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Biomedical subjects

A C Cuello

Publications and source records attributed to A C Cuello.

At least 37 records · Page 2Linked to original sources
PubMed1999

Reorganization of cholinergic terminals in the cerebral cortex and hippocampus in transgenic mice carrying mutated presenilin-1 and amyloid precursor protein transgenes.

Cholinergic deficits are one of the most consistent neuropathological landmarks in Alzheimer's disease (AD). We have examined transgenic mouse models (PS1M146L, APPK670N,M671L) and a doubly transgenic line (APPK670N,M671L + PS1M146L) that overexpress mutated AD-related genes [presenilin-1 (PS1) and the amyloid precursor protein (APP)] to investigate the effect of AD-related gene overexpression and/or amyloidosis on cholinergic parameters. The size of the basal forebrain cholinergic neurons and the pattern of cholinergic synapses in the hippocampus and cerebral cortex were revealed by immunohistochemical staining for choline acetyltransferase and the vesicular acetylcholine transporter, respectively. At the time point studied (8 months), no apparent changes in either the size or density of cholinergic synapses were found in the PS1M146L mutant relative to the nontransgenic controls. However, the APPK670N,M671L mutant showed a significant elevation in the density of cholinergic synapses in the frontal and parietal cortices. Most importantly, the double mutant (APPK670N,M671L + PS1M146L), which had extensive amyloidosis, demonstrated a prominent diminution in the density of cholinergic synapses in the frontal cortex and a reduction in the size of these synapses in the frontal cortex and hippocampus. Nonetheless, no significant changes in the size of basal forebrain cholinergic neurons were observed in these three mutants. This study shows a novel role of APP and a synergistic effect of APP and PS1 that correlates with amyloid load on the reorganization of the cholinergic network in the cerebral cortex and hippocampus at the time point studied.

Acetylcholine↗
PubMed1999

A nerve growth factor mimetic TrkA antagonist causes withdrawal of cortical cholinergic boutons in the adult rat.

Cholinergic neurons respond to the administration of nerve growth factor (NGF) in vivo with a prominent and selective increase of choline acetyl transferase activity. This suggests the possible involvement of endogenous NGF, acting through its receptor TrkA, in the maintenance of central nervous system cholinergic synapses in the adult rat brain. To test this hypothesis, a small peptide, C(92-96), that blocks NGF-TrkA interactions was delivered stereotactically into the rat cortex over a 2-week period, and its effect and potency were compared with those of an anti-NGF monoclonal antibody (mAb NGF30). Two presynaptic antigenic sites were studied by immunoreactivity, and the number of presynaptic sites was counted by using an image analysis system. Synaptophysin was used as a marker for overall cortical synapses, and the vesicular acetylcholine transporter was used as a marker for cortical cholinergic presynaptic sites. No significant variations in the number of synaptophysin-immunoreactive sites were observed. However, both mAb NGF30 and the TrkA antagonist C(92-96) provoked a significant decrease in the number and size of vesicular acetylcholine transporter-IR sites, with the losses being more marked in the C(92-96) treated rats. These observations support the notion that endogenously produced NGF acting through TrkA receptors is involved in the maintenance of the cholinergic phenotype in the normal, adult rat brain and supports the idea that NGF normally plays a role in the continual remodeling of neural circuits during adulthood. The development of neurotrophin mimetics with antagonistic and eventually agonist action may contribute to therapeutic strategies for central nervous system degeneration and trauma.

Animals↗
PubMed1999

Mitochondrial abnormalities in neuroectodermal cells stably expressing human amyloid precursor protein (hAPP751).

Metabolic hypofunction is a common finding in a number of neurodegenerative diseases, including Alzheimer's disease (AD). The strong linkage between the amyloid precursor protein (APP) and AD led us to examine whether over-expression of this protein in CNS-type cells had an effect on mitochondria. We found abnormal morphology in mitochondria of the neuroectodermal progeny of P19 cells stably transfected with human APP751. In addition, the mitochondria of APP-transfected clones had a decreased mitochondrial membrane potential. These changes were independent of Abeta toxicity and distinct from complex I inhibition. Our results have important implications for the earliest events in the pathophysiology of AD and, by extrapolation, for intervention therapies.

Amyloid beta-Protein Precursor↗
PubMed1999

Transgenic mice over-expressing substance P exhibit allodynia and hyperalgesia which are reversed by substance P and N-methyl-D-aspartate receptor antagonists.

A transgenic mouse has been developed which, during development, over-expresses nerve growth factor under the control of a myelin basic protein promoter. These animals display an ectopic network of substance P-containing sensory fibers in the white matter of the spinal cord. To study the functional significance of this model to nociception, these mice were studied in a test measuring the latency to tail withdrawal from a noxious radiant heat stimulus. Baseline reaction times were significantly less in transgenic mice, suggesting thermal allodynia. A mechanical stimulus was then applied to the tip of the tail at either 450 g or 1400 g for 2 s and tail withdrawal readings were taken for another 10 min. In control mice, the 450 g stimulus was without effect, suggesting that it is normally innocuous. In transgenic mice, this stimulus induced a transient decrease in withdrawal latency at 1 min. Thus, transgenic mice exhibited mechanical allodynia. The 1400 g stimulus decreased withdrawal latency in both transgenic and control mice. However, the response was greater in transgenic mice, indicating that they exhibited mechanical hyperalgesia. The neurokinin-1 receptor antagonist CP-96,345, but not the inactive stereoisomer CP-96,344, administered subcutaneously 30 min before the 450 g stimulus, blocked the stimulation-induced allodynia in transgenic mice, and revealed a transient antinociception in transgenic and control mice. Ketamine, an N-methyl-D-aspartate receptor antagonist, given intraperitoneally 10 min before 450 g stimulation, blocked the allodynia in transgenic mice. These results indicate that these transgenic mice display hyperalgesia and allodynia, and that these nociceptive responses are reversed by substance P and N-methyl-D-aspartate receptor antagonists.

Analgesics↗
PubMed1998

A TrkA-selective, fast internalizing nerve growth factor-antibody complex induces trophic but not neuritogenic signals.

Nerve growth factor (NGF) is a neurotrophin that induces neuritogenic and trophic signals by binding to TrkA and/or p75 receptors. We report a comparative study of the binding, internalization, and biological activity of NGF versus that of NGF in association with an anti-NGF monoclonal antibody (mAb NGF30), directed against the C termini of NGF. NGF.mAb complexes do not bind p75 effectively but bind TrkA with high affinity. After binding, NGF. mAb complexes stimulate internalization faster and to a larger degree than NGF. NGF.mAb-induced activation of TrkA, Shc, and MAPK is transient compared with NGF-induced activation; yet NGF and NGF. mAb afford identical trophic responses. In contrast, NGF induces Suc-1-associated neurotrophic activating protein phosphorylation and neuritogenic differentiation, but NGF.mAb does not. Thus, an absolute separation of trophic and neuritogenic function is seen for NGF.mAb, suggesting that biological response modifiers of neurotrophins can afford ligands with selected activities.

Antibodies, Monoclonal↗
PubMed1998

Preferential synaptic relationships between substance P-immunoreactive boutons and neurokinin 1 receptor sites in the rat spinal cord.

Substance P plays an important role in the transmission of pain-related information in the dorsal horn of the spinal cord. Recent immunocytochemical studies have shown a mismatch between the distribution of substance P and its receptor in the superficial laminae of the dorsal horn. Because such a mismatch was not observed by using classical radioligand binding studies, we decided to investigate further the issue of the relationship between substance P and its receptor by using an antibody raised against a portion of the carboxyl terminal of the neurokinin 1 receptor and a bispecific monoclonal antibodies against substance P and horseradish peroxidase. Light microscopy revealed a good correlation between the distributions of substance P and the neurokinin 1 receptor, both being localized with highest densities in lamina I and outer lamina II of the spinal dorsal horn. An ultrastructural double-labeling study, combining preembedding immunogold with enzyme-based immunocytochemistry, showed that most neurokinin 1 receptor immunoreactive dendrites were apposed by substance P containing boutons. A detailed quantitative analysis revealed that neurokinin 1 receptor immunoreactive dendrites received more appositions and synapses from substance P immunoreactive terminals than those not expressing the neurokinin 1 receptor. Such preferential innervation by substance P occurred in all superficial dorsal horn laminae even though neurokinin 1 receptor immunoreactive dendrites were a minority of the total number of dendritic profiles in the above laminae. These results suggest that, contrary to the belief that neuropeptides act in a diffuse manner at a considerable distance from their sites of release, substance P should act on profiles expressing the neurokinin 1 receptor at a short distance from its site of release.

Afferent Pathways↗
PubMed1998

Analysis of c-Fos and glial fibrillary acidic protein (GFAP) expression following topical application of potassium chloride (KCl) to the brain surface.

Application of high K+ concentrations to a limited area of the brain surface is known to trigger spreading depression. We used this model to observe the response of cortical areas, distant to the exposed site, at the cellular level. Immunostaining of glial fibrillary acidic protein (GFAP) and of the proto-oncogene c-Fos was analyzed in brain sections at different times after K+ application. Piriform and parietal cortices, as observed in coronal sections located 3 mm rostrally from the center of the stimulated area and ipsilateral to it, showed a dramatic increase in immunostaining for both markers. However, the time course for such increments was different. c-Fos protein(s) expression was high at 1.5 h and decreased at 24 h after K+ exposure and c-fos mRNA expression correlated with the immunohistochemical results. At these initial times GFAP immunoreactivity was still low but began to rise between 2 and 7 days after treatment in exactly the same areas where c-Fos expression had been up-regulated. No significant effect, for either marker, was evident in the contralateral piriform or parietal cortices. In addition, we studied the effects of the NMDA antagonist MK-801 (4 mg/kg i.p.) on the expression of mRNA for GFAP and c-fos and demonstrated a marked reduction in the upregulation of these genes.

Administration, Topical↗
PubMed1998

Synaptic numbers across cortical laminae and cognitive performance of the rat during ageing.

In this study, we have investigated the changes in the number of individual presynaptic boutons in the neocortex of rats and correlated them with cognitive performance. Brown Norway x Fischer 344 F1 hybrid rats, aged from one to 24 months, were used. Using synaptophysin as a marker for presynaptic boutons, we found that in the parietal II region of the neocortex an age-related decrease in the density of immunostained punctae representing presynaptic boutons occurred. Regression analysis showed that this decline in the number of presynaptic boutons correlates with ageing (r=0.495, P<0.05). Interestingly, we found that this age-related depletion of presynaptic boutons was more intense in the deeper cortical lamina, such as laminae V and VI (mean decrease of 18%), than in the superficial laminae (mean decrease of 8% in laminae I-IV). Using the Morris water maze test, we observed that young rats acquired the task at twice the speed of aged animals (48.9 +/- 9.0 s and 91.0 +/- 4.9 s for young and aged animals, respectively). Furthermore, at the end of the training period, the aged cohort still showed significantly higher escape latencies in the Morris water maze. The present findings support the concept that the decline in cognitive performances in ageing is related to the loss of synapses in the cerebral cortex.

Aging↗
PubMed1997

Responses of cortical noradrenergic and somatostinergic fibres and terminals to adjacent strokes and subsequent treatment with NGF and/or the ganglioside GM1.

The occurrence of sprouting by fibre systems in the neocortex following lesion is still a controversial issue. In previous studies, we showed a nerve growth factor (NGF)-induced sprouting and hypertrophy of presynaptic terminals in the cholinergic fibres of the rat neocortex following stroke-type lesions, effects that were potentiated by the monosialoganglioside GM1. The present study investigated whether exogenous NGF and/or GM1 treatment could also affect the noradrenergic and somatostinergic systems in the neocortex. Immediately following unilateral vascular decortication, adult rats received, via minipump, a 7-day infusion of vehicle, NGF (12 microg/day) and/or GM1 (1.5 mg/day) into the cerebroventricular space. Thirty days postlesion, the animals were perfused with histological fixatives, the brains were removed, and relevant sections were processed for dopamine beta-hydroxylase and somatostatin immunocytochemistry at the light and electron microscopic levels. A Quantimet 920 image analysis system was used for the quantification of fibre length and size of presynaptic boutons. The lesion caused a reduction in the dopamine beta-hydroxylase-immunoreactive fibre length, which was not attenuated by either NGF or GM1 treatment or both. The somatostatin-immunoreactive network, in contrast, was unaffected by the lesion, and there was no sprouting of somatostatin fibres following trophic factor therapy. We also found no significant differences in the size and number of synapses of both the dopamine beta-hydroxylase-immunoreactive and somatostatin-immunoreactive boutons following lesion and drug treatments. These results indicate that NGF and/or GM1 therapies do not cause regrowth in the noradrenergic and somatostatinergic cortical fibre networks or their presynaptic elements following a cortical devascularizing lesion.

Analysis of Variance↗
PubMed1997

Nerve growth factor stimulates growth of cortical pyramidal neurons in young adult rats.

The cytoarchitectonics of pyramidal neurons in the cerebral cortex of non-lesioned rats can be re-modeled by i.c.v. infusions of nerve growth factor (NGF). 4 months after the application of NGF, the pyramidal neurons in layers III and V of the motor cortex and layer V of the anterior cingulate cortex were analyzed and compared with pyramidal neurons from vehicle-treated rats. NGF-treated brains showed: (1) significant increase in dendritic branching in the basilar fields of the layer V, but not layer III, neurons; and (2) a significant increase in spine density in the terminal, but not proximal, dendritic branches. These findings indicated that, besides its known effects on forebrain cholinergic neurons, NGF produces a very generalized synaptic re-modeling involving the cells responsible for the major output of the cerebral cortex in the intact adult brain.

Animals↗
PubMed1997

Differential modulation of the cholinergic phenotype of the nucleus basalis magnocellularis neurons by applying NGF at the cell body or cortical terminal fields.

Although it is well known that exogenous nerve growth factor (NGF) can dramatically affect the phenotype of the basal forebrain cholinergic neurons in normal, aged, or lesioned animals, whether its actions are restricted to the terminal field level of these cholinergic neurons has yet to be established. In most cases, NGF has been applied into the cerebroventricle space giving it access to both the terminal fields and somatodendritic regions. The recent demonstration that TrkA, the essential component of high-affinity NGF receptors, is expressed not only at the distal fields (terminals and distal axons) but also at the proximal fields (cell bodies, dendrites, and proximal axons) of the basal forebrain cholinergic neurons has provoked renewed interest in this problem. More recently, it was further demonstrated that in Alzheimer's disease (AD), the NGF peptide increased throughout the brain but decreased in the nucleus basalis magnocellularis (NBM), suggesting that there is an impaired retrograde transport of NGF from the cortex to the NBM. Thus, it will be crucial to clarify whether or not the TrkA receptors on the somatodendritic fields of the NBM cholinergic neurons respond to exogenous NGF in order to support the rationale for site-directed neurotrophic factor therapy in AD or other neurological disorders. To clarify this issue, we delivered 2.5S purified mouse NGF locally into the cortex or corpus striatum adjacent to the NBM of naive and cortically devascularized mature male Wistar rats. The local distribution of exogenous NGF was demonstrated by immunohistochemical staining. In naive rats, an NGF dose of 84.00 or 16.80 microg infused into either the cortex or the corpus striatum for 2 weeks caused ipsilateral hypertrophy of the cholinergic neurons of the NBM. In cortically devascularized animals, an NGF dose of 84.00 microg delivered into the cortex and 84.00 microg or 16.80 microg infused into the striatum adjacent to the NBM for 2 weeks rescued the ipsilateral cholinergic phenotype of NBM neurons of the basolocortical pathway from retrograde degeneration. Thus, exogenous NGF can affect the cholinergic phenotype of the NBM regardless of whether it is presented to their nerve terminal fields or their somatodendritic region. The present results provide new evidence that the TrkA receptors present in the somatodendritic region of the cholinergic neurons of the NBM are functional and capable of modulating neuronal phenotype in the naive and lesioned CNS, when applied pharmacologically.

Animals↗
PubMed1997

Nerve growth factor treatment prevents dendritic atrophy and promotes recovery of function after cortical injury.

This study examined the behavioural and anatomical effects of intraventricular injections of nerve growth factor in rats with unilateral damage that included Zilles' areas Frl, FL, HL, ParI and the anterior portion of Oc2. Nerve growth factor-treated lesion rats showed attenuation of behavioural symptoms in measures of forelimb function (Whishaw reaching task) and hindlimb function (beam traversing task) as well as a measure of spatial navigation (Morris water task). Analysis of dendritic arborization using a modified Golgi. Cox procedure also showed a complete reversal of lesion-induced atrophy of dendritic fields in pyramidal neurons in motor (Zilles' Fr2) and cingulate (Zilles' Cgl) cortex. In addition, there was a reversal of a lesion-induced reduction in spine density. These results demonstrate that nerve growth factor treatment can facilitate functional recovery from cortical injury. This recovery may be mediated by a reorganization of intrinsic cortical circuitry that is reflected in changes in dendritic arborization and spine density of pyramidal neurons.

Animals↗
PubMed1997

Substance P and enkephalin immunoreactivities in axonal boutons presynaptic to physiologically identified dorsal horn neurons. An ultrastructural multiple-labelling study in the cat.

A combination of intracellular electrophysiological recording and injection of horseradish peroxidase with ultrastructural immunocytochemistry was used to investigate the synaptic interplay between substance P- and enkephalin-immunoreactive axonal boutons and three types of functionally characterized dorsal horn neurons in the cat spinal cord. The dorsal horn neurons were classified as nociceptive specific, wide dynamic range and non-nociceptive based on their responses to innocuous and noxious stimuli. Most of the nociceptive neurons (either nociceptive specific or wide dynamic range) contained enkephalin immunoreactivity, but none of the non-nociceptive neurons were positive for enkephalin. Three types of immunoreactive boutons were found in contact with the functionally characterized dorsal horn neurons. These boutons were positive for either substance P, enkephalin, or substance P+enkephalin. Quantitative analysis revealed that the percentages of substance P-immunoreactive boutons apposed to the cell bodies, proximal dendrites and distal dendrites of nociceptive neurons were significantly higher than those of non-nociceptive neurons. Furthermore, the percentages of substance P+enkephalin-immunoreactive axonal boutons apposed to the distal dendrites of nociceptive neurons were significantly higher than those of non-nociceptive neurons and the percentages of enkephalin-immunoreactive boutons apposed to the cell bodies and proximal dendrites of nociceptive neurons were significantly higher than in non-nociceptive neurons. Finally, neither enkephalin-immunoreactive nor substance P+enkephalin-immunoreactive boutons were ever seen presynaptic to substance P-immunoreactive boutons. These results provide evidence of an anatomical substrate within the dorsal horn for the interaction of substance P-mediated with enkephalin-mediated mechanisms. The data support the idea that the modulation of nociceptive input in the dorsal horn by enkephalinergic neurons occurs mainly via a postsynaptic mechanism, and thus suggest that dorsal horn enkephalinergic neurons participate in a local inhibitory feedback loop in a distinct pathway from the previously postulated opioid-mediated depression of substance P release from primary afferent terminals.

Animals↗
PubMed1997

Experimental neurotrophic factor therapy leads to cortical synaptic remodeling and compensates for behavioral deficits.

This brief review discusses experimental therapy with neurotrophic factors in a model of central nervous system (CNS) neural atrophy and synaptic loss resulting from unilateral cortical infarctions. It discusses the trophic factor protection of the cholinergic phenotype of neurons belonging to the forebrain-to-neocortex projection, as well as the capacity of trophic therapy to elicit synaptogenesis in the cerebral cortex of adult animals. Finally, it addresses the behavioral consequences of trophic factor-induced synaptic remodeling of the neocortex in this model.

Animals↗
PubMed1996

Quantitative analysis of substance P-immunoreactive boutons on physiologically characterized dorsal horn neurons in the cat lumbar spinal cord.

A quantitative analysis of substance P (SP)-immunoreactive (IR) terminals contacting physiologically characterized dorsal horn neurons was performed. Three types of neuron were studied: nociceptive specific (NS) from lamina I (n = 3), wide dynamic range (WDR) from laminae II-IV (n = 3), and nonnociceptive (NN) from lamina IV (n = 3). The nociceptive response of focus was a slow, prolonged depolarization to noxious stimuli, because this response was previously shown to be blocked by selective neurokinin-1 (NK-1) receptor antagonists. Ultrastructural immunocytochemistry was used to quantify the relative number of SP-IR boutons apposed to the intracellularly labeled cell per unit of length (density). Densities of the total population (SP immunoreactive+nonimmunoreactive) of apposed boutons were similar in all three regions (cell body, proximal and distal dendrites) for the three functional types of neuron. NS neurons received a significantly higher density of appositions from SP-IR boutons than NN cells in all three regions. However, compared to WDR cells, NS cells possessed a significantly higher density of appositions from SP-IR boutons only in the cell body and proximal dendrites. WDR cells had a higher density of appositions from SP-IR boutons than NN cells, but only in the proximal and distal dendrites. On average, 33.5% of the SP-IR boutons apposed to the cells displayed a synaptic contact. Finally, 30-45% of the SP-IR boutons apposed to the cells colocalized calcitonin gene-related protein (CGRP) immunoreactivity, indicating their primary sensory origin. The data indicate a direct correlation between the amount of SP-IR input and the nociceptive nature of the cells and suggest that SP acts on NK-1 receptors at a short distance from its release site.

Animals↗
PubMed1996

NGF prevents further atrophy of cholinergic cells of the nucleus basalis due to cortical infarction in adult post-hypothyroid rats but does not restore cell size compared to euthyroid [correction of euthroid] rats.

We have tested the hypotheses that nerve growth factor treatment in adult post-hypothyroid rats can: (1) restore cross-sectional area of cholinergic cells of the nucleus basalis and (2) prevent further atrophy of these neurons following cortical infarction. In addition, we assessed the expression of p75NGFR and p140trkA mRNAs in the nucleus basalis cells of post-hypothyroid rats. Rats were rendered hypothyroid by the addition of propylthiouracil to their diet beginning on embryonic day 19 until the age of 1 month. At this time both the pups and their dams continued to receive 0.05% propylthiouracil in their diet and the pups were thyroidectomized. At 60 days, propylthiouracil treatment was interrupted and thyroxine levels were restored to normal by daily subcutaneous administration of physiological levels of thyroxine. Morphometric analysis identified atrophied nucleus basalis magnocellularis cholinergic cells at two ages, days 75 and 105, identified by in situ hybridization for p75NGFR and p140trkA mRNAs in methylene blue stained cells (day 75) and choline acetyltransferase immunostaining (day 105). The mean number of silver grains (pixels) per microns2 (mean +/- S.E.M.) of cell body cross-sectional area for p75NGFR mRNA in the nucleus basalis magnocellularis of euthyroid rats was 3.43 +/- 0.89, which was not statistically different from post-hypothyroid animals (4.02 +/- 1.07). A similar finding was noted for p140trkA mRNA: mean number of grains in the euthyroid group was 5.54 +/- 0.96 and was not statistically different from the post-hypothyroid group (6.32 +/- 1.45). Nerve growth factor treatment in adulthood (between days 75 and 82) did not restore cross-sectional area from early thyroid deprivation. However, it prevented further atrophy of nucleus basalis magnocellularis neurons following cortical devascularization inflicted in adulthood (day 75).

Acetylcholine↗
PubMed1995

Ectopic substance P and calcitonin gene-related peptide immunoreactive fibres in the spinal cord of transgenic mice over-expressing nerve growth factor.

The aim of this study was to investigate the in vivo effects of CNS over-expression of nerve growth factor (NGF) on primary sensory neurons. To achieve this objective a transgenic mouse model was generated which bore a chick NGF gene driven by the myelin basic protein promoter. Northern blot analysis demonstrated that high levels of NGF mRNA were detected in the spinal cord of adult transgenic mice. Using immunocytochemistry NGF-immunoreactive (IR) oligodendrocytes were observed throughout the white matter. Furthermore, numerous ectopic substance P (SP)- and calcitonin gene-related peptide (CGRP)-IR fibres were detected in the white matter of the spinal cord of transgenic mice. NGF-IR oligodendrocytes and ectopic SP- and CGRP- fibres were entirely absent from control mice. In the cervical and lumbar dorsal root ganglia, the percentages of SP-IR neurons were significantly higher in transgenic mice when compared with controls. At the electron microscope level, ectopic SP- and CGRP-IR fibres were characterized as unmyelinated axons and axonal boutons. SP colocalized with CGRP in some of those axonal boutons and fibres. Capsaicin treatment of adult mice completely abolished the ectopic SP-IR fibres, confirming their primary sensory origin. Our results indicate that primary sensory neurons are responsive to NGF over-expression in the CNS. Ectopic SP- and CGRP-IR fibres in the white matter are likely to represent collateral sprouts of the central processes of the dorsal root ganglion cells which were triggered by NGF over-expressed in the myelinating oligodendrocytes in the spinal cord of transgenic mice.

Animals↗