SPIN-MIMS simplifying the SPIN-MAS instrumentation for online measurement of 15N-abundances of ammonium, nitrite and nitrate in aqueous solutions

Common methods for measuring selectively the 15N abundances in individual N-species such as NH4+, NO2- and NO3- in samples with multiple N-species are laborious and time consuming. The SPIN-MAS technique (Stange et al. 2007) offers an automated, rapid and selective determination of 15N abundances in NH4+, NO2- and NO3- in aqueous samples. During a SPIN-MAS measurement one of three different reaction solutions is mixed with the aqueous sample in a Sample Preparation unit for Inorganic N-species (SPIN). The reaction solution is chosen in dependence on the N-species of interest. The gaseous reaction products (N2 or NO) are then conducted to a quadrupole mass spectrometer (MAS) in a helium stream. This measurement technique is not commonly used due to its complex instrumentation. The instrumentation can be significantly simplified by the use of a membrane inlet mass spectrometer (MIMS). The presented SPIN-MIMS approach relies on the use of a reaction capillary in which the sample containing the N-species of interest is mixed with the corresponding reaction solution. The mixture of reaction solution and sample is pumped from the reaction capillary directly to the membrane inlet of the mass spectrometer. The reaction products (N2 or NO) formed during the reaction of NH4+, NO2- and NO3- with the reaction solutions are passed through the gas-permeable membrane of the inlet directly into the ion source of the mass spectrometer. 15N standards with different at% 15N (NH4+, NO2- and NO3- respectively in dist. Water) were used to assess the performance of the system. Overall, SPIN-MIMS measurements showed a good agreement between measured and expected 15N abundances (range 0.36 – 10 at% 15N deviations: <0.5 at% 15N for NH4+-, <0.23 for NO2-- and <0.15 at% 15N for NO3-- standards)

Vaginal hydrolytic enzymes, immunoglobulin A against Gardnerella vaginalis toxin, and risk of early preterm birth among women in preterm labor with bacterial vaginosis or intermediate flora

Objective: The purpose of this study was to determine whether the microbial hydrolytic enzymes, sialidase and prolidase, and immunoglobulin A against the Gardnerella vaginalis cytolysin (anti-Gvh IgA) increase the risk for early preterm birth ( 6434 weeks of gestation) among women with bacterial vaginosis or intermediate flora. Study Design: Two hundred eighteen afebrile women in preterm labor with intact membranes had a vaginal Gram stain performed, and sialidase, prolidase, and anti-Gvh IgA concentrations were determined. Results: Women with bacterial vaginosis or intermediate flora had significantly higher sialidase and prolidase concentrations than women with normal flora. Among women with bacterial vaginosis or intermediate flora, the women with sialidase had a higher rate of early preterm birth (P =.05). Sialidase had a sensitivity of 43% and specificity of 77% for early preterm birth. Prolidase and anti-Gvh IgA did not predict early preterm birth. Conclusion: Women in preterm labor with bacterial vaginosis or intermediate flora and detectable sialidase are at increased risk of early preterm birth

In vaginal fluid, bacteria associated with bacterial vaginosis can be suppressed with lactic acid but not hydrogen peroxide

<p>Abstract</p> <p>Background</p> <p>Hydrogen peroxide (H₂O₂) produced by vaginal lactobacilli is generally believed to protect against bacteria associated with bacterial vaginosis (BV), and strains of lactobacilli that can produce H₂O₂are being developed as vaginal probiotics. However, evidence that led to this belief was based in part on non-physiological conditions, antioxidant-free aerobic conditions selected to maximize both production and microbicidal activity of H₂O₂. Here we used conditions more like those <it>in vivo </it>to compare the effects of physiologically plausible concentrations of H₂O₂and lactic acid on a broad range of BV-associated bacteria and vaginal lactobacilli.</p> <p>Methods</p> <p>Anaerobic cultures of seventeen species of BV-associated bacteria and four species of vaginal lactobacilli were exposed to H₂O₂, lactic acid, or acetic acid at pH 7.0 and pH 4.5. After two hours, the remaining viable bacteria were enumerated by growth on agar media plates. The effect of vaginal fluid (VF) on the microbicidal activities of H₂O₂and lactic acid was also measured.</p> <p>Results</p> <p>Physiological concentrations of H₂O₂(< 100 μM) failed to inactivate any of the BV-associated bacteria tested, even in the presence of human myeloperoxidase (MPO) that increases the microbicidal activity of H₂O₂. At 10 mM, H₂O₂inactivated all four species of vaginal lactobacilli but only one of seventeen species of BV-associated bacteria. Moreover, the addition of just 1% vaginal fluid (VF) blocked the microbicidal activity of 1 M H₂O₂. In contrast, lactic acid at physiological concentrations (55-111 mM) and pH (4.5) inactivated all the BV-associated bacteria tested, and had no detectable effect on the vaginal lactobacilli. Also, the addition of 10% VF did not block the microbicidal activity of lactic acid.</p> <p>Conclusions</p> <p>Under optimal, anaerobic growth conditions, physiological concentrations of lactic acid inactivated BV-associated bacteria without affecting vaginal lactobacilli, whereas physiological concentrations of H₂O₂produced no detectable inactivation of either BV-associated bacteria or vaginal lactobacilli. Moreover, at very high concentrations, H₂O₂was more toxic to vaginal lactobacilli than to BV-associated bacteria. On the basis of these <it>in vitro </it>observations, we conclude that lactic acid, not H₂O₂, is likely to suppress BV-associated bacteria <it>in vivo</it>.</p

Longitudinal Study of the Dynamics of Vaginal Microflora during Two Consecutive Menstrual Cycles

Although the vaginal microflora (VMF) has been well studied, information on the fluctuation of the different bacterial species throughout the menstrual cycle and the information on events preceding the presence of disturbed VMF is still very limited. Documenting the dynamics of the VMF during the menstrual cycle might provide better insights. In this study, we assessed the presence of different Lactobacillus species in relation to the BV associated species during the menstrual cycle, assessed the influence of the menstrual cycle on the different categories of vaginal microflora and assessed possible causes, such as menstruation and sexual intercourse, of VMF disturbance. To our knowledge, this is the first longitudinal study in which swabs and Gram stains were available for each day of two consecutive menstrual cycles, whereby 8 grades of VMF were distinguished by Gram stain analysis, and whereby the swabs were cultured every 7(th) day and identification of the bacterial isolates was carried out with a molecular technique.status: publishe

The Structure of Spatial Localization

Material objects, such as tables and chairs, have an intimate relationship with space. They have to be somewhere. They must possess an address at which they are found. Under this aspect, they are in good company. Events, too, such as Caesar’s death and John’s buttering of the toast, and more elusive entities, such as the surface of the table, have an address, difficult as it may be to specify. A stronger notion presents itself, though. Some entities may not only be located at an address; they may also own (as it were) the place at which they are located, so as to exclude other entities from being located at the same address. Thus, for certain kinds of entities, no two tokens of the same kind can be located at the same place at the same time. This is typically the case with material objects. Likewise, no two particularized properties of the same level or degree of determinacy can be located at the same place at the same time (although particularized properties of different degree, such as the red of this table and the color of this table, can). Other entities seem to evade the restriction. Two events can be perfectly co-located without competing for their address. Or, to use a different terminology, events do not occupy the spatial region at which they are located, and can therefore share it with other events. The rotation of the Earth and the cooling down of the Earth take place at exactly the same regio