ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1991.tb03110.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SUMMARYWhen the zero‐loss transmission falls below 10−3for biological sections of mass‐thickness greater than 70 μg/cm2, the energy window in the electron spectroscopic imaging (ESI) mode of an energy‐filtering electron microscope (EFEM) can be shifted to the most‐probable energy loss of the electron energy‐loss spectrum. This enables mass‐thicknesses up to 150 μg/cm2or thicknesses of 1·5 μm to be examined. Electron energy‐loss spectra of thick carbon films calculated by a Fourier method agree with experimental spectra. Measurements of the electron energy‐loss spectroscopy and ESI image intensities with an additional platinum film confirm a scattering model for the calculation of the image intensity. This model considers the angular broadening at the most‐probable energy loss by introducing an effective illumination aperture of the order of the full‐width at half‐maximum

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1991.tb03111.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SUMMARYThe possibilities of using electron energy‐loss spectroscopy (EELS) for quantification of elemental concentrations in ultrathin sections are examined. Dynabeads, which are polystyrene beads with a known iron content, are proposed as internal iron standards. The quantity of an element present depends on the thickness of the specimen. A prerequisite for estimation of absolute section thicknesses with EELS is the knowledge of the mean free path λ of electrons in the specimen. This factor is determined for the embedding resins Epon and Nanoplast by comparing EELS data with directly observed thicknesses in re‐embedded sections. Dynabeads were found to include iron in a homogeneous distribution and to be stable in the electron

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1991.tb03112.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SUMMARYA computer program for quantitative spectral analysis is proposed for the elemental analysis of biological material by electron energy‐loss spectroscopy in a conventional transmission electron microscope, the Zeiss EM902. Bio‐standards are used to test the performance of this program. The application of a simplex optimization method for curve‐fitting is proposed to separate the ionization edge from the background. Making use of Ce‐, Ca‐ and Fe‐bio‐standards, this method is compared with Egerton's well‐known

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1991.tb03113.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SUMMARYElectron energy‐loss spectroscopy (EELS) has been used to determine elemental concentrations in biological specimens, consisting of ultrathin‐sectioned cells and tissues. Chelex100‐based Ca‐ and Fe Bio‐standards are used for elemental quantification to establish iron and calcium concentrations. These Bio‐standards, as well as the biological materials, are treated in a standard EM procedure such that ‘known’ and ‘unknown’ sites are located in one cross‐section.Uncertainties and variabilities present in the equations for calculating the concentration in the ‘unknown’ site (determined by comparing simplex‐fitted EEL spectra from Bio‐standards with those from tissue) are outlined in two examples. Using an H+Bio‐standard, the matrix composition of such biological cell material is analysed, leading to values which approach each other closely. Quantitative EELS, using Chelex100‐

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1991.tb03114.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SUMMARYA Zeiss EM902 microscope was connected to a PC‐AT computer, equipped with a Data Translation DT2861 frame grabber board. Using this system, the three‐window background extrapolation algorithm was implemented to perform elemental mapping in the electron spectroscopic imaging mode of an energy filtering transmission electron microsc

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1991.tb03115.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SUMMARYA personal computer combined with lotus 1‐2‐3® software, including the RS232 module of lotus measure® and a 12‐bit ADC, has been used for data acquisition of electron energy‐loss spectroscopy (EELS) spectra with the Zeiss CEM 902. The internal macro language of lotus 1‐2‐3 allows a menu‐driven procedure. Macro‐programs partly combined with externalFORTRANprograms can be chosen from the menu for background subtraction, removal of multiple scattering effects by deconvolution, elemental quantification and several utilities. For special applications or conditions the macro programs can easily be modified.Spectra from crystals of two inorganic transition metal compounds, ruthenium trichloride and vanadium disulphide, and from a biological sample are presented as examples of the application

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1991.tb03116.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SUMMARYLiving plant cells were embedded in the water‐soluble resin Nanoplast FB 101 and cut into ultrathin sections. Non‐vacuolated cells of algae and fungi showed a satisfactory preservation of fine structure. First results of elemental mapping by the ESI technique indicate that phosphorus and sulphur are neither extracted nor dislocated within the cells.The authors are members of the ‘Study Group for Electron Microscopy’ at the Hannover School of Veterinary M

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1991.tb03117.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SUMMARYComputer‐aided 3‐D reconstruction of typanosomes from 0·35‐μm‐thick sections imaged on the Zeiss 902 electron microscope are being used to study the dynamics of cell organization. Segregation of glycolytic enzymes into glycosomes raises questions concerning the distribution and biogenesis of these organelles. Direct counts of glycosomes fromTrypanosoma evansiindicate 30–40 per cell and for the closely relatedT. brucei, 65 per cell. These figures contrast with the estimates of others who have used model‐based morphometric methods to obtain a value of

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1991.tb03118.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SUMMARYDifferent conventional methods of tissue processing were studied to determine the extent to which phospholipid‐rich multilamellar bodies of pulmonary alveolar epithelial type II cells of the pig were preserved. Prolonged treatment with half‐saturated aqueous uranyl acetate yielded excellent results on the stabilization of the multilamellar substructure, irrespective of whether glutaraldehyde‐paraformaldehyde or glutaraldehydetannic acid was used as a primary fixative. The lamellar periodicities were observed to be 5·5–6·1 nm.Differences in the phosphorus distribution among several types of lipid bodies of alveolar epithelial type II cells were studied by means of electron spectroscopic imaging and electron energy‐loss spectroscopy. Multilamellar bodies gave phosphorus signals which were significantly higher than those obtained from granular regions of composite bodies, whereas homogeneous bodies gave phosphorus signals which were even lower than those obtained from mitochondria, endoplasmic reticulum membranes o

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1991.tb03119.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY