Relationship between flightlessness and brain morphology among Rallidae.

Studies have suggested that the brain morphology and flight ability of Aves are interrelated; however, such a relationship has not been thoroughly investigated. This study aimed to examine whether flight ability, volant or flightless, affects brain morphology (size and shape) in the Rallidae, which has independently evolved to adapt secondary flightlessness multiple times within a single taxonomic group. Brain endocasts were extracted from computed tomography images of the crania, measured by 3D geometric morphometrics, and were analyzed using principal component analysis. The results of phylogenetic ANCOVA showed that flightless rails have brain sizes and shapes that are significantly larger than and different from those of volant rails, even after considering the effects of body mass and brain size respectively. Flightless rails tended to have a wider telencephalon and more inferiorly positioned foramen magnum than volant rails. Although the brain is an organ that requires a large amount of metabolic energy, reduced selective pressure for a lower body weight may have allowed flightless rails to have larger brains. The evolution of flightlessness may have changed the position of the foramen magnum downward, which would have allowed the support of the heavier cranium. The larger brain may have facilitated the acquisition of cognitively advanced behavior, such as tool-using behavior, among rails.

Femtoliter Volumetric Pipette and Flask Utilizing Nanofluidics.

Microfluidics has achieved integration of analytical processes in microspaces and realized miniaturized analyses in fields such as chemistry and biology. We have proposed a general concept of integration and extended this concept to the 10-1000 nm scale exploring ultimate analytical performances (e.g. immunoassay of a single-protein molecule). However, a sampling method is still challenging for nanofluidics despite its importance in analytical chemistry. In this study, we developed a femtoliter (fL) sampling method for volume measurement and sample transport. Traditionally, sampling has been performed using a volumetric pipette and flask. In this research, a nanofluidic device consisting of a femtoliter volumetric pipette and flask was fabricated on glass substrates. Since gravity, which is exploited in bulk fluidic operations, becomes less dominant than surface effects on the nanometer scale, fluidic operation of the femtoliter sampling was designed utilizing surface tension and air pressure control. The working principle of an 11 fL volumetric pipette and a 50 fL flask, which were connected by a nanochannel, was verified. It was found that evaporation of the sample solution by air flow was a significant source of error because of the ultra-small volumes being processed. Thus, the evaporation issue was solved by suppressing the air flow. As a result, the volumetric measurement error was decreased to ±0.06 fL (CV 0.6%), which is sufficiently low for use in nanofluidic analytical applications. This study will present a fundamental technology for the development of novel analytical methods for femtoliter volume samples such as single molecule analyses.

Cytokine analysis on a countable number of molecules from living single cells on nanofluidic devices.

Analysis of proteins released from living single cells is strongly required in the fields of biology and medicine to elucidate the mechanism of gene expression, cell-cell communication and cytopathology. However, as living single-cell analysis involves fL sample volumes with ultra-small amounts of analyte, comprehensive integration of entire chemical processing for single cells and proteins into spaces smaller than single cells (pL) would be indispensable to prevent dispersion-associated analyte loss. In this study, we proposed and developed a living single-cell protein analysis device based on micro/nanofluidics and demonstrated analysis of cytokines released from living single B cells by enzyme-linked immunosorbent assay. Based on our integration method and technologies including top-down nanofabrication, surface modifications and pressure-driven flow control, we designed and prepared the device where pL-microfluidic- and fL-nanofluidic channels are hierarchically allocated for cellular and molecular processing, respectively, and succeeded in micro/nanofluidic control for manipulating single cells and molecules. 13-unit operations for pL-cellular processing including single-cell trapping and stimulation and fL-molecular processing including fL-volumetry, antigen-antibody reactions and detection were entirely integrated into a microchip. The results suggest analytical performances for countable interleukin (IL)-6 molecules at the limit of detection of 5.27 molecules and that stimulated single B cells secrete 3.41 IL-6 molecules per min. The device is a novel tool for single-cell targeted proteomics, and the methodology of device integration is applicable to other single-cell analyses such as single-cell shotgun proteomics. This study thus provides a general approach and technical breakthroughs that will facilitate further advances in micro/nanofluidics, single-cell life science research, and other fields.

Enzyme-linked immunosorbent assay utilizing thin-layered microfluidics.

A rapid and sensitive enzyme-linked immunosorbent assay (ELISA) is required for on-site clinical diagnosis. Previously, a microfluidic ELISA in which antibody-immobilized beads are packed in a microchannel for a high surface-to-volume (S/V) ratio was developed, but utilizing beads led to complicated fluidic operation. Recently, we have reported nanofluidic ELISA that utilizes antibody-immobilized glass nanochannels (102-103 nm) to achieve a high S/V ratio without beads, enabling even single-molecule detection, but it is not applicable to clinical diagnosis owing to its fL sample volume, much smaller than the nL-µL sample volume in clinical diagnosis. Here, we propose an antibody-immobilized, thin-layered microfluidic channel as a novel platform. Based on the method of nanofluidic ELISA, the channel width was expanded from 103 nm to 100 mm to expand the volume of the reaction field to 102 nL, while the channel depth (103 nm) was maintained to retain the high S/V ratio. A device design which incorporates a taper-shaped interface between the thin-layered channel and the microchannel for sample injection was proposed, and the uniform introduction of the sample into the high-aspect-ratio (width/depth ∼ 200) channel was experimentally confirmed. For the proof of concept, a thin-layered ELISA device with the same S/V ratio as the bead-based ELISA format was designed and fabricated. By measuring a standard C-reactive protein solution, the working principle was verified. The limit of detection was 34 ng mL-1, which was comparable to that of bead-based ELISA. We believe that the thin-layered ELISA can contribute to medicine and biology as a novel platform for sensitive and rapid ELISA.