Astrocyte Protoplasmic

FIGURE 1-12 A protoplasmic astrocyte abuts a blood vessel (lumen at I) in rat cerebral cortex. The nucleus shows a rim of denser chromatin, and the cytoplasm contains many organelles, including Golgi and rough endoplasmic reticulum, x 10,000. Inset (top left) Detail of perinuclear cytoplasm showing filaments. X44,000. 

Figure 14.4 Different types of glial cells. Astrocytes connect capillaries and neurones. Fibrous astrocytes, with less branching and more filamentous processes, occur mainly in white matter while protoplasmic astrocytes are located principally in the grey matter. Oligodendrocytes form the myelin sheath by wrapping themselves around axons. The connection between the myelin sheath and the oligodendrocyte is permanent and provides material for the myelin sheath. Microgliocytes (microglia) are the phagocytes of the nervous system. The ciliated ependymal cells line the cavities of the central nervous system.

The protoplasmic ash ocytes, on the other hand, have more complex morphology. They contain highly branched processes that form membranous sheets surrounding the neuronal processes, cell bodies and end-feet on capillaries. In conh ast to fibrous astrocytes, these cells have fewer IFs and a greater density of organelles. 

CNS Copper deposits affect the whole CNS. Degeneration and tissue loss as well as atrophy of the lenticular nucleus prevail. Occasionally, there are also small necrotic foci with a diffuse spot-like distribution. Micro-cavernous lesions occur due to the destruction of nerve cells. Myelinized fibres and oligodendrocytes are present, but there is also cellular hyperplasia and hypertrophy of astrocytes rich in protoplasm. The cerebral changes detectable in CT scanning do not correlate with the degree of severity of the functional disturbances (320, 335) however, there is a close correlation between the lesions detected by MRI and certain neurological findings. (350, 366, 376, 388) (s. p. 615)... 

Levine. J. M. and Card, J. P., Light and electron microscopic localisation of a cell surface antigen (NG2) in the rat cerebellum. Association with smooth protoplasmic astrocytes, J. Neumsci., 7, 2711, 1987. 

Yokoo H, Nakazato Y. A monoclonal antibody that recognizes a carbohydrate epitope of human protoplasmic astrocytes. Acta Neuropathol. 1996 91 30. 

The hbrillary astrocytoma is more common than the protoplasmic astrocytoma. " Fibrillary astrocytomas are a mixture of cellular processes (fibrils) and nuclei of greater angularity and density than normal or reactive astrocytes (Fig. 20.13 see Fig. 20.1 IB). They contain more intracytoplasmic fibrils, and their cellular processes are longer than those in protoplasmic astrocytomas. Thus, only the fibrillary astrocytoma stains well with phosphotungstic acid hematoxylin (PTAH), which stains fibrillar protein arrays, whereas both... 

Macroglial cells are of ectodermal origin and include the astrocytes, ependymal cells, oligodendrocytes, and Schwann cells. Astrocytes appear to be primarily supportive in function and under microscopic examination can be seen to envelope axons and dendrites and buttress against the adventitial layer of blood vessels. In the gray matter of brain, which is composed primarily of perikarya, they have a clear protoplasmic appearance, whereas in the white matter, which is composed primarily of neuronal processes, they appear fibrous. Ependymal cells line the ventricles of the brain, are ciliated. 

Asada, H., Ip, N. Y., Pan, L., Razack, N., Parfitt, M. M and Plunkett, R. J. (1995) Time course of ciliary neurotrophic factor mRNA expression is coincident with the presence of protoplasmic astrocytes in traumatized rat striatum. J. Neurosci. Res. 40 22-30. 

In tissue culture, the glial cells derived from posterior lobes of dog and rat had the same morphological characteristics as protoplasmic astrocytes derived from various parts of the brain (Hild 1954). Oligodendroglia cells were sometimes observed in cultures of posterior lobe macrophages, which according to the investigations of Costero (1930) are probably identical with microglial, are a very common observation. 

Astrocytes, oligodendrocytes, ependyma, and microglial cells are four major support cells in the mammalian CNS. Astrocytes provide a structural scaffold for other elements of the CNS and regulate the exchange of fluid. Fibrous and protoplasmic astrocytes are two types of astrocytes. Oligodendrocytes coat the axons in the CNS with myelin. The primary function of the ependyma is to interact with astrocytes to form a barrier separating the ventricles of the brain and cerebrospinal fluid (CSF) from the CNS... 

---