摘要:

ABSTRACTThe micronuclei of the ciliated protozoanPseudourostyla cristatawere eliminated by amputation shortly before binary fusion. The amicronucleate cell lines derived from regenerants were maintained for more than a year. They exhibited a lower viability and reduced vigor in asexual propagation. There was some improvement in the growth of the cell lines 1 mo after operation, but the growth rate remained subnormal even up to 1 yr of culture. The exact cause of the poor growth and survival in the first 3 wk after operation, whether the loss of the micronucleus or operational damage, remains to be determined. It is nevertheless clear that the micronucleus is important for subsequent asexual propagation. The amicronucleate cell lines were permanently crippled in morphogenesis, unlike the situation inParameciumamicronucleates in which stomatogenesis returned to near‐normal during asexual propagation. They always included some cells with a characteristically defective adoral zone of membranelles, reduced number of frontal‐ventral‐transverse cirri, and reduced body length. They were also reluctant to encyst. It is evident that the micronucleus is important for maintaining normality of the oral apparatus. It is postulated that the permanent stomatogenic crippling of amicronucleates might be related to genomic reduction in the developing macronucleus in sexual reproduction, as exhibited by other hypotrichs. The morphological defects associated with the adoral zone of membranelles may be rationalized as arising from the spreading of a zone of degeneration in the cortex affecting the left edge of the membran

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1989.tb05520.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACT.Using fixed sporozoites in a 3‐layer immunofluorescence assay (TLIFA), class‐specific, parasite‐specific antibody responses in chicks to single‐pulse infection withEimeria tenellahave been studied in gut contents and bile as well as plasma and feces. After infection with 103oocysts, IgA antibody was first detected in the duodenal lumen, then in bile, plasma, cecum, and the distal small intestine. The kinetics of the bile IgA response correlated with that in plasma and peaked 9 days post‐infection (d.p.i.); IgM was detected in gut contents and bile as well as plasma, and IgG was occasionally detected in gut contents, especially in the duodenum. In some experiments, IgA was detected in gut contents and bile to at least 21 d.p.i. Infection with 103oocysts resulted in an earlier and increased response and relatively high IgG titers in cecal contents. Coproantibody was detected inconsistently and at low titer. When sporozoites that excysted in vitro were incubated in specific, antibody‐positive (9 d.p.i.) cecal contents, some complement‐mediated IgG‐associated anti‐sporozoite effects were observed; however, the major effect of cecal contents and the only effect of bile was a non‐lethal agglutination of living sporozoites. By fractionation of cecal contents and imtnunoblotting this was confirmed to be IgA mediated; IgA antibodies in cecal contents and bile after infection were shown to bind to sporozoite membrane antigens by surface fluorescence as well as agglutination. Agglutination detected anti‐sporozoite antibody in gut contents and bile up to 21 d.p.i., peaking between 7 and 13 d.p.i., corresponding with TLIFA results. The immunofluorescence studies reveal the extremely labile nature of the sporozoite surface antigens and support the hypothesis that naturally elaborated IgA antibodies are involved in the modulation of complexed sporoz

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1989.tb05521.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTClathrin‐coated vesicles, identified by negative staining with uranyl acetate, were purified fromChlamydomonas rein‐hardtii.Isolated coated vesicles had diameters ranging from 70 to 140 nm (mean diameter±SD of 95±17 nm, n=300). These vesicles were markedly heterogeneous in both density and surface charge, as indicated by equilibrium density sedimentation and elution from anion‐exchange columns. Highly‐purified coated‐vesicle fractions contained 2 major polypeptides, identified as the clathrin heavy chain (185 kDa) and the clathrin light chain (40 kDa).Chlamydomonasclathrin heavy chain cross‐reacts weakly with an antibody against bovine brain clathrin heavy chain. Coat stability in several buffers was compared to that of bovine brain coated vesicles. Stability was similar, except for a greater stabilityof Chlamydomonascoated vesicles in 0.5 M T

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1989.tb05522.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACT. It is well known thatPlasmodium‐infected hosts are immunosuppressed, as shown by their depressed immune responsiveness to a variety of antigens. It is not known, however, whether the immune response of malaria‐infected animals to the malarial parasite itself is suppressed. The availability of a noninfectious, immunosuppressive factor (ISF) derived fromPlasmodium berghei‐infected rat erythrocytes made it possible to investigate this question. Mice infected withP. bergheiand injected with the ISF had higher levels of parasitemia and shorter survival times than control mice that were similarly infected but were treated with control material derived from noninfected rat erythrocytes or with saline solution. Conversely, mice immunized against the ISF and then infected withP. bergheihad lower parasitemias and longer survival times than mice immunized with the control material or with saline solution. We conclude that immunosuppression in murine malaria affects the course of malaria infe

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1989.tb05523.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACT. A procedure was developed to purify a coated vesicle fraction from the protozoan parasiteTrypanosoma brucei.Electron microscopy revealed a difference betweenT. bruceicoated vesicles and clathrin‐coated vesicles from other eukaryotes: trypanosome vesicles were larger (100 to ISO nm in diameter) and contained an inner coat of electron‐dense material in addition to the external coat. Evidence suggests that the internal coat is the parasite's variant surface glycoprotein (VSG) coat. The SDS‐PAGE analysis shows the major protein ofT. bruceicoated vesicles has a molecular mass of 61 kD, similar to VSG; this protein was recognized in an immunoblot by anti‐VSG serum. Trypanosome coated vesicles also contain a protein which comigrates with the major protein (clathrin) of coated vesicles purified from rat brains. However, this protein is a minor component and it is not serologically cross‐reactive with mammalian clathrin. Immunoblot analysis demonstrated that the parasite vesicles contained host IgG, IgM, and seru

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1989.tb05524.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACT. The marine ciliateEuplotes vannuswas used to lest whether keronopsin, the water‐soluble component of(hetoxic pigment complex fromPseudokeronopsis rubra, narcotizes cells by affecting ion conductance. Keronopsin delays the rate of rise in the regenerative component of action potentials under constant current injection. In depolarizing voltage steps it reduces the rate of rise and the final amplitude of the initial Ca2+inward current. Normal traits are restored after change to keronopsin‐free medium. Effects on locomotory behavior, spontaneous membrane depolarization, action potential, and inward current, all provide evidence that keronopsin acts on cells by obstructing Ca2+ inf

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1989.tb05525.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTTwenty‐six monoclonal antibodies were produced against membrane‐enriched preparationsof Endotrypanum schaudinniorEndotrypanumsp. promastigotes. Fifteen of these monoclonal antibodies (E1‐E15) reacted only with the standard strain ofE. schaudinni, M6159. Monoclonal antibodies E16‐E26 were consideredEndotrypanumspecific; no cross reactivity was detected with any other genus of the family Trypanosomatidae(Leishmania, Trypanosoma, Leptomonas. HerpetomonasorCrithidia)by dot‐blot radioimmune assay. By indirect immunofluorescence assay, the antigens recognized byEndotrypanumspecific monoclonal antibodies appear to be associated with the surface of the parasite. Based on Western blot analysis, 4 antigenic molecules ranging in molecular weight from 24 kD to 160 kD were identified by monoclonal antibodies specific for the strain ofE. schaudinni, M6159. Monoclonal antibodies specific for the genusEndotrypanumidentified an antigen of molecular weight 48 kD as well as a diffuse component migrating with an apparent molecular weight of

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1989.tb05526.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTThe secretory organellesof Plasmodium knowlesiwere studied ultrastructurally to examine their mode of action during invasion. The formation of lamellar structures in merozoite rhoptries within late stage schizonts is prevented by the protease inhibitors chymostatin and leupeptin. Under normal conditions vesicles lined by 6‐nm membranes are formed in rhoptries during erythrocyte invasion. Stereoscopic viewing of tilted sections shows that where the merozoite apex contacts the parasitophorous vacuole (PV) membrane during invasion, a domed elevation of the PV surface lies within the mouth of the rhoptry duct in contact with the secretory matrix. The membrane of the early invasion pit is thinner (6 nm) than the red cell membrane elsewhere, and sheets of lamellar material are frequently present on the invasion pit surface. These findings support the proposal that the rhoptry‐microneme complex is capable of generating membranous material and inserting it into the red cell surface in a controlled manner to create the parasitophorous vacuole. On the basis of this model, measurements from serial sections show that the rhoptries could provide enough material to create a membrane lining the parasitophorous vacuole, and, with the contribution of the microspheres, could double it to accommodate the early ring stage of the paras

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1989.tb05527.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1989.tb05528.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

BIOMINERALIZATION is the process by which living organisms assemble structures from naturally occurring inorganic compounds. Mineral deposition is common and widespread amongst Protozoa and in most instances the mineralized structures provide skeletal support and protection for softer organic parts [10]. The 2 most common minerals to be deposited by Protozoa are silica and calcium carbonate. Groups of Protozoa that deposit silica, which we are concerned with here, include the diatoms, chrysophytes, choanoflagellates, Radiolar‐ia, Heliozoa and testate amoebae [10].In the majority of silica‐depositing protista, silica is taken up from the medium in the form of monomelic orthosilicic acid Si(OH)4(soluble reactive silicate) and deposited as amorphous, polymerised biogenic silica or opal within membrane‐bounded vesicles known as silica deposition vesicles (SDV). Often biogenic silica is characteristically patterned and ornamented and for most protozoan groups the morphology of silicified parts is of prime taxonomic importance.By far the most extensively studied group of silica‐depositing organisms are the diatoms [1, 12, 13]. To date most of our knowledge of silica metabolism in protists has been based on investigations into this group. Diatoms require silica for the production of their frustules. Uptake and deposition of silica occurs within a closely denned portion of the cell cycle, between nuclear division and cell separation. It occupies about ± of the cell cycle and without an adequate supply of silica diatoms are unable to produce new frustule valves with the result that cell division cannot be completed. Diatoms, therefore, have an obligate requirement for silica and without this nutrient they cease to grow [11].In contrast to diatoms a number of other silica‐depositing protistan groups, such as loricate choanoflagellates and certain chrysophytes, have a facultative requirement for silica. In the past decade the ultras true ture, physiology and ecology of loricate choanoflagellates have been extensively studied by a number of different workers [7] and the significance of these studies to our understanding of the mechanisms, controls and dynamics of silica secretion is summarised and disc

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1989.tb05529.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY