摘要:

ABSTRACT.Vance Tartar (1911‐1991) has made major discoveries concerning morphogenesis, patterning, and nucleocytoplasmic relations in the giant ciliateStentor coeruleus, mostly by means of hand‐grafting using glass microneedles. This article provides a chronological account of the major events of Vance Tartar's life, a brief description of some of his major scientific achievements, and a discussion of his distinctive personality and multifaceted interests. It concludes with a consideration of how his unique style of life and work contributed to his equally unique seientific contributi

ISSN:1066-5234    

DOI:10.1111/j.1550-7408.1993.tb04873.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

ABSTRACT.Electron microsocpic investigations reveal that the Golgi apparatus ofTetrahymena thermophilaconsists of numerous tiny dictyosomes, each consisting of one or two cisternae. the dictyosomes are localized predominantly in the cell cortex closely associated with the mitochondria, arranged in meridians alternating with the ciliary meridians. We estimated about 300‐400 of these dictyosomes in the periphery of a cell, a value corresponding to the number of somatic cilia per cell. Cytochemical assays of thiamine pyrophosphatase and acid phosphatase, both marker enzymes of trans Golgi cisternae, resulted in deposits of lead or cerium phosphate in the outermost cisternae of the dictyosomes. In addition, cisternae located at the bases of the basal body/parasomal sac arrangements are stained. This indicates that these cisternae may belong to the Golgi apparatus of the cel

ISSN:1066-5234    

DOI:10.1111/j.1550-7408.1993.tb04874.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

ABSTRACT.The effects of different sulphonamides, dihydrofolate reductase inhibitors and other inhibitors of folate metabolism on growth ofAcanthamoeba culbertsoniin a chemically defined medium are reported. Among the sulphonamides, sulphamethoxazole and sulphadiazine were most effective followed by sulphanilamide and sulphaguanidine. Inhibition by each sulphonamide was reversed by p‐aminobenzoic acid as well as folic acid. 7‐Methylguanosine, a pteridine synthesis‐inhibitor, did not inhibit multiplication ofA. culbertsoni.Among the dihydrofolate reductase inhibitors, pyrimethamine blocked the amoebic growth at 100 μg/ml, while trimethoprim and cycloguanil palmoate failed to cause significant inhibition of growth even at 250 μg/ml. Metoprine inhibited amoebic growth completely at 50 μg/ml. Methotrexate and a thymidylate synthetase inhibitor 5‐fluorouracil inhibited growth strongly, with IC50values (the concentration of the drug which causes 50% inhibition of the growth at 72 h) of 1.97 and 2.45 μg/ml, respectively. Inhibition by methotrexate, metoprine or 5‐fluorouracil could not be reversed by folic acid, folinic acid, thymidine, or folinic acid plus thymidine. the results indicate unusual features inA. culbertsonifola

ISSN:1066-5234    

DOI:10.1111/j.1550-7408.1993.tb04875.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

ABSTRACT.Using monospecific antibodies, the presence and distribution of tubulin, actin, myosin, intermediate filaments, and lamins were examined in the exoerythrocytic liver schizont ofPlasmodium bergheiby conventional indirect fluorescent antibody methods and confocal laser scanning microscopy. the binding reactivity of the antibodies to parasite proteins was determined by Western blot analysis. the localisation of all antibodies in control host hepatocytes followed expected distributions in both uninfected and infected hepatocytes; by contrast, reactivity to the exoerythrocytic schizont was variable. the parasite reacted positively with selected anti‐tubulin, ‐actin, and ‐myosin antibodies in both fluorescence and Western blot analysis. Anti‐lamin antibodies were positive by confocal indirect fluorescent antibody labelling, but no labelling was detected with anti‐intermediate filament antibody. Within the technical limits of resolution of the methods as applied to asynchronous parasite infections, not one of the antibodies reacting positively with the parasite by the indirect fluorescent antibody technique could be shown to identify unequivocally the classic architectural features associated with their respective target organelles, i.e. microtubules, stress‐fibres or the nucle

ISSN:1066-5234    

DOI:10.1111/j.1550-7408.1993.tb04876.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

ABSTRACT.Pyrimidine salvage enzyme activities in cell‐free extracts ofToxoplasma gondiiwere assayed in order to determine which of these enzyme activities are present in these parasites. Enzyme activities that were detected included phosphoribosyltransferase activity towards uracil (but not cytosine or thymine), nucleoside phosphorylase activity towards uridine, deoxyuridine and thymidine (but not cytidine or deoxycytidine), deaminase activity towards cytidine and deoxycytidine (but not cytosine, cytidine 5′‐monophosphate or deoxycytidine 5′‐monophosphate), and nucleoside 5′‐monophosphate phosphohydrolase activity towards all nucleotides tested. No nucleoside kinase or phosphotransferase activity was detected, indicating thatT. gondiilack the ability to directly phosphorylate nucleosides.Toxoplasma gondiiappear to have a single non‐specific uridine phosphorylase enzyme which can catalyze the reversible phosphorolysis of uridine, deoxyuridine and thymidine, and a single cytidine deaminase activity which can deaminate both cytidine and deoxycytidine. These results indicate that pyrimidine salvage inT. gondiiprobably occurs via the following reactions: cytidine and deoxycytidine are deaminated by cytidine deaminase to uridine and deoxyuridine, respectively; uridine and deoxyuridine are cleaved to uracil by uridine phosphorylase; and uracil is metabolized to uridine 5′‐monophosphate by uracil phosphoribosyltransferase. Thus, uridine 5′‐monophosphate is the end‐product of both de novo pyrimidine biosynthesis and pyrim

ISSN:1066-5234    

DOI:10.1111/j.1550-7408.1993.tb04877.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

ABSTRACT.The gregarine parasites ofReticulitermes virginicusandReticulitermes flavipesbegin their development as trophozoites attached to the midgut epithelium by a small button‐shaped epimerite. the epimerite is lost when the parasite becomes free‐living in the gut lumen as a solitary gamont. Syzygy is late and was not observed. When full‐grown, gamonts enter the hemocoel and fuse in pairs to form large gametocysts that are attached to the midgut of the termite by a duct. Thousands of sporocysts are formed within the original gametocyst. the mature sporocysts are released into the lumen of the midgut through the connecting duct. They are then passed out with the feces. These gregarines are believed to be identical toGregarina termitisLeidy which was described from a single gamont and later erroneously placed in the genusHirmocystisby

ISSN:1066-5234    

DOI:10.1111/j.1550-7408.1993.tb04878.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

ABSTRACT.Xenosomes are infectious bacterial symbionts that exist exclusively in the cytoplasm of the small philasterine marine ciliateParauronema acutum.We have used this host‐symbiont system as a model to study infection. In the past we postulated that infection took place by a process in which the symbionts escaped digestion and entered into the host's cytoplasm through the food vacuole during phagocytosis. This is clearly not the case. We now present evidence based on electron microscopic observations that the symbionts infect in a manner involving direct penetration of the protozoan's cell membranes. We have obtained additional data that suggest that, following entrance of the symbionts into the cytoplasm, only a single xenosome is required to establish an infectio

ISSN:1066-5234    

DOI:10.1111/j.1550-7408.1993.tb04879.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

ABSTRACT.The microsporidiumChytridiopsis trichopteraen. sp., a parasite of the midgut epithelium of larvae of the caddis flyPolycentropus flavomaculatusfound in southern Sweden, is described based on light microscopic and ultrastructural characteristics. All life cycle stages have isolated nuclei. Merogonial reproduction was not observed. the sporogony comprises two sequences: one with free spores in parasitophorous vacuoles, the other in spherical, 5.6‐6.8 μm wide, sporophorous vesicles which lie in the cytoplasm. the free sporogony yields more than 20 spores per sporont. the vesicle‐bound sporogony produces 8, 12 or 16 spores. the envelope of the sporophorous vesicle is about 82 nm thick and layered. the internal layer is the plasma membrane of the sporont; the surface layer is electron dense with regularly arranged translucent components. Both spore types are spherical. They have an ∼ 35‐nm thick spore wall, with a plasma membrane, an electron‐lucent endospore, and an ∼ 14‐nm thick electron‐dense exospore. the polar sac is cup‐like and lacks a layered anchoring disc. the polar filament is arranged in two to three isofilar coils in the half of the spore opposite the nucleus. the coupling between the polar sac and the polar filament is characteristic. the surface of the polar filament is covered with regularly arranged membraneous chambers resembling a honeycomb. There is no polaroplast of traditional type. the cytoplasm lacks polyribosomes. the nucleus has a prominent, wide nucleolus. the two spore types have identical construction, but differ in dimensions and electron density. Free living spores are about 3.2 μm wide, the diameter of the polar filament proper is 102‐187 nm, the chambers of the honeycomb are 70‐85 nm high, and the polar sac is up to 425 nm wide. Living spores in the vesicle‐bound sporogony are about 2.1 μm wide, the polar filament measures 69‐102 nm, the chambers of the honeycomb are about 45 nm high, and these spores are more electron dense. Comparisons of cytology (especially the construction of the spore wall and the polar filament and associated structures) and life cycles reveal prominent differences among theChytridiopsis‐like microsporidia, and close relationships between the families Chytrid

ISSN:1066-5234    

DOI:10.1111/j.1550-7408.1993.tb04880.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

ABSTRACT.Gymnodinium sanguineum, Gyrodinium uncatenum, andCeratium furcaare large phototrophic dinoflagellates that commonly form red tides in the mesohaline portion of Chesapeake Bay during the summer. Examination of protargol‐stained specimens revealed that these dinoflagellates also feed heterotrophically as indicated by the presence of food vacuoles containing partially digested prey. Ingested prey were generally identified as nanociliates (≥20 μm) belonging to the oligotrich generaStrobilidiumandStrombidium; occasionally other small ciliates (e.g.Balanionsp. andMesodiniumsp.), dinoflagellates, and diatoms were observed in early stages of digestion. the percentage of these mixotrophs that had ingested prey was usually less than 20%, but approached 30% in some samples. Occurrence of food vacuoles inGymno. sanguineumwas positively correlated with ≤20 μm oligotrichous ciliate density; limited data forGyro. uncatenumsuggests a similar relationship, butC. furcafeeding was not related to nanociliate de

ISSN:1066-5234    

DOI:10.1111/j.1550-7408.1993.tb04881.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

ABSTRACT.Monoclonal antibodies that react with the circumsporozoite protein of the avian malariaPlasmodium gallinaceumsporozoites also reacted with circumsporozoite protein of the rodent malariaPlasmodium berghei.Two types of reactivity were identified: 1) two monoclonal antibodies reacted withP. bergheisporozoite protein by enzyme‐linked immunosorbent assay, Western blot and indirect immunofluorescence antibody, 2) six other monoclonal antibodies reacted withP. bergheisporozoites by ELISA and Western blot only. We studied whether these differences could be explained by reactivity in enzyme‐linked immunosorbent assay with differentP. bergheicircumsporozoite peptides. Although allP. gallinaceummonoclonal antibodies reacted with theP. bergheirepeats, the first group reacted with a conserved peptide sequence, N1, whereas the second group did not. These results suggest that circumsporozoite proteins fromP. gallinaceumandP. bergheishare common epitopes. the biological significance of our finding is not yet clear. Indeed, the cross‐reactive monoclonal antibodies giving a positive indirect immunofluorescence antibody with theP. bergheisporozoites only caused a borderline effect on the livingP. bergheiparasites in vitro as measured by inhibition of sporozoite infect

ISSN:1066-5234    

DOI:10.1111/j.1550-7408.1993.tb04882.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY