GABA-producing Bifidobacterium dentium modulates visceral sensitivity in the intestine.

BACKGROUND: Recurrent abdominal pain is a common and costly health-care problem attributed, in part, to visceral hypersensitivity. Increasing evidence suggests that gut bacteria contribute to abdominal pain perception by modulating the microbiome-gut-brain axis. However, specific microbial signals remain poorly defined. γ-aminobutyric acid (GABA) is a principal inhibitory neurotransmitter and a key regulator of abdominal and central pain perception from peripheral afferent neurons. Although gut bacteria are reported to produce GABA, it is not known whether the microbial-derived neurotransmitter modulates abdominal pain. METHODS: To investigate the potential analgesic effects of microbial GABA, we performed daily oral administration of a specific Bifidobacterium strain (B. dentiumATCC 27678) in a rat fecal retention model of visceral hypersensitivity, and subsequently evaluated pain responses. KEY RESULTS: We demonstrate that commensal Bifidobacterium dentium produces GABA via enzymatic decarboxylation of glutamate by GadB. Daily oral administration of this specific Bifidobacterium (but not a gadB deficient) strain modulated sensory neuron activity in a rat fecal retention model of visceral hypersensitivity. CONCLUSIONS & INFERENCES: The functional significance of microbial-derived GABA was demonstrated by gadB-dependent desensitization of colonic afferents in a murine model of visceral hypersensitivity. Visceral pain modulation represents another potential health benefit attributed to bifidobacteria and other GABA-producing species of the intestinal microbiome. Targeting GABAergic signals along this microbiome-gut-brain axis represents a new approach for the treatment of abdominal pain.

Evaporation of droplets on superhydrophobic surfaces: surface roughness and small droplet size effects.

Evaporation of a sessile droplet is a complex, nonequilibrium phenomenon. Although evaporating droplets upon superhydrophobic surfaces have been known to exhibit distinctive evaporation modes such as a constant contact line (CCL), a constant contact angle (CCA), or both, our fundamental understanding of the effects of surface roughness on the wetting transition remains elusive. We show that the onset time for the CCL-CCA transition and the critical base size at the Cassie-Wenzel transition exhibit remarkable dependence on the surface roughness. Through global interfacial energy analysis we reveal that, when the size of the evaporating droplet becomes comparable to the surface roughness, the line tension at the triple line becomes important in the prediction of the critical base size. Last, we show that both the CCL evaporation mode and the Cassie-Wenzel transition can be effectively inhibited by engineering a surface with hierarchical roughness.

The relationship between EAP and EABR thresholds and levels used to program the nucleus 24 speech processor: data from adults.

OBJECTIVE: The objective of this study was to determine the relationship between electrically evoked whole nerve action potential (EAP) and electrical auditory brain stem response (EABR) thresholds and MAP threshold (T-level) and maximum comfort level (C-level) for subjects who use the Nucleus 24 cochlear implant system. DESIGN: Forty-four adult Nucleus 24 cochlear implant users participated in this study. EAP thresholds were recorded using the Neural Response Telemetry System developed by Cochlear Corporation. EABR thresholds were measured for a subset of 14 subjects using standard evoked potential techniques. These physiologic thresholds were collected on a set of five electrodes spaced across the cochlea, and were then compared with behavioral measures of T-level and C-level used to program the speech processor. RESULTS: EAP thresholds were correlated with MAP T- and C-levels; however, the correlation was not strong. A technique for improving the correlation by combining measures of T- and C-levels made on one electrode with the EAP thresholds was presented. Correlations between predicted and measured T- and C-levels using this technique were 0.83 and 0.77, respectively. Similar results were obtained using the EABR thresholds for a smaller set of subjects. In general, EABR thresholds were recorded at levels that were approximately 4.7 programming units lower than EAP thresholds. CONCLUSIONS: Either EAP or EABR thresholds can be used in combination with a limited amount of behavioral information to predict MAP T- and C-levels with reasonable accuracy.

The comparative performance of mobile telemedical systems based on the IS-54 and GSM cellular telephone standards.

The performance of mobile telemedical communications links based on the IS-54 and GSM cellular telephone standards (the most widely used commercial systems in North America and Europe, respectively) was studied by computer simulations. A photoplethysmography signal was used to investigate the transmission of medical data over simulated mobile phone channels. Various conditions were simulated in the communications path between a mobile transmitter and receiver, from perfect to distorted conditions. The results showed successful transmission, with bit error rates of better than 10(-7) at the receiver for the IS-54 standard. The performance of the IS-54 standard was superior to that of GSM in terms of minimum path delay variations, especially in built-up (urban) areas.

Combined genetic algorithm optimization and regularized orthogonal least squares learning for radial basis function networks.

The paper presents a two-level learning method for radial basis function (RBF) networks. A regularized orthogonal least squares (ROLS) algorithm is employed at the lower level to construct RBF networks while the two key learning parameters, the regularization parameter and the RBF width, are optimized using a genetic algorithm (GA) at the upper level. Nonlinear time series modeling and prediction is used as an example to demonstrate the effectiveness of this hierarchical learning approach.