Morphology, GluR1 and GRIP-C localization differ in octopus cells of C57BL6 and B6Cast mice

The C57BL6 mouse (B6) is homozygous for the gene for age-related hearing loss (ahl/ahl) and shows normal adult-like hearing before subtle changes in hearing begin at about 30 days of age. The B6Cast mouse is congenic to B6, having the wild type allele for normal hearing from Castaneous Ei on a B6 background. It has normal hearing throughout most of its lifespan. This study characterized the morphology of octopus cell (OC) somata in the posterior-ventral cochlear nucleus and of synaptic terminals on the OC somata in 8-week-old B6 and B6Cast mice, and the immunolocalization of antibodies to GluR1 (glutamate receptor subunit 1) and GRIP-C (glutamate receptor interacting protein-C terminus). By 8 weeks of age there are significant changes in the morphology of OCs and synaptic terminals around their somata in B6 mice compared to B6Cast mice. The distribution of immunoreactivity for the proteins GluR1 and GRIP is also significantly different in B6 mice from that in B6Cast mice. The modest degenerative changes reported in some B6 outer hair cells of the basal turn at this age do not seem adequate to explain the major changes observed in most OCs at a time when physiological studies show that many measures of the animals' hearing are still near normal. The findings suggest that changes in the alpha-amino-3-hydroxy-5-methyl-4-isoxazole glutamate receptor subunits and/or their binding proteins are part of the phenotype of ahl, and may reflect a role of the glutamate receptor pathway in the mechanism of ahl.

Differential postsynaptic distribution of GluRs 1-4 on cartwheel and octopus cell somata in the gerbil cochlear nucleus

Differences were demonstrated in the distribution of glutamate receptors (GluR) 1, 2, 2/3 and 4 postsynaptic immunoreactivity (PSIR) on the somata of cartwheel and octopus cells in the adult gerbil cochlear nucleus (CN). Montages of electron micrographs of cartwheel and octopus cells immunoreacted with antibodies to GluR 1, 2, 2/3 and 4 were prepared. The number of synaptic terminals with PSIR were counted on all cells for each antibody, normalized to the total length of somatic surface analyzed. The density of terminals apposed to PSIR on octopus cells was similar for the antibodies GluR1, 2/3 and 4, but significantly less for GluR2. On cartwheel somata the numbers of terminals apposed to immunoreactive postsynaptic specializations with GluR1, 2, 2/3 or 4 were not significantly different from each other. The density of terminals apposed to GluR2/3 and 4 positive postsynaptic specializations was significantly less on cartwheel cells than on octopus somata. The data suggest that the decreased presence of the GluR2 subunit, which confers calcium impermeability to the assembled receptor and slower gating kinetics to receptors with a high GluR4 content, is the major difference in the AMPA receptors on the somata of these cell types. The presence on cartwheel cells of a majority of AMPA receptors which contain GluR2 may account for the fact that cartwheel cells respond to shocks to the auditory nerve with 100 ms excitatory postsynaptic potentials (EPSPs), while octopus cells, most of whose AMPA receptors lack GluR2, respond with 1 ms EPSPs.

The Golgi association of endothelial nitric oxide synthase is necessary for the efficient synthesis of nitric oxide

The particulate enzyme, endothelial nitric oxide synthase (eNOS), produces nitric oxide to maintain normal vasodilator tone in blood vessels. In this study, we demonstrate that eNOS is a Golgi-associated protein in cultured endothelial cells and intact blood vessels. Using a heterologous expression system in HEK 293 cells, we show that wild-type myristoylated and palmitoylated eNOS, but not mutant, non-acylated eNOS targets to the Golgi. More importantly, HEK 293 cells expressing wild-type eNOS release substantially more NO than cells expressing the mutant, non-acylated enzyme. Thus, eNOS is a novel Golgi-associated protein, and Golgi compartmentalization is necessary for the enzyme to respond to intracellular signals and produce NO.

Inducibility and expression of microvascular endothelial adhesion molecules in lesional, perilesional, and uninvolved skin of psoriatic patients

Previous studies have demonstrated 1) that patterns of inducible endothelial cell expression of endothelial leukocyte adhesion molecule-1 (ELAM-1) and vascular cell adhesion molecule-1 (VCAM-1) in response to cytokines varies both with anatomic position within the dermal microvasculature and with the presence of perivascular inflammatory infiltrates, and 2) that the anatomic architecture of the dermal superficial plexus (SVP) is altered in inflamed lesional but not in univolved skin of psoriatic patients. The present study was designed to evaluate the pattern of cytokine inducibility of ELAM-1 and VCAM-1 in altered dermal microvessels of psoriatic patients. At the light microscope level, preculture biopsies of uninvolved and perilesional skin were indistinguishable by morphology and ELAM-1 and VCAM-1 expression were virtually absent. In contrast, biopsied lesional skin showed elongated capillary loops and increased numbers of T cells compared to uninvolved and perilesional skin. The dermal microvasculature of the SVP of lesional skin contained ELAM-1+ in 29.4% of vessels and VCAM-1+ endothelial cells in 8.7% of vessels. After 24 h of organ culture in medium supplemented with tumor necrosis factor and interleukin-4, ELAM-1+ endothelial cells in the SVP were increased significantly in uninvolved (from mean 0.5% to 27% of vessels), perilesional (from mean 5.5% to 41.8% of vessels), and lesional skin (from mean 29.4% to 45.7% of vessels). VCAM-1 was not inducible on SVP endothelial cells in uninvolved skin but VCAM-1+ endothelial cells were increased significantly in perilesional (from mean 0.7% to 23.7% of vessels) and lesional skin (from mean 8.7% to 41.4% of vessels). In uninvolved and perilesional skin ELAM-1 and VCAM-1 were confined to endothelial cells below the rete. In contrast, endothelial cells of the intrapapillary part of the capillary loop of lesional skin became cytokine responsive, in that ELAM-1 and VCAM-1 could be induced at this site. By immunoelectron microscopy, expression was most intense on the luminal surface of venular endothelial cells and at the interendothelial junctions. In conclusion, we have presented evidence that the cytokine responsiveness of microvascular endothelial cells is altered in psoriasis in a pattern that may explain both the circumscribed nature and the epidermal involvement of the psoriatic plaque.

Ultrastructure and three-dimensional organization of the telangiectases of hereditary hemorrhagic telangiectasia

We studied 10 cutaneous telangiectatic lesions of hereditary hemorrhagic telangiectasia (HHT), ranging in size from pinpoint to 2 mm, by light and electron microscopy. Four representative lesions were reconstructed by computer from serial 1- or 2-mm plastic embedded sections. The earliest clinically detectable lesion of HHT is a focal dilatation of postcapillary venules, which continue to enlarge and eventually connect with dilated arterioles through capillaries. As the vascular lesion increases in size, the capillary segments disappear and a direct arterio-venous communication is formed. This entire sequence of morphologic events is associated with a perivascular mononuclear cell infiltrate in which the majority of cells are lymphocytes and the minority are monocytes/macrophages by ultrastructure. Comparison of these findings with the telangiectatic mats of scleroderma and cherry angiomas revealed that the former, previously shown to be composed of dilated postcapillary venules, are also associated with perivascular infiltrates, but the latter, which are produced by capillary loop aneurysms, are not.

Ultrastructure and three-dimensional organization of the telangiectases of hereditary hemorrhagic telangiectasia

We studied 10 cutaneous telangiectatic lesions of hereditary hemorrhagic telangiectasia (HHT), ranging in size from pinpoint to 2 mm, by light and electron microscopy. Four representative lesions were reconstructed by computer from serial 1- or 2-mm plastic embedded sections. The earliest clinically detectable lesion of HHT is a focal dilatation of postcapillary venules, which continue to enlarge and eventually connect with dilated arterioles through capillaries. As the vascular lesion increases in size, the capillary segments disappear and a direct arterio-venous communication is formed. This entire sequence of morphologic events is associated with a perivascular mononuclear cell infiltrate in which the majority of cells are lymphocytes and the minority are monocytes/macrophages by ultrastructure. Comparison of these findings with the telangiectatic mats of scleroderma and cherry angiomas revealed that the former, previously shown to be composed of dilated postcapillary venules, are also associated with perivascular infiltrates, but the latter, which are produced by capillary loop aneurysms, are not.

Correlation of laser Doppler wave patterns with underlying microvascular anatomy

Laser Doppler velocimetry (LDV) was performed on the chest, back, and abdomen of four healthy volunteers. As the probe was moved over distances of 2-6 mm, the red-cell flux varied by 100%, but was associated with three distinctive wave patterns. Correlative skin biopsies showed that a high flux, pulsatile pattern superimposed on vasomotor activity was found when the probe was directly over an ascending elastic arteriole with its immediate branches; low flux, pulsatile flow with minimal or no vasomotor activity was found when the probe was off center relative to the ascending arteriole and its branches; and a low flux, non-pulsatile pattern occurred when the probe window was situated between ascending arterioles over an area in the upper horizontal plexus composed primarily of capillaries and post-capillary venules.

Ultrastructural analysis of the endothelial-pericyte relationship in diabetic cutaneous vessels

The microvessels in the buttock skin of 15 patients with long-standing juvenile diabetes were studied both by electron microscopy and three-dimensional (3D) computer reconstruction of a prototypical diabetic postcapillary venule. Endothelial cell gaps were found in postcapillary venules and capillaries, but only in association with an increased deposition of basement membrane-like material in the vascular wall. In parallel with the increased amounts of deposited basement membrane-like material, the space between pericytes and endothelial cells was wider and the cytoplasmic processes that formed the contact points between them were longer and thinner than normal. Pericytes, devoid of any cytoplasmic contacts with the underlying endothelial cells, were observed as isolated cells within the outer third of the vascular wall in markedly thickened vessels. These observations offer an explanation for the known increased vascular permeability of diabetic vessels, and suggest a possible explanation for the development of diabetic retinopathy with aneurysm formation.