The secretory stage of amelogenesis in rat mandibular incisor teeth observed by scanning electron microscopy

In the scanning electron microscope (SEM), the structural organization of rat incisor enamel was divided into five regions: the initial prismless layer at the dentin-enamel junction; the decussating rods of inner enamel; intermediate enamel, where the structure changes from inner to outer enamel; outer enamel with parallel rods; and the surface prismless layer. There were alterations in the orientation of the ameloblasts and characteristic changes in the morphology of the Tomes’ processes during the secretion of each of these regions. Initially, the developing Tomes’ processes were seen within shallow pits which also contained fibrous material from dentin matrix. During the deposition of inner enamel, alternate rows of Tomes’ processes were held at right angles to each other by cytoplasmic projections which originated from the proximal regions of the Tomes’ processes. The cytoplasmic projections reorganized to perpendicular orientation relative to the enamel surface during the synthesis of outer enamel. Tomes’ processes of outer enamel appeared as elongated flaps extending parallel to the long axis of the tooth. In the late secretory stage, the microvillous projections disappeared and the Tomes’ processes were withdrawn into button-shaped structures which coalesced to form a smooth surface that rested on the enamel.     

The secretory stage of amelogenesis in rat mandibular incisor teeth observed by scanning electron microscopy

In the scanning electron microscope (SEM), the structural organization of rat incisor enamel was divided into five regions: the initial prismless layer at the dentin-enamel junction; the decussating rods of inner enamel; intermediate enamel, where the structure changes from inner to outer enamel; outer enamel with parallel rods; and the surface prismless layer. There were alterations in the orientation of the ameloblasts and characteristic changes in the morphology of the Tomes’ processes during the secretion of each of these regions. Initially, the developing Tomes’ processes were seen within shallow pits which also contained fibrous material from dentin matrix. During the deposition of inner enamel, alternate rows of Tomes’ processes were held at right angles to each other by cytoplasmic projections which originated from the proximal regions of the Tomes’ processes. The cytoplasmic projections reorganized to perpendicular orientation relative to the enamel surface during the synthesis of outer enamel. Tomes’ processes of outer enamel appeared as elongated flaps extending parallel to the long axis of the tooth. In the late secretory stage, the microvillous projections disappeared and the Tomes’ processes were withdrawn into button-shaped structures which coalesced to form a smooth surface that rested on the enamel.     

Lyophilized veins studied by scanning electron microscopy.

Human saphenous veins were studied by scanning electron microscopy. The intention was to analyze the suitability of lyophilized homologous veins for homografting when no autologous venous material is available for replacement of obstructed arterial segments. Cross-sectioned specimens revealed the intimal layer of the venous wall to be compactly structured, while the median and external parts were found to be loosely organized and contained numerous cavities. The luminal surface coat displayed the typical aspects of an intact endothelium with occasional fine deposits of fibrin. Defects of the inner layer were only rarely observed, and are caused when the endothelium was stuck to the PVC catheter prior to lyophilization. From a morphological point of view, lyophilized veins seem to be sutiable for replacement of arterial segments. Based on our findings suggestions are made for optimal preparation of the venous material.     

Optical microscopy versus scanning electron microscopy in urolithiasis

Stone analysis is incompletely done in many clinical centers. Identification of the stone component is essential for deciding future prophylaxis. X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy (SEM) still remains a distant dream for routine hospital work. It is in this context that optical microscopy is suggested as an alternate procedure. The objective of this article was to assess the utility of an optical microscope which gives magnification of up to 40× and gives clear picture of the surface of the stones. In order to authenticate the morphological analysis of urinary stones, SEM and elemental distribution analysis were performed. A total of 250 urinary stones of different compositions were collected from stone clinic, photographed, observed under an optical microscope, and optical photographs were taken at different angles. Twenty-five representative samples among these were gold sputtered to make them conductive and were fed into the SEM machine. Photographs of the samples were taken at different angles at magnifications up to 4,000. Elemental distribution analysis (EDAX) was done to confirm the composition. The observations of the two studies were compared. The different appearances of the stones under optical illuminated microscopy were mostly standardized appearances, namely bosselations of pure whewellite, spiculations of weddellite, bright yellow colored appearance of uric acid, and dirty white amorphous appearance of phosphates. SEM and EDAX gave clearer pictures and gave added confirmation of the stone composition. From the references thus obtained, it was possible to confirm the composition by studying the optical microscopic pictures. Higher magnification capacity of the SEM and the EDAX patterns are useful to give reference support for performing optical microscopy work. After standardization, routine analysis can be performed with optical microscopy. The advantage of the optical microscope is that, it is easy to use and samples can be analyzed in natural color.     

A study of arterial prostheses by scanning electron microscopy.

Scanning electron micrographs were taken of ten different vascular prostheses. The micrographs showed that some prostheses were damaged and some had traces of chemicals on their surface. The application of standard vascular clamps damaged most grafts and some showed remarkable changes on resterilization.     

The human bulbo-urethral glands. A transmission electron microscopy and scanning electron microscopy study

This paper investigates the ultrastructure of human bulbo-urethral glands using specimens obtained at surgery. The tubulo-alveolar endpieces of these glands are lined by typical mucous cells in different stages of the secretory cycle. The most interesting features of their cytoplasm are membrane-bounded bodies with a filamentous texture that usually fuse with the mucous droplets before they discharge into the lumen. Cells with apical dark granules are sometimes encountered in the ductal portions of the gland, which are probably ductal cells endowed with a scanty synthetic and secretory activity. Myoepithelial cells are not very numerous and are observed around mucous cells only.     

Healing of experimental ligament rupture: Findings by scanning electron microscopy

Summary The medial collateral ligaments of the knee joints of 16 rats were cut. Sixteen ligaments were allowed to heal spontaneously while the others were immediately sutured under the microscope. Four sham-operated immobilized rats served as controls. The ligamentous healing was registered after 4–5 weeks of immobilization under a scanning electron microscope (SEM). In the control ligaments, collagen bundles of variable thickness were observed as the main supporting elements. Numerous thin fibers were seen between the bundles. The surgically corrected ligaments showed a microstructural picture often difficult to distinguish from the controls. The unsutured ligaments, however, showed a much more variable picture. In some unsutured cases ligamentous regeneration was blocked by extensive scar formation. In many unsutured cases, however, signs of ligamentous regeneration were observed. It was noted that the SEM is a useful and sophisticated tool for studies on ligament healing.

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Zusammenfassung Bei 16 Ratten wurde das mediale Kollateralband der Kniegelenke durchtrennt. 16 Ligamente wurden der Spontanheilung überlassen. Die anderen 16 Bänder wurden unverzüglich unter dem Operationsmikroskop genäht. Vier scheinoperierte Ratten dienten zur Kontrolle. Die Ligamente von jeder Gruppe wurden nach einer Immobilisation von 4–5 Wochen im Raster-Elektronenmikroskop untersucht: Bei den Kontroll-Ligamenten wurden hauptsächlich Kollagen-Faserbündel von variablem Durchmesser gefunden. Zwischen den Faserbündeln lagen zahlreiche dünne Fibrillen. Die operativ wiederhergestellten Bänder zeigten ein mikroskopisches Bild, welches oft schwer von den Kontrollbildern zu unterscheiden war. Die nichtgenähten Bänder hingegen zeigten ein viel bunteres Bild. In einigen Fällen war die Ligamentheilung durch eine extensive Narbenbildung blockiert. Bei vielen nichtgenähten Bändern wurde jedoch auch eine beginnende Regeneration festgestellt. Die Untersuchung im Raster-Elektronenmikroskop hat sich für experimentelle Studien der Ligament-Heilung als sehr nützlich erwiesen.

     

Healing of experimental ligament rupture: findings by scanning electron microscopy

The medial collateral ligaments of the knee joints of 16 rats were cut. Sixteen ligaments were allowed to heal spontaneously while the others were immediately sutured under the microscope. Four sham-operated immobilized rats served as controls. The ligamentous healing was registered after 4-5 weeks of immobilization under a scanning electron microscope (SEM). In the control ligaments, collagen bundles of variable thickness were observed as the main supporting elements. Numerous thin fibers were seen between the bundles. The surgically corrected ligaments showed a microstructural picture often difficult to distinguish from the controls. The unsutured ligaments, however, showed a much more variable picture. In some unsutured cases ligamentous regeneration was blocked by extensive scar formation. In many unsutured cases, however, signs of ligamentous regeneration were observed. It was noted that the SEM is a useful and sophisticated tool for studies on ligament healing.     

Epididymal scanning electron microscopy study in hypothyroid rats

The purpose of this research was to investigate, using scanning electron microscopy, the effect of hypothyroidism on the ultrastructure of the rat cauda epididymis. Thyroidectomy was obtained by ip injection of 270 muCi of 131I per rat. One month later, several portions of cauda epididymis were examined. Morphological and physiological differences were detected in the cauda epididymis of the hypothyroid animals when compared to the control normal rats. The hypothyroid condition was associated with important changes in the luminal surface of the cauda epididymis epithelium. Broken, oblique, and loss of stereocilia, denuded epithelial cells, and flattening of the tubule were observed. The results confirm that hypothyroidism causes marked structural changes in the cauda ductus epididymis and could be adversely affect sperm maturation motility.     

Transmission and scanning electron microscopy of peripheral nerves

Electron microscopy of peripheral nerve tissue by SEM and TEM facilitates a better understanding of the complex nerve architecture described by early light microscopists. Details of axonal morphology and the Schwann cell/myelin sheath complex in healthy and diseased nerves have been described in the literature. The techniques of tissue harvesting and processing and the observed appearance of peripheral nerves by electron microscopy should be useful to clinicians and researchers involved in peripheral nerve surgery and research.     

A study of the ultrastructure of urinary calculi by scanning electron microscopy

Summary A study of urinary stones obtained from patients after surgery in the Medical College Hospital, Trivandrum, under the scanning electron microscope showed the presence of calcium oxalate and calcium biphosphate crystals as the main constituents. However, the pattern of the different phases of crystal growth was not uniform. Within the crystal lattice, fibrous structures, possibly of protein matrix, were invariably observed. Electron microscopy may be usefully adapted as a particularly suitable method for ultramicroscopic investigation of the fine structure of urinary stones including single crystal surface structure, section of urinary calculi and for possible presence of hitherto unknown components within the calculus.     

Cholangiovenous reflux pathways as defined by corrosion casting and scanning electron microscopy

Using corrosion casting and scanning electron microscopy of the rat biliary tree, we investigated the site and size of the pathways that allow bacteria to reflux from bile to blood. Nonobstructed rat biliary trees were injected retrograde with methylmethacrylate resin at a constant rate of 0.04 ml/min to volumes of 40, 60, 80, 120, 160, and 200 microliters. The infusion pressure was monitored and a pressure-volume curve was constructed. After polymerization and corrosion in 30 percent potassium hydroxide, the casts were examined with scanning electron microscopy. In addition, to identify the size of the reflux pathways, ceramic particles of 150 A, 1.7 mu, or 10 mu were added to the resin, and the studies were repeated. Finally, intact livers with casted biliary trees were processed and studied by scanning electron microscopy without corrosion. Scanning electron microscopy demonstrated fine anatomic detail of the cholangiovenous reflux pathway. At 40 microliters (20 cm water pressure), normal biliary radicals were filled. Between 40 and 80 microliters (20 to 50 cm water pressure), the cast material refluxed from the bile ductules into the spaces of Mall and Disse and then into the hepatic sinusoids. Filling of sinusoids continued at volumes between 80 to 160 microliters, and filling of collecting veins was seen above 160 microliters. Particles of 1.7 mu and smaller readily refluxed, but there was no sinusoidal reflux of casting material that contained particles of 10 mu. Casting without corrosion showed that the liver parenchyma remained intact. There was no evidence of reflux across hepatocytes. This study shows that cholangiovenous reflux occurs directly from bile ductules through the spaces of Mall and Disse into the hepatic sinusoids. The pathways measure between 1.7 and 10 mu. Since this is the path of least resistance, it may be of greater importance in the reflux of bacteria and toxins than other high-resistance pathways, for example, biliary canaliculi, tight junctions, or hepatocytes.     

Morphologic analysis of endoprosthesis materials with scanning electron microscopy

The biomaterials used in endoprosthesis are subject to great dynamic and tribologic stress which they are not always able to withstand. Wear and fatigue fractures may ensue. The SEM is a valuable tool for controlling quality and determining the nature of faults in the material. Examination of the surfaces of a fatigue fracture usually reveals the cause of the fracture. The presence of manufacturing faults shows that the producer's quality control (the non-destructive-method) was not always sufficient. The SEM is also valuable for examining the polished surfaces of the prosthesis before and after load bearing in order to evaluate wear damages.     

Morphology of mineral deposits on encrusted urinary catheters investigated by scanning electron microscopy

Struvite and hydroxyapatite were precipitated from artificial urine onto the surfaces of catheter materials by the controlled addition of urease. They were precipitated both together and separately (by omitting components of the artificial urine), and with and without the inclusion of albumin (which was intended to mimic the proteinaceous debris found in infected urine). Precipitates were identified by X-ray powder diffraction and the artificially encrusted surfaces examined by scanning electron microscopy. In the presence of protein, hydroxyapatite was precipitated as a poorly crystalline form which aggregated to form a crust. Struvite crystals could be easily identified under the scanning electron microscope by their relatively large size and characteristic appearance. Fifteen encrusted catheters from patients were also examined by scanning electron microscopy, and a further six using X-ray microanalysis. Their appearance was very similar to that of the materials encrusted in vitro. Encrustation involves the formation of hydroxyapatite and the growth of struvite crystals, intimately associated with bacteria.     

Deformed spinal needle tips and associated dural perforations examined by scanning electron microscopy

Background: The tips of modern thin Quincke-type spinal needles may be easily damaged by bone contact during the puncture. The purpose of this study was to find out the frequency of tip deformation in routine clinical work and the appearance of the dural perforations made by such damaged needles.
Methods: Two hundred and ninety-five Quincke-type needles (22G-29G) used in routine spinal anaesthesia were inspected by light microscopy. Scanning electron micrographs were taken of some of the damaged tips and of experimental dural perforations made by these.
Results: Four per cent of the needle tips were clearly bent or hooked and 11% were slightly bent. When an introducer needle was used (19 cases), one needle was clearly bent and one slightly bent. A puncture with a bone contact was associated with clear tip damage in 7%; a puncture without bone contact resulted in an undamaged or slightly bent needle tip in 99% of the cases. The numbers of bent tips among the various sizes were: 22G-2/21, 25G-13/40, 27G-28/231, 29G-1/3. In scanning electron microscopy (SEM) images of four clearly bent needle tips the deviation of the tip was between 10 μm and 20 μm. In SEM of eleven dural perforations, the holes made by needles with clearly bent tips were almost closed and three of them exhibited an "open tin can" appearance. None of the dural perforations was badly torn.
Conclusions: We verified that the tips of modern thin spinal needles are vulnerable to damage due to contact with bone. However, the holes made in dura by needles with bent tips do not appear to be excessively torn.     

Development of the renal glomerulus examined by transmission and scanning electron microscopy]

The kidneys of 2 to 10 days old albino rats were fixed by perfusion and examined by transmission and scanning electron microscopy. Furthermore, vascular casts of renal vessels in rats of the same ages were effectuated by injection of methacrylate into the aorta and observed by SEM. The observation of glomerulogenesis in different stages has indicated that the glomerular capillaries originate in the interstitial vessels which penetrate into the cleft formed in the wall of the renal vesicle. Initially the capillaries have an aspect of small sinusoids which then expand peripherally and undergo successive subdivisions: the anastomosis in each glomerular lobule persists. The podocytes originate from the cells of the renal vesicle facing the penetrating capillaries. The initially primitive cells branch off successively and extend around the expanding capillaries with their small processes -- the foot processes which interdigitate with the corresponding structures of the neighbour cells.