bluuebunny/crossref_metadata_2025_split huggingface dataset:
The etching of thick Araldite‐embedded sections for scanning electron microscopy
Authors: Thurley Kenneth W. , Mouel Walter C. 
Published: August 2011

SUMMARYA rapid method of correlation of information from the images of the scanning electron microscope, the transmission electron microscope and the light microscope, from biological tissues embedded in epoxy‐resin. It allows a perception in depth at the SEM level of areas already defined by the other two modes. One micrometre sections of Araldite‐embedded tissues are cut, dried onto glass cover slips, and the embedding medium etched away, with a saturated solution of NaOH in absolute ethanol. After washing in absolute ethanol and distilled water the resultant osmicated ‘skeleton’ is coated and viewed in the SEM.
A method for accurately determining lattice parameters using electron diffraction in a commercial electron microscope
Authors: Lodder J. C. , Berg K. G. v.d. 
Published: August 2011

SummaryIn this paper an electron diffraction method is discussed by which the lattice constants of polycrystalline thin films can be accurately determined (0.1%).The method involves the sequential examination of a standard material and the unknown material mounted on separate grids. The error which can arise through the possible difference in height of the two grids can be corrected by means of height and tilting adjustments. The analytical approach of the dependence of the camera constant on the ring diameter as given in literature appears to be insufficient. An experimental correction factor for this dependence is introduced. The accuracy of this method, and the influence of relevant sources of error, are discussed and explained in terms of some experimental results.
Complementary freeze‐etch replicas by adapting the Denton apposed specimen tooling to the Balzers unit
Authors: Demsey Anthony , Frank Hermann , Schwarz Heinz , Henne Erhard 
Published: August 2011

SUMMARYThe complementary replica technique for freeze‐etching was developed to help answer certain questions concerning fracture planes and contamination artefacts. In order to obtain this capability in our freeze‐etch laboratory we have chosen, for scientific as well as financial reasons, to adapt the Denton apposed specimen tooling to our already‐existing Balzers facilities. The method employed for this adaption and results obtained with it are reported herein.
Beam‐induced loss of organic mass under electron‐microprobe conditions
Authors: Hall T. A. , Gupta B. L. 
Published: August 2011

SUMMARYThe loss of mass from biological tissue sections during electron microprobe irradiation was observed by means of a silicon semiconductor detector set to record continuum X radiation. The rate of loss depended on several factors, conspicuously on specimen temperature. In accord with earlier observations with non‐focused beams, most of the ‘immediate’ loss occurred within an electron dose of the order of 10−10 C/μm2.
Importance of controls for the demonstration of carbohydrates in electron microscopy with the silver methenamine or the thiocarbohydrazide‐silver proteinate methods
Authors: Courtoy R. , Simar L. J. 
Published: August 2011

SUMMARYThe periodic acid‐silver methenamine method and the periodic acid‐thio‐carbohydrazide‐silver proteinate method have been used for the demonstration of carbohydrates in various plant and animal tissues. The comparison of the results obtained with both methods indicates that the periodic acid‐thiocarbohydrazide‐silver proteinate method is more specific and gives better quality pictures than the PA‐silver methenamine method. It is pointed out that adequate controls are necessary for a valid cytochemical interpretation of the results. With the PA‐thiocarbohydrazide‐silver proteinate method, no positively stained structure can be assumed to be of carbohydrate nature unless it is found unstained in non‐oxidized thiocarbohydrazide‐silver proteinate treated sections. Both methods have their limitations and do not demonstrate the total carbohydrate amount in tissue sections.
Detection of haemoglobin in red cells of Xenopus laevis by immunofluorescent double labelling
Authors: Jurd Richard D. , Maclean Norman 
Published: August 2011

SUMMARYRed cells from metamorphosing Xenopus laevis were treated with a fluorescein‐conjugated guinea‐pig antibody to Xenopus tadpole haemoglobin, a rabbit antibody to Xenopus adult haemoglobin, and a rhodamine‐conjugated goat anti‐rabbit globulin antibody. The presence of both red and green fluorescence in some cells indicated that at metamorphosis a proportion of the red cells contained both adult and tadpole haemoglobins.
Lung fixation by perfusion—a simple method to control the pressure in the perfusion circuit
Authors: Assimacopoulos A. , Kapanci Y. 
Published: August 2011

SUMMARYA simple method which maintains the hydraulic pressure at a constant level during fixation of organs by perfusion is described. This is obtained by means of a glass tube interposed between a peristaltic pump and the organ to be perfused, the specially designed glass tube acting as a safety valve. The efficiency of the system is tested by electromagnetic pressure recording.
Selection of the best method in stereology
Authors: Weibel Ewald R. 
Published: August 2011

SUMMARYA brief historical survey of the origin of stereological methods is followed by a synoptic characterization of their nature. They fall into two main classes depending on the structural models at their origin. Those methods which aim at a size analysis of the particle population provide more information, but are more subject to limitations, than those which estimate bulk parameters of the structure as a whole. The choice between the different methods must be guided by a clear definition of the most informative parameters and of the geometric properties of the structure.
Improved cathodoluminescence microscopy
Authors: Bond E. F. , Beresford Diana , Haggis G. H. 
Published: August 2011

SUMMARYMethods are described for the use of a sensitive photomultiplier, improved photomultiplier voltage supply circuitry, quartz lens and a half‐parabolic mirror to increase the amount of light collected from a luminescing specimen examined in the scanning electron microscope. The combined effect of these improvements increases cathodoluminescence detection twenty times. Sources of background light are investigated and recommendations are made for decreasing this noise component, which seriously limits sensitivity of cathodoluminescence signal detection.An appendix describes the natural luminescence (autoluminescence) of plant tissues under the impact of the electron beam. The biological applications of this mode of scanning microscopy have been little explored, but autocathodoluminescence is found to be of wide occurrence in plant tissues.
The control of the configuration of nucleic acid molecules deposited for electron microscopy, by ionic bombardment of carbon films
Authors: Highton Peter J. , Whitfield Morag 
Published: August 2011

SUMMARYDNA molecules bind to carbon films placed on the surface of aqueous solutions and are extended and oriented by the flow forces on removal from the surface. The number of molecules bound increases with ionic strength suggesting that the bonding is hydrophobic.If carbon films are subjected to ionic bombardment in a flow discharge, they can be modified so that molecules bind strongly, and are deposited in a tangled, random‐coil configuration, uninfluenced by flow forces. The strength of binding is decreased by reducing the discharge time and current, and by addition of salt (NaCl), suggesting that the bonding is ionic. When weakly bound, the molecules are condensed by ethanol. The strength of binding can be adjusted so that the molecules are largely untangled by flow, and in a form suitable for the mapping of bound enzymes, or other identifiable markers.Aggregation and extension of molecules, that occur on unmodified films, and the binding of cytochrome c, that occurs in methods based on that of Kleinschmidt & Zahn (1959) are avoided. Both double and single‐stranded molecules can be deposited and seen after rotary shadowing with Pt. The discharge can be performed in a vacuum produced by a standard oil‐filled rotary pump.
Problems in the use of selective optical spatial filtering to obtain enhanced information from electron micrographs
Authors: Taylor C. A. , Ranniko J. K. 
Published: August 2011

SUMMARYPossible hazards in the use of optical spatial filtering applied to the analysis of electron micrographs are illustrated. Two experiments show how information is either lost or spuriously introduced into reconstructed images of micrographs when (a) only one part of a two‐part micrograph image is reconstructed and (b) when noise is eliminated from the reconstruction.
A film projection system for use in quantitative morphological studies
Authors: Deter Russell L. 
Published: August 2011

SUMMARYA film projection system is described which permits stereological measurements to be made on negatives enlarged 2.7–6.7 times. The unique feature of this system is its use of the Zeiss TGZ 3 particle size analyser for determining profile size distributions. Elimination of negative printing greatly facilitates investigations requiring analysis of a large number of micrographs.
Freeze‐substitution: a method for the rapid arrest and chemical fixation of spermatozoa
Authors: Woolley D. M. 
Published: August 2011

SUMMARYA procedure for the freeze‐substitution fixation of spermatozoa has been developed. Physical fixation of the motile cells is effected very rapidly by immersing the sperm in Freon‐22 at −146°C. Chemical fixation, with glutaraldehyde, is then imposed on the immobilized sperm after substitution of the ice matrix at −50°C. The substitution is achieved with the solvent ethylene glycol in the manner described by Pease (1967). (Subsidiary experiments confirm that substitution of ice does occur at −50°C and that chemical fixation by glutaraldehyde occurs at temperatures at least as low as −20°C.) The spermatozoa are then embedded in Epon and examined as thin sections. Other techniques—substitution in acetone containing osmium tetroxide, the inclusion of formaldehyde with ethylene glycol as a chemical fixative, and the inclusion of agar in the diluent used to suspend the spermatozoa—have been tried but were unsatisfactory.Freezing stops the movement very rapidly and, as little subsequent disturbance occurs, it should be possible to preserve transient changes in the fine structure of the flagellum which might be related to a mechanism for the generation of bends. The observations in this paper are confined to the behaviour of the proximal part of the midpiece of the rat spermatozoon. It is demonstrated that bending of this part of the flagellum is restricted, to a remarkable degree, to one plane, the plane in which the sperm nucleus is flattened. This plane is almost exactly perpendicular to the plane containing the two central tubules of the axoneme. It has been confirmed that the axonemal complex has a straight course through the midpiece during those beats of the flagellum which are not accompanied by rotation of the entire cell. Lastly, it appears that the nine dense fibres do not undergo transient displacements as the flagellum bends.
Measurement of lacunar volume in bone using a stereological grid counting method evolved for the scanning electron microscope
Authors: Boyde A. , Howell P. G. T. , Jones S. J. 
Published: August 2011

SUMMARYA stereological grid method has been evolved for scanning electron microscopy using a self‐generated superimposed grid which compensates for the non‐linearity of the CRT image. The method was applied to determine the volume proportion of lacunae in monkey humerus cortical bone. Flat cut specimens of bone were prepared and photographed with a superimposed grid, and the number of lacunae on intersections of the grid were counted and compared with the total number of intersections on bone matrix. The lacunar volume proportion was 1.06% ± 0.50%.
An on‐line computer system for point counting stereology
Authors: Rätz H. U. , Gnägi H. R. , Weibel E. R. 
Published: August 2011

SUMMARYEfficient application of point counting stereological methods in quantitative microscopy in biology and materials science depends on the availability of powerful and rapid counting and computing facilities. An on‐line computer system is described which is easily programmed without knowledge of a special programming language to perform counting, computation of parameters, and statistical tests automatically. By means of a master program, provided with the system, specific user's programs are compiled on a teletype in conversation with the computer by following simple instructions. The program is distinguished by great flexibility; it provides for statistical tests on the reliability of the sample analysed at any time during analysis. The final results are printed in tabular form as means and standard errors of the mean.
The development of a zoom macroscope for radioactive nuclear materials
Authors: Banks D. A. , Eggers A. G. 
Published: August 2011

SUMMARYThe macroscopic examination of irradiated reactor materials presents special problems in handling due to the necessity of shielding the instrument from the worker with a thick lead wall. The lack of availability of a suitable instrument has prompted the design of a special inverted stage macroscope equipped for remote operation. As the size of lens prevents turret mounting, a commercial 35 mm camera telephoto lens has been adapted in a special focusing mount. This permits the illuminator and stage assembly to be made non‐adjustable, simplifying the problems of remote working. An electronic drive is fitted to each stage movement, both of which are provided with remote position indicators.
A defect produced in low power electron micrographs by thin‐foil objective apertures
Authors: Rostgaard J. 
Published: August 2011

SUMMARYAn annoying phenomenon in many low power electron microscope negatives is a centrally located overexposed spot. It is shown that its occurrence is associated with the use of thin‐foil objective apertures, and that the spot most probably is produced by electrons permeating the thin‐foil material. The overexposed spot can be avoided either by using a concentrated nearly focused illuminating beam, in practical terms by using a short exposure time, or by using a thick, disc‐shaped objective aperture.
A new specimen mounting system for scanning electron microscopy*
Authors: Lamvik M. K. , Lin S. D. 
Published: August 2011

SUMMARYA system of specimen mounting discs and holders has been developed for use in high vacuum. Discs are held in place with a tightly fitting cap, thus avoiding the use of adhesives. The mounting discs are especially convenient for biological preparations, are much less expensive than conventional SEM ‘stubs’ and are easier to handle and store.
Estimation of the size and orientation distribution of filamentary features from measurements on a two‐dimensional section
Authors: Hilliard J. E. , Anacker D. C. 
Published: August 2011

SUMMARYA procedure is described for determining the joint distribution Lv(r, ø, θ) of the radii (r) and orientation (ø, θ) of a filamentary structure from measurements on a single section. For tubular filaments it is also possible to determine the wall‐thickness distribution. The following assumptions are made: (1) that the filaments have a circular cross‐section; (2) that the length and radius of curvature of the filaments are large compared with their radii.The analysis is also applicable to transmitted images if the thickness of the slice is small compared with the average radius of the filaments.
A Fourier approach to optical shadowing with a transmission electron microscope
Authors: Scales Donald J. 
Published: August 2011

SUMMARYOptical shadowing offers the possibility of combining the high resolution of the transmission electron microscope with the study of surface detail, commonly investigated with the scanning electron microscope.Image formation in this mode of operation is treated according to the formalism of Fourier optics, where we consider the objective aperture to be a spatial filter in a coherent imaging system. For a simple specimen it is shown theoretically as well as experimentally that the image appears to be a shadowed representation of the object, when the objective aperture is moved off centre so that half of the zero‐order diffraction spot is blocked. A computer model is presented that gives a faithful description of the theoretical and experimental image intensity profile for the simple test specimen. The computer model is then used to predict image profiles for more complicated (or more realistic) specimen profiles. The calculations show that a certain ambiguity arises when one attempts to interpret the optically‐shadowed image profiles: it would be difficult to distinguish the three different edge contours based only on their appearance in this mode of operation. As with any other EM technique, then, results obtained with optical shadowing must be compared with the results obtained using the others.
The application of X‐ray analysis in the transmission electron microscope to a study of drug distribution in the parasite Schistosoma monsoni (Platyhelminthes)
Authors: Erasmus David A. 
Published: August 2011

SUMMARYThe distribution of sodium antimony dimercaptosuccinate in the helminth parasite Schistosoma monsoni was determined using a transmission electron microscope (TEM) fitted with an X‐ray non‐dispersive analysis system. Both Araldite and cryosections of the parasite were examined.The drug was found to have a marked effect on some cells of the ovary and vitelline gland and it was within these cells that the drug was demonstrated. Within the vitelline cells the drug was confined to the vitelline droplets and the analysis of both Araldite and cryosections confirmed that the absence of drug from other tissues was genuine and not due to loss during processing. Maximum retention of elements was achieved in cryosections and this type of material also enabled one to distinguish elements genuinely associated with the tissues from those present in the Araldite matrix.The combination of X‐ray analysis with TEM and cryosectioning has provided a most valuable tool for the study of drug distribution at tissue and subcellular levels and also enabled the elemental characteristics of the tissue at the precise drug locus to be determined.
The periodic wave pattern in native tendon collagen: correlation of polarizing with scanning electron microscopy
Authors: Gathercole L. J. , Keller A. , Shah J. S. 
Published: August 2011

SUMMARYA definite correlation and continuity has been obtained between the observations of ultrastructure of collagen fibres teased from rat tail tendon, by two different techniques; (1) polarizing optical microscopy and (2) scanning electron microscopy (SEM). The stereographic micrographs of the fibres taken by SEM shows that the surface periodicity is of the planar form and is similar to the model proposed by Diamant et al. (1972) from polarizing microscopic observations.
Cathodoluminescence spectra of organic compounds
Authors: De Mets M. , Howlett K. J. , Yoffe A. D. 
Published: August 2011

SummaryCathodoluminescence spectra of a selected group of organic substances have been obtained on cooled samples using a SEM‐spectrometer combination. Room temperature spectra were also recorded when possible. The emission intensity and the beam effect are favourably influenced at low temperatures. The main emission occurs in the 300–600 nm wavelength range.
Accuracy and precision of a scanning and integrating microinterferometer
Authors: Goldstein D. J. , Hartmann‐Goldstein I. J. 
Published: August 2011

SummaryInstrumental factors affecting the precision and accuracy of measurements with the Vickers M86 scanning and integrating microinterferometer were investigated. ‘Spot’ measurements of OPD (optical path difference) could be made to a precision better than 0.001 Λ (wavelengths); the coefficient of variation of scanning measurements of IOPD (integrated OPD) depended on the object, typical values being approximately ± 5% for a human erythrocyte in water, and ± 10% for a mouse sperm head in water. Repeated measurements enabled the dry mass of a specimen to be estimated to any desired precision.Instrumental calibration to give results in absolute units is described. Early prototypes required frequent calibration, but with production instruments the calibration varies little from day to day, and very similar results are obtained if a specimen is measured in different parts of the scanned field.A slight, approximately sinusoidal deviation from linearity was sometimes observed when the apparent OPD or IOPD was plotted against expected values. The error, which probably occurs with all instruments employing a Jamin double‐refracting interference system, was maximally about ± 0.02 Λ for a specimen of true OPD 0.25 Λ or 0.75 Λ, but was zero for a specimen of true OPD 0.5 Λ. The error could be minimized or eliminated by the correct choice of an interference fringe for ‘spreading’, careful adjustment of the condenser and background OPD, and especially by reduction of the condenser aperture.Scanning measurements of IOPD were shown experimentally and theoretically to be insensitive to changes in the measuring‐spot diameter or errors in focus. Valid measurements of dry mass can therefore be made even if the three‐dimensional specimen (e.g. a living cell or isolated nucleus) is considerably thicker than the depth of focus of the objective used.
A direct recording corrected microspectrofluorometer
Authors: Mayer R. T. , Novacek V. M. 
Published: August 2011

SummaryThe construction of a microspectrofluorometer with automatic correction capabilities is given. The instrument uses a quantum counting system for correction of excitation spectra and an interpolating function generator for correction of emission spectra. An inexpensive analogue computer is an integral part of the electronic portion of the instrument and allows a number of mathematical manipulations to be performed on the sample and reference signals prior to recording or display. Under the conditions stated, the sensitivity of the instrument is in the 10−9 M range for quinine sulphate irradiated at 365 nm. The linear response range for quinine sulphate is 10−3 to 10−9 M. The operational wavelength range of the machine is between 226 and 700 nm.
Problems in ultraviolet polymerization of embedding media for electron microscopy
Authors: Rostgaard J. , Buchmann B. 
Published: August 2011

SummaryA study was made of ultraviolet polymerization of methacrylate, Vestopal and Epon embedding media. By placing thermocouples in the monomeric resin during UV irradiation, it was found that the temperature of the resins was 5–10°C above the ambient temperature recorded by mercury thermometers placed adjacent to the capsules. When the resins were maintained at room temperature (22–24°C), Epon could not be polymerized with UV irradiation, but methacrylate and Vestopal polymerized within 1–2 days. By using unilateral UV irradiation directed perpendicular to thin sheets of Vestopal‐infiltrated tissue specimens, the depth of polymerization in osmium‐blackened (fixed) tissues was determined to be 0.06–0.08 mm.