Motohito Sano

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.

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.

Differential establishment and survival of Hymenolepis diminuta in syngeneic and outbred rat strains

Experimental Hymenolepis diminuta infection was carried out in inbred strains of rats (F344/N, JAR-2, LOU/M, TM, DA and DA-bg/bg) and outbred Wistar rats. All strains became infected with this cestode, but clear strain-dependent variation in the susceptibility to H. diminuta infection was observed. Marked differences in worm persistence and worm weight were found at 6 weeks post-infection in TM and DA rats. These strains would be useful to clarify the interactions between H. diminuta and its rat host.

Studies on chemotherapy of parasitic helminths: Effects of avermectin Bla on Angiostrongylus Cantonensis in rats

Abstract The in vivo effects of avermectin Bla against Angiostrongylus cantonensis in rats were examined. Two distinguishable effects of this drug were suggested; a paralyzing effect against adult worms and a direct vermicidal effect against larval worms. When the drug was given intraperitoneally at 0·01 or 0·1 mg/kg at 6 weeks after infection, a sustained paralysis of worms by this drug was suggested from the following aspects; the change of the first stage larval count in feces, histological observations of lung tissues of the host and the reproductive system of female worms, and the motility of recovered worms in vitro . However, no direct vermicidal effect was observed in this treatment, because there was no significant difference in the recovery rate of worms from that of control rats. On the other hand, when the drug was given orally at a dose of 1·0 mg/kg at 3 days after infection (larval stage treatment), a significant reduction in the recovery rate of worms was observed compared to those in the adult stage treatment (drug administration at 7 weeks after infection) and control groups.

Effects of Avermectin Bla on the motility of various parasitic helminths

Using an isotonic transducer recently devised in Japan, it was observed that Avermectin Bla, a new anthelmintic, caused paralyzing effects onAngiostrongylus cantonensis andMetastrongylus elongatus at concentrations of more than 3.6×10−18 M.

Effects of mebendazole onAngiostrongylus costaricensis in mice, with special reference to the timing of treatment

Mebendazole was given to mice infected withAngiostrongyls costaricensis at a single dose of 5 mg/kg at 6, 11, 16 or 21 days post-infection (p.i.) and in five successive doses at 5 mg/kg daily at 6, 11 or 16 days p.i. The effects were comparatively assessed by examining various parameters in host mice and worms. As a whole, the effects of mebendazole were caused more conspicuously by five successive treatments than by a single treatment. In both treatment modalities, the effects were more remarkable in earlier treatments, and nearly complete effects were caused by five successive treatments before 15 days p.i. These results suggest that the inhibition of egg formation and/or oviposition will inhibit the pathological changes caused in the disease byA. costaricensis, especially before the onset of the changes.

Effects of diethylcarbamazine on the motility ofAngiostrongylus cantonensis andDirofilaria immitis

Effects of piperazine derivatives, especially of diethylcarbamazine (DEC) on adultAngiostrongylus cantonensis andDirofilaria immitis were examined. Piperazine (3×10−5–10−4M) paralyzedA. cantonensis and the action was antagonized by picrotoxin. 1,1-dimethyl-4-phenylpiperazinium iodide (DMPP) (10−5–10−4M) caused contraction but little effect was produced by strychnine. An inhibitory effect on untreated preparations was caused by lower concentrations (3×10−6–10−5M) of diethylcarbamazine citrate (DEC) and also on the preparations contracted by eserine. A stimulatory effect was also seen when higher concentrations (10−4–3×10−4M) of this drug were applied to both preparations. The inhibitory action of DEC was antagonized by gabergic antagonists such as picrotoxin and bicuculline, but not by α-adrenergic antagonists like dibenamine and phentolamine. When the worm preparation was paralyzed by strychnine or hexylresorcinol (inhibitors of the release of acetylcholine in this worm), the stimulatory effect of DEC was blocked, but pyrantel (a nicotinic cholinergic agonist) contracted the paralyzed preparation. However, the effect of DEC onD. immitis (10−7–3×10−4M) was inhibitory, and this action was also antagonized by picrotoxin. These results suggest that the DEC inhibitory and stimulatory action is through the gabergic and cholinergic mechanisms in adultA. cantonensis andD. immitis.

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 inAngiostrongylus cantonensis.

Studies on chemotherapy of parasitic helminths (IX). Effects of praziquantel on the motility of various parasitic helminths and isolated host tissues

Praziquantel (PQ) caused spastic and/or paralytic actions on the motility of various parasitic helminths and isolated host tissue preparations, through a neuropharmacological mechanism.

Isolation and identification of paramyosin from liver fluke muscle layer

Abstract 1. 1. The ultrastructure of fluke muscle layer investigated with the electron microscope was revealed to be similar in type to lamellibranch muscle of mollusca, classified as “paramyosin smooth muscle”. 2. 2. Paramyosin-like protein was extracted and purified from the fluke muscle layer. 3. 3. The amino acid composition and the subunit molecular weight of this protein were characteristically similar to those of the known paramyosins. 4. 4. Paracrystals with an axial periodicity of about 750 A were formed, but those with 145 A periodicity were not formed.