The Design and development of secure password synchronization and querting system for the enterprise networks /

Organizations that run large computer networks should also provide maintenance for the computers on these networks. Nowadays, it is a common practice to outsource this maintenance task to specialized service firms. These service firms may not be considered trustworthy. Therefore, the local administrator password of a local machine that a maintenance technician needs to access should be changed periodically. Consequently, the technician needs a way to learn the current local administrator password of each computer. In this thesis, a secure password synchronization and querying system is presented. In this system, the local administrator passwords of computers are changed periodically in synchronization with a server managing the system. The maintenance technicians can learn the current password of a computer by querying the server. For synchronization and querying mechanisms, we propose three secure protocols that employ symmetric and asymmetric encryption techniques. Moreover, in this thesis, the proposed protocols are implemented as a software product and the performance of the system is evaluated by simulating the system. The average of the number of successful synchronizations stays constant when the number of computers is increased from 3,000 to 20,000 in the simulation. An increase in the number of computers doesn't change the behavior of the system. In addition, it is shown that the system can be configured to survive under rough network conditions. The implementation details and the performance evaluation of the system are presented in the thesis

Apoptotic rate and metallothionein levels in the tissues of cadmium- and copper-exposed rats

It is well known that cadmium (Cd) has toxic and carcinogenic effects in rodents and humans, but the effects of Cd on apoptosis are still not clear. Although some studies have shown that Cd has apoptotic potential, other studies have shown that Cd can be antiapoptotic. Parameters such as sensitivity of the exposed organism or cells and the exposure conditions should be important in delineating the effect of Cd on apoptosis. In the present study, we aimed to determine the apoptotic index (AI) of Sprague-Dawley rat tissues that are loaded at a lower Cd concentration than the critical concentration (50 mu g/g) for its toxic effects. Metallothionein (NIT) levels of tissues were also determined and the experiments repeated with copper (Cu)-exposed rats. We detected decreases in the apoptotic index in liver and lung tissues of Cd-exposed groups accompanied with an increase in MT levels. Also, decreases of Al were detected in the liver tissues of Cu-exposed groups. These findings indicate that Cd can suppress apoptosis in vivo. The possible role of NIT expression on the suppression of apoptosis and the importance of free-Cd ion concentration on switching antiapoptotic effects to proapoptotic effects are also discussed

Identification of O-GlcNAc Modification Targets in Mouse Retinal Pericytes: Implication of p53 in Pathogenesis of Diabetic Retinopathy

Abstract Hyperglycemia is the primary cause of the majority of diabetes complications, including diabetic retinopathy (DR). Hyperglycemic conditions have a detrimental effect on many tissues and cell types, especially the retinal vascular cells including early loss of pericytes (PC). However, the mechanisms behind this selective sensitivity of retinal PC to hyperglycemia are undefined. The O-linked b-N-acetylglucosamine (O-GlcNAc) modification is elevated under hyperglycemic condition, and thus, may present an important molecular modification impacting the hyperglycemia-driven complications of diabetes. We have recently demonstrated that the level of O-GlcNAc modification in response to high glucose is variable in various retinal vascular cells. Retinal PC responded with the highest increase in O-GlcNAc modification compared to retinal endothelial cells and astrocytes. Here we show that these differences translated into functional changes, with an increase in apoptosis of retinal PC, not just under high glucose but also under treatment with O-GlcNAc modification inducers, PUGNAc and Thiamet-G. To gain insight into the molecular mechanisms involved, we have used click-It chemistry and LC-MS analysis and identified 431 target proteins of O-GlcNAc modification in retinal PC using an alkynyl-modified GlcNAc analog (GlcNAlk). Among the O-GlcNAc target proteins identified here 115 of them were not previously reported to be target of O-GlcNAc modification. We have identified at least 34 of these proteins with important roles in various aspects of cell death processes. Our results indicated that increased O-GlcNAc modification of p53 was associated with an increase in its protein levels in retinal PC. Together our results suggest that post-translational O-GlcNAc modification of p53 and its increased levels may contribute to selective early loss of PC during diabetes. Thus, modulation of O-GlcNAc modification may provide a novel treatment strategy to prevent the initiation and progression of DR

Performance Assessment of a Refrigeration System Charged with Different Refrigerants Using Infrared Image Processing Techniques

This study aims to investigate the performance of R417A, R422A, R422D and R438A refrigerants as alternatives to R22, in a commercial type refrigeration system operating with R22 refrigerant. To this end, first of all, the cooling capacity and coefficient of performance (COP) values were calculated for all refrigerants used in the experimental setup. Then, two methods were proposed, Pearson's Correlation Similarity Analysis (PCSA) and surface temperature-based COP (COPST), to evaluate the success of each alternative refrigerants, and R22 with infrared image analysis, separately. The COP values obtained for the refrigerants with the mathematical method are R22 4.07, R438A 3.88, R417A 3.63, R422D 3.37, and R422A 3.18, respectively. Both the COP values and the PCSA values (R438A 0.9425, R417A 0.9343, R422D 0.9167 and R422A 0.9080) show the proximity between the R22 refrigerant and other refrigerants. Similarly, the COPST method revealed the values of R22 6.8865, R438A 5.9539, R417A 5.3273, R422D 4.9898 and R422A 4.3057, and the fact that it has the same order with the other two methods demonstrates its operability in the performance test application with the developed infrared image processing. The compatibility of the order in the experimental results obtained from the PCSA and COPST methods and the COP calculation method and has proved that thanks to infrared imaging, the remote performance analysis of the refrigeration system can be successfully performed.Scientific and Technological Research Council of Turkey (TuBTAK)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [218M936]This study was supported by The Scientific and Technological Research Council of Turkey (TuBTAK) with the project number 218M936.WOS:0006632463000012-s2.0-8510822867

High glucose alters retinal astrocytes phenotype through increased production of inflammatory cytokines and oxidative stress.

Astrocytes are macroglial cells that have a crucial role in development of the retinal vasculature and maintenance of the blood-retina-barrier (BRB). Diabetes affects the physiology and function of retinal vascular cells including astrocytes (AC) leading to breakdown of BRB. However, the detailed cellular mechanisms leading to retinal AC dysfunction under high glucose conditions remain unclear. Here we show that high glucose conditions did not induce the apoptosis of retinal AC, but instead increased their rate of DNA synthesis and adhesion to extracellular matrix proteins. These alterations were associated with changes in intracellular signaling pathways involved in cell survival, migration and proliferation. High glucose conditions also affected the expression of inflammatory cytokines in retinal AC, activated NF-κB, and prevented their network formation on Matrigel. In addition, we showed that the attenuation of retinal AC migration under high glucose conditions, and capillary morphogenesis of retinal endothelial cells on Matrigel, was mediated through increased oxidative stress. Antioxidant proteins including heme oxygenase-1 and peroxiredoxin-2 levels were also increased in retinal AC under high glucose conditions through nuclear localization of transcription factor nuclear factor-erythroid 2-related factor-2. Together our results demonstrated that high glucose conditions alter the function of retinal AC by increased production of inflammatory cytokines and oxidative stress with significant impact on their proliferation, adhesion, and migration

Identification of O-GlcNAc Modification Targets in Mouse Retinal Pericytes: Implication of p53 in Pathogenesis of Diabetic Retinopathy

<div><p>Hyperglycemia is the primary cause of the majority of diabetes complications, including diabetic retinopathy (DR). Hyperglycemic conditions have a detrimental effect on many tissues and cell types, especially the retinal vascular cells including early loss of pericytes (PC). However, the mechanisms behind this selective sensitivity of retinal PC to hyperglycemia are undefined. The O-linked β-N-acetylglucosamine (O-GlcNAc) modification is elevated under hyperglycemic condition, and thus, may present an important molecular modification impacting the hyperglycemia-driven complications of diabetes. We have recently demonstrated that the level of O-GlcNAc modification in response to high glucose is variable in various retinal vascular cells. Retinal PC responded with the highest increase in O-GlcNAc modification compared to retinal endothelial cells and astrocytes. Here we show that these differences translated into functional changes, with an increase in apoptosis of retinal PC, not just under high glucose but also under treatment with O-GlcNAc modification inducers, PUGNAc and Thiamet-G. To gain insight into the molecular mechanisms involved, we have used click-It chemistry and LC-MS analysis and identified 431 target proteins of O-GlcNAc modification in retinal PC using an alkynyl-modified GlcNAc analog (GlcNAlk). Among the O-GlcNAc target proteins identified here 115 of them were not previously reported to be target of O-GlcNAc modification. We have identified at least 34 of these proteins with important roles in various aspects of cell death processes. Our results indicated that increased O-GlcNAc modification of p53 was associated with an increase in its protein levels in retinal PC. Together our results suggest that post-translational O-GlcNAc modification of p53 and its increased levels may contribute to selective early loss of PC during diabetes. Thus, modulation of O-GlcNAc modification may provide a novel treatment strategy to prevent the initiation and progression of DR.</p></div

Effects of high glucose and O-GlcNAc modification inducers on apoptosis of retinal vascular cells.

<p>TUNEL staining was used to detect cell apoptosis (red). The nuclei were counterstained with DAPI (blue). Violet color represents TUNEL-positive nuclei on merged photos. (A): represents retinal PC grown in 5 mM glucose medium, (B): in 25 mM glucose medium, (C): treatment with 100 nM Thiamet-G for 1 day in 5 mM glucose medium, (D): positive control, cells treated with 1 µM staurosporine (STP) for 6 h. These images are representative of images evaluated at least 1000 cells for each condition with 3 replicates (original magnification x200). (E); Bar graphs quantify apoptosis, which is expressed as percentage of apoptotic cells for each condition. Data are presented as mean ± SEM (n = 3). Mean ± SEM; ****(p≤0.001) significantly different from 5 mM glucose control.</p

The list of O-GlcNAc modified proteins involved in cellular death processes.

<p>The list of O-GlcNAc modified proteins involved in cellular death processes.</p

Effects of high glucose and O-GlcNAc modification inducers on retinal vascular cell death and proliferation.

<p>Cells were assayed for cell death (A) and cell proliferation (B) under varying glucose concentration, with or without O-GlcNAcylation inhibitors, Don and Alloxan, and with or without O-GlcNAcylation inducers, Thiamet G (T–G) and PUGNAc. Cell viability was assessed by counting trypan blue-positive cells. Proliferation rates were determined by a MTS-based assay. High glucose conditions, or low glucose with O-GlcNAcylation inducers, significantly increased PC death (A) as well as decreased cell proliferation (B) compared to both EC and AC. Conversely, O-GlcNAcylation inhibitors neutralized the negative effects of high glucose on retinal PC. Mean ± SEM; ***(p≤0.01), and ****(p≤0.001) significantly different from 5 mM glucose control.</p