Strain-dependent differences in susceptibility of mice to experimental Angiostrongylus costaricensis infection.

Experimental Angiostrongylus costaricensis infection was carried out in inbred strains of mice (C57BL/6 BALB/c, DBA/2 and C3H/He). All strains became infected with this parasite. Marked differences in mortality and in worm burden were found among inbred strains of mice tested. A significant reduction was shown in worm length from mice compared to that from cotton rats.

In vivo efficacy of levamisole against larval stages of Angiostrongylus cantonensis and A. costaricensis.

Anti-larval effects of levamisole were examined on A. cantonensis in rats and A. costaricensis in mice. 1) In rats inoculated with 40 infective larvae of A. cantonensis: Compared with a non-treated control group, a significant reduction in number of worms recovered was seen in the group receiving a single dose of 1.0 mg/kg or more. A significant decrease in host lung-body weight ratio was seen in the group receiving drug of 3.0 mg/kg or more. 2) In mice inoculated with 20 infective larvae of A. costaricensis. In the non-treated control group, a severe loss in body weight and death of host animals were observed. A single dose of 30 mg/kg on 3, 4 or 5 days post-infection remarkably inhibited these changes. At 30 mg/kg for 3 or 7 days levamisole was more effective than a single dose of the drug. These results suggest that levamisole has conspicuous in vivo effects against larval stages of A. costaricensis as well as A. cantonensis.

Motility and drug susceptibility of Angiostrongylus cantonensis developing from gamma-irradiated first-stage larvae.

The effects of neuropharmacological agents on the motility of irradiated and non-irradiated Angiostrongylus cantonensis adult females were studied. GABA induced complete paralysis in non-irradiated and 5,000 R-irradiated worms, but caused only slight paralysis on 10,000 R-irradiated worms. The paralytic effect of GABA was antagonised by picrotoxin. The reason for low susceptibility of heavily irradiated worms to GABA is not known. There was no difference in susceptibility of non-irradiated and irradiated worms to other neuropharmacological agents including eserine, phenylephrine and dibenamine.

Late development and fertility of adult worms derived from gamma-irradiated first-stage larvae of Angiostrongylus cantonensis.

Effects of gamma ray irradiation on the first-stage larvae of Angiostrongylus cantonensis were studied. Compared to the non-treated controls, infection of rats with third-stage larvae which developed from irradiated first-stage larvae resulted in reduced recovery rates of adults. There was also a change in the male-female adult worm ratio and a reduction in larval output per female in relation to increasing irradiation dosage. Morphological changes in the adults were noted.

Effects of milbemycin D on adult Angiostrongylus cantonensis in rats.

Effects of milbemycin D against adult Angiostrongylus cantonensis in rats were examined. The first-stage larval counts in rat faeces (larvae per gram of faeces per female worm recovered, LPG/female) were most conspicuously reduced in the group treated with nine consecutive weekly doses of 5.0 mg/kg. The effect was more marked in the group treated with five or ten successive daily doses of 5.0 mg/kg than the group treated with a single dose of 25.0 or 5.0 mg/kg. Host lung-body weight ratio and number of recovered worms were reduced significantly only in the group treated with five or ten successive daily doses of 5.0 mg/kg. These results suggest that the action of milbemycin D on the reproductive system of the worms might be differentiated from its killing action. The in vitro motility of females recovered from rats medicated with nine consecutive weekly doses of 5.0 mg/kg was inhibited, and almost all females and males were semitransparent and colourless. Results obtained from sectioned worms showed little content in their digestive tracts and uteri. In addition, there were few eggs and first-stage larvae in the lung tissues of treated rats. These suggest that milbemycin D affects the reproductive functions of the worms through an indirect mode of action including paralysis and inhibition in food intake and energy and/or synthetic metabolism.

Pathogenic factors in the later pulmonary phase of Angiostrongylus cantonensis-infected rats.

In rats infected with different worm burdens of Angiostrongylus cantonensis, the loss of body weight was proportional to the increasing dose of infection. Body weight was correlated inversely with female worm burden (r = -0.669), the sum of mean numbers of larvae per gram of faeces (LPG) (r = -0.527) and lung weight (r = -0.761). Lung weight was positively correlated with female worm burden (r = 0.785) and the sum of mean numbers of LPG (r = 0.685). On the other hand, in rats infected with larvae developed from gamma-irradiated first-stage larvae (Experiment B) or infected rats treated with the drug ivermectin (Experiment C), body weight was inversely correlated with the sum of mean numbers of LPG (r = -0.798, Experiment B; r = -0.670, Experiment C) and lung weight (r = -0.862, Experiment B; r = -0.812, Experiment C), but not with female worm burden. Furthermore, lung weight was positively correlated with the sum of mean numbers of LPG (r = -0.783, Experiment B; r = 0.899, Experiment C), but not with the female worm burden. From these results, it is concluded that in the later pulmonary phase of infection in rats the pathogenic effects may be closely related to the increasing number of first-stage larvae produced by female worms.

Infectivity and development of the gamma-irradiated first stage larvae of Angiostrongylus cantonensis.

Effects of gamma-ray irradiation on the first-stage larvae of Angiostrongylus cantonensis were studied. There was a significant reduction in the infectivity of the 10,000 R-irradiated larvae to intermediate host snails compared to other groups. In the final host infection, both the worm populations and worm body length of irradiated groups differed markedly from those of the non-irradiated control.

Angiostrongylus cantonensis: paralysis due to avermectin B1a and ivermectin.

Paralysis due to avermectin B1a and ivermectin of Angiostrongylus cantonensis was compared to that of phenylephrine (an alpha-adrenergic agonist) and strychnine (a cholinergic inhibitor). The paralyzing action of ivermectin (2.5 X 10(-9) g/ml) was inhibited by the single, simultaneous addition of picrotoxin (3 X 10(-5) M), whereas the effect of the drug (2.5 X 10(-7) g/ml) was reversed only when picrotoxin was given with cholinergic spasmogens such as pyrantel and eserine. Bicuculline (3 X 10(-5) M) had a similar antagonistic effect for picrotoxin, but bicuculline was less effective. The paralyzing action of avermectin B1a (3.6 X 10(-14) M, 3.0 X 10(-14) g/ml) was antagonized only when picrotoxin was given with cholinergic spasmogens such as pyrantel, eserine, and N-methylcytisine (N-MC), or alpha-adrenergic antagonists such as phentolamine and dibenamine. On the other hand, the paralyzing action of strychnine (3 X 10(-6) M) or phenylephrine (3 X 10(-5) M) was relatively uninfluenced by picrotoxin, but was antagonized by pyrantel and N-MC or dibenamine. These results suggest that a gabergic mechanism is involved in the paralyzing action of ivermectin, as well as avermectin B1a, in A. cantonensis.

Effects of temperature on the larval development of Angiostrongylus cantonensis in the intermediate host, Biomphalaria glabrata.

The effects of temperature on the larval development of Angiostrongylus cantonensis in Biomphalaria glabrata were studied under controlled conditions. When B. glabrata were maintained at different, constant temperatures, the first-stage larvae developed to third-stage larvae between 20 degrees and 31 degrees C. The velocity of development to the third-stage in the snail depended on the relationship, Y = -0.1281 + 0.0081 X (Y velocity of development; X rearing temperature). The "threshold of development" was 15.8 degrees C and the thermal constant 123 degree-days. It is concluded that there might be a possibility of A. cantonensis spreading to temperate regions in the world, if, in addition to the temperature, other factors allowed the completion of the life cycle of this worm.

Fe-rich corpuscles in Diplogonoporus grandis detected using X-ray microanalysis.

An energy dispersive X-ray microanalysis of the individual corpuscles in the parenchyma of Diplogonoporus grandis was performed for the chemical identification of their inorganic composition. Besides the corpuscles showing distinct peaks for calcium, a major inorganic element, a type of corpuscle showing distinct peaks for iron was observed. It is suggested that it is necessary to examine not only the whole corpuscles isolated but also individual corpuscles in the tissue when studying the nature and roles of corpuscles in cestodes.

Studies on chemotherapy of parasitic helminths (XVIII). Mechanism of spastically paralyzing action of pyrantel in Angiostrongylus cantonensis.

Pyrantel tartrate caused spastic paralysis through stimulating nicotinic cholinoceptors in Angiostrongylus cantonensis.

Studies on chemotherapy of parasitic helminths (VII). Effects of various cholinergic agents on the motility of Angiostrongylus cantonensis.

Effects of various cholinergic agents on the motility of Angiostrongylus cantonensis were studied to define the neuropharmacological properties of this worm. Stimulation of the motility and/or contraction were shown by eserine, ACh, carbachol, nicotine, DMPP, pyrantel, and Ba2+, but not by pilocarpine and McN-A-343. Contraction was similarly observed by these agents in the preparations paralyzed with praziquantel. Paralysis was caused remarkably by d-tubocurarine and slightly by succinylcholine, while the contraction induced by eserine and DMPP was little influenced by these drugs. Both the motility and the eserine-induced contraction were little influenced by hexamethonium, but stimulated remarkably by atropine. Though hemicholinium-3, morphine, and picrate showed little effect, guanidine stimulated remarkably the motility and also the eserine-induced contraction. The stimulatory action of guanidine was antagonized by strychnine. Strychnine paralyzed the motility, and the eserine-induced contraction was antagonized by the pre- and post-treatment with strychnine. From these results, it is suggested that the excitatory cholinergic mechanism in A. cantonensis is nicotinic, and it is basically similar to that reported in Ascaris suum.

Studies on chemotherapy of parasitic helminths (VIII). Effects of some possible neurotransmitters on the motility of Angiostrongylus cantonensis.

Effects of some possible neurotransmitters such as GABA, adrenergic drugs, and 5-HT and their antagonists on the motility of Angiostrongylus cantonensis were studied. Paralysis was caused by GABA, avermectin BIa (Av-BIa), piperazine and alpha-adrenergic agonists such as adrenaline, noradrenaline, phenylephrine, clonidine and methoxamine, but not by beta-adrenergic agonists such as isoproterenol. The paralysis by GABA or Av-BIa was antagonized by GABA antagonists such as picrotoxin and/or bicuculline with cholinergic agents such as N-methylcytisine (N-MC) or eserine. The paralysis elicited by alpha-adrenergic agonists was antagonized by alpha-adrenergic antagonists such as phentolamine and dibenamine, but not by beta-adrenergic antagonists such as propranolol. 5-HT affected the motility of A. cantonensis paralytically or spastically. The paralysis induced by 5-HT was antagonized by alpha-adrenergic antagonists such as phentolamine and dibenamine, while the contraction induced by this compound was further stimulated by N-MC, but antagonized by strychnine. Other agents such as glutamine, glycine, aspartic acid, taurine, and substance P showed little effect on the motility of A. Cantonensis. From these findings on the neuropharmacological properties of A. cantonensis, it is suggested that this worm is useful as an excellent nematodal model for the investigation of anthelminthics. In addition, this worm may also useful as one of screening models of drugs affecting the central nervous system in mammals.

Studies on chemotherapy of parasitic helminths (VI) effects of various neuropharmacological agents on the motility of Dipylidium caninum.

Effects of various neuropharmacological agents on the motility of Dipylidium caninum was studied. 5-HT stimulated the motility of D. caninum, while other drugs such as GABA, adrenaline, phenylephrine, isoproterenol, dibenamine, and propranolol showed little effect. The stimulatory action of 5-HT was antagonized by tryptophol. Stibnal caused paralysis which was blocked by the pretreatment with 5-HT. Paralytic effects were caused by eserine, dichlorovos, ACh, carbachol and DMPP, but not by pilocarpine and McN-A-343. d-Tubocurarine, hexamethonium, and atropine all showed little effect on the motility and on the paralytic action of eserine. Though guanidine showed little effect, strychnine remarkably stimulated the motility. The action of strychnine was stimulated by 5-HT but partially inhibited by tryptophol. Morphine and picrate slightly stimulated the motility, but showed little influence on the paralytic action of eserine. These two agents stimulated the paralyzed preparation by tryptophol transiently and sustainedly, respectively. These results on the cholinergic and serotonergic drugs basically showed good agreement with those reported in trematodes such as Schistosoma mansoni and Fasciola hepatica.

Experimental light infection of Angiostrongylus cantonensis in rats.

An experimental infection with a smaller number of Angiostrongylus cantonensis, using rats as hosts, was carried out. When the rats were infected with one and two larvae of A. cantonensis, the infection rates were 45.5% and 73.3% and recovery rates of the adult worms were 45.5% and 66.7%, respectively. In cases when more than three larvae were given to rats, all rats were found to be infected and recovery rates were around 70%, which is the same as in the case of infection with many larvae. The recovered worms were all mature and showed no important difference in their morphological measurements. It was concluded that the larvae of A. cantonensis were able to infect rats in small numbers, and completely develop into adult worms. It is suggested that human infection could occur in the same way.

[Studies on chemotherapy of parasitic helminths (III). Effects of tuberostemonine from Stemona japonica on the motility of parasitic helminths and isolated host tissues (author's transl)].

Effects of tuberostemonine (TS), an alkaloid from Stemona japonica, on the motility of parasitic helminths and isolated frog rectus and mouse ileum were studied. 1) TS (6.7 X 10(-6) approximately 2 X 10(-5) M) paralyzed the motility of Angiostrongylus cantonensis. 2) TS (6.7 X 10(-5) M) showed contractive effects on the motility of Dipylidium caninum and Fasciola hepatica. 3) Treatment with TS (6.7 X 10(-5) approximately 4.8 X 10(-4) M) had little effect on the motility of Schistosoma japonicum. 4) TS (6.7 X 10(-5) M) paralyzed the motility of the mouse isolated ileum preparation. 5) TS (6.7 X 10(-7) 6.7 X 10(-6) M) stimulated the twitch response induced by guanidine (2.5 X 10(-3) M) in the frog isolated rectus preparation. 6) Eserine and TS acted antagonistically on all preparations with the the exception of S. japonicum. 7) TS and strychnine were antagonistic in isolated host tissues, whereas these compounds acted similarly on parasitic helminths. Thus, it is suggested that some of the experiential effects of the crude extracts of Stemona such as the anthelmintic effects are caused through the action of TS on parasitic helminths and host tissues.

[Studies on chemotherapy of parasitic helminths (IV). Effects of alkaloids from Sophora flavescens on the motility of parasitic helminths and isolated host tissues (author's transl)].

Effects of N-methylcytisine (N-MC) and matrine (Mat), alkaloids from Sophora flavescens on the motility of parasitic helminths and isolated frog rectus and mouse ileum were studied. 1) The motility of Angiostrongylus cantonensis was affected spastically by N-MC (1.2 X 10(-6) approximately 1.2 X 10(-4) M), but paralytically by Mat (10(-5) approximately 10(-4) M). 2) The motility of Dipylidium caninum and Fasciola hepatica was affected paralytically by N-MC (1.2 X 10(-4) approximately 1.2 X 10(-3) M), but spastically by Mat (10(-4) approximately 10(-3) M). 3) Treatment with N-MC (10(-3) M) and Mat (8 X 10(-4) M) had little effect on the motility of Schistosoma japonicum. 4) Both N-MC (1.2 X 10(-5) approximately 2.4 X 10(-5) M) and Mat (10(-4) M) stimulated the twitch response induced by guanidine (2.5 X 10(-5) M) in the frog isolated rectus preparation. 5) The motility of the mouse isolated ileum preparation was affected paralytically by N-MC (1.2 X 10(-5) approximately 1.2 X 10(-4) M), but spastically by Mat (10(-4) approximately 10(-3) M). Thus, N-MC and Mat acted antagonistically on all the preparations with the exception of the frog rectus preparation. From the results on interactions between these alkaloids and known neuropharmacological agents, it is suggested that the effects of both alkaloids are elicited through a neuropharmacological mechanism in parasitic helminths and host tissues.