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D C Sandeman

Publications and source records attributed to D C Sandeman.

At least 19 recordsLinked to original sources
PubMed2004

Regulation of serotonin levels by multiple light-entrainable endogenous rhythms.

This study examined whether serotonin levels in the brain of the American lobster, Homarus americanus, are under circadian control. Using high-performance liquid chromatography and semi-quantitative immunocytochemical methods, we measured serotonin levels in the brains of lobsters at six time points during a 24-h period. Lobsters were maintained for 2 weeks on a 12 h:12 h light:dark cycle followed by 3 days of constant darkness. Under these conditions, brain serotonin levels varied rhythmically, with a peak before subjective dusk and a trough before subjective dawn. This persistent circadian rhythm in constant darkness indicates that serotonin levels are controlled by an endogenous clock. Animals exposed to a shifted light cycle for >10 days, followed by 3 days in constant darkness, demonstrate that this rhythm is light entrainable. Separate analyses of two pairs of large deutocerebral neuropils, the accessory and olfactory lobes, show that serotonin levels in these functionally distinct areas also exhibit circadian rhythms but that these rhythms are out of phase with one another. The olfactory and accessory lobe rhythms are also endogenous and light entrainable, suggesting the presence of multiple clock mechanisms regulating serotonin levels in different brain regions.

Animals↗
PubMed2003

Recruitment of honeybees to non-scented food sources.

Small groups of honeybees (five to nine individuals) were trained to forage at feeders 150 m, 300 m and 800 m from an observation hive. Their behaviour in the hive and at the feeder was recorded by observers that maintained continuous radio contact with one another. At low concentrations of sugar in the feeder (0.5 mol x l(-1)) foragers do not dance in the hives, their flights to the feeder are often undertaken alone, they land immediately after arrival at the site and no recruits from the hive landed on the feeder during 30 h of observation. Raising the concentration of sugar in the feeder to 2 mol x l(-1) leads to vigorous dancing by the foragers and the gradual (over 10-15 min) synchronisation of their flights so that they arrive in groups of up to five bees at the feeder and undertake circular "buzzing" flights before landing. Such behaviour of the foragers is associated with the appearance of recruits which were never seen to fly around the feeder and land alone or before the foragers. Recruits typically circle the feeder together with foragers and land with them or continue their circling flights to land about 10 s later. While circling the feeder recruits, but not foragers, will fly after a moving lure if the presentation of the lure is accompanied by the release of geraniol scent. We propose that recruits that have witnessed a waggle dance are unlikely to find a non-scented feeder unless the foragers continue their flights to that feeder and provide supplementary visual and/or olfactory cues, at least in the vicinity of the feeder. We propose that the synchronisation of the flights of foragers and their behaviour at the feeding site is a strategy designed to overcome a navigational gap in the recruiting process in which the dance can indicate the general area of a food source but not the precise position of a highly localised site.

Adaptation, Physiological↗
PubMed1995

Ultrastructure of the synaptic terminals of the dorsal giant serotonin-IR neuron and deutocerebral commissure interneurons in the accessory and olfactory lobes of the crayfish.

The olfactory and accessory lobes in the crayfish are large spherical neuropils found on each side of its brain. The olfactory lobes receive the afferent axons of chemoreceptors that are located along the outer branches of the biramous first antennae. The accessory lobes receive a large input from interneurons whose axons lie in the deutocerebral commissure. A pair of large serotonergic neurons (the dorsal giant neurons) branch unilaterally in the accessory and olfactory lobes of each side. From physiological recordings, it has been proposed that the deutocerebral commissure interneurons synapse with elements in the accessory lobes that in turn connect to the dorsal giant neuron. It has also been proposed that the dorsal giant neuron is activated by inputs in the accessory lobe and that its output is in the olfactory lobe. This ultrastructural study tests this hypotheses by examining the polarity of synaptic terminals on dorsal giant neurons and deutocerebral interneurons that have been filled with neurobiotin. In double-labelled preparations, we found the deutocerebral interneurons to be presynaptic to elements in the accessory lobes, but none of these postsynaptic elements was identifiable as the dorsal giant neuron. The dorsal giant neurons receive many more synaptic inputs in the accessory lobes than in the olfactory lobe. Very few giant serotonin neuron output synapses were found in either lobe.

Animals↗
PubMed1994

Electrical responses and synaptic connections of giant serotonin-immunoreactive neurons in crayfish olfactory and accessory lobes.

Five pairs of identified 5HT-IR cells in the deutocerebrum of the crayfish Cherax are known to have their synaptic endings in the accessory and olfactory lobes. Two of these cells, one on each side of the brain, are significantly larger than the others. Dye fills of these "giant" cells reveal each to be an interneuron with its branches confined to, but distributed throughout, the olfactory and accessory lobes on the side of the brain ipsilateral to its cell body and with no branches to the contralateral side. Intracellular recordings from the giant cells were made while stimulating the olfactory afferents and tracts within the brain in an attempt to discover the inputs and outputs to the cells. Electrical stimulation of chemoreceptor sensilla on the outer branch of the antennule does not excite the giant 5HT neurons. Focal extracellular electrical stimulation of the olfactory globular tract containing the axons of projection neurons from the olfactory and accessory lobes produces excitatory synaptic potentials and action potentials in the giant cells. Focal extracellular electrical stimulation of the deutocerebral commissure, the axons of which terminate in the glomeruli of the accessory lobes, also results in excitation of the giant cells. We conclude that the input to the giant cells is via axons in the deutocerebral commissure and collaterals from the projection neurons, ending in the glomeruli of the accessory lobes. The output of the giant cells is to the olfactory lobes, where it may serve to modulate olfactory signals.

Action Potentials↗
PubMed1990

Substance P antibody reveals homologous neurons with axon terminals among somata in the crayfish and crab brain.

In the search for particular neurons that stain selectively and can be identified, the cerebral ganglia (brains) of the crayfish Cherax destructor and the crab Leptograpsus variegatus were immunocytochemically treated with a monoclonal antibody raised against substance P. Four large neurons in the cerebral ganglion of the crayfish and crab label selectively with a monoclonal antibody raised against substance P. Two of the large neurons have their cell bodies in the protocerebrum and two in the deutocerebrum in both animals. Each protocerebral cell in both animals projects through the ipsilateral and contralateral olfactory lobes to end among the lateral cell somata of the olfactory lobe and not in the neuropile. Electron micrographs show the presence of synapses within the cell somata area and on the cell somata themselves. Each deutocerebral cell in both animals projects only ipsilaterally and ends within the neuropile of the olfactory lobes. The immunoreactivity to substance P antibody and the shapes and the unique projections of the four cells suggest that they are homologous in the two species. Synaptic connections between axons and cell somata are rare in the arthropods but have been found on the Kenyon cells of the mushroom bodies of Limulus. This raises questions about homologies between the crustacean olfactory lobe and the mushroom bodies of Limulus and insects.

Animals↗
PubMed1990

Extraretinal photoreceptors in the brain of the crayfish Cherax destructor.

Two clusters of red-brown pigmented cell somata lie among other cell somata along the anterior margin of the cerebral ganglion in the crayfish Cherax destructor. Electron micrographs show these cells to contain round electron dense pigment granules and that the cell membranes of two or more adjacent cells fold together to form rhabdom-like structures. The pigmented cells specifically bind a monoclonal antibody against the major species of opsin in R1-7 retinula cells of the compound eye of Cherax. When stimulated with light, the pigmented cells respond with a receptor potential-like depolarization. The axons of the pigmented cells terminate in the neuropil of the protocerebral bridge, together with neuronal elements that label with antibodies against serotonin and substance P. We suggest that the brain photoreceptors of the crayfish are important in the entrainment of circadian rhythms.

Animals↗
PubMed1989

The effect of serotonin and octopamine on the optokinetic response of the crab Leptograpsus variegatus.

A standard optokinetic response of the ipsilateral and contralateral (driven) eyes of the crab Leptograpsus variegatus to a sinusoidally oscillating striped drum was established. Optokinetic responses were then measured of animals that had been treated by introducing serotonin and octopamine into the blood stream via the heart and also into the neural tissue of the optic lobes via a micropipette. Both serotonin and octopamine enhance the optokinetic effect when applied in low doses. Experiments show that serotonin is most likely acting closer to the sensory input in the optokinetic system.

Animals↗
PubMed1988

Atlas of serotonin-containing neurons in the optic lobes and brain of the crayfish, Cherax destructor.

An atlas of neurons in the brain of the crayfish Cherax destructor that are immunoreactive to antibodies raised against serotonin has been compiled from whole mount preparations. Neuronal networks of serotonin-containing cells are identified in the optic lobes and protocerebrum, in the deutocerebrum, and in the tritocerebrum. The consistency of the whole-mount technique allows 50 out of a total of about 100 immunoreactive cells to be individually identified according to their neuronal architecture or the location of their cell somata or axons. Apart from six neurons with axons in the oesophageal connectives, all the immunoreactive cells are intrinsic to the optic lobes and brain.

Animals↗
PubMed1987

Preparation of immunoperoxidase-labelled wholemounts of invertebrate brains.

An immunoperoxidase method is described for the immunocytochemical labelling of whole cerebral ganglia of the crayfish to reveal serotonin-containing neurons. Careful desheathing, unusually long immersion in antibody reagents, the inclusion of blocking reagent in every incubation and extensive washing produce immunolabelled wholemount preparations with very low background. The entire neurotransmitter system is consistently labelled and single identifiable neurons can be repeatedly recognized.

Animals↗
PubMed1977

The organisation of the lamina ganglionaris of the crabs Scylla serrata and Leptograpsus variegatus.

The gross structure and neuronal elements of the first optic ganglion of two crabs, Scylla serrata and Leptograpsus variegatus, are described on the basis of Golgi (selective silver) and reduced silver preparations. Of the eight retinula cells of each ommatidium, seven end within the lamina, while the eighth cell sends a long fibre to the external medulla. Five types on monopolar neurons are described, three types of large tangential fibres, and one fibre which may be centrifugal. The marked stratification of the lamina is produced by several features. The main synaptic region, the plexiform layer, is divided by a band of tangential fibres; the short retinula fibres end at two levels in the plexiform layer; and two types of monopolar cells have arboriasations confined to the distal or proximal parts of the plexiform layer. The information presently available concerning the retina-lamina projection in Crustacea is examined. Some of the implications of retina and lamina structure are discussed in conjunction with what is known about their electrophysiology.

Animals↗
PubMed1974

Efferent axons in the fish optic nerve and their effect on the retinal ganglion cells.

Recordings were taken from small bundles of axons dissected away from the otherwise intact optic nerve of the trigger fish, Hemibalistes chrysopterus. Proximal nerve stumps showed unitary activity of efferent axons which are activated by visual, vestibular, vibratory and tactile stimuli. Distal stumps showed predominantly the discharges of retinal ganglion cells which have a sustained response in either the light or dark and which are inhibited by the opposite condition. These retinal ganglion cells are also excited by vestibular, vibratory and tactile stimuli provided the optic nerve is almost intact. It is inferred that the excitation of the retinal ganglion cells by non-visual stimuli is effected by the centrifugal fibres mentioned above. Ablation of various lobes of the brain shows that the efferent fibres continue to respond after ablation of the frontal lobes and the cerebellum. The response is weakened by the ablation of the ipsilateral optic tectum and abolished when the contralateral tectum is removed.

Animals↗