Primary Culture of Porcine Retinal Pigment Epithelial Cells

The retinal pigment epithelium (RPE) is a monolayer of polarized pigmented epithelial cells, located between the choroid and neuroretina in the retina. ...

Xiamen University

A dolphin's biosonar may effectively discriminate subtle differences among targets. In order to investigate the possible physical mechanism of target discrimination, in this study, a finite element model excited by a biomimetic click pulse was proposed. The acoustic scattering field and stress distribution of a stainless steel shell were simulated. The biomimetic click experiments were then conducted to verify the theoretical predictions in an anechoic tank. The experimental results showed a good agreement with the model simulations. Furthermore, the elastic time-frequency features of three cylindrical shells with different wall thickness were obtained using a fractional Fourier transform filter to eliminate specular reflection and cross-term interference. To compare discrimination capacity of the time-frequency features with and without the specular reflection, a time-frequency correlator was applied to calculate the correlation coefficient between different shells. The results indicated that the time-frequency features can be represented in high resolution with less cross-term interference, and these features without specular reflection showed a good capacity to discriminate the shells with different wall thickness.

Elastic feature of cylindrical shells extraction in time-frequency domain using biomimetic dolphin click.

Atlantic bottlenose dolphins () can effectively discriminate between water-filled cylinders with different wall thicknesses. The dolphins' performance may be particularly good when the cylinders are thinner. The dolphins' performance is also asymmetric, in that the discrimination accuracy is not equal when the target thickness increases and decreases by the same amount. Inspired by this, a finite element model is proposed here to mimic a dolphin actively transmitting sound to discriminate between targets using acoustic echoes. The waveforms and frequency spectra of acoustic echoes from a standard cylinder and comparison cylinders with wall thickness differences of ±0.3 mm were compared. The employed model simulations show good agreement with previous experimental measurements by Au and Pawloski [(1992). J. Compar. Physiol. A (1), 41-47]. Asymmetric arrival time shifts were found for the echo peaks and troughs with the same sequence numbers when the wall thicknesses were increased and decreased by the same amount. This asymmetry became more significant for echo peaks and troughs with higher sequence numbers. Apart from these asymmetric arrival time shifts of the acoustic echoes, the patterns of echo waveforms, the spatial distributions of sound pressures in the water, and the particle vibratory displacements in the cylinders were also found to vary with cylinder thickness. The physical origin of this asymmetric discrimination by the dolphins was explored using both geometric acoustics and wave acoustics. The asymmetry observed might be caused by the circumferential surface (Lamb) wave in the cylinder wall, which is a wave acoustics phenomenon that cannot be derived from geometric acoustics. The findings in this paper might be valuable not just for understanding the mechanism of the effect described, but also for helping the development of biomimetic intelligence for robust signal processing in underwater target discrimination.

A study on the asymmetric cylinder wall thickness difference discrimination by dolphins.

Research into the physical mechanism of odontocetes biosonar has made great progress in the past several decades, especially on wave propagation and biosonar beam formation in the foreheads of odontocetes. Although a number of experimental studies have been performed, the physical mechanism of odontocetes underwater target discrimination has not yet been fully understood. Previous research has experimentally studied the finless porpoise's target discrimination using cylinders different in material [Nakahara, Takemura, Koido, and Hiruda (1997). Mar. Mamm. Sci. 13(4), 639-649]. The authors proposed a computed tomography based finite element biosonar model to simulate the detailed process of a finless porpoise click emission and target detection in order to gain a further understanding of the underlying physical mechanism. The numerical solutions of resonance features of both steel and acrylic cylinders in this study are very consistent with the analytic solutions. Furthermore, the simulated outgoing clicks and echoes match the experiment results measured by Nakahara et al. The beam patterns of the scattered field were extracted and the resonance features of cylinders in different materials were analyzed. This method in this study could be used to study some other odontocetes that are inaccessible for experimental work and could also provide physical information for intelligent biomimetic underwater signal processors design.

A biosonar model of finless porpoise (Neophocaena phocaenoides) for material composition discrimination of cylinders.

Tissue structural anisotropy is an important basis for heart function. Attempts to regenerate the complicated heart-tissue alignment has rarely featured macroscale 3D constructs required for myocardial tissue engineering. The feasibility of engineered scaffolds with micro/macro-architecture for guiding spatial cell alignment following complex patterns is reported. The scaffold is composed of stackable dual-structured layers with linear micro-ridge/groove patterns and macro-through-hole arrays, which enable tailorable anisotropy and interconnective free space. When human mesenchymal stem cells are seeded on the scaffold, well-organized spreading alignment showing the precise control in cellular orientation is significantly introduced over nonpatterned controls. Moreover, spatial cell distribution in the scaffold and directional changes of the layered linear patterns that made cell alignment orientations turning accordingly are observed, leading to the complex 3D pattern reconstruction of cellular alignment resembling natural myocardial tissue. This work validates the potential of micro/macro-architecture engineering for spatial cell guidance. Scaffolds with this capability can be potentially used for biomanufacturing of the structural alignment in myocardial tissue engineering.

Scaffold with Micro/Macro-Architecture for Myocardial Alignment Engineering into Complex 3D Cell Patterns.

To provide the general information on corneal transplantation (CT) in China, China Cornea Society designed a questionnaire on CT from 2014 to 2018 and entrusted it to 31 committee members for implementation of the survey nationwide. This article presents the results of the survey and compares the indicators used in the survey and those in the annual statistical report released by the Eye Bank Association of America (EBAA). The number of corneal transplantations completed by the 64 hospitals from 2014 to 2018 was respectively 5377, 6394, 7595, 8270 and 8980, totally 36,616 (22,959 male and 13,657 female). The five largest hospitals by the number of corneal transplantations completed 15,994 surgeries in total, accounting for 43.68% of all the surgeries performed in the 64 hospitals. The most common indication for corneal transplantations was corneal leukoma (7683, 20.98%), followed by bacterial keratitis (4209, 11.49%), corneal dystrophies (4189, 11.44%), keratoconus (3578, 9.77%) and corneal perforation (2839, 7.75%). The main surgical techniques were penetrating keratoplasty (PK) (19,896, 54.34%), anterior lamellar keratoplasty (ALK) (13,869, 37.88%). The proportion of PK decreased from 57.97% in 2014 to 52.88% in 2018 while the proportion of ALK increased from 36.04% in 2014 to 37.92% in 2018. The geographical distribution of keratoplasties performed in China is unbalanced. PK and ALK were the main techniques of CT and corneal leukoma, bacterial keratitis and corneal dystrophies were the main indications for CT in China.

Survey report on keratoplasty in China: A 5-year review from 2014 to 2018.

Dolphins use their biosonar to discriminate objects with different features through the returning echoes. Cross-modal matching experiments were conducted with a resident bottlenose dolphin (Tursiops aduncus). Four types of objects composed of different materials (water-filled PVC pipes, air-filled PVC pipes, foam ball arrays, and PVC pipes wrapped in closed-cell foam) were used in the experiments, respectively. The size and position of the objects remained the same in each case. The data collected in the experiment showed that the dolphin's matching accuracy was significantly different across the cases. To gain insight into the underlying mechanism in the experiments, we used finite element methods to construct two-dimensional target detection models of an echolocating dolphin in the vertical plane, based on computed tomography scan data. The acoustic processes of the click's interaction with the objects and the surrounding media in the four cases were simulated and compared. The simulation results provide some possible explanations for why the dolphin performed differently when discriminating the objects that only differed in material composition in the previous matching experiments.

Feng Wen

Xiamen University

Primary Culture of Porcine Retinal Pigment Epithelial Cells