ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1983.tb02899.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1983.tb02900.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

ABSTRACTThe rapid, synchronous differentiation ofN. gruberifrom amoebae to flagellates is a useful paradigm to study aspects of cell differentiation, including regulation of the synthesis of proteins that are related to the changes in cell shape and motility, which occur during differentiation. The differentiation requires synthesis of new RNA and protein molecules to accomplish defined morphogenetic events. Specific new proteins, including the tubulins that form the flagellar microtubules, are synthesized at various times during differentiation, and particular mRNA species appear and disappear. The time course of the synthesis of the α and β subunits of flagellar tubulin is paralleled by the programmed appearance and disappearance of flagellar tubulin mRNAs. The evidence supports the hypothesis that the synthesis of flagellar tubulin is regulated by the transcription, and subsequent disappearance, of flagellar tubulin mRNA. Translatable mRNAs for two calmodulin‐like calcium‐binding proteins appear and disappear contemporaneously with those for flagellar tubulin. During differentiation the synthesis of actin, the major protein of amoebae, is selectively shut down, and translatable actin mRNA rapidly disappears. This description of the orderly appearance, utilization, and disappearance of the mRNAs for actin, calcium‐binding proteins, and flagellar tubulin during differentiation provides means and motivation to investigate the mechanisms that regulate these

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1983.tb02902.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

ABSTRACTClassification at the species level has been difficult in the genusAcanthamoeba.The taxonomic designations of a number of strains are in doubt and new approaches to classification are needed. We describe the use of electrophoretic patterns obtained with restriction enzyme digests of mitochondrial DNA as a basis for one new approach. Results from analysis of ten strains ofA. castellanii, two ofA. polyphagaand one ofA. astronyxisare discussed. Examples both of nucleotide sequence diversity and of sequence conservation have been found among strains with the same species designation. Five strains from Europe, North America and New Zealand had identical digestion phenotypes with five enzymes; consequently, very similar nucleotide sequences are predicted. All are pathogenic to humans or mice. The mtDNA sequences of eight remaining strains are predicted to differ from this cluster and, in most cases, from each other at least as much as in sibling species ofParamecium aurelia.

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1983.tb02903.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

ABSTRACTDuring development ofAcanthamoeba castellaniiin a non‐nutrient medium, the pattern of synthesis of proteins changes. Comparison of in vivo and in vitro patterns of protein synthesis reveals concomitant relative increases of five proteins, indicating a control of synthesis of these proteins at the level of the RNA content. The decrease in the overall rate of protein synthesis and relative decreases in the synthesis of actin and ribosomal proteins during development, not accompanied by equivalent changes in the content of mRNA, suggest control mechanisms also at the level of translation. Patterns of ribosomal proteins do not change qualitatively during encystation, indicating that the inhibition in the overall rate of protein synthesis and the formation of inactive monosomes is not controlled by this mechanism; however, phosphorylation of one ribosomal protein, S 3, is observed occasionally during encystation. Phosphorylation of S 3 is also detected after transfer of stationary phase cells into fresh nutrient medium. It was found that only such cells having RNA of aberrant properties are able to phosphorylate S 3 after transfer into fresh nutrient medium. Since these changes in the property of RNA are never observed in cysts, in which phosphorylation of S 3 sometimes occurs, it is concluded that either other alterations in the properties of RNA than those detected or other parameters are responsible for changes in phosphorylation of S

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1983.tb02904.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

ABSTRACTDuring the cellular differentiation induced by starvation ofAcanthamoeba castellanii, the expression of a number of genes is regulated. Evidence is reviewed that at least one of these, the precursor ribosomal RNA transcription unit, is regulated at the level of transcription. The structure of the rRNA transcription unit and of the RNA polymerases responsible for transcription inAcanthamoebaare reviewed. Utilizing an in vitro transcription system constructed from these components, preliminary evidence has been obtained that pre‐rRNA gene expression is regulated by a modification of RNA polymerase I that affects the enzyme's ability to participate efficiently in the initiation of transcription. These results are reviewed in relation to other known mechanisms of transcriptional regulation in eukaryote

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1983.tb02905.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

ABSTRACTEarlier experimental work involving macronuclear implants inStentor coeruleushas shown that the cytoplasmic cortex of the nuclear site 1) attracts the macronucleus and 2) holds it in place during interphase. Now experiments indicate macronuclei transferred with overlying cortex elongate in the direction of the transferred cortical pigment stripes, whether or not the transferred stripes realign in the direction of the host stentor's stripes. Therefore the third function of the cortex is to determine the direction of elongation and thus assure that both daughter cells at division receive part of the macronucleus.

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1983.tb02906.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

ABSTRACTThe formation ofBabesia equisporozoites in the salivary glands of three tick species (Hyalomma anatolicum anatolicum, H. a. excavatum, Rhipicephalus turanicus) was studied by electron microscopy. The development was identical in all three vectors. On the 8th daypost repletionemkinetes ofB. equihad invaded alveoli of the nymphal salivary glands and were transformed to sporonts bounded by a single membrane. The sporonts were polymorphous bodies each with a highly lobed nucleus and numerous mitochondria. These stages persisted during ecdysis of the tick nymph to the adult stage. After attachment of these newly molted adults to a new host the formation of sporozoites was completed within five days. The sporonts occupied most of the infected alveolus and were extensively divided into cytoplasmic portions of various size. On the 4th day after attachment of the tick, sporozoite‐anlagen, into each of which a nucleus and a mitochondrion were incorporated, appeared at the periphery of the sporonts. An apical complex with a polar ring, rhoptries, and micronemes was formed at the tip of each protruding anlage. Finally thousands of pyriform sporozoites (3.0 × 1.2 μm) filled the hypertrophied alveolus. This development is similar to sporogony in the genusTheile

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1983.tb02907.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

ABSTRACTThe encystment ofLaurenliella acuminatawas divided into five stages: stage A (precystic semitransparent cell with dark‐globules), stage B (precystic transparent cell), stage C (precystic pigmented cell), stage D (spherical shape without cyst wall) and stage E (young resting cyst), on the basis of observations of changes in morphology and pigmentation during encystment. The duration of these stages was also established. Observations by electron microscopy confirmed that the cyst wall, composed of four layers, is derived from different kinds of precursors which are synthesized “de novo.” The ectocyst precursors are composed of stacks of between 5 and 12 small thin plates or discs; these stacks are about 0.9 μm in length and 0.06 μm in height. The mesocyst precursors are fibrillar bodies of variable shapes, about 2.4 μm in maximum length and 0.12–0.16 μm in diameter. These precursors appear in the cytoplasm of the precystic cell during the first precystic stage (stage A). The endocyst precursors are rounded bodies surrounded by a fine membrane, and their contents appeared similar to the endocyst. The granular layer precursors are spherical bodies about 0.1–0.2 μm in diameter, surrounded by a double membrane presenting ribosomes adhering to its outer membrane. Both endocyst and granular layer precursors are observed in the precystic cytoplasm from stage B. On the basis of ultrastructural studies, a formation and growth model of the cyst wall of the hypotrichous ciliateLaurentiella acumin

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1983.tb02908.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

RESUME.Après résorption des structures buccales du protomonte, la stomatogenèse ne commence que sur les produits de l'avant‐dernière division du tomonte. Elle se poursuit et se complète sur les tomites individualisés de la dernière division. Au niveau des extrémités antérieures des cinéties somatiques intercalaires et des extrémités rompues de cinéties bipolaires, une lère vague de proliferation des cinétosomes produit de courtes lignes, obliques, de cinétosomes isolés. Elles se transforment en lignes d'une double rangèe de cinétosomes, à la suite d'une 2ème vague de multiplication de cinétosomes. Un alignement de ces segments, procédant de gauche à droite et d'avant en arrière, constitue successivement les 3 membranelles longitudinales en doublets (M1 puis M2 et M3) ainsi que la membrane parorale, également en doublet. Une 3ème vague de proliferation cinétosomienne juxtapose une rangée de cinétosomes à droite des doublets (sauf à l'extrémité postérieure de M1 et au niveau de la parorale) transformant les promembranelles en triplets. Cette proliferation cinétosomienne se prolonge par addition d'une 4ème rangée de cinétosomes au trajet médian et postérieur de M2 et peut‐ětre à M3 et par juxtapositions successives de nouvelles rangées supplémentaires à l'extrémité postérieure de M2 (flamme). Les cinétosomes des rangées droites de promembranelles portent de larges rideaux de nombreuses fibres postciliaires. Les cinétosomes des autres rangées de M2, au moins, ont également des fibres postciliaires. Entre les cils de promembranelles il n'y a pas de couche alvéolaire, ni d'épiplasme. Une résorption des cinétosomes commence à se manifester par disparition des cinétosomes de la rangée gauche de la parorale dont subsistent les cinétosomes droits porteurs de fibres postciliaires. A vec le raccourcissement de l'aire buccale la résorption s'étend aux cinétosomes postérieurs des 2 rangées droites de M1, et des extrémités antérieures des 2 (ou 3?) rangées droites dc M3. Une invagination de la dépression buccale entraǐne vers la gauche les organelles buccaux et enfonce les cinéties vestibulaires en remontant en avant et à gauche leurs extrémités postérieures tronquées. Il y a régression postéro‐antérieure totale des cinétosomes de la parorale. M1 reste constituée au départ de 3 rangées ciliaires; M2 est également formée de 3 rangées ciliaires doublées postérieurement de nombreuses rangées constituant la flamme; M3 n'est finalement constituée que d'une seule rangée ciliaire. Une ultime proliferation cinétosomienne aux extrémités antérieures de cinéties vestibulaires serait peut‐ětre à l'origine d'un champ allongé de nouveaux cinétosomes vestibulaires.ABSTRACTAfter resorption of the buccal structures of the protomont, stomatogenesis begins only in the products of the penultimate division of the tomont. It continues to completion in the individualized tomites of the last division. At the anterior ends of the intercalary somatic kineties and the broken ends of bipolar kineties, a first wave of kinetosome proliferation produces short streak lines of isolated kinetosomes. These develop into lines formed of double rows of kinetosomes following a second wave of kinetosome multiplication. An alignment of these segments, proceeding from left to right and from front to rear, constitutes successively the three longitudinal membranelles in doublets (M1 then M2 and M3), and the paroral membrane, also a doublet. A third wave of kinetosome proliferation juxtaposes a row of kinetosomes to the right of the doublets (except at the posterior end of M1 and at the level of the paroral membrane) to give triplets. This proliferation is extended by addition of a fourth row of kinetosomes on the median and posterior path of M2 and perhaps M3, and by successive juxtaposition of further rows at the posterior end of M2 (flare). The kinetosomes of the right hand rows of promembranelles bear wide ribbons of numerous postciliary fibers. There is no alveolar layer nor epiplasm between the cilia of the promembranelles. Resorption of kinetosomes begins by disappearance of the kinetosomes of the left hand row of the paroral membrane; the right hand kinetosomes carrying postciliary fibers remain. With shortening of the buccal zone, resorption extends to the kinetosomes of the two posterior rows of M1 and the anterior ends of the two (or three?) left hand rows of M3. An invagination of the buccal cavity draws the buccal organelles to the left and pushes in the vestibular kineties while raising forward and to the left their truncated posterior ends. Total postero‐anterior regression of the kinetosomes of the paroral membrane occurs. Membranelle 1 remains composed of three rows of cilia; M2 is also composed of three rows of cilia edged posteriorly by numerous rows constituting the flare; M3 is composed of a single row of cilia. A final kinetosome proliferation at the a

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1983.tb02909.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY