RESUMEN

Trigeminal neuralgia was the focus of a recent workshop convened by the National Institute of Neurological Disorders and Stroke (NINDS) and the National Institute of Dental and Craniofacial Research (NIDCR). The workshop brought together basic scientists, clinicians, epidemiologists, and patient advocates. New research directions for epidemiology, diagnosis and assessment, pain mechanisms, and treatment were identified. (The workshop was held in Rockville MD on September 14, 1999, with financial support from NINDS, NIDCR, the NIH Office of Rare Diseases, and the NIH Pain Research Consortium.)

Asunto(s)

RESUMEN

Amyloid precursor proteins (APP) are a member of a larger family of proteins that include the amyloid precursor-like proteins (APLP) APLPI and APLP2. We have examined the expression and metabolism of APLP2 and document that APLP2 is expressed at high levels in the nervous system and in peripheral tissues. Furthermore, several APLP2 isoforms encoded by alternatively spliced transcripts are posttranslationally modified by a chondroitin sulfate glycosaminoglycan (CSGAG) chain. Furthermore, CSGAG modification is regulated by the insertion of sequences encoded by an alternatively spliced exon. Notably, expression of the CSGAG form of APLP2 appears restricted to embryonic neurons and mature neuronal populations that undergo regeneration, such as olfactory sensory neurons. Thus, differences in posttranslational modifications between the APLP2 isoforms and APP are likely to underlie differences in the regulation and function of these homologues. Our present efforts are directed towards using gene targeting strategies to disrupt the expression of the mouse APP/APLP2 genes to define the normative roles of the encoded molecules in development, plasticity, regeneration, and repair.

Asunto(s)

RESUMEN

Deposition of beta-amyloid (A beta) in senile plaques is a major pathological characteristic of Alzheimer's disease. A beta is generated by proteolytic processing of amyloid precursor proteins (APP). APP is a member of a family of related polypeptides that includes amyloid precursor-like proteins APLP1 and APLP2. To examine the distribution of APLP2 in the nervous system, we generated antibodies specific for APLP2 and used these reagents in immunocytochemical and biochemical studies of the rodent nervous system. In this report, we document that in cortex and hippocampus, APLP2 is enriched in postsynaptic compartments. In the olfactory system, however, APLP2 is abundant in olfactory sensory axons, and axon terminals in glomeruli. Confocal microscopy revealed that APLP2 is present in both pre- and postsynaptic compartments in the olfactory bulb. Notably, mRNA encoding chondroitin sulfate glycosaminoglycan (CS GAG)-modified forms of APLP2 are enriched in the olfactory epithelium, relative to alternatively-spliced mRNA, encoding CS GAG-free forms of APLP2. In addition, we demonstrate that CS-modified APLP2 forms accumulate in the olfactory bulb. CS proteoglycans are known to play an important role in regulating cell migration and neuronal outgrowth. Since sensory neurons in the olfactory epithelium are in a state of continual turnover, axons of newly generated cells must establish synaptic connections with neurons in the olfactory bulb in adult life. The presence of APLP2 in olfactory sensory axons and glomeruli is consistent with the view that this protein may play an important role in axonal pathfinding and/or synaptogenesis.

Asunto(s)

RESUMEN

Rett syndrome (RS), which affects approximately 1 in 10,000 young females, is characterized by cognitive deterioration, ataxia, apraxia, rigidity, and stereotyped hand movements. Neuropathological features include reduction in brain size and hypopigmentation of neurons of the substantia nigra pars compacta (SNpc). Neurochemical and imaging studies support nigrostriatal involvement. The results of our preliminary studies show abnormalities in neurons of the substantia nigra (SN), including decreased numbers of neurons, ubiquitin-stained neuronal inclusion bodies, decreased immunostaining for transmitter markers, and evidence of cell death using terminal deoxynucleotidyl transferase (TDT)-mediated dUTP-biotin nick end labeling (TUNEL), which labels fragmented intranucleosomal DNA. These preliminary data represent the first evidence for cell death in RS.

Asunto(s)

RESUMEN

Using choline acetyltransferase (ChAT) immunocytochemistry and acetylcholinesterase (AChE) histochemistry, we investigated regional and laminar differences in cholinergic innervation in the cerebral cortex, hippocampus, amygdala, and thalamus of mice. In mice, unlike rats, the patterns of ChAT-immunostained and AChE-positive fibers are virtually identical in the cortex and are organized in a trilaminar pattern with cholinergic processes prominent in layers I and IV and within the lower portion of layer V and upper segment of layer VI. ChAT-immunoreactive cells were not seen in cortex. In the amygdala, the basolateral nucleus showed the highest density of cholinergic processes. In the hippocampus, a thin, dense band of ChAT-labeled processes was present in the inner segment of the molecular layer of the dentate gyrus and within the stratum oriens of CA1-3, adjacent to the basal aspect of pyramidal cells. Within the thalamus, anteroventral, mediodorsal (lateral portion), intralaminar, and reticular nuclei showed high densities of cholinergic processes. The results of this study provide the basis for examining the effects of transgenes and age on forebrain cholinergic systems.

Asunto(s)

RESUMEN

Five or more dopamine receptor genes are expressed in brain. However, the pharmacological similarities of the encoded D1-D5 receptors have hindered studies of the localization and functions of the subtypes. To better understand the roles of the individual receptors, antibodies were raised against recombinant D1 and D2 proteins and were shown to bind to the receptor subtypes specifically in Western blot and immunoprecipitation studies. Each antibody reacted selectively with the respective receptor protein expressed both in cells transfected with the cDNAs and in brain. By immunocytochemistry, D1 and D2 had similar regional distributions in rat, monkey, and human brain, with the most intense staining in striatum, olfactory bulb, and substantia nigra. Within each region, however, the precise distributions of each subtype were distinct and often complementary. D1 and D2 were differentially enriched in striatal patch and matrix compartments, in selective layers of the olfactory bulb, and in either substantia nigra pars compacta or reticulata. Electron microscopy demonstrated that D1 and D2 also had highly selective subcellular distributions. In the rat neostriatum, the majority of D1 and D2 immunoreactivity was localized in postsynaptic sites in subsets of spiny dendrites and spine heads in rat neostriatum. Presynaptic D1 and D2 receptors were also observed, indicating both subtypes may regulate neurotransmitter release. D1 was also present in axon terminals in the substantia nigra. These results provide a morphological substrate for understanding the pre- and postsynaptic functions of the genetically defined D1 and D2 receptors in discrete neuronal circuits in mammalian brain.

Asunto(s)

RESUMEN

Overexpression of the gene encoding the beta-amyloid precursor protein (APP) may have a key role in the pathogenesis of both Alzheimer's disease (AD) and Down Syndrome (DS). We have therefore introduced a 650 kilobase (kb) yeast artificial chromosome (YAC) that contains the entire, unrearranged 400 kb human APP gene into mouse embryonic stem (ES) cells by lipid-mediated transfection. ES lines were generated that contain a stably integrated, unrearranged human APP gene. Moreover, we demonstrate germ line transmission of the APP YAC in transgenic mice and expression of human APP mRNA and protein at levels comparable to endogenous APP. This transgenic strategy may prove invaluable for the development of mouse models for AD and DS.

Asunto(s)

Asunto(s)

RESUMEN

Cholinergic processes in anterior temporal cortex of rhesus monkeys were identified using immunocytochemical techniques for ChAT. Labeled fibers were present throughout the temporal pole and anterior aspects of the superior temporal, middle temporal, and inferior temporal gyri. ChAT-immunoreactive fibers were most dense in layer I to superficial layer III throughout anterior temporal cortex. In temporal pole, agranular and dysgranular regions had a greater density of labeled fibers in superficial layers as compared to granular regions. In addition to the superficial concentration of cholinergic fibers in lateral temporal regions, numerous labeled fibers were also present in deep cortical layers in the inferior temporal gyrus of lateral temporal cortex, with lesser concentrations of immunoreactive fibers present in these layers in superior and middle temporal gyri. These patterns of cholinergic innervation may reflect the degree of cholinergic modulation of functions in anterior temporal cortex.

Asunto(s)

RESUMEN

Rett's syndrome (RS) is a neurologic disorder associated with severe mental deficiency and neurologic manifestations of cortical and extrapyramidal origin. The present report is a preliminary postmortem brain study that compares the levels of endogenous biogenic amines and selected neurotransmitter receptors in five cases with RS and six normal controls of similar age. The level of choline acetyltransferase activity was reduced in several cortical and subcortical regions. Endogenous levels of dopamine in the superior frontal and superior temporal gyri, occipital cortex, and putamen were reduced. The changes in specific neurotransmitter markers, particularly those associated with the basal ganglia and cortex, may underlie the progressive deterioration in motor and cognitive function characteristic of this progressive disorder.

Asunto(s)

RESUMEN

mRNAs encoding five genetically distinct muscarinic ACh receptors are present in the CNS. Because of their pharmacological similarities, it has not been possible to detect the individual encoded proteins; thus, their physiological functions are not well defined. To characterize the family of proteins, a panel of subtype-selective antibodies was generated against recombinant muscarinic receptor proteins and shown to bind specifically to each of the cloned receptors. Using immunoprecipitation, three receptor proteins (m1, m2, and m4) accounted for the vast majority of the total solubilized muscarinic binding sites in rat brain. These receptor subtypes had marked differences in regional and cellular localization as shown by immunocytochemistry. The m1-protein was present in cortex and striatum and was localized to cell bodies and neurites, consistent with its role as a major postsynaptic muscarinic receptor. The m2-receptor protein was abundant in basal forebrain, scattered striatal neurons, mesopontine tegmentum, and cranial motor nuclei; this distribution is similar to that of cholinergic neurons and suggests that m2 is an autoreceptor. However, m2 was also present in noncholinergic cortical and subcortical structures, providing evidence that this subtype may presynaptically modulate release of other neurotransmitters and/or function postsynaptically. The m4-receptor was enriched in neostriatum, olfactory tubercle, and islands of Calleja, indicating an important role in extrapyramidal function. These results clarify the roles of these genetically defined receptor proteins in cholinergic transmission in brain.(ABSTRACT TRUNCATED AT 250 WORDS)

Asunto(s)

RESUMEN

The peripheral nervous system and the central nervous system (CNS) are comprised of assemblies of neurons that communicate via electrical and chemical signals. Different disease processes selectively affect specific populations of neurons and/or specific cell functions (i.e., "selective vulnerability" of neurons is a principal determinant of phenotypes of disease). New cellular and molecular biological approaches have begun to clarify some of the mechanisms of selective cell injury in human diseases and their animal models. Following a brief review of the normal biology of nerve cells, we use illustrations drawn from studies of experimental and human diseases to discuss the mechanisms of structural/chemical abnormalities that occur in a variety of neuronal disorders.

Asunto(s)

Asunto(s)

RESUMEN

Lesions of the fimbria-fornix (FF) have been reported to cause retrograde changes in neurons of the medial septal nucleus (MSN). To analyze the nature and time course of these events, we investigated changes in cytoskeletal elements (phosphorylated and non-phosphorylated neurofilament (NF) proteins) and transmitter-related enzymes (choline acetyltransferase (ChAT) in MSN neurons following FF transection. During the first week postlesion, ChAT immunoreactivity and size of many perikarya were reduced. Irregular, swollen cholinergic fibers appeared first at postlesion day 2 in caudal septum and soon spread rostrally, reaching rostral septum by day 7. A few perikarya developed abnormal accumulations of phosphorylated NFs. At postlesion days 7-10, many neurons did not stain for ChAT. Phosphorylated NFs were present in many perikarya. At this time, cell loss was apparent in Nissl-stained material. Cholinergic cell loss continued through postlesion weeks 6-8 but at a much slower rate than during the first week. Phosphorylated NF accumulations in MSN perikarya persisted until postlesion week 6, disappearing thereafter. Double-immunostaining procedures showed that MSN neurons expressed both ChAT and phosphorylated NF immunoreactivity at postlesion day 3; however, at days 7 and 14, cells that accumulated phosphorylated NFs did not stain for ChAT. The results of this study indicate that FF transection leads to perikaryal shrinkage with loss of ChAT immunoreactivity, perikaryal phosphorylation of NFs, cholinergic fiber abnormalities, and cell loss. Recent evidence suggests that reduction of transmitter markers and aberrant phosphorylation of NFs may be involved in the pathogenesis of several neurodegenerative disorders, including Alzheimer's disease. Therefore, FF transection provides a useful animal model for further investigations of complex disorders of the central nervous system that involve degeneration of transmitter-specific pathways.

Asunto(s)

RESUMEN

Ligands that are highly specific for the mu, delta, and kappa opiate receptor binding sites in mammalian brains have been identified and used to map the distribution of these receptor types in the brains of various mammalian species. In the present study, the selectivity and binding characteristics in the pigeon brain of three such ligands were examined by in vitro receptor binding techniques and found to be similar to those reported in previous studies on mammalian species. These ligands were then used in conjunction with autoradiographic receptor binding techniques to study the distribution of mu, delta, and kappa opiate receptor binding sites in the forebrain and midbrain of pigeons. The autoradiographic results indicated that the three opiate receptor types showed similar but not identical distributions. For example, mu, delta, and kappa receptors were all abundant within several parts of the cortical-equivalent region of the telencephalon, particularly the hyperstriatum ventrale and the medial neostriatum. In contrast, in other parts of the cortical-equivalent region of the avian telencephalon, such as the dorsal archistriatum and caudal neostriatum, only kappa receptors appeared to be abundant. Within the basal ganglia, all three types of opiate receptors were abundant in the striatum and low in the pallidum. Within the diencephalon, kappa and delta binding was high in the dorsal and dorsomedial thalamic nuclei, but the levels of all three receptor types were generally low in the specific sensory relay nuclei of the thalamus. Kappa binding and delta binding were high, but mu was low in the hypothalamus. Within the midbrain, all three receptor types were abundant in both the superficial and deep tectal layers, in periventricular areas, and in the tegmental dopaminergic cell groups. In many cases, the distribution of opiate receptors in the pigeon forebrain generally showed considerable overlap with the distribution of opioid peptide-containing fiber systems (for example, in the striatal portion of the basal ganglia), but there were some clear examples of receptor-ligand mismatch. For example, although all three receptor types are very abundant in the hyperstriatum ventrale, opioid peptide-containing fibers are sparse in this region. Conversely, within the pallidal portion of the basal ganglia, opioid peptide-containing fibers are abundant, but the levels of opiate receptors appear to be considerably lower than would be expected. Thus, receptor-ligand mismatches are not restricted to the mammalian brain, since they are a prominent feature of the organization of the brain opiate systems in pigeons.(ABSTRACT TRUNCATED AT 400 WORDS)

Asunto(s)

RESUMEN

The basal forebrain magnocellular complex of primates is defined by the presence of large, hyperchromic, usually cholinergic neurons in the nucleus basalis of Meynert and nucleus of the diagonal band of Broca. Because there is growing evidence for noncholinergic neuronal elements in the basal forebrain complex, five neuropeptides and the enzyme choline acetyltransferase were studied immunocytochemically in this region of rhesus monkeys. Galaninlike immunoreactivity coexists with choline-acetyl-transferase-like immunoreactivity in most large neurons and in some smaller neurons of the primate nucleus basalis and nucleus of the diagnonal band. Four other peptides show immunoreactivity in more limited regions of the basal forebrain complex, usually in separate smaller, noncholinergic neurons. Numerous small, somatostatinlike-immunoreactive neurons occupy primarily anterior and intermediate segments of the nucleus basalis, especially laterally and ventrally. Somewhat fewer, small neuropeptide Y-like-immunoreactive somata are found in the same regions. Neurons that show neurotensinlike immunoreactivity are slightly larger than cells that contain immunoreactivity for somatostatin or neuropeptide Y, but these neurons also occur mainly in anterior and intermediate parts of the nucleus basalis. Overall, the usually small, leucine-enkephalin-like-immunoreactive neurons are infrequent in the basal forebrain complex and are most abundant in the rostral intermediate nucleus basalis. Thus, neurons that appear to contain somatostatin, neuropeptide Y, neurotensin, or enkephalin mingle with cholinergic/galaninergic neurons only in some subdivisions of the nucleus basalis/nucleus of the diagonal band, and their distributions suggest that some of these small neurons could be associated with structures that overlap with cholinergic neurons of the labyrinthine basal forebrain magnocellular complex. We also have found light microscopic evidence for innervation of basal forebrain cholinergic neurons by boutons that contain galanin-, somatostatin-, neuropeptide Y-, neurotensin-, or enkephalinlike immunoreactivity. The origins and functions of these putative synapses remain to be determined.

Asunto(s)

RESUMEN

In immunocytochemical studies, a polyclonal antiserotonin antibody was used to visualize fibers within the cingulate cortex of young and aged rhesus monkeys. Intricate and distinct patterns of serotoninergic processes were seen in anterior and posterior segments of cingulate cortex (Brodmann areas 24 and 23). In these regions of cortex, many multivaricose serotonin-immunoreactive axonal swellings were identified, and some of these immunostained neurites were associated with deposits of amyloid. These observations suggest that serotoninergic processes are involved in the formation of senile plaques in neocortex of aged macaques.

Asunto(s)

RESUMEN

Nonhuman primates experience changes in behavior as they progress into old age. Visual recognition, spatial learning, habit formation, and visuospatial manipulation are impaired in aged rhesus monkeys relative to young controls. We have begun to study the possible neural substrate for these changes, focusing on brain areas that are known, from lesion studies, to be essential for the successful performance of specific tasks. Aged nonhuman primates develop senile plaques, most commonly in amygdala, hippocampus, and neocortex. Our preliminary data suggest that the density of plaques may be related to poor behavioral performance in some aged monkeys. However, behavioral decline begins before the appearance of significant numbers of senile plaques, suggesting that other factors may interfere with cognition. Numerous studies of several genera have shown that receptors for neurotransmitters decline in number between the adolescent years and old age. Our autoradiographic analyses of primate temporal neocortex demonstrate loss of muscarinic, nicotinic, dopaminergic and serotoninergic receptor binding sites between the ages of 2 and 22 years. Preliminary data indicate that markers for adenyl cyclase and phosphatidyl inositol second-messenger systems also are reduced in temporal cortex. Although these declines represent a potential substrate for behavioral changes, no studies have directly related a decrease in receptor number to deficits in learning and memory in aged primates. Other changes in the aging brain include loss of neurons, reduced neurochemical markers, and decreased content of neuronal ribonucleic acid (RNA). All of these decrements may be interrelated to some extent in that decreased RNA could result in changes in neurochemical markers and receptors and, eventually, in dysfunction and death of neurons. These observations underscore the importance of establishing a time course for age-associated neural abnormalities, examining regions of brain in which changes are most likely to occur, and studying their relationship to the progression of behavioral dysfunction. Detailed anatomical analyses of the distribution of in situ uptake/receptor binding sites and messenger RNA (mRNA) in aged nonhuman primates may clarify some of the factors that most likely contribute to behavioral changes in elderly humans.

Asunto(s)

RESUMEN

In Caiman, calbindin D28K immunoreactivity (CaBP) was observed within many neurons of the substantia nigra (SN) but only in the caudal portion of the area ventralis of Tsai (AVT). A dense CaBP fiber plexus showing some regional inhomogeneity was observed in the dorsolateral portion of the telencephalic ventrolateral area (VLA). These results are consistent with previous reports that the SN and AVT project to the dorsolateral and medial portions of the VLA, and strongly support the theory that the caiman VLA contains cell populations homologous to those found in the mammalian corpus striatum.

Asunto(s)

RESUMEN

Immunocytochemical studies, using an antibody directed against human dopamine beta-hydroxylase, identified an extensive plexus of noradrenergic axons/terminals in normal human hippocampus. In hippocampi of individuals with Alzheimer's disease, the density of noradrenergic innervation was reduced and abnormal noradrenergic axons, which exhibited multifocal enlargements, were present in the neuropil. Some of these neurites were clustered around deposits of amyloid (senile plaques), and these abnormalities were most common in CA3-4, a region normally showing a relatively high density of noradrenergic terminals. This investigation provides direct evidence for structural abnormalities of noradrenergic axons/nerve terminals in hippocampi of individuals with Alzheimer's disease.

Asunto(s)