SEARCH · PubMed Health

Results for “Microscopy, Electron, Scanning”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 937 records · Page 52Linked to original sources

PubMed1989

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.

Durapatite↗

PubMedDate not supplied

Cause of spontaneous echocardiographic contrast as assessed by scanning electron microscopy.

Spontaneous echo contrast ("echocardiographic smoke") is known to occur in low-flow states and to require the presence of red cells and plasma proteins. Limited morphologic information regarding the microanatomic structure of red cells exhibiting spontaneous echo contrast is known. The study was designed to evaluate the microanatomic features of red cells exhibiting spontaneous echocardiographic contrast with scanning electron microscopy. With human blood, a beaker, and a stirring bar, a simple model for demonstration of spontaneous echo contrast and its reversal was devised. Blood elements were "sampled" from within this model at times of high and low spontaneous echogenicity by adherence of blood elements to poly-L-lysine-coated slides that were subsequently fixed and examined with scanning electron microscopy. Spontaneous echo contrast was maximal at complete stasis or low-flow states and could be abolished by agitation of blood with continuous stirring. Sampling during low-flow states with high echogenicity showed a preponderance of clumped red cells, whereas at high-flow and low echogenicity states red cells were dispersed and usually solitary. No morphologic features suggestive of activation of the coagulation system were noted. Spontaneous echo contrast is caused by reversible red blood cell clumping, which occurs in fresh human blood at low-flow (low shear rate) states and can be abolished by increasing flow. This phenomenon is independent of activation of the clotting system.

Blood Specimen Collection↗

PubMed1989

Sealing root canals with low-viscosity resins in vitro: a scanning electron microscopy study of canal cleansing and resin adaption.

Low-viscosity resins of the fissure sealant type have been suggested in the literature as having potential for use as root canal filling materials. A low-viscosity resin may seal a root canal by flowing into clean dentinal tubules after smear layer removal. This investigation with scanning electron microscopy examines the efficacy of two methods of root canal preparation and the effectiveness of different chemicals on smear layer removal. Ultrasonic preparation with 0.25% sodium hypochlorite solution and final agitation with 50% citric acid solution were found to produce a very clean canal wall, free of smear layer in coronal and middle parts. However, low-viscosity resin used in conditions that aimed to simulate in vivo conditions failed to penetrate open dentinal tubules to a significant extent. On the basis of these observations made with scanning electron microscopy, low-viscosity resins would not seem suitable as root canal filling materials, because they are unlikely to form a satisfactory adaption to the canal wall. In addition, if treatment fails, these resins are impossible to remove from a root canal without much destruction of tooth substance.

Citrates↗

PubMed1999

Lumbar dura mater biomechanics: experimental characterization and scanning electron microscopy observations.

UNLABELLED: There is no consensus about the anatomical structure of human dura mater. In particular, the orientation of collagen fibers, which are responsible for biomechanical behavior, is still controversial. The aim of this work was to evaluate the mechanical properties and the microstructure of the lumbar dura mater. We performed experimental mechanical characterization in longitudinal and circumferential directions and a scanning electron microscopy observation of the tissue. Specimens of human dura mater were removed from the dorsal-lumbar region (T12-L4/L5) of six subjects at autopsy; specimens of bovine dorsal-lumbar dura mater were obtained from two animals at slaughter. Human and bovine tissues both exhibited stronger tensile strength and stiffness in the longitudinal than in the circumferential direction. Scanning electron microscopy observations of dura mater showed that the collagen fibers are mainly oriented in a longitudinal direction, which accounts for its stronger tensile strength in this direction. We conclude that dura mater has a different mechanical response in the two directions investigated because the fiber orientation is predominantly longitudinal. IMPLICATIONS: In this experimental work, we studied the structural and functional relationship of human lumbar dura mater. We performed mechanical tests and microscopic observations on dura mater samples. The results show that the dura mater is mainly composed of longitudinally oriented collagen fibers, which account for higher tissue resistance in this direction.

Adult↗

PubMed1996

Morphometry, scanning electron microscopy and X-ray spectral microanalysis of protostylid pits on human lower third molars.

Protostylid pits on 50 lower third molars were studied. The depth and width of the pits, the thickness of the enamel at the pit bottom and the concavity of the dentino-enamel junction under the pit were measured by light microscopy. The pit content was examined by scanning electron microscopy and X-ray spectral microanalysis. The results show that the morphometric variables of protostylid pits are similar to those of occlusal fissures and pits. The protostylid pits were seen to contain globular formations, belonging mainly to dental calculus; organic rod-shaped bodies, which could represent remnants of the enamel organ--or more probably--foreign bodies, were frequently observed. The study suggests that the development of the most common form of protostylid is basically similar to that of an occlusal cusp, with variations attributable to the low expression of the protostylid and particularities of cusp development in the lateral tooth wall.

Calcium↗

PubMed1989

Comparison of backscattered scanning electron microscopy and microradiography of secondary caries.

Carious lesions are usually studied using light microscopy and/or microradiography which require preparation of thin sections. Backscattered scanning electron microscopy (BSEM) has received little attention although it provides information similar to that obtained with microradiographs, with the potential for higher resolution. Recently, microscopes have been introduced that can be used to study wet or nonconducting specimens, offering techniques for studying specimens without desiccation or preparation of thin sections. This investigation sought to determine if secondary carious lesions have the same characteristics when studied by microradiography as when using the "wet" BSEM mode. Microradiographs were made of thin sections from restored teeth with secondary caries induced in an artificial caries system. The thin sections were also studied by BSEM with a partial pressure in the specimen chamber to prevent specimen charging. Comparisons of the lesion size and shape were made using the two methods. Lesion depth measurements in enamel were the same; lesions that penetrated into dentin appeared to be of similar size and shape, but lesion depths measured by BSEM were slightly greater (paired t-test, p less than .05). This was a result of cracks at the carious enamel-dentin interface that probably developed during storage of the samples. Variations in the surface enamel rod structure and the development of subsurface lesions were apparent. Several zones were also apparent in the carious dentin, demonstrating loss of dentinal tubule detail in the depth of the lesion, collapse of tubules, and hypermineralized regions near the advancing front of the lesion. Several additional samples of natural carious teeth were examined. They demonstrated the characteristic structural features of the carious process.(ABSTRACT TRUNCATED AT 250 WORDS)

Dental Caries↗

PubMed1980

Using expanded polytetrafluoroethylene for bridging arterial microvascular defects: an experimental study with evaluation in the scanning electron microscopy.

In an experimental investigation the replacement of arterial microvessels with microporous expanded polytetrafluoroethylene was studied. The infrarenal segment of the rat aorta was used as the scientific model. The inside diameter of the micrograft was 1 mm. Using microvascular techniques a total of 18 prostheses were inserted. The animals were harvested at time intervals from 3 days up to 3 months. Patency was determined by angiography and at autopsy. The aorta implant junction, the characteristics of the neointima development and the differentiation of the interstitial cells were studied by scanning electron microscopy. Fourteen of the implanted micrografts remained patent at the time of sacrifice, yielding an early patency rate of 77,7%. As shown by scanning electron microscopy, the development of the neointima took place in 2 stages. The initial fibrin/platelet layer was reduced after one month and replaced by a definite neointima with mononuclear cells, connected with interstitial cells. Investigation of the aorta-implant junction showed the prosthesis functionally embedded in the structure of the aorta. Expanded polytetrafluoroethylene as a prosthetic material for microvascular prostheses was easy to handle and emerged compatible with other tissues. It can be used as a substitute for bridging arterial microvascular defects.

Animals↗

PubMed1996

First clinical application of the Medos-HIA ventricular support system: monitoring of the thrombotic risk by means of the biomarker prothrombin fragment F1 + 2 and scanning electron microscopy evaluation.

BACKGROUND: The medos-HIA ventricular support system was designed as an artificial heart assist device for intractable heart failure to act as a bridge for transplantation or recovery. The aim of this study is to report on the first clinical application of the system and to evaluate the thrombotic risk with the use of the biomarker prothrombin fragment F1 + 2 and scanning electron microscopy of the blood contacting surface. METHODS AND RESULTS: This device worked without any failure for 462 hours, and a sufficient output of 5.2 to 6 L was observed. No activation of the procoagulatory system occurred during pumping until the occurrence of the septicemia. Preseptic F1 + 2 levels were normal, at about 1 nmol/L. The blood contacting surfaces of the pump and the polyurethane valves were examined by means of scanning electron microscopy, and the surfaces were found to have smooth fibrin layers with no thrombogenic deposits. This fibrin layer is considered to prevent thrombotic adhesions, thereby minimizing the risk of thromboembolic complications. Post mortem examinations after pneumonia with septic shock showed no thrombus formation in this support system and around the inserted cannulas. CONCLUSIONS: The low risk for thromboembolic complications, no measurable activation of the coagulation system, and the excellent surface characteristics encourage further use of this inexpensive working device.

Cardiac Output↗

PubMedDate not supplied

Scanning electron microscopy of aberrant crypt foci in human colorectal mucosa.

BACKGROUND: Aberrant crypt foci (ACF) are clusters of morphologically altered crypts which can be observed by light or stereomicroscopy on the mucosal surface of the colon after staining with methylene-blue. They probably represent one of the earliest events in human colorectal carcinogenesis. The main purpose of the present study was to observe the surface features of aberrant and normal colonic crypts in humans using scanning electron microscopy (SEM) in order to find and measure differences between aberrant and normal. MATERIALS AND METHODS: Fifteen mucosal specimens containing ACF and 8 with normal mucosa taken from patients operated on for colon cancer were observed under a scanning electron microscope. RESULTS: By SEM ACF were easily observed on the mucosal surface, because they showed a well defined border and were elevated on the mucosal surface. Under higher magnification luminal openings of aberrant crypts had a larger overall average diameter than normal (37.6 microns +/- 13.5, mean +/- SD, vs 15.9 microns +/- 4.9, P = 0.001), though when crypt multiplicity of ACF (number of crypts per ACF) was higher, the diameter of luminal openings tended to be smaller and similar to those of normal crypts, with weak negative correlation between crypt multiplicity of ACF and mean diameter of aberrant luminal openings (r = 0.27). Finally, the mucosal surface among aberrant crypts was flattened because of a loss of microvilli. in conclusion, scanning electron microscopy allows a better definition of the topological features of aberrant crypt foci than light or stereomicroscopy.

Colon↗

PubMed1999

Scanning electron microscopy of the floor of the fourth ventricle in rats subjected to graded impact injury to the sensorimotor cortex.

OBJECT: Respiratory dysfunction including apnea frequently follows head injury in humans. The purpose of this study was to identify any structural alterations in the region of brainstem respiratory nuclei that might account for immediate postinjury respiratory abnormalities in anesthetized experimental animals. METHODS: Using scanning electron microscopy, the authors examined the floor of the fourth ventricle in injured rats after a piston strike to the sensorimotor cortex that depressed the dura 1, 2, or 4 mm. The rats were killed within minutes of injury. Cortical impact depths measuring either 1 or 2 mm (eight rats) produced no respiratory abnormalities, and the structural integrity of the ependymal lining of the ventricular floor in these animals was not compromised. Thirteen rats were subjected to impact to a 4-mm depth and 10 of these exhibited immediate temporary or permanent apnea. The medullae of nine of these rats were studied using scanning electron microscopy, and the fourth ventricular floors of all nine rats showed tears. Four rats that exhibited immediate, permanent apnea had tears in the caudal fourth ventricle floor near the obex, whereas five rats with no or only transient apnea had tears located more anteriorly, near the aqueduct or laterally. Changes in cerebrospinal fluid flow or pressure dynamics may have caused these tears. Light microscopy, focused near the area postrema, revealed a shearing defect through the ependyma of the fourth ventricular floor into the subjacent neuropil with a disruption of axonal pathways. CONCLUSIONS: Respiratory neuronal network components lying within 2 mm of the area postrema may well have been disrupted by the caudal tears producing permanent apnea. A similar phenomenon could account for the transient or permanent postinjury apnea seen in humans with severe head injury.

Animals↗

PubMed1983

Scanning electron microscopy of glomerular and non glomerular red blood cells.

Phase contrast microscopic examination of the urine has been recently shown to be of value in predicting whether hematuria is due to glomerulonephritis or lesions of the lower urinary tract. Glomerular red cells show variations in size and shape and have distorted surfaces. Non glomerular red cells are uniform in size and shape and have smooth surfaces. Scanning electron microscopy was performed on urine sediment containing either glomerular or non glomerular red cells to better define their surface characteristics. Glomerular red cells exhibited a variety of forms, most cells having lumpy projections from the surface, some showing fragmentation of the membrane and others showing gross distortion. In contrast non glomerular red cells show smooth surfaces and usually maintain the normal biconcave disc shape of peripheral red blood cells. Scanning electron microscopy can better define surface structural abnormalities of urinary glomerular and non glomerular red blood cells.

Analgesics↗

PubMed2004

Use of scanning electron microscopy to confirm the identity of lice infesting communally grazed goat herds.

Lice have been described on goats in commercial farming systems in South Africa but not from flocks on communal grazing. During a longitudinal survey on the causes of goat kid mortality, conducted in Jericho district, North West Province, lice were collected from communally grazed indigenous goats. These lice were prepared for and viewed by scanning electron microscopy, and micro-morphological taxonomic details are described. Three species of lice were found in the study area and identified as Bovicola caprae, Bovicola limbatus and Linognathus africanus. Sucking and biting lice were found in ten of the 12 herds of goats examined. Lice were found on both mature goats and kids. Bovicola caprae and L. africanus were the most common biting and sucking lice respectively in all herds examined. Scanning electron microscopy revealed additional features which aided in the identification of the louse species. Photomicrographs were more accurate aids to identification than the line drawings in the literature and facilitated identification using dissecting microscope.

Animals↗

PubMed2006

Scanning electron microscopy evaluation of the effect of etching agents on human enamel surface.

Acid etching promotes microporosities on enamel surface, which provide a better bonding surface to adhesive materials. The purpose of this study was to comparatively analyze the microstructure of enamel surface after etching with 37% phosphoric acid or with two self-etching primers, Non-rinse conditioner (NRC) and Clearfil SE Bond (CSEB) using scanning electron microscopy. Thirty sound premolars were divided into 3 groups with ten teeth each: Group 1: the buccal surface was etched with 37% phosphoric acid for 15 seconds; Group 2: the buccal surface was etched with NRC for 20 seconds; Group 3: the buccal surface was etched with CSEB for 20 seconds. Teeth from Group 1 were rinsed with water; teeth from all groups were air-dried for 15 seconds. After that, all specimens were processed for scanning electron microscopy and analyzed in a Jeol 6100 SEM. The results showed deeper etching when the enamel surface was etched with 37% phosphoric acid, followed by NRC and CSEB. It is concluded that 37% phosphoric acid is still the best agent for a most effective enamel etching.

Acid Etching, Dental↗

PubMed1988

Zinc deficiency: specific scalp hair defects seen by scanning electron microscopy may provide a valuable new test.

Zinc deficiency in man results in multisystem disease. It may be acquired or hereditary; the latter can be fatal if left untreated. Premature babies are particularly susceptible to zinc deficiency. Unfortunately no simple, reliable test for zinc status exists at present. Short, newly-emerging scalp hair samples from 3 classical cases of zinc deficiency all showed the same characteristic abnormalities when examined by scanning electron microscopy, i.e. straight, blunt tips bearing scales, unusually thick cuticular scales with jagged free-edges, and very fine longitudinal corrugations in individual scales. These abnormal features occurring together appear to be specific for zinc deficiency; they also varied in severity with marked variations in zinc status during follow-up studies. Due to the relative rarity of classic cases of zinc deficiency, it is not possible for one centre of our catchment size to conduct a preplanned study. However, if the present findings can be confirmed elsewhere, it is concluded that scanning electron microscopy of appropriately-selected hairs may provide a valuable new test for the diagnosis of zinc deficiency and for monitoring the response to zinc therapy.

Child, Preschool↗

PubMed1997

Starch granule surface imaging using low-voltage scanning electron microscopy and atomic force microscopy.

High resolution imaging of wheat and potato starch granule surfaces has been performed using low-voltage scanning electron microscopy and atomic force microscopy. The complimentary images of uncoated granules demonstrate that the two starch types possess substantially different surface topologies; potato starch has many protrusions (100-300 nm in diameter), above a flatter surface containing 20-50 nm structures, whilst wheat starch possesses far fewer protrusions and generally has a smoother surface composed of approximately 20 nm structures. The protrusions are believed to be carbohydrate in nature and thus represent the ends of amylopectin side-chain clusters at the granule surface.

Microscopy, Atomic Force↗

PubMedDate not supplied

The role of scanning electron microscopy in the diagnosis of human laryngeal cancer.

Malignant and non-malignant human laryngeal tissue samples (31 cases) were examined first by light microscopy (LM) and then the specimens were reprocessed for scanning electron microscopy (SEM). The presence of LM and SEM signs of malignancy were compared with each other. In all the 22 histologically unambiguous cases the LM and SEM results were in accordance with each other. From the 9 histologically doubtful cases, 2 were found malignant and 3 benign by retrospective SEM. The case histories of these 5 patients have confirmed the SEM results. This preliminary study suggests the application of SEM in histologically doubtful laryngeal biopsies.

Carcinoma, Squamous Cell↗

PubMed2003

Adhesive interactions between CD34(+)-derived dendritic cell precursors and dermal microvascular endothelial cells studied by scanning electron microscopy.

Dendritic cells are migratory cells. Before they extravasate from the circulation into the skin across capillary blood vessel walls, they have to interact with endothelial cells. Using a fluorimetric adhesion assay, we have recently shown that CD34(+)-derived dendritic cell precursors are able to bind to resting and stimulated dermal microvascular endothelial cells. In the present study, we attempted to visualize this process at an ultrastructural level. CD34(+) progenitor cells were purified from human cord blood samples by means of immunomagnetic beads, and dendritic cells were generated by culture in the presence of GM-CSF, TNF-alpha and hSCF for 5 days. Immature CD83(-) CD86(low) dendritic cells were added to human dermal microvascular endothelial cells grown to confluence on membrane chambers. After 2 h, unbound dendritic cell precursors were removed, and bound cells were prepared for routine scanning electron microscopy. We found that (1). dendritic cell precursors firmly adhere to microvascular endothelial cells, enveloping them with their surface processes; (2). dendritic cell precursors are extremely deformable as they squeeze through the dense network of microvascular endothelial cells; (3). microvascular endothelial cells form, in part, a multi-layered network rather than the typical cobblestone pattern as seen by phase-contrast microscopy. The morphology of dendritic cell precursors and of human dermal microvascular endothelial cells was examined here, for the first time, by scanning electron microscopy. These data further emphasize that CD34(+)-derived dendritic cells efficiently adhere to dermal microvascular endothelial cells.

Antigens, CD34↗

PubMed2000

Atrial endocardial changes in mitral valve disease: a scanning electron microscopy study.

BACKGROUND: The precise contribution of left atrial appendage (LAA) endocardial damage and dysfunction to the process of thrombus formation in patients with mitral valve (MV) disease, especially in the presence of atrial fibrillation (AF), has not as yet been clearly described. This may be important because the LAA is the usual site for thrombus formation. METHODS: The purpose of this study was to describe endocardial surface changes, through the use of scanning electron microscopy, in the left and right atrial appendages of patients with MV disease and the differences, if any, between patients with mitral stenosis and mitral regurgitation as well as between those with AF and sinus rhythm. Our second objective was to relate endocardial changes to plasma levels of von Willebrand factor (vWf), an established marker for endothelial damage. LAA specimens were obtained immediately after commencement of cardiopulmonary bypass from 35 patients (18 men; mean age 65 years, range 20 to 85) during surgery for MV repair or replacement. Right atrial appendage (RAA) specimens were similarly obtained as controls for individual patients. The specimens were fixed in 2.5% glutaraldehyde solution overnight, stored in Sorensen's phosphate buffer, and examined by means of scanning electron microscopy. Two independent observers documented the most advanced lesion in each specimen as follows: (1) "minimal" changes, with minimal disruption of the endocardium; (2) "intermediate" changes or prethrombotic lesions; and (3) "advanced" changes, with endocardial disruption and thrombotic lesions. Plasma levels of vWf were also measured (enzyme-linked immunosorbent assay) in all patients, and results were compared with those of age- and sex-matched healthy control patients. RESULTS: Advanced changes were more frequently seen in the endocardium of the LAA when compared with the RAA (31% vs 6%), whereas minimal changes were more frequently seen in the RAA compared with the LAA (23% vs 6%) (P =.00167). Similarly, the LAA from patients with mitral stenosis had a higher proportion of "advanced" endocardial changes when compared with patients with mitral regurgitation (67% vs 24%; P =.0066). The LAA in patients with AF had more "advanced" changes (39% vs 27%), but this was not statistically significant. Plasma vWf levels were significantly higher in patients with MV disease compared with healthy control patients (132 +/- 33 IU/dL vs 99 +/- 37 IU/dL; P =.0004) and in patients with advanced LAA changes compared with earlier changes (149 +/- 34 IU/dL vs 121 +/- 31 IU/dL; P =.042). CONCLUSIONS: Endocardial damage occurs in the atrial appendages of patients with MV disease. Potentially thrombogenic changes are more commonly seen in the LAA compared with the RAA and in patients with mitral stenosis compared with mitral regurgitation. These anatomic appearances may contribute to the risk of intra-atrial thrombus formation in patients with mitral valve disease, especially if AF is present.

Adult↗