[Nutrient accumulation and cycling in pure and mixed plantations of Azadirachta indica and Acacia auriculiformis in a dry-hot valley, Yunnan Province, southwest China].

To ease the implementation of effective nutrient management for plantations with different vegetation restoration patterns and to assist in the selection of appropriate species and forestation patterns, nutrient (N, P, K, Ca and Mg) accumulation and cycling were investigated and compared in three plantations (10-year-old Azadirachta indica, Acacia auriculiformis and mixed A. indica--A. auriculiformis plantations) in Yuanmou Valley, a dry-hot valley of Yunnan Province, Southwestern China. The result showed that total nutrient accumulations were 333.05, 725.61 and 533.85 kg x hm(-2) in pure plantations of A. indica and A. auriculiformis, and in A. indica--A. auriculiformis mixed plantation, respectively. The nutrient accumulation of various organs was ranked as branches > stems > roots > leaves > bark in the A. indica plantation and branches > stems > leaves > roots > bark both in the A. auriculiformis plantation and in the mixed plantation. Changes in accumulation of various nutrients in the mixed plantation were similar to that in the A. auriculiformis plantation (Ca > N > K > Mg > P), which were different from the A. indica plantation (Ca > K > N > Mg > P). Annual net nutrient accumulation, return and absorption in these plantations ranged from 62.72 to 162.19 kg x hm(-2) x a(-1), 48.82 to 88.86 kg x hm-2 a-1 and 111.54 to 251.05 kg x hm(-2) x a(-1), respectively, which were all the highest in the A. auriculiformis planta- tion, followed by the mixed plantation, and were the lowest in the A. indica plantation. The nutrient utilization coefficient, the cycling coefficient and the recycling period were estimated to be from 0.34 to 0.39, 0.35 to 0.44, and 6.54 to 8.17 a, respectively. The lower nutrient return and circulation rate of N or P in the A. indica plantation showed that this plantation had a poor ability to maintain soil fertility, while the highest nutrient circulation rate of N or P was observed in the A. auriculiformis plantation that displayed the advantage in maintaining soil nutrients and stand productivity. The nutrient return and nutrient absorption in the mixed plantation were 167.2% and 186.2%, of those in the A. indica plantation, and the circulation rate of N, P and K were higher than those in the A. indica plantation, while the recycling period of Ca in mixed plantation was 50% shorter than that in A. auriculiformis plantation. Soil fertility and nutrient supply were improved in the A. indica and A. auriculiformis mixed plantation.

[Vegetation biomass allocation and its spatial distribution after 20 years ecological restoration in a dry-hot valley in Yuanmou, Yunnan Province of Southwest China].

By using layering harvest method, a comparative study was conducted on the biomass allocation and its spatial distribution of 20-year-old Eucalyptus camaldulensis plantation, Leucaena leucocephala plantation, and E. camaldulensis-L. leucocephala plantation in Yuanmou dry-hot valley of Yunnan Province, Southwest China. The stand biomass in the mixed E. camaldulensis-L. leucocephala plantation (82.99 t x hm(-2)) was between that of monoculture E. camaldulensis plantation (60.64 t x hm(-2)) and L. leucocephala plantation (127.79 t x hm(-2)). The individual tree biomass of E. camaldulensis in the mixed plantation (44.32 kg) was 49.8% higher than that in monoculture plantation (29.58 kg). The branch and leaf biomass of L. leucocephala (25.4%) in monoculture plantation was larger than that of E. camaldulensis (8.9%) in monoculture plantation, and the aboveground biomass distribution ratio (78.0%) of L. leucocephala (25.4%) was also higher than that of E. camaldulensis (73.4%). The roots of L. leucocephala in both monoculture and mixed plantations were mainly distributed in 0-40 cm soil layer, while those of E. camaldulensis in monoculture and mixed plantations were mainly found in 0-80 cm and 0-60 cm, respectively. The proportion of biomass allocated to roots including medium roots, small roots, and fine roots of L. leucocephala in mixed plantation was higher than that in monoculture plantation, but it was contrary for E. camaldulensis. It was suggested that introducing L. leucocephala in E. camaldulensis plantation promoted the growth of E. camaldulensis, especially for its aboveground biomass, and increased the amount of lateral roots in 0-20 cm soil layer, which had significance in soil and water conservation in the study area.

[The strategy of posterior decompression and re-establishing the insertion of extensor for ossification of posterior longitudinal ligament involved in C(2)].

OBJECTIVE: To investigate an approach of posterior cervical spinal canal decompression and re-establishing the insertion of extensor, aim at the ossification of the posterior longitudinal ligament (OPLL) involved in C(2). METHODS: From 2002 to 2006, 10 patients with OPLL involved in C(2) underwent open-door laminoplasty, with the posterior cervical ligamentous complex and the insertion of extensor reconstructed on C(2), were reviewed retrospectively. The range of decompression was from C(2) to C(7). The sagittal diameter of C(2) vertebral canal, alignment of the cervical spine (C(2)-C(7) angle), and JOA score before and after operation were contrasted respectively. RESULTS: All patients were followed up, average 14 months. Before the operation, the average sagittal diameter of C(2) vertebral canal was 5.6 mm (4 - 8.8 mm), JOA score was 9.6 scores (6 - 12 scores), C(2)-C(7) angle was 6.5 degrees (-2 degrees - 12 degrees ). After the operation, the average sagittal diameter of C(2) vertebral canal was 13.4 mm (10 - 18.2 mm, P < 0.01), JOA score was 10.9 scores (8 - 14 scores) and the C(2)-C(7) angle was 7.4 degrees (3 degrees - 14 degrees ) in earlier. Finally, the JOA score was 13.2 scores (10 - 17 scores, P < 0.05), and the C(2)-C(7) angle was 7.0 degrees (2 degrees - 15 degrees , P > 0.05) at last. CONCLUSIONS: The open-door laminoplasty, with an approach of the posterior cervical ligamentous complex and the insertion of extensor reconstructed, is an appropriate method for treating OPLL involved in C(2). This process keeps the cervical curve in a better way, and decompresses the spinal canal effectively.

[Pelvic artery representation on three-dimensional reconstructed multislice spiral CT images: variability between the young and the elderly].

OBJECTIVE: To analyze the variability in pelvic artery representation on three-dimensional reconstructed multislice spiral CT images between young adults and the elderly. METHODS: Eight young adult volunteers from the medical staff and 8 elderly people undergoing regular coronary artery examination, who were all free of coronary artery disease and diabetes mellitus, were enrolled in this study. After administration of the contrast agent through the median cubital vein at 3.5 ml/s, the subjects underwent contrast-enhanced CT angiography of the pelvic arteries utilizing a 16-row multislice spiral CT. The images were collected and processed with volume reconstruction (VR) technique for three-dimensional reconstruction to distinguish the arteries and their branches. RESULTS: Good visualization of the pelvic artery was observed on the reconstructed CT images of the young subjects, which revealed in detail up to the third- and even the fourth-order vessels, and the arteries were smooth and had plenty of branches; but in the elderly only the second- or third-order vessels were shown, and the arteries appeared stiff with only a few branches. CONCLUSIONS: Compared with the young adults, the elderly have generally poor visualization of the pelvic arteries on three-dimensional reconstructed multislice spiral CT images possibly in association with atherosclerosis and the functional deterioration of the blood vessels in the latter, which is relative to vascular morphologic changes, suggesting the necessity of studying the pelvic vessels with developmental and functional methods.

[In vitro degradation and subsequent biomechanical changes of poly(lactide-co-glycolide) scaffolds prepared by mild heating under high pressure].

OBJECTIVE: To study the changes in biomechanics and such indices as intrinsic viscosity poly (lactide-co-glycolide) (PLGA) scaffolds produced by mild heating under high pressure after in vitro degradation. METHODS: PLGA scaffolds with the porosity of 90.0% and 92.5% respectively were immerged in 37 degrees Celsius; saline for 8 weeks, and the changes in their mass, intrinsic viscosity and loss of compressive strength were assessed on a weekly basis, and the acidity of the degradation solution was also measured regularly. RESULTS: Significant differences was noted in the mass reduction between the scaffolds, and the intrinsic viscosity began to decrease in both groups in the first week to half of the original value till the sixth week. A 50% reduction in the compressive strength of the scaffolds occurred at the fourth week, and till the eighth week, obvious structural collapse was observed. Along with the changes, the acidity of the degradation solution increased from 6.0 to 6.5, and the solution of 90.0% porosity group had lower pH value during the first 4 weeks than 92.5% porosity group, but such difference was no longer seen afterwards. CONCLUSIONS: PLGA scaffolds made by mild heating under high pressure have stable biomechanical performance with the half-life of approximately 6 weeks, which can be applicable for tissue engineering.

[Analysis of three-dimensional microstructure of poly(lactide-co-glycolide) scaffolds made by mild heating under high pressure].

OBJECTIVE: To develop a poly(lactide-co-glycolide)(PLGA) copolymer scaffold with good three-dimensional microstructure and free of organic solvent, which can be used in bone repairing for tissue engineering, and to explore a novel method for developing polymeric scaffolds. METHODS: The polymer and sodium chloride were ground to powder and mixed in 2 different proportions as the materials for preparing the scaffolds by mild heating under high pressure. The porosity and the ratio of open pores in the product were analyzed in light of its density and by sodium chloride approaches, with the pore size, surface and internal structures examined under scanning electron microscope (SEM). RESULTS: The PLGA scaffolds made by this method had porosity of 90 % and 92.5 % respectively, their pore size ranging from 200 to 250 micro m with the ratio of open pores exceeding 98 % (P<0.01). The average sodium chloride leaching time was 12 to 13 h. CONCLUSIONS: The scaffolds made in this way possess stable three-dimensional microstructure with controllable parameters and without cytotoxic effects caused by organic solvent.