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At least 1,243 records · Page 69Linked to original sources
PubMed1976

Yersiniae in pond water and snails.

A Yersinia enterocolitica serotype 9 was isolated from pond water; Y. enterocolitica-like bacteria were also isolated from pond water and from three species of snails (Lymnaea palustris elodes, Helisoma sp., Oxyloma retusa) from the Edwin S. George Reserve in southeastern Michigan. There was evidence for biochemical stability among some of the organisms over a period of years. There also was evidence of transmission of these organisms to snails from the water.

Animals↗
PubMedDate not supplied

Effect of desiccation on freshwater snail, Indoplanorbis exustus, intermediate host of schistosomiasis.

Under laboratory conditions, snail Indoplanorbis exustus exhibited a strongly positive linear correlationship between duration of desiccation to mortality and body-weight loss and also body-weight loss to mortality. The adult stage of snail is highly resistant to desiccation, whereas the juvenile stage is highly susceptible. Reasons for decrease in susceptibility to desiccation with increase in shell diameter were suggested.

Age Factors↗
PubMed1999

Allergy to house dust mite and snails: a model of cross-reaction between food and inhalant allergens with a clinical impact.

A knowledge of cross-reactions between different allergens can facilitate the diagnosis of allergy. IgE cross-reactivity has been identified between house dust mite and snails. While most patients have mild symptoms, asthma and/or anaphylaxis may occur with these and other cross-reacting foods. It may be worthwhile to include measurement of IgE to some edible invertebrate animals in asthmatics, e.g. in mite allergic asthmatic patients who eat snails.

Animals↗
PubMedDate not supplied

Two modulatory inputs exert reciprocal reinforcing effects on synaptic input of premotor interneurons for withdrawal in terrestrial snails.

A cluster of serotonergic cells in the rostral part of pedal ganglia of the terrestrial snail Helix lucorum was shown previously to participate in modulation of withdrawal behavior, and to be necessary for elaboration of aversive withdrawal conditioning in intact snails. In the present experiments local extracellular stimulation of the serotonergic cells elicited a pairing-specific increase (difference between paired and explicitly unpaired sessions was significant, P<0.01) of synaptic responses in the premotor interneurons involved in withdrawal to paired nerve stimulation. Intracellular stimulation of only one Pd4 cell from the pedal group of serotonergic neurons increased (P<0.05) synaptic responses to contingent test nerve stimulation significantly in the same premotor interneurons for 2-3 hr. Mesocerebral cells are known to participate in male sexual behavior, and their extracellular stimulation was shown previously to suppress the amplitude of synaptic responses in withdrawal interneurons. Local extracellular stimulation of the mesocerebral cells elicited a pairing-specific decrease (P<0.01) of synaptic responses to contingent test nerve stimulation in the premotor interneurons involved in withdrawal for 2-3 hr. Paired application of met-enkephaline (10(-6) M, some mesocerebral cells are enkephaline-like immunoreactive) also selectively decreased synaptic responses to contingent nerve stimulation in the premotor interneurons for hours. Thus, two modulatory inputs exert pairing-specific effects that influence the same synaptic connection in opposite directions, which may underlie the long-term up- and down-regulation of behavioral responses.

Animals↗
PubMedDate not supplied

[Mathematical model of the dual action of G protein on the Ca2+ current in identified neurons of the snail Helix aspersa].

INTRODUCTION: The effect of the dopamine on the calcium current of identified cells of the snail Helix aspersa consists on an initial decrease, followed by a subsequent increase when the drug is removed. It had been previously demonstrated that this effect is mediated by a G protein, supposing that the decrease of the current would be mediated by the G alpha subunit, while the increase would be produced by the G beta gamma subunit. OBJECTIVE: A mathematical model has been developed with the object to test if the hypothesis of the dual action of the G protein could explain the experimental results. MATERIAL AND METHODS: It has been recording by means of the 'patch-clamp' (whole cell) in identified cells of snail. On the other hand, it has been developed a mathematical model of the calcium current using a Hodgkin-Huxley model, and a simulation of the action of the G protein on this current. RESULTS: Adjusting the kinetic parameters of the channel by means of the experimental data, it has reproduced in a faithful way the behavior of the calcium current. The simulation of the action of dopamine reproduces the decrease and increase of the current by means of the serial action of the G protein's subunits. CONCLUSION: Although a mathematical model cannot demonstrate the logic necessity of the hypotheses on that is based, it is unequivocally demonstrated that the hypothesis is fully compatible with experimental results.

Animals↗
PubMed1999

[Effect of cyclic AMP on the excitation and response of command neurons responsible for the snail defensive behavior caused by sensory stimulation].

Extraneuronal application of db-cAMP or intraneuronal injection of cAMP were found to increase the neural membrane excitability and synaptic facilitation in neural responses to sensory stimulation of Lpl1 and Rpl1 neurones. The db-cAMP exerted no effects on neural responses to tactile stimulation of the snail foot or mantle. The intraneuronal injection of cAMP produced synaptic facilitation only in neural responses to quinine application to the snail head. The findings suggest the cAMP selective involvement in postsynaptic mechanisms of inducing the long-term facilitation transient stage.

Animals↗
PubMedDate not supplied

[The duration of the storage of the electrical characteristics of command neurons in the acquisition of long-term sensitization in the snail].

The retention of the long-term sensitization (LTS) of defensive reflex and dynamics of change in electric characteristics (membrane potential (Vm) and action potential generation threshold (Vt)) of command neurons of defensive reflex was studied in a snail during behavioral tests. The membrane mechanisms were analyzed by measuring electrical characteristics of the LPa3, RPa3, LPa2, and RPa2 command neurons on the 1st, 4th, 7th, 10th, and 14th days after the LTS formation and 1 month later. The membrane potential and threshold potential in sensitized snails (-54.1 +/- 2.0 and 24.5 +/- 1.4 microV, respectively) were significantly (p < 0.001) decreased in comparison with the control animals (-60.9 +/- 0.8 and 19.9 +/- 0.6 microV respectively). These changes retained within 14 days after the LTS formation. The results suggest the long-term retention of the increased excitability of command neurons. A month after the LTS formation, the duration of the defensive reflex returned to the initial level and the electric characteristics of command neurons did not significantly differ from the control (-61.1 +/- 2.0 and 19.3 +/- 1.4 microV, respectively).

Action Potentials↗
PubMedDate not supplied

[Antagonists of NMDA glutamate receptors selectively affect synaptic mechanisms of the nociceptive sensitization in the snail].

The effects of N-methyl-D-aspartate (NMDA) glutamate receptor antagonists on the mechanisms of nociceptive sensitization were studied in LPl1 and RPl1 neurons of the semiintact preparation of a Helix lucorum snail. Application of sensitizing stimuli on the head part of the control preparation led to a depolarization of the membrane and increase in its excitability. A depression of responses of neurons evoked by tactile or chemical sensory stimulation during the short-term period and significant facilitation of responses during the long-term period of sensitization were observed. Sensitization performed under conditions of application of NMDA antagonists (AP5 or MK801) produced similar changes in membrane potential, membrane excitability, and neuronal responses evoked by tactile stimulation of the head or foot. However, the chemical stimulation of the head under these conditions evoked a significant depression of responses during the short- and long-term sensitization periods. The results suggest that the NMDA glutamate receptor antagonists selectively affect the plasticity induction mechanisms of the command neuron synaptic inputs, which mediate the chemical sensory stimulation from the snail's head.

2-Amino-5-phosphonovalerate↗
PubMed2000

Mytilus inhibitory peptide (MIP) induces a Na+-activated K+-current in snail neurons.

Two microelectrode voltage-clamp and single-channel recordings were performed on D-cluster neurons of snail right parietal ganglion in order to study the properties of MIP-activated potassium current. It was found that the octapeptide member of the MIP-family, ASHIPRFVa elicits an outward current, which possesses all the properties characteristic for the hexapeptide(s) inward membrane response. The main component of the peptide elicited response is highly [K+]o dependent, however the response was attenuated in Na-free extracellular saline. The peptide elicited response was mimicked by raising the [Na+]i by pressure injection of Na+ into the cell. Single channel recordings indicated that MIP-induced outward K-current is Na-dependent. The probability to find a channel in open state increases with increasing intracellular Na+-concentration. Excised inside-out patches obtained from D-neurons contained I(K(Na)) channels could be activated by exposure of the cytoplasmic face of the patch membrane to 40 mM Na+, and 40 mM Li+, as well. The single channel current amplitude at -60 mV is 15 pA and the single channel conductance is 212 pS between -80 and 0 mV. It was concluded that MIP's activate a novel type of K+-current in the snail neurons. This current is the Na-activated K+-current. The single channel properties of the MIP activated channel is in concert with I(K(Na)) data obtained on different vertebrate and invertebrate preparations.

Amino Acid Sequence↗
PubMed2001

The growth effects of gamma-ray irradiation on third-stage larvae of Angiostrongylus cantonensis in snail.

In order to clarify growth effects of gamma-ray irradiation on the third-stage larvae of Angiostrongylus cantonensis, snails naturally infected with larvae of A. cantonensis were irradiated with a cobalt-60 source, and the total dosage of exposure was 0.1 kGy. Third-stage larvae were collected from each group of irradiated and non-irradiated snails and then administered to rats. A significant reduction was observed in the number of recovery worms from rats sacrificed at 45 days after infection compared with the control group. Moreover, there was an increase in the percentage of female worms, and the body length of the irradiated group's worms was significantly shorter than that of the control group. In ultrastructural observations by transmission electron microscope, the cuticle was thickened and the subcuticle showed partial vacuolization and separation from muscle in the irradiated group. In addition, the muscles myofibril became shorter, the microvilli of intestinal mucosa were shorter and irregular, the terminal web disappeared, and the phagocytic vesicles, mitochondria, lysosomes and secretion granules decreased in number, respectively. Focusing on the mitochondria of the epithelial cells of the intestine, there were degenerative changes in the irradiated group showing vacuolization. The gonads of female worms recovered from the irradiated group revealed degenerative vacuolization, and the gonads of male worms could not be found.

Angiostrongylus cantonensis↗
PubMed1975

Effect of anaerobiosis, dinitrophenol and fluoride on the active intestinal transport of galactose in snail.

The active transport of galactose across the intestinal wall (everted sacs) of the snail Cryptomphalus hortensis Müller has been studied in vitro, under several metabolic conditions. Anaerobiosis does not change the serosal/mucosal galactose gradients which are developed in oxygen atmosphere. Dinitrophenol (10(-4) M) greatly increased the O2 uptake by the tissue and clearly inhibits the sugar transport. At 5 times 10(-4) M concentration, DNP totally prevents the uphill transport while the O2 uptake is normal. The inhibition produced by DNP does not increase by anaerobiosis. Fluoride inhibits the galactose transport and also the O2 uptake. It is deduced that in snail intestine the energy for the active transport of galactose can be supplied by aerobic as much as by anaerobic metabolism. The inhibition by dinitrophenol seems to be independent of its uncoupling action on the oxidative phosphorylation. The inhibitory effect of NaF may be due both to glycolisis inhibition and to alteration of the digestive epithelium.

Anaerobiosis↗
PubMed1975

Sodium dependence of intestinal active transport of sugars in snail (Cryptomphalus hortensis Müller).

Active transport of sugars (D-galactose, D-glucose, 3-0-methylglucose and L-arabinose) by sacs of everted intestine of snail (Cryptomphalus hortensis) was strongly inhibited, but not abolished, when all Na from the bathing solutions was substituted by K, Tris, Mg or Ca. Absence of Na produced also a marked inhibition of O2 consumption by the tissue. Omission of other cations (K, Ca, Mg), substituted by Tris, did not affect sugar transport or O2 uptake. Sodium seems to play a specific and important but not indispensable rôle in sugar active transport by snail intestine. Since anaerobiosis did not affect sugar transport, this Na role is independent of its effect on O2 uptake.

Animals↗
PubMed1975

Biology of the snail-killing fly, Sepedon spangleri Beaver (Diptera: Sciomyzidae). I. Life history.

One complete generation of the sciomyzid fly, S. spangleri, was on the average 27.90 days at 25 +/- 3 degrees C. The egg stage lasted 3.55 days. The first, second and third instar larvae lasted 4.35, 2.95 and 4.45 respectively when fed with live snails, Australorbis glabratus. Pupae floated on the water surface for 8 days until they emerged as adults. The longevity of adults fed with crushed snails, dried milk, brewer's yeast and honey average 199.95 days for females and 136.80 days for males. Under these conditions the average number of eggs laid per female was 414.70.

Animals↗
PubMed2002

[Electrophysiological characteristics of the statocyst receptor cells in snails Helix lucorum following exposure to microgravity in unmanned spacecraft "Foton" and piloted space station "Mir"].

Following 16-, 53-, 73- and 163-d orbiting, the background pulsation of the statocyst receptor cells (statoreceptors), the equilibrium organ in land pulmonary snails Helix lucorum, was found increased. Alteration of the body spatial position (2-min tilt at 90 degrees toward the upsilateral side) in the space-flown snails was noted to occur with delayed dying away of the pulsation rate. During stepwise (30 degrees) tilts in the range from 0 to 180 degrees, the maximum of the reaction was shifted by 30 degrees from the gravitational vertical; during dynamic tilting (sine decaying oscillations) the reaction subsides more rapidly as compared with the control animals. Absence of changes in pulsation of receptor cells in statocysts deprived of feedback with the nervous centers may be suggestive of inactivation of the efferent innervation in consequence of exposure to microgravity.

Animals↗
PubMed2003

Eosinophilic meningitis caused by Angiostrongylus cantonensis associated with eating raw snails: correlation of brain magnetic resonance imaging scans with clinical findings.

Angiostrongylus cantonensis is the most common cause of eosinophilic meningitis worldwide. Human infection occurs after ingestion of the worms in raw snails or fish that serve as intermediate hosts. Two outbreaks of central nervous system infection with A. cantonensis occurred in Kaoshiung, Taiwan, during 1998 and 1999 among Thai laborers who ate raw snails. A detailed clinical studies of 17 of these patients was conducted, including study of 13 patients who underwent magnetic resonance imaging (MRI) scans of the brain. The MRI scans revealed high signal intensities over the globus pallidus and cerebral peduncle on T1-weighted imaging, leptomeningeal enhancement, ventriculomegaly, and punctate areas of abnormal enhancement within the cerebral and cerebellar hemisphere on gadolinium-enhancing T1 imaging, and a hyperintense signal on T2-weighted images. There was a significant correlation between severity of headache, cerebrospinal fluid (CSF) pleocytosis, and CSF and blood eosinophilia with MRI signal intensity in T1-weighted imaging (P < 0.05). Eosinophilic meningitis produced by A. cantonensis needs to added to the list of causes of hyperintense basal ganglia lesions found on T1-weighted MRI scans in tropical countries.

Adult↗
PubMedDate not supplied

[The structural organization of the snail sensory systems].

In the paper are reviewed the author's data on the structure of peripheral nervous system of the body wall, gravitational organs--statocysts, eyes, and organs of distant chemoreception--ommatophors, or posterior head tentacles, of the snails Helix vulgaris and Helix pomatia. Localization in the CNS of central parts of the main sensory systems is shown and some structural characteristics of them are described. The data on the organization of the procerebrum which takes part in processing of information from the receptors of the head tentacles are presented. By some morphological features the procerebrum may be considered as one of the highest associative centers of the snails. The data under consideration were obtained by means of silver impregnation by Golgi, retro- and anterograde infusion of CoCl2, horseradish peroxidase and Lucifer yellow into the nerves, as well as by means of a number of other classical histological techniques.

Animals↗
PubMed1992

Characteristics of outward current induced by application of dopamine on a snail neuron.

1. A closer characterization of the potassium channel opened by the application of dopamine (DA) on an identified Helix pomatia neuron was attempted. The effect of K+ channel blockers (TEA and 4-AP) on the DA-induced current was examined. The results indicate that the channel opened by DA does not share the pharmacological properties of other snail neuron K-channels. 2. The I-V relation for IDA was successfully fitted by the Constant Field equation except below the reversal potential where the current was smaller than expected. The assumption that DA binding is voltage-sensitive is supported by the increment of the Hill coefficient with hyperpolarization (from nH approximately equal to 1 to nH approximately equal to 2). 3. The presence of the phosphodiesterase inhibitor IBMX does not affect the DA induced outward current. However, the assumption that the snail neurons' DA receptor belongs to the D2 class is in contrast to the antagonistic effects of ergot alkaloids which, in mammalian neurons, are competitive antagonists of D1 receptors. 4. The examination of the voltage-sensitivity of the blocking action of the ergot alkaloid (Bromoergocryptinine) revealed that it does not compete with DA for the same binding site as in mammalian D1 receptors.

Animals↗
PubMed1961

The control of snail hosts of bilharziasis and fascioliasis in Southern Rhodesia.

The authors review the experimental work that has been done since the Second World War on the use of chemical molluscicides in Southern Rhodesia and describe the development of a co-operative snail control campaign involving local landowners and various Government departments. In 1959 and 1960 efforts were concentrated on four large-scale experiments to test the methods of application of copper sulfate, sodium pentachlorophenate and Bayer 73 under a variety of climatic and physiographic conditions.From this work the authors conclude that it would appear possible and practicable to control vector snails in natural water courses and reservoirs in savannah areas of Central Africa to a degree at which it is thought that transmission of bilharziasis from man to man and of fascioliasis from animal to animal does not take place.

Animals↗