The role of short daily hemodialysis in the control of hyperphosphatemia, secondary hyperparathyroidism and anemia.

BACKGROUND: Hyperphosphatemia, secondary hyperparathyroidism (SHPT) and anemia are common secondary complications in hemodialysis patients with end-stage renal disease (ESRD). Compared with conventional hemodialysis (CHD), short daily hemodialysis (sDHD) has been found to be more effective in patients with ESRD. The objective of this study was to determine whether sDHD could improve hyperphosphatemia, SHPT and anemia in patients with ESRD. METHODS: Twenty-seven patients (11 women and 16 men, 46.8 ± 13.4 years old) were switched from CHD to sDHD. All hematologic parameters were measured prior to the switch (baseline), at 3 months after the switch (sDHD(1)) and at 6 months after the switch (sDHD(2)). RESULTS: The serum phosphate decreased from 2.54 ± 0.32 mmol/L at baseline to 2.15 ± 0.36 mmol/L (p < 0.001) at sDHD(1) and 1.97 ± 0.33 mmol/L (p < 0.001) at sDHD(2). Calcium-phosphate product decreased from 5.18 ± 1.24 mmol(2)/L(2) at baseline to 4.20 ± 0.71 mmol(2)/L(2) (p < 0.001) at sDHD(1) and 4.02 ± 0.83 mmol(2)/L(2) (p < 0.001) at sDHD(2). The serum PTH levels decreased from 223.9 ± 124.7 pmol/L at baseline to 196.3 ± 101.3 pmol/L (p < 0.05) at sDHD(2). The hemoglobin concentration increased significantly from CHD to sDHD. However, the requirement for erythropoietin (EPO) dose decreased from 6847.8 ± 1057.3 u/week at baseline to 5869.6 ± 1094.6 u/week (p < 0.05) at sDHD(2). CONCLUSIONS: sDHD may decrease serum phosphate, calcium-phosphate product and PTH, increase hemoglobin levels and decrease exogenous EPO dose requirements compared with CHD in hemodialysis patients.

Carbon sequestration in two alpine soils on the Tibetan Plateau.

Soil carbon sequestration was estimated in a conifer forest and an alpine meadow on the Tibetan Plateau using a carbon-14 radioactive label provided by thermonuclear weapon tests (known as bomb-(14)C). Soil organic matter was physically separated into light and heavy fractions. The concentration spike of bomb-(14)C occurred at a soil depth of 4 cm in both the forest soil and the alpine meadow soil. Based on the depth of the bomb-(14)C spike, the carbon sequestration rate was determined to be 38.5 g C/m(2) per year for the forest soil and 27.1 g C/m(2) per year for the alpine meadow soil. Considering that more than 60% of soil organic carbon (SOC) is stored in the heavy fraction and the large area of alpine forests and meadows on the Tibetan Plateau, these alpine ecosystems might partially contribute to "the missing carbon sink".

Carbon balance in an alpine steppe in the Qinghai-Tibet plateau.

Carbon fluxes were measured using a static chamber technique in an alpine steppe in the Qinghai-Tibet Plateau from July 2000 to July 2001. It was shown that carbon emissions decreased in autumn and increased in spring of the next year, with higher values in growth seasons than in winters. An exponential correlation (E(carbon)= 0.22(exp(0.09T) + ln(0.31P+ 1)), R(2)= 0.77, P < 0.001) was shown between carbon emissions and environmental factors such as temperature (T) and precipitation (P). Using the daily temperature (T) and total precipitation (R), annual carbon emission from soil to the atmosphere was estimated to be 79.6 g C/m(2), 46% of which was emitted by microbial respiration. Considering an average net primary production of 92.5 g C/m(2) per year within the 2 year experiment, alpine steppes can take up 55.9 g CO(2)-C/m(2) per year. This indicates that alpine steppes are a distinct carbon sink, although this carbon reservoir was quite small.

[Estimation of net primary productivity in middle reaches of Yarlung Zangbo River and its two tributaries].

Based on the MODIS data and field measurement, the net primary production (NPP) in 2000 and 2006 in the middle reaches of Yarlung Zangbo River and its two tributaries in Tibet were estimated by using a mathematic model. The results showed that in study area, the NPP decreased gradually from valley to ridge, which was accorded with the gradients of precipitation and temperature. The annul NPP per unit area was averagely 86.8 g C m(-2) a(-1), and was 2.15 g C m(-2) a(-1) higher in 2006 than in 2000. Farmland ecosystem had the highest annual NPP per unit area (243.1 g C m(-2) a(-1)), while desert ecosystem had the lowest one (36.5 g C m(-2) a(-1)). The average total NPP in the two years was 512.8 x 10(10) g C a(-1), with the value in 2006 being 12.7 x 10(10) g C a(-1) higher than that in 2000. Meadow ecosystem had the highest annual total NPP (194.4 x 10(10) g C a(-1)), while desert ecosystem had the lowest one (30.3 x 10(10) g C a(-1)). In 2000-2006, the NPP value in the areas with strong human disturbance (0-4 km away from road) had a decreasing trend, while that in the areas difficult for human to reach was in adverse.

Spatial variations in daily average CO2 concentrations above wetland surface of Xianghai National Nature Reserve, China.

Horizontal and vertical variations of daily average CO2 concentration above the wetland surface were studied in Xianghai National Nature Reserve of China in August, 2000. The primary purpose was to study spatial distribution characteristics of CO2 concentration on the four levels of height(0.1 m, 0.6 m, 1.2 m and 2 m) and compare the differences of CO2 concentration under different land covers. Results showed that daily average CO2 concentration above wetland surface in Xianghai National Natural Reserve was lower than that above other wetlands in northeast China as well as the worldwide average, suggesting that Xianghai wetland absorbed CO2 in August and acted as "sink" of CO2. The horizontal variations on the four levels of height along the latitude were distinct, and had the changing tendency of "decreasing after increasing" with the increase of height. The areas with obvious variations were consistent on different levels of height, and those with the highest variations appeared above surface of shore, sloping field, Typha wetland and Phragmites wetland; the vertical variations were greatly different, with the higher variations in Phragmites wetland and Typha wetland, and the lands near the shore and the sloping field with the lower variations. Spatial variations of daily average CO2 concentrations above wetland surface were affected by surface qualities and land covers.