The semaphorins are the largest family of repulsive axon guidance molecules. Secreted semaphorins bind neuropilin receptors and repel sensory, sympathetic and motor axons. Here we show that CA1, CA3 and dentate gyrus axons from E15-E17... more
The semaphorins are the largest family of repulsive axon guidance molecules. Secreted semaphorins bind neuropilin receptors and repel sensory, sympathetic and motor axons. Here we show that CA1, CA3 and dentate gyrus axons from E15-E17 mouse embryo explants are selectively repelled by entorhinal cortex and neocortex. The secreted semaphorins Sema III and Sema IV and their receptors Neuropilin-1 and -2 are expressed in the hippocampal formation during appropriate stages. Sema III and Sema IV strongly repel CA1, CA3 and dentate gyrus axons; entorhinal axons are only repelled by Sema III. An antibody against Neuropilin-1 blocks the repulsive action of Sema III and the entorhinal cortex, but has no effect on Sema IV-induced repulsion. Thus, chemorepulsion plays a role in axon guidance in the hippocampus, secreted semaphorins are likely to be responsible for this action, and the same axons can be repelled by two distinct semaphorins via two different receptors.
Research Interests: Neuroscience, Biology, Development, Medicine, In Situ Hybridization, and 15 moreBiological Sciences, Hippocampus, Mice, Animals, Axon Guidance, Chemotaxis, Glycoproteins, Dentate Gyrus, Entorhinal Cortex, Neocortex, Axons, Neuropilin, Hippocampal formation, coculture techniques, and Medical and Health Sciences
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The hemispheric cerebellar cortex from 174- to 420-day-old nervous mice has been studied with Golgi, Cajal-reduced silver and electron microscopic techniques. In all mice, the existence of a continuous process of Purkinje cell death,... more
The hemispheric cerebellar cortex from 174- to 420-day-old nervous mice has been studied with Golgi, Cajal-reduced silver and electron microscopic techniques. In all mice, the existence of a continuous process of Purkinje cell death, indicated by the presence of few of these neurons in early stages of degeneration, has been established. The morphology of such degenerating cells, as well as the removal of the necrotic debris and the consecutive isolation of presynaptic fibers by glia are described. In the molecular layer, and in spite of the important Purkinje cell loss, numerous varicosities belonging to parallel fibers persist. They can be either synapsing on interneurons or concentrated in small clusters of 2-10 boutons covered by astrocytic processes. The synaptic investment of stellate and basket cells, as well as the length and the branching pattern of their dendritic fields are not significantly changed, besides the increase in afferent terminals deprived of their postsynaptic targets. Basket formations, as numerous as in control cerebellum, are forming a discontinuous row at the superficial third of the granular layer. Over 90% of these baskets are devoid of Purkinje cells, however, their ultrastructural features mimic those of the same terminals in control mice, with the exception that few of them can either establish heterologous synapses with granule cell dendrites, or develop gap junctions between them. The significance of the persistence of normal looking presynaptic elements long time after deprivation of their postsynaptic targets is discussed in relation to the role that function can play in the stabilization of synaptic contacts.
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Research Interests: Cognitive Science, Biology, Immunohistochemistry, Medicine, Anatomy, and 15 moreBrain, Cerebellum, Animals, Medical Physiology, Autoradiography, Postnatal development, Comparative Neurology, Cerebellar Cortex, Cell Survival, Neurosciences, Glutamate decarboxylase, Climbing Fiber, Cell count, Leucine, and Efferent
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Background. Atrial fibrillation (AF) increases the risk for stroke but also for non-stroke major adverse cardiovascular events (MACE). The 2MACE score was recently proposed to predict these events. Since the interest of microRNAs (miRNAs)... more
Background. Atrial fibrillation (AF) increases the risk for stroke but also for non-stroke major adverse cardiovascular events (MACE). The 2MACE score was recently proposed to predict these events. Since the interest of microRNAs (miRNAs) in cardiovascular diseases is increasing, we aimed to investigate whether miRNA levels may improve the predictive performance of the 2MACE score. Methods. We included consecutive AF patients stable on vitamin K antagonist therapy. Blood samples were drawn at baseline and plasma expression of miRNAs was assessed. During a median of 7.6 (interquartile range (IQR) 5.4–8.0) years, the occurrence of any MACE (nonfatal myocardial infarction/cardiac revascularization and cardiovascular death) was recorded. Results. We conducted a miRNA expression analysis in plasma from 19 patients with and without cardiovascular events. The miRNAs selected (miR-22-3p, miR-107, and miR-146a-5p) were later measured in 166 patients (47% male, median age 77 (IQR 70–81) years...
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Cyclic AMP (cAMP) is known to play a key role in regulating insulin action, and it is well documented that in several cases of physiological insulin resistance its concentration is increased. Since late pregnancy in the rat is associated... more
Cyclic AMP (cAMP) is known to play a key role in regulating insulin action, and it is well documented that in several cases of physiological insulin resistance its concentration is increased. Since late pregnancy in the rat is associated with liver insulin resistance, we have studied possible alterations of some cellular mechanisms regulating the cAMP metabolism. (1) Liver cAMP concentration was shown to be increased by some 30% and 50% at 18 and 22 days of pregnancy respectively, compared with virgins. (2) Basal adenylate cyclase activity was higher only in the 18-days-pregnant rat, and the forskolin-stimulated maximal activity was similar in the three groups of animals. (3) alpha s protein is decreased in term-pregnant rats; however, coupling between Gs and adenylate cyclase is only impaired in the 18-days-pregnant animals, and stimulation by glucagon is impaired in both groups of pregnant animals. (4) Gi-2 protein was shown to be unable to elicit the tonic inhibition of adenylate...
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Mutations affecting mobile domains of antithrombin induce conformational instability resulting in protein polymerization that associates with a severe clinical phenotype, probably by an unknown gain of function. By homology with other... more
Mutations affecting mobile domains of antithrombin induce conformational instability resulting in protein polymerization that associates with a severe clinical phenotype, probably by an unknown gain of function. By homology with other conformational diseases, we speculated that these variants might infect wild-type (WT) monomers reducing the anticoagulant capacity. Infective polymerization of WT polymers and different P1 mutants (p.R425del, p.R425C and p.R425H) were evaluated by using native gels and radiolabeled WT monomers and functional assays. Human embryonic kidney cells expressing the Epstein-Barr nuclear antigen 1 (HEK-EBNA) cells expressing inducible (p.R425del) or two novel constitutive (p.F271S and p.M370T) conformational variants were used to evaluate intracellular and secreted antithrombin under mild stress (pH 6.5 and 39°C for 5 h). We demonstrated the conformational sensitivity of antithrombin London (p.R425del) to form polymers under mild heating. Under these conditio...
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Here we report the characterization of a mouse model of the Bernard-Soulier syndrome generated by a targeted disruption of the gene encoding the glycoprotein (GP) Ibβ subunit of the GP Ib-IX complex. Similar to a Bernard-Soulier model... more
Here we report the characterization of a mouse model of the Bernard-Soulier syndrome generated by a targeted disruption of the gene encoding the glycoprotein (GP) Ibβ subunit of the GP Ib-IX complex. Similar to a Bernard-Soulier model generated by disruption of the mouse GP Ibα subunit, GP IbβNull mice display macrothrombocytopenia and a severe bleeding phenotype. When examined by transmission electron microscopy, the large platelets produced by a GP IbβNull genotype revealed α-granules with increased size as compared with the α-granules from control mouse platelets. Data are presented linking the overexpression of a septin protein, SEPT5, to the presence of larger α-granules in the GP IbβNull platelet. The SEPT5 gene resides approximately 250 nucleotides 5′ to the GP Ibβ gene and has been associated with modulating exocytosis from neurons and platelets as part of a presynaptic protein complex. Fusion mRNA transcripts present in megakaryocytes can contain both the SEPT5 and GP Ibβ c...
Research Interests: Genetics, Electron Microscopy, Molecular Biology, Flow Cytometry, Biology, and 15 moreMedicine, Brain, Mice, Animals, Blood, Gene, Clinical Sciences, Mouse Model, Model Generation, Cell Cycle Proteins, Bleeding Time, Nucleotides, Molecular Sequence Data, Blood platelets, and Cardiovascular medicine and haematology
While the origin of oligodendroglia in the prosencephalon and spinal cord has been extensively studied and accurately described, the origin of this cell type in the cerebellum is largely unknown. To investigate where cerebellar... more
While the origin of oligodendroglia in the prosencephalon and spinal cord has been extensively studied and accurately described, the origin of this cell type in the cerebellum is largely unknown. To investigate where cerebellar oligodendrocytes generate and which migratory pathways they follow to reach their final destination in the adult, in ovo transplants were performed using the quail/chick chimeric system. The chimeric embryos were developed up to HH43-49 (17-19 days of incubation) to map the location of donor cells and analyze their phenotype by immunohistochemistry. As a result, mesencephalic homotopic and homochronic transplants generated cellular migratory streams moving from the grafted epithelium into the host cerebellum, crossing the isthmus mainly through the velum medullare and invading the central white matter. From here, these mesencephalic cells invaded all the layers of the cerebellar cortex except the granular layer. The majority of the cells were detected in the central and folial white matter, as well as in superficial regions of the internal granular layer, surrounding the Purkinje cells. In the latter case, the donor cells presented a Bergmann glial morphology and were Vimentin positive, while in other areas they were PLP and Olig2-positive, indicating an oligodendroglial fate. The combinatory analysis of the different grafts allowed us to propose the fate map of chick cerebellar oligodendroglia at the neural tube stage. As a result, the majority of the cerebellar oligodendrocytes originate from the parabasal plate of the mesencephalon.
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Research Interests: Neuroscience, Electron Microscopy, Animal Behavior, Biology, Immunohistochemistry, and 15 moreMedicine, Muscle strength, DNA, Cell Differentiation, Humans, Mutation, Mice, Animals, Polymerase Chain Reaction, Lentivirus, Interpersonal Relations, Postural Balance, Axons, Cell count, and Medical and Health Sciences
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Cell suspensions from cerebellar primordia of 12-day mouse embryos were grafted into the cerebellum of 4-month-old Purkinje cell degeneration (pcd) mutant mice and examined 2-3 months later. In contrast to those of nontreated mutants, all... more
Cell suspensions from cerebellar primordia of 12-day mouse embryos were grafted into the cerebellum of 4-month-old Purkinje cell degeneration (pcd) mutant mice and examined 2-3 months later. In contrast to those of nontreated mutants, all of the grafted cerebella exhibited Purkinje cells that had migrated into the molecular layer, where they were clustered over its superficial two-thirds. These Purkinje cells develop flattened dendritic trees perpendicular to bundles of parallel fibers. Ultrastructural examination of their synaptic inputs and outputs disclosed that (i) as in normal cerebella, climbing fibers and axons from basket and stellate cells synapse on thick dendrites, whereas parallel fibers almost exclusively contact the distal spiny branchlets, and (ii) a substantial number of Purkinje cell axons reach their appropriate targets in the deep cerebellar nuclei, where they establish synaptic connections on large and small neurons. These results indicate that embryonic Purkinje...
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The hemispheric cerebellar cortex from 174- to 420-day-old nervous mice has been studied with Golgi, Cajal-reduced silver and electron microscopic techniques. In all mice, the existence of a continuous process of Purkinje cell death,... more
The hemispheric cerebellar cortex from 174- to 420-day-old nervous mice has been studied with Golgi, Cajal-reduced silver and electron microscopic techniques. In all mice, the existence of a continuous process of Purkinje cell death, indicated by the presence of few of these neurons in early stages of degeneration, has been established. The morphology of such degenerating cells, as well as the removal of the necrotic debris and the consecutive isolation of presynaptic fibers by glia are described. In the molecular layer, and in spite of the important Purkinje cell loss, numerous varicosities belonging to parallel fibers persist. They can be either synapsing on interneurons or concentrated in small clusters of 2-10 boutons covered by astrocytic processes. The synaptic investment of stellate and basket cells, as well as the length and the branching pattern of their dendritic fields are not significantly changed, besides the increase in afferent terminals deprived of their postsynaptic targets. Basket formations, as numerous as in control cerebellum, are forming a discontinuous row at the superficial third of the granular layer. Over 90% of these baskets are devoid of Purkinje cells, however, their ultrastructural features mimic those of the same terminals in control mice, with the exception that few of them can either establish heterologous synapses with granule cell dendrites, or develop gap junctions between them. The significance of the persistence of normal looking presynaptic elements long time after deprivation of their postsynaptic targets is discussed in relation to the role that function can play in the stabilization of synaptic contacts.
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The fate of embryonic Purkinje cells grafted over the brainstem surface of the adult Lurcher mouse was analyzed using anti-calbindin (CaBP) immunocytochemistry. Purkinje cells are able to migrate specifically into the molecular layer of... more
The fate of embryonic Purkinje cells grafted over the brainstem surface of the adult Lurcher mouse was analyzed using anti-calbindin (CaBP) immunocytochemistry. Purkinje cells are able to migrate specifically into the molecular layer of the host dorsal cochlear nucleus (DCoN) and develop dendritic trees that are practically isoplanar, suggesting synaptic interactions with the parallel fibres of the DCoN. These results provide a new argument in favour of the homology between the cerebellum and the DCoN.
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Research Interests: Biology, Brain development, In Situ Hybridization, Hippocampus, Cerebral Cortex, and 15 moreFemale, Animals, High Resolution, Entorhinal Cortex, Calbindin, Age Factors, Biological markers, Brain Function, Calcium Binding Protein, DAB, Interneurons, Extracellular Matrix Proteins, Diencephalon, Forebrain, and Medical and Health Sciences
Neuronal transplantation offers the advantages of a unique experimental situation that allows the in vivo study of cell-to-cell interactions between embryonic and adult neural partners. This approach was developed to study the possibility... more
Neuronal transplantation offers the advantages of a unique experimental situation that allows the in vivo study of cell-to-cell interactions between embryonic and adult neural partners. This approach was developed to study the possibility to replace missing neurons in pathological situations. In our model, the cerebellum with spontaneous mutations, Purkinje cell degeneration, nervous, Lurcher (pcd, nr, Lc) affecting Purkinje cells (PCs), this substitution occurs. Embryonic PCs can trigger in adult Bergmann fibers molecular changes required for migration and ultimate synaptic integration of the former, although this integration is not complete because the full contingent of efferent projections failed to establish. The grafting approach evolved as a suitable tool that, through heterotopic and heterochronic transplants, allowed the investigation of the role of cellular and molecular microenvironment on the acquisition of neuronal phenotypes and on the differential ability to regenerate amputated axons of specific populations of central neurons. Finally, new approaches developed in the twenty-first century, with the advent of stem cells and cell reprogramming, are mentioned and some of the earliest cerebellar trials with these pluripotent cells discussed.
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Neurons in the CNS of higher vertebrates lose their ability to regenerate their axons at a stage of development that coincides with peak circulating thyroid hormone (T(3)) levels. Here, we examined whether this peak in T(3) is involved in... more
Neurons in the CNS of higher vertebrates lose their ability to regenerate their axons at a stage of development that coincides with peak circulating thyroid hormone (T(3)) levels. Here, we examined whether this peak in T(3) is involved in the loss of axonal regenerative capacity in Purkinje cells (PCs). This event occurs at the end of the first postnatal week in mice. Using organotypic culture, we found that the loss of axon regenerative capacity was triggered prematurely by early exposure of mouse PCs to T(3), whereas it was delayed in the absence of T(3). Analysis of mutant mice showed that this effect was mainly mediated by the T(3) receptor α1. Using gain- and loss-of-function approaches, we also showed that Krüppel-like factor 9 was a key mediator of this effect of T(3). These results indicate that the sudden physiological increase in T(3) during development is involved in the onset of the loss of axon regenerative capacity in PCs. This loss of regenerative capacity might be pa...
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1. Brain Res. 1972 Oct 13;45(1):302-8. Localization of ( 3 H)GABA in tissue culture of rat cerebellum using electron microscopy radioautography. Sotelo C, Privat A, Drian MJ. PMID: 5075343 [PubMed - indexed for MEDLINE]. MeSH Terms: ...
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Research Interests: Neuroscience, Psychology, Biology, Medicine, Animals, and 6 moreDendrites, Rats, SYNAPSES, Neural pathways, Axons, and Neurosciences
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... a del Desarrollo "Profesora Remedios Caro Almel ", Instituto de Neurociencias, Universidad Miguel Hernandez, 03550 San Juan de Alicante, Spain Introduction ... Serafini, T., Kennedy TE, Galko, MI, Mirzayan, C., Jessell, TM... more
... a del Desarrollo "Profesora Remedios Caro Almel ", Instituto de Neurociencias, Universidad Miguel Hernandez, 03550 San Juan de Alicante, Spain Introduction ... Serafini, T., Kennedy TE, Galko, MI, Mirzayan, C., Jessell, TM and Tessier-Lavigne, M.. (1994) The netrins define a ...
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It has often been proposed that one way of replacing degenerating neurons in the brain is to implant embryonic neurons of the same type. However, in the case of so-called 'point-to-point' systems, as opposed to the... more
It has often been proposed that one way of replacing degenerating neurons in the brain is to implant embryonic neurons of the same type. However, in the case of so-called 'point-to-point' systems, as opposed to the 'paracrine' systems which mainly involve local release of neurotransmitter, functional recovery requires a precise re-establishment of the missing circuitry. We recently showed that in one point-to-point system, the cerebellum of adult mice homozygous for the mutation Purkinje cell degeneration (pcd)2, missing Purkinje cells can be replaced by grafting cerebellar primordia from normal mouse embryos. Here, we present studies of the cellular mechanisms underlying this successful replacement. Grafted Purkinje cells leave the graft to migrate along stereotyped pathways to their final position in the deficient molecular layer, where they receive synaptic contacts from adult host neurons. Both the detailed timetable and the precise cellular interactions observed are remarkably similar to those occurring during normal development. Our results suggest that the deficient molecular layer exerts a selective neurotropic effect on neurons of the missing category, and that the embryonic neurons are able to respond to this signal during a period defined by their own internal clock. We also raise the possibility that embryonic Purkinje cells can induce in adult neural cells a new type of plasticity, that of recreating a permissive microenvironment for the integration of embryonic neurons.
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The hyperspiny Purkinje cell (hpc) is a murine, autosomal recessive mutation affecting cerebellar Purkinje cells. Axonal abnormalities in these neurons have been revealed by selective silver impregnation, specific immunohistochemical... more
The hyperspiny Purkinje cell (hpc) is a murine, autosomal recessive mutation affecting cerebellar Purkinje cells. Axonal abnormalities in these neurons have been revealed by selective silver impregnation, specific immunohistochemical staining and electron microscopy. The main pathological feature consists of a massive axonal degeneration in the terminal domains of the Purkinje cell projection. This process starts approximately ten days postnatally, simultaneously with the onset of cerebellar symptoms, and evolves very rapidly. By 21 days, the vast majority of the terminal arbors have degenerated, resulting in an almost complete disruption of the corticonuclear projection. Axonal degeneration, although proceeding in a dying-back fashion, only provokes retrograde death in a small percentage of Purkinje cells (less than 15%). Purkinje cells exhibit other signs of axonal damage and axonal reaction: (a) Almost all of them bear gigantic varicosities (spheroids or torpedoes) along their transit through the granular layer. (b) In a small percentage of cases, a dendritic segment is inserted between the axon hillock and the initial segment (meganeurite). These ectopic dendrites receive a normal contingent of synaptic inputs, and are transient structures observed in four- to six-week-old mice. (c) The infra- and supraganglionic plexuses, formed by recurrent collaterals of Purkinje cell axons, have increased density and terminal domains. (d) In mice aged over 50 days, many Purkinje cells have developed 'arciform' axons, which is evidence of a compensatory reaction. The definite axonal pathology of hpc Purkinje cells confers to this mutation its own specificity, which differs from all other known mutations primarily affecting this neuronal population. Therefore, the hpc mutation offers a valuable tool to analyse some of the genetic factors involved in the differentiation and maintenance of cerebellar Purkinje cells.