摘要:

SUMMARYA combination of optical microscopy and electron‐probe microanalysis (EPMA) has been used to study the phases which occur during reduction of the mineral ilmenite to metallic iron and titanium oxides. Quantitative EPMA of natural and chemically‐processed minerals frequently suffers from variable specimen conductivity caused by the porosity and varying texture of the mineral grains. It has been found, however, that the element concentration ratios are largely independent of porosity and texture and can be used to identify the phases with precision.The microprobe has revealed some hitherto unsuspected effects arising from small concentrations of magnesium and manganese dissolved in the ilmenite lattice. The morphology and composition of the reduced product are in fact controlled by the way in which these impurity solutes segregate within the mineral grains during reduct

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1973.tb04624.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

SUMMARYThe most frequently used method of enabling aqueous suspensions of small, particulate, biological specimens to spread on the hydrophobic support films required for electron microscopy, is to add a surface‐active compound to the suspensions. The requirements of an ideal wetting agent for use in this situation are outlined. The polypeptide bacitracin has been found to meet all these requirements, and it is superior to the commonly‐used bovine serum albumin (BSA) in several respects. Bacitracin molecules are much smaller than those of BSA, and unlike BSA molecules they are not visualized by negative staining. Thus bacitracin produces a very even background against which the fine details of a specimen can be more easily interpreted. It facilitates the penetration of negative stain into small crevices and it produces a smaller halo of negative stain around specimen particles. Its use for spreading electron dense specimens is also demonstrated. Bacitracin is compatible with at least five commonly‐used negative stains, namely ammonium molybdate, potassium phosphotungstate (KPT), potassium silicotungstate, sodium tungstate and uranyl acetate. It is also biologically acceptable for use with a wide range of specimens. There is no evidence of bacitracin causing damage to specimens examined representing macromolecules, animal, plant and bacterial viruses, bacteria and subcellular organ

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1973.tb04625.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

SUMMARYWhen preparing specimens for shadowing it is frequently necessary to add a wetting agent to aqueous suspensions to enable them to spread on hydrophobic support films. However high‐resolution platinum/carbon shadowing is capable of visualizing wetting agent molecules, so the effect of added wetting agent on the final appearance of the specimen must be considered. To facilitate interpretation of the specimen fine detail the background should be smooth and flat. This is achieved by using the concentration of wetting agent which produces a close‐packed monolayer of wetting agent molecules after drying. Bacitracin is a better wetting agent for use when shadowing than the commonly‐used bovine serum albumin (BSA). Because its molecules are smaller than those of BSA, the size of the background granularity is smaller, which facilitates interpretation of the specimen, and the layer of wetting agent molecules is thinner, so small specimen details are less likely to be buried and rendered invisible to the shadowing process. These points are described in detail and illustrated with the help of models where nece

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1973.tb04626.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

SUMMARYThe cross‐sectional profiles of jet polished electron microscope disc specimens have been measured as a function of (1) jet diameter, (2) electrolyte velocity, (3) jet to specimen distance, (4) lip thickness of clamping disc and (5) material used for the clamping disc. It is found that the optimum values of these parameters varies according to the material/electrolyte combination. However, a fault‐finding table has been devised which enables the optimum conditions to be found rapidly for any mater

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1973.tb04627.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

SUMMARYExperimental evaluation of component volume proportions may require the introduction of a component‐biased sampling approach in order to facilitate the unequivocal identification of cell type. Such is certainly the case for macrophages, neurons and cells of the lymphocyte‐plasma cell family. With these systems, mathematical corrections are necessary so that reliable morphometric information can be computed from the biased data. The type of correction procedure adopted will depend, to some extent, on the spatial relationships between the component of interest (nucleus, nucleolus) and its containing volume (cell, nucleus). In this communication, correction formulae for the special cases of spatial concentricity and eccentricity are derived. Their usefulness is illustrated by application to a number of well‐known model systems, and a reference table for obtaining the appropriate true volume proportion from observed (biased) data is provided. The reliability of the component‐biased morphometric approach is thereby in

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1973.tb04628.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

SUMMARYStereologic point counting procedures were applied to estimate volumetric and numerical densities of tissue components residing in and forming a defined, simplified model of human marginal gingiva. This included the quantitative characterization of inflammatory cell infiltrates occurring in the epithelial as well as the connective tissue fractions of this model. The gingival tissue was harvested from defined intraoral sites of 9–15 year‐old children and processed under standardized conditions for light and electron microscopic observation. Random cross‐sections of this tissue were subjected to morphometric analysis based on a multistage sampling technique. At each sampling level, tests were performed to study (1) the suitability of different test systems, (2) the parameter variation within one and between different biopsies and (3) the comparability and reliability of the data obtained. Based on these tests, a morphometric technique was designed which resulted in an accurate estimation of the various parameters characterizing the model tissue. These parameters were the volumetric densities of the following constituents: oral epithelium, junctional epithelium and its leucocyte content, infiltrated and non‐infiltrated connective tissue, and its respective collagen fibre content. Infiltrated and non‐infiltrated connective tissue fractions were analysed for their respective volumetric and numerical densities of fibroblasts, neutrophilic granulocytes, monocytes, macrophages, small and medium‐sized lymphocytes, immunoblasts, plasma cells and mast cells. Sampling technique, test procedures and the design and results of the morphometric system ar

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1973.tb04629.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

SUMMARYA semi‐automated system has been developed for the measurement of cell (perikaryal), nuclear and nucleolar areas. The system consists essentially of a Graf/Pen data tablet (with its associated acoustical stylus and tablet electronics), an optical input system such as a camera lucida, and a small digital computer. The perikaryal, nuclear and nucleolar outlines are traced in sequence with the stylus which, on contacting the tablet surface, emits a high frequency acoustic wave that is sensed by X and Y strip microphones along the left and upper edges of the tablet. The acoustic signal is converted by a simple program into a series ofXandYcoordinates which are sampled at several points around the perimeter of the profile. When the stylus tip re‐enters a 1 mm stationary window set up around the starting point, the measurement is automatically terminated and the data for this profile is printed out and stored in memory for subsequent statistical analysis. The system has an overall accuracy of about 1% and in practice it has been possible to measure objects at least ten times more rapidly than by any of the other currently available methods. The hardware and software features of the system are detailed and a number of additional uses for the system are descri

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1973.tb04630.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

SUMMARYA new storage container for freeze‐etch specimens is described which (1) dramatically reduces the loss of liquid nitrogen from the storage dewar, (2) which always sits on the bottom of the dewar and can be quickly identified and retrieved therefrom, (3) which cannot open accidentally during long term storage and (4) which can withstand continual exposure to temperature extremes. Using such containers over 300 different kinds of specimens can be readily stored in a 30 1 liquid nitrogen dewa

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1973.tb04631.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

SUMMARYCommercially available photographic equipment can be used to study specimens histologically in three dimensions. Thirty‐five millimetre colour transparencies are made of serial sections at desired intervals using a photomicroscope with a rotatable stage. The series of transparencies is projected in alternate fashion using two identical projectors linked by a dissolve control. The method has proved useful in anatomic and embryologie studies and presentations as well as in evaluation of pathologic material in which initial histology revealed an abnormality that could be clarified by three‐dimensional st

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1973.tb04632.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

SUMMARYA device to improve the awkward handling and processing of Polaroid type 55 P/N film used with scanning electron microscopes can be constructed from Plexiglass and 1, 2 dichloroethane.

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1973.tb04633.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY