摘要:

SUMMARYThe correlation that exists between elemental concentration ratios determined using EDX and EELS is examined. EELS and EDX were recorded simultaneously from the second phase carbides of a ferritic steel and the Cr/Fe and Mn/Fe concentration ratios were determined from each spectrum. For this system, it was found that the Cr/Fe ratios could be determined by EDX to within an accuracy of 4% and these were then used to provide a check on the EELS analysis procedures. The effects of using different partial ionization cross‐section models and methods of applying these models were examined. It was found that an overall agreement of 3% between EDX and EELS was obtained in this particular experiment. Much poorer agreement was found to exist between the two techniques for the Mn/Fe ratios. The discrepancy is attributed mainly to the inadequacies of the procedure used for extracting the Mn characteristic signal in the EELS spectr

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1987.tb01322.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

SUMMARYThe techniques of reflection electron microscopy (REM) using TEM instruments and scanning reflection electron microscopy (SREM) using STEM instruments have been explored as means for the observation of surface structure with high spatial resolution, better than 1 nm in each case. Under the ordinary environment of a commercial TEM instrument, we have studied the contrast in REM images of atomic steps and made comparison with the calculated results from the multi‐slice dynamical diffraction theory. Comparison has also been made between the REM images of defects and the calculated images based on the column approximation. The influence of surface resonances on the contrast has been investigated. By SREM performed in a modified HB5 STEM with attached high vacuum preparation chamber, we have observed the formation of periodically distributed Pd particles on the surface of cleaved Mg

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1987.tb01323.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

SUMMARYThe reactions of XTH‐2 cells (line derived fromXenopus laevistadpole hearts) to cytochalasin D (CD) were followed using scanning acoustic microscopy (SAM) at 0.9 GHz, fluorescence and electron microscopy. The first reaction to CD which can be detected by SAM is a loss of image contrast, indicating a decrease in acoustic impedance of about 30%. Based on structural changes revealed by staining of actin with TRITC‐phalloidin, and taking theoretical considerations into account, a relationship between impedance decrease and tension in the actin fibrillar system is dedu

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1987.tb01324.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

SUMMARYIt has been stated that interference fringes are asymmetrically distributed in the image plane of some double‐refracting microinterferometers. This defect is especially produced by typical birefringent Wollaston prisms and is responsible for some errors in the measurement of optical path differences. In particular, the errors arise when the interfringe spacing is directly measured in the image plane or determined from an interferogram recorded on a photographic materia

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1987.tb01325.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

SUMMARYWe have designed a microcomputer system to reproduce 3‐D tissue structures graphically from serial microscopic sections. The system, based on a Hewlett‐Packard model 310 desktop computer, comprises a floppy disc drive, a hard‐disc that extends the available user memory by adding 40 Mbytes, a colour memory‐mapped graphics display, a graphics tablet and a graphics printer. A set of serial 2‐D images, manually extracted from serial sections using a microprojector, are digitized on the tablet by tracing the contours of the structure of interest; up to ten different structures can be inputted and reproduced using a ‘hidden line’ effect. The software, written mainly in HP‐BASIC 4.0, produces 3‐D pictures of a tissue structure either as a ‘stack of slices' with or without being ‘tiled’ with triangular patches, or in ‘wire framing’. Any angle of rotation around thex, yandzaxes is assigned for the image to be reconstructed, allowing the operator to obtain the best perspective. The system also discloses the internal connectivity of an object by reducing the structure to a network diagram; this is especially useful in analysing the topological properties of tissue structure. It is shown how, in some examples, the system contributes to a better understanding of tissue microstructures and their morbid changes and how, as an effective tool in morphology, it will aid future studies of h

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1987.tb01326.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

SUMMARYLocal dry mass or water fractions can be measured on frozen‐dried cryosections assuming constant section thickness in the hydrated state and no net water movements and no differential shrinkage during freezing and drying. These assumptions have been tested on a model consisting of isolated rat liver mitochondria in an albumin matrix with a concentration similar to the dry mass concentration of the cytoplasm.The dry mass concentrations of mitochondria before freezing as measured by interference microscopy and after freezing and freeze‐drying of the sections as measured by X‐ray microanalysis and scanning microdensitometry are shown to be equal as long as the ice crystals in the medium are smaller than about 100 nm. It is concluded, therefore, that the above‐mentioned assumptions could also hold for the cryopreparation of cells and

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1987.tb01327.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

SUMMARYLocal dry mass concentrations of intracellular compartments in rat heart muscle and liver cells were estimated by quantitative electron microscopy and X‐ray microanalysis of ultrathin frozen‐dried cryosections. The results were used to calculate elemental concentrations per litre of compartment water from the X‐ray microanalytical data.Water fractions were between 80.3 ± 1.3% of wet weight in the decondensed chromatin and only 45.1 ± 1.7% in mitochondria of liver cells. The lowest water fraction in heart muscle cells was also found in mitochondria. The ionic concentrations found in the cytoplasm of liver cells and in the myofibrils are in accord with the electroneutrality rule and in osmotic equilibrium with the extracellular concentrations. The concentrations of Na, K, Cl and P both in the cytoplasm and in the regions of decondensed chromatin within the nuclei were found to be equal.However, in regions of condensed chromatin K+concentrations were found to be much higher than expected for a Donnan distribution of ions free in solution. Most probably the activity coefficient for K+is lower in the condensed chromatin than in the decondensed or in the cytoplasm. The same holds true for the A‐band as compared to the I‐band in heart muscle cells. A sequestration of K+was measured also in the rough endoplasmic reticulum (RER) of hepatocytes. The Cl−concentration in mitochondria both in heart muscle and liver cells has been measured far in excess of what might be expected from a Nernstian distribution. A coupled inward Cl−transport in mitochondria must, theref

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1987.tb01328.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

SUMMARYSince commercial samples of the fluorochrome SITS (sodium 4‐acetamido‐4′‐isothiocyanatostilbene‐2,2′disulphonate) are of varied, and often of uncertain, composition, the synthesis of SITS has been repeated. The identities of SITS and certain of its precursors and derivatives have been established using modern spectroscopic methods (IR,1H and13C NMR), as well as microanalysis. When pure SITS underwent hydrolysis at room temperature the products were amines, not the expected thioureas. This suggests that SITS, contrary to previous expectations, will not bind covalently to proteins, whether immunoglobulins or membrane constituents. Again contrary to earlier statements, pure SITS is not retrogradely transported in neuronal axons. The transported material is a red‐orange impurity which arises very occasionally during the preparation of SITS. A possible structure for this red‐orange compound is proposed: namely a dimeric azo or azoxy condensation product. Comparison of pure SITS with commercial samples indicated that the latter were extremely varied in composition, with SITS contents varying from

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1987.tb01329.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

SUMMARYA method for quantitative scanning electron microscopy (SEM) at low magnifications has been developed. Quantitative measurements in SEM are rare and often not accurate, because of a systematical error, i.e. a nominal magnification exists only in one direction of the photograph. Our method is suitable for smooth surfaces as it proves the changes of magnification within the two‐dimensional range. In a first step EM‐grids are used as samples. In a second step it is shown how the method can be applied to biological specimens. We took the microstructure ofHelix pomatiashells as exam

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1987.tb01330.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

SUMMARYA synthetic corundum (Al2O3, synthetic ruby, synthetic sapphire) knife has been constructed which is suitable for the preparation of thin sections (less than 90 nm) of biological specimens for electron microscopy. The method involved cleavage or fracture of the flame‐fusion crystalline product, followed by mounting in a standard knife holder for ultramicrotomy. The cutting edge appeared flawless under 400 × and produced sections in which subcellular organelles were clearly resolved. Scanning electron microscopy of the knife revealed conchoidal fractures typical for corundum, terminating in apparent cleavage of the crystal along the knife edge. X‐ray microanalysis of the knife edge revealed essentially 100% aluminium, indicating that the aluminium oxide crystal was of a high purity. The superior toughness and low cost of synthetic corundum suggest that it may be a useful alternative to diamond or glass kn

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1987.tb01331.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY