ABSTRACT
In the present study we have observed with the electron microscope the glycogen body of the chick, Gallus domesticus, which constitutes a spinal cord circumventricular organ specific of birds. We have detected in young chickens and embryos the presence of considerable amounts of glycogen particles in the cerebrospinal and vascular compartments, coming from the glycogen body cells, which are able to discharge part of their glycogen into either the central canal or the capillary lumen, via ependymal and endothelial cells respectively. If this secretion is a physiological condition, we propose that the glycogen body would play a role in the maintenance of the hydric and glucose haemostasia in the central nervous system, as well as in the osmoregulation.
Subject(s)
Chickens/anatomy & histology , Glycogen/metabolism , Neurosecretory Systems/anatomy & histology , Animals , Capillaries/anatomy & histology , Ependyma/anatomy & histology , Epithelium/anatomy & histology , Microscopy, Electron , Neurosecretory Systems/blood supply , Spinal Cord/anatomy & histologyABSTRACT
The distribution of glial fibrillary acidic (GFA) protein was examined in cervical spinal cord of adult rat, according to the immunocytochemical peroxidase-antiperoxidase (PAP) method in semithin sections (1-2 microns). We have found astroglial cells in proximal regions of both ventral and dorsal roots. The presence of astrocytic processes reaching the central canal, only in the dorsal region suggest that they are the only radial glia cells which remain attached to the central canal.
Subject(s)
Glial Fibrillary Acidic Protein/analysis , Spinal Cord/cytology , Animals , Astrocytes/cytology , Immunoenzyme Techniques , Rats , Rats, Inbred StrainsABSTRACT
The presence and distribution of gliofibrillary acidic protein (GFAP) was studied in the postnatal spinal cord of the rat. On birth GFAP can be seen in astrocytic bodies and their processes of ventral columns; perivascular glial membrane was initially seen within white and gray matter; most of the fibers were transversally oriented. There are many mitotic cells, some of them with GFAP in their cytoplasm, while others lack it, thus providing strong evidence to identify two cellular populations as astrocytes and, possibly, oligodendrocytes and to state that neuroglial cells differentiate to astrocytes before myelination gliosis. The glia limitans membrane is continuous from the 5th day onwards and in 17-day-old animals the astrocytic framework of the spinal cord has reached its adult appearance.
Subject(s)
Astrocytes/metabolism , Intermediate Filament Proteins/metabolism , Neuroglia/metabolism , Oligodendroglia/metabolism , Spinal Cord/metabolism , Animals , Cell Differentiation , Glial Fibrillary Acidic Protein , Immunoenzyme Techniques , Mitosis , Rats , Rats, Inbred Strains , Spinal Cord/cytology , Spinal Cord/growth & developmentABSTRACT
Data about the nervous regulation of secretion in nucleus sacci vasculosi of Scylliorhinus canicula are provided in the present study. The existence of cholinergic synapsis over secretory processes and electric synapsis among amyelinic fibers is shown. Likewise, images that demonstrate the existence of a type of merocrine secretion in which the secretory granules coming from the nucleus sacci vasculosi are emptied into the vessels, conserving their completeness while they pass through the pericapillary basal membrane are provided.
Subject(s)
Cerebral Ventricles/anatomy & histology , Fishes/anatomy & histology , Neurosecretory Systems/anatomy & histology , Secretory Rate , Animals , Capillaries/innervation , Capillary Permeability , Cytoplasmic Granules/ultrastructure , Synapses/ultrastructure , Synaptic Vesicles/ultrastructureABSTRACT
Adult hamsters were used for this electron microscopic study of the hypothalamic region. Specialized contacts between astrocytes and astrocytes, and between astrocytes and other cellular elements, are described and illustrated. The specialized inter-astrocytic junctions occur primarily in perivascular and subpial regions, but also in areas of high synaptic density. The junctions between astrocytic processes are of hemidesmosomal type. Astrocytes are connected to oligodendroglial cells by means of desmosomes, and to neuronal processes by means of zonulae occludens. The functional significance of these arrangements is discussed.
Subject(s)
Astrocytes/ultrastructure , Hypothalamus/ultrastructure , Intercellular Junctions/ultrastructure , Animals , Cricetinae , Desmosomes/ultrastructure , Female , Male , Microscopy, Electron , Oligodendroglia/ultrastructureABSTRACT
Myelin-associated carbohydrates were studied by means of histochemical techniques in the central nervous system of birds and mammals. Polianions in the surface of myelin and in interfascicular oligodendroglia were detected using histochemical techniques. Glycoproteins were studied by means of concanavalin A. The Con-A-PO-DAB sequence was used. Concanavalin-A-binding sites were detected in oligodendroglia and on the myelin surface. Similar results were observed in both birds and mammals. The processes of the interfascicular oligodendroglia also contain carbohydrates. A close association between the carbohydrates of these glial processes and the myelin surface carbohydrates was demonstrated, and their probable identity is assumed.