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Query: UMLS:C0851184 (thinning)
 11,252 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A TEM specimen preparation method is described, with the aid of which electron transparent foils can be obtained across the external surface of a specimen. After careful pre-treatment, steel specimens have been electrolytically coated with nickel. Conventional thinning in a plane cutting the substrate-coating interface, gave thin foils displaying the internal structure as a function of depth under the initial free surface. The method has also been applied to minute metal particles, of dimensions too small to allow manipulating and foil preparation by conventional methods. Image examples are shown, and the applicability of the method is discussed.
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PMID:A specimen preparation technique for transmission electron microscopy of surface layers. 123 23

Photochemical etching (PCE) as a method for preparation of InP semiconductor plan view samples for the transmission electron microscope is demonstrated and compared to the methods of ion milling and chemical thinning. PCE can produce small area samples for TEM analysis quickly and accurately. Also, the resulting thin regions are surrounded by a built-in stabilizing structure that improves handleability and reduces the occurrence of handling induced fracture.
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PMID:InP sample preparation for the TEM by photochemical etching, ion milling, and chemical thinning. 147 54

Ductile phase toughened composites contain phases with significantly different physical properties. Consequently, these phases thin at different rates depending on the sample preparation procedure. A new TEM foil preparation method for the ductile phase toughened Nb-10 a/o Si material has been developed. The method involves chemical thinning in a 70% nitric acid/30% hydrofluoric acid solution followed by electropolishing in a 12.5% sulfuric acid/87.5% methanol electrolyte at -40 degrees C. This procedure for making TEM foils results in large thin areas with the minimum of artifacts. Mechanical grinding of a sample followed by either ion milling, dimpling, or electropolishing produced foils with large electron transparent areas, but with uncharacteristic features of the original Nb-10 a/o Si alloy microstructure. These artifacts were identified as dislocations, surface mottling, and antiphase domains.
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PMID:Preparation of TEM foils from Nb-10 a/o Si. 150 56

Using light, transmission (TEM) and scanning (SEM) electron microscopy, cocaine-induced defects were observed in hamster atria. Compared with controls, the treated atria from neonates show endocardial and myocardial damages as the atrial walls thicken. SEM micrographs show intensive blebbing, damage and incomplete coverage of myocardium by the endocardial endothelium. TEM data demonstrate blebs, thinning, and other endothelial cell injuries and complement the SEM findings. Areas of endothelial sloughing may facilitate the formation of luminal and mural thrombi as noticed in many neonatal atria. Adjacent subendocardial myocardial cells display contraction bands, swellings, and vacuolizations. Local and large areas of damaged myocardial cells are observed in the subendothelial spaces; they contact fibroblasts squeezed or intercalated between the subendocardial spaces and the basal side of damaged endothelial cells. Many of these defects correspond to well-known ischemic changes. One can hypothesize that cocaine-induced defects appear to be linked to membranous alterations, including those associated with the endothelial cells of the endocardium.
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PMID:Transplacental cardiotoxicity of cocaine: atrial damage following treatment in early pregnancy. 194 34

The response of ependyma to injury was investigated in rats following placement of bilateral lesions in the floor of the fourth ventricle. Animals were sacrificed from 2-60 days post-operatively and the brains were prepared in the conventional manner for comparative LM, SEM and TEM examination. For LM radioautography, randomly selected lesioned rats received either a single i.p. injection (5 muCi/g BW) or multiple injections (2 muCi/g) of 3H-thymidine prior to sacrifice. Focal disruption of the lining resulted in significant qualitative and quantitative changes in the ependyma at the wound margins. Labelling of normally quiescent ependymal cells occurred from day 2-6 post-operatively, however, the level of turnover was relatively low. Labelling was maximum on day 2 and was greater at the medial than lateral margin of the wound. During the first postoperative week, a gradual increase was observed in the number of ependymal cells per unit length at the margins of the wound concomitant with an abrupt reduction in wound diameter. This was consistent with the assumption that newly formed cells were added to the ependymal sheet at the leading edges of the wound. From 14-60 days after injury, further repair resulted from asymmetrical spreading and thinning of the ependymal sheet in the absence of mitotic activity. Quantitatively, this was reflected in a reduction in cell number at the leading edges of the wound that was most pronounced at the lateral margin. At day 60 neither epithelialization nor wound closure was complete and the normal architecture of the lining had not been fully restored. These results suggest that ependyma in the fourth ventricle of the postnatal rat undergoes a process of only limited repair following injury.
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PMID:Ependymal cells of the rat fourth ventricle: response to injury. 663 67

Industrial materials, such as alumina, often pose difficulties in their preparation for TEM examination. Composite and particulate materials are particularly difficult to prepare using conventional thinning techniques, i.e., ion beam and chemical jet thinning. Ultramicrotomy (UM) can be used to produce TEM specimens with a uniform thickness and an unaltered composition. Some crystalline materials, i.e., alumina hydrate, were difficult to section due to conflict between the cutting direction and cleavage planes. Sectioning was successful when these two directions were mutually parallel or perpendicular. At other orientations shattering occurred. Microcrystalline particulate materials, i.e., calcined alumina, were sectioned successfully in particles < 70 microns in diameter. The phases found in industrial alumina particles were gamma, delta, theta, and alpha alumina. Gamma alumina consisted of fine-grained, equiaxed crystallites. The selected area electron diffraction (SAED) patterns indicated poor crystallinity with a distinct hexagonal texture. Delta and theta alumina appeared as an undifferentiated intermediary microstructure of elongated grains. The SAED patterns indicated poor crystallinity, but without a distinct texture. Alpha alumina was found to be a coarse-grained crystalline phase with high diffraction contrast. SAED patterns consisted of fine, randomly oriented spots. Considerable variation was observed in the distribution of phases. In some specimens, discrete particles of gamma and alpha predominated. In others, particles were a mixture of phases representative of the bulk composition. To characterise these samples, TEM of numerous whole particles was required. Ultramicrotomy was the only preparation technique capable of producing such samples.
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PMID:Ultramicrotomy of industrial alumina. 754 3

The aim of this study was to examine the development of chorionic villous trees during early periods of normal intrauterinal and ectopic (tubal) pregnancies, and to study the structural specializations on the free surface of mature placental villi by scanning and transmission electron microscope (SEM and TEM). In order to study the structures of placental villi between 28 and 34 days old (pc), early, 6-8 week normal and ectopic, and full term human placenta samples were obtained from legal curettage and hysterectomized cases, and spontaneous deliveries, and tissues samples were prepared for SEM and TEM. Three-dimensional configurations of the developing chorionic villous trees were observed as large main villus groups, covered with abundant microvilli of different size and diameters. It appeared that the chorionic villous trees which emerged from the chorionic plate divided gradually into branches of which ramifications originated as buds. These buds gradually grew and were transformed into shoots. The number of developing new villi appeared to increase gradually from 28 days to 9 weeks (pm) of gestation. From the 4th week onwards the massive trophoblastic sprouts were observed on the surface of main chorionic villi which transformed into primary, secondary and tertiary villous trees. When the placental villi formation in ectopic pregnancy was compared with the intra-uterinal pregnancy, an arrested development was remarkable. The configurations of ectopic placental villi seemed to be disparate, such as curved lines or compressed and wrinkled positions so that the three dimensional aspect had been wizened. The ramification and new villi formation seen as in the normal placenta were not only decreased but also infrequent. Some placental villi samples displayed a gradually thinning terminal region. Trophoblastic degenerations were frequently found on the surface of ectopic villi ultrastructurally. According to these results, we comment that in ectopic pregnancy the placental villi formation and development could have been delayed. At term, some specialized structural modifications were observed on the free surface of the mature placental villi. The presence of some dome-like balloonings and many crateriform hollows were the most striking features of the mature intermediate and terminal villi. According to the increasing physiological needs of the growing fetus, these special structures that are related to lung-like and kidney-like functions and named "nephropneumonic-like units", formed in the mature placental barrier. We have observed that these special units were showing a smooth surface similar to an inflated balloon.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:The fine structure of normal and ectopic (tubal) human placental villi as revealed by scanning and transmission electron microscopy. 775 46

A preparational method was developed solving the problem of cross-sectional TEM preparation of thin films and layer systems deposited onto water-soluble substrates. The technique is based on the replacement of the sample onto steady substrate, followed by mechanical and ion beam thinning. Cross-sectional TEM micrographs of Ag and Ag/Ag2Se layers are shown presenting the efficiency of this novel technique.
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PMID:A novel method for the cross-sectional TEM preparation of thin films deposited onto water-soluble substrates. 835 85

A mouse model for the autosomal form of Alport syndrome was produced. These mice develop a progressive glomerulonephritis with microhematuria and proteinuria, consistent with the human disease. End-stage renal disease develops at approximately 14 weeks of age. TEM analysis of the glomerular basement membranes (GBM) during development of renal pathology revealed focal multilaminated thickening and thinning beginning in the external capillary loops at 4 weeks and spreading throughout the GBM by 8 weeks. By 14 weeks, half of the glomeruli were fibrotic with collapsed capillaries. Immunofluorescence analysis of the GBM showed the absence of type IV collagen alpha-3, alpha-4, and alpha-5 chains and a persistence of alpha-1 and alpha-2 chains (these chains normally localize to the mesangial matrix). Northern blot analysis using probes specific for the collagen chains illustrate the absence of COL4A3 in the knockout, whereas mRNAs for the remaining chains are unchanged. An accumulation of fibronectin, heparan sulfate proteoglycan, laminin-1, and entactin was observed in the GBM of the affected animals. The temporal and spatial pattern of accumulation was consistent with that for thickening of the GBM as observed by TEM. Thus, expression of these basement membrane-associated proteins may be involved in the progression of Alport renal disease pathogenesis. The levels of mRNAs encoding the basement membrane-associated proteins at 7 weeks were unchanged.
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PMID:Collagen COL4A3 knockout: a mouse model for autosomal Alport syndrome. 895 99

Poly(vinyl acetate-co-ethylene) latex dispersions are prepared and their films investigated with a focus on the effect of composition upon redispersion. Films of dispersions containing sufficient amounts of poly(vinyl alcohol) (PVA) can be redispersed in water. This property is lost in the presence of surfactant, a fact which suggests a procedure to control film formation. It is demonstrated that redispersion is due to a PVA-membrane which separates the particles. Loss of redispersibility in the presence of surfactant proceeds with the breakup of the membranes and a corresponding change of film properties. Experimental data is provided by light microscopy, mechanical testing, and TEM in conjunction with a staining method new to the field. The hypothesis is developed that interaction with surfactant leads to imperfect PVA-membranes that are no longer able to prevent latex polymer interdiffusion. Fluorescence correlation spectroscopy demonstrates the formation of surfactant micelles, as well as the simultaneous adsorption and aggregation of PVA onto the micelles. It is concluded that the competing surface of the surfactant micelles traps enough PVA to cause thinning and fragmentation of the membranes surrounding the particles, which enables interdiffusion of latex polymer. This effect can be used to convert the system from one forming a redispersible coating to one forming a nonredispersible (permanent) film. Copyright 2000 Academic Press.
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PMID:Film Formation and Redispersion of Waterborne Latex Coatings. 1070 97


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