scholarly journals THE CILIARY NECKLACE

1972 ◽  
Vol 53 (2) ◽  
pp. 494-509 ◽  
Author(s):  
Norton B. Gilula ◽  
Peter Satir
Keyword(s):  
Sea Urchin ◽  
Energy Transduction ◽  
Thin Sections ◽  
Ciliary Membrane ◽  
Membrane Particles ◽  
The Matrix ◽  
Longitudinal Fractures ◽  
Rat Trachea ◽  
Sea Urchin Sperm ◽  
Ciliary Shaft

Cilia, primarily of the lamellibranch gill (Elliptio and Mytilus), have been examined in freeze-etch replicas. Without etching, cross fractures rarely reveal the 9 + 2 pattern, although suggestions of ninefold symmetry are present. In etched preparations, longitudinal fractures through the matrix show a triplet spoke alignment corresponding to the spoke periodicity seen in thin sections. Dynein rows can be visualized along the peripheral microtubules in some preparations. Fracture faces of the ciliary membrane are smooth with few membrane particles, except in the regions adjacent to the basal plate. In the transition region below the plate, a unique particle arrangement, the ciliary necklace, is found. In the Elliptio gill, on fracture face A the necklace is comprised of three well-defined rows or strands of membrane particles that encircle the ciliary shaft. The rows are scalloped and each scallop corresponds to a peripheral doublet microtubule. In thin sections at the level of these particles, a series of champagne-glass structures link the microtubular doublets to the ciliary membrane. The ciliary necklace and this "membrane-microtubule" complex may be involved in energy transduction or the timing of ciliary beat. Comparative studies show that these features are present in all somatic cilia examined including those of the ameboflagellate Tetramitus, sea urchin embryos, rat trachea, and nonmotile cilia of cultured chick embryo fibroblasts. The number of necklace strands differs with each species. The necklace has not been found in rat or sea urchin sperm.

scholarly journals THE FINE STRUCTURE OF CORTICAL COMPONENTS OF PARAMECIUM MULTIMICRONUCLEATUM

1955 ◽  
Vol 1 (6) ◽  
pp. 583-604 ◽  
Author(s):  
Albert W. Sedar ◽  
Keith R. Porter
Keyword(s):  
Plasma Membrane ◽  
Fine Structure ◽  
Basal Body ◽  
Three Dimensional ◽  
Cell Types ◽  
The Body ◽  
Fiber System ◽  
Thin Sections ◽  
Ciliary Membrane ◽  
The Matrix

The electron microscope was used to study the structure and three dimensional relationships of the components of the body cortex in thin sections of Paramecium multimicronucleatum. Micrographs of sections show that the cortex is covered externally by two closely apposed membranes (together ∼250 A thick) constituting the pellicle. Beneath the pellicle the surface of the animal is molded into ridges that form a polygonal ridgework with depressed centers. It is these ridges that give the surface of the organism its characteristic configuration and correspond to the outer fibrillar system of the light microscope image. The outer ends of the trichocysts with their hood-shaped caps are located in the centers of the anterior and posterior ridges of each polygon. The cilia extend singly from the depressed centers of the surface polygons. Each cilium shows two axial filaments with 9 peripheral and parallel filaments embedded in a matrix and the whole surrouned by a thin ciliary membrane. The 9 peripheral filaments are double and these are evenly spaced in a circle around the central pair. The ciliary membrane is continuous with the outer member of the pellicular membrane, whereas the plasma membrane is continuous with the inner member of the pellicular membrane. At the level of the plasma membrane the proximal end of the cilium is continuous with its tube-shaped basal body or kinetosome. The peripheral filaments of the cilium, together with the material of cortical matrix which tends to condense around them, form the sheath of the basal body. The kinetodesma connecting the ciliary kinetosomes (inner fibrillar system of the light microscopist) is composed of a number of discrete fibrils which overlap in a shingle-like fashion. Each striated kinetosomal fibril originates from a ciliary kinetosome and runs parallel to other kinetosomal fibrils arising from posterior kinetosomes of a particular meridional array. Sections at the level of the ciliary kinetosomes reveal an additional fiber system, the infraciliary lattice system, which is separate and distinct from the kinetodesmal system. This system consists of a fibrous network of irregular polygons and runs roughly parallel to the surface of the animal. Mitochondria have a fine structure similar in general features to that described for a number of mammalian cell types, but different in certain details. The structures corresponding to cristae mitochondriales appear as finger-like projections or microvilli extending into the matrix of the organelle from the inner membrane of the paired mitochondrial membrane. The cortical cytoplasm contains also a particulate component and a system of vesicles respectively comparable to the nucleoprotein particles and to the endoplasmic reticulum described in various metazoan cell types. An accessory kinetosome has been observed in oblique sections of a number of non-dividing specimens slightly removed from the ciliary kinetosome and on the same meridional line as the cilia and trichocysts. Its position corresponds to the location of the kinetosome of the newly formed cilium in animals selected as being in the approaching fission stage of the life cycle.

The Outer Dynein Arms from Sea Urchin Sperm Flagella

1980 ◽  
Vol 38 ◽  
pp. 608-611
Author(s):  
W. S. Sale ◽  
W.-J. Y. Tang ◽  
I. R. Gibbons
Keyword(s):  
Sea Urchin ◽  
Energy Transduction ◽  
Cyclic Process ◽  
Cross Bridge ◽  
Bending Waves ◽  
Composition And Structure ◽  
Dynein Arms ◽  
Cilia And Flagella ◽  
Hydrolysis Of ◽  
Sea Urchin Sperm

A wide variety of experimental evidence now indicates that the bending waves of cilia and flagella are the result of coordinated, localized slid¬ing movements between doublet microtubules of the axoneme (Satir, 1968; Summers and Gibbons, 1971; Shingyoji, et al. 1977; Sale and Satir, 1977). These sliding movements are thought to occur as the consequence of a mecha¬nism in which the dynein arms on each doublet microtubule make and break cross-bridge attachments to the B-subfiber of the adjacent doublet micro¬tubule in a cyclic process involving the binding and hydrolysis of ATP (Summers and Gibbons, 1973; Gibbons and Gibbons, 1973; 1974). The structu¬ral and chemical steps of this cross-bridge cycle are only beginning to be understood (Warner, 1978; Penningroth and Witman, 1979; Sale and Gibbons, 1979; Okuno, 1979). Further understanding of the nature of the events of energy transduction will require knowledge of the composition and structure of the dynein arms.

Determination of the phase structure of polymerblends by electron microscopy

1978 ◽  
Vol 36 (1) ◽  
pp. 492-493
Author(s):  
Dr. G. Kaemof
Keyword(s):  
Screw Extruder ◽  
Electron Microscopic ◽  
Thin Sections ◽  
Single Screw Extruder ◽  
Transmission Electron ◽  
The Matrix ◽  
Twin Screw ◽  
Special Case ◽  
Microscopic Investigations

A mixture of polycarbonate (PC) and styrene-acrylonitrile-copolymer (SAN) represents a very good example for the efficiency of electron microscopic investigations concerning the determination of optimum production procedures for high grade product properties.The following parameters have been varied:components of charge (PC : SAN 50 : 50, 60 : 40, 70 : 30), kind of compounding machine (single screw extruder, twin screw extruder, discontinuous kneader), mass-temperature (lowest and highest possible temperature).The transmission electron microscopic investigations (TEM) were carried out on ultra thin sections, the PC-phase of which was selectively etched by triethylamine.The phase transition (matrix to disperse phase) does not occur - as might be expected - at a PC to SAN ratio of 50 : 50, but at a ratio of 65 : 35. Our results show that the matrix is preferably formed by the components with the lower melting viscosity (in this special case SAN), even at concentrations of less than 50 %.

scholarly journals Purification of an acrosin-like enzyme from sea urchin sperm.

1980 ◽  
Vol 255 (10) ◽  
pp. 4814-4820
Author(s):  
A.E. Levine ◽  
K.A. Walsh
Keyword(s):  
Sea Urchin ◽  
Sea Urchin Sperm

scholarly journals Structure of sea urchin sperm chromatin core particle.

1980 ◽  
Vol 255 (22) ◽  
pp. 10702-10709
Author(s):  
R.T. Simpson ◽  
L.W. Bergman
Keyword(s):  
Sea Urchin ◽  
Sperm Chromatin ◽  
Core Particle ◽  
Sea Urchin Sperm
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