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J A Armengol

Publications and source records attributed to J A Armengol.

At least 19 recordsLinked to original sources
PubMed2005

Calbindin, calretinin and parvalbumin immunoreactivity in the retina of the chameleon (Chamaeleo chamaeleon).

Apart from the pioneering studies of Ramon y Cajal [1893] and Rochon-Duvigneaud [1943], few studies have been devoted to the detailed study of the cytological and biochemical structure of the chameleon retina. In the present study we analyzed the expression of calbindin (CB), calretinin (CR) and parvalbumin (PV) immunoreactivities in the chameleon retina, and compared their distribution with those found in the retinas of other vertebrate species. CB immunoreactivity is dense in photoreceptors, horizontal and some lower amacrine cells. The most intense immunoreactivity was observed for calretinin; CR-ir amacrine cells are distributed throughout the inner nuclear, inner plexiform, and ganglion cell layers of the retina. Horizontal cells also display immunoreactivity to CR. A few retinal interneurons are weakly PV-ir. Double-labeling shows that all PV-ir or CB-ir cells, except the photoreceptors, are also strongly CR-ir. The distributions of these calcium-binding proteins in the chameleon retina share similarities with those observed in mammalian and avian retinas. In addition, the widespread distribution and co-localization of CB and CR reinforces the idea that these proteins play a general role in buffering the intracellular calcium levels in retinal cells. Furthermore, CB- and CR-immunoreactivities have enabled us to identify for the first time axon-bearing horizontal cells in the peripheral retina of the chameleon, very similar to those described in mammals.

Animals↗
PubMed2003

Gamma-aminobutyric acid-synthesizing cells in the retina of the chameleon Chamaeleo chameleon.

Antibodies directed against gamma-aminobutyric acid (GABA) and L-glutamic acid decarboxylases 65 and 67 kDa (GAD65 and -67) were used to study the GABAergic cell populations of the chameleon retina. GABA immunoreactivity was found in the two main types of retinal interneurons, amacrine and horizontal cells. Amacrine, displaced amacrine, and intra- and interplexiform cells displayed the strongest GABA immunoreactivity of all the retinal cell types. Horizontal cells formed a continuous GABA-immunoreactive cell layer lying against the outermost portion of the inner nuclear layer. In contrast to previous studies (Quesada et al. [1996] Cell Biol. Int. 20:395-400; [1999] Eur. J. Anat. 3:13-25), the present results demonstrate that the horizontal cells of the chameleon retina are GABA immunoreactive and that a subpopulation of these is immunolabelled by an antibody against GAD65. These results indicate that GABAergic synaptic transmission plays a key role in the outer plexiform layer of the vertebrate retina.

Amacrine Cells↗
PubMed2000

Phenylethanolamine N-methyltransferase-immunoreactive neurons in the medulla oblongata of the pigeon (Columba livia) projecting to the hypothalamic paraventricular nucleus.

The distribution and ascending projections to the hypothalamic paraventricular nucleus of phenylethanolamine N-methyltransferase (PNMT)-immunoreactive perikaria were studied in adult pigeons using a combination of retrograde transport of Fluorogold injected into the paraventricular nucleus, and double immunohistochemical procedures for PNMT, tyrosine hydroxylase and neuropeptide Y. PNMT-immunoreactive cell bodies were found in the subtrigeminal reticular nucleus of the ventrolateral medulla and in the nucleus of the solitary tract, mainly in the subnuclei: medialis superficialis, pars posterior, and medialis ventralis, pars posterior. PNMT-immunoreactive perikaria were also tyrosine hydroxylase immunoreactive, and are located within the rostral tyrosine hydroxylase immunoreactive cell groups of these areas. No perikaria double-labeled for neuropeptide Y and PNMT were found. Retrograde labeled cell bodies were observed in the subtrigeminal reticular nucleus and in the nucleus of the solitary tract. PNMT-immunoreactive retrogradely labeled cells were mainly observed in the subtrigeminal reticular nucleus. These data suggest the presence in the pigeon of medullary adrenergic cell groups partially comparable to mammalian C1 and C2 groups. Comparison of these results with data previously obtained in amphibians and reptiles suggests that the presence of a hypothalamically-projecting C1-like group might be a plesiomorphic medullary attribute in amniotes, whereas the variable presence of C2 and C3-like groups, as well as the content of NPY in the putative adrenergic perikaria, seem to be species-specific.

Animals↗
PubMed1998

Cellular and functional recovery of Parkinsonian rats after intrastriatal transplantation of carotid body cell aggregates.

We have tested the suitability of chromaffin-like carotid body glomus cells for dopamine cell replacement in Parkinsonian rats. Intrastriatal grafting of cell aggregates resulted in almost optimal abolishment of motor asymmetries and deficits of sensorimotor orientation. Recovery of transplanted animals was apparent 10 days after surgery and progressed throughout the 3 months of the study. The behavioral effects were correlated with the long survival of glomus cells in the host brain. In host tissue, glomus cells were organized into glomerulus-like structures and retained the ability to secrete dopamine. Several weeks after transplantation, dopaminergic fibers emerged from the graft, reinnervating the striatal gray matter. The special durability of grafted glomus cells in the conditions of brain parenchyma could be related to their sensitivity to hypoxia, which is known to induce cell growth, excitability, and dopamine synthesis. This work should stimulate research on the clinical applicability of carotid body autotransplants in Parkinson's disease.

Amphetamine↗
PubMed1997

Antibodies to macrophage inflammatory protein-1beta in preoptic area of rats fail to suppress PGE2 hyperthermia.

This study determined whether macrophage inflammatory protein-1beta (MIP-1beta) plays a role in the hyperthermia caused by prostaglandin E2 (PGE2) given intracerebroventricularly (i.c.v.) in the rat. In these experiments, anti-murine MIP-1beta antibody (anti-MIP-1beta) was micro-injected in the anterior hypothalamic, preoptic area (AH/POA) just before i.c.v. PGE2. The results showed that anti-MIP-1beta failed to alter the PGE2 hyperthermia. However, immunocytochemical studies revealed MIP-1beta immunoreactivity detectable in both the organum vasculosum laminae terminalis (OVLT) and AH/POA in the febrile rat. These data thus demonstrate that MIP-1beta is sequestered in diencephalic structures underlying thermoregulation even though it is not involved in PGE2 hyperthermia. This dissociation supports the viewpoint that at least two distinct systems exist in the brain which underlie a febrile response: MIP-1beta underlies one component whereas PGE2 comprises the other.

Animals↗
PubMed1997

Involvement of cerebellar cortex and nuclei in the genesis and control of unconditioned and conditioned eyelid motor responses.

The eyelid motor system of the cat was used here for the study of the kinetic properties of reflex and conditioned lid movements, and of the role played by the cerebellum in the acquisition and/or performance of both types of motor responses. Spontaneous blinks, eyelid reflex responses, eye-guided lid movements and conditioned lid responses were recorded in alert cats in simultaneity with unitary and field electrical activity of cerebellar cortex and nuclear zones related to the eyelid motor system. Results indicate that nuclear unitary activity does not precede unconditioned or conditioned lid responses, but that cerebellar nuclei are directly involved in the performance of the late components of reflex lid movements and in the acquisition of conditioned lid responses.

Action Potentials↗
PubMed1996

The avian inferior olive derives from the alar neuroepithelium of the rhombomeres 7 and 8: an analysis by using chick-quail chimeric embryos.

Homotopic and isochronic transplantation of the alar plate of the rhombomeres 7 and 8 was performed between chick and quail embryos at the stage of 10-14 somites. Analysis of the graft derivatives in 12-day-old chimeric embryos by means of the quail nucleolar marker showed that the ipsilateral inferior olive is formed from the transplanted neuroepithelium. In all embryos some cells originating from the graft were also found scattered throughout the contralateral inferior olive. The present results demonstrate that the inferior olive derives from the alar plate of the rhombomeres 7 and 8 and support the notion that a small contingent of inferior olivary neurones crosses the interolivary commissure during development.

Animals↗
PubMed1996

Ipsilaterally located olivocerebellar projection neurons of the chick.

The use of horseradish peroxidase (HRP) and 1,1'-Dioctadecyl-3,3,3',3'- tetramethyl-indocarbocyanine perchlorate (DiI) as retrograde tracers, applied in vitro within the olivocerebellar tract of both embryos (9 to 21 days old) and postnatal (3-60 days old) chickens, has allowed the observation of a small population of neurons located ipsilaterally to the placement of the tracer. These neurons, whose morphology indicated that they belong to the inferior olive rather than to the reticular formation or the raphe nuclei, followed the same developmental steps as normally placed inferior olivary neurons. Furthermore, pedunculotomy experiments made on 3-day-old chickens demonstrated that ipsilateral neurons sent their axons through the cerebellar peduncle. In contrast to the completely crossed arrangement of the olivocerebellar projection, the present results show the existence, as in the rat, of a few ipsilateral inferior olivary neurons whose significance is unclear.

Animals↗
PubMed1996

Naturally occurring neuronal death during the development of the inferior olive in the chick.

Naturally occurring neuronal death was found by in situ labelling of nuclear DNA fragmentation during the development of the chick inferior olive. Counting neuronal perikarya showed an evident loss of cells from embryonic day 18 to hatching. This reduction in neuronal numbers was followed by an increase of similar size from days 1-4 post-hatching. This biphasic evolution of the neuronal numbers is quite similar to that found in the inferior olive of rodents during the first two weeks of the postnatal life, a period also characterized by definitive synaptogenesis between climbing fibers and Pukinje cells in the cerebellum of the rodents. The similarity in the evolution of neuronal number in the inferior olive of both rodents and chicks, seems to indicate that definitive synaptogenesis between climbing fibers and Purkinje cells might occur from embryonic day 18 to postnatal day 3 in the chick cerebellum. Nevertheless, during the phase of cell loss the climbing fibers of chick have attained a more mature developmental stage than those of the rat. This difference suggests that naturally occurring neuronal death may be independent of the elimination of redundant axonic collaterals during the definitive climbing fibers-Purkinje cell synaptogenesis.

Animals↗
PubMed1996

Macrophage inflammatory protein-1beta (MIP-1beta) produced endogenously in brain during E. coli fever in rats.

Macrophage inflammatory protein-1 (MIP-1) evokes an intense fever, independent of a prostaglandin mechanism, and is now thought to play an important role in the defence response to bacterial pyrogens. The purpose of this study was 2-fold: (i) to determine whether the potent doublet of this cytokine, MIP-1beta, is actually produced in the brain in response to a pyrogenic dose of a lipopolysaccharide of Escherichia coli and (ii) to determine the anatomical site of synthesis of this cytokine in the brain. Following the intense fever produced by intraperitoneal administration of lipopolysaccharide in the unrestrained rat, MIP-1beta immunoreactivity was identified post mortem in two regions of the brain implicated in fever: the organum vasculosum laminae terminalis (OVLT) and the anterior hypothalamic, preoptic area (AH/POA). Microinjection of goat anti-mouse MIP-1beta antibody (anti-MIP-1beta) directly int the AH/POA markedly suppressed fever in rats in response to lipopolysaccharide. Further anti-MIP-1beta administered 180 min after the injection of lipopolysaccharide acted as an antipyretic and reversed the fever induced by the endotoxin. anti-MIP-1beta or control immunoglobulin G antibody microinjected into the hypothalamus immediately before the intraperitoneal injection of the control saline did not alter the temperature of the rats. Taken together, the present results demonstrate that MIP-1beta is produced in the brain in response to a bacterial endotoxin. These observations, in the light of earlier data on fever induced by MIP-1beta, further support the hypothesis that endogenously synthesized MIP-1beta acts as an intermediary factor in the evocation of fever by acting on the thermosensitive cells of the brain.

Animals↗
PubMed1996

Pattern of degeneration of the rat inferior olivary complex after the early postnatal axotomy of the olivocerebellar projection.

Neuronal death of inferior olivary neurons after early axotomy of the olivocerebellar tract was studied in newborn (P1) hemicerebellectomized rats during the first six days after lesion. The degeneration of the inferior olive showed a topographic pattern from one (P2) to six days after axotomy (P7), after which this complex had almost completely disappeared. The first degenerative changes were observed in the principal olive (P2), while the medial accessory olive was the later-degenerated area (P5). The analysis of these degenerative changes provides a reference for future experimental studies. Furthermore, the topographic study of the degenerative process demonstrated that: i) the most vulnerable neurons were dorsolaterally located, whereas the most resistant ones occupied the medial aspect of the inferior olivary complex, ii) the comparison between the topographical arrangement of the inferior olivary neurons according to their birth dates, and the rate of degenerative changes observed after hemicerebellectomy, open the possibility that the neuronal generation date and the response to the axotomy of the inferior olivary neurons could be related.

Animals↗
PubMed1995

A fast and easy fluorescent counterstaining method for neuroanatomical studies by using Acridine Orange.

Acridine Orange is commonly used as a fluorescent counterstain in fluorescent tract tracing techniques. Here we describe a method in which the substitution of the standard washing solutions (i.e., 0.9% saline) for a diluted solution of Acridine Orange (0.001%) during the perfusion of the animal before fixation provides a fluorescent counterstaining compatible with Fast Blue fluorescent retrograde labeling. In contrast to other fluorescent counterstaining methods, this procedure minimizes the diminution in the fluorescence of the tracer during the handling of sections.

Acridine Orange↗
PubMed1994

Morphological evidence for the presence of ipsilateral inferior olivary neurons during postnatal development of the olivocerebellar projection in the rat.

The presence of ipsilateral inferior olivary neurons during postnatal development of the olivocerebellar projection in the rat was investigated by two in vitro axonal tracing methods and by the axotomy of one olivocerebellar tract. The experiments were carried out before (P1), during (P5-P10) and after (P20) the period of multiple innervation of Purkinje cells by climbing fibers. According to present results: (1) ipsilateral inferior olivary neurons are distributed, on all analyzed days, throughout the entire inferior olive; (2) cell counts after axotomy experiments demonstrated that they represent a small population of inferior olivary neurons, whose number oscillated between 271 +/- 30 in young animals (pedunculotomized at P1 and killed at P7) and 26 +/- 12 in older ones (pedunculotomized at P20 and killed at P40). This experiment confirmed that most of these neurons are eliminated during the regressive events that take place during normal development of the olivocerebellar projection; and (3) few ipsilateral inferior olivary neurons, however, survive at P40, but their significance is still unclear.

Aging↗
PubMed1993

Transient ipsilateral innervation of the cerebellum by developing olivocerebellar neurons. A retrograde double-labelling study with fast blue and diamidino yellow.

In neonatal rats the injection of Fast Blue and Diamidino Yellow retrograde fluorescent tracers, each into separate cerebellar hemispheres, reveals the presence of double-labelled neurons positioned bilaterally in the inferior olivary complex during the early postnatal period (postnatal day 0 to postnatal day 5). This suggests that those neurons whose axons are able to take up both tracers project to both hemicerebellar during this period of postnatal development. Double-labelled neurons were observed in one- and five-day-old injected postnatal rats, but were absent in older animals (10 and 30 days old). The presence of these neurons coincides with a transient period of poly-innervation of Purkinje cells by climbing fibres. They may thus be participating in transitory interactions preceding the formation of definitive climbing fibre synaptic arrangements in the cerebellar cortex. The technique employed is unable to clearly define the pathway of this transient olivocerebellar projection into the ipsilateral cerebellum; however, in direct evidence--like the topographic distribution of double-labelled neurons relative to tracer injection sites, and the small number of single-labelled neurons within the ipsilateral olivary complex, together with previous data on the axonogenesis of olivary neurons [Bourrat and Sotelo (1988) Devl Brain Res. 39, 19-37]--suggests that these fibres reach the cerebellum through the contralateral inferior cerebellar peduncle and give rise to collaterals, some of which subsequently decussate again within the cerebellum. These fibres probably represent transient collaterals of the normally contralateral olivocerebellar fibres that cross the cerebellar midline and reach mirror-image loci within the ipsilateral hemicerebellum.

Amidines↗
PubMed1991

Early dendritic development of Purkinje cells in the rat cerebellum. A light and electron microscopic study using axonal tracing in 'in vitro' slices.

The early stages in the formation of Purkinje cell dendritic arbors have been analyzed using the horseradish peroxidase (HRP) 'in vitro' axonal tracing method, from embryonic day 19 (E19) to postnatal day 6 (P6). These stages comprise the transition from the bipolar Purkinje cell, at the end of its migration, to the phase of stellate cell with disoriented dendrites. Postmigratory Purkinje cells in the cortical plate exhibit poorly elaborated bipolar shapes, here named 'simple-fusiform' cells. They constitute the vast majority of labeled cells up to P0, and thereafter they decrease in number until P4. As a result of continuous outgrowth of new primary dendrites emerging from the apical pole but also from the basal and lateral aspects of the cell bodies, the Purkinje cells enter the 'complex-fusiform' phase, which peaks by P1 and slowly disappears by P6. The disappearance of 'complex-fusiform' cells is the result of an intense regressive process with resorption or retraction of the long dendrites that reaches a maximum by P3. We have called this stage: the Purkinje cell with 'regressive-atrophic' dendrites. This regression marks the initiation of the phase of the stellate cell, characterized by the explosive outgrowth of shorter perisomatic protrusions emerging in all directions. By P6, almost all the labeled Purkinje cells have attained this phase. The ultrastructural study of the labeled Purkinje cells has revealed that the transient dendrites of the fusiform cells have all the cytologic features of mature dendrites, particularly cytoskeletal elements (microtubules) and free polyribosomes. More importantly, axon terminals of unknown origin establish a few, constantly present, mature-like synaptic contacts on the dendritic shafts and spinous protrusions from P0, the earliest studied age. Their frequency increases on the Purkinje cells which enter the phase of stellate cell. Our results emphasize that the transformation of bipolar postmigratory Purkinje cells into the stellate cell stage results from a complex cascade of alternating creative and destructive processes, taking place in parallel with the formation and regression of mature synaptic contacts, between the remodelling dendritic arbors and unidentified afferent inputs. Purkinje cells, in all the different transitional stages, are present side by side in the same folial regions, at least until P4, and receive a similar contingent of synaptic input. This indicates that the dendritic remodelling is not driven by the synaptic inputs, but obeys either neural interactions that lead Purkinje cells to assume their monocellular layer configuration, or an internal clock depending on the Purkinje cell birthdate, or an interplay between these two kinds of mechanisms.

Animals↗
PubMed1991

Analysis of the ipsi- and contralateral location of the neurons of the nucleus reticularis tegmenti pontis projecting to the cerebellum and of the trajectory of their axons within the pons to the brachium pontis. An "in vivo" and "in vitro" study.

Using three different retrograde tracing techniques, we analysed the broad distribution of ipsi-, contra- and bilateral NRTP neurons projecting to the cerebellum in the adult rat. The placement of the tracers into the cerebellar peduncles allowed us to determine the overall pattern of the NRTP-cerebellar projection. At the same time, the HRP "in vitro" technique permitted the study of the axonal profiles of the NRTP neurons within the pons until reaching the brachium pontis. Our observations confirm: i) A symmetrical organization of the NRTP-cerebellar projection, the number and location of ipsi- and contralateral NRTP neurons being very similar in all cases; ii) The only exception is represented by the rostralmost portions of the NRTP, in which the neurons show a cluster-complementary pattern; iii) The axons of the NRTP neurons cross the pontine midline at the dorsalmost aspect of the BPN, occupying a medial location within the brachium pontis.

Animals↗