The decomposition of peroxynitrite to nitroxyl anion (NO-) and singlet oxygen in aqueous solution

The mechanism of decomposition of peroxynitrite (OONO(-)) in aqueous sodium phosphate buffer solution at neutral pH was investigated. The OONO(-) was synthesized by directly reacting nitric oxide with superoxide anion at pH 13. The hypothesis was explored that OONO(-), after protonation at pH 7.0 to HOONO, decomposes into (1)O(2) and HNO according to a spin-conserved unimolecular mechanism. Small aliquots of the concentrated alkaline OONO(-) solution were added to a buffer solution (final pH 7.0-7.2), and the formation of (1)O(2) and NO(-) in high yields was observed. The (1)O(2) generated was trapped as the transannular peroxide (DPAO(2)) of 9, 10-diphenylanthracene (DPA) dissolved in carbon tetrachloride. The nitroxyl anion (NO-) formed from HNO (pKa 4.5) was trapped as nitrosylhemoglobin (HbNO) in an aqueous methemoglobin (MetHb) solution. In the presence of 25 mM sodium bicarbonate, which is known to accelerate the rate of decomposition of OONO(-), the amount of singlet oxygen trapped was reduced by a factor of approximately 2 whereas the yield of trapping of NO(-) by methemoglobin remained unaffected. Because NO(3)(-) is known to be the ultimate decomposition product of OONO(-), these results suggest that the nitrate anion is not formed by a direct isomerization of OONO(-), but by an indirect route originating from NO(-).

Restoration of mRNA splicing by a second-site intragenic suppressor in the T4 ribonucleotide reductase (small subunit) self-splicing intron

The nrdB gene of bacteriophage T4 codes for the small subunit of ribonucleotide reductase and contains a 598-base self-splicing intron which is closely related to other group I introns of T4 and eukaryotes. Thirty-one mutants causing splicing defects in the nrdB intron were isolated. Twenty-three EMS-induced revertants for these 31 primary mutants were isolated by the strategic usage of the white halo plaque phenotype. We mapped these revertants by marker rescue using subclones of the nrdB gene. Some of these second-site mutations mapped to regions currently predicted by the secondary structure model of the nrdB intron. One of these suppressor mutants (nrdB753R) was found to be intragenic by marker rescue with the whole nrdB gene. However, this mutation failed to map within the nrdB intron. Splicing assays showed that this pseudorevertant restored splicing proficiency of the nrdB primary mutation to almost wild-type conditions. This is the first example of a mutation within the exons of a gene containing a self-splicing intron that is capable of restoring a self-splicing defect caused by a primary mutation within the intron. In addition, two other suppressor mutations are of interest (nrdB429R and nrdB399R). These suppressors were able to restore their primary 5' defect but in turn create a 3' splicing defect. Both of these revertants mapped in different regions of the intron with respect to their primary mutations.

Cladribine in the treatment of advanced relapsed or refractory low and intermediate grade non-Hodgkin's lymphoma

BACKGROUND

Cladribine (2-chlorodeoxyadenosine) is a purine nucleoside analog with cytotoxic activity against both resting and proliferating cells. Clinical studies with cladribine have reported antitumor activity against various hematologic malignancies.

METHODS

The authors studied responses to cladribine among patients with low and intermediate grade non-Hodgkin's lymphoma that had been refractory to or relapsed after prior chemotherapy. Cladribine was given intravenously over 2 hours at a dose of 0.14 mg/kg daily for 5 consecutive days, repeated every 4 weeks.

RESULTS

Twenty-eight patients (16 males, 12 females) with a median age of 58 years (range, 41-75 years) were accrued. Twenty-three patients had low grade and 5 had intermediate grade lymphoma. Stage IV disease was present in 22 (79%), and 17 (61%) had systemic B-symptoms. The majority (57%) had received 2 or more prior chemotherapy regimens (median, 2; range, 1-5); 6 had had prior fludarabine therapy. Major responses were documented in 32% (9 of 28 patients), with 4 complete remissions (CR) and 5 partial remissions (PR) after a median of 4 cycles (range, 1-9). One CR occurred in one patient with intermediate grade diffuse large cell lymphoma, and three of six patients who had had prior fludarabine therapy experienced CR or PR with cladribine. Severe hematologic toxicities included reversible neutropenia, protracted thrombocytopenia, and lymphopenia. Other reported adverse effects included mild-to-moderate fatigue, nausea, and diarrhea.

CONCLUSIONS

Cladribine is an active single agent in the treatment of patients with refractory or relapsed advanced stage indolent lymphoma, with major responses in one third of patients.

Evaluation of prostate specific antigen as a tumor marker in cancer prostate

The present study was undertaken to evaluate the prostate specific antigen (PSA) alongwith other diagnostic methods as an application for a screening test, tumor marker and its relation to post surgical situation. The PSA has shown a sensitivity of 73.3% and specificity of 77.2%. The predictive value for positive PSA was 57% and for negative test was 66.6%. Local standards for PSA values in Pakistani community need to be established. The PSA test, inspite of its low specificity holds good promise for its contributory role as a tumor marker in prostate cancer.

Isolation and characterization of EMS induced splicing defective point mutations within the intron of the nrdB gene of bacteriophage T4

The nrdB gene of bacteriophage T4 codes for the small subunit of ribonucleotide reductase and contains a 598-base-pair self-splicing intron which is closely related to other group I introns of T4 and eukaryotes. The screening, isolation, and mapping of 31 nrdB intron mutations were conducted by the strategic usage of the white halo phenotype exhibited by T4 mutants defective in dyhydrofolate reductase or thymidylate synthase. These intron mutations cluster towards the ends, mainly the 3' end, and show a defect in self-splicing. These mutations map in regions of conserved structural elements, thus supporting secondary structure predictions. A distinct pattern of clustering is observed with the highest number of mutations mapping within three of the smaller regions (A, C, and D) of the nrdB intron and no mutations mapping in the largest (B) region. The highest density of mutations mapped in the smallest region (C) of the intron, containing only 96 bases, thus showing a distinct pattern of clustering within the catalytic core.

Quantitative generation of singlet (1 delta g) oxygen from acidified aqueous peroxynitrite produced by the reaction of nitric oxide and superoxide anion

Simple acidification of aqueous alkaline peroxynitrite quantitatively generates singlet (1 delta g) molecular oxygen, detected and quantitated spectroscopically (1270 nm). This observation provides a chemical basis for physiological cytotoxicity of ONOO- generated in the diffusion - controlled reaction of cellular NO. and O2-. The experiments consist of (i) chemical generation of ONOO- from NO. gas and KO2 powder in alkaline aqueous solution; (ii) absorption spectral identification of ONOO- in the near-UV with maximum at 301 nm; (iii) spectroscopic identification of 1O2 by its emission band at 1200-1340 nm with maximum at 1275 nm; and (i.v.) quantification of 1O2 generated in ONOO-/H+ reaction by comparison of the chemiluminescence intensity at 1270 nm with that from H2O2/OCI- reaction that generates 1O2 with unit efficiency at alkaline pH. 1O2 was generated with unit efficiency with respect to ONOO- concentration by the ONOO-/H+ reaction.

Reactive oxygen species as cellular messengers

Reactive oxygen species (ROSs) have recently been found to be important signaling molecules in several cellular responses. Individual species have characteristic reactive properties, yet are easily interconverted, making it difficult to identify the ROSs involved in each response.

Near fatal gas embolism during laparoscopic cholecystectomy

Laparoscopic cholecystectomy has been greeted with enthusiasm by surgeons and patients alike. However, with the passage of time reports of complications related to this new approach are being published. We report an unusual complication of gas embolism in laparoscopic cholecystectomy. A high index of suspicion along with vigilant intraoperative monitoring will help in the early diagnosis and reduction of morbidity associated with gas embolism.

Singlet molecular oxygen in the Haber-Weiss reaction

Characteristic chemiluminescence emission of singlet (1 delta g) molecular oxygen at 1268 nm is reported from a Haber-Weiss reaction. The reaction consists of mixing aqueous hydrogen peroxide with a solution of potassium superoxide, solubilized by 18-crown-6 ether in carbon tetrachloride or in dry acetonitrile at room temperature. Since the discovery of the enzyme superoxide dismutase by J.M. McCord and I. Fridovich [(1968) J. Biol. Chem. 243, 5733-5760], the identity of the reactive oxidant in superoxide-generating systems in biology has remained a chemical mystery. The results presented here suggest strongly that the reactive species is singlet oxygen generated via the Haber-Weiss reaction and not, as usually assumed, the hydroxyl radical, .OH, generated by the same reaction.

Singlet molecular oxygen evolution upon simple acidification of aqueous hypochlorite: application to studies on the deleterious health effects of chlorinated drinking water

A study of the pH profile of the decomposition of aqueous hypochlorite has revealed the evolution (onset at pH 8) of single (1 delta g) molecular oxygen (singlet spin state dioxygen) detected spectroscopically (1268 nm), prior to the appearance of chlorine (onset at pH 5.5). The possible mechanism of the singlet state dioxygen evolution is presented, and the origin of its chloride ion dependence is discussed, especially in reference to chloride ion dependence of singlet molecular oxygen evolution in biological systems. Recent epidemiological analyses of the correlation of human cancer with chlorinated water supplies focus attention on the singlet oxygen mechanisms of DNA lesion formation.

The DAB-Mn++ cytochemical method revisited: validation of specificity for superoxide

We wished to assess whether the previously developed 3,3'-diaminobenzidine (DAB)-Mn++ cytochemical method, purportedly specific for superoxide localization, is detecting superoxide O2.- and/or the superoxide product, O2(1 delta g). We show here that polymorphonuclear leukocytes (PMNs) produce O2(1 delta g) extracellularly in response to non-phagocytic stimuli and that this production is inhibited by addition of superoxide dismutase, an enzyme typically used to demonstrate that a reaction is mediated by O2.-. Because O2(1 delta g) is highly reactive and can be generated from O2.-, the reactivity of a pure chemical source of O2(1 delta g) with the cytochemical probe DAB was examined in the presence and absence of Mn++. Reactions between DAB and O2(1 delta g), thermally released from 1,4-dimethyl-napthalene-1,4-endoperoxide (DNE), indicated that O2(1 delta g) directly reacted with DAB, forming an insoluble DAB polymer, and that this reaction was increased by the presence of Mn++. The direct reaction of O2(1 delta g) with DAB was confirmed using near-IR emission spectroscopy. The near-IR emission spectrum of DNE as it was warmed showed the characteristic energy emission peak of O2(1 delta g) and the intensity of this peak was reduced by the addition of DAB; kq = 1.7 x 10(8) M-1 sec-1. The requirement of Mn++ for oxidation of DAB by O2.- was reconfirmed using potassium superoxide as a pure chemical source of O2.-. In cell studies, however, DAB deposits were not observed in PMNs stimulated under conditions that lead to O2(1 delta g) production [e.g., 0.040 or 0.162 microM 4B-phorbol-12-myristate-13-acetate (PMA)], regardless of whether Mn++ was present in the cytochemical medium. Nor were DAB deposits found in cells stimulated with PMA in the absence of Mn++ or in unstimulated PMNs. Only cells incubated in cytochemical medium containing Mn++ and stimulated to produce large amounts of O2.- (e.g., 3.24 microM PMA) contained DAB deposits. In summary, the DAB-Mn++ cytochemical method remains an excellent method for localizing the production sites of O2.-, since the concentration of O2(1 delta g) within vesicles of stimulated cells is too low to directly oxidize DAB to an electron-dense deposit.

Extracellular production of singlet oxygen by stimulated macrophages quantified using 9,10-diphenylanthracene and perylene in a polystyrene film

The extracellular production of singlet oxygen (O2(1 delta g)) by stimulated macrophages was measured using a modification of our quantitative method initially developed to measure the intracellular production of O2(1 delta g) by neutrophils (Steinbeck, M. J., Khan, A. U., and Karnovsky, M. J. (1992) J. Biol. Chem. 267, 13425-13433). Glass coverslips were coated with the specific chemical trap for O2(1 delta g), 9,10-diphenylanthracene (DPA) and perylene, which is an internal standard, in a methylene chloride solution containing 0.3 mg/ml polystyrene. On evaporation, the polystyrene formed an even coating of DPA and perylene over the surface of a glass coverslip (PDP film). Unstimulated macrophages or macrophages stimulated with 4 beta-phorbol 12-myristate 13-acetate (PMA) or formyl-methionyl-leucyl-phenylalanine (fMLP) were then added to the PDP film in a darkened room and incubated at 37 degrees C for 30 min in a humidified 5% CO2 atmosphere. Both unstimulated and stimulated cells adhered to the PDP film in approximately equivalent numbers. Only stimulated cells produced measurable amounts of O2(1 delta g) in a dose-dependent response to either PMA or fMLP. The production of O2(1 delta g) by macrophages stimulated with PMA was maximal in response to 25 ng, 17.8 +/- 1.3 nmol of O2(1 delta g)/approximately 1.00 x 10(6) cells. The maximal response for fMLP was at a concentration of 1 microM, 18.4 +/- 1.0 nmol of O2(1 delta g)/approximately 1.00 x 10(6) cells. The specific detection of O2(1 delta g) by this method was confirmed by thermally releasing O2(1 delta g) from the DPA-O2(1 delta g) reaction product, DPA-endoperoxide, regenerating the original DPA compound. Production of O2(1 delta g) by the stimulated cells was inhibited 80-89% by the addition of 60-120 micrograms of superoxide dismutase, an enzyme that converts superoxide to hydrogen peroxide and ground state molecular oxygen or 79-84% with the addition of 2 mM histidine, an avid quencher of O2(1 delta g). Neither of these additions interfered with adhesion of the cells to the PDP film. The ability of superoxide dismutase to inhibit the production of O2(1 delta g) suggested that O2(1 delta g) was produced via a superoxide-dependent route. The ability of an oxidase to produce O2(1 delta g) secondary to superoxide production was substantiated further using a xanthine oxidase-acetaldehyde system. Purified xanthine oxidase produced both superoxide and O2(1 delta g), and their production was inhibited by the addition of superoxide dismutase.(ABSTRACT TRUNCATED AT 400 WORDS)

Spermine and spermidine protection of plasmid DNA against single-strand breaks induced by singlet oxygen

Oxidative damage to DNA induced by singlet molecular oxygen (1O2*) includes single-strand breaks, which the biologically occurring 1O2* quenchers spermine and spermidine are shown to prevent. These polyamines at a physiological concentration (10 mM) reduce the percentage of the open circular form of pBR322 plasmid DNA, which is generated at the expense of the native supercoiled form when the plasmids are incubated with a chemical source of 1O2*, the water-soluble endoperoxide of 3,3'-(1,4-naphthylidene)dipropionate. Spermine and spermidine can be expected to protect DNA against other damaging effects of 1O2*.

A proposed function for spermine and spermidine: protection of replicating DNA against damage by singlet oxygen

Like all aliphatic amines, the polyamines spermine and spermidine are physical quenchers of singlet molecular oxygen (1O2*). The rate constants of these processes were determined in vitro with photochemically generated 1O2* and the hydrocarbon rubrene as substrate, in pyridine. At millimolar concentration, spermine and spermidine should quench 1O2* in vivo and prevent it from damaging DNA. It is proposed that a biological function of polyamines is the protection of replicating DNA against oxidative damage.

Intracellular singlet oxygen generation by phagocytosing neutrophils in response to particles coated with a chemical trap

To determine if singlet oxygen (O2(1 delta g)) is produced by neutrophils (PMNs) during the process of phagocytosis, glass beads were coated with a specific chemical trap for O2(1 delta g), 9,10-diphenylanthracene (DPA). Singlet oxygen, but not other reactive oxygen species, reacts rapidly with DPA at a rate of kr = 1.3 x 10(6) M-1 s-1 to form a stable product, DPA-endoperoxide (Corey, E. J., and Taylor, W. C. (1964) J. Am. Chem. Soc. 86, 3881-3882; Wasserman, H. H., Scheffer, J. R., and Cooper, J. L. (1972) J. Am. Chem. Soc. 94, 4991-4996; Turro, N. J., Chow, M.-F., and Rigaudy, J. (1981) J. Am. Chem. Soc. 103, 7218-7224). The production of DPA-endoperoxide was determined by ultraviolet spectroscopy as a decrease in DPA absorbance at 355 nm. The absorbance of DPA was normalized to the absorbance of perylene, which was included in the coating on the beads as a nonreactive, internal standard. In the present study, DPA- and perylene-coated beads were initially allowed to adhere to fibronectin-coated coverslips. PMNs were then added to the bead-coated coverslips and allowed to adhere and phagocytose the beads for 1 h at 37 degrees C. In some experiments, 4B-phorbol-12-myristate-13-acetate (PMA) (1 ng/2.5 x 10(7) cells/ml), a known activator of the PMN NADPH-oxidase, was added as a co-stimulant. The amount of O2(1 delta g) produced by phagocytically stimulated PMNs was calculated to be 11.3 +/- 4.9 nmol of O2(1 delta g)/1.25 x 10(6) cells. Low dose PMA co-stimulation increased the production of O2(1 delta g) to 14.1 +/- 4.1 nmol/1.25 x 10(6) cells. Averaged together these amounts represent approximately 19 +/- 5.0% of the total oxygen consumed by PMNs in response to DPA- and perylene-coated beads. The specificity of the DPA reaction with O2(1 delta g) was confirmed by warming to 120 degrees C, which releases O2(1 delta g) from the DPA-endoperoxide, regenerating the parent DPA compound (Wasserman et al., 1972; Turro et al., 1981) and the absorbance at 355 nm. In addition, beta-carotene, an avid quencher of O2(1 delta g), was included in the coating of some bead preparations; assays in which these beads were used showed no change in the absorbance at 355 nm. Singlet oxygen production by myeloperoxidase was also measured using the coated bead assay and the results suggest that this is a major pathway by which singlet oxygen is generated in phagocytically stimulated PMNs.(ABSTRACT TRUNCATED AT 400 WORDS)

Polysomnographic findings in adolescents with major depression

Ten adolescents with major depression and 10 age-matched controls were studied with polysomnography for 3 consecutive nights. The sleep records were analyzed for variables pertaining to sleep continuity (total sleep time, sleep efficiency, sleep onset latency, number of awakenings, and number of stage shifts), sleep architecture (Stages 1, 2, 3, and 4), and rapid eye movement (REM) sleep (total) REM sleep time, number of REM periods, REM latency, and REM density). The experimental and control groups were compared on 14 variables with the t test for independent groups. The results indicated that none of the sleep variables differed significantly between the two groups. These results confirm earlier findings indicating that the abnormalities in REM latency and REM density that characterize adults with major depression are absent in adolescents suffering from major depression. Developmental and diagnostic variables are discussed as possible explanations for the sleep differences between adolescents and adults with depressive disorders.

Near infrared emission of singlet oxygen generated in the dark

Singlet oxygen generation is reported from (1) enzymatic reaction and (2) electron transfer reactions of the superoxide anion measured directly with an ultrasensitive near-IR emission spectrophotometer by monitoring the O2(1 delta g)----O2 (3 sigma g-) transition at 1268 nm. Near-IR emission spectra from the myeloperoxidase and lactoperoxidase enzymatic systems show only emission of singlet oxygen at 1268 nm. The lipoxygenase/Na-linoleate enzymatic reaction exhibits two emissions, 1268 nm and 1288 nm. The latter emission is identified as originating from a peroxy radical. Spectral and kinetic data giving evidence of singlet oxygen generation is obtained from the reaction of potassium superoxide solubilized by 18-crown-6-ether in acetonitrile with a series of organometallic coordination compounds.

Sensitivity and specificity of TRH stimulation test in depressed and nondepressed adolescents

The thyrotropin-releasing hormone (TRH) stimulation test was carried out in 100 acutely hospitalized adolescents (ages 13-17 years) with a variety of diagnoses. The test was positive (delta max thyrotropin less than or equal to 7 microIU/ml) in 36.6% of adolescents with major depression, 20.8% with conduct disorders, 17% with adjustment disorders, and 43% with substance abuse disorders. A X2 analysis of the data showed no significant difference among these four diagnostic groups. The test was negative in adolescents with attention deficit disorder and dysthymic disorder. Comparison of the six diagnostic groups with regard to the amount of thyrotropin (thyroid-stimulating hormone, TSH) response to TRH stimulation indicated that the groups with major depression and substance abuse disorders had significantly lower values of delta max TSH than the other groups. TSH values did not differ significantly between males and females. Similarly, there were no significant age differences (younger adolescents vs. older adolescents).

Water induced dismutation of superoxide anion generates singlet molecular oxygen

Direct spectroscopic measurement of 1268 nm singlet oxygen emission from KO2 suspensions at room temperature in three non-protonic solvents--CCl4, Cl2FCCClF2, and C6F14 by the action of water is reported. The results clearly show that the singlet oxygen generation is due to a water induced reaction, and suggest that one role of the enzyme superoxide dismutase may be the protection of biological structures, for example, lipid membranes, from degradation by singlet oxygen.

Comparison of a long-acting form of propranolol and conventional propranolol in the treatment of hypertension in elderly patients

Nineteen elderly hypertensive patients already being treated with a diuretic and, where necessary, another anti-hypertensive agent, were studied in a double-blind, randomized, crossover comparison of conventional propranolol, 40 mg three times daily, with a long-acting propranolol formulation, 160 mg once daily, as a second line agent. Patients were assessed before taking the morning's allocated medication. This was done as near as possible to 24 h after the last dose of once daily propranolol and as near as possible to 15 h after the last dose of three times daily conventional propranolol. Assessment was carried out at the time of randomization and after 4 weeks' treatment with both propranolol formulations. Heart rate and blood pressures were measured in the supine and standing positions and after exercise. Both propranolol formulations were effective as second line agents in these elderly patients and both were well tolerated. Patient compliance on both propranolol formulations was very good although the long-acting formulation may be of value in improving this still further.

Antiarthritic gold compounds effectively quench electronically excited singlet oxygen

Although certain gold [Au(I)] compounds have been used effectively in the treatment of rheumatoid arthritis for some years, the molecular basis for such therapeutic action has been unclear. One possible mechanism of the action of Au(I) compounds is that they protect unsaturated membrane lipids and proteins against oxidative degradation caused by activated phagocytes that are not properly regulated. In this study it has been shown that superoxide ion (O-2.), a product of activated phagocytes, can be oxidized to electronically excited singlet oxygen (O1(2)delta g), an agent that is capable of peroxidation of unsaturated fatty acid derivatives. It has also been shown that antiarthritic Au(I) compounds are effective deactivators of O1(2)delta g with quenching constants on the order of 10(7) M-1 sec-1.