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Query: UMLS:C0432222 (SEM)
 47,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A 1-mm-thick section of a human premolar was acid etched and observed uncoated in the SEM at accelerating voltages of 3, 5, 10 and 15 kV. Prisms and interprismatic substance were easily distinguishable. Low-voltage operation (3 and 5 kV) gave the best results. Specimen charging was detectable at 5 kV and caused reduced image quality at 10 and 15 kV. Application of silver paste did not reduce charging appreciably. Prolonged observation at high magnification (x 10 000) resulted in contamination of the specimen with consequent charging and reduced resolution. Dental enamel seems to be a material which is well suited when uncoated for observation in the SEM. This may be due both to the high content of the relatively heavy atom calcium, giving good secondary electron emission, and possibly to a certain degree of conductivity caused by diffusible ions.
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PMID:Uncoated specimen of human enamel observed in the scanning electron microscope. 694 79

Normal and ischemic myocardium was prepared by slicing and cryofracture techniques for examination with the SEM. The tissues were dehydrated in ethanol and Freon 113 (slicing method) or were cryofractured in Freon 113 cooled with liquid nitrogen, followed by critical point drying and coating with gold and palladium. Some osmicated tissue pieces were treated with thiocarbohydrazide for examination without metal coating. Some hearts were infiltrated with silver particles and were examined with backscattered electron imaging technique (BSI). The cryofractured tissue provided the most useful and consistent surface features of the cell organelles with a minimum of mechanical disorder compared to other methods. Although the myocardium prepared by slicing method revealed the interior of the cells, it contained several frayed edges and loose myofibrils making interpretation of the ischemic myocardium difficult. The normal cells exhibited myofibrils covered by transverse tubules at the level of Z bands as confirmed by BSI using silver particles as an extracellular tracer and numerous oval to elongated mitochondria located between the myofibrils. An extensive network of tubules (sarcoplasmic reticulum) over the sarcomeres and nuclei were observed. The changes observed by SEM in the ischemic hearts were consistent with those seen in TEM. With prolonged coronary ligation the changes became obvious. The T-tubules were often broken and nuclei were distorted. The myofibrils were disorganized and formed homogeneous bands. These SEM studies suggest that myocardium prepared by cryofracture technique yields information on normal and ischemic cell structure consistent with data obtained by TEM.
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PMID:Preparation of normal and ischemic myocardial tissue for scanning electron microscopy. 716 67

A technique has been developed for the localization of isotopes in the scanning electron microscope. Autoradiographic studies have been performed using a model system and a unicellular biflagellate alga. One requirement of this technique is that all manipulations be carried out on samples that are maintained in a liquid state. Observations of a source of radiation (125I-ferritin) show that the nuclear emulsion used to detect radiation is active under these conditions. Efficiency measurement performed using 125I-ferritin indicate that 125-I-SEM autoradiography is an efficient process that exhibits a 'dose dependent' response. Two types of labeling methods were used with cells, surface labeling with 125I and internal labeling with 3H. Silver grains appeared on labeled cells after autoradiography, removal of residual gelatin and critical point drying. The location of grains was examined on a flagellated green alga (Chlamydomonas reinhardi) capable of undergoing cell fusion. Fusion experiments using labeled and unlabeled cells indicate that 1. Labeling is specific for incorporated radioactivity; 2. Cell surface structure is preserved in SEM autoradiographs and 3. The technique appears to produce reliable autoradiographs. Thus scanning electron microscope autoradiography should provide a new and useful experimental approach.
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PMID:Scanning electron microscope autoradiography of critical point dried biological samples. 725 1

Heads of seven different types of unused and used intravenous catheters as well as tips of the corresponding needles for venipuncture, artificially cut and ruptured surfaces were either directly mounted on stubs or previously fixed in 1% phosphate buffered glutaraldehyde (pH 7.4), dehydrated with acidified 2, 2-dimethoxy-propane, dried in a critical point drying apparatus using CO2, mounted with silver-paint and sputter coated with 20 nm gold. In addition tensile tests of unused catheters were carried out. According to the tensile tests and to the SEM findings neither spontaneous breakage nor manufacturing defects may be reason of catheter embolism. Manufacturing defects at the tips of needles for venipuncture, as well as rough surfaces of the introducers or catheter walls may cause endothelial lesions. Settling of formed elements of the blood apparently is related to ruggedness of the catheter wall or to manufacturing defects. Thrombi, grown on he outer surface of the catheters are very rare. In Cavafix catheters thrombus formation is mostly related to the roughness of radio-opaque parts of the catheter wall. Outgrowth of the thrombus via the top to the outer surface could be demonstrated frequently
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PMID:Surface morphology and tensile force at breaking point or different kinds of intravenous catheters before and after usage. 733 May 73

Similar to mercuric chloride, silver nitrate has recently been shown to induce IgG autoantibodies targeting the nucleolar 34-kDa protein fibrillarin i SJL (H-2s) mice. In the present study we show that the autoimmunogenic effect of silver is dependent on intact T-cell function since SJL/N mice homozygous for the nude mutation (athymic), in contrast to the functionally T-cell-intact SJL/N-nu/+ littermates, did not develop anti-nucleolar/anti-fibrillarin autoantibodies (ANoA/AFA). The genetic susceptibility for silver-induced AFA was localized to the H-2A locus using congenic and intra-H-2-recombinant strains. However, background (non-H-2) genetic factors substantially influenced both the response rate and the titer of ANoA/AFA attained. Strains bearing H-2As on the SJL and A backgrounds (SJL, A.SW, A.TH) showed 100% response rate and high ANoA titers (3750 +/- 246, mean reciprocal titer +/- SEM), whereas H-2As mice on the B10 background (B10.S) showed 60% response rate and significantly lower ANoA titers (1170 +/- 305) in the responding mice. Expression of H-2E [B10.S(9R) mice] further reduced the response rate (22%) and the ANoA titer (640 +/- 0). A suppressive effect on the B10 background has previously been observed in mercury treatment, but the effect was stronger in silver-treated mice. Two major differences were noted between silver- and mercury-induced murine autoimmunity. First, silver-treated mice did not show elevated titers of other autoantibody specificities, specifically not of antichromatin and anti-histone antibodies, which develop in mercury-treated SJL mice.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Genetic susceptibility to silver-induced anti-fibrillarin autoantibodies in mice. 758 39

Nucleolar organizer regions (NORs) are loops of DNA that transcribe to ribosomal RNA. They can be visualized as intranuclear black dots by histochemical staining with a colloid silver solution. We applied this method to 78 sections of endometrial tissue obtained either from curettage or from hysterectomy specimens. The histological diagnoses were as follows: normal proliferative (N = 9) or secretory (N = 5) endometrium, simple hyperplasia (N = 10), complex hyperplasia (N = 18), atypical hyperplasia (N = 8), and adenocarcinoma (N = 28). Mean silver-stained NOR (AgNOR) counts per cell were 3.2 (standard error of the mean [SEM], 0.2) in normal proliferative and 2.7 (SEM, 0.2) in normal secretory epithelium, and increased to 4.1 (SEM, 0.3) in simple hyperplasia, to 5.4 (SEM, 0.4) in complex hyperplasia, to 8.1 (SEM, 0.7) in atypical hyperplasia, and finally to 10.0 (SEM, 0.5) in endometrial carcinoma. The differences were significant (one-factor analysis of variance [ANOVA], P < .001). A slight increase but no significant difference was seen between the mean AgNOR counts in endometrial carcinomas of different histological grades. Our study suggests that AgNOR counts are reliable markers of endometrial proliferation and allow a clear distinction between benign, premalignant, and malignant epithelial changes. Our AgNOR findings in endometrial hyperplasia support the concept of various degrees of hyperplasia that can be differentiated on morphological grounds.
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PMID:Nucleolar organizer regions as markers of endometrial proliferation: a study of normal, hyperplastic, and neoplastic tissue. 777 98

Using a stereoscopic clearing protocol and scanning electron microscopy, we investigated the extent and nature of microleakage in a total-etch, current-generation dentin adhesive by a wet-bonding technique under different handling conditions. The hypotheses were that inadequate light curing of the primer or incomplete drying of the primer solvent might adversely affect the sealing ability of an acetone-containing adhesive system. The study consisted of three experimental groups: (I) a control group with an adequate light source and with the primer solvent completely dried; (II) an "inadequate-light" group; and (III) an "incomplete evaporation of primer solvent" group. The extent of microleakage after silver staining and clearing of the specimens was scored based on a modified five-point scale. Nonparametric statistical analysis (Kruskal-Wallis ANOVA) followed by a multiple comparison test (Dunn test) indicated significant differences among the three groups (p < 0.05). SEM examination of the restorative interface revealed that microleakage appeared to be initiated from the bonding resin-hybrid layer interface in all three groups, representing the weak link in the adhesive system. In addition, microleakage was characterized by 5 zones, each delineating a stage in a continuous array of progressively deleterious microleakage patterns variously distributed among the three groups. It was suggested that, while the bonding resin-hybrid layer interface represented the intrinsic weakness in an already much improved dentin adhesive, extrinsic factors such as the adequacy of the curing light and, more importantly, complete removal of the primer solvents can and should be avoided to preserve the structural integrity of the marginal seal.
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PMID:Variability in microleakage observed in a total-etch wet-bonding technique under different handling conditions. 779 May 94

Cyclosporine A (CsA) is a widely used immunosuppressant for transplant patients and is also used for the treatment of a wide variety of systemic diseases with immunologic components. A prominent side effect of CsA administration is gingival overgrowth. It has been postulated that CsA alters fibroblast activity through effects on various cytokines such as the interleukins, however, as yet, data concerning the molecular mechanisms involved in connective tissue proliferation are still preliminary in nature. The purpose of this study was to evaluate interleukin-6 (IL-6) gene expression in gingival tissues of patients receiving CsA therapy and exhibiting gingival overgrowth. Radioimmunoassay (RIA) demonstrated a significant difference in tissue levels of IL-6 as mean +/- SEM. IL-6 content in CsA-stimulated tissue was 184.3 +/- 30.2 ng/mg total protein versus 23.3 +/- 6.5 ng/mg total protein in control tissue. In situ hybridization indicated that overgrown gingival tissues from patients taking CsA had a significantly higher content of IL-6 mRNA when compared to control tissues. Expressing IL-6 mRNA levels as silver grains/cell, CsA-stimulated tissue had 166.9 +/- 12.0 grains of IL-6 mRNA/cell while control tissue had 12.8 +/- 3.0 grains of IL-6 mRNA/cell. These results demonstrate that CsA therapy results in increased levels of IL-6 protein and IL-6 mRNA in overgrown human gingival tissues. This is the first report of CsA-upregulated IL-6 gene expression in vivo, and may explain in part the molecular mechanisms responsible for CsA-induced gingival overgrowth.
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PMID:Cyclosporine A upregulates interleukin-6 gene expression in human gingiva: possible mechanism for gingival overgrowth. 782 69

This study evaluated the effect of various types of microfiller on the in vivo wear resistance of composite resins. Experimental light-cured composites with two different microfiller systems were prepared: (1) 56 wt % fine quartz filler, 21 wt% organic filler and 3 wt% colloidal silica filler (Hybrid type 1), and (2) 64 wt% fine quartz filler and 21 wt% colloidal silica filler (Hybrid type 2). The resin monomer consisted of 50 wt % Bis-GMA and 50 wt% TEGDMA. These materials were placed in 2 mm diameter cylindrical cavities located in the OCA (occlusal contact area) or the CFA (contact free area) in cast gold-silver-palladium alloy full coverage crowns, which were temporarily set in a volunteer patient's mouth. The crowns were removed at monthly intervals for SEM observation. Hybrid type 1, which contained organic fillers, showed bulk fractures in the OCA, by the second month of the experiment. However, reinforcement of the resin matrix by dispersion of microfiller provided Hybrid type 2 with superior wear resistance for up to two months.
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PMID:In vivo wear pattern of experimental light-cured hybrid composite resins. 800 17

The purpose of this study was to investigate marginal microleakage by examining the resin/dentin interface using a cryo-SEM and a silver ion penetration method. Class 5 cervical cavities were restored using an adhesive resin system following treatment with 37% phosphoric acid gel. The cavity wall adaptation was observed using cryo-SEM to avoid specimen damage. This observation showed excellent marginal adaptation of material to cavity walls and no gap formation. However, silver ions had penetrated beneath the resin-impregnated layer when observed with conventional SEM images, which showed the leakage of silver ions between the resin and decalcified tooth structure without gap formation. This study suggests that the bonding monomers of Clearfil Photo Bond were not fully able to penetrate into the demineralized dentin after phosphoric acid etching, thus leaving a porous zone as a microleakage pathway beneath the resin-impregnated layer.
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PMID:Microporous dentin zone beneath resin-impregnated layer. 800 12


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