The effect of ammonium nitrate on the residual nitrogen content in the hemolymph of the pulmonate snail Planorbarius purpura (Mollusca: Pulmonata: Bulinidae) normally and in trematode invasion

The effect of the ammonium nitrate (concentrations 2000, 4000, 6000 mg/l) on the content of urea, urea nitrogen and residual nitrogen in the haemolymph of normal Planorbarius purpura and in trematode-infected individuals. It is shown, that stimulation of metabolic processes is more expressed in uninfected specimens, while the trematode-infected ones, the protective process is strained. When the toxin concentration reaches 6000 mg/l, the trematode infected specimens enter the phase of depression with 3.73% hyponitrogen level.     

Factors affecting the cholinomimetic activity of alkyltrimethylammonium compounds in experiments on isolated neurons of the mollusk Planorbarius corneus

It has been shown that the elementary current is independent whereas the duration of channel opening is slightly dependent on the number of methylene groups (from 1 to 9) in the molecule of alkyltrimethylammonium compounds. However, substances with more than 4 methylene groups exhibit lower cholinomimetic activity (i.e. the ability to increase the membrane current) and higher values of Q10 for the reaction with cholinoreceptor. It is suggested that lower activity of these compounds is due to a low rate of formation of a complex with cholinoreceptor because of the higher potential energy barrier.     

Effect of inhibitors of energy metabolism on potassium accumulation in the neurons of the mollusk Planorbarius corneus

Studies have been made of the effect of inhibitors of energy metabolism on maintenance of Na and K concentrations, as well as on accumulation of Rb (as an analogue of K) in single neurones of the mollusc P. corneus. Concentrations of Na, K and Rb in cells were determined by X-ray spectral microanalysis. Monoiodoacetate, an inhibitor of glycolysis, decreased concentration gradients of K and Na between cells and the external medium, decreasing accumulation of Rb. Cyanide, which is used as an antirespiratory drug, did not significantly affect neither K and Na content, nor Rb accumulation in the neurones of the mollusc, these data being different from those obtained on the nervous tissue of other animals. Monovalent T1 which is capable of inhibiting the respiratory chain and destroying mitochondrial structure, significantly inhibited Rb accumulation in the neurones. The decrease in accumulation of Rb by monoiodoacetate and T1 was less significant as compared with that produced by a specific blocker of Na/K-pump, ouabain.     

The influence of the trematode invasion on the average daily rations and electoral nourishment of Planorbarius corneus (Mollusca: Pulmonata: Bulinidae)

The influence of the Trematode invasion on the average daily rations and electoral nourishment of the two size groups in the great ramshorn snail Planorbarius corneus, "young" (12-24 mm in diameter) and "old" (24-36.5 mm in diameter), have been investigated.     

Demonstration of different type cholinoreceptors on the membrane of an isolated Planorbarius corneus mollusk membrane

In experiments on isolated and identified neurones of the pedal ganglion of the gastropod mollusc P. corneus, it was demonstrated that biphasic response to ACh may be obtained both to superfusion and electrophoretic application. Fast (depolarizing) phase may be imitated by a nicotinomimetic drug, suberyldicholine, and blocked by d-tubocurarine. These data indicate that this phase results from activation of nicotinic cholinoreceptors. Slow (hyperpolarizing) phase may be evoked by a muscarinomimetic, dioxolane F-2268, which is taken as an indication of the muscarinic nature of cholinoreceptors responsible for this phase. Experiments on completely isolated neurones directly show that both kinds of cholinoreceptors belong to the same neurone. Biphasic pattern of the response depends on the level of the membrane potential and on the conditions of ACh application. The fast phase is more evident at membrane hyperpolarization, the slow one--at depolarization. The fast phase is more readily obtained by superfusion by high concentrations of ACh or at close position of electrophoretic micropipette to neuronal surface, whereas the slow phase may be easily obtained by superfusion with low concentrations of ACh or when the micropipette is not attached so closely to the cell.     

Effect of iron chloride (III) on hematological status of the Planorbarius corneus (Mollusca: Gastropoda: Bulinidae) in normal snails and during infection with trematode parthenites

The effect of three ferric chloride concentrations (100, 200, 300 mg/l) on the acid-alkaline balance of haemolymph and haemoglobin content in Planorbarius corneus under normal conditions and in the case of infection with parthenites and larvae of Echinoparichium aconiatum was examined. In the medium with an effective concentration of ferric chloride, all snail specimens proved to have acidified haemolymph, by 40-50% in infected samples and 80-85% in uninfected ones. Statistically reliable differences in the haemoglobin content in the haemolymph of infected and uninfected specimens between the control and test media were absent, that proves a weak toxic effect of ferric ions on P. corneus.     

Changes in the neuronal membrane potential of the mollusk Planorbarius corneus under the action of cardiac glycosides

In experiments on isolated neurones from the gastropod mollusc P. corneus, strophantin and digoxin in low concentrations produce slow hyperpolarization, in higher ones--depolarization; at concentrations about 1 mM, hyperpolarization was more evident. In all cases, the decrease in membrane resistance was observed. Presumably, membrane permeability for potassium ions increases. During application of the drugs in concentrations 10-100 microM, hyperpolarization may be masked by depolarization due to block of Na,K-pump. Higher concentrations, increasing potassium permeability of the membrane, may result in substitution of depolarization by hyperpolarization.     

The reaction of the N-cholinoreceptors of the isolated neuron of the mollusk Planorbarius corneus to polymethylene-bis-trimethylammonium compounds

Experiments have been made on isolated giant neurones of the mollusc Planorbarius corneus using clamp technique at temperatures 10 and 20 degrees C. The effect of polymethylene-bis-trimethylammonium compounds with 7-18 methylene groups in the molecule (C7...C18) on N-cholinoreceptors with chloride ionic channels was investigated. All these drugs were found to be agonists. Their cholinomimetic activity depends on the number of methylene groups (up to a certain extent) in their structure. This finding stands true also for skeletal muscles of frog and chick, as it had been shown in our earlier experiments. Analysis of membrane current fluctuations showed that the elementary current, the channel opened time, temperature coefficient (Q10) of the neuronal response to application of an agonist and the calculated Q10 of the reaction rate of the agonist with cholinoreceptor did not significantly differ for C8...C18 from the reaction rate of the agonist with cholinoreceptor. As compared with C8, C12...C18 exhibited 30 ... 40 times higher cholinomimetic activity, all other parameters in them being similar. Presumably, this difference is explained by concentrating capacity of C12...C18 at the membrane site because of their higher hydrophobic properties.     

Effect of cryoprotectants on the activity of hemolymph nucleating agents in physical solutions

The ability of 11 different organic solutes in physical solution to mask the effect of nucleating agents from hemolymph of freezing tolerant insects was tested. The masking effect was tested by measuring the supercooling points of samples with various solute concentrations, with and without hemolymph. Hemolymph was obtained from freeze-tolerant Eleodes blanchardi tenebrionid beetles.The depressive effect of the solutes on the supercooling points was nearly equivalent to the corresponding melting point depression, indicating that the depression was due only to the colligative properties of the solutes. Thus, no ability for nucleator masking was demonstrated.     

Effect of different concentrations of heavy metal ions on the normal physical and chemical characteristics of the hemolymph of Palanorbarius purpura (Mollusca: Bulinidae) in the norm and during a trematode infection

Short-term simultaneous effect of high concentrations (LC25, LC50, LC75) of heavy metal ions. (Cu2+, Zn2+, Cd2+ and Pb2+) and infection with trematode partenites Echinoparyphium aconiatum onto haemolymph of mollusk has been investigated. It was noted that low doses of toxicant (2.5 and 10 maximum admitted concentrations) have variable effect. In infected molluscs the concentration of haemoglobin decreases, while in intact ones it increases. In relation to this index, it was found, that the ion Cu2+ is highly toxic, Zn2+ and Cd(2+)--toxic, Pb(2+)--moderately toxic.     

Effect of phenol and pesticides on the physicochemical properties of the hemolymph in fresh-water gastropod mollusks (Gastropoda, Pulmonata) infected by trematode parthenitae

The effect of solutions of phenol (100, 250, 400 mg/l), copper sulfate, carbophos and bazudine (0.01, 0.1, 1.0 mg/l) on physical and chemical properties of haemolymph of Lymnaea stagnalis (L.) and Planorbarius corneus (L.) infected with parthenitae of trematodes was studied. Haemolymph viscosity decreases and its active reaction shifts to weakly acid one. Haemolymph density decreases only in solutions of carbophos and bazudine. With heavy infection the concentration of haemoglobin in haemolymph of P. corneus does not change under the effect of phenol but the total volume of haemolymph reduces considerably.     

Effect of a single magnetic field pulse on the electric activity of mollusk neurons

The influence of a single impulse of magnetic field (MF) of triangular shape of neuron electrical activity (EA) of Limnaea stagnalis registered intracellulary was studied. The dependence of the neuron reaction on the MP speed changing has been found. The effective values of speeds of impulse fronts were within 0,1 to 10,0 mT/c range. The threshold amplitude of MF impulse for most neurons was between 0,1 and 1,0 mT. With increasing MF amplitude up to 10,0 mT the efficiency of the effect does not essentially increase.     

Changes in the sulfhydryl group content in the hemolymph of freshwater gastropods infected with trematode parthenitae and larvae

A study was conducted on the changes in sulphhydryl groups in the haemolymph of Lymnaea stagnalis infected with partenites of Opisthioglyphe ranae, Planorbis corneus infected with partenites of Cotylurus cornutus and females of Viviparus viviparus infected with partenites and larvae of Echinoparyphium petrowi. At the infection in the haemolymph of hosts were recorded statystically reliable changes in the protein sulphhydryl groups which are blocked by toxines excreted by the parasites. The reduction rate in the content of these substances depends on the localization of the parasites and infection intensity of the hosts.