Microenvironmental reprogramming of thymic epithelial cells to skin multipotent stem cells.

The thymus develops from the third pharyngeal pouch of the anterior gut and provides the necessary environment for thymopoiesis (the process by which thymocytes differentiate into mature T lymphocytes) and the establishment and maintenance of self-tolerance. It contains thymic epithelial cells (TECs) that form a complex three-dimensional network organized in cortical and medullary compartments, the organization of which is notably different from simple or stratified epithelia. TECs have an essential role in the generation of self-tolerant thymocytes through expression of the autoimmune regulator Aire, but the mechanisms involved in the specification and maintenance of TECs remain unclear. Despite the different embryological origins of thymus and skin (endodermal and ectodermal, respectively), some cells of the thymic medulla express stratified-epithelium markers, interpreted as promiscuous gene expression. Here we show that the thymus of the rat contains a population of clonogenic TECs that can be extensively cultured while conserving the capacity to integrate in a thymic epithelial network and to express major histocompatibility complex class II (MHC II) molecules and Aire. These cells can irreversibly adopt the fate of hair follicle multipotent stem cells when exposed to an inductive skin microenvironment; this change in fate is correlated with robust changes in gene expression. Hence, microenvironmental cues are sufficient here to re-direct epithelial cell fate, allowing crossing of primitive germ layer boundaries and an increase in potency.

Markedly reduced blood pressure responsiveness in endotoxemic rats; reversal by neuropeptide Y.

This study in conscious normotensive rats was performed to assess the effect of the vasoconstrictor peptide, neuropeptide Y (NPY), on blood pressure responsiveness to exogenous norepinephrine in endotoxaemia. NPY and endotoxin were infused at doses which had no effect on blood pressure, whether given alone or in combination. Endotoxin markedly reduced the pressor responses to bolus injections of norepinephrine. However, blood pressure responsiveness could be enhanced by infusing NPY simultaneously with the endotoxin. It is suggested that low dose NPY infusions may be clinically useful in reversing the reduced vascular responsiveness to pressor amines in shock.

Reelin controls progenitor cell migration in the healty and pathological adult brain

Understanding the signals that control migration of neural progenitor cells in the adult brain may provide new therapeutic opportunities. Reelin is best known for its role in regulating cell migration during brain development, but we now demonstrate a novel function for reelin in the injured adult brain. First, we show that Reelin is upregulated around lesions. Second, experimentally increasing Reelin expression levels in healthy mouse brain leads to a change in the migratory behavior of subventricular zone-derived progenitors, triggering them to leave the rostral migratory stream (RMS) to which they are normally restricted during their migration to the olfactory bulb. Third, we reveal that Reelin increases endogenous progenitor cell dispersal in periventricular structures independently of any chemoattraction but via cell detachment and chemokinetic action, and thereby potentiates spontaneous cell recruitment to demyelination lesions in the corpus callosum. Conversely, animals lacking Reelin signaling exhibit reduced endogenous progenitor recruitment at the lesion site. Altogether, these results demonstrate that beyond its known role during brain development, Reelin is a key player in post-lesional cell migration in the adult brain. Finally our findings provide proof of concept that allowing progenitors to escape from the RMS is a potential therapeutic approach to promote myelin repair.

Central Horner's syndrome with contralateral ataxic hemiparesis: a diencephalic alternate syndrome.

OBJECTIVE: To assess whether thalamic strokes presenting with a central Horner's syndrome (HS) show specific clinicoanatomic patterns. METHODS: From the Lausanne Stroke Registry (period 1993 to spring 2002), the authors selected all patients with thalamic stroke presenting with ipsilateral HS. Patients with complete infarction of the posterior cerebral artery territory, with involvement of middle cerebral artery territory or bilateral lesions, were excluded. Lesions on brain MRI were correlated with standard neuroanatomic templates. RESULTS: Nine patients with thalamic infarction presenting with central HS were found; all showed contralateral ataxic hemiparesis (AH). Lesions involved the anterior or paramedian thalamus and extended to the hypothalamic or rostral paramedian mesencephalic area in all but one subject. Associated clinical signs included dysphasia (two patients), somnolence (six), vertical gaze paresis (two), asterixis (two), and hemihypesthesia (three). CONCLUSION: The alternate clinical pattern of central HS with contralateral AH is a stroke syndrome of the diencephalic-mesencephalic junction, resulting from the involvement of the common arterial supply to the paramedian/anterior thalamus, the posterior hypothalamus and the rostral paramedian midbrain.

Auditory Neurons with Transitory Axons to Visual Areas Form Short Permanent Projections.

The kitten's auditory cortex (including the first and second auditory fields AI and AII) is known to send transient axons to either ipsi- or contralateral visual areas 17 and 18. By the end of the first postnatal month the transitory axons, but not their neurons of origin, are eliminated. Here we investigated where these neurons project after the elimination of the transitory axon. Eighteen kittens received early (postnatal day (pd) 2 - 5) injections of long lasting retrograde fluorescent traces in visual areas 17 and 18 and late (pd 35 - 64) injections of other retrograde fluorescent tracers in either hemisphere, mostly in areas known to receive projections from AI and AII in the adult cat. The middle ectosylvian gyrus was analysed for double-labelled neurons in the region corresponding approximately to AI and AII. Late injections in the contralateral (to the analysed AI, AII) hemisphere including all of the known auditory areas, as well as some visual and 'association' areas, did not relabel neurons which had had transient projections to either ipsi- or contralateral visual areas 17 - 18. Thus, AI and AII neurons after eliminating their transient juvenile projections to visual areas 17 and 18 do not project to the other hemisphere. In contrast, relabelling was obtained with late injections in several locations in the ipsilateral hemisphere; it was expressed as per cent of the population labelled by the early injections. Few neurons (0 - 2.5%) were relabelled by large injections in the caudal part of the posterior ectosylvian gyrus and the adjacent posterior suprasylvian sulcus (areas DP, P, VP). Multiple injections in the middle ectosylvian gyrus relabelled a considerably larger percentage of neurons (13%). Single small injections in the middle ectosylvian gyrus (areas AI, AII), the caudal part of the anterior ectosylvian gyrus and the rostral part of the posterior ectosylvian gyrus relabelled 3.1 - 7.0% of neurons. These neurons were generally near (<2.0 mm) the outer border of the late injection sites. Neurons with transient projections to ipsi- or contralateral visual areas 17 and 18 were relabelled in similar proportions by late injections at any given location. Thus, AI or AII neurons which send a transitory axon to ipsi- or contralateral visual areas 17 and 18 are most likely to form short permanent cortical connections. In that respect, they are similar to medial area 17 neurons that form transitory callosal axons and short permanent axons to ipsilateral visual areas 17 and 18.

Skew deviation [Skew deviation]

BACKGROUND: Skew deviation is a vertical ocular misalignment of prenuclear origin. Although well described in the literature, it is still probably underdiagnosed. Natural history of skew deviation is not well described in the literature. PURPOSE: To describe the clinical presentations, etiologies and follow-up of skew deviation. METHODS: Retrospective study of 29 patients diagnosed with skew deviation between 1993 and 1996. RESULTS: The commonest cause was cerebrovascular accident (12/29) and the commonest localisation was mesencephalic (9/29). Other causes included surgery (7/29), tumor (4/29), trauma (3/29), degeneration (3/29), inflammatory (2/29), increased intracranial pressure (1/29). Other localisations included cerebellum (5/29), ponto-mesencephalic (3/29), and medulla (2/29). Vertical diplopia was always accompanied by other neuro-ophthalmologic abnormalities. 69.2% (18/26) patients were totally asymptomatic after 7.5 months. 30.8% (8/26) were still symptomatic (diplopia). One patient required surgery, three patients were relieved with prisms, one patient needed monocular occlusion. One patient died during follow-up and precise data were lacking in two symptomatic patients. CONCLUSION: Skew deviation is not so rare, 10% of the cases referred to us for diplopia in 3 years. The diagnosis of skew deviation should be entertained when vertical diplopia cannot be explained by pathology of extraocular muscles, peripheral or central cranial nerve III or IV palsies, myasthenia, or orbital pathology. Prognosis for recovery in patients with skew deviation is good. 70% will recover, after a median time of 7.5 months. Surgery should be postponed at least for 12 months.

Voltage-gated sodium channel expression in mouse DRG after SNI leads to re-evaluation of projections of injured fibers.

BACKGROUND: Dysregulation of voltage-gated sodium channels (Na(v)s) is believed to play a major role in nerve fiber hyperexcitability associated with neuropathic pain. A complete transcriptional characterization of the different isoforms of Na(v)s under normal and pathological conditions had never been performed on mice, despite their widespread use in pain research. Na(v)s mRNA levels in mouse dorsal root ganglia (DRG) were studied in the spared nerve injury (SNI) and spinal nerve ligation (SNL) models of neuropathic pain. In the SNI model, injured and non-injured neurons were intermingled in lumbar DRG, which were pooled to increase the tissue available for experiments. RESULTS: A strong downregulation was observed for every Na(v)s isoform expressed except for Na(v)1.2; even Na(v)1.3, known to be upregulated in rat neuropathic pain models, was lower in the SNI mouse model. This suggests differences between these two species. In the SNL model, where the cell bodies of injured and non-injured fibers are anatomically separated between different DRG, most Na(v)s were observed to be downregulated in the L5 DRG receiving axotomized fibers. Transcription was then investigated independently in the L3, L4 and L5 DRG in the SNI model, and an important downregulation of many Na(v)s isoforms was observed in the L3 DRG, suggesting the presence of numerous injured neurons there after SNI. Consequently, the proportion of axotomized neurons in the L3, L4 and L5 DRG after SNI was characterized by studying the expression of activating transcription factor 3 (ATF3). Using this marker of nerve injury confirmed that most injured fibers find their cell bodies in the L3 and L4 DRG after SNI in C57BL/6 J mice; this contrasts with their L4 and L5 DRG localization in rats. The spared sural nerve, through which pain hypersensitivity is measured in behavioral studies, mostly projects into the L4 and L5 DRG. CONCLUSIONS: The complex regulation of Na(v)s, together with the anatomical rostral shift of the DRG harboring injured fibers in C57BL/6 J mice, emphasize that caution is necessary and preliminary anatomical experiments should be carried out for gene and protein expression studies after SNI in mouse strains.

Distribution and anatomical localization of the glucose transporter 2 (GLUT2) in the adult rat brain--an immunohistochemical study.

The aim of this work was to study the distribution and cellular localization of GLUT2 in the rat brain by light and electron microscopic immunohistochemistry, whereas our ultrastructural observations will be reported in a second paper. Confirming previous results, we show that GLUT2-immunoreactive profiles are present throughout the brain, especially in the limbic areas and related nuclei, whereas they appear most concentrated in the ventral and medial regions close to the midline. Using cresyl violet counterstaining and double immunohistochemical staining for glial or neuronal markers (GFAp, CAII and NeuN), we show that two limited populations of oligodendrocytes and astrocytes cell bodies and processes are immunoreactive for GLUT2, whereas a cross-reaction with GLUT1 cannot be ruled out. In addition, we report that the nerve cell bodies clearly immunostained for GLUT2 were scarce (although numerous in the dentate gyrus granular layer in particular), whereas the periphery of numerous nerve cells appeared labeled for this transporter. The latter were clustered in the dorsal endopiriform nucleus and neighboring temporal and perirhinal cortex, in the dorsal amygdaloid region, and in the paraventricular and reuniens thalamic nuclei, whereas they were only a few in the hypothalamus. Moreover, a group of GLUT2-immunoreactive nerve cell bodies was localized in the dorsal medulla oblongata while some large multipolar nerve cell bodies peripherally labeled for GLUT2 were scattered in the caudal ventral reticular formation. This anatomical localization of GLUT2 appears characteristic and different from that reported for the neuronal transporter GLUT3 and GLUT4. Indeed, the possibility that GLUT2 may be localized in the sub-plasmalemnal region of neurones and/or in afferent nerve fibres remains to be confirmed by ultrastructural observations. Because of the neuronal localization of GLUT2, and of its distribution relatively similar to glucokinase, it may be hypothesized that this transporter is, at least partially, involved in cerebral glucose sensing.

Patterns of calcium-binding proteins in human inferior colliculus: identification of subdivisions and evidence for putative parallel systems.

The subdivisions of human inferior colliculus are currently based on Golgi and Nissl-stained preparations. We have investigated the distribution of calcium-binding protein immunoreactivity in the human inferior colliculus and found complementary or mutually exclusive localisations of parvalbumin versus calbindin D-28k and calretinin staining. The central nucleus of the inferior colliculus but not the surrounding regions contained parvalbumin-positive neuronal somata and fibres. Calbindin-positive neurons and fibres were concentrated in the dorsal aspect of the central nucleus and in structures surrounding it: the dorsal cortex, the lateral lemniscus, the ventrolateral nucleus, and the intercollicular region. In the dorsal cortex, labelling of calbindin and calretinin revealed four distinct layers.Thus, calcium-binding protein reactivity reveals in the human inferior colliculus distinct neuronal populations that are anatomically segregated. The different calcium-binding protein-defined subdivisions may belong to parallel auditory pathways that were previously demonstrated in non-human primates, and they may constitute a first indication of parallel processing in human subcortical auditory structures.

Promoter IV of the class II transactivator gene is essential for positive selection of CD4+ T cells.

Major histocompatibility complex class II (MHCII) expression is regulated by the transcriptional coactivator CIITA. Positive selection of CD4(+) T cells is abrogated in mice lacking one of the promoters (pIV) of the Mhc2ta gene. This is entirely due to the absence of MHCII expression in thymic epithelia, as demonstrated by bone marrow transfer experiments between wild-type and pIV(-/-) mice. Medullary thymic epithelial cells (mTECs) are also MHCII(-) in pIV(-/-) mice. Bone marrow-derived, professional antigen-presenting cells (APCs) retain normal MHCII expression in pIV(-/-) mice, including those believed to mediate negative selection in the thymic medulla. Endogenous retroviruses thus retain their ability to sustain negative selection of the residual CD4(+) thymocytes in pIV(-/-) mice. Interestingly, the passive acquisition of MHCII molecules by thymocytes is abrogated in pIV(-/-) mice. This identifies thymic epithelial cells as the source of this passive transfer. In peripheral lymphoid organs, the CD4(+) T-cell population of pIV(-/-) mice is quantitatively and qualitatively comparable to that of MHCII-deficient mice. It comprises a high proportion of CD1-restricted natural killer T cells, which results in a bias of the V beta repertoire of the residual CD4(+) T-cell population. We have also addressed the identity of the signal that sustains pIV expression in cortical epithelia. We found that the Jak/STAT pathways activated by the common gamma chain (CD132) or common beta chain (CDw131) cytokine receptors are not required for MHCII expression in thymic cortical epithelia.

Beta-adrenoceptor stimulation increases neuropeptide Y release from sympathetic nerves in intact rats.

This study was undertaken to assess in conscious normotensive rats the effects of beta-adrenoceptor stimulation on plasma neuropeptide Y (NPY) levels. Wistar rats were subjected to adrenal demedullation on the right side and were either adrenalectomized or sham-operated on the left side. Eleven days later, the conscious rats were infused i.v. for 30 min with either isoproterenol (10 ng/min) or its vehicle. Plasma NPY levels were significantly lower (23.8 +/- 2.6 pM, means +/- S.E.M., n = 12, P < 0.01) in vehicle-treated medullectomized rats than in corresponding sham-operated controls (36.7 +/- 4.1 pM, n = 12). The medullectomized rats infused with isoproterenol showed plasma NPY levels (36.7 +/- 3.3 pM, n = 11) comparable to those of sham-operated rats having received the vehicle. These data therefore demonstrate that plasma NPY levels are lower in rats without adrenal medulla and that in these animals isoproterenol increases NPY release, most likely by activating pre-synaptic beta-adrenoceptors.

Tonotopic mapping of human auditory cortex.

Since the early days of functional magnetic resonance imaging (fMRI), retinotopic mapping emerged as a powerful and widely-accepted tool, allowing the identification of individual visual cortical fields and furthering the study of visual processing. In contrast, tonotopic mapping in auditory cortex proved more challenging primarily because of the smaller size of auditory cortical fields. The spatial resolution capabilities of fMRI have since advanced, and recent reports from our labs and several others demonstrate the reliability of tonotopic mapping in human auditory cortex. Here we review the wide range of stimulus procedures and analysis methods that have been used to successfully map tonotopy in human auditory cortex. We point out that recent studies provide a remarkably consistent view of human tonotopic organisation, although the interpretation of the maps continues to vary. In particular, there remains controversy over the exact orientation of the primary gradients with respect to Heschl's gyrus, which leads to different predictions about the location of human A1, R, and surrounding fields. We discuss the development of this debate and argue that literature is converging towards an interpretation that core fields A1 and R fold across the rostral and caudal banks of Heschl's gyrus, with tonotopic gradients laid out in a distinctive V-shaped manner. This suggests an organisation that is largely homologous with non-human primates. This article is part of a Special Issue entitled Human Auditory Neuroimaging.

Clinical management and outcome of histologically verified adult brainstem gliomas in Switzerland: a retrospective analysis of 21 patients.

Because of low incidence, mixed study populations and paucity of clinical and histological data, the management of adult brainstem gliomas (BSGs) remains non-standardized. We here describe characteristics, treatment and outcome of patients with exclusively histologically confirmed adult BSGs. A retrospective chart review of adults (age >18 years) was conducted. BSG was defined as a glial tumor located in the midbrain, pons or medulla. Characteristics, management and outcome were analyzed. Twenty one patients (17 males; median age 41 years) were diagnosed between 2004 and 2012 by biopsy (n = 15), partial (n = 4) or complete resection (n = 2). Diagnoses were glioblastoma (WHO grade IV, n = 6), anaplastic astrocytoma (WHO grade III, n = 7), diffuse astrocytoma (WHO grade II, n = 6) and pilocytic astrocytoma (WHO grade I, n = 2). Diffuse gliomas were mainly located in the pons and frequently showed MRI contrast enhancement. Endophytic growth was common (16 vs. 5). Postoperative therapy in low-grade (WHO grade I/II) and high-grade gliomas (WHO grade III/IV) consisted of radiotherapy alone (three in each group), radiochemotherapy (2 vs. 6), chemotherapy alone (0 vs. 2) or no postoperative therapy (3 vs. 1). Median PFS (24.1 vs. 5.8 months; log-rank, p = 0.009) and mOS (30.5 vs. 11.5 months; log-rank, p = 0.028) was significantly better in WHO grade II than in WHO grade III/IV tumors. Second-line therapy considerably varied. Histologically verification of adult BSGs is feasible and has an impact on postoperative treatment. Low-grade gliomas can simple be followed or treated with radiotherapy alone. Radiochemotherapy with temozolomide can safely be prescribed for high-grade gliomas without additional CNS toxicities.

The thalamocortical projection systems in primate: an anatomical support for multisensory and sensorimotor interplay.

Multisensory and sensorimotor integrations are usually considered to occur in superior colliculus and cerebral cortex, but few studies proposed the thalamus as being involved in these integrative processes. We investigated whether the organization of the thalamocortical (TC) systems for different modalities partly overlap, representing an anatomical support for multisensory and sensorimotor interplay in thalamus. In 2 macaque monkeys, 6 neuroanatomical tracers were injected in the rostral and caudal auditory cortex, posterior parietal cortex (PE/PEa in area 5), and dorsal and ventral premotor cortical areas (PMd, PMv), demonstrating the existence of overlapping territories of thalamic projections to areas of different modalities (sensory and motor). TC projections, distinct from the ones arising from specific unimodal sensory nuclei, were observed from motor thalamus to PE/PEa or auditory cortex and from sensory thalamus to PMd/PMv. The central lateral nucleus and the mediodorsal nucleus project to all injected areas, but the most significant overlap across modalities was found in the medial pulvinar nucleus. The present results demonstrate the presence of thalamic territories integrating different sensory modalities with motor attributes. Based on the divergent/convergent pattern of TC and corticothalamic projections, 4 distinct mechanisms of multisensory and sensorimotor interplay are proposed.

Functional compensation of motor function in pre-symptomatic Huntington's disease.

Involuntary choreiform movements are a clinical hallmark of Huntington's disease. Studies in clinically affected patients suggest a shift of motor activations to parietal cortices in response to progressive neurodegeneration. Here, we studied pre-symptomatic gene carriers to examine the compensatory mechanisms that underlie the phenomenon of retained motor function in the presence of degenerative change. Fifteen pre-symptomatic gene carriers and 12 matched controls performed button presses paced by a metronome at either 0.5 or 2 Hz with four fingers of the right hand whilst being scanned with functional magnetic resonance imaging. Subjects pressed buttons either in the order of a previously learnt 10-item finger sequence, from left to right, or kept still. Error rates ranged from 2% to 7% in the pre-symptomatic gene carriers and from 0.5% to 4% in controls, depending on the condition. No significant difference in task performance was found between groups for any of the conditions. Activations in the supplementary motor area (SMA) and superior parietal lobe differed with gene status. Compared with healthy controls, gene carriers showed greater activations of left caudal SMA with all movement conditions. Activations correlated with increasing speed of movement were greater the closer the gene carriers were to estimated clinical diagnosis, defined by the onset of unequivocal motor signs. Activations associated with increased movement complexity (i.e. with the pre-learnt 10-item sequence) decreased in the rostral SMA with nearing diagnostic onset. The left superior parietal lobe showed reduced activation with increased movement complexity in gene carriers compared with controls, and in the right superior parietal lobe showed greater activations with all but the most demanding movements. We identified a complex pattern of motor compensation in pre-symptomatic gene carriers. The results show that preclinical compensation goes beyond a simple shift of activity from premotor to parietal regions involving multiple compensatory mechanisms in executive and cognitive motor areas. Critically, the pattern of motor compensation is flexible depending on the actual task demands on motor control.