摘要:

We have expressed theParameciumcalmodulin gene inEscherichia coliby changing the four TAA codons in this gene to CAAs. This was carried out by three polymerase chain reactions (PCRs) and then cloning the product into the expression vector pKK223‐3 immediately downstream of itstrp‐lachybrid promoter. JM109 strain ofE. coli, transformed with the recombinant plasmid harboring the alteredParameciumcalmodulin gene, produces a protein judged to be calmodulin. It is recognized by a monoclonal antibody toParameciumcalmodulin; it migrates with the native protein at nearly the same rate in electrophoreses; and it shows a Ca2+‐dependent shift in electrophoretic pattern. The production of calmodulin is about 170 times as efficient withE. colias withParameciumin terms of unit volume of packed cells, and is about 400 times as efficient in unit volume of liquid culture. This method appears useful in site‐directed mutageneses and in the heterologous productions of other ciliate proteins. A critique of this method is provided. A calmodulin half‐molecule, a by‐product of this project, i

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1991.tb04814.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Sphaerospora epinephelin. sp. is described from grouper,Epinephelus malabaricus, in cage‐cultured and wild fish collected from both coastal lines of southern Thailand. Subspherical to spherical spores and mono‐ or disporous pseudoplasmodia were observed in the lumen of kidney tubules. Pseudoplasmodia were round to elongate, size range 15.6–22.9 μm (length) × 8.4–21.6 μm (width). Spores were 7.8–10.0 μm (length) × 12.3–14.5 μm (thickness), and 7.0–9.5 μm (width) with two spherical polar capsules of equal size measuring 2.9–4.4 μm in diameter and containing polar filaments with six or seven windings. Two uninucleate sporoplasms showed iodine vacuoles. Blood stages, similar to C‐blood protozoans observed from freshwater fish in Europe, were found from peripheral blood smears of grouper. Ultrastructural studies of blood stages showed a similar structure to unidentified mobile protozoans from the blood of carp. Electron dense bodies were observed in the cytoplasm of the primary cell blood stages. Infected proximal‐tubular epithelial cells showed highly vacuolated cy

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1991.tb04815.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

We previously reported that phospholipase increases host cell penetration byToxoplasma gondii. Here we show that calcium‐dependent phospholipase A (PLA) activity is found in the supernatant of sonically disruptedT. gondii. When fractions of disruptedT. gondiiwere incubated with host cells, the release of fatty acids and lysolipids was detected. Fractions of sonically disruptedT. gondiiwith PLA activity increasedT. gondiihost cell penetration in a bioassay. In addition, a protein of approximately 20 kDa was detected by immunoblot ofT. gondiiantigens with horse antiserum to snake venom, the major antibody of which recognizes PLA2. Incubation ofT. gondiiwith exogenous PLA2resulted in increased solubility of a rhoptry protein. This protein, which we previously characterized as involved with enhanced parasite invasion of host cells and which is recognized by monoclonal antibody Tg49, was detected in increased amounts in supernatant fractions of extracellular parasites treated with PLA2. Whereas without PLA2treatment, it is only slightly soluble under physiological conditions. This raises the possibility that PLA may be implicated in the release of rhoptry protein

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1991.tb04816.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

The gregarineCosmetophilus vonones, n. g., n. sp. (Sporozoasida: Actinocephalidae: Acanthosporinae) from the intestine and intestinal caeca of the harvestmanVonones sayi(Simon) (Opiliones: Cosmetidae) is described. The new internal parasite is the first recorded from a harvestman in the New World and the second from the opilion suborder Laniatores. In addition to the records from the type locality in western Texas, additional collections are reported from the same host in central and eastern Texas and Tennessee.

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1991.tb04817.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Several investigations have indicated thatTetrahymena pyriformissecretes ribonuclease activity into culture media. The extracellular ribonuclease from strain W has been purified and partially characterized. The molecular weight was determined by gel filtration to be 26,500. The amino acid composition of the enzyme was compared with those of the three intracellular ribonucleases characterized by Trangas, and substantial differences were demonstrated. The extracellular enzyme hydrolyzed both polyadenylic and polyuridylic acids, indicating lack of absolute base specificity. The hydrolysis of polyadenylic acid followed normal Michaelis‐Menten kinetics, but substrate inhibition occurred at high concentrations of polyuridylic acid. The hydrolysis of polyuridylic acid was competitively inhibited by 2′‐ and 3′‐cytidine, guanine, and uridine nucleotides, and by 2′AMP. No inhibition of the hydrolysis of Torula yeast RNA was detected. The kinetic properties of the extracellular ribonuclease are compared with those of the intracellu

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1991.tb04818.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Gregarina niphandrodes, a new species of septate eugregarine, is described from the adult mealworm,Tenebrio molitor. Measurements given are means in μm. Gamonts in association. Nuclear diameter consistent, 35.5. Primite: protomerite hemispherical; length 59.5; width 91.2; deutomerite ovoid; length 173.4; width 145.6; total length 232.9. Length of protomerite/total length index 25.7. Length of deutomerite/total length index 74.3. Length of protomerite/length of deutomerite index 35.4. Width of protomerite/width of deutomerite index 63.5. Satellite: protomerite hemispherical; length 40.2; width 81.6; deutomerite ovoid; length 177.4; width 113.9; total length 217.6. Length of protomerite/total length index 19.0. Length of deutomerite/total length index 81.0. Length of protomerite/length of deutomerite index 23.8. Width of protomerite/width of deutomerite index 76.7. Gametocysts spherical, diameter 225, producing multiple oocyst chains under dry storage in 36–52 h. Oocysts very uniform in shape and size, dorsum doliform with angles squared by enclosing sheath, length 8.8, width 5.5; flattened dorsoventrad with mesad tumidus, pleuron height 2.2. Morphological measurements, indices, and oocyst descriptions are given forG. cuneata, G. polymorphaandG. stei

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1991.tb04819.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Riboflavin deficiency inhibits the growth of malaria parasites both in vitro and in vivo in infected animals and humans. Although the precise mechanisms underlying this inhibition are unknown, they may involve enhanced requirements for riboflavin by parasites. To investigate this possibility, the rate of uptake of [14C]riboflavin and the biosynthesis of FMN and FAD from riboflavin were studied in infected (5–8% parasitemia) and uninfected human erythrocytes. All cells were incubated for 0–3 h at 37° C in phosphate buffered saline containing MgCl2, glucose, and [14C]riboflavin (2.5–7.5 μM). At hourly intervals, samples were removed, centrifuged, washed twice with cold buffer, and lysed before counting the radioactivity. The rate of in vitro biosynthesis of FMN and FAD from riboflavin in erythrocytes was measured by ion exchange chromatography and reverse isotope dilution techniques. Results showed that the rate of riboflavin uptake and the biosynthesis of FMN and FAD were enhanced in erythrocytes with parasitemia as compared with results in unparasitized erythrocytes. Riboflavin uptake in erythrocytes was proportional to the extent of parasitemia and especially to percent of schizonts present in erythrocytes. These studies indicate that the requirement for riboflavin may be greater in the parasite than in the host erythrocyte. This increased riboflavin requirement may be due to rapid multiplication, higher metabolic rate, and extreme vulnerability to oxidative stress of malaria parasites compared with that of host erythrocytes. The differential requirement of riboflavin by the host and the malaria parasite may hold important potential for developing new strategies for malaria chemo

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1991.tb04820.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

The morphology, infraciliature, and life cycle ofEndosphaera terebrans, a suctorian endocommensal of peritrichs, have been studied with the aid of silver impregnation.The life cycle ofEndosphaera terebransbegins with infection of the host cell by a small larva. The swarmer has a pointed needle‐like cellular projection and two rings of cilia. The swarmer penetrates the peritrich, loses the cilia, and then matures into an adult. The infraciliature of the adult form has four rows of barren kinetosomes that lack kinetodesmal fibers. By endogenous budding, a migratory larva is produced that leaves the host cell through the peristomial disc and that can infect other peritrich

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1991.tb04821.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

The trypanosomatid previously described asCrithidia roitmaniis characterized here at the ultrastructural and biochemical levels. The data indicates that the parasite belongs to theHerpetomonasgenus, and we therefore suggest the flagellate to be denominated asHerpetomonas roitmanin. comb. Cladistic analysis of isoenzyme data generated by eight different enzymes showed that the parasite presented a distinct banding pattern and could be grouped with someHerpetomonasspp., but not withCrithidiaspp., used as reference strains. Accordingly, when the parasites were grown for longer periods in Roitman's defined medium, expontaneous differentiation from promastigotes to opisthomastigotes (typical of theHerpetomonasgenus) occurred. Transmission electron microscopy revealed the presence of bacterium‐like endosymbionts in the cytoplasm of all evolutive forms of the parasite. All morphological alterations characteristic of endosymbiont‐bearing trypanosomatids could be obser

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1991.tb04822.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

GTP‐binding proteins act as molecular switches in a variety of membrane‐associated processes, including secretion. One group of GTP‐binding proteins, 20–30 kDa, is related to the product of therasproto‐oncogene. InSaccharomyces cerevisiae, ras‐like GTP‐binding proteins regulate vesicular traffic in secretion. The ciliate protistParamecium tetraureliacontains secretory vesicles (trichocysts) whose protein contents are released by regulated exocytosis. Using [α‐32P]GTP and an on‐blot assay for GTP‐binding, we detected at least seven GTP‐binding proteins of low molecular mass (22–31 kDa) in extracts ofParamecium tetraurelia.Subcellular fractions contained characteristic subsets of these seven; cilia were enriched for the smallest (22 kDa). The pattern of GTP‐binding proteins was altered in two mutants defective in the formation or discharge of trichocysts. Trichocysts isolated with their surrounding membranes intact contained two minor GTP‐binding proteins (23.5 and 29 kDa) and one major GTP‐binding protein (23 kDa) that were absent from demembranated trichocysts. This differential localization of GTP‐binding proteins suggests functional specialization of specific GTP‐binding proteins

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1991.tb04823.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY