摘要:

SUMMARYAt present, the only possibility for improved resolution of intracellular movement appears to be electron microscopy using a hydration chamber (EMC) at reduced gas pressures with thinned medium around the cells. The environmental constraints of examining cells under such conditions were examined in the absence of ionizing radiation by using an EMC‐analogue fitted to a light microscope. White blood cells and baby hamster kidney cells were examined. A 50% survival pressure value, for hypobaric atmospheres, was determined for these cells. Morphological changes of the hypobarically‐exposed cells are descri

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1975.tb04019.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

SUMMARYThe effects of ion etching on blood cells have previously been studied by scanning electron microscopy. This present study by transmission electron microscopy was undertaken to evaluate the effects of the etching process on the cells. Critical point dried preparations were made, etched and subsequently processed and embedded in Araldite. Examination of thin sections of erythrocytes revealed disintegration of the plasma membrane; the residual membrane destruction products formed the tips of cones produced by long etching times. The effect of etching varied in erythrocytes in the same preparation. Nucleated cells showed a similar disintegration of the plasma membrane, but membranes of mitochondria, granules, vesicles and vacuoles did not exhibit effects of etching comparable to those of the plasma membranes. After treatment with a number of different fixatives, erythrocytes on carbon‐coated copper grids were also etched and examined directly in a high voltage electron microscope at 1 MV. The effects were comparable to those seen in thin sections. To study the etch rates of biological materials, the resonant frequencies of quartz crystals were measured after application of thin films of albumen and cholesterol and again after these had been etched. The ratio of the frequency changes indicated that the etch rate of albumen was approximately 2.5 times that of cholesterol.The results are discussed in the light of theories of the mechanisms involved in ion etchin

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1975.tb04020.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

SUMMARYA freeze‐fracture apparatus of original design has been constructed which can be fitted onto a standard vacuum evaporator unit. In it, cell suspensions and organized tissue may be processed by inserting a sample into a cylindrical holder. By leaving a small part of the tissue protruding from the holder, pre‐selected and aligned portions of the specimen can subsequently be revealed by fracture under vacuum. After rapid freezing, the specimen remains firmly attached to the inner wall of the sample holder, preventing its possible loss during fracturing. A mechanism, in the form of a double‐sided converging wedge, which is operated from outside the vacuum chamber, is used to produce a fracture in the specimen. The device gently induces a fracture in the desired part of the tissue and lifts the protruding part of the specimen out of the way. In this way, reasonably flat fracture faces are produced for subsequent replication. As the fracturing mechanism comes into contact only with the outer edges of the specimen, damage and contamination liable to occur when the entire specimen is traversed by a blade, is avoided. In addition the specimen stage is surrounded by a cold metal shroud which acts as an efficient trap for contaminants. In this way, favourable vacuum conditions are produced in the vicinity of the specimen. Such effective enclosing of the specimen also facilitates controlled sublimation of the s

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1975.tb04021.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

SUMMARYThe frequency of particles on the membrane fracture faces of freeze‐etched human erythrocytes was measured, and the effect of fixation procedures on the particle frequencies was studied. Fresh blood, buffer washed cells and cells fixed in one of the following ways were examined: glutaraldehyde, glutaraldehyde followed by osmium tetroxide, osmium tetroxide alone. Quantitative analyses showed that some treatments produced a significant reduction in the number of particles on the fracture faces as compared with the fresh cells. After both osmium tetroxide fixations, the loss of particles was greater from the outer fracture face (OFF) than the inner fracture face (IFF), whilst after the other treatments approximately the same number of particles were lost from both fracture faces. The results are discussed with respect to some current concepts of the molecular architecture of the erythrocyte membrane and the action of fixatives. The reduction of particle frequencies is thought to be due to both leaching of membrane proteins, and deviations of the usual fracture plane within the membrane. Glutaraldehyde alone was shown to have less effect on particle frequency than the other fixatives and it is therefore a suitable fixative for the preparation of freeze‐etch specim

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1975.tb04022.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

SUMMARYGraphite films which are free of adhesive contamination are prepared by glueing a crystal to an adhesive coated grid and then cleaving away the top graphite layers with adhesive tape. The final graphite films in the centres of the grid openings do not come into contact with the adhesive at any time during the preparation process. Graphite crystal films a few tens of nanometres or less in thickness with large areas of uniform thickness are easily produced.

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1975.tb04023.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

SUMMARYInformation regarding the formation and the thickness of cryo‐sections is of importance for an adequate interpretation of cryo‐sectioned biological material. In this study we have taken advantage of the regular arrangement of filaments in myofibrils in an analysis of these matters. It is concluded that the sections are formed partly by fracturing in a way similar to that visualized in replicas made by the freeze‐fracturing and ‐etching pr

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1975.tb04024.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

SUMMARYThis paper describes a spraying method of producing iso‐atomic droplets (≅3 μm diameter) of uniform size, distribution and chemical composition. These droplets were used to calibrate a TEAM system operated under given conditions, so that the relative sensitivity of the instrumentation for the elements Na, Mg, P, S, (Cl), K, Ca and Co (‘overall sensitivity factors’) could be determined. These factors (15, 40, 83, 90, (43), 104, 109, 100% respectively) were used to convert observed X‐ray intensity ratios from standard droplets to relative amounts of elements with a fair degree of accuracy (error generally less than ± 10%). It was proposed that the sampling and quantification methods could be applied for the absolute quantitative bulk‐analysis of fluids and tissues (after solubilization) with an introduced reference element, e.g. cobalt, and potentially to the study of relative elemental ratios in fluid microvolumes and in biological

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1975.tb04025.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

SUMMARYFilms of formvar, 1.2–20.0 nm in thickness, collodion and a 60/40 styrene‐vinylpyridine copolymer (precipitated from solution) have been found to provide a noncharging layer on the surface of several types of specimens, including loose, or fibrous specimens. No electron build up was observed in most of the specimens when examined with a scanning beam of up to 30 kv for unlimited periods of t

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1975.tb04026.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

SUMMARYThe use of a wide angle backscattered electron detector in a scanning electron microscope, which has the capability of the specimen chamber pressure being controlled independently of the column pressure, provides a simple technique for examining frozen hydrated specimens. Large specimens have been examined within 1 min of being placed on the stub and have been examined for many hours without charging artefacts or distortion due to dehydration.

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1975.tb04027.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

SUMMARYThe quality of ultrastructural preservation of the avian erythrocyte achieved using various fixation techniques is evaluated. Different combinations of initial fixatives, buffers and post‐fixation procedures were tested as well as variations in fixative osmolarity, pH and temperature. Of the commonly used initial fixatives (glutaraldehyde, acrolein and formaldehyde), 2% glutaraldehyde, alone in a slightly hypertonic buffer containing divalent ions, produced optimum erythrocyte preservation. The osmolarity was balanced using a non‐electrolyte such as sucrose. The addition of 12% hexylene glycol to the buffer solutions also improves erythrocyte preservation, as evidenced by the increased stability of the marginal microtubules, microfilaments and proteinaceous material.The use of Spurr low‐viscosity epoxy resin enables the cells to be collected using low gravitational centrifug

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1975.tb04028.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY