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Biomedical subjects

E Martí

Publications and source records attributed to E Martí.

At least 19 recordsLinked to original sources
PubMed2004

Motor phenotypic alterations in TgDyrk1a transgenic mice implicate DYRK1A in Down syndrome motor dysfunction.

Motor deficits are among the most frequent impairments in Down syndrome (DS), but their neuropathological and molecular bases remain elusive. Here we investigate the motor profile of transgenic mice overexpressing Dyrk1a, Tg(Dyrk1a)1Cff (hereafter TgDyrk1a), a candidate gene hypothesized to cause some of the neurological defects associated with DS. We have previously shown DYRK1A expression in the cerebellum and functionally related structures, most brainstem motor nuclei and spinal cord, supporting a role for Dyrk1a in controlling motor function. Here we demonstrate that TgDyrk1a mice present DYRK1A overexpression in these areas along with specific motor dysfunction. The main finding that emerged was impairment of motor learning and alteration of the organization of locomotor behavior, which agrees with reported clinical observations in subjects with DS. These results confirm and extend previous data and provide further insight to the functional domains that might be altered in TgDyrk1a mice and underlying molecular mechanisms of DS motor dysfunction.

Animals↗
PubMed2003

Survival rate and antioxidant enzyme activity of ram spermatozoa after dilution with different extenders or selection by a dextran swim-up procedure.

The aim of this study was to evaluate the effect of four extenders (Sucrose (S), Galactose (G), milk-yolk (MY), and Fiser (F)) on the motility, membrane integrity, and functional integrity of ram spermatozoa during liquid storage at 15 degrees C. The use of either S or MY for the selection of high quality spermatozoa by a swim-up procedure was comparatively analyzed. Additionally, the activity of three antioxidant enzymes, superoxide dismutase (SOD), glutathione reductase (GR), and glutathione peroxidase (GPx) was evaluated in both swim-up selected samples maintained at 15 degrees C for 6h. Sperm motility was better preserved in MY and was significantly higher after 6h of incubation than in either S or F (P<0.0001) and G (P<0.0005). Likewise, the incidence of spermatozoa with integral and functional membranes was higher in samples diluted in MY, with no significant decrease after 6h of incubation. The comparative analysis of the swim-up procedure performed with either MY or S revealed that not only was total sperm recovery significantly (P<0.001) higher (67.3%+/-3.21 versus 47.6%+/-3.78), but also that the best survival rate of spermatozoa was found in the MY stored sample. Sperm motility, viability and response to a hypoosmotic swelling (HOS) test were also significantly higher in the MY extended sample, maintaining still significantly higher values after 6h of incubation. In addition, this sample showed higher activity values for the antioxidant defense enzyme system.

Animals↗
PubMed2001

Characterisation and evolution of a soil affected by olive oil mill wastewater disposal.

A location used for 10 years as an uncontrolled olive oil mill wastewater disposal site is studied in this work. Once it was closed the sedimented solid waste on the soil surface was removed. In order to evaluate the influence upon soil characteristics, morphological aspects and analytical parameters of a soil profile from the affected zone are compared to those of a control soil located near the landfill. The residual contamination levels in the underlying soil are determined. The results show that the wastewater infiltration in the soil has caused carbonate dissolution and redistribution and modifications in pH values, electrical conductivity, nutrient contents, phenolic compounds and biological activity of the horizons. Removal of waste, natural leaching and biological activity, in time, led to an effective decrease in electrical conductivity and phenolic compounds, although residual levels can be important even 2 years later.

Journal Article↗
PubMed2001

Neurodevelopmental delay, motor abnormalities and cognitive deficits in transgenic mice overexpressing Dyrk1A (minibrain), a murine model of Down's syndrome.

Down's syndrome (DS) is a major cause of mental retardation, hypotonia and delayed development. Murine models of DS carrying large murine or human genomic fragments show motor alterations and memory deficits. The specific genes responsible for these phenotypic alterations have not yet been defined. DYRK1A, the human homolog of the Drosophila minibrain gene, maps to the DS critical region of human chromosome 21 and is overexpressed in DS fetal brain. DYRK1A encodes a serine-threonine kinase, probably involved in neuroblast proliferation. Mutant Drosophila minibrain flies have a reduction in both optic lobes and central brain, showing learning deficits and hypoactivity. We have generated transgenic mice (TgDyrk1A) overexpressing the full-length cDNA of Dyrk1A. TgDyrk1A mice exhibit delayed cranio-caudal maturation with functional consequences in neuromotor development. TgDyrk1A mice also show altered motor skill acquisition and hyperactivity, which is maintained to adulthood. In the Morris water maze, TgDyrk1A mice show a significant impairment in spatial learning and cognitive flexibility, indicative of hippocampal and prefrontal cortex dysfunction. In the more complex repeated reversal learning paradigm, this defect turned out to be specifically related to reference memory, whereas working memory was almost unimpaired. These alterations are comparable with those found in the partial trisomy chromosome 16 murine models of DS and suggest a causative role of DYRK1A in mental retardation and in motor anomalies of DS.

Animals↗
PubMed2001

Functional genomics of Down syndrome: a multidisciplinary approach.

The availability of the DNA sequence of human chromosome 21 (HSA21) is a landmark contribution that will have an immediate impact on the study of the role of specific genes to Down syndrome (DS). Trisomy 21, full or partial, is a major cause of mental retardation and other phenotypic abnormalities, collectively known as Down syndrome (DS), a disorder affecting 1 in 700 births. The identification of genes on HSA21 and the elucidation of the function of the proteins encoded by these genes have been a major challenge for the human genome project and for research in DS. Over 100 of the estimated 300-500 genes of HSA21 have been identified, but the function of most remains largely unknown. It is believed that the overexpression of an unknown number of HSA21 genes is directly or indirectly responsible for the mental retardation and the other clinical features of DS. For this reason, HSA21 genes that are expressed in tissues affected in DS patients are of special interest.

Adaptor Proteins, Vesicular Transport↗
PubMed2001

Brain-derived neurotrophic factor reduces cortical cell death by ischemia after middle cerebral artery occlusion in the rat.

Stroke is the major cause of adult brain dysfunction. In an experimental approach to evaluate the possible beneficial effects of administration of neurotrophic factors in stroke, we have used a model of distal middle cerebral artery (MCA) occlusion in adult rats. In this model, we found: (1) a permanent reduction of brain-derived neurotrophic factor (BDNF) and its full-length receptor, TrkB, in the infarcted core; (2) a transient increase in BDNF immunoreactivity in the internal region of the border of the infarct (penumbra area) at 12 h after MCA occlusion; (3) increased truncated TrkB immunoreactivity in astrocytes surrounding the area of the infarction; and (4) increased full-length TrkB immunoreactivity in scattered neurons, distant from the infarct, in ipsilateral and contralateral cortices at 24 and 48 h after MCA occlusion. We next studied the regulation of TrkB expression by BDNF, after ischemia, and its neuroprotective effects in vivo. In control non-ischemic rats, grafting of mock- or BDNF-transfected fibroblasts (F3A-MT or F3N-BDNF cell lines, respectively) in the medial part of the somatosensory cortex increased truncated TrkB immunoreactivity in neighboring astrocytes. Grafting alone also increased full-length TrkB in the vicinity of the mock graft (at 24 and 48 h) and the BDNF-grafted graft (at 4 days). Interestingly, ischemic animals grafted with the mock-transfected cell line did not show any further regulation of TrkB receptors. However, ischemic animals grafted with the BDNF cell line showed an up-regulation of full-length TrkB expression in neurons located in the internal border of the infarct. Analysis of nuclear DNA fragmentation in situ, combined with microtubule-associated protein 2 immunohistochemistry, revealed that most cells dying in the borders of the infarct (penumbra area) at 48 h following MCA occlusion were neurons. No differences in the infarct size were found between MCA occluded, mock-transfected MCA-occluded, and BDNF-transfected MCA-occluded rats. Moreover, cell death was similar in nongrafted and mock-grafted rats subjected to MCA occlusion. However, the number of cells with nuclear DNA breaks was significantly reduced in the penumbra area close to the BDNF graft in ischemic rats. Thus, our results show that BDNF specifically up-regulates its full-length TrkB receptor in cortical neurons of the penumbra area and prevents their death in an in vivo model of focal ischemia.

Animals↗
PubMed2001

Differential regulation of chromogranin A, chromogranin B and secretoneurin protein expression after transient forebrain ischemia in the gerbil.

The chromogranin/secretogranin family of proteins is widely distributed in the central nervous system, where they are stored in large dense-core vesicles. These proproteins are actively processed into small neuroactive peptides, which influence neurotransmitter release, microglial activation and monocyte migration. These properties suggest a possible role of chromogranins/secretogranins in the response that follows central nervous system injury. In the present study, the temporal pattern of expression and the distribution of chromogranin A, chromogranin B and secretoneurin, the major proteolytic product of secretogranin-II, have been studied by immunohistochemistry after 5 min of transient forebrain ischemia in the Mongolian gerbil. A strong increase in the immunoreactivity for chromogranin A and secretoneurin was found in the CA3 pyramidal cell layer of the hippocampus, starting at 12 h, with a peak at 24 h and decrease at 48 h after transient forebrain ischemia. In the hippocampal formation, a rise in chromogranin A immunoreactivity was detected in neurons of the subiculum and the granule cell layer of the dentate gyrus. In addition, increase in the immunoreactivity for chromogranin A and secretoneurin was found in selected neurons of the neocortex. Chromogranin A and secretoneurin immunostaining patterns were similar in ischemic and control gerbils at 4 and 7 days following the ischemic insult. Chromogranin A and secretoneurin immunoreactivity in consecutive sections showed co-localization of both antigens but also selective overexpression of chromogranin A or secretoneurin in various neurons. No changes in chromogranin B immunoreactivity were detected across the time course following transient forebrain ischemia. These data indicate that changes in the expression of the chromogranin family of proteins after ischemia are selective for chromogranin A and secretoneurin. To our knowledge, this is the first study showing that the expression of the chromogranin family of proteins is differentially regulated after an ischemic insult in selected neuronal populations of the hippocampal formation and the cerebral cortex. Furthermore, the present data suggest a possible implication of chromogranin A and secretoneurin in the pathophysiology of transient forebrain ischemia.

Animals↗
PubMed2001

Control of retinal ganglion cell axon growth: a new role for Sonic hedgehog.

Retinal ganglion cell (RGC) axons grow towards the diencephalic ventral midline during embryogenesis guided by cues whose nature is largely unknown. We provide in vitro and in vivo evidence for a novel role of Sonic hedgehog (SHH) as a negative regulator of growth cone movement. SHH suppresses both the number and the length of neurites emerging from the chick retina but not from neural tube or dorsal root ganglia explants, without interfering with their rate of proliferation and differentiation. Similarly, retroviral-mediated ectopic expression of Shh along the chick visual pathway greatly interferes the growth of RGC axons. Upon SHH addition to grown neurites, the intracellular level of cAMP decreases, suggesting that the dampening of growth cone extension mediated by SHH may involve interaction with its receptor Patched which is expressed by RGC. Based on these findings, we propose that Shh expression at the chiasm border defines a constrained pathway within the ventral midline which serves to guide the progression of RGC axons.

Animals↗
PubMed2001

Vitronectin regulates Sonic hedgehog activity during cerebellum development through CREB phosphorylation.

During development of the cerebellum, Sonic hedgehog (SHH) is expressed in migrating and settled Purkinje neurons and is directly responsible for proliferation of granule cell precursors in the external germinal layer. We have previously demonstrated that SHH interacts with vitronectin in the differentiation of spinal motor neurons. Here, we analysed whether similar interactions between SHH and extracellular matrix glycoproteins regulate subsequent steps of granule cell development. Laminins and their integrin receptor subunit alpha6 accumulate in the outer most external germinal layer where proliferation of granule cell precursors is maximal. Consistent with this expression pattern, laminin significantly increases SHH-induced proliferation in primary cultures of cerebellar granule cells. Vitronectin and its integrin receptor subunits alpha(v) are expressed in the inner part of the external germinal layer where granule cell precursors exit the cell cycle and commence differentiation. In cultures, vitronectin is able to overcome SHH-induced proliferation, thus allowing granule cell differentiation. Our studies indicate that the pathway in granule cell precursors responsible for the conversion of a proliferative SHH-mediated response to a differentiation signal depends on CREB. Vitronectin stimulates phosphorylation of cyclic-AMP responsive element-binding protein (CREB), and over-expression of CREB is sufficient to induce granule cell differentiation in the presence of SHH. Taken together, these data suggest that granule neuron differentiation is regulated by the vitronectin-induced phosphorylation of CREB, a critical event that terminates SHH-mediated proliferation and permits the differentiation program to proceed in these cells.

Animals↗
PubMed2001

Identification of Kir2.1 channel activity in cultured trabecular meshwork cells.

PURPOSE: To study the presence of inwardly rectifying K(+) (Kir) channels in cultured bovine (BTM) and human (HTM) trabecular meshwork cells. METHODS: Cultures of BTM and HTM cells were obtained by an extracellular matrix digestion technique. Whole-cell patch-clamp recordings of BTM cells were performed with the appropriate solutions to detect K(+) currents. Also, Western blot analysis of Kir2.1 protein expression was performed on both cultured BTM and HTM cells. RESULTS: A strong inwardly rectifying current at negative potentials to the equilibrium potential for K(+) (E(K+)) and highly selective for K(+) was detected in 60% of cultured BTM cells. The slope conductance of the inward rectification was more pronounced when the extracellular [K(+)] was increased and was proportional to [K(+)](0.45). The current was blocked by Ba(2+) and Cs(+) in a voltage- and concentration-dependent manner, with K(d) at 0 mV, of 74.7 microM and 45.6 mM, respectively. Current amplitude was reduced by increasing extracellular [Ca(2+)]. The current was insensitive to 10 microM glibenclamide and 10 nM tertiapin. The application of 100 microM 8-Br-cAMP reduced the current by 50%. Kir2.1 channel expression was detected in confluent monolayers of BTM and HTM cells by Western blot analysis. CONCLUSIONS: A population of cultured BTM cells expressed an inwardly rectifying K(+) current that illustrates the biophysical and pharmacologic characteristics of the detected Kir2.1 channel protein. Kir2.1 channels are also thought to be present in HTM cells. Kir2.1 channels could be related to TM physiology, because they are involved in contractile and cell volume regulatory responses, two mechanisms that modify TM permeability.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed2000

Expression of chick BMP-1/Tolloid during patterning of the neural tube and somites.

The expression pattern described here is that of the chick BMP-1/Tolloid family of secreted metalloproteinases during early stages of development. BMP-1/Tolloid transcripts are expressed in the blastoderm, at gastrulation stages and as the neural plate forms and neural tube folds, BMP-1/Tolloid is found at the neural plate/ectodermal transition. Expression is maintained in the premigratory neural crest, and transiently in the migrating cephalic neural crest cells. BMP-1/Tolloid is also expressed in the caudal, but not in the anterior notochord, and in the ventral neural tube at the time of dorso-ventral patterning. Further sites of BMP-1/Tolloid expression are the lateral plate mesoderm and the dermotome and the myotome of the somites.

Animals↗
PubMed2000

Differential c-Fos and caspase expression following kainic acid excitotoxicity.

Caspases play crucial roles in the inflammatory response and in the cell pathway leading to apoptosis. Caspase 1 (ICE), 2 (Nedd2), 3 (CPP32), 6 (Mch2) and 8 (Mch5, FLICE) expression was examined using immunohistochemistry in the brains of rats and gerbils following systemic administration of kainic acid (KA). The distribution of caspase expression was compared with the distribution of c-Fos expression, a transcription factor that is produced in response to the excitotoxic insult. Strong caspase 2 immunoreactivity was found in microglia up to 6 h following KA administration. Focal strong expression of caspases 1, 2, 3, 6 and 8 was observed in astrocytes and neurons, from 12 to 48 h after KA injection, in areas in which a number of neurons were committed to die. This distribution was in contrast with the generalised distribution of c-Fos expression following KA administration. Only a minority of neurons in the entorhinal cortex, amygdala and hilus, but a majority of neurons in selected thalamic nuclei, exhibited strong caspase expression in KA-treated rats. Similar findings, although minimised, were observed in KA-treated gerbils. Double-labelling caspase immunohistochemistry and in situ end-labelling of nuclear DNA fragmentation disclosed co-localisation of strong caspase expression and nuclear DNA breaks in a small percentage of neurons but no co-localisation in astrocytes. Western blots of entorhinal cortex and neocortex homogenates showed cleavage of certain caspase substrates in KA-treated rats. The intensity of the bands corresponding to lamin B and protein kinase C-delta was decreased in the entorhinal cortex following KA administration. Several bands appeared in the entorhinal cortex and neocortex paragraph signin Western blots processed for the demonstration of poly(ADP-ribose) polymerase (PARP), thus indicating that other proteases, in addition to caspases, cleaved PARP following KA administration. Taken together, these findings indicate that KA excitotoxicity triggers caspase expression which, although predominant in regions subjected to irreversible cell damage, has only a weak association with the presence of nuclear DNA breaks and neuron cell death. Although these results suggest caspase activation, further studies have to be performed to elucidate whether caspase activation plays a crucial role in KA excitotoxicity.

Animals↗
PubMed2000

Prion protein deposition and abnormal synaptic protein expression in the cerebellum in Creutzfeldt-Jakob disease.

Prion protein (PrP(C)) is a cell membrane-anchored glycoprotein, which is replaced by a pathogenic protease-resistant, beta-sheet-containing isoform (PrP(CJD) or PrP(SC)) in human and animal prion encephalopathies, including sporadic Creutzfeldt-Jakob disease. Cell fractionation methods show that PrP(C) localizes in presynaptic membrane-enriched fractions. Following infection, abnormal PrP accumulates in nerve cell processes and synaptic regions. The present study examines the possible correlation between abnormal PrP deposition and the expression of synaptic proteins controlling neurotransmission in the cerebellum of six 129 Met/Met sporadic cases of Creutzfeldt-Jakob disease. Aggregates of protease-resistant PrP-positive granules, reminiscent of cerebellar glomeruli, were found in the granular cell layer, whereas fine punctate PrP-immunoreactive deposits occurred in the molecular layer. Small numbers of diffuse, irregular plaque-like PrP deposits in the molecular and granular cell layers were present in every case. The somas of Purkinje cells, and stellate, basket and Golgi neurons, were not immunostained. PrP-immunoreactive fibres were found in the album of the cerebellum and hilus of the dentate nucleus. Punctate PrP deposition decorated the neuropil of the dentate nucleus and the surface of dentate neurons. Synaptic protein expression was examined with synaptophysin, synapsin-1, synaptosomal-associated protein of 25,000 mol. wt, syntaxin-1 and Rab3a immunohistochemistry. Reduced synaptophysin, synapsin-1, synaptosomal-associated protein of 25,000 mol. wt, syntaxin-1 and Rab3a immunoreactivity was noted in the granular cell layer in every case, but reduced expression was inconstant in the molecular layer. Synaptophysin accumulated in axon torpedoes, thus indicating abnormal axon transport. Expression of synaptic proteins was relatively preserved in the dentate nucleus, although synaptophysin immunohistochemistry disclosed large coarse pericellular terminals in Creutzfeldt-Jakob disease, instead of the fine granular terminals in control cases, around the soma of dentate neurons. Finally, Rab3a accumulated in the cytoplasm of Purkinje cells, thus suggesting major anomalies in Rab3a transport. These observations demonstrate, for the first time, abnormal expression of crucial synaptic proteins in the cerebellum of cases with Creutzfeldt-Jakob disease. However, abnormal PrP deposition is not proportional to the degree of reduction of synaptic protein expression in the different layers of the cerebellar cortex and in the dentate nucleus. Therefore, it remains to be elucidated how abnormal PrP impacts on the metabolism of proteins linked to exocytosis and neurotransmission, and how abnormal PrP deposition results in eventual synaptic loss.

Aged↗
PubMed2000

Sonic hedgehog synergizes with the extracellular matrix protein vitronectin to induce spinal motor neuron differentiation.

Patterning of the vertebrate neural tube depends on intercellular signals emanating from sources such as the notochord and the floor plate. The secreted protein Sonic hedgehog and the extracellular matrix protein Vitronectin are both expressed in these signalling centres and have both been implicated in the generation of ventral neurons. The proteolytic processing of Sonic hedgehog is fundamental for its signalling properties. This processing generates two secreted peptides with all the inducing activity of Shh residing in the highly conserved 19 kDa amino-terminal peptide (N-Shh). Here we show that Vitronectin is also proteolitically processed in the embryonic chick notochord, floor plate and ventral neural tube and that this processing is spatiotemporally correlated with the generation of motor neurons. The processing of Vitronectin produces two fragments of 54 kDa and 45 kDa, as previously described for Vitronectin isolated from chick yolk. The 45 kDa fragment lacks the heparin-binding domain and the integrin-binding domain, RGD, present in the non-processed Vitronectin glycoprotein. Here we show that N-Shh binds to the three forms of Vitronectin (70, 54 and 45 kDa) isolated from embryonic tissue, although is preferentially associated with the 45 kDa form. Furthermore, in cultures of dissociated neuroepithelial cells, the combined addition of N-Shh and Vitronectin significantly increases the extent of motor neuron differentiation, as compared to the low or absent inducing capabilities of either N-Shh or Vitronectin alone. Thus, we conclude that the differentiation of motor neurons is enhanced by the synergistic action of N-Shh and Vitronectin, and that Vitronectin may be necessary for the proper presentation of the morphogen N-Shh to one of its target cells, the differentiating motor neurons.

Animals↗
PubMed1999

Transient increase of synapsin-I immunoreactivity in the mossy fiber layer of the hippocampus after transient forebrain ischemia in the mongolian gerbil.

Synapsin-I is a vesicular phosphoprotein, which regulates neurotransmitter release, neurite development, and maturation of synaptic contacts during normal development and following various brain lesions in adulthood. In the present study, we have examined by immunohistochemistry possible modifications in the expression of synapsin-I in the hippocampus of Mongolian gerbils after transient forebrain ischemia. The animals were subjected to 5 min of transient forebrain ischemia through bilateral common carotid occlusion, and were examined at different time-points post-ischemia. Transient forebrain ischemia produces cell death of the majority of CA1 pyramidal neurons of the hippocampus and polymorphic hilar neurons of the dentate gyrus. This is followed by reactive changes, including synaptic reorganization and modifications in the expression of synaptic proteins, which provide the molecular bases of synaptic plasticity. Transient decrease of synapsin-I immunoreactivity was observed in the inner zone of the molecular layer of the dentate gyrus, thus suggesting denervation and posterior reinervation in this area. In addition, a strong increase in synapsin-I immunoreactivity was observed in the hilus of the dentate gyrus and in the mossy fiber layer of the hippocampus at 2, 4 and 7 days after ischemia. Parallel increases in synaptophysin immunoreactivity were not observed, thus suggesting a selective induction of synapsin-I after ischemia. The present results indicate that synapsin-I participates in the reactive response of granule cells to transient forebrain ischemia in the hippocampus of the gerbil, and suggest a role for this protein in the plastic adaptations of the hippocampus following injury.

Animals↗
PubMed1999

Expression of proteins linked to exocytosis and neurotransmission in patients with Creutzfeldt-Jakob disease.

In order to characterize synaptic involvement in human spongiform encephalopathies, the expression of synaptic vesicle-associated proteins, synaptophysin and synapsin-I, and presynaptic plasma membrane proteins, synaptosomal-associated protein of 25 kDa (SNAP-25) and syntaxin-I, was examined in the brains of four patients who had suffered from sporadic Creutzfeldt-Jakob disease. Nerve cell loss, spongiform degeneration, astrocytosis, and deposition of prion protein (PrP) were observed in the cerebral cortex in every case. Decreased immunoreactivity for synaptophysin, synapsin-I, SNAP-25, and syntaxin-I was observed in the cerebral cortex in every case, thus showing generalized reduction of proteins involved in exocytosis of synaptic vesicles in the brains of patients with spongiform encephalopathy. Upregulation of synaptophysin and SNAP-25, a feature associated with beta A4 deposits in Alzheimer's disease (AD), was not observed in associated with PrP deposition. The present results indicate that synaptic pathology is a major event in spongiform encephalopathy, and suggest that synaptic loss, together with neuron loss and selective involvement of certain populations of local-circuit neurons, as shown in other studies, may account for the dramatic neurological decay and for the main neurological symptoms in patients with CJD.

Aged↗