Zeitschrift fur Parasitenkunde (Berlin, Germany)最新文献

As a first step towards hydatid disease control, the in vitro survival of protoscolices of Echinococcus granulosus was investigated for various media and temperatures. Higher percentage survival was obtained than previously reported: at 4 degrees C, 100% survival was obtained for 20 days in medium 199 (GIBCO) and for 25 days in hydatid fluid from the host of origin. Maximal survival was 30% at 55 days in these conditions. Flame cell activity was the criterion of choice for viability. At 37 degrees C survival rates were lower and morphological changes in protoscolices were observed.

The freeze fracture replica technique has been used to compare the plasma membranes of amastigote and promastigote stages of Leishmania mexicana mexicana with respect to intramembranous particle (integral protein) distribution and to beta-hydroxysterols content as revealed by the distribution of lesions induced by the polyene antibiotic filipin. Intramembranous particle (IMP) density was greater in promastigote than in amastigote plasma membranes. Intramembranous particles were more abundant in the protoplasmic face (PF) than in the exoplasmic face (EF) of promastigotes, but this situation was found to be reversed in amastigotes. Filipin-induced lesions in glutaraldehyde-fixed parasites indicated higher levels of beta-hydroxysterols in the amastigote than in the promastigote plasma membrane, and in the promastigote flagellar membrane than in the body membrane. Amphotericin B (a related polyene antibiotic used in chemotherapy of leishmaniasis) induced IMP aggregation in the PF of unfixed amastigotes but did not appear to influence sterol distribution as demonstrated by freeze-fracture of subsequently-fixed and filipin-treated organisms.

The ultrastructure of the mitotic nucleus in Leishmania braziliensis braziliensis, L. mexicana and L. donovani was studied by serial thin sections and three-dimensional reconstructions of each divisional stage. The structures of the interphase and four stages of dividing nuclei were described. Attention was paid to dense plaques and spindle microtubules. At the beginning of the nuclear division, a set of six dense plaques was found in association with spindle microtubules in the vicinity of the equatorial region of the nucleus. The number of the plaques was the same in the three species examined. Each plaque was divided into two, forming hemiplaques at the elongational stage of the division; these two sets then migrate to the poles. The plaques appeared to correspond with centromeres of metazoan cells and play an important role in the process of nuclear division.

The infective third-stage juvenile of Trichostrongylus colubriformis is surrounded by its own cuticle as well as the incompletely moulted cuticle of the second-stage juvenile, which is referred to as the sheath. The sheath comprises an outer epicuticle, an amorphous cortical zone, a fibrous basal zone and an inner electron-dense layer. The basal zone of the sheath consists of three layers of fibres; the fibres are parallel within each layer, but the fibre direction of the middle layer is at an angle to that of the inner and outer layers. The cuticle comprises a complex outer epicuticle, an amorphous cortical zone and a striated basal zone. The lateral alae of the cuticle and the sheath are aligned and overlie the lateral hypodermal cords. The lateral alae of the sheath consist of two wing-like expansions of the cortical zone with associated specializations of the inner electron-dense layer which form a groove. The cuticular lateral alae consist of two tube-like expansions of the cortical zone. The lateral alar complex of the cuticle and the sheath may maximise locomotory efficiency and prevent rotation of the juvenile within the sheath.

The consequences of infection of rainbow trout, Salmo gairdneri Richardson, by an acanthocephalan, Pomphorhynchus laevis Muller, have been studied using light and electron microscopy. The mucosal epithelium, of the gut adjacent to the metasoma of the worm suffered compression and abrasion. The praesoma of P. laevis penetrated the mucosal epithelium, lamina propria, stratum compactum, stratum granulosum, muscularis and serosa of the gut wall, and was invested by a fibrous capsule of inflammation tissue. This was composed of four principal cell types: eosinophilic granular cells (EGCs), type A cells, type B cells and fibroblasts. Some melanocytes and lymphocytes were also present. The role of the EGCs in the inflammation response is not known, but may not be an active one. The type A cells resembled neutrophils of other fish species, and have tentatively been placed in this category. The type B cells, with large cisternae formed by the RER, resembled plasma cells and may have been involved in a humoral response to the acanthocephalan. The integument of P. laevis did not appear to be damaged by the cells of the inflammation tissue, and it seems likely that this host response was incapable of rejecting the parasite.

Examination of 471 sheep, 118 goats, 157 cattle and 56 camels slaughtered in abattoirs in North Jordan was carried out during March-May 1984. Drought conditions that prevailed during the preceding winter led to slaughtering old female sheep (greater than or equal to 4 years) due to scarcity of food, which allowed us to analyse the prevalence of hydatidosis in various age groups of sheep. An overall infection rate of 27.8, 1.7, 5.8 and 10.7 percent was found in sheep, goats, cattle and camels, respectively. The infection rate was as low as 1.5 percent in male and 1.9 percent in female sheep under 2 years of age. However, the rate of hydatid infection increased with age and reached as high as 63.7 percent in ewes 4 years of age and older. The percentage of animals with fertile cysts was also highest in sheep (68.7 percent of infected animals) and increased with age reaching 100 percent in ewes which were 10 years of age or older. Analysis of all cysts recovered from the livers and lungs of infected ewes from various age groups revealed a sharp increase in the mean total number of cysts in age groups over 8 years of age. The fertility rate of the cysts in the liver was significantly greater in ewes 6 years old or more (64.8--78.6 percent) than in younger age groups (8.7-46.2 percent). In the lung, the fertility rate increased progressively with age reaching as high as 97.9 percent in ewes 10 years old or more. These findings of high infection and fertility rates of hydatid disease in sheep, particularly of older age groups, prompt plans for further epidemiological studies and control programmes.

Malarial parasites reproduce asexually inside the erythrocytes of their vertebrate host. Relatively little is known about the interaction between host cell and parasite metabolism. In the present study the effect of host cell cation composition and osmotic shrinkage on in vitro growth and propagation of Plasmodium falciparum in human erythrocytes was investigated. It is shown that throughout the parasite cell cycle, infected cells lose potassium and gain sodium. Compartment analysis of infected cells revealed that host cell cytosol is poor in potassium and rich in sodium while in the parasite this relationship is reversed, indicating that the parasite is able to regulate its ionic composition independently. Parasites proceeded normally through their cell cycle in the presence of the sodium-pump inhibitor ouabain, although host cells lost up to 75-80% of their normal potassium content. Potassium-depleted erythrocytes harboring trophozoites and schizonts also display normal rates of protein synthesis as measured by isoleucine incorporation. Parasite growth was inhibited when infected cells were osmotically shrunken in hypertonic media, but this was not due to parasite dehydration. It is suggested that increased viscosity of host cell cytosol and/or hemoglobin gelation, are responsible for the effect, probably through interference with parasite feeding. The relevance of these results to understanding of the cellular mechanism involved in the inhibiton of parasite growth in deoxygenated sickle-trait erythrocytes is discussed.

When microfilariae (Mf) of Dirofilaria immitis, both uterine and systemic, were incubated in an in vitro cytotoxicity assay with neutrophils and sera from dogs with occult infections, some Mf remained free of adherent cells and consequently evaded cytotoxicity. The ability to evade cytotoxicity could not be related to the age of the Mf, and host albumin was not detected on any Mf, either uterine or systemic. However, it was shown that some Mf failed to bind IgM, IgG and C3 when incubated with occult sera. It is suggested that the ability of some Mf to evade serum-dependent, neutrophil-mediated cytotoxicity in vitro was related to differences in their antigenicity.

Sera from rats with chronic Trypanosoma brucei gambiense infection were tested for autoantibodies by an indirect immunofluorescence assay. All the sera contained IgM autoantibodies which reacted with blood vessel walls. On cultured vascular smooth muscle cells positive sera reacted with cytoplasmic filaments which were rearranged into perinuclear coils of filaments in colcemid-pretreated smooth muscle cells. These observations strongly suggest that the cytoplasmic autoantigens are intermediate filaments (I.F.). It is probable that the anti-intermediate filament autoantibodies result from polyclonal lymphocyte activation, since in rats experimentally infected with T.b. gambiense the appearance of these autoantibodies occurs already 1 week post-infection.