Regulatory peptide immunocytochemistry at light- and electron microscopical levels

Summary Immunocytochemical techniques applied at both light- and electron microscopical levels are valuable in the study of regulatory peptide distribution in normal and diseased tissue, whether in the form of sections or whole cell preparations. Successful immunolocalisation depends on 1) adequate preservation of the peptide antigen and the tissue structure in which it resides; 2) a suitably specific and sensitive labelled antibody detecting system. In general, peptides are stable molecules, most of which retain their antigenicity after conventional cross-linking fixation and tissue processing, allowing standard immunocytochemical methods to be used for light- and electron microscopy. Regulatory peptides are derived from precursor molecules and several families of structurally similar peptides are now generally recognised. Region-specific antibodies may be needed to overcome problems of cross-reactivity or to identify a bioactive form in the presence of its precursor. Multiple co-localisation of different related and unrelated peptides in the same cell or even storage granule is now recognised and can be identified by immunocytochemistry.     

Intracellular topography of immunoreactive gastrin demonstrated using electron immunocytochemistry

Summary Gastrin (G)-producing cells from the mammalian gastric antrum have been investigated using computer-assisted morphometry and a novel double colloidal gold-labeled-immunoglobulin electron immunocytochemical procedure. Correlation analysis of human antral G-cells indicates (p<0.001) that a single population of granules exists with small (160 nm) electron-dense and large (240 nm) electron-lucent forms representing the extremes. Non-crossreacting region-specific antisera have been used to visualize G-17 and G-34 (progastrin) to the small electron-dense granules and G-17 to the other intermediate forms. From the results we propose a topographic segregation of immunoreactive gastrins within 2 apparently distinct granule subclasses and suggest that this may represent the pathway of granule maturation.     

Regulatory peptide receptors: visualization by autoradiography

Summary The receptors for regulatory peptides have been extensively characterized using radioligand binding techniques. By combining these binding techniques with autoradiography it is possible to visualize at the light and electron microscopic levels the anatomical and cellular localization of these receptors. In this review we discuss the procedures used to label peptide receptors for autoradiography and the peculiarities of peptides as ligands. The utilization of autoradiography in mapping peptide receptors in brain and peripheral tissues, some of the new insights revealed by these studies particularly the problem of mismatch between endogenous peptides and receptors, the existence of multiple receptors for a given peptide family and the use of peptide receptor autoradiography in human tissues are also reviewed.     

Regulatory peptide receptors: visualization by autoradiography

The receptors for regulatory peptides have been extensively characterized using radioligand binding techniques. By combining these binding techniques with autoradiography it is possible to visualize at the light and electron microscopic levels the anatomical and cellular localization of these receptors. In this review we discuss the procedures used to label peptide receptors for autoradiography and the peculiarities of peptides as ligands. The utilization of autoradiography in mapping peptide receptors in brain and peripheral tissues, some of the new insights revealed by these studies particularly the problem of 'mismatch' between endogenous peptides and receptors, the existence of multiple receptors for a given peptide family and the use of peptide receptor autoradiography in human tissues are also reviewed.     

An electron microscopical demonstration of the permeability of cerebral and retinal capillaries to ions

Résumé Des injections intra-thécales et intra-vitreuses d'ions de ferrocyanure et de sulfate dans les rats étudiés au microscope électronique, permettant de constater que les jonctions endothéliales des vaisseaux cérébraux et rétinaux sont perméable aux petites molécules.     

A new dopaminergic terminal plexus in the ventral horn of the rat spinal cord. Immunohistochemical studies at the light and electron microscopic levels

Summary It has been thought that the ventral motor column in the rat spinal cord is virtually free of dopaminergic fibers. However, a new dopaminergic terminal plexus was visualized at all spinal levels in the ventral horn using electron as well as light microscopic immunohistochemistry.     

APUD characteristics and immunocytochemistry of avian pituitary corticotrophs.

L-DOPA is taken up and decarboxylated by cells in the avian adenohypophysis, which are situated largely in the cephalic lobe. These APUD cells have been shown by sequential formaldehyde-induced and immunofluorescence to be corticotrophs and the relationship between the two procedures has been found to have a reciprocal quality.     

Processing of peptide and hormone precursors at the dibasic cleavage sites

Many functionally important cellular peptides and proteins, including hormones, neuropeptides, and growth factors, are synthesized as inactive precursor polypeptides, which require post-translational proteolytic processing to become biologically active polypeptides. This is achieved by the action of a relatively small number of proteases that belong to a family of seven subtilisin-like proprotein convertases (PCs) including furin. In view of this, this review focuses on the importance of privileged secondary structures and of given amino acid residues around basic cleavage sites in substrate recognition by these endoproteases. In addition to their participation in normal cell functions, PCs are crucial for the initiation and progress of many important diseases. Hence, these proteases constitute potential drug targets in medicine. Accordingly, this review also discusses the approaches used to shed light on the cleavage preference and the substrate specificity of the PCs, a prerequisite to select which PCs are promising drug targets in each disease.     

The relative antiquity of fenestrated blood capillaries and lymphatics,and their significance for the uptake of large molecules: an electron microscopical investigation in an elasmobranch

Résumé Le requin n'a pas de vrais vaisseaux lymphatiques, mais ses capillaires sanguins sont fénestrés. On suppose que les grandes molécules sont éliminées des tissus par ces fenestrae.     

Electron microscopical observation of the contact between ribosomes and detergent-resistant cytofilaments

The contact of cytofilaments with ribosome-like particles in Triton X-100-treated cells of Zajdela ascites hepatoma was revealed. It is suggested that cytofilaments are engaged in the transport of ribosomes from the nuclear surface into definite areas of cytoplasm.     

Electron microscopical observation of the contact between ribosomes and detergent-resistant cytofilaments

Summary The contact of cytofilaments with ribosome-like particles in Triton X-100-treated cells of Zajdela ascites hepatoma was revealed. It is suggested that cytofilaments are engaged in the transport of ribosomes from the nuclear surface into definite areas of cytoplasm.     

Mouse sex vesicle. C-band and pairing at the light and electron microscope

Summary C banded mouse pachytene chromosomes were studied with the light and electron microscopes by the whole mount technique. The X and Y chromosomes show pairing by the long, by the short or by both long and short arms. Assuming Lyon's hypothesis, the latter suggests that the Y segment transferred to the X is intercalar. With the light microscope, a negative image of the synaptonemal complex is evidenced.This work was supported by grants of the Brazilian Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) and Fundo Especial de Despesas do Instituto Butantan (FEDIB).We acknowledge Dr. N. Leon for his editorial suggestions.     

Effects of handling normal and bulbectomized rats at adrenal and plasma corticosterone levels

Summary Normal and bulbectomized adult rats, male and female, handled daily for 4 weeks, show plasma and adrenal corticosterone values significantly lower than the non-handled ones.