Reliable subsurface scattering for volume rendering in three-dimensional ultrasound imaging.

Light effects have been frequently used in volume rendering because they can depict the shapes of objects more realistically. Global illumination reflects light intensity values at relevant pixel positions of reconstructed images based on the considerations of scattering and extinction phenomena. However, in the cases of ultrasound volumes that do not use Cartesian coordinates, internal lighting operations generate errors owing to the distorted direction of light propagation, and thus increase the amount of light and its effects according to the position of the volume inside. In this study, we present a novel global illumination method with calibrated light along the progression direction in accordance with volume ray casting in non-Cartesian coordinates. In addition, we reduce the consumption of lighting operation in these lighting processes using a light-distribution template. Experimental results show the volume rendering outcomes in non-Cartesian coordinates that realistically visualize the global illumination effect. The light scattering effect is expressed uniformly in the top and bottom areas where many distortions are generated in the ultrasound coordinates by using the light template kernels adaptively. Our method can effectively identify dark areas that are invisible owing to differences in brightness at the upper and lower regions of the ultrasound coordinates. Our method can be used to realistically show the shapes of the fetus during relevant examinations with ultrasonography.

Two helices in the third intracellular loop determine anoctamin 1 (TMEM16A) activation by calcium.

Anoctamin 1 (ANO1)/TMEM16A is a Cl(-) channel activated by intracellular Ca(2+) mediating numerous physiological functions. However, little is known of the ANO1 activation mechanism by Ca(2+). Here, we demonstrate that two helices, "reference" and "Ca(2+) sensor" helices in the third intracellular loop face each other with opposite charges. The two helices interact directly in a Ca(2+)-dependent manner. Positively and negatively charged residues in the two helices are essential for Ca(2+)-dependent activation because neutralization of these charges change the Ca(2+) sensitivity. We now predict that the Ca(2+) sensor helix attaches to the reference helix in the resting state, and as intracellular Ca(2+) rises, Ca(2+) acts on the sensor helix, which repels it from the reference helix. This Ca(2+)-dependent push-pull conformational change would be a key electromechanical movement for gating the ANO1 channel. Because chemical activation of ANO1 is viewed as an alternative means of rescuing cystic fibrosis, understanding its gating mechanism would be useful in developing novel treatments for cystic fibrosis.

The calcium-activated chloride channel anoctamin 1 acts as a heat sensor in nociceptive neurons.

Nociceptors are a subset of small primary afferent neurons that respond to noxious chemical, thermal and mechanical stimuli. Ion channels in nociceptors respond differently to noxious stimuli and generate electrical signals in different ways. Anoctamin 1 (ANO1 also known as TMEM16A) is a Ca(2+)-activated chloride channel that is essential for numerous physiological functions. We found that ANO1 was activated by temperatures over 44 °C with steep heat sensitivity. ANO1 was expressed in small sensory neurons and was highly colocalized with nociceptor markers, which suggests that it may be involved in nociception. Application of heat ramps to dorsal root ganglion (DRG) neurons elicited robust ANO1-dependent depolarization. Furthermore, knockdown or deletion of ANO1 in DRG neurons substantially reduced nociceptive behavior in thermal pain models. These results indicate that ANO1 is a heat sensor that detects nociceptive thermal stimuli in sensory neurons and possibly mediates nociception.