Studies on the Development of Ameloblasts

1972 ◽  
Vol 11 (2) ◽  
pp. 415-447 ◽  
Author(s):  
E. KATCHBURIAN ◽  
S. J. HOLT
Keyword(s):  
Endoplasmic Reticulum ◽  
Golgi Complex ◽  
Structural Changes ◽  
Surface Membrane ◽  
Secretory Cells ◽  
Enamel Matrix ◽  
Coated Pits ◽  
Cytoplasmic Extension ◽  
Distal Surface ◽  
Oriented Parallel

The cellular and fine-structural changes which take place during differentiation of ameloblasts into highly secretory cells involve growth and elongation of the cytoplasm, a change in polarity, and sequential development of organelles. The undifferentiated cells of the ameloblastic layer seem to be mainly concerned with the production of material for internal use, as they are rich in free ribosomes and have only few profiles of rough-surfaced endoplasmic reticulum. First signs of differentiation are detected when the cells begin to elongate and large numbers of microtubules oriented parallel to the cell long axis appear in the distal cytoplasm. This suggests that the microtubules provide directional guidance for the elongation of the cells. The next stage of differentiation is characterized by proliferation of the rough-surfaced endoplasmic reticulum in the distal cytoplasm and the migration of the small Golgi complex, initially at the base of the cell, to the distal cytoplasm. Intracisternal accumulation of enamel matrix-like material in the rough-surfaced endoplasmic reticulum at this stage suggests that the Golgi complex is unable to process for secretion the materials synthesized in the rough-surfaced endoplasmic reticulum. However, the presence of enamel matrix-like material in the intercellular spaces may indicate an attempt to secrete matrix by a mechanism which by-passes the Golgi complex. With further differentiation the Golgi complex reaches the distal cytoplasm where it develops and becomes very extensive. The appearance of enamel matrix-like material in the cisternae of the mature Golgi complex and in large secretion granules in secretory ameloblasts suggests that secretory material is processed in a manner similar to that of other exocrine cells. As soon as enamel matrix begins to be deposited at the distal surface, ameloblasts withdraw, leaving the cytoplasmic extension (Tomes process) in the early calcifying enamel. The presence of microtubules and filaments in both the early and late developing Tomes process suggests that they play a role in the directional and localized growth of this constricted cell extension. Based on previous evidence that the Tomes process has an extensive lysosomal system and on the observation that its surface membrane possesses numerous invaginations and coated pits, it is concluded that the present findings support the concept that the Tomes process - via its lysosomal vacuolar apparatus - plays a role in the changes which occur in the enamel matrix in early amelogenesis.

scholarly journals Lectin-labeled membrane is transferred to the Golgi complex in mouse pituitary cells in vivo.

1987 ◽  
Vol 35 (4) ◽  
pp. 489-498 ◽  
Author(s):  
B J Balin ◽  
R D Broadwell
Keyword(s):  
Golgi Complex ◽  
Secretory Granules ◽  
Surface Membrane ◽  
Dense Core ◽  
Secretory Cells ◽  
Pituitary Cells ◽  
Posterior Pituitary ◽  
Peroxidase Reaction ◽  
Mouse Pituitary

Labeling of the Golgi complex with the lectin conjugate wheat germ agglutinin-horseradish peroxidase (WGA-HRP), which binds to cell surface membrane and enters cells by adsorptive endocytosis, was analyzed in secretory cells of the anterior, intermediate, and posterior lobes of mouse pituitary gland in vivo. WGA-HRP was administered intravenously or by ventriculo-cisternal perfusion to control and salt-stressed mice; post-injection survival times were 30 min-24 hr. Peroxidase reaction product was identified within the extracellular clefts of anterior and posterior pituitary lobes through 24 hr but was absent in intermediate lobe. Endocytic vesicles, spherical endosomes, tubules, dense and multivesicular bodies, the trans-most saccule of the Golgi complex, and dense-core secretory granules attached or unattached to the trans Golgi saccule were peroxidase-positive in the different types of anterior pituitary cells and in perikarya of supraoptico-neurohypophyseal neurons; endoplasmic reticulum and the cis and intermediate Golgi saccules in the same cell types were consistently devoid of peroxidase reaction product. Dense-core secretory granules derived from cis and intermediate Golgi saccules in salt-stressed supraoptic perikarya likewise failed to exhibit peroxidase reaction product. The results suggest that in secretory cells of anterior and posterior pituitary lobes, WGA-HRP, initially internalized with cell surface membrane, is eventually conveyed to the trans-most Golgi saccule, in which the lectin conjugate and associated membrane are packaged in dense-core secretory granules for export and potential exocytosis of the tracer. Endoplasmic reticulum and the cis and intermediate Golgi saccules appear not to be involved in the endocytic/exocytic pathways of pituitary cells exposed to WGA-HRP.

Ultrastructural Changes in Pig Hepatocytes During the Transitional Period from Late Foetal to Early Neonatal Life

1969 ◽  
Vol 4 (2) ◽  
pp. 381-395
Author(s):  
M. B. BISCHOFF ◽  
W. R. RICHTER ◽  
R. J. STEIN
Keyword(s):  
Endoplasmic Reticulum ◽  
Microscopic Study ◽  
Golgi Complex ◽  
Structural Changes ◽  
Bile Canaliculus ◽  
Transitional Period ◽  
Ultrastructural Changes ◽  
Synthetic Activity ◽  
Electron Microscopic ◽  
Neonatal Life

A light-and electron-microscopic study of pig hepatocytes from late prenatal to early neonatal animals shows changes which reflect an increasing rate of synthetic activity. The granular endoplasmic reticulum (ER) in the prenatal pig hepatocyte is situated along the periphery of the cytoplasm and in the region immediately surrounding the nucleus. Mitochondria are most abundant in the area adjacent to the nucleus, while the Golgi complex is generally located in the region of the bile canaliculus. The remaining portion of the hepatocyte is occupied with glycogen. A few hours after birth the hepatocyte increases about twofold in size with the nucleus shifting from a peripheral to a more centrally located position. The glycogen decreases quickly coincident with a rapid increase in the amount of granular ER and the dispersion of the mitochondria throughout the cell. The Golgi complex becomes distended and numerous vesicles appear in its immediate vicinity containing a moderately dense material. Numerous peribiliary inclusions appear during the second postnatal day. These structural changes are an indication of the increased synthetic activity occurring within the hepatocytes of rapidly developing animals.

Cyclic structural changes of endoplasmic reticulum and Golgi complex in hippocampal neurons of ground squirrels during hibernation

2011 ◽  
Vol 5 (3) ◽  
pp. 243-254 ◽  
Author(s):  
L. S. Bocharova ◽  
R. Ya. Gordon ◽  
V. V. Rogachevsky ◽  
D. A. Ignat’ev ◽  
S. S. Khutzian
Keyword(s):  
Endoplasmic Reticulum ◽  
Golgi Complex ◽  
Hippocampal Neurons ◽  
Structural Changes ◽  
Ground Squirrels

Organisation in the Structure of the Cytoplasmic Ground Substance

1978 ◽  
Vol 36 (3) ◽  
pp. 627-639
Author(s):  
K.R. Porter
Keyword(s):  
Endoplasmic Reticulum ◽  
Golgi Complex ◽  
Random Distribution ◽  
Ground Substance ◽  
The Matrix ◽  
Cell Processes ◽  
Cytoplasmic Ground Substance

Most types of cells are known from their structure and overall form to possess a characteristic organization. In some instances this is evident in the non-random disposition of organelles and such system subunits as cisternae of the endoplasmic reticulum or the Golgi complex. In others it appears in the distribution and orientation of cytoplasmic fibrils. And in yet others the organization finds expression in the non-random distribution and orientation of microtubules, especially as found in highly anisometric cells and cell processes. The impression is unavoidable that in none of these cases is the organization achieved without the involvement of the cytoplasmic ground substance (CGS) or matrix. This impression is based on the fact that a matrix is present and that in all instances these formed structures, whether membranelimited or filamentous, are suspended in it. In some well-known instances, as in arrays of microtubules which make up axonemes and axostyles, the matrix resolves itself into bridges (and spokes) between the microtubules, bridges which are in some cases very regularly disposed and uniform in size (Mcintosh, 1973; Bloodgood and Miller, 1974; Warner and Satir, 1974).

Analysis of the Anterior Secretory Cells of Onchidohs Muricata (Nudibranchia)

1981 ◽  
Vol 39 ◽  
pp. 614-615
Author(s):  
Roy Skidmore
Keyword(s):  
Endoplasmic Reticulum ◽  
Secretory Granules ◽  
Golgi Body ◽  
The Body ◽  
Secretory Cells ◽  
Secretory Vesicles ◽  
High Magnification ◽  
Large Numbers ◽  
Membrane Bound ◽  
Sole Of The Foot

The long-necked secretory cells in Onchidoris muricata are distributed in the anterior sole of the foot. These cells are interspersed among ciliated columnar and conical cells as well as short-necked secretory gland cells. The long-necked cells contribute a significant amount of mucoid materials to the slime on which the nudibranch travels. The body of these cells is found in the subepidermal tissues. A long process extends across the basal lamina and in between cells of the epidermis to the surface of the foot. The secretory granules travel along the process and their contents are expelled by exocytosis at the foot surface.The contents of the cell body include the nucleus, some endoplasmic reticulum, and an extensive Golgi body with large numbers of secretory vesicles (Fig. 1). The secretory vesicles are membrane bound and contain a fibrillar matrix. At high magnification the similarity of the contents in the Golgi saccules and the secretory vesicles becomes apparent (Fig. 2).

scholarly journals Prohibitin: A Novel Molecular Player in KDEL Receptor Signalling

2015 ◽  
Vol 2015 ◽  
pp. 1-13 ◽  
Author(s):  
Monica Giannotta ◽  
Giorgia Fragassi ◽  
Antonio Tamburro ◽  
Capone Vanessa ◽  
Alberto Luini ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Golgi Complex ◽  
Membrane Trafficking ◽  
Transmembrane Domain ◽  
Cell Cycle Control ◽  
Retrograde Transport ◽  
Multifunctional Protein ◽  
G Protein Coupled ◽  
Kdel Receptor ◽  
Prohibitin 1

The KDEL receptor (KDELR) is a seven-transmembrane-domain protein involved in retrograde transport of protein chaperones from the Golgi complex to the endoplasmic reticulum. Our recent findings have shown that the Golgi-localised KDELR acts as a functional G-protein-coupled receptor by binding to and activating Gs and Gq. These G proteins induce activation of PKA and Src and regulate retrograde and anterograde Golgi trafficking. Here we used an integrated coimmunoprecipitation and mass spectrometry approach to identify prohibitin-1 (PHB) as a KDELR interactor. PHB is a multifunctional protein that is involved in signal transduction, cell-cycle control, and stabilisation of mitochondrial proteins. We provide evidence that depletion of PHB induces intense membrane-trafficking activity at the ER–Golgi interface, as revealed by formation of GM130-positive Golgi tubules, and recruitment of p115,β-COP, and GBF1 to the Golgi complex. There is also massive recruitment of SEC31 to endoplasmic-reticulum exit sites. Furthermore, absence of PHB decreases the levels of the Golgi-localised KDELR, thus preventing KDELR-dependent activation of Golgi-Src and inhibiting Golgi-to-plasma-membrane transport of VSVG. We propose a model whereby in analogy to previous findings (e.g., the RAS-RAF signalling pathway), PHB can act as a signalling scaffold protein to assist in KDELR-dependent Src activation.

scholarly journals The Lamellar Systems of Cytoplasmic Membranes in Dividing Spermatogenic Cells of Drosophila virilis

1960 ◽  
Vol 7 (3) ◽  
pp. 433-441 ◽  
Author(s):  
Susumu Ito
Keyword(s):  
Endoplasmic Reticulum ◽  
Golgi Complex ◽  
Light And Electron Microscopy ◽  
Primary Spermatocyte ◽  
Drosophila Virilis ◽  
Spermatogenic Cells ◽  
Membrane Systems ◽  
Cytoplasmic Membranes ◽  
Pas Reaction ◽  
Staining Methods

Spermatogenic cells of Drosophila virilis were studied by light and electron microscopy. The persistence of a "nuclear wall" during the meiotic divisions has been reported by a number of early cytologists, but this interpretation has been a subject of debate. Electron micrographs of dividing spermatocytes reveal the presence of multiple layers of paired membranes surrounding the nuclear region. These lamellar membrane systems are not typical of the nuclear envelope, but were interpreted as such by light microscopists. The membranes constituting a pair are separated by an interspace of ∼ 100 A and successive pairs are 200 to 400 A apart. These spacings are similar but not identical to those found in the lamellar systems of the Golgi complex. The cisternae of the endoplasmic reticulum in this material are devoid of attached ribonucleoprotein particles, are more precisely ordered than in vertebrate cells, and show a uniform, narrow intracisternal space of ∼ 100 A. The conspicuous asters appear to be made up of similar paired membranes radiating from the centriolar region. The primary spermatocyte has numerous dictyosomes and a well developed endoplasmic reticulum in cisternal form, but no typical Golgi complex or endoplasmic reticulum is found during the meiotic division stages of metaphase to telophase. Evidence is presented that these cytoplasmic organelles contribute to the formation of the extensive lamellar systems that appear during meiosis. The results of the Golgi silver staining methods and staining tests for phospholipids, basophilia, and the PAS reaction, indicate that the lamellar arrays of membranes present during meiosis are indistinguishable from the Golgi complex in their tinctorial properties.

scholarly journals Receptor-mediated endocytosis of alpha 2-macroglobulin in cultured fibroblasts.

1980 ◽  
Vol 28 (8) ◽  
pp. 818-823 ◽  
Author(s):  
M C Willingham ◽  
F R Maxfield ◽  
I Pastan
Keyword(s):  
Endoplasmic Reticulum ◽  
Cell Surface ◽  
Coated Pits ◽  
Cultured Fibroblasts ◽  
Receptor Mediated Endocytosis ◽  
Cytoplasmic Vesicles

Alpha 2-macroglobulin is internalized into cultured fibroblasts by receptor-mediated endocytosis. This ligand binds initially to diffusely distributed receptors on the cell surface which cluster rapidly into bristle-coated pits. Within a few minutes at 37 degrees C, these complexes are internalized into uncoated cytoplasmic vesicles, called receptosomes, which move about in the cell by saltatory motion. These vesicles interact with the Golgi-endoplasmic reticulum-lysosome system in the cell to deliver the ligand to newly formed lysosomes within 30--60 min.

Sign in / Sign up

Export Citation Format

Share Document