Human cultured fibroblasts were fed with G,, ganglioside species isotopically labeled at C3 of C1 Ssphingosine, or at C3 of C18-sphinganine, or at the sialic acid acetyl group, and with C18-sphingosine and CIS-sphinganine, both labeled at C1. After a lipid pulse the cells were subjected until 7-day chase; measurements were then made of the radioactive products resulting from the administered long-chain base and ganglioside species catabolism and the salvage processes of catabolic fragments. From the data we drew the following conclusions.The G,, species differing in the long-chain base structure were taken up by the cells and metabolized. About 80% of the total catabolic CIS-sphingosine and C18-sphinganine were recycled for the biosynthesis of complex sphingolipids, the rest being degraded.Results obtained by administering ganglioside species of G,, containing radioactive sphingosine or the free radioactive sphingosine to fibroblasts suggested the existence in the cells of two quite separate pools of sphingosine. One pool was the direct result of either the catabolism of radioactive G,, highdensity microdomains or the diffusion of exogenous sphingosine into the cell; this pool was mainly used for the biosynthesis of the G,, species that contain palmitic and stearic acids. The other pool of sphingosine, the cell basal pool, came from the catabolism of radioactive sphingolipids in the recycling of sphingosine, and was used for the biosynthesis of the G,, species that mainly contain very long fatty acid chains, the main fibroblast endogenous species of GD3. Administration of the ganglioside species of G,, containing sphinganine or free sphinganine to fibroblasts yielded the G,, species containing mainly very long-chain fatty acids and sphingosine.These results show the possible existence of a pool of ganglioside-derived sphingosine, quite separate from the cell basal pool of sphingosine, suggesting that sphingosine derived from sphingolipid catabolism is reduced to sphinganine before entering the sphingolipid biosynthetic pathway.Keywords: ganglioside ; biosynthesis ; sphingosine ; sphinganine ; recycling.Gangliosides, sialic acid containing glycosphingolipids that are normal components of plasma membranes [I], are biosynthesized in the Golgi apparatus and degraded in the lysosomes [2] to fragments that are recycled for biosynthetic purposes [3-61. Among the ganglioside catabolic fragments, sphingosine has attracted scientific interest and increasing attention. It has been shown to act as an intracellular effector through the modulation of protein kinase C and other enzyme activities [7-91. Most of our present information arises from the administration of sphingosine to cells, but little is known about a potential role of a pool of sphingosine originated from ganglioside catabolism in modulating cell function.Catabolic sphingosine is partly recycled, but much of it is degraded [6, ; thus it is difficult to determine to what degree this recycling affects the overall sphingolipid turnover. Moreover, the de novo biosy...

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Chondrocytes may play an Important role in the inflammatory reactions involving intervertebral discs: the role of metalloproteases (MMP.) and the imbalance between proteases and their inhibitors seems to play a crucial role in the disc degenerative process. In the present study we have analysed the production of collagenase-1 and stromelysin in different parts of herniated intervertebral discs. Ten samples of herniated lumbar discs were obtained from adult patients operated on for primary microdiscectomy because of persistent radicular symptoms and subdivided into three samples: 1. The nearest to the nerve root in close contact with it, 2. the sample obtained from the intervertebral space, and 3. the sample obtained from the vertebral plates. The DNA content of each specimen was measured in order to obtain the best estimate of the cell content as well as to normalise the content of collagenase-1 and stromelysin found in the same tissues with respect to the number of cells. In 9 out of the 7 0 cases the DNA content was significantly higher in samples obtained from the intervertebral plates than in samples obtained near the nerve root or the intervertebral space. DNA content did not show any significant difference considering disc samples contiguous to the nerve root and samples obtained from the intervertebral space. The production of collagenase-1 did not show a specific pattern, being produced in similar quantities in the three disc compartments. The production of stromelysin was significantly lower in disc samples obtained from the intervertebral plates. In conclusion the results of the present study suggest firstly that in the herniated lumbar disc the reactivity and the production of pro-inflammatory agents is independent of DNA content, i.e. the cellularity of the sample, and secondly that activated cells in the intervertebral space and in the part of the disc in contact with the nerve root, even if scarce in number, are able to synthesise a proportionally higher quantity of MMP than the high-cellular disc fragments from the intervertebral plates, potentially playing a specific role in the inflammatory reactions. [Neurol Res 1999; 21: 677-681].

Immunocytochemical analysis of the laminin alpha-2 (merosin) chain in the muscle of patients with Classic Congenital Muscular Dystrophy (Cl-CMD) differentiates the types of the disease associated with a merosin deficit from those that are merosin positive. Patients with Central Nervous System involvement in merosin negative Cl-CMD always present alterations of the white matter at RMI, but usually these are not clinically significant. While ocular malformations (microphthalmia, alterations of the anterior chamber, of the retina, or of the angle and cataract) and damage to the Central Nervous System are described in some subtypes of CMD (Muscle Eye Brain disease, Walker Warburg Syndrome), ocular involvement and retino-cortical conduction in merosin negative Cl-CMD are not well known. This study reports on four patients affected by merosin negative Cl-CMD. All these patients presented important alterations of the white matter associated with ventricular enlargement and, in one case, with pachygyria and micropolygyria. Refraction, visual acuity, ocular motility, anterior segment and fundus were examined. ERG Maximal, Cone and Rod response, VEP transient pattern reversal was carried out as well. Significant alterations at the standard ophthalmologic examination or of the electroretinogram responses were not registered while, in all cases, important modifications in retino cortical conduction (reduction in amplitude, increase in latency, reduction in amplitude on the lateral derivations) were observed, demonstrating involvement of the optic pathway at different levels during the course of this disease.