摘要:

ABSTRACT. The behavior of nuclear envelopes during mitosis inAmoeba proteuswas studied by means of indirect immunofluo‐rescence staining using a monoclonal antibody against a 220‐kD membrane‐associated protein of amoebae in conjunction with DAPI staining of chromatin. The antibody selectively recognized antigens on nuclear envelopes during interphase but did not react with the nuclear membranes during mitosis until after cytokinesis had been completed. Thus, it appeared that the membrane‐associated protein reacting with the monoclonal antibody and normally present on the nuclear membranes was absent from fragmented nuclear membranes or nuclear membranes that were continuous but did not have the honey‐comb lamina. The findings suggested that the 220‐kD nuclear‐membrane protein may be involved in the dissolution and reformation of the honey‐comb lamina during mit

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1989.tb01078.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACT. Phorbol 12‐myristate 13‐acetate increased the number of gametocytes by 50 to 100% in well or petri dish cultures of the HB‐3 clone ofPlasmodium falciparum. Phorbol dibutyrate had a similar effect. The optimal concentration for each of these agents was 20 ng/ml or approximately 30 nM. No effect of forskolin was found, other than a general inhibition of growth at concentrations over 10 μM. An inhibitor of phosphodiesterase, 8‐bromo cyclic adenosine monophosphate (at concentrations of 0.1 and 1.0 μM) also significantly increased the number of gametocytes formed by t

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1989.tb01079.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACT. The presence of repeated DNA sequences encoding RNA inEntamoeba histolyticahas been reported. In the present study we demonstrate by agarose gel electrophoresis, DNase digestion and electron microscopic analysis that these genes are located on extrachromosomal circular DNA molecules with an approximate size of 26 kb. Detection of replication intermediates suggests the episomal nature of these molecules.Amplified, extrachromosomal rRNA genes appear to be a common feature among the lower eukaryotes, occurring more commonly as linear molecules and less commonly as circles.Entamoeba histolyticais 1 of the few organisms studied in which rRNA genes are located predominantly on extrachromosomal circles.

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1989.tb01080.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACT. Dividing tachyzoites ofNeospora caninumwere 4x3 μm and had ultrastructural characteristics typical for the cyst‐forming coccidia. Unusual ultrastructural characteristics of fully‐formed tachyzoites included no micropores, 8–12 anterior and 4–6 posterior rhoptries, and a few posterior micronemes. Most tachyzoites were located free in the host cell cytoplasm; only a few occurred within a parasitophorous vacuole. Parasite multiplication appeared to be rapid because most organisms were in various stages of endodyogeny. Neural tissue cysts ofN. caninumwere 24.3 × 19.2 μm and contained 50–200 bradyzoites (7.3 × 1.5 μm), which lacked micropores. The cyst wall was 0.74–1.12 μm thick and consisted of the primary cyst wall (the parasitophorous vacuole membrane) and a thick granular layer with electr

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1989.tb01081.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACT. This essay considers the responses ofParameciumand other ciliates to the inorganic ion environment from an elec‐trophysiological point of view. In reviewing data from published and unpublished sources it is shown that ions affect the cellular behaviour in multiple ways because the transmembrane potential can change due to the alteration of equilibrium potentials, ion conductances and surface charges of the membrane. Sensory input including effects from the ionic environment converge upon the membrane potential which has a temporal and spatial summing function. Hyperpolarizing and depolarizing potential shifts from the set point are near‐simultaneously and omnidirectionally transmitted along the membrane including the ciliary boundaries. The membrane potential regulates ciliary motility via an intraciliary messenger, Ca2+, which can enter, and presumably leave, the cytosol directly adjacent to the ciliary motor. Integration of the responses of thousands of cilia occurs in accordance with the electrical and structural provisions of the cell. Potential‐regulated motor and behavioural responses attenuate with time. This phenomenon, which has been loosely termed adaptation, has an electrophysiological basis in analogy to membrane accommodation following sustained stimulus input. The mechanisms of adaptation serve to restore, in principle, the membrane resting state and, thereby, the sensitivity to depolarizing and hyperpolarizing shifts of the membrane potential and the cell's responsiveness to environmental stimuli, respectively. For the inorganic ions involved in chemosensation the terms attractant and repellent are not applicable. They should be reserved to signalling substances which per se can define the behaviour of the

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1989.tb01082.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTThe ultrastructure of sporozoites and zoites ofHammondia heydorniwas studied in cultured bovine cells. In addition to ultrastructural features typical of coccidian parasites,H. heydornisporozoites and zoites contain rhoptries that are located posteriorly as well as anteriorly. Also, sporozoites contain a posteriorly located crystalloid body (1.2 μm in diameter); a small crystalloid body (0.5 μm in diameter) was occasionally seen in the anterior end. Zoites resulting from the 1st division of endodyogeny contain a posteriorly located crystalloid body, which is absent in zoites formed by subsequent divisions. Zoites contain posteriorly located amylopectin granules and a relatively large anterior vacuole which is not present in sporozoites. During penetration, the host cell plasmalemma ballooned laterally around the sporozoite creating a large cavity, which later disappeared. Sporozoites and zoites undergoing cell penetration usually exhibit partially empty anterior rhoptries; no changes occur in posterior rhoptries. Lysosomes fuse with the par‐asitophorous vacuole surrounding killed sporozoites but not live sporozoi

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1989.tb01083.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTThe effects of the 2 ornithine decarboxylase inhibitors α‐difluoromethylomithine (DFMO) and α‐monofluoromethyl‐dehydroormithine methyl ester (ΔMFMO‐ME) on growth ofBabesia bovisblood stages in vitro were tested. The DFMO had no apparent effects on in vitro growth ofB. bovisnor on the morphology of the parasite at concentrations up to 20 mM. In contrast, ΔMFMO‐ME had cytotoxic effects onB. bovisat 0.5 mM which were more pronounced at 5 mM. ΔMFMO‐ME caused both a decrease in percentage parasitized erythrocytes and a degeneration of parasites after 12 h exposure, and the magnitude of both effects was dose‐dependent. The effects of ΔMFMO‐ME were not reversible forB. bovisprecultured for 12 h (5 mM) or 24 h (0.5 mM) in drug before culturing the parasite in drug‐free medium. Unexpectedly, 300 μM putrescine did not reverse the effects of ΔMFMO‐ME onB. bovisblood stage, raising the possibility that inhibition of omithine decarboxylase is not re

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1989.tb01084.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACT. Ornithine decarboxylase and trypanothione reductase are the key enzymes in polyamine and trypanothione metabolism in kinetoplastids. Using a heterologousTrypanosoma brucei bruceiprobe for ornithine decarboxylase and a mixed synthetic probe of 29 oligonucleotides for trypanothione reductase, we have detected the putative genes for these enzymes by Southern blot hybridization using genomic DNA ofLeishmania braziliensis guyanensisMHOM/SR/80/CUMC I. The trypanothione reductase probe was constructed both from the conserved codon usage of the redox active site for other flavin oxidoreductases over a wide evolutionary scale, and the preferred codon usage for other genes in species ofLeishmania.

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1989.tb01085.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACT. Two strains of theLeishmania braziliensiscomplex have been adapted to grow extracellularly at elevated temperature as amastigote‐like forms in a cell‐free medium. These parasites can be serially cultivated and maintained at 32°C forL. panamensis(WR442;L. braziliensis panamensis) and at 28°C forL. braziliensis(M5052;L. braziliensis braziliensis). Several observations are presented that the forms adapted at elevated temperature are amastigote‐like. Morphologically, the amastigote‐like organisms appear rounded to ovoid and are immotile and smaller than promastigotes; the flagellum of the amastigote‐like forms does not extend beyond the flagellar pocket. In comparison, the promastigotes are very elongated, with a nucleus at mid‐cell length and a very long flagellum. By electron microscopy, the short flagellum of the amastigote‐like form is within a distended flagellar pocket; the 9 + 2 axonemal configuration is present but the paraxial rod is not observed. By contrast, the flagellum of the promastigote has a paraxial rod which extends from the axosome level. In addition, these amastigote‐like forms ofLeishmaniaare able to infect, to survive and to divide within the macropha

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1989.tb01086.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTImmunochemical evidence, employing monoclonal antibodies, shows that the forms ofL. braziliensiscomplex axenically grown at elevated temperature are amastigote‐like. The monoclonal antibodies were raised against membrane proteins of amastigote‐like forms, strains of bothL. panamensis(WR442) andL. braziliensis(M5052), which were grown axenically. The specificities of these antibodies were examined by indirect radioimmune binding assay, indirect immunofluorescent assay and Western blot analyses. Two distinct groups of monoclonal antibodies were obtained and their specificities were consistent with the 3 methods used. Four antibodies are specific for the speciesL. panamensisand react with both developmental stages. Six antibodies specifically recognize amastigote‐like forms grown at elevated temperature and intracellular amastigotes of bothL. panamensis(WR442) andL. braziliensis(M5052). These monoclonal antibodies do not bind to promastigotes of these species, nor to promastigotes of any other species ofLeishmania. Therefore these antibodies are specific for amastigotes ofL. panamensis(WR442) andL. braziliensis(M5052), and suggest that immunochemically both amastigote forms (culture and macrophage) are developmentally very close, if not identical. The molecules associated with the amastigote‐specific antigenic determinants consist of a Mr 12‐kD component and a heterogeneous component (Mr from 50 kD to>200 kD); these molecules appear to be identical for both amastigote‐like forms and amastigotes isolated from

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1989.tb01087.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY