Hypertrophy of intestinal smooth muscle

Proximal to an experimental stenosis of the small intestine of rats and guinea-pigs a remarkable hypertrophy of the muscle coat develops 3-5 weeks after the operation. There is no increase in the length of the intestine but an overall increase in volume of the muscularis externa up to 10 times. This increase is accounted for by an increase in size and in number (by mitosis) of smooth muscle cells of both the longitudinal and circular layers. Bundles of newly-formed smooth cells appear in the serosa and are circularly arranged. In the hypertrophic smooth muscle cells of the circular layer the ratio of surface to volume is 0.80 (0.80 mum2 of cell surface for every mum3 of cell volume) as against 1.4 in the control muscle. The hypertrophic muscle cells have a highly developed sarcoplasmic reticulum and show a large number of nexuses. The density of innervation (number of axons per given number of smooth muscle cells) is smaller than in controls. Few collagen fibrils are visible in the extracellular space.     

Reversal of muscle hypertrophy in the rat urinary bladder after removal of urethral obstruction

We studied the ultrastructure of the bladder musculature after first inducing hypertrophy by means of urethral obstruction and subsequently removing the obstruction. With hypertrophy the bladder musculature increases ten-fold or more in volume; after de-obstruction approximately 4/5 of the hypertrophic muscle weight and volume is lost within six weeks. In spite of this very large decrease in muscle mass there is no degeneration of muscle cells or nerve endings or of other cell types in the de-obstructed bladder either at 5 days or at 6 weeks. The individual muscle cells are smaller in size than in the hypertrophic bladder but still larger than control muscle cells. The decrease in muscle cell size is more substantial than the decrease in muscle cell surface. There are no lysosomes or other signs of intracellular degradation in any cells of the muscle layer. The musculature contains a very large amount of intercellular material, mainly collagen. This study documents the great plasticity of the musculature in the reduction of muscle mass after de-obstruction. However, some of the fine structural features are almost as different from the controls as in the hypertrophic muscle.     

Scanning electron microscopy of the muscle coat of the guinea-pig small intestine

Summary We have studied the layers of the muscular coat of the guinea-pig small intestine after enzymatic and chemical removal of extracellular connective tissue. The cells of the longitudinal muscle layer are wider, have rougher surfaces, more finger-like processes and more complex terminations, but fewer intercellular junctions than cells in the circular muscle layer. A special layer of wide, flat cells with a dense innervation exists at the inner margin of the circular muscle layer, facing the submucosa. The ganglia of the myenteric and submucosal plexuses are covered by a smooth basal lamina, a delicate feltwork of collagen fibrils, and innumerable connective tissue cells. The neuronal and glial cell processes at the surface of ganglia form an interlocking mosaic, which is loosely packed in newborn and young animals, but becomes tightly packed in adults. The arrangement of glial cells becomes progressively looser along finer nerve bundles. Single varicose nerve fibres are rarely exposed, but multiaxonal bundles are common. Fibroblast-like cells of characteristic shape and orientation are found in the serosa; around nerve ganglia; in the intermuscular connective tissue layer and in the circular muscle, where they bridge nerve bundles and muscle cells; at the submucosal face of the special, flattened inner circular muscle layer; and in the submucosa. Some of these fibroblast like cells correspond to interstitial cells of Cajal. Other structures readily visualized by scanning electron microscopy are blood and lymphatic vessels and their periendothelial cells. The relationship of cellular elements to connective tissue was studied with three different preparative procedures: (1) freeze-cracked specimens of intact, undigested intestine; (2) stretch preparations of longitudinal muscle with adhering myenteric plexus; (3) sheets of submucosal collagen bundles from which all cellular elements had been removed by prolonged detergent extraction.     

Biochemical and cytochemical characterization of extracellular proteoglycans in the inner circular smooth muscle layer of dog small intestine

Current literature concerning smooth muscle blood vessels has shown versican as the main proteoglycan (PG) component of the matrix. To show whether smooth muscle matrix has the same PG distribution when present in organs, other than the blood vessels, the inner circular smooth muscle layer of the small intestine was obtained by dissection as a highly purified tissue and analyzed by biochemical and cytochemical methods. The smooth muscle layer PGs were extracted from dog small intestine with 4 M guanidine-HCl in the presence of proteinase inhibitors, purified by charge equilibrium, isolated by equilibrium CsCl density gradients, and analyzed in terms of anion exchange, size, and glycosaminoglycan (GAG) distribution. Proteoheparan sulfate itself represented 91.5% of the PGs present in this tissue. The remainder was proteodermatan sulfate. Cytochemical analyses using the cationic dye cuprolinic blue associated with enzymatic treatments with chondroitinases ABC and heparitinase III showed the arrangement and identification of PGs in basal lamina and intramuscular connective tissues. The PGs in the basal lamina were proteoheparan sulfate, and those associated with collagen fibrils in the endomysium and perimysium were rich in dermatan sulfate. In contrast to the blood vessels, inner circular muscle smooth tissue in intestine has, as the main PG, perlecan.     

Immunoelectron microscopic localization of fibronectin in the smooth muscle layer of mouse small intestine

We studied the ultrastructural distribution of fibronectin in the smooth muscle layer of mouse small intestine with affinity-purified antibodies using the immunogold technique. Fibronectin was present over the pericellular area extending from the cell membrane to the extracellular matrix beyond the basal lamina. Distribution of the glycoprotein over the pericellular area was heterogeneous, i.e., it was localized more abundantly in the narrow space between smooth muscle cells, the gaps having a width of 60-80 nm where the two dense bands in adjacent cells matched each other. Such localization suggests that fibronectin contributes to cell adhesion. Within the basement membrane, gold label was localized both in lamina lucida and lamina densa, more densely in the latter than in the former. Fibronectin was also co-distributed with collagen fibers in the extracellular matrix. Within smooth muscle cells, gold particles were observed on rough endoplasmic reticulum and secretory vesicle-like structures. These results suggest that smooth muscle cells synthesize fibronectin and secrete it as a component of the basal lamina and extracellular matrix.     

Age-related changes in the ultrastructural organization of the human gingival epithelium

By means of transmissive and scanning electron microscopy 103 gingival bioptates in practically healthy persons at the age of 18-80 years have been studied. At ageing essential changes take place in all structural elements of the epithelium. The basal membrane is intermittent and loose. In cytoplasm of the cells of the basal layer epithelium the amount of microfilaments increases essentially, and as a result it becomes electron opaque. Tonofibrillar fasciculi of the spinous layer cells are fragmented, their contours are indistinct. In cytoplasm of the granular layer cells amount of keratohyalin granules increases, their size becomes large and their typical form is lost. In cytoplasm of the basal, spinous and granular layer cells the amount of organells decreases. Mitochondria acquire the appearance of electron translucent cavities with discomplexic, and sometimes, destroyed cristae. Rather great changes occur in intercellular interrelations. In all the layers some intercellular spaces are widen, in the spaces formed isolated desmosomes and other debries of cellular structures are formed. Sharp changes of microrelief of the granular layer epitheliocytes are observed. The ultrastructural rearrangements of epitheliocytes, revealed in the human gingiva, demonstrate certain disturbances in keratinization processes, in mechanical firmness, as well as in barrier function of the epithelial layer.     

Urinary bladder of rat: fine structure of normal and hypertrophic musculature

Summary The fine structure of the muscle of the urinary bladder in female rats is similar to that of other visceral muscles, although it is arranged in bundles of variable length, cross-section and orientation, forming a meshwork. When distended, the musculature is 100–120 m thick, with some variation and occasional discontinuity. Extended areas of cell-to-cell apposition with uniform intercellular space occur between muscle cells, whereas attachment plaques for mechanical coupling are less common than in other visceral muscles. There are no gap junctions between muscle cells. Many bundles of microfilaments and small elastic fibres run between the muscle cells. After chronic partial obstruction of the urethra, the bladder enlarges and is about 15 times heavier, but has the same shape as in controls; the growth is mainly accounted for by muscle hypertrophy. The outer surface of the hypertrophic bladder is increased 6-fold over the controls; the muscle is increased 3-fold in thickness, and is more compact. Mitoses are not found, but there is a massive increase in muscle cell size. There is a modest decrease in percentage volume of mitochondria, an increase in sarcoplasmic reticulum, and no appreciable change in the pattern of myofilaments. Gap junctions between hypertrophic muscle cells are virtually absent. Intramuscular nerve fibres and vesicle-containing varicosities appear as common in the hypertrophic muscle as in controls. There is no infiltration of the muscle by connective tissue and no significant occurrence of muscle cell death.     

Electronmicroscopic observations on the visceral and parietal rat's pleura after contralateral pneumonectomy

The mechanism of compensatory growth and healing of the pleura remains unresolved. Contralateral visceral and parietal (diaphragmatic and costal) pleura were investigated by transmission electron microscopy, following an experimental pneumonectomy (EP). Fifteen young-adult Wistar rats were divided into three groups and with survival times of 1, 5 and 8 days respectively after EP. Three sham-operated (thoracic cavity opened and closed) and three unoperated rats served as controls. One day following EP the superficial mesothelial cells have more microvilli and microvesicles, but a lower number of specialized contacts. Multiplication of extravasal cells leads to an increase of the thickness of the layer over the basal lamina and of the submesothelial layer. Five days after EP the superficial cells show a stratified arrangement in longer sectors of both pleural sheets. Along with typical mesothelial cells there are three new populations of cells: (1) with an abundant granular endoplasmic reticulum and secretory granules, (2) with fibroblast-like characteristics and (3) with a more extensive lysosomal system. The submesothelial layer is thickened due to newly formed blood vessels and collagen bundles. Eight days after EP the mesothelial cells build multi-row arrangement sectors and surround intercellular dilatations covered with microvilli. 'Activated' high mesothelial cells characterize the monolayer sectors. The submesothelial layer remains thicker due to larger collagen bundles and elastic fibers. The changes in the mesothelium and in the connective tissue layer suggest the existence of two periods. The first one is characterized by different mesothelial cell populations, new vasculogenesis and starting of fibrillogenesis. In the second period there are 'activated' mesothelial cells, pleural villi, groups of lymphatic lacunae and significant fibrillogenesis.     

Intralobular lymphatic vessels and their relationship to blood vessels in the mouse thymus

Summary The spatial distribution and fine structure of the lymphatic vessels within the thymic lobules of normal and hydrocortisone-injected mice were studied by light- and electron microscopy. The lymphatic vessels of the cortex and medulla of normal thymus are irregularly shaped spaces closely associated with branches of the intralobular artery and vein. The overall distribution of these vessels in the greatly involuted thymus of hydrocortisone-treated mice is essentially the same as in the normal thymus. The wall of the lymphatic vessels consists of only a layer of endothelial cells supported by underlying reticular cells. The luminal surface of the endothelial cell is smooth, but trabecular processes are often seen. There are three morphological types of intercellular contacts between contiguous cells, namely, end-to-end, overlapping and interdigitating. The lymphatic vessel has anchoring filaments and collagen fibrils, but a basal lamina is either absent, or if present, is discontinuous. This is in contrast to the continuous basal lamina of the venule. The perivascular space surrounding the postcapillary venule opens into a terminal lymphatic vessel at the cortico-medullary junction and in the medulla. Lymphocytes are seen penetrating the lymphatic endothelium, particularly in acutely involuted thymuses. These findings suggest that the intralobular lymphatic vessels may originate from the vacuities that surround the postcapillary venules, and the lymphatic system may function as a pathway for the migration of lymphocytes into or out of the lymphatic circulation.     

A comparative microscopic and ultrastructural study of perichondrial tissue in cartilage of Octopus vulgaris (Cephalopoda, Mollusca)

The microscopic and submicroscopic structures of perichondrial tissues in the head cartilages of Octopus vulgaris were studied by polarized light and transmission electron microscopy. The orbital cartilages possess a birefringent layer parallel to the surface of the cartilage; ultrastructurally, this layer, which may be considered perichondrial tissue, has the typical organisation of connective tissue but does not possess the stratification of collagen laminae found in vertebrate perichondria. Perichondrial extracellular matrix is clearly distinct from that of cartilage because its collagen fibrils are of a larger diameter than collagen fibrils from cartilage. In addition, perichondrial fibroblasts are characteristically located at the center of collagen fibers. In the cerebral cartilage, the perichondrium is absent or discontinuous in relation to complex interconnections between cartilage and connective fibres, muscle fibres, blood vessels and nerve. Distinctive cartilage-lining cells, rich in electron dense cytoplasmatic granules, are stratified either along the cartilage surface or along vessels and muscle fibres that penetrate within the cartilage. The perichondrium of cephalopod cartilage, whose structure varies according to the location and function of its skeletal segments, mimics that of vertebrate perichondrium, exemplifying the high level of tissue differentiation attained by cephalopods.     

Distribution and the fine structure of serotonin-containing fibers in the rat small intestine

Serotonin immunoreactive fibers were observed under the electron microscopy in all layers of the small intestine, with greatest abundance in the mucosa. Submucosal blood vessels were often surrounded by immuno positive nerves. In the inner circular muscle layer the immunoreactive serotonin positive fibers were closely associated with the smooth muscle cells. In the ganglia of the myenteric and submucous plexuses, labelled fibers surrounded the immunonegative neural cell bodies, but rarely formed conventional synaptic junctions. It is concluded that the serotoninergic system of the small intestine may influence the activity of associated structures in a diffuse non-synaptic manner.     

Immunohistochemical and histoenzymological characteristics of the arterial intimal cells in nonspecific aorto-arteritis

Enzymatic activity of cells, antigenic cellular markers and extracellular matrix of the hyperplastic intima of the aorta and carotid arteries was investigated in non-specific aorto-arteritis by immunomorphological and histochemical techniques. The cells of subendothelial layer of thickened arterial intima contained smooth muscle cell myosin, gave positive reactions to myosin ATP-ase and revealed high activity of thiamine pyrophosphatase. Fibronectin and type IV and V collagen were located in close proximity to these cells. The data obtained make it possible to consider these cells as modified smooth muscle cells. Type III collagen was the prevalent type of extracellular matrix of the thickened intima. A great number of blood vessels of the capillary and precapillary types have been found to penetrate into the intima from the adventitia. A possible role of pericytes surrounding newly formed capillaries as the precursors of subendothelial cell population in the hyperplastic intima is discussed.     

Structural characterization of the mandibular condyle in human fetuses: light and electron microscopy studies.

Mandibular condyles from 18- to 20-week-old human fetuses were examined in the light and electron microscope with particular attention to intratissue organization and extracellular matrix. In the human fetus the condyle has been divided into five layers: (1) the most superficial, articular layer, (2) chondroprogenitor cell layer, (3) condroblast cell layer, (4) nonmineralized hypertrophic cell layer, and (5) mineralized hypertrophic cell layer. The articular layer is rich in collagen fibers (mostly of the type I collagen), but the cells seldom divide. By contrast, in the chondroprogenitor cell layer and upper part of the chondroblastic cell layer mitosis gives rise to new cells. The matrix in the latter layer is composed of thick banded 'lucent' fibrils in a loose feltwork of granules representing cartilage proteoglycans. The daughter cells in the progenitor cell layer undergo differentiation which is apparently completed along the lower border of the mineralized hypertrophic cell layer--the ossification front. The matrix in the hypertrophic cell layer reveals distinct matrix vesicles that undergo mineralization and subsequently coalesce to form larger sheets of mineralized extracellular matrix. Mineralized cartilage serves as a backbone for new bone formation as marrow-derived osteoblasts and osteoclasts attach to remnants of mineralized cartilage, which enables the turning on of the remodeling cycles involved in new bone formation. It can be concluded that the process of endochondral ossification as has been reported in lower animals is recapitulated in the human fetus, thus the dynamics associated with condylar morphogenesis is maintained through phylogeny.     

Ultrastructural study of the effects of 17 beta-oestradiol on the lateral prostate and seminal vesicle of the castrated guinea pig

Administration of oestradiol to castrated animals induced hypertrophy of the secretory cells in the lateral prostate and seminal vesicle. In the lateral prostate, increases in the number of small highly electron-dense granules, multivesicular bodies and intercellular spaces were the prevailing effects 2 weeks after oestradiol treatment. There was also an apparent increase in the amount of cytokeratin intermediate filaments. Prolonged oestradiol administration for 4 weeks showed no appreciable changes in the glandular epithelium when compared with 2-week treatment. However, an increase in the thickness of the fibromuscular layer was observed. In the seminal vesicle, basal cell hyperplasia was associated with a concurrent increase in the size of intercellular spaces 2 weeks after oestradiol administration. There were also apparent increases in the volume of the lamina propria and in the number of stromal cells. An apparent increase in the density of collagen fibres in the stroma was observed 2 and 4 weeks after oestradiol administration. In conclusion, the responses of the epithelium of the lateral prostate and seminal vesicle to a pharmacological dose of oestradiol are different. Prolonged oestradiol administration exerts a more prominent effect on the smooth muscle in the lateral prostate but not in the seminal vesicle. The effects of oestradiol may be mediated directly or indirectly through the other hormones.     

Hypertrophic smooth muscle

Summary An extensive hypertrophy of the muscle coat develops in the small intestine of the guinea pig oral to an experimental stenosis. The profiles of smooth muscle cells become larger and irregular in shape. From the analysis of serial sections the arrangement of the muscle cells is less orderly than in control muscles. Many muscle cells are split into two or more branches over part of their length. The average cell volume is 3–4 times that of control muscle cells; the cell surface increases less dramatically and, in spite of the appearance of deep invaginations of the cell membrane, the surface-to-volume ratio falls from 1.4 to 0.8. The average cell length is only slightly increased compared with controls. Smooth muscle cells in mitosis are observed in all the hypertrophic muscles examined, in both muscle layers; in the circular musculature they occur mainly found in the middle part of the layer.The author thanks Miss Eva Franke for excellent technical assistance. This work was supported by grants from the Medical Research Council and the Central Research Funds of the University of London     

Accumulation of components of basal laminae: association with the failure of neural crest cells to colonize the presumptive aganglionic bowel of ls/ls mutant mice

Aganglionosis occurs in the terminal colon of the ls/ls mouse because an intrinsic defect of the presumptive aganglionic tissue prevents the entry and colonization of this portion of the bowel by migrating neural crest cells. The current study was undertaken to determine if abnormalities of the extracellular matrix could be identified in this segment that might account for migratory failure. Since basal laminae of the muscularis mucosa are overproduced in the aganglionic segment of adult ls/ls mice, we examined components of basal laminae in fetal gut from Day E 11 to Day E 16 of gestation. This period spans the time of enteric ganglion formation. Laminin and collagen type IV were studied by immunocytochemistry and proteoglycans by staining glycosaminoglycans with Alcian blue. Abnormalities of each of these components occur during development of the presumptive aganglionic bowel in the ls/ls mouse and could be detected as early as Day E 11. These defects consist mainly of an overabundance of these materials, both in defined basal laminae and throughout the extracellular space of the mesenchyme. Electron microscopic observations in the presumptive aganglionic ls/ls colon revealed a thickening of basal laminae and exceptionally wide intercellular spaces between smooth muscle myoblasts that contained an irregular fibrillar material, consisting of 4.5- to 6.0-nm filaments associated with 14- to 20-nm granules. Fibrillar and flocculant material was continuous with formed basal laminae, and was concentrated in the same areas found to have an overabundance of laminin immunoreactivity. These observations indicate that there is an accumulation of extracellular matrix material, including components of basal laminae, that (i) precedes the formation of enteric ganglia, (ii) is in the path through which enteric neural precursors from the crest would have to migrate, and (iii) is limited to the aganglionic and hypoganglionic ls/ls bowel. These data are consistent with the hypothesis that components of basal laminae contribute to the inability of crest cells to colonize the terminal bowel of ls/ls mice.     

Gene expression and extracellular matrix ultrastructure of a mineralizing chondrocyte cell culture system

Conditions were defined for promoting cell growth, hypertrophy, and extracellular matrix mineralization of a culture system derived from embryonic chick vertebral chondrocytes. Ascorbic acid supplementation by itself led to the hypertrophic phenotype as assessed by respective 10- and 15-fold increases in alkaline phosphatase enzyme activity and type X synthesis. Maximal extracellular matrix mineralization was obtained, however, when cultures were grown in a nutrient-enriched medium supplemented with both ascorbic acid and 20 mM beta-glycerophosphate. Temporal studies over a 3-wk period showed a 3-4-fold increase in DNA accompanied by a nearly constant DNA to protein ratio. In this period, total collagen increased from 3 to 20% of the cell layer protein; total calcium and phosphorus contents increased 15-20-fold. Proteoglycan synthesis was maximal until day 12 but thereafter showed a fourfold decrease. In contrast, total collagen synthesis showed a greater than 10-fold increase until day 18, a result suggesting that collagen synthesis was replacing proteoglycan synthesis during cellular hypertrophy. Separate analysis of individual collagen types demonstrated a low level of type I collagen synthesis throughout the 21-d time course. Collagen types II and X synthesis increased during the first 2 wk of culture; thereafter, collagen type II synthesis decreased while collagen type X synthesis continued to rise. Type IX synthesis remained at undetectable levels throughout the time course. The levels of collagen types I, II, IX, and X mRNA and the large proteoglycan core protein mRNA paralleled their levels of synthesis, data indicating pretranslational control of synthesis. Ultrastructural examination revealed cellular and extracellular morphology similar to that for a developing hypertrophic phenotype in vivo. Chondrocytes in lacunae were surrounded by a well-formed extracellular matrix of randomly distributed collagen type II fibrils (approximately 20-nm diam) and extensive proteoglycan. Numerous vesicular structures could be detected. Cultures mineralized reproducibly and crystals were located in extracellular matrices, principally associated with collagen fibrils. There was no clear evidence of mineral association with extracellular vesicles. The mineral was composed of calcium and phosphorus on electron probe microanalysis and was identified as a very poorly crystalline hydroxyapatite on electron diffraction. In summary, these data suggest that this culture system consists of chondrocytes which undergo differentiation in vitro as assessed by their elevated levels of alkaline phosphatase and type X collagen and their ultrastructural appearance.(ABSTRACT TRUNCATED AT 400 WORDS)     

Ultrastructural Studies of the Visceral Muscles of Chaetognaths

The visceral musculature of Chaetognaths was studied with special attention given to the digestive apparatus muscle. In the head the digestive apparatus muscle is relatively thick; individual muscles are difficult to distinguish at the anatomical level; in the anterior part of the oesophagus discontinuous bundles and layers of cross-striated fibers are found. As a group however, the oesophageal musculature completely covers the oesophageal epithelium. The prominent muscle layers around the oesophagus probably help to force food into the intestine against the turgor pressure of the trunk cavity which tends to collapse the intestine. Around the intestine the musculature is largely circular and smooth. The intestinal epithelium is ciliated despite its muscular covering. Muscle fibers are not individually innervated. They form myoepithelial structures with various intercellular junction types. In the intestinal muscle the fibers show myoendothelial-like junctions. Sphincters composed of myoepidermal cells surround the anus and the female gonopores. The somatic side of the general cavity is lined with a polymorphic squamous epithelium. Sometimes myoepithelial cells are found, with the occasional presence of extracellular matrix basal to the layer of the squamous epithelium. The ontogenetic relations between the polymorphic epithelium and the composite ‘mesenteries’ remain to be established. We have now some idea about the architecture of the body of Chaetognaths in relation to contractile structures.     

Morphogenetic determination of the dermoepidermal interface during tail regeneration in Rana catesbeiana.

During regeneration of the amputated tadpole tail, reconstruction of the epithelial basal lamina and basement lamella occurs only after the other major morphogenetic processes are well established. At 4 days after tail transection of the bullfrog tadpole, electron microscopy of the internal surface of the basal cell layer of the blastemal epithelium reveals it to be relatively free of extracellular matrix. By 11 days a basal lamina of distinct regularity has formed, and the first rodlets and fibers signaling the replacement of the collagenous basement lamella are identified. At 15 days the basal cells of the epithelium start to exhibit specialization of their internal cell surfaces: Hemidesmosomes and associated tonofilaments appear, and the adepidermal globular layer is formed. Orthogonal packing of collagen plies begins by 19 days after transection, the number of layers exceeding 22 in the latter stages of regeneration.     

Effect of calcitonin on fibroblasts and collagen formation in rabbits: an ultrastructural and scanning electron microscopic study

Transmission and scanning electron microscopic studies demonstrate the stimulatory effect of synthetic salmon calcitonin on the fine structure of fibroblasts and on collagen formation in cutaneous wounds experimentally induced in rabbits. Long-term administration of calcitonin enhances fibroblast growth and collagen synthesis. The fibroblasts hypertrophy and exhibit a highly developed rough endoplasmic reticulum (RER), several polyribosomes, large nuclei, hypertrophic Golgi complex, and many dense granules and lysosomes. Mitochondria are elongate and ramify; intracellular as well as extracellular synthesis of collagen increases. Fibrils appear tightly packed, in large heaps or spicula, with a characteristic periodicity and striation. Scanning electron micrographs of topography and relationships with collagen fibers and fibrils and cells surface changes demonstrate an extensive network of fine fibrils between collagen fibers, marked ruffling of cell membranes as well as numerous blebs on the cell surface. The latter are significant in collagen formation and egestion.