Effect of clinical signs, endocrinopathies, timing of surgery, hyperlipidemia, and hyperbilirubinemia on outcome in dogs with gallbladder mucocele.

Gallbladder mucocele (GBM) is a common extra-hepatic biliary syndrome in dogs with death rates ranging from 7 to 45%. Therefore, the aim of this study was to identify the association of survival with variables that could be utilized to improve clinical decisions. A total of 1194 dogs with a gross and histopathological diagnosis of GBM were included from 41 veterinary referral hospitals in this retrospective study. Dogs with GBM that demonstrated abnormal clinical signs had significantly greater odds of death than subclinical dogs in a univariable analysis (OR, 4.2; 95% CI, 2.14-8.23; P<0.001). The multivariable model indicated that categorical variables including owner recognition of jaundice (OR, 2.12; 95% CI, 1.19-3.77; P=0.011), concurrent hyperadrenocorticism (OR 1.94; 95% CI, 1.08-3.47; P=0.026), and Pomeranian breed (OR, 2.46; 95% CI 1.10-5.50; P=0.029) were associated with increased odds of death, and vomiting was associated with decreased odds of death (OR, 0.48; 95% CI, 0.30-0.72; P=0.001). Continuous variables in the multivariable model, total serum/plasma bilirubin concentration (OR, 1.03; 95% CI, 1.01-1.04; P<0.001) and age (OR, 1.17; 95% CI, 1.08-1.26; P<0.001), were associated with increased odds of death. The clinical utility of total serum/plasma bilirubin concentration as a biomarker to predict death was poor with a sensitivity of 0.61 (95% CI, 0.54-0.69) and a specificity of 0.63 (95% CI, 0.59-0.66). This study identified several prognostic variables in dogs with GBM including total serum/plasma bilirubin concentration, age, clinical signs, concurrent hyperadrenocorticism, and the Pomeranian breed. The presence of hypothyroidism or diabetes mellitus did not impact outcome in this study.

The role of sulphur peptide functions in free radical transfer: a pulse radiolysis study.

Cascading transfers of free radical centres, involving sulphur and aromatic protein functions, have been studied in further detail. The disulphide radical anion appears to be an important terminus of both oxidative and reductive radical transfer. In deaerated solutions of cysteine (20 mmol dm-3) the yield of Cys2/SS.- closely resembles the yield of all primary free radicals generated by water radiolysis (.OH, H. and eaq-). The alanyl Ala/C beta., formed by electron addition to cysteine and subsequent SH- elimination, oxidizes cysteine with a rate constant of k8 = 5.0 x 10(6)dm3mol-1s-1 at pH 6 to 7 and 3.6 x 10(6)dm3mol-1s-1 at pH 9 to 10. In the case of glutathione (GSH) the eaq--induced carbon-centred radical oxidizes the parent thiol with rate constants k(G. + GSH) of 7.0 x 10(6) and 1.3 x 10(6)dm3mol-1s-1 at pH 8 and pH 10, respectively; and with dithiothreitol (D(SH)2) the corresponding reaction rate is k(.DSH + D(SH)2) = 5.5 x 10(6)dm3mol-1s-1 at pH 7.0. The decarboxylated methionyl Met/C. alpha, formed by reaction of .OH with methionine, is capable of electron transfer to cystine, indicating a reduction potential for decarboxylated methione more negative than -1.6 V. The ring-closed methionyl radical cation Met/SN.+, formed by reaction of .OH with Met-Gly, oxidizes azide via equilibration, Met/SN.+ + H+ + N3- in equilibrium Met + N3., which enables an estimate to be given for the one-electron reduction potential: E degrees (Met/SN.+ + H+; Met) = +1.42 +/- 0.3 V (pH 6.8). Some further reactions of oxidizing dimeric Met2/SS.+ species in neutral solution have been demonstrated. The direction and nature of the transfers can be expressed by the scheme: (formula; see text).

Reductive activation of mitomycin C.

Mitomycin C, an antitumor antibiotic, is known to require reductive activation in order to function as an alkylating agent. In this work reduction has been carried out by using radiolytically produced formate radicals that reduce mitomycin C to its semiquinone in a clean rapid one-electron reaction. The ultimate products of the reduction are cis- and trans-2,7-diamino-1-hydroxymitosene (B1 and B2) and 2,7-diaminomitosene (C). The yields of these compounds were found to be the same when the rate of reduction was varied by 11 orders of magnitude. At pH 7, one mitosene molecule is formed for every two formate radicals, while at pH 9.1, about eight mitosene molecules are formed per formate radical. The ratio of (B1 + B2)/C is less than 0.4 at pH 5.7, 1.0 at pH 7, and greater than 3.5 at pH 9.1. Observations have been made of changes in optical absorption due to the formation of the semiquinone and hydroquinone of both mitomycin C itself and 2,7-diamino-1-hydroxymitosene (B). The direct conversion of the semiquinone form of mitomycin C into the semiquinone of B proceeds slowly, if at all. The semiquinone form of B will rapidly reduce mitomycin C (k = 7.2 X 10(8) M-1 s-1). The hydroquinone of mitomycin C undergoes changes resulting in the formation of B and C. The yields of B and C depend on pH.(ABSTRACT TRUNCATED AT 250 WORDS)

Evidence from pulse radiolysis and flash photolysis of the environment of tryptophan and tyrosine in the coat protein of fd phage.

Charge transfer has been observed between oxidised tryptophan-26 units and the tyrosine-21 or -24 of the coat protein of fd phage. The transfer is likely to be intramolecular. The rates suggest that the aromatic units are in a rigid region and that they may have at least two different environments. No apparent interaction occurs with the DNA, consistent with tryptophan and tyrosine units not being in contact with the bases.

Unpaired electron migration between aromatic and sulfur peptide units.

Cysteine thiyl radicals (Cys/S.) were found capable of one-electron oxidation of tyrosine. Equilibration occurred, using Cys and Gly-Tyr, with an equilibrium constant of K5 = 20 +/- 4 at pH 9.15: Cys/S. + Tyr in equilibrium Cys + Tyr/O. (5) Hence the reduction potentials of these couples differ at pH 9.15 by E(Cys/S., Cys) - E(Tyr/O., Tyr) = 80 mV. Oxidation of Trp-Gly by Cys/S. was not detectable from pH 7 to 12. The methionyl radical cation (Met/S.N), formed via .OH-attack on Met-Gly, reacts with Trp-Gly to generate the indolyl radical (Trp/N.). New results on intramolecular Trp/N.----Tyr/O. transitions indicate that the reaction requires direct contact between the two redox centers. Various possible pathways for migration of unpaired electrons between peptide units are compiled in a scheme.

Possible intermediates in the action of adriamycin--a pulse radiolysis study.

Over a wide range of pH, the semiquinone free radicals formed by reduction of adriamycin exist as a form which is strongly stabilised by internal hydrogen bonding and resonance. They protonate with pKa = 2.9. Below this pH they exhibit absorption maxima at 430 nm (Emax = 13,200 dm3 mol-1 cm-1) and approximately 720 nm (Emax = 4,200 dm3 mol-1 cm-1). Above pH 2.9 they have maxima at 480 nm (Emax = 14,600 dm3 mol-1 cm-1) and approximately 700 nm (Emax = 3,400 dm3 mol-1 cm-1). In acid and alkaline solution the radicals rapidly disappear by disproportionation, but within the approximate pH range 6 to 11 they appear to be relatively stable for at least 10-20 ms, existing in transient equilibrium with parent adriamycin and the full reduced form. Some rate constants for the formation and reactions of the semiquinone are given, including the reaction with oxygen to give O2.-. Fully reduced adriamycin has absorption maxima at 410 nm (Emax = 11,000 dm3 mol-1 cm-1) at pH 5 and 430 nm (Emax = 19,000 dm3 mol-1 cm-1) at pH 11. It undergoes decomposition within a few hundred ms. The intermediates from daunomycin would be expected to have properties similar to those from adriamycin.

The radiation chemistry of some platinum-containing radiosensitizers and related compounds.

Oxidation and reduction of cis- and trans-dichlorodiammine platinum II (cis- and trans-PDD), cis-dichlorobis(1-(2-hydroxyethyl)-2-methyl-5-nitroimidazole-N3)-p latinum II (cis-Flap), and cis-dichlorobis(isopropylamine)-trans-dihydroxyplatinum IV (Chip) have been studied using pulse radiolysis. Spectra corresponding to platinum in various oxidation states have been observed and several rate constants have been obtained. Reduction of all the compounds, except cis-Flap, produces species of a lower oxidation state of platinum which subsequently have both chloride ligands replaced. Ultimately, these products disproportionate. In the case of cis-Flap, reduction occurred on the nitroimidazole ligand. This was verified by the absence of platinum metal after disproportionation. Oxidation of all four compounds consists of production of a higher oxidation state of platinum followed by replacement of chloride ligands and finally disproportionation of the products. Only cis-Flap and Chip could be reduced by oxidized DNA bases. The one-electron reduction potential of cis-Flap was found to be -370 +/- 10 mV. trans-Flap had almost the same value. It was not possible to measure the potentials of the other compounds since their ligands were replaced rapidly but it is estimated that the one-electron reduction potentials decrease in the order cis- or trans-Flap greater than Chip greater than cis-PDD greater than trans-PDD.

Reactions of the semiquinone free radicals of anti-tumour agents with oxygen and iron complexes.

The rates of reaction of the semiquinone radicals of adriamycin and mitomycin C with oxygen and several iron (III) complexes have been determined. These rates have been used to explain enhanced free radical damage produced by semiquinone radicals in a model system and to assess the feasibility of these types of reactions occurring in hypoxic cells.

Influence of DNA binding on the formation and reactions of tryptophan and tyrosine radicals in peptides and proteins.

The rate constant of the one-electron oxidation of the tryptophan (Trp) or tyrosine (Tyr) residues by Br- X 2 radical anions is strongly decreased when the peptides are bound to DNA. Oxidation by N X 3 is much less affected by binding. These results can be explained by electrostatic repulsion between the charged polyphosphate backbone and the Br- X 2 radicals. Once oxidized, the interacting aromatic residues react with the DNA in a first order process with a rate constant of the order 10(3) s-1. These results have been extended to the single strand binding protein: the product of gene 32 of phage T4 (gp 32). The pulse radiolysis study suggests that one Trp residue of the protein oxidized by the Br- X 2 radicals reacts with the DNA in the complex while one Tyr residue is buried upon association. It is also shown that the exposure of Trp and Tyr residues to radical attack depends on whether the T4 SSB protein is bound to native or heat-denatured DNA.