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1.
The molluscicide Frescon (N-(triphenylmethyl)morpholine) induces prolonged, irreversible contractions (contractures) in the isolated heart ventricle, penis retractor, and foot muscles of the aquatic snail Lymnaea stagnalis. It also causes contracture of the penis retractor muscle, but not the heart ventricle, of the terrestrial snail Helix aspersa. Since Frescon-induced contracture is not accompanied by a depolarization of the sarcolemma of Lymnaea heart ventricle muscle cells, it is suggested that the action of this molluscicide is associated with a membrane potential-independent activation of the contractile machinery. The rapid response of Lymnaea musculature to Frescon suggests that the direct contracture-inducing action of this molluscicide could explain its toxicity to the whole animal.  相似文献   

2.
The action of the molluscicide Frescon, which induces contractures in smooth and cross-striated muscles of the freshwater snail Lymnaea stagnalis, was compared with the action of caffeine. The results indicate that the latter agent promotes contractions in Lymnaea muscles by releasing Ca2+ from intracellular stores. Such a release could not be attributed to the action of Frescon. Furthermore, the molluscicide did not appear to alter muscle function at the level of the contractile apparatus as it did not affect the time course of caffeine-induced contractions. These results favor the hypothesis that Frescon increases sarcolemmal Ca2+ permeability.  相似文献   

3.
The molluscicide Frescon induces irreversible contracture in smooth and cross-striated muscles of the freshwater snail Lymnaea stagnalis. This contracture can be inhibited or reversed by elevated Mg2+ and reduced Ca2+ concentrations, by the heavy metals Ni2+, Co2+, and Mn2+, by the rare earth La3+, and by the calcium channel blocker D-600. The removal of extracellular Ca2+ also prevents the expression of Frescon action. These results are consistent with the hypothesis that Frescon causes an increase in the Ca2+ permeability of the sarcolemma.  相似文献   

4.
Although the molluscicide Frescon is a strong neurotoxin to the Lymnaea stagnalis central nervous system in vitro, it is probable that the exposure of the whole animal to this molluscicide fails to result in central nervous system abnormalities: Frescon does not appear to reach the brain in sufficient quantity to disrupt its normal activity. However, only those Frescon analogs found to be neurotoxic were molluscicidal, suggesting some related mode, if not site, of action. Frescon and its analogs may act by affecting excitable tissues other than the nervous system (e.g., the snail musculature) by altering certain functional and/or structural membrane properties.  相似文献   

5.
Frescon (N-triphenylmethyl morpholine) is a strong neurotoxic agent when applied to the in vitro brain of Lymnaea stagnalis. Ten Frescon analogs were tested in order to determine their degree of neurotoxicity. Nine of the ten analogs were found to be neurotoxic to a greater or lesser degree. Triphenylmethanol (a hydrolysis product of Frescon), however, did not exhibit neurotoxicity. These results form part of an investigation to determine the plausibility of the snail central nervous system being a target for Frescon action.  相似文献   

6.
The development of large complex irrigation systems presents problems of pest control which are likely to become increasingly difficult to solve by established application methods. By applying a chemical at one point in such a system use can be made of the flow of water through the system to effect the necessary distribution. This technique has been used most effectively with the molluscicide Frescon (N-tritylmorpholine). However, the complexity of many irrigation systems precludes the optimisation of the necessary rate of addition of molluscicide by any simple method. In this paper a mathematical model of an irrigation system is described which enables a detailed study of this type of application to be made with speed and economy. An analogue computer has been used to solve the equations subject to the operating conditions of the irrigation system.  相似文献   

7.
The calcium entry blockers sodium nitroprusside (10?2M) and sodium pentobarbital (5 × 10?3M) had different effects on high-potassium-induced and Frescon-induced contractures in a smooth and a cross-striated muscle of the snail Lymnaea stagnalis. This suggests that Frescon causes an increase in sarcolemmal calcium permeability by a mechanism which is different from that utilized by high extracellular potassium.  相似文献   

8.
Snail control is one of the important methods in the campaign to reduce the incidence of fascioliasis and schistosomiasis. In order to achieve this objective, the method of bait formulation containing an attractant and a molluscicide is an appropriate approach to lure the target snail population to the molluscicide. In the present study snail attractant pellets (SAP) were prepared from binary combination of carbohydrates (10 mM) and amino acids (20 mM) in 2% agar solution. These were tested on Lymnaea acuminata, an intermediate host of the digenean trematodes Fasciola hepatica and Fasciola gigantica. The behavioral responses of snails to these binary combination were examined. The fraction of snails that was in contact with the SAP at different times was used as a measure of attraction. Among all the binary combination of carbohydrates; (sucrose + starch)—72.9%, binary combination of amino acids; (proline + serine)—48.0% and binary combination of carbohydrates and amino acids; (sucrose + serine)—69.5%, emerged as the strongest attractant pellets. Toxicity of these SAP containing different concentrations of molluscicides were used as bait against the snail, L. acuminata. Thymol containing SAP emerged as the strongest bait formulation (96 h LC50 0.540%, 0.318% and 0.305%) against L. acuminata.  相似文献   

9.
The zebra mussel, Dreissena polymorpha Pallas, is a biofouling freshwater pest for which alternative control methods to the use of chlorine are sought. Metaldehyde, a molluscicide used primarily for control of terrestrial slugs, has also been shown to have efficacy and specificity in the control of aquatic snails. To test its potential for zebra mussel control, we investigated its effects on zebra mussel viability and on contractility of siphon/mantle muscle preparations in vitro. Metaldehyde caused zebra mussel mortality within 48 h at concentrations of approximately 0.1 and 0.2 g litre−1. The same concentrations of metaldehyde activated a complex, excitatory response in previously quiescent siphon/mantle preparations but did not modify the contractile responses of the preparations to acetylcholine. The relatively low level of toxicity of metaldehyde to zebra mussels, compared to its toxicity to snails and slugs, and the difficulty of applying this relatively insoluble molluscicide in the aqueous environment suggest that metaldehyde would not be an effective zebra mussel control agent. © 2000 Society of Chemical Industry  相似文献   

10.
Chemical control of the intermediate hosts of schistosomiasis, based on copper sulphate, has been practised in the Sudan Gezira since 1956. A continued use of the more recent trifenmorph blanket-treatments raises the question of eventual resistance to this molluscicide. Two collections of Bulinus truncatus (Audouin), from a treated and an untreated area of the Gezira, have therefore been subjected to laboratory rearing, bioassay and measurement of the rate of uptake of the chemical into the snail. A difference in susceptibility could be shown and this has been tentatively attributed to the rather more marked difference, in penetration rate of the molluscicide, between the two groups of snails.  相似文献   

11.
The molluscicide N-tritylmorpholine (FRESCON,
  • 1 FRESCON is a Shell trade mark.
    • trifenmorph) is used for the control of the intermediate snail hosts of fascioliasis in livestock. Laboratory and field studies have been undertaken to establish the fate of the compound following its use on pasture. Radiochemical techniques have been used under laboratory conditions to identify the potential degradation products. The major one has been shown to be triphenylcarbinol. Triphenylcarbinol was detected on pastures treated at 0.4 to 0.5 kg/ha under practical conditions but the residues of it and of the parent molluscicide were generally below 0.3 mg/kg within 8 weeks of the application. On the pasture grass half of the initial deposit of N-tritylmorpholine was lost within 1 to 3 weeks and on soils it was lost within 1 to 4 weeks. Residues could not be detected in the tissues of sheep feeding on the treated pasture. Whilst small residues (0.023 mg/kg or less) were detected in the milk of some cows feeding on the pasture soon after application they were absent (below 0.002 mg/kg) in the milk at 10 days or more from treatment.  相似文献   

    12.
    Ginkgolic acids (GAs) from the leaves and sarcotesta of Ginkgo biloba L. represent a new kind of molluscicide agent. To date, the mechanism(s) for the observed molluscicidal activity remains largely unknown. Since GA-C13:0 has effectively inhibited snail mobility, we examined the effects of the compound on mitochondrial function and gene expression as compared to niclosamide. Snail mitochondrial damage induced by GAs was tested using transmission electron microscopy (TEM) and gene-expression profiling of five mitochondrial enzymes using real-time PCR. GA-C13:0 was found to have a pronounced effect on snail mitochondria with gross ultrastructural changes. In addition, GA-C13:0 was also found to inhibit the gene expression of four mitochondrial enzymes including cytochrome c oxidase, adenosine triphosphate (ATP) synthase, cytochrome b and dihydronicotinamide adenine dinucleotide (NADH) dehydrogenase. In contrast, niclosamide did not show such effects on mitochondrial function and gene expression, suggesting that the molluscicidal activity of GA-C13:0 and niclosamide differed. Our results imply that snail mitochondria are a potential target for the molluscicidal activity of ginkgolic acids.  相似文献   

    13.
    Chloride ion-selective microelectrodes were used to measure the intracellular chloride activity of Lymnaea stagnalis neurons. Values ranged from 3 to 23.5 mM in different cells. Neurons with inhibitory postsynaptic potentials had significantly lower chloride activity levels than cells without such inputs. Bicarbonate-buffered saline reduced intracellular chloride levels compared with those in Hepes-buffered saline. Frescon (Shell Chemicals) produced an increase in intracellular chloride activity in 14 out of 22 neurons (mean rate of increase, 0.09 mM/min). This increase was insensitive to changes in the membrane potential: the rate of increase was reduced in bicarbonate-buffered saline. The mechanism of Frescon action is discussed in terms of a bicarbonate/chloride exchange mechanism.  相似文献   

    14.

    Background

    In Kenya, rice (Oryza sativa L.) is mainly produced under irrigation by small-scale farmers. Mwea irrigation scheme (MIS) in Kirinyaga County accounts for 80–88% of rice production. Here, rice is the main source of livelihood and a source of revenue generation for the county. However, a recently established invasive freshwater snail, Pomacea canaliculata (Lamarck) (family: Ampullariidae), a species of apple snail, presents a serious threat to rice production.

    Results

    Household surveys, focus group discussions and key informant interviews highlight apple snail as a serious problem in MIS. Households that observed at least a moderate level of infestation (>20% of cultivated area) experienced significant reductions in rice yield (~14%) and net rice income (~60%). Farmers reported increased use of chemical pesticides for management of apple snail. In addition, the cost of hired labor for physical removal of egg masses and snails is resulting in substantial negative effects on net income. Farmer age, area of land owned, responsibility for decision-making, receipt of extension advice, training, and membership of a farmer organization, were all statistically significant variables to explain farmers awareness of the need for area-wide apple snail management.

    Conclusion

    Strategies to limit the spread of apple snail are urgently needed. A Multi-Institutional Technical Team (MITT) has been established to spearhead management efforts and consolidate advice to farmers on how to manage apple snail. However, without action to mitigate spread, the consequences could be disastrous for rice production and food security in Kenya, and for other rice growing regions across Africa. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.  相似文献   

    15.
    The cyclic depsipeptide PF1022A, given orally to mice, showed very good anthelmintic activity against Heligmosomoides polygyrus and Heterakis spumosa at 50 mg kg−1. In vitro, PF1022A was very active against Trichinella spiralis and had good activity against Nippostrongylus brasiliensis at 1 μg ml−1. An 18-membered enniatin analogue, JES 1798, showed good activity only against N. brasiliensis at 10 μg ml−1. The optical antipode of PF1022A had poor activity even at 100 μg ml−1. The effects of PF1022A on the membrane potential and input conductance of somatic muscle of Ascaris suum were examined using a two-microelectrode current-clamp technique. PF1022A did not antagonize the effects of the selective nicotinic agonist levamisole. PF1022A and an analogue, JES 1798, but not the PF1022A antipode, produced a small time-dependent increase in input conductance associated with no potential change. The increase in input conductance did not occur in the Cl−-free bathing solution, suggesting that the increase in input conductance was mediated by Cl− ions. The addition of high concentrations of Ca2+ to the preparation after the addition of PF1022A did not lead to production of Ca2+-activated Cl− channels, suggesting that its mode of action was not that of a Ca2+ ionophore. The mechanism by which the cyclic depsipeptide might increase the Cl− conductance is discussed.  相似文献   

    16.
    The neuropeptide AF2 has a complex set of actions on the dorsal muscle strip of Ascaris suum, including a potentiation of the acetylcholine-stimulated muscle contraction. Caffeine at 100 μm and 5 mm inhibited this potentiation, as did 100 μm theophylline in two out of six studies. The cyclic-AMP-potentiating compounds IBMX, dibutyryl cAMP and forskolin had no effect on the AF2-induced potentiation of the acetylcholine-stimulated muscle contraction. These preliminary data suggest that the potentiating action of AF2 is not mediated by a cAMP pathway.  相似文献   

    17.
    Three previously reported methanesulfonate insecticides, 6-isobutylthio-2-pyridyl methanesulfonate ( I ) and its sulfoxide ( II ) and sulfone ( III )analogues were examined in two insect species Lucilia cuprina and Blattella germanica and in tissues from vertebrates. The results of B. germanica tests and cholinesterase assays confirmed the insecticidal activity of the compounds, with cholinesterase inhibition being the most likely mode of insecticidal action. The inactivity of the sulfide I and sulfoxide II in vertebrate in-vitro studies may indicate that conversion, in vivo, of the sulfide and sulfoxide methanesulfonates to the sulfone ( III ) is a requirement for activity. In mouse toxicity tests, matching high toxicity was observed for the alkylthio-, alkylsulfoxy- and alkylsulfone analogues indicating fast metabolic oxidation of the injected alkylthio- and alkylsulfoxy-compounds. However, in in-vitro tissue tests, the sulfone, although active, did not exhibit the characteristic pharmacological profile of the standard acetylcholinesterase inhibitor, physostigmine. The sulfone demonstrated a mixed action, with indications that it acts as an inhibitor of specific cholinesterase isozymes, or that it may modify responses at cholinoceptors.  相似文献   

    18.
    Abstract

    The golden apple snail, Pomacea canaliculata (Lamarck, 1822) (Mesogastropoda: Pilidae), has recently been introduced to several Asian countries where it has unexpectedly developed into a pest of rice. Reasons for the introduction as well as the economic and ecological impact of the snail are described. Most farmers have resorted to chemical control, with implications for human health and the environment. Integrated snail management practices are summarized including the use of the snail as a valuable aquatic resource. It is concluded that research on control strategies is urgently needed but requires sound knowledge of the ecology of the snail in its natural habitat.  相似文献   

    19.
    The structure-activity relationships between five amides previously isolated from the root extract of Piper guineense Schum and Thonn were studied. The methyl-terminated amides, pellitorine and kalecide, were found to be more polar and caused higher knockdown, but showed less lethal action against insects than their methylenedioxyphenyl-terminated counterparts, pipercide and guineensine. Guineensinamide showed weak activity and this was correlated with higher unsaturation and the presence of a pyrrolidyl group in the molecule. There was an association between the polarity of the amides and the recovery of the insects from their effects, much more recovery being observed with the methylterminated than with the methylenedioxyphenyl-terminated amides. Electrophysiological investigations of the effects of pellitorine and pipercide on miniature excitatory postsynaptic potentials (MEPSPs) from the locust retractor unguis nerve-muscle preparation showed that the amides caused a reduction in both the frequency and amplitude of MEPSPs, pipercide being between 100 and 1000 times more effective than pellitorine. An action of the amides on presynaptic transmission is suggested. The effects of pipercide and pellitorine on the isolated nerve-muscle preparation were correlated with the symptoms of poisoning at the whole animal level.  相似文献   

    20.
    The hydrolysis rates, particle sizes in suspension, and the relative lipophilicity of Frescon and its analogs were determined and compared with their neurotoxic and molluscicidal effectiveness. The hydrolysis rates of these compounds were closely correlated to their neurotoxicity, and, with one exception, to their molluscicidal effectiveness as well. The aberrant behavior of the one analog could not be attributed to a retarded penetration rate or an excessively large particle size in suspension. There appears to be some, as yet, unidentified factor which determines the molluscicidal activity of this analog. However, it is likely that both neurotoxicity and molluscicidal action are the result of a nucleophilic displacement reaction, although at different targets. Also, differences in the relative molluscicidal effectiveness of the Frescon analogs at different concentrations were possibly due to variations in particle size, which appears to be a function of the type and amount of emulsifier used.  相似文献   

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