Oligodendroglia in developmental neurotoxicity.

The developing nervous system has been long recognized as a primary target for a variety of toxicants. To date, most efforts to understand the impact of neurotoxic agents on the brain have focused primarily on neurons and to a lesser degree astroglia as cellular targets. The role of oligodendroglia, the myelin-forming cells in the central nervous system (CNS), in developmental neurotoxicity has been emphasized only in recent years.

Protein kinase C activation is required for the lead-induced inhibition of proliferation and differentiation of cultured oligodendroglial progenitor cells.

Lead (Pb) is a common neurotoxicant of major public health concern. Previous studies revealed that cultured oligodendrocyte progenitor cells (OPCs) are highly vulnerable to Pb toxicity. The present study examines the effect of Pb on the survival, proliferation and differentiation of OPCs in vitro.

Lead alters the developmental profile of the galactolipid metabolic enzymes in cultured oligodendrocyte lineage cells.

Lead is a neurotoxicant that can cause myelin deficits. Galactolipids are expressed during differentiation of oligodendrocyte lineage cells and accumulate in myelin. To examine the impact of lead on oligodendroglial differentiation, galactolipid metabolism in cultured oligodendrocyte lineage cells exposed to the metal was studied.

Lead causes human fibroblasts to mis-sort arylsulfatase A.

Lead exposure causes cognitive and behavioral deficits in some children. We have proposed that the effects of single nucleotide polymorphisms (SNP) of the human pseudodeficient arylsulfatase A (ARSA) gene that result in reduced levels of the enzyme, and lead concentrations that decrease ARSA activity, culminate in cellular enzymic activity that is below a critical threshold required for the normal nervous system function. Human fibroblasts grown in the presence of lead acetate exhibit a 65% decrease in ARSA protein, resulting in a significant decrease in the ability to catabolize sulfatide in cells from individuals with the SNP(s) of pseudodeficient ARSA, but not those from subjects with the normal gene (Poretz et al.

Lead exposure delays the differentiation of oligodendroglial progenitors in vitro.

Lead (Pb) is an environmental neurotoxicant that can cause hypo- and demyelination. Oligodendrocytes (OLs), the myelin-forming cells in the central nervous system, may be a possible target for Pb toxicity. The present study describes the effect of Pb on the maturation of rat OL progenitor (OP) cells and the developmental expression of myelin-specific galactolipids.

Lead exposure affects levels of galactolipid metabolic enzymes in the developing rat brain.

Lead poisoning is known to cause myelin defects. Galactolipids are the major lipid components of myelin and myelin-competent oligodendrocytes. The present study examines the cellular activity of enzymes involved in the galactolipid pathway, tissue concentrations of galactolipids, and the cellular activity of 2',3'-cyclic nucleotide 3'-phosphohydrolase (CNPase) in rat pups exposed to lead in utero and subsequently through maternal milk from exposed mothers and in drinking water following weaning.

The interaction of lead exposure and arylsulfatase A genotype affects sulfatide catabolism in human fibroblasts.

Lead exposure causes cognitive and behavioral deficits in some affected children. We propose that a contributing mechanism for the neurological damage is that lead induces critically low levels of arylsulfatase A (ASA) at sensitive stages of nervous system development. It is hypothesized that the combined effects of a single nucleotide polymorphism (SNP) in human ASA which results in reduced levels of the enzyme, and lead concentrations which decrease ASA activity culminate in cellular enzymic activity that is below a critical threshold required for the maintenance of normal nervous system function.

Sites of photodamage induced by photodynamic therapy with a chlorin e6 triacetoxymethyl ester (CAME).

The acetoxymethyl ester of chlorin e6 (CAME) was initially designed to be a hydrophobic photosensitizing agent that would be recognized by an endocytic pathway and initially accumulated in lysosomes. This was expected to lead to hydrolysis of the ester groups, followed by redistribution of the free chlorin to other subcellular sites. In this study, we examined the patterns of localization of CAME and of subsequent photodamage in murine leukemia L1210 cells.

Effect of dietary chlorophyll derivatives on mutagenesis and tumor cell growth.

Much attention in recent years has been given to the antigenotoxicity of chlorophyll. Chlorophyll, however, is known to be converted into pheophytin, pyropheophytin, and pheophorbide in processed vegetable food and following ingestion by humans. Studies were conducted on the antimutagenic and tumoricidal potencies of these compounds.

The R496H mutation of arylsulfatase A does not cause metachromatic leukodystrophy.

Deficiency of arylsulfatase A (ARSA) enzyme activity causes metachromatic leukodystrophy (MLD). A number of ARSA gene mutations responsible for MLD have been identified. Recently, the R496H mutation of ARSA was proposed to be a cause of MLD (Draghia et al.

An acidic modification of the cytoplasmic domain contributes to the charge heterogeneity of the MHC class I antigens.

Polypeptide phosphorylation and sialylation of the glycan moieties contribute to the charge heterogeneity of the class I major histocompatibility complex glycoproteins. The present study demonstrates that a unique acidic modification unrelated to phosphorylation or glycosylation also affects the charge heterogeneity of the H2-Kk heavy chain of BW5147 lymphoma cells. In vitro cultivation of BW5147 cells results in changes in charge heterogeneity of the H2-Kk heavy chains due to the unique acidic modification.

Antimutagenicity, cytotoxicity and composition of chlorophyllin copper complex.

The preparation of chlorophyllin copper complex (CCC), shown to be a tumor promoter in an animal model (Nelson, R.L. (1992) Chlorophyllin, an antimutagen, acts as a tumor promoter in the rat-dimethylhydrazine colon carcinogenesis model.

A novel arylsulfatase A protein variant and genotype in two patients with major depression.

A new, 'diffuse, multiple banding', electrophoretic variant of arylsulfatase A protein was found in two patients with major depression. Protein analyses showed that this variant and the normal enzyme differed in amino acid sequence and/or post-translational modifications unrelated to phosphate groups and oligomannose glycans. Analysis of the arylsulfatase A genes from a subject with the new variant identified three mutations; one gene had the two mutations associated with arylsulfatase A pseudodeficiency, and the other had a G to T transversion which changes a tryptophan to cysteine in the protein.

Arylsulfatase A: relationship of genotype to variant electrophoretic properties.

Previous work has shown that specific electrophoretic variants of arylsulfatase A occur more frequently among alcoholic patients than among psychiatric and normal controls. The present study sequenced the gene for two of these electrophoretic variants, IIIa and IIIb. Both contain an A-to-G transition corresponding to substitution of Asn350 by Ser, with the resulting loss of an N-glycosylation site.

Structural characterization of variant forms of arylsulfatase A that associate with alcoholism.

Several electrophoretic forms of human platelet arylsulfatase A (ASA), including variant type IIIa and normal type IV(a), have been identified by nondenaturing polyacrylamide gel electrophoresis. An alcoholic population that we have analyzed is enriched in variant type IIIa compared with nonalcoholic psychiatric and normal controls. Individuals with the IIIa enzyme possess greatly reduced levels of ASA activity.

Association of alcoholism with the N-glycosylation polymorphism of pseudodeficient human arylsulfatase A.

The IIIa and IIIb electrophoretic variants of arylsulfatase A (EC 3.1.6.

In-vitro photocytotoxicity of lysosomotropic immunoliposomes containing pheophorbide a with human bladder carcinoma cells.

Pheophorbide a is a photocytotoxic agent. To develop a tissue-specific, intracellularly targeted photoactive system, pheophorbide a was incorporated into immunoliposomes coated with a monoclonal antibody (T-43) directed against the T-24 bladder tumor cell line. The efficacy of this system was studied in vitro using the human bladder tumor cell line MGH-U1.

Metabolically convertible lipophilic derivatives of pH-sensitive amphipathic photosensitizers.

We propose the use of acetoxymethyl esters of pH-sensitive amphipathic photosensitizers (PS) for photodynamic therapy (PDT). These compounds may be applicable for PDT involving endocytosis of lipophilic carriers leading to lysosomal uptake of the esterified PS by target cells. Partial and/or total enzymatic de-esterification may result in the extralysosomal distribution of the photoactive agents, possibly culminating in a multisite photochemical response.

Covalent attachment of peptides to membranes for dot-blot analysis of glycosylation sites and epitopes.

Noncovalent binding of proteins to membranes is often employed for dot-blot analysis with various visualization techniques. These techniques are usually not applicable to peptide dot-blot analysis due to peptide wash-off during the staining procedure. As exemplified with a synthetic peptide and peptides produced by proteolysis of a protein, it is possible to achieve efficient covalent attachment to Immobilon-AV membranes.

Two-dimensional poly(acrylamide) electrophoresis of fluoresceinated glycopeptides. Resolution and structural characterization of ovalbumin glycans.

The microheterogeneous mixture of fluoresceinated glycopeptides (FGPs) obtained from the single site of glycosylation of chicken ovalbumin was resolved by a combination of discontinuous electrophoresis in a high-density poly(acrylamide) gel (PAGE) for sizing, in conjunction with borate-PAGE. Two FGPs of similar size but with different mobilities in borate-PAGE were purified and characterized by sequential exoglycosidase digestion and sizing on the discontinuous PAGE system, as well as by methylation analysis. The two FGPs of identical size are distinct and have structures beta-D-Glc pNAc-(1-->2)-alpha-D-Man p-(1-->3)-[beta-D-Glc pNAc-(1-->4)]-[beta-D-Glc pNAc-(1-->2)-alpha-D- Man p-(1-->6)]-beta-D-Man-p-(1-->4)-beta-D-Glc pNAc-(1-->4)-beta-D-Glc pNAc-1-->R and alpha-D-Man p-(1-->2)-alpha-D-Man p-(1-->3 or 6)-[alpha-D-Man p-(1-->3)-[alpha-D-Man p-(1-->6)]-alpha-D-Man p-(1-->6 or 3)]-beta-D-Man p-(1-->4)-beta-D-Glc pNAc-(1-->4)-beta-D-Glc pNAc-1-->R (R = Asn-(amino acids)-fluorescein).

The structural basis for the electrophoretic isoforms of normal and variant human platelet arylsulphatase A.

Human platelet arylsulphatase A (ASA) exhibits a multiple banding pattern when examined by PAGE. The isoform pattern (IVa) of the enzyme obtained from normal subjects differs from variants (IIIa, IIIb, IVb) which are primarily found in alcoholic patients. Alkaline phosphatase and endo-N-acetylglucosaminidase H treatments, as well as ion-exchange chromatography, demonstrate that the isoforms of ASA arise because of charge heterogeneity caused by phosphoglycan moieties.

Pheophorbide a-induced photo-oxidation of cytochrome c: implication for photodynamic therapy.

Pheophorbide a-induced photo-oxidation, in vitro, of cytochrome c oxidase and cytochrome c results in irreversible modifications to both protein components. Photo-oxidation of cytochrome c, as exhibited by change in its heme oxidation state, displays exponential kinetics and is detected with a lag period. Both the photo-induced inactivation of the enzyme, and destruction of the substrate ability of cytochrome c occur as complex multi-process events.

The (1----3)-linked alpha-L-fucosyl group of the N-glycans of the Wistaria floribunda lectins is recognized by a rabbit anti-serum.

An increasing number of plant glycoproteins have been shown to possess a characteristic N-glycan component containing a beta-(1----2)-linked D-xylose unit on the core beta-D-mannose unit, and an alpha-(1----3)-linked L-fucose unit on the asparagine-linked 2-acetamido-2-deoxy-D-glucose unit. Wistaria floribunda seeds have two distinct lectins; the erythroagglutinin, WFA, and the lymphocyte mitogen, WFM. Earlier studies indicated that both lectins belong to such a class of glycoproteins.

Hybrid myeloma cells which secrete heterodimeric IgG: a model to study the N-linked glycan.

Fundamental questions remain unanswered regarding the effect of the acceptor polypeptide structure on the fine structure of the N-linked glycan of glycoproteins and conversely, the effect of the glycan structure of IgG on the function and structure of the protein. The construction of myeloma hybrids capable of secreting multiple IgG which differ with regard to the fine structure of their N-linked oligosaccharides would be a valuable model for studying these questions. P3X63Ag8 analogous glycan of the IgG2b secreted by Sp2/HLBu.