Surface and branching of placental villi in early abortion: relationship to karyotype Scanning electron microscopic study

Summary The placental villi of 61 early abortions with known karyotype and 7 legally induced abortions were investigated by scanning electron microscopy and documented in standardised enlargements. Five groups were established from the findings: uniformly branched villi with a velvety surface (group A) were found in 4 of the 7 induced abortions, abundant syncytial sprouts (group B) in 4 of the 6 cases with monosomy X; all 5 cases of triploidy were classified in the group bulbous or spherical villi (group C); 13 out of 25 cases of trisomy were found to have little branching and a surface densely covered with microvilli (group D), while 14 out of the 25 cases of euploidy belonged in the group with slender villi and surface with focal areas of denudation (group E). Forty of the 68 cases were properly assignable to the correct groups (58.8%). The non-uniformity of the villous morphology in the case of induced abortions shows that there is no uniform development of the (early) placenta. The variable morphology seen in abortions with euploidy reflects the various mechanisms of abortion applicable to this group.     

Scanning electron microscopic studies of reticular framework in the rat mesenteric lymph node

Background: The reticular framework in the lymph node has in the past been studied mainly by light microscopy of silver-impregnated specimens. The aim of the present study is to understand three-dimensionally the ultrastructure and organization of the reticular framework better than before. Methods: The mesenteric lymph nodes of the rat were prepared either an alkali-water maceration method or a conventional method and were observed in a scanning electron microscope (SEM). Results: The SEM study of alkali-water macerated tissues visualized directly the reticular fiber network in the lymph node. The reticular fibers consisted of thin bundles of collagem fibrils. They were continuous with the collagen fibriliar sheaths of blood vessels and lymphatic sinuses as well as with the fibrous capusule, thus acting as a skeleton of the lymph node. The arrangement of the reticulum was variable, depending on individual compartments. The SEM study of conventionally treated tissues, on the other hand, clarified the shape of reticular cells and their relationship with the reticular fibers. The sinus reticular cells connected with the sinus lining cells but separated from the parenchymal reticular cells, indicating that the former two originate from lymphatic endothelial cells. The parenchymal reticular cells varied in shape depending on their locations but essentially shared features with fibroblasts. Conclusions: The arrangements of the reticular fibers in the parenchyma were closely related to the associated reticular cells, showing the possibility that the reticular cells maintain the shape of the reticular framework suitable for each compartment of the lymph node. © 1995 Wiley-Liss, Inc.     

Scanning electron microscopic examination of reversible hyperplasia of the rat urinary bladder.

Urinary bladder damage caused by surgical incision, freeze-ulceration, or formalin instillation in male Fischer 344 rats was studied by light and scanning electron microscopy. The first two methods resulted in focal ulceration of the urinary bladder; the last induced diffuse mucosal damage. With each method, the damage was followed by regenerative hyperplasia and repair, the bladder mucosa returning to normal in 3-4 weeks. Epithelial cells in the hyperplastic areas had ropy microridges and uniform short microvilli on their luminal surfaces as observed by scanning electron microscopy. When the hyperplasia was marked, with nodular and papillary formation, occasional epithelial cells had pleomorphic microvilli on their surfaces. Rats treated either by surgical incision or freeze-ulceration had normal bladders after a 2-year observation period. Combined with results from previous experiments, pleomorphic microvilli are not a marker of neoplasia or irreversibility but appear with marked or prolonged mucosal proliferation even if reversible.     

Scanning and transmission electron microscopic study of visceral and parietal peritoneal regions in the rat

The visceral peritoneum of intraabdominal organs (spleen, stomach, liver, small intestine), omentum majus and the parietal peritoneum of the anterior abdominal wall and the diaphragm were studied in adult Wistar rats by combined scanning and transmission electron microscopy (SEM, TEM). In general, the peritoneal surface consisted of a mesothelium composed of cubic, flat or intermediate cell types delimited by a basal lamina. Cubic mesothelial cells predominated in parenchymal organs (spleen, liver) and were characterized by prominent and indentated nuclei, a cytoplasm richly supplied with organelles, a dense microvillous coat, basal invaginations and elaborate intercellular contacts. Flat mesothelial cells were observed in the intestinal, omental and parietal peritoneum (tendinous diaphragm, abdominal wall) and showed elongated nuclei, scant cytoplasm, a poorly developed organelle apparatus and sparsely distributed microvilli. An intermediate mesothelial cell type was described within the gastric peritoneum characterized by a central cytoplasmic protrusion at the nuclear region containing most of the cytoplasmic organelles and by thin finger-like cytoplasmic processes. The submesothelial connective tissue layer was composed of collagen fiber bundles, fibroblasts and free cells (macrophages, granulocytes, mast cells) and contained blood and lymphatic vessels. In the spleen, elastic fibers formed a membranous structure with intercalated smooth muscle cells. Mesothelial openings were observed as tunnel-like invaginations within the hepatic peritoneum and as clusters of peritoneal stomata within the parietal peritoneum of the anterior abdominal wall and the muscular diaphragm. The round or oval openings of the peritoneal stomata were frequently occluded by overlapping adjacent mesothelial cells and their microvillous coat or obstructed by cellular material. At the side of the peritoneal stomata the mesothelial cell layer was interrupted to allow a direct access to the underlying submesothelial lymphatic system. The mesothelium and lymphatic endothelium shared a common basal lamina. The endothelial cells were discontinuous and displayed valve-like plasmalemmatic interdigitations facilitating an intercellular transport of fluids and corpuscular elements from the peritoneal cavity to the submesothelial lymphatic lacunae. The findings underline the morphological heterogeneity of the peritoneum in visceral and parietal regions, suggesting different functional implications, and further support the presence of extra-diaphragmatic peritoneal stomata.     

Scanning electron microscopic study of fourDiphyllobothrium species

Three-dimensional observation was carried out on plerocercoids and adults ofDiphyllobothrium dendriticum, D. ditremum, D. latum, andD. vogeli using scanning electron microscopy. The species-specific differences between plerocercoids were recognized in the shapes of the whole body, scolex, and bothrium and the wrinkle pattern on the body surface. The differences between adult worms were also observed in the shapes of the scolex, neck, and genital papillae around the genital pore and the pattern on the egg surface. The significance of species specificity in the three-dimensional morphology of diphyllobothriid cestodes is briefly discussed.     

Scanning electron microscopic studies on the subepithelial tissue of the gastrointestinal mucosa of the rat

The three-dimensional architecture of the subepithelial tissue of the gastric, the small and the large intestinal mucosa of the rat was observed by scanning electron microscopy (SEM) after removal of cellular elements through prolonged osmication followed by ultrasonication (the method by Highison and Low, 1982), or by cell-maceration with a low temperature NaOH solution (the method by Ohtani, 1987). The basal lamina was exposed by the former method, and the collagenous fibrous sheet immediately under the basal lamina was disclosed by the latter. The surface of the subepithelial tissue is grossly smooth in the pyloric gland and crypts of the small and the large intestine. However, in the fundic glands of the stomach, the surface structure of the subepithelial tissue greatly differs according to glandular location. In the pit of the fundic glands, the surface of both the basal lamina and the sub-basal laminar fibrous sheet is smooth. In the neck region, however, shallow round depressions are seen. The most striking feature of the subepithelial tissue of the fundic glands is the presence of numerous hemispherical concavities in the middle and basal regions of the glands which harbor parietal cells. On the surface of the small intestinal villi, the basal lamina is elevated by the underlying capillary network and forms a meshwork of ridges that surround shallow basins in which numerous round fenestrations 1-5 microns in diameter are seen. The fibrous sheath of the marginal arteriole is observed as a cord-like protuberance on the apical margin of the villi; this suggests its role in the maintenance of the structural integrity of the villi. In the large intestine, well defined round fenestrations are clearly seen, mainly distributed on the upper third of the crypts, and continuing to the lamina propria.     

Scanning electron microscopic study of follicular lymphoma

Nine cases of follicular lymphoma were studied by scanning electron microscopy. The morphological findings by this method emphasizes the heterogeneity of the cellular composition of the follicles, even in the cases not labelled as mixed type, and the degree to which the anatomy of a normal secondary follicle is mimicked. Large nonlymphoid cells, presumably dendritic, are present in the follicles. There are no differences in the surface features of the follicular and interfollicular lymphoid cells.     

Scanning electron microscopic studies of the vascular smooth muscle cells and pericytes in the rat heart

The cytoarchitecture of smooth muscle cells and pericytes in the rat cardiac vessels was studied by scanning electron microscopy after the removal of connective tissue matrices using a modified KOH-collagenase digestion method. The initial stem of the coronary arteries had groups of smooth muscle cells which ran in various directions on the outermost layer of the media. Although smooth muscle cells in coronary arteries of more than 100 microm in the outer diameter were arranged in a rough circle around the vessel axis, oblique and/or longitudinal muscle bundles were often present in the medio-adventitial border of the vessels. The presence of irregularly oriented muscular bundles is probably connected with resistance against the stretching force induced by the beating of the heart. As the vessel size decreased toward the periphery, almost all of the smooth muscle cells became spindle-shaped with several tiny processes and ran circularly or helicaly to the vessel axis. In the precapillary arterioles (6-12 microm), smooth muscle cells acquired various cytoplasmic processes which helicaly surrounded endothelial cells. Unmyelinated nerves were often associated with arterioles. Blood capillaries were morphologically divided into three segments: arterial capillaries which had pericytes with wide and circularly oriented processes, true capillaries whose pericytes extended long and thin primary processes bilaterally along the vessel axis, and venous capillaries surrounded irregularly and loosely by wide pericytic processes. The stellate pericytes in the postcapillary venules (10-30 microm) gradually changed into flat tape-like smooth muscle cells, which ran circularly in the collecting venules and veins (30-200 microm). The large collecting veins were finally overwhelmed by superficial thin layer of the myocardium, their own smooth muscle cells being very sparse. This suggests that large veins have poor ability to contract by themselves but are influenced by the surrounding myocardial cells.     

Scanning electron microscopic study of the human auditory ossicles

The human mallei, incudes and stapedes from 34 cadavers were examined using scanning electron microscope (SEM) to compare the bone surface type among different regions of auditory ossicles for males and females. On the malleus of both males and females, almost all of the surfaces showed a smooth fibrous appearance, characteristic of resting surface. Limited bone-forming or resorbing surfaces were identified on the malleus. As compared with the malleus, the percentage area of the resorbing surface and the vascular canal openings were higher on the incus and stapes, especially on the long process (Crus longum) of the incus and the neck of the stapes for both males and females. The percentage area occupied by the resorbing surface of the long process of the incus and the neck of the stapes correlated with that of the vascular canal openings. We consider that the malleus maintained the stable condition, while the long process of the incus and the neck of the stapes demonstrated marked bone resorption. We suppose that the bone erosion may be related to the vascularization in these regions. Though the percentage area of the resorbing surface and the vascular canal openings had the tendency to be high in females, we did not find any significant differences between the males and females. There was no significant correlation between the age and the area of resorbing surface or vascular canal openings.     

Scanning electron microscopic observations on bone.

The maceration technique employed in the preparation of specimens of bone for museum purposes has also been found to be of use in the preparation of fresh specimens for study with the scanning electron microscope. The technique requires less technical supervision, permits a greater underprocessing to overprocessing margin, and allows comparability of recent biopsy material with previously macerated bone specimens with no less detail than that found by other authors using other techniques on biopsy material.     

Scanning electron microscopic observations of the periodontal ligament fibers and cells in rat molar teeth.

The periodontal ligament of rat molar teeth was observed with scanning electron microscopy (SEM) using two different methods: NaOH maceration and KOH-collagenase treatments. Rat jaws with molar teeth were fixed, demineralized with 10% EDTA, and cut into several pieces. After maceration with 5% NaOH for 5 days at room temperature, the cellular elements were completely removed and the periodontal ligament fibers appeared as bundles of collagen fibrils. The fibers branched and anastomosed but did not spread fibrils randomly. In some regions near the alveolar bone, collagen fibrils circularly binding the fibers were found. When treated with 30% KOH for 7 to 10 minutes at 60 degrees C and with 0.1% collagenase, the periodontal ligament fibers were removed and the cells appeared as spindle and stellate shapes, and combined with the irregular cell processes of each other. Thus, the interaction between the periodontal ligament fibers and cells were three-dimensionally visualized by using the two different methods.     

Scanning electron microscopic study of spinal arachnoid plaques

Calcified or ossified plaques within the spinal arachnoid membranes are often reported at autopsy and are occasionally incriminated as the cause of neurological symptoms in patients undergoing surgery. Histological studies of plaques have been done, but to our knowledge no studies using the scanning electron microscope (SEM) have been reported. In this study, portions of the spinal cord with plaques were removed from adult human cadavers in the dissecting laboratory and processed for SEM and energy-dispersive x-ray analysis (EDAX). The surfaces of the plaques appeared to be fibrous in some areas, studded with irregularly shaped projections or nodules in others, and smooth in yet other areas. Cells were seen in lacunae-like depressions on the surfaces of some plaques and EDAX revealed the presence of calcium on and near the cells. In some areas calcium and phosphorus were both detected, but not in the ratios seen in bone. No calcium was seen on smooth or fibrous areas. It is suggested that the plaques sampled in this study were composed largely of fibrous tissue encrusted in some areas with calcium salts. There was no evidence that any of the plaques contained bone.     

Scanning electron microscopic study of hyalocytes in the guinea pig eye

The ultrastructure and distribution of hyalocytes were examined in guinea pig eyes by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Hyalocytes were distributed randomly on the vitreous surface of the retinal inner limiting membrane, where they were elongated in shape with a spherical perikaryon and a few stout processes. On the epithelial surface of the ciliary body, however, the cells were stellate with some short processes. The cells of both regions included typical dense hyalocyte granules in the cytoplasm. The surface morphology of hyalocytes indicates that the cells are wandering macrophages. The abundance of free cells in the ciliary body epithelium suggests that the area is a site for the emigration of hyalocytes or their precursors from the ciliary stroma. The homogeneous population of hyalocytes in the posterior part of the eyeball may be useful for experimental studies of the cell in vivo or their isolation for study in vitro.     

Scanning electron microscopic observation of Merkel cells in the lamprey epidermis

The Merkel cell in the epidermis has generally been regarded as a mechanoreceptor which detects tissue deformations with its microvilli, and subsequently releases certain transmitters to nerve endings. In order to analyze the mechanism of mechanoreception, the fine structure of lamprey Merkel cells and their relationships with surrounding tissue were examined by scanning electron microscopy (SEM) after exposure of the cells by NaOH maceration, as well as by transmission electron microscopy (TEM) according to a conventional method. By SEM, lamprey Merkel cells revealed small round cell bodies bearing numerous microvilli on the upper and lower poles in accord with previous TEM reports. Combined SEM and TEM observations showed that the Merkel cell bodies were tightly held in corresponding concavities of other epidermal cells, with some desmosomes connecting the cells with each other. On the other hand, microvilli of the Merkel cells extended freely in intercellular spaces bound with complex microplicae of epidermal cells. The regional difference in mechanical anchorage of the Merkel cells probably leads to transient deflection and subsequent recovery of their microvilli during a given mechanical stimulation, suggesting rapidly adapting mechanoreception by the cells.