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W Nacimiento

Publications and source records attributed to W Nacimiento.

At least 37 records · Page 2Linked to original sources
PubMed1998

A novel early component of the cell body response in axotomized Clarke's nucleus neurons revealed by monoclonal antibody Py.

The monoclonal antibody Py was initially developed as a tool for the identification of subpopulations of hippocampal neurons. Recently it has also been demonstrated to be a useful marker for other populations of midbrain and spinal cord neurons in which the antigen showed a strong colocalization with cytoskeletal elements. To assess the possible usefulness of Py as a tool for studying lesion-induced cell body changes, densitometric analysis of altered Py-immunoreactivity (Py-IR) has been compared with that of microtubule-associated protein 2 (MAP2) in Clarke's nucleus following axotomy. One week after a unilateral transection of the dorsal spinocerebellar tract at Th9-10, Py-IR in the Clarke's nucleus ipsilateral and caudal to the lesion was reduced by approximately 40%. By 21 days, Py-IR was reduced by approximately 50% (a near maximal reduction) and remained constant up to 5 months after the lesion (the longest survival time studied). Alterations of MAP2-IR in Clarke's nucleus were later in onset, slower to develop, and less marked. The differential distribution of the Py antigen in the CNS and its rapid and long lasting loss indicate that the Py antibody is a sensitive tool for studying novel early alterations of the cytoskeleton which may be important molecular events in axotomy-induced pathological processes.

Animals↗
PubMed1998

Distribution of B-50(GAP-43) mRNA and protein in the normal adult human spinal cord.

B-50(GAP-43) is a phosphoprotein mainly found in the nervous system which plays a major role in neurite growth during development and regeneration as well as in synaptic remodelling. In the mature intact central nervous system, intense B-50 immunoreactivity (B-50-IR) can still be detected in regions which maintain residual capacity for structural re-organization. B-50 expression has been studied extensively in laboratory animals; however, its distribution and regulation in the human spinal cord is largely unknown. As a first step to analyze lesion-induced structural alterations, we investigated the distribution of B-50 protein and mRNA in the normal adult human spinal cord and dorsal root ganglia. Intense B-50-IR was localized to the superficial laminae of the dorsal horn at all segmental levels, the intermediolateral nucleus at thoracic levels and Onuf's nucleus at sacral levels. Scattered neurons, particularly in the ventral horn of lumbar and sacral segmental levels (and occasionally also in Clarke's nucleus) displayed intense B-50-IR in close apposition to the perikaryal and proximal dendritic surfaces. Nonradioactive in situ hybridization indicated that B-50 mRNA could also be detected in neurons of the ventral horn and also in the intermediolateral nucleus. The distribution of B-50 mRNA and protein in the normal human spinal cord shows a marked similarity to that reported in experimental animals, including the selective labelling of Onuf's nucleus. However, the strong B-50-IR on the surface of some large anterior horn motor neurons has not been observed in other mammals. This finding might reflect a particular state of readiness for synaptic plasticity.

Aged↗
PubMed1998

Dynamics of microglial activation in the spinal cord after cerebral infarction are revealed by expression of MHC class II antigen.

Microglial reactivity associated with induction of MHC class II (HLA-DR) antigen is a sensitive indicator for pathological events in the CNS. To assess the response of glial cells after lesions of supraspinal descending tracts, HLA-DR, CD68 and GFAP were studied immunohistochemically on spinal cord tissue of 5 patients who died after unilateral infarction of the middle cerebral artery territory, and 5 control cases. In patients who died shortly after a stroke (4-14 days) increased HLA-DR-immunoreactivity (HLA-DR-IR) could be observed in the intermediate grey matter and in the ventral horn. The CD68-IR was much less intense. After longer survival times (5 weeks to 4 months). HLA-DR-IR in the grey matter was clearly lower than that observed in the spinal cord of short survival times, but very abundant in the dorsolateral funiculus, specifically within the corticospinal tract. In white matter areas, CD68-IR was almost identical to the HLA-DR-IR. Within the grey matter, CD68-IR was similar to the control tissue. A moderate increase of GFAP-positive astrocytes could be seen only in the grey matter after longer survival times. It seems probable, that the dynamics of HLA-DR-positive microglia reflect the early phagocytosis of presynaptic terminals by microglia in target regions of descending fibre tracts. In the white matter, the removal of degenerating axons by phagocytosing microglia expressing HLA-DR and CD68 antigens is a slower process which occurs over a period of months.

Adult↗
PubMed1997

Differential distribution of immunoreactivity in the adult rat spinal cord revealed by the monoclonal antibody, Py: a light and electron microscopic study.

The monoclonal antibody Py has previously been shown to be a useful marker for subpopulations of neurons in the rat brain. However, the distribution of Py immunoreactivity in other regions of the CNS and PNS is not known. Here, we present a light and electron microscopic investigation into the distribution of Py immunoreactivity in the adult rat spinal cord, dorsal root ganglia, and peripheral nerves. Py immunoreactivity was associated with cytoskeletal elements in the cell body and dendrites of large-diameter neurons (particularly motoneurons, Clarke's nucleus neurons, and some dorsal root ganglion cells). Small-diameter neurons of lamina II (substantia gelatinosa) were Py negative. Py immunoreactivity was also detected in some populations of nerve fibers, notably axons located in the corticospinal tract, axons in the region of the white matter bordering the gray matter (presumably propriospinal axons), and also motor axons of the ventral root, but not in peripheral nerve. Dorsal roots were largely unstained. The present observations suggest a possible involvement of the Py antigen in the function or maintenance of the cytoskeleton of some populations of neurons and that the antibody may be a potentially useful tool for studying lesion-induced cytoskeletal alterations, particularly in alpha-motoneurons and Clarke's nucleus neurons.

Animals↗
PubMed1997

Axotomy-induced alterations in the red nucleus revealed by monoclonal antibody, Py, following a low thoracic spinal cord lesion in the adult rat.

The monoclonal antibody Py was previously developed as a tool for the identification of subpopulations of hippocampal neurons. Here, the differential distribution of Py immunoreactivity in the mid-brain is described showing that Py also serves as a useful marker for other populations of neurons. Medium to strong immunoreactivity was observed in the cell body and dendrites of neurons of the oculomotor nucleus, superior colliculus and substantia gelatinosa reticulata. However, particularly intense Py-immunoreactivity was identified in the magnocellular neurons in the caudal pole of the red nucleus. Unilateral transection of the rubrospinal tract at Th9-10 induced a marked reduction of Py immunoreactivity in the ventrolateral territory of the caudal pole of the axotomised red nucleus. A small but statistically significant reduction of Py-immunoreactivity was first seen at 7 days after surgery and a maximal loss of immunoreactivity (reduced to 66% of control levels) was observed by 21 days after surgery. Immunoreactivity in the axotomised red nucleus was reduced for the duration of the experiment but at the longer survival times studied (3 and 6 months) a small degrees of recovery of staining was observed in small-medium diameter atrophic neurons. These results indicate that monoclonal antibody Py, may be a useful novel and sensitive tool for investigating the cell body reaction of particular populations of axotomised CNS neurons following spinal cord injury.

Animals↗
PubMed1997

Ultrastructural characteristics of glutamatergic and GABAergic terminals in cat lamina IX before and after spinal cord injury.

The present study was designed to: 1) morphologically characterize cat glutamate and GABAergic synaptic terminals in lamina IX in the intact spinal cord at the electron microscopic level using postembedding immunochemical techniques and .2), begin an analysis of how the synaptic architecture of glutamate and GABAergic terminals changes after an ipsilateral spinal cord hemisection. The present study shows that glutamate immunoreactive terminals are characterized by a wide synaptic cleft, asymmetric synaptic membrane densities and spherical synaptic vesicles. Most of the glutamatergic terminals are presynaptic to small or medium size dendrites. In contrast, GABAergic terminals display typical pleomorphic synaptic vesicles, a narrow synaptic cleft and a symmetrical membrane density. Qualitative analysis indicated that 13-17 months after hemisection, the length of the synaptic active zones in both glutamatergic and GABAergic terminals ipsilateral to hemisection is longer than those observed in the terminals contralateral to hemisection orfin normal control cats. Furthermore, the perimeters of both dendrites and either glutamate or GABA immunoreactive terminals are longer on the hemisected side compared with those observed in the nonhemisected side of the spinal cord. The results are important for complete understanding of the mechanisms which underlie locomotor recovery in mammals following spinal cord injury.

Animals↗
PubMed1996

Transient decrease of acetylcholinesterase in ventral horn neurons caudal to a low thoracic spinal cord hemisection in the adult rat.

Light microscopic enzyme histochemistry was employed to study the alterations of acetylcholinesterase (AChE) within lumbosacral ventral horn neurons at survival times of 1, 4, 7, 14, 28, 60, and 90 days after low thoracic spinal cord hemisection in adult rats. The intensity of histochemical staining was quantified using densitometric techniques. Virtually all ventral horn neurons of sham-operated and unoperated animals, which served as controls, displayed intense AChE staining. Hemisection of the spinal cord induced a transient ipsilateral decrease of AChE staining in most neuronal cell bodies and in the neuropil of lamina IX at all segmental levels caudal to the lesion. Quantitative analysis of representative segments revealed a reduction of AChE in the ventral horn during a postoperative (p.o.) period of 1 to 28 days followed by a phase of recovery over the next two months. AChE activity still remained slightly reduced, even at 90 days p.o. The transient decrease in AChE is a well-known metabolic response of axotomized motoneurons. However, the observed changes of AChE reactivity in intact motoneurons ipsilateral and caudal to the hemisection are presumably induced by the interruption of supraspinal descending pathways. These metabolic changes may functionally affect the whole motor unit and be involved in the disturbances of motor function following spinal cord injury.

Acetylcholinesterase↗
PubMed1996

Recovery of locomotion after spinal cord hemisection: an X-ray study of the cat hindlimb.

Hemisection of the spinal cord in adult cats is a suitable model to st udy the mechanisms underlying recovery of motor functions. The initial paresis of the hindlimb is followed by a considerable improvement of locomotor functions of the affected hindlimb. Kinematic analyses of treadmill locomotion were performed from 10 days to 8 months after complete hemisections (right side) of the spinal cord at the thoracolumbar level, using X-ray cinematography for precise measurements of the hindlimb joint angles. The footfall pattern and the electromyogram were recorded. Motor control of both proximal and distal hindlimb joints improved substantially during the 1st postoperative month. However, persistent locomotor deficits were still present several months after hemisection. They could be divided into three groups of symptoms: (1) The gait pattern was disturbed with regard to interlimb coordination. The stance-phase duration of the right hindlimb was shortened. (2) The flexor capacity of the affected hindlimb was reduced, resulting in a slow insufficient flexion of the hip, knee, and ankle during the swing phase. (3) The timing of the flexion-extension events was impaired. The onset of the E1-extension was delayed and the amplitude was reduced. Electromyographic patterns of muscle activity during locomotion of the lesioned side limb differed from the contralateral hindlimb, which served as a contro. The results indicate that in spite of a good short-term functional improvement there are long-term locomotor deficits present after spinal cord hemisection.

Animals↗
PubMed1995

B-50 (GAP-43) in the rat spinal cord caudal to hemisection: lack of intraspinal sprouting by dorsal root axons.

The controversial hypothesis that intraspinal sprouting by dorsal root axons promotes reinnervation of partially denervated neurons caudal to a low thoracic cord hemisection was re-investigated in rats using quantitative immunohistochemical analysis of the neural specific growth-associated protein B-50 (GAP-43) at postoperative survival times of 3, 10, 21, 42, and 90 days. The lack of increase in B-50-immunoreactivity in all segments below the hemisection at all survival times does not support the concept of intraspinal sprouting following the removal of supraspinal descending pathways.

Animals↗
PubMed1995

Structural changes of anterior horn neurons and their synaptic input caudal to a low thoracic spinal cord hemisection in the adult rat: a light and electron microscopic study.

Structural changes in lumbosacral ventral horn neurons and their synaptic input were studied at 3, 10, 21, 42, and 90 days following low thoracic cord hemisection in adult rats by light microscopic examination of synaptophysin immunoreactivity (SYN-IR) and by electron microscopy. There was an ipsilateral transient decrease in SYN-IR at the somal and proximal dendritic surfaces of anterior horn neurons which extended caudally from the site of injury over a postoperative (p.o.) period of 42 days. Concomitantly, at 21 days p.o., perineuronal SYN-IR started to recover in upper lumbar segments. By 90 days p.o., a normal staining pattern of SYN was noted in upper and mid lumbar segments, but the perineuronal SYN-IR was still slightly below normal levels in low lumbar and sacral segments. Electron microscopy revealed ultrastructural changes coincident with the alterations in SYN-IR. At 3 days p.o., phagocytosis of degenerating axon terminals by activated microglial cells was observed at the somal and proximal dendritic surfaces of ventral horn neurons. These changes were most prominent up to two segments caudal to the lesion. At 10 days p.o., advanced stages of bouton phagocytosis were still detectable in all lumbosacral motor nuclei. Additionally, abnormal axon terminals, with a few dispersed synaptic vesicles and accumulations of large mitochondria, appeared at the scalloped somal surfaces of anterior horn neurons. At 21 days p.o., several large lumbosacral motoneurons had developed chromatolysis-like ultrastructural alterations and motoneuronal cell bodies had become partially covered by astrocytic lamellae. At 42 days p.o., there was a transient appearance of polyribosomes in some M-type boutons. In addition, at 42 and 90 days p.o., a few degenerating motoneurons were detected in all lumbosacral segments, but most displayed normal neuronal cell bodies contacted by numerous intact synapses as well as by astrocytic processes. In contrast to these striking alterations of synaptic input at somal and proximal dendritic surfaces of motoneurons, relatively few degenerating boutons were detected in the neuropil of motor nuclei at all the p.o. times studied. We suggest that the preferential disturbance of the predominantly inhibitory axosomatic synapses on ventral horn neurons may be involved in the mechanisms which influence the well-established increase in motoneuronal excitability after spinal cord injury.

Animals↗
PubMed1995

[Interventional closure of an open foramen ovale in a patient with recurrent cerebral ischemia].

In a 24-year-old female patient suffering from recurrent ischemia, an aneurysm of the atrial septum and a patent foramen ovale with significant right-to-left shunt during the Valsalva maneuver were detected by means of contrast Doppler echocardiography. After other causes had been excluded, paradoxical embolism was suspected to be the cause of the cerebral symptoms. The defect was closed by a 17-mm Rashkind occluder without complications. Six months later no residual shunt was detected and no further neurological event had occurred. This case demonstrates the feasibility of non-operative closure of those defects. This new technique could represent an alternative to long-term anticoagulation or operative procedures in selected patients.

Adult↗
PubMed1993

B-50 (GAP-43) in the spinal cord caudal to hemisection: indication for lack of intraspinal sprouting in dorsal root axons.

Sprouting of dorsal root axons has been suggested to occur in the mature cat spinal cord caudal to a hemisection at a low thoracic level sparing the dorsal columns. The lesion interrupts supraspinal descending projections, while leaving ascending collaterals of dorsal root axons intact. This hypothesis was re-evaluated by comparing the light and electron microscopic immunoreactivity of B-50 (GAP-43) on both sides of the postulated target regions for sprouting, the intermediate gray and the dorsal horn. The neural-specific phosphoprotein B-50 is involved in regenerative and developmental axonal outgrowth and synaptic plasticity. The light microscopic distribution pattern and density of B-50 immunostaining, measured by quantitative densitometry, were bilaterally symmetrical in all segments below the hemisection 3.5, 8, 14, 21, and 56 days postoperatively, as they were in the intact animal. Ultrastructurally, growth cone-like profiles were not detectable during putative periods of sprouting in regions of interest. After removal of degenerated axon terminals, vacated postsynaptic places appeared to be covered by astrocytic processes. These results indicate that, under the present experimental conditions, sprouting of primary afferents in adult cats is unlikely to be involved in functional plasticity after removal of descending pathways.

Animals↗
PubMed1993

B-50 (GAP-43) in Onuf's nucleus of the adult cat.

The nucleus of Onuf in the sacral spinal cord contains motoneurons that innervate the pelvic floor muscles and possess somatic and autonomic characteristics. We show in this study that in the intact adult cat, the immunocytochemical labelling of the nervous tissue-specific growth-associated protein, B-50 (GAP-43), which persists in Onuf's nucleus, differs markedly from that in the remaining 'purely somatic' motor nuclei of the sacral spinal cord. At the light microscopic level, an intense B-50 (GAP-43) immunoreactivity (B-50-IR) in the neuropil of Onuf's nucleus contrasts with a faint staining in the other spinal motor nuclei. Ultrastructurally, B-50-IR is found in Onuf's nucleus within some unmyelinated small diameter nerve fibres and numerous axon terminals on dendritic and somatic surfaces. Conversely, in all other motor nuclei only a few of these structures are stained. No other cellular profiles show B-50-IR in the tissue examined. According to the proposed functions of B-50 (GAP-43), its persistence in mature spinal axon terminals may indicate a latent capability of functional and structural remodeling, as well as an involvement in long-term enhancement in synaptic transmission. If so, these properties would be considerably more pronounced in Onuf's nucleus as compared to purely somatic motor nuclei.

Animals↗
PubMed1993

Immunocytochemistry of B-50 (GAP-43) in the spinal cord and in dorsal root ganglia of the adult cat.

The distribution of the neural-specific growth associated protein B-50 (GAP-43), which persists in the mature spinal cord and dorsal root ganglia, has been studied by light and electron microscopic immunohistochemistry in the cat. Throughout the spinal cord, B-50 immunoreactivity was seen confined to the neuropil, whereas neuronal cell bodies were unreactive. The most conspicuous immunostaining was observed in the dorsal horn, where it gradually decreased from superficial laminae (I-II) toward more ventral laminae (III-V), and in the central portion of the intermediate gray (mainly lamina X). In these regions, the labelling was localized within unmyelinated, small diameter nerve fibres and axon terminals. In the rest of the intermediate zone (laminae VI-VIII), B-50 immunoreactivity was virtually absent. The intermediolateral nucleus in the thoracic and cranial lumbar cord showed a circumscribed intense B-50 immunoreactivity brought about by the labelling of many axon terminals on preganglionic sympathetic neurons. In motor nuclei of the ventral horn (lamina IX), low levels of B-50 immunoreactivity were present in a few axon terminals on dendritic and somal profiles of motoneurons. In dorsal root ganglia, B-50 immunoreactivity was mainly localized in the cell bodies of small and medium-sized sensory neurons. The selective distribution of persisting B-50 immunoreactivity in the mature cat throughout sensory, motor, and autonomic areas of the spinal cord and in dorsal root ganglia suggests that B-50-positive systems retain in adult life the capacity for structural and functional plasticity.

Animals↗
PubMed1992

Contralateral early blink reflex in patients with facial nerve palsy: indication for synaptic reorganization in the facial nucleus during regeneration.

Fifty patients with Bell's palsy and 30 patients with etiologically different symptomatic peripheral facial nerve palsy were studied by means of electrically evoked blink reflexes 1-23 days after onset of paresis. Their results were compared with a normal control group of 30 healthy subjects. In a significant number of patients (64% in Bell's palsy and 53% in symptomatic facial nerve palsy) a contralateral early blink reflex response (R1) could be elicited upon stimulation of the normal side as compared to 13% in the control group. It is suggested that this result may be explained by synaptic reorganization of the facial nucleus leading to functional unmasking of pre-existing crossed trigemino-facial reflex pathways during regeneration. This view is in line with previous experimental data in animals on the time course of structural changes in the facial nucleus after lesioning of the ipsilateral facial nerve.

Adolescent↗
PubMed1991

Cytochemistry of 5'-nucleotidase in the superior cervical ganglion of cat and guinea pig.

The localization of 5'-nucleotidase, an adenosine-producing ectoenzyme, was studied by a cytochemical method in the superior cervical ganglion of the adult cat and guinea pig. The following subcellular sites of enzymatic activity were detected: (1) the surface of Schwann and satellite cells including the extracellular space between these cells and neuronal profiles; (2) the plasmalemma and pinocytotic vesicles of capillary endothelial cells; and (3) the synaptic clefts between cholinergic preganglionic axon terminals and sympathetic neurons. The simultaneous presence of 5'-nucleotidase at both glial elements and synapses within the adult peripheral nervous system (PNS) constitutes a novel distribution pattern for this enzyme which does not apply to the mature central nervous system (CNS), but which is rather typical for the developing CNS. These distributions of 5'-nucleotidase activity may reflect specific cellular requirements for nucleosides involved in parenchymal metabolism, in vascular transport processes and, possibly, in synaptic plasticity.

5'-Nucleotidase↗