Golgi apparatus composition

The most important membranes in animal cells are the plasma membrane, the inner and outer nuclear membranes, the membranes of the endoplasmic reticulum (ER) and the Golgi apparatus, and the inner and outer mitochondrial membranes. Lysosomes, peroxisomes, and various vesicles are also separated from the cytoplasm by membranes. In plants, additional membranes are seen in the plastids and vacuoles. All membranes show polarity—e., there is a difference in the composition of the inner layer (facing toward the cytoplasm) and the outer layer (facing away from it). 

In an attempt to gain further insight into the origin of the milk lipid globule membrane, the composition of this membrane has been compared to that of secretory vesicle membranes (Keenan et al. 1979). The vesicle membrane was found to be compositionally intermediate between Golgi apparatus membranes and lipid globule membrane. However, the isolation procedure yielded a fraction enriched in immature secretory vesicles and mature secretory vesicles may more closely resemble lipid globule membrane in composition. 

Keenan, T. W. and Huang, C. M. 1972B. Membranes of mammary gland. VI. Lipid and protein composition of Golgi apparatus and rough endoplasmic reticulum from bovine mammary gland. J. Dairy Sci. 55, 1586-1596. 

Keenan, T. W. and Morr6, D. J. 1970. Phospholipid class and fatty acid composition of Golgi apparatus isolated from rat liver and comparison with other cell fractions. Biochemistry 9, 19-25. 

The typical ultrastructural ganglion cell abnormalities consist of membranous cytoplasmic bodies (MCB) (see fig. 3) which are round or oval, measure 0.5 to 2.0// in diameter and may occupy a considerable portion of the cytoplasm (Terry and Weiss 1963, Korey et al. 1963a, b, Samuels et al. 1962, 1963, 1965, Terry and Korey 1960, 1963). They are also found in the axis cylinders, glial cells and perivascular cells. Their composition and pathogenesis is discussed in detail below. Other intracellular components appear diminished in number. Vacuoles and small channels may be seen which impinge on the Golgi apparatus. The mitochondria appear normal, even in highly abnormal cells, and ribosomes are plentiful. 

The process by which one membrane type is progressively transformed from one type of cell component into another through changes in the composition or arrangement of its constituents, e.g., transformation of Golgi apparatus cisternae from ER-like on one face of the stack to plasma membrane-like on the opposite face of the stack. This provides a mechanism whereby different membrane types may share common origins. 

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