Advances in ultrastructural postembedment localization of antigens in Epon sections with peroxidase labelled antibodies

Development of a Pseudocellular System to Quantify Specific Interactions Determining the G-Quadruplex Function in Cells

Intracellular chemical microenvironments, including ion concentrations and molecular crowding, play pivotal roles in cell behaviors, such as proliferation, differentiation, and cell death via regulation of gene expression. However, there is no method for quantitative analysis of intracellular environments due to their complexity. Here, we have developed a system for highlighting the environment inside of the cell (SHELL). SHELL is a pseudocellular system, wherein small molecules are removed from the cell and a crowded intracellular environment is maintained. SHELL offers two prominent advantages: (1) It allows for precise quantitative biochemical analysis of a specific factor, and (2) it enables the study of any cell, thereby facilitating the study of target molecule effects in various cellular environments. Here, we used SHELL to study G-quadruplex formation, an event that implicated cancer. We show that G-quadruplexes are more stable in SHELL compared with in vitro conditions. Although malignant transformation perturbs cellular K+ concentrations, environments in SHELL act as buffers against G-quadruplex destabilization at lower K+ concentrations. Notably, the buffering effect was most pronounced in SHELL derived from nonaggressive cancer cells. Stable G-quadruplexes form due to the binding of the G-quadruplex with K+ in different cancer cells. Furthermore, the observed pattern of G-quadruplex-induced transcriptional inhibition in SHELL is consistent with that in living cells at different cancer stages. Our results indicate that ion binding to G-quadruplexes regulates gene expression during pathogenesis.

Adult rat cardiomyocytes cultured in creatine-deficient medium display large mitochondria with paracrystalline inclusions, enriched for creatine kinase

In adult regenerating cardiomyocytes in culture, in contrast to fetal cells, mitochondrial creatine kinase (Mi-CK) was expressed. In the same cell, two populations of mitochondria, differing in shape, in distribution within the cell and in content of Mi-CK, could be distinguished. Immunofluorescence studies using antibodies against Mi-CK revealed a characteristic staining pattern for the two types of mitochondria: giant, mostly cylindrically shaped, and, as shown by confocal laser light microscopy, randomly distributed mitochondria exhibited a strong signal for Mi-CK, whereas small, "normal" mitochondria, localized in rows between myofibrils, gave a much weaker signal. Transmission EM of the giant mitochondria demonstrated paracrystalline inclusions located between cristae membranes. Immunogold labeling with anti-Mi-CK antibodies revealed a specific decoration of these inclusions for Mi-CK. Addition of 20 mM creatine, the substrate of Mi-CK, to the essentially creatine-free culture medium caused the disappearance of the giant cylindrically shaped mitochondria as well as of the paracrystalline inclusions, accompanied by an increase of the intracellular level of total creatine. Replacement of creatine in the medium by the creatine analogue and competitor beta-guanidinopropionic acid caused the reappearance of the enlarged mitochondria. It is believed that the accumulation of Mi-CK within the paracrystalline inclusions, similar to those observed in certain myopathies, represents a compensatory effect of the cardiomyocytes to cope with a metabolic stress situation caused by low intracellular total creatine levels.

Immunogold localization of peroxisomal enzymes in Epon-embedded liver tissue. Enhancement of sensitivity by etching with ethanolic sodium hydroxide

Epon-embedded biological materials exhibit well preserved ultrastructure but generally weak antigenicity. Brief etching of ultrathin Epon sections with resin solvent, ethanolic sodium hydroxide, brought about a nearly 2-fold increase in the immunogold labeling density of rat and human hepatic peroxisomes after incubation with antisera against catalase and 3 enzymes of lipid beta-oxidation: acyl-CoA oxidase, bifunctional protein (enoyl-CoA hydratase-3-hydroxyacyl-CoA dehydrogenase) and 3-ketoacyl-CoA thiolase. The etching was superior to pretreatment with an oxidant, sodium metaperiodate. Despite some deterioration of the cellular ultrastructure, the obtained enhancement of the sensitivity of the protein A-gold method may be helpful in cases when the antigenicity to be detected is strongly inhibited by epoxy resin embedding.

Immunoelectron microscopic localization of renin in the juxtaglomerular cells of the amphibian Bufo bufo

The ultrastructural localization of renin in the juxtaglomerular apparatus of the kidney of the toad Bufo bufo has been examined using an immunogold staining method for electron microscopic immunocytochemistry and an antiserum to renin isolated from the submandibular gland of the mouse. Renin immunoreactivity was confined to lamellated granules in the cytoplasm of epitheloid or juxtaglomerular cells in the glomerular afferent arterioles and also in the media cells of larger arteries. Mouse kidney tissue, examined for purposes of comparison, showed immunolabeling limited to the granules of the juxtaglomerular cells. The presence of renin or a renin-like substance in the juxtaglomerular granules of the toad kidney is discussed in relation to the lysosomal nature of these granules. A model is presented linking the lysosomal function of the juxtaglomerular granules and the release of renin mediated by beta-adrenergic receptors present on the surface of the juxtaglomerular cells.

Light microscopic histochemistry on plastic sections

As compared with conventional paraffin, celloidin, and frozen sections, semithin plastic sections offer a superior quality of the light microscopic image in terms of better resolution, absence of distortion and shrinkage artifacts, and suitability for calcified tissues. Application of histochemical methods to such sections often encounters, however, serious difficulties resulting from a considerably reduced reactivity of plastic-embedded biological material. Factors involved include a poor penetration of reagents into plastic embedding media due to a steric or hydrophobic hindrance, as well as a blockade of the reactive chemical groups in the sample due to interactions with fixatives and plastics. Embedding in polar (hydrophilic) plastics, such as glycol methacrylate, permits carrying out a large number of histochemical reactions, including the demonstration of enzymatic activities, directly on sections, but is less suitable for combined light/electron microscopic studies because of an imperfect ultrastructural preservation of tissues. Embedding in nonpolar epoxy resins, particularly if combined with a double aldehyde-osmium fixation, results in a high quality ultrastructure but almost fully inhibits the histochemical reactivity of the embedded material. In order to restore this reactivity, i.e. to unmask chemical groups bound by the polymerized resin, semithin epoxy sections require the removal of the embedding matrix by alkoxides prior to the histochemical procedure. Additional steps are also often necessary: treatment of osmium-fixed sections with oxidative agents, e.g., hydrogen peroxide or periodate which reoxidize the bound osmium and remove it from tissue, and a controlled proteolytic digestion, especially useful in immunocytochemical studies, which probably cleaves the bonds between the primary aldehyde fixative, and the reactive sites. This article reviews histochemical methods which have been successfully applied to plastic-embedded material. Using polar methacrylates and/or nonpolar epoxy resins as embedding media, it has been possible to demonstrate proteins and aminoacid residues, carbohydrates, lipids, nucleic acids, biogenic amines, inorganic ions, and some enzymes, although the spectrum of methods found as suitable for plastic-embedded material is far narrower than that available for paraffin or frozen sections.(ABSTRACT TRUNCATED AT 400 WORDS)

Visualization of epidermal growth factor receptors in human epidermis

The localization of epidermal growth factor (EGF) receptors in normal human epidermis was examined with two independent experimental methods. The distribution of EGF receptor sites was studied using light microscopic autoradiography with [125I]EGF and direct immunocytochemical techniques with EGF receptor antibodies and protein A-colloidal gold complexes. Direct visualization by autoradiography indicated that the concentration of EGF receptors was greatest in the lower epidermal layers. Ultrastructural morphometric analysis of protein A-gold complexes showed that EGF receptors were primarily associated with the plasma membranes although intranuclear and cytoplasmic localization was also evident. This postembedment immunolocalization method also confirmed the relative differences in the number of EGF receptors found in individual epidermal layers (basalis greater than spinosum greater than granulosum greater than corneum layers). This inverse relationship between numbers of EGF receptors and the degree of epidermal differentiation and/or keratinization may suggest a physiologic role for EGF in these processes in human epidermis.