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R Insausti

Publications and source records attributed to R Insausti.

At least 55 records · Page 3Linked to original sources
PubMed1988

Distribution of somatostatin immunoreactivity in the human dentate gyrus.

In previous immunohistochemical studies in the rat and monkey, a system of somatostatin-positive neurons and fibers was observed in the dentate gyrus of the hippocampal formation. In both species, somatostatin-immunoreactive cell bodies are located primarily in the deep or polymorphic layer of the dentate gyrus, and they give rise to a fiber system that terminates principally in the outer two-thirds of the molecular layer. In the present study, we employed the same antisera and staining procedures to determine whether the organization of the somatostatin system in the human dentate gyrus is similar to that seen in the rat and nonhuman primate. Sections of human postmortem brain material incubated with antisera directed against somatostatin 28 (S320) or somatostatin 28 (S309) demonstrated a heterogeneous population of immunoreactive cells in the hilar region of the human dentate gyrus. Fiber staining was observed both in the hilar region and throughout the molecular layer, but the densest fiber and terminal plexus were observed in the outer two-thirds of the molecular layer. In addition, there were forms of somatostatin-immunoreactive profiles in the human sections that were not previously observed in the rat or monkey. Immunoreactive, grapelike clusters of apparently large, axonal varicosities were commonly observed, for example, as were dendritic profiles containing typical dendritic spines. In general, however, staining for somatostatin immunoreactivity in the human dentate gyrus presented a picture qualitatively similar to that observed in the rat and monkey. Thus, immunohistochemical methods have allowed the analysis of a chemically defined neural system in the human brain that has been extensively studied in rat and monkey brains with both experimental and immunohistochemical methods. That the pattern of labeling in the human sections closely parallels that observed in the experimental animals provides support for the contention that immunohistochemical methods can reliably be employed to determine the normal neuroanatomical organization of the human brain. These methods may also be particularly applicable for the analysis of pathological brain conditions. In particular, alterations of the hippocampal somatostatin system have been associated with both Alzheimer's disease and temporal lobe epilepsy. It would be of interest, therefore, to apply immunohistochemical procedures to determine whether the anatomical organization of the human hippocampal somatostatin system is altered in these diseases.

Animals↗
PubMed1987

The entorhinal cortex of the monkey: I. Cytoarchitectonic organization.

As an essential preliminary to a series of experimental studies of the afferent and efferent connections of the monkey entorhinal cortex, we have carried out a detailed analysis of its cytoarchitectonic organization. Primarily on the basis of features observed in Nissl- and fiber-stained preparations, supplemented with Golgi-stained material and preparations stained for heavy metals by Timm's method and histochemically for acetylcholinesterase, the entorhinal cortex has been divided into seven fields that are named according to their rostrocaudal and mediolateral positions except for one rostrally located field that is named for the prominent input that it receives from the olfactory bulb. At rostral levels, the entorhinal cortex is marked by a number of morphological inhomogeneities. The neurons tend to be organized in patches that are surrounded by large, thick, radially oriented bundles of fibers. At caudal levels, the entorhinal cortex has a more distinctly laminated appearance, reminiscent of that in the neocortex, and most of the neurons and fiber fascicles are arranged in discrete radial columns. The cortical region adjoining the entorhinal cortex laterally, which is commonly known as the "perirhinal cortex," is in fact composed of two separate fields corresponding to areas 35 and 36 of Brodmann. Area 35 occupies the fundus and part of the lateral aspect of the rhinal sulcus. Area 36 extends from the lateral bank of the rhinal sulcus into the inferior temporal gyrus, where it borders fields TA and TE rostrally, and field TF of the parahippocampal gyrus caudally. The surface extents of each of the entorhinal fields have been determined by making "unfolded" two-dimensional maps of the region and measuring the areas with a computerized digitizing system.

Acetylcholinesterase↗
PubMed1987

The entorhinal cortex of the monkey: II. Cortical afferents.

The entorhinal cortex of the monkey is commonly viewed as the major link between the cerebral cortex and the other fields of the hippocampal formation. Until recently, however, little was known about the origins of the cortical projections to the entorhinal cortex, and most of the available information is still based on degeneration studies. We have carried out a systematic analysis of these connections by placing small injections of the retrograde tracer wheat germ agglutinin conjugated to horseradish peroxidase into each of the fields of the entorhinal cortex of the Macaca fascicularis monkey. Retrogradely labeled cells were observed in several areas of the frontal and temporal lobes, the insula, and the cingulate cortex. In the frontal lobe, the greatest number of labeled cells were observed in the orbital region and specifically in areas 13 and 13a: labeled cells were also seen in areas 14, 11, and 12. In the dorsolateral frontal cortex, labeled cells were observed mainly in the rostral half of area 46; occasionally cells were also seen in areas 9, 8, and 6. In the cingulate cortex, labeled cells were observed in area 25, area 32, and rostral levels of area 24; fewer cells were observed at caudal levels of area 24 or in area 23. The retrosplenial region (areas 30 and 29), including its caudal extension along the rostral calcarine sulcus and its ventral extension into the temporal lobe, contained numerous labeled cells. In the temporal lobe, retrogradely labeled cells were arranged in two rostrocaudally oriented bands. Rostral to the hippocampal formation, the first band encompassed the piriform and periamygdaloid cortices and areas 35 and 36; the labeling in area 36 was continuous to the temporal pole. At more caudal levels this band was located immediately lateral to the hippocampal formation and included areas 35 and 36 rostrally and areas TH and TF caudally. The second band was situated in the superior temporal gyrus where labeled cells were observed in several distinct cytoarchitectonic fields, including the parainsular cortex in the fundus of the inferior limiting sulcus. In the insula proper, retrogradely labeled cells were seen mainly in the rostral or agranular division; far fewer were observed in the dysgranular and granular insula. Whereas there is little available physiological information concerning many of the cortical regions that project to the entorhinal cortex, on anatomical grounds they may be generally characterized as polysensory associational regions.

Afferent Pathways↗
PubMed1987

The entorhinal cortex of the monkey: III. Subcortical afferents.

The subcortical afferent connections of the entorhinal cortex of the Macaca fascicularis monkey were investigated by the placement of small injections of the retrograde tracer wheat germ agglutinin conjugated to horseradish peroxidase into each of its subdivisions. Retrogradely labeled cells were observed in several subcortical regions including the amygdaloid complex, claustrum, basal forebrain, thalamus, hypothalamus, and brainstem. In the amygdala, labeled cells were observed principally in the lateral nucleus, the accessory basal nucleus, the deep or paralaminar portion of the basal nucleus, and the periamygdaloid cortex. Additional retrogradely labeled cells were found in the endopiriform nucleus, the anterior amygdaloid area, and the cortical nuclei. Retrogradely labeled cells were observed throughout much of the rostrocaudal extent of the claustrum and tended to be located in its ventral half. In the basal forebrain, retrogradely labeled cells were observed in the medial septal nucleus, the nucleus of the diagonal band, and to lesser extent within the substantia innominata. Several of the cells in the latter region were large and located within the densely packed neuronal clusters of the basal nucleus of Meynert. Most of the labeled cells in the thalamus were located in the midline nuclei. Many were found in nucleus reuniens, but even greater numbers were located in the centralis complex. Additional labeled cells were located in the paraventricular and parataenial nuclei. In all cases, numerous retrogradely labeled cells were observed in the medial pulvinar. In the hypothalamus, most of the retrogradely labeled cells were located in the supramamillary area, though scattered cells were also observed in the perifornical region and in the lateral hypothalamic area. Caudal to the mamillary nuclei there were labeled cells in the ventral tegmental area. There were relatively few labeled cells in the brainstem and these were invariably located either in the raphe nuclei or locus coeruleus.

Amygdala↗
PubMed1985

Postnatal development of the ipsilateral retinocollicular projection and the effects of unilateral enucleation in the golden hamster.

Anterograde transport of wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP) was used to study the normal development of the ipsilateral retinocollicular projection in golden hamsters, and to examine the effect of enucleation of the other eye at birth. In neonatal animals there were retinal fibers and sparsely distributed granular labeling in the superficial layers of the ipsilateral superior colliculus over its entire areal extent. Differences in the uncrossed projections of normal and enucleated animals first became clear at day 5. In normal animals, retinal fibers withdrew from the superficial layers of the superior colliculus, and the projection became concentrated in the stratum opticum, where denser clumps of label in the rostral part of the superior colliculus were first seen at day 5. In enucleated animals, the retinal projection persisted in the most superficial layers, and the density of labeling was higher than in normals. The very sensitive WGA-HRP technique showed retinal fibers extending to the caudal pole of the superior colliculus at all ages: even in normal animals more than 2 weeks of age some fibers reached as far as the inferior colliculus. When the shrunken size of the superior colliculus in the enucleated animals was taken into account, the total areal distribution of the ipsilateral projection was similar in normal animals and enucleates. The major difference between the two groups was in the higher density of ipsilateral labeling, especially in the caudal part of the superior colliculus, and in its more superficial laminar distribution in the enucleated animals.

Aging↗
PubMed1985

Spinal topography of the projection of the auricular nerve in the rabbit: a transganglionic WGA-HRP study.

The central projections of the nervous branches supplying the rabbit's concha auriculae have been determined by means of the transganglionic transport of WGA-HRP. Labeling appeared in trigeminal, C2 and C3 ganglion cells, but terminals were observed only at spinal levels (C2 and C3). There, they formed a wedge-shaped column of label centered mainly in lamina II; scattered terminals appeared in lamina III and I. These terminals constitute the afferent link of the pathway that accounts for the analgesia obtained after electrical stimulation of the concha auriculae.

Analgesia↗
PubMed1984

The commissural connections of the monkey hippocampal formation.

The commissural connections of the hippocampal formation have been analyzed in the monkey (Macaca fascicularis) using both anterograde and retrograde labeling techniques. We have observed a number of striking differences between the organization of the commissural projections in the monkey and that observed in the rodent brain. In particular, only the rostral (or uncal) part of Ammon's horn (or hippocampus proper) and the associated part of the dentate gyrus have been found to be connected by commissural fibers. This is in marked contrast to the organization of the crossed connections in the rodent brain where both major fields of the hippocampus (i.e., the regio superior and the regio inferior) receive a strong, topographically organized, projection throughout their rostrocaudal extent from the regio inferior of the opposite side, while the inner third of the molecular layer of the entire dentate gyrus receives a topographically organized input from cells in the hilar region of the contralateral dentate gyrus. The subicular complex of the monkey gives rise to a substantially greater number of commissurally directed fibers. The subiculum itself projects to the posterior portion of the contralateral medial entorhinal cortex and receives a less substantial reciprocal projection from this same area; the subiculum does not appear to be homotopically interconnected. The presubiculum gives rise to the major commissural projection of the monkey hippocampal formation. From all rostrocaudal levels of the presubiculum there is a robust projection to the contralateral medial entorhinal cortex. This projection seems to be topographically organized and terminates most heavily in layers III and IV of the entorhinal cortex. This crossed presubiculo-entorhinal projection is paralleled in its organization by an associational projection from the presubiculum to the ipsilateral entorhinal cortex, but interestingly, the presubiculum does not seem to project to the presubiculum of the opposite side. The parasubiculum projects to neither the contralateral entorhinal cortex nor the contralateral parasubiculum. However, the subicular complex as a whole appears to be in receipt of a minor input from the contralateral parahippocampal gyrus (fields TF and TH of Bonin and Bailey). Cells primarily in layer III of the medial entorhinal cortex (area 28a) project homotopically to the contralateral entorhinal cortex where they terminate in layer III. The medial entorhinal cortex also gives rise to a minor projection to the contralateral parasubiculum and to the regio superior of the contralateral hippocampus and the caudalmost part of the outer molecular layer of the dentate gyrus.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1983

Evidence for a direct projection from the superior temporal gyrus to the entorhinal cortex in the monkey.

During the course of a larger study of the afferent and efferent connections of the entorhinal cortex in the macaque monkey we have found evidence for a hitherto undescribed projection to the entorhinal cortex from the superior temporal gyrus. The evidence is derived principally from experiments in which small volumes of wheat germ agglutinin-conjugated horseradish peroxidase (WGA-HRP) were injected into different parts of the entorhinal cortex, but has been confirmed by 3H-amino acid autoradiography. After WGA-HRP injections into the entorhinal cortex, retrogradely labeled neurons have been seen mainly in layer III, but also to some extent in layer VI, throughout much of the superior temporal gyrus. The projection appears to be topographically organized in the sense that the ventral insular cortex and the adjoining temporal operculum have been found to project to the periamygdaloid cortex and the lateral division of the entorhinal cortex; the convexity of the superior temporal gyrus and the cortex along the dorsal bank of the superior temporal gyrus project further caudally to the medial division of the entorhinal cortex; and the cortex surrounding the fundus of the superior temporal sulcus projects to the perirhinal cortex. Following an injection of 3H-amino acids into the convexity of the superior temporal gyrus, terminal labeling has been seen over layers I and II of the entorhinal cortex and over layer I in the most lateral portion of the presubiculum. While the distribution of retrogradely labeled cells in our WGA-HRP experiments encompasses several cytoarchitectonically distinguishable areas in the superior temporal gyrus, the most heavily labeled field appears to coincide with what Gross and his colleagues have termed the 'superior temporal polysensory area' on the dorsal bank of the superior temporal sulcus.

Afferent Pathways↗
PubMed1981

[Primary trigeminal projection to the brain stem-reticular formation. Experimental study in the rat].

By means of a transauricular approach, the trigeminal ganglion of the rat was lesioned in order to study the presence and distribution of the primary trigeminal afferents to the brain stem reticular formation. We could observe such projections to the reticular formation close to the trigeminal nuclei (lateral part of the n. reticularis ventralis and dorsalis, n. reticularis parvocellularis, reticular zone between the trigeminal n. principalis and the n. motorius trigemini) and also to the reticular formation more medially situated (medial part of the n. reticularis dorsalis and ventralis, n. reticularis gigantocellularis and n. reticularis pontis caudalis). Topographically, those projections correlated fair well with the extent of the trigeminal nuclei more related with sensorial transmission (n. principalis and subnuclei oralis and caudalis), specially the most medial of them. Moreover, although in a very much lesser intensity, we could see projections on the nuclei pallidus and magnus of the raphe system, and on the caudodorsal part of the central grey matter. The possible modulatory actions on the sensorial transmission and motor coordination of those projections are discussed.

Afferent Pathways↗
PubMed1980

Fibers of trigeminal mesencephalic neurons in the maxillary nerve of the rat.

Indirect Wallerian degeneration after sectioning the infraorbital nerve, and retrograde axonal transport following injection of horseradish peroxidase (HRP) into the maxillary nerve were studied in rats. These experiments showed the existence of primary trigeminal neurons in the pars caudalis of the ipsilateral trigeminal mesencephalic nucleus and in the supratrigeminal nucleus of Lorente de Nó. Such neurons were interpreted as being responsible for the sensitive innervation of the periodontal membrane.

Animals↗
PubMed1977

The perirenal venous arch of the rat: its functional significance.

A functional and morphological study of the perirenal venous arch of the rat has been carried out. The various drainage possibilities of this arch through its multiple collaterals are demonstrated. Venous renal blood can reach the adrenal gland via the perirenal arch. The endocrine interactions between these organs are discussed.

Adrenal Glands↗
PubMed1976

The structure of the suprarenal venous system and its possible functional significance.

The structure of the suprarenal venous system of 25 human suprarenal glands has been studied. From a structural point of view, four portions of the suprarenal vein have been distinguished: the proximal section, the hilus section, the section of the prehilus collaterals, and the distal section. In the hilus section and the section of the prehilus collaterals, the structure of the tunica media is more complex. In the hilus section, spiral fibres are found besides the longitudinal muscle fibres. Three strata of fibres can be observed in the section of the prehilus collaterals at the point where these veins drain into the central vein: two longitudinal strata, external and internal, and a third intermediate stratum corresponding to the looped fibres. The spiral and looped fibres, on contracting, can function as a sphincter. The longitudinal fibres, by means of the traction they exert on the stroma and connective capsule of the suprarenal, increase the intraglandular pressure while decreasing the periglandular pressure. A sympathetic stimulus provokes an increase in the secretion of adrenalin, and, at the same time, a contraction of the muscle fibres of the suprarenal venous system. Under these conditions, the venous return makes use of the emissary veins; and in this way, the secreted adrenalin establishes a close contact with the cortico-suprarenal parenchyma.

Adrenal Glands↗
PubMedDate not supplied

Volumes of the entorhinal and perirhinal cortices in Alzheimer's disease.

We measured the volumes of the entorhinal, perirhinal, and temporopolar cortices on magnetic resonance images by using a recently designed histology-based protocol in 30 patients with early Alzheimer's disease (AD) and 32 healthy control subjects. Compared to the controls, all of these cortical regions were significantly atrophied in AD patients (p < 0.0001). However, the entorhinal cortex was the most severely involved brain region studied, with 40% volume loss, and this region provided the highest discriminative accuracy (92%) in separating patients with AD from healthy control subjects. Importantly, the entorhinal volume loss was evident already in mild AD. In addition, the volume of the entorhinal cortex was not dependent on age, but it did correlate significantly with the severity of the disease. Because it assesses the major site of initial neuropathological changes in AD, magnetic resonance imaging volumetric measurement of the entorhinal cortex can offer a tool for distinguishing AD patients even in the very early stages of the disease from healthy aged subjects.

Aged↗
PubMedDate not supplied

Comparative aspects of the olfactory portion of the entorhinal cortex and its projection to the hippocampus in rodents, nonhuman primates, and the human brain.

The entorhinal cortex is a component of the hippocampal formation characterized by its projection to the dentate gyrus. Cortical input is relayed to the hippocampus through the entorhinal cortex. The entorhinal cortex can be recognized best in mammals, and it reaches its maximal importance in both human and nonhuman primates. In primates, but not in rodents, the olfactory projection from the olfactory bulb is the only direct sensory projection reaching the entorhinal cortex, where it defines a rostromedial subfield (olfactory subfield of the entorhinal cortex, EO). In this communication, we consider some comparative aspects of this projection in rodents, nonhuman primates, and human brains, in relation to the forward projection to the hippocampus. We base our analysis on the following three considerations: (1) Topology: Topologically, the entorhinal cortex lies medial to the rhinal fissure, well developed in all mammals except in humans. EO maintains the same topological relationship to the rhinal fissure in the three mammalian orders. (2) Cytoarchitecture: The rostromedial portion shows poorer lamination compared with caudomedial portions of the entorhinal cortex in the three mammalian orders examined. (3) Connectivity: In rodents, the olfactory projection covers the whole extent of the entorhinal cortex, whereas it decreases substantially in macaques, where it roughly covers 15% of the entorhinal cortex. The human EO as defined by topological and cytoarchitectonic criteria may be even less than in macaques. Interestingly, good evidence exists that all of these mammalian orders maintain the same topographical scheme of projection to the rostral end of the hippocampus.

Animals↗
PubMedDate not supplied

Ganglion cell death during development of ipsilateral retino-collicular projection in golden hamster.

In rats and hamsters all parts of the superior colliculus (SC) receive a topographically organized projection from the retina of the contralateral eye, and the rostral part also has a direct input from the lower temporal crescent of the ipsilateral retina, which views the central, binocular portion of the visual field. Initially the uncrossed projection covers the entire SC, but over the first 2 weeks of postnatal life it becomes progressively restricted to its adult distribution. However, if the opposite eye is removed at birth there is a persistent widespread uncrossed projection to the SC. We have used short- and long-term retrogradely transported neuronal markers to examine the distribution and fate of the ganglion cells of origin of the uncrossed retino-collicular projection throughout postnatal development. We conclude that the withdrawal of the early exuberant projection to the caudal SC is associated with death of ganglion cells and their virtual elimination outside the temporal crescent of the ipsilateral retina. Early enucleation of the other eye rescues many of these cells.

Animals↗
PubMedDate not supplied

[Effects of selective vegetative denervation on the urinary bladder of the adult rat].

The present work is a study of the plastic capacity of the peripheral nervous system subjected to different aggressions in the case of 28 rats of the Wistar breed. They were divided into four groups: 1) sympathetic deafness (n=9); 2) parasympathetic deafness (n=9); 3) evaluation of regeneration (n=9); 4) control group (n=5). An image analyser was used to study the acetylcholinesterase (AChE) and Tyrosine Hydroxylase (TH) positive ganglionic neurones of the pelvic ganglion (GP) as well as the dorsal ganglions (GRD) compared with the control group. With group 3 a study was also made of the possible plasticity of the transacted axons using a wheat germ agglutinin conjugated-horseradish peroxidase (WGA-HRP) neurotracer. The statistical study was carried out by means of the analysis of variance (ANOVA), Fisher test and Scheffe method, with a p<0.05 taken as significant. The results show the predominant role of the pelvic nerve in the modulation of the plastic changes produced at the ganglionic level, with a lesser influence of the hypogastric nerve. Further studies are needed in order to define the specific role of each of these in the act of miction.

English Abstract↗
PubMedDate not supplied

[Functional activity of auditory cortex studied with SPECT: methodology validation and application in bilateral profound deafness].

To evaluate the differences in the functional activity of the auditory cortex between normal hearing and profound deafness, a perfusion single photon emission tomography (SPECT) study was designed. SPECT stereotaxic localisation of the auditory cortex was previously validated in 2 brains by means of an anatomical study of the macroscopic localisation and cytoarchitecture of the auditory cortex. Additionally, 15 controls with normal hearing and 30 patients with profound bilateral deafness were scanned using external anatomical point sources (glabela, ineon) for stereotaxic location of the auditory cortex. The normal controls were scanned in auditive deprivation and, in 10 cases, during a monoaural tonal stimulation. Cerebral blood flow relative to cerebellum (relCBF) was assessed in the auditory cortex. The anatomical study showed that mean differences between the true auditory cortex size and the measured SPECT value were less than 2.5 mm. Nevertheless, only the caudal aspect of this area corresponded to the primary auditory cortex in the cytoarchitectonic study. During tonal stimulation, control subjects presented a significant increase of relCBF in the auditory cortex bilaterally, with significant differences in the asymmetry index (contralateral to the side of stimulation). The relCBF in the auditory cortex of controls in deprivation conditions was significantly higher than in deaf patients. There were no significant differences between groups of deaf patients, however the highest values were seen after cochlear implant. SPECT is a suitable method for studying changes in auditory cortex activity relative to different functional conditions, with a possible role in cochlear implant candidates in predicting the future benefit of the implantation.

English Abstract↗