bluuebunny/crossref_metadata_2025 huggingface dataset:
A method for increasing the photographic contrast of electron micrographs
Authors: Farnell G. C. , Flint R. B.
Published: August 2011

Emulsion‐developer combinations used regularly in conventional electron micrography yield an approximately linear relationship between density (D) and exposure (E) up to quite high densities (> 2.0). This is due to the fact that over the corresponding exposure range the density yield per electron is approximately constant. A practical consequence is that the slope of the D/log10 curve, termed the contrast, is a function of D only, i.e. it is independent of the emulsion‐developer combination.

To achieve higher than normal contrast requires that the density yield per electron should increase with exposure over some exposure range, at least. This effect may be obtained by using what are known commercially as ‘lith’ films and a system of infectious development. The high contrast of such films results from an acceleration of development rate when the developer oxidation products reach a critical concentration.

Sensitometric data are presented for electron exposures which show that for average densities of ∼ 1.0 in a micrograph a six‐fold increase of contrast can be obtained with a ‘lith’ system. It is also shown that though the special development effect gives higher granularity than that obtained at the same exposure with a conventional system, the signal/noise ratio is not adversely affected. Practical demonstrations of the effectiveness of the ‘lith’ system are presented.
The use of the ‘tissue sectioner’ in selecting histological features for electron microscopical study
Authors: Hallowes R. C. , Streek P. W.
Published: August 2011

A method is described which enables rapid and accurate localization of scattered or randomly occurring histological features in 10–30 mm3 of tissue for subsequent examination with the electron microscope. Examples of selecting a histological feature and individual cells are illustrated.
Reconstruction of microscopic objects by photographing serial sections onto cine film for projection
Authors: Senior W.
Published: August 2011

By using standard cine‐micrography apparatus in conjunction with a simple turntable under the microscope it is possible to locate and orient serial sections for sequential photography on cine film. The location of the sections is sufficiently accurate to enable the film to be projected at normal speeds. The effect is to produce a steady image giving the viewer the impression of travelling through the specimen. This can assist in the interpretation of serial sections and in the three‐dimensional reconstruction of microscopic structures.

The film loops thus obtained can also be used directly for teaching purposes, allowing students to obtain quickly the mental images required for a three‐dimensional understanding of microstructure.

The method can be used in interpreting any series of sections without special preparation. It is particularly valuable for embryological studies and for investigating elongated sub‐structures such as blood vessels.
Negative staining and cellulose microfibril size
Authors: Preston R. D.
Published: August 2011

Reason is given for the belief that an overlapping of images ensures a gross underestimate of cellulose microfibril width in plant cell walls observed both in section and negatively stained. Both theory and optical simulation of the electron‐microscope situation suggest that the error involves a factor of at least two or three times. These, and other considerations render doubtful the existence of elementary microfibrils as components of the broad (c. 20 nm) microfibrils of some seaweeds.
Aspects of scanning microdensitometry: II. Spot size, focus and resolution
Authors: Goldstein D. J.
Published: August 2011

In scanning microdensitometry increasing the size of the measuring spot, or throwing the specimen out of focus, decreases the apparent integrated absorbance ApEp of a discrete specimen. Both experimental observations and elementary geometrical theory (i.e. ignoring diffraction effects) show that with moderate spot sizes the relative error in ApEp is greater with small objects or objects of high absorbance, and that with a given object the absolute error is approximately proportional to the spot diameter (round spot) or spot width (square spot). From the observed apparent integrated absorbances AE1 and AE2 obtained using measuring spots of width s1 and s2 respectively, the true integrated absorbance AE0 corresponding to zero spot size can therefore be calculated from the approximate expression

which reduces to

With very large spot sizes, or with the specimen grossly out of focus, the apparent integrated absorbance of a specimen of radius R and transmittance It tends theoretically to a limit:

ApEp = 0.4343πR2 (I‐It). Provided the true absorbance of the specimen does not exceed about 0.5 at any point, the true integrated absorbance could in principle be estimated with less than 3% error from the expression

but in practice ApEp can probably not be measured with sufficient accuracy.

In scanning measurements of apparent specimen area, the results depend both on the threshold absorbance used and the size of the flying spot. With low thresholds the apparent area of the specimen at first increases and later decreases, as the spot size is increased or as the focus is changed.
Preparation of plant material for scanning electron microscopy*
Authors: Idle D. B.
Published: August 2011

A general method is described which reduces shrinkage in plant material and which avoids the need for metal coating. The method must be adapted to particular tissues and techniques of observation.
Correlateci light optical and scanning electron microscopy of Gram smears of bacteria and paraffin sections of cardiac muscle*
Authors: Geissinger H. D.
Published: August 2011

Light‐microscope slides (3 in. × 1 in.) bearing Gram smears of Erysipelothrix rhusiopathiæ, or Staphylococcus aureus, after preliminary examination under the light‐optical microscope (LM), were cut down in size, glued onto specimen stubs, coated with gold and examined in the scanning electron microscope (SEM). These preparations served as a control for investigations into bacteria‐cell junctions in tissue.

Cover‐slips from stained sections of staphylococcal or swine erysipelas endocarditis mounted on 3 in. × 1 in. microscope slides (which had been intensively studied previously with conventional light microscopy) were floated off by immersing the slides in xylol. After dehydration of the tissues on the slides, the preparations were treated similarly to the Gram smears, and were examined with the SEM. Lesions of endocarditis were thus examined, and the information gained from these preliminary examinations shed new light on the pathogenesis of the disease. This information had not previously been available by any other technique. Because of this, and in view of the simplicity of preparing sections for scanning electron microscopy, it is suggested that the SEM might be a useful tool to be applied to routine histological sections.
Preparing chromosomes for scanning electron microscopy without enzymic digestion*
Authors: Pawlowitzki I. H. , Blaschke R.
Published: August 2011

Chromosomes can be visualized in the scanning electron microscope only after the surface coating of non‐chromosomal proteins has been removed. A method of removal is described which is based on the principle of protein extraction following mechanical injury to living cells.
Rapid preparation of plant tissues for electron microscopy
Authors: Bain Joan M. , Gove D. W.
Published: August 2011

Various plant tissues were prepared for electron microscopy using a rapid process similar to that of Hayat & Giaquinta (1970) for animal tissue. The entire preparation took less than 4 h instead of the several days taken for the usual method and gave very good results. Root, leaf and fruit tissues were used.
The passage of cytoplasmic vesicles across endothelial and mesothelial cells
Authors: Smith J. R. Casley‐ , Chin J. C.
Published: August 2011

The proportions of labelled cytoplasmic vesicles, at increasing distances across mouse heart endothelium and diaphragmatic mesothelium, were studied using the following electron‐microscopical tracers: ferritin, horseradish peroxidase and sodium ferrocyanide. The cells were incubated in Hank's solution containing the tracer for periods of 2 sec up to 30 min.

Peroxidase labelled the vesicles well, but ferrocyanide may have escaped from them into the cytoplasm. Both passed down the intercellular junctions. Ferritin showed evidence of molecular sieving when entering the vesicles, and probably also suffered from this on leaving them. It was possible to allow for these effects.

The vesicles containing tracers were found to have traversed the cells after only a few seconds; by approximately 10 sec a steady‐state was observed, after which there were constant proportions of labelled vesicles. These proportions decreased slightly, but not sharply, across the cells. It was found that the observed distributions across the cells were very similar to those predicted by diffusion theory, assuming the following postulates: (1) the vesicles are moved solely by Brownian motion; (2) a low (i.e. α = 0.05) probability that a collision with a plasma membrane results in fusion. If however it was assumed that the fusion probability (α) were unity, the observed distributions of labelled vesicles differed very significantly from those predicted. A possible explanation of the observed low value of α is suggested, based on mutually‐repelling charges on the vesicles and membranes.

If α is given a value of around 0.05, the observations agree with calculated predictions that the median transit times for vesicles through cells 0.3–0.5 μm wide are approximately 3–5 sec and that the cytoplasmic viscosity is approximately 0.2–0.3 poise. The predictions of vesicular median free lives of‐ sec and median attachment times of 3–5 sec also received confirmation, as did the prediction that some 40% of the released vesicles regain the membrane on the opposite side of the cell.
A method for preparing complementary halves of freeze‐etch replicas of micro‐organisms for transmission electron microscoy
Authors: Veltri B. J. , Mcalear J. H.
Published: August 2011

Freeze‐etch replicas are frequently difficult to interpret because of uncertainties arising from various artifacts arising mainly from height differences and the plane of fracture. Some of this confusion has been clarified by the production of complementary replicas (Steere, 1969), and the use of stereography (McAlear et al., 1969; McAlear, Shatos & Veltri, 1969), which enable the relativeposition of structural elements to be determined more accurately. This report describes the application of stereography to freeze‐etch replicas of both complementary halves of a fracture sample. A replica of each half is micrographed in stereo by tilting the specimen between micrographs (McAlear & Veltri, 1971). These are then displayed as adjacent complementary images which may be viewed in stereo.
High‐resolution scanning electron microscopy of the surface of red blood cells
Authors: Clarke J. A. , Broers A. N. , Salsbury A. J.
Published: August 2011

Examination of normal human red blood cells with a high (2.5 nm) resolution scanning electron microscope revealed a definite surface pattern. The pattern was slightly more pronounced in specimens dried in air after fixation than in those dried by the critical‐point method. There was a radial arrangement of filament like elevations at the periphery of the red cell and a more reticular pattern to wards the centre of the cell. The appearances probably represented a network of elenin fibres lying just under the surface of the red cell.
A simple method for cutting out selected areas from material embedded on slides for electron microscoy
Authors: Ellis D. S.
Published: August 2011

A simple apparatus is described which enables small plugs of resin containing required specimens to be removed from material (such as smears) previously embedded for electron microscopy on flat microscope slides, without damage, and leaving the remaining material protected for further use.
Visualization of collagen cross‐banding in the scanning electron microscope
Authors: Finlay J. B. , Hunter J. A. A.
Published: August 2011

Micrographs are presented to show that the characteristic molecular cross‐banding of human dermal collagen can be visualized in the scanning electron microscope. The specimen‐preparation technique used is described together with a discussion of the various conditions necessary for the visualization of the cross‐banding.
The preparation of field‐ion‐microscope specimens containing grain boundaries
Authors: Papazian J. M.
Published: August 2011

A back polishing technique has been devised which increases the efficiency of a field‐ion‐microscope study of grain boundaries. The rate of back polishing is predicted from the relationship dmd = 2·5 × 104 nm2/msec. This relationship is shown to be valid experimentally and theoretically. Its validity implies the persistence of constant current density conditions during electropolishing of sharp, needle‐shaped specimens down to diameters of 100 nm.
Dark‐field electron microscopy of unstained and unshadowed DNA*
Authors: Haydon Glen B. , Lemons Ross A. , Clayton David A.
Published: August 2011

The vastly increased contrast made possible by tilted‐beam dark‐field electron microscopy enables strands of DNA prepared by the Kleinschmidt technique to be clearly imaged without the heavy‐metal staining or shadowing usually required. This technique is applicable over a wide range of magnifications and is easily accomplished with several commercial instruments.
Vermiculite lamellae as substrates for transmission electron microscopy
Authors: Manley J. H. , Williams D. L. , Okinaka R.
Published: August 2011

Chemically exfoliated vermiculite has been investigated as a specimen‐support film for electron microscope. The thinnest lamellæ obtained appear to be less than 1 μg/cm2 (∼4 nm) thick, have low electron noise and show good stability in the electron beam. Their surface is smooth and hydrophilic and phase texture is low.
The use of polarized light microscopy in examining the structure of carbon fibres*
Authors: Knibbs R. H.
Published: August 2011

The structure of carbon fibres has been examined using the optical microscope. Three types of fibre structure have been identified which differ in the orientation of the graphite crystallites within the transverse plane, the type of precursor can be identified by the shape of the carbonized fibre. The particular type of structure is determined by the process conditions which the fibre has undergone. Subsequent heat treatment merely enhances the crystallite alignment of the structure without altering the direction of preferred orientation.
An improved microspectrofluorimeter with automatic digital data logging: Construction and operation
Authors: Rost F. W. D. , Pearse A. G. E.
Published: August 2011

This paper describes an instrument for microspectrofluorimetry, based on the Leitz microspectrograph. Important features are monochromatic epi‐illumination, a reference channel and a measuring system using photon counting with automatic recording of data in digital form. To minimize fading, measurements of fluorescence intensity can be made within as little as 200 msec from the commencement of irradiation.
Some microscopic aspects of the mild wear of steel*
Authors: Quinn T. F. J.
Published: August 2011

The paper reviews the experimental classifications of the unlubricated sliding wear of metals, together with some of the suggested relationships between the wear rates, the real area of contact, the load, the hardnesses of the metals and the probability of producing wear particles at the real areas of contact. The microscopic nature of the interactions between sliding surfaces is discussed, with special emphasis on the advantages (and limitations) of using electron microscopy for studying these interactions, and the importance of using X‐ray diffraction techniques to complementthe electron microscopy.

Examples are then given of how the use of electron microscopy has revealed many facets of the mild wear of steel which would not otherwise have been suspected. For instance, the areas of contact between sliding steel surfaces are comparatively large and few in number, in contradistinction to the situation occurring in stationary contact. These large contact areas crack in a characteristic fashion reminiscent of fatigue failure or brittle fracture. They then flake off at a critical thickness (∼ 10−4cm) to provide the source for the wear debris. The wear debris collects initially in the rough regions which are left behind when the flakes become detached. In this position, the wear debris probably acts in an abrasive fashion.

Eventually, the wear debris is thrown clear of the contact area. Analysis of this debris using X‐ray diffraction techniques has shown that there is a strong correlation between the presence of certain oxides in the wear debris and the severity or mildness of the wear. It has also been used to estimate the temperatures occurring between the areas in sliding contact. This estimate is consistent with previously published dynamic thermocouple measurements. It also gives rise to consistent values of the activation energy required for oxidation during wear.
Metal oxide structure investigated using a variety of light‐ and electron‐microscopical techniques*
Authors: Fursey Anita
Published: August 2011

Special techniques for examining the same specimen area of metal oxides with different instruments, for example light microscopy and scanning electron microscopy of identical features are described. Transmission electron microscopy and diffraction on stripped oxide films have been augmented by electron‐probe microanalysis both in a conventional microanalyser and in a combined electron‐microscope microanalyser EMMA‐4. Examples of scanning electron microscopy of oxidized sheet‐metal specimens and stripped films are given and probe analysis in the Stereoscan is illustrated. High‐voltage electron microscopy of oxide nodules reveals additional detail. Techniques for examining thick oxide scales are also described. The illustrations are taken from the oxidation of iron 10% chromium alloy at 500−600°C in air.
Electron‐microscope preparation techniques applied to the light microscopy of the cambium and its derivatives in Pinus radiataD. Don.
Authors: Barnett J. R.
Published: August 2011

Epon 812 was used successfully as an embedding medium for the preparation of the secondary meristem and its derivatives in Pinus radiata for light microscopy. Specimens were fixed in glutaraldehyde followed by osmium tetroxide solution, using a schedule developed for the electron microscopy of these tissues. Sections from 2 to 5 μm thick were cut using an LKB Ultratome III and glass knives. Sections were evaluated without prior removal of the embedding medium using bright‐field, phase‐contrast and interference‐contrast microscopy. Results for cambium were generally superior to those obtained by using the conventional fixatives for light microscopy and paraffin embedding. The advantages and disadvantages of this technique are discussed and it is concluded that the use of Epon for embedding this type of material is easier and gives better results than older established methods. It is suggested that methods of electron microscopy be considered when the preparation of a material for light microscopy has proved difficult or impossible by other means, or when particularly thin sections are required.
A method for preparing living plant cell walls for scanning electron microscopy
Authors: Briarty L. G.
Published: August 2011

A method is described for the preparation for scanning electron microscopy of cell walls from living plant cells. The method involves digestion with a protease followed by freeze‐drying, and enables wall details to be clearly observed.
Capillary‐tube units for individual block preparation in light and electron microscopy*
Authors: Galey Frank R. , Dunn Robert F.
Published: August 2011

Short lengths of 4‐mm capillary tubing are fitted with teflon caps for processing individual blocks in preparation for light‐ and electron‐microscopic observation. The processing units hold a nickel mesh grid to prevent tissue loss. Advantages include: (1) the ability to process very small blocks otherwise lost during processing; (2) separation of tissue from specifically mapped areas; (3) conservation of processing fluids and time.

For routine tissue dehydration and infiltration, it is generally possible to process many tissue blocks collectively. However, instances frequently occur in which it is necessary to treat individual blocks separately. Examples include processing of single muscle fibres, and individual sensory regions where it is desirable to separate various segments of the sensory organ.

This paper describes specially prepared capped capillary tubes for the purpose of individual block preparation. These containers are advantageous in conservation of fluids, ease of specimen transfer, and most importantly strict isolation of the individual blocks of tissue.
The effect of radio‐frequency sputter ion etching and ion‐beam etching on biological material: a scanning electron microscope study
Authors: Hodges Gisele M. , Muir Marjorie D. , Sella C. , Carteaud A. J. P.
Published: August 2011

Mammalian and avian cells have been examined in the scanning electron microscope either after prior radio‐frequency sputter ion etching with different ions (hydrogen, helium, argon, oxygen) or after argon ion bombardment in the SEM. Whilst the pattern of erosion is similar in the different specimens, the etching pattern varies with the different gases. It has not been possible to relate the etching patterns to characteristic subsurface structures.
Evidence against through‐section thawing whilst cutting on the ultracryotome
Authors: Hodson Stuart , Marshall John
Published: August 2011

We present evidence that ultrathin frozen sections cut on the ultracryotome only partially thaw during the cutting action. This conclusion is derived from calculations of the loss of mechanical energy as the specimen strikes the knife. The mechanical energy is assumed to be completely transformed into heat which warms the freshly cut section.
Field‐ion microscopy in colour using multiple imaging gases
Authors: Schubert C. C.
Published: August 2011

When channel plate intensification methods are used in field‐ion microscopy, image gases other than hydrogen and helium give bright images easily photographed with colour film. Since different phases in the specimen image differently with differing gases, colour photography through filters yields micrographs which accentuate these phase differences.
The use of silver nitrate as a stain for scanning electron microscopy of arterial intima and paraffin sections of kidney
Authors: Geissinger H. D.
Published: August 2011

The suitability of silver nitrate as a stain for scanning electron microscopy was investigated. Accordingly en face preparations of arterial intima were impregnated with silver nitrate, fixed with formalin, and coated with platinum‐palladium alloy. In SEM images, the silver lines surrounding the endothelial cells, and the deposits on the intima appear as white lines or dots on a darker background. Similar results were noted for nitrocellulose‐embedded endothelium. Paraffin sections of kidney treated with silver nitrate (von Kossa's stain) were also examined. Deposits of the calcium salts of phosphates and carbonates (stained with silver nitrate) were easily differentiated from other tissue components. Results were compared with those obtained with the light microscope. The scanning electron microscopic examination provided a finer definition of the silver granules relative to the surrounding architecture. The limitations and advantages of these techniques and possible further applications of silver nitrate as a stain for scanning electron microscopy are discussed. The use of silver nitrate as a stain for some SEM preparations is recommended.
A three‐dimensional model of membrane ruffling from transmission and scanning electron microscopy of cultured monkey kidney cells (LLCMK2)*
Authors: Price Zane H.
Published: August 2011

Three‐dimensional models of ruffling membrane were constructed by assembling enlarged Styrofoam duplicates of serial sections. The serial sections were taken from a cultured monkey kidney (LLCMK2) cell and were cut at right angles to the plane of the substrate. Various features of the models were corroborated by scanning electron microscopy.
A new single‐drop technique for the observation of dynamic blood coagulation
Authors: Ford Brian J.
Published: August 2011

A single‐drop method is described in which blood specimens may be observed in dynamic coagulation, in an artificially produced cellular environment. The method is eminently suitable for rapid, repeatable observations of hæmostatic phenomena on a routine basis.
The problem of paired spheres and of straight chains of spheres in slices or polished sections
Authors: Hennig August
Published: August 2011

The starting point is the problem of finding the percentage q2 of paired nuclei in liver cells, when the percentage p2 of twin cuts in slices is known. The general solution for unequal spheres becomes most simple for equal spheres and leads to an extrapolation for endless straight chains of equal spheres, at first for closed and then for open series with constant intervals. Three total sums of endless series of fractions are a welcome mathematical extra.

The microscopist will prefer instructions which are generalized from counts in final rows of spheres. With them he can analyse the composition of a mixture of limited chains, with different numbers of spheres.
Interference microscopy of polymer fibres*
Authors: Pluta M.
Published: August 2011

The paper describes the use of a double refracting interference microscope with variable amount and direction of wavefront shear for the study of synthetic polymer fibres. General theoretical aspects of the field of the differential interference contrast method, and practical problems related to the application of this method in fibre examination are discussed. Some improvements in the micro‐interferometric measurement of the birefringence and refractive indices of fibres are suggested. Advantages of the developed double refracting interference microscope with variable wavefront shear are discussed from the point of view of fibre microscopy, and illustrated by photomicrographs.
Fracture faces of the tonoplast in root tips after various conditions of pretreatment prior to freeze‐etching
Authors: Fineran B. A.
Published: August 2011

Roots grown in glycerol and frozen‐etched show fracture faces of the tonoplast covered with particles having a density distribution on face A different from that on face B. In contrast, roots prefixed in glutaraldehyde prior to freezing show tonoplasts either with particle populations comparable to those in frozen living cells, particles interspersed with plaques, plaques only, or surfaces devoid of both particles and plaques. Membranes with plaques are the most frequently found. Plaques occur as slightly raised structures and with approximately equal frequency on faces A and B of the tonoplast. Other membranes of the cell seldom show plaques and resemble those of unfixed roots. Plaques occur independently of the concentration of glutaraldehyde or glycerol, the stage at which buffer is added during the schedule, and whether fixation is simultaneous with glycerination or followed by glycerination. It is argued that plaques are the result of contamination during etching rather than being due to an alteration in the plane of fracturing. It would appear that prefixation enhances the formation of plaques by altering the properties of the tonoplast so that the membrane acts as a site for the selective condensation of contaminant material.
A preliminary field‐ion microscopic study of a Co‐Ti alloy
Authors: Davies D. M. , Ralph B.
Published: August 2011

A study has been made of the initial stages of decomposition of a supersaturated solid solution of a cobalt alloy containing 7·5 atomic percent titanium. It is shown that the initial precipitation of Co‐Ti is periodic (along < 100 >) and that spacings and sizes measured by field‐ion microscopy agree well with those measured by transmission electron microscopy and from ‘sidebands’ on X‐ray diffraction photographs. The experimental conditions under which contrast between the precipitate and matrix may be obtained are discussed.
A method for quantifying electron staining, obtaining the dry specific gravity of specimens in sections, and measuring section thickness
Authors: Casley‐Smith J. R.
Published: August 2011

Methods are described for the estimation of the dry specific gravities (SG) of specimens in thin sections, especially for the comparison of one group with another and for the quantification of electron stains. Variations in section thickness are overcome by using the naked supporting film as a base‐line, and relating the SG of the specimen to that of the resin, which acts as a standard. Section thicknesses may also be estimated by using similar methods. The optical densities of their images are compared with those of standards; knowledge of the SG of the resin allows one to calculate its thickness.
Two electronic devices for cinemicrography of living cells
Authors: Parsons Roger , Blogg T. , Smith J. W.
Published: August 2011

Electronic devices for the control of culture environmental temperature and for a more flexible operation of the cine camera are described with circuit diagrams. The advantage(s) and limitations of each device are discussed.
An inexpensive device for increasing the usefulness of the comparison eyepiece in examining slide‐mounted ectoparasitic insects
Authors: Pilgrim R. L. C.
Published: August 2011

Construction and use are described for a stand to enable either or both microscopes to be rotated while examining pairs of specimens through a comparison eyepiece. The device facilitates accurate orientation of the images, enabling rapid and critical detection of similarities or differences between them.
The Biomicroscope and Vickers image splitting eyepiece applied to the diurnal variation in human central corneal thickness
Authors: Gerstman Daniel R.
Published: August 2011

To summarize, it is found that the human cornea thins approximately 7% throughout the waking hours in air. Assuming the corneal constants given by Gullstrand for his schematic eye No. 1, a 7% decrease in corneal thickness would represent a decrease of only 0·00385 diopters in the refractive power of the human cornea.
Reduction of polymer growth in electron microscopes by use of a fluorocarbon oxide pump fluid
Authors: Ambrose B. K. , Holland L. , Laurenson L.
Published: August 2011

A commonly experienced contamination problem in electron microscopes is the growth of electron induced polymer films on the electrodes and specimens in instruments evacuated by oil pumps. Hydrocarbon fluids are generally used in the vacuum pumps and experiments have been made to reduce the contamination rate in a transmission instrument (AEI 802) by using fractional distillates of a new fluorocarbon oxide compound. The rotary pump was replaced by one charged with a fluorocarbon oxide lubricant and the fluid charge in the diffusion pump replaced by a fluorocarbon oxide evaporant. Both specimen and electrode contamination were greatly reduced by the use of the new fluid. Electron micrographs of a gold film are shown comparing contamination levels produced in organic and fluorocarbon oxide atmospheres after prolonged exposure to the electron beam.
A microwelder for the preparation of electron microscope central wire beam‐stopping apertures
Authors: Brown J. N.
Published: August 2011

A simple capacitor discharge microwelder is described together with a method for the preparation of electron microscope central wire beam‐stopping apertures.
The stereology of projected images
Authors: Underwood Ervin E.
Published: August 2011

A generalized, geometrical approach is adopted in reviewing the basic relationships of projected structures. Projections of features from a plane to a projection line, and from a three‐dimensional foil to a projection plane are considered briefly. The relationships that apply to apparent and total projections are next assembled for lines, surfaces and bounded regions. The properties of convex bodies, the geometrical attributes, and the related projected quantities are enumerated. The inter‐relationships of important microstructural parameters are expressed for convex bodies in space, in sections, and in the projection plane.

Based on the important concept of total projection, expressions are obtained that correct for truncation and overlap of particles in foils. Approximations to the total projection are developed for lines obscured by surfaces, and for points hidden by surfaces in space. Finally methods for determining size distributions of particles in thin foils are reviewed and recent modifications to the original procedures are discussed.
Stereological methods applied to mineralogy, petrology, mineral deposits and ceramics
Authors: Amstutz G. C. , Giger H.
Published: August 2011

Firstly, the present development towards a quantitative stereometric (or stereofabric) analysis of mineral aggregates (rocks, ores, concentrates, snow, slags, ceramic materials, cements, etc.) is put into a historic framework. Secondly, the details of the methods and the difficulties still existing are outlined. Finally, a summary is given of the mathematical approaches (with a tabulation of basic formulae), together with some typical examples.
Stereological methods in the analysis of neuronal parameters in the central nervous system*
Authors: Haug Herbert
Published: August 2011

The structure of the central nervous system (CNS) is briefly explained. It is compared with the electronic computer and the differences between the two are stated. The methods of measuring this structure and its function are reported.

The surface of the cortex as well as the volume of different grey and white matters making up the brain can macroscopically be evaluated on serial slices with the aid of stereological procedures. There is an exponential correlation between volume of the cortex and volume of brain and body in mammals (Fig. 3).

The density of neurons and the lengths of their processes can be examined by light microscopy. An improved procedure of counting neurons in the cortex is described. With regard to mammals it is interesting that the densities of neurons in larger brains are lower than in smaller ones. The correlation is negatively exponential. Man and primates have a higher density of cells than the rest of the mammals; their neurons, however, are small. This corresponds to a specialization that can be considered to represent a miniaturization of the neurons (Fig. 4). The topological analysis of dendritic trees is mentioned. The lengths, surfaces and volumes of processes of cells and the amount of synapses can be measured on electron micrographs. The principles and problems of stereology are described by an example of how to measure the myelinated fibres. Some results of the development of these fibres from birth on are reported upon (Fig. 6). In conclusion, some data of the probable dimensions of the human brain are given.
A stereological method for estimating volume and surface of sarcoplasmic reticulum
Authors: Weibel Ewald R.
Published: August 2011

The stereological analysis of volume and surface of sarcoplasmic reticulum tubules in muscle cells meets with particular problems because these structures are (a) highly oriented in the longitudinal direction of the muscle cells, (b) lined up in parallel, (c) periodically arranged in relation to sarcomeres and (d) internally symmetrical in analogy to sarcomere symmetry. On the whole this system may be characterized as a parallel linear array of units with translational‐reflexive symmetry. On the basis of a simple model it is demonstrated that the problems of sampling and stereological measurement can be overcome if a combination of oblique and transverse sections are used. The procedure can be simplified to operate exclusively with oblique sections only slightly inclined to the transverse plane if a small systematic error can be accepted.
A computer technique for the estimation of the absolute three‐dimensional array of basal dendritic fields using data from projected histological sections
Authors: Berry M. , Anderson E. M. , Hollingworth T. , Flinn R. M.
Published: August 2011

The standard projection methods of dendritic field analysis have revealed that dendritic density decays exponentially with increasing distance from the centre of the perikaryon and present ideas about dendritic connectivity are largely based on this theory. However, inherent in the projection method are a series of errors which have not hitherto been defined and which indicate that much of the data obtained by the projection technique may be an artefact of the method itself. However, it is possible, given the projection data from a sample of neurons, to extrapolate the three‐dimensional array of dendritic fields by employing a computer technique.

In this technique the perikaryon is enclosed in concentric spheres set 20 mμ apart and dendritic endings (E) and branching nodes (B) are positioned within the volume of the total sphere according to known distributions. The number of dendritic intersections (I) at the surface of the nth concentric sphere can be calculated given the number of primary dendrites from the relationship; I(n − 1) + Bn — En. These numbers may then be corrected for the distortion due to projection and sectioning. Comparison of these corrected data with those obtained from conventional histological methods suggests that the distribution of dendritic parameters may be quite different from the conventionally held view and that the decay of dendritic density is not exponential.
Influence of depth of information and of resolution in stereologic evaluation of surface electron micrographs
Authors: Bode M. , Pfefferkorn G. , Schur K. , Wegmann L.
Published: August 2011

Due to the difference in preparation technique, the submicroscopic structure of metals, minerals and ceramics is often easier to evaluate with surface electron micrographs of bulk specimens than with transmission electron micrographs of thin films. As in the latter case, a surface electron micrograph also contains information from a certain depth which for stereologic evaluation necessitates a correction. This correction depends on the relation of grain size, depth of information and resolution. Experimental studies lead to the following results:

With 20 keV scanning electron micrographs showing a material contrast resolution between 50 and 200 nm, depending on the material, stereometric analyses are influenced by the depth of information for grain sizes between 1 and 25 μm. Furthermore, the results of analysis are influenced by ‘microscope distortion’ and by ‘distortion of single micrographs’. Depth of information and distortions have the effect that the grain distribution image of polished sections may differ by some percent from an ideal section image. An automatic microstructure analysis seems to be nearly impossible because of variations of photographic density obtained from different particles of one and the same phase.

For photo‐emission electron micrographs with a material resolution between 15 and 30 nm depending on the material, the influence of the depth of information, microscope distortion and distortions of single micrographs may be neglected. Therefore, such micrographs are well suited for manual or automatic stereometric analysis.
Morphometric analysis of a fibre system in the central nervous system
Authors: Tlreff W. M. , Meyer‐König E. , Schlote W.
Published: August 2011

The authors have studied the size and composition of the rat optic nerve at three points along its course.

The relative volume of myelinated nerve fibres increases that of the chiasma, whereas the relative volume of interstitium decreases. The decrease of interstitial volume is mainly related to the decrease of glial cell number. Determination of absolute volumes of myelinated fibres and interstitium shows that the volume changes are due to two factors:

(a) From the eyebulb to the intermediate portion the interstitial volume decreases, whereas the absolute volume of myelinated fibres remains constant.

(b) From the intermediate portion to the chiasma the volume of myelinated fibres increases significantly, whereas the further decrease of interstitial volume is small.

The diameter of nerve cross‐section is significantly smaller in the intermediate portion of the optic nerve than near the eyebulb and the chiasma. Here the nerve passes the canalis opticus. The density of glial cells decreases from eyebulb to the chiasma as does the density of pericytes and endothelial cells. The latter makes up only 2·3–3·9% of the density of cells in the interstitial space. The mean volume of a glial cell remains constant at about 1260 μm3 along the path of the optic nerve from eyebulb to chiasma. The number of myelinated nerve fibres is also constant along the path of the optic nerve. There are 107,000 ± 6900 fibres.
A histometric thyroid gland activation index (preliminary report)
Authors: Kališnik Miroslav
Published: August 2011

A histometric thyroid gland activation index has been proposed as a quotient between the mean voluminal percentage of the epithelial cells and the colloid. A positive correlation between the blood TSH level and this index is supposed.
The photo‐emission electron microscope: Its technique and applications
Authors: Wlegmann L.
Published: August 2011

This article gives a survey of the actual experience with the relatively new technique of photo‐emission electron microscopy. After describing the principal technique and the features of a modern high resolution instrument, the questions of image generation, contrast formation and resolution are considered. In particular the influence of the depth of information on resolution for flat polished sections is studied and some comparisons with the scanning electron microscope (SEM) are made.* The different fields of application of the photo‐EEM are shown by examples.
Light microscopic demonstration of myoid fibres in the nervous system
Authors: Waldrop Faye Sweat , Puchtler Holde , Valentine Linda S.
Published: August 2011

In 1968 Puszkin and co‐workers isolated from brain an actomyosin‐like protein which was not derived from the vascular system. Since corresponding myofibrils had not been described in histology, the tannic acid‐phosphomolybdic acid‐Levanol Fast Cyanine 5RN stain for myosin and related proteins was applied to methacarn‐fixed paraffin sections of human central nervous system (CNS) and peripheral nerve. Extensive meshworks of myoid fibres were found in the marginal layer and in white matter. Spider‐like cells containing myoid fibres were found in some areas of grey matter. Many axons of peripheral nerves were surrounded by myoid material, but myelin sheaths in CNS were apparently extracted by the fixative.

Correlation of these observations with histochemical, electron microscopic and X‐ray diffraction data indicated similarity of the distribution of myoid fibres and fibrous astrocytes; the astrocyte fibres show the X‐ray diffraction pattern of a‐helical proteins. The myoid material in peripheral nerve is apparently associated with the myelin sheath. This pilot study suggests that the actomyosin‐like protein isolated from brain is probably derived from glia fibres which show the staining and X‐ray diffraction properties of proteins of the myosin‐fibrin group.
A theory of field‐ion imaging: I. A quasi‐classical site‐current formula
Authors: Forbes Richard G.
Published: August 2011

A quasi‐classical formulation of field‐ion imaging theory is defined and discussed. Concepts and terminology are defined, and a formula is established for the ion current generated above a single surface site.
The design and construction of a computer‐compatible system to measure and record optical retardation with a polarizing or interference microscope
Authors: Dvorak James A. , Clem Thomas R. , Stotler Woodrow F.
Published: August 2011

The design, construction and operation of a computer‐compatible system to measure and record optical retardation with a polarizing or interference microscope is described. The system consists of a high precision potentiometer linked directly to the drum vernier of a compensator or analyser. A highly stabilized fixed voltage is applied to the potentiometer and the voltage difference between the potentiometer wiper and one end of the resistance element is directly proportional to the compensator or analyser angle. This voltage is converted to a digital format, interfaced with a digital time base and stored on punched paper tape for subsequent computer analysis.
A new slide rule for electron microscopy
Authors: Emanuilov Ivan
Published: August 2011

The principle and the mechanism of a new slide rule is explained and its possible application to solving all of the tasks in electron microscopy with respect to the calculation of sizes, magnifications etc.
A method of freeze‐drying and fixing spermatazoa for electron microscopy
Authors: Johnston H. S. , Reid O.
Published: August 2011

A procedure is described whereby freshly ejaculated bull semen is freeze‐dried, then treated by glutaraldehyde fixative and processed for electron microscope observation of the spermatozoa. Some of the structural features of bull spermatozoa are demonstrated in electron micrographs.

In general the procedure may be found useful as an alternative technique for the examination of such cell‐carrying fluids as whole blood, cerebrospinal fluid, as well as bacterial cultures.
Autoradiographic studies on the mode of growth in jejunal crypt cells of the mouse
Authors: Maurer W. , Schultze B. , Schmeer A. C. , Haack V.
Published: August 2011

Cell kinetic parameters of the jejunal crypt epithelia of the mouse were reinvestigated to determine if a steady state system with constant frequency distribution of cells throughout the cycle exists and if all cells which are labelled after an injection of 3H‐thymidine subsequently divide.

3H‐ and 14C‐thymidine double labelling experiments indicated that the cell flux into and out of S‐phase is equal and are a direct experimental proof of the existence of a steady state.

A generation time of 14 h was obtained by a 3H‐ and 14C‐thymidine double labelling modification of the percent labelled mitoses method and a proliferative pool size of 75% determined.

Evidence is presented that synthesis of metabolic DNA does not occur in the crypt.
An evaluation of various double labelling and autoradiographic techniques for the measurement of DNA synthesis time in leukaemic cells*
Authors: Harriss E. B. , Hoelzer D.
Published: August 2011

Before applying the double labelling technique to the measurement of DNA synthesis time in leukaemic cells, various methods of labelling and of autoradiography were compared.

The use of low and high doses of 3H‐thymidine proved to be impracticable because, owing to a wide range of uptake per cell, it was impossible to make a clear distinction between ‘lightly’ and ‘heavily’ labelled cells. Two consecutive doses of 3H‐thymidine resulted in only a small increase in labelling index because of the low percentage of cells in the S‐phase and the long duration of DNA synthesis. Consequently, it was not possible to establish the DNA synthesis time with any degree of accuracy by this method.

The remaining method employs 3H‐thymidine and 14C‐thymidine. Auto‐radiographs made with a single emulsion proved difficult to interpret since some 14C‐labelled cells give the appearance of being labelled with 3H‐thymidine only. A double emulsion autoradiographic technique is to be preferred, but even then, more than one interval between the two isotopes is necessary in order to eliminate an error in the recognition of 14C‐labelled cells.