Fine structure of the atrioventricular node as viewed in serial sections

1973 ◽  
Vol 136 (1) ◽  
pp. 43-65 ◽  
Author(s):  
J. C. Thaemert
Keyword(s):  
Fine Structure ◽  
Atrioventricular Node ◽  
Serial Sections

Re-evaluation of the structure of the atrioventricular node and its connections with the atrium

EP Europace ◽  
2020 ◽  
Vol 22 (5) ◽  
pp. 821-830 ◽  
Author(s):  
Robert H Anderson ◽  
Damian Sanchez-Quintana ◽  
Shumpei Mori ◽  
Jose Angel Cabrera ◽  
Eduardo Back Sternick
Keyword(s):  
Atrioventricular Node ◽  
Atrial Septum ◽  
Atrioventricular Conduction ◽  
Marked Variation ◽  
Compelling Evidence ◽  
Serial Sections ◽  
Atrial Myocardium ◽  
Cavotricuspid Isthmus ◽  
Fibrous Body ◽  
Bundle Of His

Abstract Aims The anatomic substrates for atrioventricular nodal re-entry remain enigmatic, but require knowledge of the normal arrangement of the inputs and exist from the atrioventricular node. This knowledge is crucial to understand the phenomenon of atrioventricular nodal re-entry. Methods and results We studied 20 human hearts with serial sections covering the entirety of the triangle of Koch and the cavotricuspid isthmus. We determined the location of the atrioventricular conduction axis and the connections between the specialized cardiomyocytes of the conduction axis and the adjacent working atrial myocardium. The atrioventricular node was found at the apex of the triangle of Koch, with entry of the conduction axis to the central fibrous body providing the criterion for distinction of the bundle of His. We found marked variation in the inferior extensions of the node, the shape of the node, the presence or absence of a connecting bridge within the myocardium of the cavotricuspid isthmus, the connections between the compact node and the myocardium of the atrial septum, the presence of transitional cardiomyocytes, and the ‘last’ connection between the working atrial myocardium and the conduction axis before it became the bundle of His. Conclusion The observed variations of the inferior extensions, combined with the arrangement of the ‘last’ connections between the atrial myocardium and the conduction axis prior to its insulation as the bundle of His, provide compelling evidence to support the concept for atrioventricular nodal re-entry as advanced by Katritsis and Becker.

scholarly journals A STUDY OF PHAGOCYTOSIS IN THE AMEBA CHAOS CHAOS

1965 ◽  
Vol 25 (3) ◽  
pp. 443-457 ◽  
Author(s):  
Richard G. Christiansen ◽  
John M. Marshall
Keyword(s):  
Electron Microscopy ◽  
Fine Structure ◽  
Living Cell ◽  
Serial Sections

The process of phagocytosis was investigated by observing the interactions between the ameba Chaos chaos and its prey (Paramecium aurelia), by studying food cup formation in the living cell, and by studying the fine structure of the newly formed cup using electron microscopy of serial sections. The cytoplasm surrounding the food cup was found to contain structures not seen elsewhere in the ameba. The results are discussed in relation to the mechanisms which operate during food cup formation.

Techniques Involved in the Acquisition of Serial Sections of the Atrioventricular Node for Light and Electron Microscopy

1968 ◽  
Vol 26 ◽  
pp. 226-227
Author(s):  
Sheila S. Emmett ◽  
J. C. Thaemert
Keyword(s):  
Electron Microscopy ◽  
Osmium Tetroxide ◽  
Light And Electron Microscopy ◽  
Atrioventricular Node ◽  
Electron Microscopic Level ◽  
Serial Sections ◽  
Electron Microscopic ◽  
Trapezoidal Shape ◽  
Old Mice

The acquisition of serial sections of the atrioventricular node for light and electron microscopy is a formidable task. Ordinary techniques are not adequate if the best possible results are to be achieved at the electron microscopic level. The techniques outlined below have proven to be valuable in locating and determining the position of the AV node.Whole hearts of 2-week old mice were fixed, in situ, by perfusion with 1% phosphate-buffered osmium tetroxide. The hearts were removed from the animals, sectioned transversely into 3 slices approximately equal in thickness, dehydrated in graded concentrations of ethanol and embedded in Epon 812. The block faces were trimmed to a trapezoidal shape ranging in size from 0.75 x 1 mm to 4 x 5 mm. Serial sections approximately 2 microns in thickness were cut with glass knives on a Porter-Blum MT-2 Ultramicrotome. While floating on a drop of water on the knife, each section was stretched with 1 drop of a 1:1, xylene in chloroform mixture applied directly to the section. The sections were picked up individually with a brush, transferred to a glass slide and oven dried for several hours prior to staining.

Fine structure of Classopollis exines

1986 ◽  
Vol 64 (12) ◽  
pp. 3059-3074 ◽  
Author(s):  
John R. Rowley ◽  
Satish K. Srivastava
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Fine Structure ◽  
Upper Jurassic ◽  
Thin Sheets ◽  
Serial Sections ◽  
Thin Sections ◽  
Band Area ◽  
Transmission Electron ◽  
Oxidative Etching

Serial sections for light microscopy or transmission electron microscopy of two Classopollis pollen tetrads show that the exine structure, except for the nexine, has radially arranged rodlike units interwoven with transverse subunits. The nexine consists of strands or thin sheets except in the equatorial infratectal striate band area, where it is up to ca. 1 μm thick. Nexine is absent in the areas of the distal cryptopore and the subequatorial circumpolar infratectal canal. It is very thin or absent in the tetrad scar. Native contrast and reactivity to stain disappeared on immersion of thin sections in 1 M NaOH or HCl or in water. Reactivity to stains was regained after oxidizing the sections in KMnO4. Reactivity to stains appears to be dependent upon non-sporopollenin molecules embedded within exines. The above immersions remove stain reactive sites. Oxidative etching of sporopollenin exposes new sites. The specimens of Classopollis classoides Pflug studied and illustrated were picked from an Upper Jurassic sample (CRC 31519-2) collected at Osmington Mills locality, Dorset, England.

The fine structure of ascospore delimitation in the yeast Wickerhamia fluorescens

1973 ◽  
Vol 19 (11) ◽  
pp. 1389-1392 ◽  
Author(s):  
Lynn Rooney ◽  
Peter B. Moens
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Fine Structure ◽  
Outer Membrane ◽  
Spindle Pole Body ◽  
Spindle Pole ◽  
Spore Wall ◽  
Serial Sections ◽  
Spore Body ◽  
Pole Body ◽  
Spindle Pole Bodies

Photographic records of complete serial sections of asci in different stages of sporulation show that one of the four nuclear lobes produced during meiosis in the ascus of the yeast Wickerhamia fluorescens has a complex spindle-pole body, which is the site from where the presumptive ascospore wall, or prospore wall, develops and eventually surrounds the ascospore nucleus and associated cytoplasm. The three remaining nuclei develop spindle-pole bodies and prospore walls to lesser and varying degrees. With few exceptions, all three degenerate. The outer membrane of the prospore wall forms a fold, or rim, on the outside of the spore. Thickening of the spore wall takes place first in the asymmetric ring, then around the spore body, and finally at the site where the nucleus is associated with the wall. It is shown that ascospore delimitation in W. fluorescens and Saccharomyces cerevisiae are similar to each other, and that it differs from the type observed in a number of Euascomycetes.

Three-dimensional morphometry of biological fine structure using HVEM stereo images

1991 ◽  
Vol 49 ◽  
pp. 432-433
Author(s):  
Kiyoshi Hama
Keyword(s):  
Fine Structure ◽  
Tilt Angle ◽  
Three Dimensional ◽  
Serial Sections ◽  
Analysis Method ◽  
Stereo Images ◽  
Advantages And Disadvantages ◽  
Paired Electron ◽  
Fine Structures ◽  
The Given

There are several approaches of extracting three dimensional (3D) morphometrical information from biological fine structures, computer 3D reconstruction using thin serial sections, stereologica1 analysis of random thin section images, reconstruction from the results obtained by Fourier analysis of continuously tilted images, and so on. We have developed a computer analysis method of HVEM stereo images of thick biological specimens. Each method has advantages and disadvantages and one can choose one or other method according to the nature of samples and/or the nature of the required information.In our method, stereo paired electron micrographs are processed to produce skeletonized images, they are automatically traced, and the z coordinates of the given specimen points are calculated from the parallaxes between the two tilted images and the tilt angle.

Observations on the Fine Structure and Development of the Spindle at Mitosis and Meiosis in a Marine Centric Diatom (Lithodesmium Undulatum)

1969 ◽  
Vol 5 (1) ◽  
pp. 271-298
Author(s):  
IRENE MANTON ◽  
K. KOWALLIK ◽  
H. A. VON STOSCH
Keyword(s):  
Fine Structure ◽  
Chromosome Structure ◽  
Centric Diatom ◽  
Serial Sections ◽  
Ground Plan ◽  
Living Culture ◽  
Full Discussion ◽  
Two Stages ◽  
Mitosis And Meiosis ◽  
Spindle Structure

Various cytoplasmic phenomena, including spindle structure and development during prophase of the first meiotic division, are described and illustrated. The living culture is represented by a timed sequence of photographs continuing those previously published with respect to mitotic stages in the same filament. The meiotic preliminaries include the so-called swelling phase, by which the parental frustule is forced open, liberating the contained spermatocytes. This occurs during pachytene on evidence of chromosome structure which is illustrated. A spindle precursor is shown to be present before opening of the frustule; this resembles structurally the mitotic equivalent though the ground plan is oblong instead of square. Growth of the precursor continues until after opening of the frustule, when the spindle itself begins to be laid down. Two stages of developing spindles during the later prophases are illustrated by sections cut in three planes and by serial sections. Preliminary comparisons are made with metaphase I and with mitosis, both qualitatively and quantitatively, but a full discussion is deferred pending completion of the record for the later meiotic stages.

Comparative ultrastructure and biochemistry of chytridiomycetous fungi and the future of the Harpochytriales

1980 ◽  
Vol 58 (19) ◽  
pp. 2098-2109 ◽  
Author(s):  
Larry P. Gauriloff ◽  
Rona J. Delay ◽  
Melvin S. Fuller
Keyword(s):  
Fine Structure ◽  
Ribosomal Rna ◽  
Posterior Region ◽  
Anterior Region ◽  
Serial Sections ◽  
Molecular Weights ◽  
Body Complex ◽  
Translucent Material ◽  
Relationship Of ◽  
Comparative Ultrastructure

The ultrastructure of the zoospores of Oedogoniomyces lymnaeae and Monoblepharella sp. are reexamined using serial sections. The relative molecular weights of the ribosomal RNA of various chytridiomycetous fungi are also determined and compared. The fine structure of each of these zoospores is very similar. The nucleus and "nuclear cap" are centrally located in the zoospores. The anterior region contains lipid globules, a few large, empty vacuoles and numerous, small vesicles. The posterior region is filled with an electron-translucent material throughout which are scattered spherical mitochondria and large vacuoles with electron-opaque inclusions. The basal body complex is located at the center of the posterior end, and the rumposomal complex is adjacent to the plasmalemma in the posterior region of these zoospores. A system of cisternae that are associated with microbodies appears to connect the lipid globules in the anterior region with the rumposomal complex in the posterior region of these zoospores. Small differences in the structure and distribution of certain organelles are considered minor compared with the overall similarities between these two zoospores. It is suggested that Oedogoniomyces be transferred to the Monoblepharidales. The fine structure of the Harpochytrium hedinii zoospore is not only similar to that of the zoospores studied herein, but also resembles the zoospores of chytrids. The possible relationship of Harpochytrium to the Chytridiales is supported by zoospore ultrastructure and the relative molecular weights of ribosomal RNA. The data available at the present time suggest that the order Harpochytriales be abandoned and that Harpochytrium be considered either a genus of nematosporangial, operculate, eucarpic chytrids or a monoblepharidalean genus with Oedogoniomyces. It is recommended that speculation concerning the taxonimic relationship between Harpochytrium and other Chytridiomycetes be delayed until more data concerning other species of Harpochytrium and monoblepharidalean fungi are available.

Ultrastructural organization of Rhizophlyctis harderi zoospores and redefinition of the type 1 microbody – lipid globule complex

1992 ◽  
Vol 70 (4) ◽  
pp. 750-761 ◽  
Author(s):  
Martha J. Powell ◽  
Sonali Roychoudhury
Keyword(s):  
Fine Structure ◽  
Three Dimensional ◽  
Ultrastructural Organization ◽  
Serial Sections ◽  
Dense Cores ◽  
Lipid Globule ◽  
Computer Aided ◽  
Glycogen Particles ◽  
Peripheral Cytoplasm

Because ultrastructural features of zoospores are considered primary characters in Chytridiomycete systematics, computer-aided three-dimensional reconstructions of serial sections were used to analyze zoospore fine structure of Rhizophlyctis harderi, a questionable member of the genus Rhizophlyctis. A secondary centriole was parallel to the kinetosome, but the nucleus was not structurally or spatially associated with the kinetosomes. Mitochondria and cisternae associated with vesicles bounded a ribosomal aggregation in which the nucleus was partially embedded. The peripheral cytoplasm between the plasma membrane and ribosomal aggregation contained α-glycogen particles, vacuoles with osmiophilic globules, vesicles with clear matrices, and vesicles with electron-dense cores. A new, compound form of microbody – lipid globule complex (MLC) was identified. This type of MLC incorporated posteriorly located lipid globules associated with rumposomes and anteriorly located lipid globules associated with simple cisternae, microbodies, and highly branched mitochondria. Based on these and other recent observations, the concept of the type 1 MLC was redefined. Sources for variation in ultrastructural features of zoospores are discussed. Zoospore ultrastructure of R. harderi is different from that described for other chytrid zoospores. Key words: Chytridiomycetes, microbody – lipid globule complex, Rhizophlyctis, taxonomy, ultrastructure, zoospore.

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