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R Insausti

Publications and source records attributed to R Insausti.

At least 19 recordsLinked to original sources
PubMed2006

Thiamine-like fibers in the monkey brain: an immunocytochemical study.

The distribution of thiamine-immunoreactive structures was studied in the brain of the monkey using an indirect immunoperoxidase technique. Fibers containing thiamine, but no thiamine-immunoreactive cell bodies, were found. The highest density of fibers containing thiamine was observed in the pulvinar nucleus and in the region extending from the pulvinar nucleus to the caudate nucleus. In the mesencephalon, immunoreactive fibers containing thiamine were only found at rostral level close to the medial lemniscus (at the mesencephalic-diencephalic junction). In the thalamus, the distribution of thiamine-immunoreactive structures was more widespread. Thus, immunoreactive fibers were found in nuclei close to the midline (centrum medianum/parafascicular complex), in the ventrolateral thalamus (medial geniculate nucleus, inferior pulvinar nucleus), and in the dorsolateral thalamus (lateral posterior nucleus, pulvinar nucleus). Finally, in the anterior commissure and in the cerebral cortex a low density immunoreactive fibers was visualized. Thus, in the brainstem, no immunoreactive structures were visualized in the medulla oblongata, pons, or in the medial-caudal mesencephalon, and no immunoreactive fibers were observed in the cerebellum, hypothalamus and in the basal ganglia. The present report describes the first visualization and the morphological characteristics (thick, smooth and short, medium or long in length) of the thiamine-immunoreactive fibers in the primate central nervous system using an antiserum directed against this vitamin. The distribution of thiamine-immunoreactive structures in the monkey brain suggests that this vitamin could be involved in several physiological mechanisms.

Animals↗
PubMed2006

Riboflavin-like inmunoreactive fibers in the monkey brain.

Using an antiserum directed against the vitamin riboflavin, we studied the distribution of riboflavin-like immunoreactive structures in the monkey brain. In the mesencephalon, at the level of the mesencephalic-diencephalic junction, single riboflavin-like immunoreactive fibers were observed in its dorsal part, whereas a low density of immunoreactive fibers was found below the surface of the section and close to substantia nigra, and a high density was observed above the substantia nigra and close to the medial geniculate nucleus. In the thalamus, single riboflavin-like immunoreactive fibers were found in the ventral regions of the lateral posterior and the medial geniculate nuclei; a low density in the region located above the medial and lateral geniculate nuclei and a high density in the ventral part of the pulvinar nucleus and in the region extending from this latter to the caudate nucleus. Immunoreactive fibers were not observed in the medulla oblongata, pons, cerebellum, hypothalamus, basal ganglia and cerebral cortex. Moreover, no riboflavin-like immunoreactive cell bodies were observed in the monkey brain. The distribution of riboflavin-like immunoreactive fibers in the monkey suggests that this vitamin could be involved in several physiological mechanisms.

Animals↗
PubMed2005

Reciprocal connections between olfactory structures and the cortex of the rostral superior temporal sulcus in the Macaca fascicularis monkey.

Convergence of sensory modalities in the nonhuman primate cerebral cortex is still poorly understood. We present an anatomical tracing study in which polysensory association cortex located at the fundus and upper bank of the rostral superior temporal sulcus presents reciprocal connections with primary olfactory structures. At the same time, projections from this polysensory area reach multiple primary olfactory centres. Retrograde (Fast Blue) and anterograde (biotinylated dextran-amine and 3H-amino acids) tracers were injected into primary olfactory structures and rostral superior temporal sulcus. Retrograde tracers restricted to the anterior olfactory nucleus resulted in labelled neurons in the rostral portion of the upper bank and fundus of superior temporal sulcus. Injections of biotinylated dextran-amine at the fundus and upper bank of the superior temporal sulcus confirmed this projection by labelling axons in the dorsal and lateral portions of the anterior olfactory nucleus, as well as piriform, periamygdaloid and entorhinal cortices. Retrograde tracer injections at the rostral superior temporal sulcus resulted in neuronal labelling in the anterior olfactory nucleus, piriform, periamygdaloid and entorhinal cortices, thus providing confirmation of the reciprocity between primary olfactory structures and the cortex at the rostral superior temporal sulcus. The reciprocal connections between the rostral part of superior temporal sulcus and primary olfactory structures represent a convergence for olfactory and other sensory modalities at the cortex of the rostral temporal lobe.

Amino Acids↗
PubMed2004

Folic acid in the monkey brain: an immunocytochemical study.

The present report describes the first visualization of folic acid-immunoreactive fibers in the mammalian central nervous system using a highly specific antiserum directed against this vitamin. The distribution of folic acid-immunoreactive structures was studied in the brainstem and thalamus of the monkey using an indirect immunoperoxidase technique. We observed fibers containing folic acid, but no folic acid-immunoreactive cell bodies were found. In the brainstem, no immunoreactive structures were visualized in the medulla oblongata, pons, or in the medial-caudal mesencephalon, since at this location immunoreactive fibers containing folic acid were only found at the rostral level in the dorsolateral mesencephalon (in the mesencephalic-diencephalic junction). In the thalamus, the distribution of folic acid-immunoreactive structures was more widespread. Thus, we found immunoreactive fibers in the midline, in nuclei close to the midline (dorsomedial nucleus, centrum medianum/parafascicular complex), in the ventral region of the thalamus (ventral posteroinferior nucleus, ventral posteromedial nucleus), in the ventrolateral thalamus (medial geniculate nucleus, lateral geniculate nucleus, inferior pulvinar nucleus) and in the dorsolateral thalamus (lateral posterior nucleus, pulvinar nucleus). The highest density of fibers containing folic acid was observed in the dorsolateral mesencephalon and in the pulvinar nucleus. The distribution of folic acid-immunoreactive structures in the monkey brain suggests that this vitamin could be involved in several mechanisms, such as visual, auditory, motor and somatosensorial functions.

Animals↗
PubMed2003

Postnatal development of calcium-binding proteins immunoreactivity (parvalbumin, calbindin, calretinin) in the human entorhinal cortex.

The entorhinal cortex is an essential component in the organization of the human hippocampal formation related to cortical activity. It transfers, neocortical information (ultimately distributed to the dentate gyrus and hippocampus) and receives most of the hippocampal output directed to neocortex. At birth, the human entorhinal cortex presents similar layer organization as in adults, although layer II (cell islands) and upper layer III have a protracted maturation. The presence of interneurons expressing calcium-binding proteins (parvalbumin, calbindin-D28K (calbindin) and calretinin) is well documented in the adult human entorhinal cortex. In many of them the calcium binding is co-localized with GABA. Parvalbumin-immunoreactive cells and fibers were virtually absent at birth, their presence increasing gradually in deep layer III, mostly in the lateral and caudal portions of the entorhinal cortex from the 5th month onwards. Calbindin immunoreactive cells and fibers were present at birth, mainly in layers II and upper III; mostly at rostral and lateral portions of the entorhinal cortex, increasing in number and extending to deep layers from the 5th month onwards. Calretinin immunoreactivity was present at birth, homogeneously distributed over layers I, II and upper V, throughout the entorhinal cortex. A substantial increase in the number of calretinin neurons in layer V was observed at the 5th month. The postnatal development of parvalbumin, calbindin and calretinin may have an important role in the functional maturation of the entorhinal cortex through the control of hippocampal, cortical and subcortical information.

Calbindin 1↗
PubMed2002

Spinal implants of olfactory ensheathing cells promote axon regeneration and bladder activity after bilateral lumbosacral dorsal rhizotomy in the adult rat.

PURPOSE: We performed spinal implantation of olfactory ensheathing cells to demonstrate dorsal root afferent regeneration as well as bladder activity restoration after lumbosacral L6 to S2 rhizotomy. MATERIALS AND METHODS: Spinal segments receiving bladder innervation, usually L6, S1 and S2, were identified by bipolar stimulation of the ventral roots. Bilateral section of the identified dorsal roots L6 to S2 was performed in 18 male Wistar rats. Immediately after rhizotomy olfactory ensheathing cells or vehicle was unilaterally injected in the vicinity of the sacral parasympathetic nucleus in 9 rats each using a glass micropipette and air pulse system. The severed roots were reattached to the cord with fibrin glue and the animals recovered under antibiotic prophylaxis. RESULTS: Anatomical regeneration of bladder wall primary afferents was demonstrated by the presence of labeled wheat germ agglutinin-horseradish peroxidase fibers in the dorsal horn and sacral parasympathetic nucleus in 8 of 9 cases of olfactory ensheathing cell implantation but not in the 9 controls injected with vehicle. One week after surgery all rats had an atonic bladder on cystometrography. At 6 weeks 8 of the 9 olfactory ensheathing cell implanted rats had recovered bladder activity. No recovery was observed in controls, in which vehicle was injected instead of olfactory ensheathing cells. CONCLUSIONS: Regenerated primary afferent fibers from the bladder project to the sacral parasympathetic nucleus, where they presumably form synapses mediating the recovery of bladder activity. Thus, olfactory ensheathing cell implants in the adult rat promote sensory axon regeneration, target reinnervation and bladder activity restoration.

Afferent Pathways↗
PubMed2001

Serotonin 5-HT(1A) receptor expression is selectively enhanced in the striosomal compartment of chronic parkinsonian monkeys.

Cynomolgus monkeys (Macaca fascicularis) were chronically treated with the dopaminergic neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) until stable parkinsonism was reached. Two months later, monkeys were sacrificed and monoamine content was measured in different brain regions of the lesioned monkeys and of age-matched controls. 5-HT(1A) serotonin receptor density was measured in coronal sections labeled with [(3)H]8-OH-DPAT. As expected, dopamine was virtually nonexistent in the caudate nucleus and putamen of MPTP-treated monkeys. Serotonin levels were significantly reduced in different brain regions, particularly in the raphe nuclei. 5-HT(1A) receptor density of control animals was high in the hippocampus, notably in the CA1 field and also in the raphe nuclei, and much lower in the striatum, where 5-HT(1A) receptors showed a patchy distribution which corresponded to striosomes with poor calbindin immunostaining. 5-HT(1A) receptor density was reduced in hippocampal fields and in the raphe nuclei of parkinsonian monkeys. Conversely, in the severely lesioned striatal nuclei 5-HT(1A) receptor density was increased at caudal levels of the striatum, particularly in the putamen. The results tend to support the possibility of an increased synthesis of 5-HT(1A) receptors in brain regions with higher neuronal cell death. Upregulation of this 5-HT receptor subtype in the limbic compartment of the striatum may represent a compensatory event for the serotonergic dysfunction and associated mental disorders in neurodegenerative diseases such as Parkinson disease.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed2001

Cortical projections of the non-entorhinal hippocampal formation in the cynomolgus monkey (Macaca fascicularis).

Episodic memory consolidation requires the integrity of the anatomical pathways between the cerebral cortex and the hippocampal formation. Whilst the largest cortical output of the hippocampal formation originates in the entorhinal cortex, direct projections from CA1, subiculum and presubiculum to the cortex have been reported. The aim of this study is the assessment of the extent, topography and relative strength of those projections, as a parallel/alternate route of memory processing. A total of 45 injections in 28 Macaca fascicularis monkeys were used. Cortical deposits of fluorescent tracers (20 cases, 3% Fast Blue, 2% Diamidino Yellow) or 1% WGA-HRP (eight cases) were made in different cortical areas of the frontal, temporal and parietal lobes, as well as cingulate cortex by direct exposure of the cortical surface. After appropriate survival, animals were perfused and the brains serially sectioned at 50 microm and the retrograde labelling charted with an X-Y digitizing system. Retrograde neuronal labelling was observed in CA1, subiculum, presubiculum and parasubiculum; it was absent in the dentate gyrus, CA3 and CA2. Compared to other portions of the hippocampal formation, the CA1-subiculum border had the highest number of labelled neurons (especially after deposits in the rostral perirhinal cortex), followed by medial frontal cortex, temporal pole, orbitofrontal, anterior and posterior cingulate cortices, parietal and inferotemporal cortices, and no labelling after posterior inferotemporal and lateral frontal cortices. Our results indicate that CA1, subiculum, presubiculum and parasubiculum send direct output to cortical areas. This nonentorhinal, hippocampal formation cortical output may be relevant in memory processing.

Animals↗
PubMed2000

Implanted BDNF-producing fibroblasts prevent neurotoxin-induced serotonergic denervation in the rat striatum.

Degeneration of serotonergic fibers in the rat striatum was produced by local administration of the serotonergic neurotoxin 5, 7-dihydroxytryptamine (5,7-DHT) or the dopaminergic neurotoxin 1-methyl-4-phenylpyridinium (MPP(+)), which is also toxic to serotonergic neurons. One week before neurotoxin administration, fibroblasts engineered to express the human BDNF gene were grafted into the mesencephalon, dorsal to the substantia nigra. Rats implanted with fibroblasts expressing the LacZ gene were used as controls, as well as sham-operated animals (not injected with any neurotoxin). After a survival period of 1 week, the serotonergic innervation of the striatum was assessed by measuring serotonin (5-HT) content and by immunohistochemical detection of 5-HT positive fibers. BDNF-producing cells prevented the striatal 5-HT loss induced by local administration of either 5,7-DHT or MPP(+), as well as the striatal dopamine (DA) loss induced by the latter neurotoxin. Grafting of fibroblasts carrying the BDNF or the Lac-Z gene did not modify striatal 5-HT or DA content in sham-operated animals. In 5, 7-DHT-lesioned rats, implanted or not with control Lac-Z fibroblasts, a striking reduction in the density of 5-HT immunoreactive fibers was observed. By contrast, the density of 5-HT fibers was similar in rats implanted with BDNF-producing fibroblasts as compared to sham-operated controls. The protective effect of BDNF on the damage to serotonergic terminals induced by the two neurotoxins suggests the interest of this neurotrophin in the treatment of behavioral disorders associated to neurodegenerative diseases.

1-Methyl-4-phenylpyridinium↗
PubMed2000

Experimental study following inactive implantation of an auditory brain stem implant in nonhuman primates.

We report changes in the cochlear nuclei (CNs) after 3 months of bilateral auditory deafferentation and simultaneous unilateral implantation of a dummy auditory brain stem implant (ABI) in 6 nonhuman primates (Macaca fascicularis). These specimens were compared to CNs of 9 controls and 7 bilaterally deafferented animals without implantation. The ABI array consists of 3 platinum electrodes mounted on a silicone pad with the back side covered with Dacron. No migration of the ABI was observed. All deafferented animals showed astrocytic reorganization in the CNs. Histologic changes consisted of superficial reactions around the implant, with formation of fibrillar bundles of fusiform cells, and the presence of giant cells close to the Dacron. Other findings were related to surgical trauma. The dummy ABI did not itself provoke serious adverse reactions in the CNs. Our observations support the possibility of ABI reimplantation surgery.

Animals↗
PubMed1999

Stereological assessment of the glial reaction to chronic deafferentation of the cochlear nuclei in the macaque monkey (Macaca fascicularis).

Neurectomy of the auditory nerve produces a massive deafferentation of the cochlear nuclei (CN) in the brainstem. Degenerating primary afferents are removed in the acute phase, and this is followed by a synaptic reorganization in the CN. As part of an ongoing study on the effect and applicability of auditory brain implants in the CN of Macaca fascicularis monkeys, we studied the chronic response of astrocytes in the CN to bilateral deafferentation of the VIIIth cranial nerve. Four control and five deafferentated animals were employed. The treated animals had a bilateral extradural section of the VIIIth cranial nerve and a survival of 3 months. Animals were euthanized and perfused, and the brainstem was serially sectioned. The astrocyte population of the CN was studied by glial fibrillary acidic protein (GFAP) immunohistochemistry and quantified by unbiased stereological methods. The total length of astrocyte processes, L(proc), was estimated as the product of nuclear volume V(nuc), which was estimated by the Cavalieri method, times the ratio L(V)(proc, nuc) of process length to nuclear volume. Mean nuclear volume was significantly lower in deafferented animals, whereas the mean ratio L(V)(proc, nuc) was higher (albeit no statistical significance was reached). However, the mean total astrocytic process length was virtually the same in both groups. The absence of a length increase in the glial processes indicates a decrease of the astrocytic reaction after the acute phase. No glial scar is present in the CN of the monkey after long-term deafferentation, so the usefulness of auditory brain implants to stimulate CN neurons directly as a means to overcome deafness resulting from direct damage to the VIIIth cranial nerve (i.e., acoustic neuromas) is plausible.

Animals↗
PubMed1999

Projections from the lateral, basal, and accessory basal nuclei of the amygdala to the hippocampal formation in rat.

The amygdaloid complex and hippocampal formation mediate functions involving emotion and memory. To investigate the connections that regulate the interactions between these regions, we injected the anterograde tracer Phaseolus vulgaris-leucoagglutinin into various divisions of the lateral, basal, and accessory basal nuclei of the rat amygdala. The heaviest projection to the entorhinal cortex originates in the medial division of the lateral nucleus which innervates layer III of the ventral intermediate and dorsal intermediate subfields. In the basal nucleus, the heaviest projection arises in the parvicellular division and terminates in layer III of the amygdalo-entorhinal transitional subfield. In the accessory basal nucleus, the parvicellular division heavily innervates layer V of the ventral intermediate subfield. The most substantial projection to the hippocampus originates in the basal nucleus. The caudomedial portion of the parvicellular division projects heavily to the stratum oriens and stratum radiatum of CA3 and CA1. The accessory basal nucleus projects to the stratum lacunosum-moleculare of CA1. The subiculum receives a substantial input from the caudomedial parvicellular division. The parasubiculum receives dense projections from the caudal portion of the medial division of the lateral nucleus, the caudomedial parvicellular division of the basal nucleus, and the parvicellular division of the accessory basal nucleus. Our data show that select nuclear divisions of the amygdala project to the entorhinal cortex, hippocampus, subiculum, and parasubiculum in segregated rather than overlapping terminal fields. These data suggest that the amygdaloid complex is in a position to modulate different stages of information processing within the hippocampal formation.

Amygdala↗
PubMed1999

Anxiogenic-like effects and reduced stereological counting of immunolabelled 5-hydroxytryptamine6 receptors in rat nucleus accumbens by antisense oligonucleotides.

The physiological role of 5-hydroxytryptamine6 receptors in the central nervous system has not yet been elucidated. The high affinity of various psychotropic drugs for 5-hydroxytryptamine6 receptors has led to the suggestion that this receptor type may be a novel target in neuropsychiatry. We have found that continuous intracerebroventricular administration of a 5-hydroxytryptamine6 receptor antisense oligonucleotide, but not of a missense oligonucleotide, produced an anxiogenic-like response in rats using two different models of anxiety, the social interaction test and the elevated plus-maze. Neither oligonucleotide treatment modified locomotor activity, rectal temperature or food intake, suggesting a low or null neurotoxicity. The effectiveness of the treatment with the designed antisense oligonucleotide to block the synthesis of the protein encoded by the target mRNA was assessed by immunolabelling 5-hydroxytryptamine6 receptors in the nucleus accumbens, where this receptor is highly expressed, using previously characterized specific antibodies. The density of the immunostaining was quantified by means of an unbiased three-dimensional stereologic procedure, which revealed a significant reduction (-25%) in the number of immunolabelled neuronal elements. These results suggest that, in addition to other 5-hydroxytryptamine receptor subtypes, 5-hydroxytryptamine6 receptors in the nucleus accumbens may participate in anxiety-related neurobiological mechanisms.

Animals↗
PubMed1999

Antibodies and antisense oligonucleotide for probing the distribution and putative functions of central 5-HT6 receptors.

Among the recently cloned serotonin (5-hydroxytryptamine, 5-HT) receptors, the 5-HT6 subtype is of special interest for at least two reasons: 1) it is abundant in limbic areas which participate in the control of mood and emotion; and 2) some antidepressants and antipsychotics are potent 5-HT6 receptor antagonists. Studies using polyclonal anti-5-HT6 receptor antibodies and an antisense oligonucleotide were performed in order to investigate further the function(s) of 5-HT6 receptors in the rat brain. Immunocytochemistry at the light and electron microscope levels showed that 5-HT6 receptors are mainly confined to the dendritic compartment, suggesting that they could mediate 5-HT actions on neuronal firing. In some limbic areas, 5-HT6 receptor-like immunoreactivity is also associated with neuronal cilia with yet unknown functions. Continuous i.c.v. infusion with an antisense oligonucleotide for 3-4 days resulted in decreased 5-HT6 receptor-like immunostaining of the nucleus accumbens and anxiogenic behaviours in the social interaction and elevated plus maze tests. Selective 5-HT6 receptor ligands are eagerly expected to investigate further the potential implication of these receptors in limbic-dependent behaviours.

Amino Acid Sequence↗
PubMed1999

Recovery of chronic parkinsonian monkeys by autotransplants of carotid body cell aggregates into putamen.

We have studied the effect of unilateral autografts of carotid body cell aggregates into the putamen of MPTP-treated monkeys with chronic parkinsonism. Two to four weeks after transplantation, the monkeys initiated a progressive recovery of mobility with reduction of tremor and bradykinesia and restoration of fine motor abilities on the contralateral side. Apomorphine injections induced rotations toward the side of the transplant. Functional recovery was accompanied by the survival of tyrosine hydroxylase-positive (TH-positive) grafted glomus cells. A high density of TH-immunoreactive fibers was seen reinnervating broad regions of the ipsilateral putamen and caudate nucleus. The nongrafted, contralateral striatum remained deafferented. Intrastriatal autografting of carotid body tissue is a feasible technique with beneficial effects on parkinsonian monkeys; thus, this therapeutic approach could also be applied to treat patients with Parkinson's disease.

Animals↗
PubMed1998

Human medial temporal lobe in aging: anatomical basis of memory preservation.

The integrity of the hippocampal formation is necessary for the correct function of declarative memory for facts and events. Normal aging is associated with a widespread decrease in cortical volume, including the hippocampal formation and related cortical areas, although in many cases, memory is only minimally impaired. In the present study, we quantified the extent of the parahippocampal gyrus (entorhinal cortex, as well as the medial temporal lobe proisocortical areas related to memory function, such as temporopolar cortex, perirhinal cortex, and posterior parahippocampal cortex) in 42 control cases. After detailed cytoarchitectonic analysis (based on homology with the nonhuman primate medial temporal lobe), planimetric measurement (calculated area) of a two-dimensional reconstruction of the parahippocampal gyrus was performed, and cases older than 70 years were compared with cases younger than 70 years. All areas showed atrophy with aging (average, entorhinal cortex, 5%; perirhinal cortex, 4%; posterior parahippocampal cortex, 15%; temporal pole, not assessable). Both entorhinal and posterior parahippocampal cortices reached statistical significance. Our results suggest that cortical areas relevant in memory function, and anatomically linked to the hippocampus, present a small degree of atrophy with aging, thereby permitting the reciprocal flow of information between the hippocampus and the cerebral cortex necessary for memory encoding and retrieval.

Age Factors↗
PubMed1998

Hippocampal volume and neuronal number in Ts65Dn mice: a murine model of Down syndrome.

Ts65Dn mouse displays a partial triplication of chromosome 16 and is adopted as a model for Down syndrome (DS). It is known that Ts65Dn mice present memory deficiencies. In order to gain insight into the cause of these deficiencies, we studied the possibility of changes in volumes and neuronal numbers in different regions of the hippocampus (dentate gyrus, CA3, CA2 and CA1) in trisomic mice as compared to control littermates using stereological methods. The mean hippocampal volumes of Ts65Dn mice did not show significant differences as compared to controls, except in CA2 where there was a barely significant decrease. However, mean neuron number was significantly lower in Ts65Dn mice than in controls in dentate gyrus (43.7 x 10(4), CV 21%, n = 5, vs. 30.4 x 10(4), CV 18.1%, n = 4) and higher in CA3 (23.1 x 10(4), CV 18.9% vs. 33.3 x 10(4), CV 14.9%). These quantitative changes may account for the memory deficiencies observed in Ts65Dn mice.

Animals↗