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Query: UMLS:C0019829 (Hodgkin's disease)
 30,247 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The statistical relationship between multi-unit spike activity and simultaneously recorded local dendritic field potentials in the olfactory system of the waking rat was studied with chronically placed electrodes. The relationship had the form of a sigmoid increase in axonal firing probability conditional on the amplitude of dendritic potentials. These data were fitted with an asymmetric sigmoid curve previously derived from the Hodgkin-Huxley equations. The curve was fitted using non-linear regression to optimize its parameter: the maximal firing rate. The maximal rate also gave the steepness of the slope of the sigmoid. Pulse trains were recorded from excitatory and inhibitory neurons in the olfactory cortex (including the anterior olfactory nucleus, the prepyriform cortex and the lateral entorhinal area) as identified by the phase relations of the pulse probability and the dendritic potentials, and from the excitatory neurons in the bulb (the inhibitory granule cells do not give extracellularly detectable action potentials). All these neurons are known to interact in disynaptic negative feedback loops giving rise to oscillations. The same sigmoid function fit the data from both types of neurons in all locations. The curves for neurons in all parts of the olfactory cortex had a 3-fold higher slope and maximal value than the curves from bulbar neurons. The significances of this difference and of the asymmetric sigmoid are discussed in terms of models for olfactory oscillatory dynamics and pattern recognition.
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PMID:Asymmetric sigmoid non-linearity in the rat olfactory system. 174 47

The olfactory neuroblastoma or esthesioneuroblastoma is a rare neuroectodermal tumor originating from the olfactory neuroepithelium, which can metastasis via cerebrospinal fluid pathways. In the present case of an extensive nasal malignancy with cervical lymph node metastases in a 75-year old woman, its difficult histology alternatively led to a diagnosis of anaplastic carcinoma and non-Hodgkin lymphoma. The patient died from complications following spread of the tumor to the spinal cord and cauda equina. Review of the literature shows that this tumor is notorious for its chameleonic character. In view of its clearly demonstrated malignancy an aggressive therapeutic approach is advocated.
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PMID:Olfactory neuroblastoma with spinal metastasis--a problem in diagnosis. 302 77

1. Detailed compartmental computer simulations of single mitral and granule cells of the vertebrate olfactory bulb were constructed using previously published geometric data. Electrophysiological properties were determined by comparing model output to previously published experimental data, mainly current-clamp recordings. 2. The passive electrical properties of each model were explored by comparing model output with intracellular potential data from hyperpolarizing current injection experiments. The results suggest that membrane resistivity in both cells is nonuniform, with somatas having a substantially lower resistivity than the dendrites. 3. The active properties of these cells were explored by incorporating active ion channels into modeled compartments. On the basis of evidence from the literature, the mitral cell model included six channel types: fast sodium, fast delayed rectifier (Kfast), slow delayed rectifier (K), transient outward potassium current (KA), voltage- and calcium-dependent potassium current (KCa), and L-type calcium current. The granule cell model included four channel types: rat brain sodium, K, KA, and the non-inactivating muscarinic potassium current (KM). Modeled channels were based on the Hodgkin-Huxley formalism. 4. Representative kinetics for each of the channel classes above were obtained from the literature. The experimentally unknown spatial distributions of each included channel were obtained by systematic parameter searches. These were conducted in two ways: large-scale simulation series, in which each parameter was varied in turn, and an adaptation of a multidimensional conjugate gradient method. In each case, the simulated results were compared wtih experimental data using a curve-matching function evaluating mean squared differences of several aspects of the simulated and experimental voltage waveforms. 5. Systematic parameter variations revealed a single distinct region of parameter space in which the mitral cell model best fit the data. This region of parameter space was also very robust to parameter variations. Specifically, optimum performance was obtained when calcium and slow K channels were concentrated in the glomeruli, with a lower density in the soma and proximal secondary dendrites. The distribution of sodium and fast potassium channels, on the other hand, was highest at the soma and axon, with a much lighter distribution throughout the secondary dendrites. The KA and KCa channels were also concentrated near the soma. 6. The parameter search of the granule cell model was much less restrained by experimental data. Several parameter regimes were found that gave a good match to the data.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Exploring parameter space in detailed single neuron models: simulations of the mitral and granule cells of the olfactory bulb. 768 98

When applied from the cytoplasmic side, cyclic 3',5'-adenosine and guanosine monophosphates reversibly increased the ion permeability of inside-out patches of carp olfactory neuron plasma membrane. The cAMP (cGMP)-induced permeability via cAMP (cGMP) concentration was fitted by Hill's equation with the exponents of 1.07 +/- 0.15 (1.12 +/- 0.05) and EC50 = 1.3 +/- 0.6 microM (0.9 +/- 0.3 microM). Substitution of NaCl in the bathing solution by chlorides of other alkali metals resulted in a slight shift of reversal potential of the cyclic nucleotide-dependent (CN) current, which indicates a weak selectivity of the channels. Permeability coefficients calculated by Goldman-Hodgkin-Katz's equation corresponded to the following relation: PNa/PK/PLi/PRb/PCs = 1:0.98:0.94:0.70:0.61. Ca2+ and Mg2+ in physiological concentrations blocked the channels activated by cyclic nucleotides (CN-channels). In the absence of divalent cations the conductance of single CN-channels was equal to 51 +/- 9 pS in 100 mM NaCl solution. Channel density did not exceed 1 micron-2. The maximal open state probability of the channel (Po) tended towards 1.0 at a high concentration of cAMP or cGMP. Dichlorobenzamil decreased Po without changing the single CN-channel' conductance. CN-channels exhibited burst activity. Mean open and closed times as well as the burst duration depended on agonist concentration. A kinetic model with four states (an inactivated, a closed and two open ones) is suggested to explain the regularities of CN-channel gating and dose-response relations.
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PMID:Cyclic nucleotide-activated channels in carp olfactory receptor cells. 833 39

Human BCL6, also called LAZ3, is a protein involved in gene regulation and abnormal expression of BCL6 and has been implicated in the tumorigenesis of non-Hodgkin lymphoma. We have analyzed the expression of murin bcl6 in pre- and postnatal mouse using in situ hybridization histochemistry and Northern blotting. The developing olfactory epithelium in the nasal cavity was the only tissue displaying a positive bcl6 mRNA signal in the day 14 embryo. At gestational day 17, expression was primarily seen in skeletal muscle, olfactory epithelium, and thymus, and also in the epithelium lining the upper airways and esophagus. In selected tissues from postnatal mouse, bcl6 expression was detected in brain, renal cortex, spleen, and thymus. The expression in brain was restricted to the pyramidal cell layer of the cerebral cortex and the hippocampus regions CA1 and CA2, and the dentate gyrus. Our results show that bcl6 expression is not confined only to organs of the lymphatic system, such as spleen and thymus. Thus, bcl6 may be active as a regulator of gene transcription in many different cell types, including epithelial and nerve cells.
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PMID:Expression of the BCL6 gene in the pre- and postnatal mouse. 964 31

Cells, identified as supporting cells by Lucifer Yellow injection, were recorded from slices of frog olfactory epithelium using patch-clamp recordings. Cell-attached single-channel recordings indicated that the intracellular potential (IP) was -68 +/- 7 mV (n = 22) with 4 mM K+ in the bath ([K+]o). IP was -67 +/- 4 mV (n = 32) in whole-cell conditions with 100 mM KCl inside the cell, suggesting a low membrane permeability for Cl-. IP depended on [K+]o in a manner described by the Goldman-Hodgkin-Katz equation with a permeability ratio pk+:PNa+ of 40. The input resistance was 32 +/- 14 M omega (n = 15), indicating a high membrane conductance at rest. Odorant stimulations evoked passive membrane depolarizations, probably reflecting an increase in [K+]o due to the neuronal activation. Whole-cell recordings with 100 mM CsCl instead of KCl in the pipette, together with the block of gap-junctions with octanol, indicated the existence of an electrical coupling between supporting cells. The electrical coupling between these glial-like cells could facilitate the clearance of K+ ions released by olfactory receptor neurons during odorant stimulation.
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PMID:Electrophysiological properties of frog olfactory supporting cells. 966 50

Carcinomas of the nasal cavity and paranasal sinuses represent 3% of tumors of the head and neck. Their histology and location vary widely. We reviewed the case histories of patients with malignant tumors of the nasal sinuses seen by us between 1975 and 1996, a total of 37 suitable cases. The site of origin of the tumor was the maxillary sinus in 16 cases, ethmoid sinus in 15, nasal septum in 3, nasal roof in 2, and nasal floor in 1 case. Fifty percent of the tumors were squamous cell carcinomas, 11% undifferentiated carcinomas, 13% non-squamous carcinomas, 5% melanomas, 5% olfactory neuroblastomas, 3% chondrosarcomas and 8% non-Hodgkin lymphomas. When diagnosed, one patient had carcinoma in situ, 3 stage I, 5 stage II, 12 stage III and 16 stage i.v. The cumulative survival was 63% after 3 years and 47% after 5 years.
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PMID:[Twenty years of retrospective study of malignant paranasal sinus tumors]. 970 38

In olfactory mitral cells, dual patch recordings show that the site of action potential initiation can shift between soma and distal primary dendrite and that the shift is dependent on the location and strength of electrode current injection. We have analyzed the mechanisms underlying this shift, using a model of the mitral cell that takes advantage of the constraints available from the two recording sites. Starting with homogeneous Hodgkin-Huxley-like Na(+)-K(+) channel distribution in the soma-dendritic region and much higher sodium channel density in the axonal region, the model's channel kinetics and density were adjusted by a fitting algorithm so that the model response was virtually identical to the experimental data. The combination of loading effects and much higher sodium channel density in the axon relative to the soma-dendritic region results in significantly lower "voltage threshold" for action potential initiation in the axon; the axon therefore fires first unless the voltage gradient in the primary dendrite is steep enough for it to reach its higher threshold. The results thus provide a quantitative explanation for the stimulus strength and position dependence of the site of action potential initiation in the mitral cell.
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PMID:Computational analysis of action potential initiation in mitral cell soma and dendrites based on dual patch recordings. 1060 36

We study the stability and information encoding capacity of synchronized states in a neuronal network model that represents part of thalamic circuitry. Our model neurons have a Hodgkin-Huxley-type low-threshold calcium channel, display postinhibitory rebound, and are connected via GABAergic inhibitory synapses. We find that there is a threshold in synaptic strength, tau(c), below which there are no stable spiking network states. Above threshold the stable spiking state is a cluster state, where different groups of neurons fire consecutively, and each neuron fires with the same cluster each time. Weak noise destabilizes this state, but stronger noise drives the system into a different, self-organized, stochastically synchronized state. Neuronal firing is still organized in clusters, but individual neurons can hop from cluster to cluster. Noise can actually induce and sustain such a state below the threshold of synaptic strength. We do find a qualitative difference in the firing patterns between small (approximately 10 neurons) and large (approximately 1000 neurons) networks. We determine the information content of the spike trains in terms of two separate contributions: the spike-time jitter around cluster firing times, and the hopping from cluster to cluster. We quantify the information loss due to temporally correlated interspike intervals. Recent experiments on the locust olfactory system and striatal neurons suggest that the nervous system may actually use these two channels to encode separate and unique information.
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PMID:Synchronous clusters in a noisy inhibitory neural network. 1094 92

We present an experimental study of the phase relationships observed in small reactor networks consisting of two and three continuous flow stirred tank reactors. In the three-reactor network one chemical oscillator is coupled to two other reactors in parallel in analogy to a small neural net. Each reactor contains an identical reaction mixture of the excitable Belousov-Zhabotinsky reaction which is characterized by its bifurcation diagram, where the electrical current is the bifurcation parameter. Coupling between the reactors is electrical via Pt-working electrodes and it can be either repulsive (inhibitory) or attractive (excitatory). An external electrical stimulus is applied to all three reactors in the form of an asymmetric electrical current pulse which sweeps across the bifurcation diagram. As a consequence, all three reactors oscillate with characteristic oscillation patterns or remain silent in analogy to the firing of neurons. The observed phase behavior depends on the type of coupling in a complex way. This situation is analogous to the in vivo measurements on single neurons (local neurons and projection neurons) performed by G. Laurent and co-workers on the olfactory system of the locust. We propose a simple neural network similar to the reactor network using the Hodgkin-Huxley model to simulate the action potentials of the coupled single neurons. Analogies between the reactor network and the neural network are discussed.
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PMID:The phases of small networks of chemical reactors and neurons 1096 7


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