Effects of Peroxisomal Catalase Inhibition on Mitochondrial Function

Peroxisomes produce hydrogen peroxide as a metabolic by-product of their many oxidase enzymes, but contain catalase that breaks down hydrogen peroxide in order to maintain the organelle’s oxidative balance. It has been previously demonstrated that, as cells age, catalase is increasingly absent from the peroxisome, and resides instead as an unimported tetrameric molecule in the cell cytosol; an alteration that is coincident with increased cellular hydrogen peroxide levels. As this process begins in middle-passage cells, we sought to determine whether peroxisomal hydrogen peroxide could contribute to the oxidative damage observed in mitochondria in late-passage cells. Early-passage human fibroblasts (Hs27) treated with aminotriazole (3-AT), an irreversible catalase inhibitor, demonstrated decreased catalase activity, increased levels of cellular hydrogen peroxide, protein carbonyls, and peroxisomal numbers. This treatment increased mitochondrial reactive oxygen species levels, and decreased the mitochondrial aconitase activity by ∼85% within 24 h. In addition, mitochondria from 3-AT treated cells show a decrease in inner membrane potential. These results demonstrate that peroxisome-derived oxidative imbalance may rapidly impair mitochondrial function, and considering that peroxisomal oxidative imbalance begins to occur in middle-passage cells, supports the hypothesis that peroxisomal oxidant release occurs upstream of, and contributes to, the mitochondrial damage observed in aging cells

What is a War Crime?

What is a war crime? The question appears to have a simple answer: a war crime is a violation of the law of war. But do all violations of the law of war qualify as war crimes? And are all war crimes violations of the law of war? These questions are not new. In 1942, Hersch Lauterpacht, a leading international lawyer who assisted the prosecution of the Nazis for war crimes at the International Military Tribunal (IMT) in Nuremberg, wrote a memo in which he asked, “Is there a definition of war crimes?” More than seven decades later, the answer to his question remains unsettled

Further Examination of the Geographic Range of Eriogonum corymbosum var. nilesii (Polygonaceae, Eriogoneae)

The wild buckwheat Eriogonum corymbosum is widely distributed throughout the southwestern United States, forming a complex of eight varieties. E. corymbosum var. nilesii is a predominantly yellow-flowered variant reported primarily from Clark Co., Nevada. A previous genetic study by our research group found that var. nilesii is genetically distinct from other E. corymbosum varieties, based on a limited number of populations. Here, we assess genetic variation in 14 newly sampled yellow-flowered populations from southern Nevada, southern Utah, and northern Arizona, and compare them to genetic variation in six populations of previously determined E. corymbosum varieties. Of the new populations, we identified four as var. nilesii, four as var. aureum, three as var. glutinosum, two as apparent hybrids involving vars. aureum and nilesii, and one as a more distantly related admixture involving E. thompsoniae. Our results extend the range and area of E. corymbosum var. nilesii considerably from that traditionally stated in the literature. However, this extended range is confined to the Mojave Desert region of southern Nevada, and the number of known populations remains limited

On the Nature of the X-ray Emission from the Ultraluminous X-ray Source, M33 X-8: New Constraints from NuSTAR and XMM-Newton

We present nearly simultaneous NuSTAR and XMM-Newton observations of the nearby (832 kpc) ultraluminous X-ray source (ULX) M33 X-8. M33 X-8 has a 0.3-10 keV luminosity of LX ~ 1.4 x 10^39 erg/s, near the boundary of the "ultraluminous" classification, making it an important source for understanding the link between typical Galactic X-ray binaries and ULXs. Past studies have shown that the 0.3-10 keV spectrum of X-8 can be characterized using an advection-dominated accretion disk model. We find that when fitting to our NuSTAR and XMM-Newton observations, an additional high-energy (>10 keV) Comptonization component is required, which allows us to rule out single advection-dominated disk and classical sub-Eddington models. With our new constraints, we analyze XMM-Newton data taken over the last 17 years to show that small (~30%) variations in the 0.3-10 keV flux of M33 X-8 result in spectral changes similar to those observed for other ULXs. The two most likely phenomenological scenarios suggested by the data are degenerate in terms of constraining the nature of the accreting compact object (i.e., black hole versus neutron star). We further present a search for pulsations using our suite of data; however, no clear pulsations are detected. Future observations designed to observe M33 X-8 at different flux levels across the full 0.3-30 keV range would significantly improve our constraints on the nature of this important source.Comment: Accepted for publication in ApJ (15 pages, 4 tables, 6 figures

Heterogeneity in the histidine-brace copper coordination sphere in auxiliary activity family 10 (AA10) lytic polysaccharide monooxygenases

Copper-dependent lytic polysaccharide monooxygenases (LPMOs) are enzymes that oxidatively deconstruct polysaccharides. The active site copper in LPMOs is coordinated by a histidine-brace. This utilizes the amino group and side chain of the N-terminal His residue with the side chain of a second His residue to create a T-shaped arrangement of nitrogen ligands. We report a structural, kinetic, and thermodynamic appraisal of copper binding to the histidine-brace in an auxiliary activity family 10 (AA10) LPMO from Streptomyces lividans (SliLPMO10E). Unexpectedly, we discovered the existence of two apo-SliLPMO10E species in solution that can each bind copper at a single site with distinct kinetic and thermodynamic (exothermic and endothermic) properties. The experimental EPR spectrum of copper-bound SliLPMO10E requires the simulation of two different line shapes, implying two different copper-bound species, indicative of three and two nitrogen ligands coordinating the copper. Amino group coordination was probed through the creation of an N-terminal extension variant (SliLPMO10E- Ext). The kinetics and thermodynamics of copper binding to SliLPMO10E-Ext are in accord with copper binding to one of the apo-forms in the wild-type protein, suggesting that amino group coordination is absent in the two-nitrogen coordinate form of SliLPMO10E. Copper binding to SliLPMO10B was also investigated, and again it revealed the presence of two apo-forms with kinetics and stoichiometry of copper binding identical to that of SliLPMO10E. Our findings highlight that heterogeneity exists in the active site copper coordination sphere of LPMOs that may have implications for the mechanism of loading copper in the cell

Microglial Inflammation and Cognitive Dysfunction in Comorbid Rat Models of Striatal Ischemic Stroke and Alzheimer\u27s Disease: Effects of Antioxidant Catalase-SKL on Behavioral and Cellular Pathology

Ischemic stroke often co-occurs with Alzheimer\u27s disease (AD) leading to a worsened clinical outcome. Neuroinflammation is a critical process implicated in AD and ischemic pathology, associated with cognitive decline. We sought to investigate the combined effects of ischemic stroke induced by endothelin-1 injection in two AD rat models, using motor function, memory and microglial inflammation in the basal forebrain and striatum as readouts. In addition, we sought to determine the effectiveness of the antioxidant biologic CAT-SKL in one of the models. The early AD model employed the bilateral intracerebroventricular injections of the toxic β-amyloid peptide Aβ25–35, the prodromal AD model used the transgenic Fischer 344 rat overexpressing a pathological mutant human amyloid precursor protein. Motor function was assessed using a cylinder, modified sticky tape and beam-walk tasks; learning and memory were tested in the Morris water maze. Microglial activation was examined using immunohistochemistry. Aβ25–35 toxicity and stroke combination greatly increased microglial inflammation in the basal forebrain. Prodromal AD-pathology coupled with ischemia in the transgenic rat resulted in a greater microgliosis in the striatum. Combined transgenic rats showed balance alterations, comorbid Aβ25–35 rats showed a transient sensorimotor deficit, and both demonstrated spatial reference memory deficit. CAT-SKL treatment ameliorated memory impairment and basal forebrain microgliosis in Aβ25–35 rats with stroke. Our results suggest that neuroinflammation could be one of the early processes underlying the interaction of AD with stroke and contributing to the cognitive impairment, and that therapies such as antioxidant CAT-SKL could be a potential therapeutic strategy

Exile Vol. XVI No. 2

PREFACE 3 ESSAY Observations At The Gap by Paul A. Dimitruk 4 Those Who Choose Words By Keith McWalter 5-6 On Victoria\u27s England by Paul A. Dimitruk 7-8 Facts Are The Enemy of Truth by Nancy Gutierrez FICTION Harmon by Barbara Mackey 22-25 Pilgrimage by Keith McWalter 35-44 ARTWORK by Wandi Solez: 6, 15, 23, 27 by Ken Wernz 10 by Stephen Swift 11 by Laura M. Hyslop 12 by Skip Staudt 19 by W. A. Hoffman 25 by Mary Ann Kowaski 34 by Jo Ann Orgo 40 PHOTOGRAPHY by Roger Block 16 by Tim Heath- all other POETRY My Poems by Susan Hallock 13 Counter-Fugue At Six-Thirty by Sherry Stodola 14-16 Apple Tree Poem by Darby Williams 17 When Snow Falls Into A Pond by Bruce Kidd 17 Woman-Man by Darby Williams 18 Transcendence by Wandi Solez 20 Paris Reflection by Wandi Solez 20 A Sleepless Night In Valencia, Spain by Wandi Solez 21 # 319 by Wandi Solez 21 Strange Lady by John Gillespie 26 Strange Lady II by John Gillespie 26 Where The Hell Is Rembrandt? by John Loveland 26 Years Ago by John Whitt 29 I\u27ve Finished Growing Now by Keith McWalter 29 Charisma by John Whitt 30 I Thought Of Cutting by John Loveland 31 Make Me Eat Peanut Butter by Fred Walton 31 The Cat by John Loveland 32 On The Rim by John Whitt 33 Undercurrent by Keith McWalter 33 Cover: Gail Lutsch Layouts: Keith McWalte

CHK1 inhibition is synthetically lethal with loss of B-family DNA polymerase function in human lung and colorectal cancer cells

Checkpoint kinase 1 (CHK1) is a key mediator of the DNA damage response that regulates cell cycle progression, DNA damage repair and DNA replication. Smallmolecule CHK1 inhibitors sensitise cancer cells to genotoxic agents and have shown single agent preclinical activity in cancers with high levels of replication stress. However, the underlying genetic determinants of CHK1 inhibitor sensitivity remain unclear. We used the developmental clinical drug SRA737 in an unbiased largescale siRNA screen to identify novel mediators of CHK1 inhibitor sensitivity and uncover potential combination therapies and biomarkers for patient selection. We identified members of the B-family of DNA polymerases (POLA1, POLE and POLE2) whose silencing sensitised the human A549 non small cell lung cancer (NSCLC) and SW620 colorectal cancer cell lines to SRA737. B-family polymerases were validated using multiple siRNAs in a panel of NSCLC and colorectal cancer cell lines. Replication stress, DNA damage and apoptosis were increased in human cancer cells following depletion of the B-family DNA polymerases combined with SRA737 treatment. Moreover, pharmacological blockade of B-family DNA polymerases using aphidicolin or CD437 combined with CHK1 inhibitors led to synergistic inhibition of cancer cell proliferation. Furthermore, low levels of POLA1, POLE and POLE2 protein expression in NSCLC and colorectal cancer cells correlated with single agent CHK1 inhibitor sensitivity and may constitute biomarkers of this phenotype. These findings provide a potential basis for combining CHK1 and B-family polymerase inhibitors in cancer therapy

A search for temperature and density variations in NGC 7027 with the Hubble Space Telescope

We observed the young planetary nebula NGC 7027 with the HST Imaging Spectrograph (STIS) in long-slit mode at five slit positions along the major axis of the nebula, over the wavelength range from 3000 to ~10,000 Å. We used dereddened line ratios to determine line-of-sight average values for (1) He^(++) and He^+ ionization fractions from He II λ4686 and He I λ5876; (2) electron density from both [S II] (λ6716/λ6731) and [Ar IV] (λ4711/λ4740); and (3) temperature from [O III] (λ4959 + λ5007)/λ4363. The He^(++)/H^+ ratio varies across the nebula, with values up to 0.06 over the central parts, falling off to 0.03 at offsets of 5"-6" from the central star. The line-of-sight mean densities vary by factors of ~5 on angular scales as small as ~1". The average electron temperatures are generally consistent with a constant = 13,800 ± 2000 K within the uncertainties, except for ~2% of measured pixels where T_e > 18,000 K. The variations of density along the slits are not obviously correlated with variations in extinction. The ionization structure of the nebula varies on both large and small scales. [O I] λ6300, Hα, and He II λ4686 intensity profiles along each slit appear to trace ionization gradients at Hα peaks, with the highest ionization on the side toward the central star and lowest ionization on the far side. These structures may result from effects of stellar radiation, shocks from a fast stellar wind, or some combination of the two processes

Synthesis and activation for catalysis of Fe-SAPO-34 prepared using iron polyamine complexes as structure directing agents

This work was supported by Johnson Matthey PLC, UK. Solid-state NMR spectra were obtained at the EPSRC UK National Solid-state NMR Service at Durham.The use of transition metal cations complexed by polyamines as structure directing agents (SDAs) for silicoaluminophosphate (SAPO) zeotypes provides a route, via removal of the organic by calcination, to microporous solids with well-distributed, catalytically-active extra-framework cations and avoids the need for post-synthesis aqueous cation exchange. Iron(II) complexed with tetraethylenepentamine (TEPA) is found to be an effective SDA for SAPO- 34, giving as-prepared solids where Fe2+-TEPA complexes reside within the cha cages, as indicated by Mössbauer, optical and X-ray absorption near edge spectroscopies. By contrast, when non-coordinating tetraethylammonium ions are used as the SDAs in Fe-SAPO-34 preparations, iron is included as octahedral Fe3+ within the framework. The complex- containing Fe-SAPO-34(TEPA) materials give a characteristic visible absorption band at 550 nm (and purple colouration) when dried in air that is attributed to oxygen chemisorption. Some other Fe2+ polyamine complexes (diethylenetriamine, triethylenetetramine and pentaethylenehexamine) show similar behaviour. After calcination in flowing oxygen at 550 °C, ‘one-pot’ Fe(TEPA) materials possess Fe3+ cations and a characteristic UV-visible spectrum: they also show appreciable activity in the selective catalytic reduction of NO with NH3.PostprintPostprintPeer reviewe