Arterial stiffness using radial arterial waveforms measured at the wrist as an indicator of diabetic control in the elderly

Although current technique of photoplethysmography (PPG) is a popular noninvasive method of waveform contour analysis in assessing arterial stiffness, data obtained are frequently affected by various environmental and physiological factors. We proposed an easily operable air pressure sensing system (APSS) for radial arterial signal capturing. Totally, 108 subjects (young, the aged with or without diabetes) were recruited from July 2009 to May 2010. Arterial waveform signals from the wrist were obtained and analyzed using Hilbert-Huang transformation (HHT). Through ensemble empirical mode decomposition (EEMD), the signals were decomposed into eight intrinsic mode functions (IMF1-8) of which IMF5 was found to be the desired signal with a discernible diastolic peak. The results showed significant differences in reflection index (RI) and stiffness index (SI) from the young subjects and those from the aged participants with or without diabetes. Significant differences in RI and SI were also noted between subjects with well-controlled diabetes and those without. Good reproducibility and correlation were demonstrated. In conclusion, the present study proposed the application of radial arterial signal capturing subsystem and HHT in acquiring more reliable data on RI and SI compared with the conventional PPG method.     

Directed evolution combined with rational design increases activity of GpdQ toward a non-physiological substrate and alters the oligomeric structure of the enzyme

Directed evolution was used to enhance the activity of the glycerophosphodiesterase enzyme from Enterobacter aerogenes, GpdQ, toward bis(para-nitrophenol) phosphate (BpNPP), a substrate that is frequently used to assay phosphodiesterases. Native GpdQ has a low level of activity toward BpNPP while the evolved enzymes exhibited k(cat) values that were well over 100 times better while improvements in k(cat)/K(m) of around 500 times were observed along with improved activity we observed a change in the oligomeric structure in the evolved enzymes. The native enzyme is a hexamer with tightly associated dimers related by a 3-fold axis. The stability of the dimer was attributed in part to the cap domain that forms a disulfide bond with its 2-fold-related subunit and in part due to the fact that dimerization results in burying 23.6% of the monomer's accessible surface area. The cap domain also forms the top of the active site and contributes an essential part of the interface between 3-fold-related molecules. The evolved proteins quickly lost one of the cysteine residues that formed the disulfide bond and other mutations that might stabilize the cap domain. The likely effect of these mutations was to open up the active site for the new substrate and to favor the formation of dimeric molecules. The breakdown of the oligomeric structure was accompanied by a reduction in the thermal stability of the protein-as monitored by the residual activity of the native and mutant proteins following pre-incubation at elevated temperatures. A discussion on the evolutionary implications of these studies is presented.     

A semisupervised segmentation model for collections of images

In this paper, we consider the problem of segmentation of large collections of images. We propose a semisupervised optimization model that determines an efficient segmentation of many input images. The advantages of the model are twofold. First, the segmentation is highly controllable by the user so that the user can easily specify what he/she wants. This is done by allowing the user to provide, either offline or interactively, some (fully or partially) labeled pixels in images as strong priors for the model. Second, the model requires only minimal tuning of model parameters during the initial stage. Once initial tuning is done, the setup can be used to automatically segment a large collection of images that are distinct but share similar features. We will show the mathematical properties of the model such as existence and uniqueness of solution and establish a maximum/minimum principle for the solution of the model. Extensive experiments on various collections of biological images suggest that the proposed model is effective for segmentation and is computationally efficient.