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AbstractReelin is an extracellular matrix glycoprotein that plays a key role in cortical development, maturation, synaptic plasticity, and memory formation in the adult mammalian brain. Glycosylation is a significant post- and co-translational modification of proteins. Although glycosylation contributes to the characteristic of proteins from their production to molecular interactions, the knowledge about the glycosylation pattern of reelin is very limited. In this study, we aimed to predict the potential glycosylation pattern of the 5th-6threpeat of central reelin fragment that responsible for their signaling, by using in silico methods. We found that the predicted glycosylation pattern of the 5th-6threpeat of human reelin was highly conserved between vertebrate species. However, this conservation was not observed in analyzed invertebrates. For the first time, we described the sites of glycosylation at a three-dimensional protein structure in human reelin. Because the sites were very closed to EGF-like repeats and receptor binding sites, they could contribute the interaction with a partner of reelin in addition to the effect of thermostability to protein. Many of the residues related glycosylation were also conserved in analyzed species. These findings may guide biochemical, genetic, and glycobiology base on further experiments about reelin glycosylation. The understanding of reelin glycosylation might change the point of view of treatment for many pathological conditions in neurodegenerative diseases such as Alzheimer’s disease. Communicated by Ramaswamy H. Sarma

Abstract: Selenium is a cellular growth inhibitor in many mammary tumor cells. To comprehend the mechanism for the selenium-induced cell death, we examined the effects of sodium selenite, which has been one of the most extensively investigated selenium compounds, in human hepatoma Hep G2 cells. Cell viability gradually decreased after treatment with sodium selenite within the concentration range of 10–50 µM. Low (10 µM) selenite has shown a high-percentage laddering pattern compared to the high (25 µM) cytotoxic selenium concentration in agarose gel electrophoresis. G2M-phase enrichment was also concentration dependent. The most consistent transmission electron microscopic finding was the existence of large lysosomes. Based on these data, we hypothesize that sodium selenite predominantly shows its apoptotic effect over hydrogen selenite accumulation.

Abstract: Cadmium is a toxic transition heavy metal of continuing occupational and environmental concern, with a wide variety of adverse effects on regulation of gene expression and cellular signal transduction pathways. Injury to cells by cadmium leads to a complex series of events that can culminate in the death of the cell. It has been reported that cadmium induces apoptosis in many cell lines. However, the morphological characteristics leading to apoptosis or subsequent regeneration in cells exposed to cadmium have not been clarified. We evaluated whether human hepatoma cells maintained in culture undergo apoptosis when exposed to cadmium. Cytotoxic activity of cadmium on Hep G2 cells determined using 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide assay. A DNA ladder assay was performed by electrophoresis. Cell cycle analysis was quantified by flow cytometry. Nuclear morphology was studied by fluorescence microscopy after staining with propidium iodide and Hoechst 33342. Morphologic alterations in culture hepatocytes treated with CdCl2 were observed by transmission electron microscopy. We have demonstrated that apoptosis is a major mode of elimination of damaged HepG2 cells in cadmium toxicity and it precedes necrosis.

The detection of sialic acids (Sias) in insects is important for establishing the universal nature of Sias. In this study the amounts of Sia in hemolymphs of solitary adults Dociostaurus maroccanus Thun. (Orthoptera) were determined through gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). Sialic acid contents in dried hemolymph samples were found to be 0.054% and 0.007% for males and females, respectively.

Earlier work showed the existence of sialic acid (SA) in the prothoracic glands (PGs) of Galleria mellonella (Karacali et al., 1997). In this paper we investigated the role of SA during the degeneration process of PGs. Neuraminidase-digested larval PGs were incubated within the hemolymph collected from same age larvae. Light and electron microscopic observations showed incomplete capsule formation by the accumulation of hemocytes around desialylated gland cells, but not in the control group. Desialylated larval PG cells were recognized as a foreign structure or non-self by hemocytes. The result indicates that SA acts as a mask for hemocytic receptors during the larval period under normal conditions. However, in the absence of SA, the glands start to degenerate. We provide an explanation for the role of SA in the recognition process of hemocytes that initiates the degeneration of PGs in pupal cells and show the functionality of SA in insects, confirming that SA is a universal molecule.

The wide availability of sialic acids (SAs) in many organisms emphasizes their role for biological processes. The detection of SAs in insects is important for reinforcing the universal nature of SAs. In this study, the amounts and the types of SAs in testis of Galleria mellonella were investigated through gas chromatography (GC) and gas chromatography-mass (GC-MS) spectroscopy. GC analysis showed that the amount of SAs significantly decreased from young pupae to adults. The ratio of the levels of SAs in young pupa:old pupa:adult was found to be 16:5:1. Neu5Ac, Neu5Gc, Neu4,5Ac2, Neu5,9Ac2, and Neu2en5Ac were found in young pupae by GC-MS analysis. Neu5Ac, Neu5Gc Neu9Ac5Gc and Neu5,8,9Ac3 were detected in old pupae. Neu5Ac and Neu5Gc were encountered in adults. In addition to this trend of decreasing SA amounts, the variety of SA types present also decreased from young pupae to adults.