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1.
A study of larval development of Schistosoma haematobium in the snail Planorbarius metidjensis infected by transplanted sporocysts showed that some embryos in daughter sporocysts have characters intermediate between cercariae and sporocysts. These embryos are interpreted to be nearly mature cercariae that have partially reverted to be secondary sporocysts. If this explanation is correct, it would mean that the embryos which develop within trematode daughter sporocysts can differentiate either into cercariae or into a new generation of sporocysts, but originate from a single type of germinal cell.  相似文献   

2.
SYNOPSIS. The excystation of sporozoites from intact Toxoplasma gondii oocysts or mechanically released sporocysts was studied by light and electron microscopy. Both intact oocysts and free sporocysts excysted in 5% bovine bile in 0.9% NaCl solution after 30–60 min incubation at 37 C. Sporozoites were first activated in either intact sporocysts or oocysts within 2–12 min of incubation in bile. Sporozoites escaped from sporocysts through 4 plate-like sutures in the sporocyst wall, and from the oocyst as the oocyst wall ruptured at one or more points.  相似文献   

3.
In vitro excystation of sporozoites of the heteroxenous coccidian Caryospora simplex Léger, 1904 (Apicomplexa: Eimeriorina) is described. Sporocysts freed mechanically from oocysts released a maximum of 51% of their sporozoites within 45 min at 25°C and a maximum of 74% within 20 min at 37°C when incubated in a 0.25% (w/v) trypsin–0.75% (w/v) sodium taurocholate (bile salt) excystation solution. At emergence from sporocysts, sporozoites were weakly motile then became highly active after about 2 min in excystation solution. Sporozoites within sporocysts exposed to bile salt only became highly motile within 25 min at 25°C and within 15 min at 37°C but did not excyst. When exposed only to trypsin at the above temperatures, the Stieda body dissolved; the substieda body remained intact, and the sporozoites exhibited only limited motility within sporocysts; only a few excysted. Intact, sporulated oocysts incubated at 25° or 37°C in 0.02 M cysteine-HC1 and a 50% CO2 atmosphere for 18 h had no morphologic changes in the oocyst wall. Further incubation of these intact oocysts in excystation solution for 30 min at 37°C caused neither motility of sporozoites within sporocysts nor excystation. Grinding oocysts for 30 sec in a motor-driven, teflon-coated tissue grinder caused motility of some sporozoites within sporocysts but did not result in excystation.  相似文献   

4.
5.
Ten domestic dogs became infected with Sarcocystis when fed simple portions of heart, esophagus and diaphragm from a two-year-old female wapiti (Cervus canadensis). The prepatent period was 14 days in all exposed dogs; the patent period ranged from 8 to 20 days. Neither the 10 control dogs, nor two dogs fed sporocysts collected from the infected dogs passed sporocysts within the study period. Sporocysts averaged 16.5 by 11.1 micron in size.  相似文献   

6.
In juvenile Biomphalaria glabrata snails exposed to irradiated Echinostoma lindoense miracidia, the sporocysts migrated to the heart at the same speed as did nonirradiated sporocysts in control snails. However, in each snail so exposed to irradiated miracidia, amebocyte clumps in the snail's heart destroyed the sporocysts within 2–9 days post-exposure. This process induced a strong, highly specific resistance to homologous reinfection in these previously susceptible snails. The snails remained susceptible to Schistosoma mansoni and Paryphostomum segregatum (Echinostomatidae), but were partially resistant to Echinostoma paraensei and E. liei, two echinostome species closely related to E. lindoense.  相似文献   

7.
Daughter sporocysts of Sanguinicola armata are represented by several generations, changes of which goes synchronously with the changes of year seasons. Young individuals beginning the reproductions form exclusively cercariae. The old sporocysts begin to produce sporocysts only. These young sporocysts do not quite the organism of the old sporocyst. Therefore, series of sporocysts inside other sporocysts are often observed in hystological cross-sections. Germinal masses of daughter sporocysts of S. armata have some specific characters, which are not observed in analogous organs in daughter sporocysts of other trematode species.  相似文献   

8.
Equine protozoal myeloencephalitis is a major cause of neurological disease in horses from the Americas. Horses are considered accidental intermediate hosts. The structure of sporocysts of the causative agent, Sarcocystis neurona, has never been described. Sporocysts of S. neurona were obtained from the intestines of a laboratory-raised opossum fed skeletal muscles from a raccoon that had been fed sporocysts. Sporocysts were 11.3 by 8.2 microm and contained 4 sporozoites. The appearance of the sporocyst residuum was variable. The residuum of some sporocysts was composed of many dispersed granules, whereas some had granules mixed with larger globules. Excystation was by collapse of the sporocyst along plates. The sporocysts wall was composed of 3 layers: a thin electron-dense outer layer, a thin electron-lucent middle layer, and a thick electron-dense inner layer. The sporocyst wall was thickened at the junctions of the plates. Sporozoites were weakly motile and contained a centrally or posteriorly located nucleus. No retractile or crystalloid body was present, but lipidlike globules about 1 microm in diameter were usually present in the conoidal end of sporozoites. Sporozoites contained 2-4 electron-dense rhoptries and other organelles typical of coccidian zoites. Sporozoites entered host cells in culture and underwent schizogony within 3 days.  相似文献   

9.
Two populations of Biomphalaria glabrata snails differing slightly in their susceptibility to Schistosoma mansoni infection showed dramatic differences in cercarial output per snail. Exposed to five or more miracidia, snails from a group with a 90-100% susceptibility rate (Group A) produced nearly twice the number of cercariae as those from a group with a 70-80% susceptibility rate (Group B). Exposure of individual snails to known numbers of miracidia resulted in higher numbers of primary (mother) sporocysts in Group A snails than in Group B snails. However, monomiracidial exposure of snails from both groups resulted in equivalent numbers of cercariae produced per positive snail, indicating that, once established, all primary sporocysts possess a similar reproductive potential. Morphometric analysis of serially sectioned 9-day-old primary sporocysts supported this conclusion; the size of the primary sporocysts and the size and numbers of secondary (daughter) sporocysts within each primary sporocyst were comparable in snails from both groups. The data indicate cercarial production in this system is regulated prior to, and/or during, early development of the primary sporocyst.  相似文献   

10.
Aggregata Frenzel, 1885 (Apicomplexa) are dangerous protozoan parasites that cause malabsorption syndrome in wild and reared cephalopod species, resulting in significant economic loss to fishery and aquaculture industries. The new parasitic species, Aggregata aspera n. sp., in the digestive tract of Amphioctopus ovulum and Amphioctopus marginatus from an area in the Western Pacific Ocean was identified, it is the second two-host parasite species of Aggregata. Mature oocysts and sporocysts were spherical to ovoid in shape. Sporulated oocysts were 380.6–1,158.4 μm in length and 284.0–1,090.6 μm in width. The mature sporocysts were 16.2–18.3 μm in length and 15.7–17.6 μm in width, with irregular protuberances on the lateral wall of the sporocysts. Sporozoites within mature sporocysts were curled in shape and measured 13.0–17.0 μm in length and 1.6–2.4 μm in width. Each sporocyst contained 12–16 sporozoites. Phylogenetic tree analysis, based on 18S rRNA gene partial sequences, indicated that Ag. aspera forms a monophyletic cluster within the genus Aggregata and has a sister relationship with Ag. sinensis. These findings will provide the theoretical basis for the histopathology and diagnosis of coccidiosis in cephalopods.  相似文献   

11.
The distribution of acetylcholinesterase in mother and daughter sporocysts of Schistosoma mansoni was studied histochemically. In young mother sporocysts derived from miracidia cultured in vitro the miracidial neural mass and flame cells were shown to persist. The nerve trunks and commissures, as well as papillae, are apparently lost in the transformation process. In young daughter sporocysts freshly dissected from mother sporocysts there was little enzyme activity except for a sparse distribution in the tegument. After cultivation, intense enzyme activity was associated with developing cercarial embryos. A similar distribution of activity was observed in older daughter sporocysts obtained from the digestive gland of snails. No evidence of flame cells, neural mass, or commissures was detected in daughter sporocysts by the methods employed.  相似文献   

12.
Twenty-one coccidia-free dogs were fed either experimentally infected or naturally infected beef in 4 experiments. The pretreatment period ranged from days 9 to 33; 7 dogs shed their first sporocysts on day 12. The full length of the patent period was not determined because most dogs were still shedding sporocysts when experiments ended on days 40 and 60. Although the patent period was long, sporocysts were not shed continuously; the total number of days sporocysts were actually shed ranged from 3 to 40. The average number of sporocysts shed by dogs fed 454 to 908 g of beef ranged from 861,000 to over 20 million. Most sporocysts were shed from days 15 to 30; peak numbers were shed on days 23 and 24. Average peak numbers ranged from 145,000 to 408,400 sporocysts. Such data can be applied to facilitate collection of sporocysts in the laboratory or to estimate the potential for transmission of infective organisms under field conditions.  相似文献   

13.
Sarcocystis neurona has become recognized as the major causative agent of equine protozoal myeloencephalitis (EPM) in the Americas. At least 3 pathogenic species of Sarcocystis, including S. neurona, can be isolated from opossums. Methods are needed to ascertain whether these isolates are viable and capable of causing infections. In this study, the nuclear stain propidium iodide (PI) was used to differentiate between live (viable) and heat-killed (nonviable) S. neurona sporocysts. PI was excluded by live sporocysts but penetrated compromised sporocyst membrane and stained sporozoite nuclei of dead sporocysts. After live and dead sporocysts were mixed at various ratios, the number of unstained sporocysts detected after the staining procedure correlated significantly (r2 = 0.9978) with the expected numbers of live sporocysts. Sporocyst mixtures were also assayed for in vitro excystation and development in tissue cultures. The correlation between the percentage of plaques formed in tissue cultures and the percentage of expected infectious (live) sporocysts in each mixture was r2 = 0.6712. By analysis of variance, no statistically significant difference was measured between the percentage of viable sporocysts and the percentage of infectious sporocysts (P = 0.3902) in each mixture. In addition, there was evidence of a relation between PI impermeability of sporocysts and animal infectivity. These results suggest that the PI dye-exclusion technique can be a useful tool in identifying viability and potential infectivity of S. neurona sporocysts and in differentiating between viable and nonviable sporocysts.  相似文献   

14.
A monoclonal antibody, recognizing a carbohydrate epitope associated with several tegumental surface components on Schistosoma mansoni primary sporocysts, was used to follow tegumental formation during transformation of the miracidium to sporocyst and its subsequent development in vitro and in vivo. Indirect fluorescent antibody and direct immunogold labeling methods confirm a structural connection between the intercellular ridges and a submuscular, multinucleate syncytium in the miracidium. Immunoreactive vesicles within this latter system directly contribute to elaboration of the tegumental surface membrane, through the process of membrane fusion. Lateral expansion of intercellular ridges by vesicular fusion ultimately result in fully transformed sporocysts exhibiting vesicular membrane epitopes as prominent tegumental surface components. Light microscopical and ultrastructural observations, together with Western immunoblot analyses, suggest a gradual depletion of intracellular and surface immunoreactive material of vesicular origin in primary sporocysts grown in culture for up to 12 days. In contrast, similar immunoreactive vesicles appear to be continuously synthesized throughout in vivo primary sporocyst development. Monoclonal antibody reactive epitopes appear to be uniquely expressed in the miracidium/primary sporocyst since similar molecules are absent from daughter sporocysts, cercariae, adults, and snail tissues.  相似文献   

15.
During the life cycle of Schistosoma mansoni the production of sporocysts of a higher order than secondary is a normal mode of larval multiplication which intervenes in asexual reproduction of the parasite. The sequence of reconversion of sporocysts producing cercariae to those producing sporocysts III, IV, etc... can be divided into three principal steps: (1) cessation of cercariae production; (2) degeneration of cercariae contained in the sporocyst, and (3) production of the new generation of sporocysts. Degeneration of intrasporocystic larval material seems to be an indispensable step for the new orientation of production. The signifance of this method os multiplication in the ecology of transmission is discussed.  相似文献   

16.
The effect of moist heat and several disinfectants on Sarcocystis neurona sporocysts was investigated. Sporocysts (4 million) were suspended in water and heated to 50, 55, 60, 65, and 70 C for various times and were then bioassayed in interferon gamma gene knockout (KO) mice. Sporocysts heated to 50 C for 60 min and 55 C for 5 min were infective to KO mice, whereas sporocysts heated to 55 C for 15 min and 60 C or more for 1 min were rendered noninfective to mice. Treatment with bleach (10, 20, and 100%), 2% chlorhexidine, 1% betadine, 5% o-benzyl-p-chlorophenol, 12.56% phenol, 6% benzyl ammonium chloride, and 10% formalin was not effective in killing sporocysts. Treatment with undiluted ammonium hydroxide (29.5% ammonia) for 1 hr killed sporocysts, but treatment with a 10-fold dilution (2.95% ammonia) for 6 hr did not kill sporocysts. These data indicate that heat treatment is the most effective means of killing S. neurona sporocysts in the horse feed or in the environment.  相似文献   

17.
The outcome of the interaction between Biomphalaria and Schistosoma mansoni depends on the response of the host internal defence system (IDS) and the escape mechanisms of the parasite. The aim of this study was to evaluate the responsiveness of the IDS (haemocytes and soluble haemolymph factors) of resistant and susceptible Biomphalaria tenagophila lineages and Biomphalaria glabrata lineages in the presence of in vitro-transformed primary sporocysts and secondary sporocysts obtained from infected B. glabrata. To do this, we assayed the cellular adhesion index (CAI), analysed viability/mortality, used fluorescent markers to evaluate the tegumental damage and transplanted secondary sporocysts. B. tenagophila Taim was more effective against primary and secondary sporocystes than the susceptible lineage and B. glabrata. Compared with secondary sporocysts exposed to B. tenagophila, primary sporocysts showed a higher CAI, a greater percentage of dead sporocysts and were labelled by lectin from Glycine max and Alexa-Fluor 488 fluorescent probes at a higher rate than the secondary sporocysts. However, the two B. tenagophila lineages showed no cercarial shedding after inoculation with secondary sporocysts. Our hypothesis that secondary sporocysts can escape the B. tenagophila IDS cannot be confirmed by the transplantation experiments. These data suggest that there are additional mechanisms involved in the lower susceptibilty of B. tenagophila to S. mansoni infection.  相似文献   

18.
Eight Polled Dorset lambs were orally inoculated with Sarcocystis ovicanis sporocysts. Two lambs that received 100,000 or 200,000 sporocysts became clinically ill, recovered, and were killed 67 and 88 days after inoculation (DAI). Numerous intramuscular cysts were found in their skeletal and cardiac muscles. Three lambs received 100,000 sporocysts, three lambs received 1 million sporocysts, and three lambs received no sporocysts. After an acute clinical illness characterized by anemia, inappetence, weight loss, fever, and reduced serum protein, all lambs that received 100,000 sporocysts died 27 to 29 DAI and all that received 1 million sporocysts died 24 or 25 DAI. Hemorrhage involving the striated muscle and visceral organs was the most apparent gross lesion. The heart appeared most severely affected. Schizonts were found in vascular endothelial cells of all six inoculated lambs. Uninoculated lambs remained healthy, and neither lesions nor parasites were found in any tissues. Dogs fed tissues containing S. ovicanis cysts produced sporocytes 11 to 37 days after feeding; cats fed similar stages produced no sporocysts. Dogs fed tissues containing schizonts produced no sporocysts.  相似文献   

19.
Morphology of the Helicometra fasciata Rud., 1819 parthenogenetic generation from the Black Sea gastropods Gibbula adriatica (Phil.) was studied for the first time. Data on seasonal dynamics of the hemipopulation of daughter sporocysts are given. Daughter sporocysts of H. fasciata infest 10 +/- 0.2 % of G. adriatica (mainly specimens of larger size and elder age classes). As a rule, local microhemipopulations of daughter sporocysts castrate mollusc hosts. Reproduction of H. fasciata daughter sporocysts is asynchronous: daughter sporocysts born specimens of next sporocyst generation during autumn and winter, and then they begin producing cercaria. In winter development of the cercaria embryo is blocked. Second change of the character of the each sporocyst' posterity is impossible because of the annual life cycle of G. adriatica. Endogenous agglomeration of the H. fasciata daughter sporocysts is extremely little: individuals of next sporocyst generation develop from no more than 2 % of embryonic balls. Energy resources of the mollusc host are used by the H. fasciata daughter sporocysts mainly for producing cercaria; this fact can be interpreted as an adaptation of H. fasciata to using medium-sized, short-living mollusc hosts.  相似文献   

20.
The fate of Schistosoma mansoni (Trematoda) sporocysts in its molluscan host Biomphalaria glabrata (Gastropoda) is determined by circulating phagocytes (hemocytes). When the parasite invades a resistant snail, it is attacked and destroyed by hemocytes, whereas in a susceptible host it remains unaffected. We used 3 inbred strains of B. glabrata: 13-16-R1 and 10-R2, which are resistant to the PR-1 strain of S. mansoni, and M-line Oregon (MO), which is susceptible to PR-1. In an in vitro killing assay using plasma-free hemocytes from these strains, the rate of parasite killing corresponded closely to the rate by which S. mansoni sporocysts are killed in vivo. Hemocytes from resistant snails killed more than 80% of S. mansoni sporocysts within 48 hr, whereas sporocyst mortality in the presence of hemocytes from susceptible snails was <10%. Using this in vitro assay, we assessed the involvement of reactive oxygen species (ROS) produced by resistant hemocytes, during killing of S. mansoni sporocysts. Inhibition of NADPH oxidase significantly reduced sporocyst killing by 13-16-R1 hemocytes, indicating that ROS play an important role in normal killing. Reduction of hydrogen peroxide (H2O2) by including catalase in the killing assay increased parasite viability. Reduction of superoxide (O2-), however, by addition of superoxide dismutase or scavenging of hydroxyl radicals (*OH) and hypochlorous acid (HOCl) by addition of hypotaurine did not alter the rate of sporocyst killing by resistant hemocytes. We conclude that H2O2 is the ROS mainly responsible for killing.  相似文献   

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