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At least 1,225 records · Page 68Linked to original sources
PubMed1958

Electrical activity in the chemoreceptors of the blowfly. II. Responses to electrical stimulation.

An analysis of the various parts of the electrical responses to the chemical and electrical stimulation of a single labellar chemosensory hair of the blowfly, Phormia regina, indicates that the recording conditions for the spike potentials approximate the intracellular recordings made in other types of sense cells. The large positive resting potential probably arises from the basement membrane of the hypodermal cells and neurilemma rather than from the neurons at the base of the chemosensory hair. The responses to polarizing currents passed through single chemosensory hairs support this analysis. The behavioral responses to similar polarizing currents are shown to result from the action of the current on the neurons at the bases of the adjacent chemosensory hairs. The reported neural interaction of the two chemosensory neurons associated with the chemosensory hair is probably due to the physical-chemical attributes of the stimulating solution rather than to any real neural interaction. Observations on the latency of the initial nerve impulse in response to chemical stimulation indicate that the chemosensory neurons are normally free from spontaneous spike activity.

Action Potentials↗
PubMed1965

ELECTRICAL ACTIVITY IN THE CHEMORECEPTORS OF THE BLOWFLY. 3. DENDRITIC ACTION POTENTIALS.

All sizes of the chemosensory hairs on the labellum of the blowfly, Phormia regina, contain neurons which respond to chemical stimulation with diphasic impulses if the recording electrode is at the tip of the hair. The impulses are initially positive, then become negative and return to the base line. The negative phase can be abolished by the action of anesthetics (xylocaine, cocaine, procaine, chloral hydrate) and tetrodotoxin, an extract from the puffer fish. The negative phase is increased by strong salts, mechanical injury, and thermal injury, which also act to reduce or abolish the positive phase. Simultaneous recordings from the side and the tip of the hair show that both positive and negative phases appear first at the side. These results indicate that the impulse is initiated in or near the cell body at the base of the hair and under certain conditions is propagated antidromically up the dendrite to the tip.

Action Potentials↗
PubMed1972

The effects of temperature on the labellar chemoreceptors of the blowfly.

In the labellar chemosensory hairs of the blowfly, Phormia regina Meigen, stationary amplitudes of the slow potentials induced by salt and sugar stimulations were decreased to 50-80% at 12 degrees C of the values measured at 28 degrees C. The amplitudes induced by water did not show any dependence on temperature change. The maximum rate of rise of the receptor potentials was strongly increased with rising temperature. The value of K(b), the apparent Michaelis constant, was less by a factor of six at 28 degrees C compared to the 12 degrees C value for the sugar receptor.

Air↗
PubMed1989

Low pO2 selectively inhibits K channel activity in chemoreceptor cells of the mammalian carotid body.

The hypothesis that changes in environmental O2 tension (pO2) could affect the ionic conductances of dissociated type I cells of the carotid body was tested. Cells were subjected to whole-cell patch clamp and ionic currents were recorded in a control solution with normal pO2 (pO2 = 150 mmHg) and 3-5 min after exposure to the same solution with a lower pO2. Na and Ca currents were unaffected by lowering pO2 to 10 mmHg, however, in all cells studied (n = 42) exposure to hypoxia produced a reversible reduction of the K current. In 14 cells exposed to a pO2 of 10 mmHg peak K current amplitude decreased to 35 +/- 8% of the control value. The effect of low pO2 was independent of the internal Ca2+ concentration and was observed in the absence of internal exogenous nucleotides. Inhibition of K channel activity by hypoxia is a graded phenomenon and in the range between 70 and 120 mmHg, which includes normal pO2 values in arterial blood, it is directly correlated with pO2 levels. Low pO2 appeared to slow down the activation time course of the K current but deactivation kinetics seemed to be unaltered. Type I cells subjected to current clamp generate large Na- and Ca-dependent action potentials repetitively. Exposure to low pO2 produces a 4-10 mV increase in the action potential amplitude and a faster depolarization rate of pacemaker potentials, which leads to an increase in the firing frequency. Repolarization rate of individual action potentials is, however, unaffected, or slightly increased. The selective inhibition of K channel activity by low pO2 is a phenomenon without precedents in the literature that explains the chemoreceptive properties of type I cells. The nature of the interaction of molecular O2 with the K channel protein is unknown, however, it is argued that a hemoglobin-like O2 sensor, perhaps coupled to a G protein, could be involved.

Adenosine Triphosphate↗
PubMed1982

Increased sensitivity of the arterial chemoreceptor drive in young men with mild hypertension.

Ventilatory, airway occlusion pressure, arterial blood pressure and heart rate responses to isocapnic progressive hypoxia and to hypercapnia in high oxygen, both induced by a rebreathing method, were measured in 20 hypertensive male subjects aged 20 to 21 years with a diastolic blood pressure of 13.1 KPa +/- 0.34 SD (98 mmHg +/- 2.6 SD) and in 20 age-matched normotensive male subjects. Ventilatory, airway occlusion pressure and blood pressure response to hypoxia was significantly greater in the hypertensive subjects. Hypoxic ventilatory drive measured as the parameter A denoting the shape of the V1-O2 curve was 28.8 +/- 2.7 SEM (range 7.0 to 44.2) in the normotensive group and 116.1 +/- 10.5 SEM (range: 71.6 to 234.77) in the hypertensive group, the difference being highly significant (P less than 0.001). The magnitude of respiratory sinus arrhythmia (RSA) recorded during progressive hypoxia and plotted against either PA. O2 or VI values was significantly greater in the hypertensive group. The difference in ventilatory and circulatory responses to hyperoxic hypercapnia between the two groups of subjects was not significant. There was a significant correlation between the responses to hypoxia and hypercapnia in the normotensive subjects (r = 0.56, t = 2.861, P less than 0.01) but no correlation in the hypertensive subjects (r = 0.07). It is concluded that dissociation of the responsiveness of the peripheral and central chemosensitivity, the former being significantly increased and predominant, occurs in early, mild hypertension.

Adult↗
PubMed2006

The chemoreceptor superfamily in the honey bee, Apis mellifera: expansion of the odorant, but not gustatory, receptor family.

The honey bee genome sequence reveals a remarkable expansion of the insect odorant receptor (Or) family relative to the repertoires of the flies Drosophila melanogaster and Anopheles gambiae, which have 62 and 79 Ors respectively. A total of 170 Or genes were annotated in the bee, of which seven are pseudogenes. These constitute five bee-specific subfamilies in an insect Or family tree, one of which has expanded to a total of 157 genes encoding proteins with 15%-99% amino acid identity. Most of the Or genes are in tandem arrays, including one with 60 genes. This bee-specific expansion of the Or repertoire presumably underlies their remarkable olfactory abilities, including perception of several pheromone blends, kin recognition signals, and diverse floral odors. The number of Apis mellifera Ors is approximately equal to the number of glomeruli in the bee antennal lobe (160-170), consistent with a general one-receptor/one-neuron/one-glomerulus relationship. The bee genome encodes just 10 gustatory receptors (Grs) compared with the D. melanogaster and A. gambiae repertoires of 68 and 76 Grs, respectively. A lack of Gr gene family expansion primarily accounts for this difference. A nurturing hive environment and a mutualistic relationship with plants may explain the lack of Gr family expansion. The Or family is the most dramatic example of gene family expansion in the bee genome, and characterizing their caste- and sex-specific gene expression may provide clues to their specific roles in detection of pheromone, kin, and floral odors.

Animals↗
PubMed2006

Determinants of chemoreceptor cluster formation in Escherichia coli.

Chemotactic stimuli in bacteria are sensed by large sensory complexes, or receptor clusters, that consist of tens of thousands of proteins. Receptor clusters appear to play a key role in signal processing, but their structure remains poorly understood. Here we used fluorescent protein fusions to study in vivo formation of the cluster core, which consists of receptors, a kinase CheA and an assisting protein CheW. We show that receptors aggregate through their cytoplasmic domains even in the absence of other chemotaxis proteins. Clustering is further enhanced by the binding of CheW. Surprisingly, we observed that some fragments of CheA bind receptor clusters well in the absence of CheW, although the latter does assist the binding of full-length CheA. The resulting mode of receptor cluster formation is consistent with an experimentally observed flexible stoichiometry of chemosensory complexes and with assumptions of recently proposed computer models of signal processing in chemotaxis.

Bacterial Proteins↗