Different Golgi ultrastructure across species and tissues: Implications under functional and pathological conditions, and an attempt at classification.

The Golgi complex (GC) is the central station of the secretory pathway, through which several paths of intracellular transport are connected. The main function of the GC is glycosylation of proteins and lipids, and their subsequent sorting. The structure of the GC is extremely complicated, although in general it is unbelievably similar across different cells types and under different functional and pathological conditions. However, there are also a lot of differences between the GCs in different cells and under different normal and pathological conditions. Here, we compare the phenotypes of the GCs in different organisms under these different conditions, in particular according to morphological criteria. We propose a classification of the GC types that reflects the different features of the GC, and that depends on the different molecular machines.

Neurons of the lateral spinal nucleus in the rat spinal cord - A Golgi study

The neurons of the lateral spinal nucleus in the spinal cord of young adult rats were studied in transverse and longitudinal planes using the Golgi-Kopsch method and electron microscope. The perikarya were mainly polygonal or spindle shaped, and measured 20 to 35 pm in the longest diameter. They formed a dense column in the dorsolateral funiculus underneath the pial surface. The dendrites followed three patterns. Several of them turned laterally and approached the surface of the spinal cord. Another group of dendrites ran longitudinally within the column of the perikarya. A third group of dendrites turned medially or ventromedially and coursed towards the reticulated portion of the gray matter. Medium-sized neurons located at the margin of this latter portion of the spinal cord sent some of their straight dendrites into the dorsolateral funiculus. Thus, the dendrites of these two populations of neurons appeared as rungs of a ladder in longitudinally-cut spinal cord specimens. Only the initial portions of the axons of the LSN neurons could be impregnated. They originated with a regular axon hillock from either the perikaryon or from one of the primary dendrites and became unimpregnated after a 20 to 40 ?m long course, indicating their myelinated character. Preliminary ultrastructural observations revealed that the laterally directed dendrites of the neurons in the lateral spinal nucleus approached the free surface of the spinal cord and ended immediately underneath the pia mater. Large numbers of fine, unmyelinated fibers were found in the dorsolateral funiculus coursing perpendicular to the laterally and medially oriented dendrites (AU)

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Functional organization of the Golgi apparatus in glycosphingolipid biosynthesis. Lactosylceramide and subsequent glycosphingolipids are formed in the lumen of the late Golgi.

Biosynthesis of plasma membrane sphingolipids involves the coordinate action of enzymes localized to individual compartments of the biosynthetic secretory pathway of proteins. These stations include the endoplasmic reticulum and the Golgi apparatus. Although a precise localization of all the enzymes that synthesize glycosphingolipids has not been achieved to date, it is assumed that the sequence of events in glycosphingolipid biosynthesis resembles that in glycoprotein biosynthesis, i.e. that early reactions occur in early stations (endoplasmic reticulum and cis/medial Golgi) of the pathway, and late reactions occur in late stations (trans Golgi/trans Golgi network). Using truncated analogues of ceramide and glucosylceramide that allow measurement of enzyme activities in intact membrane fractions, we have reinvestigated the localization of individual enzymes involved in glycosphingolipid biosynthesis and for the first time studied the localization of lactosylceramide synthase after partial separation of Golgi membranes as previously described (Trinchera, M., and Ghidoni, R. (1989) J. Biol. Chem. 264, 15766-15769). Here, we show that the reactions involved in higher glycosphingolipid biosynthesis, including lactosylceramide synthesis, all reside in the lumen of the late Golgi compartments from rat liver.

A Golgi Type II neuron in trigeminal nucleus oralis: a Golgi study in the rat.

This Golgi study identifies a class of small neurons in trigeminal nucleus oralis (Vo) that satisfies all the morphological criteria for a Golgi Type II neuron. The cylindrical-shaped dendritic arbor extends up to 500 micron in the rostrocaudal axis and is confined to Vo. The unmyelinated axon generates a highly branched collateral axonal plexus within or near the dendritic tree and it does not project out of Vo. This Golgi Type II neuron is considered to be an inhibitory interneuron and probably participates in a variety of inhibitory phenomena known to occur in Vo.