5,619 research outputs found
Vitamin B-12 deficiency stimulates osteoclastogenesis via increased homocysteine and methylmalonic acid
No full textThe risk of nutrient deficiencies increases with age in our modern Western society, and vitamin B(12) deficiency is especially prevalent in the elderly and causes increased homocysteine (Hcy) and methylmalonic acid (MMA) levels. These three factors have been recognized as risk factors for reduced bone mineral density and increased fracture risk, though mechanistic evidence is still lacking. In the present study, we investigated the influence of B(12), Hcy, and MMA on differentiation and activity of bone cells. B(12) deficiency did not affect the onset of osteoblast differentiation, maturation, matrix mineralization, or adipocyte differentiation from human mesenchymal stem cells (hMSCs). B(12) deficiency caused an increase in the secretion of Hcy and MMA into the culture medium by osteoblasts, but Hcy and MMA appeared to have no effect on hMSC osteoblast differentiation. We further studied the effect of B(12), Hcy, and MMA on the formation of multinucleated tartrate-resistant acid phosphatase-positive osteoclasts from mouse bone marrow. We observed that B(12) did not show an effect on osteoclastogenesis. However, Hcy as well as MMA were found to induce osteoclastogenesis in a dose-dependent manner. On the basis of these results, we conclude that B(12) deficiency may lead to decreased bone mass by increased osteoclast formation due to increased MMA and Hcy levels
A qualitative study of a primary-care based intervention to improve the management of patients with heart failure : the dynamic relationship between facilitation and context
No full textBackground:
There is currently a growing emphasis in primary care on upscaling the provision of evidence-based services for specific conditions, such as heart failure (HF), which have traditionally been seen as part of a specialist’s domain. While contextual challenges associated with improvement in primary care have been documented previously, we still know relatively little about how the intentional, theory-informed facilitation of evidence-based change is shaped by contextual factors within this healthcare setting. Hence, a qualitative study was conducted to address the question: How is the process of facilitating evidence-based practice affected by the context of primary care?
Methods:
Data collection took place across general practices in northwest England as part of a process evaluation of the Greater Manchester HF Investigation Tool (GM-HFIT) - a programme of work aiming to improve the management of HF in primary care. Semi-structured interviews, with purposefully selected GM-HFIT team members (n = 9) and primary care practitioners (n = 7), were supplemented by observational data and a three-month diary reflecting on facilitation activities. Framework analysis was used to manage and interpret data.
Results:
We describe a complex and dynamic interplay between facilitation and context, focusing on three major themes: (1) Addressing macro and micro agendas; (2) Forming a facilitative unit; (3) Maintaining momentum. We show that HF specialist nurses (HFSNs) have a high level of professional credibility, which allows them to play a key role in making recommendations to practices for improving patient care. At the same time, we argue that contextual factors, such as top-level endorsement, the necessity to comply with a performance measurement system, and the varying involvement of practice nurses produce tensions that can have both an enabling and constraining effect on the process of facilitation
Original Mycobacterial Sin, a consequence of highly homologous antigens?
No full textThe role of antigens shared between Mycobacteria in in-vivo cross-reactive immune responses in host animals, have been reported to be responsible for reduced BCG vaccination efficacy as well reduced specificity of routine immunological diagnostic tests. This presents with significant disease control challenges in humans and animals. The present review highlights the results of previous studies on the effect of pre-sensitization to environmental mycobacteria on either pathogenic mycobacteria and/or M. bovis BCG, in experimental animals. It also takes an in-depth view into assessing the genetic similarities and relationships between atypical mycobacteria and Mycobacterium tuberculosis complex (MTBC) and how they might explain the immunological imprint of environmental mycobacteria in directing the hosts’ immune response upon subsequent exposure to other classes of mycobacteria. The outcome of this review suggests that genetic closeness between particular atypical mycobacteria and MTBC usually indicate a higher level of homology for certain shared protective antigens. This ultimately results in a higher level of cross reactive immune responses as compared with other atypical mycobacteria that are further away genetically. This would explain the different effects of environmental mycobacteria on MTBC that have been reported in the different studies. In other words the direction of the host immune system in response to exposure to MTBC would depend on the type of environmental mycobacteria that was encountered in the initial exposure. We also explain these mycobacterial interactions in the context of the phenomenon of “Original Mycobacterial Sin”. The effects of these inevitable mycobacterial interactions on field diagnosis and control by vaccination and how to circumvent them are discussed
Cardiovascular risk factor management in patients with RA compared to matched non-RA patients
No full textObjective. RA is associated with a 50-60% increase in risk of cardiovascular (CV) death. This study aimed
to compare management of CV risk factors in RA and matched non-RA patients.
Methods. A retrospective cohort study was conducted using UK clinical practice data. Patients presenting
with an incident RA diagnosis were matched 1:4 to non-RA patients based on a propensity score for RA,
entry year, CV risk category and treatment received at index date (date of RA diagnosis). Patients tested
and treated for CV risk factors as well as those attaining CV risk factor management goals were evaluated
in both groups.
Results. Between 1987 and 2010, 24 859 RA patients were identified and matched to 87 304 non-RA
patients. At index date, groups had similar baseline characteristics. Annual blood pressure, lipids and
diabetes-related testing were similar in both groups, although CRP and ESR were higher in RA patients at
diagnosis and decreased over time. RA patients prescribed antihypertensives increased from 38.2% at
diagnosis to 45.7% at 5 years, from 14.0 to 20.6% for lipid-lowering treatments and from 5.1 to 6.4% for
antidiabetics. Similar treatment percentages were observed in non-RA patients, although slightly lower for
antihypertensives. Modest (2%) but significantly lower attainment of lipid and diabetes goals at 1 year was
observed in RA patients.
Conclusion. There were no differences between groups in the frequency of testing and treatment of CV
risk factors. Higher CV risk in RA patients seems unlikely to be driven by differences in traditional CV risk
factor management
Rayleigh number dependence of the Archimedes number dependent large-scale flow structure formation in mixed convection
No full textWe report on experimental investigations of large-scale flow structure formation in mixed convection. We characterize the flow field by measuring the velocity fields within a rectangular model room using 2D2C PIV. The control parameters are the Reynolds number Re, the Rayleigh number Ra and the Prandtl number Pr. All parameters are linked through the Archimedes number Ar. In 6.4x10-2 ≤ Ar ≤ 1.39x101, 4.2x103 ≤ Re ≤ 6.35x104 and Ra = 3.1x107, Ra = 1.8x108 and Pr = 0.713 we found flow 3 different flow structures. While keeping Ra and Pr constant and varying Ar through Re variations, we found an Ar dependence of the largescale flow structure formation within 6.4x10-2 ≤ Ar ≤ 1.39x101. Furthermore, we found a Ra dependence of the structure formation, which shifts the transition points between the structures to higher Archimedes numbers and reduces the mean velocities within the investigated domain
Reynolds numbers near the ultimate state of turbulent Rayleigh-Bénard convection
No full textWe report on measurements of the mean-flow Reynolds number ReU and the rms fluctuation Reynolds number ReV in turbulent Rayleigh-Bénard convection as a function of the Rayleigh number Ra for 4 x 1011 < Ra < 2 1014 and Pr ' 0:8. Both can be described by the same power law with an effective exponent = 0:44, in agreement with predictions for ReU but in disagreement with predictions for ReV
Logarithmic variance profiles and the corresponding f-1 spectra of temperature fluctuations in turbulent Rayleigh-Bénard convection
No full textWe report experimental results for the temperature variance 2(z) and the corresponding frequency spectra P(f) in turbulent Rayleigh-Bénard convection (RBC) in a cylindrical sample of aspect ratioT= D/L = 1:00 (D = 1:12 m is the diameter and L = 1:12 m the height). The measurements were conducted in the Rayleigh-number range 1011 < Ra < 1:35 1014 and Pr ' 0:8. For Ra = 1:35x1014, 2(z) could be described well by a logarithmic dependence on the vertical position z in a range of z 1 < z < z 2 with z 1 ' 70 and z 2 = 0:1L. Here L=(2Nu) is the thickness of a thin thermal sublayer adjacent to the horizontal plate where the heat flux (denoted by the Nusselt number Nu) is carried mostly by thermal diffusion. In the log layer, we found that the temperature spectra had a significant frequency range over which P(f) f with close to 1. As Ra decreased, increased so that the log layer became thinner. At Ra = 2:05 1011, z 2 < z 1 and therefore there was no range for a log layer. Correspondingly, the temperature spectrum near the horizontal plate did not have the f1 scaling form either
Lagrangian Raylaigh-Bénard convection
No full textUsing passive tracers as sensors, we obtain Lagrangian measurements of tracers position, velocity and temperature in Rayleigh-Bénard convection at Ra=10^7-10^9. We report on statistics of temperature, velocity, and heat transport (Nusselt number). We observe that the Nusselt number is characterized by a largely intermittent behavior, likely due to the interaction of temperature with turbulent velocity fluctuations
Photochemical behavior of some p-styryistilbenes and related compounds: Spectral properties and photoisomerization in solution and in solid state
No full textAuthor Posting. © The Authors (2006) This is the author's version of the work. It is posted here for personal use, not for redistribution. The definitive version was published in PHOTOCHEMISTRY AND PHOTOBIOLOGY, 82(6): 1645-1650. https://doi.org/10.1562/2006-01-17-RA-780ArticlePhotochemistry and Photobiology. 82(6): 1645-1650 (2006)journal articl
Aspect-ratio dependence of the transition to the ultimate state of turbulent Rayleigh-Bénard convection
No full textWe report on measurements of the ultimate-state transition in turbulent Rayleigh-B\'enard convection obtained in a large facility known as the ``Uboot of G\"ottingen" and using pressurized sulfur hexafluoride as the convecting fluid. We found that the transition occurs over a range of which becomes more narrow as increases, ranging from which is at most weakly dependent on and close to to which varies from about for to about for
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