摘要:

ABSTRACTCB1‐glycoprotein is a component of flagellar pocket, endosome, and lysosome membranes of long, slender bloodstream forms of theTrypanosoma bruceisubgroup of African trypanosomes. We have used immunoblotting, immunofluorescence, and cryoimmunoelectron microscopy to study CB1‐glycoprotein expression as long, slender bloodstream forms of pleomorphicT. b. bruceiandT. b. gambiensetransform through intermediate stages into short, stumpy forms. Intermediate and stumpy forms express more CB1‐glycoprotein than long, slender forms. These results, coupled with previous work showing that procyclic forms do not express CB1‐glycoprotein, show that the expression of lysosomal membrane glycoproteins is regulated coordinately with other aspects of lysosome and endosome function as these trypanosomes go through their lif

ISSN:1066-5234    

DOI:10.1111/j.1550-7408.1994.tb01512.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

ABSTRACTIsocitrate lyase was purified to homogeneity from ethanol‐grownEuglena gracilis. The specific activity was 0.26 μmol/min/mg protein. The molecular mass of the enzyme was calculated to be 380 kDa by gel filtration on a Superose 6 column. The subunit molecular mass of the enzyme was 116 kDa as determined by SDS‐polyacrylamide gel electrophoresis. These results showed that the native form of this enzyme was a trimer composed of three identical subunits. The pH optimum for cleavage and condensation reactions was 6.5 and 7.0, respectively. The Kmvalues for isocitrate, glyoxylate and succinate were 3.8, 1.3 and 7.7 mM, respectively. Isocitrate lyase absolutely required Mg for enzymatic activity. This is the first report of the purification of isocitrate lyase to homogeneity fromEuglena grac

ISSN:1066-5234    

DOI:10.1111/j.1550-7408.1994.tb01513.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

ABSTRACTA model for the in vivo evaluation of antipneumocystis drugs has been developed inSCIDmice infected intratracheally with cryopreserved mouse‐derivedPneumocystis carinii. The development of a highly reproducible fatalP. cariniipneumonia occured within 10 weeks (mean survival time ± SEM = 72.2 ± 1.2 days). Continuous administration of dexamethasone (2 mg/liter in the drinking water) exacerbated the rate of onset of severeP. cariniipneumonia (mean survival time ± SEM = 63 ± 1.3 days) inSCIDmice. The number of cysts per g of lung homogenate (homogenate counts) were maximal with an inoculum of 20,000 cysts at 6 weeks post infection. Homogenate counts correlated with infection scores (graded assessments of immunofluorescent cysts on lung impression smears) suggesting that infection scoring accurately and rapidly reflects the severity ofP. cariniipneumonia inSCIDmice. These studies led to the development of a drug screening protocol in whichPneumocystis‐free femaleSCIDmice (20–25 g) were started on dexamethasone 7 days prior to IT inoculation with a single dose of 20,000 cysts. Drugs were evaluated either for: a) prophylaxis (continuously from day 1 post infection) or b) treatment (from day 21 post infection) until day 42 post infection, when all mice were killed and infection scores determined. Co‐trimoxazole (at 250 mg sulfamethoxazole + 50 mg trimethoprim/kg/day) given in the drinking water was found to be highly effective in both the prophylaxis and treatment of mouseP. cariniipneumonia. Co‐trimoxazole remained very effective in the prophylaxisP. cariniipneumonia in theSCIDmouse at 125 mg sulfamethoxazole + 25 mg trimethoprim/kg/day p.o. and showed some enhancement of efficacy over sulfamethoxazole alone at 125 mg/kg/day p.o., suggesting limited synergy between sulfamethoxazole and trimethoprim. The results presented provide confirmation of the usefulness and predictability

ISSN:1066-5234    

DOI:10.1111/j.1550-7408.1994.tb01514.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

ABSTRACTThe role of the cilia in the locomotion (“gliding”) ofTetrahymena thermophilain a semi‐solid medium has been studied when cells were migrating in gradients of attractant. Video recordings and computer‐aided motion analysis of migrating cells and their ciliary activity show thatTetrahymena thermophilamigrate by swimming forward in semi‐solid methyl cellulose, using their cilia. Ciliary reversals occur at certain intervals and cause a termination (“stop”) of cellular migration. Cells with reversed cilia resume forward migration when normal ciliary beating resumes. In gradients of attractants, cells migrating towards the attractant suppress ciliary reversals, which leads to longer runs between stops than in control cells. Cells migrating away from the attractant have a higher frequency of ciliary reversals than the control cells resulting in shorter runs. Stimulated cells adapt to a particular ambient concentration of attractant several times during migration in the gradient. Adaptation is followed by de‐adaptation, which occurs during the “stop”. In the presence of cycloheximide, a strong inhibitor of chemoattraction, the attractant‐induced suppression of ciliary reversal is abolished (cells become desensitized to the attractant). It is concluded thatTetrahymenahas a short‐term memory during adaptation. This is important for the efficiency of migratio

ISSN:1066-5234    

DOI:10.1111/j.1550-7408.1994.tb01515.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

ABSTRACTThe enzymes of the arginine dihydrolase pathway were demonstrated inTritrichomonas foetusand their subcellular localization determined for bothT. foetusandTrichomonas vaginalis. Ornithine carbamyltransferase (anabolic and catabolic activities), ornithine decarboxylase and carbamate kinase activity were localized predominately (56–80%) in the non sedimentable fraction of both species. A large proportion (35–40%) of the arginine deiminase was, however, recovered in the large granular fraction, and this distribution was unchanged by increasing the ionic strength of the buffer. Upon density gradient centrifugation the particles containing arginine deiminase activity had an isopycnic density of 1.09 g/ml in percoll, and separated from hydrogenosomes (1.18 g/ml) and lysosomes (1.12 g/ml). Arginine deiminase was also the only enzyme of the dihydrolase pathway which demonstrated latency upon treatment of the 1.09 g/ml fraction with non‐ionic detergents. The results demonstrate the presence of the arginine dihydrolase pathway inT. foetusand indicate that at least a portion of the arginine deiminase in trichomonads is membrane assoc

ISSN:1066-5234    

DOI:10.1111/j.1550-7408.1994.tb01516.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

ABSTRACTTrichocyst discharge is an effective defense ofParameciumagainstDileptus margaritifer.The possible defensive function of backward swimming, which often follows trichocyst discharge uponParamecium‐Dileptusencounters was studied. Mutants incapable of backward swimming (pawnAinP. tetraurelia, cnrAinP. caudatum) escaped from dilepti nearly as frequently as wild‐type cells. Double mutants (pawnA‐nd7, cnrA‐tnd2) were eaten nearly as frequently as mutants incapable of trichocyst discharge. Thus, in the defense ofParameciumagainstD. margaritifer, the role of backward swimming is minor, if any, compared to trichocyst discharge. Among escaped cells, about a half of wild‐type and essentially none ofpawnA(cnrA) cells showed backward swimming.Parameciumbehavior during the encounter can be mimicked by the local, not global, application of lysozyme which is a strong secretagogue of t

ISSN:1066-5234    

DOI:10.1111/j.1550-7408.1994.tb01517.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

ABSTRACTImmunofluorescence was used to reveal the presence of a rhodopsin‐like molecule on the plasma membrane of the photoresponsive ciliateFabrea salina.The ciliate, fixed on a glass support, showed a spontaneous red‐orange fluorescence. Cells incubated with a fluoresceinated, anti‐bovine opsin, sheep polyclonal antiserum showed instead a green fluorescence typical of fluorochrome excited at 436 nm, whereas cells incubated with a fluoresceinated, nonimmune sheep serum kept their original red fluorescence. Excess bovine opsin did not inhibit the antibody reaction, but detergent‐coated purified bovine opsin was proven able to bind to the cell membrane. Since rhodopsin belongs to a gene‐related protein family, which includes adrenergic or cholinergic receptors, the cell response to acute exposure to muscarinic and adrenergic agonist and antagonist drugs was investigated. Acetylcholine, atropine, hexamethonium, noradrenaline, or phenoxybenzamine in the culture medium (10‐4M) did not influence motion behaviour nor phototaxis ofFabrea salina.These findings raise the possibility that a rhodopsin‐like molecule is present on the surface ofFabrea salina.Nevertheless, they do not prove that this surface antigen is a rhodopsin, or that this molecule is responsible for photoresponsiveness in

ISSN:1066-5234    

DOI:10.1111/j.1550-7408.1994.tb01518.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

ABSTRACTDescriptive information is provided for five ciliates collected from marine coastal British Columbian surface waters. In this paper we identify three new species,Strobilidium neptunin. sp.,Strobilidium veniliaen. sp., andStrombidinopsis multiaurisn. sp.; provide a new name and description for one previously described species,Strombidium siculumnom. nov. and provide more taxonomic data forStrombidinopsis cheshiriSnyder and Ohman, 1991.

ISSN:1066-5234    

DOI:10.1111/j.1550-7408.1994.tb01519.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

ABSTRACTChesapeake Bay populations of the red‐tide dinoflagellateGymnodinium sanguineumwere regularly infected by the parasitic dinoflagellateAmoebophrya ceratiiduring the summers of 1988–1991. Infections developed inside the nucleus ofG. sanguineumand were always lethal to the host. Parasite generation time was ˜ 40 h at 23° C, with the intracellular, trophont phase lasting 39.5 ± 0.3 h, and the extracellular, vermiform stage persisting for ˜ 20 min. Near surface accumulations ofG. sanguineumsometimes exceeded 1,000 cells/ml; however, host abundance was relatively low when integrated over the surface mixed layer of each station (mean = 12.2 cells/ml ± 2.96 SE; n = 60). Parasitized hosts were encountered in 75% of the samples where host abundance was ≥ 1 per ml, and epidemic outbreaks (20–40% hosts infected) were observed on several occasions. Epidemic infections were generally located several meters below surface accumulations ofG. sanguineumand were always restricted to a narrow region near the pycnocline. Consequently, integrated station values for parasite prevalence were low, with an average 2.7% (± 0.31 SE; n = 60). Parasite induced mortality removed up to 8% ofG. sanguineumpopulations per day, but averaged<2% of host biomass throughout the Bay. Thus, parasitism byA. ceratiidoes not appear to be a major factor regulatingG. sanguineumbloom in the main stem of C

ISSN:1066-5234    

DOI:10.1111/j.1550-7408.1994.tb01520.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

ABSTRACTChlamydomonas reinhardtiiexhibits photophobic and positive and negative phototactic responses that can be defined for cell populations using computerized cell tracking and motion analysis. Mutants CC‐2359 and FN68 are pigment deficient mutants that are blocked in carotenoid synthesis and lack these photo responses. In particular, neither mutant exhibits flash‐induced photophobic responses to visible light stimuli to which wild‐type gametic cells exhibit a strong response, with several behavioral stages. Upon addition of all‐transretinal to these mutants, the photophobic responses are restored with minor quantitative differences from wild‐type populations. Using both light and electron microscopy, we have compared the ultrastructural characteristics of wild‐typeC. reinhardtiito those of both mutants. As previously described, wild‐type cells contain an eyespot consisting of 2–4 layers of pigmented granules encased within thylakoid membranes, located between the distal extremities of the flagellar root. This structure is also visible as an orange‐red spot in light microscopy. The photoreceptor is thought to be concentrated in the plasma membrane above the eyespot. The mutant, CC‐2359, lacks this eyespot as seen by both light and electron microscopy, even when the photophobic response has been restored. FN68‐like mutants studied earlier by Morel‐Laurens and Feinlieb and others contain an eyespot which can be seen only by electron microscopy. In FN‐68, the eyespot generally has the same dimensions as in wt cells, differing mainly in pigment granule appearance. Consistent with these findings, several laboratories have shown that the full range of phototactic responses can be reconstituted in FN68 and CC‐2359, but that negative phototaxis requires a significantly stronger light stimulus in the latter strain. We confirm the suggestion that the eyespot is not necessary for the photophobic response, and is not critical for the appropriate assembly and function of the photophobic response receptor in the membrane. Furthermore, the locus of reconstitution of the functional receptor is not the eyespot. Because of the definitive demonstration of the absence of the eyespot in CC‐2359, however, the eyespot may play

ISSN:1066-5234    

DOI:10.1111/j.1550-7408.1994.tb01521.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY