A phase Ib dose-escalation study of the MEK inhibitor trametinib in combination with the PI3K/mTOR inhibitor GSK2126458 in patients with advanced solid tumors.

Introduction This Phase Ib trial investigated the safety, tolerability, and recommended phase 2 dose for the pan-PI3K/mTOR inhibitor, GSK2126458 (GSK458), and trametinib combination when administered to patients with advanced solid tumors. Patients and Methods Patients with advanced solid tumors received escalating doses of GSK458 (once or twice daily, and continuous or intermittent) and trametinib following a zone-based 3 + 3 design to determine the maximum tolerated dose (MTD). Assessments included monitoring for adverse events and response, and evaluating pharmacokinetic (PK) measures. Archival tissue and circulating free DNA samples were collected to assess biomarkers of response in the PI3K and RAS pathways. Results 57 patients were enrolled onto the continuous dosing cohort and 12 patients onto an intermittent BID dosing cohort. Two MTDs were established for the continuous daily dosing: 2 mg of GSK458 with 1.0 mg of trametinib or 1.0 mg of GSK458 with 1.5 mg of trametinib; no MTD was determined in the intermittent dosing cohort. The most frequent adverse events were rash (74 %) and diarrhea (61 %). Dose interruptions due to adverse events occurred in 42 % of patients. No significant PK interaction was observed. One patient achieved partial response and 12 patients had stable disease >16 weeks. Mutations in RAS/RAF/PI3K were detected in 70 % of patients, but no pattern emerged between response and mutational status. Conclusion GSK458 plus trametinib is poorly tolerated, due to skin and GI-related toxicities. Responses were minimal, despite enrichment for PI3K/RAS pathway driven tumors, which may be due to overlapping toxicities precluding sufficient dose exposure.

Corneal transplantation activity over 7 years: changing trends for indications, patient demographics and surgical techniques from the Corneal Transplant Epidemiological Study (CORTES).

This study aims to examine evolving indications and changing trends for corneal transplantation in Italy. Corneal transplantations performed with donor tissues distributed by the Veneto Eye Bank Foundation between 2002 and 2008 were prospectively evaluated. Of the 13,173 keratoplasties performed on 11,337 patients, 10,742 (81.5%) were penetrating (PK), 1644 (12.5%) were anterior lamellar (ALK), and 787 (6.0%) were endothelial (EK). Keratoconus (42.5%), regraft (18.9%), and pseudophakic bullous keratopathy (PBK, 11.9%) were the leading indications for PK, with keratoconus (69.6%) and regraft (6.5%) showing higher indications for ALK, whereas pseudophakic bullous keratopathy (50.1%) and regraft (18.7%) were the major indications for EK. There was an overall decrease observed in corneal grafting for keratoconus (P = .0048) and an increase for PBK (P = .0653) and regrafting (P = .0137). These indications differed by age and gender. The number of keratoplasties over 7 years was stable (P = .2394), although the annual number of PKs declined by 34.0% (P = .0250), ALKs began to rise from 2005 (P = .0600), whereas EKs showed a huge growth, with their number tripling in 2007 and further doubling in 2008 (P = .0004). Leading indications for keratoplasty showed similar data that have been reported elsewhere for Western countries over the past few decades, albeit with a higher percentage of keratoconus. However, the overall number of keratoplasties for keratoconus was in decline, whereas regraft keratopathy and PKs increased due to the application of the newer surgical techniques for corneal grafting. This highlights an important shift in managing corneal diseases toward the application of selective and more conservative surgeries and changes in indications in corneal transplantation.

Integrative population pharmacokinetic and pharmacodynamic dose finding approach of the new camptothecin compound namitecan (ST1968).

AIMS: Namitecan is a new camptothecan compound undergoing early clinical development. This study was initiated to build an integrated pharmacokinetic (PK) and pharmacodynamic (PD) population model of namitecan to guide future clinical development. METHODS: Plasma concentration-time data, neutrophils and thrombocytes were pooled from two phase 1 studies in 90 patients with advanced solid tumours, receiving namitecan as a 2 h infusion on days 1 and 8 every 3 weeks (D1,8) (n = 34), once every 3 weeks (D1) (n = 29) and on 3 consecutive days (D1-3) (n = 27). A linear three compartment PK model was coupled to a semiphysiological PD-model for neutrophils and thrombocytes. Data simulations were used to interrogate various dosing regimens and give dosing recommendations. RESULTS: Clearance was estimated to be 0.15 l h(-1), with a long terminal half-life of 48 h. Body surface area was not associated with clearance, supporting flat-dosing of namitecan. A significant and clinically relevant association was found between namitecan area under the concentration-time curve (AUC) and the percentage drop of neutrophils (r(2) = 0.51, P < 10(-4)) or thrombocytes (r(2) = 0.49, P < 10(-4)). With a target for haematological dose-limiting toxicity of <20%, the recommended dose was defined as 12.5 mg for the D1,8 regimen, 23 mg for the once every 3 week regimen and 7 mg for the D1-3 regimen. CONCLUSION: This is the first integrated population PK-PD analysis of the new hydrophilic topoisomerase I inhibitor namitecan, that is currently undergoing early clinical development. A distinct relationship was found between drug exposure and haematological toxicity, supporting flat-dosing once every 3 weeks as the most adequate dosing regimen.

Phase I study of olaparib in combination with liposomal doxorubicin in patients with advanced solid tumours.

BACKGROUND: Olaparib, an oral PARP inhibitor, has shown antitumour activity as monotherapy in patients with germline BRCA1/2 (gBRCA)-mutated breast and ovarian cancer. This study evaluated olaparib capsules in combination with liposomal doxorubicin (PLD) in patients with advanced solid tumours (NCT00819221). METHODS: Patients received 28-day cycles of olaparib, continuously (days 1-28) or intermittently (days 1-7), plus PLD (40 mg m(-2), day 1); seven olaparib dose cohorts (50-400 mg bid) were explored to determine the recommended dose. Assessments included safety, pharmacokinetics, pharmacodynamics and preliminary efficacy (objective response rate (ORR)). RESULTS: Of 44 patients treated (ovarian, n=28; breast, n=13; other/unknown, n=3), two experienced dose-limiting toxicities (grade 3 stomatitis and fatal pneumonia/pneumonitis (200 mg per 28-day cycle); grade 4 thrombocytopenia (400 mg per 7-day cycle)). The maximum tolerated dose was not reached using continuous olaparib 400 mg bid plus PLD. Grade ≥3 and serious AEs were reported for 27 (61%) and 12 (27%) patients, respectively. No major pharmacokinetic interference was observed between olaparib and PLD. The ORR was 33% (n=14 out of 42; complete response, n=3). A total of 13 responders had ovarian cancer: 10 were platinum-sensitive, 11 had a gBRCA mutation. CONCLUSIONS: Continuous/intermittent olaparib (up to 400 mg bid) combined with PLD (40 mg m(-2)) was generally tolerated and showed evidence of antitumour activity in ovarian cancer.

Seminars in clinical pharmacology: an introduction to MET inhibitors for the medical oncologist.

MET is a tyrosine kinase receptor for hepatocyte growth factor (HGF), primarily expressed on epithelial cells; the activation of MET induces several biological responses relevant for the development and growth of many human cancers. Several human malignancies present altered expression of MET and this is usually associated with poor prognosis and aggressive phenotype. The majority of MET inhibitors in clinical development target directly the receptor through the use of monoclonal antibodies (MAbs) or through small molecule inhibitors of MET kinase activity; small molecule inhibitors are very potent but less specific than MAbs. MET inhibitors are of great clinical interest because of the extensive crosstalk of the HGF/MET axis with many other signaling pathways, including growth factor-dependent pathways (like PI3K/AKT/mTOR,RAS/RAF/ERK) and vascular endothelial growth factor (VEGF) axis. In preclinical studies, the treatment with MET inhibitors could prevent or reverse resistance to inhibitors of growth factor-dependent signaling; this hypothesis is currently tested in phase III trials with anti-epidermal growth factor receptor (EGFR) inhibitors in non-small-cell lung cancer (NSCLC). Based on preclinical and preliminary clinical results, a rational strategy for the clinical development of MET antagonists should include a selection of the tumors with MET overexpression, the identification of prognostic/predictive biomarkers, the evaluation of combinations with anti-VEGF compounds.

Transitory and activity-dependent expression of neurogranin in olfactory bulb tufted cells during mouse postnatal development.

Neurogranin (Ng) is a brain-specific postsynaptic calmodulin-binding protein involved in synaptic activity-dependent plasticity. In the adult olfactory bulb (OB), Ng is expressed by a large population of GABAergic interneurons in the granule cell layer. We show here that, during postnatal development, Ng is also expressed by OB neurons in the superficial external plexiform layer (sEPL) and glomerular layer (GL). These Ng-positive neurons display morphological and neurochemical features of superficial and external tufted cells. Ng expression in these cells is transient during OB development: few elements express Ng at postnatal day (P) 5, increasing in number and reaching a peak at P10, then progressively decreasing. At P30, Ng is rarely detectable in these neurons. Ng expression in developing tufted cells is also modulated at the cellular level: at earlier stages, Ng labeling is distributed throughout the cell body and dendritic arborization in the GL, but, at P20, when the glomerular circuits are fully matured, Ng becomes restricted to the soma and proximal portion of tufted cell apical dendrites. We show that olfactory deprivation at early postnatal stages induces a strong increase in Ng-positive tufted cells from P10 to P20, whereas no changes have been observed following olfactory deprivation in adult mice. These findings demonstrate that Ng expression in sEPL-GL is restricted to developmental stages and indicate its activity-dependent regulation in a time window critical for glomerular circuit development, suggesting a role for Ng in maturation and dendritic remodeling of tufted cells.

From chemical neuroanatomy to an understanding of the olfactory system.

The olfactory system is the appropriate model for studying several aspects of neuronal physiology spanning from the developmental stage to neural network remodelling in the adult brain. Both the morphological and physiological understanding of this system were strongly supported by classical histochemistry. It is emblematic the case of the Olfactory Marker Protein (OMP) staining, the first, powerful marker for fully differentiated olfactory receptor neurons and a key tool to investigate the dynamic relations between peripheral sensory epithelia and central relay regions given its presence within olfactory fibers reaching the olfactory bulb (OB). Similarly, the use of thymidine analogues was able to show neurogenesis in an adult mammalian brain far before modern virus labelling and lipophilic tracers based methods. Nowadays, a wealth of new histochemical techniques combining cell and molecular biology approaches is available, giving stance to move from the analysis of the chemically identified circuitries to functional research. The study of adult neurogenesis is indeed one of the best explanatory examples of this statement. After defining the cell types involved and the basic physiology of this phenomenon in the OB plasticity, we can now analyze the role of neurogenesis in well testable behaviours related to socio-chemical communication in rodents.

Expression and localization of the calmodulin-binding protein neurogranin in the adult mouse olfactory bulb.

Neurogranin (Ng) is a brain-specific postsynaptic protein involved in activity-dependent synaptic plasticity through modulation of Ca(2+)/calmodulin (CaM)-dependent signal transduction in neurons. In this study, using biochemical and immunohistochemical approaches, we demonstrate Ng expression in the adult mouse olfactory bulb (OB), the first relay station in odor information processing. We show that Ng is principally associated with the granule cell layer (GCL), which is composed of granule cell inhibitory interneurons. This cell type is continuously renewed during adult life and plays a key role in OB circuits, integrating and modulating the activity of mitral/tufted cells. Our results indicate that Ng localizes in the soma and dendrites of a defined subpopulation of mature GABAergic granule cells, enriched in the deep portion of the GCL. Ng-immunopositive cells largely coexpress the Ca(+)/CaM-dependent kinase IV (CaMKIV), a downstream protein of CaM signaling cascade, whereas no colocalization was observed between Ng and the calcium-binding protein calretinin. Finally, we demonstrate that adult neurogenesis contributes to the Ng-expressing population, with more newly generated Ng-positive cells integrated in the deep GCL. Together, these results provide a new specific neurochemical marker to identify a subpopulation of olfactory granule cells and suggest possible functional implications for Ng in OB plasticity mechanisms.

Translational research in phase I trials

"Translational research" (TR) has the main aim of transferring the results of preclinical research into clinical practice and includes the study of the biology of the disease to provide solid rationales for the development or improvement of new drugs, the evaluation of the biological effects of the drugs in animals to define how to best use those drugs in humans and the study of the biological effects of those drugs in humans. To facilitate the development of new cancer targeted therapies, TR focuses its efforts on the discovery and validation of biomarkers, defined as "a characteristic that is objectively measured and evaluated as an indicator of normal biological processes, pathogenic processes or pharmacologic responses to a therapeutic intervention". Biomarkers could allow a rational development of targeted agents, based on the mechanistic assessment of their effects. This knowledge can then be used during the subsequent steps of drug discovery, screening, preclinical and clinical testing. This review will focus on the contributions provided by biomarkers to facilitate the development of new targeted therapies (AU)

Integration and sensory experience-dependent survival of newly-generated neurons in the accessory olfactory bulb of female mice.

Newborn neurons generated by proliferative progenitors in the adult subventricular zone (SVZ) integrate into the olfactory bulb circuitry of mammals. Survival of these newly-formed cells is regulated by the olfactory input. The presence of new neurons in the accessory olfactory bulb (AOB) has already been demonstrated in some mammalian species, albeit their neurochemical profile and functional integration into AOB circuits are still to be investigated. To unravel whether the mouse AOB represents a site of adult constitutive neurogenesis and whether this process can be modulated by extrinsic factors, we have used multiple in vivo approaches. These included fate mapping of bromodeoxyuridine-labelled cells, lineage tracing of SVZ-derived enhanced green fluorescent protein-positive engrafted cells and neurogenesis quantification in the AOB, in both sexes, as well as in females alone after exposure to male-soiled bedding or its derived volatiles. Here, we show that a subpopulation of SVZ-derived neuroblasts acquires proper neurochemical profiles of mature AOB interneurons. Moreover, 3D reconstruction of long-term survived engrafted neuroblasts in the AOB confirms these cells show features of fully integrated neurons. Finally, exposure to male-soiled bedding, but not to its volatile compounds, significantly increases the number of new neurons in the AOB, but not in the main olfactory bulb of female mice. These data show SVZ-derived neuroblasts differentiate into new functionally integrated neurons in the AOB of young and adult mice. Survival of these cells seems to be regulated by an experience-specific mechanism mediated by pheromones.

Clinical and pharmacological phase I evaluation of Exherin (ADH-1), a selective anti-N-cadherin peptide in patients with N-cadherin-expressing solid tumours.

BACKGROUND: Upregulation of N-cadherin promotes dysregulated cell growth, motility, invasiveness, plus maintenance of vascular stability and is associated with cancer progression in several human tumour types. N-cadherin is expressed also on tumour cells and the anti-N-cadherin cyclic pentapeptide ADH-1, tested in the present study, can exert a direct antitumour effect. PATIENTS AND METHODS: Adult patients with advanced solid malignancies expressing N-cadherin on tumour biopsies carried out in the previous 12 months received escalating i.v. doses of ADH-1 given weekly (initially for 3 of 4 weeks, then every week). Plasma pharmacokinetics (PK) was studied at cycle 1. Blood flow changes were assessed after first dosing in all patients treated in the initial regimen. RESULTS: In all, 129 patients were screened, 65 (50%) were N-cadherin positive, and 30 were enrolled. The doses ranged from 150 to 2400 mg/m(2); no maximum tolerated dose was reached. Treatment was well tolerated with asthenia as the most frequent adverse event. Two patients with ovarian cancer showed prolonged disease stabilisation while one patient with fallopian tube carcinoma achieved a mixed response. PK was linear in the range of doses tested. CONCLUSION: ADH-1 is the first anti-N-cadherin compound tested in humans. In N-cadherin-positive patients, ADH-1 showed an acceptable toxicity profile, linear PK and hints of antitumour activity in gynaecological cancers.

Developmental regulation of metabotropic glutamate receptor 1 splice variants in olfactory bulb mitral cells.

Alternative splicing of the metabotropic glutamate receptor 1 (mGluR1) receptor gene generates two major receptor isoforms, mGluR1a and mGluR1b, differing in intracellular function and distribution. However, little is known on the expression profiles of these variants during development. We examined the mRNA expression profile of mGluR1a/b in microdissected layers and acutely isolated mitral cells in the developing mouse olfactory bulb. This analysis showed that the two mGluR1 variants are differentially regulated within each bulb layer. During the first postnatal week, the mGluR1a isoform replaces GluR1b in the microdissected mitral cell layer (MCL) and in isolated identified mitral cells, coinciding with a developmental epoch of mitral cell dendritic reorganization. Although mGluR1a mRNA is expressed at high levels in both the adult external plexiform layer (EPL) and MCL, Western blotting analysis reveals a marked reduction of the mGluR1a protein in the MCL, where mitral cell bodies are located, and strong labeling in the EPL, which contains mitral cell dendrites. This suggests that there is increased dendritic trafficking efficiency of the receptor in adult. The temporal and spatial shift in mGluR1b/a expression suggests distinct roles of the mGluR1 isoforms, with mGluR1b potentially involved in the early mitral cell maturation and mGluR1a in dendritic and synapse function.

BDNF/ TrkB interaction regulates migration of SVZ precursor cells via PI3-K and MAP-K signalling pathways.

Neuroblasts born in the subventricular zone (SVZ) migrate along the rostral migratory stream, reaching the olfactory bulb (OB) where they differentiate into local interneurons. Several extracellular factors have been suggested to control specific steps of this process. The brain-derived neurotrophic factor (BDNF) has been demonstrated to promote morphological differentiation and survival of OB interneurons. Here we show that BDNF and its receptor TrkB are expressed in vivo throughout the migratory pathway, implying that BDNF might also mediate migratory signals. By using in vitro models we demonstrate that BDNF promotes migration of SVZ neuroblasts, acting both as inducer and attractant through TrkB activation. We show that BDNF induces cAMP response element-binding protein (CREB) activation in migrating neuroblasts via phosphatidylinositol 3-kinase (PI3-K) and mitogen-activated protein kinase (MAP-K) signalling. Pharmacological blockade of these pathways on SVZ explants significantly reduces CREB activation and impairs neuronal migration. This study identifies a function of BDNF in the SVZ system, which involves multiple protein kinase pathways leading to neuroblast migration.

Maternal deprivation and early handling affect density of calcium binding protein-containing neurons in selected brain regions and emotional behavior in periadolescent rats.

Adverse early life experiences can induce neurochemical changes that may underlie modifications in hypothalamic-pituitary-adrenal axis responsiveness, emotionality and cognition. Here, we investigated the expression of the calcium binding proteins (CBPs) calretinin, calbindin and parvalbumin, which identify subpopulations of GABAergic neurons and serve important functional roles by buffering intracellular calcium levels, following brief (early handling) and long (maternal deprivation) periods of maternal separation, as compared with non-handled controls. CBP-expressing neurons were analyzed in brain regions related to stress and anxiety. Emotionality was assessed in parallel using the social interaction test. Analyses were carried out at periadolescence, an important phase for the development of brain areas involved in stress responses. Our results indicate that density of CBP-immunoreactive neurons decreases in the paraventricular region of deprived rats but increases in the hippocampus and lateral amygdala of both early-handled and deprived rats when compared with controls. Emotionality is reduced in both early-handled and deprived animals. In conclusion, early handling and deprivation led to neurochemical and behavioral changes linked to stress-sensitive brain regions. These data suggest that the effects of early experiences on CBP containing neurons might contribute to the functional changes of neuronal circuits involved in emotional response.

Expression of the secreted factors noggin and bone morphogenetic proteins in the subependymal layer and olfactory bulb of the adult mouse brain.

The antagonism between noggin and the bone morphogenetic proteins (BMPs) plays a key role during CNS morphogenesis and differentiation. Recent studies indicate that these secreted factors are also widely expressed in the postnatal and adult mammalian brain in areas characterized by different types of neural plasticity. In particular, significant levels of noggin and BMP expression have been described in the rodent olfactory system. In the mammalian forebrain, the olfactory bulb (OB) and associated subependymal layer (SEL) are documented as sites of adult neurogenesis. Here, using multiple approaches, including the analysis of noggin-LacZ heterozygous mice, we report the expression of noggin and two members of the BMP family, BMP4 and BMP7, in these regions of the adult mammalian forebrain. We observe that along the full extent of the SEL, from the lateral ventricle to the olfactory bulb, noggin and BMP4 and 7 are mainly associated with the astrocytic glial compartment. In the OB, BMP4 and 7 proteins remain primarily associated with the SEL while strong noggin expression was also found in cells located in different OB layers (i.e. granule, external plexiform, glomerular layers). Taken together our data lead us to hypothesize that within the SEL the antagonism between noggin and BMPs, both produced by the glial tubes, act through autocrine/paracrine inductive mechanisms to maintain a neurogenetic environment all the way from the lateral ventricle to the olfactory bulb. In the OB, their expression patterns suggest multiple regulatory roles on the unusual neural plasticity exhibited by this region.

HuC/D confocal imaging points to olfactory migratory cells as the first cell population that expresses a post-mitotic neuronal phenotype in the chick embryo.

In the present study, the expression of the HuC/D RNA-binding proteins, a marker of neurons that have left the mitotic cycle, in cells migrating from the olfactory neuroepithelium toward the telencephalon in the chick embryo was investigated by means of immunofluorescence and confocal laser microscopy. Results showed that this migratory cell population is early and massively labeled by the a-HuC/D antibody starting from the first olfactory pit stage. At this developmental stage, olfactory migratory cells appeared to be the only neuronal population that expressed the HuC/D antigens in the whole embryo. In following developmental stages, the great majority of migratory cells, the number of which increased progressively, continued to be heavily immunopositive for the a-HuC/D antibody while immunopositivity to this antibody begins to be detected in other regions of the nervous system. HuC/D immunopositivity persisted until stage 30 HH (about 6.5 days), the later developmental stage investigated in this study, when colocalization with GnRH was detected. Negativity to the anti-proliferating cell nuclear antigen (anti-PCNA) immunostaining, a marker of S-phase, showed that migratory olfactory cells have left the mitotic cycle. Altogether, these results suggest that we have identified the first population of post-mitotic neurons in the developing nervous system of the chick embryo.

Glia-independent chains of neuroblasts through the subcortical parenchyma of the adult rabbit brain.

In the brains of adult mammals long-distance cell migration of neuronal precursors is known to occur in the rostral migratory stream, involving chains of cells sliding into astrocytic glial tubes. By combining immunocytochemistry for polysialylated neural cell adhesion molecule (PSA-NCAM), neuronal and glial antigens, endogenous and exogenously administered cell-proliferation markers, and light and electron microscopy 3D reconstructions, we show that chains of newly generated neuroblasts exist both inside and outside the subventricular zone of adult rabbits. Two groups of chains were detectable within the mature brain parenchyma: anterior chains, into the anterior forceps of the corpus callosum, and posterior chains, close to the external capsule. Parenchymal chains were not associated with any special glial structures, thus coming widely in contact with the mature nervous tissue, including unmyelinated/myelinated fibers, astrocytes, neurons, and oligodendrocytes. These chains of cells, unlike those in the subventricular zone, do not display cell proliferation, but they contain BrdUrd administered several weeks before. Telencephalic areas, such as the putamen, amygdala, claustrum, and cortex, adjacent to the chains harbor numerous PSA-NCAM-positive cells. The counting of newly generated cells in these areas shows small differences in comparison with others, and a few cells double-labeled for BrdUrd/PSA-NCAM (after 1-month survival) and for BrdUrd/NeuN (after 2 months) were detectable. These results demonstrate the occurrence of glial-independent chains of migrating neuroblasts, which directly contact the mature brain parenchyma of adult mammals. These chains could provide a possible link between the adult germinative layers and a very low-rate/long-term process of cell addition in the telencephalon.

Hepatocyte growth factor/scatter factor facilitates migration of GN-11 immortalized LHRH neurons.

The molecular cues regulating the migratory process of LHRH neurons from the olfactory placode into the brain are not well known, but gradients of chemotropic and chemorepellent factors secreted by the targets are likely to play a key role in guidance mechanisms. Hepatocyte growth factor/scatter factor (HGF/SF) is a pleiotropic cytokine inducing cell migration. It is involved in a variety of developmental processes through interaction with its receptor c-Met. Here we show that c-Met-antibody labels LHRH migrating neurons in the olfactory mesenchyme of E12 mouse and analyze the potential chemotropic effect of HGF/SF on two immortalized LHRH cell lines, GT1-7 and GN11, isolated from tumors developed in the hypothalamus and in the olfactory bulb, respectively. By RT-PCR analysis, Western blotting, and immunocytochemistry, we provide evidence for a high level of c-Met expression in GN11, but not in GT1-7, cells. In addition, HGF/SF treatment promotes specific migratory activity of GN11 cells, as demonstrated by collagen gel assay, time-lapse video microscopy, and Boyden's chamber experiments. Such promotion is inhibited by the neutralizing antibody. The data reported here represent the first direct evidence of a chemotactic effect of HGF/SF on immortalized LHRH neurons.

Sexually dimorphic neurogenesis is topographically matched with the anterior accessory olfactory bulb of the adult rat.

The accessory olfactory bulb (AOB) is a sexually dimorphic structure of the vomeronasal system, which plays a role in the control of sexual behaviors. In adult rats, we have demonstrated previously that the migrating neuroblasts of the subependymal layer (SEL) directed to the main olfactory bulb (MOB) also reach the AOB. To tackle the relation between sexual dimorphism and targeted cell migration, we quantified the neo-neurogenesis in the AOB of adult rats of both sexes. Our results confirm a morphological sexual dimorphism in the AOB granular layer volumes. We showed that the number of newly generated cells reaching the AOB in both sexes was considerable, even if lower than those directed to the MOB. Moreover, we demonstrated that the rate of neurogenesis in the anterior AOB of the two sexes was significantly different.

Evidence of very early neuronal migration from the olfactory placode of the chick embryo.

Cell migration from the olfactory neuroepithelium is a very peculiar phenomenon in the development of the nervous system. In this paper, we provide evidence that, in the chick embryo, migration of cells from the olfactory neuroepithelium begins earlier than previously reported, namely at the same time as the first olfactory placode differentiation, that occurs several hours before the superficial ectodermal invagination that gives rise to the olfactory pit. Moreover, we provide evidence that very early migrating cells express the HuC/D RNA-binding protein antigen, a specific neuronal marker. These observations refocus our knowledge on the very first developmental stages of olfactory neuroepithelium.