Brainstem glioma progression in juvenile and adult rats.

OBJECT: Brainstem gliomas are common in children and have the worst prognosis of any brain tumor in this age group. On the other hand, brainstem gliomas are rare in adults, and the authors of some clinical studies have suggested that this lesion behaves differently in adults than in children. In the present study, the authors test an orthotopic C6 brainstem glioma model in juvenile and adult rats, and investigate the biological behavior of this lesion in the 2 age groups. METHODS: The C6 glioma cells were stereotactically implanted into the pons of juvenile or adult male rats. Neurological presentation and survival time were recorded. Tumor proliferation and the number of apoptotic cells in brainstem gliomas of young and adult rats were determined by immunohistochemical staining with Ki 67 and terminal deoxynucleotidyl transferase 2'-deoxyuridine 5'-triphosphate-mediated nick-end labeling assay. RESULTS: Striking differences in the onset of neurological signs, duration of symptoms, survival time, tumor growth pattern, tumor proliferation, and number of apoptotic cells were found between the gliomas in the 2 groups of rats. The lesions were relatively focal in adult rats but more diffuse in young rats. Furthermore, brainstem gliomas in adult rats were less proliferative and had more apoptotic cells than those in young rats. CONCLUSIONS: The authors found that the C6 brainstem glioma model in young and adult rats closely imitates the course of brainstem glioma in humans both in neurological findings and histopathological characteristics. Their findings also suggest that the different growth pattern and invasiveness of these lesions in children compared with that in adults could be due to different cellular environments in the 2 age groups, and warrants further investigation into the difference in the host response to brainstem gliomas in children and adults.

Comparison of expression profile of neurotrophins and their receptors in primary and transformed rat retinal ganglion cells.

PURPOSE: To determine the expression profile of neurotrophins and their receptors in cultured primary rat retinal ganglion cells (RGCs) and the transformed RGC-5 cells. METHODS: Confocal microscopic immunocytochemistry with double fluorescent labeling with thy-1 as a marker for RGCs was used to demonstrate expression of neurotrophins and their receptors. An enzyme-linked immunosorbent assay (ELISA) was used to detect secretion of neurotrophins by RGC-5 cells. RESULTS: Primary RGCs and RGC-5 cells expressed brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), neurotrophin-3 (NT3), neurotrophin-4 (NT4), and receptors TrkA, p75, with low levels of TrkB. However, minimal if any, expression of TrkC was observed in these cells. RGC-5 cells also secreted NT3 (1311+/-21 pg/ml), BDNF (92+/-9 pg/ml), NGF (86+/-7 pg/ml), and NT4 (21+/-1 pg/ml) into the cultured media. CONCLUSIONS: These results demonstrated that neurotrophins and TrkA, p75 with low levels of TrkB receptors are expressed by RGCs. Specific neurotrophins acting through TrkA, TrkB, and p75 receptors within the RGCs may be involved in the survival and apoptosis of the RGCs in various retinopathies, such as glaucoma.

Ethanol withdrawal posttranslationally decreases the activity of cytochrome c oxidase in an estrogen reversible manner.

Cytochrome c oxidase (COX) is a key mitochondrial enzyme that catalyzes electron transfer at the terminal stage of respiratory chain and is composed of multisubunits. We hypothesize that ethanol withdrawal (EW) impairs the activity of COX and estrogen deprivation exacerbates this problem. Five-month-old ovariectomized rats with or without 17beta-estradiol (E2) replacement received a control dextrin or a liquid ethanol diet (6.5%, 5 weeks). They were then sacrificed either during ethanol exposure or at 24h of EW (EW group). Mitochondria of the cerebellum and cortex were processed to measure the activities of total COX, COX subunit I, and IV. The effects of EW and E2 on the protein levels of these subunits were also assessed using an immunoblotting method. As compared to the control dextrin and ethanol exposure, EW decreased the activities of total COX, COX I, and COX IV. E2 treatment prevented the effects of EW on the activities of total COX and COX IV but not COX I. Neither EW nor E2 altered the protein levels of the subunits. These findings suggest that a counteracting relationship exists between the effects of EW and E2 on the activity of COX in a subunit specific manner.

Cells of the human optic nerve head express glial cell line-derived neurotrophic factor (GDNF) and the GDNF receptor complex.

PURPOSE: Glial cell-line derived neurotrophic factor (GDNF) is a distant member of the TGFbeta family of growth factors and has wide ranging effects within the central nervous system. In the present study we profile the expression of GDNF and its receptor complex (Ret and GFRalpha-1) in cells isolated from the human optic nerve head (ONH). METHODS: Lamina cribrosa (LC) cells and ONH astrocytes were used from normal donors of various ages. Total RNA was isolated and subjected to reverse transcriptase-polymerase chain reaction (RT-PCR) to examine mRNA expression of GDNF, Ret, and GFRalpha-1. Western immunoblotting and immunohistochemistry was used to study protein expression of GDNF and GDNF receptor complex proteins in cultured ONH cells. An immunoassay system (ELISA) was used to examine secretion of GDNF by ONH cells. Cell proliferation was examined following exogenous administration of GDNF. RESULTS: Lamina cribrosa cells, ONH astrocytes, and LC tissues expressed messenger RNA for GDNF, Ret and GFRalpha-1. Lamina cribrosa cells and ONH astrocytes also expressed protein for GDNF, Ret, and GFRalpha-1. Secretion of GDNF by either cell type was not detected. Exogenous GDNF caused a significant increase in cell proliferation of LC cells but not ONH astrocytes. CONCLUSIONS: Cells from the human lamina cribrosa express mRNA and protein for GDNF and its receptor complex. LC cells proliferate in response to exogenous GDNF. The potential for autocrine and/or paracrine GDNF signaling thus exists within the lamina cribrosa, a tissue involved in glaucoma pathogenesis.

Expression of bone morphogenetic proteins (BMP), BMP receptors, and BMP associated proteins in human trabecular meshwork and optic nerve head cells and tissues.

PURPOSE: Bone morphogenetic proteins (BMPs) are multi-functional cytokines that have wide ranging effects on a variety of cells and tissues. In the present study, we profile the expression of BMPs, BMP receptors, and BMP associated proteins in the human trabecular meshwork (TM) and optic nerve head (ONH), two tissues involved in glaucoma pathogenesis. METHODS: Total RNA was isolated and subjected to reverse transcriptase-polymerase chain reaction (RT-PCR) to examine the expression of BMP, BMP receptor, and BMP associated proteins in tissues and cultured cells from the human TM and ONH (ONH astrocytes and lamina cribrosa cells). Western immunoblotting was used to study the expression of BMP and BMP receptor proteins in cultured human TM and ONH cells. RESULTS: Both TM and ONH cells and tissues expressed mRNAs for BMP2, BMP4, BMP5, BMP7, BMP-RIA, BMP-RIB, BMP-RII, DRM (gremlin), follistatin, chordin and NMA (BAMBI). The proteins for BMP2, BMP4, BMP5, BMP7, and all three BMP receptors were expressed in cultured human TM and ONH cells. CONCLUSIONS: Members of the BMP family of genes, including BMPs, BMP receptors, and inhibitory BMP associated proteins are expressed in the human TM and ONH. These molecules may be involved in the normal formation and function of these tissues. Altered expression of members of this gene family may lead to functional changes in the TM and ONH. These genes and their respective signaling pathways merit further research to examine their possible role in glaucoma.