摘要:

ABSTRACT.Twenty different clonal strains of marine and brackishEuplotes, representing four morphotypes, were tested for hyposalinity tolerance by a method which gradually acclimated the cells to lower salinity medium. The lowest salinities in which the strains could thrive ranged from 60% of normal seawater to complete freshwater. The morphological effects of culture medium salinity were also examined for two strains of a small“Euplotes charon”morphotype, as well as for two mating compatible“Euplotes vannus”strains and several of their exconjugates. There were no differences between the euryhaline strains grown in fresh or saltwater, except for a slight increase in overall cell size in one strain when cultured in freshwater medium.E. vannusstrains increased in overall cell size with decreased salinity; also, the dorsal surface of the cells can become disorganized when the cells are cultured in 30% normal s

ISSN:1066-5234    

DOI:10.1111/j.1550-7408.1994.tb06083.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

ABSTRACT.Classical genetic techniques were applied to clonal cultures of theEuplotes vannus‐crassus‐minutasibling species complex in an effort to provide some resolution to the species problem among these hypotrichs. Complex mating interactions were observed among clonal stock cultures derived from samples collected from sympatric and allopatric populations in a wide geographic survey. These results suggested that the classical model for the mating type inheritance and determination in theseEuplotesis necessary but not sufficient to describe the mating mating interactions among populations of these ciliates. Successful conjugation between the nominal speciesE. crassusandE. vannuswas observed routinely, and crosses between these two nominal species did not differ significantly from those among the other clonal stock cultures with respect to mating intensity and exconjugant survival. Data from backcrosses suggests thatE. vannusandE. crassuscan and do exchange genes. Based upon these data, we conclude thatE. vannusandE. crassuscomprise a single, highly polymorphic species with countless small populations, among which incomplete genetic exchange takes pl

ISSN:1066-5234    

DOI:10.1111/j.1550-7408.1994.tb06084.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

ABSTRACT.A method for discriminating amongLeishmaniais described, based upon small subunit ribosomal DNA sequence differences. The method was to amplify the entire 2.2 kb small subunit rDNA by polymerase chain reaction using conserved primers specific for the 5′ and 3′ termini of the small subunit ribosomal RNA, and then hybridize the product dotted onto nylon membranes with labeled oligonucleotides. The design of the hybridization probes was based upon complete small subunit rDNA sequences fromL. amazonensis, L. majorandL. guyanensisand partial sequences ofL. mexicana, L. braziliensis, L. tropicaandL. chagasi.A high degree of sequence similarity (>99%) among species was found. However, sufficient sequence divergence occurred to permit the design of internal oligonucleotide probes specific for species complexes. This procedure successfully discriminated amongst a wide range ofLeishmaniaisolates. The method detected as few as 10 cultured organisms and detected parasites in tissue samples from experimentally infected animals. Non‐radioactive labeling showed the same specificity and sensitivity as radioactive p

ISSN:1066-5234    

DOI:10.1111/j.1550-7408.1994.tb06085.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

ABSTRACT.Large percentages ofToxoplasma gondiitachyzoites could be induced to display two types of movement associated with active invasive behavior by exposing them for 1 min to 0.002% trypsin in phosphate‐buffered saline (PBS). The motile activity, consisting of clockwise rotation around the posterior end (about 20 revolutions per min) and twirling‐gliding over a poly‐L‐lysine substrate (1.2 ± 0.2 μm/s standard deviation), was observed and recorded by video‐enhanced contrast microscopy. The number of active tachyzoites reached a maximum 1 min after trypsinization; the motile response of the population lasted for about 5 min. Activation was prevented by soybean trypsin‐inhibitor, and could not be induced again in previously treated specimens. Electron‐microscopy of trypsinized tachyzoites fixed in the presence of ruthenium‐red revealed discrete discontinuities of the plasma membrane, which sealed within 90 min after washing with PBS. Treated tachyzoites were able to invade cultured epithelial cells with a higher relative infectivity than that of untreated parasites. Perfusion of trypsinized tachyzoites with 1 mM of either CaCl2or MgCl2and 1 mM ATP increased the number of activated parasites to over 60%; on the other hand, all induced motility was inhibited or blocked by agents that chelate divalent cations. The present preparation, which provided the first serial illustrations ofT. gondiimovements induced by a defined chemical stimulus, may offer a useful experimental model for the study of motility

ISSN:1066-5234    

DOI:10.1111/j.1550-7408.1994.tb06086.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

ABSTRACT.Highly‐pathogenic, mouse‐passagedNaegleria fowleriamoebae are complement resistant. The present study evaluates the effect of complement onN. fowleriand the virulence of the amoebae after animal passage and growth in two different axenic media. PathogenicN. fowlerimaintained in “enriched” Cline medium are virulent for mice and resistant to complement lysis. A rapid decline in resistance to complement and virulence for mice is observed when highly‐pathogenicN. fowleriare grown in Nelson medium lacking hemin.N. fowlerimaintained in Nelson medium can be rendered complement‐resistant by shifting the amoebae to growth in Cline medium for 2 h prior to the addition of complement. Cycloheximide treatment ofN. fowlerimaintained in Nelson medium blocks the transition to a complement‐resistant phenotype following a shift in growth medium. Proteins were radiolabeled with [35S] during a shift from Nelson to Cline medium to identify specific polypeptides which may be associated with the functional activities related to virulence and resistance

ISSN:1066-5234    

DOI:10.1111/j.1550-7408.1994.tb06087.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Lagenophrys novazealandaen. sp. occurs on the gills ofParanephrops zealandicus, a parastacid crayfish from New Zealand. The new species has the hemispheroidal lorica most common among members of its genus and is distinguished by its possession of large tubercles on the thickened edge of the anterior lip of the lorica aperture, a deep cleft in the left side of the lip's edge, and a ovoid to reniform macronucleus located in the right‐hand part of the body. It is probable that an as yet unnamed species ofLagenophrysknown to occur on another species ofParanephropsin New Zealand is distinct fromL. novazealandaebut phylogenetically related to it.Lagenophrys petilan. sp. occurs on setae ofParastacoides tasmanicus, a parastacid from Tasmania. The new species has an ovoid lorica tapering to a slender pseudostalk at the posterior end, a type of lorica possessed by only two other members of its genus that also attach to their host's setae. It is distinguished from the other ovoid species by the proportions of the lorica, the extreme shortness of the lips of the lorica aperture, and an ovoid macronucleus located in the right, anterior part of the body. Clefts in the lips ofL. novazealandaeand other members ofLagenophrysmay function as points of flexure to allow the lips to bend in ways that accommodate interspecific differences in the size of the epistomial disk and its operation during suspension feedin

ISSN:1066-5234    

DOI:10.1111/j.1550-7408.1994.tb06088.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

ABSTRACT.The microsporidiumNadelspora cancerin. g., n. sp., is described from the striated musculature of the Dungeness crab (Cancer magister) in Oregon, USA. The needle‐shaped spores were rounded anteriorly, tapered to a posterior point and measured 7.1–11.8 × 0.2–0.3 μm in fixed preparations. The extremely narrow spore diameter prevented observation of morphological details at the light microscopic level and ultrastructural details of mature spores were difficult to resolve. Meronts were not observed and the monokaryotic merozoites and sporonts were not contained within either parasitophorous or sporophorous vesicles. Sporonts were disporoblastic and gave rise to monokaryotic sporoblasts that became narrow and elongate as they developed into immature spores with a developing polar filament. The nucleus was not clearly resolved in mature spores and may have been surrounded by the lamellar polaroplast. The polar filament was of nearly uniform diameter throughout most of its length and ended abruptly about three‐fourths of the distance from the anterior end of the spore. Unusual spherical non‐membrane bound granules surrounded the polar filament in a spiral arrangement. The new microsporidium resembles members of the family Mrazekiidiae, but differs in lacking a diplokaryon at any stage. It is probably most closely related toBaculea daphniaefrom which it differs primarily by spore shape and size. The familial relationships of the genusBaculeahave not been determined and it is proposed to include it withNadelsporain the new family Na

ISSN:1066-5234    

DOI:10.1111/j.1550-7408.1994.tb06089.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

ABSTRACT.Parasitic amebas propagate among hosts through cysts, the resistant forms in their life cycle. In spite of their key role in infection, little is known about the encystation process and the mechanisms involved in reaching this stage. Two features drastically affected by encystation are motility and cell shape, both of which are determined by the cytoskeleton, composed mainly of actin in these organisms. Therefore, we studied the occurrence and relative levels of actin and actin synthesis during encystation ofEntamoeba invadens.Using a cDNA actin probe obtained from a library ofE. histolyticaand a monoclonal antibody against actin, we found that, while the total actin levels sharply decrease as encystation proceeds, the levels of actin mRNA are reduced only in mature cysts. Moreover, actin synthesis does not take place in precysts and the later stages of cyst formation. In contrast, the levels of other proteins remain stable in trophozoites, precysts and cysts, and stage specific peptides are actively synthesized in precysts. The results indicate that encystation is accompanied by a preferential down‐regulation of actin synthesis and a decrease in actin levels. The reorganization of the cytoskeleton occurring as trophozoites transform into round, quiescent cells, could be a regulatory factor in the observed change

ISSN:1066-5234    

DOI:10.1111/j.1550-7408.1994.tb06090.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

ABSTRACT.Metanophrys diminutan. sp., a marine philasterine scuticociliate collected from the south Florida coast, was preserved for transmission electron microscopy using a mixed fixation technique. Rough endoplasmic reticulum profiles were found proximal to mitochondria and within mitochondrial fenestrations (or deep pockets). In longitudinal sections mitochondrial profiles appear to be very long, occupying almost the entire length of the cell. The micronucleus is roughly spherical to ovoid, semi‐enclosed in the macronucleus. The oral polykinetid #1 is composed of two files of kinetosomes. The c segment of the oral dikinetid is composed of three to four kinetosomes. This species is the smallest within the genusMetanophry

ISSN:1066-5234    

DOI:10.1111/j.1550-7408.1994.tb06091.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

ABSTRACT.The clonal life history of ciliated protists is characterized by a sequence of phenotypes; sexual immaturity, maturity, and senescence. The distinctiveness of immaturity and maturity has been investigated. Standard assays of the onset of maturity of progeny clones from a cross between stocks EC1 and EC2 ofEuplotes crassusdemonstrated significant differences among clones and among testers within clones. They also revealed that the first positive test(s) of a progeny subclone were typically followed by at least one negative test. Special protocols were devised to investigate if maturity was reversible at the cellular level. In these experiments, the first mating pair of a progeny subclone was split before the consummation of mating. From these two cells as well as from control progeny and tester cells, subclones were established and every leftover cell was tested for maturity after each transfer. Both standard and split‐pair progeny subclones had immature and slow‐ to‐mate cells. The number of fissions before progeny exhibited sexual behavior indistinguishable from the testers was more than twice that to the first mating reaction of a subclone. At the first sign of maturity, progeny lines are a heterogeneous population of cells able and not able to mate, but remarkably, clonal descendants of those able to mate may become unable to mate. The development of maturity is progressive, quantitative and non‐monotonic rather than an instantaneous

ISSN:1066-5234    

DOI:10.1111/j.1550-7408.1994.tb06092.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY