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Results for “Chemoreceptor Cells”

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PubMed1992

Differential effects of long-term hypoxia on norepinephrine turnover in brain stem cell groups.

The influence of long-term hypoxia on noradrenergic cell groups in the brain stem was assessed by estimating the changes in norepinephrine (NE) turnover in A1, A2 (subdivided into anterior and posterior parts), A5, and A6 groups in rats exposed to hypoxia (10% O2-90% N2) for 14 days. The NE turnover was decreased in A5 and A6 groups but failed to change significantly in A1. The NE turnover was increased in the posterior part of A2 and remained unaltered in the anterior part. In normoxic rats, the hypotensive drug dihydralazine induced a reverse effect, namely increased NE turnover in anterior A2 and no change in posterior A2. The neurochemical responses to hypoxia were abolished by transection of carotid sinus nerves. The results show that long-term hypoxia exerts differential effects on the noradrenergic cell groups located in the brain stem. Peripheral chemosensory inputs control the hypoxia-induced noradrenergic alterations. The A2 cell group displays a functional subdivision: the posterior part is influenced by peripheral chemosensory inputs, whereas the anterior part may be concerned with barosensitivity.

Animals↗

PubMed1994

Protein gene product 9.5 in the developing and mature rat vomeronasal organ.

Protein gene product 9.5 (PGP 9.5) was immunocytochemically identified in structures of the developing and mature rat vomeronasal organ (VNO). This study started with embryos at 17 days of gestation. By this stage, PGP 9.5 was immunolocalized within both the receptor cells of the neuroepithelium and cells of the receptor-free epithelium, located on the opposite side of the lumenal space. Nerve fibers surrounding the nascent vomeronasal vein also showed PGP 9.5 immunoreactivity. Labeling was retained in the neuroepithelium and nerve fibers around the vein during development and into adulthood. Within the pool of receptor cells of the adult neuroepithelium, labeling was observed within the cytoplasm of the somata and dendrites; some receptor cells also expressed nuclear labeling. The number of immunoreactive cells in the receptor-free epithelium appeared to increase postnatally but by adulthood immunoreactivity virtually was absent. These results suggest a role for PGP 9.5 in development and maturation of the VNO and a continuing role within the steadily renewing receptor cell population found in the mature neuroepithelium. The findings of this study also suggest that PGP 9.5 is localized within the nerve fibers surrounding the vomeronasal vein from early in development through adulthood.

Aging↗

PubMed2004

Basic anatomy and physiology of olfaction and taste.

The chemical senses of taste and smell are important to survival and quality of life. Both senses rely on the binding of odorant molecules to receptors located on the receptor cells. Olfaction and gustation have complex systems of coding, but they display differing methods for coding the receptor stimulus. Both have numerous central projections that allow for the perception and interpretation of these important sensory inputs.

Chemoreceptor Cells↗

PubMed2005

Postnatal growth of the carotid body.

The size of the carotid body (CB) is increased significantly during the postnatal period. Type I cells in the CB are the chemoreceptive element and possess many neuron-like characteristics. In contrast to previous opinions that the number of type I cells is determined before birth, we have found that type I cells continue to proliferate over a period of at least 1 month after birth in rats. The proliferation of type I cells is influenced by oxygen concentration in ambient air. Specifically, hyperoxia inhibits the type I cell proliferation, resulting in small CBs throughout life and the permanent impairment of CB chemoreception. On the other hand, hypoxia enhances the type I cell proliferation. Whether hypoxia causes long-lasting effects on CB morphology and function remains to be determined. Besides type I cell proliferation, other cellular components in the CB undergo proliferation and growth as well. In the nearby petrosal ganglion and superior cervical ganglion, both involved in CB chemoreception, cellular proliferation is limited to glial cells and no proliferation of neurons is observed. Also, expression of neurotrophic factors, particularly, BDNF and GDNF, is observed in type I cells of neonatal rats. Taken together, the CB undergoes significant morphological and functional changes during the postnatal period over at least 1 month. This process can be altered by oxygen concentration in ambient air.

Animals↗

PubMed2005

The UNC-3 Olf/EBF protein represses alternate neuronal programs to specify chemosensory neuron identity.

Neuronal identities are specified by the combinatorial functions of activators and repressors of gene expression. Members of the well-conserved Olf/EBF (O/E) transcription factor family have been shown to play important roles in neuronal and non-neuronal development and differentiation. O/E proteins are highly expressed in the olfactory epithelium, and O/E binding sites have been identified upstream of olfactory genes. However, the roles of O/E proteins in sensory neuron development are unclear. Here we show that the O/E protein UNC-3 is required for subtype specification of the ASI chemosensory neurons in Caenorhabditis elegans. UNC-3 promotes an ASI identity by directly repressing the expression of alternate neuronal programs and by activating expression of ASI-specific genes including the daf-7 TGF-beta gene. Our results indicate that UNC-3 is a critical component of the transcription factor code that integrates cell-intrinsic developmental programs with external signals to specify sensory neuronal identity and suggest models for O/E protein functions in other systems.

Animals↗

PubMed1985

Purification and characterisation of an odorant-binding protein from cow nasal tissue.

Cow nasal tissue contains a protein which shows specific binding activity for 'green' smelling compounds such as 2-isobutyl-3-methoxypyrazine. This protein has now been purified using anion-exchange fast protein liquid chromatography. The protein has a relative molecular mass of 40 0000-44 000, s = 3.1 +/- 0.3 S, pI = 4.7 +/- 0.1 with an absorbance maximum at 278 nm, and consists of two subunits with an identical relative molecular mass of 19 000. It is localised in the soluble fraction of cells from the olfactory mucosa and respiratory mucosa from the middle part of the maxillary and nasal turbinates, and is absent from all other tissues tested.

Animals↗

PubMed1986

[Surface structure of the olfactory organ of marine teleosts].

By means of the electron scanning microscope, structure of the olfactory rosella has been investigated in 5 species of marine Teleostei. Among the species investigated variability in number and arrangement is observed in the olfactory rosella folds. Arrangement order of the receptor and indifferent epithelia of the fold is presented by four types. Interspecies differences in organization of the sensory epithelium is revealed in ratio of various types of receptor and secretory cells. In Teleostei flagellar olfactory cells are the most numerous. In the Limanda yokohamae sensory epithelium certain flagella are described, that essentially differ by their size from usual receptor flagella and, evidently, are their complexes. The secretory cells are found in indifferent and sometimes in sensory epithelium as dark ostia; they are most numerous in mediosmatics. Some of the ostia are like wide craters and are, evidently, ostia of ducts of multicellular olfactory glands.

Animals↗

PubMed2004

The antennal benzoic acid receptor cell of the female silk moth Bombyx mori L.: structure-activity relationship studies with halogen substitutes.

Studies on structure-activity relationships were carried out to characterize the response specificity of the benzoic acid cell of the female of the moth Bombyx mori by means of single sensillum electrophysiological recordings. We demonstrated that this cell type responds best to a natural key substance (benzoic acid) and has similar response profiles for less effective compounds, including various halogen substitutes of benzoic acid, benzaldehyde and other derivates of the key compound. Using different halogen substitutes (F, Cl, Br, I), we showed that the cellular response decreases with increasing atomic size of the substitute and that halogen substitutes were most effective in the meta-position. Thus, m-fluor benzoic acid was even more effective than benzoic acid. These results indicate that a critical feature of the stimulus molecule is the inductive effect generated by the halogen substitutes. Increasing the atomic size of the halogen substitute impairs the recognition of the molecule by the receptor cell, possibly due to steric effects. Decreasing the electron density in the aromatic ring improves the receptor response. The benzoic acid receptor cell can be considered as specialist despite not being involved in pheromone detection as it responds maximally to a key substance and has similar response profiles for less effective compounds.

Action Potentials↗

PubMed2001

A peripheral mechanism for behavioral adaptation to specific "bitter" taste stimuli in an insect.

Animals have evolved several chemosensory systems for detecting potentially dangerous foods in the environment. Activation of specific sensory cells within these chemosensory systems usually elicits an aversive behavioral response, leading to avoidance of the noxious foods. Although this aversive behavioral response can be adaptive, there are many instances in which it generates "false alarms," causing animals to reject harmless foods. To minimize the number of false alarms, animals have evolved a variety of physiological mechanisms for selectively adapting their aversive behavioral response to harmless noxious compounds. We examined the mechanisms underlying exposure-induced adaptation to specific "bitter" compounds in Manduca sexta caterpillars. M. sexta exhibits an aversive behavioral response to many plant-derived compounds that taste bitter to humans, including caffeine and aristolochic acid. This aversive behavioral response is mediated by three pairs of bitter-sensitive taste cells: one responds vigorously to aristolochic acid alone, and the other two respond vigorously to both caffeine and aristolochic acid. We found that 24 hr of exposure to a caffeinated diet desensitized all of the caffeine-responsive taste cells to caffeine but not to aristolochic acid. In addition, we found that dietary exposure to caffeine adapted the aversive behavioral response of the caterpillar to caffeine, but not to aristolochic acid. We propose that the adapted aversive response to caffeine was mediated directly by the desensitized taste cells and that the adapted aversive response did not generalize to aristolochic acid because the signaling pathway for this compound was insulated from that for caffeine.

Adaptation, Physiological↗

PubMed2001

The SAD-1 kinase regulates presynaptic vesicle clustering and axon termination.

During synapse formation, presynaptic axon outgrowth is terminated, presynaptic clusters of vesicles are associated with active zone proteins, and active zones are aligned with postsynaptic neurotransmitter receptors. We report here the identification of a novel serine/threonine kinase, SAD-1, that regulates several aspects of presynaptic differentiation in C. elegans. In sad-1 mutant animals presynaptic vesicle clusters in sensory neurons and motor neurons are diffuse and disorganized. Sensory axons fail to terminate in sad-1 mutants, whereas overexpression of SAD-1 causes sensory axons to terminate prematurely. SAD-1 protein is expressed in the nervous system and localizes to synapse-rich regions of the axons. SAD-1 is related to PAR-1, a kinase that regulates cell polarity during asymmetric cell division. Overexpression of SAD-1 causes mislocalization of vesicle proteins to dendrites, suggesting that sad-1 affects axonal-dendritic polarity as well as synaptic development.

Animals↗

PubMed1979

Protein and phospholipid methylation during chemotaxis in Dictyostelium discoideum and its relationship to calcium movements.

Suspensions of cyclic AMP sensitive cells of Dictyostelium discoideum responded to a cyclic AMP pulse with increased methylation of a protein of molecular weight about 120,000 and increased phospholipid demethylation. Protein methylation reached its peak 15-30 sec after cyclic AMP addition. Phospholipid demethylation reached its maximum within 2 min and basal levels were recovered in 3 min. S-Adenosyl-L-methionine is probably the methyl donor. In vitro addition of 0.25 mM and 25 microM S-adenosyl-L-methionine to sonicated D. discoideum cells inhibited ATP-dependent 45Ca2+ uptake by 70% and 25%, respectively. Based on these lines of evidence we propose that protein and phospholipid methylation are involved in D. discoideum chemotaxis probably by regulation of intracellular Ca2+ movements.

Calcium↗

PubMed1986

Human peripheral monocytes express putative receptors for neuroexcitatory amino acids.

Human peripheral mononuclear cells responded chemotactically to 4-carboxyl-L-glutamic acid. The maximal chemotactic response occurred at 0.1 nM. No chemotactic response was found with neutrophils or fetal bovine fibroblasts. Glutamic acid, a neuroexcitatory dicarboxylic amino acid and the parent compound of 4-carboxyglutamic acid, did not stimulate chemotaxis in any of the cells tested. However, it functioned as an antagonist to 4-carboxyglutamic acid (ED50 approximately 2 pM; ED100 approximately 10 pM). In contrast to the lack of response to glutamic acid, its dicarboxylic cyclic analogue, kainic acid, excited a chemotactic response in mononuclear cells. The data suggest that mononuclear phagocytes have receptors for dicarboxylic neuroexcitatory amino acids, and we speculate that 4-carboxyglutamic acid, a tricarboxylic acid, may have a previously unrecognized role as a neuroexcitatory amino acid.

1-Carboxyglutamic Acid↗

PubMed1991

Effects of extracellular pH, PCO2 and HCO3- on intracellular pH in isolated type-I cells of the neonatal rat carotid body.

1. The effects of changing PCO2 extracellular pH (pHo) and HCO3- on intracellular pH (pHi) were studied in isolated neonatal rat type-I carotid body cells using the pH-sensitive fluoroprobe, carboxy-SNARF-1. 2. Simulated respiratory acidosis and alkalosis (i.e. changes in PCO2 at constant HCO3-) led to rapid (half-time t0.5 = 3 s) monotonic changes in pHi. The relationship between pHi and pHo under these conditions was linear, steep (0.63 pHi/pHo) and remarkably similar to the response predicted from a passive cell model (i.e. a cell lacking pHi regulation). 3. In order to model the above pHi changes (point 2), it was necessary to determine beta i (intrinsic intracellular buffering power). By using small incremental acid loads in the cell (progressive [NH4+]o removal), beta i was determined as a function of pHi to be: beta i = 127.6-16.04 pHi. 4. Changes in PCO2 at constant pHo (i.e. simultaneously changing HCO3-) caused rapid transient changes in pHi but did not significantly affect steady-state pHi over the range 1-10% CO2. 5. When PCO2 was held constant (5%), changing HCO3- and thus pHo (i.e. a simulated metabolic acidosis/alkalosis) led to much slower changes in pHi (t0.5 approximately 1 min). Steady-state pHi showed an almost identical dependence on pHo (slope 0.68) to that found for simulated respiratory acidosis/alkalosis. Therefore, over the range of pHo, PCO2 and [HCO3-]o tested, steady-state pHi appeared to be a unique function of pHo and independent of PCO2 and [HCO3-]o. 6. The effects on pHi of respiratory acidosis, metabolic acidosis and increases of PCO2 at constant pHo (present work) were compared with previously published work on the ability of similar manoeuvres to increase the carotid sinus nerve (CSN) discharge rate. The two sets of data showed several striking similarities: (i) in both cases, the response to a respiratory acidosis was rapid in onset, maintained and reversible; (ii) in both cases, the speed of response to a metabolic acidosis was significantly slower than in (i) but, again, it was maintained and reversible; (iii) in both cases, increases in PCO2 at constant pHo elicited a rapid response but one which was only transient with no change in the steady-state value. 7. The close correlation between the effects of changing pHo, PCO2 and [HCO3-]o on pHi and on CSN discharge suggests that a change in type-I cell pHi is the first step in the chemoreception of blood pH by the carotid body.(ABSTRACT TRUNCATED AT 400 WORDS)

Acidosis↗

PubMed1975

Single gene cricket mutations: effects on behavior, sensilla, sensory neurons, and identified interneurons.

Crickets are suitable for studying the effects of single gene mutations on single nerve cells. In one mutant, three classes of sensilla are lost sequentially. The absence of one class of mechanoreceptors throughout postembryonic development deprives certain sensory neurons of normal stimulation and results in abnormal physiological and structural development of an identified interneuron.

Animals↗

PubMed1983

Investigations of the discriminative properties of the frog's olfactory mucosa using a photoactivable odorant.

The photoactivable compound phenylazide interacts reversibly with the frog's olfactory epithelium when delivered as an olfactory stimulus. Its application together with UV irradiation resulted in a differential reduction of the responses (electro-olfactogram) to several odorants. It was found that this chemical modification of the sensory membrane affected the responses in relative ratios which could be predicted from a classification of the odorants based upon independent studies of receptor cell odor sensitivity. The responses to chemicals representative of the 'aromatic group' were clearly more reduced than those to compounds of the 'camphoraceous group'. It is suggested that the olfactory discrimination mechanisms can be approached by the use of this method.

Animals↗

PubMed1989

Antigen-induced lung solute clearance in rats is dependent on capsaicin-sensitive nerves.

Chemosensitive sensory nerves have an important effector role in the control of vascular permeability in rat airways after neurogenic inflammation. To investigate whether they also have a role in antigen-induced lung inflammation, we have studied the changes in lung solute clearance (LSC) in sensitized rats after aerosol challenge with allergen and the effect of prior capsaicin-induced denervation on these changes. Sprague-Dawley rats were immunized with egg albumin (EA), using aluminum hydroxide and Bordetella pertussis as adjuvants. After 11 days, the animals were challenged for 5 min with aerosolized EA, and the clearance from the lungs of aerosolized 99mTc diethylenetriamine pentaacetic acid (99mTc-DTPA) over 7.5 min (LSC 7.5) was subsequently measured at various times after challenge as an index of epithelial permeability or integrity. Sensitized animals responded to the challenge with immediate respiratory symptoms and with an increased 99mTc-DTPA clearance rate that was detectable at 20 min (mean +/- SE LSC 7.5: baseline, 6 +/- 1%; 20 min, 17 +/- 3%; p less than 0.05), persisted at 4 h (14 +/- 1%; p less than 0.05), and returned to normal values after 24 h. Unsensitized rats exposed to EA and sensitized rats exposed to PBS or to bovine serum albumin did not show any change. Bronchoalveolar lavage failed to show significant changes of cell populations until 24 h, when an increased presence of lymphocytes, PMN, and eosinophils was observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Aerosols↗

PubMed2003

Chemosensory tuning to a host recognition cue in the facultative specialist larvae of the moth Manduca sexta.

Larvae of Manduca sexta are facultative specialists on plants in the family Solanaceae. Larvae reared on solanaceous foliage develop a strong preference for their host; otherwise, they remain polyphagous. The host-specific recognition cue in potato foliage for Manduca larvae is the steroidal glycoside, indioside D. Two pairs of galeal taste sensilla, the lateral and medial sensilla styloconica, are both necessary and sufficient for the feeding preferences of host-restricted larvae. We conducted electrophysiological tip recordings from sensilla of solanaceous or wheat germ diet-reared larvae. For each animal, recordings of the responses to indioside D, glucose, tomatine and KCl were compared. All responses included both phasic and tonic portions. The sensilla styloconica of solanaceous-reared larvae were tuned to indioside D, defined as maintaining a high sensitivity to indioside D, while showing lower sensitivity to other plant compounds. Half of the sensillar neurons of solanaceous-reared larvae were 'tuned' to indioside D, whereas those of wheat germ diet-reared larvae were not. The different responses between the two types of animals were a result of changes of individual receptor cells' responses in the sensilla. Feeding on solanaceous foliage therefore appears to result in a modification of the physiological responses of individual taste receptor cells that causes them to be tuned to the host-recognition cue indioside D. We propose that this tuning is the basis for the host-restricted larvae's strong behavioral preferences for solanaceous foliage.

Analysis of Variance↗

PubMed2006

Secretory cells of the airway express molecules of the chemoreceptive cascade.

Airway secretion is maintained by specialized non-ciliated epithelial cells whose phenotype varies with their topographical location. In addition, specialized epithelial cells located in the airway contain the molecular machinery of chemoreceptive elements. Our aim has been to evaluate whether the secretory cells themselves possess a chemoreceptive capability, which requires the simultaneous presence of chemosensory and secretory mechanisms. We performed immunohistochemical analysis with antibodies against the Clara-cell-specific secretory proteins, CC10 and CC26, as secretory markers. As chemoreceptive markers, we employed antibodies against alpha-gustducin and phospholipase C beta 2 (PLCbeta2), two components of the taste transduction pathway. We also attempted to characterize further the secretory cell type by using a marker of chloride secretion, cystic fibrosis transmembrane regulator (CFTR). We found alpha-gustducin localized in non-ciliated cells of the epithelium lining the trachea and bronchioles of adult rats, where it was also co-expressed with CC10 and CC26. Ultrastructural immunohistochemistry revealed alpha-gustducin in the apical cytoplasm of secretory cells, concentrated around and inside the granules. CFTR was also observed in a subpopulation of non-ciliated epithelial cells, co-localized with some alpha-gustducin- and PLCbeta2-immunoreactive cells, at all levels of the airway epithelium. We conclude that non-ciliated epithelial cells of the rat airway express components of distinct signaling mechanisms and suggest that secretory events are driven by a molecular mechanism activated by the binding of luminal substances to G-protein-coupled receptors.

Animals↗