The role of non-protein sulphydryls in determining the chemical repair rates of free radical precursors of DNA damage and cell killing in Chinese hamster V79 cells. I

Chinese hamster V79 fibroblasts were irradiated in the gas explosion apparatus and the chemical repair rates of the oxygen-dependent free radical precursors of DNA double-strand breaks (dsb) and lethal lesions measured using filter elution (pH 9.6) and a clonogenic assay. Depletion of cellular GSH levels, from 4.16 fmol/cell to 0.05 fmol/cell, by treatment with buthionine sulphoximine (50 mumol dm-3; 18 h), led to sensitization as regards DNA dsb induction and cell killing. This was evident at all time settings but was particularly pronounced when the oxygen shot was given 1 ms after the irradiation pulse. A detailed analysis of the chemical repair kinetics showed that depletion of GSH led to a reduction in the first-order rate constant for dsb precursors from 385 s-1 to 144 s-1, and for lethal lesion precursors from 533 s-1 to 165 s-1. This is generally consistent with the role of GSH in the repair-fixation model of radiation damage at the critical DNA lesions. However, the reduction in chemical repair rate was not proportional to the severe thiol depletion (down to almost-equal-to 1% for GSH) and a residual repair capacity remained (almost-equal-to 30%). This was found not to be due to compartmentalization of residual GSH in the nucleus, as the repair rate for dsb precursors in isolated nuclei, washed virtually free of GSH, was identical to that found in GSH-depleted cells (144 s-1), also the OER remained substantially above unity. This suggests that other reducing agents may have a role to play in the chemical repair of oxygen-dependent damage. One possible candidate is the significant level of protein sulphydryls present in isolated nuclei.

A multiple-radical model for radiation action on DNA and the dependence of OER on LET

We have a developed a multiple-radical model of the chemical modification reactions involving oxygen and thiols relevant to the interactions of ionizing radiations with DNA. The treatment is based on the Alper and Howard-Flanders equation but considers the case where more than one radical may be involved in the production of lesions in DNA. This model makes several predictions regarding the induction of double strand breaks in DNA by ionizing radiation and the role of sensitizers such as oxygen and protectors such as thiols which act at the chemical phase of radiation action via the involvement of free radicals. The model predicts a decreasing OER with increasing LET on the basis that as radical multiplicity increases so will the probability that, even under hypoxia, damage will be fixed and lead to lesion production. The model can be considered to provide an alternative hypothesis to those of 'interacting radicals' or of 'oxygen-in-the-track'.

Further evidence for double-strand breaks originating from a paired radical precursor from studies of oxygen fixation processes

By using a fast reaction technique which employs H2S gas as a fast-reacting chemical repair agent, it is possible to measure the competition kinetics between chemical repair reactions and oxygen fixation reactions in model DNA and cellular systems. In plasmid pBR322 DNA irradiated with electrons, we have compared the oxygen fixation reactions of the free radical precursors that lead to the production of single-strand (SSBs) and double-strand breaks (DSBs). For the oxygen-dependent fixation of radical damage leading to SSBs, a second-order rate constant of 2.3 x 10(8) dm(3) mol(-1) s(-1) was obtained compared to 8.9 x 10(7) dm(3) mol(-1) s(-1) for DSBs. The difference is in general agreement with predictions from a multiple-radical model where the precursor of a DSB originates from two radicals. The fixation of this precursor by oxygen will require both radicals to be fixed for the DSB to be formed, which will have slower kinetics than that of single free-radical precursors of SSBs. (C) 1999 by Radiation Research Society.

Radical Change, Accounting and Public Sector Reforms: A Comparison of Italian and Canadian Municipalities

NPM has been generally regarded as an administrative reform for which resilience and consequences have been mainly investigated at a country level. Although accounting played a central role in NPM reforms over the last decades, how accounting change actually took place, and through what organizational dynamics, has been under-investigated. This paper adopts a new perspective, archetype theory, and looks into how intra-organizational dynamics (values, interests, power, capabilities) combine with reform processes to influence the outcome of accounting change. Evidence from Italian (disruptive process) and Canadian (sedimented process) municipalities shows that radical change is associated with specific configurations of intra-organizational dynamics.

Defective O-antigen polymerization in tolA and pal mutants of Escherichia coli in response to extracytoplasmic stress

We have previously shown that the TolA protein is required for the correct surface expression of the Escherichia coli O7 antigen lipopolysaccharide (LPS). In this work, delta tolA and delta pal mutants of E. coli K-12 W3110 were transformed with pMF19 (encoding a rhamnosyltransferase that reconstitutes the expression of O16-specific LPS), pWQ5 (encoding the Klebsiella pneumoniae O1 LPS gene cluster), or pWQ802 (encoding the genes necessary for the synthesis of Salmonella enterica O:54). Both DeltatolA and delta pal mutants exhibited reduced surface expression of O16 LPS as compared to parental W3110, but no significant differences were observed in the expression of K. pneumoniae O1 LPS and S. enterica O:54 LPS. Therefore, TolA and Pal are required for the correct surface expression of O antigens that are assembled in a wzy (polymerase)-dependent manner (like those of E. coli O7 and O16) but not for O antigens assembled by wzy-independent pathways (like K. pneumoniae O1 and S. enterica O:54). Furthermore, we show that the reduced surface expression of O16 LPS in delta tolA and delta pal mutants was associated with a partial defect in O-antigen polymerization and it was corrected by complementation with intact tolA and pal genes, respectively. Using derivatives of W3110 delta tolA and W3110 delta pal containing lacZ reporter fusions to fkpA and degP, we also demonstrate that the RpoE-mediated extracytoplasmic stress response is upregulated in these mutants. Moreover, an altered O16 polymerization was also detected under conditions that stimulate RpoE-mediated extracytoplasmic stress responses in tol+ and pal+ genetic backgrounds. A Wzy derivative with an epitope tag at the C-terminal end of the protein was stable in all the mutants, ruling out stress-mediated proteolysis of Wzy. We conclude that the absence of TolA and Pal elicits a sustained extracytoplasmic stress response that in turn reduces O-antigen polymerization but does not affect the stability of the Wzy O-antigen polymerase.

Neoadjuvant hormone therapy for radical prostate radiotherapy:bicalutamide monotherapy vs. luteinizing hormone-releasing hormone agonist monotherapy: a single-institution matched-pair analysis

The purpose of this study was to compare the prostate-specific antigen (PSA) response to either neoadjuvant bicalutamide (BC) monotherapy or neoadjuvant luteinizing hormone-releasing hormone agonist (LHRHa) monotherapy and the subsequent effect on biochemical failure-free survival (BFFS) in men receiving radical radiotherapy (RT) for localized prostate cancer.

Class, Factionalism, and the Radical Retreat: Black Laborers and the Republican Party in South Carolina, 1865-1900

a chapter-length piece in a collection which I've co-edited and written the introduction for, which examines class and other tensions in the ranks of the Republican party during and after Reconstruction in South Carolina, with a focus on the confrontation between insurgent former slaves and Party moderates over the social content of the RP programme.

Changed reactivity of the 1-bromo-4-nitrobenzene radical anion in a room temperature ionic liquid

Radical anions of 1-bromo-4-nitrobenzene (p-BrC6H4NO2) are shown to be reactive in the room temperature ionic liquid N-butyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide, ([C(4)mPyrr][NTf2]), by means of voltammetric measurements. In particular, they are shown to react via a DISP type mechanism such that the electrolysis of p-BrC6H4NO2 occurs consuming between one and two electrons per reactant molecule, leading to the formation of the nitrobenzene radical anion and bromide ions. This behaviour is a stark contrast to that in conventional non-aqueous solvents such as acetonitrile, dimethyl sulfoxide or N,N-dimethylformamide, which suggests that the ionic solvent promotes the reactivity of the radical anion, probably via stabilisation of the charged products.

Plasma polymerization of 2-iodothiophene

Continuous wave rf plasma polymerization of 2-iodothiophene has been studied using X-ray photoelectron spectroscopy (XPS), X-ray absorption near-edge spectroscopy (XANES), and Fourier transform infrared spectroscopy (FTIR). The variation in plasma polymer stoichiometry and the extent of monomer fragmentation are found to be critically dependent upon the electrical discharge power.

Cannibale, Frigidaire, and the Multitude: Post-1977 Italian Comics through Radical Theory

A direct connection between comics and contemporary critical theory is to be found in the activity of the collective of artists who created "Cannibale" and "Frigidaire", the two most innovative Italian comics magazines of the late 1970s and early 1980s. The work of Andrea Pazienza, Filippo Scòzzari, Stefano Tamburini, Tanino Liberatore and Massimo Mattioli should be regarded as an expression of the radical movements from which Marxist Autonomist thinkers such as Antonio Negri, Franco ‘Bifo’ Berardi and Paolo Virno also emerged in the same period. As a consequence, the writings of the latter can be used to analyse the narrative and visual style, the recurring themes, and the editorial characteristics of the comics of the former. Moreover, an interesting parallel can also be drawn between the work of the most influential of these artists, Andrea Pazienza, and the thought of another prominent Italian philosopher, Giorgio Agamben, whose earliest books were published at that time too. The aim of this article is to show that the ideas of a number of the thinkers who have recently become internationally known as representatives of radical Italian theory, are useful to understand the work of this group of comics authors.