Morphogenesis of intestinal villi

Development ◽  
1975 ◽  
Vol 34 (3) ◽  
pp. 723-740
Author(s):  
David R. Burgess
Keyword(s):  
Electron Microscopy ◽  
Epithelial Cells ◽  
Cross Section ◽  
Cytochalasin B ◽  
Light And Electron Microscopy ◽  
Apical Region ◽  
Basal Region ◽  
Circular Smooth Muscle ◽  
Epithelial Tube ◽  
Three Stages

Villi lining the avian intestine originate from longitudinal folds (previllous ridges) running the length of the embryonic intestine. The morphogenetic events that occur in the epithelium during initial ridge formation in the chick embryo duodenum were examined by light and electron microscopy. The epithelium, in cross-section, undergoes three stages prior to the formation of ridges; termed the circle (4½–6 days), the ellipse (6–8½ days), and the triangle (8½–9 days). At about 9 days of development three ridges form with three more forming one day later. The mechanisms responsible for folding of the epithelium were examined. Microdissection followed by organ culture demonstrated that constriction by the surrounding circular smooth muscle cannot account for folding of the epithelium. Mitotic pressure within the epithelium also cannot account for folding since there is no difference in the number of epithelial cells per cross-section between the ellipse and the triangle stages and the epithelial tube is not restricted from expanding. Active constrictions in groups of epithelial cells, mediated by bands of microfilaments, are thought to cause folding. Bundles of microfilaments are localized in the apical region of all epithelial cells at all stages studied and are localized in the basal region of those cells occupying the crests of the forming ridges. Cytochalasin B-treatment prevented ridge formation and disrupted the bundles of microfilaments.

scholarly journals Effects of the cationic protein poly-L-arginine on airway epithelial cellsin vitro

2002 ◽  
Vol 11 (3) ◽  
pp. 141-148 ◽  
Author(s):  
Shahida Shahana ◽  
Caroline Kampf ◽  
Godfried M. Roomans
Keyword(s):  
Electron Microscopy ◽  
Epithelial Cells ◽  
Cell Membrane ◽  
Cell Damage ◽  
Membrane Damage ◽  
Light And Electron Microscopy ◽  
Airway Epithelial Cells ◽  
Airway Epithelial ◽  
Cationic Protein ◽  
Induced Apoptosis

Background: Allergic asthma is associated with an increased number of eosinophils in the airway wall. Eosinophils secrete cationic proteins, particularly major basic protein (MBP).Aim: To investigate the effect of synthetic cationic polypeptides such as poly-L-arginine, which can mimic the effect of MBP, on airway epithelial cells.Methods: Cultured airway epithelial cells were exposed to poly-L-arginine, and effects were determined by light and electron microscopy.Results: Poly-L-arginine induced apoptosis and necrosis. Transmission electron microscopy showed mitochondrial damage and changes in the nucleus. The tight junctions were damaged, as evidenced by penetration of lanthanum. Scanning electron microscopy showed a damaged cell membrane with many pores. Microanalysis showed a significant decrease in the cellular content of magnesium, phosphorus, sodium, potassium and chlorine, and an increase in calcium. Plakoglobin immunoreactivity in the cell membrane was decreased, indicating a decrease in the number of desmosomes.Conclusions: The results point to poly-L-arginine induced membrane damage, resulting in increased permeability, loss of cell-cell contacts and generalized cell damage.

Functional medial thickening and folding of the internal elastic lamina in coronary spasm

2011 ◽  
Vol 300 (2) ◽  
pp. H423-H430 ◽  
Author(s):  
Yasumi Uchida ◽  
Yasuto Uchida ◽  
Akimasa Matsuyama ◽  
Atsushi Koga ◽  
Yuko Maezawa ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Structural Changes ◽  
Light And Electron Microscopy ◽  
Coronary Spasm ◽  
Cellular Level ◽  
Internal Elastic Lamina ◽  
Circular Smooth Muscle ◽  
The Media ◽  
Medial Thickening ◽  
Elastic Lamina

Although there are a number of studies on vasospastic angina, the structural changes at the cellular level that occur in the coronary arterial wall during spasm are not well known. Coronary spasm was induced by brushing the coronary adventitia in nine anesthetized beagles, and structural changes in the spastic coronary segments were examined by light and electron microscopy, making comparisons with the adjacent nonspastic segments. The % diameter stenosis of the spastic segments as measured angiographically was 79.4 ± 12% (mean ± SD). Light microscopic changes in the spastic and nonspastic segments were as follows: medial thickness 1,512 vs. 392 μm ( P < 0.0001) and % diameter and % area stenoses of spastic segment 81.0% and 96.5%, respectively, indicating that spasm was induced by medial thickening. Circular smooth muscle cells (SMCs) in the media were arranged in parallel with the internal (IEL) and external (EEL) elastic lamina in nonspastic segments but radially rearranged in spastic segments. SMCs were classified by their patterns of connection to IEL into six types by electron microscopy. Of these, three contracted and pulled the IEL toward the EEL, causing folding of the IEL and waving of EEL resulting in thickening of the media and narrowing of the lumen. We conclude that coronary spasm was elicited by radial rearrangement of the medial SMCs due to their own contraction and resultant medial thickening and folding of IEL, creating a piston effect to narrow the lumen, i.e., spasm.

Observations on the nephridial system of the cestode Moniezia expansa (Rud., 1805)

Parasitology ◽  
1969 ◽  
Vol 59 (2) ◽  
pp. 449-459 ◽  
Author(s):  
R. E. Howells
Keyword(s):  
Electron Microscopy ◽  
Fine Structure ◽  
Epithelial Cells ◽  
Connective Tissue ◽  
Intercellular Space ◽  
Technical Assistance ◽  
Light And Electron Microscopy ◽  
Flame Cell ◽  
Research Scholarship ◽  
Research Facilities

The nephridial system of M. expansa has been studied using light and electron microscopy, and a number of histochemical techniques have been used on sections of the worm. The organization of the nephridial system and the fine structure of the flame cells and the nephridial ducts are described. Pores, which connect the nephridial lumen to the intercellular space of the connective tissue, exist at the junction of a flame cell and a nephridial duct. These pores may be considered nephrostomes and the system therefore is not protonephridial as defined by Hyman (1951).The epithelium lining the nephridial ducts has a structure which suggests that it is metabolically active. It is postulated that the beating of the cilia of the flame cells draws fluid into the ducts via the nephrostomes, with absorption and/or secretion of solutes being carried out by the epithelial cells of the duct walls. The function of the nephridial system is discussed.I am grateful to Professor James Brough for the provision of research facilities at the Department of Zoology, University College, Cardiff, andtoDrD. A. Erasmus for much helpful advice during the course of the work. I wish to thank Professors W. Peters and T. Wilson for critically reading the manuscript and Miss M. Williams and Mr T. Davies for expert technical assistance.I also wish to thank the Veterinary Inspector and his staff at the Roath Abattoir, Cardiff, for their kind co-operation and assistance in obtaining material.The work was carried out under the tenure of an S.R.C. research scholarship.

scholarly journals The Fine Structure of the Wheat Scutellum During Germination

1972 ◽  
Vol 25 (3) ◽  
pp. 469 ◽  
Author(s):  
JG Swift ◽  
TP O'brien
Keyword(s):  
Electron Microscopy ◽  
Fine Structure ◽  
Epithelial Cells ◽  
Light And Electron Microscopy ◽  
Cell Types ◽  
Wall Material ◽  
Cytological Evidence ◽  
Starch Grains ◽  
Parenchyma Cells ◽  
Cytological Changes

The cytological changes that take place in the scutellar epithelium and parenchyma during the first 5 days of germination are described by light and electron microscopy. Within 6 hr small starch grains appear in the plastids of both cell types and the size and number of starch grains increase gradually as germination proceeds. Later in germination starch disappears again from the plastids in the epithelial cells, but large starch grains still remain in the parenchyma cells. The reserves of the protein bodies are hydrolysed and the residual vacuoles undergo extensive coales-cence. Modifications in the appearance of the wall material of the epithelial cells as these cells elongate are illustrated and possible functional bases for these changes are suggested. The cells of the scutellar epithelium show no cytological evidence for their known functions of diastase secretion and nutrient absorption.

scholarly journals Immunocytochemical localization of actin in epithelial cells of rat small intestine by light and electron microscopy.

1988 ◽  
Vol 36 (7) ◽  
pp. 717-727 ◽  
Author(s):  
S J Hagen ◽  
J S Trier
Keyword(s):  
Electron Microscopy ◽  
Small Intestine ◽  
Epithelial Cells ◽  
Light And Electron Microscopy ◽  
Basal Membrane ◽  
Ground Substance ◽  
Structural Protein ◽  
Thin Sections ◽  
Filament Bundles ◽  
Lowicryl K4m

We used post-embedding immunocytochemical techniques and affinity-purified anti-actin antibody to evaluate localization of actin in epithelial cells of small intestine by fluorescence and electron microscopy. Small intestine was fixed with 2% formaldehyde-0.1% glutaraldehyde and embedded in Lowicryl K4M. One-micron or thin sections were stained with antibody followed by rhodamine- or colloidal gold-labeled goat anti-rabbit IgG, respectively. Label was present overlying microvilli, the apical terminal web, and the cytoplasm directly adjacent to occluding and intermediate junctions. Label was associated with outer mitochondrial membranes of all cells and the supranuclear Golgi region of goblet cells. Lateral cytoplasmic interdigitations between mature cells and subplasmalemmal filaments next to intrusive cells were densely labeled. The cytoplasm adjacent to unplicated domains of lateral membrane was focally labeled. Label was prominent over organized filament bundles within the subplasmalemmal web at the base of mature cells, whereas there was focal labeling of the cytoplasm adjacent to the basal membrane of undifferentiated cells. Basolateral epithelial cell processes were labeled. Label was focally present overlying the cellular ground substance. Our results demonstrate that actin is distributed in a distinctive fashion within intestinal epithelial cells. This distribution suggests that in addition to its function as a structural protein, actin may participate in regulation of epithelial tight junction permeability, in motile processes including migration of cells from the crypt to the villus tip, in accommodation of intrusive intraepithelial cells and in adhesion of cells to one another and to their substratum.

The ultrastructual morphology of the midgut diverticulum of the calanoid copepod Calanus helgolandicus (Claus) (Crustacea)

1970 ◽  
Vol 18 (1) ◽  
pp. 9 ◽  
Author(s):  
JE Ong ◽  
PS Lake
Keyword(s):  
Amino Acids ◽  
Epithelial Cells ◽  
Myoepithelial Cell ◽  
Calanoid Copepod ◽  
Apical Region ◽  
Basal Region ◽  
Epithelial Layer ◽  
Apical Half ◽  
Mammalian Stomach ◽  
Blue Reaction

The midgut diverticulum of the marine calanoid copepod C. helgolandicus consists of a columnar epithelial layer, a myoepithelial layer, and between these a well-developed basement membrane. The apical region of the epithelial cell is thrown into tightly packed microvilli which showed an alcian blue reaction indicating the presence of acid mucopolysaccharides. The apical half of the cell contains numerous microvesicles and mitochondria as well as tiny Golgi-like bodies. The plasma membrane of the basal region of the epithelium is extremely digitated. The digitations contain numerous mitochondria and the whole structure resembles mitochondrial pumps. The epithelial cells contain a large centrally situated oval nucleus with its single nucleolus. The myoepithelial cell is squamous and contains a flattened nucleus as well as very well-developed circularly and longitudinally arranged myofibrils. It is suggested that the midgut diverticulum of Calanus is probably analogous to the mammalian stomach in that food is mechanically churned. However, it does not appear to be involved in the secretion of digestive juices but only mucopolysaccharides; it is probably involved in the absorption of amino acids which are probably actively transported, by the "mitochondrial pump" in the basal region of the epithelial cells, into the haemocoel.

Development of intercellular junctions in the pulmonary epithelium of the foetal lamb

1978 ◽  
Vol 32 (1) ◽  
pp. 307-324
Author(s):  
E.E. Schneeberger ◽  
D.V. Walters ◽  
R.E. Olver
Keyword(s):  
Electron Microscopy ◽  
Epithelial Cells ◽  
Tight Junctions ◽  
Lung Development ◽  
Light And Electron Microscopy ◽  
Intercellular Junctions ◽  
Intercellular Spaces ◽  
Thin Sections ◽  
Epithelial Tight Junctions ◽  
Foetal Lamb

The integrity of epithelial tight junctions in foetal mammalian lungs is essential to maintain the unique ionic composition of lung liquid, and to prevent leakage of serum proteins into peripheral air spaces. In the present study the development of intercellular junctions of the lining epithelium of foetal lamb lungs during gestation was examined by light and electron microscopy. Both thin sections and freeze-fracture replicas were examined by electron microscopy. By 39 days of gestation, epithelial tight junctions consist of a minimum of 3.1 +/− 1.6 (s.D.) and a maximum of 5.8 +/− 2.0 discontinuous rows of particles and short segments of strands on P face ridges and in complementary E face grooves, while from 58 to 76 days they are composed of a network of 4.3 +/− 1.6 to 7.7 +/− 1.9 focally interrupted P face strands. Complementary replicas show that many of the discontinuities on the P face are due to separation of junctional particles on to the E face during fracturing, and not to an absence of junctional particles. From 76 days to term, epithelial tight junctions (exclusive of upper airway epithelium which was not examined) resemble those of adult lungs, and consist of a continuous network of 4.5 +/− 2.0 to 7.5 +/− 2.5 P face strands and complementary particle-free grooves. Permeability measurements, published elsewhere, indicate that the epithelium is functionally ‘tight’ from 69 days onwards. Tight junctions in peripheral air-space epithelium, therefore, are structurally continuous and functionally ‘tight’ early in foetal lung development, and form seals at one end of long, narrow intercellular spaces; these features may be important for coupled ion and water transport. When the bounding epithelial cells become flattened, these narrow intercellular spaces remain intact as a result of complex interdigitations of adjacent cell membranes. Desmosomes were present throughout gestation near the abluminal side of the tight junctions and occasionally near the base of the intercellular space. These junctions may serve to connect cells to each other at a time when tight junctions may be mechanically weak. In addition, gap junctions are associated with tight junctions from the glandular through the canalicular stages of lung development. They disappear by 120 days when the epithelial cells are differentiated.

scholarly journals FORMATION OF BONE TISSUE IN CULTURE FROM ISOLATED BONE CELLS

1974 ◽  
Vol 61 (2) ◽  
pp. 427-439 ◽  
Author(s):  
Itzhak Binderman ◽  
Dan Duksin ◽  
Arieh Harell ◽  
Ephraim Katzir (Katchalski) ◽  
Leo Sachs
Keyword(s):  
Electron Microscopy ◽  
Bone Tissue ◽  
Bone Cells ◽  
Light And Electron Microscopy ◽  
Bone Collagen ◽  
The Matrix ◽  
Three Stages ◽  
And Function

A system is described for the formation of bone tissue in culture from isolated rat bone cells. The isolated bone cells were obtained from embryonic rat calvarium and periosteum or from traumatized, lifted periosteum of young rats. The cells were cultured for a period of up to 8 wk, during which time the morphological, biochemical, and functional properties of the cultures were studied. Formation of bone tissue by these isolated bone cells was shown, in that the cells demonstrated osteoblastic morphology in light and electron microscopy, the collagen formed was similar to bone collagen, there was mineralization specific for bone, and the cells reacted to the hormone calcitonin by increased calcium ion uptake. Calcification of the fine structure of the cells and the matrix is described. Three stages in the calcification process were observed by electron microscopy. It is concluded that these bone cells growing in vitro are able to function in a way similar to such cells in vivo. This tissue culture system starting from isolated bone cells is therefore suitable for studies on the structure and function of bone.

Role of M Cells and Macrophages in the Entrance of Mycobacterium paratuberculosis into Domes of Ileal Peyer's Patches in Calves

1988 ◽  
Vol 25 (2) ◽  
pp. 131-137 ◽  
Author(s):  
E. Momotani ◽  
D. L. Whipple ◽  
A. B. Thiermann ◽  
N. F. Cheville
Keyword(s):  
Electron Microscopy ◽  
Cross Section ◽  
Light And Electron Microscopy ◽  
Peyer's Patches ◽  
Dense Material ◽  
M Cells ◽  
Mycobacterium Paratuberculosis ◽  
Electron Dense Material ◽  
Acid Fast Bacilli

Ligated ileal loops of calves were inoculated with live and heat-killed Mycobacterium paratuberculosis and were examined by light and electron microscopy. At 5 hours after inoculation, acid-fast bacilli were in subepithelial macrophages, but not in M cells covering domes. At 20 hours, more than 50 acid-fast bacilli per cross section were in subepithelial macrophages in domes. Both living and heat-killed bacilli passed into domes. Addition of anti- M. paratuberculosis bovine scrum to the inoculum enhanced entry of bacteria into domes. By electron microscopy, intact bacilli with electron-transparent zones (peribacillary spaces) were in the supranuclear cytoplasm of M cells at 20 hours. M cells also contained vacuoles, including electron-dense material interpreted as degraded bacilli. Subepithelial and intraepithelial macrophages contained bacilli and degraded bacterial material in phagosomes. These results suggest that calf ileal M cells take up bacilli, and that subepithelial and intraepithelial macrophages secondarily accept bacilli or bacterial debris which are expelled from M cells.

scholarly journals THE GOLGI APPARATUS IN NEURONS AND EPITHELIAL CELLS OF THE COMMON LIMPET PATELLA VULGATA

1957 ◽  
Vol 3 (5) ◽  
pp. 779-796 ◽  
Author(s):  
Dennis Lacy
Keyword(s):  
Electron Microscopy ◽  
Epithelial Cells ◽  
Golgi Apparatus ◽  
Light And Electron Microscopy ◽  
Neutral Red ◽  
Continuous Phase ◽  
Common Source ◽  
Patella Vulgata ◽  
Dense Substance ◽  
The Common

1. In view of widely diverse views held about the identity and structure of the Golgi apparatus in neurons of Mollusca, particularly gastropods, a study has been made on neurons of the common limpet, Patella vulgata, both by light and electron microscopy. A report is given also of observations made on epithelial cells of Patella by electron microscopy. 2. As revealed by Kolatchev's method, the Golgi apparatus in neurons consists basically of black filaments lying to one side of the nucleus. The filaments generally anastomose to form networks of various complexity. Rarely some cells contain only discrete filaments. Associated with some of the filaments is a weakly osmiophilic substance identified as archoplasm. Kolatchev's method also revealed spheroidal bodies (neutral red bodies, "lipochondria," etc.). 3. It has not been possible to demonstrate the Golgi apparatus using either iron-haematoxylin or Sudan black. 4. Examination of Kolatchev's preparations by electron microscopy has revealed that some of the Golgi filaments consist of chromophilic and chromophobic components. The chromophilic component consists of dense lamellae. 5. After fixation in buffered osmium tetroxide solution and examination by electron microscopy, it has been concluded that (a) the chromophilic component of the Golgi apparatus corresponds to a system of paired membranes (which usually enclose an inner dense substance), (b) the chromophobic component corresponds to a substance lying within small dilations of the paired membrane, and (c) the archoplasm corresponds to numerous small vesicles. 6. The paired membranes branch, anastomose, and can often be traced back to a common source. They are interpreted as lamelliform folds, and occasionally tubular processes, of essentially a single Golgi membrane. In cells containing a Golgi network it is suggested that the membrane extends through the whole of the apparatus in such a way that the substance it encloses may be regarded as being in a continuous phase. 7. Epithelial cells of Patella contain a juxtanuclear Golgi apparatus with an ultrastructure similar to that described for neurons.

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