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Biomedical subjects

A Gelperin

Publications and source records attributed to A Gelperin.

At least 55 records · Page 3Linked to original sources
PubMed1983

Dopamine elicits feeding motor program in Limax maximus.

A neural system within the cerebral and buccal ganglia of the terrestrial mollusc Limax maximus responds to lip chemostimulation by emitting a feeding motor program (FMP) in vivo and in vitro. We have analyzed chemically the cerebral and buccal ganglia of Limax for neurotransmitters involved in controlling expression of FMP. Dopamine was found in clusters of cells in and the neuropil of the cerebral ganglia at a concentration of 62 pmol/ganglion; a large proportion of such dopamine-containing cells projected to the lips. The buccal ganglia contained several small dopaminergic cells and large amounts of dopamine in the neuropil; the measured concentration was 10 pmol/ganglion. Exogenous dopamine applied to the cerebral and buccal ganglia in vitro between 10(-7) M and 3 X 10(-6) M excited an autoactive salivary duct motor neuron (FB) and inhibited an autoactive secretomotor neuron (BSN). Concentrations of dopamine between 3 X 10(-6) M and 3 X 10(-5) M triggered FMP output, with an increased probability of triggering at higher concentrations of dopamine. ADTN and SK&F38393 were potent agonists in this system, whereas ergonovine was the only potent antagonist found; none of the neuroleptics tested was effective. Thus, the Limax system shows agonist responses similar to the vertebrate D1 receptors, but its antagonist-binding properties appear to have requirements quite different from vertebrate receptors. The effects of exogenous serotonin differed from dopamine's effects; serotonin excited BSN and several buccal motor neurons, could not elicit synchronized motor program cycling, and was not efficiently blocked by ergonovine. These data suggest that dopamine is a good candidate as an endogenous triggering and sustaining transmitter for the Limax feeding motor program.

Animals↗
PubMed1982

Exogenous choline augments transmission at an identified cholinergic synapse in terrestrial mollusk Limax maximus.

1. A variety of pharmacological tests indicate that the neuromuscular junction between the salivary burster neuron (SB) and the salivary duct muscle (SD) in the terrestrial mollusk Limax maximus is cholinergic. These include the effects of curare, atropine, and hexamethonium. 2. Exogenously applied choline can act both presynaptically and postsynaptically at the synapse between the SB and SD. a) When the SB-SD synapse is bathed in 30 microM choline, there is no measurable direct postsynaptic effect at the SB-SD synapse. After several hours of choline incubation, however, an increase is observed in the size of SB-elicited junction potentials recorded from the SD. b) When the synapse is bathed in 300 microM choline, a short-term decrease is seen in the amplitudes of junction potentials (JPs) recorded from the SD. This effect is interpreted as competition between choline and acetylcholine (ACh) for postsynaptic receptor sites on the SD, since the response of the denervated SD to ACh is diminished in the presence of 300 microM choline. c) After several hours incubation in 300 microM choline, the amplitudes of JPs elicited by the SB on the SD increase. 3. The long-term effect of exogenous choline is blocked by the choline-uptake inhibitor, hemicholinium 3. 4. We conclude that exogenous choline is taken up by the presynaptic terminals of the SB and converted to ACh. Transmitter output rises with growing transmitter stores, producing an increase in the size of SB-elicited JPs recorded from the SD.

Acetylcholine↗
PubMed1982

Dietary choline augments blood choline and cholinergic transmission in terrestrial mollusk Limax maximus.

1. A radioenzymatic assay was used to determine the concentration of choline in the hemolymph of the terrestrial mollusk Limax maximus maintained on choline-enriched and choline-deficient diets. The levels of free choline in the slug's hemolymph varied with the availability of choline in the diet. The concentration of choline in the plasma of choline-enriched animals averaged 5.5 microM while the mean circulating choline level of choline-deprived slugs was 3.3 microM. The difference in choline levels between the two groups was statistically significant. 2. Neurophysiological measurements of transmission at the isolated cholinergic synapses between the salivary burster neuron (SB) and the salivary duct muscle (SD) showed that this synapse was sensitive to fluctuations in the external choline concentration within the physiological range. Increases in exogenous choline from 0.5 to 2.0 microM, from 2.5 to 5.0 microM, and from 5.0 to 15.0 microM were followed by increases in the amplitudes of SB-elicited junction potentials recorded from the SD by a focal extracellular electrode. 3. Thus, the SB-SD synapse is sensitive to the fluctuations in exogenous choline that can occur with a change in diet.

Acetylcholine↗
PubMed1981

[3H]-2-deoxyglucose autoradiography in a molluscan nervous system.

We have used [3H]2-deoxyglucose autoradiography to correlate the labeling of individual neurons with electrical activity within the central nervous system of a terrestrial mollusc, Limax maximus. In an electrically quiescent control preparation where a single neuron is impaled with a glass microelectrode but not stimulated, several somata are uniformly labeled at 3-5 times background. In preparations where a single cell is impaled and stimulated, one or more somata are heavily labeled with [3H]2-deoxyglucose at 10-50 times tissue background. This technique may be useful for surveying metabolically active neurons during spontaneous and driven electrical activity.

Animals↗
PubMed1981

One-trial associative learning modifies food odor preferences of a terrestrial mollusc.

We present evidence of rapid and reliable associative learning by the terrestrial mollusc, Limax maximus. Slugs were exposed once to a pairing of a highly attractive food odor (potato or carrot) and a saturated solution of quinidine sulfate, a bitter-tasting plant substance. In comparison with control slugs, the exposed slugs subsequently displayed a markedly reduced preference for the odor paired with quinidine. This reduced odor preference was limited to the specific odor paired with quinidine and did not generalize to other food odors.

Journal Article↗
PubMed1980

Localization of[3H]-2-deoxyglucose in single molluscan neurones.

The glucose analogue 2-deoxyglucose (2-DG) can be used quantitatively to measure metabolic activity and is widely used qualitatively for mapping functional activity in the brain. The resolution (meaning the full width at half maximum of the grain density distribution around a line source) of the technique using [14C]-2-DG and X-ray film is limited to about 100 micrometers. Attempts have been made to improve the resolution using [3H]-2-DG (ref. 6) and cellular resolution has been achieved in the goldfish retina and with cultured mouse neurones. An anatomical technique for mapping the metabolic activity of individual neurones would be useful for studying invertebrate central nervous systems, which are relatively simple and stereotyped compared to vertebrate brains. The [3H]-2-DG technique was applied to an invertebrate in a study of the Drosophila visual system, though without cellular resolution. We present here modifications of the [3H]-2-DG technique to demonstrate localization of 2-DG in single neurones of Limax maximus, a gastropod mollusc, with a resolution of less than 1 micrometer.

Acetone↗
PubMed1980

Rapid taste-aversion learning by an isolated molluscan central nervous system.

The isolated lips and nervous system of the terrestrial slug Limax maximus will produce some of the feeding behavior of the intact animal; i.e., they generate the rhythmic neural activity characteristic of ingestion in response to food extracts applied to the lips. This preparation will respond to a variety of food extracts that elicit feeding in the whole animal. This provides the opportunity for aversive conditioning experiments involving taste discrimination. Pairing lip chemostimulation by attractive food extracts with lip chemostimulation by using bitte plant secondary substances can cause the isolatd brain to selectively suppress its neural response to one food extract while remaining responsive to another. Such isolated brains can learn after one or two trials and retain the learning for more than 8 hr.

Action Potentials↗
PubMed1980

Feeding motor programme in Limax. II. Modulation by sensory inputs in intact animals and isolated central nervous systems.

The sources of variability in feeding motor programme (FMP) of the terrestrial slug, Limax maximus, were examined in relation to: (1) changes in load on the feeding apparatus; (2) changes in concentration of attractive food stimuli; and (3) changes in satiety signalled by feedback from the gut. These sources of variability, which affect both timing of the central pattern generator for feeding and probability of occurrence of FMP, were compared in intact animals and in isolated brain preparations. The load on feeding apparatus of intact animals is altered by varying the hardness of their food. An animal will show a higher 'bite cycle' frequency on soft food as compared with hard food. In physiological preparations, weights attached to buccal muscles similarly increase load. Cycle frequency of FMP triggered by food extracts is increased when buccal muscles are unloaded compared with FMP when muscles are loaded. Increasing the chemostimulant concentration of food results in greater numbers of intact animals feeding for longer periods. Increasing the food extract concentration used to trigger FMP in physiological preparations causes similar increases in feeding duration. Intact animals use cues from gut distention to indicate satiation and terminate feeding. Inflation of the crop in physiological preparations causes an early termination of feeding activity, along with decreased FMP cycle frequency.

Animals↗
PubMed1979

An ultrastructural analysis of the salivary system of the terrestrial mollusc, Limax maximus.

The bilateral salivary glands, ducts, and nerves of the giant garden slug Limax maximus control the secretion of saliva and its transport to the buccal mass. Each salivary nerve, which originates at the buccal ganglion, contains over 3000 axon profiles. The axons innervate the musculature of the duct and branch within the gland. The salivary duct is composed of several muscular layers surrounding an epithelial layer which lines the duct lumen. The morphology of the duct epithelium indicates that it may function in ion or water balance. The salivary gland contains four major types of secretory cells. The secretory products are released from vacuoles in the gland cells, and are presumably transported by cilia in the collecting ducts of the gland into the larger muscular ducts.

Animals↗
PubMed1978

Feeding motor program in Limax. I. Neuromuscular correlates and control by chemosensory input.

The feeding motor program(FMP) of the terrestrial slug Limax maximus was examined in vivo and in vitro. The feeding pattern of intact animals shows an initial increase in bite frequency followed by a plateau phase. Recordings obtained from semi-intact preparations of the lips, brain, and buccal mass established the correlation of activity in buccal ganglion nerve roots with the protraction-retraction bite cycle. A preparation of the lips, cerebral ganglia, and buccal ganglia was developed, such that, repetitive chemostimulation of the lips yields reproducible bouts of FMP. Sources of proprioceptive feedback from buccal muscles were demonstrated. The feasibility of computer scoring of the FMP is documented. The results demonstrate that aspects of in vivo feeding behavior are retained and identifiable in highly dissected, in vivo preparations.

Animals↗
PubMed1978

Our elderly. Who are they?

Why are today's elderly remarkable? They are the small minority who represent the survivors of Americans and immigrants born during the period 1870-1913. The mortality experience during that period shows the dramatic changes that have occurred. The future populations of the elderly are developing with an ever-increasing number of people kept alive by the mass use of vaccines, the application of new medical, surgical and psychologic diagnoses and therapies, effective antibiotics, rapid communication, proper nutrition, safe water, a high level of health insurance coverage, and available education at all levels for those who want to participate.

Aged↗
PubMed1977

A circadian rhythm in the locomotive behaviour of the giant garden slug Limax maximus.

The locomotor activity of the garden slug Limax maximus was examined for components of circadian rhythmicity. Behavioural (running wheel) studies clearly demonstrated that the activity satisfies the principal criteria of circadian rhythmicity. In constant darkness at a constant temperature, the locomotor activity freeran with a period of about 24 h (range 23-6-24-6 h). The rhythm was also expressed in constant light with a period for individual slugs that tended to be shorter in LL than in DD. The period of the rhythm was temperature compensated (11-5-21-5 degrees C) with a Q10 approximately equal to 1-00. The locomotor rhythm could be entrained to 24 h LD cycles such that the circadian activity peak occurred during the dark. The phase angle between the onset of activity and lights-off was not fixed, but was a function of the photoperiod of the entraining light cycle.

Animals↗