Prion Strain Differences in Accumulation of PrPSc on Neurons and Glia Are Associated with Similar Expression Profiles of Neuroinflammatory Genes: Comparison of Three Prion Strains

Misfolding and aggregation of host proteins are important features of the pathogenesis of neurodegenerative diseases including Alzheimer’s disease, Parkinson’s disease, frontotemporal dementia and prion diseases. In all these diseases, the misfolded protein increases in amount by a mechanism involving seeded polymerization. In prion diseases, host prion protein is misfolded to form a pathogenic protease-resistant form, PrPSc, which accumulates in neurons, astroglia and microglia in the CNS. Here using dual-staining immunohistochemistry, we compared the cell specificity of PrPSc accumulation at early preclinical times post-infection using three mouse scrapie strains that differ in brain regional pathology. PrPSc from each strain had a different pattern of cell specificity. Strain 22L was mainly associated with astroglia, whereas strain ME7 was mainly associated with neurons and neuropil. In thalamus and cortex, strain RML was similar to 22L, but in substantia nigra, RML was similar to ME7. Expression of 90 genes involved in neuroinflammation was studied quantitatively using mRNA from thalamus at preclinical times. Surprisingly, despite the cellular differences in PrPSc accumulation, the pattern of upregulated genes was similar for all three strains, and the small differences observed correlated with variations in the early disease tempo. Gene upregulation correlated with activation of both astroglia and microglia detected in early disease prior to vacuolar pathology or clinical signs. Interestingly, the profile of upregulated genes in scrapie differed markedly from that seen in two acute viral CNS diseases (LaCrosse virus and BE polytropic Friend retrovirus) that had reactive gliosis at levels similar to our prion-infected mice.     

Quantifying and Understanding Voltage Losses Due to Nonradiative Recombination in Bulk Heterojunction Organic Solar Cells with Low Energetic Offsets

Open‐circuit voltage (V_OC) losses in organic photovoltaics (OPVs) inhibit devices from reaching V_OC values comparable to the bandgap of the donor–acceptor blend. Specifically, nonradiative recombination losses (?V_nr) are much greater in OPVs than in silicon or perovskite solar cells, yet the origins of this are not fully understood. To understand what makes a system have high or low loss, an investigation of the nonradiative recombination losses in a total of nine blend systems is carried out. An apparent relationship is observed between the relative domain purity of six blends and the degree of nonradiative recombination loss, where films exhibiting relatively less pure domains show lower ?V_nr than films with higher domain purity. Additionally, it is shown that when paired with a fullerene acceptor, polymer donors which have bulky backbone units to inhibit close π–π stacking exhibit lower nonradiative recombination losses than in blends where the polymer can pack more closely. This work reports a strategy that ensures ?V_nr can be measured accurately and reports key observations on the relationship between ?V_nr and properties of the donor/acceptor interface.     

Colistin heteroresistance in Enterobacter cloacae is regulated by PhoPQ‐dependent 4‐amino‐4‐deoxy‐l‐arabinose addition to lipid A

The Enterobacter cloacae complex (ECC) consists of closely related bacteria commonly associated with the human microbiota. ECC are increasingly isolated from healthcare‐associated infections, demonstrating that these Enterobacteriaceae are emerging nosocomial pathogens. ECC can rapidly acquire multidrug resistance to conventional antibiotics. Cationic antimicrobial peptides (CAMPs) have served as therapeutic alternatives because they target the highly conserved lipid A component of the Gram‐negative outer membrane. Many Enterobacteriaceae fortify their outer membrane with cationic amine‐containing moieties to prevent CAMP binding, which can lead to cell lysis. The PmrAB two‐component system (TCS) directly activates 4‐amino‐4‐deoxy‐l ‐arabinose (l ‐Ara4N) biosynthesis to result in cationic amine moiety addition to lipid A in many Enterobacteriaceae such as E. coli and Salmonella. In contrast, PmrAB is dispensable for CAMP resistance in E. cloacae. Interestingly, some ECC clusters exhibit colistin heteroresistance, where a subpopulation of cells exhibit clinically significant resistance levels compared to the majority population. We demonstrate that E. cloacae lipid A is modified with l ‐Ara4N to induce CAMP heteroresistance and the regulatory mechanism is independent of the PmrAB_Ecl TCS. Instead, PhoP_Ecl binds to the arnB_Ecl promoter to induce l ‐Ara4N biosynthesis and PmrAB‐independent addition to the lipid A disaccharolipid. Therefore, PhoPQ_Ecl contributes to regulation of CAMP heteroresistance in some ECC clusters.     

Apps can help bridge restoration science and restoration practice

Scientists need to find innovative ways to communicate their findings with restoration practitioners in an era of global change. Apps are a promising bridge between restoration science and practice because they apply broad scientific concepts to specific situations. For example, habitat connectivity promotes ecological function, but practitioners lack ways to incorporate connectivity into decision‐making. We created an app where users calculate how habitat restoration or loss affects connectivity. By providing our app as an example and discussing the benefits and challenges in creating apps for practitioners, we encourage other restoration ecologists to similarly create apps that bridge science with practice.     

Global DNA methylation (LINE-1) associated with exposure to arsenic-contaminated environment and with type of arsenical skin lesions in Thailand

The effects of chronic arsenic exposure mode on DNA methylation and skin lesion type are unclear. These relationships were investigated in an arsenic-contaminated area of southern Thailand. Cases with arsenical skin lesions (n = 131) and lesion-free controls (n = 163) were selected from an arsenic-contaminated sub-district, as well as 105 controls from a non-contaminated area. Type and severity of skin lesions and salivary global DNA methylation (LINE-1) were determined. Arsenic exposure was characterized as occupational, domestic and current (toe-nail arsenic). Associations were explored using logistic regression. Cases and controls had lower LINE-1 methylation and higher toenail arsenic than external controls (74.65% and 74.61% vs 76.05%, p < 0.001 for each). Cases were more likely to have been exposed domestically (OR_total 1.76, 95% ci 1.00, 3.11; and 2.22, 95% ci 1.22, 4.03; P_trend = 0.005 for exposure <36 and ≥36 years). More severe spotty hyperpigmentation was related to higher LINE-1 methylation (P_trend=0.006). LINE-1 methylation was positively associated with toenail arsenic only among non-symptomatic exposed subjects (OR 1.31, 95% ci 1.06, 1.64; p = 0.014). Exposure to an arsenic-contaminated environment results in global DNA hypomethylation. However, among symptomatic subjects, increased global DNA methylation was associated with increased severity of spotty hyperpigmentation.     

Neuropathological correlates of amyloid PET imaging in Down syndrome

Down syndrome (DS) results in an overproduction of amyloid‐β (Aβ) peptide associated with early onset of Alzheimer's disease (AD). DS cases have Aβ deposits detectable histologically as young as 12–30 years of age, primarily in the form of diffuse plaques, the type of early amyloid pathology also seen at pre‐clinical (i.e., pathological aging) and prodromal stages of sporadic late onset AD. In DS subjects aged >40 years, levels of cortical Aβ deposition are similar to those observed in late onset AD and in addition to diffuse plaques involve cored plaques associated with dystrophic neurites (neuritic plaques), which are of neuropathological diagnostic significance in AD. The purpose of this review is to summarize and discuss findings from amyloid PET imaging studies of DS in reference to postmortem amyloid‐based neuropathology. PET neuroimaging applied to subjects with DS has the potential to (a) track the natural progression of brain pathology, including the earliest stages of amyloid accumulation, and (b) determine whether amyloid PET biomarkers predict the onset of dementia. In addition, the question that is still incompletely understood and relevant to both applications is the ability of amyloid PET to detect Aβ deposits in their earliest form.     

Immunodominant tuberculosis CD8 antigens preferentially restricted by HLA-B

CD8(+) T cells are essential for host defense to intracellular bacterial pathogens such as Mycobacterium tuberculosis (Mtb), Salmonella species, and Listeria monocytogenes, yet the repertoire and dominance pattern of human CD8 antigens for these pathogens remains poorly characterized. Tuberculosis (TB), the disease caused by Mtb infection, remains one of the leading causes of infectious morbidity and mortality worldwide and is the most frequent opportunistic infection in individuals with HIV/AIDS. Therefore, we undertook this study to define immunodominant CD8 Mtb antigens. First, using IFN-gamma ELISPOT and synthetic peptide arrays as a source of antigen, we measured ex vivo frequencies of CD8(+) T cells recognizing known immunodominant CD4(+) T cell antigens in persons with latent tuberculosis infection. In addition, limiting dilution was used to generate panels of Mtb-specific T cell clones. Using the peptide arrays, we identified the antigenic specificity of the majority of T cell clones, defining several new epitopes. In all cases, peptide representing the minimal epitope bound to the major histocompatibility complex (MHC)-restricting allele with high affinity, and in all but one case the restricting allele was an HLA-B allele. Furthermore, individuals from whom the T cell clone was isolated harbored high ex vivo frequency CD8(+) T cell responses specific for the epitope, and in individuals tested, the epitope represented the single immunodominant response within the CD8 antigen. We conclude that Mtb-specific CD8(+) T cells are found in high frequency in infected individuals and are restricted predominantly by HLA-B alleles, and that synthetic peptide arrays can be used to define epitope specificities without prior bias as to MHC binding affinity. These findings provide an improved understanding of immunodominance in humans and may contribute to a development of an effective TB vaccine and improved immunodiagnostics.     

Assessment of developmental toxicity of vorinostat, a histone deacetylase inhibitor, in Sprague-Dawley rats and Dutch Belted rabbits

BACKGROUND: The developmental toxicity potential of vorinostat (suberoylanilide hydroxamic acid [SAHA], ZOLINZA), a potent inhibitor of histone deacetylase (HDAC), was assessed in Sprague-Dawley rats and Dutch Belted rabbits. HDAC inhibitors have been shown to mediate the regulation of gene expression, induce cell growth, cell differentiation, and apoptosis of tumor cells. Range-finding studies established oral dose levels of 5, 15, or 50 mg/kg/day and 20, 50, or 150 mg/kg/day in rats and rabbits, respectively. METHODS: Animals were dosed on Gestation Days 6-20 or 7-20, respectively, with litter/fetal parameters evaluated on GD 21 and 28, respectively. Separate studies evaluated toxicokinetic parameters at the mid- and high-dose levels. RESULTS: There was no maternal toxicity observed at the highest dose levels; however, hematology and serum biochemistry changes were characterized in the range-finding studies. Vorinostat did not induce morphological malformations in either rat or rabbit fetuses. In rats, drug-related developmental toxicity was observed only in the high-dose group and consisted of markedly decreased fetal weight and increases in fetuses with a limited number of skeletal variations. In rabbits, drug-related developmental toxicity was also observed only in the high-dose group and consisted of slightly decreased fetal weight and increases in fetuses with a short 13th rib and incomplete ossification of metacarpals. Maternal exposures to vorinostat based on AUC and Cmax values were comparable at the high-dose levels of both species. Rabbits tolerated higher dosages probably due to more extensive metabolism. Maternal concentrations of vorinostat were approximately 1,000-fold above the known in vitro HDAC inhibitory concentration. CONCLUSIONS: Review of previous work with valproic acid, another HDAC inhibitor, suggest that the developmental toxicity profiles of these 2 compounds are not the result of HDAC inhibition but involve other mechanisms.     

Computational models evaluating the impact of sieve plates and radial water exchange on phloem pressure gradients

The sugar conducting phloem in angiosperms is a high resistance pathway made up of sieve elements bounded by sieve plates. The high resistance generated by sieve plates may be a trade‐off for promoting quick sealing in the event of injury. However, previous modeling efforts have demonstrated a wide variation in the contribution of sieve plates towards total sieve tube resistance. In the current study, we generated high resolution scanning electron microscope images of sieve plates from balsam poplar and integrated them into a mathematical model using Comsol Multiphysics software. We found that sieve plates contribute upwards of 85% towards total sieve tube resistance. Utilizing the Navier–Stokes equations, we found that oblong pores may create over 50% more resistance in comparison with round pores of the same area. Although radial water flows in phloem sieve tubes have been previously considered, their impact on alleviating pressure gradients has not been fully studied. Our novel simulations find that radial water flow can reduce pressure requirements by half in comparison with modeled sieve tubes with no radial permeability. We discuss the implication that sieve tubes may alleviate pressure requirements to overcome high resistances by regulating their membrane permeability along the entire transport pathway.