Quantitative determination of the neutral glycosyl ceramides in bovine thyroid gland

The shuttling of dolichol between VLDL and HDL: involvement of a protein factor from lipoprotein-deficient human serum

The occurrence of a dolichol transfer factor in LPDS has been demonstrated using three different transfer assays. Applying a three step purification procedure, the transfer factor could be enriched 4000-5000-fold with a recovery of 1-2%. SDS-gel electrophoresis revealed a molecular weight of 64 kDa. Kinetics as well as the influence of a series of effectors were studied. Transfer was not accompanied by a concurrent esterification and the HDL3 subpopulation showed the highest acceptor capacity. The transfer factor also affected liposomal stability based on calcein fluorescence dequenching upon release. The characteristics of this dol-TP are discussed in view of these other plasma LTPs. Dol-TP might play a role in dolichol transfer from VLDL to HDL, observed in vivo.

Sex-specific difference of the galabiosylceramide level in the glycosphingolipids of human thyroid

The glycosphingolipids of human thyroid were isolated and characterized by gas-liquid chromatography and sequential enzymic hydrolysis. The major purified components were identified as glucosyl- and galactosyl-ceramides, lactosyl- and galabiosylceramides, globotriaosyl- and globotetraosylceramides. The long-chain base analyses showed a high proportion of phytosphingosine in glycosylceramide and galabiosylceramide. Fatty acids in 22:0, 24:0, 24:1 prevailed, especially in the cerebroside fraction, with a significant content of alpha-hydroxylated species in galactosylceramide. Female thyroid had a very low content of galabiosylceramide and a higher content of glucosylceramide, as compared to male. No significant difference was found in the other neutral glycosphingolipids and gangliosides.

Fluidity characteristics of bovine thyroid plasma membranes

Highly purified plasma membranes of bovine thyroid were obtained by differential pelleting followed by discontinuous gradient centrifugation in a swing-out rotor. Subfractions of plasma membranes were prepared by affinity chromatography on Con A-Sepharose. The final membrane fractions were enriched 25-30-fold over homogenate in 5'-nucleotidase and alkaline phosphatase and displayed a protein to phospholipid ratio of 1.67 and a cholesterol to phospholipid molar ratio of 0.55. The phospholipid composition did not deviate appreciably from that of whole tissue except for the higher sphingomyelin level (22.5 vs. 14.0%). The predominant fatty acids were palmitic (16:0), oleic (18:1), stearic (18:0) and linoleic (18:2) acid. The physical state of the membrane was studied by (i) calculation of the lipid structural order parameter SDPH from steady-state fluorescence anisotropy determinations of the hydrophobic probe 1,6-diphenyl-1,3,5-hexatriene (DPH); (ii) estimation of the lateral diffusion coefficient of pyrene following excimer formation. These parameters were determined in native thyroid plasma membranes and in reconstituted vesicles, obtained by detergent dialysis from octylglucoside solubilized membrane components. The presence of membrane protein or neutral lipids induced more restraint on the movements of the fluorophores. The lipid order parameter, SDPH was mainly determined by the neutral lipids. Subfractions of plasma membrane enriched in luminal membranes have a slightly lower fluidity (higher SDPH and lower Ddiff values) than subfractions enriched in basolateral membranes. This difference appears to be due to both differences in lipid as well as protein composition. Under physiological conditions, no significant alterations in probe dynamics could be observed upon addition of thyrotropin or cholera toxin, even at micromolar concentrations.

Isolation and identification of polyprenols from bovine thyroid gland

The presence of polyprenols in bovine thyroid was demonstrated. After preparative isolation, the structure was elucidated by chemical and spectroscopic techniques. The main polyprenol homologue has a molecular weight of 1380 corresponding to the presence of 20 isoprene units. From NMR studies it appears that 18 units have the cis configuration and that the 2 others are trans isoprene units. The dolichol content amounts to 0.2 mg/g wet weight. About 5% was found in the esterified form.

Two cases of mucopolysaccharidosis type III (Sanfilippo). A biochemical study

The mucopolysaccharide and lipid composition of human nervous tissue and viscera from one case of Sanfilippo disease type A and one case of Sanfilippo disease type C, were investigated. In the brain a moderate increase of acid glycosaminoglycans occurred. This phenomenon was much more pronounced in the viscera, especially in the liver. In all tissues this increase was mainly due to an accumulation of heparan sulphate. Changes in lipid composition were noted, but can be regarded as secondary effects. The biochemical results reported also suggest some general conclusions. (a) AGAG and lipid analyses do not permit differentiation between the subtypes of Sanfilippo disease. (b) The differences in lipid composition can probably be considered as consequences of variation in secondary effects. (c) The severe demyelination in brain correlates well with the biochemical lipid analysis. However, in other instances it remains difficult to bridge the gap still existing between some morphological and biochemical data.

Structure of neutral glycolipids in bovine thyroid tissue

Four asialo glycolipid fractions have been isolated from bovine thyroid glands. The structures were elucidated by partial hydrolysis, periodate oxidation, permethylation analysis and sequential enzymatic degradation studies. The following structures were identified: GL-1a glucosyl-beta-(1 leads to 1)ceramide; GL-1b galactosyl-beta-(1 leads to 1)ceramide: GL-2 galactosyl-beta-(1 leads to 4)glucosyl-beta-(1 leads to 1)ceramide: GL-3 galactosyl-alpha-(1 leads to 4)galactosyl-beta-(1 leads to 4)glucosyl-beta-(1 leads to 1)-ceramide; GL-4 N-acetylgalactosaminyl-beta-(1 leads to 3)galactosyl-alpha-(1 leads to 4)galactosyl-beta-(1 leads to 4)glucosyl-geta-(1 leads to 1)ceramide.