No abstract

Possible biological effects of mobile phone microwaves were investigated in vitro. In this study, which was part of the 5FP EU project REFLEX (Risk Evaluation of Potential Environmental Hazards From Low-Energy Electromagnetic Field Exposure Using Sensitive in vitro Methods), six human cell types, immortalized cell lines and primary cells, were exposed to 900 and 1800 MHz. RNA was isolated from exposed and sham-exposed cells and labeled for transcriptome analysis on whole-genome cDNA arrays. The results were evaluated statistically using bioinformatics techniques and examined for biological relevance with the help of different databases. NB69 neuroblastoma cells, T lymphocytes, and CHME5 microglial cells did not show significant changes in gene expression. In EA.hy926 endothelial cells, U937 lymphoblastoma cells, and HL-60 leukemia cells we found between 12 and 34 up- or down-regulated genes. Analysis of the affected gene families does not point towards a stress response. However, following microwave exposure, some but not all human cells might react with an increase in expression of genes encoding ribosomal proteins and therefore up-regulating the cellular metabolism.

Podocalyxin is a membrane protein of rat podocytes and endothelial cells. It has not been described in other cell types, and no amino acid or DNA sequence data are available about it. Here we show that podocalyxin antigens are present in rat platelets and megakaryocytes. In resting platelets, the antigens are mainly intracellular but become surface exposed after thrombin stimulation, as shown by immunofluorescence and flow cytometry. By Western blotting, platelet podocalyxin has an apparent Mr of 140,000. Cytocentrifuge slides of rat bone marrow show that anti-podocalyxin antibodies recognize large polyploid cells also expressing CD62P, indicating that the cells are megakaryocytes. From a rat glomerular cDNA library we isolated a clone covering the carboxyl-terminal nucleotides of rat podocalyxin. Its putative transmembrane or intracellular domains are 100% or >93% identical, respectively, with the human and rabbit podocalyxin-like proteins. The truncated extracellular domain extends to include two of the four conserved cysteines shared by podocalyxin-like proteins. By Northern blotting, a 5.5-kb renal cortical transcript is seen. By in situ hybridization, cRNA probes recognize podocytes, endothelial cells, and megakaryocytes, and by reverse transcription polymerase chain reaction, platelets are shown to contain podocalyxin mRNA. Our results show that rat podocalyxin is a homologue of the previously cloned podocalyxin-like proteins and suggest that also in mammals podocalyxin has a role in hematopoiesis, as previously shown in the chicken.

We argue that the use of high-throughput screening techniques, although expensive and laborious, is justified and necessary in studies that examine biological effects of mobile phone radiation. The "case of hsp27 protein" presented here suggests that even proteins with only modestly altered (by exposure to mobile phone radiation) expression and activity might have an impact on cell physiology. However, this short communication does not attempt to present the full scientific evidence that is far too large to be presented in a single article and that is being prepared for publication in three separate research articles. Examples of the experimental evidence presented here were designed to show the flow of experimental process demonstrating that the use of high-throughput screening techniques might help in rapid identification of the responding proteins. This, in turn, can help in speeding up of the process of determining whether these changes might affect human health.*

Despite the increasing knowledge of the role of gangliosides in normal and diseased tissues, little is known of the presence, distribution and functions of these molecules in the kidney. In this study we analyzed the main gangliosides of isolated glomeruli and cortical, medullary and papillary fractions of the human, rat and bovine kidneys biochemically. In addition, we used immunohistochemistry to visualize the distribution of GM1/GM2, GD2, GD3 and O-acetyl GD3 gangliosides along the nephron. Furthermore, we explored the species specific expression of gangliosides by comparing those from the rat, bovine and human kidney, and studied the pattern of ganglioside expression during development. In glomeruli, cortical tubuli, medullae and papillae, a relatively simple pattern of main gangliosides was observed as revealed by thin layer chromatographic (TLC) analysis in each species studied. Furthermore, considerable changes in the glomerular gangliosides during maturation were observed, with a complex type of gangliosides predominating during the fetal age and with a preference to more simple precursors upon maturation. Interestingly, the immunohistochemical detection revealed a distinct pattern of ganglioside compartmentation to various nephron segments or cell types. These findings provide a basis for studying the role of segment- and cell type-specific gangliosides for local functions.

O-acetyl GD3 ganglioside is a cell surface molecule of some neural, neural crest and renal cells. Here we show, by using mAbs specific for O-acetyl GD3 (clone 27A) and flow-cytometric, biochemical or immunological techniques, that it is also expressed at high intensity level on the surface of 49.6% (median) of the CD3+ cells (T lymphocytes), at medium level in 16.2% of the CD16+ (natural killer) cells, at very low level in 51.9% of CD14+ cells (monocytes) and in 6.9% of CD20+ cells (B lymphocytes), but not in other human blood cells. Of the CD4+ or CD8+ cells, 52.6 or 36.5% respectively were 27A+. Furthermore, 81.6% of the CD45RO+ lymphocytes carried the O-acetyl GD3 ganglioside. It was not detected in the thymus, although its immediate precursor, the GD3 ganglioside, was present in the medullary thymocytes, suggesting that O-acetyltransferases are regulated by maturation events taking place in the periphery. The anti-O-acetyl GD3 antibodies induced a strong mitogenic response in cultured peripheral blood mononuclear cells, but not in purified T cells. However, in combination with phorbol myristate acetate the antibodies induced proliferation also in purified T cells, suggesting that protein kinase C priming is needed for this effect. This and the restricted expression of O-acetyl GD3 suggest a functional role for this ganglioside in T cell subpopulations.

We recently described a monoclonal antibody (clone 27A) that detected a membrane antigen specific for glomerular podocytes in adult rat kidney. After binding in vivo, the antibodies induced rapid changes in the foot processes. Here we show that in other rat tissues the antigen is detectable only in cells of adrenal medulla, in some cells of neural or neural crest origin, and in 1 to 5% of the cells of a rat pheochromocytoma cell line PC-12. Attempts to isolate the antigen revealed that it is an acidic, sialic acid containing lipid, as shown by thin layer chromatography and immuno-overlay techniques. Further characterization of the gangliosides extracted from rat glomeruli, bovine kidney, rat adrenal glands, or from PC-12 cells by ion exchange, thin layer, and gas liquid chromatography identified the antigenic lipid as a modified disialosyllactosylceramide (GD3). The results of mild alkaline treatment or periodate oxidation of the antigenic ganglioside, as well as chemical O-acetylation studies of standard gangliosides, showed that the modified ganglioside is O-acetylated, most probably at the 9-carbon of its terminal sialic acid residue. To our knowledge this is the first report of cell-type specific expression of gangliosides in the kidney.

Retrograde differentiation (or dedifferentiation) has recently been proposed as a pathogenetic mechanism involved also in various renal diseases. Here we studied whether evidence of these mechanisms can be found in the kidneys of patients with congenital nephrotic syndrome of the Finnish type (CNF). These patients show isolated massive proteinuria but no primary symptoms from any other organ systems. For the analysis we used antibody markers of early (fibronectin, stem cell factor, Wilms' tumor gene product, cytokeratin) and later (laminin, midgestation and kidney, heparin binding growth-associated molecule) stages of nephron differentiation as well as for apoptosis (acridine orange staining), rescue from apoptosis (anti-Bcl-2 antibodies) and cell proliferation (antibodies to proliferating cell nuclear antigen). In the peritubular spaces atypically organized areas were found which appeared positive with markers of low stages of differentiation, but neither abnormal cell proliferation nor activation of the apoptotic pathway could be detected. As morphologic signs of abnormal tissue organization, we found clusters of tightly compacted and large glomeruli corresponding to the size of two to three normal glomeruli. However, all individual glomerular cell compartments (mesangial, endothelial, visceral epithelial cells) appeared balanced in relative cell numbers. Together these results may indicate abnormal early mesenchymoepithelial tissue interaction leading to excessive and poorly organized formation of glomeruli. This could be causally related also to the serious functional immaturity of CNF kidneys presented as isolated proteinuria.