Experimental Final Hosts of Metagonimus Hakubaensis (Trematoda: Heterophyidae) and Their Suitability to the Fluke

Seven laboratory mammal and bird species were orally inoculated with 200–1,000 encysted Metagonimus hakubaensis metacercariae that had been isolated from naturally infected lampreys (Lethenteron reissneri) captured in Aomori Prefecture. At 8 and 15 days post-infection, adult flukes were recovered from all of the laboratory animals tested, and therefore, hamster, rat, mouse, dog, cat, chicken and quail were considered as final hosts of M. hakubaensis. Recovery rates of the fluke were higher in dogs and hamsters than in cats, rats, mice, chickens and quails. The flukes recovered from dogs and hamsters showed increased body length and higher fecundity than those recovered from the other hosts. These results indicate that the suitability of dogs and hamsters for M. hakubaensis infection is higher than that of the other laboratory animals.     

Raccoon dogs (Nyctereutes procyonoides) are the new natural definitive hosts of Metagonimus hakubaensis

The definitive hosts of Metagonimus hakubaensis are reported to be hamsters, rats, mice, dogs, cats, chickens, and quails in experimental infection and Japanese water shrews in natural infection. Here we report that raccoon dogs are new natural definitive hosts of M. hakubaensis, based on morphological and molecular analyses of Metagonimus flukes collected from the host species from Aomori Prefecture, Japan. Moreover, M. hakubaensis recovered from raccoon dogs showed higher fecundity than those recovered from Japanese water shrews. Therefore, raccoon dogs were considered as a more suitable natural definitive host of M. hakubaensis than Japanese water shrews.     

盐生植物海蓬子对不同形式的氮源的响应

Salt-affected soils are agricultural and environmental problems on a global scale. Plants suffer from saline stresses in these soils and show nitrogen (N) deficiency symptoms. However, halophytes grow soundly under saline conditions. In order to clarify the N nutrition of the halophyte Salicornia bigelovii, it was grown at several N levels (1, 2, 3, and 4 mmol L^-1), supplied in the form of NO₃^- or ammonium (NH₄⁺), under high NaCl conditions (200 mmol L^-1). NH₄⁺-fed plants showed better growth than NO₃^--fed plants at 1-3 mmol L^-1 N, and plants in both treatments showed the same growth at 4 mmol L^-1 N. Nitrogen contents in NO₃^--fed plants increased with the N concentrations in solution; competitive inhibition of NO₃^- absorption by Cl^- was observed under lower N conditions. In addition, shoot dry weight was significantly correlated only with shoot N content. Therefore, growth of NO₃^--fed plants was regulated by N absorption. Inc ontrast, N contents of shoots in NH₄⁺-fed plants did not change with N concentration. Shoot Na content decreased with increasing N concentration, while K content increased. Dry weight was highly correlated only with K content in NH₄⁺-fed plants. These observations indicated that growth of NH₄⁺-fed plants was mainly regulated by K absorption.     

Detection of thyroid hormone receptors in the olfactory system and brain of wild masu salmon,Oncorhynchus masou (Brevoort), during smolting by in vitro autoradiography

Thyroid hormone regulates a number of physiological functions during smolting in salmonids. However, the target sites and roles of thyroid hormone in the central nervous system (CNS) are not known in detail. We detected thyroid hormone-specific binding sites (i.e. thyroid hormone receptors) in the olfactory epithelium and the brain (the olfactory bulb, the telencephalon, the mid-brain and the cerebellum) of wild masu salmon, Oncor- hynchus masou (Brevoort), during smolting by means of in vitro autoradiography with frozen sections. A saturation experiment with the brain indicated the presence of a single class of binding sites of high affinity. T3-specific binding was detected in the olfactory epithelium and in all regions of the brain except the olfactory bulb. The T3-specific binding value in the olfactory epithelium was higher than in all other regions of the brain. This binding value in the olfactory epithelium increased at the full-smolt stage. The presence of thyroid hormone receptors in various regions of the CNS suggests that thyroid hormone plays an important role in the functional change in the brain and the olfactory epithelium during smolting.     

Efficacy of levamisole alone and in combination with mebendazole against Gongylonema pulchrum infection in rabbits

Gongylonema pulchrum is an important parasite of captive primates. Twelve rabbits were infected with 30 third-stage larvae of G. pulchrum. At 4–7 months post-infection, animals were administered levamisole at a single dose of 12 mg/kg, levamisole at 8 mg/kg three times at 2-day intervals, levamisole at a single dose of 8 mg/kg after administration of mebendazole at 70 mg/kg for 3 days or 8 ml of distilled water for 3 days (control). Necropsy at 14 days after treatment revealed that single and multiple dosages of levamisole reduced nematode burdens by 68.4% and 89.5%, respectively. The combined regimen of mebendazole and levamisole exhibited high efficacy for treating G. pulchrum located widely within the upper digestive tract, with a reduction of 98.2%. These results suggest that this combined chemotherapy treatment may be effective against G. pulchrum infection, including buccal and lingual gongylonemiasis in primates.