bluuebunny/crossref_metadata_2025_split huggingface dataset:
A capillary fluorescence standard for microfluorometry*
Authors: Sernetz M. , Thaer A. 
Published: August 2011

SUMMARYQuartz glass capillaries of about 6 μm inside diameter were filled with fluorochrome solutions of accurately known concentrations and embedded as microscopical objects. The fluorescence intensity of a constant capillary volume has been found to be directly proportional to the amount of the excited fluorochrome in this volume within the fluorochrome concentration range 1:103. The capillary volume can be determined accurately by microinterferometric measurement of the inside diameter.The capillary section irradiated by the exciting light may be considered as very small in comparison with the total length of the capillary tube. During and after irradiation the excited part of fluorochrome solution is continuously renewed by convectional flow and diffusion. Therefore photodecomposition does not affect the measured fluorescence intensity, and the standard value remains unchanged even after numerous measurements. Thus, these fluorescence standards may be used to make successive calibrations of a microfluorometer and to check the constancy and reproducibility of measuring conditions. In certain circumstances it also permits measured fluorescence intensity to be interpreted in terms of the amount of fluorochrome or fluorescent substance.The results achieved with the capillary fluorescence standard are compared with those obtained by means of conventional methods. In addition, some essential optical properties of the microfluorometer equipment required for the proper use of this standard are discussed.
Electron cytochemical localization of cystine in plant cell walls
Authors: Thompson E. , Colvin J. Ross 
Published: August 2011

SUMMARYA method for specific, cytochemical staining of cystine residues was applied to thin sections of human hair keratin, two yeasts, one fungus and one green alga, for observations in the electron microscope. The method, which deposits granules of metallic silver at or close to the site of cystine residues, may be a useful means of investigating the detailed distribution of disulphide bonds in cells provided that the following criteria are rigorously applied. First, grains of metallic silver must remain after exhaustive sodium thiosulphate extraction; second, the deposition of grains of metallic silver must be inhibited by prior alkylation of the disulphide linkage. Finally, the method should be used in conjunction with other available means of analysis.
Electron staining of synaptic vesicles using the Champy‐Maillet technique
Authors: de Iraldi Amanda Pellegrino , Suburo Angela Maria 
Published: August 2011

SUMMARYSynaptic vesicles from rat pineal nerves can be stained by Champy‐Maillet mixtures containing osmium tetroxide and a soluble iodide. Two components of the vesicle (the matrix and the dense core) are revealed in a different way depending on at least two factors: the iodide employed and the final pH of the mixture. We have tried the following mixtures: zinc iodide at pH 5·5 (ZIO), cadmium iodide at pH 6·0 (CIO) and potassium iodide at pH 7·2 (KIO‐7) or pH 5·5 (KIO‐5). The matrix is more reactive with ZIO, while the dense core is more reactive with CIO and especially with KIO‐7. With the only difference of a lower pH, KIO‐5 stains the whole matrix of some vesicles and also reveals some tubular structures which are more frequently found in preterminal axons.
Silver staining of collagen and reticulin fibres and cerebral capillaries by means of physical development
Authors: Gallyas F. 
Published: August 2011

SUMMARYA method for demonstrating collagen and reticulin fibres and the network of brain capillaries has been worked out on the basis of a new silver staining principle. It may be applied to sections as thick as 200 μm from both frozen and embedded material. The principle is as follows: the 1,2‐glycol groups of tissue elements, including connective tissues, are converted to aldehyde groups by periodic acid. The aldehyde groups form colloidal silver particles in an ammoniated silver nitrate solution of pH 13. At this pH value, however, it is only the connective tissue that can bind the colloidal silver which is being formed. After the silver ions have been washed out of the sections, the silver grains deposited in the connective tissue are finally enlarged to microscopic dimensions by physical development.
A simple microscope warm stage
Authors: Guntrip A. V. 
Published: August 2011

SUMMARYMicroscopical examination of cells, particularly spermatozoa, often necessitates the preservation of a temperature of 37°C on the stage itself. A microscope warm stage should provide a surface at this temperature and allow microscopical examination of a series of pre‐warmed sample slides. A further desirable quality would be the total absence of ancillary apparatus. An apparatus has been designed and built which effectively provides these features. It measures 10·5 × 6·5 × 1·3 cm, weighs 320 g with wiring and plug and provides a thermostatically controlled temperature of 37 ± 0·5°C 5 min after connection with the electrical supply (240 V A.C.).
Enhanced contrast in electron microscopy of unstained biological material: II. Defocused contrast of large objects
Authors: Johnson H. M. , Parsons D. F. 
Published: August 2011

SUMMARYA contrast minimum is observed when 88 nm diameter polystyrene latex spheres are underfocused, which is related to the wide‐angle scattering peaks. Images due to scattered and non‐scattered wave components are displaced due to objective‐lens spherical aberration and defocus. Maximum overlap of these components produces a contrast minimum at underfocus, related to the spherical aberration of the particular lens used.Similarly, a high‐contrast band at carbon‐film edges arises from spherical aberration and defocus separation of non‐scattered and wide‐angle scattered waves. This band increases in contrast with film thickness and in width with lens defocus.These geometrical effects account for the well‐known ‘blinking’ of contrast of large biological objects upon swinging through focus without an objective aperture, and for the general contrast increase of defocused large objects. Fresnel fringes account for only a narrow band of enhanced contrast at distinct edges and cannot account for contrast enhancement of large objects lacking distinct edges.
Examination of rock surfaces with the scanning electron microscope
Authors: Gillott J. E. 
Published: August 2011

SUMMARYA fracture surface of rock (greywacke) was examined with the scanning electron microscope prior to, and after, surface etching for successively increasing time intervals in 2 m NaOH at 38°C (100°F). The same area of rock was successfully relocated in the microscope so that the effect of the alkali upon minerals and micro‐structure could be observed by direct comparison of micrographs. Layer‐structure silicates showed exfoliation.
Polyester resin as a mounting medium for light microscopy
Authors: Senior W. 
Published: August 2011

SUMMARYThe use of a commercially available polyester resin is described for the production of whole‐mount preparations and as a mounting medium for histological sections. Any standard technique can be used which involves xylene as the clearing agent. It is considered that the slides produced are much stronger than those made with traditional mounting media and do not require long drying times before use. The method is particularly suitable for mounting thick specimens for teaching purposes.
Reduction of compression artifacts in ultra‐thin sections by the application of heat
Authors: Roberts I. M. 
Published: August 2011

SUMMARYCutting compression in ultra‐thin sections prepared for electron microscopy was decreased when sections floating in the knife trough were exposed to radiation from a V‐shaped, heated wire filament. The apparatus is called a ‘heat pen’ and consists of a filament mounted in a ball‐point pen body and heated by a step‐down transformer. The method gave less residual compression than conventional solvent vapour methods without any apparent ill effects on staining properties, specimen stability or resolution. For specimens which were prone to wrinkling caused by shrinkage following vapour stretching, this technique gave much improved results. Heat stretching also eliminates the need to use solvent vapours which may be harmful to the microtomist.
Permanent fluorescent test slides
Authors: Walker P. J. , Watts Janet M. A. 
Published: August 2011

SUMMARYPermanent test slides for fluorescence microscopy can easily be prepared by suspending Helecon fluorescent pigments, numbers 2225 and 2266, in DPX and mounting under a cover glass in the usual way. These two pigments simulate the excitation and emission of fluorescein conjugates and acridine orange. Eight other pigments have been tested and their properties are described.
A modified aldehyde perfusion technique for preventing certain artifacts in electron microscopy of the central nervous system
Authors: Schultz Robert L. , Case Norman M. 
Published: August 2011

SUMMARYThe production of vacuolated mitochondria and myelin figures can be markedly reduced with aldehyde perfusion fixation by perfusing a concentrated aldehyde solution before the conventional perfusate. A method is presented for accomplishing this with no practical time delay. Factors causing myelin figures and damaged mitochondria are discussed.Gum acacia helps prevent ‘washed‐out’ cells and processes, and seems to aid myelin preservation. A clear solution is necessary for a good perfusion. Techniques for accomplishing this are presented.A concentrated formaldehyde solution perfused as a small volume immediately prior to the conventional perfusate causes alterations of the endoplasmic reticulum, including the subsurface cisterns, and an increase in numbers of spine apparatuses. Evidence is presented by using tubes of gelatin containing Schiff's reagent that formaldehyde is the fastest penetrating aldehyde but that it only fixes about half the distance it penetrates. Acrolein penetrates more rapidly than glutaraldehyde but fixes only as far as formaldehyde. Glutaraldehyde fixes as far as it penetrates.
The effects of various pre‐treatments on the freeze‐etching of root tips
Authors: Fineran B. A. 
Published: August 2011

SUMMARYResults of experiments on the pre‐treatment of root tips for freeze‐etching are outlined. Successful freeze‐fixation of viable roots was obtained using seedlings of Avena, Triticum and Zea. The seeds were germinated in contact with water, then placed on top of tubes of filter paper impregnated with glycerol; this allowed aeration of the roots. Most roots grew slightly on exposure to glycerol and remained turgid. Avena and Triticum gave good freeze‐fixation after 7 days in contact with 20% glycerol and after contact with 20% glycerol for 3 days followed by 25% glycerol for 3 days. Good preservation was also obtained with Zea but results were more variable than in Avena and Triticum.Root tips fixed in glutaraldehyde, either in glycerol or followed by glycerol, gave consistent freeze‐fixation in all species. Results were comparable to those obtained from viable material. However, in some instances there was shrinkage of the organelles and the plane of fracture within certain membranes was altered.
Polarized light and phase‐contrast studies of stained and unstained plant cell nucleoli
Authors: Kordan H. A. 
Published: August 2011

SUMMARYNucleolar morphology in interphase nuclei of non‐growing and growing plant cells has been studied by polarized light and phase‐contrast microscopy. Variation in the optical properties of the nucleoli in unstained preparations are indicative of different morphological stages of this cell organelle with respect to the physiological status of the cells in which these variations occur. A filamentous nucleolar component, the nucleolonema, was evident in unstained nucleoli of explants cultured in vitro and in hypocotyls of germinating seeds. Unstained and stained preparations indicate that the polarized‐light effects observed in nucleoli of previous investigations are primarily associated with this filamentous nucleolar structure.
Leaf wax fine structure and ontogeny in Eucalyptus demonstrated by means of a specialized fixation technique
Authors: Hallam N. D. 
Published: August 2011

SUMMARYThe epidermal cells of Eucalyptus leaves are not well preserved by the conventional sectioning methods used for electron microscopy. More satisfactory preservation results from the use of an in vivo perfusion technique using glutaraldehyde or glutaraldehyde‐formaldehyde mixtures. This technique preserves wax on the cuticle surface, rendering it insoluble in the organic solvents used for dehydration and embedding in epoxy resins. Using this method, no direct connection is apparent between leaf wax, cuticle, cell wall and cytoplasm. The Golgi bodies appear to produce vesicles which migrate only in the direction of the outer cell wall, and which might liberate wax precursors into the wall, from where they could diffuse through cuticular lamell to polymerize or oxidize at the leaf surface as waxes of characteristic morphology.
A method for increasing the photographic contrast of electron micrographs
Authors: Farnell G. C. , Flint R. B. 
Published: August 2011

SUMMARYEmulsion‐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

SUMMARYA 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

SUMMARYBy 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

SUMMARYReason 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

SUMMARYIn 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 expressionwhich 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 expressionbut 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.
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

SUMMARYLight‐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

SUMMARYChromosomes 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

SUMMARYVarious 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

SUMMARYThe 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

SUMMARYFreeze‐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.