Iron oxide-promoted photochemical oxygen reduction to hydrogen peroxide (H2O2)

Hydrogen peroxide (H2O2) is a valuable green oxidant with a wide range of applications. Furthermore, it is recognized as a possible future energy carrier achieving safe operation, storage and transportation. The photochemical production of H2O2 serves as a promising alternative to the waste- and energy-intensive anthraquinone process. Following the 12 principles of Green Chemistry, we demonstrate a facile and general approach to sustainable catalyst development utilizing earth-abundant iron and biobased sources only. We developed several iron oxide (FeOx) nanoparticles (NPs) for successful photochemical oxygen reduction to H2O2 under visible light illumination (445 nm). Achieving a selectivity for H2O2 of >99%, the catalyst material could be recycled for up to four consecutive rounds. An apparent quantum yield (AQY) of 0.11% was achieved for the photochemical oxygen reduction to H2O2 with visible light (445 nm) at ambient temperatures and pressures (9.4-14.8 mmol g-1 L-1). Reaching productivities of H2O2 of at least 1.7 ± 0.3 mmol g-1 L-1 h-1, production of H2O2 was further possible via sunlight irradiation and in seawater. Finally, a detailed mechanism has been proposed on the basis of experimental investigation of the catalyst's properties and computational results.

P586Left ventricular volume and mass adaptation after 58-days head-down bed-rest assessed by cine-MRI, and effectiveness of high-intensity jump training countermeasure

Aims

Prolonged immobilization generates cardiac deconditioning, a risk factor for cardiovascular disease, and efficient countermeasures (CM) are needed to prevent it. Our aim was to assess by Cine-MRI the effects of long-term strict head-down (−6 degrees) bed-rest (BR) deconditioning, and the effectiveness of high-intensity jump training CM, on left ventricular (LV) function and mass.

Methods

23 male participants (29±6 years, 181±6 cm, 77±7 kg) were enrolled. The experiment was conducted at: envihab (Koln, DLR, Germany) as part of the European Space Agency BR studies. Volunteers were randomly allocated to the jump training group (JUMP, n=12) or the control group (CTRL, n=11). A typical training session consisted of 4x10 countermovement jumps and 2x10 hops in a sledge jump system, with 5–6 sessions per week.

Steady-state free precession cine-MRI images were obtained (25 frames/cardiac cycle, 8mm thickness, no gap, no overlap) as stack of short-axis images covering the whole LV from base to apex, before (PRE) and after 58-days (HDT58) of BR. Endocardial and epicardial semi-automated contouring was performed using custom software.

Results

In CTRL group, at HDT58 a reduction in LV mass (9%), end-diastolic (21%), end-systolic (8%) and stroke volume (23%) were observed, while ejection fraction did not change. In JUMP group, the reduction in LV end-diastolic volume was only by 9%, followed by a decrease in end-systolic (10%) and stroke volume (10%), with a preservation of LV mass. In both groups, ejection fraction did not change.

Left ventricular changes after 58d BR EDV (ml) ESV (ml) SV (ml) EF (%) Mass (g) CTRL PRE 171 (163; 191) 60 (58; 65) 113 (102; 124) 64 (63; 67) 133 (121; 160) HDT58 143 (131; 149)* 56 (50; 58)* 86 (83; 92)* 62 (60; 63)* 127 (106; 138)* JUMP PRE 156 (140; 204) 70 (61; 84) 91 (78; 117) 58 (56; 60) 118 (104; 134) HDT58 141 (135; 175)* 63 (54; 69)* 90 (78; 92)* 58 (55; 60) 113 (105; 128) Results expressed as median (25th; 75th percentiles). *p<0.05 Wilcoxon non parametric paired test (PRE vs HDT58). CTRL: control group; JUMP: countermeasure group.

Conclusions

Cardiac adaptation to deconditioning due to immobilization induced by BR resulted in a reduction of cardiac volumes and function, together with a decrease in LV mass. Interestingly, the applied JUMP countermeasure appeared able to partially reverse these effects, in particular by reducing the decrease in end-diastolic volume and preserving LV mass. This information could be useful for better understanding physiologic changes in patients undergoing long periods of immobilization, as well as to apply the studied countermeasure during space flight to reduce cardiac deconditioning.

Acknowledgement/Funding

Italian Space Agency (contract 2018-7-U.0),CNES/DAR 48ehz747.01950965,BELSPO, via the European Space Agency PRODEX program (PEA 4000110826)

Mn Self-Doping of Orthorhombic RMnO3 Perovskites: (R0.667Mn0.333)MnO3 with R = Er-Lu

Orthorhombic rare-earth trivalent manganites RMnO₃ (R = Er-Lu) were self-doped with Mn to form (R_0.667Mn_0.333)MnO₃ compositions, which were synthesized by a high-pressure, high-temperature method at 6 GPa and about 1670 K from R₂O₃ and Mn₂O₃. The average oxidation state of Mn is 3+ in (R_0.667Mn_0.333)MnO₃. However, Mn enters the A site in the oxidation state of 2+, creating the average oxidation state of 3.333+ at the B site. The presence of Mn²⁺ was confirmed by hard X-ray photoelectron spectroscopy measurements. Crystal structures were studied by synchrotron powder X-ray diffraction. (R_0.667Mn_0.333)MnO₃ crystallizes in space group Pnma with a = 5.50348(2) Å, b = 7.37564(1) Å, and c = 5.18686(1) Å for (Lu_0.667Mn_0.333)MnO₃ at 293 K, and they are isostructural with the parent RMnO₃ manganites. Compared with RMnO₃, (R_0.667Mn_0.333)MnO₃ exhibits enhanced Néel temperatures of about T_N1 = 106-110 K and ferrimagnetic or canted antiferromagnetic properties. Compounds with R = Er and Tm show additional magnetic transitions at about T_N2 = 9-16 K. (Tm_0.667Mn_0.333)MnO₃ exhibits a magnetization reversal or negative magnetization effect with a compensation temperature of about 16 K.

Formation of a K-In-Se Surface Species by NaF/KF Postdeposition Treatment of Cu(In,Ga)Se2 Thin-Film Solar Cell Absorbers

A NaF/KF postdeposition treatment (PDT) has recently been employed to achieve new record efficiencies of Cu(In,Ga)Se₂ (CIGSe) thin film solar cells. We have used a combination of depth-dependent soft and hard X-ray photoelectron spectroscopy as well as soft X-ray absorption and emission spectroscopy to gain detailed insight into the chemical structure of the CIGSe surface and how it is changed by different PDTs. Alkali-free CIGSe, NaF-PDT CIGSe, and NaF/KF-PDT CIGSe absorbers grown by low-temperature coevaporation have been interrogated. We find that the alkali-free and NaF-PDT CIGSe surfaces both display the well-known Cu-poor CIGSe chemical surface structure. The NaF/KF-PDT, however, leads to the formation of bilayer structure in which a K-In-Se species covers the CIGSe compound that in composition is identical to the chalcopyrite structure of the alkali-free and NaF-PDT absorber.

Pronounced Surface Band Bending of Thin-Film Silicon Revealed by Modeling Core Levels Probed with Hard X-rays

Enhancing the probing depth of photoemission studies by using hard X-rays allows the investigation of buried interfaces of real-world device structures. However, it also requires the consideration of photoelectron-signal attenuation when evaluating surface effects. Here, we employ a computational model incorporating surface band bending and exponential photoelectron-signal attenuation to model depth-dependent spectral changes of Si 1s and Si 2s core level lines. The data were acquired from hydrogenated boron-doped microcrystalline thin-film silicon, which is applied in silicon-based solar cells. The core level spectra, measured by hard X-ray photoelectron spectroscopy using different excitation energies, reveal the presence of a 0.29 nm thick surface oxide layer. In the silicon film a downward surface band bending of eVbb = -0.65 eV over ∼6 nm obtained via inverse modeling explains the observed core level shifts and line broadening. Moreover, the computational model allows the extraction of the "real" Si 1s and Si 2s bulk core level binding energies as 1839.13 and 150.39 eV, and their natural Lorentzian line widths as 496 and 859 meV, respectively. These values significantly differ from those directly extracted from the measured spectra. Because band bending usually occurs at material surfaces we highly recommend the detailed consideration of signal integration over depth for quantitative statements from depth-dependent measurements.

The complex interface chemistry of thin-film silicon/zinc oxide solar cell structures

The interface between solid-phase crystallized phosphorous-doped polycrystalline silicon (poly-Si(n(+))) and aluminum-doped zinc oxide (ZnO:Al) was investigated using spatially resolved photoelectron emission microscopy. We find the accumulation of aluminum in the proximity of the interface. Based on a detailed photoemission line analysis, we also suggest the formation of an interface species. Silicon suboxide and/or dehydrated hemimorphite have been identified as likely candidates. For each scenario a detailed chemical reaction pathway is suggested. The chemical instability of the poly-Si(n(+))/ZnO:Al interface is explained by the fact that SiO2 is more stable than ZnO and/or that H2 is released from the initially deposited a-Si:H during the crystallization process. As a result, Zn (a deep acceptor in silicon) is "liberated" close to the silicon/zinc oxide interface presenting the inherent risk of forming deep defects in the silicon absorber. These could act as recombination centers and thus limit the performance of silicon/zinc oxide based solar cells. Based on this insight some recommendations with respect to solar cell design, material selection, and process parameters are given for further knowledge-based thin-film silicon device optimization.

The effect of using laparoscopic instruments on muscle activation patterns during minimally invasive surgical training procedures

BACKGROUND

Many surgeons report pain as a result of muscle fatigue during laparoscopy. Therefore, determining how surgical task or instrument selection influences the duration of muscle activation may provide insight into the relationship between laparoscopic instrumentation and muscle fatigue.

METHODS

Surface electromyography (EMG) electrodes were placed over the right deltoid, trapezius, bicep, pronator teres, flexor carpi ulnaris, and extensor digitorum superficialis muscles of four surgeons. These surgeons were then asked to perform a targeted grasp and release (T1), a simulated bowel inspection (T2), and a cable-tying exercise (T3) while using three different inline finger-looped graspers. The graspers included a nonratcheted handle with a single-action blunt-end effector (G1) and two models that had ratcheted handles with dual-action end effectors (G2, G3). Resting and maximal voluntary contraction EMG values for each muscle were used to normalize the data and to determine percentage of activation during each task. A multivariate analysis of variance (ANOVA) was used to compare EMG relative time of activation (RAT) patterns with grasper, task, and grasper and task interaction.

RESULTS

In general, when grasper and task were considered individually, G1 and T3 demonstrated the highest RAT. Findings showed that RAT was most affected by the use of either G1 or G2 during T2 or T3.

CONCLUSION

Task, grasper, and the interaction between grasper and task all appear to influence the RAT and therefore, to varying degrees, all three may play a role in influencing muscle fatigue.

Quitting cigarette smoking produces minimal loss of chronic tolerance to nicotine

RATIONALE

Long-term exposure to nicotine is associated with chronic tolerance to its acute effects, adaptation that may lead to tobacco dependence. The time course for loss of this tolerance after cessation of exposure is not known in humans but could relate to risk of smoking relapse.

OBJECTIVES

We examined changes in responses to nicotine as a function of days, weeks, or years of smoking cessation in formerly dependent smokers to determine at what point sensitivity to nicotine is reinstated (i.e., loss of tolerance).

METHODS

Acute subjective, cardiovascular, performance, and reinforcing (self-administration) effects of nicotine nasal spray (0-20 microg/kg) were assessed prospectively in men and women smokers before and then day-by-day (study 1) or 3 weeks (study 2) after stopping smoking. A smoking resumption period (study 1) and a group of non-quitting smokers (study 2) were included to control for the passage of time. These effects were also compared cross-sectionally between those who had quit for 1-4 years and those who had for 6-19 years in a separate sample of long-time ex-smokers to determine whether lengthier abstinence causes greater loss of tolerance (study 3).

RESULTS

No clear loss of tolerance was observed on any measure in studies 1 or 2, suggesting that chronic tolerance is fully maintained for at least weeks after quitting smoking. Sensitivity to nicotine's effects was also not different as a function of years quit in study 3.

CONCLUSIONS

Chronic tolerance to nicotine is not lost within several weeks of quitting smoking and may not change even after years of abstinence from tobacco use.

Pyrogenicity and cytokine-inducing properties of Streptococcus pyogenes superantigens: comparative study of streptococcal mitogenic exotoxin Z and pyrogenic exotoxin A

Streptococcal mitogenic exotoxin Z (SMEZ), a superantigen derived from Streptococcus pyogenes, provoked expansion of human lymphocytes expressing the Vbeta 2, 4, 7 and 8 motifs of T-cell receptor. SMEZ was pyrogenic in rabbits and stimulated the expression of the T-cell activation markers CD69 and cutaneous lymphocyte-associated antigen. A variety of cytokines was released by human mononuclear leukocytes stimulated with SMEZ, which was 10-fold more active than streptococcal pyrogenic exotoxin A. Th2-derived cytokines were elicited only by superantigens and not by streptococcal cells.

Sex differences in the subjective and reinforcing effects of visual and olfactory cigarette smoke stimuli

Although nicotine intake clearly reinforces cigarette smoking behavior, non-nicotine smoke stimuli may become conditioned reinforcers of smoking. In Study 1, we compared the acute subjective and reinforcing effects of cigarette smoking in men and women under two conditions: blockade of visual and olfactory/taste smoke stimuli vs. no blockade. Subjective hedonic ratings of 'like puffs' and 'satisfying', but not 'strength', 'high in nicotine', or CO boost, were significantly reduced under the blockade vs. no blockade conditions. During subsequent ad lib puffing, significantly fewer puffs were self-administered under the blockade condition, particularly among women. In Study 2, we examined the influences of these stimuli separately and found that olfactory/taste stimuli, but not visual stimuli, reduced hedonic ratings and puff self-administration in women but not in men. In Study 3, procedures similar to those in Study 1 were used to examine whether this sex difference in responses to conditioned stimuli generalizes to a non-drug consummatory behavior, eating (pizza). However, hedonic ratings and ad lib consumption of pizza were substantially reduced in both men and women following blockade of visual and olfactory/taste food stimuli. These results indicate that the presumably conditioned stimuli of olfactory/taste from cigarette smoke may influence subjective hedonic ratings and reinforcement from smoking more in women than in men. However, this sex difference may not generalize beyond smoking or other drug reinforcement.

Neopterin production and tryptophan degradation in humans infected by Streptococcus pyogenes

Streptococcus pyogenes may cause tonsillitis, scarlet fever and so-called "streptococcal toxic shock-like syndrome" (STSS). These streptococci produce exotoxins which are implicated as superantigens in the pathogenesis of STSS and scarlet fever. Using human peripheral blood-derived mononuclear cells in vitro, such toxins were shown to induce neopterin production and degradation of the amino acid tryptophan to metabolites such as kynurenine by activating indoleamine (2,3)-dioxygenase via interferon-gamma. We investigated the sera of seven patients with streptococcal tonsillitis and of four patients with STSS. Those with STSS showed higher serum neopterin concentrations (median: 152 nmol/l; 95th percentile in healthy controls: 8.7 nmol/l) than those with tonsillitis (median: 12 nmol/l). Similarly, kynurenine to tryptophan ratios were increased in tonsillitis and extremely high in patients with STSS. Highly increased neopterin production and tryptophan degradation in patients with STSS suggest an association between a high degree of T cell activation and the severity of the disease manifestation.

Basic streptococcal superantigens (SPEX/SMEZ or SPEC) are responsible for the mitogenic activity of the so-called mitogenic factor (MF)

The mitogenic factor (MF) of group A streptococci has been reported to be a superantigen stimulating human T cells carrying Vbeta2, 4 and 8 and has been designated streptococcal pyrogenic exotoxin F (SPEF). MF was also shown to possess DNase activity. Here we have purified MF from culture supernatants of different Streptococcus pyogenes strains. Surprisingly, the MF preparations from different strains showed different Vbeta specificities depending on the expression of SPEC or SMEZ3 by the producing strain. Their mitogenic activity decreased upon further purification. In addition, the mitogenic activity could be only neutralized by antibodies against the basic streptococcal superantigens SPEC or SPEX (SMEZ3) but not by antibodies against MF itself although the latter were able to neutralize completely the DNase activity of MF. We found that streptodornase type B (SDB) was expressed in two molecular forms (SDBI and SDBII), differing only by one additional N-terminal arginine at SDBI. MF was found identical to the enzyme SDBII but is devoid of superantigenic properties and should no longer be called a superantigen or a pyrogenic exotoxin.

Virulence of group A streptococci in fertile hens eggs is mainly effected by M protein and streptolysin O

In this study we have investigated whether streptolysin O contributes to the virulence of group A streptococci. For this purpose we generated M-negative and SLO-negative mutants by insertion mutagenesis into the chromosome of an M type 1 strain. The inactivation of M1 protein expression was achieved by the construction of the integrative plasmid pSFABS, which contains the internal fragment abs of the emm1 gene. Integration of pSFABS by homologous recombination into the chromosome of strain 38 541 resulted in the generation of mutant EMM1. Inactivation of slo with plasmid pFWSLOD resulted in two different mutant forms. The homologous recombination with plasmid pFWSLOD carrying the two slo fragments slo1 (899 base pairs in the 5' region) and slo2 (709 base pairs in the downstream part) resulted in mutants SLO3, SLO4 and SLO17. In SLO17 a double crossover event took place with insertion of the spectinomycin resistance gene aad9 between the slo fragments 1 and 2. In mutants SLO3 and SLO4 the homologous recombination with the same plasmid led to the integration of the whole plasmid construct into the chromosome of strain 38 541. Both forms of mutation failed to express SLO. In mutant SLO4 additionally M1 protein expression was significantly decreased. The mutants EMM1 (M-, SLO+) and SLO4 (M decreased, SLO-) showed a reduced binding to collagen-coated surfaces. In contrast the mutants SLO3 and SLO17 (both M+, SLO-) and the wild-type strain 38 541 (M+, SLO+) showed an affinity to collagen similar to purified M1 protein. All mutants were less virulent for chicken embryos compared to the wild-type strain after infection by intravenous injection as well as by application onto the chorioallantoic membrane. The results show that besides M protein SLO can also influence virulence of group A streptococci. Moreover, it became obvious that streptococci need more than one tool to fully develop their infectious potential.

Dissociation of nicotine tolerance from tobacco dependence in humans

Chronic functional tolerance to nicotine generally is believed to be associated with processes responsible for tobacco dependence. The dose-related effects of nicotine (0-20 microg/kg by nasal spray) on subjective, cardiovascular, and performance responses were compared among four groups varying in current or past dependence: dependent smokers (21 cigarettes per day for 20 years; n = 45), nondependent smokers (three cigarettes per day for 14 years; n = 12), former dependent smokers (mean of 7 years quit after smoking 25 cigarettes per day for 19 years; n = 17), and life-long nonsmokers (n = 19). Chronic tolerance was determined by a shift to the right, or flattening, of the dose-response curve relative to the curve for nonsmokers. Responses were corrected for plasma nicotine concentration to rule out dispositional tolerance. Chronic tolerance was observed for most subjective responses, but little or none for cardiovascular and performance effects. Tolerance was substantial and virtually identical between dependent and nondependent smokers, whereas tolerance of former smokers was intermediate between nonsmokers and dependent smokers. Identical chronic tolerance between dependent and nondependent smokers indicates that tolerance is not a linear function of smoking exposure and does not require presence of dependence. Thus, the wide variability in daily smoking rate among smokers cannot be attributed to differences in tolerance and must involve other processes of adaptation to nicotine. The modest reversal of tolerance in long-time former smokers suggests that such tolerance reversal is either limited or extremely slow after extended abstinence, despite loss of dependence. These results suggest there is no close link between nicotine tolerance and dependence and question the utility of tolerance as one of the criteria for defining dependence.

Greater sensitivity to subjective effects of nicotine in nonsmokers high in sensation seeking

The personality characteristic of sensation seeking is associated with risk of smoking, perhaps because of greater initial sensitivity to nicotine. Young healthy nonsmokers (N = 37) were administered 0, 10, and 20 microg/kg nicotine by nasal spray in 3 separate sessions, and subjective responses were assessed. Sensation-Seeking Scale (SSS) scores were then correlated with these responses. A comparison group of smokers (N = 55) was included to determine whether sensation seeking was associated specifically with initial sensitivity to nicotine or with general sensitivity regardless of past nicotine exposure. SSS subscales, particularly Experience Seeking and Disinhibition, were correlated with subjective responses to nicotine in nonsmokers but generally not in smokers. These findings indicate that sensation seeking is associated with greater initial sensitivity to nicotine's subjective effects and may provide directions for further study of individual-differences characteristics that predispose people to the risk of becoming smokers.

The SpeB virulence factor of Streptococcus pyogenes, a multifunctional secreted and cell surface molecule with strepadhesin, laminin-binding and cysteine protease activity

The interactions between pathogenic bacteria and the host need to be resolved at the molecular level in order to develop novel vaccines and drugs. We have previously identified strepadhesin, a novel glycoprotein-binding activity in Streptococcus pyogenes, which is regulated by Mga, a regulator of streptococcal virulence factors. We have now identified the protein responsible for the strepadhesin activity and find that (i) strepadhesin activity is carried by SpeB, streptococcal pyrogenic exotoxin with cysteine protease activity; (ii) SpeB carries laminin-binding activity of the bacteria; and (iii) SpeB is not only a secreted molecule but also occurs unexpectedly tightly bound to the bacterial cell surface. Thus, in contrast to the previous view of SpeB as mainly an extracellular protease, it is also present as a streptococcal surface molecule with binding activity to laminin and other glycoproteins.

The NAD-glycohydrolase (nga) gene of Streptococcus pyogenes

The gene for NAD-glycohydrolase (nga) of group A streptococci (Streptococcus pyogenes) was identified and shown to be located immediately adjacent to the gene for streptolysin O (slo). The nga gene contains 1341 base pairs and encodes a protein of 447 amino acids, including an N-terminal signal peptide. Results from analysis with the polymerase chain reaction indicated that the nga gene is present in all of the strains tested. Functional extracellular NAD-glycohydrolase, also known as NADase, was detected among a wide variety of clinical isolates and known laboratory strains and shown to be present in 72% of 100 strains examined. In contrast, 92% of strains isolated from patients with invasive streptococcal infections were positive for NADase production.

Purification and biochemical characterization of a basic superantigen (SPEX/SMEZ3) from Streptococcus pyogenes

A potent basic superantigen (designated streptococcal pyrogenic exotoxin X, SPEX/SMEZ3) was purified to homogeneity from culture supernatants of a Streptococcus pyogenes scarlatina strain of type 12 (genotype speA(-), speC(-)) and characterized. Sequence alignments revealed SPEX to be an allele of the streptococcal mitogens type Z (SMEZ). The N-terminal amino acid sequence of SPEX was found with LEVDNNSLLR to be identical to the recently described acidic superantigen SMEZ. Although SPEX/SMEZ genes were present in all of the streptococcal strains tested, a toxin production could only be detected in a small number of strains. The produced toxin concentration in the culture supernatants of positive strains differed between 0 and 20 ng ml(-1). The purified SPEX stimulated human T-lymphocytes with Vbeta8 specificity at extremely low concentrations (lower than 100 pg ml(-1)).

Influence of growth conditions on expression of immunoglobulin G binding in group A streptococci

Many group A streptococci (GAS) bind the Fc part of IgG. In the present work, the possible influence of growth time and incubation atmosphere on the expression of the IgG binding activity by GAS of various serotypes was studied. Among 13 GAS reference strains, two categories were distinguished on aerobic incubation at 37 degrees C, one expressing similar IgG binding activity at 6 h and 18 h (types M1, M4, M13, M15), and a second one which showed higher binding at 6 h than at 18 h (M9, M14, M22, M25, M48, M49). Only one strain (M36) bound less IgG at 6 h than at 18 h. Seven of the strains (M5, M6, M22, M25, M36, M48, M49) showed higher binding of IgG when grown in a 5% CO2 atmosphere than in air, whereas one strain (M14) showed a reverse pattern and in the remaining five strains, no influence was found. Protease activity was detected in the growth supernatant of most of the strains. For five selected strains, the time of appearance of supernatant protease activity coincided with a decay of surface IgG binding activity. Purified streptococcal cysteine protease was found to reduce or abolish the binding of IgG by each of three studied strains (M1, M13 and M15) and of type M1 or M15 purified IgG binding material. When tested in the stationary phase, a majority of 62 clinical GAS isolates belonging to 6 different M types showed high protease activity but low binding of IgG. We conclude that streptococcal IgG binding is often better expressed on growth in 5% CO2 atmosphere than in air. Furthermore, due to its sensitivity to streptococcal protease, the IgG binding activity is mostly higher during the logarithmic than during the stationary phase of growth.

Extracellular superoxide dismutase from Streptococcus pyogenes type 12 strain is manganese-dependent

Highly purified extracellular superoxide dismutase was obtained from Streptococcus pyogenes strain 12,714 (type 12) by adsorption of culture supernatant on phenyl-Sepharose following preparative isoelectric focusing of eluates and a final gel filtration purification on Superdex 200. The purified superoxide dismutase of S. pyogenes was found to be a homodimer. The monomeric protein had a molecular mass of 22,442 Da and an isoelectric point of 4.0. The enzymatic activity was strongly manganese-dependent. The N-terminal sequence of the purified mature protein was AIILPELPYAYDALEPQUFDA and corresponded to the first amino acids following the methionine initiation codon with no evidence of a leader sequence for the mature protein. The DNA sequence of the superoxide dismutase gene of strain 12,714 was found to be almost identical to the corresponding sequences reported in the gene bank data from other S. pyogenes serotypes and showed strong homology to superoxide dismutases from other Gram-positive bacteria.

Streptococcal erythrogenic toxins induce tryptophan degradation in human peripheral blood mononuclear cells

BACKGROUND

In various cells including monocytes the cytokine interferon-gamma as well as lipopolysaccharide induce indoleamine 2,3-dioxygenase which degrades tryptophan to form L-kynurenine. We addressed the question of whether the exposure of human peripheral mononuclear cells to superantigens derived from streptococci is associated with tryptophan degradation in vitro.

METHODS

Peripheral blood mononuclear cells were exposed to streptococcal erythrogenic toxins A and B and a streptococcal-derived mitogen named BX. In addition, the myelomonocytic cell line THP-1 was treated with these toxin preparations.

RESULTS

In peripheral blood mononuclear cells all three toxins induced tryptophan degradation. In parallel, production of interferon-gamma was found, and the tryptophan degradation could be blocked by antihuman interferon-gamma antibodies. Tryptophan degradation was not induced when the human myelocytoma cell line THP-1 was stimulated with these toxins, but there was a costimulatoty effect to interferon-gamma.

CONCLUSIONS

In peripheral blood mononuclear cell culture streptococcal erythrogenic toxins are able to stimulate tryptophan degradation in humans via the induction of interferon-gamma production. There seems to be no direct effect on myelomonocytic THP-1 cells. Because some of the degradation products of tryptophan, such as quinolinic acid and kynurenic acid, are toxic, superantigen-driven degradation oftryptophan may play a role for example in the development of the toxic-shock-like syndrome associated with severe group A streptococcal infections.

Exclusion of bioactive contaminations in Streptococcus pyogenes erythrogenic toxin A preparations by recombinant expression in Escherichia coli

The streptococcal erythrogenic exotoxin A (SPEA) belongs to the family of bacterial superantigens and has been implicated in the pathogenesis of a toxic shock-like syndrome and scarlet fever. Concerning its biological activity, mainly T-cell-stimulatory properties, conflicting data exist. In this study, we show that most of the SPEA preparations used so far contain biologically active contaminations. Natural SPEA from the culture supernatant of Streptococcus pyogenes NY-5 and recombinant SPEA purified from the culture filtrate of S. sanguis are strongly contaminated with DNases. We show that natural SPEA induces more tumor necrosis factor alpha (TNF-alpha) than recombinant SPEA, but we also show that DNases are able to induce TNF-alpha. In commercial SPEA preparations, we identified a highly active protease, which was shown not to be SPEB. To exclude these contaminations, we overexpressed SPEA cloned in the effective high-level expression vector pIN-III-ompA2 in Escherichia coli. The expressed SPEA shows the same amino acid composition as natural SPEA, whereas functional studies reported so far were carried out with toxins containing an incorrect amino terminus. We describe the rapid purification of lipopolysaccharide-, DNase-, and protease-free SPEA in two steps from the host's periplasm and its structural characterization by circular dichroism. Our results represent for the first time the production in E. coli of recombinant SPEA with the authentic N-terminal sequence and a proven superantigenic activity. Collectively, our results indicate that immunological studies of superantigens require highly purified substances free of biologically active contaminations.

Streptococcal pyrogenic exotoxin A (SPE A) superantigen induced production of hematopoietic cytokines, IL-12 and IL-13 by human peripheral blood mononuclear cells

A quantitative and kinetic study of the release of the hematopoietic cytokines IL-3, IL-5 and GM-CSF, the immunoregulatory cytokine IL-12 heterodimer (and its p40 subunit) and IL-13 by human peripheral blood mononuclear cells (PBMC) stimulated in vitro with the superantigen streptococcal pyrogenic (erythrogenic) exotoxin A (SPE A) from Streptococcus pyogenes is reported. PBMC were stimulated in parallel with heat-killed group A streptococcal cells, E. coli lipopolysaccharide (LPS) and with concanavalin A (Con A) in certain experiments for comparative purposes. The cytokines were assayed in the supernatant fluids by ELISA. IL-13 expression was also determined by a quantitative competitive PCR. IL-3, IL-5, GM-CSF, IL-12 p40, IL-12 heterodimer and IL-13 expression was induced by SPE A in a time- and dose-dependent manner in rather substantial amounts except the IL-12 heterodimer, which was released in small quantities. In contrast to SPE A, IL-3, IL-5 and IL-13 were not or poorly elicited by streptococcal cells or LPS whereas these two stimulants induced relatively high amounts of GM-CSF. Interestingly, both IL-12 p40 and IL-12 heterodimer were released in much higher amounts by streptococcal cells. Con A induced IL-3, IL-5, GM-CSF and IL-13 production in amounts comparable to those elicited by SPE A. The possible pathophysiological relevance of the elicitation by SPE A and streptococcal cells of these cytokines is discussed.

Conformation and stability of streptokinases from nephritogenic and nonnephritogenic strains of streptococci

Conformation and stability of three Sks from Streptococcus equisimilis strain H46A, Streptococcus pyogenes strain A374, and Streptococcus pyogenes strain AT27 were compared by limited proteolysis, CD, and fluorescence measurements and by DSC. The general similarity of the peptide CD spectra in the spectral region 185 to 260 nm indicates the same type of folding for the three proteins. Fluorescence and aromatic CD spectra are consistent with a predominant surface localization of the aromatic amino acids and a low rigidity of their surroundings. A major difference among the three Sks is shown by deconvolution of their excessive heat capacity functions. Deconvolution reveals two energetic folding units in Sk H46A but three energetic folding units in Sk A374 and Sk AT27. Digestion of the Sks with trypsin indicates a reduced sensitivity of the C-terminal region of Sk A374 and Sk AT27 in comparison to Sk H46A. This suggests that amino acids of the C-terminal region participate in the formation of the third folding unit of Sk A374 and Sk AT27.

Firearm fatalities and injuries from hunting accidents in Germany

Accidental hunting firearm injuries and fatalities (257 cases from 1961 to 1992) were evaluated in detail. Most persons responsible for the accident were more than 40 years old and experienced in hunting, and 26% of the gunshot wounds were fatal. In 77% of cases the victim was shot by another person and in 23% the wound was self-inflicted. The firearms/ammunition used were pellets from shotguns (63%), bullets from rifles (31%), shotgun slugs (3.5%) and bullets from handguns (2.5%). In 22% of all accidents from pellets severe eyeball injuries were involved, and 38% of the wounds were caused from a distance of 5 m or less, including all self-inflicted injuries. The most frequent factors responsible for the accident were: improper handling of the firearm (37%), failure to notice the victim (24.1%), covering the victim while swinging on the game (14.8%), ricocheting projectiles (13.6%), inadequate storage of the firearm (11.7%) and mistaking the victim for game (9.3%). In some cases more than one factor contributed to the accident. Defective firearm/ammunition, as the only non-human factor, was involved in only 1.6% of accidents. Some aspects of the prevention and the forensic investigation of hunting accidents are discussed.

Streptococcal erythrogenic toxins induce neopterin formation in human peripheral blood mononuclear cells but not in the human myelomonocytoma cell line THP-1

We tested whether the exposure of human monocytic cells to streptococcal erythrogenic toxins A, B, C and a streptococcal-derived Mitogert BX is associated with synthesis of neopterin in vitro. Neopterin production was not induced when the human myelomono-cytoma cell line THP-1 was stimulated with these toxins, and there was only a slight co-stimulatory effect of streptococcal erythrogenic toxin A together with interferon-gamma stimulation. However, these toxins induced interferon-gamma and further neopterin production in peripheral blood mononuclear cells of three healthy individuals. This neopterin formation could be blocked by anti-human interferon-gamma. From our investigations we conclude that there is no direct effect of streptococcal erythrogenic toxins on neopterin production by monocytic cells. However, the data obtained in peripheral blood mononuclear cell culture imply that these toxins are able to stimulate neopterin production in humans via the induction of huge amounts of interferon-gamma.

Human pro- and anti-inflammatory cytokine patterns induced by Streptococcus pyogenes erythrogenic (pyrogenic) exotoxin A and C superantigens

The superantigenic streptococcal erythrogenic toxins A and C (ETA/SPEA and ETC/SPEC) elicit the production by human peripheral blood mononuclear cells of substantial amounts of Th1-derived cytokines (interleukin-2 [IL-2] and gamma interferon) as well as anti-inflammatory cytokines (IL-10 and IL-1 receptor antagonist). In contrast, very low levels of IL-4 and no alpha interferon were induced. The production of these cytokines after stimulation with Streptococcus pyogenes heat-killed bacteria and lipopolysaccharide from gram negative bacteria differed qualitatively and quantitatively from that elicited by the superantigens.

Purification and some properties of streptococcal NAD-glycohydrolase

NAD-glycohydrolase (NADase) was purified from culture supernatant fluids of group C streptococci by adsorption on silica gel, chromatography on hydroxyapatite and ion exchange on Mono S column. After inactivation of a chymotrypsin-like protease, a homogeneous enzyme was isolated with an N-terminal sequence of VSGKEGKKSDVKYEMTKVMEANATSSKEDKHVMHTLDKVM. According to serological methods, the purified enzyme of group C streptococci was identical to the group A enzyme showing a specific activity of 10 000 000 U mg-1. It did not attack NADH, NADP or NADPH. In addition, a streptodornase was isolated having an N-terminal sequence of KTVSVNQTYGE.

Mitogenicity of M5 protein extracted from Streptococcus pyogenes cells is due to streptococcal pyrogenic exotoxin C and mitogenic factor MF

M proteins of Streptococcus pyogenes are virulence factors which impede phagocytosis, bind to many plasma proteins, and induce formation of cross-reactive autoimmune antibodies. Recently, it has been reported that some M proteins, extracted with pepsin from streptococci (pep M), are superantigens. One of these, pep M5, was investigated in detail and was shown to stimulate human T cells bearing V beta 2, V beta 4, and V beta 8. In the present study, we extracted and purified M5 protein by different biochemical methods from two M type 5 group A streptococcal strains. The crude extracts were fractionated by affinity chromatography and ion-exchange chromatography. All fractions were tested in parallel for M protein by immunoblotting and for T-cell-stimulating activity. Although several crude preparations of M5 protein were associated with mitogenicity for V beta 2 and V beta 8 T cells, the M5 proteins, irrespective of the extraction method, could be purified to the extent that they were no longer mitogenic. The mitogenic activity was not destroyed during the purification procedures but was found in fractions separated from M protein. In these fractions, streptococcal pyrogenic exotoxin C and mitogenic factor MF could be detected by protein blotting and enzyme-linked immunosorbent assay. Moreover, anti-M protein sera did not inhibit the mitogenic activity of crude extracts, but antisera which contained anti-streptococcal pyrogenic exotoxin C antibodies showed inhibition. The inability of M5 protein to stimulate T cells was confirmed with recombinant pep M5 produced in Escherichia coli. Our data strongly suggest that the mitogenic activity in M protein preparations is caused by traces of streptococcal superantigens different from M protein.

Sister chromatid exchange-inducing DNA lesions and depression of activation markers on the surface of cultured peripheral blood mononuclear cells after the addition of streptococcal pyrogenic exotoxins A and C

Cultivation of peripheral blood mononuclear cells (PBMC) in the presence of streptococcal pyrogenic exotoxins (SPE) A and C resulted in a significant induction of sister chromatid exchange (SCE)-inducing DNA lesions. Concomitantly, the expression of interleukin-2 receptor alpha chain (IL-2R alpha chain), transferrin receptor (TfR), and major histocompatibility complex class II molecule HLA-DR on the surface of phytohemagglutinin-activated T cells from whole blood culture cells (WBCC) significantly decreased within 72 h, that is at least two cell cycles, whereas unstimulated T cells from WBCC did not express these markers but had lost their CD3 molecules, an effect reported to precede apoptosis as part of a T cell inactivation pathway. However, no apoptotic cells were observed within a cultivation period of 120 h. We observed clearcut differences in the responses towards SPE A in WBCC and isolated lymphocytes, since SPE A-treated lymphocytes showed an increase in the [3H]thymidine incorporation and did express IL-2R alpha chain and TfR on their cell surface. Regardless of the precise underlying mechanism, T cells from WBCC seem to be in a state of functional incompetence. The data presented here are the first to provide strong evidence that streptococcal toxins produce SCE-inducing DNA lesions in PBMC, an effect that might contribute to the process of immune cell lethality in streptococcal toxic shock-like syndrome and could be of pivotal importance in the pathogenesis of severe streptococcal disease.