Differentiation of Neurosensory Cells in Hydra

1969 ◽  
Vol 5 (3) ◽  
pp. 699-726
Author(s):  
LOWELL E. DAVIS
Keyword(s):  
Endoplasmic Reticulum ◽  
Fine Structure ◽  
Electron Microscope ◽  
Basal Body ◽  
Neurosecretory Cells ◽  
Nerve Cells ◽  
Granular Endoplasmic Reticulum ◽  
Structural Variations ◽  
Intercellular Bridges ◽  
Undifferentiated Cells

The differentiation of neurosensory cells in Hydra has been studied at the level of the electron microscope. These cells arise from interstitial cells (undifferentiated cells) and not from pre-existing nerve cells. Furthermore, there is no evidence to suggest that neurosensory cells represent a stage in the development of other nerve cells, i.e. ganglionic and neurosecretory cells. Major cytoplasmic changes in fine structure during differentiation include development of a cilium and associated structures (basal body, basal plate, rootlets), development of microtubules and at least two neurites, increase in Golgi lamellae and formation of dense droplets typical of neurosecretory droplets, structural variations in mitochondria and a decrease in the number of ribosomes. Granular endoplasmic reticulum is characteristically poorly developed in all stages of differentiation, including the mature neurosensory cell. Nuclear and nucleolar changes also occur during differentiation but these are less dramatic than the cytoplasmic events. The possibility of neurosensory cells being bi- or multiciliated and the presence of intercellular bridges between these cells are considered. The function of neurosensory cells is discussed briefly in relation to the function of the cilium and neurosecretory droplets.

Insect frontal ganglion: fine structure of its neurosecretory cells in diapause and non-diapause larvae of Diatraea grandiosella

1975 ◽  
Vol 53 (8) ◽  
pp. 1093-1100 ◽  
Author(s):  
C.-M. Yin ◽  
G. M. Chippendale
Keyword(s):  
Endoplasmic Reticulum ◽  
Fine Structure ◽  
Neurosecretory Cells ◽  
Granular Endoplasmic Reticulum ◽  
Diatraea Grandiosella ◽  
Corn Borer ◽  
Golgi Bodies ◽  
Juvenile Hormone Mimic ◽  
Frontal Ganglion ◽  
Southwestern Corn Borer

The fine structure of the neurosecretory (NS) cells of the frontal ganglion (FG) of diapause and non-diapause mature larvae of the southwestern corn borer, Diatraea grandiosella, was compared. Two large (15- to 20-μm diam) NS cells are typically found in each FG. Their cytoplasm stained deeply purple with paraldehyde fuchsin and contained granules 1500–2500 Å in diameter. The granules in the NS cells of non-diapause larvae were often associated with Golgi bodies whereas those of the diapause larvae were associated with dilated cisternae of the granular endoplasmic reticulum. Fewer Golgi bodies were observed in sections of NS cells of the FG of diapause larvae than in those of non-diapause larvae. Sections prepared from diapause larvae obtained conventionally by exposure to low temperatures, and experimentally by treatment with a juvenile hormone mimic, gave similar results.Our findings show that granules accumulate in the perikaryon of the NS cells of the FG of diapause larvae and suggest that the granular endoplasmic reticulum is involved in their formation. The shutdown of the transport of these NS granules from the FG appears to be a factor in some yet to be determined phase of the neuroendocrine regulation of diapause.

scholarly journals THE EFFECTS OF ENUCLEATION ON THE CYTOPLASMIC MEMBRANES OF AMOEBA PROTEUS

1968 ◽  
Vol 37 (2) ◽  
pp. 300-315 ◽  
Author(s):  
Charles J. Flickinger
Keyword(s):  
Endoplasmic Reticulum ◽  
Fine Structure ◽  
Electron Microscope ◽  
Golgi Apparatus ◽  
Amoeba Proteus ◽  
Granular Endoplasmic Reticulum ◽  
Whole Cells ◽  
Golgi Bodies ◽  
Cytoplasmic Membranes ◽  
In Cells

The dependence of cytoplasmic membranes upon the nucleus was studied by examining enucleated amebae with the electron microscope at intervals up to 1 wk after enucleation. Amebae were cut into two approximately equal parts, and the fine structure of the enucleated portions was compared with that of the nucleated parts and starved whole cells which had been maintained under the same conditions. Golgi bodies were diminished in size 1 day after enucleation and were not detected in cells enucleated for more than 2 days. The endoplasmic reticulum of enucleated cells appeared to increase in amount and underwent changes in its morphology. The sparsely scattered short tubules of granular endoplasmic reticulum present in unmanipulated amebae from stock cultures were replaced in 1–3-day enucleates by long narrow cisternae. In 3–7-day enucleates, similar cisternae of granular endoplasmic reticulum encircled areas of cytoplasm partially or completely. It was estimated that in most cases hundreds of these areas encircled by two rough membranes were formed per enucleated cell. The number of ribosomes studding the surface of the endoplasmic reticulum decreased progressively with time after enucleation. In contrast, the membranes of nucleated parts and starved whole cells did not undergo these changes. The possible identification of membrane-encircled areas as cytolysomes and their mode of formation are considered. Implications of the observations regarding nuclear regulation of the form of the Golgi apparatus and the endoplasmic reticulum are discussed.

scholarly journals THE FINE STRUCTURE OF NEURONS

1955 ◽  
Vol 1 (1) ◽  
pp. 69-88 ◽  
Author(s):  
Sanford L. Palay ◽  
George E. Palade
Keyword(s):  
Endoplasmic Reticulum ◽  
Fine Structure ◽  
Electron Microscope ◽  
Cerebellar Cortex ◽  
Dorsal Root Ganglia ◽  
Medulla Oblongata ◽  
Dorsal Root ◽  
Thin Sections ◽  
Lipid Inclusions ◽  
Nissl Substance

1. Thin sections of representative neurons from intramural, sympathetic and dorsal root ganglia, medulla oblongata, and cerebellar cortex were studied with the aid of the electron microscope. 2. The Nissl substance of these neurons consists of masses of endoplasmic reticulum showing various degrees of orientation; upon and between the cisternae, tubules, and vesicles of the reticulum lie clusters of punctate granules, 10 to 30 mµ in diameter. 3. A second system of membranes can be distinguished from the endoplasmic reticulum of the Nissl bodies by shallower and more tightly packed cisternae and by absence of granules. Intermediate forms between the two membranous systems have been found. 4. The cytoplasm between Nissl bodies contains numerous mitochondria, rounded lipid inclusions, and fine filaments.

The fine structure of the ookinete of Parahaemoproteus velans (= Haemoproteus velans Coatney and Roudabush) (Haemosporidia: Haemoproteidae)

1972 ◽  
Vol 50 (5) ◽  
pp. 477-480 ◽  
Author(s):  
Sherwin S. Desser
Keyword(s):  
Endoplasmic Reticulum ◽  
Fine Structure ◽  
Granular Endoplasmic Reticulum ◽  
Central Nucleus ◽  
Apical Region ◽  
Cylindrical Structures ◽  
Inner Surface

The ookinete of Parahaemoproteus velans is bounded externally by a trilaminar membrane, beneath which lies a fibrillar zone. Below this zone and forming the inner surface of the pellicle is a second, dense, membranelike layer. The specialized apical region of the ookinete is modified into a thickened "caplike" structure. The inner layer of the pellicle in this region is thickened and wavy in appearance. In a sub-pellicular space in the cap region lie about 27 elongate cylindrical structures, and beneath these about 50 microtubules ring the cytoplasm. Numerous dense spherical bodies are located in the anterior cytoplasm of the parasite. A large, more or less central nucleus, often containing microtubular elements, lies in a cytoplasm richly endowed with granular endoplasmic reticulum. Two or more areas containing a "crystalloid" material lie anterior and posterior to the nucleus.

The Cartilaginous Nature of the Cervine Antler

1970 ◽  
Vol 28 ◽  
pp. 154-155
Author(s):  
William J. Banks ◽  
Jennifer Neal
Keyword(s):  
Endoplasmic Reticulum ◽  
Progenitor Cells ◽  
Distal Portion ◽  
Frontal Bone ◽  
Granular Endoplasmic Reticulum ◽  
Exact Nature ◽  
Undifferentiated Cells ◽  
Hyperplastic Tissue ◽  
Ossification Process

The histomorphology and ossification process of the antler has been a subject of controversy. The exact nature of antler cartilage, based on light microscopic and limited histochemical analyses, has not been clarified. This report presents evidence that the ultrastructural features of antler progenitor cells and chondrocytes are similar to other cartilaginous systems which arise from reserve, undifferentiated cells.An extensive fibrocellular cap covered the distal portion of the growing antler and was continuous with the typical periosteum of the antler shaft and frontal bone. This hyperplastic tissue (Fig. 1) was composed of fibroblastlike cells which contained large nuclei with 1 or 2 nucleoli (N). The cytoplasm contained numerous free ribosomes and polyribosomes, as well as granular endoplasmic reticulum (ER). The latter was tubular or vesicular; some exhibited dilations.

Fine structure and early fertilization changes of the animal pole in eggs of the river lamprey, Lampetra fluviatilis

Development ◽  
1968 ◽  
Vol 19 (3) ◽  
pp. 319-326
Author(s):  
Lennart Nicander ◽  
Björn A. Afzelius ◽  
Inger Sjödén
Keyword(s):  
Endoplasmic Reticulum ◽  
Fine Structure ◽  
Electron Microscope ◽  
Marine Invertebrates ◽  
Bivalve Mollusc ◽  
Annulate Lamellae ◽  
Animal Pole ◽  
River Lamprey ◽  
Vertebrate Eggs

Fertilization is accompanied by changes in the structure of the egg cytoplasm (cf. Rothschild, 1958; Raven, 1961). At the level of fine structure such changes have mainly been studied in some marine invertebrates with small eggs that can easily be fertilized in vitro (Pasteels & de Harven, 1963; Schäfer, 1966). Vertebrate eggs are less favourable in this respect, but electron microscope studies have been made on eggs of mammals (Fléchon, 1966; Zamboni & Mastroianni, 1966; Zamboni, Mishell, Bell & Baca, 1966) and Xenopus (van Gansen, 1966). Changes generally observed soon after fertilization include the formation of polysomes or an increase in their number, a hypertrophy of the Golgi complexes, and the appearance of granulated endoplasmic reticulum and annulate lamellae. Afzelius (1957) observed the dispersal of mitochondria in fertilized sea-urchin eggs. Pasteels & de Harven (1963) reported that the structure and distribution of cytoplasmic organelles in eggs of the bivalve mollusc, Barnea Candida, are not altered by fertilization.

Some Aspects of the Cytology of Polycelis nigra

1961 ◽  
Vol s3-102 (59) ◽  
pp. 295-317
Author(s):  
R. J. SKAER
Keyword(s):  
Fine Structure ◽  
Epithelial Cells ◽  
Basement Membrane ◽  
Muscle Fibre ◽  
Cell Body ◽  
Basal Body ◽  
Sense Organs ◽  
Gland Cells ◽  
Secretion Granules ◽  
Undifferentiated Cells

The triclad, Polycelis nigra, has been found to be fully cellular. Gland-cells, undifferentiated cells, and the cell-bodies of muscle-cells, make up the parenchyma. The fine structure of the component cells of the parenchyma, nervous, and excretory systems, testis, pharynx, and epidermis is described. Acidophil secretion granules, produced by certain parenchymatous gland-cells, have a characteristic, doubly-banded ultrastructure which is not invariably associated with the property of adhesiveness. The parenchymatous cell-body of the muscles is often up to 10 µ. from the musclefibre, to which it is joined by tenuous cytoplasmic connexions. The muscle-fibre itself consists of coarse and fine sets of hexagonally arranged myofilaments, but is unhanded. The basement membrane of the epidermis is composed of fine, banded fibrils, apparently randomly arranged in the plane of the membrane. Permeating the epidermis at a level just above the basement membrane is a system of extracellular spaces, which may have a hydrostatic function and assist in the extrusion of secretion granules. Epidermal sense organs, whose fine structure resembles the basal body of the cilia, are considered to have a functionally significant distribution on the surface of the animal. The rhabdites have been shown to develop in special cells of the parenchyma. Such rhabdite-forming cells, together with their contained rhabdites, have been found apparently passing through the basement membrane of the epidermis. As all the epidermal epithelial cells contain rhabdites, it is suggested that the epidermis as a whole is renewed by centrifugal migration of rhabdite-forming cells. The rhabdites themselves appear to consist of arginine and some tyrosine, together with a purine, probably adenine. They may be an excretory product.

The fine structure and development of chlamydospores of Fusarium oxysporum

1972 ◽  
Vol 18 (7) ◽  
pp. 997-1002 ◽  
Author(s):  
I. L. Stevenson ◽  
S. A. W. E. Becker
Keyword(s):  
Endoplasmic Reticulum ◽  
Cell Wall ◽  
Fine Structure ◽  
Electron Microscope ◽  
Cell Surface ◽  
Outer Layer ◽  
Outer Wall ◽  
Wall Layer ◽  
Thin Sections ◽  
Hyphal Wall

Methods have been developed for the rapid, reproducible induction of high-density populations of F. oxysporum chlamydospores. On transferring washed pregerminated conidia to a simple two-salts medium, chlamydospore morphogenesis was evident by 12 h and masses of mature spores could be harvested at the end of 4 days. Electron-microscope studies of thin sections of mature chlamydospores reveal a thick triple-layered cell wall. The cytoplasm contains, in addition to large lipid deposits, a nucleus, mitochondria, and endoplasmic reticulum all typical of fungal cells. Chlamydospores of F. oxysporum exhibit two distinct types of cell surface in thin section. The outer wall layer of two of the isolates studied was smooth-surfaced while the outer layer of the two other isolates was distinctly fibrillose. Some evidence is presented suggesting that the fibrillose material arises through the partial breakdown of the original hyphal wall.

Hymenolepis nana: the fine structure of the ‘penetration gland’ and nerve cells within the oncosphere

Parasitology ◽  
1981 ◽  
Vol 82 (3) ◽  
pp. 445-458 ◽  
Author(s):  
I. Fairweather ◽  
L. T. Threadgold
Keyword(s):  
Fine Structure ◽  
Secretory Granules ◽  
Polar Filament ◽  
Secretory Activity ◽  
Muscle Cells ◽  
Neurosecretory Cells ◽  
Nerve Cells ◽  
Epithelial Layer ◽  
Hymenolepis Nana ◽  
Penetration Gland

SUMMARYThe fine structure of the oncosphere of Hymenolepis nana has been investigated by transmission and scanning electron microscopy, together with light microscope observations of JB–4 embedded material. The outer surface of the oncosphere is covered by an epithelial layer, termed the embryonic epithelium. Cell types present within the oncosphere include the penetration gland cell, oncoblast, or hook-forming cells, nerve cells, muscle cells (both somatic and hook), and undifferentiated ‘stem’ cells. The penetration gland is a large, U-shaped structure, situated in the anterior region of the oncosphere, and filled with secretory granules of 2 distinct morphological types. Histochemically, the secretory material yields reactions characteristic of an acid mucopolysaccharide. A proteinaceous-substance and small amounts of glycogen are also present. Up to 4 pairs of ducts from the penetration gland have been observed. They pass through the basal lamina and the epithelial layer to open against the polar filament layer at the anterior end of the oncosphere. Nerve cells are described in a cestode oncosphere for the first time. The cells are paraldehyde-fuchsin-positive and show a high level of secretory activity, as evidenced by the large numbers of dense-cored vesicles produced by the Golgi apparatus in the perikarya; consequently, they are tentatively regarded as possible neurosecretory cells. The vesicles are transported down the axon to be stored in specialized swollen axon terminals, which form definite junctions with the muscle cells.

The fine structure of the developing macrogamete of Eimeria maxima

Parasitology ◽  
1979 ◽  
Vol 79 (2) ◽  
pp. 259-265 ◽  
Author(s):  
R. M. Pittilo ◽  
S. J. Ball
Keyword(s):  
Endoplasmic Reticulum ◽  
Fine Structure ◽  
Parasitophorous Vacuole ◽  
The Other ◽  
Granular Endoplasmic Reticulum ◽  
Type I ◽  
Type Ii ◽  
Eimeria Maxima ◽  
Lipid Inclusions

SUMMARYThe fine structure of the developing macrogamete of Eimeria maxima was studied from chicks killed at intervals from 138 to 147 h after inoculation. The macrogamete developed within a parasitophorous vacuole. Lying within this vacuole and extending for some distance around the periphery of the macrogamete were intravacuolar tubules, grouped in certain areas, and in some cases they were seen to make direct connexions with the cytoplasm of the parasite. During development, electron-pale vesicles were pinched off externally from the surface of the macrogamete. There appeared to be 2 forms of wall-forming bodies of the Type I during development, one form being less osmiophilic than the other. Other organelles present, such as wall-forming bodies of Type II, granular endoplasmic reticulum, mitochondria, canaliculi, lipid inclusions and intravacuolar folds, were similar in structure to those of other Eimeria species.

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