Yoichi Ishii

Ultrastructural Studies on Spermatogenesis in a Parthenogenetic Type of Paragonimus westermani (Kerbert 1878) Proposed as P. pulmonalis (Baelz 1880)

Spermatogenesis in a parthenogenetic type of P. westermani (Kerbert 1878) called P. pulmonalis (Baelz 1880) throughout this study, was observed by light microscopy (LM), scanning (SEM), and transmission (TEM) electron microscopy. During spermatogenesis, most of the cells became degenerated or malformed as a result of aberrations during spermatogenesis. Vacuolated cells were often found in the testicular lumen. In some nuclei of spermatocytes, synaptonemal complexes were formed and this indicated that some pairing of homologous chromosomes did occur, but only rarely. Cytophores in some rosettes were broken down into small fragments and the cells separated from each other. Norman spermatozoa were very rarely found in the testis and never in the seminal receptacle, where egg and vitelline cells were present instead. Throughout spermatogenesis, Golgi complexes, mitochondria, ribosomes, and endoplasmic reticulum were not abundant, and this suggested that cell activities and protein synthesis were greatly reduced.

LARVAL GNATHOSTOMES FOUND IN REPTILES IN JAPAN AND EXPERIMENTAL LIFE CYCLE OF GNATHOSTOMA NIPPONICUM

As only the adult of Gnathostoma nipponicum is known, 129 snakes and 33 weasels obtained in Kagawa Prefecture, Japan were examined for larvae. Hitherto undocumented larvae, later identified as G. nipponicum, were recovered from three snakes and one weasel. The life cycle was experimentally completed from eggs to adult worms. Cyclops, the first intermediate hosts, were infected by feeding them newly hatched larvae from uterine eggs. Advanced third-stage larvae were obtained from two rats and one mouse which had ingested early third-stage larvae from cyclops. A ferret fed advanced third-stage larvae from rats had adult worms in esophageal tumors 100 days after exposure.

The value of external morphology in the identification of larval anisakid nematodes: a scanning electron microscope study

We studied larval nematodes of four genera of the Anisakidae using a scanning electron microscope (SEM). The anterior and posterior extremities and cuticular structures of the 3rd-stage larvae (L3) ofAnisakis type I,Pseudoterranova decipiens, Contracaecum type B andHysterothylacium were examined. The 4th-stage larvae (L4) ofAnisakis type I,P. decipiens, recovered after infection into laboratory rats, and the L3 and L4 ofAnisakis type I larvae from human were also examined in the same way. There were generic differences in the shape and size of the lip bulges, external papillary structures, the appearance of the boring tooth, the width and depth of the grooves and ridges of the cuticle and the caudal structures of the L3. InAnisakis type I andP. decipiens L3, changes were seen in the anterior extremity, cuticle and posterior extremity after molting to the L4. Similar changes can be expected in larvae infecting man. The L4 ofAnisakis type I from rat and man were similar, while the L4 ofAnisakis type I andP. decipiens showed differences. These ultrastructural differences might be of value in the identification of fragments recovered during endoscopy in man.

Development of Microphalloides japonicus (Osborn, 1919) metacercariae in vitro (Trematoda: Microphallidae).

Metacercariae of the trematode Microphalloides japonicus (Osborn, 1919) were cultivated in various media to gravid adults, and the results were compared with those in vivo. A few eggs were produced in the uterus even in balanced salt solution, although cultivation in Eagles MEM and NCTC 109 media was much better. Addition of heat-inactivated serum resulted in even better development. Encysted metacercariae also produced eggs in some media, but most of them were incomplete and without shells.

Comparative studies on surface ultrastructure of newly excysted metacercariae of Japanese lung flukes

The surface ultrastructure of excysted metacercariae of five species of Japanese lung flukes: Paragonimus westermani, P. pulmonalis, P. miyazakii, P. ohirai and P. iloktsuenensis, were studied. Some differences were observed in the distribution of the spines and papillae among the five species. Single-pointed spines were generally developed in the antero-ventral region, and their development varied among species. Three morphological types of papillae were observed: large-domed, small-domed and pit type. Large-domed papillae were regularly located on the lip of suckers without variation among the five species. The small-domed and pit type papillae were arranged bilaterally and symmetrically on the body surface, and the distribution varied among the species, especially around the suckers. These results suggest that metacercariae of Paragonimus species can be distinguished by surface ultrastructure, especially by the distribution of papillae.

The ultrastructural characterization of the tegument of Clonorchis sinensis (Cobbold, 1875) cercaria.

SummaryThe tegumental ultrastructure of the cercaria of the liver fluke,Clonorchis sinensis (Cobbold, 1875), was studied by scanning and transmission electron microscopy. The body surface is almost encircled by many rows of regularly arranged spines. The tegumental syncytium of the body contains many rod-shaped dense granules and central electron-lucent bodies, neither of which are present in the tail tegument. There are four rows of hooked teeth and modified spines on the oral cone. These teeth are differentiated morphologically and probably functionally from the other body spines. Disc-shaped papillae with long or short cilia are distributed on the body in a bilaterally symmetrical pattern dorsally and ventrally. There are 30 to 37 papillae with much longer cilia laterally. Four pairs of papillae were found on the tail. From their structure and location these papillae appear to have a mainly tango-or rheoreceptive function. Another type of sheathed papillae is situated around the oral sucker. The cuticular tegument is expanded laterally at the base of the tail, forming a characteristic sac-like structure.

A comparative ultrastructural and histochemical study of the metacercarial cyst walls of four species of Paragonimus (Troglotrematidae : Trematoda)

The metacercarial cyst walls ofParagonimus westermani, P. miyazakii, P. ohirai, andP. iloktsuenensis were examined using ultrastructural and histochemical techniques. The cyst walls ofP. westermani, P. miyazakii, andP. ohirai were found to have five distinct layers, whereas the wall ofP. iloktsuenensis had only two. The so-called outer cyst wall recognized on light microscopy by Miyazaki (1961) was composed of layers I–III and the so-called inner cyst wall comprised layers IV and V. The outermost layer (I) consisted of collagen fibers and probably originated from the host. Layer III detached easily from layer IV on removal of the cysts from the host tissues. Layer IV was composed of proteoglycans, and layer V consisted of protein alone. A regular hexagonal pattern in layer V appeared to be characteristic ofP. westermani. Although the basic morphological patterns observed in the layers constituting the cyst walls were similar in all species examined, the thickness of each layer was apparently different. This characteristic seems to be a suitable criterion for the identification of metacercarial cysts ofParagonimus species.

Comparative ultrastructural topography of the gut epithelia of some trematodes

Abstract The gut epithelia of six species of digenetic trematodes, Clonorchis sinensis, Eurytrema pancreaticum, Haematoloechus lobatus, Echinostoma hortense, Schistosoma japonicum and Fasciola hepatica , were studied with scanning and also transmission electron microscopy. Morphological differences in cytoplasmic projections of the gut of adult flukes were demonstrated stereoscopically among these species. The cytoplasmic projections vary considerably in shape, but are roughly separated into three groups by their essential forms: ribbon-shaped narrow type in C. sinensis and E. pancreaticum , broad, triangular with filamentous extensions distally and/or marginally as in F. hepatica and E. hortense , and broad, sheet-like or triangular with the distal ends blunt or rounded as in H. lobatus and S. japonicum . This character appears rather constant, without regional differences in the gut. No marked correlation was found between the gut projections of the parasites and their host or food. There are also specific discriminations in the ultrastructure of the cellular organization among the species examined.

Studies on host specificity in Paragonimus westermani. II: Histochemical and cytochemical characterization of metacercariae and worms from rats and dogs

Histochemical tests were done on newly excysted metacercariae and worms recovered from an abnormal host (rat) and the definitive host (dog) for some oxidoreductases, phosphatases and glycosidases. The results demonstrate that rat worms have enzymatic distribution and intensities more similar to those of metacercariae than to adult worms from dogs. Ultracytochemical examination of acid and alkaline phosphatase and Mg-ATPase activity was also carried out. Acid phosphatase activity occurred exceptionally in the excretory bladder and caeca of dog worms. No activity was observed in rat worms except for lysosomal granules in the tegument. Alkaline phosphatase activity was exhibited in the excretory bladder in both dog and rat worms. Mg-ATPase activity occurred in the tegument and parenchymal cells in dog worms and in the excretory bladder in rat worms. In metacercariae, little or no reaction for these enzymes was present except for Mg-ATPase activity on the excretory ducts. These observations, together with the histochemical results, indicate that metabolic activity in rat worms is higher than in metacercariae although it is strongly reduced compared with dog worms.

Immunocytochemical localization of gut-associated circulating anodic antigen in Schistosoma japonicum

The localization of the gut-associated circulating anodic antigen inSchistosoma japonicum adults was revealed by means of the immunofluorescence and a peroxidase-anti-peroxidase method with the electron microscope. The reaction sites were confined to amorphous material in the cecal lumen. The cecal lumen generally was infolded with lamellae. The antigenic material appeared to be secreted by the rough endoplasmic reticulum, probably through the Golgi apparatus, into the lumen. Observations of male and female worms showed that there was a clear difference between the sexes in antigen concentration. The thick epithelium of the female worm, with well-developed cisternae on the endoplasmic reticulum, produced a lot more antigen than the male. Positive staining with ruthernium red confirmed that the antigenic material was a negatively charged polysaccharide as had been previously reported.