[Effect of nitrogen and phosphorus addition on soil enzyme activities: A meta-analysis]. / æ•´åˆåˆ†æžæ°®ç£·æ·»åŠ å¯¹åœŸå£¤é ¶æ´»æ€§çš„å½±å“.

We conducted a meta-analysis to analyze the effects of nitrogen (N) and combined N and phosphorus (N+P) addition on soil enzyme activities, which being involved in soil carbon (C), N, and P cycles as well as oxidative processes. Nitrogen addition significantly increased the activities of soil C acquisition enzymes, N acquisition enzymes, and P acquisition enzymes by 6.9%, 5.6% and 10.7%, respectively, while the enhancement was much stronger under N+P treatment with 13.4%, 37.4% and 13.3%, respectively. In contrast, both N addition and N+P addition decreased the activities of oxidative enzymes by 6.1% and 0.4%, respectively. The effect sizes of N and N+P addition on soil enzyme activities varied with ecosystem types, N fertilizer types, N addition rates, and the duration of fertilization experiments. Our results suggested that the changes in soil microbes and their enzymes under increasing N deposition and P addition would have profound impacts on soil biogeochemical processes and functions.

Hyperexcitability to electrical stimulation and accelerated muscle fatiguability of taut bands in rats.

OBJECTIVE: Myofascial trigger points contribute significantly to musculoskeletal pain and motor dysfunction and may be associated with accelerated muscle fatiguability. The aim of this study was to investigate the electrically induced force and fatigue characteristics of muscle taut bands in rats. METHODS: Muscle taut bands were dissected out and subjected to trains of electrical stimulation. The electrical threshold intensity for muscle contraction and maximum contraction force (MCF), electrical intensity dependent fatigue and electrical frequency dependent fatigue characteristics were assessed in three different sessions (n=10 each) and compared with non-taut bands in the biceps femoris muscle. RESULTS: The threshold intensity for muscle contraction and MCF at the 10th, 15th and 20th intensity dependent fatigue stimuli of taut bands were significantly lower than those of non-taut bands (all p<0.05). The MCF at the 15th and 20th intensity dependent fatigue stimuli of taut bands were significantly lower than those at the 1st and 5th stimuli (all p<0.01). The MCF in the frequency dependent fatigue test was significantly higher and the stimulus frequency that induced MCF was significantly lower for taut bands than for non-taut bands (both p<0.01). CONCLUSIONS: The present study demonstrates that the muscle taut band itself was more excitable to electrical stimulation and significantly less fatigue resistant than normal muscle fibres.