SEARCH · PubMed Health

Results for “Chemoreceptor Cells”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

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

At least 847 records · Page 47Linked to original sources

PubMed2003

Low rates of change enhance effect of humidity on the activity of insect hygroreceptors.

The inability to measure humidity during stimulation has so far prevented us from understanding the contribution of moist cells and dry cells to orientation in a gradient of humidity. The problem was solved in the present study by means of a UV-absorption hygrometer that made it possible to monitor humidity at a rate of 100 Hz. The antennal moist and dry cells of the cockroach were exposed to humidities alternatively falling or rising at low rates between -1% RH s(-1) and +1% RH s(-1) (relative humidity). Impulse frequency of both types of cells depended simultaneously on instantaneous humidity and its rate of change. High frequencies of the moist cells signal high humidity. But at a given humidity, the response frequency is higher still when humidity is also rising. Conversely, high frequencies of the dry cell signal low humidity, and frequency is higher still at a given humidity when humidity is also falling. These responses ensure that the cockroach spent a minimum time in environments where desiccation or hydration occur and may thus protect the animal from emerging accidentally from under cover into moving air. In the constant-humidity retreat of the cockroach, fluctuating or even drifting discharge frequencies could serve as an early warning: return!

Animals↗

PubMed1995

Identification of a Drosophila G protein alpha subunit (dGq alpha-3) expressed in chemosensory cells and central neurons.

We have identified another Drosophila GTP-binding protein (G protein) alpha subunit, dGq alpha-3. Transcripts encoding dGq alpha-3 are derived from alternative splicing of the dGq alpha locus previously shown to encode two visual-system-specific transcripts [Lee, Y.-J., Dobbs, M.B., Verardi, M.L. & Hyde, D.R. (1990) Neuron 5, 889-898]. Immunolocalization studies using dGq alpha-3 isoform-specific antibodies and LacZ fusion genes show that dGq alpha-3 is expressed in chemosensory cells of the olfactory and taste structures, including a subset of olfactory and gustatory neurons, and in cells of the central nervous system, including neurons in the lamina ganglionaris. These data are consistent with a variety of roles for dGq alpha-3, including mediating a subset of olfactory and gustatory responses in Drosophila, and supports the idea that some chemosensory responses use G protein-coupled receptors and the second messenger inositol 1,4,5-trisphosphate.

Amino Acid Sequence↗

PubMed1997

Rhythmic bursting of pre- and post-inspiratory neurones during central apnoea in mature mice.

1. Stimulation of pulmonary vagal C fibres (PCFs) inhibits inspiration but the response pattern of respiratory rhythm-generating neurones is unknown. This study provides the first description of the effects of PCF stimulation on six different types of respiratory neurones located in the ventrolateral medulla of the mature mouse. 2. Studies were performed in both urethane-anaesthetized (1.5 g kg-1 I.P.) mature mice and in an arterially perfused working heart-brainstem preparation (WHBP). In both preparations the respiratory motor pattern of phrenic and recurrent laryngeal nerves were comparable. Stimulation of PCFs, using phenylbiguanide (2-5 micrograms) injected into the right atrium, evoked a similar respiratory and cardiac response pattern in both anaesthetized and perfused mice, which included: (i) a significant prolongation of the inter-inspiratory interval; (ii) an increase in the duration and amplitude of post-inspiratory (PI) activity; and (iii) an atropine-sensitive bradycardia (50-260 beats min-1). 3. In the WHBP, PCF stimulation evoked a depolarization (11 +/- 1 mV) and high frequency tonic discharge (up to 64 Hz) in ten out of twenty-one PI neurones. During the PCF-induced prolongation of PI activity all other PI neurones (n = 11), as well as pre-inspiratory neurones (PreI; n = 11), displayed oscillations in membrane potential and/or rhythmic bursting at a similar frequency of 0.7-1.0 Hz. Other respiratory neurones recorded, including stage II expiratory neurones (n = 7), early- (n = 6), ramp- (n = 16) and late-inspiratory neurones (n = 4), ceased firing rhythmically during PCF stimulation. 4. The firing behaviour of PI and PreI neurones was assessed after switching to a low Ca2+ (0.2 mM)-high Mg2+ (5.25 mM) perfusate to block synaptic transmission in the WHBP. In the absence of synaptic transmission, PreI neurones (n = 7/8) continued to discharge rhythmically, whereas all other respiratory cell types (including PI neurones, n = 5) fired tonically. 5. In conclusion, stimulation of PCFs elicits a reflex-evoked prolongation of the PI phase of the respiratory cycle and excitation of PI neurones including rhythmic discharging. It is suggested that this rhythmic bursting depends on inhibitory connections from PreI neurones. The functional significance of these central 'apnoeic rhythms' are discussed.

Age Factors↗

PubMed1992

Androgen and estrogen concentrating neurons in chemosensory pathways of the male Syrian hamster brain.

The medial preoptic area (MPOA), bed nucleus of the stria terminalis (BNST), and medial amygdaloid nucleus (Me) are essential for male sexual behavior in the Syrian hamster. These nuclei received chemosensory stimuli and gonadal steroid signals, both of which are required for mating behavior. The objective of this study was to compare the distribution of androgen- and estrogen-concentrating neurons in MPOA, BNST, and Me in the adult male hamster using steroid autoradiography for estradiol (E2), testosterone (T) and dihydrotestosterone (DHT). Adult males (n = 4 per group) received two i.p. injections of tritiated steroid 4-7 days after castration. Six-microns frozen sections through the brain were mounted onto emulsion-coated slides, and exposed for 11-16 months. In MPOA, BNST, and Me, neurons were more abundant and heavily labelled after [3H]E2 treatment than after either [3H]T or [3H]DHT. Tritiated estradiol- and DHT-labeled cells were found throughout the rostrocaudal extent of Me, with a high concentration in posterodorsal Me. Tritiated testosterone treatment labelled cells largely within posterodorsal Me. In MPOA, the majority of E2-, T-, and DHT-labelled neurons were in the medial preoptic nucleus (MPN) and the preoptic continuation of the posteromedial bed nucleus of the stria terminalis (BNSTpm). Few T-labelled cells were present outside these subdivisions. In the BNST, E2- and DHT-labelled neurons were present in all subdivisions, whereas T labelling was confined to the antero- and posteromedial subdivisions of BNST. These results suggest that the distribution of androgen- and estrogen receptor-containing neurons overlap considerably in nuclei which transmit chemosensory signals in the control of mating behavior.

Animals↗

PubMed1991

Differential spatial and temporal expression of two type III intermediate filament proteins in olfactory receptor neurons.

Olfactory receptor neurons (ORNs) do not express the typical neuronal intermediate filament proteins (IFPs), the neurofilament triplet proteins. Immunocytochemical evidence shows that ORNs coexpress vimentin and peripherin but distribute them differently. Specifically, ORNs contain vimentin in dendrites, cell bodies, and axons, but not in terminals in glomeruli; peripherin is present in axons, but excluded from dendrites, cell bodies, and terminal glomeruli. In adult rats, ORN axon fascicles are variably stained with antisera for peripherin; in juvenile rats, staining of fascicles is uniform. Staining with antibody to vimentin is uniform in both adult and juvenile ORN axon fascicles. The unusual pattern of IFP expression and intracellular sorting may have implications for the unique plastic and regenerative capacities of these neurons.

Age Factors↗

PubMed2001

Evidence that extrapancreatic GLUT2-dependent glucose sensors control glucagon secretion.

GLUT2-/- mice reexpressing GLUT1 or GLUT2 in their beta-cells (RIPGLUT1 x GLUT2-/- or RIPGLUT2 x GLUT2-/- mice) have nearly normal glucose-stimulated insulin secretion but show high glucagonemia in the fed state. Because this suggested impaired control of glucagon secretion, we set out to directly evaluate the control of glucagonemia by variations in blood glucose concentrations. Using fasted RIPGLUT1 x GLUT2-/- mice, we showed that glucagonemia was no longer increased by hypoglycemic (2.5 mmol/l glucose) clamps or suppressed by hyperglycemic (10 and 20 mmol/l glucose) clamps. However, an increase in plasma glucagon levels was detected when glycemia was decreased to < or =1 mmol/l, indicating preserved glucagon secretory ability, but of reduced sensitivity to glucopenia. To evaluate whether the high-fed glucagonemia could be due to an abnormally increased tone of the autonomic nervous system, fed mutant mice were injected with the ganglionic blockers hexamethonium and chlorisondamine. Both drugs lead to a rapid return of glucagonemia to the levels found in control fed mice. We conclude that 1) in the absence of GLUT2, there is an impaired control of glucagon secretion by low or high glucose; 2) this impaired glucagon secretory activity cannot be due to absence of GLUT2 from alpha-cells because these cells do not normally express this transporter; 3) this dysregulation may be due to inactivation of GLUT2-dependent glucose sensors located outside the endocrine pancreas and controlling glucagon secretion; and 4) because fed hyperglucagonemia is rapidly reversed by ganglionic blockers, this suggests that in the absence of GLUT2, there is an increased activity of the autonomic nervous system stimulating glucagon secretion during the fed state.

Animals↗

PubMed2000

Binding sites of Drosophila melanogaster sex peptide pheromones.

Drosophila melanogaster sex peptide (SP) and Ductus ejaculatorius peptide (DUP99B) are male pheromones transferred in the seminal fluid to the female during copulation. Both reduce sexual receptivity and stimulate oviposition in females. The presence of high-affinity SP and DUP99B binding sites in the female were investigated by incubation of cryostat tissue sections with (125)I-iodinated peptides and subsequent autoradiography. We found that in adult females radiolabeled SP and DUP99B bind to peripheral nerves, the subesophageal ganglion, the cervical connective, to discrete parts of the thoracic ganglion, and to the genital tract. Weak and uniform labeling was detected in the neuropil of the brain and the thoracic ganglion. The labeling pattern in the nervous system suggests binding of the peptides to sensory afferents or glial cells. Scatchard analysis of the binding of (125)I-DUP99B to antennal nerves yielded a dissociation constant K(d) of 6.4 nM. Competition experiments with peptide fragments show that the peptides bind with their homologous C-terminal regions. Binding sites in the nervous system of females are established throughout sexual maturation. Prominent binding of the peptides to afferent nerves suggests modification of sensory input.

Animals↗

PubMed2000

Effects of 2,4-dinitrophenol (DNP) on the relationship between the chemosensory activities of the rat carotid body and the intracellular calcium of glomus cells.

To test the hypothesis that the uncoupler 2,4-dinitrophenol (DNP) increases [Ca2+]i equally well, independent of pHi, we studied the effects of 250 microM DNP on [Ca2+]i and carotid sinus nerve (CSN) activity of rat carotid body (CB). CSN activity was measured in CB perfused and superfused with hypocapnic (pHo 7.80) and normocapnic (pHo 7.42) Tyrode solutions. [Ca2+]i of glomus (type I cells) was assessed by superfusion techniques under identical conditions as for CSN recording experiments. The results indicate that 250 microM DNP increased [Ca2+]i of type I cells as well as CSN activity at both pHos, although alkalosis diminished these responses. Given that pHi will change with pHo, DNP did not make any additional pHi change, although [Ca2+]i changed. We conclude that DNP effects were due to [Ca2+]i change alone, and the relationship between [Ca2+]i and CSN activity are internally consistent.

2,4-Dinitrophenol↗

PubMed2003

Glycosyl phosphatidylinositol-anchored proteins in chemosensory signaling: antisense manipulation of Paramecium tetraurelia PIG-A gene expression.

Glycosyl phosphatidylinositol (GPI)-anchored proteins are peripheral membrane proteins tethered to the cell through a lipid anchor. GPI-anchored proteins serve many functions in cellular physiology and cell signaling. The PIG-A gene codes for one of the enzymes of a complex that catalyzes the first step in anchor synthesis, and we have cloned the Paramecium tetraurelia pPIG-A gene using homology PCR. To understand the function of pPIG-A and the significance of GPI-anchored proteins in Paramecium, we reduced the mRNA for pPIG-A in transformed cells using an expression vector that transcribed antisense mRNA. The amount of transcript is reduced to approximately 0.3% of the mRNA in control-transformed cells. Compared to control cells, cells transformed with the antisense pPIG-A vector show reduced synthesis of GPI anchor intermediates catalyzed in their endoplasmic reticula and a very few GPI-anchored proteins among the peripheral proteins that can be recovered from their surfaces. They also show specific defects in chemoresponse to glutamate and folate. Other cellular functions, such as growth and mating, seem to be normal.

Amino Acid Sequence↗

PubMed1990

Influence of hypercapnia on rabbit intrapulmonary neuroepithelial bodies: microfluorimetric and morphometric study.

The present investigation was undertaken to investigate the influence of hypercapnia on intrapulmonary neuroepithelial bodies (NEB). Rabbits were mechanically ventilated with a hypercapnic gas mixture (7% carbon dioxide, 20% oxygen, 73% nitrogen). Lung samples were examined by a microspectrographical analysis of the NEB formaldehyde-induced fluorescence to quantify the cytoplasmic 5-hydroxy-tryptamine (5HT) content and by electron microscopy to determine morphometrically the extent of the secretory exocytosis at the basal poles of the NEB epithelial cells. In contrast to our earlier studies on the effects of hypoxia and/or vagal stimulation, hypercapnia did not alter significantly the NEB cytoplasmic fluorescence nor did it affect the corpuscular epithelial exocytosis. NEB appear not to be influenced by hypercapnia to discharge their contents of 5HT and peptides. This investigation appears to support a high selectivity of the intrapulmonary NEB to local hypoxia and changes in vagal efferent output.

Animals↗

PubMed1990

Synaptology of luteinizing hormone-releasing hormone (LHRH)-immunoreactive cells in the nervus terminalis of the gray short-tailed opossum (Monodelphis domestica).

Light and electron microscopic immunocytochemistry were used to examine the structure of LHRH neurons and fibers in the nervus terminalis of the gray short-tailed opossum (Monodelphis domestica). LHRH-immunoreactive neurons and fibers form a loose plexus within the fascicular network of the ganglion terminale on the median surface of the olfactory bulb. There are at least two populations of LHRH-immunoreactive neurons within the network of the ganglion terminale: fusiform and round neurons similar to those described in the forebrain. At the ultrastructural level, axosomatic and axodendritic contacts were seen between LHRH-immunoreactive and nonimmunoreactive elements in the ganglion terminale. These contacts were classified as 1) synaptic input, with asymmetric synapses seen between a nonimmunoreactive axon terminal and a LHRH-immunoreactive cell body or a nonimmunoreactive axon terminal and a LHRH-immunoreactive dendritic process. 2) synaptic output, with symmetric synapses seen between LHRH-immunoreactive and nonimmunoreactive processes. This study is the first systematic examination of the ultrastructure of the LHRH-immunoreactive neurons and their synaptic contacts in the nervus terminalis. The possible integrative roles for this LHRH-immunoreactive system are discussed.

Animals↗

PubMed2002

Two second messengers mediate amino acid responses in olfactory sensory neurons of the salamander, Necturus maculosus.

Odor transduction mediated by the adenylyl cyclase/cAMP pathway has been well studied, but it is still uncertain whether this pathway mediates the transduction of all odors in vertebrates. We isolated olfactory sensory neurons from the salamander Necturus maculosus and used calcium imaging with the indicator dye fura-2 to examine olfactory responses elicited by amino acids. The properties of approximately two-thirds of the odor responses suggested they were mediated by the adenylyl cyclase/cAMP pathway, but one-third of the responses were not mimicked by cAMP analogs nor blocked by inhibition of adenylyl cyclase, suggesting that these odor responses were mediated differently. Responses that were unaffected by inhibition of adenylyl cyclase were blocked by neomycin, an inhibitor of phospholipase C, implying that they were transduced by activation of phospholipase C. Some cells which responded to more than one amino acid appeared to employ both pathways, but each was used to transduce different odors. In addition, many responses that were mediated by the adenylyl cyclase/cAMP pathway were enhanced following inhibition of phospholipase C, suggesting that the phospholipase C pathway has a role not only in odor transduction, but also in the modulation of olfactory responses.

Action Potentials↗

PubMed1999

Seven-transmembrane proteins as odorant and chemosensory receptors.

The olfactory systems of various species solve the challenging problem of general molecular recognition in widely differing ways. Despite this variety, the molecular receptors are invariably G protein-coupled seven-transmembrane proteins, and are encoded by the largest gene families known to exist in a given animal genome. Receptor gene families have been identified in vertebrates and two invertebrate species, the nematode Caenorhabditis elegans and the fruit fly Drosophila melanogaster. The complexity of the odorant receptor repertoire is estimated in mouse and rat at 1000 genes, or 1 percent of the genome, surpassing that of the immunoglobulin and T cell receptor genes combined. Two distinct seven-transmembrane gene families may encode in rodents the chemosensory receptors of the vomeronasal organ, which is specialized in the detection of pheromones. Remarkably, these five receptor families have practically no sequence homology among them. Genetic manipulation experiments in mice imply that vertebrate odorant receptors may fulfill a dual role, also serving as address molecules that guide axons of olfactory sensory neurons to their precise target in the brain.

Animals↗

PubMed1977

Neural control of ventilation in the lamprey.

Tidal breathing of adult lampreys is produced by a single phase of excitation that compresses the branchial basket for exhalation. Inhalation is due to passive recoil. Motoneurons are located primarily in the ipsilateral motor nucleus of the vagus and exhibit periodic bursts of excitatory synaptic potentials from unidentified generator cells in the medulla. Respiratory discharges continue in the isolated brain and can be recorded from the vagal roots. The frequency of bursts increases with temperature in a manner roughly similar to that of intact animals. However, the discharges of the isolated brain are not very sensitive to altered pH or oxygen content in the bathing fluid. Mechanoreceptors in the gill can initiate "cough" responses and may modulate normal breathing.

Action Potentials↗

PubMed1994

Extracellular Ca2+ sensing is modulated by pH in human osteoclast-like cells in vitro.

Osteoclasts are polarized cells with a basolateral and an apical membrane exposed to different extracellular Ca2+ ([Ca2+]o) and H+ (pHe) concentrations. Osteoclast bone resorption is inhibited in vitro by increases of [Ca2+]o slightly above physiological levels, detected by a [Ca2+]o sensing causing elevations of the intracellular signal, [Ca2+]i. Nevertheless, during bone resorption the apical membrane is exposed to [Ca2+]o severalfold higher than physiological without apparent inhibition of osteoclast functions. Because pHe facing the apical membrane is acidic, in this single-cell [Ca2+]i and intracellular pH study we addressed the question of whether the responses of human osteoclast-like cells from a giant cell tumor of bone to elevated [Ca2+]o are altered by reducing pHe. We first observed that low pHe stimulated Ca2+ efflux and cell acidification. We then demonstrated that the amplitude of the [Ca2+]o-dependent [Ca2+]i "spikes" is downregulated by low pHe, with approximately 70-fold higher [Ca2+]o required to induce significant responses at pHe 6.0 compared with pHe 7.4. Similar downregulation was observed in authentic freshly isolated rat osteoclasts. Finally, we observed that occupancy of the [Ca2+]o sensing by Ca2+ prompted rapid and transient cell acidification partially counteracted by a Na(+)-dependent amiloride derivative-sensitive H+ transport. These results demonstrate that the cascade of events triggered by activation of the [Ca2+]o sensing is affected by environmental pH and in turn influences cellular H+ transport. Such pH-related features of the [Ca2+] o sensing mechanism might be relevant for the regulation of osteoclast-like function.

Calcium↗

PubMed2002

Identification of the Ca2+ conductance responsible for K+-induced backward swimming in Paramecium caudatum.

Membrane potential responses of Paramecium caudatum to an application of K+-rich solution were examined to understand the mechanisms underlying K+-induced backward swimming. A wild-type cell impaled by a microelectrode produced action potentials followed by a sustained depolarization in response to an application of a K+-rich test solution. After termination of the application, a prolongation of the depolarization (depolarizing after-potential) took place. Behavioral mutants incapable of exhibiting K+-induced backward swimming did not show depolarizing afterpotentials. Upon short application of K+-rich solution, the timing and duration of the ciliary reversal of the wild-type cell coincided well with the K+-induced depolarization. The duration of the depolarizing afterpotential decreased as the duration of the application increased. The depolarizing afterpotential recovered slowly after it had been suppressed by a preceding application of the K+-rich solution. By injection of an outward current into the wild-type cell, the action potentials were evoked normally during the period when the K+-induced depolarizing afterpotential was suppressed. We concluded that the prolongation of the depolarizing membrane potential response following the application of the K+-rich solution represents the Ca2+ conductance responsible for the K+-induced backward swimming in P. caudatum and that the characteristics of the K+-induced Ca2+ conductance are distinct from those of the Ca2+ conductance responsible for the action potentials.

Animals↗

PubMed1987

Taste receptors in crayfish: recording of single nicotinamide-activated channels.

The patch clamp technique was adapted to chemoreceptive sensory cells in the claw of Austropotamobius torrentium. In cell-attached and in outside-out patches, concentrations of nicotinamide from 10(-6) mol/liter to 5 X 10(-5) mol/liter activated openings of single channels located in the cell body of the sense cell. The characteristics of these single channel openings were similar to those of neurotransmitter activated channels: the I/V curve was approximately linear, showing a reversal potential of about +15 mV and a conductance of about 33 pS. The mean open time was 1-2 ms. A similar concentration dependence was found for the activation of single channel openings as shown previously for the action potential discharge elicited by nicotinamide at the same preparation.

Action Potentials↗

PubMed1978

Glucose, glycine and diglycine in test meals at stimuli to a duodenal osmoreceptor slowing gastric emptying.

1. Five subjects took 210 test meals of 750 ml. water containing 30--300 m-molal glucose or glycine, or 15--150 m-molal diglycine, or plain water. 2. The greater the concentration of solute, the greater was the volume of original meal recovered from the stomach after a fixed time. 3. On a molal basis glucose was half as effective as diglycine in slowing gastric emptying. This was consistent with the osmoreceptor being exposed to the diglycine after it had been split by the hydrolase of the cytosol of enterocytes (the absorbing cells of the small intestine). 4. The slowing of gastric emptying (ml./mole.1.) was about 10% greater for glycine than it was for glucose. There was apparently a threshold concentration below which glycine did not slow gastric emptying. 5. It was proposed that the response of the doudenal osmoreceptor might depend upon shrinking and swelling of the lateral intercellular space around the enterocytes.

Chemoreceptor Cells↗