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.

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.

Gland cells and secretions in the miracidium of Fasciola hepatica

Parasitology ◽  
1971 ◽  
Vol 63 (2) ◽  
pp. 225-231 ◽  
Author(s):  
R. A. Wilson
Keyword(s):  
Fine Structure ◽  
Epithelial Cells ◽  
Intermediate Host ◽  
Fasciola Hepatica ◽  
Accessory Gland ◽  
Gland Cells ◽  
Mucous Coat ◽  
Snail Intermediate Host ◽  
Apical Papilla ◽  
Ciliated Epithelial Cells

SUMMARYThe distribution and fine structure of gland cells in the miracidium of Fasciola hepatica is described. There is a large flask-shaped, multinucleate, apical gland lying ventrally in the anterior. On each side of this are pairs of uninucleate accessory gland cells. Both apical gland and accessory gland cells communicate with the tip of the apical papilla. A third group of vesiculated gland cells opens by ducts at the base of the apical papilla. The miracidium is covered with a surface mucous coat and this appears to be directly extruded from the underlying ciliated epithelial cells. The findings are discussed with relevance to attachment to, and penetration of, the snail intermediate host.

scholarly journals The Anatomy of Secretion in the Follicular Cells of the Thyroid Gland

1960 ◽  
Vol 7 (3) ◽  
pp. 419-432 ◽  
Author(s):  
Steven L. Wissig
Keyword(s):  
Fine Structure ◽  
Thyroid Gland ◽  
Epithelial Cells ◽  
Golgi Apparatus ◽  
Basement Membrane ◽  
Particulate Material ◽  
Capillary Endothelium ◽  
Follicular Cells ◽  
Normal Rat ◽  
Membrane Bound

The paper contains a description of the fine structure of the thyroid gland of the normal rat. The follicular colloid, a homogeneous substance of faintly granular texture, is bounded by cuboidal or low columnar epithelial cells. Numerous pleomorphic microvilli, often permeated by small vesicles extend from the apices of the epithelial cells into the colloid. Many small, membrane-limited vesicles lie in the superficial cytoplasmic layer just below the apical plasmalemma. The ergastoplasmic sacs of the follicular cells are dilated and contain a substance resembling colloid. They are of irregular outline, and the larger sacs tend to be located in the base of the cells. The Golgi apparatus lies in the vicinity of the nucleus and consists primarily of numerous small, membrane-bound droplets with a homogeneous content. Droplets, similar to the Golgi vesicles but larger, lie in the same vicinity and are tentatively identified as colloid droplets. The colloid droplets contain an extremely fine, dense particulate material. Other droplets with a denser, more heterogenous content are also present. Both the follicular cells and the perifollicular capillaries are bounded by a continuous basement membrane. The capillary endothelium is in certain regions extremely attenuated and is pierced by numerous patent pores, 450 A in diameter. The marked similarity between the presumptive colloid droplets and vesicles of the Golgi apparatus suggests that the droplets arise from this organelle. On morphological grounds alone no relation can be established between any of the organelles of the follicular cell and the process of colloid resorption.

scholarly journals CHANGES IN FINE STRUCTURE DURING SILK PROTEIN PRODUCTION IN THE AMPULLATE GLAND OF THE SPIDER ARANEUS SERICATUS

1969 ◽  
Vol 42 (1) ◽  
pp. 284-295 ◽  
Author(s):  
Allen L. Bell ◽  
David B. Peakall
Keyword(s):  
Fine Structure ◽  
Epithelial Cells ◽  
Protein Production ◽  
Distal Portion ◽  
Silk Gland ◽  
The Body ◽  
Single Type ◽  
Secretory Cells ◽  
The Web ◽  
Tunica Intima

The ampullate silk gland of the spider, Araneus sericatus, produces the silk fiber for the scaffolding of the web. The fine structure of the various parts of the gland is described. The distal portion of the duct consist of a tube of epithelial cells which appear to secrete a substance which forms the tunica intima of the duct wall. At the proximal end of the duct there is a region of secretory cells. The epithelium of the sac portion contains five morphologically distinct types of granules. The bulk of the synthesis of silk occurs in the tail of the gland, and in this region only a single type of secretory droplet is seen in the epithelium. Protein synthesis can be stimulated by the injection of 1 mg/kg acetylcholine into the body fluids. 10 min after injection, much of the protein stored in the cytoplasm of the epithelial cells has been secreted into the lumen. 20 min after stimulation, the ergastoplasmic sacs form large whorls in the cytoplasm. Protein, similar in electron-opacity to protein found in the lumen, begins to form in that portion of the cytoplasm which is enclosed by the whorls. The limiting membrane of these droplets is formed by ergastoplasmic membranes which lose their ribosomes. No Golgi material has been found in these cells. Protein appears to be manufactured in the cytoplasm of the tail cells in a form which is ready for secretion.

scholarly journals Die Kaliumhydrogenphosphat-induzierte Nephropathie des Hundes. I. Pathogenese der Tubulusatrophiee [Potassium Hydrogen Phosphate Induced Nephropathy in the Dog. I. Pathogenesis of Tubular Atrophy—author's trans.]

1980 ◽  
Vol 17 (6) ◽  
pp. 699-719 ◽  
Author(s):  
P. Schneider ◽  
G. Pappritz ◽  
R. Müller-Peddinghaus ◽  
M. Bauer ◽  
H. Lehmann ◽  
...  
Keyword(s):  
Acid Phosphatase ◽  
Epithelial Cells ◽  
Basement Membrane ◽  
Basement Membranes ◽  
Tubular Epithelial Cells ◽  
Beagle Dogs ◽  
Lysosomal Degradation ◽  
Tubular Basement Membrane ◽  
Tubular Atrophy ◽  
Study Results

A nephropathy with severe tubular atrophy was observed in Beagle dogs after oral administration of K2HPO4 for 14 or 38 weeks. We describe the complete lysosomal degradation of atrophying tubular epithelial cells. During two experiments of 14 and 38 weeks duration, respectively, a total of 15 Beagle dogs received 0.8 g K2HPO4/kg body weight daily with their food. All dogs were examined clinically at regular intervals. Renal biopsies were taken in the fourth week from beagles of the 14-week study. Results were compared with those of control dogs. At the end of the experiments the animals were killed and necropsies done. Different stains and histochemical reactions were applied to paraffin sections of the kidneys. Acid phosphatase and β-glucuronidase were found on cryostat sections. Kidneys fixed by perfusion of five Beagles from the 38-week study and three Beagles of the 14-week study, and from five control dogs, were examined electron microscopically. Ultrahistochemically, acid phosphatase was demonstrated. Clinically, the dogs in both experiments vomited, were cachectic, and had elevated creatinine and blood urea nitrogen. Morphologically, qualitatively identical changes were seen, but the renal damage was most marked at 38 weeks. There were disseminated tubular atrophy (usually of the proximal tubules), focal scar tissue and nephrocalcinosis. The following pathogenesis was established for the lesions of the proximal tubule: Tubular atrophy begins with loss of differentiation of epithelial cells. Enzyme histochemistry, ultrahistochemistry and electron microscopy show an increase in autophagic vacuoles and autophagolysosomes. The lysosomal bodies showing fusion enclose large parts of the cytoplasm as the process continues. Complete lysosomal degradation of epithelial cells and extrusion of large lysosomes into the tubular lumen follow. After complete enzymatic digestion of the intratubular detritus, the residue is empty, convoluted and collapsed tubular basement membrane. Atrophic tubular epithelial cells have many organelle-free zones at their base, which contain fine filamentous material resembling that of the basement membrane. The degradation processes described here may explain why clinically the urinary sediment contains few cylinders and epithelial cells and why proteinuria decreases significantly toward the end of the experiment. So far, it is not clear whether the tubular basement membrane is synthesized by the tubular cells, by fibroblasts or by both cell types. The presence of basement membrane-like material in tubular epithelial cells and in parietal epithelial cells of the glomerulus favors the view that epithelial cells produce the basement membranes and that increased production of basement membrane-like material is a sign of loss of differentiation.

Fine structure and development of schizonts, merozoites and macrogamonts of Eimeria acervulina in the goblet cells of the duodenal epithelium of experimentally infected birds

Parasitology ◽  
1975 ◽  
Vol 70 (2) ◽  
pp. 223-229 ◽  
Author(s):  
E. Michael
Keyword(s):  
Fine Structure ◽  
Epithelial Cells ◽  
Golgi Apparatus ◽  
Host Cell ◽  
Goblet Cells ◽  
Cellular Level ◽  
Site Specificity ◽  
Eimeria Acervulina ◽  
Duodenal Epithelium

The fine structure of trophozoites, schizonts, merozoites and macrogamonts of Eimeria acervulina found in goblet cells of the duodenal epithelium of chicks is described and compared with the corresponding stages formed in other epithelial cells. Complete schizogony, with the formation of mature merozoites, occurred freely in goblet cells. Developing macrogamonts (but no microgamonts) were rarely found in goblet cells. The stages observed were confined to the cytoplasm of the host cell above the Golgi apparatus and were usually seen between the mucous granules. The stages seen appeared normal, and contained similar structures to corresponding stages developing in other cells. The finding of developing stages of E. acervulina in goblet cells provides further evidence that site specificity of Eimeria at the cellular level is not as strict as previously thought.

Role of laminin in the attachment of PAM 212 (epithelial) cells to basement membrane collagen

Cell ◽  
1980 ◽  
Vol 22 (3) ◽  
pp. 719-726 ◽  
Author(s):  
Victor P. Terranova ◽  
David H. Rohrbach ◽  
George R. Martin
Keyword(s):  
Epithelial Cells ◽  
Basement Membrane ◽  
Basement Membrane Collagen ◽  
Membrane Collagen

Ionizing radiation enhances matrix metalloproteinase-2 production in human lung epithelial cells

2001 ◽  
Vol 280 (1) ◽  
pp. L30-L38 ◽  
Author(s):  
Jun Araya ◽  
Muneharu Maruyama ◽  
Kazuhiko Sassa ◽  
Tadashi Fujita ◽  
Ryuji Hayashi ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Ionizing Radiation ◽  
Basement Membrane ◽  
Lung Injury ◽  
Human Lung ◽  
A549 Cells ◽  
Lung Epithelial Cells ◽  
Lung Epithelial ◽  
Radiation Induced ◽  
Human Lung Epithelial Cells

Radiation pneumonitis is a major complication of radiation therapy. However, the detailed cellular mechanisms have not been clearly defined. Based on the recognition that basement membrane disruption occurs in acute lung injury and that matrix metalloproteinase (MMP)-2 can degrade type IV collagen, one of the major components of the basement membrane, we hypothesized that ionizing radiation would modulate MMP-2 production in human lung epithelial cells. To evaluate this, the modulation of MMP-2 with irradiation was investigated in normal human bronchial epithelial cells as well as in A549 cells. We measured the activity of MMP-2 in the conditioned medium with zymography and the MMP-2 mRNA level with RT-PCR. Both of these cells constitutively expressed 72-kDa gelatinolytic activity, corresponding to MMP-2, and exposure to radiation increased this activity. Consistent with the data of zymography, ionizing radiation increased the level of MMP-2 mRNA. This radiation-induced increase in MMP-2 expression was mediated via p53 because the p53 antisense oligonucleotide abolished the increase in MMP-2 activity as well as the accumulation of p53 after irradiation in A549 cells. These results indicate that MMP-2 expression by human lung epithelial cells is involved in radiation-induced lung injury.

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