Evolving concepts on the pathogenic mechanisms of aniridia related keratopathy

Heterozygosity for PAX6 deficiency (PAX6+/-) results in aniridia. Corneal changes in aniridia-related keratopathy (ARK) include corneal vascular pannus formation, conjunctival invasion of the corneal surface, corneal epithelial erosions and epithelial abnormalities, which eventually result in corneal opacity and contribute to visual loss. Corneal changes in aniridia have been attributed to congenital deficiency of corneal limbal stem cells. The aim of this paper is to review the potential mechanisms that may underlie the pathogenesis of aniridia related keratopathy. Current evidence, based on clinical observations and an animal model of aniridia suggest that the proliferative potential of the corneal limbal stem cells may not primarily be impaired. The corneal changes in aniridia may be related to an abnormality within the limbal stem cell niche. The mechanisms underlying progressive corneal pathology in aniridia appear multi-factorial and include: (1) abnormal corneal healing responses secondary to anomalous extracellular matrix metabolism; (2) abnormal corneal epithelial differentiation leading to fragility of epithelial cells; (3) reduction in cell adhesion molecules in the PAX6 heterozygous state, rendering the cells susceptible to natural shearing forces; and (4) conjunctival and corneal changes leading to the presence of cells derived from conjunctiva on the corneal surface.     

Inactivation of viruses and cells by mustard gas

The action of mustard gas on six animal, one plant, and two bacterial viruses; also on bacteria, yeast, and the pneumococcus-transforming principle has been studied. The viruses include Newcastle's disease of chickens, equine encephalomyelitis (Eastern strain), feline pneumonitis (Baker), rabbit papilloma (Shope), fixed rabies, rabbit myxoma, tobacco mosaic, T(2)r(+) phage of E. coli B, and a Staphylococcus muscae phage. The cells include bakers' yeast, E. coli B, Staphylococcus muscae, and swine plague bacillus. The rates of inactivation of the viruses and cells were of the same order of magnitude and faster than those of enzymes. Of the viruses examined those containing desoxyribose nucleic acid were inactivated faster than those containing ribosenucleic acid. Preparations of the pneumococcus-transforming principle which were largely desoxyribose nucleic acid have shown the greatest sensitivity to mustard gas of all systems examined. An expression was derived describing the inactivation rate when mustard gas decreases during the experiment.     

Soil biotransformation of thiodiglycol, the hydrolysis product of mustard gas: understanding the factors governing remediation of mustard gas contaminated soil

Thiodiglycol (TDG) is both the precursor for chemical synthesis of mustard gas and the product of mustard gas hydrolysis. TDG can also react with intermediates of mustard gas degradation to form more toxic and/or persistent aggregates, or reverse the pathway of mustard gas degradation. The persistence of TDG have been observed in soils and in the groundwater at sites contaminated by mustard gas 60 years ago. The biotransformation of TDG has been demonstrated in three soils not previously exposed to the chemical. TDG biotransformation occurred via the oxidative pathway with an optimum rate at pH 8.25. In contrast with bacteria isolated from historically contaminated soil, which could degrade TDG individually, a consortium of three bacterial strains isolated from the soil never contaminated by mustard gas was able to grow on TDG in minimal medium and in hydrolysate derived from an historical mustard gas bomb. Exposure to TDG had little impacts on the soil microbial physiology or on community structure. Therefore, the persistency of TDG in soils historically contaminated by mustard gas might be attributed to the toxicity of mustard gas to microorganisms and the impact to soil chemistry during the hydrolysis. TDG biodegradation may form part of a remediation strategy for mustard gas contaminated sites, and may be enhanced by pH adjustment and aeration.     

Chagas disease: Present status of pathogenic mechanisms and chemotherapy

There are approximately 7.8 million people in Latin America, including Chile, who suffer from Chagas disease and another 28 million who are at risk of contracting it. Chagas is caused by the flagellate protozoan Trypanosoma cruzi. It is a chronic disease, where 20%-30% of infected individuals develop severe cardiopathy, with heart failure and potentially fatal arrhythmias. Currently, Chagas disease treatment is more effective in the acute phase, but does not always produce complete parasite eradication during indeterminate and chronic phases. At present, only nifurtimox or benznidazole have been proven to be superior to new drugs being tested. Therefore, it is necessary to find alternative approaches to treatment of chronic Chagas. The current treatment may be rendered more effective by increasing the activity of anti-Chagasic drugs or by modifying the host's immune response. We have previously shown that glutathione synthesis inhibition increases nifurtimox and benznidazole activity. In addition, there is increasing evidence that cyclooxygenase inhibitors present an important effect on T. cruzi infection. Therefore, we found that aspirin reduced the intracellular infection in RAW 264.7 cells and, decreased myocarditis extension and mortality rates in mice. However, the long-term benefit of prostaglandin inhibition for Chagasic patients is still unknown.     

Genetic distance and heterosis in Indian mustard: developmental isozymes as indicators of genetic relationships

The use of isozymes as indicators of genetic diversity and as markers for the selection of agronomic traits has been proposed in different crop species. The present investigation was conducted to study the use of isozyme-derived genetic distance between parents in predicting the F₁ heterosis in Indian mustard. In addition, the interaction of isozyme-based diversity with quantitative trait and pedigree-based diversity measures, and its role in predicting hybrid heterosis has also been examined. Sixteen Indian mustard lines and their 48 crosses (12 × 4, line x tester crossing) were evaluated over two environments for isozyme and quantitative morphological characters. The results from this study suggest that the heterotic response to isozymic changes is more responsive in crosses derived from morphologically and pedigree-wise related parents in comparison to crosses derived from unrelated parents. It was possible to improve heterosis predictions by partitioning the isozyme-based genetic distance into general genetic distance and specific genetic distance and correlating the latter with the specific combining ability of morphological traits. The possible reasons for these observations are discussed.     

The use of human epidermal keratinocytes in culture as a model for studying the biochemical mechanisms of sulfur mustard toxicity

Human epidermal keratinocytes in culture were studied to evaluate their usefulness in demonstrating toxic events following exposure to sulfur mustard. Exposure of keratinocytes to sulfur mustard over a concentration range of 1–1000 μM HD, reduced NAD+ levels from 96% to 32% of control levels. When keratinocytes were exposed to a concentration of 300 μM HD, NAD+ levels began to fall at 1 hour and reached a plateau of 47% of control levels at 4 hours. Niacinamide, an inhibitor of the enzyme poly(ADP-ribose) polymerase, partially protected mustard-exposed cells against NAD+ depletion. It also protected cellular viability as assessed by vital staining 24 hours after exposure. This protection was not seen in long-term (72 hr) cultures. These studies suggest that human epidermal keratinocytes in culture can serve as a usefulin vitro model for research into the biochemical mechanisms of sulfur mustard-induced cutaneous injury.     

Fusobacterium necrophorum infections in animals: pathogenesis and pathogenic mechanisms

Fusobacterium necrophorum, a Gram-negative, non-spore-forming anaerobe, is a normal inhabitant of the alimentary tract of animals and humans. Two subspecies of F. necrophorum, subsp. necrophorum (biotype A) and subsp. funduliforme (biotype B), have been recognized, that differ morphologically, biochemically, and biologically. The subsp. necrophorum is more virulent and is isolated more frequently from infections than the subsp. funduliforme. The organism is an opportunistic pathogen that causes numerous necrotic conditions (necrobacillosis), either specific or non-specific infections, in a variety of animals. Of these, bovine liver abscesses and foot rot are of significant concern to the cattle industry. Liver abscesses arise with the organisms that inhabit the rumen gaining entry into the portal circulation, and are often secondary to ruminal acidosis and rumenitis complex in grain-fed cattle. Foot rot is the major cause of lameness in dairy and beef cattle. The pathogenic mechanism of F. necrophorum is complex and not well defined. Several toxins or secreted products, such as leukotoxin, endotoxin, hemolysin, hemagglutinin, proteases, and adhesin, etc., have been implicated as virulence factors. The major virulence factor appears to be leukotoxin, a secreted protein of high molecular weight, active specifically against leukocytes from ruminants. The complete nucleotide sequence of the leukotoxin operon of F. necrophorum has been determined. The operon consists of three genes (lktBAC) of which the second gene (lktA) is the leukotoxin structural gene. The leukotoxin appears to be a novel protein and does not share sequence similarity with any other leukotoxin. F. necrophorum is also a human pathogen and the human strains appear to be different from the strains involved in animal infections.     

Testing environmental and social indicators for biorefineries: bioethanol and biochemical production

Purpose

The article aims to test indicators for assessing the environmental and social impacts of biorefineries. Testing environmental and social impact categories and indicators, and selecting the most suitable ones, will simultaneously contribute to the further development of social life cycle assessment (S-LCA) methodologies while assessing several dimensions of sustainability at biorefineries.

Methods

The work applies two methodologies, environmental LCA (E-LCA) and social LCA (S-LCA), to two hypothetical production processes of second-generation bioethanol and biochemical in two alternative locations (Norway and the USA). Five impact categories were chosen for the E-LCA. The S-LCA was performed in two stages: a generic assessment (top-down approach) using the social hotspot database (SHDB 2013) to screen for potential social issues in the stakeholder group Worker in Norway and the USA and a specific assessment (bottom-up approach) for collecting data and confirming or refuting the SHDB results in the Norwegian case only.

Results and discussion

Bioethanol produced in the Norwegian biorefinery would perform relatively well in relation to climate change targets, with emissions of approximately 11 g CO₂-eq/MJ. The same production process located in the USA would produce emissions of approximately 29 g CO₂-eq/MJ. Other biorefinery products are difficult to compare because of a lack of clear alternatives. Bioethanol and biochemicals produced in the hypothetical USA production process have higher burdens than those from the Norwegian production process in all environmental categories assessed. For both production processes, the main social risks were in the category Health and safety followed by Labor rights and decent work. More detailed investigations in an existing Norwegian biorefinery value chain confirmed some of the risk issues but discarded others, demonstrating the necessity of providing specific data and results for the social dimension.

Conclusions

E-LCA and S-LCA make it possible to highlight the main environmental and social challenges when producing biochemicals. The SHDB has potential as a social screening tool although social indicators are not yet well established. Hence, specific assessment is necessary for validating the results in the social dimension. S-LCA is still in its infancy and needs to be applied in order to develop the best practice. The two methodologies addressed bioethanol and biochemical production performance in two different dimensions (environmental and social), and their combination makes it possible to achieve results that integrate the product-oriented approach with the more location-specific approach.

     

Imiquimod: The biochemical mechanisms of immunomodulatory and anti-inflammatory activity

Imidazoquinolines are a new group of compounds that recently have been introduced into clinical practice as antitumor and antiviral immunomodulators. Structurally, they are low molecular weight synthetic guanosine-like molecules. Although imiquimod, the most widely used imidazoquinoline, has been recommended for treatment of several forms of skin cancer and papillomas, its molecular mechanisms of action are not fully understood. In particular, imiquimod is known as a specific agonist of Toll-like receptor 7 (TLR7) and this capacity is widely used in a large number of experimental studies and clinical trials. Nevertheless, detailed analysis of the published data suggests that the biological activity of imiquimod can not be explained only by its interaction with TLR7. Certain evidence exists that imiquimod directly interacts with adenosine receptors and other molecules that regulate synthesis of cyclic adenosine monophosphate. A detailed understanding of the biochemical basis of immunomodulating and antitumor effects of imiquimod will increase its clinical effectiveness and accelerate the development of new drugs with similar but improved pharmaceutical characteristics. This review summarizes the published data about effects of imiquimod on various intracellular biochemical processes and signaling pathways.     

Iron uptake mechanisms of pathogenic bacteria

Abstract: Most of the iron in a mammalian body is complexed with various proteins. Moreover, in response to infection, iron availability is reduced in both extracellular and intracellular compartments. Bacteria need iron for growth and successful bacterial pathogens have therefore evolved to compete successfully for iron in the highly iron-stressed environment of the host's tissues and body fluids. Several strategies have been identified among pathogenic bacteria, including reduction of ferric to ferrous iron, occupation of intracellular niches, utilisation of host iron compounds, and production of siderophores. While direct evidence that high affinity mechanisms for iron acquisition function as bacterial virulence determinants has been provided in only a small number of cases, it is likely that many if not all such systems play a central role in the pathogenesis of infection.     

Virulence of Streptococcus mutans: biochemical and pathogenic characteristics of mutant isolates.

The in vitro dextran-sucrase activities and adherence to glass of S. mutans 6715 and PS14 wild types and mutants were quantitated and compared with their in vivo cariogenicity in young, gnotobiotic rats. In general, S. mutans PS14 mutants B414 and B421 and 6715 mutant C4 demonstrated less dextran-sucrase activity and adherence than parental strains and caused fewer carious lesions in gnotobiotic rats. Rats monoinfected with either PS14 mutants B414 or B421 had less plaque and viable S. mutans in plaque than rats infected with parental strain. Both S. mutans 6715 mutants C211 and C229, demonstrated greater enzyme activity and adherence than the parental strain and produced more carious lesions.     

Nimesulide inhibits pathogenic fungi: PGE2-dependent mechanisms

Certain non-steroidal anti-inflammatory drugs can inhibit fungal growth, fungal prostaglandin E2 production, and enzyme activation. This study aims to investigate the antifungal effect of nimesulide against pathogenic filamentous fungi and yeast. The experiments detailed below were also designed to investigate whether the action is dependent on E2 fungal prostaglandins. Our data showed that nimesulide exhibited potent antifungal activity, mainly against Trichophyton mentagrophytes (ATCC 9533) and Cryptococcus neoformans with MIC values of 2 and 62 μg/mL, respectively. This drug was also able to inhibit the growth of clinic isolates of filamentous fungi, such as Aspergillus fumigatus, and dermatophytes, such as T. rubrum, T. mentagrophytes, Epidermophyton floccosum, Microsporum canis, and M. gypseum, with MIC values ranging from 112 to 770 μg/mL. Our data also showed that the inhibition of fungal growth by nimesulide was mediated by a mechanism dependent on PGE2, which led to the inhibition of essential fungal enzymes. Thus, we concluded that nimesulide exerts a fungicidal effect against pathogenic filamentous fungi and yeast, involving the inhibition of fungal prostaglandins and fungal enzymes important to the fungal growth and colonization.