Posterior Flagellum Research Articles

A RIBOSOMAL DNA PHYLOGENY SUPPORTS THE CLOSE EVOLUTIONARY RELATIONSHIPS AMONG THE SPOROCHNALES, DESMARESTIALES, AND LAMINARIALES (PHAEOPHYCEAE)1

ABSTRACTWe report six complete 18S ribosomal DNA (rDNA) sequences representing five brown algal orders: Sporochnus comosus C. A. Agardh (Sporochnales), Chorda tomentosa Lyngbye (Chordaceae, Laminariales), Saccorhiza polyschides (Lightfoot) Batters (Phyllariaceae, Laminariales), Desmarestia ligulata (Lightfoot) Lamouroux (Desmarestiales), Ectocarpus siliculosus (Dillwyn) Lyngbye (Ectocarpales), and Scytosiphon lomentaria (Lyngbye) J. G. Agardh (Scytosiphonales). These sequences were compared with published laminarialean (Alaria marginata Postel et Ruprecht [Alariaceae] and Macrocystis integrifolia Bory [Lessoniaceae]) and fucalean (Fucus gardneri Silva) rDNA sequences for phylogeny inference using both the distance‐matrix and parsimony methods. The inferred 18S phylogenies clustered Sporochnus, Desmarestia, Chorda, Saccorhiza, Alaria, and Macrocystis in an assemblage. This Sporochnales–Desmarestiales–Laminariales (S‐D‐L) complex was consistently separated from the Ectocarpales, Scytosiphonales, and Fucales by bootstrap analyses. The inferred phylogenies are consistent with several possible evolutionary processes leading to this S‐D‐L complex. Members in this assemblage lack eyespots in their sperm, and their sperm have the atypical brown algal flagellation: shorter anterior and longer posterior flagella. In addition, they are oogamous with a heteromorphic alternation of generations between a microscopic gametophyte and a macroscopic sporophyte. Members of the S‐D‐L complex can be separated into different phylogenetic lines based on the presence/absence of eyespots in their meiospores. Our findings support the contention that the Sporochnales, Desmarestiales, and Laminariales are closely related. In addition, our rDNA tree suggests that the Laminariales is paraphyletic.

1120 Spinal neurons innervating the liver in culture -a study by dii labeling method and scanning electron microscopy (SEM)

Tritrichomonas foetus (T. foetus) is the causal agent of bovine tritrichomonosis (BT), a venereal disease that causes significant economic losses in the bovine livestock industry. The structural organization of T. foetus presents a cell membrane, an undulating membrane which extends along the parasite, three anterior flagella and a recurrent posterior flagellum. The interaction between the superficial glycoconjugates of the parasite and the host cell is one of the most relevant pathogenic mechanisms. In the present study, we analyzed the saccharide pattern through lectincytochemistry of the cell membrane, undulating membrane, cytoplasm and flagella of 28 isolates of T. foetus. Lectins that labeled most of the isolates were WGA, Con-A, RCA-I, LCA, GS-II and PHA-E showing the presence of D-mannose, D-glucose, N-acetylglucosamine and sialic acid. On the other hand, no labeling was observed in any of the structures with VVA, STA, LEA, Jacalin, GS-I, SJA, PHA-L, DSA, and weak labeling was observed with DBA, PNA, SBA and UEA I, showing therefore a low expression of N-acetylgalactosamine, L-fucose and galactose. In addition, GS II labeled in a granular pattern when lectincytochemistry was positive, whereas LCA strongly labeled the membranes and weakly the cytoplasms. The labeling variations observed among the isolates analyzed in the present work, could be related to differences in the pathogenic behavior of the isolates.

Spironucleus vortens N. Sp. from the Freshwater Angelfish Pterophyllum scalare: Morphology and Culture

ABSTRACT. A new diplomonad flagellate, Spironucleus vortens n. sp., is described from the intestinal lumen of the freshwater angelfish, (Pterophyllum scalare), bred in Florida. Live organisms are pyriform, and measure 12.5–20.5 μm long by 5.0–11.2 üm wide. Scanning electron microscopy shows that the trophozoite bears two compound lateral longitudinal ridges, each originating posterior to three emerging anterior flagella, and continuing posteriorly to the emergence of the posterior flagellum. Each ridge comprises a broad central part, surrounded by a peripheral ridge. At the opening of the flagellar pocket, the broader right peripheral ridge crosses to the other side of the body, and then back again. The posterior end of the body bears two papillae. Transmission electron microscopy shows that the compound lateral ridges are supported by microtubules, and bear microfibrillar structures in discrete longitudinal plaques. The serendipitous growth of S. vortens in a culture system with lip tumor tissue, facilitated axenic cultivation in a modified TYM medium (trypticase, yeast extract, maltose). The flagellate is now routinely maintained in an axenic TYI‐S‐33 medium (trypticase, yeast extract, iron serum), and is stabilized in the cryopreserved state. Spironucleus vortens is an aerotolerant anaerobe that can be cultured at 25° C, 28° C and 30° C.

Microtubule polarity and dynamics in the control of organelle positioning, segregation, and cytokinesis in the trypanosome cell cycle.

Trypanosoma brucei has a precisely ordered microtubule cytoskeleton whose morphogenesis is central to cell cycle events such as organelle positioning, segregation, mitosis, and cytokinesis. We have defined microtubule polarity and show the + ends of the cortical microtubules to be at the posterior end of the cell. Measurements of organelle positions through the cell cycle reveal a high degree of coordinate movement and a relationship with overall cell extension. Quantitative analysis of the segregation of the replicated mitochondrial genome (the kinetoplast) by the flagellar basal bodies identifies a new G2 cell cycle event marker. The subsequent mitosis then positions one "daughter" nucleus into the gap between the segregated basal bodies/kinetoplasts. The anterior daughter nucleus maintains its position relative to the anterior of the cell, suggesting an effective yet cryptic nuclear positioning mechanism. Inhibition of microtubule dynamics by rhizoxin results in a phenomenon whereby cells, which have segregated their kinetoplasts yet are compromised in mitosis, cleave into a nucleated portion and a flagellated, anucleate, cytoplast. We term these cytoplasts "zoids" and show that they contain the posterior (new) flagellum and associated basal-body/kinetoplast complex. Examination of zoids suggests a role for the flagellum attachment zone (FAZ) in defining the position for the axis of cleavage in trypanosomes. Progression through cytokinesis, (zoid formation) while mitosis is compromised, suggests that the dependency relationships leading to the classical cell cycle check points may be altered in trypanosomes, to take account of the need to segregate two unit genomes (nuclear and mitochondrial) in this cell.

Synthesis and assembly of flagellar surface antigens during zoosporogenesis inPhytophthora cinnamomi

Cryomicrotomy and immunofluorescence microscopy employing three different categories of monoclonal antibody (MAb) that label antigens on the surface of one or both flagella ofPhytophthora dnnamomi have been used to follow the synthesis and assembly of flagellar surface components. MAb Zf 1 binds to the surface of both the anterior tinsel and posterior whiplash flagella, as well as to a nuclear component. The labeling of the flagella is punctate in nature, is brighter at the flagellar base, and does not always extend to the distal tip of the flagella. MAbs in the Zt group recognise an antigen that is located along the sides of the tinsel flagellum and may be associated with the base of the mastigonemes. Immunodot-blot analysis has shown that binding of Zt MAbs is abolished by pretreatment with either pronase or periodate oxidation indicating that the antigen is a glycoprotein. MAbs in the Zg group bind to the mastigonemes on the tinsel flagellum and to packets of mastigonemes in the cytoplasm of zoospores. Zt and Zg antigens increase in abundance during zoosporogenesis and are present throughout the life cycle of the fungus, whereas the non-nuclear localisation of the Zf antigen appears only during sporulation. Prior to association with the flagellar surface, all three components become clustered in the groove region of zoospores. They do not become associated with the flagellar surface until at least 15 min after the flagellar axoneme has formed.

Green flagellar autofluorescence in brown algal swarmers and their phototactic responses

A flavin-like green autofluorescent substance is noticed to occur in one of the flagella of flagellated cells in the Phaeophyceae, Chrysophyceae, Synurophyceae, Xanthophyceae and Prymnesiophyceae. In the phaeophycean swarmers the autofluorescence occurs in the posterior flagellum throughout its length. It is considered to be involved in the photoreception of phototaxis, since it almost always occurs in the swarmers which have a flagellar swelling and stigma and show phototaxis. In the phaeophycean swarmers, the stigma is shown to act as a concave reflector mirror focusing the reflection light onto the flagellar swelling. In the action spectrum studies, phaeophycean swarmers showed phototaxis between 370 and 520 nm, having two major peaks at 420 or 430 nm and 450 or 460 nm. Their responses were true phototactic and not photophobic. Rotation of the swarmer was shown to be essential in the photoreception ofEctocarpus gametes.

Ultrastructure of Amastigomonas bermudensis ATCC 50234 sp. nov. : A new heterotrophic marine flagellate

The ultrastructure of a new marine heterotrophic flagellate is described. The cell is dorso-ventrally flattened and displays a steady gliding forward movement. A longitudinal groove whose lips are appressed to the substrate runs along the ventral aspect of the cell. The two heterodynamic flagella originate from the proximal end of a cytoplasmic sheath that enfolds most of the length of the anterior flagellum. The lips of this sheath are continuous with the margins of the ventral groove. The posterior trailing flagellum is held closely appressed to the cell body on one side of the ventral groove. Three bands of microtubules extend posteriorly into the cell body and are associated with the kinetosomes. The part of the surface membrane extending over the cell's dorsal and lateral aspect is five-layered, giving the semblance of two fused cell membranes. There is a fibrillar layer underneath these membranes. There is also a fibrous network whose arrays are oriented in different directions within the cytoplasm. Mitochondria have tubular cristae. Based on a comparison with previously described species of Amastigomonas, we establish the species, A. bermudensis n.sp. We further conclude that Thecamonas is a junior synonym of Amastigomonas and move the three nominal species to the latter genus.

Biflagellate spermatozoids in the Dictyotales: the structure of gametes and gametangia in Zonaria angustata (Dictyotales, Phaeophyta)

The spermatozoids of Zonaria angustata (Kützing) Papenfuss (Phaeophyta) are biflagellate, and not uniflagellate as reported in other species of the Dictyotales. The anterior flagellum is 20–27 μm long and, in addition to mastigonemes and a terminal acronema, has a row of 23–33 spines distributed along its length. The posterior flagellum is very short, 1–1.5 μm long. Gametangial walls are not contiguous and sterile cortical cells occur between oogonia. The outer tier of the antheridia consists of sterile cells containing numerous physodes. It is argued that these characteristics of Z. angustata indicate that the order Dictyotales is more closely related to other brown algae than was previously thought, and the possibility of a phylogenetic relationship between the orders Dictyotales and Cutleriales is discussed.

Leucodictyon marinum n. gen., n. sp., a plasmodial protist with zoospore formation from the Japanese coast

Summary Leucodictyon marinum n. gen., n. sp., deriving from tide pools near the Shimoda Marine Research Center (Japan), could be isolated and cultivated with the pennate diatom Amphiprora spec. as food organism. Like Reticulosphaera japonensis ( Grell 1990 a ) from the same habitat, it is a meroplasmodial protist, consisting of small cell bodies which form a common network of slender reticulopodia. Each cell body is enclosed by a loaf-shaped lorica. Through its aperture a reticulopodial root connects the cell body with the remaining network. If the diatoms become sparse, many cell bodies carry out an unequal binary fission. The smaller daughter cell remains within the lorica. The larger daughter cell transforms into a biflagellate zoospore which leaves the lorica through the aperture. The anterior flagellum of the zoospore is short and propels the cell by gyration, whereas the posterior flagellum is long and “trails” behind. Since plastids are lacking, classification is difficult. An ultrastructural study may clarify the taxonomic position.

The fine structure of the zoospore of Sorochytrium milnesiophthora

As a part of an investigation of Sorochytrium milnesiophthora Dewel, a parasite of the tardigrade Milnesium tardigradum, the ultrastructure of the zoospore was examined. In overall organization, the zoospore is similar to the spores of the Blastocladiales. The nucleus is conical and located in the posterior third of the cell. A large nuclear cap is anterior to the nucleus. In an arrangement unique for members of the Blastocladiales, the nuclear cap contains, in addition to aggregated ribosomes, a single complex mitochondrion, lipid globules, and microbodies. Portions of the nuclear cap extend posteriorly and partially surround the kinetosome. The kinetosome has nine anterior rootletlike projections that link it to the mitochondrion and nine posterior kinetosomal props that attach it to the plasmalemma. It lies at the base of the nucleus as an anchor for a single, posterior whiplash flagellum. A nonkinetosomal centriole is positioned at an approximate 45° angle to the kinetosome. In the peripheral cytoplasm, there are three structurally distinct types of inclusions hypothesized to be adhesion vesicles, phosphate storage bodies, and gamma-like particles. Therefore, the ultrastructure of the zoospore supports the inclusion of this fungus in the Blastocladiales. Key words: Blastocladiales, zoospore, ultrastructure.

The molecular nature of Fucus serratus sperm surface antigens recognised by monoclonal antibodies FS1 to FS12

Sperm of the brown alga Fucus serratus are highly differentiated, biflagellate, naked cells. Immunolocalisation studies, employing monoclonal antibodies (MAbs - designated FS1 to FS12) raised against antigens of these sperm cells, have revealed that some sperm surface components are distributed over the entire cell, whereas others are restricted to, or occur preferentially on, the surface of the anterior flagellum or cell body. This report describes the use of these MAbs in Western-blot procedures and antigen-modification binding assays to determine the nature of these sperm surface components. Monoclonal antibodies which bind to antigens found on the cell body and both flagella (FS3, FS4, FS6, FS8, FS10) recognise carbohydrate epitopes of a high-molecular-weight glycoprotein (Mr=205 kDa). These MAbs were initially chosen at random from a much larger number of antibodies which bound to sperm in a similar fashion, indicating that this glycoprotein is an immunodominant antigen. Though these MAbs compete under conditions of limited antigen availability, differences in the effects of periodate on antibody binding and differences in other binding data indicate that the MAbs recognise epitopes of this glycoprotein which are neighbouring or overlapping, rather than common. The MAb FS9, which has a similar binding pattern to the above antibodies, also seems to bind to carbohydrate epitopes, but the antigen recognised by this antibody could not be identified in Western-blotting procedures. The MAbs FS7 and FS12, which bind to the mastigonemes on the anterior flagellum and to the cell body and posterior flagellum, recognise a set of glycoproteins in the molecular-weight range 40-250 kDa. The evidence indicates that the antibodies are binding to N-linked carbohydrate side chains of these glycoproteins. Three MAbs that bind to the anterior flagellum (FS2, FS5 and FS11) recognise protein antigens in the molecular-weight range 90-250 kDa; it is not known whether these antigens are glycosylated. The MAb FS1, which binds primarily to the sperm cell body, could not be used in enzyme-linked immunosorbent assays or Western-blotting procedures and the antigen recognised by this antibody is so far uncharacterised.

Adherence of Tritrichomonas foetus to bovine vaginal epithelial cells

Adherence of Tritrichomonas foetus to bovine vaginal epithelial cells (VECs) in vitro was investigated with fresh washed bovine VECs and log-phase cultures of T. foetus. Observation under phase-contrast microscopy showed that T. foetus usually adhered first by the posterior flagellum and later by the body. Significantly more keratinized squamous epithelial cells were detected with attached parasites than nonkeratinized round epithelial cells. The optimal pH range for attachment was 6.0 to 7.5, with peak attachment at pH 6.5 for squamous VECs. Surface-reactive bovine antiserum to T. foetus prevented adherence to bovine squamous VECs. Inhibition of adherence occurred at nonagglutinating, nonimmobilizing serum dilutions. Antiserum fractions enriched for immunoglobulin G1 inhibited adherence, but fractions enriched for immunoglobulin G2 did not. The inhibitory antiserum was specific for several medium- to high-molecular-weight membrane antigens as detected in Western blots (immunoblots). The ability of surface-reactive antibodies to prevent adherence and to agglutinate and immobilize T. foetus indicates that they may be protective.

The flagellar developmental cycle in algae: flagellar transformation inCyanophora paradoxa (Glaucocystophyceae)

Flagellar development during cell division was studied inCyanophora paradoxa using agarose-embedded cells, Nomarski optics and electronic flash photography. The cells bear two heterodynamic and differently oriented (anterior and posterior) flagella. Prior to cell division, cells produce two new anterior flagella while the parental anterior flagellum transforms into a posterior flagellum. The parental posterior flagellum remains a posterior flagellum throughout this and subsequent cell divisions. The development of a single flagellum thus extends through at least two cell cycles and flagellar heterogeneity is achieved by semiconservative distribution of the flagella during cell division. Based on these principles a universal numbering system for basal bodies and flagella of eukaryotic cells is proposed.

Light and electron microscopical studies on Pseudoscourfieldia marina, a primitive scaly green flagellate (Prasinophyceae) with posterior flagella

The supposedly primitive prasinophyte Pseudoscourfieldia marina has been established in culture and examined in detail. The cells swim by means of two unequal but parallel posterior flagella. Pseudoscourfieldia differs from other green flagellates in the structure of the flagellar root system, possession of a conspicuous leaflike attenuated extension from one basal body into the cell, the structure of the pyrenoid, which is invaginated by long extensions from the mitochondrial complex, and the structure of the scaly covering on the body. Pseudoscourfieldia shows distinct similarities to Nephroselmis, which is laterally biflagellate, and to the Tetraselmis group, which possesses four anterior flagella. The attachment of the hair scales on the flagella has been examined in detail for the first time in a green flagellate. The very short hair scales attach to the flagellar surface between each pair of longitudinal rows of scales known as Melkonian's rows, associated with the inside of every third scale in one row. This is probably a feature common to all prasinophytes with Melkonian's rows. Based on the many investigations now published, a classification for the prasinophytes, supposedly some of the most primitive green algae, is suggested. One class, two orders, and four families are recognized and defined, with 15 genera.

A FLAVIN‐LIKE AUTOFLUORESCENT SUBSTANCE IN THE POSTERIOR FLAGELLUM OF GOLDEN AND BROWN ALGAE1

ABSTRACTAn autofluorescent substance occurs in the flagella of flagellate cells of the golden and brown algae. It is localized only in the posterior (short) flagellum and could not be detected in the anterior (long) one. It showed maximum fluorescence emission at 515–520 nm upon excitation of 440 nm; therefore, it is considered to be a flavin. This substance is distributed widely among flagellate cells of golden and brown algae irrespective of their nature (vegetative cells, zoospores, gametes, or sperm). It is absent, however, in some brown algal zoospores and sperm which lack an eyespot and flagellar swelling and are considered to lack phototaxis. Because the flagellar swelling in the posterior flagellum is a presumptive photoreceptor for phototaxis in these groups, it is suggested that the flavin located in the posterior flagellum acts as a photoreceptor pigment in phototaxis.

Observations on the flagellar apparatus and peripheral endoplasmic reticulum of the coccolithophorid, Pleurochrysis carterae (Prymnesiophyceae)

The flagellar apparatus of the motile, coccolith-bearing cells of Pleurochrysis carterae (Braarud & Fagerlund) Christensen is described in detail. The basal part of the flagellar axoneme contains a previously undescribed spiral structure (a helical band) and the transition region consists of a distinctive axosome and at least five tiers of transitional rings. The longer flagellumis shown to be the left (posterior) flagellum of accepted prymnesiophyte nomenclature. The microtubular flagellar roots are similar to those in Pleurochrysis sp. (Inouye & Pienaar 1985); however, we show that the root that consists of a broad sheet of microtubules is associated, at its proximal end, with the forming face of the Golgi body and then becomes partially enveloped by peripheral endoplasmic reticulum (PER) as it extends for the entire length of one side of the cell–this whole structure is termed a cytoplasmic tongue. The PER exhibits a distinctive decoration at specific points on its membrane surface; the importance of this decoration is discussed, along with the ramification of the PER and its possible role in scale/coccolith secretion and the endocytosis of particulate material from the medium. A putative example of endocytosis in P. carterae is presented.

Microtubule cytoskeleton and morphogenesis in the amoebae of the myxomycete Physarum polycephalum.

The amoebae of the myxomycete Physarum polycephalum are of interest in order to analyze the morphogenesis of the microtubule and microfilament cytoskeleton during cell cycle and flagellation. The amoebal interphase microtubule cytoskeleton consists of 2 distinct levels of organization, which correspond to different physiological roles. The first level is composed of the 2 kinetosomes or centrioles and their associated structures. The anterior kinetosomes forming the anterior and posterior flagella are morphologically distinguishable. Each centriole plays a role in the morphogenesis of its associated satellites and specific microtubule arrays. The 2 distinct centrioles correspond to the 2 successive maturation stages of the pro-centrioles which are built during prophase. The second level of organization consists of a prominent microtubule organizing center (mtoc 1) to which the anterior centriole is attached at least during interphase. The mtoc plays a role in the formation of the mitotic pole. These observations based on ultrastructural and physiological analyses of the amoebal cytoskeleton are now being extended to the biochemical level. The complex formed by the 2 centrioles and the mtoc 1 has been purified without modifying the microtubule-nucleating activity of the mtoc 1. Several microtubule-associated proteins have been characterized by their ability to bind taxol-stabilized microtubules. Their functions (e.g., microtubule assembly, protection of microtubules against dilution or cold treatment, phosphorylating and ATPase activities) are under investigation. These biochemical approaches could allow in vitro analysis of the morphogenesis of the amoebal microtubule cytoskeleton.

External morphology of Lagenidium giganteum zoospores (Oomycetes: Lagenidiales)

The external morphology of Lagenidium giganteum was studied with the aid of Nomarski differential interference microscopy, scanning electron microscopy and unidirectional shadow-casting techniques. Zoospores were ovoid, bluntly pointed and flattered on one side at the anterior end. On one side of the zoospore, a groove ran from end to end parallel to the long axis. Protruding from the groove were two flagella, a posterior whiplike flagellum and an anterior tinsel flagellum with lateral hair. Features of the zoospore surface included an irregular reticulate pattern of ridges and mounds marked by deep irregular pits scattered randomly over the zoospore surface.

Aspects of the Biology of Pseudocarcinonemertes homari and Its Association with the American Lobster, Homarus americanus

Pseudocarcinonemertes homari can reproduce on and destroy the egg mass of both the American (Homarus americanus) and the European lobster (H. gammarus) but does not appear to be a problem for brachyuran species. The eggs of P. homari are subspherical, average 251 × 260 μm, and are contained in individual compartments in a membranous brood sac that is attached to the lobster abdomen or egg mass. An average of 39 eggs occur in a brood sac. Newly hatched larvae are ciliated, lack anterior and posterior tufts, cirri or flagella, and are retained in the brood sac. Larval development is direct, and there is no free-swimming stage. After the larvae break out of the brood sac they join the adults and juveniles on the lobster egg mass. Many lobsters gradually remove infested eggs, but on those that do not, the nemertean population can increase to more than 14 000 individuals. After the lobster eggs are destroyed, the nemerteans disperse. Some form mucoid aggregations at protected sites on the exoskeleton; others move to the branchial chamber and gills or transfer to other lobsters. Reproduction occurs almost exclusively on the lobster egg mass, but P. homari appears capable of reproducing on lobster gills if denied access to lobster eggs for extended periods.

Fine structure of the tail in the spermatozoa of the Mexican axolotl Ambystoma mexicanum

The structure of the spermatozoa represents an extreme degree of diversity among the various species of metazoa. This diversity is most probably a reflection of the adaptation to the variable conditions for fertilization. The Axolotl sperm consists of head and tail. The tail is the subject of the present communication. It consists of neck region, intermediary and principal pieces. I. The neck (∼10μm) is inserted in the nucleus and can be designated as a region between immediately above the mitochondria (a construction zone between nucleus and sustained filament) and the upper region of the anterior centriole. In longitudinal section (Fig.l) it consists of a pair of centrioles and a mass of granular fibrillar substance. The anterior centriole (0.26 x 0.5μm) appears free, while the posterior one is continuous with the flagellum. The appearance of two central filaments indicates the transition between posterior centriole and flagellum. In front of the centrioles,there is a mass of granulo-fibrillar substance (Fig.l) which in vertical section (Fig.4) appear to be semi-circular and relatively thick (0.3μm). The granulo-fibriliar substance protrude outward (Fig.l,3,4) and thus the term protuberance seems appropriate. II.