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R Spreafico

Publications and source records attributed to R Spreafico.

At least 55 records · Page 3Linked to original sources
PubMed1998

One hundred years of Golgi's "perineuronal net": history of a denied structure.

Perineuronal nets are reticular structures enwrapping cell bodies and the largest dendrites of several neuronal populations. Discovered by Camillo Golgi, who described them in detail in 1898, they were intensely studied by the most famous contemporary neurohistologists for about twenty years. The opinion of Ramon y Cajal that perineuronal nets were a fixation artifact ended the first period of studies. Only a few researchers, among whom the Italian neurologists Besta and Belloni, went on with their studies up to the 1930s documenting the morphology of perineuronal nets of different mammals and of man both in normal and in pathological conditions. Only after about fifty years, the advances in the field of cytochemistry allowed the elucidation of not only the actual existence of perineuronal nets, but also their chemical nature, showing conclusively that they are complex organisations of extracellular matrix molecules, namely glycoproteins and proteoglycans. The research on perineuronal nets today involves several groups engaged to elucidate their biological properties and functional role.

Animals↗
PubMed1998

Perineuronal nets: past and present.

Golgi ranked the peripheral reticulum--which adheres intimately to nerve cell surfaces--alongside the intracellular reticulum, or Golgi apparatus,which immortalized his name. At first dismissed as an artefact of capricious staining techniques, this peripheral reticulum, or perineuronal net, is now recognized as a genuine entity in neurocytology. It represents a complex of extracellular matrix molecules interposed between the meshwork of glial processes, from which they are indistinguishable, and nerve-cell surfaces. In no other branch of neuroscience has the waxing and waning of interest in any morphological entity been so pronounced as in the case of the perineuronal net. This review traces the history of this enigmatic structure from its conception to the present time, brings to light the keen observational powers of morphologists at the turn of the century and reveals how their sagacious forethought anticipated current thinking on the role of perineuronal nets.

Animals↗
PubMed1998

Calcium-binding protein immunoreactivity in the piriform cortex of the guinea-pig: selective staining of subsets of non-GABAergic neurons by calretinin.

Selective immunostaining for calcium-binding proteins identifies subpopulations of neurons with hypothetical distinct functional roles. The neuronal localization of calcium-binding proteins calretinin, parvalbumin and calbindin is here correlated to GABA and glutamate immunoreactivity in the guinea-pig piriform cortex. In the external border of the molecular layer, neurons positive for calretinin with morphological features of Cajal-Retzius cells were found. Rare GABA immunoreactive cells were observed in the same subpial region, whereas neurons containing GABA were abundant within layers Ia and Ib. Aspartate- and glutamate-immunoreactive cells were also found in the outer Ia layer. A distinct band of calretinin-immunoreactive fibres and terminals localized in layer Ia, where the afferent fibres originating from the olfactory bulb are segregated. In layer II the number of cells containing calretinin exceeded the number of neurons positive for the anti-GABA antibody. Part of the layer II calretinin-positive neurons with pyramidal shape and large apical dendrites directed toward the surface were found to be immunoreactive for the anti-glutamate antibody on adjacent sections. Neurons in layer II immunoreactive for either parvalbumin or calbindin showed morphological features of interneurons, and their number matched the count of GABA containing cells. Calretinin-positive neurons with the general morphological features of interneurons were scarcely represented in the deep piriform cortical layers, where large multipolar and small bipolar calbindin-positive cells prevailed. The present data show that in the piriform cortex of the guinea-pig calretinin, although expressed in Cajal-Retzius-like cells as in other cortical areas, also marks a subpopulation of glutamate containing pyramidal-like neurons in layer II.

Animals↗
PubMed1998

Calretinin immunoreactivity in the developing thalamus of the rat: a marker of early generated thalamic cells.

The present work was aimed to study the immunocytochemical localization of the calcium-binding protein, calretinin, in the rat thalamus from embryonic day 14 to the third postnatal week. In the adult rat thalamus, calretinin immunoreactivity is intensely expressed in some intralaminar and midline nuclei, as well as in selected regions of the reticular nucleus. At embryonic day 14, calretinin was expressed by immature and migrating neurons and fibres laterally to the neuroepithelium of the diencephalic vesicle in the region identified as reticular neuroepithelium. At embryonic day 16, immunoreactive neurons were present in the primordium of the reticular nucleus and in the region of the reticular thalamic migration, where neurons showed the morphology of migratory cells. At the end of embryonic development and in the first postnatal week, calretinin-positive neurons were observed in selected region of the reticular nucleus and it was intensely expressed in some intralaminar and midline nuclei. Bands of immunopositive fibres were also observed crossing the thalamus. During the second postnatal week, the immunolabelling in the reuniens, rhomboid, paraventricular and central medial thalamic nuclei remains very intense while a decrease of immunoreactivity in mediodorsal, centrolateral and laterodorsal nuclei was observed. The immunostaining of fibres, particularly evident in the perinatal period, progressively decreased and it was no longer visible by the end of the second postnatal week when the distribution and intensity of calretinin immunostaining was similar to that observed in the adult rat thalamus. The present findings indicate that the immunolocalization of calretinin can be used to identify subsets of thalamic neuronal population during pre- and postnatal maturation allowing also the detection of the migratory pattern of early generated reticular thalamic neurons.

Aging↗
PubMed1998

Immunocytochemical investigation on dysplastic human tissue from epileptic patients.

In this report we describe three patients with developmental cortical abnormalities (generally referred as cortical dysplasia), revealed by MRI and operated on for intractable epilepsy. Tissue, removed for strictly therapeutic reasons, was defined as the epileptogenic area by electroclinical data and stereo EEG (SEEG) recordings. Tissue samples were processed initially for histology, and selected sections were further processed for immunocytochemical investigation in order to determine whether the region of cortical dysplasia was co-extensive with the epileptogenic area. In two patients with nodular heterotopia, disorganized aggregates of neurons (as revealed by neuronal cytoskeletal markers) were found within the nodules. Both pyramidal and local circuit neurons were present in the nodules, but no reactive gliosis was present. When nodules reached the cortex, the cortical layers were disrupted. In the patient with localized cortical dysplasia, a complete disorganization of the cortical lamination was found, and numerous neurons were also present in the white matter. Disoriented pyramidal neurons weakly labelled with cytoskeletal neuronal markers were also present but no cytomegalic cells were found. One of the patients with nodular heterotopia underwent only partial resection of both the 'epileptogenic area' and of the lesion; this patient still presents with seizures. The other patient with nodular heterotopia is seizure-free after a complete lesionectomy and excision of the epileptogenic area. The third patient, with focal cortical dysplasia, had two surgeries; she became seizure-free only after the excision of the epileptogenic area detected by SEEG recording. The present data suggest that the dysplastic areas identified by MRI should not be considered as the only place of origin of the ictal discharges. From the neuropathological point of view, the focal cortical dysplasia can be considered as a pure form of migrational disorder. However, the presence of large aggregates of neurons interspersed within the white matter, in the subcortical nodular heterotopia, suggests that a defect of neuronal migration could be associated with an exuberant production of neuroblasts and/or a disruption of mechanisms for naturally occurring cell death.

Cerebral Cortex↗
PubMed1998

Altered connections between neocortical and heterotopic areas in methylazoxymethanol-treated rat.

We are currently investigating various treatments which could determine, in the rat brain, structural abnormalities mimicking those reported in human brain dysgeneses. We can induce the formation of neuronal heterotopia in the progeny of rats by means of a double injection of the cytotoxic agent methylazoxymethanol acetate (MAM) on embryonic day 15. We have now investigated the anatomical connections of these heterotopia by means of anterograde and retrograde tract tracing techniques. The induced heterotopia along the border of the lateral ventricles shared common anatomical features with the periventricular nodules in human periventricular or subcortical nodular heterotopia (PNH). The tract tracing data demonstrated the existence of reciprocal connections between the neuronal heterotopia and the ipsilateral and contralateral cortical areas, and the presence of abnormal cortico-hippocampal and cortico-cortical connections. On the basis of the connectivity patterns, it may be speculated that some cells in the heterotopia could be neurons originally committed to the cortex, that were interrupted in their migration by the MAM treatment. Given the common morphological features seen in human PNH and MAM-induced brain heterotopia, the anatomical and developmental analysis of MAM-treated rats may shed light on the mechanisms by which human brain dysgeneses develop in human patients.

Animals↗
PubMed1998

Clinical and molecular findings in the first identified Italian family with dentatorubral-pallidoluysian atrophy.

OBJECTIVES: Dentatorubral-pallidoluysian atrophy (DRPLA) is a rare autosomal dominant neurodegenerative disorder mostly observed in Japan, rarely reported in American and North European populations. The aim of this study is to characterize the clinical and molecular features of the first identified Italian DRPLA family. PATIENTS AND METHODS: We describe a 33-year-old female presenting with ataxia, intellectual decline, epilepsy, and choreoathetosis with an adult age onset. Genomic DNA was isolated from peripheral blood lymphocytes of the patient and of her healthy family members following standard procedures. Molecular tests were performed including genetic analysis for SCA1, 2, and 3 (spinocerebellar ataxias), Huntington's disease (HD) and DRPLA, due to a possible overlapping in clinical presentation. RESULTS: Molecular analysis revealed in our patient the presence of a pathological CAG expansion within the DRPLA gene. We have also documented the presence of a smaller CAG expansion in her apparently healthy brother, excluding the possibility of a de novo mutation. CONCLUSION: We conclude that both siblings may have inherited the molecular lesion from their deceased father, the mother being normal at molecular evaluation. Our kindred and a previously reported family from the island of Malta suggest that hereditary DRPLA may also be present in the Mediterranean area.

Adult↗
PubMed1998

Cortical dysplasia: an immunocytochemical study of three patients.

Human cortical dysplastic lesions are frequently associated with severe partial epilepsies. We report an immunocytochemical investigation on cortical tissue from three surgically treated patients, 20, 38, and 14 years old, with intractable epilepsy due to cortical dysplasia. The studies were performed using antibodies recognizing cytoskeletal proteins, calcium-binding proteins, and some subunits of glutamate receptors. The specimens from the three patients displayed common features: (1) focal cytoarchitectural abnormalities with an increased number of giant pyramidal neurons through all cortical layers except layer I; (2) large, round-shaped balloon cells mainly concentrated in the deepest part of the cortex and in the white matter; (3) a decrease of calcium binding protein immunopositive gamma-aminobutyric acid (GABA)ergic neurons; and (4) abnormal baskets of parvalbumin-positive terminals around the excitatory (pyramidal and large, round-shaped) neurons. These data provide evidence that the epileptogenicity in these types of cortical dysplasia is due to an increase in excitatory neurons coupled with a decrease in GABAergic interneurons.

Adolescent↗
PubMed1998

Long-term selective IgG immuno-adsorption improves Rasmussen's encephalitis.

We report that long-term selective immunoglobulin G immunoadsorption by protein A (PAI) improved seizure frequency and neuropsychological deficits in a 16-year-old patient with severe treatment-resistant Rasmussen's encephalitis (RE). Clinical improvement correlated with reduction of antiglutamate receptor 3 antibodies. The efficacy of PAI in our patient supports the autoimmune hypothesis of RE and suggests its application to avoid, or at least delay, functional hemispherectomy in selected cases.

Adolescent↗
PubMed1997

Calretinin in the thalamic reticular nucleus of the rat: distribution and relationship with ipsilateral and contralateral efferents.

In order to investigate the existence of anatomical subdivisions within the thalamic reticular nucleus (Rt), the distribution of reticular neurons expressing the calcium binding protein calretinin was investigated in the rat by means of immunocytochemistry. Calretinin immunoreactive (Cr-ir) neurons were mainly distributed in the lateral and ventral regions, and along the medial border of the Rt rostral pole. Caudal to the rostral pole, many neurons were Cr-ir in the more dorsal part of the rostral two-thirds (the "dorsal cap") of the Rt. Fewer Cr-ir neurons were present more caudally along the lateral and medial borders, and in the caudalmost part of the nucleus, related to the acoustic thalamus. The distribution of Cr-ir neurons in the rostral Rt was compared with that of neurons projecting to the ipsilateral and contralateral anterior, intralaminar, midline, and mediodorsal nuclei, or to the contralateral rostral Rt. The retrograde transport of Fluorogold revealed a remarkably precise topography of the rostral Rt: different reticular areas were found to project to different thalamic nuclei, or to different rostrocaudal or mediolateral portions of the same thalamic nucleus, with a limited degree of overlap. The double-labeling experiments demonstrated that the reticular neurons projecting to the ipsilateral anterodorsal, midline, mediodorsal, and anterior intralaminar nuclei frequently expressed calretinin; by contrast, the majority of the reticular commissural neurons did not express the protein, with the exception of neurons projecting to the contralateral mediodorsal and midline nuclei. The ipsilaterally projecting calretinin-positive neurons were frequently located along the medial edge of the rostral pole and in the dorsal cap of the nucleus, segregated from the commissural calretinin-negative neurons. The combined analysis of calretinin expression patterns and tract tracing data provided further insight in the anatomical organization of the thalamic reticular nucleus, suggesting a different neurophysiological role for the ipsilaterally vs. the contralaterally projecting reticular neurons in the modulation of the synaptic activity of the dorsal thalamus.

Animals↗
PubMed1997

Lesionectomy in epileptogenic temporal lobe lesions: preoperative seizure course and postoperative outcome.

A series of 54 patients operated on for temporal epileptogenic lesions is reported: 36 had slow growing tumours, 18 supratentorial cavernous angiomas. The patients were divided into two different groups according to the presence of seizures controlled (group 1) or not controlled (group 2) by antiepileptic drugs (AEDs). All the patients underwent preoperative scalp EEG and magnetic resonance imaging (MRI). They were operated on by pure lesionectomy, associated with amygdalo-hippocampectomy in 8 cases of uncontrolled seizures. Postoperatively they underwent MRI examination which revealed an incomplete lesionectomy in 12 cases. Patients were followed up after surgery for at least 2 years, 6 of them were reoperated on for the persistence (or regrowth) of the tumour. The results of epilepsy outcome are reported. These cases underline the importance of preoperative electroclinical study, in order to determine the relationship between lesion location and epileptic focus. If good concordance is present, a complete lesionectomy is enough to cure the patient. In other cases associated amygdalo-hippocampectomy leads to better results, while more complicated cases may need preoperative stereo-EEG studies.

Adolescent↗
PubMed1997

Gene transfer of suicide genes for the treatment of malignant gliomas: efficacy, limitations, and perspectives for a combined immunotherapy.

The potential of gene therapy strategies for malignant gliomas that are based on retroviral-mediated transfer of a "suicide gene" such as Herpes Simplex Virus-thymidine kinase HSV-tk and subsequent treatment by a prodrug (ganciclovir, for example), has been emphasized by the promising results obtained by several groups. However, further experimental data as well as preliminary clinical results indicate that the low efficiency of retroviral-mediated gene transfer in vivo as well as difficulties for the diffusion of the prodrug inside the tumour mass can limit the efficacy of this form of gene therapy. To achieve a more effective limitation of tumour growth other approaches may be combined with the "suicide gene" strategy and the enhancement of the immunological response to the tumour by cytokine gene transfer is prominent among these approaches. The authors' experiments in nude mice confirm the antineoplastic role of IL-4 and encourage testing the effects of the simultaneous transfer of IL-4 and HSV-tk genes in immunocompetent animals.

Animals↗
PubMed1997

Glutamate, aspartate and co-localization with calbindin in the medial thalamus. An immunohistochemical study in the rat.

Topographical and quantitative features of medial thalamic neurons in which aspartate (ASP) or glutamate (GLU) might act as neurotransmitters were investigated in the rat. The calcium-binding protein calbindin D-28k (CB) was exploited as a marker of neuronal subsets, thus allowing us to study also the relationships between the CB-containing neurons and those immunoreactive to excitatory amino acids. Double immunocytochemistry of ASP and CB or GLU and CB was performed in 40-microm-thick sections. The three markers were distributed in the thalamic midline, mediodorsal, anterior intralaminar and ventromedial nuclei, with regional variations. ASP-immunoreactive neurons appeared more numerous than the GLU-immunoreactive ones throughout these structures; ASP-CB or GLU-CB double-immunostained neurons were evident. ASP-, GLU- and CB-immunoreactive cells were then quantitatively evaluated in 5-microm-thick consecutive sections. Interindividual variations and different anti-ASP and anti-GLU antibodies did not result in significant differences. ASP and GLU were not co-localized. Single ASP- or GLU-immunoreactive neurons accounted for 60% of the total number of immunostained cells, and single ASP-immunopositive cells represented more than half of these neurons. Among the CB-immunoreactive cells (40% of the total), half were double immunostained; the proportion of double CB-ASP-immunopositive neurons was sevenfold higher than that of the CB-GLU-immunoreactive ones. These results indicate that ASP may act as excitatory neurotransmitter in a relatively high proportion of medial thalamic neurons, in which ASP frequently coexists with CB. Approximately 50% of the CB-immunoreactive cells did not contain either ASP or GLU, suggesting that some medial thalamic neurons may utilize a different neurotransmitter.

Animals↗
PubMed1997

Postnatal development of GABA-immunoreactive terminals in the reticular and ventrobasal nuclei of the rat thalamus: a light and electron microscopic study.

The postnatal development of inhibitory GABAergic circuits in the thalamic reticular and ventrobasal nuclei was studied in rats ranging from the day of birth to the end of the third postnatal week by means of a postembedding immunogold staining procedure to visualize GABA. In the reticular nucleus, GABA labeling was present from birth in cell bodies, dendrites, growth cones and a few synaptic terminals, whereas in the ventrobasal nucleus it was exclusively in axonal processes identifiable as growth cones, vesicle-rich profiles and synaptic terminals. In both nuclei, GABA-labeled synaptic terminals were, however, very scarce and immature in neonatal animals and they became numerous and morphologically mature only after the end of the second postnatal week. These findings suggest that inhibitory synaptic responses in the somatosensory thalamus are not yet fully mature throughout the first two postnatal weeks and support the hypothesis that GABA may initially play trophic roles. The relatively late maturation of the thalamic GABAergic system may have important functional consequences, as the reticulothalamic circuits are responsible for the generation of spindle wave oscillations whose cellular mechanisms are also involved in the generation of spike-and-wave (absence) seizures in humans and in animal models.

Animals↗
PubMed1997

GABAergic neurons in mammalian thalamus: a marker of thalamic complexity?

The present study evaluated the occurrence, distribution, and number of GABAergic neurons in the thalamus of different mammalian species (bat, mouse, rat, guinea pig, rabbit, cat, monkey, humans), by means of light microscopical immunoenzymatic localization of GABA or of its biosynthetic enzyme glutamic acid decarboxylase and by ultrastructural immunogold detection of GABA. Our data demonstrated that: 1) GABAergic local circuit neurons were detected in the thalamic visual domain in all the species analyzed, whereas in other thalamic nuclei their presence and number varied among species; 2) the number of GABAergic local circuit neurons progressively increased in the dorsal thalamus of species with more complex behavior; 3) the presence of local circuit neurons conferred a similar intrinsic organization to the dorsal thalamic nuclei, characterized by complex synaptic arrangements; 4) in the reticular thalamic nucleus, whose neurons were GABA-immunoreactive in all the examined species, the cellular density decreased from the bat to humans. These findings strongly suggest that thalamic GABAergic local circuit neurons are not directly related to the ability to perform specific sensorimotor tasks, but they are likely to reflect an increasing complexity of the local information processing that occurs at thalamic level.

Animals↗
PubMed1997

Function and organization in dysgenic cortex. Case report.

Cerebral dysgenesis is a subject of interest because of its relationship to cerebral development and dysfunction and to epilepsy. The authors present a detailed study of a 16-year-old boy who underwent surgery for a severe seizure disorder. This patient had dysgenesis of the right hemisphere, which was composed of a giant central frontoparietal nodular gray matter heterotopia with overlying large islands of cortical dysplasia around a displaced central fissure. Exceptional insight into the function, biochemistry, electrophysiology, and histological structure of this lesion was obtained from neurological studies that revealed complementary information: magnetic resonance (MR) imaging, [18]fluoro-2-deoxy-D-glucose positron emission tomography (PET), functional PET scanning, proton MR spectroscopic (1H-MRS) imaging, intraoperative cortical mapping and electrocorticography, in vitro electrophysiology, and immunocytochemistry. These studies demonstrated compensatory cortical reorganization and showed that large areas of heterotopia and cortical dysplasia in the central area may retain normal motor and sensory function despite strikingly altered cytoarchitectonic organization and neuronal metabolism. Such lesions necessitate appropriate functional imaging studies prior to surgery and cortical mapping to avoid creating neurological deficits. Integrated studies, such as PET, 1H-MRS imaging, cortical mapping, immunocytochemistry, and electrophysiology may provide information on the function of developmental disorders of cerebral organization.

Adolescent↗
PubMed1996

Ultrastructural characterization of the postnatal development of the thalamic ventrobasal and reticular nuclei in the rat.

Electron microscopy has been employed to analyze the normal maturational sequence that characterizes the postnatal development of synaptic circuits in the ventrobasal (VB) and reticular (Rt) thalamic nuclei of rats at different ages (from birth to the end of the third postnatal week). Throughout the first postnatal week, similar signs of immaturity are observed in both nuclei, mainly consisting in scarcity of cytoplasmic organelles, presence of wide extracellular spaces, and absence of myelinated fibers. Several synaptic terminals are however present from birth, thus indicating that some of the afferents have already reached and contacted their thalamic target during embryonic life. Most of the terminals are small and contain only a few round, clear vesicles, and therefore their cytological features do not allow the identification of their origin. In particular, in both nuclei, terminals with flat vesicles and symmetric specialization are only rarely observed, and in VB the ascending terminals are not distinguishable from terminals of other sources as they are in adults. During the second postnatal week, progressive maturational changes in VB and Rt lead to neurons having well-developed cytoplasmic organelles and to an elaborate neuropil containing myelinated fibers and synaptic terminals that are morphologically heterogeneous and resemble the adult ones. The permanence of growth cone-like profiles and of numerous somatic and dendritic protrusions, often contacted by synaptic terminals, indicates that a certain degree of reorganization is still taking place in both nuclei. By the end of the third postnatal week the synaptic organization of VB and Rt is indistinguishable from that observed in adults. This ultrastructural study shows that the appearance of the neuropil of VB and Rt and the morphological complexity of the synaptic arrangements characteristic of the adult rat are not present in neonates, but are gradually acquired during the first three postnatal weeks, and that they result from progressive modifications in circuit organization involving both pre- and postsynaptic elements.

Animals↗