Bone loss after liver transplantation McDonald, Jennifer A.; Dunstan, Colin R.; Dilworth, Pamela ...
Hepatology (Baltimore, Md.),
October 1991, Letnik:
14, Številka:
4
Journal Article
Recenzirano
We studied 35 adult patients (mean age = 43 yr) referred for orthotopic liver transplantation. Spinal bone mineral density was measured by quantitative computed tomography scanning before ...transplantation (n = 35) and at 3 mo (n = 21) and 12 mo (n = 11) after orthotopic liver transplantation. The readings were corrected to age 50 yr, using the regression equations derived from normal control subjects. Quantitative bone histological studies were performed in 17 patients before orthotopic liver transplantation and 3 mo after orthotopic liver transplantation. Before orthotopic liver transplantation, the corrected spinal bone mineral density in men was 108 ± 20 mg/cm3, less than in male control subjects (129 ± 22 mg/cm3, p < 0.005). In women patients the value was 117 ± 27 mg/cm3, and in female control subjects 126 ± 19 mg/cm3 (NS). However, women patients with primary biliary cirrhosis had lower spinal bone mineral density (106.5 ± 14.8) than female control subjects (p < 0.005). Histologically, the resorbing surface was near the normal mean, whereas the osteoblast surface, tetracycline surface and bone formation rate was lower in men (p < 0.05) but not women. Spinal bone mineral density decreased by 24% in the first 3 mo after orthotopic liver transplantation with no further decrease at 12 mo. Five patients had vertebral fractures within 6 mo of orthotopic liver transplantation. One patient fractured a wrist and three had osteonecrosis of the hip or knee. Bone histological studies 3 mo after orthotopic liver transplantation showed no change in resorbing surface but an increase in osteoblast surface from 2.1% ± 3.0% to 6.0% ± 7.0% (p < 0.05), increased bone formation in men (21 ± 31 to 80 ± 96 μm2/mm2 p < 0.05) and serum osteocalcin increased from 2.3 ± 0.3 pg/ml before transplantation to 5.9 ± 1.8 pg/ml (p <0.05). Bone loss was related to the number of hospital days after orthotopic liver transplantation (r = 0.79, p < 0.001) but not to any other factor, including prednisone and cyclosporin dose.
The study shows that bone mass is reduced in men with end‐stage liver failure and that considerable bone loss occurs in the first 3 mo after orthotopic liver transplantation, frequently resulting in vertebral fractures. The exact cause of the bone loss is not clear, although immobilization appears to be important, probably in combination with corticosteroid therapy. The cellular changes causing this bone loss must occur very early after orthotopic liver transplantation because by 3 mo after transplantation, increased bone formation had begun to occur. (HEPATOLOGY 1991;14:613–619.)
Phase transitions of atmospheric water play a ubiquitous role in the Earth's climate system, but their direct impact on atmospheric dynamics has escaped wide attention. Here we examine and advance a ...theory as to how condensation influences atmospheric pressure through the mass removal of water from the gas phase with a simultaneous account of the latent heat release. Building from fundamental physical principles we show that condensation is associated with a decline in air pressure in the lower atmosphere. This decline occurs up to a certain height, which ranges from 3 to 4 km for surface temperatures from 10 to 30 °C. We then estimate the horizontal pressure differences associated with water vapor condensation and find that these are comparable in magnitude with the pressure differences driving observed circulation patterns. The water vapor delivered to the atmosphere via evaporation represents a store of potential energy available to accelerate air and thus drive winds. Our estimates suggest that the global mean power at which this potential energy is released by condensation is around one per cent of the global solar power - this is similar to the known stationary dissipative power of general atmospheric circulation. We conclude that condensation and evaporation merit attention as major, if previously overlooked, factors in driving atmospheric dynamics.
Some patients with the loin pain/hematuria syndrome suffer incapacitating flank pain. No effective therapy has been reported. Uncertainty persists concerning the authenticity of the pain and the role ...of surgery in treatment. Forty-six patients with loin pain/hematuria syndrome and intractable pain were evaluated following treatment either by renal autotransplantation (30 patients, 10 bilaterally) or by renal denervation (20 patients, four bilaterally) over a 13-year period. All patients had concomitant renal nerve excision and ligation and capsulotomy. There were 37 (80%) women and nine men aged 18 to 61 years (mean age, 33 years). Excretion urography and angiography were normal in all patients. Nineteen of 25 (76%) patients in whom renal autotransplantation was successfully accomplished and who completed a follow-up questionnaire were free of pain, including eight of 10 with bilateral procedures. The follow-up periods ranged from 1 to 13 years (mean, 8.4 years). Six patients have been free of pain for 10 to 13 years. Of 18 patients treated with renal neurectomy who were available for follow-up examination, 12 (67%) developed recurrent renal pain, including four who had pain relief on the other side following previous renal autotransplantation. The follow- up period for these patients ranged from 6 to 9.9 years (mean, 8.0 years). Three of four patients with recurrent renal pain following neurectomy were treated successfully by renal autotransplantation. The loin pain/hematuria syndrome is a rare cause of incapacitation, predominantly of relatively young females. The pain of the syndrome is organic. Renal autotransplantation achieves pain relief in three quarters of patients, but the procedure is often (30%) required bilaterally and has significant complications. Renal neurectomy is followed by an excessive incidence of recurrent renal pain. (Am J Kidney Dis 1998 Aug;32(2):215-20)
Camera traps deployed in grids or stratified random designs are a well‐established survey tool for wildlife but there has been little evaluation of study design parameters.
We used an empirical ...subsampling approach involving 2,225 camera deployments run at 41 study areas around the world to evaluate three aspects of camera trap study design (number of sites, duration and season of sampling) and their influence on the estimation of three ecological metrics (species richness, occupancy and detection rate) for mammals.
We found that 25–35 camera sites were needed for precise estimates of species richness, depending on scale of the study. The precision of species‐level estimates of occupancy (ψ) was highly sensitive to occupancy level, with <20 camera sites needed for precise estimates of common (ψ > 0.75) species, but more than 150 camera sites likely needed for rare (ψ < 0.25) species. Species detection rates were more difficult to estimate precisely at the grid level due to spatial heterogeneity, presumably driven by unaccounted habitat variability factors within the study area. Running a camera at a site for 2 weeks was most efficient for detecting new species, but 3–4 weeks were needed for precise estimates of local detection rate, with no gains in precision observed after 1 month. Metrics for all mammal communities were sensitive to seasonality, with 37%–50% of the species at the sites we examined fluctuating significantly in their occupancy or detection rates over the year. This effect was more pronounced in temperate sites, where seasonally sensitive species varied in relative abundance by an average factor of 4–5, and some species were completely absent in one season due to hibernation or migration.
We recommend the following guidelines to efficiently obtain precise estimates of species richness, occupancy and detection rates with camera trap arrays: run each camera for 3–5 weeks across 40–60 sites per array. We recommend comparisons of detection rates be model based and include local covariates to help account for small‐scale variation. Furthermore, comparisons across study areas or times must account for seasonality, which could have strong impacts on mammal communities in both tropical and temperate sites.
RESUMEN
Las trampas cámara desplegadas en cuadrículas o diseños aleatorios estratificados son una herramienta bien establecida para inventarios de vida silvestre, pero ha habido poca evaluación de los parámetros de diseño del estudio.
Utilizamos un enfoque empírico de submuestreo que involucra 2,225 implementaciones de cámaras en 41 áreas de estudio en todo el mundo para evaluar tres aspectos del diseño del estudio de trampa cámara (número de sitios, duración y temporada de muestreo) y su influencia en la estimación de tres métricas ecológicas (riqueza de especies, ocupación y tasa de detección) para mamíferos.
Encontramos que se necesitaban 25–35 sitios de cámara para estimar con precisión la riqueza de especies, dependiendo de la escala del estudio. La precisión de las estimaciones de ocupación a nivel de especie (ψ) fue muy sensible al nivel de ocupación, con menos de 20 sitios de trampas cámara necesarios para estimaciones precisas de especies comunes (ψ > 0.75), pero es probable que se necesiten más de 150 sitios de trampas cámara para especies raras (ψ < 0.25) especies. Las tasas de detección de especies fueron más difíciles de estimar con precisión a nivel de cuadrícula debido a la heterogeneidad espacial, presumiblemente impulsada por factores de variabilidad del hábitat no contabilizados dentro del área de estudio. Hacer funcionar una cámara en un sitio durante dos semanas fue más eficiente para detectar nuevas especies, pero se necesitaron de tres a cuatro semanas para estimar con precisión la tasa de detección local, sin ganancias de precisión observadas después de un mes. Las métricas para todas las comunidades de mamíferos fueron sensibles a la estacionalidad, el 37%–50% de las especies en los sitios que examinamos fluctuaron significativamente en sus tasas de ocupación o detección durante el año. Este efecto fue más pronunciado en sitios templados, donde las especies estacionalmente sensibles variaron en abundancia relativa en un factor promedio de 4–5, y algunas especies estuvieron completamente ausentes en una temporada debido a hibernación o migración.
Recomendamos las siguientes pautas para obtener de manera eficiente estimaciones precisas de la riqueza de especies, la ocupación y las tasas de detección con matrices de cámaras trampa: desplegar cada cámara durante 3–5 semanas en 40–60 sitios por arreglo. Recomendamos que las comparaciones de las tasas de detección se basen en modelos e incluyan covariables locales para ayudar a explicar la variación a pequeña escala. Además, las comparaciones entre áreas o tiempos de estudio deben tener en cuenta la estacionalidad, que podría tener un fuerte impacto en las comunidades de mamíferos tanto en sitios tropicales como templados.
摘要
红外相机是一种成熟的野生动物调查工具, 通常以网格化或分层随机的方案布设, 但目前很少有研究评估红外相机技术的实验设计参数。
我们对全球41个研究区域内的2225台相机数据使用二次抽样方法评估了红外相机实验设计的三个参数（相机位点数、监测时长和季节, 及其对估计兽类群落物种数、占有率和探测率的影响。
取决于研究尺度, 我们发现需要25–35个相机位点才能精确估计物种数。物种水平占有率（ψ）估计的精确度对占有率大小非常敏感: 对于常见种（ψ > 0.75), 不到20个相机位点便可以精确估计物种的占有率, 但是对于稀有种（ψ < 0.25）, 则需要150个甚至更多的相机位点。由于空间异质性, 基于网格化布设的红外相机更难以精确地估计物种的探测率, 这大概是由于所在研究区域内未解释的生境差异因素所导致的。在同一个位点持续监测2周可以最有效地探测到新物种, 但是精确估计本地探测率则需要3–4周, 而持续置放1个月后不会继续提高估计的精确度。所有兽类群落的生态指标（物种数、占有率和探测率）都对季节性敏感。在本研究的相机位点内, 37%–50%的物种在一年中占有率或探测率具有非常显著的波动。这种影响在温带地区更为明显: 温带地区对季节性敏感的物种的相对丰度变化幅度为平均的4–5倍, 并且一些物种因冬眠或迁徙会在一个季节内完全不出现。
为了有效地获得红外相机阵列中物种数、占有率和探测率的精确估计, 我们建议以下调查准则: 每批红外相机至少需布设40–60个相机位点, 且每台相机持续监测3–5周。我们建议探测率的比较研究需要基于模型, 并包括局部协变量以帮助解释小尺度的差异。此外, 不同研究区域或时间之间的比较必须考虑季节的因素, 因为季节性可能对热带和温带地区的兽类群落产生强烈的影响。
PDF
