Reactive astrocytes upregulate one or more gene products that are recognized by monoclonal antibody H.

We generated a panel of monoclonal antibodies (mAbs) selected to recognize components from a Triton X-100 extract of ovine oligodendrocytes. One of these Abs, mAb H, recognizes an O-linked N-acetyl glucosamine residue in a specific conformation and/or environment. mAb H stained, weakly, two bands with Mr x 10(-3) of 209 and 62 in lysates of cultured rat astrocytes, suggesting antigens of low abundance. We have employed immunohistochemistry to investigate the cell and tissue distribution of the mAb H antigen(s). In normal rat and human brains, the sparse reaction products detected were confined, mostly, to fibrous astrocytes. In sharp contrast, when pathological specimens from a variety of brain lesions, including anisomorphic and isomorphic gliosis, were examined, a strong reaction with mAb H was in evidence in all reactive astrocytes, independent of the origin or nature of the lesions. This we interpret as meaning that the gene product(s) recognized by this mAb is (are) upregulated or induced following injury to the brain. Hence, epitope H represents a new addition to the list of molecules that are affected by brain injury. Structural and functional identification of the antigen(s) should shed light on its (their) relevance to the pathophysiology of the disease process.

Neurotoxicity of 2,4-dichlorophenoxyacetic butyl ester in chick embryos.

Fertilized hens' eggs were externally treated, before starting incubation, with a single dose of 2,4-Dichlorophenoxyacetic butyl ester (2,4-D b.e., 3.1 mg/egg). Chicks at different developmental stages were examined, extending from 10 day embryos to one day after hatching. Previously, we demonstrated that 2,4-D b.e. produces hypomyelination in chicks born from treated eggs. In search of the causes of this hypomyelination, "myelin markers" such as sulphatides, cerebrosides and 2'3'-cyclic nucleotide 3'-phosphohydrolase (CNPase) activity, as well as protein and nucleic acid contents were determined in the embryonic brains. We have shown in the present study that the chemical alterations occurred even before the period of active myelination, since myelin appears in chicken brain stem and cerebrum approximately after 17 days of incubation, and most of the chemical parameters studied are diminished before that time. The DNA content in brain of treated group is increased from the 14th embryonic day (with a transient diminution at 12th day) to the first hatching day, when compared to the control, suggesting a proliferation of glial cells, possibly oligodendrocytes.

Vulnerability of myelin development of the chick to the herbicide 2,4-Dichlorophenoxyacetic butyl ester.

Fertilized hens' eggs were treated externally with 2,4-Dichlorophenoxyacetic butyl ester (2,4-D b.e.) (3.1 mg/egg) immediately before starting incubation, and after different times of incubation (5, 10 and 15 days). Controls were treated externally with ether. Hatchability studies demonstrated that fetotoxic effects of 2,4-D b.e. were similar on the 0, 5 and 10 incubation day, but the 15 Day Group improved the hatching percentage. One day after hatching, chicks were decapitated, and CNS tissue was dissected. Myelin markers, as cerebrosides and CNP, were determined in cerebrum, cerebellum, brain stem and spinal cord of the four groups. They were reduced in cerebrum and brain stem of the 0, 5 and 10 Day Groups, but in the 15 Day Group they were in normal levels. Cerebellum presented normal myelin marker contents in each group studied, while spinal cord only presented decreased marker contents in the 5 Day Group. UDP galactose-ceramide galactosyl transferase (EC 2.4.1.45) activity was reduced in whole brain of chicks born from eggs treated preincubation. The results show the importance of time drug application and suggest that the vulnerable period in CNS development includes proliferation and development of myelin forming cells. Among CNS regions, cerebrum and brain stem seem to be the most vulnerable to the toxic action of 2,4-D b.e. in the chick.

Nucleic acid content and residue determination in tissues of chicks born from 2,4-dichlorophenoxyacetic butyl ester treated eggs.

The effects of 2,4-dichlorophenoxyacetic butyl ester (2,4-D b.e.) on protein and nucleic acid contents of different tissues of chicks born from externally treated hen's eggs were studied. Residues of 2,4-D b.e. were also determined and quantified by gas liquid chromatography (GLC). A diminished DNA content was observed in skeletal muscle and stomach, an increased one was found in cerebrum and cerebellum, whereas no variations were observed in the other analysed tissues. Protein levels were found decreased in kidney, cerebrum and heart. Besides, the GLC determinations revealed the presence of the 2,4-D b.e. in all the studied tissues finding the highest concentrations in kidney. 2,4-D did not appear to be a significant metabolite of 2,4-D b.e. in this experimental system. The dissimilar effects of 2,4-D b.e. on protein and nucleic acid contents of the studied tissues would be related to a different tissue susceptibility to the drug and/or to drug distribution.

Changes in fatty acid composition in myelin lipids after 2,4-dichlorophenoxyacetic butyl ester treatment.

Previous studies have shown that 2,4-Dichlorophenoxyacetic butyl ester (2,4-D b.e.) causes hypomyelination in chicks born from eggs externally treated and alters the myelin chemical composition. In this paper the effect of 2,4-D b.e. on myelin phospholipid and fatty acid composition has been examined. The results of our investigations show significant variations in the phospholipid composition, with the phosphatidyl inositol content increased and sphingomyelin and phosphatidyl ethanolamine contents diminished. The fatty acid pattern of the individual myelin lipids is also significantly altered, with an important reduction of long chain fatty acids and an increase of saturated fatty acids. The observed changes in the chemical composition implicate alterations in the intrinsic properties of this membrane.

Chick brain hypomyelination produced by 2,4-dichlorophenoxyacetic butyl ester treatment.

Fertilized hens' eggs were externally treated with 2,4-dichlorophenoxyacetic (2,4-D) butyl ester (2.4 mg/egg) before starting incubation. The specific activity of 2',3'-cyclic nucleotide 3'-phosphohydrolase (CNPase) was diminished in the whole brain of animals born from treated eggs, as compared with controls. Myelin was isolated by ultracentrifugation from the central nervous system. Treatment with 2,4-D butyl ester produced a 65% reduction. There were no statistically significant differences in myelin phospholipids, cerebrosides, sulphatides and gangliosides between control and treated animals. Cholesterol was diminished by 12% in the treated group, while cholesterol esters were not detectable in either myelin fraction. Total myelin proteins were also decreased by 40%, without variations in their pattern. There were changes in the following ratios in the myelin of the treated group: lipid/protein, cholesterol/phospholipids, cholesterol/protein, phospholipids/protein. Collectively these findings indicate that 2,4-D butyl ester produced hypomyelination.