The effect of testosterone on the biosynthesis of the neutral glycosphingolipids in the C57-BL mouse kidney

alpha-Gal epitopes in animal tissue glycoproteins and glycolipids

alpha-Gal terminated saccharides are present on the cell surface both as glycolipids and glycoproteins in all mammals except Old World monkeys and humans. The structural diversity among identified saccharides terminated by this epitope in animal tissues is steadily increasing. The majority of these saccharides have the alpha-Gal linked to lactosamine but other core saccharides exist. The alpha-Gal terminated saccharides are recognized by the immune system as a specific antigen and antibodies directed to the alpha-Gal, which do not cross-react with the classic blood group B trisaccharide, are found in man and Old World monkeys. Similar to other complex carbohydrate cell surface antigens, the alpha-Gal epitope is heterogeneously distributed in different organs and in different cells within an organ. It is present on the vascular endothelium and it is the primary target for human naturally occurring antibodies following pig to primate/man xenotransplantation leading to hyperacute rejection of the graft. Important for the future will be to further structurally characterize this antigen system, its cellular/subcellular distribution, and to identify possible of additional glycosyltransferases, related to the already described alpha 1,3galactosyltransferase that may explain the structural diversity. Such information will be of importance in the studies of, for example, the pathogenesis of autoimmune diseases and for the production of genetically modified pigs to prevent xenograft rejection.

Quantitation of the rabbit intestinal glycolipid receptor for Shiga toxin. Further evidence for the developmental regulation of globotriaosylceramide in microvillus membranes

Shiga toxin, produced by Shigella dysenteriae 1, causes enterotoxic, cytotoxic, and neurotoxic effects, which may be mediated by a glycolipid receptor, globotriaosylceramide, Gb3. To study the relationship of this receptor and toxin effects, globotriaosylceramide was quantitated and further characterized in rabbit small intestinal microvillus membranes at various ages. Glycolipids were extracted from rabbit microvillus membranes, purified on Unisil columns, and quantitated by high-performance liquid chromatography. The major glycolipid peaks were hydroxylated fatty acid-containing glucosylceramide, lactosylceramide, and globotriaosylceramide. There was a marked increase of globotriaosylceramide levels with age, ranging from 0.02 to 16.2 pmol/micrograms microvillus membrane protein in neonates and adults, respectively. The globotriaosylceramide peak was susceptible to alpha-galactosidase treatment, which produced an elevation in the lactosylceramide peak, but markedly reduced globotriaosylceramide content in 34-day-old rabbits. Binding of iodinated Shiga toxin to globotriaosylceramide was documented on high-performance thin-layer chromatography plates by autoradiography. The glycolipid receptor for Shiga toxin in rabbit microvillus membranes is thus a hydroxylated fatty acid-containing globotriaosylceramide. This moiety is virtually absent in neonates and gradually increases with age. Quantitative differences in globotriaosylceramide may be the underlying basis for the age-specific differences in functional responsiveness of rabbit intestinal tissue to Shiga toxin.

Estrogen-induced alterations of the acidic and neutral glycosphingolipids of rat kidney

In order to determine whether female sex hormones could influence the glycosphingolipid composition of the rat kidney, male albino rats of the Sherman strain were subcutaneously administered the synthetic estrogen, ethinylestradiol (5 mg/kg body wt. per day) or vehicle for 5 days, and the ganglioside, ceramide and neutral glycosphingolipid compositions of the kidneys of these animals were analyzed and compared. The results of these experiments demonstrate that estrogen treatment: (1) increased the ceramide, acidic and neutral glycosphingolipid contents of this tissue; (2) decreased the relative percentages of glucosyl- and globotetraosylceramide and hematoside (GM3), but increased the relative percentage of globotriaosylceramide and 'other' gangliosides; (3) increased the relative percentage of N-acetyl- to N-glycolylneuraminic acid in GM3; and (4) altered the long-chain bases of GM3, glucosyl- and globotetraosylceramide in this organ. These data, therefore, demonstrate that estrogen administration induces quantitative and qualitative alterations in the gangliosides, neutral glycosphingolipids and ceramide of the rat kidney. This data as well as a discussion of the possible physiological consequences of these estrogen-induced alterations in kidney glycosphingolipids serve as the basis for this report.

Dexamethasone-induced alterations in the glycosphingolipids of rat kidney

To determine whether glucocorticoids would influence the glycosphingolipid composition of the rat kidney, male albino rats of the Sherman strain were subcutaneously administered dexamethasone (100 micrograms/100 g body wt/day) or diluent for four days. The compositions of ceramide and of acidic and neutral glycosphingolipids of the kidneys of these animals were then examined and compared. The results demonstrated that dexamethasone administration: 1) increased the content of ceramide and of acidic and neutral glycosphingolipids in kidney; 2) increased the relative percentage of globotriaosyl- and globotetraosyl-ceramide, but decreased the relative percentages of glucosylceramide; 3) decreased the relative percentages of GM3 and increased other gangliosides; 4) increased the relative percentages of N-glycolylneuraminic acid in GM3; 5) did not appear to influence significantly the long-chain bases of the major glycosphingolipids; and 6) altered the relative percentages and chain length of the hydroxy and nonhydroxy fatty acids of the major acidic and neutral glycosphingolipids in this tissue. The data show that dexamethasone administration induces quantitative and qualitative changes in the glycosphingolipids of the rat kidney.

Glycosphingolipid patterns in primary mouse kidney cultures

Primary kidney cultures from C57BL/6J mice, 6 weeks of age or older, were produced using D-valine medium to select for epithelial cell growth. After allowing the cells to attach and proliferate for 1 week following plating, medium was changed once per week. Cells formed nearly confluent monolayers during the second week of culture. The cultured cells contained all of the glycosphingolipids seen in the adult kidney, analyzed by high performance liquid chromatography as their perbenzoyl derivatives. Glucosylceramide, however, was highly predominant in the cultured cells, whereas dihexosyl- and trihexosylceramides predominate in the intact kidney. Sex differences in glycolipid contents found in the intact kidney were also apparent in these cultured cells: The concentration of neutral glycolipids, in general, was higher in male cells than in those derived from females, and the male-specific glycolipid nonhydroxy fatty acid digalactosylceramide was high in male cells but very low in female cells. Neutral glycosphingolipids were labeled in 2-week-old cultures using [3H]palmitate. The [3H]palmitate was incorporated into all of the glycolipids within 2 hr of labeling. Hence, adult mouse kidney cells in D-valine medium retain their differentiated characteristics for a sufficient period of time to allow investigation of glycolipid syntheses in monolayer cultures of epithelial cells derived from this organ.

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.

Inhibition of polyamine synthesis blocks urinary secretion of beta-glucuronidase from mouse kidney

The effect of inhibition of polyamine synthesis on castrated male mouse kidney beta-glucuronidase induction and secretion by testosterone was studied. Inhibition of the activities of polyamine synthesis key-enzymes, L-ornithine and S-adenosyl-L-methionine decarboxylases, was performed with the combined treatment of 2-difluoromethylornithine and methylglyoxal' bis(guanylhydrazone). Blockage of polyamine synthesis did not affect testosterone-induced increase in renal beta-glucuronidase but blocked its secretion into the urine. After withdrawal of inhibitor-treatment beta-glucuronidase secretion normalized, and repeated testosterone administration produced undisturbed beta-glucuronidase secretion peak in urine suggesting that blockage of beta-glucuronidase secretion was not due to the tissue damage produced by inhibitors. These results indicate that the stimulation of renal polyamine synthesis by testosterone is not necessary for the induction of beta-glucuronidase but is required for the urinary secretion of this protein.

Glycosylceramide synthesis in the developing spinal cord and kidney of the twitcher mouse, an enzymatically authentic model of human Krabbe disease

UDP-galactose:ceramide galactosyltransferase activity was assayed in the spinal cord and kidney of the recently discovered neurological mutant, the twitcher mouse, which is an enzymatically authentic model of human globoid cell leukodystrophy (Krabbe disease). The activity in the spinal cord was essentially normal during the early myelination period up to 15 days. There was a slight reduction at 20 days. At 25 and 33 days, the galactosyltransferase activity was drastically reduced compared to controls. In contrast, the galactosyltransferase activity in the kidney of twitcher mice remained normal throughout the developmental stages examined. Activity of the control enzyme UDP-glucose:ceramide glucosyltransferase was always normal in both the spinal cord and kidney. Thus, reduction of galactosylceramide synthesis occurs in the CNS secondarily to the pathological alteration of the oligodendroglia. No such reduction occurs in the kidney, at least for the last step of galactosylceramide synthesis. Reduced synthesis as the result of metabolic regulation in the presence of the catabolic block is therefore unlikely to be the cause of the lack of abnormal accumulation of galactosylceramide in the kidney of patients with globoid cell leukodystrophy.

Lipid composition of the superficial stratum corneum cells of pig epidermis

Stratum corneum was removed from the surface of pig skin using a wet brushing technique. The material so obtained was fractionated into cell clumps, discrete cells and fine material by differential filtration through nylon gauzes. Ceramide, cholesterol and free fatty acid accounted for about 95% of the lipid present in each fraction: phospholipid and glycolipid were not detected. Material removed by successive brushings showed no detectable differences in lipid composition.

Mitochondria and nuclei of pig and human epidermis: isolation and lipid composition

Pig and human epidermis were mechanically disrupted with a Polytron homogenizer and mitochondria and nuclei were isolated from homogenates in buffered sucrose and 2.5% citric acid solution, respectively, by differential and density-gradient centrifugation. Examination of the mitochondrial preparations by electron microscopy and the assay of several marker enzymes indicated that they consisted mostly of mitochondria with some microsomal contamination. The nuclear preparations were substantially free from contaminants as judged by particle counts with the aid of phase and electron microscopy. The lipid compositions of the mitochondria from both species were characterized by a high concentration of cardiolipin and low concentration of cholesterol and sphingomyelin and an absence of glycosphingolipids as compared with the lipid composition of the whole epidermal cell. The lipid compositions of the nuclei were characterized by a high proportion of phosphatidyl choline and an absence of glycosphingolipids. The neutral lipids accounted for an unusually high proportion of the total lipids especially in human epidermal nuclei. Although the technical difficulties in isolating subcellular organelles from mammalian epidermis limit the yield and quality of the mitochondria, these preparations as well as those of nuclei are superior to preparations reported previously and are pure enough for a valid comparison with other membrane systems of the epidermal cell.

Sexual differences in galactose metabolism: galactosyl ceramide galactosidase and other galactosidases in mouse kidney

Male and female mice were compared at two ages, 15 and 50 days, with respect to the activities of three galactosidases in kidney. No sex difference in enzyme activity was seen in the young mice, but appreciable differences were found in the older animals. The male kidneys had about one-third higher specific activities of cerebroside beta-galactosidase and nitrophenyl beta-galactosidase, but there was no difference with nitrophenyl alpha-galactosidase. A listing and discussion of other galactose-metabolizing enzymes influenced by sex differences is presented.