Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Nephropidae”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

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

At least 217 records · Page 12Linked to original sources
PubMed1996

Relationship between burst properties and sensitivity to input: a theoretical analysis.

This paper examines the sensitivity of endogenous bursters to a brief input pulse. The interneurons of the lobster cardiac ganglion were selected as a case study. Using a mathematical model specifically developed for the neurons in the cardiac ganglion of the lobster (Av-Ron et al., 1993), we show a tight link between burst characteristics and certain other parameters. We show that cells with different burst properties differ in their sensitivity to an input of a brief pulse. Irrespective of these differences, all cells display a bimodal response to a brief pulse applied during the quiescent period. During the first three-quarters of the quiescent period, they respond by producing a single spike at most. During the remaining one-quarter, the brief pulse can initiate the cells' intrinsic burst. Our predictions fit experimental results obtained by Tazaki and Cooke (1979). The results obtained herein are discussed with respect to fault tolerance considerations.

Animals↗
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↗
PubMed1992

Mechanosensory afferents innervating the swimmerets of the lobster. I. Afferents activated by cuticular deformation.

The mechanosensory innervation of the lobster (Homarus americanus) swimmeret was examined by electrophysiologically recording afferent spike responses initiated by localized mechanical stimulation of the caudal surface of the swimmeret. Two functional groups of subcuticular hypodermal mechanoreceptors innervate the swimmeret. Afferents of one group innervate the small discrete "ridges" of calcified cuticle lining the margins of both swimmeret rami. Putative ridge receptors are bipolar sensory neurons responding phasically to deformation of the ridge cuticle with the number and frequency of impulses produced dependent on stimulus strength and velocity. Afferents of the second group, which innervate substantial areas of hypodermis underlying the soft, flexible cuticular regions of the swimmeret, were designated "wide-field" hypodermal mechanoreceptors. These neurons have multiterminal receptive fields and respond phaso-tonically to cuticular distortion. The response properties of both types of hypodermal mechanoreceptors imply that they are activated during the characteristic beating movements of the swimmerets.

Animals↗
PubMed1992

Mechanosensory afferents innervating the swimmerets of the lobster. II. Afferents activated by hair deflection.

Feathered hair sensilla fringe both rami of the lobster (Homarus americanus) swimmeret. The sensory response to hair displacement was characterized by recording afferent impulses extracellularly from the swimmeret sensory nerve while deflecting sensilla with a rigidly-coupled probe or controlled water movements. Two populations of hairs were observed: "distal" hairs localized to the distal 1/3 of each ramus and "proximal" hairs near its base. Distal hairs are not innervated by a mechanosensory neuron but instead act as levers producing strain within adjacent cuticle capable of activating a nearby hypodermal mechanoreceptor. Hair deflections of 25 degrees or more are required to evoke an afferent response and this response is dependent on hair deflection direction. The frequency and duration of the afferent discharge evoked are determined by the velocity of hair displacement. Each proximal hair is innervated by a single mechanosensory neuron responding phasically to hair deflections as small as 0.2 degrees in amplitude. Deflection at frequencies up to 5 Hz elicits a single action potential for each hair movement; at higher frequencies many deflections fail to evoke an afferent response. These sensilla, which are mechanically coupled, may be activated by the turbulent flow of water produced by the swimmerets during their characteristic beating movements.

Animals↗
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↗
PubMed1992

Elevated temperature alters the ionic dependence of amine-induced pacemaker activity in a conditional burster neuron.

The anterior burster neuron of the lobster (Panulirus interruptus) stomatogastric ganglion is a conditional burster that functions as the primary pacemaker for the pyloric motor network. When modulatory inputs to this cell are blocked, it loses its bursting properties and becomes quiescent. Applications of the monoamines, dopamine, octopamine or serotonin restore rhythmic bursting in this cell (Flamm and Harris-Warrick 1986). At 15 degrees C, serotonin- and octopamine-induced oscillations depend critically upon sodium entry (blocked by low sodium saline or tetrodotoxin); dopamine-induced oscillations depend upon calcium entry (blocked by reduced extracellular calcium; Harris-Warrick and Flamm 1987). We show here that the ionic dependence of amine-induced oscillations in the anterior burster cell differs at 15 and 21 degrees C. At 21 degrees C, all amines have the potential to induce rhythmic oscillations in saline containing tetrodotoxin. At the elevated temperature and in tetrodotoxin, both calcium and sodium currents are essential for the maintenance of dopamine-induced oscillations; serotonin-induced oscillations do not depend upon either calcium or sodium alone; octopamine-induced oscillations do not depend upon calcium and show a variable dependence upon sodium. Thus, multiple ionic mechanisms, which vary with both the modulator and the ambient temperature, can be recruited to support rhythmic activity in a conditional burster neuron.

Animals↗
PubMed1993

A basic biophysical model for bursting neurons.

Presented here is a basic biophysical cell model for bursting, an extension of our previous model (Av-Ron et al. 1991) for excitability and oscillations. By changing a limited set of model parameters, one can describe different patterns of bursting behavior in terms of the burst cycle, the durations of oscillation and quiescence, and firing frequency.

Animals↗
PubMed1995

Modulated excitability: a new way to obtain bursting neurons.

Classical burster models are based on a fast system that either oscillates or is quiescent, depending on temporarily fixed values of slow variables. In a study of the lobster heart ganglion, we found a new type of burster for which the fast system is globally stable for all relevant fixed values of the slow variables. We describe how this burster works and speculate on its biological significance.

Animals↗
PubMed1975

Larval and adult eye of the western rock lobster (Panulirus longipes).

A number of differences exists between the compound eyes of larval and adult rock lobsters, Panulirus longipes. The larval eye more closely resembles the apposition type of compound eye, in which retinula cells and rhabdom lie immediately below the cone cells. The adult eye, on the other hand, is a typical clear-zone photoreceptor in which cones and retinula cell layers are separated by a wide transparent region. The rhabdom of the larval eye, if cut longitudinally, exhibits a "banded" structure over its entire length; in the adult the banded part is confined to the distal end, and the rhabdom is tiered. Both eyes have in common an eighth, distally-located retinula cell, which possesses orthogonally-oriented microvilli, and a peculiar lens-shaped "crystal", which appears to focus light onto the narrow column of the distal rhabdom. Migration of screening pigment on dark-light adaptation is accompanied by changes in sensitivity and resolution of the eye. Retinula cells belonging to one ommatidium do not arrange into one single bundle of axons, but interweave with axons of four neighbouring facets in an extraordinarily regular fashion.

Animals↗
PubMed1996

The effects of in vivo exposure to cadmium, copper and zinc on the activities of gill ATPases in the Norway lobster, Nephrops norvegicus.

Norway lobsters, Nephrops norvegicus were exposed for 18 days to combinations of cadmium, copper and zinc at three sublethal concentrations (1, 5, 25 micrograms/L for Cd and Cu, and 8, 40 and 200 micrograms/L for Zn). Male animals were exposed to all three concentrations, while female animals were studied only in one (highest) concentration of the metals. Activities of Na,K-ATPase and both oligomycin-sensitive and insensitive Mg-ATPase were investigated in relation to metal exposure. A group of male Nephrops of different size groups from a single location in the Clyde Sea was also sampled to investigate the relationship between size and ATPase activity. Cadmium concentrations increased significantly with increases in exposure concentrations in both male and female animals, whereas copper and zinc increased significantly only in the highest treatment in males. There was no significant difference in concentrations of the metals in control male and female animals, whereas males accumulated significantly higher levels of copper and zinc in the highest concentrations of the metals. Control males showed higher activity of Na,K-ATPase than control females. Na,K-ATPase activity was significantly inhibited in male animals exposed to metals whereas in female animals there was only a significant inhibition in total Mg-ATPase activity. Na,K-ATPase activity had a negative relationship with copper in males, while in treated females this ATPase had positive relationship with zinc and copper. There were negative relationships between the activities of Na,K-ATPase and oligomycin sensitive Mg-ATPase with carapace length of the animals.

Animals↗