Remziye Deveci

Cleavage of Atg3 protein by caspase-8 regulates autophagy during receptor-activated cell death.

Autophagy is an evolutionarily conserved mechanism contributing to cell survival under stress conditions including nutrient and growth factor deprivation. Connections and cross-talk between cell death mechanisms and autophagy is under investigation. Here, we describe Atg3, an essential regulatory component of autophagosome biogenesis, as a new substrate of caspase-8 during receptor-mediated cell death. Both, tumor necrosis factor α and tumor necrosis factor-related apoptosis inducing ligand induced cell death was accompanied by Atg3 cleavage and this event was inhibited by a pan-caspase inhibitor (zVAD) or a caspase-8-specific inhibitor (zIETD). Indeed, caspase-8 overexpression led to Atg3 degradation and this event depended on caspase-8 enzymatic activity. Mutation of the caspase-8 cleavage site on Atg3 abolished its cleavage both in vitro and in vivo, demonstrating that Atg3 was a direct target of caspase-8. Autophagy was inactive during apoptosis and blockage of caspases or overexpression of a non-cleavable Atg3 protein reestablished autophagic activity upon death receptor stimulation. In this system, autophagy was important for cell survival since inhibition of autophagy increased cell death. Therefore, Atg3 provides a novel link between apoptosis and autophagy during receptor-activated cell death.

Characterization of the Cellular Response During Apoptosis Induction in Cadmium-Treated Hep G2 Human Hepatoma Cells

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.

Griscelli syndrome: Report of a case and review of the literature

characterized by pigmentary dilution and variable immunodeficiency.1 The clinical symptoms consist of silver–gray hair and relatively light skin color, recurrent episodes of fever, with or without pyogenic infections, hepatosplenomegaly and lymphadenopathy.2 Central nervous system involvement has also been described in most patients.3 Clinical onset usually occurs between 4 months and 7 years of age.1–5 In the present study, we report on a 6-week-old Turkish boy with Griscelli syndrome.

Presence of sialic acid in prothoracic glands of Galleria mellonella (Lepidoptera)

The presence of sialic acid (SA) in prothoracic glands (PGs) of Galleria mellonella was determined by the methods of electron microscopy (EM), histochemistry, spectrophotometry (SP) and electronic ionization (EI)-mass spectroscopy. Histochemical observations were carried out by the cationic dye ruthenium red (RR), staining with and without neuraminidase digestion in the larval stage. Neuraminidase-sensitive SA was demonstrated by the decrease in the amount of RR-binding following neuraminidase digestion. The total amount of SA was found to be 0.09016 mg g(-1) in dry tissue by spectrophotometric determination. EI-mass spectroscopy results confirmed the EM and SP observations. The fragmentation scheme derived from EI-mass analysis exhibited the presence of the lactonized form of Neu5Gc7, 9Ac(2). On the basis of the various pieces of evidence described above, it was firmly concluded that Neu5Gc7, 9Ac(2) molecules were present in PGs of G. mellonella.

Sialic acids in developing testis of Galleria mellonella (Lepidoptera)

Summary 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.

Predicting the Intra-Yarn Porosity by Image Analysis Method

The flow mechanism that is realized in 3-D depending on the fabric’s porosity structure determines the fabric’s permeability performance. During the flow movement that happens both in the in-plane and through-plane directions, not only the inter-yarn pore properties but inter-fiber pore properties play a significant role as well. The aim of this study is to offer a new method to identify intra-yarn porosity, which has mostly been neglected during the theoretical studies. In this method, initially the cross-sectional images of the cotton yarn in the fabric were achieved, and then the intra-yarn porosity was predicted via image processing and analysis steps. Besides, intra-yarn porosity was calculated theoretically depending on fiber and yarn parameters. The results that were obtained through the image analysis method and theoretical approaches were compared with the experimental data achieved by using Stereo Investigator. As a result, it was observed that the image analysis method was giving fast, objective, successful and expected results while predicting the intra-yarn porosity.

Adhesion of hemocytes to desialylated prothoracic glands of Galleria mellonella (Lepidoptera) in the larval stage.

Summary Earlier work showed the existence of sialic acid (SA) in the prothoracic glands (PGs) of Galleria mellonella (Karaçali 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.

Biochemical and morphological characteristics of selenite-induced apoptosis in human hepatoma hep G2 cells

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.

Determination of the type and quantity of sialic acid in the egg jelly coat of the sea urchin Paracentrotus lividus using capillary LC‐ESI‐MS/MS

Sialic acid is a terminal sugar of carbohydrate chains that participates in numerous biological events. Recent studies have explored the mechanism of carbohydrate‐mediated fertilisation to understand the biochemistry of fertilisation, although the type and quantity of sialic acid and the role of sialic acid during fertilisation remain unknown. Echinoderm fertilisation in particular has been studied extensively, yet our understanding of the mechanisms of carbohydrate‐mediated fertilisation and the role of sialic acid remains incomplete. In this study, we characterised the sialic acid types in the egg jelly coat of the sea urchin, Paracentrotus lividus, using the sensitive analytical system capillary liquid chromatography electro‐spray ionisation tandem mass spectrometry (capLC‐ESI‐MS/MS). First, we isolated the egg jelly coat and released its sialic acid using acid treatment. These sialic acids were derivatised with 1,2‐diamino‐4,5‐methylenediaoxy‐benzene dihydrochloride (DMB) and injected into the capLC‐ESI‐MS/MS system. When compared with standards, we identified twelve different types of sialic acid according to their retention times and collision‐induced dissociation fragments. The mass spectral data revealed that Neu5Gc, Neu5Ac, Neu5GcS, and Neu5Gc9Ac were the predominant types of sialic acid in the sea urchin jelly coat, with Neu5Gc being the most abundant. Other types of sialic acid detected included Neu5AcS, Neu5Gc7,9Ac2, Neu5,9Ac2, Neu5Gc8Ac, Neu5Gc7Ac, Neu5,7Ac2, Neu5Gc8,9Ac2, and Neu5,8Ac2. The types and quantities of sialic acid that we detected in the egg jelly coat will aid in the discovery of new sialic acid‐specific receptors on the sperm membrane. Mol. Reprod. Dev. 82: 115–122, 2015.

Morphological and ultrastructural characterization of sea urchin immune cells

The free circulating coelomocytes in the coelomic cavity of echinoderms are considered to be immune effectors by phagocytosis, encapsulation, cytotoxicity, and by the production of antimicrobial agents. Although echinoderms (especially sea urchin embryo) have been used as a model organisms in biology, no uniform criteria exist for classification of coelomocytes in echinoderms, and few studies have reported about the biological functions of their coelomocytes. Hence, we study the coelomocytes in the echinoid sea urchin, Paracentrotus lividus, and describe their morphological and ultrastructural features using light and transmission electron microscopes. We classify the coelomocytes of P. lividus into red spherule and colorless spherule cells, small cells, vibratile cells, and phagocytic cells; petaloid and filopodial cells. To our knowledge, this is the first report describing ultrastructural details of the coelomocytes of P. lividus. J. Morphol. 276:583–588, 2015.