摘要:

AbstractIn order to have available a specimen holder suited to measure the beam current as is often required in quantitative electron probe X‐ray microanalysis, the rod of a low background beryllium specimen holder of a transmission electron microscope was modified. The tip was electrically insulated from the mass of the microscope and connected electrically to the central contact of a BNC connector mounted on the specimen holder handle. With this modified specimen holder the current absorbed by the specimen and/or the specimen holder could be measured easily and accurately. The modified specimen holder has been used to measure the beam current stability of an analytical electron microscope under various conditions. Data were obtained for tungsten as well as lanthanum hexaboride cathodes. Small changes to other types of specimen tips made it possible to exchange these for the low background ti

ISSN:0741-0581    

DOI:10.1002/jemt.1060030402

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractA computer‐aided graphics approach to correlating transmission electron microscope images of freeze‐fractured and thin‐sectioned samples is outlined. Any three‐dimensional model of the imaged structure can be mathematically sectioned to provide a two‐dimensional representation of the model in the “fracture” plane. The method is used to demonstrate that the structure of lamellar liquid crystalline liposomes is based on a family of Dupin cyclides; closed, parallel surfaces with a conjugate ellipse and hyperbola as curv

ISSN:0741-0581    

DOI:10.1002/jemt.1060030403

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractA method is described that allows a three‐dimensional object to be reconstructed from micrographs of serial sections by means of computer graphics. The reconstructed object, which can be rotated three‐dimensionally, is displayed on a colour visual display unit, and the object is shaded in order to provide an illusion of a three‐dimensional structure. Moreover, the technique makes it possible to observe an inner structure as seen through an oute

ISSN:0741-0581    

DOI:10.1002/jemt.1060030404

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractThe surface layer of mucus, which obscures the epithelium from view, is a major obstacle when performing scanning electron microscopic studies of the nasal mucosa. Samples treated with a 1% mixed glycosidase solution for 1 or 2 minutes, followed by agitation, removed most of the mucus from the conchae without damaging the underlying epithelium. Removal of mucus allows the complete evaluation of the underlying epithelium in normal animals and the localization and characterization of lesions in animals exposed to nasal toxicants.

ISSN:0741-0581    

DOI:10.1002/jemt.1060030405

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractReliable ultrastructural techniques are applied for cytochemical identification of glycogen and localization of glucose‐6‐phosphatase (G6Pase) activity within neurons and glia of theadultmammalian CNS. Modulations in the cerebral localizations of glycogen and G6Pase activity are identified during various experimental conditions (i.e., salt‐stress, fasting, and trauma). The cytochemical reaction for demonstration of G6Pase activity implies that the enzyme acts as a phosphohydrolase to convert glucose‐6‐phosphate to glucose. The degradation of glycogen in vivo is one source of glucose‐6‐phosphate as a substrate for G6Pase. Glycogen is preserved by perfusion‐fixation of the brain with 2% glutaraldehyde‐2% formaldehyde. Chopper sections of this material are postfixed in buffered 1% osmium tetroxide‐1.5% potassium ferrocyanide, which serves as a contrast stain for glycogen, or in buffered 1% osmium tetroxide. Plastic‐embedded ultrathin sections of CNS tissue postfixed in 1% osmium tetroxide are stained for glycogen with periodic acid–thiocarbohydrazide‐silver protein. Intracellular glycogen appears as electron‐dense isodiametric particles and, under normal and experimental conditions, is most abundant within astrocytes. Neuronal glycogen is sparse to negligible normally but appears increased within specific neuronal populations during stressful states.Optimal preservation of G6Pase activity in the brain is obtained by brief perfusion‐fixation with 2% glutaraldehyde. Tissue sections are incubated in a modified Leskes medium containing glucose‐6‐phosphate or mannose‐6‐phosphate as substrate and lead nitrate. Utilizing the Gomori lead capture technique, G6Pase reaction product is localized within the lumen of the endoplasmic reticulum (ER) and related organelles (i.e., nuclear envelope, Golgi complex) of perikarya, dendrites, and glia. The ER in axons and axon terminals fails to express G6Pase activity under normal conditions but does so in some neurons exhibiting a degenerating appearance. A transient, cytochemical decrease in G6Pase activity may occur within some perikarya during stressed conditions.The results indicate that within neurons and glia of the adult CNS cytochemical stains are well suited for ultrastructural identification of glycogen and localization of G6Pase activity. Modulations in glycogen particle concentration and in localization of G6Pase activity in the neuron can occur in response to conditions that influence the energy metabolism of the cell. These modulations may reflect differences in the regional utilization of glucose as an energy‐producing substrate and as a deri

ISSN:0741-0581    

DOI:10.1002/jemt.1060030406

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractMonolayer freeze‐fracture of biological membranes is a valuable tool for integrating membrane morphology with biochemical analysis of membrane components. This correlation has been restricted by the purity of the biochemical sample. In this article, the method is reviewed, and an improved method is described. The essential modification was the use of a polysaccharide‐coated microscope slide, instead of a copper plate, to cover cells attached to a polylysine‐coated coverslip. It was found that proper freeze‐fracture will not occur unless there is a distinct temperature gradient, with its accompanying stresses, across the cell monolayer during the freezing process. This gradient is achieved by using glass slides of different thickness to cover each side of the monolayer. Comparison of the results with those obtained when using a copper‐glass system demonstrated a consistently purer sample for the glass‐glass system, with whole‐cell contamination of the external membrane leaflet being reduced to 0.4%. Problems associated with obtaining pure samples for biochemical analysis are discussed, and the results of freeze‐fracture with the glass‐glass and glass‐copper systems are compared. Sodium dodecyl sulfate polyacrylamide gel electrophoresis of polypeptides associated with the separate halves of the erythrocyte membrane demonstrated that band 3, the anion transport protein, separates with the cytoplasmic face, whereas only sialoglycoproteins and their fragments are retained in the external face. This finding, obtained with the glass‐glass system, is consistent with results of our earlier freeze‐fracture study that used a copper‐glass system which showed that covalent bonds may be bro

ISSN:0741-0581    

DOI:10.1002/jemt.1060030407

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

ISSN:0741-0581    

DOI:10.1002/jemt.1060030408

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

ISSN:0741-0581    

DOI:10.1002/jemt.1060030409

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

ISSN:0741-0581    

DOI:10.1002/jemt.1060030410

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

ISSN:0741-0581    

DOI:10.1002/jemt.1060030411

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY