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During early pregnancy, the absence of fully developed internal organs means that the embryo is dependent on highly differentiated adnexal structures such as the secondary yolk sac and free-floating amniotic membrane as well as the placental trophoblast. In this review, we describe and illustrate the ultrastructural characteristics of these different cellular barriers which separate maternal and embryonic...
The structure of mouse skin collagen fibrils, after treatment with lithium chloride at a dose of 0.7 meq/kg of body weight, was studied by electron microscopy. Animals were sacrificed 1-day, 1-, 2- and 6-months after the end of 30 consecutive days experimental period. Fibrils in disarray interspersed with normal ones were seen, although there were areas where the normal parallel packing of fibrils...
This review is centered on the applications of thin sections to the study of intracellular precursors of bacteriophage heads. Results obtained with other preparation methods are included in so far as they are essential for the comprehension of the biological problems. This type of work was pioneered with phage T4, which contributed much to today's understanding of morphogenesis and form determination...
Keyhole limpet haemocyanin (KLH) from almost all newly captive animals contains a mixture of KLH1 and KLH2. We show that the dissociation of KLH2 can be produced during EM specimen preparation by the negative staining-carbon film (NS-CF) procedure and in solution by ammonium molybdate-PEG solutions at slightly acidic pHs. The KLH2 multidecamers split apart in the pH range 7.5-6.5 and in the pH range...
This article examines the published evidence in support of the classification of organisms into three groups (Bacteria, Archae, and Eukarya) instead of two groups (prokaryotes and eukaryotes) and summarizes the comparative biochemistry of each of the known histone-like, nucleoid DNA-binding proteins. The molecular structures and amino acid sequences of Archae are more similar to those of Eukarya than...
The muscles of teleost fish are different in ultrastructure from those of most other kinds of vertebrate. A distinct difference is that they are much more highly ordered than the frog, rabbit or human muscles conventionally used as vertebrate muscle stereotypes. The improved order permits the full application of powerful techniques such as electron microscopy and image processing, and X-ray diffraction...
Applications of the Sayre equation to the electron crystallographic analysis of protein structures are demonstrated. Starting with a lower-resolution basis phase set obtained from the Fourier-transform of an electron micrograph, it is possible, for example, to extend directly to the higher resolution of the electron diffraction pattern. Examples of such analyses include bacteriorhodopsin, halorhodopsin...
Colloidal gold is the most widely used electron dense marker in biological electron microscopy. The development of procedures for making gold particles of very defined sizes has made double or even multiple labelling possible using gold of two or more different sizes. Lately a new type of electron dense marker has been developed consisting of ligand-stabilized metal atom clusters rather than colloidal...
Sequential removal of the 33-, 23-, and 16-kDa extrinsic subunits of higher plant photosystem II (PSII) by various salt-washing procedures has been monitored by gel electrophoresis and oxygen evolution activity measurements. Structural changes induced by the subunit removal were followed by electron microscopy in conjunction with image processing of two-dimensional (2-D) crystals of PSII. In addition...
The purpose of this study was to improve the immunogold labeling of epoxy sections and to increase our knowledge of the mechanism for how antigens become immunolabeled on resin sections. Tissues from pancreas, thyroid and fibrin clots were embedded in an epoxy resin and LR-White. The epoxy mixture was composed and treated in different ways, especially with respect to altered amounts of accelerator...
The purpose of this study was to examine how the intensity of the immunogold labeling on epoxy sections was affected by the use of propylene oxide as an agent in addition to ethanol in the dehydration and infiltration, and also to examine the effect on the immunogold labeling by adding small amounts of propylene oxide to the embedding mixture. Increased knowledge of the mechanism for antigen detection...
The articulating surfaces of bones which ossify in mesenchyme, like the mandible, are covered by a layer of dense, fibrous tissue. The purpose of the present study was to examine the structure of the mandibular condyle in the monkey. Young Rhesus monkeys (Macaca mulatta) were perfused with glutaraldehyde-paraformaldehyde. Small pieces of the condyles were dissected out, demineralized in 0.5 M EDTA...
High quality InAlSb/InSb bilayers and superlattices have been grown by magnetron sputter epitaxy and the physical structure has been characterized by transmission electron microscopy. It was found that single layers of InAlSb, whose thicknesses greatly exceeded the equilibrium critical thickness, could be grown coherently on (001) InSb for Al concentrations approaching 13–15%. Also, it was observed...
The kinematic theory of electron scattering is used to estimate the dark-field, weak-beam image contrast of a stacking fault with an associated fault vector which has a component in the direction perpendicular to the plane of the fault. It is shown, using the rigid ion model of the crystal potential, that the average contrast of the image depends on the sign of the diffraction vector. The difference...
The nucleosome is the ubiquitous and fundamental DNA-protein complex of the eukaryotic chromosome, participating in the packaging of DNA and in the regulation of gene expression. Biophysical studies have implicated changes in nucleosome structure from chromatin that is quiescent to active in transcription. Since DNA within the nucleosome contains a high concentration of phosphorus whereas histone...
The purpose of this study was to examine how antigen retrieval affected the yield of immunogold labeling on epoxy sections based on embedding with different amounts of accelerator. The concentration of accelerator DMP-30 (tri(dimethyl amino methyl) phenol) was varied in the range of 0–8% in the processing of the tissue for epoxy embedding. Immunogold labeling was performed on epoxy sections and LR-White...
The phosphoenolpyruvate synthase (EC 2.7.9.2) of the hyperthermophilic archaeonStaphylothermus marinus forms an unusually large (2.25 MDa) homomultimeric complex of 24 94 kDa subunits. This assembly stands in contrast with the more usual dimeric or tetrameric quaternary arrangements of phosphoenolpyruvate utilising enzymes from eukaryotes and eubacteria. Here, computerised image analysis and reconstruction...
Structural alterations of mouse skin collagen fibrils brought about by treatment with lithium chloride at various doses, as studied by electron microscopy, are discussed. The effect of the duration of treatment on such fibrils is also investigated. An analysis of positive staining patterns from fibrils from mice treated with lithium is included. In addition, this review describes how computer analyses...
Yeasts are unicellular eukaryotes, and are used widely as a model system in basic and applied field of life science, medicine, and biotechnology. The ultrastructure of yeast cells was first studied in 1957 and the techniques used have advanced greatly in the 40 years since then; an overview of these methods is first presented in this review. The ultrastructure of budding and dimorphic yeast cells...
Preliminary results on the feasibility of using co-evaporation of eutectic Au/Sn solder for semiconductor packaging are presented. Gold is electron beam evaporated, while Sn is thermally evaporated, onto Ti/Pt/Au metallized InP substrates. Electron microscopy is utilized to determine the composition and uniformity of the solder and to characterize interfacial reactions between the solder and the semiconductor...
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