Biomedical subjects

C D Derby

Publications and source records attributed to C D Derby.

At least 37 records · Page 2Linked to original sources

PubMed1996

Responses of olfactory receptor neurons in the spiny lobster to binary mixtures are predictable using a noncompetitive model that incorporates excitatory and inhibitory transduction pathways.

Coding of binary mixtures by a population of olfactory receptor neurons in the spiny lobster (Panulirus argus) was examined. Extracellular single-unit responses of 50 neurons to seven compounds and their binary mixtures were recorded. The ability of a noncompetitive model with correction for binding inhibition to predict responses to mixtures based on responses to their components was compared with the predictive abilities of other models. This model assumes that different compounds activate different transduction processes in the same neuron leading to excitation or inhibition, and it includes a term quantifying the degree to which binding of an odorant to its receptor sites is inhibited by other compounds. The model accurately predicted the absolute response magnitude of the population of neurons for 13 of 15 mixtures assessed, which is superior to the predictive power of any of the other models. The model also accurately predicted the across neuron patterns generated by the binary mixtures, as evaluated by multidimensional scaling analysis. The results suggest that there is no emergence of unique qualities for binary mixtures relative to components of these mixtures.

Animals↗

PubMed1996

Distribution of dopamine-like immunoreactivity suggests a role for dopamine in the courtship display behavior of the blue crab, Callinectes sapidus.

Injection of dopamine initiates a posture in the blue crab, Callinectes sapidus, identical to courtship display behavior of the male crab. The threshold for proctolin-induced rhythmic components of courtship display is lowered in preparations when dopamine is co-applied with proctolin. To elucidate the anatomical substrate of this behavior, immunocytochemistry was used to map dopamine-immunoreactive neurons. Courtship display is sex-specific, and dependent on the hormonal, developmental, and seasonal state of the animal. We compared the distribution of dopamine-like immunoreactivity between adults and juveniles of both sexes across seasons, with hormonal alteration, and with the distribution of proctolin-like immunoreactivity. Dopamine-like immunoreactivity was found throughout the nervous system in identical patterns between the sexes and hormonal states. Differences were found between juveniles and adults that are not obviously correlated with the development of behavior. Two areas of staining were of interest: neurites that longitudinally traverse and terminate in the posterior ventral nerve cord, and a neuron in the esophageal ganglion that has projections to the pericardial organ. The results do not suggest that proctolin-like and dopamine-like immunoreactivity co-localize, but in the subesophageal ganglion there was a region of close proximity.

Animals↗

PubMed1996

Sexually dimorphic patterns of neural organization in the feeding appendages of fiddler crabs.

The organization of sensory nerves and sensilla was examined in the feeding claw of two species of fiddler crabs, Uca pugnax and U. pugilator, using neuroanatomical and behavioral techniques. Surveys of the populations of axons indicate that claws of adult crabs contain 25000-40000 neurons. Approximately 85% of the population consists of axons with diameters less than 1 microm, suggesting they may represent chemosensory neurons. Females show an enhanced population of these small (putative chemosensory) axons relative to males, providing a mechanism to explain previously observed sexual differences in behavioral chemosensitivity to feeding stimulants. Surveys of the claw surface show a variety of external structures that could contain either chemo- or mechanosensory receptor neurons. There are hair-like sensilla of several types, some of which are more abundant in females than in males. In addition, claws show previously undescribed pit sensilla reminiscent of known bimodal chemo- and mechanosensory sensilla found in certain decapod crustaceans. Morphological properties of hair-like sensilla, as well as their small number in relation to the large population of presumptive chemosensory axons, suggest that they have a limited role in chemosensation. Most of the chemosensory axons probably originate in the pit sensilla.

Animals↗

PubMed1996

Generalization among related complex odorant mixtures and their components: analysis of olfactory perception in the spiny lobster.

We investigated the processing of odorant mixtures containing two to seven components by the spiny lobster Panulirus argus. The chemicals tested were food-related compounds that are attractive to spiny lobsters, and include adenosine-5'-monophosphate, betaine, L-cysteine, L-glutamate, DL-succinate, taurine, and ammonium. Components were tested at concentrations that produced search behavioral responses of equal magnitude in unconditioned animals. Responses of unconditioned animals to mixtures and their components reveal hypoadditivity, in which the response to a mixture is less than the sum of the responses to that mixture's components. Aversive conditioning coupled with generalization testing was used to evaluate generalization and hence perceptual similarity between related mixtures. Animals were conditioned to either an individual odorant, a four-compound mixture, or a seven-compound mixture, followed by generalization testing with submixtures or larger mixtures containing the conditioned stimulus. Animals tended not to generalize, but significant generalization between a more simple conditioned stimulus and more complex mixtures containing that conditioned stimulus occurred in 2 of 11 cases, and significant generalization between a conditioned mixture and its submixtures was observed in 4 of 9 cases. Both the number and chemical identity of components of mixtures may contribute to the degree of generalization between mixtures. Overshadowing, in which the ability to learn about a chemical is affected by simultaneous presentation of other chemicals, occurred in two of three cases. We discuss implications of these findings with respect to elemental and configural processing of odorant mixtures in the spiny lobster, possible neural mechanisms responsible for these results, and the potential utility of generalization and overshadowing to the spiny lobster's natural behavior.

Animals↗

PubMed1996

Identification and partial characterization of putative taurine receptor proteins from the olfactory organ of the spiny lobster.

To explore the initial stages of olfactory transduction, we have used biochemical techniques to characterize proteins associated with the dendritic plasma membrane from the olfactory receptor neurons of the spiny lobster Panulirus argus. In particular, we have studied proteins that interact with taurine, an amino acid that is an important odorant for this species. The cross-linker bis(sulfosuccinimidyl)suberate (BS3) was used to covalently link [3H]-taurine to cell surface proteins on membrane from the aesthetasc (olfactory) sensilla of the lateral filament of the antennule. A radioligand-receptor binding assay was used to show that this cross-linkage was highly specific for taurine at 0.2 mM BS3. In inhibition studies, of all the unlabeled odorants tested at excess concentrations (taurine, L-glutamate, adenosine-5'-monophosphate), only taurine significantly inhibited the cross-linkage of [3H]-taurine to the membrane. Membranes containing cross-linked proteins were solubilized, and proteins were separated on SDS-PAGE and examined with autoradiography. Bands with molecular weights of 100, 82, 62, 51, and 34kD were evident on the gels. However, only the 100 and 62 kD bands were consistently labeled with [3H]-taurine, and this labeling was completely inhibited in the presence of excess unlabeled taurine but not adenosine-5'monophosphate. The taurine-evoked behavioral search response of spiny lobsters was significantly reduced following treatment of their antennules with BS3 + taurine as compared with animals treated with BS3 alone, suggesting that the taurine-labeled binding proteins include taurine receptor proteins involved in the first stage of olfactory transduction.

Adenosine Monophosphate↗

PubMed1995

Mixture suppression without inhibition for binary mixtures from whole cell patch clamp studies of in situ olfactory receptor neurons of the spiny lobster.

Whole cell patch clamping was used to investigate mechanisms of mixture suppression for in situ olfactory receptor neurons (ORNs) of the spiny lobster Panulirus argus. We used a set of single compounds and binary mixtures that have been used in previous biochemical studies of receptor-odorant binding, electrophysiological studies of spiking output from ORNs, and behavioral studies. These odorants were adenosine 5'-monophosphate (AMP), betaine (Bet), L-cysteine (Cys), L-glutamate (Glu), taurine (Tau), ammonium chloride, D,L-succinate, binary mixtures of these compounds, as well as a 33-component artificial oyster mixture (AOM). For the 40 ORNs studied, these stimuli more frequently elicited inward than outward currents. AMP, Glu, Tau and Bet evoked the largest and most numerous inward currents; Cys most commonly evoked outward currents. Na+ was an important charge-carrying ion for the Glu-evoked response in one ORN and the Bet-evoked response in another ORN. Mixture suppression, defined conservatively in this study as cases where the response to a binary mixture was less than the response to the more excitatory component of that mixture, was observed in 6 ORNs. In all 6 cases, neither component of the mixture evoked an outward conductance (i.e. neither was inhibitory). Five of these cases of mixture suppression involved a mixture containing two excitatory compounds (i.e. producing inward conductances): four ORNs were excited by both Glu and AMP, and one ORN was excited by both Tau and Glu. One case of mixture suppression occurred for a compound (Tau) tha did not produce a current when presented alone but which when added to Bet suppressed the inward current generated by Bet. Mechanisms for these suppressions are discussed, including inhibition of receptor binding by the components of a binary mixture and effects on second messengers or ion channels.

Adenosine Monophosphate↗

PubMed1995

Coordination and neuromuscular control of rhythmic behaviors in the blue crab, Callinectes sapidus.

The stereotypical courtship display (CD) behavior of the male blue crab, Callinectes sapidus, includes an unusual component: the rhythmic waving of the swimming appendages above the carapace. This behavior occurs in a unique context but it resembles two other rhythmic behaviors performed using the swimming legs: sideways swimming and backward swimming. As a first step to understanding the mechanisms that allow the expression of apparently different rhythmic motor patterns, we have examined these behaviors using slow motion video analysis and electromyography of the basal muscles of the swimming legs in freely behaving crabs. The results show that these behaviors are distinguished by four parameters: the frequency of leg waving, the phase relationship between the legs, the presence of a stationary pause in basal muscle activity combined with rotation of the distal leg during CD, and an extended range of motion of these legs during CD and backward swimming, relative to sideways swimming. EMG analysis revealed that during sideways swimming, the sequence of muscular activity between the two legs was different. In contrast, during CD and backward swimming the sequence of activity for these legs is identical.

Animals↗

PubMed1995

Modulation of behavior by biogenic amines and peptides in the blue crab, Callinectes sapidus.

Using the blue crab Callinectes sapidus as a model system, we have investigated the effects of potential neuromodulators on freely behaving animals. Of interest is the modulatory effect of a number of drugs on three rhythmic behaviors of the blue crab: courtship display (CD) of the male crab, sideways swimming and backward swimming. The drugs tested were proctolin, dopamine, octopamine, serotonin, and norepinephrine. Injection of each drug elicited a unique posture or combination of limb movements. These experiments showed two results pertinent to CD behavior: A posture identical to the CD posture was displayed after dopamine injection; and rhythmic leg waving similar to CD was evoked by proctolin. An unusual combination of flexion and extension of all limbs and movements of some limbs occurred after serotonin injection. Injection of octopamine led to a posture antagonistic to CD posture. The effects of these drugs were concentration- and time-dependent. Injection of dopamine, octopamine, or serotonin produced effects that were seasonally-dependent, and the influence of proctolin proved to be dependent on developmental stage. Quantitative analysis of leg waving movements after proctolin injection allowed for comparison of these movements to naturally-occurring behavior.

Aging↗

PubMed1995

Regulation of sex-specific feeding behavior in fiddler crabs: physiological properties of chemoreceptor neurons in claws and legs of males and females.

This study examined properties of chemoreceptor neurons in the claws and legs of the fiddler crabs Uca pugilator and U. pugnax. The primary goal was to establish the neural basis of previously observed greater female sensitivity to feeding stimulants, and secondarily to compare physiological properties of chemoreceptor neurons in these semi-terrestrial crustaceans with those of fully aquatic forms. Sensitivity of chemoreceptor neurons in claws and legs is sex-specific; individual neurons of females respond to lower stimulus concentrations than male chemoreceptor neurons, and equivalent concentrations elicit greater spiking in female vs male chemoreceptor neurons. Thus, the population of chemoreceptor neurons in females expresses lower thresholds and greater average sensitivity than in males. Greater sensitivity of claw neurons explains observations indicating that females continue to feed at food levels too low to stimulate males. Sensitivity differences in leg neurons of males vs females have no clear behavioral correlate, but suggest that females can orient to more dilute stimuli than males. Chemoreceptor neurons of fiddler crabs have low sensitivities and slow rates of adaptation compared to other crustaceans. Also, neurons in claws adapt less slowly than neurons in legs, which may reflect subtle differences in the chemical stimulus environment experienced by claws vs legs.

Amino Acids↗

PubMed1995

Inhibition of taurine and 5'AMP olfactory receptor sites of the spiny lobster Panulirus argus by odorant compounds and mixtures.

1. The effects of the odorant compounds adenosine-5'-monophosphate (5'AMP), ammonium, betaine, L-cysteine, L-glutamate, DL-succinate, and taurine and of mixtures of these compounds on binding of taurine and 5'AMP to dendritic membrane from the olfactory organ of spiny lobsters (Panulirus argus) were quantified to evaluate the contribution of inhibition of odorant-receptor binding to the generation of physiological responses to mixtures. 2. Taurine binding sites belong to two affinity classes, while 5'AMP binding sites belong to a single affinity class. Binding of either taurine or 5'AMP was partially inhibited in an apparently noncompetitive, concentration dependent fashion by most odorant compounds, with 25-40% inhibition by 1 mM of odorant. Mixtures of two or more odorant compounds also inhibited binding of taurine or 5'AMP to its sites. However, the inhibition by mixtures was often significantly less than expected from the inhibition produced by a mixture's components assuming either a noncompetitive or competitive mechanism. 3. By including this binding inhibition between compounds into models for predicting physiological responses to mixtures from the responses to the components, the predictive power of the models is significantly improved. This result strongly suggests that binding inhibition can influence the physiological responsiveness of chemoreceptor cells to mixtures.

Adenosine Monophosphate↗

PubMed1994

Non-reciprocal cross-adaptation of spiking responses of individual olfactory receptor neurons of spiny lobsters: evidence for two excitatory transduction pathways.

Single-unit spiking responses of 72 olfactory receptor neurons (ORNs) in the olfactory organ of the spiny lobster Panulirus argus were recorded extracellularly during presentation of a set of seven odorant stimuli (adenosine-5'-monophosphate, ammonium chloride, betaine, L-cysteine, L-glutamate, D,L-succinate and taurine) and analyzed in order to evaluate the response specificities of single ORNs and the independence of receptor sites. Individual ORNs often had narrow excitatory response spectra, but the most excitatory compound was different from neuron to neuron. These results suggest that these compounds can exert most of their excitatory effects through relatively independent receptor site types. To determine the relative independence of excitatory transduction processes in single ORNs for these stimuli, single-unit spiking responses of these neurons under conditions of self- and cross-adaptation were analyzed. The results demonstrate extensive cross-adaptation between pairs of the seven stimuli. When averaged across all neurons and all cross-adaptation conditions, cross-adaptation resulted in a mean reduction of 81% of the unadapted response. However, there were differences in the degree and pattern of adaptation for different pairs of compounds and for different neuron types (defined by most excitatory or 'best' chemical). For a given neuron type, there were significant levels of non-reciprocal cross-adaptation: neurons cross-adapted more when adapted to their best chemical than when adapted to their non-best chemicals. These results suggest the existence of two excitatory transduction pathways within an olfactory receptor neuron: one pathway activated exclusively by the best chemical and a second pathway activated by a broader spectrum of chemicals.

Acclimatization↗

PubMed1994

Perception of odor mixtures by the spiny lobster Panulirus argus.

We used spiny lobsters (Panulirus argus) in a discrimination learning procedure with aversive conditioning to examine their behavioral discrimination of adenosine-5'-monophosphate (AMP), betaine, L-cysteine and their binary mixtures. Our results show that spiny lobsters can clearly discriminate among binary mixtures and their components. Lobsters aversively conditioned to avoid responding to a binary mixture continued to respond to that mixture's components, and lobsters that were aversively conditioned to avoid responding to a compound tended to continue to respond to binary mixtures containing that compound. Thus, responses of conditioned lobsters to binary mixtures were not usually intermediate between the responses to the mixtures' components, which might be expected for response-matched compounds. This result might arise from any of several factors. First, it might result from mixture interactions in the peripheral olfactory system, if the responses of olfactory receptor neurons to one component of a binary mixture were suppressed by the other component, making the response to the mixture more similar to the suppressing component. Electrophysiological data from a population of 50 singly-recorded olfactory receptor neurons (Daniel and Derby, 1994) do not consistently support this idea. A second possible reason for the behavioral response to a binary mixture not being intermediate between the responses to its components involves higher order processing, such as mixture interactions generated in olfactory interneurons in the CNS (which is known to occur: Derby et al., 1985; Ache, 1989), configural learning or associative processing.

Adenosine Monophosphate↗

PubMed1993

Ultrastructural localization of 5'AMP odorant receptor sites on the dendrites of olfactory receptor neurons of the spiny lobster.

A unique probe--biotinylated adenosine-5'-monophosphate (5'AMP-biotin)--was used in transmission electron microscopic (TEM) studies to localize 5'AMP odorant binding sites on the dendrites of olfactory receptor neurons in the aesthetasc sensilla of the spiny lobster, Panulirus argus. This probe is capable of both binding to and exciting 5'AMP-sensitive olfactory receptor neurons, as revealed through biochemical and electrophysiological assays. TEM studies showed that 5'AMP-biotin binding sites are distributed along the entire dendritic region that is exposed to odorants, including the transitional zone (between the inner and outer dendritic segments, including the ciliary segment) and all of the outer dendritic segment. The density of 5'AMP binding sites per micron2 of membrane is similar along the length of the olfactory dendrite. However, the relative number of 5'AMP-biotin binding sites per micron2 of sensillar area diminishes in the distal 30% of the aesthetasc due to a decrease in the amount of dendritic membrane in that region. The distribution of these 5'AMP binding sites is therefore much more extensive than that of enzymes that inactivate 5'AMP--5'ectonucleotidase/phosphatase--which are restricted to the transitional zone (Gleeson et al., 1991). Taken together, these results suggest that 5'AMP-biotin is labeling 5'AMP-specific olfactory receptor sites that are located along the entire outer dendritic segment and that can be coupled to olfactory transduction. This study represents the first in situ localization of specific olfactory receptor sites using a specific, functionally defined ligand.

Adenosine Monophosphate↗

PubMed1992

Biochemical characterization of independent olfactory receptor sites for 5'-AMP and taurine in the spiny lobster.

To understand the initial events in chemosensory transduction (i.e. binding of odorants to olfactory receptor sites), we have utilized a radioligand-receptor binding assay on a tissue preparation that is enriched in dendritic membrane from olfactory receptor cells in the spiny lobster Panulirus argus. Radioligands used were tritiated adenosine 5'-monophosphate (AMP) and taurine, which are two of the most excitatory compounds for spiny lobsters. Our results indicate the existence of two independent types of binding sites--a taurine binding site and an AMP binding site. For both the taurine and AMP binding sites, odorant binding is rapid, reversible, and saturable. KD values for the taurine and AMP binding sites are 2.3 and 2.0 microM, respectively, and Bmax values are 159 and 3.2 fmol/micrograms protein, respectively. The fact that the specificity, affinity, and independence of these two binding sites as defined in these biochemical studies are in agreement with those from electrophysiological studies suggests that these binding sites are olfactory receptor sites involved in sensory transduction.

Adenosine Monophosphate↗

PubMed1991

Chemosensory responses to mixtures: a model based on composition of receptor cell types.

Previous mixture models have assumed that members of a population of chemoreceptor cells are homogeneous in type, i.e., with either single shared or multiple independent receptor sites. In reality, many chemosensory systems actually consist of a heterogeneous population of receptor cells, consisting of both highly specific cells as well as more broadly and variably tuned cells. A mixed receptor composition model for binary mixtures is described which can be applied to chemosensory systems with heterogeneous receptor cell compositions. The model incorporates information on a) the number of receptor sites/transduction processes per cell, b) the specificity of receptor cells, and c) the contribution of the magnitude of response of each receptor cell to the overall response magnitude of the population of all receptor cells. The predictions of this model can be compared to behavioral responses of animals towards binary mixtures, or at any level of sensory processing which involves the input of the receptor cell population, in order to detect possible mixture interactions.

Animals↗

PubMed1991

Mixture suppression in behavior: the antennular flick response in the spiny lobster towards binary odorant mixtures.

The behavioral responses of Florida spiny lobsters towards various concentrations of binary mixtures and their constituents (AMP, betaine, cysteine, succinate, and taurine) were measured using an antennular flicking assay. The rate of flicking increases with dose and has low thresholds: flick rates towards each of the five chemicals increased with concentration with thresholds between 1 nM and 100 microM. A mixed receptor composition model, which incorporates knowledge of the composition of receptor site types and their distribution across receptor cells (15), was used to predict responses to binary mixtures based on responses to the individual constituents. Nine of the ten binary mixtures elicited response magnitudes which were less than predicted by this model, suggesting mixture suppression. These mixture interactions appear to be independent of the concentration of the mixture tested; rather, they occur with the same magnitude at all concentrations. These behavioral results corroborate findings in olfactory receptor cell studies which indicate the significant prevalence of mixture suppression towards some of the same binary mixtures (19,20).

Animals↗

PubMed1991

Effects of stimulus intensity and quality on discrimination of odorant mixtures by spiny lobsters in an associative learning paradigm.

The Florida spiny lobster, Panulirus argus, can behaviorally discriminate between members of a set of four artificial odorant mixture types: crab, mullet, oyster, and shrimp. The present experiments were designed to examine the effects of both intensity and quality on discrimination of odorant mixtures. This was accomplished by conditioning lobsters to only one concentration (0.5 mM) of shrimp mixture and testing them with four concentrations (0.005, 0.05, 0.5 and 5.0 mM) of shrimp mixture and two concentrations (0.05 and 0.5 mM) of oyster mixture. For the two appetitive behaviors examined, lobsters did not discriminate the conditioned mixture (0.5 mM shrimp) from any other of the same-type nonconditioned mixtures. For a third behavior, active avoidance, lobsters discriminated, to a significant degree, the 0.5 mM shrimp mixture from all of the nonconditioned mixtures. However, aversion values for the nonconditioned shrimp mixtures were markedly and consistently higher than those for the nonconditioned oyster mixtures for all three behaviors. Thus, when spiny lobsters are forced to use intensity as a cue (as in an aversive conditioning situation), they have the ability to discriminate between mixtures of the same quality but different intensity. Nevertheless, based on examination of post-conditioning decreases in appetitive behaviors, it is most likely that the intensity of an odorant mixture has a relatively minor effect on the discrimination of the quality of that mixture by these animals, at least over a 1000-fold concentration range.

Animals↗

PubMed1991

Responses of olfactory receptor cells of spiny lobsters to binary mixtures. I. Intensity mixture interactions.

1. Neural coding of chemical mixtures was studied with the use of the peripheral olfactory system of the spiny lobster. The occurrence of mixture interactions (i.e., where the observed response to a mixture deviates significantly from the expected response) in individual cells and the effect of such mixture interactions on the coding of odorant intensity by populations of cells were examined. 2. Extracellular recordings of spiking activity of 98 primary olfactory receptor cells in the antennules were measured in response to seven compounds [adenosine-5'-monophosphate (AMP), betaine (Bet), L-cysteine (Cys), L-glutamate (Glu), ammonium chloride (NH4), DL-succinate (Suc), and taurine (Tau)] and their binary mixtures. To identify mixture interactions, observed responses to a range of concentrations of a binary mixture were compared with the predicted responses based on three mathematical models: a single receptor model, which assumes that the two compounds of a mixture bind to the same receptor site; a multiple receptor model, which assumes that the two compounds bind to two independent receptor sites; and a mixed composition receptor model, which incorporates our current state of knowledge of transduction processes in olfactory receptor cells of spiny lobsters. 3. Mixture interactions in individual cells were common: statistically significant mixture interactions were observed in 25% of the possible cases (Fig. 5). Suppression was much more common than enhancement. 4. Mixture interactions had significant effects on the absolute response magnitudes for a population of cells, which could be used as the neural code for stimulus intensity in this system. These effects are called intensity mixture interactions (Figs. 6-11). Intensity mixture interactions occurred for approximately 50% of the binary mixtures and were almost exclusively suppression (Figs. 12 and 13). The intensity mixture interactions were concentration independent. 5. The results suggest that mixture interactions in individual olfactory cells can result in intensity mixture interactions in the neuronal population such that there is a decrease in sensitivity to binary mixtures relative to what is expected based on the responses to individual components of the mixtures.

Animals↗