[Applicability of Bioavailable Phosphorus in Sediments to Indicating Trophic Levels of Lakes and Reservoirs].

Twelve lakes and reservoirs with different water depths and different water residence times were studied to identify the applicability of bioavailable phosphorus of sediments in indicating trophic levels. Water and sediment samples were collected in these 12 lakes and reservoirs to analyze the relationship of nutrient levels between the sediment and the water column. Sodium hydroxide extracted phosphorus (NaOH-P) determined using the SMT classification method is defined as the bioavailable phosphorus of sediment. The results showed that total phosphorus levels in sediments in different lakes and reservoirs ranged from 225 to 760 mg·kg-1 (mean value 502 mg·kg-1); the NaOH-P levels in sediments ranged from 86 to 584 mg·kg-1 (mean value 263 mg·kg-1); the total phosphorus concentrations in the water was 0.02-0.35 mg·L-1 (mean value 0.11 mg·L-1), and the chlorophyll a concentrations in the water were 3-349 µg·L-1 (mean value 51 µg·L-1). It was found that NaOH-P was more effective than total phosphorus in indicating the trophic status of the lakes and reservoirs. However, the NaOH-P levels were significantly related to the phosphorus concentrations in the water column only in shallow water with a long residence time. It was revealed that water residence time and water depth are two key factors that affect the relationship of the phosphorus content between the sediment and the water column. In deep waters or waters with short residence time, the NaOH-P content in the sediment hardly influenced the phosphorus concentration in the water columns, even at high levels. However, in shallow waters with long residence time, the sediment acted as both sources and sinks and frequently exchanged nutrients with the overlying water, especially during bloom periods in summer. Thus NaOH-P could be a potential risk of eutrophication in such waters.

Electroacupuncture and moxibustion promote regeneration of injured sciatic nerve through Schwann cell proliferation and nerve growth factor secretion.

Using electroacupuncture and moxibustion to treat peripheral nerve injury is highly efficient with low side effects. However, the electroacupuncture- and moxibustion-based mechanisms underlying nerve repair are still unclear. Here, in vivo and in vitro experiments uncovered one mechanism through which electroacupuncture and moxibustion affect regeneration after peripheral nerve injury. We first established rat models of sciatic nerve injury using neurotomy. Rats were treated with electroacupuncture or moxibustion at acupoints Huantiao (GB30) and Zusanli (ST36). Each treatment lasted 15 minutes, and treatments were given six times a week for 4 consecutive weeks. Behavioral testing was used to determine the sciatic functional index. We used electrophysiological detection to measure sciatic nerve conduction velocity and performed hematoxylin-eosin staining to determine any changes in the gastrocnemius muscle. We used immunohistochemistry to observe changes in the expression of S100-a specific marker for Schwann cells-and an enzyme-linked immunosorbent assay to detect serum level of nerve growth factor. Results showed that compared with the model-only group, sciatic functional index, recovery rate of conduction velocity, diameter recovery of the gastrocnemius muscle fibers, number of S100-immunoreactive cells, and level of nerve growth factor were greater in the electroacupuncture and moxibustion groups. The efficacy did not differ between treatment groups. The serum from treated rats was collected and used to stimulate Schwann cells cultured in vitro. Results showed that the viability of Schwann cells was much higher in the treatment groups than in the model group at 3 and 5 days after treatment. These findings indicate that electroacupuncture and moxibustion promoted nerve regeneration and functional recovery; its mechanism might be associated with the enhancement of Schwann cell proliferation and upregulation of nerve growth factor.