摘要:

ABSTRACTUltrastructural investigations ofP. falciparumcultivated in vitro in human erythrocytes revealed new features of the feeding mechanism of the parasite. Mature trophozoites and schizonts take up a portion of the host cytosol by endocytosis which is restricted to cytostomes and which involves the invagination of both parasitophorous and parasite membranes. The resulting endocytic vesicles, surrounded by two concentric membranes, migrate towards the central food vacuole membrane. The external membrane of the endocytic vesicles apposes that of the food vacuole, leading to the internalization of vesicles bounded by a single membrane into the vacuolar space where they are rapidly degraded. We conclude from this sequence of events that endocytic vesicles fuse with the food vacuole. Treatment of infected cells with therapeutic concentrations of chloroquine inhibited the last step of the feeding process, i.e. vacuolar degradation. This was manifested by the accumulation within the vacuolar space of intact vesicles bounded by single membranes. The implications of these findings for the antimalarial activity of chloroquine are discussed.

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1984.tb02981.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

ABSTRACTThe large cytopharyngeal pouch of the macrostomal form ofTetrahymena vorax, following the addition of calcium, can form a sealed, empty vacuole. The open cytostomal region of this cell, which averages about 16 μ in diameter, is closed by an upward (ventral) movement of the right and posterior ribbed walls, both of which project into the cytostomal cavity. At the same time, the anterior and left walls of the cytostome‐cytopharyngeal complex move to the right, forming a diagonally (right to left) placed furrow in the floor of the buccal cavity as these walls meet. As a result of the movement, the edges of the single membrane‐bounded cytopharyngeal pouch are brought together and fuse, producing the closed vacuole. Elements of the cytoskeleton appear to participate in the closure process. Three major groups of ribbed wall microtubules support the open cytostome. The anterior ribbed wall microtubules pass laterally along the anterior (dorsal) portion of the cytopharyngeal pouch to the left where they end in the specialized cytoplasm. Middle oral rib microtubules terminate at the right and posterior margin of the cytopharynx while microtubules from the most posterior region of the ribbed wall pass to the left terminating in the specialized cytoplasm. The fine filamentous reticulum, a striated reticulum that borders the right, posterior, and anterior margins of the cytostome‐cytopharyngeal complex, is in an ideal position to participate in these movements. It is anchored anteriorly high up in the buccal cavity to the cross‐connective between the third membranelle and the undulating membrane complex. It courses beneath the right and posterior ribbed walls and runs laterally along the anterior margin of the cytopharynx to the left side. Contraction or pulling of this reticulum would act to bring the microtubule‐reinforced walls of the cytopharynx together permitting fusion of the cytopharyngeal pouch membranes to form a seal

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1984.tb02982.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

ABSTRACTIn vitro culture ofPlasmodium falciparum‐infected human erythrocytes (RBC) has permitted systematic study of human host‐parasite relations. In this study the effect of aspirin in the culture system was examined by using serum from blood of fasting, healthy male volunteers, before and after the ingestion of aspirin. The addition of aspirin‐containing serum disturbed parasite growth and development: 0‐1/2 dilutions of treated/control sera inhibited parasite development, with nuclear pyknosis, pyknotic extracellular parasites (trophozoites) in the media, decreased numbers and sizes of “rings” (early trophozoites), and an increased number of later trophozoites and schizonts. Paradoxically, while the incorporation of [3H]isoleucine into protein was not affected by the aspirin‐containing sera, the incorporation [3H]hypoxanthine was significantly changed and did not correlate with morphological evidence of cytotoxicity. Thus, the so‐called “incorporation” of a radioactive tracer is not a fully reliable index of parasite growth in the presence of certain compounds. The findings underscore the importance, in this culture system which employs human serum, of avoiding serum from donors who have recent

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1984.tb02983.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

ABSTRACTLight microscopy studies ofCulicosporella lunata(Hazard&Savage), a parasite of the mosquitoCulex pilosus(Dyar&Knab), revealed two sporogonial sequences. One sequence begins with diplokaryotic meronts that undergo repeated nuclear divisions to produce sporogonial plasmodia with nuclei in diplokaryotic arrangement. These plasmodia form rosette‐like clusters of sporoblasts during incomplete cytokinesis and, eventually, binucleate spores. These spores initiate infections in healthy larvae when they ingest spores. The second sequence begins with diplokaryotic meronts that undergo karyogamy and meiosis to formThelohania‐like sporonts and haploid spores. Anomalies are often observed in these sporonts which result in aberrant spores, usually fewer than eight, in an accessory (pansporoblastic) membrane. Normal haploid spores are morphologically similar to those of species ofAmblyospora. The genus and the type species are redefined based on new information presented here and it and the type species are placed in the family Amblyospori

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1984.tb02984.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

ABSTRACTDevelopmental stages ofCaryospora simplexwere found in connective tissue of the cheek, tongue, and nose of Swiss‐Webster and C57 BL/6 mice (Mus musculus) from 8 through 70 days after oral inoculation with 50,000 or 250,000 oocysts, or 60,000 free sporocysts of the same species obtained from an Ottoman viper,Vipera xanthina xanthina. The earliest developmental stages were seen on day 8 post‐inoculation (PI) and consisted of two types of meronts and gamonts (undifferentiated sexual stages). Gamonts, microgametocytes, macrogametes, and unsporulated oocysts were found on days 10 and 12 PI. Fully sporulated, thin‐walled oocysts containing eight sporozoites surrounded by a thin sporocyst membrane were first seen 12 days PI. Monozoic cysts (caryocysts) were first seen 12 days PI and appeared fully viable throughout the duration of the study, 70 days PI. Four mice injected intra‐peritoneally with 150,000 free sporozoites and killed 12 days PI contained unsporulated and sporulated oocysts in connective tissues of the cheek, tongue, and nose, suggesting that sporozoites may be carried to the site of infection via the lymphatic/circulatory system. Four cotton rats,Sigmodon hispidus, inoculated orally with 250,000 oocysts all had unsporulated and sporulated oocysts ofC. simplexin connective tissue of the cheek, tongue, and nose when killed on day 12 PI, indicating extraintestinal development in the secondary host is not species specific. This is the first report of a heteroxenous coccidium with both asexual and sexual development in the primary (predator) and secondary (prey

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1984.tb02985.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

ABSTRACTLeighton tubes containing monolayers of human embryonic lung cells were inoculated with 70,000 or 30,000 sporozoites of the viperid coccidiumCaryospora simplexand examined at 1, 2, 4, 6, 8, 10, 12, 14, 16, and 18 days post‐inoculation (PI). By day 1 PI, sporozoites had penetrated cells and were within parasitophorous vacuoles. Most sporozoites became spherical and then underwent karyokinesis several times between days 2 and 6 PI. Mature Type I meronts were found on days 6–16 PI and contained 8 to 22 short, stout merozoites. Mature Type II meronts were present on days 10–18 PI and contained 8 to 22 long, slender merozoites. Developing gamonts (undifferentiated sexual stages) were observed on days 14 and 16 PI. Mature micro‐ and macrogametes and thin‐walled unsporulated oocysts were present on days 16 and 18 PI. Attempts to sporulate oocysts in tissue culture medium or in a 2.5% (w/v) aqueous solution of K2Cr2O7at 25/°C and 37°C were unsuccessful; only a few oocysts developed to the contracted sporont stage. Four Swiss‐Webster mice injected intraperitoneally with merozoites obtained from Leighton tubes on day 10 PI did not acquire infections. This is the second coccidium reported to complete its entire development, from sporozoite to oocyst, in

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1984.tb02986.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The ultrastructure of the sexual stages ofPlasmodium gallinaceumduring gametogenesis, fertilization, and early zygote transformation is described. New observations are made regarding the parasitophorous vacuole (PV) of gametocytes and the process of emergence in male and female gametocytes. Whereas female gametocytes readily disrupted both the PV membrane and host cell plasmalemma during emergence, male gametocytes frequently failed to break down the plasmalemma of the host cell. New observations and hypotheses are presented on the behavior of the male gamete nucleus. Following fertilization, the male nucleus appears to travel through a channel of endoplasmic reticulum in the female gamete before fusing with the female nucleus at a region in which the nuclear envelope is thrown into extensive convoluted folds. Polarization of the zygote nucleus, in association with the appearance of a perinuclear spindle of cytoplasmic microtubules, preceded all other changes in the developing zygote. After nuclear polarization becomes apparent, electron‐dense material is deposited beneath the zygote pellicle, and a canopy is formed which eventually extends over the entire apical end of the developing ookinete. As the apical end begins to extend outward, polar rings, micronemes, and subpellicular microtubules become visible in this portion and a “virus‐like” inclusion known as a crystalloid is formed in the posterior portion of the zygote. When female gametes are prevented from being fertilized, the cytoplasm at 24 h after gametogenesis is devoid of most of those organelles found in the developing zygote or the mature ookinete. The cell is surrounded only by a single membrane. Although at various points beneath the membrane there are deposits of electron‐dense material reminiscent of those deposited in the zygote, no further development of ookinete structures takes place in the unfertilized fema

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1984.tb02987.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

ABSTRACTLepidotrachelophyllum fornicisn. g., n. sp. was discovered in White Lake, Ontario, Canada, under winter ice. The genus isTrachelophyllum‐like, being highly flattened, elongate, and very extensible. The major feature that separates it from other genera in the family Trachelophyllidae is the presence of a dense layer of organic scales which covers the exterior of the cell and through which the cilia emerge. The scales are composed of filamentous material which is organized as an ovoid structure. The “rim” of the baseplate is formed of interwoven filaments. The baseplate is broken by circular or polygonal apertures. The same filaments form an arched superstructure broken by even larger, less regular aper

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1984.tb02988.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

ABSTRACTEvidence for meiosis was demonstrated electron microscopically for the first time inPneumocystis cariniiin rat alveoli by the observation of synaptonemal complexes followed by nuclear divisions. Synaptonemal complexes indicating meiotic nuclear divisions were observed in uninuclear precysts. Additionally, owing to the use of tannic acid as a fixative, spindle microtubules were also observed for the first time in the precyst. Based on these facts, a new life cycle of the organism is proposed. The precyst has generally been considered an intermediate form between the trophozoite and the cyst. The present paper proposes that the precyst is additionally defined as the cell in which eight intracystic bodies are produced through meiotic reduction. The most characteristic feature of the precyst is a clump of mitochondria in the cytoplasm. We divide the precyst phase into three forms, which are named early, intermediate, and late. Synaptonemal complexes were only observed in the early precyst, which is a uninuclear cell with a thin pellicle. In the intermediate precyst, nuclear divisions are observed as follows: meiosis I produces two haploid nuclei and each of these divides at meiosis II producing four nuclei. After that, another postmeiotic mitosis takes place, resulting in eight haploid nuclei. In the late precyst, a delimiting membrane originates from the mother plasmalemma and surrounds the daughter nuclei and a small portion of the adjacent cytoplasm. Finally, when the eight intracystic bodies are complete, the precyst changes to a cyst. Thus, we deduce that intracystic bodies resulting from meiotic nuclear division are haploid and, after excystation, they are haploid trophozoites. We consider that this process can be called sporogony. Although we could not distinguish between the haploid and the diploid trophozoite, it is quite plausible that copulation occurs, probably in host alveoli.

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1984.tb02989.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

ABSTRACTTrypanosoma lucknowin. sp. was isolated in culture from one of 126Macaca mulattaoriginating from the vicinity of Lucknow, Uttar Pradesh, India.Trypanosoma lucknowiis distinctive because of the large number of epimastigotes and trypomastigotes which, in culture, exhibit no movement or only a slight bending of the flagellar end. This limited motility coincides with a free flagellum which is either completely absent or rudimentary. The microorganism is cloned readily, and the description is based upon such cultures.Trypanosoma lucknowishows pronounced differences from other trypanosomes of South Asian macaques and from “aflagellar” African trypanosomes. The ultrastructural demonstration of a cytostome and contractile vacuole suggests ultimate grouping with stercorarian trypanosomes. A 3‐D reconstruction of the flagellar pocket/cytostome region is inc

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1984.tb02990.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY