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Basal Bodies (basal + body)

Distribution by Scientific Domains

Life Sciences	86%
Medical Sciences	10%

Selected Abstracts

Ultrastructure of the biflagellate gametes of Collinsiella cava (Ulvophyceae, Chlorophyta)

PHYCOLOGICAL RESEARCH, Issue 2 2000
Takeshi Nakayama
SUMMARY The fine structure of the biflagellate gametes of Collinsiella cava (Yendo) Printz was investigated in detail to clarify the species's taxonomic and phylo-genetic position. Gametes are covered by small square scales with no distinct substructure. The chloroplast of the gamete includes an eyespot comprised of two layers of globules, and a pyrenoid that is traversed by one or a few thylakoids. Basal bodies overlap at their proximal ends and are offset in a counterclockwise orientation. Each basal body has a small bipartite terminal cap, a prominent proximal sheath comprised of two unequal subunits and a circular element situated at the cartwheel portion. A distal fibre, a connecting fibre and linkage between proximal sheaths connect the two basal bodies. Microtubular roots are comprised of two dexter (d) roots, subtended by the system I fibre, and two sinister (s) roots. Gametes have a single rhizoplast which extends parallel to one of the two d roots and extends to the mating structure. The ultrastructure of Collinsiella gametes is very similar to that of Mono-stroma and other members of the Ulotrichales, Ulvophyceae, and we concluded that the genus Collinsiella should be treated as a member of the Monostromat-aceae. The planozygote has four basal bodies, eight microtubular roots and two eyespots always situated at the same face of the cell. From observations of the planozygotes, the position of the mating structure relative to the flagellar apparatus is not consistent, but converse, between two mating types. A comparison of the location of the mating structure in Chlamydomonas and other green algae is presented. [source]

Centrioles are freed from cilia by severing prior to mitosis,

CYTOSKELETON, Issue 7 2010
Jeremy D.K. Parker
Abstract Cilia are necessary for normal tissue development and homeostasis and are generally present during interphase, but not in mitosis. The precise mechanism of premitotic ciliary loss has been controversial, with data supporting either sequential disassembly through the transition zone or, alternatively, a severing event at the base of the cilia. Here we show by live cell imaging and immunofluoresence microscopy that resorbing flagella of Chlamydomonas leave remnants associated with the mother cell wall. We postulated that the remnants are the product of severing of doublet microtubules between the basal bodies and the flagellar transition zone, thereby freeing the centrioles to participate in spindle organization. We show via TEM that flagellar remnants are indeed flagellar transition zones encased in vesicles derived from the flagellar membrane. This transition zone vesicle can be lodged within the cell wall or it can be expelled into the environment. This process is observable in Chlamydomonas, first because the released flagellar remnants can remain associated with the cell by virtue of attachments to the cell wall, and second because the Chlamydomonas transition zone is particularly rich with electron-dense structure. However, release of basal bodies for spindle-associated function is likely to be conserved among the eukaryotes. © 2010 Wiley-Liss, Inc. [source]

Centrioles to basal bodies in the spermiogenesis of Mastotermes darwiniensis (Insecta, Isoptera)

CYTOSKELETON, Issue 5 2009
Maria Giovanna Riparbelli
Abstract In addition to their role in centrosome organization, the centrioles have another distinct function as basal bodies for the formation of cilia and flagella. Centriole duplication has been reported to require two alternate assembly pathways: template or de novo. Since spermiogenesis in the termite Mastotermes darwiniensis lead to the formation of multiflagellate sperm, this process represents a useful model system in which to follow basal body formation and flagella assembly. We present evidence of a possible de novo pathway for basal body formation in the differentiating germ cell. This cell also contains typical centrosomal proteins, such as centrosomin, pericentrin-like protein, ,-tubulin, that undergo redistribution as spermatid differentiation proceeds. The spermatid centrioles are long structures formed by nine doublet rather than triplet microtubules provided with short projections extending towards the surrounding cytoplasm and with links between doublets. The sperm basal bodies are aligned in parallel beneath the nucleus. They consist of long regions close to the nucleus showing nine doublets in a cartwheel array devoid of any projections; on the contrary, the short region close to the plasma membrane, where the sperm flagella emerge, is characterized by projections similar to those observed in the centrioles linking the basal body to the plasma membrane. It is hypothesized that this appearance is in connection with the centriole elongation and further with the flagellar axonemal organization. Microtubule doublets of sperm flagellar axonemes are provided with outer dynein arms, while inner arms are rarely visible. Cell Motil. Cytoskeleton 2009. © 2009 Wiley-Liss, Inc. [source]

Evolution and persistence of the cilium

CYTOSKELETON, Issue 12 2007
Peter Satir
Abstract The origin of cilia, a fundamental eukaryotic organelle, not present in prokaryotes, poses many problems, including the origins of motility and sensory function, the origins of nine-fold symmetry, of basal bodies, and of transport and selective mechanisms involved in ciliogenesis. We propose the basis of ciliary origin to be a self-assembly RNA enveloped virus that contains unique tubulin and tektin precursors. The virus becomes the centriole and basal body, which would account for the self-assembly and self-replicative properties of these organelles, in contrast to previous proposals of spirochaete origin or endogenous differentiation, which do not readily account for the centriole or its properties. The viral envelope evolves into a sensory bud. The host cell supplies the transport machinery and molecular motors to construct the axoneme. Polymerization of cytoplasmic microtubules in the 9 + 0 axoneme completes the 9 + 2 pattern. Cell Motil. Cytoskeleton 2007. © 2007 Wiley-Liss, Inc. [source]

Glutamylated tubulin: Diversity of expression and distribution of isoforms

CYTOSKELETON, Issue 1 2003
Marie-Louise Kann
Abstract Glutamylation of , and , tubulin isotypes is a major posttranslational modification giving rise to diversified isoforms occurring mainly in neurotubules, centrioles, and axonemes. Monoglutamylated tubulin isoforms can be differentially recognized by two mAbs, B3 and GT335, which both recognize either polyglutamylated isoforms. In the present study, immunoelectron microscopy and immunofluorescence analyses were performed with these two mAbs to determine the expression and distribution of glutamylated tubulin isoforms in selected biological models whose tubulin isotypes are characterized. In mouse spermatozoa, microtubules of the flagellum contain polyglutamylated isoforms except in the tip where only monoglutamylated isoforms are detected. In spermatids, only a subset of manchette microtubules contain monoglutamylated tubulin isoforms. Cytoplasmic microtubules of Sertoli cells are monoglutamylated. Mitotic and meiotic spindles of germ cells are monoglutamylated whereas the HeLa cell mitotic spindle is polyglutamylated. Three models of axonemes are demonstrated as a function of the degree and extent of tubulin glutamylation. In lung ciliated cells, axonemes are uniformly polyglutamylated. In sea urchin sperm and Chlamydomonas, flagellar microtubules are polyglutamylated in their proximal part and monoglutamylated in their distal part. In Paramecium, cilia are bi- or monoglutamylated only at their base. In all cells, centrioles or basal bodies are polyglutamylated. These new data emphasize the importance of glutamylation in all types of microtubules and strengthen the hypothesis of its role in the regulation of the intracellular traffic and flagellar motility. Cell Motil. Cytoskeleton 55:14,25, 2003. © 2003 Wiley-Liss, Inc. [source]

Transient concentration of a ,-tubulin-related protein with a pericentrin-related protein in the formation of basal bodies and flagella during the differentiation of Naegleria gruberi

CYTOSKELETON, Issue 2 2002
Mi Ra Suh
Abstract The distribution of two proteins in Naegleria gruberi, N-,TRP (Naegleria ,-tubulin-related protein) and N-PRP (Naegleria pericentrin-related protein), was examined during the de novo formation of basal bodies and flagella that occurs during the differentiation of N. gruberi. After the initiation of differentiation, N-,TRP and N-PRP began to concentrate at the same site within cells. The percentage of cells with a concentrated region of N-,TRP and N-PRP was maximal (68%) at 40 min when the synthesis of tubulin had just started but no assembled microtubules were visible. When concentrated tubulin became visible (60 min), the region of concentrated N-,TRP and N-PRP was co-localized with the tubulin spot and then flagella began to elongate from the region of concentrated tubulin. When cells had elongated flagella, the concentrated N-,TRP and N-PRP were translocated to the opposite end of the flagellated cells and disappeared. The transient concentration of N-,TRP coincided with the transient formation of an F-actin spot at which N-,TRP and ,-tubulin mRNA were co-localized. The concentration of N-,TRP and formation of the F-actin spot occurred without the formation of microtubules but were inhibited by cytochalasin D. These observations suggest that the regional concentration of N-,TRP and N-PRP is mediated by actin filaments and might provide a site of microtubule nucleation for the assembly of newly synthesized tubulins into basal bodies and flagella. Cell Motil. Cytoskeleton 52:66,81, 2002. © 2002 Wiley-Liss, Inc. [source]

Changes in the oviducal epithelium during the estrous cycle in the marsupial Monodelphis domestica

JOURNAL OF ANATOMY, Issue 4 2007
Annetrudi Kress
Abstract The Monodelphis oviduct can be divided into four anatomical segments: preampulla (comprising fimbriae and infundibulum), ampulla, isthmus with crypts and uterotubal junction. Ovaries are enclosed in a periovarial sac, the bursa, and in some specimens tubules of an epoophoron could be identified. In both structures non-ciliated cells develop small translucent vesicles, which accumulate in the cell apices and presumably produce fluid as often seen in the bursa and in the tubules of the epooophoron. These vesicles do not stain with Alcian blue or PAS. The same applies also to the non-ciliated cells of the fimbriae. The oviducal epithelium of ampulla and the surface epithelium of the isthmus consisting of ciliated and non-ciliated, secretory cells undergo considerable changes during the estrous cycle. Proestrus shows low numbers of ciliated cells, some are in the process of neo-ciliogenesis, non-ciliated cells carry solitary cilia and few remnant secretory granules from the previous cycle may be found. At estrus the amount of ciliated cells in ampulla and isthmus has increased, most non-cililated cells lost the solitary cilia, developed longer microvilli and formed numerous secretory granules in their cell apices. At postestrus secretory products, often surrounded by membranes, are extruded into the oviducal lumen and contribute towards egg coat formation. First signs of deciliation processes are apparent. Solitary cilia reappear. At metestrus only few secretory cells are left with some secretory material. The lumen is often filled with shed cilia and cell apices. Proliferation of basal bodies within non-secretory cells indicate the formation of new ciliated cells. The non-ciliated epithelial cells of the isthmic crypts form no secretory granules but accumulate a great number of translucent vesicles, which in contrast to the secretory granules do not stain with Alcian blue or PAS. [source]

TWO SNOW SPECIES OF THE QUADRIFLAGELLATE GREEN ALGA CHLAINOMONAS (CHLOROPHYTA, VOLVOCALES): ULTRASTRUCTURE AND PHYLOGENETIC POSITION WITHIN THE CHLOROMONAS CLADE,

JOURNAL OF PHYCOLOGY, Issue 4 2008
Philip M. Novis
The quadriflagellate snow alga Chlainomonas Christen, distributed in New Zealand and North America, has several unusual structural attributes. A process assumed to be cytokinesis involves extrusion of protoplasm from the parent through a narrow canal, C. kolii (J. T. Hardy et Curl) Hoham produces a net-like outer envelope rather than a cell wall, and the flagellar basal apparatus of Chlainomonas consists of two semi-independent pairs of basal bodies. Structural connections between basal body pairs appear minimal, but a connecting system different from that observed in other genera exists within each pair. Phylogenetic analysis using rbcL sequences places Chlainomonas in the Chloromonas clade, other known members of which are all biflagellate. Chlainomonas is split into two robust lineages, with New Zealand collections sharing an origin with northern North American collections. Although the quadriflagellate condition is regarded as ancestral in the Chlorophyceae, we speculate,based on ultrastructural and molecular data presented here,that Chlainomonas represents a derived form that has arisen from fusion of two ancestral biflagellate cells. Other explanations (for example, that Chlainomonas represents a diploid form of a biflagellate species) are remotely possible but are presently at odds with extensive observations of field material. Improvements in techniques for experimental manipulation of these sensitive cryophiles will be required to fully characterize their structure and progress our understanding of their biology. [source]

PSEUDULVELLA AMERICANA BELONGS TO THE ORDER CHAETOPELTIDALES (CLASS CHLOROPHYCEAE), EVIDENCE FROM ULTRASTRUCTURE AND SSU RDNA SEQUENCE DATA,

JOURNAL OF PHYCOLOGY, Issue 4 2006
M. Virginia Sanchez-Puerta
The genus Pseudulvella Wille 1909 includes epiphytic, freshwater, or marine disk-shaped green microalgae that form quadriflagellate zoospores. No ultrastructural or molecular studies have been conducted on the genus, and its evolutionary relationships remain unclear. The purpose of the present study is to describe the life history, ultrastructural features, and phylogenetic affiliations of Pseudulvella americana (Snow) Wille, the type species of the genus. Thalli of this microalga were prostrate and composed of radiating branched filaments that coalesced to form a disk. Vegetative cells had a pyrenoid encircled by starch plates and traversed by one or two convoluted cytoplasmic channels. They had well-defined cell walls without plasmodesmata. Asexual reproduction was by means of tetraflagellate zoospores formed in numbers of two to eight from central cells of the thallus. The flagellar apparatus of zoospores was cruciate, with four basal bodies and four microtubular roots. The paired basal bodies lay directly opposite (DO) one another. The microtubular root system had a 5-2-5-2 alternation pattern, where the "s" roots contained five microtubules in a four-over-one configuration. A tetralobate nonstriated distal fiber connected all four basal bodies. A wedge-shaped proximal sheath subtended each of the basal bodies. The ultrastructural features of the zoospores were those of members of the order Chaetopeltidales. Phylogenetic analyses based on SSU rDNA placed P. americana sister to Chaetopeltis orbicularis in a well-supported Chaetopeltidales clade. Such a combination of features confirmed that this alga is a member of the order Chaetopeltidales. [source]

ULTRASTRUCTURAL STUDIES ON BIGELOWIELLA NATANS, GEN.

JOURNAL OF PHYCOLOGY, Issue 4 2001
ET SP.
Three isolates from the Provasoli-Guillard National Center for Culture of Marine Phytoplankton at Bigelow Laboratory, previously labeled Pedinomonas sp. and Pedinomonas minutissima from the green algal class Pedinophyceae, have been examined by light microscopy and TEM and shown to belong to the Chlorarachniophyceae, a class of nucleomorph-containing amebae. The three isolates represent the first chlorarachniophycean flagellates to be discovered. The ultrastructure of the cells has been examined in detail, with particular emphasis on the flagellar apparatus, a feature not examined in detail in chlorarachniophytes before. Cells are basically biflagellate, but the second flagellum is represented by a very short basal body only. Flagellar replication has shown this flagellum to be the mature stage, that is, the no. 1 flagellum, whereas the long emergent flagellum is the no. 2 flagellum that shortens into a short basal body during cell division. Mitosis is open with a pair of centrioles at each pole. Emergent flagella are absent during mitosis. Cells may form cysts, and the flagellar basal bodies and part of the flagellar roots are maintained in the cysts. Four microtubular roots emanate from the basal bodies, and the path of one of them is very unusual and very unlike any other known flagellate. No striated roots were observed. Other fine-structural features of the cell include a very unusual type of pyrenoid and a special type of extrusome. Cells are mixotrophic. The three isolates are very similar and are described as Bigelowiella natans, gen. et sp. nov. Ultrastructurally, chlorarachniophytes do not show close relationship to any known group of algae or other protists. [source]

ULTRASTRUCTURE OF THE BASAL BODY COMPLEX AND PUTATIVE VESTIGIAL FEEDING APPARATUS IN PHACUS PLEURONECTES (EUGLENOPHYCEAE)

JOURNAL OF PHYCOLOGY, Issue 2001
Article first published online: 24 SEP 200
Shin, W.1, Boo, S. M.2, & Triemer, R. E.1 1Department of Life Science, Rutgers University, Piscataway, New Jersey 08854, USA; 2Department of Biology, Chungnam National University, Daejon 305-764, Korea Phacus pleuronectes (O. F. Müller) Dujardin is a phototrophic euglenoid with small discoid chloroplasts, a flat, rigid body, and longitudinally arranged pellicular strips. The flagellar apparatus consisted of two basal bodies and three flagellar roots typical of many phototrophic euglenoids, but also had a large striated fiber that connected the two basal bodies and associated with the ventral root. The three roots, in combination with the dorsal microtubular band, extended anteriorly and formed the major cytoskeletal elements supporting the reservoir membrane and ultimately the pellicle. A cytoplasmic pocket arose in the reservoir/canal transition region. It was supported by the ventral root and a C-shaped band of electron-opaque material that lined the cytoplasmic side of the pocket. A large striated fiber extended from this C-shaped band toward the reservoir membrane. The presence of striated fibers in the basal apparatus and associated with the microtubule reinforced pocket suggested that P. pleuronectes may be at the base of the Phacus lineage and may be more closely related to the phagotrophic euglenoids than to Phacus species which are ovoid in shape and have thicker pellicle strips. [source]

Ultrastructure of Lobocharacium coloradoense, gen. et sp. nov. (Chlorophyta, Characiosiphonaceae), an unusual coenocyte from Colorado

JOURNAL OF PHYCOLOGY, Issue 2 2000
Paul Kugrens
Light and electron microscopic descriptions are provided for Lobocharacium coloradoense, gen. et sp. nov., a unicellular coenocytic green alga isolated from a power plant's retaining pond in north-central Colorado. Vegetative cells range from 120,230 ,m in length and 80,120 ,m in diameter in culture. The large vegetative cells are attached to substrates by small discoid attachment pads. The cells are multinucleate and consist of distinct cytoplasmic lobes, with each lobe containing a chloroplast and a basal nucleus. Chloroplasts are somewhat cone-shaped in profile and stellate or lobed when viewed from the surface, and each has a central, basal pyrenoid. Hundreds of these cytoplasmic lobes occur within a cell, and thin cytoplasmic bridges interconnect the lobes. When a vegetative cell matures, each of the cytoplasmic lobes cleaves to form numerous fusiform zoospores or spherical isogametes. The biflagellate isogametes range in size from 4,10 ,m, they lack a cell wall, they have a cup-shaped chloroplast with a pyrenoid and stigma, and they have a nucleus close to the basal bodies. Isogametes are incapable of forming vegetative cells. Zoospores are biflagellate and fusiform, measuring 8,12 ,m in length and 4,6 ,m in diameter. Each zoospore has a cell wall, a single parietal chloroplast with a prominent pyrenoid in the center of the chloroplast, and a long oval stigma. Gamete and zoospore release involves a dissolution of the entire vegetative wall. Released zoospores usually settle and cluster near the vegetative cell from which they were produced, attach to the substrate with their flagella, and, shortly after losing their flagella, extrude mucilage through the flagellar pores in the wall to form a small discoid attachment pad. The incipient vegetative cell is fusiform and uninucleate, but it becomes more rounded and multinucleate as enlargement occurs. Most vegetative cells in culture become dormant, and the chloroplast becomes orange in color. Some cells form single aplanospores that can withstand desiccation, but occasionally numerous aplanospores may also be formed later in the larger vegetative cells. [source]

Alcohol Stimulates Ciliary Motility of Isolated Airway Axonemes Through a Nitric Oxide, Cyclase, and Cyclic Nucleotide-Dependent Kinase Mechanism

ALCOHOLISM, Issue 4 2009
Joseph H. Sisson
Background:, Lung mucociliary clearance provides the first line of defense from lung infections and is impaired in individuals who consume heavy amounts of alcohol. Previous studies have demonstrated that this alcohol-induced ciliary dysfunction occurs through impairment of nitric oxide (NO) and cyclic nucleotide-dependent kinase-signaling pathways in lung airway ciliated epithelial cells. Recent studies have established that all key elements of this alcohol-driven signaling pathway co-localize to the apical surface of the ciliated cells with the basal bodies. These findings led us to hypothesize that alcohol activates the cilia stimulation pathway at the organelle level. To test this hypothesis we performed experiments exposing isolated demembranated cilia (isolated axonemes) to alcohol and studied the effect of alcohol-stimulated ciliary motility on the pathways involved with isolated axoneme activation. Methods:, Isolated demembranated cilia were prepared from bovine trachea and activated with adenosine triphosphate. Ciliary beat frequency, NO production, adenylyl and guanylyl cyclase activities, cAMP- and cGMP-dependent kinase activities were measured following exposure to biologically relevant concentrations of alcohol. Results:, Alcohol rapidly stimulated axoneme beating 40% above baseline at very low concentrations of alcohol (1 to 10 mM). This activation was specific to ethanol, required the synthesis of NO, the activation of soluble adenylyl cyclase (sAC), and the activation of both cAMP- and cGMP-dependent kinases (PKA and PKG), all of which were present in the isolated organelle preparation. Conclusions:, Alcohol rapidly and sequentially activates the eNOS,NO,GC,cGMP,PKG and sAC,cAMP, PKA dual signaling pathways in isolated airway axonemes. These findings indicate a direct effect of alcohol on airway cilia organelle function and fully recapitulate the alcohol-driven activation of cilia known to exist in vivo and in intact lung ciliated cells in vitro following brief moderate alcohol exposure. Furthermore, these findings indicate that airway cilia are exquisitely sensitive to the effects of alcohol and substantiate a key role for alcohol in the alterations of mucociliary clearance associated with even low levels of alcohol intake. We speculate that this same axoneme-based alcohol activation pathway is down regulated following long-term high alcohol exposure and that the isolated axoneme preparation provides an excellent model for studying the mechanism of alcohol-mediated cilia dysfunction. [source]

Behavior of flagella and flagellar root systems in the planozygotes and settled zygotes of the green alga Bryopsis maxima Okamura (Ulvophyceae, Chlorophyta) with reference to spatial arrangement of eyespot and cell fusion site

PHYCOLOGICAL RESEARCH, Issue 4 2010
Shinichi Miyamura
SUMMARY Behaviors of male and female gametes, planozygotes and their microtubular cytoskeletons of a marine green alga Bryopsis maxima Okamura were studied using field emission scanning electron microscopy, high-speed video microscopy, and anti-tubulin immunofluorescence microscopy. After fusion of the biflagellate male and female gametes, two sets of basal bodies lay side by side in the planozygote. Four long female microtubular roots extended from the basal bodies to the cell posterior. Four short male roots extended to nearly half the distance to the posterior end. Two flagella, one each from the male and female gametes, become a pair. Specifically, the no. 2 flagellum of the female gamete and one male flagellum point to the right side of the eyespot of the female gamete, which is located at the cell posterior and which is associated with 2s and 2d roots of the female gamete. This spatial relationship of the flagella, microtubular roots, and the eyespot in the planozygote is retained until settlement. During forward swimming, the planozygote swings the flagella backward and moves by flagellar beating. The male and female flagella in the pair usually beat synchronously. The cell withdraws the flagella and becomes round when the planozygote settles to the substratum 20 min after mixing. The axoneme and microtubular roots depolymerize, except for the proximal part and the basal bodies. Subsequently, distinct arrays of cortical microtubules develop in zygotes until 30 min after mixing. These results are discussed with respect to the functional significance of the spatial relationships of flagellar apparatus-eyespot-cell fusion sites in the mating gametes and planozygote of green algae. [source]

Ultrastructure of the biflagellate gametes of Collinsiella cava (Ulvophyceae, Chlorophyta)

The molecular basis of oral-facial-digital syndrome, type 1,

AMERICAN JOURNAL OF MEDICAL GENETICS, Issue 4 2009
Marina Macca
Abstract Oral,facial,digital syndrome type 1 (OFDI; OFD1; OMIM 311200) is a rare developmental disorder transmitted as an X-linked dominant condition with embryonic male lethality. OFD1 is characterized by malformation of the oral cavity, face, and digits. Central nervous system (CNS) abnormalities and cystic kidney disease can also be part of this condition. This disorder is due to mutations in the OFD1 gene that encodes a centrosomal protein localized at the basal bodies at the origin of primary cilia. Characterization of in vitro and in vivo models demonstrated that, similarly to what described for other ciliary proteins, Ofd1 inactivation is associated to defective sonic hedgehog (Shh) and canonical Wnt signaling pathways. Functional studies have demonstrated that OFD1 has a crucial role in the biology of primary cilia thus ascribing this pleiotropic disease to the growing number of disorders associated to dysfunction of primary cilia. OFD1 shares phenotypic similarities with this latter group of disorders, such as cystic kidneys, skeletal, and CNS abnormalities. Future studies will address whether all clinical manifestations of these diseases can be entirely explained by cilia dysfunction or may also be due to direct roles of the proteins involved. © 2009 Wiley-Liss, Inc. [source]

Ellis,van Creveld syndrome and Weyers acrodental dysostosis are caused by cilia-mediated diminished response to hedgehog ligands,

AMERICAN JOURNAL OF MEDICAL GENETICS, Issue 4 2009
Victor L. Ruiz-Perez
Abstract Ellis,van Creveld syndrome (EvC; OMIM 225500) is a recessive disorder comprising chondrodysplasia, polydactyly, nail dysplasia, orofacial abnormalities and, in a proportion of patients, cardiovascular malformations. Weyers acrodental dysostosis (Weyers; OMIM 193530) is an allelic dominant disorder comprising polydactyly, nail dysplasia, and orofacial abnormalities. EvC results from loss-of-function mutations in EVC or EVC2, the phenotype associated with the mutations in these two genes being indistinguishable. Three convincing causative mutations have been identified in patients with Weyers acrodental dysostosis, which are clustered in the last coding exon of EVC2 and lead to production of a truncated protein lacking the final 43 amino acids. Localization and function of EVC and EVC2 are inferred from studying the murine orthologs. Both Evc and Evc2 proteins localize to the basal bodies of primary cilia and analysis of an Ellis,van Creveld mouse model, which includes the limb shortening and tooth abnormalities of EvC patients, has demonstrated Hedgehog signaling defects in the absence of Evc. The loss of Evc2 has not been studied directly, but Hedgehog signaling is impaired when a mutant murine Evc2 Weyer variant is expressed in vitro. We conclude that the phenotypic abnormalities in EvC and Weyers syndrome result from tissue specific disruption of the response to Hh ligands. © 2009 Wiley-Liss, Inc. [source]

Ultrastructure of the Harmful Unarmored Dinoflagellate Cochlodinium polykrikoides (Dinophyceae) with Reference to the Apical Groove and Flagellar Apparatus

THE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 4 2010
MITSUNORI IWATAKI
ABSTRACT. The external and internal ultrastructure of the harmful unarmored dinoflagellate Cochlodinium polykrikoides Margalef has been examined with special reference to the apical groove and three-dimensional structure of the flagellar apparatus. The apical groove is U-shaped and connected to the anterior sulcal extension on the dorsal side of the epicone. The eyespot is located dorsally and composed of two layers of globules situated within the chloroplast. A narrow invagination of the plasma membrane is associated with the eyespot. The nuclear envelope has normal nuclear pores similar to other eukaryotes but different from the Gymnodinium group with diagnostic nuclear chambers. The longitudinal and transverse basal bodies are separated by approximately 0.5,1.0 ,m and interconnected directly by a striated basal body connective and indirectly by microtubular and fibrous structures. Characteristic features of the flagellar apparatus are as follows: (1) a nuclear extension projects to the R1 (longitudinal microtubular root) and is connected to the root by thin fibrous material; (2) fibrillar structures are associated with the longitudinal and transverse flagellar canal; and (3) a striated ventral connective extends toward the posterior end of the cell along the longitudinal flagellar canal. We conclude, based on both morphological and molecular evidence, that Cochlodinium is only distantly related to Gymnodinium. [source]

Urotricha psenneri n. sp. and Amphileptus piger (Vuxanovici, 1962) n. comb., Two Planktonic Ciliates (Protozoa, Ciliophora) from an Oligotrophic Lake in Austria

THE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 6 2004
BETTINA SONNTAG
ABSTRACT Two euplanktonic ciliates, Urotricha psenneri n. sp. (Prostomatida) and Amphileptus piger (Vuxanovici, 1962) n. comb. (Pleurostomatida), were discovered in the surface plankton of the oligotrophic Lake Traunsee in Austria. Their morphology and infra-ciliature were studied in live cells as well as in specimens impregnated with protargol and silver nitrate. Urotricha psenneri is a small urotrichid, less than 50 ,m length and with a single caudal cilium. It is unique in having (i) a massive oral basket projecting as a conspicuous bulge with cylindrical microfibrillar annulus and (ii) a curved brosse row 1 in the broad, barren circumoral area. Amphileptus piger (Vuxanovici, 1962) is about 55 × 13 ,m in vivo, has two macronuclear nodules with a single micronucleus in between in the posterior body half, has a single contractile vacuole with a terminal excretory pore, and few, but thick and thus highly conspicuous extrusomes. The amphileptid ciliary pattern (spica) is difficult to recognise due to the widely spaced basal bodies. [source]

Golgi biogenesis in simple eukaryotes

CELLULAR MICROBIOLOGY, Issue 3 2007
Cynthia Y. He
Summary The accurate duplication of cellular organelles is important to ensure propagation through successive generations. The semi-conserved replication of DNA and DNA-containing organelles has been well studied, but the mechanisms used to duplicate most other organelles remain elusive. These include the centrosomes, which act as microtubule organizing centres during interphase and orient the mitotic spindle poles during mitosis. Centrosomes can also act as basal bodies, nucleating the growth of cilia or flagella. Even less understood are the mechanisms used to duplicate membrane-bound organelles that do not contain DNA. These include organelles involved in the secretory pathway such as the endoplasmic reticulum and the Golgi apparatus. This review will summarize the current knowledge of Golgi biogenesis in simple eukaryotic organisms, in particular, two protozoan parasites, Toxoplasma gondii and Trypanosoma brucei. [source]

Centrioles to basal bodies in the spermiogenesis of Mastotermes darwiniensis (Insecta, Isoptera)

Evolution and persistence of the cilium

Axonemal localization of Chlamydomonas PACRG, a homologue of the human Parkin -coregulated gene product

CYTOSKELETON, Issue 11 2007
Kazuho Ikeda
Abstract A homologue of mammalian PACRG was identified in Sarkosyl-extracted Chlamydomonas axonemes as a protein that may interact with Rib72 (a component of the protofilament ribbon within the outer doublet microtubules). PACRG is a protein whose expression is co-regulated with the Parkin gene implicated in Parkinson's disease. Although subsequent analyses did not confirm a Rib72-PACRG interaction, both proteins display similar localization in the axoneme. Immuno-localization of PACRG required pretreatment of the axoneme with Sarkosyl, suggesting that the antigen is buried in the wall of the microtubule. Indirect immunofluorescence localized PACRG to the entire length of the axoneme and the basal body, and immuno-electron microscopy showed that the PACRG antigen is densely distributed along the outer doublets in frayed axonemes. In thin-section images, the PACRG signals were frequently found between the A- and B-tubules of adjacent outer doublets. From these and other results, we propose that PACRG is a structural component of the doublet and triplet microtubules possibly involved in inter-tubule linkage. Cell Motil. Cytoskeleton, 2007. © 2007 Wiley-Liss, Inc. [source]

Evidence for a sliding-resistance at the tip of the trypanosome flagellum

CYTOSKELETON, Issue 12 2006
David Woolley
Abstract Motility in trypanosomes is achieved through the undulating behaviour of a single "9 + 2" flagellum; normally the flagellar waves begin at the flagellar tip and propagate towards the base. For flagella in general, however, propagation is from base-to-tip and it is believed that bend formation, and sustained regular oscillation, depend upon a localised resistance to inter-doublet sliding - which is normally conferred by structures at the flagellar base, typically the basal body. We therefore predicted that in trypanosomes there must be a resistive structure at the flagellar tip. Electron micrographs of Crithidia deanei, Herpetomonas megaseliae, Trypanosoma brucei and Leishmania major have confirmed that such attachments are present. Thus, it can be assumed that in trypanosomes microtubule sliding at the flagellar tip is resisted sufficiently to permit bend formation. Cell Motil. Cytoskeleton 2006. © 2006 Wiley-Liss, Inc. [source]

Spermatogenesis in Boccardiella hamata (Polychaeta: Spionidae) from the Sea of Japan: sperm formation mechanisms as characteristics for future taxonomic revision

ACTA ZOOLOGICA, Issue 4 2010
Arkadiy A. Reunov
Abstract Reunov, A.A., Yurchenko, O.V., Alexandrova, Y.N. and Radashevsky, V.I. 2009. Spermatogenesis in Boccardiella hamata (Polychaeta: Spionidae) from the Sea of Japan: sperm formation mechanisms as characteristics for future taxonomic revision. ,Acta Zoologica (Stockholm) 91: 477,456. To characterize novel features that will be useful in the discussion and validation of the spionid polychaete Boccardiella hamata from the Sea of Japan, the successive stages of spermatogenesis were described and illustrated. Spermatogonia, spermatocytes and early spermatids are aflagellar cells that develop synchronously in clusters united by a cytophore. At the middle spermatid stage, the clusters undergo disintegration and spermatids produce flagella and float separately in coelomic fluid as they transform into sperm. Spermatozoa are filiform. The ring-shaped storage platelets are located along the anterior nuclear area. The nucleus is cupped by a conical acrosome. A nuclear plate is present between the acrosome and nucleus. The nucleus is a cylinder with the implantation fossa throughout its length and with the anterior part of the flagellum inside the fossa. There is only one centriole, serving as a basal body of the flagellum, situated in close vicinity of the acrosomal area. A collar of four mitochondria is located under the nuclear base. The ultrastructure of B. hamata spermatozoa from the Sea of Japan appears to be close to that of B. hamata from Florida described by Rice (Microscopic Anatomy of Invertebrates, Wiley-Liss, Inc., New York, 1992), suggesting species identity of the samples from the two regions. However, more detailed study of Florida's B. hamata sperm is required for a reliable conclusion concerning the similarity of these two polychaetes. In addition to sperm structure, features such as the cytophore-assigned pattern of spermatogenic cell development, the synchronous pattern of cell divisions, the non-flagellate early spermatogenic stages, and the vesicle amalgamation that drives meiotic cell cytokinesis and spermatid diorthosis will likely be useful in future testing of the validity of B. hamata and sibling species throughout the world. [source]

Larval development in the Homoscleromorpha (Porifera, Demospongiae)

INVERTEBRATE BIOLOGY, Issue 3 2003
Nicole Boury-Esnault
Abstract. Embryonic development from coeloblastula to fully developed larva was investigated in 8 Mediterranean homoscleromorph species: Oscarella lobularis, O. tuberculata, O. microlobata, O. imperialis, Plakina trilopha, P. jani, Corticium candelabrum, and Pseudocorticium jarrei. Morphogenesis of the larva is similar in all these species; however, cell proliferation is more active in species of Oscarella than in Plakina and C. candelabrum. The result of cell division is a wrinkled, flagellated larva, called a cinctoblastula. It is composed of a columnar epithelium of polarized, monoflagellated cells among which are scattered a few non-flagellated ovoid cells. The central cavity always contains symbiotic bacteria. Maternal cells are also present in O. lobularis, O. imperialis, and P. jarrei. In the fully developed larva, cell shape and dimensions are constant for each species. The cells of the anterior pole have large vacuoles with heterogeneous material; those of the postero-lateral zone have an intranuclear paracrystalline inclusion; and the flagellated cells of the posterior pole have large osmiophilic inclusions. Intercellular junctions join the apical parts of the cells, beneath which are other specialized cell junctions. A basement membrane underlying the flagellated cells lines the larval cavity. This is the first observation of a basement membrane in a poriferan larva. The basal apparatus of flagellated cells is characterized by an accessory centriole located exactly beneath the basal body. The single basal rootlet is cross striated. The presence of a basement membrane and a true epithelium in the larva of Homoscleromorpha,unique among poriferan clades and shared with Eumetazoa,suggests that Demospongiae could be paraphyletic. [source]

ULTRASTRUCTURAL STUDIES ON BIGELOWIELLA NATANS, GEN.

Flagellar apparatus of south-seeking many-celled magnetotactic prokaryotes

MICROSCOPY RESEARCH AND TECHNIQUE, Issue 1 2007
Karen Tavares Silva
Abstract Magnetotactic bacteria orient and migrate along geomagnetic field lines. Each cell contains membrane-enclosed, nano-scale, iron-mineral particles called magnetosomes that cause alignment of the cell in the geomagnetic field as the bacteria swim propelled by flagella. In this work we studied the ultrastructure of the flagellar apparatus in many-celled magnetotactic prokaryotes (MMP) that consist of several Gram-negative cells arranged radially around an acellular compartment. Flagella covered the organism surface, and were observed exclusively at the portion of each cell that faced the environment. The flagella were helical tubes never as long as a complete turn of the helix. Flagellar filaments varied in length from 0.9 to 3.8 ,m (average 2.4 ± 0.5 ,m, n = 150) and in width from 12.0 to 19.5 nm (average 15.9 ± 1.4 nm, n = 52), which is different from previous reports for similar microorganisms. At the base of the flagella, a curved hook structure slightly thicker than the flagellar filaments was observed. In freeze-fractured samples, macromolecular complexes about 50 nm in diameter, which possibly corresponded to part of the flagella basal body, were observed in both the P-face of the cytoplasmic membrane and the E-face of the outer membrane. Transmission electron microscopy showed that magnetosomes occurred in planar groups in the cytoplasm close and parallel to the organism surface. A striated structure, which could be involved in maintaining magnetosomes fixed in the cell, was usually observed running along magnetosome chains. The coordinated movement of the MMP depends on the interaction between the flagella of each cell with the flagella of adjacent cells of the microorganism. Microsc. Res. Tech., 2006. © 2006 Wiley-Liss, Inc. [source]

Ultrastructure of the biflagellate gametes of Collinsiella cava (Ulvophyceae, Chlorophyta)

Ultrastructural Description of Breviata anathema, N. Gen., N. Sp., the Organism Previously Studied as "Mastigamoeba invertens"

THE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 2 2006
GISELLE WALKER
ABSTRACT. An understanding of large-scale eukaryotic evolution is beginning to crystallise, as molecular and morphological data demonstrate that eukaryotes fall into six major groups. However, there are several taxa of which the affinities are yet to be resolved, and for which there are only either molecular or morphological data. One of these is the amoeboid flagellate Mastigamoeba invertens. This organism was originally misidentified and studied as a pelobiont using molecular data. We present its first light microscopical and ultrastructural characterisation. We demonstrate that it does not show affinities to the amoebozoan pelobionts, because unlike the pelobionts, it has a double basal body and two flagellar roots, a classical Golgi stack, and a large branching double membrane-bound organelle. Phylogenetic analyses of small subunit ribosomal RNA suggest an affinity with the apusomonads, when a covariotide correction for rate heterogeneity is used. We suggest that previous molecular results have been subject to artefacts from an insufficient correction for rate heterogeneity. We propose a new name for the taxon, Breviata anathema; and the unranked, apomorphy-based name "Breviates" for Breviata and its close relatives. [source]