bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

SUMMARYThe 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

SUMMARYDue 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

SUMMARYThe 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.
The photo‐emission electron microscope: Its technique and applications
Authors: Wlegmann L. 
Published: August 2011

SUMMARYThis 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

SUMMARYIn 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.
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

SUMMARYThe 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 method of freeze‐drying and fixing spermatazoa for electron microscopy
Authors: Johnston H. S. , Reid O. 
Published: August 2011

SUMMARYA 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

SUMMARYCell 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

SUMMARYBefore 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.
Microautoradiography of diffusible ions in plant tissues: problems and methods
Authors: Sanderson J. 
Published: August 2011

SUMMARYA procedure for the preparation of autoradiography of diffusible ions in plant tissues is described. Special procedures are necessary to support the tissue, and minimize redistribution of ions during the various stages of the preparation.The principal features of the procedure are: rapid freezing of tissues after harvest; tissue embedding in methyl cellulose; section cutting in the cryostat at −20°C and section mounting onto photographic emulsion at −20°C; photographic exposure at −25°C; and finally development and mounting so that the autoradiograph lies over the section.By comparing the grain densities on autoradiographs of plant sections with autoradiographs prepared from standard sources, of known specific activity, it is possible to evaluate the results quantitatively.
High voltage electron microscopy of the central nervous system in Golgi preparations
Authors: Palay Sanford L. , Chan‐Palay Victoria 
Published: August 2011

SUMMARYHigh voltage electron microscopy was applied to sections of cerebellar cortex prepared by the Golgi method and embedded in epoxy resin. The silver chromate deposit in the cells consists of a fine, fibrillar meshwork upon which dense globules of various sizes may be superimposed. At the light microscope level finer images are obtained from specimens in which the fibrillar meshwork is incrusted with the fewest globules or are without incrustation. The varicosities in nerve fibres display light circular patches which represent the sites of synaptic junctions. The velamentous processes of neuroglial cells are also well demonstrated in these preparations.
The geometry of dislocation loops generated in α‐iron by 1 MeV electron irradiation at 550°C
Authors: Little E. A. , Eyre B. L. 
Published: August 2011

SUMMARYRectilinear dislocation loops are observed to grow in thin foils of α‐iron during 1 MeV electron irradiation at 550°C in the beam of a high voltage electron microscope. A diffraction analysis indicates that the loops have sides parallel to <100> directions and are pure edge with a <100> Burgers vector. Only interstitial type loops have been identified. The geometry of the loops can be accounted for by an established model of loop nucleation.
Micromagnetic structures in single crystal specimens of intermediate thickness studied by Lorentz microscopy
Authors: Harrison C. G. , Leaver K. D. 
Published: August 2011

SUMMARYStripe domains in (001) nickel occur in a variety of structures due to the large number of easy directions present. We have given below a tentative analysis of two of these structures, not previously studied by Lorentz microscopy. In particular it has been shown that, as used hitherto, the technique has not been a reliable method of observing stripe domains since some structures may be invisible until the specimen is tilted.
The effect of room temperature pre‐strain on grain boundary cavitation in Nimonic 8oA
Authors: Dyson B. F. , Henn D. E. 
Published: August 2011

SUMMARYSpecimens of the alloy Nimonic 80A have been pre‐strained 11% in tension at room temperature and then heated to 750°C for various times either with or without the application of stress. Examination by means of a high voltage electron microscope revealed large numbers of spherical submicron diameter cavities. The cavities all lay on grain boundaries but were inhomogeneously distributed; a grain boundary usually contained either many cavities or none at all. It is concluded that the cavitation is a direct result of decohesion at the grain boundaries during the pre‐straining and not due to any creep process.
A high voltage electron microscope study of recrystallization in copper alloys
Authors: Ray R. K. , Hutchinson W. B. , Besag F. M. C. , Smallman R. E. 
Published: August 2011

SUMMARYRecrystallization and recovery have been studied in the high voltage electron microscope (HVEM) in pure copper and two copper‐phosphorus alloys following heavy rolling deformation. Prior to the nucleation of recrystallized grains, extensive subgrain growth occurs by sub‐boundary migration. In the alloys, the first recrystallized grains are observed to nucleate within deformed matrix regions of the same orientation. The orientations of these grains are in close agreement with the crystallographic texture of the metal at complete recrystallization. Growth selection of orientation does not appear to be important. In pure copper, cube‐oriented recrystallized grains form after those of some other orientations, but grow more rapidly and absorb these during growth.
In situ superplasticity experiments in the 1 million volt electron microscope
Authors: Naziri H. , Pearce R. , Brown M. Henderson , Hale K. F. 
Published: August 2011

SUMMARYIn situ tensile straining was carried out in the 1 million volt electron microscope in an attempt to clarify the mechanism(s) of superplasticity in the Zn/Al eutectoid alloy. The dynamic microstructural observations in the 1 MV microscope at 100°C at an m value of ∼0.3 were consistent with 100 kV observations of specimens thinned from the bulk and showed that under the experimental conditions used, the predominant mechanism is diffusion of the zinc‐rich (β) phase. It has been theoretically predicted by Lifshitz that diffusional creep and grain‐boundary sliding are inseparable. This is verified by these in situ observations.
In situ observations of the nitriding of tantalum
Authors: Swann P. R. , Thomas G. , Tighe N. J. 
Published: August 2011

SUMMARYA gas reaction cell developed for the AEI EM7 has been used to observe directly the structural changes which occur when tantalum is heated in nitrogen. It is demonstrated that sharp images of the microstructure can be obtained from specimens at temperature while surrounded by a 5.5 mm thick layer of the reaction gas at a pressure of 35 torr. The usefulness of the in situ technique for studying gas/metal reactions is assessed.
Transmission electron microscopy at 2.5 MeV
Authors: Thomas Gareth , Lacaze J.‐C. 
Published: August 2011

SUMMARYMeasurements of penetration on silicon and austenitic stainless steel have been continued using the same criteria as previously reported (Thomas, 1968) up to 2.5 MeV using the 3 MeV Toulouse electron microscope. The results show that penetration increases to about 14 μm at 2.5 MeV for silicon although the curve starts to flatten out above 1.5 MeV, but no significant gain was found for stainless steel ≃2μm at 2.5 MeV). Primary knock‐on damage occurs readily in both materials. The critical voltages for 440 silicon and 422 tantalum were measured, and both found to be 1.4 MeV (± 10 kV).Attempts to measure the variation of radiation damage with beam voltage in crystalline amino acids as indicated by the fading of diffraction patterns indicated that the damage rates apparently decrease as the voltage is raised to 2.5 MeV. However, it was not possible to determine this variation quantitatively because of difficulties in measuring the absolute values of the critical exposures.
A technique for the cytochemical demonstration in the electron microscope of glucose‐6‐phosphate dehydrogenase activity in erythrocytes of malaria‐infected animals
Authors: Theakston R. D. G. , Fletcher K. A. 
Published: August 2011

SUMMARYA technique for the cytochemical demonstration in the electron microscope of glucose‐6‐phosphate dehydrogenase activity in malaria‐infected erythrocytes is described. Reaction product occurred as diffuse electron‐dense deposits of the formazan of MTT in the red cells. No activity was observed within the malaria parasites themselves, except in the contents of food vacuoles. The results of a series of control experiments are also described.
Methods for electron microscopy of the lamellated osmiophilic bodies of the lung
Authors: Schock C. , Pattle R. E. , Creasey J. M. 
Published: August 2011

SUMMARYA study has been made of methods of fixing, staining, and embedding for electron microscopy the lamellated osmiophilic bodies (LOPBs) of the type II cells of the lung, which are probably connected with the lung surfactant. The preferred method for fixing and staining uses successively 2% glutaraldehyde, 1% osmium tetroxide, and a mixture of 10 vol M/40 lead nitrate with 10.5 vol M/60 potassium ferricyanide: all reagents are in cacodylate buffer. Unless the ferri‐cyanide is in excess, the sections show blotchy precipitation. The bodies are damaged by ethanol and 1:2 epoxypropane. Dioxan or (with a quick time schedule) acetone may be used as a dehydrant and thinner prior to Araldite embedding. Durcupan water‐soluble resin may also be used for dehydration and embedding; the preferred embedding mixture is: 5 ml resin A, 11.7 ml hardener B, 1.5 ml hardener C, and 0.4 ml plasticizer D, cured for 24–48 h at 60°C. Examination of LOPBs on a goniometer stage shows that they are composed of layers spaced at 4 nm, each lamella containing several such layers. Further evidence is adduced linking the LOPBs with the surfactant, and the application of the new methods to various problems involving the LOPBs is discussed.
Electron microscopy of cellulose in entire tissue
Authors: Cox Guy , Juniper Barrie 
Published: August 2011

SUMMARYMicrofibrillar structures can be seen in ultrathin sections of cell walls which have been post‐stained with uranyl acetate and lead citrate. This stain is removable by washing, suggesting that a physical mechanism is involved. It is suggested that these structures are the cellulose microfibrils of the wall; they appear to be 3.5 nm in diameter and not fasciated into larger units. Freeze‐etching of untreated tissue supports this conclusion. These two techniques seem to have many advantages over methods previously used for the study of microfibril arrangement and structure.
Permanent preparations of stained whole‐body sections using ‘Trycolac‘
Authors: Farebrother Derek A. , Woods Nicholas C. 
Published: August 2011

SUMMARYPermanent preparations of whole‐body sections cut by Ullberg's technique can be prepared using a ‘spray‐on’ mountant (‘Trycolac’), which does away with the necessity for glass slides and coverslips. Routine staining methods can be used, providing the alcohol content of the stain is low. Glycerol is used for dehydration and clearing and a covering of ‘Trycolac’ is sprayed on.
Direct examination of chip formation during metal machining by scanning electron microscopy
Authors: Ramalingam S. , Bell A. C. , Black J. T. 
Published: August 2011

SUMMARYNew insights into the mechanics and morphology of chip formation in metal cutting have been obtained by direct observation of an orthogonal cutting process in progress in a scanning electron microscope. A specimen stage specifically designed for this purpose is described. This stage permits dynamic viewing of all accessible areas of interest at magnifications up to ×5000 during cutting. Permanent records are obtained by videotaping each experiment. A brief summary of results is given, and extensions of the technique of dynamic scanner observation are suggested.
Identification of elastic tissue in human skin viewed in the scanning electron microscope
Authors: Hunter John A. A. , Finlay Bryan 
Published: August 2011

SUMMARYElastic tissue has been identified in the scanning electron microscope by two independent methods. In one case specifically stained fibres were examined by both light and scanning electron microscopy and in the other chemically purified elastic fibres from ligamentum nuchae were studied.Elastic fibres above 2 μm diameter were found to have a central amorphous core and an irregularly corrugated and undulating outer surface. This model is in good agreement with that proposed on the basis of previous transmission electron microscopic studies.
Estimation of number and diameter of isodiametric spherical particles in microtome sections
Authors: Davies A. G. 
Published: August 2011

SUMMARYIn microtome sections small invisible and unrecognizable fragments cause errors in estimation of particle number and diameter. These errors can be reduced by rejecting fragments whose apparent diameter is larger than the true radius of the particles. Formulae for the calculation of diameter and number are given and the size of the errors is examined.
The principles and practice of the weak‐beam method of electron microscopy
Authors: Cockayne D. J. H. 
Published: August 2011

SUMMARYThe weak‐beam method of electron microscopy enables the high resolution capabilities of the electron microscope to be used in the study of lattice defects. In this paper, the principles of the method are outlined and the experimental procedures for obtaining weak‐beam images are discussed. The experimental diffraction conditions necessary for obtaining quantitative results and the limitations of the method are summarized, and applications of the method to various problems in defect studies are reviewed.