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Selected AbstractsThe active methanotrophic community in hydromorphic soils changes in response to changing methane concentrationENVIRONMENTAL MICROBIOLOGY, Issue 2 2006Claudia Knief Summary Methanotrophic communities were studied in several periodically water-saturated gleyic soils. When sampled, each soil had an oxic upper layer and consumed methane from the atmosphere (at 1.75 ppmv). In most gleyic soils the Km(app) values for methane were between 70 and 800 ppmv. These are higher than most values observed in dry upland soils, but lower than those measured in wetlands. Based on cultivation-independent retrieval of the pmoA -gene and quantification of partial pmoA gene sequences, type II (Alphaproteobacteria) methanotrophs of the genus Methylocystis spp. were abundant (> 107pmoA target molecules per gram of dry soil). Type I (Gammaproteobacteria) methanotrophs related to the genera Methylobacter and Methylocaldum/Methylococcus were detected in some soils. Six pmoA sequence types not closely related to sequences from cultivated methanotrophs were detected as well, indicating that diverse uncultivated methanotrophs were present. Three Gleysols were incubated under different mixing ratios of 13C-labelled methane to examine 13C incorporation into phospholipid fatty acids (PLFAs). Phospholipid fatty acids typical of type II methanotrophs, 16:0 and 18:1,7c, were labelled with 13C in all soils after incubation under an atmosphere containing 30 ppmv of methane. Incubation under 500 ppmv of methane resulted in labelling of additional PLFAs besides 16:0 and 18:1,7c, suggesting that the composition of the active methanotrophic community changed in response to increased methane supply. In two soils, 16:1 PLFAs typical of type I methanotrophs were strongly labelled after incubation under the high methane mixing ratio only. Type II methanotrophs are most likely responsible for atmospheric methane uptake in these soils, while type I methanotrophs become active when methane is produced in the soil. [source] Effects of PTH and Alendronate on Type I Collagen Isomerization in Postmenopausal Women With Osteoporosis: The PaTH Study,,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 9 2008Patrick Garnero Abstract Fracture efficacy of PTH and alendronate (ALN) is only partly explained by changes in BMD, and bone collagen properties have been suggested to play a role. We analyzed the effects of PTH(1,84) and ALN on urinary ,,/,, CTX ratio, a marker of type I collagen isomerization and maturation in postmenopausal women with osteoporosis. In the first year of the previously published PaTH study, postmenopausal women with osteoporosis were assigned to PTH(1,84) (100 ,g/d; n = 119), ALN (10 mg/d; n = 60), or PTH and ALN together (n = 59). We analyzed patients on ALN alone (n = 60) and a similar number of patients assigned to PTH alone (n = 63). During the second year, women on PTH in the first year were reallocated to placebo (n = 31) or ALN (n = 32) and women with ALN continued on ALN. During the first year, there was no significant change in ,,/,, CTX ratio with PTH or ALN. At 24 mo, there was a marked increase of the ,,/,, CTX ratio in women who had received PTH during the first year, followed by a second year of placebo (median: +45.5, p < 0.001) or ALN (+55.2%, p < 0.001). Conversely, the ,,/,, CTX ratio only slightly increased (+16%, p < 0.05) after 2 yr of continued ALN. In conclusion, treatment with PTH(1,84) for 1 yr followed by 1 yr of placebo or ALN may be associated with decreased type I collagen isomerization. The influence of these biochemical changes of type I collagen on bone fracture resistance remains to be studied. [source] External cephalic version induced fetal cerebral and umbilical blood flow changes are related to the amount of pressure exertedBJOG : AN INTERNATIONAL JOURNAL OF OBSTETRICS & GYNAECOLOGY, Issue 5 2004Tak Yeung Leung Objective To correlate the applied pressure during external cephalic version with the changes in fetal middle cerebral arterial and umbilical arterial flow before and after the procedure. Design A prospective observational study over a two-year period. Setting External cephalic version was performed in a university hospital. Population Sixty-nine women with singleton breech-presenting pregnancy at or above 36 weeks of gestation undergoing external cephalic version. Methods During external cephalic version, the operator wore a pair of pressure-sensing gloves which had thin piezo-resistive sensors positioned on the palmar surface. During each version procedure, real-time pressure readings were recorded from all sensors, and then analysed with a computer program. The amount of pressure applied over time was presented by pressure,time integral. The pulsatility indices of both fetal middle cerebral artery and umbilical artery before and after external cephalic version were measured. The changes of pulsatility indices of both middle cerebral artery and umbilical artery were presented as a ratio of the post-external cephalic version pulsatility indices to pre-external cephalic version pulsatility indices, denoted by middle cerebral artery pulsatility index ratio and umbilical artery pulsatility index ratio, respectively. The statistical correlation between pressure,time integral and middle cerebral artery pulsatility index ratio and umbilical artery pulsatility index ratio are analysed using Pearson's correlation test. Main outcome measures Changes in pulsatility indices of fetal middle cerebral and umbilical arteries and fetal heart rate after external cephalic version. Results The overall success rate of external cephalic version was 77%. There was a significant negative correlation between pressure,time integral and both middle cerebral artery pulsatility index ratio (P= 0.001) and umbilical artery pulsatility index ratio (P= 0.012). When women were categorised according to placental site, pressure,time integral was negatively correlated with middle cerebral artery pulsatility index ratio only when the placenta was posteriorly located (P= 0.003), and with umbilical artery pulsatility index ratio only when the placenta was laterally located (P= 0.03). Conclusions The greater the force applied during external cephalic version, the greater the reduction in pulsatility indices of middle cerebral artery and umbilical artery, indicating an increase in blood flow through these arteries. The increase in cerebral blood flow after external cephalic version is more prominent when the placenta is lying posteriorly, while the increase in umbilical flow is more prominent when the placenta is lying laterally. These findings suggest that the vascular changes probably represent a direct effect of force exerted on the fetal head and the placenta. [source] An in vivo comparison of photoactivatable fluorescent proteins in an avian embryo modelDEVELOPMENTAL DYNAMICS, Issue 6 2007Danny A. Stark Abstract Tracing the lineage or neighbor relationships of cells in a migratory population or deep within an embryo is difficult with current methods. The recent explosion of photoactivatable fluorescent proteins (PAFPs) offers a unique cell labeling tool kit, yet their in vivo performance in intact embryos and applicability have not been thoroughly explored. We report a comparison study of PAGFP, PSCFP2, KikGR, and Kaede analyzed in the avian embryo using confocal and 2-photon microscopy. PAFPs were introduced into the chick neural tube by electroporation and each photoconverted in the neural crest or cells in the neural tube with exposure to 405 nm light, but showed dramatic differences in photoefficiency and photostability when compared at the same 2% laser power. KikGR and Kaede photoconverted with ratios only slightly lower than in vitro results, but cells rapidly photobleached after reaching maximal photoefficiency. PSCFP2 had the lowest photoefficiency and photoconverted nearly 70 times slower than the other dual-color PAFPs tested, but was effective at single-cell marking, especially with 2-photon excitation at 760 nm. The dual-color PAFPs were more effective to monitor cell migratory behaviors, since non-photoconverted neighboring cells were fluorescently marked with a separate color. However, photoconverted cells were limited in all cases to be visually distinguishable for long periods, with PSCFP2 visible from background the longest (48 hr). Thus, photoactivation in embryos has the potential to selectively mark less accessible cells with laser accuracy and may provide an effective means to study cell,cell interactions and short-term cell lineage in developmental and stem cell biology. Developmental Dynamics 236:1583,1594, 2007. © 2007 Wiley-Liss, Inc. [source] Corporate Governance and Performance: The REIT EffectREAL ESTATE ECONOMICS, Issue 1 2010Rob Bauer Real estate investment trusts (REITs) offer a natural experiment in corporate governance due to the fact that they leave little free cash flow for management, which reduces agency problems. We exploit a unique and leading corporate governance database to test whether corporate governance matters for the performance of U.S. REITs. We document for a sample including governance ratings of more than 220 REITs that firm value is significantly related to firm-level governance for REITs with low payout ratios only. Repeating the analysis with the complete database that includes more than 5,000 companies and a control sample of firms with high corporate real estate ratios, we find a strong and significantly positive relation between our governance index and several performance variables, indicating that the partial lack of a relation between governance and performance in the real estate sector might be explained by a REIT effect. [source] Are There Enough Doctors in My Rural Community?THE JOURNAL OF RURAL HEALTH, Issue 2 2009Perceptions of the Local Physician Supply ABSTRACT:,Purpose: To assess whether people in the rural Southeast perceive that there is an adequate number of physicians in their communities, assess how these perceptions relate to county physician-to-population (PtP) ratios, and identify other factors associated with the perception that there are enough local physicians. Methods: Adults (n = 4,879) from 150 rural counties in eight southeastern states responded through a telephone survey. Agreement or disagreement with the statement "I feel there are enough doctors in my community" constituted the principal outcome. Weighted chi-square analysis and a generalized estimating equation (GEE) assessed the strength of association between perceptions of an adequate physician workforce and county PtP ratios, individual characteristics, attitudes about and experiences with medical care, and other county characteristics. Findings: Forty-nine percent of respondents agreed there were enough doctors in their communities, 46% did not agree, and 5% were undecided. Respondents of counties with higher PtP ratios were only somewhat more likely to agree that there were enough local doctors (Pearson's correlation coefficient = 0.09, P < .001). Multivariate analyses revealed that perceiving that there were enough local physicians was more common among men, those 65 and older, whites, and those with lower regard for physician care. Perceptions that the local physician supply was inadequate were more common for those who had longer travel distances, problems with affordability, and little confidence in their physicians. Perceptions of physician shortages were more common in counties with higher poverty rates. Conclusions: County PtP ratios only partially account for rural perceptions that there are or are not enough local physicians. Perceptions of an adequate local physician workforce are also related to how much people value physicians' care and whether they face other barriers to care. [source] Deep Fractionation of Clinopyroxene in the East Pacific Rise 13°N: Evidence from High MgO MORB and Melt InclusionsACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 2 2009Guoliang ZHANG Abstract: Mid-ocean ridge basalts (MORBs) from East Pacific Rise (EPR) 13°N are analysed for major and trace elements, both of which show a continuous evolving trend. Positive MgO,Al2O3 and negative MgO,Sc relationships manifest the cotectic crystallization of plagioclase and olivine, which exist with the presence of plagioclase and olivine phenocrysts and the absence of clinopyroxene phenocrysts. However, the fractionation of clinopyroxene is proven by the positive correlation of MgO and CaO. Thus, MORB samples are believed to show a "clinopyroxene paradox". The highest magnesium-bearing MORB sample E13,3B (MgO = 9.52%) is modelled for isobaric crystallization with COMAGMAT at different pressures. Observed CaO/Al2O3 ratios can be derived from E13,3B only by fractional crystallization at pressure >4 ±1 kbar, which necessitates clinopyroxene crystallization and is not consistent with cotectic crystallization of olivine plus plagioclase in the magma chamber (at pressure ,1 kbar). The initial compositions of the melt inclusions, which could represent potential parental magmas, are reconstructed by correcting for post-entrapment crystallization (PEC). The simulated crystallization of initial melt inclusions also produce observed CaO/Al2O3 ratios only at >4±1 kbar, in which clinopyroxene takes part in crystallization. It is suggested that MORB magmas have experienced clinopyroxene fractionation in the lower crust, in and below the Moho transition zone. The MORB magmas have experienced transition from clinopyroxene+plagioclase+olivine crystallization at >4±1 kbar to mainly olivine+plagioclase crystallization at <1 kbar, which contributes to the explanation of the "clinopyroxene paradox". [source] | |||||||||||||