The fine structure of the hypodermis of Nippostrongylus brasiliensis, a parasitic nematode of the rat, was studied in free-living third-stage filariform (infective) larvae, and in parasitic forms undergoing the third molt. In filariform larvae the hypodermis displayed a comparatively poorly developed RER, and few Golgi complexes, mitochondria, and vesicles. Nuclei contained large amounts of heterochromatin and no nucleoli. After worms reached the lungs and the third molt began, the RER, Golgi complexes, mitochondria, multivesicular bodies, and coated vesicles greatly increased in amounts. Nuclei displayed less heterochromatin and contained prominent nucleoli. These morphological changes were associated with transition from the free-living to the parasitic mode in life. The results were correlated with the fact that the hypodermis in N. brasiliensis is actively synthesizing culticular collagen during the third molt.

Ultrastructure of the hypodermis during cuticle formation in the third molt of the nematode Nippostrongylus brasiliensis.

The effect of isatin on the Echinococcus granulosus cyst in an experimental host.

1. 1. Large numbers of the free-living stages of Nippostrongylus brasiliensis can be grown synchronously in vitro on formalin-killed Escherchia coli supplemented with cholesterol. 2. 2. Actinomycin-D (AM-D) has a marked inhibitory effect on the post-embryonic development of the worm, which appears to be dosage dependent and is reversible. 3. 3. AM-D inhibits RNA, DNA and protein synthesis of the larvae. 4. 4. Synthesis of the third cuticle is inhibited by treatment of the second-stage larva with AM-D. 5. 5. N. brasiliensis requires RNA, protein and possibly DNA synthesis for continued postembryonic development.

Genic control of the postembryonic development of Nippostrongylus brasiliensis

Litomosoides chagasfilhoi is a filariid nematode parasite of the abdominal cavity of the wild rodent Akodon cursor (Winge, 1887), that has been described and used in Brazil as a new model for human filariasis. The fine structure of the intestine of this nematode was analyzed based on observations made by light and transmission electron microscopies of serial sections along the body. Cytochemical analysis was carried out to investigate the composition of the intestinal wall. This structure consisted of a basal lamina and an epithelium of variable thickness, composed of cells that have an irregular shape. The cytoplasm of intestinal cells contains few organelles: vacuoles, lysosomal bodies, spheroid bodies, endoplasmic reticulum, and many large lipid droplets. In the anterior portion of the intestine, the lysosomal bodies, spheroid bodies, and vacuoles presented positive reaction for acid phosphatase, and carbohydrates were detected in lysosomal bodies. The midbody and posterior regions presented less organelles and lipid droplets, and nuclei were more abundant. Residues of L-fucose were detected by Ulex europaeus lectin binding in the midbody sections. Basic proteins were associated to lipid droplets, in the posterior region. In the whole extension of the intestine, carbohydrates were detected on tight junctions. These results indicate that the metabolized material in the epithelium can contribute to the microfilariae development and also probably can be involved with the excretory/secretory mechanism of these nematodes.

Fine structure and cytochemical analysis of the intestinal wall along the body of adult female of Litomosoides chagasfilhoi (Nematoda: Filarioidea)

Ozet: Ciona intestinalis (Tunicata, Ascidiacea) noral kompleks elemanlar›ndan serebral ganglion ve noral bezde gorulen zars› ve miyelin benzeri yap›daki hucre ici oluflumlar›n bulunufl nedenleri, yap›sal ve lokal ozellikleri cal›fl›lm›flt›r. Literaturdeki bilgilere de dayanarak bunlar›n normal hucrede goruldukleri, ancak fizyolojik olaylara bal› olarak say›ca artabilecekleri ve daha komplike bir morfoloji gosterebilecekleri saptanm›flt›r. Abstract: A study was conducted on the existence, structure and localization of membraneous and myelinated bodies which appear within the cerebral ganglion and neural gland, which are the components of the neural complex of Ciona intestinalis (Tunicata, Ascidiacea). According to the literature, these structures occur within the cytoplasm of a normal cell, but it was observed that they increase in number and show exhibit greater morphological intricacy in connection with certain physiological events.

Ciona intestinalis (Tunicata, Ascidiacea)'de Nöral Kompleks Hücrelerinde Zars› Oluflumlar ve Miyelin Benzeri Yap›lar

The general fine structure of intestinal cells and changes which occur in ultrastructure during development from fourth-stage to adult N. dubius are reported. In fourth-stage worms pigment granules are prominent in intestinal cells. In adults the number of pigment granules appears to be reduced and phagolysosomes containing membranous profiles and pigment material increase in number. Another reorganization of cell structure involves mitochondria which are randomly distributed in the cytoplasm of cells in fourth-stage worms, concentrated in the apical cytoplasm in worms in the molting process, and confined to the base of cells in adult worms. Other changes involved structure of the nucleus, rough endoplasmic reticulum and glycogen content of cells.

F. J. Etges

Papers

Changes in the ultrastructure of Nematospiroides dubius (nematoda) intestinal cells during development from fourth stage to adult.