and 127% respectively. In summary, these results indicate that the postnatal establishment of the monoaminergic innervation of limbic areas is modulated in response to early emotional experience, and that this environmental morphological adaptation is highly region specific.

Exposure to retinoic acids in non-pregnant women following high vitamin A intake with a liver meal

Animal liver is a rich source of vitamin A. Due to retinoic acid (RA) metabolites, vitamin A has a teratogenic potential and women are generally advised to avoid or to limit the consumption of liver during pregnancy. In a recent study in non-pregnant female volunteers following single and repeated doses of up to 30,000 IU/day of vitamin A as a supplement, the plasma concentration time curve of all-trans RA acid showed a diurnal-like profile. But, the overall exposure (AUC24h) remained essentially unaltered whereas AUC24h increased linearly with dose for 13-cis and 13-cis-4-oxo RA. The current study in non-pregnant female volunteers showed that a single high vitamin A intake with a liver meal (up to 120,000 IU) exhibited a similar diurnal-like plasma concentration time curve for all-trans RA and its overall exposure remained also unaltered, despite a temporary two-fold increase in peak plasma concentration. Concentrations of 13-cis and 13-cis-4-oxo RA increased several-fold after a liver meal, and exposure (AUC24h) increased three- to five-fold. Pooling our results with data in the literature revealed a linear relation between the mean AUC24h of 13-cis and 13-cis-4-oxo RA and vitamin A intake with liver. Metabolism to all-trans RA of vitamin A with liver seems not to be of safety concern. However, the observed increase of plasma concentrations and the dose-dependent increase in exposure to 13-cis and 13-cis-4-oxo RA support the current safety recommendations on vitamin A intake and suggest that women should be cautious regarding their consumption of liver-containing meals during pregnancy.

Analysis of intestinal haem-oxygenase-1 (HO-1) in clinical and experimental colitis

Haem-oxygenase-1 (HO-1) has been shown to exert anti-inflammatory, anti-apoptotic and anti-proliferative effects. We investigated HO-1 expression in patients with inflammatory bowel disease (IBD) and could demonstrate a scattered expression of HO-1 in the intestinal epithelium of severely inflamed colonic mucosa of patients with IBD compared to control specimens such as diverticulitis, suggesting dysregulated expression in IBD. To further analyse potential mechanisms of HO-1 induction in the intestine we employed an in vitro epithelial cell apoptosis model and an experimental colitis model. In vitro induction of HO-1 by the HO-1 inducer cobalt protoporphyrin (CoPP) resulted in a dose-dependent down-regulation of caspase-3 activation in HT-29 cells, indicating an anti-apoptotic function of HO-1 in the intestine. In vivo, preventive HO-1 induction by CoPP in acute dextran sodium sulphate (DSS)-induced colitis led to a significant down-regulation of colonic inflammation (P < 0.01) with a concomitant reduction in interferon (IFN)-gamma - but unaffected interleukin (IL)-10-secretion by isolated mesenteric lymph nodes (P < 0.01). Additionally, TUNEL staining of colonic sections demonstrated fewer apoptotic epithelial cells in the colon of CoPP treated animals. No beneficial effects were observed if HO-1 was induced by CoPP after the onset of acute colitis or in chronic DSS-induced colitis. In conclusion, the data suggest a protective role of HO-1 if it is induced before the onset of inflammation. However, as shown by the lack of effects in established acute or in chronic colitis, the induction of HO-1 may not be a promising approach for the treatment of IBD.

Exposure to retinyl esters, retinol, and retinoic acids in non-pregnant women following increasing single and repeated oral doses of vitamin A

BACKGROUND

High intakes of vitamin A cause congenital malformations in experimental animals with elevated generation of retinoic acids (RA). Results in humans are conflicting.

OBJECTIVE

To evaluate plasma concentration-time curves of retinyl esters, retinol and their metabolites at increasing doses of vitamin A.

METHODS

An open-label dose-response study. Non-pregnant females (3 groups with n = 12; 18-40 years) received once daily oral doses of vitamin A palmitate up to 30,000 IU/day over 21 days. The area under the plasma concentration-time curve (AUC(24h)) served as indicator for exposure.

RESULTS

AUC(24h) of retinyl esters increased linearly with dose. Retinol concentrations were unaffected. All-trans RA exhibited a diurnal-like concentration-time profile (Cmax at 3 h; Cmin at 8 h), concentrations decreasing below pre-dose levels at 5 h and regaining pre-dose levels at 16 h. The maximum temporary increase in exposure was 33% (single dose) and 19% (repeated doses) above baseline, but AUC(24h) remained unaltered. AUC(24h) increased linearly with dose for 13-cis RA and 13-cis-4-oxo RA. Repeated doses caused a 25% increase in exposure with the highest vitamin A intake. Accumulation of 13-cis-4-oxo RA at 30,000 IU/day doubled compared to the 4,000 IU/day intake.

CONCLUSION

Repeated oral doses of up to 30,000 IU of vitamin A in addition to dietary vitamin A were without safety concern. Safe doses are probably higher, since plasma concentrations and exposure to RA remained at levels earlier shown to be without increased risk of teratogenicity in pregnant women.

The chicken immediate-early gene ZENK is expressed in the medio-rostral neostriatum/hyperstriatum ventrale, a brain region involved in acoustic imprinting, and is up-regulated after exposure to an auditory stimulus

The immediate-early gene zenk (an acronym for the avian orthologue of the mammalian genes zif-268, egr-1, ngfi-a and krox-24) has been extensively employed, in studies on oscine birds, as a marker of neuronal activity to reveal forebrain structures that are involved in the memory processes associated with the acquisition, perception and production of song. Audition-induced expression of this gene, in brain, has also recently been reported for the domestic chicken (Gallus gallus domesticus) and the Japanese quail (Coturnix coturnix japonica). Whilst the anatomical distribution of zenk expression was described for the quail, corresponding data for the chicken were not reported. We have, therefore, used in situ hybridisation to localise the mRNA that encodes the product of the zenk gene (which we call ZENK) within the brain of the 1-day-old chick. We demonstrate that this transcript is present in a number of forebrain structures including the medio-rostral neostriatum/hyperstriatum ventrale (MNH), a region that has been strongly implicated in auditory imprinting (which is a form of recognition memory), and Field L, the avian analog of the mammalian auditory cortex. Because of this pattern of gene expression, we have compared the level of the ZENK mRNA in chicks that have been subjected to a 30-min acoustic imprinting paradigm and in untrained controls. Our results reveal a significant increase (P< or =0.05) in the level of the ZENK mRNA in MNH and Field L, and in the two forebrain hemispheres; no increase was seen in the ectostriatum, which is a visual projection area. The data obtained implicate the immediate-early gene, zenk, in auditory imprinting, which is an established model of juvenile learning. In addition, our results indicate that the ZENK mRNA may be used as a molecular marker for MNH, a region that is difficult to anatomically and histochemically delineate.

Early socio-emotional experience induces expression of the immediate-early gene Arc/arg3.1 (activity-regulated cytoskeleton-associated protein/activity-regulated gene) in learning-relevant brain regions of the newborn chick

We have cloned a full-length complementary DNA from the chicken (Gallus gallus domesticus), which encodes a polypeptide that exhibits approximately 75% identity to the product of the mammalian gene Arc (activity-regulated cytoskeleton-associated protein), also known as arg3.1 (activity-regulated gene). Since this gene is an immediate-early gene that has been suggested to play a role in synaptic plasticity and learning and memory processes, its expression has been analyzed in a juvenile form of learning, namely, filial imprinting. Our results demonstrate that Arc/arg3.1 mRNA is detectable in the newborn chick brain, and that at this early age the level of this transcript can be altered by brief sensory/emotional experience. After postnatal exposure to a novel 30-min auditory imprinting stimulus, Arc/arg3.1 mRNA was found to be significantly increased in two higher associative areas, the mesopallium intermediomediale (P = 0.002) and the nidopallium dorso-caudale (P = 0.031), compared with naïve controls. The transcript level was also significantly elevated after imprinting in Area L pallii (P=0.045), which is analogous to the mammalian auditory cortex. In addition, increases were seen in the medio-rostral nidopallium/mesopallium (P = 0.054), which is presumed to be the analog of the mammalian prefrontal cortex, and the hyperpallium intercalatum (P = 0.054), but these did not quite reach significance. We discuss these data in the light of those obtained in an earlier study, in the same paradigm, for the avian immediate-early gene, zenk (an acronym for zif-268, egr-1, ngfi-a and krox-24, which are different names for the orthologous mammalian gene). We conclude that, although both the Arc/arg3.1 and zenk genes are induced by auditory imprinting, they are significantly up-regulated in different learning-relevant brain regions. It is, therefore, evident that they must be activated by different mechanisms.

Intracellular acidification by inhibition of the Na+/H+-exchanger leads to caspase-independent death of cerebellar granule neurons resembling paraptosis

Potassium withdrawal is commonly used to induce caspase-mediated apoptosis in cerebellar granule neurons in vitro. However, the underlying and cell death-initiating mechanisms are unknown. We firstly investigated potassium efflux through the outward delayed rectifier K+ current (Ik) as a potential mediator. However, tetraethylammoniumchloride, an inhibitor of Ik, was ineffective to block apoptosis after potassium withdrawal. Since potassium withdrawal reduced intracellular pH (pHi) from 7.4 to 7.2, we secondly investigated the effects of intracellular acidosis. To study intracellular acidosis in cerebellar granule neurons, we inhibited the Na+/H+ exchanger (NHE) with 4-isopropyl-3-methylsulfonylbenzoyl-guanidine methanesulfonate (HOE 642) and 5-(N-ethyl-N-isopropyl)-amiloride. Both inhibitors concentration-dependently induced cell death and potentiated cell death after potassium withdrawal. Although inhibition of the NHE induced cell death with morphological criteria of apoptosis in light and electron microscopy including chromatin condensation, positive TUNEL staining and cell shrinkage, no internucleosomal DNA cleavage or activation of caspases was detected. In contrast to potassium withdrawal-induced apoptosis, cell death induced by intracellular acidification was not prevented by insulin-like growth factor-1, cyclo-adenosine-monophosphate, caspase inhibitors and transfection with an adenovirus expressing Bcl-XL. However, cycloheximide protected cerebellar granule neurons from death induced by potassium withdrawal as well as from death after treatment with HOE 642. Therefore, the molecular mechanisms leading to cell death after acidification appear to be different from the mechanisms after potassium withdrawal and resemble the biochemical but not the morphological characteristics of paraptosis.

Haloperidol impairs auditory filial imprinting and modulates monoaminergic neurotransmission in an imprinting-relevant forebrain area of the domestic chick

In vivo microdialysis and behavioural studies in the domestic chick have shown that glutamatergic as well as monoaminergic neurotransmission in the medio-rostral neostriatum/hyperstriatum ventrale (MNH) is altered after auditory filial imprinting. In the present study, using pharmaco-behavioural and in vivo microdialysis approaches, the role of dopaminergic neurotransmission in this juvenile learning event was further evaluated. The results revealed that: (i) the systemic application of the potent dopamine receptor antagonist haloperidol (7.5 mg/kg) strongly impairs auditory filial imprinting; (ii) systemic haloperidol induces a tetrodotoxin-sensitive increase of extracellular levels of the dopamine metabolite, homovanillic acid, in the MNH, whereas the levels of glutamate, taurine and the serotonin metabolite, 5-hydroxyindole-3-acetic acid, remain unchanged; (iii) haloperidol (0.01, 0.1, 1 mm) infused locally into the MNH increases glutamate, taurine and 5- hydroxyindole-3-acetic acid levels in a dose-dependent manner, whereas homovanillic acid levels remain unchanged; (iv) systemic haloperidol infusion reinforces the N-methyl-d-aspartate receptor-mediated inhibitory modulation of the dopaminergic neurotransmission within the MNH. These results indicate that the modulation of dopaminergic function and its interaction with other neurotransmitter systems in a higher associative forebrain region of the juvenile avian brain displays similar neurochemical characteristics as the adult mammalian prefrontal cortex. Furthermore, we were able to show that the pharmacological manipulation of monoaminergic regulatory mechanisms interferes with learning and memory formation, events which in a similar fashion might occur in young or adult mammals.

Ceramide inhibits the potassium channel Kv1.3 by the formation of membrane platforms

Previous studies suggested a central role of sphingomyelin- and cholesterol-enriched membrane rafts in the initiation of signaling via many receptors. Here, we investigated the role of membrane rafts for the function of the voltage-gated potassium channel Kv1.3. We demonstrate that Kv1.3 localizes in the cell membrane to pre-existing small, sphingolipid- and cholesterol-enriched membrane rafts. Transformation of these small rafts to large ceramide-enriched membrane platforms was achieved by stimulation of the endogenous acid sphingomyelinase, addition of exogenous sphingomyelinase or treatment of the cells with C(16)-ceramide and resulted in clustering of Kv1.3 within ceramide-enriched membrane platforms and inhibition of the channel's activity. Likewise, disruption of pre-existing small rafts inhibited Kv1.3 activity. This indicates that intact small membrane rafts are required for Kv1.3 activity and an alteration of the lipid environment of rafts inhibits Kv1.3. These data, thus, may suggest a novel concept for the regulation of ion channels by the cell membrane composition.

The transmembranous domain of CD40 determines CD40 partitioning into lipid rafts

Stimulation of CD40 has been previously shown to result in a release of ceramide in small sphingolipid-enriched rafts in the cell membrane [Grassmé et al., J. Immunol. 168 (2002) 298-307]. Those rafts fused to larger signaling platforms that served to cluster CD40. Here, we defined molecular mechanisms of CD40 clustering in membrane platforms. To this end, we replaced the transmembranous domain of CD40 with that of CD45, a molecule known to be excluded from lipid rafts. Murine T cells were stably transfected with wild-type CD40 or chimeric CD40/CD45. Flow cytometry confirmed normal binding properties of the mutant to CD40 ligand. Stimulation with CD40 ligand resulted in clustering of wild-type CD40, while the chimeric CD40/45 receptor failed to cluster. This correlated with a deficiency of the chimeric receptor to activate JNK, p38 MAP kinase and SAPK, known signaling molecules of the intracellular pathway initiated by CD40. Forced crosslinking of the CD40/45 chimeric receptor restored, at least partially, these signaling events. The results suggest that the transmembranous domain of CD40 is central for the recruitment to and clustering of CD40 in membrane platforms.

Role of mitochondria in apoptosis

Apoptosis is an evolutionary-conserved physiological mechanism to remove cells from an organism. Cellular apoptosis is mediated via an intracellular signalling programme that involves a variety of signalling molecules and cellular organelles including caspases, sphingomyelinases, Bcl-2-like proteins and proteins to cleave the DNA and mitochondria. Mitochondria contain several pro-apoptotic molecules that activate cytosolic proteins to execute apoptosis, block anti-apoptotic proteins in the cytosol and directly cleave nuclear DNA. Mitochondria trap these pro-apoptotic proteins and physically separate pro-apoptotic proteins from their cytoplasmic targets. Apoptosis is then initiated by the release of mitochondrial pro-apoptotic proteins into the cytosol. This process seems to be regulated by Bcl-2-like proteins and several ion channels, in particular the permeability transition pore (PTP) that is activated by almost all pro-apoptotic stimuli.