Microvascular lesions of diabetic retinopathy: clues towards understanding pathogenesis?

Retinopathy is a major complication of diabetes mellitus and this condition remains a leading cause of blindness in the working population of developed countries. As diabetic retinopathy progresses a range of neuroglial and microvascular abnormalities develop although it remains unclear how these pathologies relate to each other and their net contribution to retinal damage. From a haemodynamic perspective, evidence suggests that there is an early reduction in retinal perfusion before the onset of diabetic retinopathy followed by a gradual increase in blood flow as the complication progresses. The functional reduction in retinal blood flow observed during early diabetic retinopathy may be additive or synergistic to pro-inflammatory changes, leucostasis and vaso-occlusion and thus be intimately linked to the progressive ischaemic hypoxia and increased blood flow associated with later stages of the disease. In the current review a unifying framework is presented that explains how arteriolar dysfunction and haemodynamic changes may contribute to late stage microvascular pathology and vision loss in human diabetic retinopathy.

The role of lipids and protein kinase Cs in the pathogenesis of diabetic retinopathy

Diabetic retinopathy is one of the most common complications of diabetes and is a major cause of new blindness in the working-age population of developed countries. While the exact pathogenic basis of this condition remains ill defined, it is clear that hyperglycaemia is a critical factor in its aetiology. Protein kinase C (PKC) activation is one of the sequelae of hyperglycaemia and it is thought to play an important role in the development of diabetic complications. This review questions the currently held dogma that PKC stimulation in diabetes is solely mediated through the overproduction of palmitate and oleate enriched diacylglycerols. Blood glucose concentrations are closely tracked by changes in the levels of free fatty acids and these, in addition to oxidative stress, may account for the aberrant activation of PKCs in diabetes. Little is known about why PKCs fail to downregulate in diabetes and efforts should be directed towards acquiring such information. Considerable evidence implicates the PKCbeta isoform in the pathogenesis of diabetic retinopathy, but other isoforms may also be of relevance. In addition to PKCs, it is evident that novel diacyglycerol-activated non-kinase receptors could also play a role in the development of diabetic complications. Therapeutic agents have been developed to inhibit specific PKC isoforms and PKCbeta antagonists are currently undergoing clinical trials to test their toxicity and efficacy in suppressing diabetic complications. The likely impact of these drugs in the treatment of diabetic patients is considered.

Unique Challenges in WiFi Intrusion Detection

The Intrusion Detection System (IDS) is a common means of protecting networked systems from attack or malicious misuse. The deployment of an IDS can take many different forms dependent on protocols, usage and cost. This is particularly true of Wireless Intrusion Detection Systems (WIDS) which have many detection challenges associated with data transmission through an open, shared medium, facilitated by fundamental changes at the Physical and MAC layers. WIDS need to be considered in more detail at these lower layers than their wired counterparts as they face unique challenges. The remainder of this chapter will investigate three of these challenges where WiFi deviates significantly from that of wired counterparts:

• Attacks Specific to WiFi Networks: Outlining the additional threats which WIDS must account for: Denial of Service, Encryption Bypass and AP Masquerading attacks.

• The Effect of Deployment Architecture on WIDS Performance: Demonstrating that the deployment environment of a network protected by a WIDS can influence the prioritisation of attacks.

• The Importance of Live Data in WiFi Research: Investigating the different choices for research data sources with an emphasis on encouraging live network data collection for future WiFi research.

MHJ_0125 is an M42 glutamyl aminopeptidase that moonlights as a multifunctional adhesin on the surface of Mycoplasma hyopneumoniae

Bacterial aminopeptidases play important roles in pathogenesis by providing a source of amino acids from exogenous proteins, destroying host immunological effector peptides and executing posttranslational modification of bacterial and host proteins. We show that MHJ_0125 from the swine respiratory pathogen Mycoplasma hyopneumoniae represents a new member of the M42 class of bacterial aminopeptidases. Despite lacking a recognizable signal sequence, MHJ_0125 is detectable on the cell surface by fluorescence microscopy and LC-MS/MS of (i) biotinylated surface proteins captured by avidin chromatography and (ii) peptides released by mild trypsin shaving. Furthermore, surface-associated glutamyl aminopeptidase activity was detected by incubation of live M. hyopneumoniae cells with the diagnostic substrate H-Glu-AMC. MHJ_0125 moonlights as a multifunctional adhesin, binding to both heparin and plasminogen. Native proteomics and comparative modelling studies suggest MHJ_0125 forms a dodecameric, homopolymeric structure and provide insight into the positions of key residues that are predicted to interact with heparin and plasminogen. MHJ_0125 is the first aminopeptidase shown to both bind plasminogen and facilitate its activation by tissue plasminogen activator. Plasmin cleaves host extracellular matrix proteins and activates matrix metalloproteases, generating peptide substrates for MHJ_0125 and a source of amino acids for growth of M. hyopneumoniae. This unique interaction represents a new paradigm in microbial pathogenesis.

Glycation and oxidation:a role in the pathogenesis of atherosclerosis

Reactions involving glycation and oxidation of proteins and lipids are believed to contribute to atherogenesis. Glycation, the nonenzymatic binding of glucose to protein molecules, can increase the atherogenic potential of certain plasma constituents, including low-density lipoprotein (LDL). Glycation of LDL is significantly increased in diabetic patients compared with normal subjects, even in the presence of good glycemic control. Metabolic abnormalities associated with glycation of LDL include diminished recognition of LDL by the classic LDL receptor; increased covalent binding of LDL in vessel walls; enhanced uptake of LDL by macrophages, thus stimulating foam cell formation; increased platelet aggregation; formation of LDL-immune complexes; and generation of oxygen free radicals, resulting in oxidative damage to both the lipid and protein components of LDL and to any nearby macromolecules. Oxidized lipoproteins are characterized by cytotoxicity, potent stimulation of foam cell formation by macrophages, and procoagulant effects. Combined glycation and oxidation, "glycoxidation," occurs when oxidative reactions affect the initial products of glycation, and results in irreversible structural alterations of proteins. Glycoxidation is of greatest significance in long-lived proteins such as collagen. In these proteins, glycoxidation products, believed to be atherogenic, accumulate with advancing age: in diabetes, their rate of accumulation is accelerated. Inhibition of glycation, oxidation, and glycoxidation may form the basis of future antiatherogenic strategies in both diabetic and nondiabetic individuals.

Pathophysiology and Pathogenesis of Diabetic Retinopathy

Diabetic retinopathy is traditionally viewed as a disease of the retinal blood vessels, although there is increasing evidence that retinal neurons and glial cells are also affected. This article describes the changes in the diabetic retina that precede the development of clinical diabetic retinopathy, including changes in the rate of retinal blood flow, alterations in the electroretinogram and breakdown of the integrity of the blood-retinal barrier. The long term lesions of diabetic retinopathy are characterised by a complex array of vasodegenerative changes that lead directly to areas of retinal ischaemia. This frequently triggers the onset of macular oedema and/or the proliferative stages of diabetic retinopathy with risk of visual impairment and blindness. Neurodegeneration has also been reported in the retina during both human and experimental diabetic retinopathy, although presently it remains unclear to what extent such changes contribute to visual loss in diabetic retinopathy.

Cathelicidin LL-37:a defense molecule with a potential role in psoriasis pathogenesis

Epidermal keratinocytes produce and secrete antimicrobial peptides (AMPs) that subsequently form a chemical shield on the skin surface. Cathelicidins are one family of AMPs in skin with various further immune functions. Consequently, dysfunction of these peptides has been implicated in the pathogenesis of inflammatory skin disease. In particular, the cathelicidin LL-37 is overexpressed in inflamed skin in psoriasis, binds to extracellular self-DNA released from dying cells and converts self-DNA in a potent stimulus for plasmacytoid dendritic cells (pDCs). Subsequently, pDCs secrete type I interferons and trigger an auto-inflammatory cascade. Paradoxically, therapies targeting the vitamin D pathway such as vitamin D analogues or UVB phototherapy ameliorate cutaneous inflammation in psoriasis but strongly induce cathelicidin expression in skin at the same time. Current evidence now suggests that self-DNA present in the cytosol of keratinocytes is also pro-inflammatory active and triggers IL-1β secretion in psoriatic lesions through the AIM2 inflammasome. This time, however, binding of LL-37 to self-DNA neutralizes DNA-mediated inflammation. Hence, cathelicidin LL-37 shows contrasting roles in skin inflammation in psoriasis and might serve as a target for novel therapies for this chronic skin disease.

Role of saphenous vein wall in the pathogenesis of primary varicose veins

UNLABELLED: Varicose veins may be due to weakness of the vein wall as a result of structural problems. There are conflicting findings in the literature about these problems especially concerning collagen, elastin and smooth muscle cells content. The aim of this study was to look at the structural abnormalities of varicose veins (with and without valvular incompetence).

MATERIALS AND METHODS: We studied 70 specimens of long saphenous veins from 35 patients (24 with varicose and 11 with normal veins). Two specimens were taken from each vein approximately 3-4 cm from the saphenofemoral junction. Vein specimens were processed for histological and electron microscopic studies. Both qualitative and quantitative analyses were performed to assess the degree of wall changes. Using the image analyzer, contents of collagen, elastin and smooth muscle cells, in addition to intimal and medial thickness, were measured.

RESULTS: Light microscopy revealed significant increase in intimal and medial thickness and collagen content of media and significant decrease in elastin content in varicose veins compared with normal veins. There was no statistical significant difference between varicose veins with and without saphenofemoral valve incompetence. Electron microscopy showed marked degenerative changes in intima and media of varicose veins.

CONCLUSION: The findings in our study supported the theory of primary weakness of the vein wall as a cause of varicosity. This weakness is due to intimal changes, disturbance in the connective tissue components and smooth muscle cells.

A unique and robust single slice FPGA identification generator

In this paper, a new field-programmable gate array (FPGA) identification generator circuit is introduced based on physically unclonable function (PUF) technology. The new identification generator is able to convert flip-flop delay path variations to unique n-bit digital identifiers (IDs), while requiring only a single slice per ID bit by using 1-bit ID cells formed as hard-macros. An exemplary 128-bit identification generator is implemented on ten Xilinx Spartan-6 FPGA devices. Experimental results show an uniqueness of 48.52%, and reliability of 92.41% over a 25°C to 70°C temperature range and 10% fluctuation in supply voltage

Within-host evolution of Burkholderia pseudomallei over a twelve-year chronic carriage infection

UNLABELLED: Burkholderia pseudomallei causes the potentially fatal disease melioidosis. It is generally accepted that B. pseudomallei is a noncommensal bacterium and that any culture-positive clinical specimen denotes disease requiring treatment. Over a 23-year study of melioidosis cases in Darwin, Australia, just one patient from 707 survivors has developed persistent asymptomatic B. pseudomallei carriage. To better understand the mechanisms behind this unique scenario, we performed whole-genome analysis of two strains isolated 139 months apart. During this period, B. pseudomallei underwent several adaptive changes. Of 23 point mutations, 78% were nonsynonymous and 43% were predicted to be deleterious to gene function, demonstrating a strong propensity for positive selection. Notably, a nonsense mutation inactivated the universal stress response sigma factor RpoS, with pleiotropic implications. The genome underwent substantial reduction, with four deletions in chromosome 2 resulting in the loss of 221 genes. The deleted loci included genes involved in secondary metabolism, environmental survival, and pathogenesis. Of 14 indels, 11 occurred in coding regions and 9 resulted in frameshift mutations that dramatically affected predicted gene products. Disproportionately, four indels affected lipopolysaccharide biosynthesis and modification. Finally, we identified a frameshift mutation in both P314 isolates within wcbR, an important component of the capsular polysaccharide I locus, suggesting virulence attenuation early in infection. Our study illustrates a unique clinical case that contrasts a high-consequence infectious agent with a long-term commensal infection and provides further insights into bacterial evolution within the human host.

IMPORTANCE: Some bacterial pathogens establish long-term infections that are difficult or impossible to eradicate with current treatments. Rapid advances in genome sequencing technologies provide a powerful tool for understanding bacterial persistence within the human host. Burkholderia pseudomallei is considered a highly pathogenic bacterium because infection is commonly fatal. Here, we document within-host evolution of B. pseudomallei in a unique case of human infection with ongoing chronic carriage. Genomic comparison of isolates obtained 139 months (11.5 years) apart showed a strong signal of adaptation within the human host, including inactivation of virulence and immunogenic factors, and deletion of pathways involved in environmental survival. Two global regulatory genes were mutated in the 139-month isolate, indicating extensive regulatory changes favoring bacterial persistence. Our study provides insights into B. pseudomallei pathogenesis and, more broadly, identifies parallel evolutionary mechanisms that underlie chronic persistence of all bacterial pathogens.