Recording and analysis of slow waves of the small intestine of mice with heart failure.

BACKGROUND: Gastrointestinal (GI) symptoms in heart failure (HF) patients are associated with increased morbidity and mortality. We hypothesized that HF reduces bioelectrical activity underlying peristalsis. In this study, we aimed to establish a method to capture and analyze slow waves (SW) in the small intestine in mice with HF. METHODS: We established a model of HF secondary to coronary artery disease in mice overexpressing tissue-nonspecific alkaline phosphatase (TNAP) in endothelial cells. The myoelectric activity was recorded from the small intestine in live animals under anesthesia. The low- and high-frequency components of SW were isolated in MATLAB and compared between the control (n = 12) and eTNAP groups (n = 8). C-kit-positive interstitial cells of Cajal (ICC) and Pgp9.5-positive myenteric neurons were detected by immunofluorescence. Myenteric ganglia were assessed by hematoxylin and eosin (H&E) staining. RESULTS: SW activity was successfully captured in vivo, with both high- and low-frequency components. Low-frequency component of SW was not different between endothelial TNAP (eTNAP) and control mice (mean[95% CI]: 0.032[0.025-0.039] vs. 0.040[0.028-0.052]). High-frequency component of SW showed a reduction eTNAP mice relative to controls (0.221[0.140-0.302] vs. 0.394[0.295-0.489], p < 0.01). Dysrhythmia was also apparent upon visual review of signals. The density of ICC and neuronal networks remained the same between the two groups. No significant reduction in the size of myenteric ganglia of eTNAP mice was observed. CONCLUSIONS: A method to acquire SW activity from small intestines in vivo and isolate low- and high-frequency components was established. The results indicate that HF might be associated with reduced high-frequency SW activity.

[Enrichment of denitrifying phosphate accumulating organisms in sequencing batch membrane bioreactors].

The enrichment and characteristics of denitrifying phosphate accumulating organisms (DPAO), which are capable of utilizing nitrate as electron acceptor, was investigated in a laboratory-scale sequencing batch membrane bioreactors (SBMBR). The results demonstrated that the proportion of DPAO increased from 19.4% to 69.6% of total phosphate accumulating organisms after anaerobic-aerobic and anaerobic-anoxic-aerobic phases. SBMBR system could operate steadily when 120 mg nitrate was added continuously during the anoxic phase every period. Simultaneous phosphate uptake and biological denitrification with good performance could be obtained in SBMBR operated in steady-state. Nitrate and phosphorus removal efficiency were above 100% and 84% respectively during anoxic phase, however, the effluent TP concentration was low than 0.5 mg/L, the total phosphorus removal efficiency was 96.1%. Furthermore, the ammonium nitrogen removal efficiency of SBMBR could be maintained at 92.2%, and the cumulation of nitrite and nitrate was not observed clearly.

[Comparisons of simultaneous phosphorus and nitrogen removal in sequencing batch membrane bioreactors].

Two SBMBRs run in AO and A2O mode were operated in parallel to compare their ability of simultaneous phosphorus and nitrogen removal. The results showed that the removals of COD and ammonium nitrogen were averaged over 90% and 95%, respectively. A2O MBR has the stronger anaerobic phosphorus release ability; its SPRR30 outdoes 47.5% compared to AO MBR. SPUR30 of A2O MBR was lower which may attribute to the higher effluent TP content. The ratio of DPAO was enhanced 57% compared to AO MBR. And when nitrate as the only electron accepter, the phosphorus uptake mass with unit electron transfer was 30% higher in A2O MBR. This two factors lead to the stronger denitrifying phosphorus removal ability of A2O MBR. Furthermore, the membrane fouling was mitigated in A2O MBR though the aerobic time was half to that of AO MBR. The membrane filter function made SBMBR's effluent free of the sludge settlement ability.