We compared the reactivity and microbial reduction potential of Fe(III) minerals in the rhizosphere and non-rhizosphere soil to test the hypothesis that rapid Fe(III) reduction rates in wetland soils ...are explained by rhizosphere processes. The rhizosphere was defined as the area immediately adjacent to a root encrusted with Fe(III)-oxides or
Fe plaque, and non-rhizosphere soil was >0.5 cm from the root surface. The rhizosphere had a significantly higher percentage of poorly crystalline Fe (66
±
7%) than non-rhizosphere soil (23
±
7%); conversely, non-rhizosphere soil had a significantly higher proportion of crystalline Fe (50
±
7%) than the rhizosphere (18
±
7%,
P<0.05 in all cases). The percentage of poorly crystalline Fe(III) was significantly correlated with the percentage of FeRB (
r=0.76), reflecting the fact that poorly crystalline Fe(III) minerals are labile with respect to microbial reduction. Abiotic reductive dissolution consumed about 75% of the rhizosphere Fe(III)-oxide pool in 4 h compared to 23% of the soil Fe(III)-oxide pool. Similarly, microbial reduction consumed 75–80% of the rhizosphere pool in 10 days compared to 30–40% of the non-rhizosphere soil pool. Differences between the two pools persisted when samples were amended with an electron-shuttling compound (AQDS), an Fe(III)-reducing bacterium (
Geobacter metallireducens), and organic carbon. Thus, Fe(III)-oxide mineralogy contributed strongly to differences in the Fe(III) reduction potential of the two pools. Higher amounts of poorly crystalline Fe(III) and possibly humic substances, and a higher Fe(III) reduction potential in the rhizosphere compared to the non-rhizosphere soil, suggested the rhizosphere is a site of unusually active microbial Fe cycling. The results were consistent with previous speculation that rapid Fe cycling in wetlands is due to the activity of wetland plant roots.
To determine the prevalance, associated biometric factors, and rate of disappearance of neonatal retinal hemorrhage.
Cross-sectional and natural history study.
Healthy newborns (n = 149) at an urban ...hospital were examined using indirect ophthalmoscopy within 30 hours of birth. Newborns with retinal hemorrhage were reexamined biweekly until hemorrhage resolved.
Neonatal and maternal biometric factors, and incidence and rate of resolution of retinal hemorrhage.
Intraretinal hemorrhage was present in 34% of newborns and varied from a single dot hemorrhage in one eye to bilateral widespread hemorrhages, occasionally with white centers. The incidence of hemorrhage was higher for vacuum-assisted (75%) than for spontaneous vaginal deliveries (33%) and was least for infants delivered by cesarean section (7%). The mean maternal age was greater for infants with retinal hemorrhage. By 2 weeks after birth, retinal hemorrhage resolved in 86% of eyes, and at 4 weeks no intraretinal hemorrhage was detected, although a single subretinal hemorrhage persisted until 6 weeks after birth.
Intraretinal hemorrhages are common in the immediate postnatal period and resolve by 1 month of age. Retinal hemorrhage in infants older than 1 month should heighten suspicion that the hemorrhage is associated with factors other than birth.
Abstract
We report on the discovery of a fourth component in the HD 221356 star system, previously known to be formed by an F8V, a slightly metal poor primary (Fe/H = −0.26), and a distant M8V+L3V ...pair. In our ongoing common proper motion search based on Visible and Infrared Survey Telescope for Astronomy (VISTA) Hemisphere Survey (VHS) and Two Micron All Sky Survey (2MASS) catalogues, we have detected a faint J = 13.76 ± 0.04 mag comoving companion of the F8 star located at angular separation of 12.13 ± 0.18 arcsec (position angle of 221°.8 ± 1°.7), corresponding to a projected distance of ∼317 au at 26 pc. Near-infrared spectroscopy of the new companion, covering the 1.5-2.4 μm wavelength range with a resolving power of R ∼ 600, indicates an L1 ± 1 spectral type. Using evolutionary models the mass of the new companion is estimated at ∼0.08 M⊙, which places the object close to the stellar-substellar borderline. This multiple system provides an interesting example of objects with masses slightly above and below the hydrogen-burning mass limit. The low-mass companions of HD 221356 have slightly bluer colours than field dwarfs with similar spectral type, which is likely a consequence of the subsolar metallicity of the system.
General knowledge of dioxygen-activating mononuclear non-heme iron(II) enzymes containing a 2-His-1-carboxylate facial triad has significantly expanded in the last few years, due in large part to the ...extensive library of crystal structures that is now available. The common structural motif utilized by this enzyme superfamily acts as a platform upon which a wide assortment of substrate transformations are catalyzed. The facial triad binds a divalent metal ion at the active site, which leaves the opposite face of the octahedron available to coordinate a variety of exogenous ligands. The binding of substrate activates the metal center for attack by dioxygen, which is subsequently converted to a high-valent iron intermediate, a formidable oxidizing species. Herein, we summarize crystallographic and mechanistic features of this metalloenzyme superfamily, which has enabled the proposal of a common but flexible pathway for dioxygen activation.
The VMC Survey Cioni, M-R L; Kamath, D; Rubele, S ...
Astronomy and astrophysics (Berlin),
01/2013, Letnik:
549
Journal Article
Recenzirano
The number and spatial distribution of confirmed quasi-stellar objects (QSOs) behind the Magellanic system is limited. This undermines their use as astrometric reference objects for different types ...of studies. We have searched for criteria to identify candidate QSOs using observations from the VISTA survey of the Magellanic Clouds system (VMC) that provides photometry in the YJKsubs bands and 12 epochs in the Ksubs band. By extrapolating the number of QSO candidates to the entire VMC survey area we expect to find about 1200 QSOs behind the LMC, 400 behind the SMC, 200 behind the Bridge and 30 behind the Stream areas, but not all will be suitable for astrometry. Further, the Ksubs, band light-curves can help support investigations of the mechanism responsible for the variations.
Objective To investigate whether real-time audio and visual feedback during cardiopulmonary resuscitation outside hospital increases the proportion of subjects who achieved prehospital return of ...spontaneous circulation.Design A cluster-randomised trial.Subjects 1586 people having cardiac arrest outside hospital in whom resuscitation was attempted by emergency medical services (771 procedures without feedback, 815 with feedback).Setting Emergency medical services from three sites within the Resuscitation Outcomes Consortium in the United States and Canada.Intervention Real-time audio and visual feedback on cardiopulmonary resuscitation (CPR) provided by the monitor-defibrillator.Main outcome measure Prehospital return of spontaneous circulation after CPR.Results Baseline patient and emergency medical service characteristics did not differ between groups. Emergency medical services muted the audible feedback in 14% of cases during the period with feedback. Compared with CPR clusters lacking feedback, clusters assigned to feedback were associated with increased proportion of time in which chest compressions were provided (64% v 66%, cluster-adjusted difference 1.9 (95% CI 0.4 to 3.4)), increased compression depth (38 v 40 mm, adjusted difference 1.6 (0.5 to 2.7)), and decreased proportion of compressions with incomplete release (15% v 10%, adjusted difference −3.4 (−5.2 to −1.5)). However, frequency of prehospital return of spontaneous circulation did not differ according to feedback status (45% v 44%, adjusted difference 0.1% (−4.4% to 4.6%)), nor did the presence of a pulse at hospital arrival (32% v 32%, adjusted difference −0.8 (−4.9 to 3.4)), survival to discharge (12% v 11%, adjusted difference −1.5 (−3.9 to 0.9)), or awake at hospital discharge (10% v 10%, adjusted difference −0.2 (−2.5 to 2.1)).Conclusions Real-time visual and audible feedback during CPR altered performance to more closely conform with guidelines. However, these changes in CPR performance were not associated with improvements in return of spontaneous circulation or other clinical outcomes.Trial Registration Clinical Trials NCT00539539
Iron (III) plaque forms on the roots of wetland plants from the reaction of Fe(II) with O2 released by roots. Recent laboratory studies have shown that Fe plaque is more rapidly reduced than ...non-rhizosphere Fe(III) oxides. The goals of the current study were to determine in situ rates of: (i) Fe(III) reduction of root plaque and soil Fe(III) oxides, (ii) root Fe(III) deposition, and (iii) root and soil organic matter decomposition. Iron (III) reduction was investigated using a novel buried-bag technique in which roots and soil were buried in heat-sealed membrane bags (Versapor 200 membrane, pore size = 0.2 micrometer) in late fall following plant senescence. Bags were retrieved at monthly intervals for 1 yr to assess changes in total C and Fe mass, Fe mineralogy, Fe(II)/Fe(III) ratio, and the abundances of Fe(II)-oxidizing bacteria (FeOB) and Fe(III)-reducing bacteria (FeRB). The soil C and Fe pools did not change significantly throughout the year, but root C and total root Fe mass decreased by 40 and 70%, respectively. When total Fe losses were adjusted for changes in the ratio of Fe(II)/Fe(III), over 95% of the Fe(III) in the plaque was reduced during the 12-mo study, at a peak rate of 0.6 mg Fe(III) g dry weight(-1) d(-1) (gdw(-1) d(-1)). These estimates exceed the crude estimate of Fe(III) accumulation 0.3 mg Fe(III) g dry weight(-1) d(-1) on bare-root plants that were transplanted into the wetland for a growing season. We concluded that root plaque has the potential to be reduced as rapidly as it is deposited under field conditions.
Hepatitis C virus (HCV) is an important cause of chronic liver disease worldwide. Development of vaccines to prevent HCV infection, or at least prevent progression to chronicity, is a major goal. In ...mice and rhesus macaques, a DNA vaccine encoding cell-surface HCV–envelope 2 (E2) glycoprotein stimulated stronger immune responses than a vaccine encoding intracellular E2. Therefore, we used DNA encoding surface-expressed E2 to immunize chimpanzees 2768 and 3001. Chimpanzee 3001 developed anti-E2 after the second immunization and antibodies to hypervariable region 1 (HVR1) after the third immunization. Although chimpanzee 2768 had only low levels of anti-E2 after the third immunization, an anamnestic response occurred after HCV challenge. CTL responses to E2 were not detected before challenge, but a strong response was detected after HCV challenge in chimpanzee 2768. An E2-specific CD4+ response was detected in chimpanzee 2768 before challenge and in both chimpanzees postchallenge. Three weeks after the last immunization, animals were challenged with 100 50% chimpanzee-infectious doses (CID50 ) of homologous monoclonal HCV. As a control, a naive chimpanzee was inoculated with 3 CID50 of the challenge virus. The vaccine did not generate sterilizing immunity because both vaccinated chimpanzees were infected. However, both vaccinated chimpanzees resolved the infection early whereas the control animal became chronically infected. Compared with the control animal, hepatitis appeared earlier in the course of the infection in both vaccinated chimpanzees. Therefore, DNA vaccine encoding cell surface–expressed E2 did not elicit sterilizing immunity in chimpanzees against challenge with a monoclonal homologous virus, but did appear to modify the infection and might have prevented progression to chronicity.
(Hepatology 2000;32:618-625.)
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