The fine structure of zoospores of Harpochytrium hedinii

1980 ◽  
Vol 58 (19) ◽  
pp. 2090-2097 ◽  
Author(s):  
Larry P. Gauriloff ◽  
Rona J. Delay ◽  
Melvin S. Fuller
Keyword(s):  
Fine Structure ◽  
Basal Body ◽  
Posterior Region ◽  
Anterior Region ◽  
Serial Sections ◽  
Wide System ◽  
Body Complex

The fine structure of the Harpochytrium hedinii Wille zoospore is reexamined using serial sections. All of the major organelles are located in the posterior two-thirds of the zoospore; the anterior region contains only a few vacuoles and a network of filaments. The basal body complex is located at the center of the posterior end of the zoospore. The nucleus and "nuclear cap" are located directly anterior to the basal body complex on one side of the zoospore. All of the microbodies, lipid globules, and mitochondria are arranged into a complex associated with the rumposome along the opposite side of the zoospore. A spore-wide system of cisternae, the vesicular system, is continuous throughout the posterior region of the zoospore. The overall arrangement of organelles in the H. hedinii zoospore most closely resembles the internal morphologies of certain chytridialean zoospores. This suggests that Harpochytrium may be more closely related to the chytrids than has been previously assumed.

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.

scholarly journals THE FINE STRUCTURE OF EPENDYMA IN THE BRAIN OF THE RAT

1963 ◽  
Vol 19 (2) ◽  
pp. 415-439 ◽  
Author(s):  
M. W. Brightman ◽  
S. L. Palay
Keyword(s):  
Fine Structure ◽  
Basal Body ◽  
Intercellular Space ◽  
Proximal Region ◽  
Luminal Surface ◽  
Zonula Occludens ◽  
Dense Bodies ◽  
Body Complex ◽  
Basal Foot ◽  
The Brain

The ciliated ependyma of the rat brain consists of a sheet of epithelial cells, the luminal surface of which is reflected over ciliary shafts and numerous evaginations of irregular dimensions. The relatively straight lateral portions of the plasmalemma of contiguous cells are fused at discrete sites to form five-layered junctions or zonulae occludentes which obliterate the intercellular space. These fusions occur usually at some distance below the free surface either independently or in continuity with a second intercellular junction, the zonula adhaerens. The luminal junction is usually formed by a zonula adhaerens or, occasionally, by a zonula occludens. The finely granular and filamentous cytoplasm contains supranuclear dense bodies, some of which are probably lysosomes and dense whorls of perinuclear filaments which send fascicles toward the lateral plasmalemma. The apical regions of the cytoplasm contain the basal body complexes of neighboring cilia. These complexes include a striated basal foot and short, non-striated rootlets emanating from the wall of each basal body. The rootlets end in a zone of granules about the proximal region of the basal body, adjacent to which may lie a striated mass of variable shape. All components of the basal body complex of adjacent cilia are independent of each other.

scholarly journals A highly polarized excitable cell separates sodium channels from sodium-activated potassium channels by more than a millimeter

2015 ◽  
Vol 114 (1) ◽  
pp. 520-530 ◽  
Author(s):  
Yue Ban ◽  
Benjamin E. Smith ◽  
Michael R. Markham
Keyword(s):  
Ion Channels ◽  
Three Dimensional ◽  
Electric Organ ◽  
Metabolic Cost ◽  
Great Distance ◽  
Posterior Region ◽  
Anterior Region ◽  
Cell Periphery ◽  
Spatial Coupling ◽  
Eigenmannia Virescens

The bioelectrical properties and resulting metabolic demands of electrogenic cells are determined by their morphology and the subcellular localization of ion channels. The electric organ cells (electrocytes) of the electric fish Eigenmannia virescens generate action potentials (APs) with Na+ currents >10 μA and repolarize the AP with Na+-activated K+ (KNa) channels. To better understand the role of morphology and ion channel localization in determining the metabolic cost of electrocyte APs, we used two-photon three-dimensional imaging to determine the fine cellular morphology and immunohistochemistry to localize the electrocytes' ion channels, ionotropic receptors, and Na+-K+-ATPases. We found that electrocytes are highly polarized cells ∼1.5 mm in anterior-posterior length and ∼0.6 mm in diameter, containing ∼30,000 nuclei along the cell periphery. The cell's innervated posterior region is deeply invaginated and vascularized with complex ultrastructural features, whereas the anterior region is relatively smooth. Cholinergic receptors and Na+ channels are restricted to the innervated posterior region, whereas inward rectifier K+ channels and the KNa channels that terminate the electrocyte AP are localized to the anterior region, separated by >1 mm from the only sources of Na+ influx. In other systems, submicrometer spatial coupling of Na+ and KNa channels is necessary for KNa channel activation. However, our computational simulations showed that KNa channels at a great distance from Na+ influx can still terminate the AP, suggesting that KNa channels can be activated by distant sources of Na+ influx and overturning a long-standing assumption that AP-generating ion channels are restricted to the electrocyte's posterior face.

scholarly journals Nasal Wall Oriented Implants for All-on-4 Fix-Detachable Maxillary Reconstruction

2020 ◽  
pp. 151-160
Author(s):  
Jean Uhlendorf ◽  
Carolina A. Cartelli ◽  
Larissa C. Trojan ◽  
Geninho Thomé ◽  
Marcos B. Moura
Keyword(s):  
Case Report ◽  
Dental Implants ◽  
Dental Care ◽  
Clinical Case ◽  
Posterior Region ◽  
Anterior Region ◽  
Second Step ◽  
Immediate Loading ◽  
Viable Option ◽  
Tapered Connection

Immediate loading of full-arch prostheses on dental implants in the upper arch is challenging, as the bone is of low quality and obtaining sufficient torque may be difficult. The purpose of this case report is to describe the rehabilitation of a full-arch by means of placement of four internal tapered connection tilted implants and immediate loading. A 65-year-old man sought dental care with a partially edentulous upper arch. The teeth presented mobility and were extracted. In a second step, two conventional-length implants were placed in the anterior region and two tilted and nasal wall–directed extra-long implants in the posterior region. The insertion torques of 60 N.cm allowed the installation of an immediate prosthesis (hybrid). The clinical case report suggests that the placement of tilted and extra-long implants in the paranasal bone and immediate loading may be a viable option for rehabilitation of the edentulous upper arch.

Memoirs: The Morphology and Development of the Genitalia and Genital Ducts of Homoptera and Zygoptera as Shown in the Life Histories of Philaenus and Agrion

1928 ◽  
Vol s2-72 (287) ◽  
pp. 447-483
Author(s):  
C. J. GEORGE
Keyword(s):  
Anterior Part ◽  
Ejaculatory Duct ◽  
Accessory Gland ◽  
Posterior Region ◽  
Anterior Region ◽  
Vaginal Opening ◽  
Forward Region ◽  
Efferent System ◽  
Accessory Glands ◽  
The Common

1. In the male Philaenus and Agrion the vasa deferentia terminate on the ninth segment in the early stages. An ectodermal invagination from that segment joins them subsequently and thus the male gonopore is established. 2. The accessory glands develop in Philaenus male from the anterior end of the swollen extremities of the vasa deferentia and the vesiculae seminales from a still more forward region. 3. The accessory glands of the male are mesodermal in origin and not ectodermal as some authors state. 4. There is no evidence as to the existence of a ‘pair of ectodermal ejaculatory’ ducts either in Philaenus orin Agrion, and reasons are adduced to show that they do not exist at all in the higher Insecta. 5. In the female nymph of Philaenus the oviducts terminate on the seventh segment. They are subsequently joined by an ectodermal invagination from the seventh segment. The common oviduct is formed in two parts: the anterior part is derived from the posterior region of the invagination on the seventh and the posterior region is formed as a groove from the ectodermis of the eighth segment and subsequently this groove is converted into a tube. When the second part is completed it is in connexion with the invagination from the seventh and opens to the outside on the eighth segment. The ectodermal invagination from the seventh also gives rise to the spermatheca. A median accessory gland develops as an invagination from the ninth segment between the bases of the inner ovipositor lobes. A pair of accessory glands develop as paired imaginations from the anterior region of the ninth segment. 6. In the female nymph of Agrion the oviducts fuse to form a single duct and terminate in the middle of the eighth segment. Posteriorly an ectodermal invagination from the eighth segment meets this duct and lies in a position dorsal to it. Later on the ectodermal invagination develops a spermatheca dorsally and the mesodermal and the ectodermal ducts unite into one. The accessory glands develop as paired ectodermal invaginations from the anterior region of the ninth segment. 7. The female gonopore is not homologous in the different groups of insects. The vaginal opening in Orthoptera, Hymenoptera, Homoptera, Diptera, and Lepidoptera is homologous. The vaginal opening in Coleoptera is homologous with the oviducal opening of Lepidoptera, with the opening of the accessory gland of Homoptera, Hymenoptera, Diptera, Isoptera, and the opening of the spermatheca in some Orthoptera. 8. The common oviduct, being formed differently in the different groups is not homologous. The accessory organs, e. g. spermatheca, are not homologous in the different groups. 9. There is no evidence to show that the common oviduct is of paired origin. 10. The occurrence of a median accessory structure on the ninth segment which develops in the young as an invagination between the bases of the inner ovipositor lobes is very general in the higher Insecta. In some it functions as a gland, in others as a storehouse for spermatozoa. 11. The homology of the paired accessory glands is indicated. 12. The male genital ducts are not strictly homologous with those of the female. The homologue of the ejaculatory duct is the invagination from the ninth segment in the female. 13. The Odonata stand isolated in having a mesodermal region for the common oviduct and in the peculiar development of the two processes between the anterior ovipositor lobes. 14. The probable lines of evolution of the female efferent system in Insecta are indicated. The study of the development of the female efferent system indicates that the groups Orthoptera, Homoptera, Lepidoptera, and Diptera are very closely allied. Coleoptera seem to have had quite a different line of evolution from the above groups in this respect. 15. The adult Odonatan anatomy of the genital organs in the female as observed by me is in some respects different from that described by Tillyard. In conclusion I wish to express my deep sense of gratitude towards Professor Balfour-Browne and Dr. J. W. Munroe, both of whom have always been ready to help me. My colleague Mr. R. I. Nel, who is working on similar lines in this department,, has rendered me valuable help, not only in matters connected with the subject proper but also in translating difficult German references. I am also indebted to Mr. Peter Gray who helped me a good deal in translating references in Italian.

Palate Morphogenesis

Development ◽  
1979 ◽  
Vol 53 (1) ◽  
pp. 75-90
Author(s):  
Elizabeth L. Wee ◽  
Bruce S. Babiarz ◽  
Stephen Zimmerman ◽  
Ernest F. Zimmerman
Keyword(s):  
Embryo Culture ◽  
Posterior Region ◽  
Anterior Region ◽  
Serotonin Antagonists ◽  
A Cell ◽  
Pharmacologic Agents ◽  
Muscle Contractile ◽  
Contractile Cells

Previous studies have localized non-muscle contractile systems in the posterior (region 2) and the anterior (region 3) ends of mouse palates at the time of shelf movement. In order to determine whether these contractile systems function in shelf rotation, effects of pharmacologic agents have been analyzed in embryo culture. First, it was shown that the posterior end of the palate rotates before the anterior end, and its rotation in culture was proportionally greater as development of the embryo progressed. Generally, the posterior end of the palate was more easily inhibited in embryo culture than the anterior end. Serotonin at 10–−8 M to 10–−5 M was shown to significantly stimulate rotation atthe anterior end of the palate after 2 h in embryo culture. The effect on the posterior palate was less pronounced. To investigate further the role of this neurotransmitter on palate shelf rotation, serotonin antagonists were employed. Methysergide (10–−4 M) inhibited anterior shelf rotation to 12% of control values (P < 0·005), while not significantly affecting the posterior end. Ergotamine (10–−6 M) significantly inhibited the stimulation induced by 10–−5 M serotonin (P < 0·025). Cyproheptadine (10–−9 M) partially inhibited anterior and posterior shelf rotation in embryo culture. When injected into the pregnant dam, cyproheptadine partially inhibited shelf rotation and fusion. The palate was examined histologically after embryo culture. In the presence of 10–−4 M methysergide, the elongated contractile cells in region 3 at the anterior and midpalatal mesenchyme were prevented from rounding. Thus, serotonin may be regulating rotation of the anterior end of the palate by an effect on a cell-mediated process.

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

1977 ◽  
Vol 25 (1) ◽  
pp. 205-232
Author(s):  
C.F. Bardele
Keyword(s):  
Fine Structure ◽  
Conformational Changes ◽  
Basal Body ◽  
Basic Unit ◽  
Lateral Growth ◽  
Secondary Nucleation ◽  
Body Formation ◽  
Pattern Control ◽  
Nucleation Sites ◽  
Equilateral Triangles

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.

Fine structure of the dendritic junction body region of the antennal sensory cone in a larval elaterid (Coleoptera)

1971 ◽  
Vol 49 (6) ◽  
pp. 817-821 ◽  
Author(s):  
David A. Scott ◽  
R. Y. Zacharuk
Keyword(s):  
Fine Structure ◽  
Basal Body ◽  
Sense Organ ◽  
Body Region ◽  
Ultrastructural Evidence ◽  
Primary Function ◽  
Secretory Products

The component ciliary collar, basal body, ciliary rootlets, trichogen–dendrite secretory junctions and secretory inclusions of the junction body region of dendrites in the wireworm antennal sensory cone are described. The primary function ascribed to the junction body region, based on the ultrastructural evidence presented, is one of secretion. The hypothesis that the secretory products produced in the junction body region are transported to the dendritic terminations in the sense organ is discussed and supported.

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