Effect of changing heart rate on the ocular pulse and dynamic biomechanical behavior of the optic nerve head

Purpose: To study the effect of changing heart rate on the ocular pulse and the dynamic biomechanical behavior of the optic nerve head (ONH) using a comprehensive mathematical model. Methods: In a finite element model of a healthy eye, a biphasic choroid consisted of a solid phase with connective tissues and a fluid phase with blood, and the lamina cribrosa (LC) was viscoelastic as characterized by a stress-relaxation test. We applied arterial pressures at 18 ocular entry sites (posterior ciliary arteries), and venous pressures at four exit sites (vortex veins). In the model, the heart rate was varied from 60 to 120 bpm (increment: 20 bpm). We assessed the ocular pulse amplitude (OPA), pulse volume, ONH deformations, and the dynamic modulus of the LC at different heart rates. Results: With an increasing heart rate, the OPA decreased by 0.04 mm Hg for every 10 bpm increase in heart rate. The ocular pulse volume decreased linearly by 0.13 µL for every 10 bpm increase in heart rate. The storage modulus and the loss modulus of the LC increased by 0.014 and 0.04 MPa, respectively, for every 10 bpm increase in heart rate. Conclusions: In our model, the OPA, pulse volume, and ONH deformations decreased with an increasing heart rate, whereas the LC became stiffer. The effects of blood pressure/heart rate changes on ONH stiffening may be of interest for glaucoma pathology

Transmittance measurement using scanning LED

In order to measure the transmittance for a large field of view (FOV), a system based on scanning LED is developed. The system mainly consists of tunable LEDs, a glass diffuser and a camera. The LED panel would display different colors in the CIE color space. An algorithm of converting the light wavelength to the RGB values is adopted. The images are captured using a monochrome camera. Depending on the number of colors displayed, the transmittance map for the entire spread of visible colors can be determined. Results are compared with those measured through a spectrometer. The spectral transmittance for the two methods exhibit good similarity. The system provides a means of measuring transmittance with no moving parts and can be extended to other hyperspectral imaging applications.Published versio

3D/4D multiscale imaging in acute lymphoblastic leukemia cells-visualizing dynamics of cell death

Quantitative phase detection is a new methodology that provides quantitative information on cellular morphology to monitor the cell status, drug response and toxicity. In this paper the morphological changes in acute leukemia cells treated with chitosan were detected using d’Bioimager a robust imaging system. Quantitative phase image of the cells was obtained with numerical analysis. Results show that the average area and optical volume of the chitosan treated cells is significantly reduced when compared with the control cells, which reveals the effect of chitosan on the cancer cells. From the results it can be attributed that d’Bioimager can be used as a non-invasive imaging alternative to measure the morphological changes of the living cells in real time.Published versio

Excessive fatty acid oxidation induces muscle atrophy in cancer cachexia

Cachexia is a devastating muscle-wasting syndrome that occurs in patients who have chronic diseases. It is most commonly observed in individuals with advanced cancer1, 2, presenting in 80% of these patients, and it is one of the primary causes of morbidity and mortality associated with cancer3, 4, 5. Additionally, although many people with cachexia show hypermetabolism3, 6, the causative role of metabolism in muscle atrophy has been unclear. To understand the molecular basis of cachexia-associated muscle atrophy, it is necessary to develop accurate models of the condition. By using transcriptomics and cytokine profiling of human muscle stem cell–based models and human cancer-induced cachexia models in mice, we found that cachectic cancer cells secreted many inflammatory factors that rapidly led to high levels of fatty acid metabolism and to the activation of a p38 stress-response signature in skeletal muscles, before manifestation of cachectic muscle atrophy occurred. Metabolomics profiling revealed that factors secreted by cachectic cancer cells rapidly induce excessive fatty acid oxidation in human myotubes, which leads to oxidative stress, p38 activation and impaired muscle growth. Pharmacological blockade of fatty acid oxidation not only rescued human myotubes, but also improved muscle mass and body weight in cancer cachexia models in vivo. Therefore, fatty acid–induced oxidative stress could be targeted to prevent cancer-induced cachexia.ASTAR (Agency for Sci., Tech. and Research, S’pore)NMRC (Natl Medical Research Council, S’pore