Retrospective thermal neutron fluence determination using lithium-ion mobile telephone batteries

Fortuitous dosimeters are radiosensitive objects carried by an individual who was exposed to radiation. These objects can be analyzed some time after exposure and the results can be used to aid in calculating radiation fields and doses received by individuals. Items that make good fortuitous dosimeters are those that are consistent in their manufacture and are carried by a large percentage of the population. Some materials are more suitable than others for retrospective dosimetry, depending upon their sensitivity, signal retention (i.e. fading), and the type of radiation to which they respond. The effectiveness and sensitivity of lithium-ion (Li-ion) mobile telephone batteries as fortuitous neutron dosimeters is investigated in this research. Neutron fluences are estimated based upon the activation products formed in batteries during exposure. In the past, objects such as keys and coins were used for retrospective neutron dosimetry. Mobile phone batteries were chosen as possible candidates for dosimeters because of their widespread use by the general population and the observation that most users carry these objects on or near the torso. Lithium-ion mobile-phone batteries were irradiated with neutrons in beam port #4 of the Oregon State University TRIGA® reactor and subsequently analyzed using gamma spectroscopy in order to identify activation products formed, and to determine the linearity of their response to several neutron fluences. Batteries exposed to thermal neutron fluencies ranging from 2.8x10⁸ n·cm⁻² to 3.4x10¹⁰ n·cm⁻² generated ⁶⁰Co count rates ranging from 0.022 (±4.5%) cps to 2.890 (±0.6%) cps. Cobalt emerged as an element commonly found in Li-ion battery cathodes as a candidate for neutron activation analysis months to years following their irradiation. This is due to the relatively high cobalt content by weight found in these batteries and its 5.27 year half-life. Thermal neutron fluences were estimated with accuracy ranging from 2% to 23% of actual fluences, with an average accuracy of 12%. The activation of cobalt in the samples was highly linear with fluence (R²=0.995)

Comment on "Effect of biofilm formation by clinical isolates of Helicobacter pylori on the efflux-mediated resistance to commonly used antibiotics".

Attaran et al[1] have recently shown that decreased susceptibility of established Helicobacter pylori (H. pylori) biofilms to specific antibiotics, was associated with the overtly enhanced transcription of two efflux pump genes, hp1165 and hefA, involved in specific resistance to tetracycline and multiple antibiotics, respectively. Apart from antibiotic exposure, secretion of multiple antimicrobial peptides, such as human ?-defensins (h?Ds), by the gastric epithelium upon Hp challenge, may act as early triggering events that positively impact biofilm formation and thus, antibiotic resistance. In this regard, we undertook genomic transcriptional studies using Hp 26695 strain following exposure to sublethal, similar to those present in the gastric niche, concentrations of h?Ds in an attempt to provide preliminary data regarding possible mechanisms of immune evasion and selective sensitivity of Hp. Our preliminary results indicate that h?D exposure ignites a rapid response that is largely due to the activation of several, possibly interconnected transcriptional regulatory networks - origons - that ultimately coordinate cellular processes needed to maintain homeostasis and successful adaptation of the bacterium in the gastric environment. In addition, we have shown that both antibiotic and h?D resistance are mediated by dedicated periplasmic transporters, including the aforementioned efflux pump genes hp1165 and hefA, involved in active export of antibiotics from the cell membrane and/or, as recently suggested, substrate sensing and signalling. Furthermore, it appears that sublethal doses of h?Ds may enhance biofilm formation by the sustained expression of, mainly, quorum sensing-related genes. In conclusion, we provide additional data regarding the role of specific innate immune molecules in antibiotic cross-resistance mechanisms that may deepen our understanding in the context of the development of novel eradication regimens

Campylobacter jejuni outer membrane vesicle-associated proteolytic activity promotes bacterial invasion by mediating cleavage of intestinal epithelial cell E-cadherin and occludin.

Outer membrane vesicles (OMVs) play an important role in the pathogenicity of Gram-negative bacteria. Campylobacter jejuni produces OMVs that trigger IL-8, IL-6, hBD-3 and TNF-α responses from T84 intestinal epithelial cells and are cytotoxic to Caco-2 IECs and Galleria mellonella larvae. Proteomic analysis of 11168H OMVs identified the presence of three proteases, HtrA, Cj0511 and Cj1365c. In this study, 11168H OMVs were shown to possess proteolytic activity that was reduced by pretreatment with specific serine protease inhibitors. OMVs isolated from 11168H htrA, Cj0511 or Cj1365c mutants possess significantly reduced proteolytic activity. 11168H OMVs are able to cleave both E-cadherin and occludin, but this cleavage is reduced with OMVs pretreated with serine protease inhibitors and also with OMVs isolated from htrA or Cj1365c mutants. Co-incubation of T84 monolayers with 11168H OMVs results in a visible reduction in both E-cadherin and occludin. The addition of 11168H OMVs to the co-culture of live 11168H bacteria with T84 cells results in enhanced levels of bacterial adhesion and invasion in a time-dependent and dose-dependent manner. Further investigation of the cleavage of host cell structural proteins by C. jejuni OMVs should enhance our understanding of the interactions of this important pathogen with intestinal epithelial cells

Re-annotation and re-analysis of the Campylobacter jejuni NCTC11168 genome sequence

BACKGROUND: Campylobacter jejuni is the leading bacterial cause of human gastroenteritis in the developed world. To improve our understanding of this important human pathogen, the C. jejuni NCTC11168 genome was sequenced and published in 2000. The original annotation was a milestone in Campylobacter research, but is outdated. We now describe the complete re-annotation and re-analysis of the C. jejuni NCTC11168 genome using current database information, novel tools and annotation techniques not used during the original annotation. RESULTS: Re-annotation was carried out using sequence database searches such as FASTA, along with programs such as TMHMM for additional support. The re-annotation also utilises sequence data from additional Campylobacter strains and species not available during the original annotation. Re-annotation was accompanied by a full literature search that was incorporated into the updated EMBL file [EMBL: AL111168]. The C. jejuni NCTC11168 re-annotation reduced the total number of coding sequences from 1654 to 1643, of which 90.0% have additional information regarding the identification of new motifs and/or relevant literature. Re-annotation has led to 18.2% of coding sequence product functions being revised. CONCLUSIONS: Major updates were made to genes involved in the biosynthesis of important surface structures such as lipooligosaccharide, capsule and both O- and N-linked glycosylation. This re-annotation will be a key resource for Campylobacter research and will also provide a prototype for the re-annotation and re-interpretation of other bacterial genomes

The Campylobacter jejuni MarR-like transcriptional regulators RrpA and RrpB both influence bacterial responses to oxidative and aerobic stresses.

The ability of the human intestinal pathogen Campylobacter jejuni to respond to oxidative stress is central to bacterial survival both in vivo during infection and in the environment. Re-annotation of the C. jejuni NCTC11168 genome revealed the presence of two MarR-type transcriptional regulators Cj1546 and Cj1556, originally annotated as hypothetical proteins, which we have designated RrpA and RrpB (regulator of response to peroxide) respectively. Previously we demonstrated a role for RrpB in both oxidative and aerobic (O2) stress and that RrpB was a DNA binding protein with auto-regulatory activity, typical of MarR-type transcriptional regulators. In this study, we show that RrpA is also a DNA binding protein and that a rrpA mutant in strain 11168H exhibits increased sensitivity to hydrogen peroxide oxidative stress. Mutation of either rrpA or rrpB reduces catalase (KatA) expression. However, a rrpAB double mutant exhibits higher levels of resistance to hydrogen peroxide oxidative stress, with levels of KatA expression similar to the wild-type strain. Mutation of either rrpA or rrpB also results in a reduction in the level of katA expression, but this reduction was not observed in the rrpAB double mutant. Neither the rrpA nor rrpB mutant exhibits any significant difference in sensitivity to either cumene hydroperoxide or menadione oxidative stresses, but both mutants exhibit a reduced ability to survive aerobic (O2) stress, enhanced biofilm formation and reduced virulence in the Galleria mellonella infection model. The rrpAB double mutant exhibits wild-type levels of biofilm formation and wild-type levels of virulence in the G mellonella infection model. Together these data indicate a role for both RrpA and RrpB in the C. jejuni peroxide oxidative and aerobic (O2) stress responses, enhancing bacterial survival in vivo and in the environment

Revisiting Campylobacter jejuni Virulence and Fitness Factors: Role in Sensing, Adapting, and Competing.

Campylobacter jejuni is the leading cause of bacterial foodborne gastroenteritis world wide and represents a major public health concern. Over the past two decades, significant progress in functional genomics, proteomics, enzymatic-based virulence profiling (EBVP), and the cellular biology of C. jejuni have improved our basic understanding of this important pathogen. We review key advances in our understanding of the multitude of emerging virulence factors that influence the outcome of C. jejuni-mediated infections. We highlight, the spatial and temporal dynamics of factors that promote C. jejuni to sense, adapt and survive in multiple hosts. Finally, we propose cohesive research directions to obtain a comprehensive understanding of C. jejuni virulence mechanisms

Virulence characteristics of hcp (+) Campylobacter jejuni and Campylobacter coli isolates from retail chicken.

BACKGROUND: Recently the Type VI secretion system (T6SS), which can play a significant role in bacterial survival and pathogenesis, was reported in Campylobacter spp., having the hcp gene as a key component. METHODS: Campylobacteriosis is associated with the consumption of infected chicken meat. Our study aimed to explore the presence of T6SS in C. jejuni (n = 59) and C. coli (n = 57) isolates, from retail raw chicken and to investigate their pathogenic potential. The hcp gene was used as an indicator for the T6SS presence. RESULTS: Using multiplex PCR we have identified a significantly higher prevalence of hcp in C. coli isolates (56.1%) than in C. jejuni (28.8%) and AFLP analysis of the isolates showed a high degree of genetic similarity between the isolates carrying the hcp gene. Genome sequencing data showed that 84.3% of the C. coli and 93.7% of the C. jejuni isolates had all 13 T6SS open reading frames. Moreover, the virulence characteristics of hcp + isolates, including motility and the ability to invade human intestinal epithelial cells in vitro, were significantly greater than in the control strain C. jejuni 12502; a human isolate which is hcp positive. CONCLUSION: Overall, it was discovered that hcp (+) C. coli and C. jejuni isolated from retail chicken isolates posses genetic and phenotypic properties associated with enhanced virulence. However, since human infections with C. coli are significantly less frequent than those of C. jejuni, the relationship between virulence factors and pathogenesis requires further study

Investigating the interaction between Campylobacter jejuni and intestinal epithelial cells resulting in activation of the unfolded protein response

Problem Statement Campylobacter jejuni adheres, invades and resides within intestinal epithelial cells (IECs). However, the exact process at the cellular level leading to diarrhoeal disease is poorly understood. There have been studies that link intestinal inflammation and the unfolded protein response (UPR), which is a conserved pathway to restore homeostasis in the endoplasmic reticulum. Recent data has shown that C. jejuni activates UPR through IRE1α pathway. Here, we investigated the activation of the UPR through PERK, IRE1α, and ATF6 pathways by C. jejuni. Approach To investigate whether C. jejuni infection induces UPR in IECs, T84 cells were infected with C. jejuni 11168H, 81-176, and 488 wild-type strains with different exposure times. RNA and proteins were isolated from infected cells, and the induction of UPR by C. jejuni wild-type strains was observed using transcription and proteomic methods. Results The activation of all three UPR branches, PERK, IRE1α, and ATF6 was demonstrated by increased levels of transcription of chop, spliced xbp1, and atf6, respectively compared to uninfected control. The upregulation of these genes was confirmed by western blot, which showed increased amount of proteins for CHOP, phosphorylated eIF2α, and spliced XBP1 compared to the control. Conclusions The combined results demonstrate that C. jejuni induces the UPR through all three pathways. This study opens the way forward for improved understanding of the interaction between C. jejuni and IECs via UPR activation leading to intestinal inflammation. This understanding will further benefit the investigation of cellular pathways triggered by C. jejuni which can lead to diarrhoeal disease

Campylobacter jejuni modulates reactive oxygen species production and NADPH oxidase 1 expression in human intestinal epithelial cells

Campylobacter jejuni is the major bacterial cause of foodborne gastroenteritis worldwide. Mechanistically, how this pathogen interacts with intrinsic defence machinery of human intestinal epithelial cells (IECs) remains elusive. To address this, we investigated how C. jejuni counteracts the intracellular and extracellular reactive oxygen species (ROS) in IECs. Our work shows that C. jejuni differentially regulates intracellular and extracellular ROS production in human T84 and Caco-2 cells. C. jejuni downregulates the transcription and translation of Nicotinamide adenine dinucleotide phosphate (NAPDH) oxidase (Nox1), a key ROS-generating enzyme in IECs and antioxidant defence genes cat and sod1. Furthermore, inhibition of Nox1 by diphenylene iodonium (DPI) and siRNA reduced C. jejuni ability to interact, invade and intracellularly survive within T84 and Caco-2 cells. Collectively, these findings provide mechanistic insight into how C. jejuni modulates the IEC defence machinery