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C F Bardele

Publications and source records attributed to C F Bardele.

16 recordsLinked to original sources
PubMed1987

The fine structure of the paralabial organelle in the rumen ciliate Ophryoscolex purkinjei Stein, 1858.

The paralabial organelle of the rumen ciliate Ophryoscolex purkinjei, located on the ventral side of the ciliophor, is a highly specialized part of the somatic cortex. It consists of alternating rows of short modified cilia and thin pellicular folds which form a ridge-like structure. The central "top kinety" is composed of monokinetids which bear cilia with 9 + 2 axonemes and 2 microns in length. The top kinety is accompanied by a comb-shaped fold on its distal side and by a broad wedge-shaped fold on its proximal side. To both sides there follow two or three lateral kineties made of dikinetids. The anterior kinetosome of each pair bears a clavate cilium, only 0.5-0.7 micron in length and with a 9 + 0 axoneme while the cilium of the posterior kinetosome is even shorter. Lateral folds with numerous microtubules cover these lateral kineties and rows of barren basal bodies. The fine structure of this supposed sensory organelle show a basic pattern in four other ophryoscolecids, and its increasing complexity parallels the suggested phylogenetic line of evolution of these ciliates.

Animals↗
PubMed1983

Mapping of highly ordered membrane domains in the plasma membrane of the ciliate Cyclidium glaucoma.

The entire cortex of Cyclidium glaucoma has been analysed in a correlated freeze-fracturing and ultrathin-sectioning study. Three types of highly ordered domains of intramembranous particles were found in the plasma membrane; owing to the many landmarks in the cortex of C. glaucoma it was possible to map their location in relation to the precisely known position of every single cilium. Eight particle plates made of parallel tripartite particle ridges have been found in precisely determined locations at the anterior pole of the cell and in the buccal cavity. It is suggested that these membrane specializations represent mechanosensitive sites. An array of three parallel rows of particles, termed a 'simple pellicular rug', forms a second type of membrane domain, which is closely associated with somatic dikinetids found exclusively in the anterior half of the cell. A third extremely complex array, termed a 'complex pellicular rug', is associated with the monokinetids in the posterior half of the cell. There is no gradient in the distribution of these domains but a sharp boundary at the level of the future fission zone. The function of the pellicular rugs is unknown, but their specific distribution will be helpful in further studies on their assembly prior to or during cell division. The intracellular diversification of the cell surface is further augmented by the disclosure of three different aspects of the proximal part of the ciliary membrane. Beyond the double-stranded ciliary necklace, which is a common feature of all cilia, only the motile somatic cilia of C. glaucoma have typical ciliary plaques made of three rows of particles, while all oral cilia have modified plaques, which consist of four rows of particles. the single stiff caudal cilium has no plaques at all. The functional significance of the topographic differences in the plaque areas is discussed. Obviously, the plasma membrane and at least parts of the ciliary membrane form a non-fluid mosaic membrane.

Animals↗
PubMed1982

Differential distribution of voltage-dependent calcium channels and guanylate cyclase in the excitable ciliary membrane from Paramecium tetraurelia.

A novel method for isolation of cilia and ciliary membrane vesicles from Paramecium tetraurelia has been developed. Using a continuous Percoll gradient of low osmolarity after fragmentation of purified cilia by French Press treatment two membrane fractions with different buoyant densities were obtained. These fractions were further purified by conventional discontinuous sucrose density gradients and characterized biochemically and by electron microscopy. Guanylate cyclase, a membrane bound enzyme, was found almost exclusively in membrane vesicles of high buoyant density while the voltage-sensitive calcium-channel of the ciliary membrane was predominantly localized in low density vesicles. Examination of both fractions by SDS polyacrylamide gel electrophoresis revealed only minor differences in protein pattern in the 34 and 64 kilodaltons range. Morphologically both membrane vesicle fractions had a diameter of about 300 nm, however, the high density vesicle fraction contained a considerably larger amount of multilamellar structures with a multishell, onion-like appearance. Freeze-fracture analysis failed to detect differences in intramembrane particle content between low and high density vesicles. The possible biological relevance of the spatial separation of the calcium-sensor enzyme guanylate cyclase and the voltage-sensitive calcium-channels in the ciliary membrane is discussed in terms of a diffusion controlled mechanism for graded signal transmission.

Animals↗
PubMed1981

Functional and phylogenetic aspects of the ciliary membrane: a comparative freeze-fracture study.

This paper illustrates the structural diversity of the ciliary membrane of the somatic ciliature in 68 ciliate genera and describes the interior architecture of several presumptive sensory cilia. Freeze-fracture technique reveals a variety of intramembrane particle arrays known as ciliary necklace, ciliary plaques, and ciliary rosettes. While the function of these arrays is still largely unknown, their distribution among ciliates suggests a phylogenetic correlation. Whereas current systems of ciliate classification are primarily based on the character of the ciliature which surrounds the cytostome as well as on the morphogenesis of this oral ciliature, the data presented in this paper are well suited to emphasize the significance of the somatic ciliature for the reconstruction of ciliate phylogeny. This is particularly evident when the freeze-fracture data are mapped in parallel with a simplified phylogenetic tree based on the appearance of both the oral and the somatic ciliature. The freeze-fracture data are in agreement with hypothesis of a non-hymenostome origin of the spirotrichs and suggest a close relationship with respect to the origin of the Hymenostomatida from the Colpodida instead of from the Nassulida. The presumptive sensory cilia show a significantly greater particle density than most somatic cilia. While the particles may represent receptor proteins or ion channels, with the freeze-fracture technique it is at present impossible to specify the modalities of such "sensory" cilia.

Animals↗
PubMed1978

[Microtubules].

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Animals↗
PubMed1977

Organization and control of microtubule pattern in centrohelidan heliozoa.

Comparative studies of axopodial microtubule pattern in 10 different centrohelidan Heliozoa belonging to the genera Acanthocystis, Raphidiophrys and Heterophrys suggest that 2 basic principles govern pattern formation in centrohelidan Heliozoa. While the larger "open" arrays with unspecified number of microtubules, e.g. in A. aculeata and R. ambigua, may result from self-linkage of additional microtubules around centroplast-nucleated "starter microtubules," the smaller "closed" arrays with specified microtubule number, e.g. in A. pectinata and H. marina, favor a template-driven linkage mechanism. The centroplast is a highly complex microtubule organizing center involved in the control of orientation, number, and diameter of the axonemes. Its shell may serve as a surface upon which the microtubule nucleating sites assemble, but how the precise positioning of these sites occurs is still open to debate. Some of the unsolved problems of microtubule pattern formation may be explained by the "linker nucleation hypothesis" which is an extension of the "gradion hypothesis" by Roth et al. It is shown how both the formation of closed arrays and the balanced lateral growth of open arrays may result from linker-induced microtubule nucleation.

Allosteric Regulation↗
PubMed1977

Comparative study of axopodial microtubule patterns and possible mechanisms of pattern control in the centrohelidian heliozoa Acanthocystis, Raphidiophrys and Heterophrys.

The axopodial microtubule pattern of 9 centrohelidians belonging to the genera Acanthocystis, Raphidiophrys and Heterophrys, as well as the fine structure of their microtubule organizing centre, the centroplast, was studied to determine the rules which govern their patterns. Microtubules capable of binding a xamimum of 4 linkers are arranged in regularly distorted hexagons and equilateral triangles. The number of microtubules present in each axoneme ranges from some 140 in Acanthocystis turfacea to as few as 6 in Heterophrys marina (Stock I). In the later species each axoneme contains a single hexagon of microtubules only. In other Heterophrys species, the central hexagon is surrounded by closely packed microtubules or by microtubules arranged in pentagons; only the central hexagon is anchored in the centroplast shell, whereas additional microtubules seem to originate from secondary nucleation sites somewhat distal to the centroplast. It is argued that the distortion of the basic unit hexagon (with alternate angles close to 134 degrees and 106 degrees) indicates that the microtubules are composed of 13 protofilaments. While in the larger Acanthocystis and Raphidiophrys species, the pattern may result from self-linkage, the arrays found in the Heterophrys species seem to favour a template-determined linkage. To explain the formation of the central hexagon in Heterophrys and balanced lateral growth in the larger microtubule arrays, a 'linker-nucleation hypothesis' is proposed. The assumption is made that graded conformational changes in the microtubule subunits not only specify the position where the next linker will bind, but that this linker, through linkage, becomes able to induce secondary microtubule nucleation, which will result in balanced lateral growth of the array. The application of this hypothesis to other microtubule systems, e.g. basal body formation, is discussed.

Animals↗
PubMed1975

The fine structure of the centrohelidian heliozoan Heterophrys marina.

The fine structure of Heterophrys marina (Centrohelidia, Heliozoa) is described with special reference to centroplast structure, morphogenesis and "behavior" of kinetocysts (= axopodial granules which perform saltatory movement), and formation of organic spicules in a new type of organelle located in the plasma membrane. A low calcium pretreatment and fixation was used to improve preservation of highly labile axopodia which near their distal end contain a single microtubule (MT) only. Two varieties of H. marina with a respective maximum of 6 and 12 MTs per axopodium, and 2 hitherto undescribed species, H. elati and H. multipoda, were found among 9 stocks collected in Europe and North America. In all species only the central 6 MTs of each axoneme originate from a scaffolding layer of electron dense material which surrounds the central granule. Evidence is presented which indicates that in Heterophrys self-linkage is not the only principle of MT pattern generation but that instead precisely localized MT nucleation and specific linkage of MTs within the cortex of the centroplast lead to the MT patterns observed. Prekinetocysts originate from vesicles found in the neighborhood of the dictyosomes. After maturation the kinetocysts become attached to the plasma membrane which seems to play an important role both in selection of particles transported in the axopodia and particle movement as well.

Animals↗
PubMedDate not supplied

Particle movement in heliozoan axopods associated with lateral displacement of highly ordered membrane domains.

Freeze-fracture studies reveal that extrusive organelles displaying saltatory particle movements in centrohelidian axopod are attached to highly ordered domains within the plasma membrane. It is postulated that the motive force for lateral displacement of these membrane domains with the adhering organelle is located immediately underneath the plasma membrane being either part of the peripheral membrane proteins or attached filaments alined parallel to the axopodial microtubules. The attachment domain is interpreted as a "frozen" membrane area preventing untimely organelle discharge by membrane fusion.

Animals↗