Singlet molecular oxygen from superoxide anion and sensitized fluorescence of organic molecules

The superoxide anion, O(2)-, evolves singlet molecular oxygen in dimethylsulfoxide solution. Pronounced water quenching of superoxide-sensitized luminescence is indicative of the preferential generation of the (1)sigma(g)+ state. Recent identification of O(2)- in the xanthine oxidase system suggests that the generation of singlet oxygen may also occur in enzymatic systems.

Mechanism of four-level laser action in solution excimer and excited-state proton-transfer cases

Four-level laser energy level schemes are compared from the mechanistic spectroscopic viewpoint: (i) noble-gas excimer, (ii) solution molecular excimer, (iii) conventional dye laser, and (iv) intramolecular proton transfer. The lasing action of the chlorophyll special pair is discussed as an example of a solution excimer laser, and the lasing action of 3-hydroxyflavone and other molecules is discussed as an example of an intramolecular proton-transfer laser.

Chloroperoxidase generation of singlet Delta molecular oxygen observed directly by spectroscopy in the 1- to 1.6-mum region

The (0,0) (1)Delta(g) --> (3)Sigma(-) (g) singlet molecular oxygen chemiluminescence emission from a biological reaction system, chloroperoxidase (EC 1.11.1.10) acting on hydrogen peroxide at low pH (phosphate buffer, pH 2.85) with Cl(-) as a cosubstrate, was recorded with an ultrasensitive IR spectrometer. The strong chemiluminescence emission peak observed at 1.30 mum provides clear evidence of the enzymatic generation of (excited) singlet oxygen from peroxide in this system.

Direct spectroscopic observation of singlet oxygen emission at 1268 nm excited by sensitizing dyes of biological interest in liquid solution

The direct observation of dye-photosensitized 1268-nm emission of the (1)Delta(g) --> (3)Sigma(g) transition of molecular oxygen in liquid solution at room temperature is reported. Singlet oxygen was photosensitized by UV excitation of perfluorobenzophenone in fluorocarbon solvent, by 3,4-benzpyrene and hematoporphyrin in carbon tetrachloride, and by methylene blue in water. Also reported is the development of an extremely sensitive near-infrared spectrophotometer that uses a thermoelectrically cooled lead sulfide detector, optimized optics, and a boxcar integrator as a data processor.

Loop ileostomy following anterior resection: is it really temporary?

INTRODUCTION

A temporary loop ileostomy is often created to minimize the impact of peritoneal sepsis if anastomotic dehiscence occurs following low colorectal anastomosis. Although it has been suggested that a loop ileostomy should be reversed within 12 weeks of formation, this is often not the case. We set out to analyse the use of loop ileostomy following elective anterior resection in England and to identify factors associated with non and delayed reversal.

METHOD

Hospital episode statistics for the years 2001-2006 were obtained from the Department of Health. Patients undergoing elective anterior resection with a loop ileostomy for a primary diagnosis of rectal or recto-sigmoid cancer between April 2001 and March 2003 were identified as the study cohort. This cohort was followed until March 2006 to identify patients undergoing reversal of an ileostomy in an English NHS Hospital.

RESULTS

A total of 6582 patients had an elective anterior resection between April 2001 and March 2003, of which 964 (14.6%) also had an ileostomy. Seven hundred and two (75.1%) patients were reversed before March 2006. Advancing age and comorbidity were statistically related to nonreversal. Median time to reversal was 207 days (Interquartile range 119-321.5 days). Postoperative chemotherapy and comorbidity significantly delayed reversal.

CONCLUSIONS

One in four loop ileostomies performed to defunction an elective anterior resection is not reversed, and in the presence of significant comorbidity one in three is not reversed. Only 12% is reversed within 12 weeks.

Risk factors for extended-spectrum beta-lactamase producing Escherichia coli and Klebsiella pneumoniae acquisition in a neonatal intensive care unit

This study was made to find the prevalence of extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli and Klebsiella pneumoniae in neonatal intensive care unit (NICU) and to identify the risk factors associated with the acquisition of these organisms. Risk factors associated with ESBL-producing E. coli and/or K. pneumoniae acquisition status of neonates were assessed. Of 253 neonates admitted, 238 entered the active surveillance system. ESBL-producing K. pneumoniae was responsible for 7 infections and 51 colonizations while ESBL-producing E. coli was responsible for 9 infections and 88 colonizations. Concurrent isolation of both the organisms occurred in 30 neonates. The logistic regression model identified 'length of stay in the NICU' as the single independent risk factor. Imipenem, cefepime and amikacin can be suggested as the drugs of choice in our study.

Doripenem versus bacteria: an emerging battleground

Doripenem is a new 1-beta-methyl carbapenem with broad-spectrum activity against clinically important pathogens. Its activity matches imipenem or ertapenem against Gram-positive bacteria and meropenem against Gram-negative bacteria. It may offer slightly more activity than meropenem against selected pathogens. It does not require the addition of cilastatin. Doripenem is stable to hydrolysis by most of the beta-lactamases, excluding carbapenem-hydrolyzing beta-lactamases. We performed dockings of imipenem, meropenem, ertapenem and doripenem with imipenem-hydrolyzing beta-lactamase, Sme1, separately. Energy calculations revealed that the complex involving doripenem was much less stable. Hence doripenem resists attack by carbapenem-hydrolyzing beta-lactamases at least to some extent. Empiric therapy with doripenem may be useful in hospital settings where multidrug resistance has emerged. However, the proper place for this drug in current antibiotic prescribing practices needs to be determined.

A unique group of self-splicing introns in bacteriophage T4

We describe in this review, the salient splicing features of group I introns of bacteriophage T4 and propose, a hypothetical model to fit in the self-splicing of nrdB intron of T4 phage. Occurrence of non-coding sequences in prokaryotic cells is a rare event while it is common in eukaryotic cells, especially the higher eukaryotes. Therefore, T4 bacteriophage can serve as a good model system to study the evolutionary aspects of splicing of introns. Three genes of T4 phage were found to have stretches of non-coding sequences which belonged to the group IA type introns of self-splicing nature.

A new injectable bulking agent for treatment of stress urinary incontinence: results of a multicenter, randomized, controlled, double-blind study of Durasphere

OBJECTIVES

To assess the safety and effectiveness of Durasphere compared with bovine collagen in the treatment of stress urinary incontinence (SUI) due to intrinsic sphincter deficiency (ISD).

METHODS

This multicenter, randomized, controlled, double-blind trial was composed of 355 women diagnosed with SUI due to ISD and used a standardized pad test and the Stamey continence grade as the primary endpoints. The participants' ages ranged from 26 to 84 years. All patients had an abdominal leak point pressure of less than 90 cm H(2)O (average 51).

RESULTS

At 12 months after the first injection, the two materials were equivalent with respect to the improvement in continence grade and pad weight testing. Less Durasphere was injected to obtain comparable clinical results (Durasphere 4.83 mL versus bovine collagen 6.23 mL, P <0.001). When examined 1 year after the date of the last treatment, 49 (80.3%) of the 61 women treated with Durasphere showed improvement of 1 continence grade or more compared with 47 (69.1%) of 68 women treated with bovine collagen (P value for difference = 0.162). Although the adverse events reported for both groups were similar, the Durasphere group had an increased short-term risk of urgency and urinary retention.

CONCLUSIONS

The use of Durasphere for the treatment of SUI due to ISD was equally effective as bovine collagen and used less material. The U.S. Food and Drug Administration granted market approval for Durasphere on September 13, 1999. The product design and initial clinical data suggest the potential for greater durability of the clinical benefit, with the possibility of a permanent solution for SUI due to ISD in some patients.

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.