Superoxide anion curbs nitric oxide modulation of afferent arteriolar ANG II responsiveness in diabetes mellitus.

Experiments were performed to test the hypothesis that the impact of endogenous nitric oxide (NO) on ANG II-induced renal arteriolar constriction is reduced in rats with insulin-dependent diabetes mellitus (65 mg/kg streptozotocin; STZ). Arteriolar diameter responses to exogenous ANG II were quantified before and during NO synthase inhibition (100 microM N(omega)-nitro-L-arginine; L-NNA) by using the in vitro blood-perfused juxtamedullary nephron technique. Afferent arteriolar lumen diameter averaged 20.7 +/- 2.0 micrometer in Sham kidneys and 25.9 +/- 1.3 micrometer in STZ kidneys (P < 0.05). Efferent arteriolar diameter did not differ between Sham and STZ rats. In kidneys from Sham rats, afferent and efferent arteriolar responses to ANG II (0.1-10.0 nM) were exaggerated significantly by L-NNA. L-NNA also augmented efferent arteriolar ANG II responses in kidneys from STZ rats (high-glucose bath) but did not alter ANG II responses in afferent arterioles from STZ rats. L-NNA also accentuated efferent, but not afferent, arteriolar ANG II responses in STZ kidneys during acute restoration of bath glucose to normal levels. Superoxide dismutase (150 U/ml) restored the ability of L-NNA to allow exaggerated afferent arteriolar responses to ANG II in kidneys from STZ rats. These observations indicate that superoxide anion suppresses the modulatory influence of endogenous NO on ANG II-induced afferent arteriolar constriction in diabetes mellitus.

Immunological distinction between neurofilament and glial fibrillary acidic proteins by mouse antisera and their immunohistological characterization.

Antisera were raised in mice to the presumed protein subunits of the two types of 100 A filaments in nervous tissue, glial fibrillary acidic (GFA) protein and neurofilament (NF) protein. These antisera detect a pronounced antigenic distinction between these two proteins. Antiserum to GFA protein reacts only with astroglial cells and is therefore similar to antisera prepared in rabbits. Mouse antiserum to NF protein reacts with neurons and their processes known to be rich in 100 A filaments. Postsynaptic densities do not detectably react with anti-NF antiserum when assayed by the indirect immunoperoxidase method and studied at the electron microscopic level. The two antisera do not react with actin, myosin oe nervous system, NF protein is immunohistologically detectable at embryonic day 13 (the earliest stage tested). GFA protein is not detectable with this method during embryonal development but becomes apparent only at early postnatal ages. In several species (rabbit, rat, chicken, fish, turtle, and frog) anti-NF protein antiserum only reacts with neurons, and anti-GFA protein antiserum stains glia exclusively. On the surface of trypsin-dissociated, single liver cerebellar cells from 7-day-old mice, each antiserum detects antigenic specificities which are cross-reactive with its corresponding antigen.

Cellular and subcellular localization of LETS protein in the nervous system.

In the nervous system of several mammalian and submammalian species, LETS protein is detectable on endothelial cells, choroid epithelial cells, fibroblasts and leptomeningeal cells. On endothelial cells LETS is present at the cell surface facing the blood vessel lumen, but not the glia limitans nor its basal lamina. Choroid epithelial cells do not carry LETS at their apices protruding into the ventricle, but are antigen-positive at their basal ends, in basal lamina and plasma membrane. Fibroblasts in the leptomeninges express LETS at their cell surface only, whereas pial and arachnoidal cells contain the protein also intracellularly. Neither glial nor neuronal cells express LETS protein. This pattern of LETS localization in nervous tissue was observed for adult and developing (embryonal day 9 onwards) animals of two species: mouse and chicken.

Ultrastructural localization of glial fibrillary acidic protein in mouse cerebellum by immunoperoxidase labeling.

Glial fibrillary acidic protein was localized at the electron microscope level in the cerebellum of adult mice by indirect immunoperoxidase histology. In confirmation of previous studies at the light microscope level, the antigen was detectable in astrocytes and their processes, but not in neurons or their processes, or in oligodendroglia. Astrocytic processes were stained in white matter, in the granular layet surrounding synaptic glomerular complexes, and in the molecular layer in the form of radially oriented fibers and of sheaths surrounding Purkinje cell dendrites. Astrocytic endfeet impinging on meninges and perivascular membranes were also antigen positive. In astrocytic perikarya and processes, the immunohistochemical reaction product appears both as a diffuse cytoplasmic label and as elongated strands, which by their distribution and frequency could be considered glial filaments.