Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Neurons”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 685 records · Page 38Linked to original sources
PubMed1990

Image analysis of Nissl-stained neuronal perikarya in the primary visual cortex of the rat: automatic detection and segmentation of neuronal profiles with nuclei and nucleoli.

An image analysing procedure for the morphometric characterization of cortical neurons in Nissl-stained brain sections is described. It consists of the automatic detection of cellular profiles and their compartments: cytoplasm, nucleus and nucleolus. The algorithm was designed to cope with the large morphological spectrum of cortical perikarya (e.g. geometrical properties of perikarya, staining intensities of cell compartments and nucleo-plasmic area-ratio) including pyramidal (Golgi-category I) and non-pyramidal (Golgi-category II) neurons. Clusters of cells were separated and non-neuronal structures (e.g. glia, endothelial cells) as well as tangential, non-nucleolated sections through neuronal perikarya recognized and excluded from further analysis without requiring interactive procedures. The performance of the profile recognition procedure was evaluated using 426 nucleolated and non-nucleolated profiles of different types of neurons in the primary visual cortex of the rat. Nucleolated profiles were recognized as such with a 91% accuracy, non-nucleolated profiles were rejected correctly in 90% of cases. After automatic segmentation and selection of nucleolated neuronal profiles from the microscopic field, a large set of quantitative morphological features including geometrical, densitometrical and textural parameters can be measured using high power light microscopy. This permits quantitative morphometric characterization of different neuronal types. This procedure is the first part of a system for the automatic classification of Nissl-stained cortical neurons.

Algorithms↗
PubMed2006

The BH3-only protein Puma is both necessary and sufficient for neuronal apoptosis induced by DNA damage in sympathetic neurons.

DNA damage activates apoptosis in several neuronal populations and is an important component of neuropathological conditions. While it is well established that neuronal apoptosis, induced by DNA damage, is dependent on the key cell death regulators p53 and Bax, it is unknown which proteins link the p53 signal to Bax. Using rat sympathetic neurons as an in vitro model of neuronal apoptosis, we show that cytosine arabinoside is a DNA damaging drug that induces the expression of the BH3-only pro-apoptotic genes Noxa, Puma and Bim. Increased expression occurred after p53 activation, measured by its phosphorylation at serine 15, but prior to the conformational change of Bax at the mitochondria, cytochrome c (cyt c) release and apoptosis. Hence Noxa, Puma and Bim could potentially link p53 to Bax. We directly tested this hypothesis by the use of nullizygous mice. We show that Puma, but not Bim or Noxa, is a crucial mediator of DNA damage-induced neuronal apoptosis. Despite the powerful pro-apoptotic effects of overexpressed Puma in Bax-expressing neurons, Bax nullizygous neurons were resistant to Puma-induced death. Therefore, Puma provides the critical link between p53 and Bax, and is both necessary and sufficient to mediate DNA damage-induced apoptosis of sympathetic neurons.

Animals↗
PubMed1978

Pharmacological and electrophysiological studies of morphine and enkephalin on rat supraspinal neurones and cat spinal neurones.

1 The actions of morphine, methionine and leucine enkephalin, administered electrophoretically, were studied on supraspinal neurones in the cortex and brainstem of the rat anaesthetized with urethane and on spinal Renshaw cells and dorsal horn interneurones in the cat anaesthetized with pentobarbitone.2 The majority of Renshaw cells and cortical and brainstem neurones were excited by all three compounds although some supraspinal neurones were depressed.3 Naloxone reversibly antagonized both excitatory and depressant actions of morphine and enkephalin. Acetylcholine-induced excitation but not amino acid-induced excitation was also antagonized by naloxone.4 Neither morphine nor the enkephalins had any naloxone-reversible action on dorsal horn neurones when ejected from conventional multibarrelled electrodes. However, morphine but not enkephalin, administered into the substantia gelatinosa region of the spinal cord selectively reduced responses to noxious stimuli of neurones in deeper laminae. Naloxone administered into the same region antagonized this action of morphine.5 Intravenous morphine also antagonized responses of dorsal horn neurones to noxious stimuli and subsequent intravenous naloxone reversed this effect.6 It was concluded that the excitatory and inhibitory effects of morphine and enkephalin on central neurones may be mediated by actions on different opiate receptors and that depression of noxious responses of dorsal horn neurones may be relevant to the analgesic action of morphine.

Animals↗
PubMed2002

p38 MAP kinase is involved in lipopolysaccharide-induced dopaminergic neuronal cell death in rat mesencephalic neuron-glia cultures.

Immune stimulants, such as the bacterial endotoxin, lipopolysaccharide (LPS), the human immunodeficiency virus-1 coat protein gp120, or beta-amyloid peptides, lead to glial activation and production of various immune mediators, such as nitric oxide (NO) and proinflammatory cytokines in the brain. These mediators appear to contribute to neuronal cell death in neurodegenerative diseases. However, the signaling pathways, which mediate the neurotoxic effect by the endotoxin, are not understood. The purpose of this study was to determine the role of mitogen-activated protein kinase (MAPK) in LPS-induced neurodegeneration using mesencephalic dopaminergic neuron/glia cultures. We have found that the p38 MAPK is important in LPS-induced death of mesencephalic neurons in rat neuron-glia mixed cultures. Upon treatment with 10 ng/ml LPS, the number of dopaminergic neurons decreased by 80% within 48 h, preceded by a significant production of NO by glia. Neuroprotection by selective inhibition of p38 MAPK activity paralleled a decrease in LPS-induced inducible nitric oxide synthase (iNOS) expression. These events were significantly reduced by the selective p38 MAPK inhibitor, SB202190, but not by the inactive analogue SB202474. Inhibition of iNOS activity and NO production by treatment with GW274150 was also neuroprotective. Although the p38 MAPK inhibitor afforded significant neuroprotection from LPS toxicity in the neuron-glia mixed culture, it failed to protect dopaminergic neurons from 6-hydroxy-dopamine-induced toxicity, which acts directly on dopaminergic neurons by inducing hydroxyl radical formation from the mitochondria. The results suggest that p38 MAPK in glia plays a significant role in the LPS-induced death of mesencephalic neurons through induction of nitric oxide synthase and resulting NO production.

Animals↗
PubMed1997

Programmed cell death in neurons: focus on the pathway of nerve growth factor deprivation-induced death of sympathetic neurons.

Extensive programmed cell death (PCD) occurs in the developing nervous system. Neuronal death occurs, at least in part, because neurons are produced in excess during development and compete with each other for the limited amounts of the survival-promoting trophic factors secreted by target tissues. Neuronal death is apoptotic and utilizes components that are conserved in other PCD pathways. In this review, we discuss the mechanism of trophic factor-dependent neuronal cell death by focusing on the pathway of nerve growth factor (NGF) deprivation-induced sympathetic neuronal death. We describe the biochemical and genetic events that occur in NGF-deprived sympathetic neurons undergoing PCD. Participation of the Bcl-2 family of proteins and the interleukin-1beta-converting enzyme family of proteases (caspases) in this and other models of neuronal death is also examined. The order and importance of these components during NGF deprivation-induced sympathetic neuronal death are discussed.

Animals↗
PubMed2004

Heterogeneity of P2X receptors in sympathetic neurons: contribution of neuronal P2X1 receptors revealed using knockout mice.

P2X receptors are highly expressed throughout the nervous system, where ATP has been shown to be a neurotransmitter. The aim of this study was to characterize P2X receptor expression within sympathetic postganglionic neurons from the superior cervical ganglia. Reverse transcription-polymerase chain reaction showed the presence of mRNA for all P2X receptors, raising the possibility of multiple subunit expression within these ganglia. Whole-cell patch-clamp and calcium imaging studies revealed a heterogeneous population of P2X receptors in approximately 70% of neurons. We propose that the heterogeneity in properties could be caused by differential expression and/or subunit composition of the P2X receptor. The dominant phenotype was P2X2-like; neurons showed slow desensitization, sensitivity to antagonists, and a profile of ionic modulation that is characteristic of P2X2 receptors: potentiation by acidification and extracellular Zn2+ and attenuation by high extracellular Ca2+ and pH. A subpopulation of neurons (10-15%) were alpha,beta-methylene ATP (alpha,beta-meATP) sensitive, and in neurons from P2X1 receptor-deficient mice the alpha,beta-meATP response was reduced to 2% of all neurons, demonstrating a direct role for P2X1 subunits. Control alpha,beta-meATP responses were eliminated by high extracellular Ca(2+) and pH, indicating the presence of heteromeric channels incorporating the properties of P2X1 and P2X2 receptors. This study demonstrates that in neurons, the P2X1 receptor can contribute to the properties of heteromeric P2X receptors. Given the expression of P2X1 receptors in a range of neurons, it seems likely that regulation of the properties of P2X receptors by this subunit is more widespread.

Animals↗
PubMed1984

Response properties of neurons in posterior parietal cortex of monkey during visual-vestibular stimulation. I. Visual tracking neurons.

Extracellular recordings were obtained from 163 visual tracking neurons in area 7a or PG (24) of alert monkeys. The firing patterns were observed during movements of the chair in which the monkey was seated with its head fixed and of a visual target that the monkey was trained to fixate continuously. Horizontal visual tracking neurons were classified into three groups, A, B, and C, on the basis of the following two discharge characteristics: directional preference for visual tracking and response to horizontal sinusoidal oscillation of the chair in the dark. Those neurons that did not respond to chair oscillations in the dark were classified as type A (26/53). Of the remainder, those that responded with the same directional preference as during visual tracking were classified as type B (19/53), and those that showed the opposite directional preference were classified as type C (8/53). When the target and the chair were oscillated together and the monkey canceled the vestibuloocular reflex (VOR) (combined eye and head tracking), most of the visual tracking neurons (types A and B, 32/38) continued to respond in the same way as during visual tracking when the chair was stationary. Type C neurons showed only weak responses. When the monkey fixated an earth-fixed target while the chair was oscillated sinusoidally (VOR target task), responses of the types A and B neurons were much smaller than during visual tracking, while type C neurons were clearly modulated. The results suggest that visual tracking neurons receive information concerning the smooth-pursuit command during combined eye and head (gaze) movements; some also receive vestibular information in addition to the pursuit command information.

Animals↗
PubMed1992

Encoding of sound-source location and movement: activity of single neurons and interactions between adjacent neurons in the monkey auditory cortex.

1. Neuronal mechanisms for decoding sound azimuth and angular movement were studied by recordings of several single units in parallel in the core areas of the auditory cortex of the macaque monkey. The activity of 180 units was recorded during the presentation of moving and static sound stimuli. Both the activity of single units and the interactions between neighboring neurons in response to each stimulus were analyzed. 2. Sixty-two percent of the units showed significant modulation of their firing rates as a function of the stimulus azimuth. Contralateral stimuli were preferred by the majority (approximately 60%) of these neurons. Thirty-five percent of the units showed mild but statistically significant modulation of their firing rates, which was specifically attributed to the angular movement of the sound source. 3. Eighty-nine percent of the "movement-sensitive" units were also "azimuth sensitive." The sound source's azimuth determined the pattern of the response components (on, sustained, off), whereas the source's movement affected only the magnitude of these components, typically the sustained component. Most neurons for which the sustained response to static sounds was greater for contralateral than ipsilateral stimuli preferred moving sounds that were moving into the contralateral hemifield. 4. Cross-correlation analysis was carried out for 245 neuron pairs. Cross-correlograms were computed for each pair under all stimulus conditions to allow comparison of the neuronal interactions under the various conditions. The shapes of some correlograms (after subtraction of direct stimulus effects) were dependent on specific stimulus conditions, suggesting that the effective connectivity between these neurons depended on the location and/or movement of the sound stimuli. Furthermore, joint peristimulus time (JPST) analysis indicated that modifications of connectivity may be temporally related to the stimulus and may occur over short periods of time. These results could not have been predicted from analysis of the independent single-unit responses to the stimuli. 5. The data suggest that both firing rates and correlated activity between adjacent neurons in the auditory cortex encode sound location and movement.

Acoustic Stimulation↗
PubMed1993

Ion channels in spinal cord astrocytes in vitro. III. Modulation of channel expression by coculture with neurons and neuron-conditioned medium.

1. Astrocytes cultured from rat spinal cord express voltage-activated Na+ channels in high densities (up to 8 channels per microns2). Stellate astrocytes express Na+ currents at all times in vitro. In pancake astrocytes, Na+ channel expression shows a distinct temporal pattern, an absence of channel expression at 1-3 days in vitro (DIV), and peak Na+ channel density at 7-8 DIV. 2. Coculture of spinal cord astrocytes with dorsal root ganglion (DRG) neurons substantially reduces the expression of voltage-activated Na+ channels in both spinal cord astrocyte types. In pancake spinal cord astrocytes, both the percentage of cells expressing Na+ channels and the channel density in Na+ channel-expressing cells are markedly reduced. In stellate spinal cord astrocytes, the percentage of Na+ channel-expressing cells is unchanged, but the Na+ channel density per cell is markedly reduced in coculture. 3. Culturing spinal cord astrocytes in neuron-conditioned media reduces Na+ channel expression in both spinal cord astrocyte types to levels intermediate between coculture and control, suggesting that, at least in part, neuronal effects on Na+ channel expression are mediated by a soluble factor secreted into the media by neurons. 4. As with the expression of voltage-activated Na+ channels, the expression of voltage-activated K+ channels is reduced in both spinal cord astrocyte types cocultured with DRG neurons. The effect is not mimicked by culturing cells in neuron-conditioned media, suggesting that effects on K+ channel expression are mediated by a less stable and more readily degradable factor. 5. Coculture with DRG neurons or culture in neuron-conditioned media do not alter the biophysical properties of voltage-activated Na+ currents in pancake spinal cord astrocytes. Thus steady-state activation, steady-state inactivation, and the time constants of activation and inactivation are virtually unchanged under the various culture conditions.

Animals↗
PubMed2000

Perimembrane localization of the estrogen receptor alpha protein in neuronal processes of cultured hippocampal neurons.

There is clear evidence of rapid, nongenomic responses to estrogen in a variety of neuronal model systems. To address the question of whether some of these rapid estrogen signals might be transduced by the classical estrogen receptor (ER) alpha or a closely related protein in nontransformed neurons, we undertook the present study using isolated fetal rat hippocampal neurons. Several antibodies developed to detect ERalpha were tested in this system and showed positive membrane staining in nonpermeabilized neurons. MC-20, an affinity purified anti-ERalpha, rabbit polyclonal IgG antibody which does not recognize ERbeta was selected to carry out the majority of the experiments. When permeabilized, the hippocampal neurons exhibited low levels of nuclear staining for ERalpha, but abundant labeling for ERalpha throughout the entire cell including the neurites. In addition to traditional immunocytochemistry controls, incubation of neurons for 24 h in the presence of 10 microM antisense oligonucleotide directed against the translation start site of ERalpha reduced ERalpha immunoreactivity throughout the neurons providing further evidence that the immunostaining was specific for ERalpha. Confocal and conventional microscopy demonstrated that the antigen was predominately extranuclear and localization of ERalpha in the neurites suggests that the receptor is in close proximity to the plasma membrane. This localization is consistent with a role for ERalpha as a transducer of rapid, nongenomic estrogen responses in hippocampal neurons.

Amino Acid Sequence↗
PubMed2005

Progesterone-receptive beta-endorphin and dynorphin B neurons in the arcuate nucleus project to regions of high gonadotropin-releasing hormone neuron density in the ovine preoptic area.

Progesterone inhibits gonadotropin-releasing hormone (GnRH) secretion through interneuronal systems located in the mediobasal hypothalamus in ewes. Endogenous opioid peptides are implicated in this inhibition of GnRH secretion. The distributions of endogenous opioid peptides are known to overlap with progesterone receptors (PR) in the arcuate nucleus. We investigated whether PR is expressed by beta-endorphin and dynorphin B neurons in the arcuate nucleus and if a subset of double-labeled cells projects to the preoptic area where most GnRH neurons are detected. Injection of a retrograde tracer, Fluorogold, into the rostral preoptic area was performed in ovariectomized ewes pretreated with estrogen and progesterone. Brain sections were processed using double immunocytochemistry. Only brains of ewes with an injection site encompassing at least 80 GnRH neurons were processed for PR and then either beta-endorphin or dynorphin B immunocytochemistry. Antigen retrieval is essential for PR detection but causes Fluorogold to fade. Thus, quantitative analysis was performed on photographs taken before and after antigen retrieval. We found that 25-30% of PR-containing neurons, 20% of beta-endorphin cells and 22% of dynorphin B neurons in the arcuate nucleus project toward the preoptic area. From the PR/beta-endorphin double-labeled cells that represent 25 and 36% of PR and beta-endorphin cells, respectively, 35% were labeled with Fluorogold. From the PR/dynorphin B double-labeled cells that account for 39 and 62% of PR and dynorphin B neurons, respectively, 26% contained Fluorogold. These data strongly support the hypothesis that progesterone acts in the arcuate nucleus through beta-endorphin and dynorphin B neurons to affect preoptic area GnRH neurons.

Animals↗
PubMed1989

Corticotropin-releasing factor neurons innervate dopamine neurons in the periventricular hypothalamus of juvenile macaques. Synaptic evidence for a possible companion neurotransmitter.

Corticotropin-releasing factor (CRF) and dopamine (DA) are important integrators of the endocrine and autonomic response to stress. CRF neurons in the anterior portions of the periventricular nucleus (PV) and parvocellular paraventricular nucleus (pvPVN) occur close to A14 DA neurons in these same locations. Since CRF has been shown to act as an excitatory neurotransmitter, possible CRF interactions with the DA system were investigated using double-label immunocytochemistry. Coronal vibratome sections through the PV and pvPVN were obtained from colchicine-treated and nontreated juvenile female cynomolgus macaques. They were sequentially immunostained for tyrosine hydroxylase (TH) (to identify DA neurons) with PAP and DAB, and for CRF using 15 nm colloidal gold. By light microscopy, areas of coincidence of TH- and CRF-immunoreactive cell bodies in the PV and pvPVN were obvious, but double-stained elements were not observed. By electron microscopy, asymmetrical synapses frequently occurred between CRF axons and TH dendrites or somata. Symmetrical axosomatic synapses sometimes appeared adjacent to these CRF/TH synapses, while symmetrical axoaxonic synapses were rare. We conclude that CRF neuronal efferents synaptically activate A14 DA neurons in the primate PV and pvPVN. Parallel CRF/DA symmetrical synapses also suggest coexistence of a companion transmitter within some of these same CRF neurons. Our own previous work and recent independent studies indicate that this transmitter is probably GABA. Thus the CRF neuronal system, which is known to alter secretion of several pituitary hormones, may also act through hypothalamic periventricular DA neurons to mediate other responses to stress.

Animals↗
PubMedDate not supplied

Integrated evaluation of central nervous system lesions: stains for neurons, astrocytes, and microglia reveal the spatial and temporal features of MK-801-induced neuronal necrosis in the rat cerebral cortex.

Routinely processed, hematoxylin and eosin (H&E)-stained slides are typically used to assess the morphologic integrity of the central nervous system in neurotoxicity safety studies. However, the value of special stains for improving neuropathologic evaluations during the assessment of neurotoxicity has been emphasized in the neuroscience literature and by regulatory agencies. The primary objective of the present study was to characterize the spatial and temporal changes in neurons, astrocytes, and microglia after dizocilpine maleate (MK-801)-induced focal neuronal necrosis in the posterior cingulate/retrosplenial (PC/RS) cortex of the rat. A secondary objective was to evaluate the application of special stains and a novel sectioning procedure for detecting neurotoxicity. Sixty adult male Sprague-Dawley rats were treated with sterile water vehicle or 10 mg/kg MK-801 and perfused through the left ventricle (pumped at 65 mm Hg pressure) with 10% neutral buffered formalin or 4% paraformaldehyde at 4 hr and on days 1, 3, 7, 14, and 28 after treatment. For light microscopic evaluation, brain sections were stained with H&E, a special cupric-silver (CS) stain that selectively impregnates degenerating neurons and makes them readily evident, glial fibrillary acidic protein (GFAP) immunohistochemistry for astrocytes, and Griffonia simplicifolia isolectin B4(GSA) histochemistry for microglia. Brains perfusion-fixed with 4% paraformaldehyde were prepared for CS staining with a novel frozen-sectioning procedure for multiple embedding in a composite gelatin block. In H&E sections from treated rats, necrotic nerve cell bodies were observed in PC/RS cortical layers 3 and 4 on days 1, 3, 7, and 14, but not on day 28. These necrotic neurons required high magnification for detection (x20 objective, x10 ocular). In contrast, degenerating neurons selectively stained with CS were observed in the same location as necrotic neurons seen with H&E but at low magnification (x2 objective, x10 ocular). Cupric-silver staining showed details not seen with H&E, including dendritic and axonal degeneration with progressive fragmentation. Beginning on day 3, GFAP immunohistochemistry revealed hypertrophic astrocytes in a diffuse pattern throughout the region of cell body necrosis, a change that persisted throughout the study. However, GSA lectin histochemistry identified a few reactive microglia on day 1 in a multifocal pattern throughout the region of cell body necrosis. Reactive microglia were observed on days 3, 7, and 14, but not on day 28. Glial changes observed with H&E staining were limited to an increase in the cellularity of glial cell nuclei in the area of neuronal necrosis. This study provides a comprehensive and integrated view of the temporal changes occurring in neurons, astrocytes, and microglia during acute neurotoxic injury. Moreover, advantages for using new staining and sectioning methodologies to enhance the toxicologic evaluation of the central nervous system are demonstrated.

Animals↗
PubMed1996

Histochemical and immunohistochemical detection of neurons that produce nitric oxide: effect of different fixative parameters and immunoreactivity against non-neuronal NOS antisera.

This study focused on two points concerning the histochemical and immunohistochemical detection of neurons that produce nitric oxide (NO): (a) the effect of fixation and other methodological parameters on the staining pattern of both NADPH-diaphorase (NADPH-d) histochemistry and nitric oxide synthase (NOS) immunohistochemistry, and (b) the possibility that neurons display immunoreactivity against NOS antisera obtained from non-neuronal sources. Frontal sections of rat brains, fixed with 4% paraformaldehyde according to different protocols, were processed for single and double labeling using NADPH-d histochemistry and neuronal (nNOS), macrophagic (macNOS), and endothelial (eNOS) NOS immunohistochemistry. Our results show that variations in the fixative schedule, even within standard parameters, produce qualitative and quantitative changes in NADPH-d labeling. The effect of fixative on weakly stained neurons is different from that on heavily stained neurons. In subfixed brains, a large number of NOS-positive neurons lose their NADPH-d activity, whereas NOS immunolabeling remains unaltered. This finding may be particularly interesting in morphological studies that compare NADPH-d activity under experimental conditions that can affect brain perfusion. On the other hand, many cortical and subcortical neurons show macNOS immunoreactivity, most of it colocalized with nNOS.

Animals↗
PubMed2003

Gamma-aminobutyric acid neurons integrate and rapidly transmit permissive and inhibitory metabolic cues to gonadotropin-releasing hormone neurons.

Negative energy balance inhibits fertility by decreasing GnRH release; however, the mechanisms are not well understood. GnRH neurons can be excited by activation of gamma-aminobutyric acid (GABA)(A) receptors, and GABAergic neurons provide a major synaptic input. We hypothesized that permissive metabolic signals mediated by leptin and inhibitory signals conveyed by neuropeptide Y (NPY) and opiates rapidly alter GABA(A) receptor-mediated drive to GnRH neurons. In fed and fasted female mice, GABAergic postsynaptic currents (PSCs) were recorded from GnRH neurons before and after in vitro treatment with leptin, NPY, or met-enkephalin. Leptin increased PSC frequency in fed and fasted mice, indicating that it increased presynaptic activity. Leptin also increased PSC size. Inhibiting leptin receptor signaling pathways within GnRH neurons abolished the latter effect, indicating a direct action on these cells. In fed, but not fasted, mice, NPY and met-enkephalin decreased PSC frequency in an antagonist-reversible manner, but did not alter PSC size. NPY-1 receptor antagonists alone increased frequency in fed and fasted mice, as did opiate receptor blockade in fasted animals, suggesting that endogenous NPY and opiates modulate GABAergic drive to GnRH neurons. These data suggest that GABAergic afferents integrate metabolic signals for delivery to GnRH neurons. Decreased sensitivity to NPY and opiates in fasted mice indicate that these peptides send physiologically relevant signals regarding energy balance to GnRH neurons.

Age Factors↗
PubMed1991

Ultrastructural evidence for luteinizing hormone-releasing hormone neuronal control of estrogen responsive neurons in the preoptic area.

Both estrogen receptor (ER) immunoreactive (ir) and LHRH-ir neurons and processes are present in the preoptic area of the guinea pig. This experiment was conducted to determine if LHRH-ir terminals interact synaptically with ER-ir cells. A light microscopic dual chromogen immunocytochemical technique employing diaminobenzidine (DAB) and nickel-enhanced DAB for LHRH and ER localization, respectively, revealed that many varicose LHRH-ir fibers coursed in close proximity to ER-ir cells in the anterior part of the preoptic area at the preventricular periventricular nucleus (Pep), suggesting the likelihood of synaptic interactions. Ultrastructural analysis was performed using DAB and 3,3',5,5'-tetramethylbenzidine (TMB) for LHRH and ER localization, respectively. DAB labeling in LHRH-ir neurons appeared as a dense flocculent product dispersed throughout the cytoplasm. TMB stained ER-ir neurons contained electron dense crystalline spicules located predominantly in their nuclei. Numerous TMB labeled ER-ir neurons were present in the Pep, and occasionally occurred in clusters, closely apposed to one another. Many LHRH-ir terminals made synaptic contact or were apposed to unlabeled dendrites, while fewer contacted perikarya. Most significantly, ER-ir neurons showing clear evidence of intranuclear TMB crystals received synaptic input from LHRH-ir terminals. In addition, LHRH-ir terminals lacking synaptic specializations were also in direct apposition to ER-ir perikarya. These results provide morphological evidence that LHRH-ir neurons can regulate ER-ir neurons in the preoptic area. Since LHRH-ir cells are thought to be regulated by estrogen responsive neurons, interaction of LHRH terminals with ER-ir cells may represent a regulatory feedback circuit between the two systems.

3,3'-Diaminobenzidine↗
PubMed1994

Detection of cortical neuron loss in motor neuron disease by proton magnetic resonance spectroscopic imaging in vivo.

We performed proton magnetic resonance spectroscopic imaging (1H-MRSI) in patients with motor neuron disease (MND) to evaluate the distribution and extent of cortical neuron damage or loss as reflected by decreased N-acetyl (NA) to creatine (Cr) resonance intensity ratios. We examined premotor (superior frontal gyrus), primary motor (precentral gyrus), primary sensory (postcentral gyrus), and parietal (superior parietal gyrus/precuneus) neocortical regions of 12 patients with MND and six normal control subjects. Patients with MND were representative of three syndromes: amyotrophic lateral sclerosis (ALS) with definite lower motor neuron and upper motor neuron signs, MND with probable upper motor neuron signs (PUMNS), and progressive spinal muscular atrophy (PSMA) with lower motor neuron signs only. Compared with healthy controls, ALS patients had a significant decrease in NA/Cr resonance intensity ratios, most prominently in the primary motor cortex (p < 0.001) but also, to varying degrees, in primary sensory (p < 0.01), posterior premotor, and parietal (p < 0.05) regions. Patients classified as ALS-PUMNS showed less prominent reduction in NA/Cr ratios in the same regions; patients with PSMA had normal cortical NA/Cr ratios. Sequential studies in one patient suggested that 1H-MRSI could document progression of the NA/Cr abnormality. Decreased NA/Cr ratios on 1H-MRSI provide an index of cortical motor neuron loss and/or dysfunction in MND patients. Clinical applications of 1H-MRSI could include documenting the extent of upper motor neuron involvement, aiding diagnosis of syndromes presenting with an ALS-like picture, and monitoring disease progression.

Adult↗
PubMed1993

Non-neuronal cells inhibit catecholaminergic differentiation of primary sensory neurons: role of leukemia inhibitory factor.

Although some sensory ganglion cells in mature animals are catecholaminergic, most mammalian sensory neurons that express the catecholamine-synthesizing enzyme tyrosine hydroxylase (TH) do so only transiently during early gangliogenesis in vivo. The lack of TH expression at later stages appears to be due to modulation of this catecholaminergic potential. A previous study showed that the phenotype reappears, for example, when E16.5 and older sensory ganglia are dissociated in culture into single cells, suggesting that extracellular influences can modulate TH expression. Moreover, TH expression in dissociate cultures is cell-density dependent, as a four-fold increase in plating density led to a 30% decrease in the percentage of TH neurons. The present study demonstrates that inhibition of TH expression in high density cultures is mediated by ganglionic non-neuronal cells (NNC), as removal of NNC abolished density-dependent inhibition. Moreover, plating E16.5 trigeminal neurons at low density on top of NNC monolayers resulted in an 85% decrease in the percentage of TH neurons. Treatment of cultures with non-neuronal cell conditioned medium (NNC-CM) reproduced the effect of coculture with NNC, suggesting that diffusible factors from NNC were involved in the inhibition of TH. The inhibitory effect of NNC-CM was mimicked by treatment of dissociate cultures with ciliary neurotrophic factor (CNTF) and leukemia inhibitory factor (LIF). However, immunoprecipitation of NNC-CM with antibodies against LIF or CNTF showed that only anti-LIF antibodies were able partially to remove the TH inhibitory activity of NNC-CM. Therefore, LIF is one, but not the only, factor mediating NNC inhibition of TH expression in cultured sensory neurons. In summary, these data indicate that ganglionic NNC can regulate sensory transmitter phenotype in culture by inhibiting expression of specific molecular traits. The finding that LIF can partially account for the inhibitory effect of ganglionic NNC on TH expression suggests a novel role for this cytokine in regulating differentiation of catecholaminergic properties in sensory neurons.

Animals↗