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  • 1
    Electronic Resource
    Electronic Resource
    Diversity of microtubular doublets in insect sperm tails: A computer-aided image analysis (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 19 (1991), S. 282-289 
    Details
    ISSN: 0886-1544
    Keywords: sperm flagellum ; microtubular protofilaments ; dynein arms ; computer reconstruction ; computer analysis ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Axonemal doublets of some insect spermatozoa were fixed in a mixture of glutaraldehyde and tannic acid, post-fixed in uranyl acetate, and examined by electron microscopy, in order better to characterize the protofilament pattern. Most species had outer and inner dynein arms; others had only the inner one or none. Electron micrographs show the individual protofilaments to be well resolved and to be separated by an electron dense material. A certain “noise” inherent in the electron-microscopical technique was found and is believed to be due to irregularities in fixation, embedding, and section staining, and to beam damage. The noise level was reduced by using a computer program in which similar picture elements are averaged. The resulting averaged images of the axonemal doublets show a few widened “gaps” in the wall of protofilaments. These widened gaps coincide with the location of dynein arms, spokes, or intertubular material. There were, on the other hand, no widened gaps at the level of attachement of the accessory tubules. We tentatively conclude that at least some of the proteins that associate with microtubules are inserted deep inside the microtubular wall rather than having a superficial attachement. The internal structure of the A-subtubule is rather constant in species where both sets of dynein arms are present, whereas that of the B-tubule is more variable.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970190407
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  • 2
    Electronic Resource
    Electronic Resource
    Native microtubules with a variable number of protofilaments (1993)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 24 (1993), S. 49-53 
    Details
    ISSN: 0886-1544
    Keywords: insect sperm tail ; trichopteran axoneme ; computer image analysis ; axonemal ultrastructure ; accessory tubules ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Insect spermatozoa are characterized by having a set of accessory tubules that surrounds the microtubular doublets of the axoneme and that are formed from the B-subtubules of the doublets. In trichopteran species, the accessory tubules have an unusually large diameter. Those of one species, Odontocerum albicorne, were seen to have a number of protofilaments that is 19 in the main part of the axoneme, but gradually decreasing to 18, 17, and 16 near the distal tip. The accessory tubule of the trichopteran axoneme has an asymmetrical shape and a skewed orientation, which makes it easy to distinguish a tubule that is viewed from its plus-end from one viewed from the minus-end. The shape of a cross-sectioned protofilament in the trichopteran accessory tubules differs from that of microtubules in general, including accessory tubules of other insects, by being polygonal with the most acute angle pointing centripetally. © 1993 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970240106
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  • 3
    Electronic Resource
    Electronic Resource
    Junctional complexes of the branchia and gut of the tunicate, Pyrosoma atlanticum (Pyrosomatida, Thaliacea) (1992)
    Springer
    Cell & tissue research 267 (1992), S. 357-364 
    Details
    ISSN: 1432-0878
    Keywords: Branchial stigmata ; Gut ; Epithelium ; Cell junctions ; Pyrosomatida, Pyrosoma atlanticum (Tunicata)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The branchia of pyrosomes has been found to be like that of ascidians in that it shares with the latter, besides the presence of peribranchial chambers, stigmata bordered by clusters of seven rows of flattened cells, each bearing a single row of long cilia. The intercellular junctions between ciliated cells of the branchial basket and between the cells lining the gut, in pyrosomes, have been studied in thin sections and by freeze-fracture. In both tissues tight and gap junctions are present, but the former are much more extensive in the gut. The gap junctions in the branchial basket exhibit some atypical features. Moreover, although there are extensive zonulae adhaerentes between the ciliated cells of the branchial basket, there are none between the epithelial cells of the intestinal tract. This feature of the branchiae, together with the alignment of their cells into highly ordered rows of seven cells, are similar to those found in some groups of ascidians. The evolutionary relationships between pyrosomes and the aplousobranch ascidians are considered in the light of these results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00302974
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  • 4
    Electronic Resource
    Electronic Resource
    Unusual features of intercellular junctions in the larvacean Oikopleura dioica (1990)
    Springer
    Cell & tissue research 260 (1990), S. 299-305 
    Details
    ISSN: 1432-0878
    Keywords: Intercellular junctions ; Alimentary tract ; Freeze fracture ; Oikopleura dioica (Copelata)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary In the pelagic larvacean Oikopleura dioica, the epithelium lining the alimentary tract consists of ciliated and unciliated cell types. The ciliated cells also exhibit an apical border of long microvilli. Between the microvilli, the cellular membrane often projects deeply down into the cytoplasm; the membranes of these invaginations and those of apicolateral interdigitations may be associated with one another by tight junctions. Some of these junctions may be autocellular. The tight junctions are seen by freeze-fracture to be very simple in construction, composed of a single row of intramembranous particles, which may be fused into a P-face ridge. There is a dense cytoplasmic fuzz associated with these tight junctions which may extend into adjoining zonula adhaerens-like regions. The invaginations of the apical membranes are, in addition, associated by gap junctions which may also be autocellular. More conventional homocellular and heterocellular tight and gap junctions occur along the lateral borders of ciliated cells and between ciliated and unciliated cells. These gap junctions possess a reduced intercellular cleft and typical P-face connexons arranged in macular plaques, with complementary E-face pits. Both cell types exhibit extensive stacks of basal and lateral interdigitations. The tight junctions found here are unusual in that they are associated with a dense cytoplasmic fuzz which is normally more characteristic of zonulae adhaerentes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00318632
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  • 5
    Electronic Resource
    Electronic Resource
    Bizarre flagellum of thrips spermatozoa (Thysanoptera, Insecta) (1991)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 209 (1991), S. 343-347 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The flagellum of the thysanopteran spermatozoon has been examined by electron microscopy and computer-aided image analysis. The flagellum consists of 27 microtubular elements that probably are formed as outgrowths from three separate basal bodies. Nine of the elements are normal microtubular doublets that carry dynein arms and nine are doublets without dynein arms. The remaining nine elements are microtubular singlets that apparently bear dynein arms and have the same appearance as A-subtubules of microtubular doublets. The 27 elements are arranged in a fixed pattern that consists of nine groups, each of which begins with a microtubular singlet and ends with an arm-less microtubular doublet. Computer-aided image analysis has shown that the A-subtubules of the doublets and the microtubular singlets have lumens with very similar patterns. The sperm tail is known to have some motility; it generates fast waves running along its length. The amalgamated axonemes hence act as a functional flagellum. The thysanopteran sperm tail is the only type of flagellum known to us that consists of microtubules in a highly asymmetric array.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1052090309
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